MM Study on ALU

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Module 1Multiband Multilayer Network Architecture


Section 1Multiband & Multilayer

Optimization

EVOLIUM Base Station SubsystemMultiband and Multilayer GSM network radio optimization - B10

3FL11535ADAAZZZZA Issue 01





EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimization · Multiband Multilayer Network Architecture

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First editionLast name, first nameYYYY-MM-DD01

RemarksAuthorDateEdition

Document History






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Module Objectives

Upon completion of this module, you should be able to:

� Define relevant architectures for multilayer networks design

� Define relevant architectures for multiband networks design






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Module Objectives [cont.]







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Table of Contents

Switch to notes view! Page

1 Concepts and Strategies 72 Cellular Network Architecture 123 Choosing a Relevant Architecture 194 Requirements 27






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Table of Contents [cont.]

Switch to notes view!







1 · 1 · 7

1 Concepts and Strategies






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Introduction to Multilayer Networks

� Multiband/Multilayer network: a powerful solution for:

� Network capacity enhancement

� extra capacity provided by new cells / new TRXs

� specific radio algorithms send MSs to these new cells

� Coverage increase

� when introducing microcells (better indoor penetration, even for outdoor microcells)

� While keeping a good QoS

� Confined coverage for microcells � easier frequency planning

� New frequency band � less tigh frequency planning

� Less congestion






1 · 1 · 9


Support of Multilayer and Multiband Features

� Alcatel-Lucent is providing multilayer solutions:

� Mini, microcells and Indoor layer

� smart speed discrimination

� external Directed Retry

� Alcatel-Lucent is providing multiband solution

� Multiband BSC

� Multiband cells

If the speed discrimination process is activated then MSs will be sent more or less quickly according to the load of

the umbrella cell.






1 · 1 · 10


Network Strategy (Multilayer)

� Multilayer networks can be introduced as continuous layer or hotspots, for:

� Capacity increase

� Coverage increase

� Indoor solution

� All types of mobiles can use both layers






1 · 1 · 11


Network Strategy (Multiband)

� The new band introduction can be done

� In a mono-layer network

� In the same layer

� In a new layer

� In a Multilayer network

� In the upper layer

� In the lower layer

� As part of an existing cell design: multiband cells

� Depending on the architecture chosen:

� Different parameters settings

� Different ways of QoS and traffic monitoring

� Each architecture has drawbacks and advantages

� The main issue is to achieve an efficient traffic sharing between the 2 bands

� Risk of congestion on one band and low traffic on the other band






1 · 1 · 12

2 Cellular Network Architecture






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Cell Environment

� Conventional

� Single cell

� Concentric cell

� Extended cell

� Multiband cell

� Hierarchical: introducing Upper and Lower cell layers

� Indoor cell

� Micro cell

� Mini cell

� Umbrella cell

� Multiband: Classical and Preferred frequency bands

Preferred band is usually DCS1800, and classical band is GSM900






1 · 1 · 14


Cell Profile

� One unique combination of the five parameters

� CELL_DIMENSION_TYPE: macro, micro

� CELL _LAYER_ TYPE : single, upper, lower, indoor

� CELL _PARTITION_ TYPE : normal, concentric

� CELL _RANGE: normal, extended inner, extended outer

� FREQUENCY_RANGE : PGSM(GSM900); DCS1800; EGSM; DCS1900; PGSM-DCS1800; EGSM-DCS1800 and GSM 850

� based on BCCH frequency

� A multiband cell is defined by:

� FREQUENCY_RANGE = “PGSM-DCS1800” or “EGSM-DCS1800”

� CELL _PARTITION_ TYPE of the cell is then forced to concentric

Extended cell : different than the concentric cells ! Made up of two different cells, with 2 BCCH : the inner cell

can cover MS up to 35km, and the outer cell can cover MS between 35km and 70km.

Difference between PGSM and EGSM :

PGSM : primary GSM : 890–915 Mhz 935–960 Mhz

EGSM : extended GSM : 880–915 925–960 Mhz






1 · 1 · 15

Exercise

� Link the logical cell types (as defined in the OMC-R) with the cell profile parameters.

Indoor

Micro

Mini

Umbrella

Cell Layer TypeCell Dimension

TypeCell Type

5 minutes

A cell's profile parameters define the behavior of handovers from and toward this cell : certain handovers are

available only for "UPPER" cells or "MICRO" cells.






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Mono-Band Cell Profiles

DCS1800 or DCS1900DCSNormalNormalIndoorMicroDCS indoor micro cell

PGSM or EGSMGSMNormalNormalIndoorMicroGSM indoor micro cell

DCS1800 or DCS1900DCSNormalConcentricUpperMacroDCS concentric umbrella

PGSM or EGSMGSMNormalConcentricUpperMacroGSM concentric umbrella

DCS1800 or DCS1900DCSNormalConcentricSingleMacroDCS concentric cell

PGSM or EGSMGSMNormalConcentricSingleMacroGSM concentric cell

DCS1800 or DCS1900DCSExtended-outerNormalSingleMacroDCS extended outer cell

PGSM or EGSMGSMExtended-outerNormalSingleMacroGSM extended outer cell

DCS1800 or DCS1900DCSExtended-innerNormalSingleMacroDCS extended inner cell

PGSM or EGSMGSMExtended-innerNormalSingleMacroGSM extended inner cell

DCS1800 or DCS1900DCSNormalNormalUpperMacroDCS umbrella cell

PGSM or EGSMGSMNormalNormalUpperMacroGSM umbrella cell

DCS1800 or DCS1900DCSNormalNormalLowerMacroDCS mini cell

PGSM or EGSMGSMNormalNormalLowerMacroGSM mini cell

DCS1800 or DCS1900DCSNormalNormalLowerMicroDCS micro cell

PGSM or EGSMGSMNormalNormalLowerMicroGSM micro cell

DCS1800 or DCS1900DCSNormalNormalSingleMacroDCS single cell

PGSM or EGSMGSMNormalNormalSingleMacroGSM single cell

Frequency rangeCell band

type

Cell

range

Cell partition

type

Cell layer

type

Cell dimension

type

Parameters

Cell Profile






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Multiband Cell Profiles

PGSM-DCS1800 or EGSM-DCS1800

DCSNormalConcentricIndoorMicroDCS multiband indoor micro cell


GSMNormalConcentricIndoorMicroGSM multiband indoor micro cell


DCSNormalConcentricUpperMacroDCS multiband umbrella cell


GSMNormalConcentricUpperMacroGSM multiband umbrella cell


DCSNormalConcentricLowerMacroDCS multiband mini cell


GSMNormalConcentricLowerMacroGSM multiband mini cell


DCSNormalConcentricLowerMicroDCS multiband micro cell


GSMNormalConcentricLowerMicroGSM multiband micro cell


DCSNormalConcentricSingleMacroDCS multiband single cell


GSMNormalConcentricSingleMacroGSM multiband single cell

Frequency rangeCell band typeCell rangeCell partition typeCell layer typeCell dimension typeParameters

Cell Profile






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Cell Profiles: Example

Exercise : find out what is the profile of each cell ?






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3 Choosing a Relevant Architecture






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Concept

� Multilayer concept: 3 available layer types

� All these cells can be or not operating in the same band and defined as concentric cells

mini

umbrella

micro

indoor

micro micro

umbrella

micro

indoor

single

mini

umbrellaUPPER

SINGLE

LOWER

INDOOR

3 layers are defined in the system, but more layers can be created by parameter tuning. For example,

skyscrapers specific configuration is made up of several consecutive layers designed with cells of the same

“system” layer.






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Microcell Classes

� Microcells configuration will depend on their position in the lower layer

� Microcell “classes” are introduced to deal with typical parameters settings in each of these cases

Indoor Microcell

Border Microcell

Inner MicrocellHotspot Microcell

Defining microcell classes is a very efficient way to set network parameters. It avoids defining a specific

configuration for each cell.






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Mono-layer architecture

� In a mono-layer network, a new band may be introduced:

� In the same layer

� Macro 900 (single)

� Macro 1800 (single)

� 900-1800 interworking managed by priority set by the operator

� In a separate layer

� Macro 900 (umbrella)

� Macro 1800 = mini

� 900-1800 interworking driven by a dual layer architecture (easier to introduce but less flexible)

900 900 1800 1800

900 900

mini1800 mini1800

All examples in this document will be using 900 as an “historical” band and 1800 as a “new” band (thus preferred

band).

All other network configurations are anyway possible.

The dual layer configuration is interesting in case the dual band implementation strategy is traffic driven due to a

low penetration rate of multiband MSs.

A dual layer allows for example, for a multiband MS located in a 900 cell, to discriminate its behavior between a

Forced Directed Retry and an emergency HO. 1800 neighboring cells can be favored for a FDR whereas 900

neighboring cells will be preferred on an emergency HO.

A dual layer also allows to decide the MS transfer from 900 to 1800 band on speed criterion instead of on traffic

criterion if needed (macro 1800 hot spot for instance).






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Multilayer architecture (1/3)

� In a multilayer network, a new band may be introduced:

� In the upper layer



� Micro 900

� In the lower layer


� Macro 1800 = mini

� Micro 900

900 900 1800 1800

900 900

mini1800

µ900 µ900

µ900 µ900

In the first configuration, the major difficulty is to manage 900-1800 interworking in the upper layer. But once it

is done, it is the simplest solution to manage.

In the second configuration, the operator has to deal with priority between the preferred cells: mini or micro? For

both selections in idle mode and capture from the upper layer. A lot of handovers might occur, and it requires

more engineering analysis ressources






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� Higher Priority to 1800 macrocell

� GSM 900 macrocell as a pool of traffic resources when the preferred cell is congested

2

1

Initial access

3

Traffic

based

handover21

Directed retry

Emergency Handover

900

900

1800

Next chapters will explain all parameters for

Initial access

DR and emergency HO

Traffic based HO

With this solution, risk of unloading the micro900 too much.






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� Higher Priority to 900 microcell

� GSM 900 & 1800 macrocell as a pool of traffic resources when the preferred cell is congested

1

2

Initial access

3

Traffic

based

handover12

Directed retry

Emergency Handover

900

900

1800

It is the best solution in case of 3 layers, the most logical.

Previous solution might unload the 900 micro too much.






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Multiband cell solution

� Also called “single BCCH”

� Based on the concentric cell feature

� New band is introduced in existing cells

� In the INNER zone (contains only TCH)

� The OUTER zone contains BCCH, SDCCH and TCH

9001800 9001800

µ900






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4 Requirements






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4 Requirements

Software & Hardware Requirements

� Multilayer architecture

� Hardware: All generations

� Note : Any BTS can be declared with the cell type = MICRO

� Software

� External Directed Retry in B6.2 (µ cells and umbrella cells from different BSC possible)

� INDOOR layer

� Multiband architecture

� Hardware :

� The BSC can manage TRXs from different bands

� The Evolium BTS can support TRXs from different bands within one cell

� 1 cell can be split over 2 BTS's (TRX 900 and TRX 1800 in different BTS's possible)






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4 Requirements

“Cell split” for the multiband cells

� 1 cell can be split over 2 BTS HW

� As soon as these BTSs share the same clock

� Master / Slave configuration needed

� G2 & G3 BTSs can be mixed

� Example of site configurations:

� G2 BTS 3x4 TRX 900 + 1 Evolium BTS 3x4 TRX 1800

� 3 multiband cells 4(900)+4(1800) TRX

� Evolium BTS 6+6 TRX 900 + Evolium BTS 6 TRX 900+ Evolium BTS 3*4 TRX 1800

� 3 multiband cells 6(900)+4(1800) TRX

Master / Slave configuration:

� max. 1 Master + 3 Slaves

Constraints :

• Maximal number of TRX per cell is 16.

• Maximal number of cabinets between which a given cell is shared is 2.

• Cabinets between which a cell is shared are clock synchronized in a master / slave configuration

Such clock synchronization between BTSs in master / slave mode is possible both between A9100 BTSs and

between A9100 BTSs and BTSs of previous generations.






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Exercise

� Give the major advantages and drawbacks of the multiband cells solution

15 minutes






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Self-Assessment on the Objectives

� Please be reminded to fill in the formSelf-Assessment on the Objectivesfor this module

� The form can be found in the first partof this course documentation






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End of ModuleMultiband Multilayer Network Architecture






Module 2Algorithms and Associated Parameters



Optimization







EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimisation · Algorithms and Associated Parameters

1 · 2 · 2

Blank Page




Document History






1 · 2 · 3

Module Objectives


� Describe algorithms dedicated to multilayer and multiband networks management






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Table of Contents


1 Introduction 72 Neighboring cells list 103 Idle Mode Selection and Reselection 194 Call Setup 375 Handover Strategies 516 Main Standard Handover Algorithms 597 Emergency Handover Algorithms for MBML Networks 988 Better Conditions Handover Algorithms for MBML Networks 1109 Multiband Cells 13610 Candidate Cell Evaluation 161






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1 Introduction






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1 Introduction

Justification

� Multiband/Multilayer brings new features and algorithms :

� Designing, managing and monitoring complex networks is more difficult

� A relevant choice of architecture and parameters settings will precede the introduction of a new layer in the existing network

� To be sure to implement correctly the best strategy for your network, knowledge of all algorithms and parameters is mandatory.






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1 Introduction

Typing Conventions

� In all this document

� SYSTEM PARAMETERS (can be set at the OMC-R level) will always be written in BLUE BOLD FONT

� VARIABLES (averages, internal system variables, etc.) will be typed in NORMAL FONT






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2 Neighboring cells list






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Purpose

� Neighboring cells list is sent to the MS regularly and contains all BCCH frequencies of neighbor cells to be monitored by the MS

� The MS measures them regularly in order to :

� Perform cell selection & reselection (in idle mode)

� Report 6 BCCH RxLev to the BSS for handovers (in dedicated mode)

798798 2020

4545

800800

805805

22

MS shall measure the BCCH of neighbor cells and decode their BSIC at least once every 10 seconds.






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Idle Mode

� 2 possibilities, the MS camps on either :

� A cell with a BCCH on a DCS 1800 frequency

� Or a cell with a BCCH on a GSM 900 frequency

805805BCCH 1800

SI 2 and 2bis : 1800 neighboring cells

SI 2ter : 900 neighboring cells

2020BCCH 900

SI 2: 900 neighboring cells

SI 2ter (& 2bis): 1800 neighboring cells

SI : Sytem Information Messages

Description of all SI messages : 3GPP TS 44.018 Mobile radio interface layer 3 specification; Radio Resource Control (RRC) protocol, several chapters starting from §9.1.31

It takes up more space to broadcast 1800 frequencies, therefore 2 SI are necessary.






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Dedicated Mode

� 2 possibilities, the call is performed on either :

� A cell with a BCCH on a DCS 1800 frequency

� Or a cell with a BCCH on a GSM 900 frequency

805805SACCH

SI 5 and 5bis: 1800 neighboring cells

SI 5ter: 900 neighboring cells

2020SACCH

SI 5: 900 neighboring cells

SI 5ter (& 5bis): 1800 neighboring cells

SACCH can be either on a 1800 MHz TRX or a 900 MHz TRX.






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Multiband configuration

� Which ever is the band of the current cell, the MS can receive BCCH list that belongs to the other band only with :

� SI-2ter

� SI-5ter

� To enable/disable this SI messages on BCCH and SACCH

� EN_INTERBAND_NEIGH = enable (1)

� EN_INTERBAND_NEIGH = disable (0)

� Description : BSC parameter that enables / disables the multiband operation by filtering the sending of SYSTEM INFORMATION TYPE 2ter/5ter.

Note : on the OMC-R "cell edit" screen, this parameter is named "EN_INTERBAND_HO".






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Cell Monitoring

� In dedicated mode, a MS can only report 6 measurements :

� Standard behavior in a mono-band network : MS reports the 6 strongest cells

� Problem : in a multiband network, 1800 cells provides less signal strength and might not be included in the 6 strongest neighbors !

805805

MEAS REPORT…

N1 : (BSIC, RXLEV)

N2 : (BSIC, RXLEV)

N3 : (BSIC, RXLEV)

N4 : (BSIC, RXLEV)

N5 : (BSIC, RXLEV)

N6 : (BSIC, RXLEV)

MEASUREMENT REPORT is sent on the UL SACCH of the dedicated TCH, every 480ms.






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Cell Monitoring [cont.]

� Reported neighbors from each band can be forced thanks to the cell parameter :

� MULTIBAND_REPORTING

� 4 possible values

� 0: 6 strongest cells irrespective of the frequency band

� 1: 1 strongest cell (non-serving cell frequency band) + 5 strongest cells(serving cell frequency band)

� 2: 2 strongest cells (non-serving cell frequency band) + 4 strongest cells(serving cell frequency band)

� 3: 3 strongest cells (non-serving cell frequency band) + 3 strongest cells(serving cell frequency band)

� Default value:

� 0 for mono-band network

� 3 for multiband network

For a multi band MS, the number of cells per freq band which shall be included in the measurement report is

indicated by the parameter MULTIBAND_REPORTING, broadcast on BCCH.

An MS attached to GPRS shall use the parameter broadcast on BCCH. The parameter may also be sent to the MS

on SACCH.

The meaning of different values of the parameter is specified as follows:

Value Meaning

00 Normal reporting of the six strongest cells, with known and allowed NCC part of BSIC, irrespective

of the band used.

01 The MS shall report the strongest cell, with known and allowed NCC part of BSIC, in each of the

frequency bands in the BA list, excluding the frequency band of the serving cell. The remaining positions in the

measurement report shall be used for reporting of cells in the band of the serving cell. If there are still

remaining positions, these shall be used to report the next strongest identified cells in the other bands

irrespective of the band used.

10 The MS shall report the two strongest cells, with known and allowed NCC part of BSIC, in each of

the frequency bands in the BA list, excluding the frequency band of the serving cell. The remaining positions in

the measurement report shall be used for reporting of cells in the band of the serving cell. If there are still



11 The MS shall report the three strongest cells, with known and allowed NCC part of BSIC, in each

of the frequency bands in the BA list, excluding the frequency band of the serving cell. The remaining positions

in the measurement report shall be used for reporting of cells in the band of the serving cell. If there are still








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Cell Monitoring Optimization

� MULTIBAND_REPORTING has to be tuned carefully in multiband network, since no handover can be done to a cell which is not reported

� The parameter value is depending on network strategy and may be tuned differently in each band

Example: give priority to 1800 cells

� In 900 layer cells

MULTIBAND_REPORTING = 1 is most of the time sufficient to make a handover towards the preferred band

� In 1800 layer cells

MULTIBAND_REPORTING = 3 : 1800 neighboring cells have to be reported to keep the MS in the same band when possible, but 900 cells should be reliably reported as they are rescue cells.






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Number of neighboring cells

� Neighboring cells list limited to 32 BCCH's in OMC-R :

� Limit easily reached in a network with 3 or 4 layers, and 2 bands

� A special care must be taken when defining the list of neighboring cells

� The multiband cells solution dramatically reduces this problem when introducing new frequency band






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3 Idle Mode Selection and Reselection






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Strategy

� Adding a new band/layer is a powerful way of increasing network capacity if the MS can be sent to the preferred cell

� In dedicated mode: see next sections

� But also in idle mode, so that the call is established directly in the preferred cell

� Really increase capacity

� Maintain high QoS level, without creating extra HO






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Selection and Reselection Principle

� At startup (IMSI Attach), the MS is selecting cell with

� Defined priorities with CELL_BAR_QUALIFY

� Best C1 amongst highest priority cells (using CBQ)

� Once “camped on” one cell (in idle mode)…

� … The MS can decide to reselect another one if:

� C1 criterion < 0

� The MS cannot decode downlink signalling blocks of Paging Channel

� The current cell is becoming forbidden (e.g. barred)

� A random access attempt is still unsuccessful after "Max retrans" repetitions

� MS detects the network has failed authentication check

� There is a better cell, regarding C2 criterion

MAX_RETRANS is a cell parameter, transmitted in SI-2.

Authentication check : during SDCCH phase (call setup, location update)

Note:

Cell selection (first selection) is performed using C1 criterion only (the chosen cell is the one with the best C1)

Reselection is done using the mechanisms referenced above.

e.g., the MS cannot access the cell.

It can be linked to SDCCH congestion, filtering of CHARQD due to TA greater than RACH_TA_FILTER, radio access

problem during the Radio Link Establishment phase.

� If SDCCH is to be seized for LU purpose, the MS will reselect on another cell.

� If SDCCH is seized for something else (e.g., MOC), the MS « may » reselect (this is up to the MS vendor

choice!!!). Some MSs do nothing. Call will never be possible. Some others do reselect. In that case, the user has

to reattempt his call (after the reselection, but before the MS is back to the original cell due to better C2, etc.

(done after 5 s, etc.)).






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Cell Selection with CBQ

� Cell selection, use of CELL_BAR_QUALIFY:

� Set on a per cell basis

� Broadcast on the BCCH

� 2 possible values:

� 0 = normal priority (default value)

� 1 = lower priority

� The MS selects the suitable (C1 > 0) cell with the highest C1 belonging to the list of highest priority

The CELL_BAR_QUALIFY parameter is not understood by phase 1 MS.






1 · 2 · 23


Cell Selection with CBQ [cont.]

� Example: highest priority set on microcell

� The MS will select the microcell (if available, C1>0), whatever the level of the macrocell

2525 microcell

CELL_BAR_QUALIFY = 0

2020

macrocell

CELL_BAR_QUALIFY = 1






1 · 2 · 24


Cell Selection with CBQ [cont.]

�WARNING: usage of CELL_BAR_QUALIFY:

� interacts with CELL_BAR_ACCESS

� A cell with low priority (CELL_BAR_QUALIFY = 1) cannot be barred

� Some MSs will be able to access it, whatever the value of CELL_BAR_ACCESS

normal (see note 1)low11

normal (see note 1)low01

barredbarred10

normalnormal00

Status for cell reselectionCell selection priorityCELL_BAR

ACCESS

CELL_BAR

QUALIFY

NOTE 1: Two identical semantics are used for cross phase compatibility reasons. This allows an operator to

declare a cell always as a low priority one for a phase 2 MS, but keeps the opportunity for an operator to

decide whether a phase 1 MS is permitted to camp on such a cell or not.

Because phase-1 MS do not support this feature, it is recommended to keep cell bar qualify = 0.

Also, some early phase-2 MS do not handle this parameter properly.

This is only useful during selection (switching the MS, before C1 computation). Afterwards, only reselection will

take place.






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C1 Criterion

� C1

� ensures that, if a call was attempted, it would be done with a sufficient downlink and uplink received level

� based on 2 parameters, broadcast on the BCCH

� RXLEV_ACCESS_MIN [dBm]� Minimum level to access the cell

� Default value (for Evolium): -103 dBm

� MS_TXPWR_MAX_CCH [dBm]� Maximum level for MS emitting

� Default value: 33 dBm






1 · 2 · 26


C1 Criterion [cont.]

� C1

� evaluated every 5 s (minimum)

� C1 = A - MAX(0,B) > 0

� A = RxLev - RXLEV_ACCESS_MIN

� assess that the MS received level is sufficient

� B = MS_TXPWR_MAX_CCH - P

� P maximum power of MS

� assess that the BTS received level will be sufficient

� if MS_TXPWR_MAX_CCH < P

C1 is computed for each neighbor, using the parameters broadcasted in each neighbor !

For cell a and cell b :

C1(a) = RxLev - RXLEV_ACCESS_MIN(a) – max(0,MS_TXPWR_MAX_CCH(a)- P)

C1(b) = RxLev - RXLEV_ACCESS_MIN(b) - max(0,MS_TXPWR_MAX_CCH(b)- P)






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C2 Criterion

� C2

� If CELL_RESELECT_PARAM_IND= not present

C2=C1






1 · 2 · 28



� C2

� If CELL_RESELECT_PARAM_IND= present

� And if PENALTY_TIME ≠ Infinity (≠ 640s)

Cell is arriving in neighbor list :

C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET (T)

Cell has been in neighbor list for more than PENALTY_TIME

C2 = C1 + CELL_RESELECT_OFFSET

CELL_RESELECT_OFFSET used to favor a cell among other (e.g. micro-cell vs. umbrella, once T > PENALTY_TIME)

Step size = 20s. 0: 20s, 1: 40s, ..., 30: 620s, 31: TEMPORARY OFFSET ignored and cell_RESELECT_OFFSET has a

negative value

This formula is very useful to favor an indoor cell or a microcell.






