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Module 1Multiband Multilayer Network Architecture

3JK11166AAAAWBZZA Issue 01

Section 1Multiband & Multilayer

Optimization

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

3FL11535ADAAZZZZA Issue 01

maha.tarekCallout


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

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Blank Page



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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!



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Table of Contents [cont.]




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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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

900 900

900 900



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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 handover2

1

Directed retryEmergency Handover

900

900

1800



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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 handover1

2

Directed retryEmergency Handover

900

900

1800



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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

900



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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 ( 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



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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

Do not delete this graphic elements in here:


Module 2Algorithms and Associated Parameters

3JK11167AAAAWBZZA Issue 01

Section 1Multiband & Multilayer

Optimization

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

3FL11535ADAAZZZZA Issue 01



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Blank Page



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Module Objectives

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

Describe algorithms dedicated to multilayer and multiband networks management



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Module Objectives [cont.]



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Table of Contents




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Table of Contents [cont.]




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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)

7987982020

4545

800800

805805

22



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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 1800SI 2 and 2bis : 1800 neighboring cellsSI 2ter : 900 neighboring cells

2020BCCH 900SI 2: 900 neighboring cellsSI 2ter (& 2bis): 1800 neighboring cells



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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

805805SACCHSI 5 and 5bis: 1800 neighboring cellsSI 5ter: 900 neighboring cells

2020SACCHSI 5: 900 neighboring cellsSI 5ter (& 5bis): 1800 neighboring cells



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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.



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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)



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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



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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



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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



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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 microcellCELL_BAR_QUALIFY = 0

2020

macrocell

CELL_BAR_QUALIFY = 1



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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



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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



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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



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C2 Criterion

C2

If CELL_RESELECT_PARAM_IND= not present

C2=C1



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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)



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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



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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



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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)



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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 ?





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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 :



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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



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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



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4 Call Setup



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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?



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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)



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4 Call Setup

Algorithms Principles

New capacity

Trafficincrease

Old capacity



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4 Call Setup

Algorithms Principles (cont.)

New capacity

Trafficincrease

Old capacity

Water Valve with filter:

Dual layer algorithms



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4 Call Setup

Algorithms Principles (cont.)

New capacity

Trafficincrease

Old capacity

Water Pump:

Forced

Directed Retry and

Fast Traffic

handover



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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



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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



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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



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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



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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



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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



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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



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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 1 83

5 Handover Strategies



1 1 84


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 1 85


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 1 86


Handover Algorithms

Next parts will detail available HO causes for multilayer network management

Standard Handovers

Multilayer and Multiband Handovers

Concentric cell "Interzone" Handovers



1 1 87


Functional Entities

RadioLink Measurements

ActiveChannelPre-processing

Assignment of HO functions in the ALCATEL BSC

BSC

HO DetectionHO CandidateCell Evaluation

HO management

MSCHO protocol

BTS



1 1 88


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



1 1 89


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 1 90


HO Causes Priority

cause 7 : consecutive bad SACCH frames received in a microcell cause 17 : too low level on the uplink in a cell compared to a high threshold cause 18 : too low level on the downlink in a cell 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



1 1 91

6 Main Standard Handover Algorithms



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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



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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 L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO



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Handover Cause 3: UL Level

CAUSE 3: too low level on the uplink



QUAL

LEV

AV_RXQUAL_UL_HO



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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 L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO



1 1 96


Handover Cause 5: DL Level

CAUSE 5: too low level on the downlink



QUAL

LEV

AV_RXQUAL_UL_HO



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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

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO = ENABLED



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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)

May be triggered

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 1 99


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





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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





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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



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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

OUTER



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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



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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)



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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.



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If EN_MULTIBAND_PBGT_HO = disable

Single 900

Upper 900

900

900 1800

indoor900

Upper 1800

900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

fast

fast

fast

fast

fast

Upper

Upper



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If EN_MULTIBAND_PBGT_HO = enable

Single 900

Upper 900

900

900 1800

indoor900

Upper 1800

900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

Upper

Upper

fast

fast

fast

fast

fast



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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)

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)

(A)

(B)

(C)

(D)



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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 (*)





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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)



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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)



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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



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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






1 1 114


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




1 1 115


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



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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)



1 1 117


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



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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



1 1 119


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



1 1 120


Exercise

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

UMBRELLA

LOWER

INDOOR



1 1 121


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



1 1 122


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



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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

May be triggered

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 1 124


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 1 125


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



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Detection of cause 12

Parameters settings

No Power Control DL, no anti ping-pong

EN_PBGT_HO = enable

EN_TRAFFIC_HO(0,n) = disable


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 1 127

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



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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 1 129


Exercise [cont.]


EN_MULTIBAND_PBGT_HO = ENABLE

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



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7 Emergency Handover Algorithms for MBML Networks



1 1 131


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 1 132


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

umbrella single

mini

umbrella

mini



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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

May be triggered

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



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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


EVOLIUM Base Station Subsystem Multiband and Multilayer GSM network radio

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