19 HCS Handover

RAN Feature Description Table of Contents

Table of Contents

Chapter 19 HCS Handover........................................................................................................19-1

19.1 Introduction to HCS......................................................................................................19-1

19.1.1 Definition...........................................................................................................19-1

19.1.2 Purposes...........................................................................................................19-2

19.1.3 Terms and Abbreviations...................................................................................19-2

19.2 Availability....................................................................................................................19-3

19.2.1 Network Elements Involved...............................................................................19-3

19.2.2 Software Releases............................................................................................19-3

19.3 Impact.......................................................................................................................... 19-4

19.3.1 On System Performance...................................................................................19-4

19.3.2 On Other Features.............................................................................................19-4

19.4 Technical Description...................................................................................................19-4

19.4.1 HCS Handover Configuration Model.................................................................19-4

19.4.2 Overview...........................................................................................................19-5

19.4.3 Speed Estimation for UE...................................................................................19-6

19.4.4 HCS Handover Based on Speed Estimation...................................................19-10

19.4.5 Signaling Procedure for HCS Handover..........................................................19-11

19.4.6 HCS Handover and Other Features................................................................19-11

19.5 Specifications.............................................................................................................19-12

19.6 Implementation..........................................................................................................19-12

19.6.1 Enabling HCS..................................................................................................19-12

19.6.2 Reconfiguring HCS Parameters......................................................................19-14

19.6.3 Disabling HCS Handover.................................................................................19-16

19.7 Maintenance Information............................................................................................19-17

19.7.1 MML commands..............................................................................................19-17

19.7.2 Alarms.............................................................................................................19-18

19.7.3 Counters..........................................................................................................19-18

19.8 References................................................................................................................. 19-18

Huawei Technologies Proprietary

i

RAN Feature Description List of Figures

List of Figures

Figure 19-1 HCS with three hierarchies..............................................................................19-1

Figure 19-2 HCS Handover configuration model................................................................19-5


ii

RAN Feature Description List of Tables

List of Tables

Table 19-1 NEs required for HCS handover........................................................................19-3

Table 19-2 RAN products and related versions...................................................................19-4

Table 19-3 Commands for reconfiguring speed estimation algorithm parameters.............19-14


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RAN Feature Description Chapter 19 HCS Handover

Chapter 19 HCS Handover

19.1 Introduction to HCS

19.1.1 Definition

In 3G network, the so-called hot spots in radio communications may appear with the

increase of subscribers and traffic. This requires more cells to increase the network

capacity. More cells and smaller cell radius indicate that more frequent handovers of

UEs take place. For a UE in fast speed, frequent handovers reduce call quality,

increase uplink interference, and increase signaling load.

In this situation, Hierarchical Cell Structure (HCS) is required to divide cells into

different hierarchies.

Huawei RNC supports the HCS with 8 hierarchies, Figure 19-1 shows a HCS with

three hierarchies.

Figure 19-1 HCS with three hierarchies

The features of different cells are as follows:

macro cell

Large coverage

Continuous coverage networking

Low requirement on capacity

Fast-moving environment

Micro cell

Densely populated areas

High requirement on capacity

Slow-moving environment

Pico cell


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Indoor coverage

Outdoor dead-area coverage

Where, the pico cell has the highest priority and the macro cell has the lowest priority.

19.1.2 Purposes

According to speed estimation, the RNC order the fast-moving UE to handover to the

cells of lower priority to reduce the number of handovers, and order the slow-moving

UEs to handover to the cells of higher priority to increase network capacity. The cells

of lower priority have larger coverage, and the cells of higher priority have smaller

coverage.

19.1.3 Terms and Abbreviations

I. Terms

Term Description

Hot Spot A cell that has high traffic and a large quantity of users

1D event Best cell updating event

II. Abbreviations

Abbreviation Full Spelling

3G 3rd Generation

3GPP 3rd Generation Partnership Project

CN Core Network

DL Downlink

DRNC Drift RNC

DS-CDMA Direct-Sequence Code Division Multiple Access

FDD Frequency Division Duplex

HCS Hierarchical Cell Structure

HO Handover

IE Information Element

MS Mobile Station


2


Abbreviation Full Spelling

PC Power Control

RL Radio Link

RNC Radio Network Controller

RRM Radio Resource Management

SHO Soft Handover

SIR Signal to Interference Ratio

SRNC Serving RNC

TPC Transmit Power Control

UE User Equipment

UL Uplink

UTRAN UMTS Terrestrial Radio Access Network

WCDMA Wideband Code Division Multiple Access

19.2 Availability

19.2.1 Network Elements Involved

The realization of HCS handover depends on the cooperation of the UE and RNC.