1 · 2 · 29



� C2

� If CELL_RESELECT_PARAM_IND= present

� And if PENALTY_TIME = Infinity (= 640s)

C2 = C1 - CELL_RESELECT_OFFSET

CELL_RESELECT_OFFSET used to handicap some cells among others

Step size = 20s. 0: 20s, 1: 40s, ..., 30: 620s, 31: TEMPORARY OFFSET ignored and cell_RESELECT_OFFSET has a

negative value

This formula is very useful to favor an indoor cell or a microcell.






1 · 2 · 30



� Case of "better cell" reselection

� The MS will select the neighbor cell if :

� Cells in same Location Area

C2neighbor > C2current

� Cells in different Location Area

C2neighbor > C2current + CELL_RESELECT_HYSTERESIS

CELL RESELECT HYSTERESIS is a parameter defined in the current cell.






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C2 Parameters

� CELL_RESELECT_PARAM_IND

� C2 parameters are broadcast if = ENABLE (default)

� otherwise C2 = C1

� PENALTY_TIME

� From 20s to 620s, in "20s" increment step

� Default value = 20s

� 640s : infinite penalty

� CELL_RESELECT_OFFSET

� From 0 dB to 126 dB, in "2dB" increment step

� Default value = 0dB

� TEMPORARY_OFFSET

� From 0 dB to 60 dB, in "10dB" increment step (+ Infinity)

� Default value = 0dB






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Applications

MINIMINI UMBUMB

MS in Idle Mode

RxLev(Mini) = -70dBm � C2(Mini) = …

RxLev(Umb) = -65dBm � C2(Umb) = …

=> Which cell is favored in Idle Mode ?

MINI 900CELL_RESELECT_OFFSET = 6 dBTEMPORARY_OFFSET = 0 dBPENALTY_TIME = 0 (20 s)

UMBRELLA 900CELL_RESELECT_OFFSET = 0 dBTEMPORARY_OFFSET = 0 dBPENALTY_TIME = 0 (20 s)

For both cells :

RX_LEV_ACCESS_MIN = -104dBm

MS_TXPWR_MAX_CCH = 33dBm

CELL_RESELECT_PARAM_IND = 1

Recommendation : CELL_RESELECT_OFFSET for lower layers between 4 to 12 dB






1 · 2 · 33


Applications [cont.]

MINIMINI UMBUMB

MS in Idle Mode

RxLev(M900) = -70dBm � C2(M900) = …

RxLev(M1800) = -72dBm � C2(M1800) = …

=> Which cell is favored in Idle Mode ?



For both cells :

RX_LEV_ACCESS_MIN = -104dBm

MS_TXPWR_MAX_CCH = 33dBm

CELL_RESELECT_PARAM_IND = 1






1 · 2 · 34


CRO Tuning

In a multiband network :

� Differences in TRX output power

� TRX 1800 MP (TRADE) = 45.4 dBm

� TRX 900 MP (TRAGE) = 46.5 dBm

� Differences in path loss

� On a same path :

Average propagation loss = difference in path loss + difference in TRX output power = 10dB approx.






1 · 2 · 35


CRO Tuning [cont.]

� Therefore, a 1800 cell will provide less coverage than a 900 cell

� Delta = 8~10dB

� Less traffic is carried by 1800 cells (more capacity available)

� Additionally, the 1800 frequency planning is usually cleaner than the 900 one.

Even at low RxLev, a 1800 cell might provide a coverage with good quality and good capacity

For this reason, CRO is used to advantage 1800 cells over 900 cells.

� Within a same layer : CRO(1800) = CRO(900) + 2~8dB

� Among different layers : CRO(1800) = CRO(900) + 4~12dB






1 · 2 · 36


Exercise

� Is there a way to keep fast-moving mobiles in the upper layer ?

2 minutes

� TEMPORARY_OFFSET(lower/indoor) = Infinity

� PENALTY_TIME(lower/indoor) = 20s






1 · 2 · 37

4 Call Setup






1 · 2 · 38

4 Call Setup

Principles

� Call setup is made on the cell (re)selected in idle mode

� Idle mode parameters favour the preferred cells

� Lower layers

� Preferred band

� What is the risk?






1 · 2 · 39

4 Call Setup

Congestion in the Preferred Cell

� The risk is to have congestion in the preferred cell!

� Classical band / upper cells are unloaded…

� … as all MSs are sent to new cells in idle mode

� This phenomenon is further amplified by handovers behavior

� Multiband/multilayer algorithms are based on CAPTURE mechanisms

� Send the MS in the preferred cell as soon as it is OK…

� … Without comparing serving and preferred cells…

� … to reach the maximum capacity increase

(See handover parts for details)

When a MS camps on a cell in Idle mode, it will perform call setup on this cell (and all other procedures : location

update, SMS, etc.).






1 · 2 · 40

4 Call Setup

Algorithms Principles

New capacity

Trafficincrease

Old capacity






1 · 2 · 41

4 Call Setup

Algorithms Principles (cont.)

New capacity

Trafficincrease

Old capacity

Water Valve with filter:

Dual layer algorithms

As seen earlier :

Cell Selection & Reselection can favor new cells

Handovers can capture traffic from old cells and push it to new cells






1 · 2 · 42

4 Call Setup

Algorithms Principles (cont.)

New capacity

Trafficincrease

Old capacity

Water Pump:

Forced

Directed Retry and

Fast Traffic

handover

By sending too much traffic on new cells, there is a risk of congestion. It can be avoided by Forced Directed Retry

and Fast Traffic HO.






1 · 2 · 43

4 Call Setup

Directed Retry Principles

� A Directed Retry:

� SDCCH to TCH intercell handover

� Triggered during a call setup procedure

MSServingCell BSC MSC

Assignment Request

SDCCH Assignment PhaseSDCCH Assignment Phase

SDCCH PhaseSDCCH Phase(SDCCH)

T11

ChannelActivation

HandoverHandover

(TCH)

TargetCell

HO Command

ack

HO Access

HO CompleteAssignment Complete

Serving cell is congested, waiting to find a neighbor cell

� After channel request, a SDCCH is allocated to the MS

� If no TCH is available, the MS is queued in the TCH QUEUE

� If a HO is detected & the target cell has a TCH availble

� � The MS obtains a TCH in the target cell !






1 · 2 · 44

4 Call Setup

Directed Retry Principles [cont.]

� Internal and External Directed Retries are possible

Handover detection based on standard intercell HO algorithms:

- Too low level- Too bad quality- Power Budget / Traffic HO- Capture (14, 21, 24)- etc. (except Fast Traffic HO)

Handover detection based on a specific algorithm (Cause 20).

Candidate cell evaluation based on specific criteria.

Normal Directed RetryNormal Directed Retry Forced Directed RetryForced Directed Retry






1 · 2 · 45

4 Call Setup

Normal Directed Retry

� Set on a per cell basis with parameter EN_DR

� EN_DR = enable (DR execution is enabled in the cell)

� EN_DR = disable (DR execution is disabled in the cell)

� Executed only if no TCH available in serving cell and standard intercell HO detected

� Except Intracell HO causes 10, 11 and 13 (concentric cells) and causes 15 and 16 (interference HO)

� Except Cause 28 (Fast Traffic HO)

� The target cell is chosen by the BSC based on the HO detected

If the target cell is congested, the counter MC555 is incremented :

Definition : Number of incoming internal directed retry (forced or normal) -preparation failures due to

congestion (on Air or A-bis interface). The target TCH channel can be in HR or FR usage.

Trigger condition

1) Whenever there are no free TCH in the target cell during a forced or normal internal directed retry.

2) Whenever no TCH resource is available on A-bis interface for a forced or normal internal directed retry.

(not valid in B7)

EN_EXT_DR : enables/disables the Outgoing External Directed Retry procedure (on a per BSC basis)






1 · 2 · 46

4 Call Setup

Forced Directed Retry (Cause 20)

� CAUSE 20: Forced Directed Retry

� To activate FDR : EN_FORCED_DR = Enable AND EN_DR = Enable

� AV_RXLEV_NCELL_DR(n) is calculated with the A_PBGT_DR window

� If less than A_PBGT_DR samples are available

� AV_RXLEV_NCELL_DR(n) is calculated with the available "n" samples and remaining "A_PBGT_DR – n" are filled with -110 dBm

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)

And EN_FORCED_DR = ENABLED

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)

And EN_FORCED_DR = ENABLED

AV_RXLEV_NCELL_DR(n) is calculated for each neighbor (neighbor's BCCH), and compared to the

L_RXLEV_NCELL_DR(n) of this neighbor, within the BSC.






1 · 2 · 47

4 Call Setup

FDR Parameters

� L_RXLEV_NCELL_DR(n): level required in the neighboring cell n

� The parameter considered is the one set in the neighboring cell

� The default value depends on the network architecture

� See the next slide

� Freelevel_DR(n): number of free TCH channels required in the neighboring cell n

� The parameter considered is the one set in the neighboring cell

� Default value = 0 to 4 TCHs (linked to the nb of TRXs)

� (cf. Candidate Cell Evaluation)

� A_PBGT_DR: average window

� Default value = 4 SACCHs






1 · 2 · 48

4 Call Setup

Managing DR Parameters

� Normal DR

� Pro's: no radio problem as MS's remain within the service area of the new serving cell

� Con's: poor probability of happening, as MS is already camping on the best server cell

� Forced DR

� Pro's: Probability of detecting a FDR depends on parameter settings.

� Con's: Interference problems because MS is perhaps outside the cell normal service area

Umbrella cell

Micro cell

FDRcapture

Forced Directed Retry strategy:

� Between one micro cell and its umbrella macro cell

� OK: same service area

� Simple parameters settings

� Between 2 micro or 2 macro cells

� According to the frequency plan






1 · 2 · 49

4 Call Setup

Access Strategy

� Prevention of congestion in the “old” cells

� MSs are sent in idle mode to the “preferred cell”

� HO strategy favoring the “preferred cell” in dedicated mode

� Prevention of congestion in the “preferred cell”

� Forced Directed Retry to the “old” cells






1 · 2 · 50

� A dual layer network is considered

� Umbrella cells 900

� Micro cells 900

� Set FDR parameters to avoid interference and allow a powerful TCH resource usage

Umbrella cells

Microcells

Time allowed:

10 minutes

4 Call Setup

Exercise






1 · 2 · 51

5 Handover Strategies






1 · 2 · 52


Objectives

1. Maximize capacity of the network, with:

� Intelligent MS sharing between available resources

� Avoid congestion of historical band (for old MS)

� Consider traffic conditions of all layers

� Use full capacity of new resources (1800 band is offering more channels)

� Consider MS speed for layer discrimination

� Avoid too many handovers

� Degradation of voice quality

� In order to ease traffic analysis, it is recommended to avoid too many handovers between layers.






1 · 2 · 53


Objectives [cont.]

2. Insuring good quality communications and avoiding call drops

� Send MS towards the layer that will provide the best QoS

� Minimize the number of HO between cells for good speech Quality

� Fast moving mobiles are handled by the macrocell layer

� Identify a best target for emergency handovers cases

� The tuning of the parameters will result in trade-offs






1 · 2 · 54


Handover Algorithms

� Next parts will detail available HO causes for multilayer network management

� Standard Handovers

� Multilayer and Multiband Handovers

� Concentric cell "Interzone" Handovers






1 · 2 · 55


Functional Entities

RadioLink

Measurements

ActiveChannel

Pre-processing

Assignment of HO functions in the ALCATEL BSC

BSC

HO DetectionHO Candidate

Cell Evaluation

HO

management

MSCHO

protocol

BTS






1 · 2 · 56


HO Causes

� Standard HO causes

� cause 2 : too low quality on the uplink

� cause 3 : too low level on the uplink

� cause 4 : too low quality on the downlink

� cause 5 : too low level on the downlink

� cause 6 : too large distance between the MS and the BTS

� cause 15 : high interference on the uplink (intra-cell HO)

� cause 16 : high interference on the downlink (intra-cell HO)

� cause 26 : AMR channel adaptation HO (HR to FR)

� cause 12 : power budget evaluation

� cause 23 : traffic

� cause 27 : AMR channel adaptation HO (FR to HR)

� cause 28 : Fast traffic HO

� cause 29 : TFO HO

� cause 20 : FDR

EM

BC

These causes will always work, whether the network is monoband monolayer, or multiband multilayer.






1 · 2 · 57


HO Causes [cont.]

� HO causes for multilayer and multiband networks

� cause 10 : too low level on the uplink in the inner zone

� cause 11 : too low level on the downlink in the inner zone

� cause 7 : consecutive bad SACCH frames received in a microcell

� cause 17 : too low level on the uplink in a microcell compared to a high threshold

� cause 18 : too low level on the downlink in a microcell compared to a high threshold

� cause 13 : too high level on the uplink and the downlink in the outer zone

� cause 14 : high level in the neighboring cell of a lower or indoor layer for slow mobile

� cause 21 : high level in the neighboring cell in the preferred band

� cause 24 : general capture

EM

BC






1 · 2 · 58


HO Causes Priority

� cause 7 : consecutive bad SACCH frames received in a microcell� cause 17 : too low level on the uplink in a µcell compared to a high threshold� cause 18 : too low level on the downlink in a µcell compared to a high threshold� cause 2 : too low quality on the uplink � cause 3 : too low level on the uplink � cause 4 : too low quality on the downlink � cause 5 : too low level on the downlink � cause 6 : too large distance between the MS and the BTS� cause 10 : too low level on the uplink in the inner zone� cause 11 : too low level on the downlink the in inner zone� cause 26 : AMR channel adaptation HO (HR to FR)� cause 15 : high interference on the uplink (intra-cell HO)� cause 16 : high interference on the downlink (intra-cell HO)

� cause 21 : high level in the neighboring cell in the preferred bandcause 14 : high level in neighboring cell of a lower or an indoor layer cell for slow mobilecause 24 : general capturecause 12 : power budget evaluationcause 23 : traffic

� cause 13 : too high level on the uplink and downlink in the outer zone� cause 27 : AMR channel adaptation HO (FR to HR)� cause 20 : Forced Directed Retry DR� cause 28 : Fast traffic HO

EM

BC

The handover causes are checked with the priority order defined here.

The better condition causes 21, 14, 24, 12 and 23 have the same priority. For each cell in the list of possible

candidate cells is associated a cause.

If a cell is in the candidate cells list because of 2 different causes, only the one with the highest priority in the

ordered list (cause 21, cause 14, cause 24, cause 12 and cause 23) in which cause 21 has the highest priority is

kept.






1 · 2 · 59

6 Main Standard Handover Algorithms






1 · 2 · 60


Emergency Intercell Algorithms

� Emergency intercell handovers

� cause 2 : too low quality on the uplink

� cause 3 : too low level on the uplink

� cause 4 : too low quality on the downlink

� cause 5 : too low level on the downlink

� cause 6 : too large distance between the MS and the BTS

� May be triggered

� From any serving cell (any band, any zone, any layer)

� Towards any neighbour, except the serving cell

� Note : EM HO detected while in the inner zone of a cell

� the outer zone is a candidate






1 · 2 · 61


Handover Cause 2: UL Quality

� CAUSE 2: too low quality on the uplink

� Size of window for averaging quality: A_QUAL_HO

� Size of window for averaging level: A_LEV_HO

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO <= RXLEV_UL_IH

and MS_TXPWR = min (P, MS_TXPWR_MAX)

and EN_RXQUAL_UL= ENABLED

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO <= RXLEV_UL_IH


and EN_RXQUAL_UL= ENABLED

QUAL

LEV

Quality and Level causes (2, 3, 4, 5, 15, 16)

The aim of these causes is to keep the call going when the radio link is degrading otherwise the radio link failure might be detected and the call released. These causes wait generally for the power control process to increase the BTS and MS power to their maximum values, except for the causes specific to microcellular environment.

Handover on "too low level" is used to avoid situations where the interference level is low, while the attenuation is quite high. These conditions may appear for example in big city streets which ENABLED a line of sight propagation from the BTS antenna. There is in this case a risk of abrupt quality degradation, if the MS moves away from the line of sight street.

In case of simultaneous low-level and low-quality signals, an intercell handover is requested.






1 · 2 · 62


Handover Cause 3: UL Level

� CAUSE 3: too low level on the uplink



QUAL

LEV

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_UL_H


and EN_RXLEV_UL= ENABLED

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_UL_H


and EN_RXLEV_UL= ENABLED






1 · 2 · 63


Handover Cause 4: DL Quality

� CAUSE 4: too low quality on the downlink



QUAL

LEV

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO <= RXLEV_DL_IH

and BS_TXPWR = BS_TXPWR_MAX

and EN_RXQUAL_DL = ENABLED

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO <= RXLEV_DL_IH


and EN_RXQUAL_DL = ENABLED






1 · 2 · 64


Handover Cause 5: DL Level

� CAUSE 5: too low level on the downlink



QUAL

LEV

AV_RXQUAL_UL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_DL_H


and EN_RXLEV_DL= ENABLED

AV_RXQUAL_UL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_DL_H


and EN_RXLEV_DL= ENABLED






1 · 2 · 65


Handover Cause 6: Distance

� CAUSE 6 : Too long distance

� Size of window for averaging distance : A_RANGE_HO

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO = ENABLED


and EN_DIST_HO = ENABLED

This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, due to

propagation conditions of the operational network. These spurious coverages is the probable production of a high

level of co-channel interference.

This cause is different from the others as it is more preventive. It does not make use of the propagation

conditions of a call. It just does not allow an MS to talk to a BTS if it is too far away.

It may happen for example that some peculiar propagation conditions exist at one point in time that provide

exceptional quality and level although the serving BTS is far and another is closer and should be the one the

mobile should be connected to if the conditions were normal.

It may then happen that these exceptional conditions suddenly drop and the link is lost, which would not have

happened if the mobile had been connected to the closest cell. For these reasons also, this cause does not wait

for the power control to react.






1 · 2 · 66


Emergency Intracell Handovers

� Emergency intracell handovers

� cause 15 : high interference on the uplink (intra-cell HO)

� cause 16 : high interference on the downlink (intra-cell HO)


� From any serving cell (any band, any zone, any layer)

� Towards only the serving cel

� Note : If the MS is on a non-hopping TRX, the BSC will tend to allocate a TCH on another TRX.






1 · 2 · 67


Handover Cause 15: UL Interference

� CAUSE 15: High interference on the uplink



AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO > RXLEV_UL_IH

and EN_CAUSE_15 = ENABLED

and [ no previous intracell handover for this connection failed or EN_INTRACELL_REPEATED = ENABLED ]

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO > RXLEV_UL_IH



THR_RXQUAL_CAUSE_15 and EN_CAUSE_15 are not parameters but variables defined just after.






1 · 2 · 68


Handover Cause 16: DL Interference

� CAUSE 16: High interference on the downlink



AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO > RXLEV_DL_IH



AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO > RXLEV_DL_IH



THR_RXQUAL_CAUSE_16 and EN_CAUSE_16 are not parameters but variables defined after.






1 · 2 · 69


New Parameters for Causes 15 & 16

� CAUSE 15 and CAUSE 16:

� THR_RXQUAL_CAUSE_15 (or 16) and EN_CAUSE_15 (or 16) are specific to variable computed by the BSC :

� THR_RXQUAL_CAUSE_15 (or 16) =

� L_RXQUAL_XX_H for a non AMR call (same threshold as CAUSE 2 or CAUSE 4)

� L_RXQUAL_XX_H_AMR for an AMR call

� EN_ CAUSE _15 (or 16) =

� EN_INTRA_XX for a non-AMR call

� EN_INTRA_XX_AMR for an AMR call

XX = UL or DL

For a non AMR call, the thresholds used are identical to the ones used for CAUSE 2 and CAUSE 4.

In this case and if EN_INTRACELL_REPEATED = DISABLED, when a HO CAUSE 15 (or 16) fails, it can be modified as

UPLINK (or DOWLINK) QUALITY, HO CAUSE 2 (respectively HO CAUSE 4).






1 · 2 · 70


Causes 15 & 16: specific case of concentric cells

� For an MS in the INNER zone, if cause 15 or 16 is triggered:

� TCH may be allocated in the outer zone or in the inner zone

� For an MS in the OUTER zone, if cause 15 or 16 is triggered:

� TCH is always allocated in the outer zone

INNER

OUTE

R






1 · 2 · 71


Handover Cause 12: Power Budget

�Definition of PBGT HO :

� “Comfort” handover type, no matter of emergency

� Possible targets depend on the cells layer type :

Single or UpperSingle or UpperSingle

MS Speed = FASTMS Speed ≠ FAST

Indoor

Lower

Single or Upper

Target Layer Type

Upper or Indoor

Upper or Lower

Single or Upper

Serving Layer Type

Indoor

Lower

Upper

If the MS is measured as fast, HO preferably towards upper cells with

low traffic load






1 · 2 · 72


Handover Cause 12: Power Budget [cont.]


� Possible targets depend also on the cells band type :

GSMAnyGSM

EN_MULTIBAND_PBGT_HO= Disable

EN_MULTIBAND_PBGT_HO= Enable

Any

Target Band Type

DCS

Serving Band Type

(MS not in inner zone of a MB cell)

DCS

A multiband cell is "GSM" if the outer zone is in GSM (cf. note)

The cell band type is an internal variable in the BSC, it depends on the BCCH frequency only. Therefore a

multiband cell has a cell band type = GSM if the outer zone is in GSM900.






1 · 2 · 73




� … And if the MS is in the inner zone of a multiband concentric cell :

GSM-DCSAnyGSM

EN_MULTIBAND_PBGT_HO= Disable

EN_MULTIBAND_PBGT_HO= Enable

Any

Target Frequency Band

GSM-DCS

Serving Band Type

(MS in inner zone of a MB cell)

DCS

When in the MB inner zone, it is possible to force PBGT HO only towards other

MB cell.

Serving cell is a multiband cell : Band type depends on the BCCH frequency.






1 · 2 · 74



� If EN_MULTIBAND_PBGT_HO = disable

Single 900

Upper 900

µ900

900 1800

indoor900

Upper 1800

µ900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

fast

fast

fast

fastfast

Upper

Upper

This scheme highlights well the difficulty of introducing multiband cells if EN_MULTIBAND_PBGT_HO is disabled

(this was the only configuration in the first B6.2 networks): Multiband cells interoperate only with, etc.

multiband cells.






1 · 2 · 75



� If EN_MULTIBAND_PBGT_HO = enable

Single 900

Upper 900

µ900

900 1800

indoor900

Upper 1800

µ900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

Upper

Upper

fast

fast

fast

fastfast






1 · 2 · 76



� Based on Power budget equation

� Size of window for level averaging: A_PBGT_HO

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO

- (BS_TXPWR_MAX – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)

- PING_PONG_MARGIN(n, call_ref)


- (BS_TXPWR_MAX – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)


(A)

(B)

(C)

(D)

The value of PBGT(n) is calculated every SACCH period for each neighboring cell n whose measures are kept in

the book-keeping list

A : favor cell with highest difference between RXLEV(n) and RXLEV(s)

B : compensate for effect of the power control in DL (if PC DL attenuates BS TXPWR by 4dB, the RXLEV(s) is also

attenuated by 4dB)

C : favor the cell where the MS is the most limited in TX power (to limit UL interference and extend battery life)

� automatic bonus of +3dB from 900-serving to 1800-neighbours.

� automatic handicap of -3dB from 1800-serving to 900-neighbours.






1 · 2 · 77



� A Handover cause 12 is detected only if the following conditions are met :


if EN_TRAFFIC_HO(0,n) = DISABLED

then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER (*)

and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO

and EN_PBGT_HO = ENABLED

if EN_TRAFFIC_HO(0,n) = DISABLED

then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER (*)



(*) OFFSET_HO_MARGIN_INNER is applied only if the MS is currently located in the inner zone of a concentric

cell (multiband or monoband). This parameter will be explained in chapter 7.






1 · 2 · 78



� In case the feature "Traffic HO" is enabled, the previous condition is modified :


if EN_TRAFFIC_HO(0,n) = ENABLED

then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER (*)+ max(0, DELTA_HO_MARGIN(0,n))



if EN_TRAFFIC_HO(0,n) = ENABLED

then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER (*)+ max(0, DELTA_HO_MARGIN(0,n))



max(0, DELTA_HO_MARGIN(0,n)) is always positive � it increases the HO_MARGIN(O,n)max(0, DELTA_HO_MARGIN(0,n)) is always positive � it increases the HO_MARGIN(O,n)

Cause 12 HO is correlated with cause 23 HO. This is why there is a difference according to the activation of cause

23 HO (EN_TRAFFIC_HO).

(*) OFFSET_HO_MARGIN_INNER is applied only if the MS is currently located in the inner zone of a concentric

cell (multiband or monoband). This parameter will be explained in chapter 7.






1 · 2 · 79



� DELTA_HO_MARGIN(0,n): evaluated according to the traffic situation of the serving cell and the neighboring cell n (Traffic_load(n)) in the following way:

� Philosophy:

This mechanism aims at penalizing cause 12 detection when the traffic in the serving cell is low and is high in the cell n

If Traffic_load(0) = high and Traffic_load(n) = low,

� DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_MARGIN

If Traffic_load(0) = low and Traffic_load(n) = high,� DELTA_HO_MARGIN(0,n) = + DELTA_INC_HO_MARGIN

Else DELTA_HO_MARGIN(0,n) = 0

If Traffic_load(0) = high and Traffic_load(n) = low,

� DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_MARGIN

If Traffic_load(0) = low and Traffic_load(n) = high,� DELTA_HO_MARGIN(0,n) = + DELTA_INC_HO_MARGIN

Else DELTA_HO_MARGIN(0,n) = 0

(A)

(B)

(C)

Don't forget :

PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER + max(0, DELTA_HO_MARGIN(0,n))

In case (A) : DELTA HO MARGIN is negative, therefore "0" is used in the PBGT algorithm.

Only cases (B) and (C) can occur for cause 12.






1 · 2 · 80



� What is the traffic_load() ?

� Computed for every cell by the BSC

� Not available for neighbour cells that are external (different BSC's)

� Can have three values:

� HIGH: cell is loaded

� LOW: cell is unloaded

� INDEFINITE: cell load is neither loaded nor unloaded, or unknown

� Modified according to the long term traffic evaluation algorithm using the following parameters:

� A_TRAFFIC_LOAD, N_TRAFFIC_LOAD : averaging windows

� HIGH_TRAFFIC_LOAD, IND_TRAFFIC_LOAD, LOW_TRAFFIC_LOAD: load thresholds

� TCH_INFO_PERIOD: cannot be modified (5 s)Annex 1

TCH_INFO_PERIOD = 5 s period used by the BSC to count the number of free TCH.






1 · 2 · 81


Handover Cause 12: Inter-band situation

Separated 900 – 1800 coverages

� Allow the flow of PBGT HO between the 2 bands

� EN_MULTIBAND_PBGT_HO = enable

1800 cells 900 cells

EN_MULTIBAND_PBGT_HO = enable or disable

HO_MARGIN(0,n) =5 dB HO_MARGIN(0,n) = 5 dB

HO_MARGIN(0,n) = 8 dB

EN_MULTIBAND_PBGT_HO = enable


EN_MULTIBAND_PBGT_HO = enable

Typical example: dense urban area covered in 1800, and surrounding cells, outside the city area, are in 900.

For cells which are not in the vicinity of cells from other band, the parameter " EN_MULTIBAND_PBGT_HO" has no

impact on HO detection (except for multiband cells)

Note : to ease design of parameters, one can use the following syntax (i.e. for the case above) :

HO_MARGIN(900,900) = 5dB


HO_MARGIN(1800,1800) = 5dB


EN_MULTIBAND_PBGT_HO(900) = enable

EN_MULTIBAND_PBGT_HO(1800) = enable

Why 8dB ? Because there is a automatic bonus of 3dB from 900 � 1800 (cf p.77). In order keep a difference of

5dB of RXLEV, it is necessary to increase the HO_MARGIN by 3dB.






1 · 2 · 82


Handover Cause 12: Inter-band situation [cont.]

Common 900 – 1800 coverages

� Solution 1 : Allow the exit from "border 1800", but use other HO causes to manage "core 1800"

macro 900

macro 1800


HO_M(1800,900)

= 2 dB

"Border" strategy

Smooth exit of the 1800 area

EN_MULTIBAND_PBGT_HO = Enable"Core" strategy

Prevent PBGT HO, to keep MS in 1800

EN_MULTIBAND_PBGT_HO = Disable

HO_MARGIN(900,1800)

= 8 dB


Dual coverage of an area : full coverage in 1800 and full coverage in 900. However, to compensate for line (C) in

slide 77, we must compensate by 3 dB.

This way, there is no priority given to the 1800 band nor the 900 band.






1 · 2 · 83


Handover Cause 12: Inter-band situation [cont.]

Common 900 – 1800 coverages

� Solution 2 : Manage all intra-layer HO with HO cause 12.

macro 900

macro 1800

HO_M = 2 dB

"Border" strategy

Smooth exit of the 1800 area

EN_MULTIBAND_PBGT_HO = Enable"Core" strategy

Allow PBGT HO, favour MS in 1800

EN_MULTIBAND_PBGT_HO = Enable

HO_M = 8 dB

HO_M(900,900) = 5 dB

HO_M(1800,900)

= 8dB

HO_M(900,1800)

= 2dB

HO_M(1800,1800) = 5 dB

Same management of HO at the "border" zone, but "core" zone is managed with PBGT HO also. Except the

HO_MARGIN are different :

HO_MARGIN(1800,900) = 8dB (6dB harder than default "2dB")

HO_MARGIN(900,1800) = 2dB (6dB easier than default "8dB")






1 · 2 · 84


HO Cause 12: Tuning of Microcells Parameters

� HO_MARGIN(0,n) optimization

� Not triggering too many HOs(ping-pong)

� Not triggering HO to a transient cell (for example, the perpendicular cell at a crossroads)

� Avoid emergency HO to the umbrella if there is an available microcell (after a street corner).

Micro 1Micro 2

Micro 3

PBGT HO between micro cells 1, 2

-110

-100

-90

-80

-70

-60

-50

1 3 5 7 9

11

13

15

17

19

rxlev(cell 1)

rxlev(cell 2)

rxlev(cell 3)

Too many handovers can be perceived as a degradation of the voice quality (i.e. in QVoice)

Transient cell : the Rxlev of this cell is good only for a short duration (= passing cell)






1 · 2 · 85


HO Cause 12: Tuning of Microcells Parameters [cont.]

� HO_MARGIN(0,n)

� Avoid ping-pong HO in urban environment

� Avoid emergency HO after street corners

� Avoid transcient PBGT HO

� Default value: up to 10 dB in dense urban microcellular area, with short A_PBGT_HO.

� Optimized: can be reduced to 5dB or 0dB when applying an anti ping-pong mechanism and long A_PBGT_HO.

� A_PBGT_HO

� To find a compromise with HO_MARGIN(0,n)

� Default value: 8 SACCHs for urban microcells, 6 for dense urban






1 · 2 · 86


HO Cause 12: Tuning of Microcells Parameters [cont.]

� HO_MARGIN optimization

� if HO_MARGIN(0,n) > 5dB

�PBGT HO delayed

�C/I might drop below -9dB

�in case of adjacent frequencies between 2 neighbouring microcells, degradation of voice quality

� if HO_MARGIN(0,n) ≤ 5dB (0dB)

�adjacent frequencies between neighbouring microcells can be used

�BUT A_PBGT_HO should be increased

�AND the anti ping-pong mechanism should be applied (PING_PONG_HCP & T_HCP)

BTS1

BTS2

Building

Interferer

fn

fn+1

Area of potential interferences: (C/I)adj < -6dB

C/I = -9dB, means that the RXLEV(serving) is 9dB lower than the RXLEV(neighbour)

Alcatel recommends C/I > -6dB [BCCH] and > -9dB [TCH] in case of adjacent channels, to avoid call quality

degradation.






1 · 2 · 87


Cause 12: Speed Discrimination in Lower/Indoor

� Transfer of fast MSs from lower or indoor layers to upper layer

� If EN_SPEED_DISC = ENABLED

Traffic Load = low Traffic Load ≠≠≠≠ low

HO

HO (12) HO (12) HO (12)

HO (12)

MIN_CONNECT_TIME

At call setup: C_DWELL = 0 and is incremented by 1 every MEASUREMENT REPORTMS_SPEED is set to indefinite

After 1st HO: MS_SPEED is kept at indefinite, and C_DWELL reinits to 0Next HO: MS_SPEED is set to fast if

C_DWELL < 2 x MIN_CONNECT_TIMEHO is a Power Budget HO (cause 12)EN_SPEED_DISC = ENABLED in serving cell

Otherwise MS_SPEED is kept at indefinite and C_DWELL reinits to 0

At call setup: C_DWELL = 0 and is incremented by 1 every MEASUREMENT REPORTMS_SPEED is set to indefinite

After 1st HO: MS_SPEED is kept at indefinite, and C_DWELL reinits to 0Next HO: MS_SPEED is set to fast if

C_DWELL < 2 x MIN_CONNECT_TIMEHO is a Power Budget HO (cause 12)EN_SPEED_DISC = ENABLED in serving cell

Otherwise MS_SPEED is kept at indefinite and C_DWELL reinits to 0

If the handover is an intracell HO, nothing happens : C_DWELL continues to be incremented.

If the handover is an external HO (different BSC), then there is a reinitialisation of the variables C_DWELL and

MS_SPEED as after a call setup.






1 · 2 · 88


Exercise

� Draw arrows to indicate among which cells the HO cause 12 can be detected

UMBRELLA

LOWER

INDOOR

SPEED_DISC is enable in lower and indoor layers

Case 1 : all cells belong to the same BSC

Case 2 : the umbrella cells belong to another BSC






1 · 2 · 89


Handover Cause 23: Traffic

� The aim of this cause is to speed-up HO detection when

� The serving cell is loaded

� The target cell is unloaded

� Counter-reaction of cause 12

� Checked between :

� LAYER :

� Cells with the same CELL_LAYER_TYPE

� BAND :

� If EN_MULTIBAND_PBGT_HO = disable � Cells with the same CELL_BAND_TYPE

� if MS in inner zone of a multiband cell, it can only go to another multiband cell

� If EN_MULTIBAND_PBGT_HO = enable � Any CELL_BAND_TYPE

CAUSE 23

CAUSE 12

In some multiband networks, the radio coverage is ensured by DCS cells in one geographical area and by GSM cells

in another geographical area. As these cells form a multiband and mono-layer network, the capture handovers

between cells of different bands will be inefficient to regulate the CS traffic load in the serving cell

neighboringhood.

The solution consists in allowing intra-layer traffic handovers (Cause 23) based on a power budget evaluation

between cells of different bands.






1 · 2 · 90


Handover Cause 23: Traffic [cont.]

� CAUSE 23: Traffic Handover

� Size of window for level average: A_PBGT_HO

� DELTA_HO_MARGIN(0,n) uses the same algorithm as in p.77.

DELTA_HO_MARGIN(0,n) < 0 dB

AND PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ DELTA_HO_MARGIN(0,n)

AND EN_TRAFFIC_HO(0,n) = ENABLED

DELTA_HO_MARGIN(0,n) < 0 dB

AND PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ DELTA_HO_MARGIN(0,n)

AND EN_TRAFFIC_HO(0,n) = ENABLED

The principle of this handover is to reduce the size of the serving cell when it is high loaded relatively to a low loaded cell.

When the mobile moves away from the BTS, the power budget will increase and a better cell handover will be triggered earlier.

It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enough resources to receive incoming handovers due to congestion of neighboring cells. Moreover because of the great variation of traffic in the 1 TRX cells, traffic load is never considered as low.

This cause is inhibited for handover from SDCCH to SDCCH.

Cause 23 is checked over all the neighboring cells belonging to the same layer. It means that it is checked between cells whose CELL_LAYER_TYPE is single or upper, between cells whose CELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor.

In addition to the condition on the cell layer type, the cell frequency band condition for checking Cause 23 is as follows whether or not the MS is in the inner zone of a multiband cell:

� The MS is not in the inner zone of a multiband cell

� If the flag EN_MULTI-BAND_PBGT_HO is set to “disabled”, Cause 23 must not be checked between cells which use different frequency bands (i.e cells having different CELL_BAND_TYPE).

� If the flag EN_MULTI-BAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all theneighboring cells without any cell frequency band restriction.

� The MS is in the inner zone of a multiband cell

� If the flag EN_MULTI-BAND_PBGT_HO is set to “disabled”, Cause 23 is checked over all the neighboring cell multiband cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.

� If the flag EN_MULTI-BAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all theneighboring cells without any cell frequency band restriction.






1 · 2 · 91


Handover Cause 28: Fast Traffic HO

� CAUSE 28: Fast Traffic Handover

� Push out of a cell a mobile in dedicated mode to allow a queued request to be served in the serving cell


� From any non-concentric cell OR concentric outer zone

� Towards any cell except the serving one

HO

New call attempt Most appropriate MS

to be pushed out

Congested cell

New call attempt

HO

Most appropriate MS

to be pushed out

Upper Layer Cell






1 · 2 · 92


Handover Cause 28: Fast Traffic HO [cont.]


� Cause 28 is only checked if the channel of the candidate MS can support the channel rate (HR or FR) required by the queued request:

� HO is triggered when a request is queued at the top of the queue

FR (whatever the TRX type)FR

HR

or

FR on dual rate TRX

HR

Candidate MSQueued Request






1 · 2 · 93


Handover Cause 28: Fast Traffic HO [cont.]


� Size of window for averaging level: A_PBGT_DR

� Same thresholds and window as Cause 20 (FDR)

� EN_CAUSE_28 is an internal HOP process variable, ENABLED when a request is queued

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max (0, [MS_TXPWR_MAX(n) - P])

and t(n) > FREELEVEL_DR(n)


and EN_FAST_TRAFFIC_HO = ENABLED

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max (0, [MS_TXPWR_MAX(n) - P])

and t(n) > FREELEVEL_DR(n)


and EN_FAST_TRAFFIC_HO = ENABLED

HO cause 28 process:

� If EN_FAST_TRAFFIC_HO = enabled, when an assignment request (or external emergency HO request) is queued,

the RAM process sends to the HOP process a Fast Traffic HO request which contains the queued request reference

and its channel rate.

� Then, HO cause 28 becomes checkable (EN_CAUSE_28=enabled).

� Once an HO alarm for cause 28 is triggered, the flag EN_CAUSE_28 is set to “disabled” so as not to perform

more than one handover. In the same time, the HOP process gets back to the RAM process a Fast Traffic HO

Acknowledge which contains the queued request reference and the reference of the MS that can perform HO.

� If several answers are sent to the RAM process, only the first one corresponding to the queued request is taken

into account.

� The RAM process checks if the request is still queued. If it is so, RAM asks HOP to start HO for this mobile;

otherwise the process is stopped.

� Once the HOP process receives this message, the first two conditions of Cause 28 (good enough level, enough

free resources in the target cell) are checked one more time. If the conditions are fulfilled, the HOP process

sends an alarm to the HOM entity and the timer T_FILTER is started; otherwise the process is stopped.

Note: the first two conditions of cause 28 are tested twice in order to be sure that the candidate cells are still

valid when the « cause 28 start HO » message is received from the RAM process.






1 · 2 · 94

� Detection of cause 12

� Parameters settings

� No Power Control DL, no anti ping-pong

� EN_PBGT_HO = enable

� EN_TRAFFIC_HO(0,n) = disable

� HO_MARGIN(0,n) = 5 dB

� RXLEV_LIMIT_PBGT_HO = -47 dBm

� BS_TXPWR_MAX_INNER = 0 dB

� OFFSET_HO_MARGIN_INNER = 0 dB

� In each case, determine if cause 12 is detected or not

30 minutes


Exercise






1 · 2 · 95

� Is cause 12 triggered?

� EN_MULTIBAND_PBGT_HO = ENABLE


Exercise [cont.]

9009001800900Band

FastFastSlowIndMS speed

Cause 12 ?

PBGT ?

-80 dBm-65 dBm- 65 dBm-80 dBmRx_Lev(n)

HIGHLOWLOWINDTraffic(n)

MicroUmbrellaUmbrellaSingleType

Target

-90 dBm-90 dBm- 90 dBm-85 dBmRx_Lev(0)

NoYesYesNoEN_SPEED_DISC

900900900900Band

MiniMicroMicroSingleType

Source

Case 4Case 3Case 2Case 1Inputs






1 · 2 · 96


Exercise [cont.]


� EN_MULTIBAND_PBGT_HO = DISABLE

Cause 12 ?

PBGT ?

-65 dBm-65 dBm-65 dBm-70 dBm-80 dBmRx_Lev(n)

9009009001800900Band

Multiband

UpperSingleSingleSingleSingleType

Target

-90 dBm-90 dBm-90 dBm-85 dBm-85 dBmRx_Lev(0)

InnerOuterInner------Zone

900900900900900Band

Multiband

Upper

Multiband

Upper

Multiband

UpperSingleSingleType

Source

Case 5Case 4Case 3Case 2Case 1Inputs






1 · 2 · 97


Exercise [cont.]


� EN_MULTIBAND_PBGT_HO = ENABLE

Cause 12 ?

PBGT ?


9009009001800900Band

Multiband

UpperSingleSingleSingleSingleType

Target


InnerOuterInner------Zone

900900900900900Band

Multiband

Upper

Multiband

Upper

Multiband

UpperSingleSingleType

Source







1 · 2 · 98

7 Emergency Handover Algorithms for MBML Networks






1 · 2 · 99


Emergency Handovers: Introduction

� In a hierarchical network, the MS can camp in any layer. Each layer is characterized by a certain cell type.

� Depending on the dimension type, the BSC is able to trigger some specific "microcell" emergency handovers in order to save the call.

Micro

Micro

Macro

Macro

Macro

Dimension Type

YESYESMicro

NOYESSingle

Micro

(7,17,18)

Standard

(2,3,4,5,6)

YES

YES

YES

Available Emergency HO causes

YES

NO

NO

Serving Cell Type

Indoor

Mini

Umbrella






1 · 2 · 100


Emergency Handovers: Introduction [cont.]

� Recommended strategies :

� An MS is located in a micro or an indoor cell

� During an emergency HO, the MS is directed preferably towards an upper or a single cell

� An MS is located in a mini cell

� During an emergency HO, the MS is directed preferably towards neighboring mini cells

in µ

umbrella single

mini

umbrella

mini






1 · 2 · 101


Emergency Handovers Specific to Microcells

� Emergency handovers specific to microcells

� cause 7 : consecutive bad SACCH frames received in a microcell

� cause 17 : too low level on the uplink in a microcell compared to a high threshold

� cause 18 : too low level on the downlink in a microcell compared to a high threshold


� From microcells only (cell_dimension_type = micro)

� Outdoor microcell (micro layer)

� Indoor microcell (indoor layer)

� Towards any cell except the serving one

� Note : If the MS in inner zone of a multiband cell, the serving cell is a candidate






1 · 2 · 102


Microcell Emergency Handovers

� CAUSE 7: consecutive bad SACCH frames received in a microcell

� N_BAD_SACCH

� Rule : "Radio Link Recovery shall be triggered before the handover"

� N_BAD_SACCH > RADIOLINK_TIMEOUT_BS - N_BSTXPWR_M

� Default values:

RADIOLINK_TIMEOUT_BS = 18 SACCH

N_BSTPWR_M = 15 SACCH

� N_BAD_SACCH = 4 SACCH

Last N_BAD_SACCH frames received are not correct

and EN_MCHO_RESCUE = ENABLE

Last N_BAD_SACCH frames received are not correct

and EN_MCHO_RESCUE = ENABLE






1 · 2 · 103


Microcell Emergency Handovers [cont.]

� CAUSE 17: too low level on the UL in a microcell compared to a high threshold

� Averaging window: A_LEV_MCHO

AV_RXLEV_UL_MCHO(i) <= U_RXLEV_UL_MCHO

and AV_RXLEV_UL_MCHO(i-1) > U_RXLEV_UL_MCHO

and EN_MCHO_H_UL = ENABLE

AV_RXLEV_UL_MCHO(i) <= U_RXLEV_UL_MCHO

and AV_RXLEV_UL_MCHO(i-1) > U_RXLEV_UL_MCHO

and EN_MCHO_H_UL = ENABLE






1 · 2 · 104


Microcell Emergency Handovers [cont.]

� CAUSE 18: too low level on the DL in a microcell compared to a high threshold

� Averaging window: A_LEV_MCHO

AV_RXLEV_DL_MCHO(i) <= U_RXLEV_DL_MCHO

and AV_RXLEV_DL_MCHO(i-1) > U_RXLEV_DL_MCHO

and EN_MCHO_H_DL = ENABLE

AV_RXLEV_DL_MCHO(i) <= U_RXLEV_DL_MCHO

and AV_RXLEV_DL_MCHO(i-1) > U_RXLEV_DL_MCHO

and EN_MCHO_H_DL = ENABLE






1 · 2 · 105


Cause 17 & 18: Comparison to High Threshold

� High threshold (U_RXLEV_XX_MCHO)

� the HO is triggered when the signal drops under the threshold

� the corresponding HO causes consist in comparing, at 2 successive SACCH periods, the DL and UL levels in the serving microcell with a high threshold

� Beginning a call under the threshold does not trigger an HO

ii-1

t

AV_RXLEV_XX_MCHO

High Threshold

HO alarm

ii-1

t

AV_RXLEV_XX_MCHO

High Threshold

no HO alarm






1 · 2 · 106


Cause 17 & 18: Comparison to High Threshold [cont.]

� High threshold (U_RXLEV_XX_MCHO)

� With high value, mobiles will be sent too early to the macro layer

� With low value, mobiles turning at a street corner will be maintained in the microcell layer during a longer period

� Problems for MS's with a signal strength level close to the high threshold : due to fading, multiple handovers can be triggered during a call:

MS in Indoor cell : decrease in RXLEV leads to emergency HO � Umbrella

MS in Umbrella : RXLEV of indoor cell becomes good again, capture HO � Indoor

… and so on.






1 · 2 · 107


Cause 17 & 18: Comparison to High Threshold [cont.]

� U_RXLEV_XX_MCHO compared to L_RXLEV_XX_H

� Default settings recommends a +2dB gap :

� for DL:

� L_RXLEV_DL_H = -93 dBm

� U_RXLEV_DL_MCHO = -91 dBm

� for UL:

� L_RXLEV_UL_H = -95 (M2M), -98 (M4M), -102 (Evolium) dBm

� U_RXLEV_UL_MCHO = -93 (M2M), -96 (M4M), -100 (Evolium) dBm

� Averaging:

� A_LEV_MCHO : 10 SACCH

� A_LEV_HO : 4 (dense urband) ~ 6 (urban) SACCH

A_LEV_MCHO

� The averaging window size shouldn’t be too small in order to:

� avoid triggering too easily an HO on fading and overloading needlessly the macrocell

� favor as much as possible between 2 micro cells PBGT HO

� Typical value: 10 SACCHs

� The high threshold is used to modelize a slow decrease of the signal level at microcell border

� Really urgent handovers will be triggered using the Low Threshold (cause 3 & 5) with a short averaging

window size






1 · 2 · 108


Cause 17 & 18: Default Strategy

� Default strategy : U_RXLEV_XX_MCHO > L_RXLEV_XX_H

ii-1

t

AV_RXLEV_XX_MCHO

High Threshold

µHO alarm

t

Standard Threshold

High Threshold

Standard Threshold

Std HO alarm

Based on 10-SACCH sliding averagesGoal : detect slow degradation

Based on 4-SACCH sliding averagesGoal : detect quick drops in level

AV_RXLEV_XX_HO






1 · 2 · 109


Cause 17 & 18: Alternative Strategy

� Alternative strategy : U_RXLEV_XX_MCHO < L_RXLEV_XX_H

ii-1

t

AV_RXLEV_XX_MCHO

High Threshold

µHO alarm

t

Standard Threshold

High Threshold

Standard Threshold

Std HO alarm

Based on 4-SACCH sliding averagesGoal : detect corner street effects

Based on 10-SACCH sliding averagesGoal : detect MS slowly exiting the cell

AV_RXLEV_XX_HO

Alternative strategy offers a different approach :

The "high" treshold U_RXLEV_XX_MCHO is not "high" anymore. Use this threshold as "emergency" exit from a

microcell, when the MS turns around a street corner.

The standard threshold should be used as a standard exit from microcell : don't forget that HO cause 12 towards

another cell in the same layer might not always be possible. In this case, the only way to exit a micro cell or an

indoor cell is to perform an emergency HO !

Therefore it is necessary to use one dedicated emergency HO as a "safe exit" HO, to keep a good RXLEV while

performing a HO towards another layer.

Example :

U_RXLEV_DL_MCHO =-92dBm

L_RXLEV_DL_H = -83dBm

A_LEV_MCHO : 4 SACCH

A_LEV_HO : 10 SACCHEN_MCHO_H_DL = ENABLE

In Uplink, default values can be kept for the standard emergency HO, and EN_MCHO_H_UL = DISABLE (exit performed with DL is enough)






1 · 2 · 110

8 Better Conditions Handover Algorithms for MBML Networks






1 · 2 · 111


Cause 14: Lower/Indoor Capture for Slow MS

� Capture handover

� Improved in B7 (indoor & anti ping-pong)

� Send traffic in lower layers, even though the call is fine in upper layers


� From upper layer cells

� Towards lower or indoor layer cells

� From lower layer cells

� Towards indoor layer cells

� Note : It can be triggered between different frequency bands or not

mini

umbrella

micro

indoor

LOWER

UPPER

INDOOR






1 · 2 · 112


Cause 14: Lower/Indoor Capture for Slow MS [cont.]

� In order to keep dual band MSs in the preferred band

� Cause 14 is not checked if

� serving cell or zone is "preferred band" AND target cell is "non preferred"

� AND EN_BI-BAND_MS(n) = DISABLED

CELL_BAND_TYPE = Preferred_band

CELL_LAYER_TYPE =

upper

CELL_LAYER_TYPE =

lower or indoor

EN_BI-BAND_MS = DISABLED

CELL_BAND_TYPE = CELL_BAND_TYPE(0)


CELL_BAND_TYPE ≠ Preferred_band

CELL_BAND_TYPE = Preferred_bandCELL_BAND_TYPE <> Preferred_band

EN_BI-BAND_MS(n) should be disabled in the TARGET cell in order to prevent cause 14.

Definition : Enables/disables the incoming handovers of bi-band MSs from the preferred-band into a classical

band cell.

Beware : it is also used in cause 24 (general capture)






1 · 2 · 113



� If cell_layer_type (0) = upper

� Averaging window: A_PBGT_HO

� Anti ping-pong: not checked if T_INHIBIT_CPT is running

mini

umbrella

micro indoor

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n)

and MS_SPEED = SLOW

and EN_MCHO_NCELL = ENABLED


and MS_SPEED = SLOW







1 · 2 · 114



� If cell_layer_type (0) = lower


� Anti ping-pong: not checked if T_INHIBIT_CPT is running

mini micro

indoor


and MS_SPEED ≠ FAST



and MS_SPEED ≠ FAST


MS_SPEED different than fast, because at call setup, the MS SPEED is set to indefinite. It cannot be set to "SLOW".

A "SLOW" MS might be a MS that came from an umbrella previously.

Therefore, in a mini cell, a MS with MS SPEED = indefinite should be able to be sent to an indoor cell.






1 · 2 · 115


Cause 14: Speed Discrimination

� Only available for UPPER layers (umbrella cells)

� Speed discrimination objectives :

� Maximize capacity (maximum traffic in lower/indoor cells)

� While optimizing quality (minimize the number of handovers)

� Smart speed discrimination :

1. If the load of umbrella is too high � reduce the time a MS can stay in the umbrella

2. If the load of umbrella is low � increase the time a MS can stay in the umbrella

3. If the MS speed is fast in lower/indoor cells � it is sent to the umbrella cell

Benefits of the smart speed discrimination :

Case 1 : The umbrella cell is kept "less loaded" in order to accept incoming handovers and call setups (most of

call setups will be done on the umbrella cells, because of the better coverage). The extra-capacity of

lower/indoor cells is fully used.

Case 2 : No HO is performed in this case, because the umbrella has room to keep the calls. It is interesting to

avoid handovers, because less HO during a call � better voice quality.

Case 3 : a fast moving user should stay in upper layers, in order to avoid performing too many HO (increase the

risk of call drops, especially in lower layers)






1 · 2 · 116


Cause 14: Speed Discrimination [cont.]

� Interlayer HO are based on speed discrimination

Lower layer

Upper layer

Indoor layer

Cause12MS_speed = FAST

Cause12MS_speed = FAST

Cause14MS_speed = SLOW or INDEFINITE

Cause14MS_speed = SLOW






1 · 2 · 117



� MS speed in umbrella cells :

� Speed estimation based on the consecutive time the same lower/indoor cell is received as a neigbour by the MS

� If for one neighboring cell n, C_DWELL(n) ≥ 2 x MIN_DWELL_TIME

� MS_SPEED is set to SLOW

Upper layer

Lower layerCell 1 Lower layer

Cell 2

C_DWELL(1) �

C_DWELL(2)

To dwell : to reside

� If this dwell time exceeds MIN_DWELL_TIME, the MS is slow and is sent to the lower/indoor cell

� C_DWELL(n) is a counter measuring the number of SACCH periods of monitoring neighbour cell n over the

threshold L_RXLEV_CPT_HO(0,n)

� There is one C_DWELL() per neighbour cell

� MIN_DWELL_TIME is a variable linked to the load of the serving umbrella cell






1 · 2 · 118



� Initialization of C_DWELL(n) in serving umbrella cell :

� if EN_SPEED_DISC = ENABLE

� C_DWELL(n) = 0

� MSs will handover to the lower/indoor layer after MIN_DWELL_TIME seconds

� if EN_SPEED_DISC = DISABLE

� C_DWELL(n) = 2 x (MIN_DWELL_TIME - L_MIN_DWELL_TIME)

� MSs will handover to the lower/indoor layer after L_MIN_DWELL_TIME seconds

MIN_DWELL_TIME is not a parameter ! It is a variable computed by BSC : it varies, depending on the umbrella

traffic load.

Default : EN_SPEED_DISC = Disable






1 · 2 · 119



� Example with default values (EN_SPEED_DISC = disable)

� Initialization values

H_MIN_DWELL_TIME = 20s (= MIN_DWELL_TIME at initialization)

L_MIN_DWELL_TIME = 8s

C_DWELL(n) = 2 x (MIN_DWELL_TIME - L_MIN_DWELL_TIME)

= 2 x (20 - 8) = 24 SACCH (= 12 seconds)

� Algorithm

MS is deemed as slow if C_DWELL(n) > 2 x MIN_DWELL_TIME

C_DWELL(n) starts at 24, and is increased by 1 when RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n)

0 4 8 12 16 20 24 28 32 36 40 44

: EN_SPEED_DISC = Disable

: EN_SPEED_DISC = Enable

INDEFINITE or FAST SLOW

Maximum time to reach

MIN_DWELL_TIME

=

L_MIN_DWELL_TIME

C_DWELL MIN_DWELL_TIMEC_DWELL

MIN_DWELL_TIME is in seconds, whereas C_DWELL is in SACCH. This is the reason why MIN_DWELL_TIME is

multiplied by 2.

1 SACCH = 480ms (approx. 0.5s)






1 · 2 · 120



� Traffic regulation through the variation of MIN_DWELL_TIME

Default valuesdependent onthe number of TRXs

H_LOAD_OBJ

L_LOAD_OBJ

Traffic load umbrella

H_MIN_DWELL_TIME20 s

DWELL_TIME_STEP2 s

L_MIN_DWELL_TIME8 s

Start of day

low traffic

End of day

low traffic

End of BH

decreasing traffic

What are the values of MIN_DWELL_TIME during the day ?

Summary of parameters that controls the speed discrimination in the umbrella cells:

H_MIN_DWELL_TIME, L_MIN_DWELL_TIME, DWELL_TIME_STEP, H_LOAD_OBJ, L_LOAD_OBJ






1 · 2 · 121


Cause 24: General Capture

� capture handover

� Improved in B7 (anti ping-pong)

� Can be used to capture traffic by any cell, whatever its type, band, etc.

YES

NO

MS in inner zone of a multiband cell

EN_BI-BAND_MS(n) = ENABLE

Or CELL_BAND_TYPE(n) ≠ CELL_BAND_TYPE(0)Preferred band

EN_BI-BAND_MS(n) = ENABLE

Or CELL_BAND_TYPE(n) = PREFERRED_BANDPreferred band

Not preferred band

Not preferred band

Serving cell

Band Type

Any cell

Any cell

Possible Neighbours

The target cell can not be the serving cell






1 · 2 · 122


Cause 24: General Capture [cont.]

� In order to keep dual band MS in the preferred band, cause 24 is not checked when EN_BI-BAND_MS(n) = DISABLED, from preferred cell to classical cell.


CELL_BAND_TYPE = CELL_BAND_TYPE(0)




CELL_BAND_TYPE = Preferred_band






1 · 2 · 123


Cause 24: General Capture [cont.]

� CAUSE 24: general capture

� Size of window for averaging level: A_PBGT_HO

� CAPTURE_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW

� Anti ping-pong: not checked when T_INHIBIT_CPT is running

AV_RXLEV_NCELL(n) >

L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = CAPTURE_TRAFFIC_CONDITION

and Traffic_load(n) ≠≠≠≠ HIGH

and EN_GENERAL_CAPTURE_HO = ENABLED

AV_RXLEV_NCELL(n) >

L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = CAPTURE_TRAFFIC_CONDITION


and EN_GENERAL_CAPTURE_HO = ENABLED






1 · 2 · 124

� Use of cause 21 or 14?

� Considering the following network

� Which cause has to be used for capture? 14 or 21?

� Highlight one complexity linked to causes 14 and 21 interworking when using traffic discrimination

Time allowed: 5 minutes


Exercise

Umbrella 900

Mini 1800

CAUSE 21: high level in the neighboring cell in the preferred band

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = MULTI-BAND_TRAFFIC_CONDITION


and EN_PREFERRED_BAND_HO = ENABLED

� Size of window for average level: A_PBGT_HO

� MULTI-BAND_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW






1 · 2 · 125

� Input settings for the next slide

� EN_MCHO_NCELL(source) = ENABLED

� L_RXLEV_CPT_HO(source, target) = -85 dBm

� Is cause 14 triggered in each of the following cases ?

� See next slide



Exercise [cont.]






1 · 2 · 126


Exercise [cont.]

FastIndefiniteSlowSlowSlowSlowSlowSlowMS Speed

DisableEnableDisableDisableDisableDisableEnableEnableEn Biband

MS

HIGHLOWHIGHINDINDHIGHINDINDSpeed Disc

-80 dBm

1800

Mini

-90 dBm

Outer

900

Multiband

Case 5

-80 dBm

1800

Mini

-90 dBm

Inner

900

Multiband

Case 6

-70 dBm

900

Indoor

-60 dBm

---

900

Micro

Case 7

Cause 14 ?


18009001800900900Band

IndoorMiniMiniMicroMicroType

Target


---------------Zone

9001800900900900Band

MiniUmbrellaUmbrellaUmbrellaSingleType

Source







1 · 2 · 127

� Speed discrimination

� What is the role of parameter EN_SPEED_DISC?

� If EN_SPEED_DISC is disabled, can fast MSs be directed toward microcells?

� What is the difference between EN_SPEED_DISC = DISABLED and EN_SPEED_DISC = ENABLED when L_LOAD_OBJ = 0% and H_LOAD_OBJ = 100%?



Exercise [cont.]






1 · 2 · 128


Cause 21: Preferred Band

� Capture handover

� Improved in B7 (anti ping-pong)

� Send traffic in preferred cells, even though the call is fine in classical cells


� From Classical cells

� Towards Preferred layer cells

� Note : It can be triggered between

different layers or not

Cell

Cell

Cell 1800

900






1 · 2 · 129


Cause 21: Preferred Band [cont.]

� Cause 21: high level in the neighboring cell in the preferred band


� MULTIBAND_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW

� Anti ping-pong: not checked when T_INHIBIT_CPT is running


and TRAFFIC_LOAD(0) = MULTIBAND_TRAFFIC_CONDITION

and TRAFFIC_LOAD(n) ≠ HIGH

and EN_PREFERRED_BAND_HO = ENABLE


and TRAFFIC_LOAD(0) = MULTIBAND_TRAFFIC_CONDITION

and TRAFFIC_LOAD(n) ≠ HIGH

and EN_PREFERRED_BAND_HO = ENABLE






1 · 2 · 130


Capture handovers

� Tuning of L_RXLEV_CPT_HO(0,n)

� Recommended range of investigation: from -65dBm to -85dBm

� Propose a method to define the initial setting

� Propose a method to tune this value






1 · 2 · 131


Capture handovers [cont.]

� Tuning of MULTIBAND_TRAFFIC_CONDITION andCAPTURE_TRAFFIC_CONDITION

� Recommended setting: ANY_LOAD

� If HIGH or NOT_LOW:

� Capture to the preferred cell is limited to the loaded hours

� This choice is sensible: during unloaded hours, the non-preferred cells provide a good coverage, with little interference.

� The following parameters will impact the computation of traffic_load :

� Avg windows: TCH_INFO_PERIOD, A_TRAFFIC_LOAD, N_TRAFFIC_LOAD

� Thresholds: LOW_TRAFFIC_LOAD, IND_TRAFFIC_LOAD, HIGH_TRAFFIC_LOAD






1 · 2 · 132


Capture handovers [cont.]

� Inhibition of capture handovers

Cell B

Cell A

Cell C

1

3 1

2

3

During T_INHIBIT_CPT_HO, a capture HO towards cell B is inhibited for this call.

The MS experiences a poor RXQUAL, and a HO due to quality is triggered (causes 2, 4 or 7)

A capture HO to another cell is still possible

2

QUAL HO

T_INHIBIT_CPT_HOCPT HO

CPT HO

Refer to comments for further details

In this example, T_INHIBIT_CPT_HO is started only if either:

Cell A is UPPER or SINGLE and Cell B is LOWER or INDOOR,

or Cell A is LOWER and Cell B is INDOOR,

or Cell A is in a different frequency band than Cell B

Note : The cause 24 between two cells with same frequency band and same layer cannot be inhibited !!

A "handover due to quality" can be :

� Cause 2, 4 or 7: ULQ, DLQ or Bad SACCH

� OR external HO with A interface cause Uplink Quality or Downlink Quality

Generally the T_INHIBIT_CPT is set to a high value, such as 60s.






1 · 2 · 133


Exercise

� Input settings for the next slide

� EN_PREFERRED_BAND_HO(0) = ENABLED

� L_RXLEV_CPT_HO(0,n) = -85 dBm

� MULTIBAND_TRAFFIC_CONDITION = NOT_LOW

� Is cause 21 triggered in each of the following cases ?

� See next slide

Time allowed:

10 minutes






1 · 2 · 134


Exercise [cont.]

HIGHINDLOWINDINDLOWINDINDTraffic(n)

HIGHLOWHIGHINDINDHIGHINDINDTraffic(0)

-80 dBm

1800

Single

-84 dBm

Inner

900

Multiband

Upper

Case 5

-80 dBm

900

Multiband

Upper

-90 dBm

Outer

900

Multiband

Upper

Case 6

-70 dBm

1800

Single

-80 dBm

---

900

Single

Case 7

Cause 21 ?


18001800180018001800Band

SingleSingleMiniSingleSingleType

Target


---Outer---------Zone

900900900900900Band

SingleMultiband

SingleSingleMicroSingleType

Source







1 · 2 · 135


Exercise [cont.]

� In a multiband network,

� How can you ensure capture will be performed from 900 cell towards 1800 cell, until 80% traffic load is achieved in the 1800 cell ?

� Parameters ?

� Settings ?

� Once this load is exceeded,

� What happens ?

� Will the 1800 cell accept more traffic ?

� What are the other possibilities of incoming traffic ?

Time allowed:

10 minutes






1 · 2 · 136

9 Multiband Cells






1 · 2 · 137

9 Multiband Cells

Introduction

� When changing a cell from "normal" to "concentric", 3 more handovers are available !

� Those are only INTRA-CELL handovers

� Cause 13 : entry in inner zone, from outer zone

� Causes 10 & 11 : exit to outer zone, from inner zone

Cell A

inner

outer

cause 13

cause 10/11

The activation of causes 10 and 11 is automatic, as soon as a cell type is defined as "CONCENTRIC"

The activation of cause 13 is controlled by EN_BETTER_ZONE_HO.

The parameters HO_INTRACELL_ALLOWED and EN_INTRACELL_REPEATED have no impact on those handovers, they

are used only for causes 15 & 16 (interference) and 25 & 26 (AMR).






1 · 2 · 138

9 Multiband Cells

Introduction [cont.]

� Setting these 3 handover causes is simple

1. Work with downlink thresholds first

2. Propose an entry threshold, i.e. -75dBm

� MS enters in the inner zone only if the expected received level in the inner zone is above -75dBm

3. Propose an exit threshold, i.e. -83dBm

� MS exits the inner zone if the received level is less than -83dBm

Cell A

inner

outer

-75dBm

-83dBm






1 · 2 · 139

9 Multiband Cells


4. Compute the entry threshold as measured from the outer zone

� Due to 10dB propagation loss, it should be -65dBm

5. Compute the difference between

� the entry threshold from outer zone (-65dBm)

� the exit threshold (-83dBm)

Cell A

inner

outer

-75dBm

-83dBm

-65dBm

18dB

Only these two values are needed in order to tune a concentric cell






1 · 2 · 140

9 Multiband Cells

Cause 10: Low uplink level in inner zone

� CAUSE 10: too low level on the uplink in inner zone

� Averaging window: A_LEV_HO

AV_RXLEV_UL_HO < RXLEV_UL_ZONE

and MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)

AV_RXLEV_UL_HO < RXLEV_UL_ZONE

and MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)






1 · 2 · 141

9 Multiband Cells

Cause 11: Low downlink level in inner zone

� CAUSE 11: too low level on the downlink in inner zone

� Averaging window: A_LEV_HO

AV_RXLEV_DL_HO < RXLEV_DL_ZONE

and BS_TXPWR = BS_TXPWR_MAX_INNER

AV_RXLEV_DL_HO < RXLEV_DL_ZONE

and BS_TXPWR = BS_TXPWR_MAX_INNER






1 · 2 · 142

9 Multiband Cells

Cause 13: High UL & DL level in outer zone

� CAUSE 13: too high level on the UL and the DL in the outer zone

� Averaging windows: A_LEV_HO

and A_PBGT_HO (for AV_RXLEV_NCELL_BIS)

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL+ (MS_TXPWR - MS_TXPWR_MAX_INNER)+ PING_PONG_MARGIN(0, call_ref)

And AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYS_DL+ (BS_TXPWR - BS_TXPWR_MAX_INNER)+ PING_PONG_MARGIN(0, call_ref)

And AV_RXLEV_NCELL_BIS(n) ≤ NEIGHBOUR_RXLEV(0,n)

And EN_CAUSE_13 = ENABLE

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL+ (MS_TXPWR - MS_TXPWR_MAX_INNER)+ PING_PONG_MARGIN(0, call_ref)

And AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYS_DL+ (BS_TXPWR - BS_TXPWR_MAX_INNER)+ PING_PONG_MARGIN(0, call_ref)








1 · 2 · 143

9 Multiband Cells

Cause 13: High UL & DL level in outer zone [cont.]

� ZONE_HO_HYS_DL and ZONE_HO_HYS_UL

� Differences between "entry threshold" and "exit threshold"

� They must be greater than the propagation loss, by at least a certain hysteresis

� There are 3dB difference between UL and DL, due to the value

"MS_TXPWR - MS_TXPWR_MAX_INNER" = 3dB

ZONE_HO_HYS_DL = 12dB … 16dB

ZONE_HO_HYS_UL = 9dB … 13dB

ZONE_HO_HYS_DL = 12dB … 16dB

ZONE_HO_HYS_UL = 9dB … 13dB

Recommended valuesRecommended values






1 · 2 · 144

9 Multiband Cells


� PING_PONG_MARGIN(0,call_ref) = penalty of PING_PONG_HCP during T_HCP only if

� MS is coming from the inner zone to the outer zone with an interzonehandover

� In all other cases, PING_PONG_MARGIN(0,call_ref) = 0

MS in the 1800 inner zone of a cell can perform an emergency "intercell" HO towards the outer zone. In this case, the penaltyis not applied.

innerouter






1 · 2 · 145

9 Multiband Cells


� NEIGHBOUR_RXLEV(0,n)

� Avoid sending a MS in the inner zone if a neighbour cell is too strong

� Tuning depends on frequency planning

� By default, NEIGHBOUR_RXLEV(0,n) = 47dBm

� When inner zone frequency planning is very tight (i.e. reuse cluster = 3)

In this example, the inner zone of cell C_3 can be interfered locally by the inner zone of cell B_2C_2 by E_3…

Therefore, to avoid degraded situations:NEIGHBOUR_RXLEV(C_3, B_2) = -70dBmNEIGHBOUR_RXLEV(C_2, E_3) = -70dBm…

A

B

C

D

E

F

G

Practically, an inner zone reuse cluster between 4 and 7 is more realistic. With a large reuse cluster, this

parameter is not useful anymore.






1 · 2 · 146

9 Multiband Cells


� EN_CAUSE_13: Traffic Load balancing

� MS will not be sent in the inner zone if the inner zone is more loaded than the outer zone

� Depends on EN_LOAD_BALANCE & current load in each zone

� EN_LOAD_BALANCE = ENABLE

� Outer zone more loaded (Load_sample_inner ≤ Load_sample_outer)

� EN_CAUSE_13 = ENABLE

� Inner zone more loaded (Load_sample_inner > Load_sample_outer)

� EN_CAUSE_13 = DISABLE

� EN_LOAD_BALANCE = DISABLE

� EN_CAUSE_13 = DISABLE

LOAD_SAMPLE_INNER: Ratio of TCH occupancy in the inner zone:

LOAD_SAMPLE_INNER = (NB_USED_TS_INNER / NB_TS_INNER) * 100

LOAD_SAMPLE_OUTER: Ratio of TCH occupancy in the outer zone:

LOAD_SAMPLE_OUTER = (NB_USED_TS_OUTER / NB_TS_OUTER) * 100

A load sample is computed every TCH_INFO_PERDIO (= 5s.), it is an actual snapshot of the load of the cell.

The reactivity of this condition is very fast.






1 · 2 · 147

9 Multiband Cells


� RXLEV_UL_ZONE : Uplink level threshold for inner to outer zone handover. From -110dBm to -47dBm. [-86 dBm]

� RXLEV_DL_ZONE : Downlink level threshold for inner to outer zone handover. From -110dBm to -47dBm. [-78 dBm]

� ZONE_HO_HYST_UL: Hysteresis applied to RXLEV_DL_ZONE for outer to inner zone handover. From -40dB to +40dB. [13 dB]

� ZONE_HO_HYS_DL: Hysteresis applied to RXLEV_UL_ZONE for outer to inner zone handover. From -40dB to +40dB. [16 dB]

� MS_TXPWR_MAX_INNER: MS maximum allowed transmission power in the inner zone of a concentric or multiband cell. From 5dBm to 43dBm. [30 or 33 dB]

� BS_TXPWR_MAX_INNER) : This parameter defines the power reduction relative to the maximum GMSK output power of the TRX of the inner zone in a concentric or multiband cell. From -30dB to 0dB. [0dB]

� NEIGHBOUR_RXLEV(0,n) : Threshold of maximum received level from the neighbour cells for cause 13. From -110dBm to -47dBm. [-47dBm]






1 · 2 · 148

9 Multiband Cells

Call Setup

1. Radio Link Establishment Phase

2. SDCCH Phase

3. TCH Assignment Phase

In which zone will the TCH be allocated?

� The TCH is allocated in the inner zone if :

� UL and DL RxLev in outer zone are satisfying

� BSC can allocate a TCH in inner zone

� MS is multiband

� Otherwise, TCH is allocated in the outer zone

INNEROUTE

R

??

The cell's RXLEV is the one being measured by the MS while performing SDCCH phase and TCH Assignment phase.

Therefore, it is measuring only the outer zone RXLEV !!






1 · 2 · 149

9 Multiband Cells

Call Setup [cont.]

� The choice of inner or outer TCH is based on :

IF

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL+ (MS_TXPWR - MS_TXPWR_MAX_INNER)

And AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYS_DL+ (BS_TXPWR - BS_TXPWR_MAX_INNER)



THEN : The TCH is allocated in the INNER zone

ELSE : The TCH is allocated in the OUTER zone

IF

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL+ (MS_TXPWR - MS_TXPWR_MAX_INNER)

And AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYS_DL+ (BS_TXPWR - BS_TXPWR_MAX_INNER)



THEN : The TCH is allocated in the INNER zone

ELSE : The TCH is allocated in the OUTER zone

MS_TXPWR - MS_TXPWR_MAX_INNER = 33 – 30 = 3dB

To take into account the limitation of MS POWER at 30dBm in UL in the inner zone.

Averaging Windows : A_LEV_HO for AV_RXLEV_UL_HO , AV_RXLEV_DL_HO

A_PBGT_HO(n) for AV_RXLEV_NCELL_BIS(n)

If less measurements done than the averaging windows, the averaging is done on the available measurements (no

filling up with "-110dBm"). It allows a fast decision (the MS is not in the queue ! The call setup shall be

performed as quickly as possible)






1 · 2 · 150

9 Multiband Cells

Outgoing intercell HO

� What are the possible outgoing handovers from the inner zone ?

� Emergency ?

� Better conditions ?

� Only 2 parameters have an influence

� EN_BI-BAND_MS(n)

� EN_MULTIBAND_PBGT_HO(0)

innerouter

GSM900

DCS1800

serving cell innerouter

YES

YES

EN_MULTIBAND_PBGT_HO : Enable/disable the power budget handovers Cause 12 and the traffic handovers

Cause 23 between cells belonging to different frequency bands

Recommended value: Enable

EN_BI-BAND_MS(n) : Enables/disables the incoming handovers of bi-band MSs from the preferred-band into a

classical band cell, in cause 14 and cause 24

Recommended value: Enable

From inner zone of a multiband cell, if both parameters are set to enable, all outgoing HO's are possible

If EN_MULTIBAND_PBGT_HO = Disable, cause 12 only possible to other multiband concentric cells (very

restrictive !)

If EN_BI-BAND_MS(n) = Disable, cause 14 and cause 24 only possible towards cells with the same frequency bandas the inner zone (i.e. DCS1800 cells)






1 · 2 · 151

9 Multiband Cells

HO Cause 12

� If the MS in inner zone of a concentric cell, the PBGT equation is modified :


- (BS_TXPWR_MAX_INNER – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX_INNER)



- (BS_TXPWR_MAX_INNER – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX_INNER)


9001800 900 1800Cell 1 Cell 2

RxLev on TCH = -79dBm RxLev of BCCH = -70dBm

The parameter HO_MARGIN(cell 1, cell 2) is set to 5 dB

If RxLev(cell 2) = -70 dBm, PBGT(cell 2) = +6 dB

� Cause 12 is triggered, the MS is sent in the outer zone of cell 2, with RxLev(cell 2) = -70 dBm.Let's assume that

the "outer�inner" HO is triggered: the MS enters the inner zone of cell 2.

The received level of cell 1 is NOT -79 dBm (this was the level of the inner TCH).

Field results show that a 900 BCCH will be received roughly at -79+10=-69 dBm.

The received level of cell 2 is NOT -70dBm (that was the RXLEV of the outer zone). In the inner zone, the RXLEV =

-70dBm – 10dBm = -80dBm.

PBGT(cell 1) = (-69+80)-3 = +8dB � PBGT HO is triggered from cell 2 to cell 1!!

In fact, cause 12 HO cell 1 � cell 2 should NOT have been triggered in the first place.

A solution is to be found in tuning OFFSET_HO_MARGIN_INNER used in cause 12 equation. See next slide.






1 · 2 · 152

9 Multiband Cells

HO Cause 12 [cont.]

� What is happening in this situation ?

� How to fix the problem ?

� HO_MARGIN(1,2) = 5dB and HO_MARGIN(2,1) = 5dB

� OFFSET_HO_MARGIN_INNER= 0dB

� Inner zone entry threshold DL = -70dBm

9001800 900 1800Cell 1Serving

Cell 2Target

RxLev on TCH = -75 dBm RxLev of BCCH = -66 dBm

10 minutes

Inner zone entry threshold DL is a combination of 2 parameters :

RXLEV_DL_ZONE + ZONE_HO_HYST_DL

(cf. § HO cause 13)

To fix the problem : find the OFFSET_HO_MARGIN_INNER that would lead to leave the inner zone only for a

neighbour that is 5dB greater than the outer zone. This tends to reproduce a standard behaviour.






1 · 2 · 153

9 Multiband Cells

HO Cause 12 [cont.]

� If the MS in inner zone of a concentric cell :

� HO cause 12 is detected if :

� OFFSET_HO_MARGIN_INNER is used to compensate the difference of propagation between inner and outer zones (carrying BCCH)

OFFSET_HO_MARGIN_INNER = 0dB [monoband concentric cell]

OFFSET_HO_MARGIN_INNER = 7 … 12dB [multiband concentric cell, with BS_TXPWR_MAX_INNER = 0]

� Warning : The OFFSET_HO_MARGIN_INNER is used regardless of the frequency band of the target cell !

PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNERPBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

In monoband CC cells, it is most of the time compensated by MS_TXPWR_MAX_INNER

If BS_TXPWR_MAX_INNER is reduced compared to BS_TXPWR_MAX, MS_TXPWR_MAX_INNER may be reduced in

the same manner. Therefore the PBGT equation is already taken the compensation into account. No need for

the OFFSET_HO_MARGIN_INNER.






1 · 2 · 154

9 Multiband Cells

Incoming intercell HO

� Is an incoming handover directly to the inner zone possible ?

� Emergency ?

� Better conditions ?

innerouter

GSM900

DCS1800

target cellinner

outer

YES

YES

EN_MULTIBAND_PBGT_HO : Enable/disable the power budget handovers Cause 12 and the traffic handovers

Cause 23 between cells belonging to different frequency bands

EN_BI-BAND_MS(n) : Enables/disables the incoming handovers of bi-band MSs from the preferred-band into a

classical band cell, in cause 14 and cause 24

Towards inner zone of a multiband cell, if both parameters are set to enable, all incoming HO's are possible

If EN_MULTIBAND_PBGT_HO = Disable, cause 12 only possible from other multiband concentric cells and cells

from preferred band (i.e. GSM900)

If EN_BI-BAND_MS(n) = Disable, cause 14 and cause 24 only possible from cells from preferred band (i.e. GSM900)






1 · 2 · 155

9 Multiband Cells

Incoming intercell HO [cont.]

� It can be done if

� TCH available in the inner zone

� MS is dual-band

� Serving cell is internal (same BSC)

� The following conditions are verified:

AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL

+ (BS_TXPWR - BS_TXPWR_MAX_INNER)

And EN_BETTER_ZONE_HO = ENABLE


AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL

+ (BS_TXPWR - BS_TXPWR_MAX_INNER)

And EN_BETTER_ZONE_HO = ENABLE







1 · 2 · 156

9 Multiband Cells

Intracell Handovers

� Interference: Causes 15 & 16

� MS in the inner zone, all TRX's are candidate

� MS in the outer zone, only outer TRX's are candidate

� Note: the serving TRX can never be a candidate

� For other intracell handovers, the MS will stay in the same zone as before (TFO, AMR, return to CS zone)






1 · 2 · 157

9 Multiband Cells

Limitations

� Power Control

� Same target levels are used for the inner zone and the outer zone, based on:

� L_RXLEV_DL_P & U_RXLEV_DL_P (resp. UL)

� L_RXQUAL_DL_P & U_RXQUAL_DL_P (resp. UL)

� A_LEV_PC, A_QUAL_PC

� Rule : ensure 10dB separation between

RXLEV_DL_ZONE and L_RXLEV_DL_P

RXLEV_UL_ZONE and L_RXLEV_UL_P

� Packet Switched service and Voice Group Call service

� PDCH or VGCH timeslots can be allocated only in the outer zone

� Preemption of a MS in the inner zone is not possible

� External handovers are always sent in the outer zone of the target cell






1 · 2 · 158

9 Multiband Cells

Additional Features

� Multiband cell secured TCH assignment

� Subsequent TCH allocation in outer zone, if previous attempt in the inner zone failed

� Improved CSSR (TCH assignment failure due to radio is reduced)

� EN_LOAD_OUTER

� ENABLE: all load computations (short, medium and long terms) are based on the outer zone load

� DISABLE [default]: all load computations are based on the overall amount of timeslots (inner + outer)

� Enable only if ratio of dualband MS is very small

Subsequent allocation of outer TCH is failure during assignment of an inner zone TCH :

RTCH_assign_fail_radio = MC746b 1/ incremented when a failure in inner zone isfollowed by subsequent failure in outer zone2/ not incremented when failure in inner zone is followed by success in outer zone






1 · 2 · 159

Cumulated traffic per RxLevel

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[-110,-

104]

]-104,-97] ]-97,-91] ]-91,-85] ]-85,-79] ]-79,-72] ]-72,-66] ]-66,-60] ]-60,-53] ]-53,-47]

RxLevel ( dBm )

Cumulated traffic

distribution

9 Multiband Cells

Exercise

� Accordingly to this RMS report (monoband cell), find the initial settings for the planned urban multiband cell

� 3 TRX in outer zone

� 2 TRX in inner zone

Cumulated traffic per RxLevel

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[-110,-

104]

]-104,-97] ]-97,-91] ]-91,-85] ]-85,-79] ]-79,-72] ]-72,-66] ]-66,-60] ]-60,-53] ]-53,-47]

RxLevel ( dBm )

Cumulated traffic

distribution

-67dBm

OUTER

INNER

Additional inputs : In our urban environment, for 5 TRX, 4 SDCCH timeslots are needed.

The Erlang B law gives, at 2% blocking rate:

22 TCH ≈ 14.9 erlangs














1 · 2 · 160

9 Multiband Cells

Exercise [cont.]

� Multiband cells parameters tuning

� An important parameter to be tuned in a multiband cell is OFFSET_HO_MARGIN_INNER

� Takes into account the propagation difference between 900 and 1800

� Proposed values between 7dB to 12dB

� Using all available optimization tools (RNO, drive-tests, traces, …), propose a method for tuning accurately this parameter

9001800






1 · 2 · 161

10 Candidate Cell Evaluation






1 · 2 · 162

� As soon as an intercell HO alarm has been detected

� HO Detection sends to Candidate Cell Evaluation

� the list of potential candidates (it depends on type of handover cause)

� the HO cause value

� the preferred layer for the target cell indicated by the variable PREF_LAYER (it depends on the cell network architecture and on the operator strategy)


From HO Detection to Candidate Cell Evaluation

CandidateCell

Evaluation

Handover

Detection

Raw cell list

cell 1: cause C1

cell 2: cause C2

cell 3: cause C3

…

Max 32 cells

PREF_LAYER

BSCBSC

For intracell handovers, the only target cell is the serving cell � the raw cell list and the candidate cell

evaluation processes are skipped.






1 · 2 · 163


Raw Cell List and PREF_LAYER

� Standard cell environment

� CELL_LAYER_TYPE = SINGLE

� Better condition HO cause

� Emergency HO cause

* if the MS is in the DCS 1800 inner zone of a multiband cell then it includes the serving cell

upper + singlePREF_LAYER

subset of cells verifying the HO causesRaw cell list


all neighboring cells*Raw cell list






1 · 2 · 164


Raw Cell List and PREF_LAYER [cont.]

� Hierarchical cell environment

� CELL_LAYER_TYPE = UPPER




nonePREF_LAYER

subset of cells verifying the HO causesRaw cell list


all neighboring cells*Raw cell list






1 · 2 · 165



� CELL_LAYER_TYPE = LOWER or INDOOR




noneUpperPREF_LAYER

Subset of cells verifying the HO causes

Subset of cells verifying the HO causes plus all neighboring umbrella cells with Traffic_Load(n) = LOW

Raw cell list

MS_SPEED <> FAST or

HO Cause <> 12

MS_SPEED = FAST and

There is a cell in the list because of cause 12

noneLower + indoorUpper + SinglePREF_LAYER

All neighboring cells except umbrella cells which do not verify AV_Rxlev_Ncell(n) > OUTDOOR_UMB_LEV(0,n)

Raw cell list

EN_RESCUE_UM = indefiniteEN_RESCUE_UM = DISABLEDEN_RESCUE_UM = ENABLED






1 · 2 · 166



� Emergency handovers from lower or indoor layers

� Standard parameter settings for minicells

� EN_RESCUE_UM = DISABLED

� Because a LOWER/INDOOR layer composed of MINI cells should offer good coverage

� Standard parameter settings for microcells

� EN_RESCUE_UM = ENABLED

� Because a LOWER/INDOOR layer composed of MICRO cells might not offer continuous coverage

� Risk of choosing a neighbor cell from LOWER/INDOOR layer with poor coverage

Depending on your network planning, these standard parameters can be further optimized.

EN_RESCUE_UM shall be set in the mini, micro or indoor cells. It cannot be set in umbrellas or single cells,

because it has no use in those cells.






1 · 2 · 167


Summary

� Fill up this table

IndoorIndoor

None

subset of cells

verifying the HO

causes

Depends on

EN_RESCUE_UM

All, except umbrellas with

AV_Rxlev_Ncell(n) <

OUTDOOR_UMB_LEV(0,n)

LowerMini/Micro

None

subset of cells

verifying the HO

causes

Upper + SingleAllUpperUmbrella

Upper + Single

subset of cells

verifying the HO

causes

Upper + SingleAllSingleSingle

PREF_LAYERRaw cell listPREF_LAYERRaw cell list

BC HO

(incl. FDR and Fast Traffic HO)EM HO






1 · 2 · 168

HO Candidate Cells Evaluation


Evaluation Process

HO Detection

Cause 2: uplink quality

Cause 3: uplink level

Cause 4: downlink quality

Cause 5: downlink level

Cause 6: distance

Cause 12: power budget

Performed every SACCH

MeasurementPreprocessing

A_LEV_HO

A_QUAL_HO

A_PBGT_HO

A_RANGE_HO

Performed every SACCH

Max

every SACCH

Preprocessmeasurement

Measurementresult

Grade

Priority (0, n) = 0

Cell 4: cause C2

Cell 2: cause C2

Cell 3: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Order

Priority (0, n) = 0

Cell 4: cause C2

Cell 3: cause C2

Cell 2: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Cell evaluation process (Order or Grade)

Priority (0, n) = 0

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

PBGT filteringHO_MARGIN_XX(0,n)

Pre-ranking

Priority (0, n) = 0

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Priority (0, n) = 1

Cell 1: cause C2

Priority (0, n) = 2

Priority (0, n) = 3

Cell 5: cause C2

Cell 6: cause C2

Cell 7: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Raw cell list

Cell 1: cause C2

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Cell 5: cause C2

Cell 6: cause C2

Cell 7: cause C2

Cell 8: cause C2

... max 32 cells

The HO candidate evaluation process is run after all intercell handover alarms.

In case of intra-cell handover alarm (HO causes 10, 11, 13, 15, 16), the candidate cell evaluation process is

skipped: the target cell is the serving cell.

The handover detection gives as indication the raw cell list (built from the book-keeping list) and the preferred

layer for the handover.In case of emergency handover alarms or cause 20 alarm, the cell evaluation will order the

cells given in the raw list, putting in the first position the cells belonging to the preferred layer, having the

highest priority (if EN_PRIORITY_ORDERING=ENABLED) and/or having the same frequency band type as the serving

cell. In case of an intercell handover alarm, if the serving cell belongs to the raw cell list (emergency handover

from the DCS 1800 inner zone of a multiband cell), this cell is put at the end of the candidate cell list with the

MS zone indication OUTER.

In case of better condition handover alarms (except cause 20), the cell evaluation will order the cells given in the

raw list, putting in the first position the cells belonging to the preferred layer and having the highest priority (if

EN_PRIORITY_ORDERING=ENABLED).






1 · 2 · 169


Evaluation Process [cont.]

Raw cell list

Cell 1

Cell 2

Cell 3

Cell 4

Cell 5

Cell 6

Cell 7

Cell 8

� Case of MS in "MINI" cell, HO cause 2 detected :

Layer Type Priority Band Type Power Budget Filtering Cell Evaluation Process

Preferred Band

Non Preferred Band

Priority(0,n) = 0

= Serving Cell

≠ Serving Cell

Priority(0,n) = 0

= Serving Cell

≠ Serving Cell

Priority(0,n) = 0

= Serving Cell

≠ Serving Cell

List 1

List 2

List 3

List 4

List 5

List 6

List 1

List 2

List 3

List 4

List 5

List 6

Cell 1

Cell 2

Cell 3

Cell 4Cell 5

Cell 6

Cell 7

Cell 8

Cell 1

Cell 4

Cell 5

Cell 6

Cell 7

Cell 1

Cell 4Cell 5

Cell 6

Cell 7

Cell 2

Cell 3

Cell 8

Cell 4

Cell 5

Cell 7

Cell 1Cell 6

Cell 2

Cell 3

Cell 8

NONE

Cell 4Cell 5Cell 7

Cell 1

Cell 6

Cell 2

Cell 3

Cell 8

Cell 1

Cell 4Cell 5Cell 7

1. Cell 1

1. Cell 72. Cell 43. Cell 5






1 · 2 · 170


Pre-Ranking in Complex Networks [cont.]

� Pre-ranking in case of emergency HO, plus cause 20 and 28 :

Cell_layer_type = Pref_layer

Cell_layer_type ≠ Pref_layer

Raw cell list

Cell_band_type = serving cell

Cell_band_type ≠ serving cell

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Cause 20 : Forced Directed Retry

Cause 28 : Fast Traffic Handover






1 · 2 · 171


Pre-Ranking in Complex Networks [cont.]

� Pre-ranking in case of better condition HO:

Cell_layer_type = Pref_layer

Cell_layer_type ≠ Pref_layer

Raw cell list

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5






1 · 2 · 172


Pre-Ranking in Standard Networks

� With PRIORITY(0,n) settings

� One target cell can be favourized or penalized.

� From 0 (max) to 5 (min).

� It cannot supersede PREF_LAYER.

� Two main purposes:

� Favour 1800 cells, when exiting 900 cells.

� Direct traffic flow towards a certain neighbour.

� Safety belt:

� Favourite target would still be filtered out if its level is not good enough.

Serving cell

Candidate cell 1: RxLev: - 70 dBm, pbgt: + 10 dB

Candidate cell 2: Rxlev: - 90 dBm, PBGT: + 5dB

P0

P1

PRIORITY(0,n) can take 6 different values since B7, to take into account new indoor layers.






1 · 2 · 173


PBGT Filtering

� PBGT filtering

� Enabled with EN_PBGT_FILTERING

� For Emergency HO and Fast Traffic HO only

� Filter out cells from the target list that do not fulfill:

� OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric or multi band cell

� The average window is A_PBGT_HO

PBGT(n) > HO_MARGIN_QUAL (0,n) for causes 2, 4, 7or PBGT(n) > HO_MARGIN_LEV (0,n) for causes 3, 5, 17, 18, 28or PBGT(n) > HO_MARGIN_DIST (0,n) for cause 6

PBGT(n) > HO_MARGIN_QUAL (0,n) for causes 2, 4, 7or PBGT(n) > HO_MARGIN_LEV (0,n) for causes 3, 5, 17, 18, 28or PBGT(n) > HO_MARGIN_DIST (0,n) for cause 6

PBGT(n) > HO_MARGIN_XX (0,n) + OFFSET_HO_MARGIN_INNERPBGT(n) > HO_MARGIN_XX (0,n) + OFFSET_HO_MARGIN_INNER

HO_MARGIN_xx, with xx = LEV, DIST or QUAL accordingly to the HO Cause.

Note: the average window used for this process is A_PBGT_HO (even for emergency handovers, where handover alarm could

have been raised through A_LEV_HO or A_QUAL_HO samples).

Beware: HO_MARGIN is used for handover detection (cause 12 or 23), HO_MARGIN_xx are used for candidate cell evaluation.

Let us see three examples:

� If HO_MARGIN_xx = 5 dB, risk that no target cell is found !

In that case, when an emergency handover is triggered (level, quality, distance, etc.), all neighboring cells are filtered

regarding their PBGT compared to 5 dB! By the way, if a cell that is not greater than the serving one + 5 dB will be filtered

out: this handover, detected as an emergency case, is in fact a better cell one.

� If HO_MARGIN_xx = -30 dB, risk of ping-pong emergency handovers

For example, all cells have L_RXLEV_DL_H = -97dBm. If Lev(cell1)=-98dBm, HO can be triggered to cell2 with level -99dBm

(-99>-98-30), and then, as -99<-97, HO is triggered back to cell1: ping-pong of emergency HO.

� HO_MARGIN_xx can be used to simulate PBGT HO (for example, usage of distance HO to simulate 900-1800 PBGT HO

before it was existing).

HO_MARGIN_DIST is very small (e.g., 2 on 1800). Thus, a Distance HO alarm is raised very early. If HO_MARGIN_DIST

(1800,900)= 8 dB, no HO will be in fact triggered before the level of the 900 neighboring cell is greater than the one of

1800 + 8 dB: this distance HO is in fact a PBGT HO between bands.






1 · 2 · 174


PBGT Filtering [cont.]

� Recommended values

A neighbor cell with a lower RxLevcan be a good candidate, but there is a risk of PBGT HO back to the serving

cell.

A neighbor cell with a lower RxLevwill also trigger an emergency HO

A neighbor cell with a lower RxLevcan be a good candidate, but there is a risk of PBGT HO back to the serving

cell.

Strategy

� -127dB if mandatory HO, with anti ping-pong mechanism (*)

� +2dB if optional HO (*)

+2dB … +5dB

� MICRO/INDOOR : -127dB, with anti ping-pong mechanism

� Other cells : -5dB … +2dB

Proposed values

HO_MARGIN_DIST

HO_MARGIN_QUAL

HO_MARGIN_LEV

Parameter

Mandatory Distance HO : i.e. if the MS goes beyond the U_TIME_ADVANCE = 64, the call will drop.

Optional Distance HO : i.e. if the MS goes beyond the U_TIME_ADVANCE, the call can still be kept until a better

neighbour is found.

Anti ping-pong mechanism : can be based on HO_MARGIN and/or T_INHIBIT_CPT.






1 · 2 · 175


Level Filtering

� For all HO causes, this last filter is used:

� Cell "n" is kept if:

AV_RXLEV_NCELL (n) > RXLEVmin (n)

+ max [0;(MS_TXPWR_MAX(n)-P)]

AV_RXLEV_NCELL (n) > RXLEVmin (n)

+ max [0;(MS_TXPWR_MAX(n)-P)]






1 · 2 · 176


Order Evaluation

� CELL_EV = ORDER

� For all HO causes, candidate "n" is ranked among others according to the best ORDER:

� If EN_LOAD_ORDER = ENABLED and cell n is internal to the BSC

� LINK_FACTOR(0,n) is an operator parameter to give a bonus/penalty to a cell

� FREEfactor(0) and FREEfactor(n) are a bonus/penalty based on the absolute load of the cell

� If EN_LOAD_ORDER = DISABLED or cell n is external to the BSC

ORDER(n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)ORDER(n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

ORDER(n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

+ [ FREEfactor(n) - FREEfactor(0) ]

ORDER(n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

+ [ FREEfactor(n) - FREEfactor(0) ]

Two types of cell evaluation algorithms can be used: ORDER and GRADE.

ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or ’figure of merit’ to each candidate cell.

The basic differences between ORDER and GRADE are that:

� with ORDER:

� The candidate cell evaluation process interacts with the handover detection by use of cause dependent handover margins.

� The candidate cell evaluation process takes into account the number of free TCH in the candidate cells.

� with GRADE,:

� The candidate cell evaluation process does not interact with the handover detection.

� The candidate cell evaluation process takes into account the relative load of traffic channels in the candidate cells.

The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to the BSC with the parameter CELL_EV

HO_MARGIN_XX = HO_MARGIN in case of better cell HO causes, otherwise HO_MARGIN_xx, with xx = LEV, DIST or QUAL accordingly to the HO Cause.

For any handover cause, the first cell in the list is taken as the target cell, i.e. the cell with the highest value of ORDER(n). The cells do not need to fulfil any other condition.

If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out.

Note: the A_PBGT_HO average window is used for this process.






1 · 2 · 177


Grade Evaluation

� CELL_EV = GRADE [Recommended]

� For all HO causes, candidate "n" is ranked among others according to the best GRADE:

� If EN_LOAD_ORDER = ENABLED and cell n is internal to the BSC

� LINK_FACTOR(0,n) is an operator parameter to give a bonus/penalty to a cell

� LOADfactor(n) is a bonus/penalty based on the relative load of the cell

� If EN_LOAD_ORDER = DISABLED or cell n is external to the BSC

GRADE(n) = PBGT(n) + LINK_FACTOR(0,n)GRADE(n) = PBGT(n) + LINK_FACTOR(0,n)

GRADE(n) = PBGT(n) + LINK_FACTOR(0,n) – LOAD_FACTOR(n)GRADE(n) = PBGT(n) + LINK_FACTOR(0,n) – LOAD_FACTOR(n)

LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

LINKfactor(n1,n2) allows the operator to handicap or to favor the cell n1 with respect to its neighboring cell n2.

In particular, it can be used to disadvantage an external cell when an internal cell is also a possible candidate.

For any handover cause the first cell in the list is taken as the target cell, i.e. the cell with the highest value of

GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target

cell list is empty and no further action is carried out.

Note: the A_PBGT_HO average window is used for this process.

Note: an example summarizing all steps of candidate cell evaluation, in case of a multiband network, can be

given here: MS on a 1800 cell, 3 possible neighboring cells (1*900 + 2*1800). P(1800,900)=1 and P(1800,1800)=0.

All HO_MARGIN_xx = 0 dB. PBGT:

� PBGT (900) = +5 (second cell seen in the book-keeping list)

� PBGT (1800_1) = -2 (first cell seen in the book-keeping list)

� PBGT (1800_2) = +2 (third cell seen in the book-keeping list)

Cell (1800_2) is chosen.






1 · 2 · 178


Forced Directed Retry is different!

� Pre-ranking

� using PREF_LAYER, PRIORITY(0,n), frequency band

� Filtering process

� AV_RXLEV_NCELL_DR(n) > RXLEVmin(n) + max(0,MS_TXPWR_MAX(n) - P)

� Number of free TCHs t(n) > FREElevel_DR(n)

� The remaining cells are sorted according to their PBGT_DR(n) (averaging window A_PBGT_DR)

� PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR

� (BS_TXPWR_MAX - BS_TXPWR)

� (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

For external cells, t(n) is fixed to the arbitrary value t(n) = 255. Therefore, setting FREElevel_DR(n) to 255 for an

external cell inhibits outgoing external fast traffic handover towards this cell. Setting FREElevel_DR(n) to any

other value will allow outgoing external fast traffic handover towards this cell.

If the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH






1 · 2 · 179

��PBGT DR Ordering

��PBGT Filtering

��Level Filtering

��Order/Grade Evaluation

��Free TS filtering

��Same Freq Band

��Priority

��PREF_LAYER

FTHFDRBC HOEM HO

PBGT DR Ordering

PBGT Filtering

Level Filtering

Order/Grade Evaluation

Free TS filtering

Same Freq Band

Priority

PREF_LAYER

FTHFDRBC HOEM HO


Summary

� Fill up this table






1 · 2 · 180

� In a hierarchical network (umbrella + micro cells)

� EN_SPEED_DISC is ENABLED

� A slow moving MS starts a call in lower layer

� After a while, this MS becomes a fast moving MS (for example, a car starting at traffic light)

� Explain the exact process that will send the MS towards the umbrella layer

Time allowed:

5 minutes


Exercise






1 · 2 · 181

� Which is the best target cell?

� Emergency qual ho triggered in serving cell

� HO_MARGIN_QUAL(0,n) = -2 dB

� PRORITY(0,n) = 1

� LINK_FACTOR(0,n) = 0 dB

Time allowed:

5 minutes


Exercise [cont.]

1800900900Band

SlowMS speed

Best Target ?

-84 dBm-80 dBm-74 dBmRx_Lev(n)

DisabledEnabledDisabledEN_BI-BAND_MS

Single (3)Umbrella (2)Single (1)Type

Possible Target

-82 dBmRx_Lev(0)

YesEN_SPEED_DISC

1800Band

SingleType

Source

EN_LOAD_ORDER = Disabled.

EN_PBGT_FILTERING = Enabled.

RXLEVmin= -100 dBm.






1 · 2 · 182




� PRORITY(0,n) = 1, LINK_FACTOR(0,n) = 0 dB

Time allowed:

5 minutes


Exercise [cont.]

-82 dBm

Disabled

1800

Single (3)

-75 dBm

Disabled

900

Micro (4)

-85 dBm

Disabled

1800

Micro (5)

900900900Band

SlowMS speed

Best Target ?


EnabledEnabledDisabledEN_BI-BAND_MS

Indoor (6)Umbrella

(2)Single (1)Type

Possible Target

-76 dBmRx_Lev(0)

YesEN_SPEED_DISC

900Band

UmbrellaType

Source



RXLEVmin= -100 dBm.






1 · 2 · 183




� PRORITY(0,n) = 1, LINK_FACTOR(0,n) = 0 dB

� EN_RESCUE_UM = Enabled

Time allowed:

5 minutes


Exercise [cont.]

-82 dBm

Disabled

1800

Single (3)

-75 dBm

Disabled

900

Micro (4)

-85 dBm

Disabled

1800

Micro (5)

900900900Band

SlowMS speed

Best Target ?


EnabledEnabledDisabledEN_BI-BAND_MS

Indoor (6)Umbrella

(2)Single (1)Type

Possible Target

-68 dBmRx_Lev(0)

NoEN_SPEED_DISC

900Band

MicroType

Source



RXLEVmin= -100 dBm.






1 · 2 · 184



� EN_PBGT_FILTERING=Enable

� HO_MARGIN_QUAL(0,n)=-2dB

� CELL_EV=GRADE EN_LOAD_ORDER=Disable

� LINK_FACTOR(0,n)=0dB RXLEVmin=-100 dBm

-84 dBm

0

1800

Single (3)

-101 dBm

0

1800

Single (4)

1800900900Band

Best Target ?


000PRIORITY

Single (5)Umbrella

(2)Single (1)Type

Possible Target

-82 dBmRx_Lev(0)

1800Band

SingleType

Source

10 minutes


Exercise [cont.]






1 · 2 · 185







10 minutes

-84 dBm

1

1800

Single (3)

-101 dBm

1

1800

Single (4)

1800900900Band

Best Target ?


100PRIORITY

Single (5)Umbrella

(2)Single (1)Type

Possible Target

-82 dBmRx_Lev(0)

1800Band

SingleType

Source


Exercise [cont.]






1 · 2 · 186







� OFFSET_HO_MARGIN_INNER = 10 dB

10 minutes

900Band

-84 dBm

0

1800

Single (3)

-101 dBm

0

1800

Single (4)

1800900900Band

Best Target ?


000PRIORITY

Single (5)Umbrella

(2)Single (1)Type

Possible Target

-82 dBmRx_Lev(0)

InnerZone

Single Multiband

Type

Source


Exercise [cont.]






1 · 2 · 187


Exercise [cont.]

� If a call is setup, what will happen next ?

� What changes can you propose ?

B : Single cell 900

HO_MARGIN(B,A) = 5dB

A : Concentric cell 900 (monoband)

BS_TXPWR_MAX = 0dB

BS_TXPWR_MAX_INNER = -10dB

MS_TXPWR_MAX_INNER = 33dBm

RXLEV_DL_ZONE = - 85dBm

ZONE_HO_HYST_DL/UL = 6dB

RXLEV_UL_ZONE = - 95dBm

HO_MARGIN(A,B) = 5dB

HO_MARGIN_INNER_OFFSET = 0dB

EN_LOAD_BALANCE = Enable

-- IDLE mode --RxLev(A) = -71dBm C2 = 29RxLev(B) = -75dBm C2 = 25

A

B13/19

8/16

used_ts / nb_ts

Describe the different possible steps, and refer to pages of this document describing the algorithms :

-------- At call setup ------------

SDCCH allocation, TCH allocation

-------- After call setup ------------

HO detection

** problem 1 **

solution :

** problem 2 **

solution :

alternative solution :






1 · 2 · 188









1 · 2 · 189

End of ModuleAlgorithms and Associated Parameters






Module 3Creating a Multilayer Network



Optimization







EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimisation · Creating a Multilayer Network

1 · 3 · 2

Blank Page




Document History






1 · 3 · 3

Module Objectives


� Define relevant parameters settings to introduce a new layer in an existing network






1 · 3 · 4








1 · 3 · 5

Table of Contents


1 Adding a Microcellular Layer 72 Adding Hot Spot Microcell for Traffic 293 Monitoring QoS in a Multilayer Network 33






1 · 3 · 6









1 · 3 · 7

1 Adding a Microcellular Layer






1 · 3 · 8


Introduction

� The principle is to implement antennas below roof level

�confined propagation and low Tx power

�interferences avoided

�easier frequency planning

� Benefits :

� Higher network capacity per sq. km

� The right capacity at the right place (Airport, shopping malls, etc.)

� Improve the outdoor coverage and the indoor coverage (at street level)

� Improve the voice quality, thanks to cleaner frequencies

0 100 m

Confined micro cell propagation






1 · 3 · 9



� Field Example: Busy Hour Traffic

� 20% of new traffic generation

� 50% of old macro traffic is handled by microcells

70.5

31.4

19.2

71

71.6 72.5

76.8

72.3

29.1

17.9

71.1 78

95.9 95.1 98.4 94.6

100.7

41.736.4

94.398.4

117.9114

116.9

54.7

42.9

116.1112.5

118.5

121.6

121.6

60

45.9

115.1

124.5

70.6

68.6

0

20

40

60

80

100

120

140

8/9

9/9

10/9

11/9

12/9

13/9

14/9

15/9

16/9

17/9

18/9

19/9

20/9

21/9

22/9

23/9

24/9

25/9

26/9

27/9

28/9

29/9

30/9

Macrocells Microcells

Microlayer commercial opening

This example corresponds to the following network design:

� Lower layer: 16 micro cells (37 TRXs)

� 11 outdoor micro cells with 2 TRXs

� 1 outdoor micro cell with 3 TRXs

� 2 indoor micro cells (pico cells) with 2 TRXs

� 2 indoor micro cells (pico cells) with 4 TRXs

� Upper layer: 12 macro cells

� umbrella macro cells are concentric (but not multiband)

� 4 belong to the same BSS as the micro cells

� 8 belong to another BSS

All micro cells were declared as micro and not as indoor.






1 · 3 · 10



� Keep a good QoS

� Avoid call drops on microcells

� Specific emergency HO towards umbrella rescue cells

� Avoid unnecessary handovers

� To ensure good QoS and speech quality

� Force idle mode in microcells to avoid subsequent capture

� Fast MSs are kept in the umbrella layer






1 · 3 · 11


Architecture

� Capture towards microcells, emergency towards umbrella

� Capture HO is used to send slow MSs to the overlaid layer

� Capture HO (cause 14):

� PBGT HO (cause 12):

� Emergency HO (Level or Quality):

umbrella

micro micro micro

umbrella

micro

single UPPER/SINGLE

LOWER






1 · 3 · 12


Strategy

� Choose a handover to push traffic from these cells to the microlayer

� Cause 24 if all collocated cells and micro cells are all "Single"

� Cause 14 if collocated cells are Umbrella and micro cells are Micro

� The exercise next slide will show the best solution






1 · 3 · 13


Exercise

� Case 1 : Strategy based on cause 24

� Case 2 : Strategy based on cause 14

NORMAL CELLS

MICROCELLS

What are the pro's and con's of each solution ?

Which one would you choose ?

10 minutes






1 · 3 · 14


Call Setup

� Only slow MS reselects a MICRO

MICROMICRO UMBUMB

MICRO 900CELL_RESELECT_OFFSET = 10 dBTEMPORARY_OFFSET = infinityPENALTY_TIME = 0 (20 s)

UMBRELLACELL_RESELECT_OFFSET = 0 dBTEMPORARY_OFFSET = 0 dBPENALTY_TIME = 0 (20 s)

CELL_RESELECT_OFFSET(MICRO) = 10 dB

This setting is highly dependent on MICRO cells density : the more MICRO per sq.km, the higher the CRO can be,

without any risk of degrading quality. In very dense network, a CRO(Micro) = 40dB can be set.

On the contrary, if there are only few micro cells per sq.km, then a CRO=10dB might be too high ! Reduce it to

CRO=6dB.






1 · 3 · 15


Call Setup [cont.]

� DR and FDR are ENABLED

� An FDR (cause 20) is triggered when the average level of a neighboring cell is higher than L_RXLEV_NCELL_DR(n)

UmbrellaEN_DR = ENABLED

EN_FORCED_DR = DISABLED

L_RXLEV_NCELL_DR(n) = -88 dBm

FREElevel_DR(n) = 0

MicroEN_RESCUE_UM = ENABLED

EN_DR = ENABLED

EN_FORCED_DR = ENABLED

L_RXLEV_NCELL_DR(n) = -47 dBm

FREElevel_DR(n) = 0

DR & FDR

PRIORITY(micro, umb) = 1

DR only

PRIORITY(umb, umb) = 1

DR only

PRIORITY(umb, micro) = 0

DR & FDR

PRIORITY(micro, micro) = 1

The Setting of PRIORITY(0,n) is very important as network behavior will not be driven by Pref_layer which is

equal to "none" in this case.

But setting L_RXLEV_NCELL_DR(n) to -47 dBm in the micro cells inhibits the incoming FDR to them. Therefore

Priority(0,n) can be kept to the same value everywhere.

Priority(umb,micro) is set to 0 for Better Cell purpose (see the next pages).






1 · 3 · 16


Microcell Classes

� Parameter settings will depend on the microcells position in the lower layer

� Microcell “classes” are introduced to deal with typical parameters settings in each of these cases

Indoor Microcell

Border Microcell

Inner Microcell






1 · 3 · 17


Inner Microcell Class

� Definition

� A microcell surrounded by other microcells in a dense environment

� Rule

� The MS is comfortably installed in the microcell area. Calls have to be handled by a micro layer, which is a “traffic-catcher”

� Fast capture HO from the umbrella to micro cell

� If the MS is already on call in the micro-layer, it must stay on it

� Favour PBGT handover to neighbour microcells

Inner Microcell






1 · 3 · 18


Inner Microcell: Better Condition Handovers

� Causes 12 and 14

UmbrellaEN_PBGT_HO = ENABLED

EN_MCHO_NCELL = ENABLED

EN_SPEED_DISC = DISABLED


Inner MicrocellEN_PBGT_HO = ENABLED

EN_SPEED_DISC = ENABLED

A_PBGT_HO = 6

Cause 14


L_RXLEV_CPT_HO(umb, micro)

= -80 dBm

Cause 12 / 23


HO_MARGIN(umb, umb) = 5 dB

DELTA_INC_HO_MARGIN = 2 dB

DELTA_DEC_HO_MARGIN = 2 dB

Cause 12

PRIORITY(micro, micro) = 1

HO_MARGIN(micro, micro) = ?dB

Only fast mobiles can perform a PBGT

HO to an umbrella cell (with low load)

HO_MARGIN(micro, umb) = 5dB

A capture towards a microcell is triggered after L_MIN_DWELL_TIME. A low value is chosen, as we consider an

inner microcell.

In an umbrella 900 cell, a capture to a micro cell is preferred to a PBGT HO to a neighboring 900 cell using

Priority(0,n).






1 · 3 · 19


Inner Microcell: Tuning of Cause 12 Parameters

� HO_MARGIN(micro,micro) and A_PBGT_HO(micro) tuning

� Case 1 : Avoid PBGT HO to a transcient cell (i.e. micro 3)

� Case 2 : Avoid an EM HO to an umbrella

�Reduce A_PBGT_HO & increase HO_MARGIN

or …

�Increase A_PBGT_HO & decrease HO_MARGIN

Micro 1Micro 2

Micro 3

HO_MARGIN tuning will be detailed in section 4: case studies.






1 · 3 · 20


Inner Microcell: Emergency Handovers

� Use Level, Quality causes

UmbrellaPref_layer = upper + single

Inner MicrocellEN_RESCUE_UM = ENABLED

Pref_layer = upper + single

A_QUAL_HO = 4

A_LEV_HO = 4

L_RXLEV_DL_H = -90 dBm

PRIORITY(umb,micro) = 0

PRIORITY(umb,umb) = 1

PRIORITY(micro,micro) = 1

PRIORITY(micro,umb) = 1

EN_RESCUE_UM is set to ENABLED for an emergency handovers behavior (send MSs towards the upper layer).






1 · 3 · 21


Inner Microcell: Candidate Cells Evaluation Process

UmbrellaEN_PRIORITY_ORDERING = ENABLED

EN_PBGT_FILTERING = ENABLED

CELL_EV = GRADE

Inner MicrocellEN_PRIORITY_ORDERING = ENABLED

EN_PBGT_FILTERING = ENABLED

CELL_EV = GRADE

EN_RESCUE_UM = ENABLED

HO_MARGIN_LEV(umb,umb)= 2 dB

HO_MARGIN_QUAL(umb,umb)= -2 dB

HO_MARGIN_DIST(umb,umb)= 2 dB

HO_MARGIN_LEV(micro,umb)= -127 dB

HO_MARGIN_QUAL(micro,umb)= -127 dB

HO_MARGIN_DIST(micro,umb)= -127 dB

OUTDOOR_UMB_LEV(micro,umb)=

-100 dBm

HO_MARGIN_LEV(umb,micro)= 2 dB

HO_MARGIN_QUAL(umb,micro)= -2 dB

HO_MARGIN_DIST(umb,micro)= 2 dB

HO_MARGIN_LEV(micro,micro)= 2 dB

HO_MARGIN_QUAL(micro,micro)= -2 dB

HO_MARGIN_DIST(micro,micro)= 2 dB

The upper layer is a rescue layer for microcells: thus, all HO_MARGIN_XX(micro,umb) are set to -127 dB.

OUTDOOR_UMB_LEV is set to -100 dBm: all umbrella cells with a received level lower than -100 dBm will be

filtered out at candidate cell evaluation.






1 · 3 · 22


Border Microcell Class

� Definition

� A microcell bordering the microcell area

� Hybrid situation between the inner microcell and the hotspot microcell

� Rule

� Ensure the MS is slow & well covered before a capture in microlayer

� Ensure a MS will exit this cell safely

� PBGT HO are of no use here

Border Microcell

The upper layer is a rescue layer for microcells: thus, all HO_MARGIN_XX(micro,umb) are set to -127 dB.

OUTDOOR_UMB_LEV is set to -100 dBm: all umbrella cells with a received level lower than -100 dBm will be

filtered out at candidate cell evaluation.






1 · 3 · 23


Border Microcell: Better Condition Handovers


UmbrellaEN_SPEED_DISC = ENABLED


H_MIN_DWELL_TIME = 16s

Border Microcell

Cause 14


= -75 dBm

Cause 12 / 23

Cause 12




All other parameters not shown here are identical to inner microcells.

A capture towards a microcell is triggered after MIN_DWELL_TIME which will vary from H_MIN_DWELL_TIME down

to L_MIN_DWELL_TIME if the umbrella 900 cell is loaded. MIN_DWELL_TIME is increased to prevent tangential MSs

from being captured by the border microcell.

L_RXLEV_CPT_HO is increased.






1 · 3 · 24


Border Microcell: Emergency Handovers



Border MicrocellEN_RESCUE_UM = ENABLED

EN_MCHO_H_DL = ENABLED



A_LEV_HO = 6

U_RXLEV_DL_MCHO = -90 dBm

A_LEV_MCHO = 4

Emergency HO considered as a "safe exit" HO, based on cause 5.

A high threshold HO is used to trigger HO towards the umbrella cell for the microlayer zone exit.






1 · 3 · 25


Indoor Microcell Class

� Definition

� An indoor area located within the micro cell area

� This indoor cell aims at absorbing traffic in a strategic building

� Rules

� Absorb indoor traffic, and only indoor traffic

� Do not catch outdoor MS (Idle or Dedicated)

� An MS nearby the building door but still outside should camp on the outdoor cell

� Beware of "indoor" exit strategy

� Beware of jamming at higher floor

Indoor Microcell

Another type of indoor microcell can be defined:

Indoor microcell for coverage, when the indoor cell is a hotspot and the indoor coverage from the macro layer is

not good. This chapter does not deal with this case. See the next slides for detailed parameter settings of indoor

microcell for coverage.






1 · 3 · 26


Indoor Microcell: Better Condition Handovers







Indoor MicrocellEN_PBGT_HO = ENABLED

EN_SPEED_DISC = DISABLED

Cause 14



= -75 dBm

Cause 12 / 23

Cause 12




L_RXLEV_CPT_HO tuning is closely linked to real radio propagation and cell coverage. Values given on this slide

are just examples.






1 · 3 · 27


Indoor Microcell: Emergency Handovers





PRIORITY(micro,micro) = 1


Indoor MicrocellEN_RESCUE_UM = ENABLED




A_LEV_HO = 6


A_LEV_MCHO = 4







1 · 3 · 28


Indoor Microcell: High Floors Case

� In high floors, the level from surrounding umbrella cells is very high

� More than 6 cells might be measured at -47dBm (maximum measured value)

� How can we ensure the indoor cell is included in the chosen 6 ?

� One solution

� Dedicate one cell to cover these floors

� Set a high CRO (8dB … 12dB) : the C2 is not limited

� Define many incoming adjacencies but just few selected outgoing adjacencies

� Use SFH with broad band to avoid interferences







1 · 3 · 29

2 Adding Hot Spot Microcell for Traffic






1 · 3 · 30


Hotspot Microcell Class

� Definition

� A microcell totally isolated from any other microcell

� Rules

� Capture shall occur only if the MS is not moving

� There are no neighbour from the same layer

�No better cell handover can be triggered

�An emergency HO shall be used as an exit strategy

Hotspot Microcell






1 · 3 · 31


Hotspot Microcell: Better Condition Handovers







Hotspot Microcell

Cause 14



= -75 dBm

Cause 12 / 23


HO_MARGIN(umb, umb) = 5 dB

DELTA_INC_HO_MARGIN = 2 dB

DELTA_DEC_HO_MARGIN = 2 dB

No better condition HO from a micro

to an umbrella cell (different layers)

Fast MS detection is not possible






1 · 3 · 32


Hotspot Microcell: Emergency Handovers






Hotspot MicrocellEN_RESCUE_UM = ENABLED




A_LEV_HO = 6


A_LEV_MCHO = 4

A_QUAL_HO = 4






1 · 3 · 33

3 Monitoring QoS in a Multilayer Network






1 · 3 · 34


Indicators Monitoring

� QoS indicators in each layer� Create a cell zone for each cell type : Umbrella, Mini, Micro, Indoor, Single

� Perform your QoS Monitoring per cell zone

� Goal 1 : Traffic split� RTCH_Load_BH (TCTRBHR) in lower layers above 80%

� RTCH_Load_BH in upper layers below congestion

� RTCH_duration_avg (TCTRMHT) should be long in lower layers (> 20s)

� …and might be shorter in umbrellas, because of cause 14 (Min Dwell Time)

� Goal 2 : Quality of Service� Main KPI's shall be better or identical in lower than in upper

� TCH Drop Rate, CSSR, SDCCH Congestion rate

� HO Incoming & Outgoing efficiency rates

� Handover causes split should reflect your parameter settings� DL Level HO (5) as exit strategy for hotspot/border cells

� Capture HO (14) shall be the main cause of HO for Umbrellas

RTCH Duration Average is related to the HO/Call indicator. But it gives a better physical sense of possible ping

pong handovers.






1 · 3 · 35


Indicators Monitoring [cont.]

� Goal 3: Simplicity of parameter settings

� Apply the same settings within each cell type

� Find the best "overall" settings in order to obtain the best results (regarding goal 1, goal 2 or both)

� Once this is achieved, fine tune problematic cells only

� Additional investigation : Forced Directed Retry

� With good settings, FDR should not occur too much

� But if it does, ensure it is working correctly

� DR_Out_success_rate (DRORSUR) in lower layers

� DR_Inc_internal_success_rate (DRIBSUR) in upper layers

� Specific indicators : Traffic flows

� HO per couple of cells (PMC type 180)

� In case of problem, use ODMC type 26 and 27 for detailed incoming and outgoing HO causes (max. 40 cells)






1 · 3 · 36









1 · 3 · 37

End of ModuleCreating a Multilayer Network






Module 4Creating a Multiband Network



Optimization







EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimisation · Creating a Multiband Network

1 · 4 · 2

Blank Page




Document History






1 · 4 · 3

Module Objectives


� Define relevant parameters settings to introduce a new band in an existing network






1 · 4 · 4








1 · 4 · 5

Table of Contents


1 Introduction 72 Collocate the new band in a monolayer network 103 Collocate the new cells in upper layer of a multilayer network 184 Collocate the new cells in lower layer of a multilayer network 265 QoS Monitoring 34






1 · 4 · 6









1 · 4 · 7

1 Introduction






1 · 4 · 8

1 Adding a Microcellular Layer for Traffic and Coverage Increase

Strategies

� Several cases should be considered in order to cover all the possibilities

� What is the current architecture prior to the introduction of the new band ?

1. Monolayer

2. Multilayer

� What is the planned architecture after the introduction of the new band ?

1. Monolayer : the new band is located in the current layer

2. Multilayer : the new band is located within an existing layer

3. Multilayer : the new band is located within a dedicated layer

� In order to save cost, the new cells will be collocated with the existing cells

1. Dual-BCCH ? (two different cells)

2. Single-BCCH ? (multiband concentric cells)

� For each architecture, which settings to choose ?






1 · 4 · 9

1 Introduction

Examples

� The main situations will be studied :

� Collocate the new band with :

1. Existing single cells (monolayer)

2. Existing umbrella cells� Existing micro cells in classical band

3. Existing mini cells� Existing umbrella cells in classical band

� Implement the new band in a new layer

1. New micro layer (for hotspot coverage)� refer to previous chapter "Adding a Microcellular Layer"

2. New mini layer (for continuous coverage)� this solution is not practical: macro cells in the new band are always Collocated with

existing cells

3. New umbrella layer (for extension of coverage)� this solution is not realistic: umbrella cells are always deployed first in a network

�

�

�

In this course, we focus only on realistic solutions which are chosen by all operators : the new band is never

deployed in a country without colocation with existing cells.






1 · 4 · 10

2 Collocate the new band in a monolayer network






1 · 4 · 11


Single vs. Umbrella

� If the network is monolayer, there is no difference between Singles and Umbrellas.

� The only difference will appear if introduction of microcells in the future :

1. For Umbrellas, the cause 14 is available to push traffic to microlayer

2. For Single, the cause 24 (General Capture Handover) must be enabled

� In a case study, we will see the differences between the two solutions.

� Future proof solution: set all your cells as "Umbrella"






1 · 4 · 12


Collocated cells

� If the cells are collocated, two solutions…

� Dual-BCCH or Single BCCH

Single-BCCH Dual-BCCH

Cell B

Cell A

cause ?

cause ?

CRO(B)

CRO(A)

Cell A

inner

outer

cause 13

cause 10/11

CRO(A)






1 · 4 · 13


Collocated cells [cont.]

� For single-BCCH cells, refer to algorithms of causes 10, 11 and 13.

Cell A

inner

outer

cause 13

cause 10/11

CRO(A)

CELL_RESELECT_OFFSET must be set accordingly to the other cells

CAUSE 13: Entry HO, based on DL and UL RxLevof the outer zone

RXLEV_UL_ZONE & DL_ZONEZONE_HO_HYST_UL & DLMS and BS_TXPWR_MAX_INNERNEIGHBOUR_RXLEV(0,n)EN_BETTER_ZONE_HOEN_LOAD_BALANCEPING_PONG_HCP, T_HCP

CAUSE 10/11: Exit HO, based on DL or UL RxLevof the inner zone

RXLEV_UL_ZONE & DL_ZONE

INTERCELL HO: no changesOFFSET_HO_MARGIN_INNER

Rule : OFFSET_HO_MARGIN_INNER ≥ ∆ Propagation - ∆ MS TxPwrRule : OFFSET_HO_MARGIN_INNER ≥ ∆ Propagation - ∆ MS TxPwr

∆ Propagation : 10dB∆ MS TxPwr : 33 – 30 = 3dB

�� OFFSET_HO_MARGIN_INNER ≥ 7dB






1 · 4 · 14



� For dual-BCCH cells, use "Preferred band HO" (cause 21)

CELL_RESELECT_OFFSET(A) > CELL_RESELECT_OFFSET(B)

Cell B

Cell A

cause 21

cause 5

CRO(B)

CRO(A)

CAUSE 21: Entry HO, based on DL RxLev of cell BL_RXLEV_CPT_HO(A,B)MS_TXPWR_MAX(B)MULTIBAND_TRAFFIC_CONDITION(B)HIGH_TRAFFIC_LOAD(A)EN_PREFERRED_BAND_HO(B)T_INHIBIT_CPT(A)

CAUSE 5: Exit HO, based on DL RxLev of cell BL_RXQUAL_DL_H(B)L_RXLEV_DL_H(B)EN_RXLEV_DL(B)

Avoid ping-pong HOHO_MARGIN(B,A) = +127dB

Rule : L_RXLEV_DL_H(B) ≤ L_RXLEV_CPT_HO(A,B) – 5dBRule : L_RXLEV_DL_H(B) ≤ L_RXLEV_CPT_HO(A,B) – 5dB






1 · 4 · 15



� For dual-BCCH cells, beware of neighbour cells

Cell B

Cell A

PBGT HOEN_MULTIBAND_PBGT_HO(A) = EnableEN_MULTIBAND_PBGT_HO(B) = Enable

With 900 cellsHO_MARGIN(B, 900) = ∆ Propag + 5-3 = 12dBHO_MARGIN(A, 900) = 5dB

With "standalone 1800 cells"HO_MARGIN(B, 1800) = ∆ Propag + 5 = 15dBHO_MARGIN(A, 1800) = 2dBHO_MARGIN(1800, A) = 8dBHO_MARGIN(1800, B) = 5dB

With "collocated 1800 cells"HO_MARGIN(B, 1800) = 5dBHO_MARGIN(A, 1800) = -2dB

At network level, such settings are unmanageable !At network level, such settings are unmanageable !

All these computations are based on having a difference of RxLev of 5dB between the "outer" cells.

For example, from cell B to a standalone 1800 cell (called cell C):

- Cell A would perform a PBGT HO if the ∆ RxLev(C – A) is above 5dB, therefore the HO_Margin(A,C) is 2dB

- Cell B should perform a PBGT HO to C, only if the cell C is 5dB above cell A (in order to avoid ping pong back to

cell A !)

- Because cell B is 10dB less than cell A (diff of propagation), then Cell C should be 15dB above cell B.

It results that after the MS leaves cell B to cell C with a PBGT, then the cell C is more than 5dB above cell B. This

tends to avoid ping pong HO.

It is however possible to reduce this HO MARGIN(B,C) down to 10dB, but this increases the risk of ping pong.






1 · 4 · 16



� For dual-BCCH cells, beware of neighbour cells

Cell B

Cell A

PBGT HOEN_MULTIBAND_PBGT_HO(A) = DisableEN_MULTIBAND_PBGT_HO(B) = Disable

With 900 cellsHO_MARGIN(A, 900) = 5dB

With "standalone 1800 cells"HO_MARGIN(B, 1800) = ∆ Propag + 5 = 15dB

With "collocated 1800 cells"HO_MARGIN(B, 1800) = 5dB

It is easier to manageTypical interband HO are only cause 21 or cause 5

It is easier to manageTypical interband HO are only cause 21 or cause 5






1 · 4 · 17



� Regarding Radio Parameters :

� Single-BCCH:

1. Less parameters

2. Much simpler settings, especially adjacency parameters

3. PBGT HO towards all neighbours are possible

� Dual-BCCH:

1. Cause 21 is using load conditions in serving and target cells

2. Cause 21 can push a MS from one 900 cell to its collocated cell and to other 1800 cells as well

�






1 · 4 · 18

3 Collocate the new cells in upper layer of a multilayer network






1 · 4 · 19


Single-BCCH strategy

� As seen earlier, it is simpler to use single-BCCH

� In the OMC-R, create your collocated cells as "Concentric"

� Choose a handover to push traffic from these cells to the microlayer

� Cause 24 if collocated cells and micro cells are all "Single"

� Cause 14 if collocated cells are "Umbrella" and micro cells are "Micro"

� The choice has been done previously:

� The best solution is "cause 14" in order to take into account fast moving mobiles.

This strategy was fully studied in "Adding a Microcellular Layer""






1 · 4 · 20


Dual-BCCH strategy

� In case this solution is preferred, some settings to manage Umbrella 1800 / Umbrella 900 were given in the previous chapter.

� In this chapter, we introduce a Microcell layer.

(5)(14)

(14)

(5)

(5)(21)

UMBRELLA 900

UMBRELLA 1800

MICRO 900






1 · 4 · 21


Call Setup

MICROMICRO

UMBUMB

MICRO 900CELL_RESELECT_OFFSET = 8 dBTEMPORARY_OFFSET = infinityPENALTY_TIME = 0 (20 s)


UMBUMB


CELL_BAR_QUALIFY can be set to 0 by default.






1 · 4 · 22

Umbrella


Better Conditions HO

Traffic routed to Micro

12

12

12 21

21

14

14

12

12

L_Rxlev_Cpt_Ho(900,µ)= -80dBm

L_Rxlev_Cpt_Ho(900,µ) = -80dBm

L_Rxlev_Cpt_Ho(1800,µ) = -80dBm

Ho_Margin(900,900)=5dB

Ho_Margin(1800,1800)=5dB

Ho_Margin(µ,µ)=0…10dB

EN_Pbgt_Ho = EnableEN_Multiband_Pbgt_Ho = DisableEN_Preferred_Band_Ho = EnableEN_Mcho_Ncell = EnableL_RxLev_Cpt_Ho(0,n) = -80dBm

Multi_Band_Traffic_Condition=Any_LoadEN_Speed_Disc = EnableH_Load_Obj = 70% / L_Load_Obj = 30% L_Min_Dwell_Time = 8sH_Min_Dwell_Time = 20s

Micro

EN_Pbgt_Ho = EnableEN_Preferred_Band_Ho = Disable

EN_Speed_Disc = EnableHigh_Traffic_Load = 80% : Fast MS only

Priority(0,n) is useless here : HO cause priority : 21 > 14 > 12

21 is likely to be triggered before 14 anyway (A PBGT HO vs. MIN DWELL TIME), so using priority to favour the

cause 14 will not work.






1 · 4 · 23

Umbrella


Emergency HO

Favour umbrella 900 + Preventive exit from Micro

Pref_Layer = single + upper [fixed]

By default, same band as serving is preferred

T_HCP = 60s

Micro

EN_Rescue_Um = Enable� Pref_Layer = upper

EN_Mcho_H_DL = DisableL_RxLev_DL_H ≤ -86dBmOutdoor_Umb_Lev(mini,umb) = -100dBm

If microcell 900

10

1

1

1

1

1

1

1

1

: top choice: second choice: third choice: last choice

Priority(0,n) is used to favour emergency HO from 1800 umbrella towards its Collocated 900 umbrella. This is

useful also for Forced Directed Retry.

It migh be complex to define priority(1800, Collocated 900) = 1 and priority(1800, other 900) = 0. However, by

using NPO, it is possible to customize adjacency types to take into account this specificity. Then, by using a

NPO Tuning Session, the tuning is very straight forward.






1 · 4 · 24

Umbrella


Forced Directed Retry & Fast Traffic HO

Rescue capacity with umbrella 900 & 1800

Pref_Layer = none [fixed]

L_RxLev_Ncell_DR = -85dBmFree_Level_DR = 0EN_DR = EnableEN_Fast_Traffic_Ho = Disable

EN_FDR(900) = DisableEN_FDR(1800) = Enable

Micro


L_RxLev_Ncell_DR = -47dBmFree_Level_DR = 0EN_DR = EnableEN_FDR = EnableEN_Fast_Traffic_Ho = EnableHO_Margin_Lev(µ,umb) = -5dB

If microcell 900

10

1

1

1

: top choice: second choice: third choice: last choice

Directed Retry shall always be enabled : it will act as a standard HO (better cell or emergency, depending on the

trigger cause). Refer to previous slides (EM HO and BC HO). The possible DR are not represented by arrows on

this slide, because it can work from any cell towards any cell.

Fast Traffic HO shall be enabled in microcells : an upper layer might not be available to each user, so the FDR

might not work (esp. in case of indoor situation). In order to have a higher probability of F.T.H, it is necessary

to lower the HO MARGIN LEV(micro, umbrella).

The more this value is reduced, the higher the efficiency of F.T.H.

Priority(1800, Collocated 900) is one more time very useful here. Since the Collocated 900 is fully overlapping the

1800, there is absolutely no degradation of quality whether the call is on the umbrella 900 or umbrella 1800.






1 · 4 · 25

Umbrella


Candidate Cell Evaluation

Easy exit from micro

En_Priority_Ordering = EnableEn_Pbgt_Filtering = EnableCell_Ev = GRADE

Ho_Margin_Lev(0,n) = 2dBHo_Margin_Qual(900,coloc1800) = -12dBHo_Margin_Qual(0,n) = -2dB Ho_Margin_Dist(0,n) = 2dB

Micro


Ho_Margin_Lev(µ,umb) = -5dBHo_Margin_Qual(µ,umb) = -127dBHo_Margin_Dist(µ,umb) = -127dB

Ho_Margin_Lev(µ, µ) = 2dBHo_Margin_Qual(µ, µ) = -2dBHo_Margin_Dist(µ, µ) = 2dB

If microcell 900

: special settings: default settings

Umbrella :

HO MARGIN LEV and HO MARGIN DIST shall be set above 0dB, in order to avoid emergency HO ping pong (which

might be rare in a city anyway). Def value = 2dB.

HO MARGIN QUAL is different. If there is a quality issue in the 900 (since the 900 frequency band is more

interfered, this situation is probable), the Collocated 1800 must be a possible candidate. But don't forget that

the Collocated 1800 is 10dB lower than the 900 : the HO MARGIN QUAL should not filter out this cell.

So a HO MARGIN QUAL = -12dB is chosen.

HO MARGIN QUAL(umb 900, coloc 1800) = -12dB

HO MARGIN QUAL(umb 900, other 1800) = -2dB

HO MARGIN QUAL(umb 900, umb 900) = -2dB

HO MARGIN QUAL(umb 1800, umb *) = -2dB

HO MARGIN QUAL(umb *, µ)= -2dB

Micro :

The Umbrellas 900 & 1800 are a rescue for a micro. If there is a quality/interference problem in a micro, the

RxLev(Micro) may be very high. Therefore we need to put a very low HO MARGIN QUAL, in order to accept a

target cell with a lower RxLev than the micro.

The HO MARGIN LEV is set to -5dB, in order to give Fast Traffic HO a higher chance of happening (refer to

previous slide)






1 · 4 · 26

4 Collocate the new cells in lower layer of a multilayer network






1 · 4 · 27


Single-BCCH vs. Dual-BCCH

� Assumptions:

� New cells are Collocated with classical Mini cells

� Umbrella cells are in the classical band

� The easiest solution is to create Concentric Multiband Mini cells

� Refer to "Create a multilayer network"

� The new band is "transparent", it does not impact algorithms other than intra-zone handovers (causes 10, 11, 13)

� In this chapter, the dual-BCCH solution is studied






1 · 4 · 28


Call Setup

MINIMINI

UMBUMB



MINIMINI


The Mini coverage is assumed to be continuous and can be used to capture Fast MS immediately.






1 · 4 · 29


Better Conditions HO

Umbrella

Mini

EN_Pbgt_Ho = EnableEN_Multiband_Pbgt_Ho = DisableEN_Preferred_Band_Ho = DisableEN_Mcho_Ncell = Enable

EN_Speed_Disc = DisableL_Min_Dwell_Time = 6s

L_Rx_Lev_Cpt_Ho(0,n) = -80dBm

EN_Pbgt_Ho = EnableEN_Preferred_Band_Ho = EnableL_Rx_Lev_Cpt_Ho(0,n) = -80dBmEN_Speed_Disc = DisableHigh_Traffic_Load = 80%

21

14

14

21

12

12

12

1212

12

Traffic routed to Mini 1800

: Fast MS only

Umbrella will unload with cause 14, with a dwell time of 6 seconds.

We need to favour direct HO from umbrella to mini 1800, rather than doing Umbrella � Mini 900 � Mini 1800.

The Mini 900 is received 10 dB greater than the Mini 1800. So by default, with" cause 14" candidate cell

evaluation, the Mini 900 will have a better ORDER than the Mini 1800 (the PBGT(900) is 7dB greater than

PBGT(1800))

To reverse this situation, we need to favour the Mini 1800, either with :

1) priority(umb, mini 1800) = 0 or

2) with link_factor(umb, 1800) = +12dB (so ORDER(1800) are 5dB greater than ORDER(900))

We will study these possibilities later.






1 · 4 · 30


Emergency HO (1/2)

Umbrella

Mini

Umbrella is the rescue cell



T_HCP = 60s

EN_Rescue_Um = Enable� Pref_Layer = upper

L_RxLev_DL_H ≤ -86dBmOutdoor_Umb_Lev(mini,umb) = -100dBm

: top choice: second choice: last choice

There is a risk that the umbrella will collect too much taffic in this situation !






1 · 4 · 31


Emergency HO (2/2)

Umbrella

Mini

Rescue cells are from the same layer



T_HCP = 60s

EN_Rescue_Um = Disable� Pref_Layer = lower + indoor

L_RxLev_DL_H ≤ -86dBmOutdoor_Umb_Lev(mini,umb) = -100dBm


This solution is closer to what we want : the mini cells offer a good coverage. If no mini cells are available, it is

not a problem : the umbrella can still be a valid target cell.

Special attention must be paid to PBGT Filtering : Mini cells can be filtered out, but Umbrellas should stay in the

list.

Remark : Priority(0,n) = 1, for all adjacencies.

Regarding the possibility to use priority(umb, mini1800) = 0 (cf. "Better conditions HO" in this chapter) : it will

impact the EM HO from umbrella. The end result will be :

EM HO from umbrella � other umbrella > mini 1800 > mini 900.

The link factor is therefore a better choice, so far.






1 · 4 · 32


Forced Directed Retry and Fast Traffic HO

Umbrella

Mini

Rescue capacity in Umbrella


EN_DR = EnableEN_FDR = DisableEN_Fast_Traffic_Ho = Disable

L_RxLev_Ncell_DR = -85dBmFree_Level_DR = 0


EN_DR = EnableEN_FDR = EnableEN_Fast_Traffic_Ho = Enable

L_RxLev_Ncell_DR = -47dBmFree_Level_DR = 0HO_Margin_Lev(mini,umb) = -5dB

�


(�) In order to activate FDR towards MINI 900, if Umbrella are full and Mini 1800 are still congested, it is simple :

Gradually decrease the value of L_RxLev_Ncell_DR(Mini 900) from -60dBm to -80dBm, until a significant decrease

of the congestion in MINI1800 occur.

HO MARGIN LEV(mini, umb)=-5dB : in order to increase the probability to perform a fast traffic HO. To increase

the probability, decrease to -10dB, and so on.






1 · 4 · 33


Candidate Cell Evaluation

Umbrella

Mini

Use 1800 band for quality HO : special settings: default settings


Ho_Margin_Lev(umb,n) = 2dBHo_Margin_Qual(umb,n) = -2dB Ho_Margin_Dist(umb,n) = 2dB

Ho_Margin_Qual(umb, mini 1800) = -12dBLink_Factor(umb, mini1800) = +12dB

En_Priority_Ordering = EnableEn_Pbgt_Filtering = EnableCell_Ev = GRADEHo_Margin_Dist(mini, n) = 2dB

Ho_Margin_Lev(mini,umb) = -5dBHo_Margin_Qual(mini,umb) = -127dBHo_Margin_Lev(mini, mini) = 2dBHo_Margin_Qual(mini, mini) = -2dBHo_Margin_Qual(mini, coloc1800) = -12dB

Quality HO in an umbrella : As the mini 1800 is seen 10dB lower than the mini 900, there is a risk the mini 1800

will be filtered out during PBGT filtering.

Quality HO in a mini 900 : If no other Mini 900 is around with less than -2dB difference, then the next choice will

be a mini 1800. In order to keep the mini 1800 Collocated in the list, it is necessary to reduce the HO MARGIN

QUAL(mini900, coloc1800) below -10dB.

Ho_Margin_Lev(mini,umb) = -5dB � For Fast Traffic HO

Link_Factor(umb, mini1800) = +12dB � For better condition HO : cause 14 towards Mini 1800 rather than towards

Mini 900.






1 · 4 · 34

5 QoS Monitoring






1 · 4 · 35

5 QoS Monitoring

Indicators Monitoring

� QoS indicators in each layer

� Create a cell zone for each cell type & band

� Umbrella 900

� Mini 900

� Micro 900

� Indoor 900

� Perform your QoS Monitoring per cell zone

� Goal 1: Intelligent traffic split

� Goal 2: Balanced QoS between different layers and bands

� Goal 3: Globalized settings

� Umbrella 1800

� Mini 1800

� Micro 1800

� Indoor 1800






1 · 4 · 36

5 QoS Monitoring

Investigation

� Special attention to:

� HO/Call and RTCH Duration Avg in intermediate layer

Too many incoming HO from top layer (probably due to capture)

Too many outgoing HO CPT (towards bottom layer)

Action 1: L_RxLev_Cpt_Ho(top, intermediate) = -80dBm � -70dBm

Action 2: Cell_Reselect_Offset(bottom) = 8dB � 12dB

capture

capture

TOP

INTERMEDIATE

BOTTOM

�

��capture

Intermediate layer :

1. Umbrella 1800 in case of Umbrella 900 / Umbrella 1800 / Micro

2. Mini 900 in case of Umbrella 900 / Mini 900 / Mini 1800






1 · 4 · 37









1 · 4 · 38

End of ModuleCreating a Multiband Network






Module 5Case Studies



Optimization







EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimisation · Case Studies

1 · 5 · 2

Blank Page




Document History






1 · 5 · 3

Module Objectives


� Define relevant parameter settings for the following field cases






1 · 5 · 4








1 · 5 · 5

Table of Contents


1 Radar Cell 72 Symmetric Microcells at a Street Corner 93 Asymmetric Microcells at a Street Corner 114 Indoor Microcell within a Monolayer Network 135 Trilayer Network: Indoor Cell within a Multi-Layer Network 156 Indoor Cell Congestion 177 Transforming a Microcell into an Indoor Cell 198 Picocells in Skyscrapers 21






1 · 5 · 6









1 · 5 · 7

1 Radar Cell






1 · 5 · 8

1 Radar Cell

Exercise

� A radar cell is covering an industrial zone

� Find relevant parameter settings to favor IZ cells in idle and connected mode

� Propose 2 architectures






1 · 5 · 9

2 Symmetric Microcells at a Street Corner






1 · 5 · 10

2 Symmetric Micorcells at a Street Corner

Exercise

� An indoor microcell is introduced within a monolayer network, for a new coverage

� Define relevant parameter settings to obtain good QoS in the microcell layer for

� symmetric microcells at a street cornerCell B

Cell Ad

d






1 · 5 · 11

3 Asymmetric Microcells at a Street Corner






1 · 5 · 12

3 Aymmetric Micorcells at a Street Corner

Exercise

� Define relevant parameter settings to obtain good QoS in the microcell layer for

� Asymmetric microcells at a street corner

� 1 < x < 2.5

Cell B

Cell Ax.d

d






1 · 5 · 13

4 Indoor Microcell within a Monolayer Network






1 · 5 · 14

4 Indoor Microcell withing a MonolayerNetwork

Exercise

� An indoor microcell is introduced within a monolayer network, for a new coverage

� Define parameter settings for both idle and connected mode

Indoor Microcell






1 · 5 · 15

5 Trilayer Network: Indoor Cell within a Multi-Layer Network






1 · 5 · 16

5 Trilayer Network: Indoor Microcell withing a Multi-Layer Network

Exercise

� An indoor microcell is introduced within a multi-layer network (macro + micro cells), for capacity & coverage increase

� So called « trilayer » network

� Define parameter settings for both idle and connected mode






1 · 5 · 17

6 Indoor Cell Congestion






1 · 5 · 18

6 Indoor Cell Congestion

Exercise

� An indoor microcell has been introduced within a multi-layer network (macro + micro), based on the previous exercise recommendations

� When an indoor microcell is congested, the FDR may not be working as some MSs can be covered only by this cell

� Define parameter settings to find a good solution in case of indoor cell congestion






1 · 5 · 19

7 Transforming a Microcell into an Indoor Cell






1 · 5 · 20

7 Transforming a Microcell into an Indoor Cell

Exercise

� Within a multi-layer network, a microcell has been designed in the micro-layer, with parameters of the microcell class

� One may want to configure this cell in the « indoor » layer

� Propose parameter settings






1 · 5 · 21

8 Picocells in Skyscrapers






1 · 5 · 22

8 Picocells in Skyscrapers

Exercise

� Skyscrapers may need several picocells to achieve a sufficient coverage while avoiding interference (sufficient received level from the serving cell

� Define parameters settings to deal with this configuration






1 · 5 · 23









1 · 5 · 24

End of ModuleCase Studies






Module 6Appendix



Optimization







EVOLIUM Base Station Subsystem · Multiband and Multilayer GSM network radio optimization - B10Multiband & Multilayer Optimisation · Appendix

1 · 6 · 2

Blank Page




Document History






1 · 6 · 3

Module Objectives


� Describe …

� List …

� Explain …

� Identify ...






1 · 6 · 4








1 · 6 · 5

Table of Contents


1 Load and Traffic Evaluation 72 Extended Cell Overview 19






1 · 6 · 6









1 · 6 · 7

1 Load and Traffic Evaluation






1 · 6 · 8


Cell TCH Radio Resource Evaluation Usage

Power budget Handover

Traffic Handover

Multiband capture Handover

General capture Handover

N_TRAFFIC_LOAD x A_TRAFFIC_LOAD x TCH_INFO_PERIOD

long term

Speed discrimination for hierarchical network

Full Rate / Half Rate channel allocationLOAD_EV_PERIOD x TCH_INFO_PERIOD

medium term

FREEfactors

LOADfactorsTCH_INFO_PERIODshort term

UsagePeriodLoad

evaluation

BackCause 12






1 · 6 · 9


Short Term Evaluation

� LOADfactors and FREEfactors are determined from Nb free TCH samples every TCH_INFO_PERIOD seconds (short term evaluation)

� LOADlevels are boundaries of load intervals associating a LOADfactor(db) to a Nb free TCH sample

� FREElevels are boundaries of Nb free TCH intervals associating aFREEfactor (db) to a Nb free TCH sample






1 · 6 · 10


Short Term Evaluation [cont.]

� FREEfactor determination:

� FREElevel in absolute number of TCHs

� FREEfactor in dB

FREEfactor_5FREELevel_4< t

FREEfactor_4FREELevel_3< t <= FREElevel_4



FREEfactor_1t <= FREElevel_1

Nb free TCHNb free TCH






1 · 6 · 11



� LOADfactor determination:

� LOADlevel in %

� LOADfactor in dB

LOADfactor_5LOADLevel_4< t

LOADfactor_4LOADLevel_3< t <= LOADlevel_4



LOADfactor_1t <= LOADlevel_1

LOADfactort = (1 - Nb free TCH/Total Nb TCH) x 100






1 · 6 · 12



� Example: cells with 4 TRXs (28 TCHs)

Nb free TCH = 4

Load = 85,7%

Cell 0�

FREEfactor(0) = -8 dBm

LOADfactor(0) = -15 dBm

Nb free TCH = 20

Load = 28,6%

Cell n

FREEfactor(n) = +7 dBm

LOADfactor(n) = 0 dBm

�

• in ORDER(n): + FREEfactor(n) - FREEfactor(0) = +7 - (-8) = +15 dB

• in GRADE(n): + LOADfactor(n) = +0 = 0 dB

in evaluation of cell n for outgoing HO from cell 0 :

HO?

-15 dB80% < t

-10 dB50% < t <= 80%

0 dB25% < t <= 50%

+5 dB10% < t <= 25%

+10 dBt <= 10%

LOADfactorLoad = (1-Nb free TCH/Total TCH)x 100

+10 dB21 < t

+7 dB15 < t <= 21

0 dB8 < t <= 15

- 8 dB3 < t <= 8

- 16 dBt <= 3

FREEfactorNb free TCH






1 · 6 · 13


Medium Term Evaluation

� Medium term measurement of the load of a cell

� corresponds to function AV_LOAD(cell)

� a new sample of the “Nb free TCHs” in the cell is available every TCH_INFO_PERIOD seconds

� AV_LOAD() is a non-sliding window load average from Nb free TCH samples updated every LOAD_EV_PERIOD x TCH_INFO_PERIOD s






1 · 6 · 14


Medium Term Evaluation [cont.]

� AV_LOAD(cell n) calculated from N Nb free TCH samples available during LOAD_EV_PERIOD x TCH_INFO_PERIOD s

100*)(n) TCHTot Nb

(n) TCH free Nb1(

Nsamples

1 = AV_LOAD(n)

Nsamples

1 = i

∑ −






1 · 6 · 15


Long Term Evaluation

� Long term measurement of the load of a cell

� corresponds to function Traffic_load(cell)

� Traffic_load() value is determined from a number N_TRAFFIC_LOAD of consecutive non-sliding window load averages AV_TRAFFIC_LOAD calculated from Nb free TCH samples updated every A_TRAFFIC_LOAD x TCH_INFO_PERIOD s






1 · 6 · 16


Long Term Evaluation [cont.]

� 3 possible values for Traffic_load(): high, low, indefinite

� initialization: Traffic_load() = indefinite

� Traffic_load() becomes : corresponds to function Traffic_load(cell)

� high if the last N_TRAFFIC_LOAD consecutive AV_TRAFFIC_LOAD load averages are all greater than the HIGH_TRAFFIC_LOAD threshold

� low if the last N_TRAFFIC_LOAD consecutive AV_TRAFFIC_LOAD load averages are all lower than the LOW_TRAFFIC_LOAD threshold






1 · 6 · 17



� Traffic_load() becomes indefinite if:

� Traffic_load() was high and the last AV_TRAFFIC_LOAD load average is lower than LOW_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

� Traffic_load() was low and the last AV_TRAFFIC_LOAD load average is greater than HIGH_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

� Traffic_load(n) is always equal to indefinite if cell n is external to the BSC

� HIGH_TRAFFIC_LOAD ≥ IND_TRAFFIC_LOAD ≥ LOW_TRAFFIC_LOAD






1 · 6 · 18



� Example with N_TRAFFIC_LOAD = 3

BackCause 12






1 · 6 · 19

2 Extended Cell Overview






1 · 6 · 20


Presentation -General

� One BTS (G3 or G4): 2 cells

� INNER cell: range from 0 to 35 km

� OUTER cell: range from 33 to 70 km

The extended cell has up to 4 TRX in the inner cell and up to 4 TRX in the outer cell.






1 · 6 · 21


Presentation - Synchronization

� Freq BCCH OUTER <> Freq BCCH INNER

� MS reports measurements on both cells for the handover algorithms

� BSICINNER = BSICOUTER

� INNER cell can decode the RACH received on OUTER BCCH frequency

� INNER cell always BARRED

� MS always camps on OUTER cellOUTER cell

INNER cell

At the border of the two cells, an overlapping area allows to provide a continuous coverage. When the MS moves

from one cell to the other, a handover is triggered in the overlap zone. Two BCCH channels are needed (one for

the inner cell, one for the outer cell), so that the MS reports measurements on both cells for the handover

algorithms.

The TRXs of the inner cell and of the outer cell are synchronised, but the reception of the outer cell is delayed

by 60bits period to account for the propagation delay.

In the inner cell, the MS can receive the BCCH inner frequency as wells as the outer BCCH frequency. To avoid to

manage RACH reception on two different frequencies in the inner cell, the MS is forced to access the inner cell

on the outer BCCH frequency. For this purpose, the RACH reception (BCCH TRX) of the inner cell is tuned to the

outer BCCH frequency, and the inner cell is barred1. So on time slot 0 of the inner cell, transmission is done on

the inner cell BCCH frequency, and reception is done on outer BCCH frequency.

The chosen implementation allows to make use of all timeslots2 of the TDMA frame and to use the combined

configuration for the CCCH channel.






1 · 6 · 22


Presentation - RF Interference

� UL interference on TS0 of the INNER cell if

� Access burst received in the INNER cell (on frequency BCCH OUTER)

AND

� Call on TS7 of the OUTER cell

� Then, TS7 of the OUTER cell is always set to IDLE (never used)






1 · 6 · 23


Radio Link Establishment - MS Located in the Outer Cell Area

The inner cell is always barred, so the MS cannot camp on the inner cell, even if located in the inner cell range. In the whole

extended cell coverage, the MS has a good reception of the outer cell BCCH, so the MS will always be camping in the outer

cell, whether in the inner cell or outer cell range.

For this reason, a special radio and link establishment procedure is used to cope with this behaviour .

It consists of receiving the CHANNEL REQUEST messages on outer BCCH frequency, and allocating the SDCCH channel

according to the MS estimated position. The IMMEDIATE ASSIGNMENT COMMAND for an SDCCH is sent on the outer cell BCCH

frequencies, but the SDCCH may be allocated in either inner or outer cell, depending on the MS position.

(1) The MS camping on the outer cell sends an access burst on the RACH on outer cell BCCH frequency. These bursts will be

received successfully in the inner cell by the BCCH TRE. In the outer cell, the access burst arrives too early and cannot be

decoded.

(2) The inner cell BCCH TRE sends a CHANNEL REQUIRED message to the BSC containing the random reference sent by the

mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

(3) The TCU controlling this TRE allocates an SDCCH subchannel to the transaction in the inner cell and asks the BTS to

activate this subchannel.

(4) The BTS activates the requested channel and sends back and acknowledgement, once this is done.

(5) The TCU sends the IMMEDIATE ASSIGNMENT COMMAND (which provides the description of the allocated SDCCH) to the BCCH

TRE of the inner cell.

The TCU controlling the inner cell BCCH sends a copy of the message to the TCU handling the BCCH of the outer cell. This

is done if and only if the timing advance IE included in the CHANNEL REQUIRED is smaller than 60, thus indicating that the

MS is strictly in the inner cell (in order to avoid that the MS receives two Immediate Assignment messages when located in

the overlap zone).

The TCU controlling the outer cell BCCH forwards the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

(6) The IMMEDIATE ASSIGNMENT message is sent over the air to the MS on the AGCH of the outer cell.

(6') The IMMEDIATE ASSIGNMENT message sent by the inner cell is lost, because the MS listens to the outer cell frequency.

(7) The mobile switches its transceiver to the SDCCH allocated in the inner cell and sends repeatedly an SABM frame to

establish the layer 2 connection with the BTS.

(8) The BTS acknowledges the establishment of the LapDm link to the MS with a UA frame sent on the SDCCH allocated to the

MS.






1 · 6 · 24


Radio Link Establishment - MS Located in the Inner Cell Area

The TCU sends the IMMEDIATE ASSIGNMENT COMMAND (which provides the description of the allocated SDCCH ) to the BCCH TRE of the inner cell.

The TCU controlling the inner cell BCCH sends a copy of the message to the TCU handling the BCCH of the outer cell. This is done if and only if the timing advance IE included in the CHANNEL REQUIRED is smaller than 60, thus indicating that the MS is strictly in the inner cell (in order to avoid that the MS receives two Immediate Assignment messages when located in the overlap zone).

The TCU controlling the outer cell BCCH forwards the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

(1) The MS in the outer cell sends an access burst on the RACH of the outer cell. This burst is successfully received by the outer cell BCCH TRE. In the inner cell, the access burst arrives too late to be successfully decoded.

(2) The outer cell BCCH TRE sends a CHANNEL REQUIRED message to the BSC containing the random reference sent by the mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

(3) The TCU controlling this TRE allocates an SDCCH subchannel in the outer cell to the transaction and asks the BTS to activate this subchannel.

(4) The BTS activates the requested channel and sends back an acknowledgement, once this is done.

(5) The TCU then sends the description of the channel in the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

(6) The IMMEDIATE ASSIGNMENT message is sent over the air to the MS on the AGCH of the outer cell.

(7) The mobile switches its transceiver to the required channel and sends repeatedly an SABM frame to establish the layer 2 connection with the BTS.

(8) The BTS acknowledges the establishment of the LAPDm link to the MS with a UA frame sent on the SDCCH allocated to the MS.






1 · 6 · 25


Radio Link Establishment - MS Located in the Overlap Zone






1 · 6 · 26


Radio Link Establishment - MS Located in the Overlap Zone [cont.]

(1a&b) The MS camping on the outer cell sends an access burst on the RACH. This burst is correctly received by the inner cell BCCH TRE and

outer cell BCCH TRE.

(2a&b) The inner cell and outer cell BCCH TRE send a CHANNEL REQUIRED message to the BSC containing the random reference sent by the

mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

(3a&b) Both TCUs controlling the TREs having BCCH allocate an SDCCH subchannel to the transaction and ask the BTS to activate this

subchannel.

(4a&b) The BTS activates the requested channels and sends back an acknowledgement for each, once this is done.

(5b) The TCU controlling the outer cell, sends the IMMEDIATE ASSIGNMENT COMMAND with SDCCH description in the outer cell to the outer cell

BCCH TRE.

(5a&c)The TCU controlling the inner cell sends in the IMMEDIATE ASSIGNMENT COMMAND with SDCCH description in the inner cell. Two cases

are possible:

� Access Delay IE > 59 the inner cell TCU will not send a copy of the IMMEDIATE ASSIGNMENT command to the outer cell TCU. This is the

desired behaviour.

� Access Delay in [58,59] range, the inner cell TCU sends a copy of the IMMEDIATE ASSIGNMENT command to the outer cell TCU. This is

not the desired behaviour (corresponds to inner cell scenario). This is due to the fact that the BSC definition of the overlap zone does

not match the exact BTS overlap area (negative values of TOA in the outer cell up to –2, are clipped to 0).

(6b) The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in outer cell, is sent to the MS on the outer cell BCCH frequency. In

most cases this message should be received by the MS (except if 6c is received first)

(6a) The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in inner cell is lost on the inner cell air interface, because the MS

does not listen to that frequency. The unused SDCCH will be released by the BSC when the supervising timer expires6.

(6c) Access Delay in [58,59] range: The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in inner cell is sent on the BCCH

frequency of the outer cell. In most cases, the MS should have received message (6b) before and has already switched to the SDCCH in the

outer cell, and so this message is lost. It is however possible, in case the message (6b) is delayed in the inner cell, that the message (6c) is

received earlier by the MS. In this case establishment will occur on the SDCCH allocated in the inner cell (not drawn).

(7b) The mobile receives the IMMEDIATE ASSIGNEMENT describing the SDCCH allocation in outer cell on the BCCH outer cell frequency. It then

switches to the designated channel and sends repeatedly an SABM frame to establish the layer 2 connection with the BTS in the outer cell. If

the message (6c) is received before (6b), then the establishment will occur in the inner cell.

(8b) The BTS acknowledges the establishment of the LapDm link to the MS with a UA frame sent on the SDCCH allocated to the MS.

(9) The unused SDCCH is released in the inner cell (double SDCCH allocation). If message 6c arrives first, then the unused SDCCH release will

occur in the outer cell.






1 · 6 · 27


Handover - From the INNER Cell to the OUTER Cell

� CAUSE 6 : Too long distance


and EN_DIST_HO = ENABLE

� U_TIME_ADVANCE = 62

� EN_PBGT_FILTERING = Disable

In the extended cell , the handover procedure is purely controlled by settings of the handover detection

parameters. Two special causes allow handover from the inner cell to the outer cell and handover from the outer

cell to the inner cell. There is no change in the BSC handover algorithm either for handover preparation or

execution.

From the inner cell to the outer cell , the handover alarm is only triggered by the handover cause “too long MS-BS

distance”. When this cause is triggered the extended outer cell is always a candidate cell.

However the operator setting of the handover parameters must insure that this cause is only triggered when the

distance from the serving inner cell BTS is greater than the limit of the overlap zone (TA > 62) by setting

U_TIME_ADVANCE to 62.

In order to avoid the extended outer cell to be filtered by the filtering process the flag EN_PBGT_FILTERINGmust be set to DISABLE.

The candidate cell evaluation process is recommended to be the GRADE mode.






1 · 6 · 28


Handover - From the OUTER Cell to the INNER Cell

� CAUSE 22 : Too short distance

AV_RANGE_HO < L_TIME_ADVANCE

� L_TIME_ADVANCE = 0

� EN_PBGT_FILTERING = Disable

� Cause 22 is only checked if

� Cell_range(serving) = extended_outer

In the same way, from the outer cell to the inner cell , the handover alarm is only triggered by the handover

cause “too short MS-BS distance”. When this cause is triggered the extended inner cell is always a candidate cell.

However the operator setting of the handover parameters must insure that this cause is only triggered when the

timing advance applied by the mobile reaches 0, this is achieved by setting L_TIME_ADVANCE to 0.

In order to avoid the extended inner cell to be filtered by the filtering process the flag EN_PBGT_FILTERINGmust be set to DISABLE.

The candidate cell evaluation process is recommended to be the GRADE mode.






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Handover - From the INNER Cell to the OUTER Cell toward Another Cell

� All the standard HO causes can be used

� Emergency HO causes 2, 3, 4, 5

� Better condition HO causes 12, 23, 24

� The OUTER or INNER cell is always present in the Candidate CellEvaluation

The setting of the handover parameter does not prevent any handover cause to trigger an alarm for a handover

towards a third cell.

It is possible to use exactly the same rules and parameters for handover towards a third cell as in the macro

cellular normal cases.

The synchronous handover does not work between the inner and the outer cell.

In order to avoid call terminations due to directed retry into the inner or outer cell with an incorrect distance

range it is recommended to disable the forced directed retry towards the inner and the outer cell. For this

purpose, the parameter FREELEVEL_DR(n) is set to the maximum value (255) for the inner and the outer cell.

But the Normal DR can be activated.






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Packet Service (B9 MR4)

� Activation of the PS service in an Extended cell

� No specific parameter is foreseen

� Same procedure as the one used for standard cell is applied

� TRX_PREF_MARK = 0

� If used, PS must be activated in both INNER and OUTER cell

� Reselection

� Because the INNER cell is barred� this cell should must not be declared in the neighbor cells reselection adjacencies

� NC2 is not allowed

� NACC and (P)SI STATUS are not allowed The INNER cell and OUTER cell must belong to the same location area

� The Master channel is not allowed in both INNER and OUTER cell






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Packet Service (B9 MR4) [cont.]

� Packet access procedure

� Same principle as in CS, since it’s performed on CCCH only

� The MS always performs its access on the RACH of the outer BCCH frequency

� The BTS provides the BSC with the initial TA

� Depending on the TA value, the BSC chooses the suitable cell (INNER or OUTER)

� In UL, whatever the multislot class of the MS, only one PDCH is allocated

� Its right or left TS can not be allocated neither for PS nor for CS (see comment)

� This TS is considered as a restricted TS by the MSF

� The same constraint is applied in DL for the TS carrying the PACCH

UL

Restricted

Allocated

Restricted

Allocated

INNEROUTER

When a MS passes from inner/outer cell to outer/inner cell, the TA estimated by the BTS stalls progressively. So

the MS is not able to apply the suitable correction of its TA for its uplink transfer (data and/or signaling). This

leads progressively to the impossibility for the BTS to decode the uplink radio blocks because they shift out of

their allocated RTS.

For a given MS, its uplink radio blocks progressively come out of its allocated RTS and jams the neighbor RTS.

� It jams the right RTS when the MS moves from inner to outer cell. This right RTS can also be the RTS0 of the

next TDMA frame if the RTS7 is allocated to a TBF.

� It jams the left RTS when the MS moves from outer to inner cell. This left RTS can also be the TS7 of the

previous TDMA frame if the RTS0 is allocated to a TBF.

If the neighboring RTS is dedicated to other MS for PS or CS call, this jam causes interferences on these RTS and

the BTS can not decode the radio blocks of those MS leading to the drop of these calls.

This drawback only occurs for the uplink direction. The downlink direction does not raise any problem.

To overcome this drawback, some radio resource allocation constraints are to be applied:

� An UL TBF is only allocated on one RTS.

� On BCCH or non BCCH inner TRX,

� A RTS is allocable to a UL TBF if its right RTS is allocated for PS traffic to the MFS, and is not used by a UL

TBF.

� When a RTS is allocated, its right RTS cannot be allocated to PS call.

� On BCCH or non BCCH outer TRX,

� A RTS is allocable to a UL TBF if its left RTS is allocated for PS traffic to the MFS, and is not used by a UL

TBF.

� When a RTS is allocated, its left RTS cannot be allocated to PS call.






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PS Parameters Setting

� NETWORK_CONTROL_ORDER = NC0

� EN_NACC = Disable

� EN_PSI_STATUS = Disable

� NB_TS_MPDCH= Disable

� MAX_PDCH, MAX_PDCH_HIGH_LOAD and MIN_PDCH must be set to even values (see comments)

� EN_STREAMING = Disable

As in UL TBF allocation, the MFS uses at least 2 TS (a “restricted” one and the one allocated in UL) the number of

PDCH allocable in the extended cells (MAX_PDCH, MIN_PDCH, MAX_PDCH_HIGH_LOAD ) must be even.






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End of ModuleAppendix

Documents

MM Study on ALU