Table 19-1 shows the Network Elements (NEs) required for HCS handover.

Table 19-1 NEs required for HCS handover

UE NodeB RNCMSC

ServerMGW SGSN GGSN HLR

√ – √ – – – – –

Note:

–: not required

√: required


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19.2.2 Software Releases

Table 19-2 describes the versions of the RAN products that support the HCS

handover.

Table 19-2 RAN products and related versions

Product Version

RNC BSC6800 V100R006 and later releases

19.3 Impact

19.3.1 On System Performance

The impacts of HCS handover on system performance are as follows:

Improve the conversation quality for fast-moving UEs

Improve the system capacity

Reduce the signaling load

19.3.2 On Other Features

The impacts of HCS handover on other features are as follows:

The HCS handover does not interfere with other RAN features' ability to take

effect.

For more about the relationship between HCS handover and other features, see

section 19.4.6 "HCS Handover and Other Features."

19.4 Technical Description

19.4.1 HCS Handover Configuration Model

The configuration model for HCS Handover is as show in Figure 19-2.


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CELLHCSHO.Class

RNC

RadioClass

GlobalParaClass CellClass

Period of UE slow speed decision

Time window for UE slow speed decision

HCSHO.Class

Threshold for UE slow speed decision

Threshold for UE fast speed decision

Time window for UE fast speed decision

Related length for 1D records

Figure 19-2 HCS Handover configuration model

19.4.2 Overview

The HCS handover is divided into the following two phases:

I. Speed Estimation

The speed estimation on each hierarchy of an HCS cell falls into one of the following

types:

Fast speed

Normal speed

Slow speed

According to the number of changes of the best cell within time unit, speed estimation

algorithm estimates the moving speed of the UEs. See details as follows:

If the number of changes of best cell for a UE is above the fast-speed threshold,

this UE is decided in fast speed;

If the number of changes of best cell for a UE is below the slow-speed threshold,

this UE is decided in slow speed;

if the number of changes of best cell for a UE is between fast-speed threshold

and slow-speed threshold, this UE is decided in normal speed.


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II. HCS Handover Based on Speed Estimation

After the moving speed of the UE is estimated, inter-hierarchy handover algorithm

initiates the corresponding handover based on this speed decision.

According to the results of speed estimation,

The UE in fast speed is handed over to the cell of lower priority.

The UE in slow speed is handed over to the cell of higher priority.

The UE in normal speed is not required to be handed over to any cell.

19.4.3 Speed Estimation for UE

I. Fast Speed Estimation

The UE fast speed decision is triggered by 1D event.

Tfast: time for UE fast speed decision Time window for UE fast speed

decision

Nfast: threshold for UE fast speed decision Threshold for UE fast speed

decision

Handover procedures:

(1) The UE fast speed decision is triggered after the 1D report is received.

(2) The UE is decided in fast speed if the number of changes of best cells for the

UE is above Threshold for UE fast speed decision within Time window for

UE fast speed decision.

Parameters:

Parameter Name Time window for UE fast speed decision

Parameter ID TFASTSPDEST

GUI Range 0–511

Physical Range& Unit 0–511, Unit: s

Default Value 180

Optional/Mandatory Optional

MML Command ADD CELLHCSHO / MOD CELLHCSHO

SET HCSHO

Description:

Statistic duration for UE fast speed decision


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Parameter Name Threshold for UE fast speed decision

Parameter ID NFASTSPDEST

GUI Range 1–16

Physical Range& Unit 1–16

Default Value 15



SET HCSHO

Description:

Threshold of the number of the best cell changes during [TFastSpdEst] for UE fast

speed decision. UE is considered in fast state when the number of the best cell

changes during [TFastSpdEst] is larger than [NFastSpdEst].

II. Slow Speed Estimation

The UE slow speed decision is triggered by the expiry of the periodical timer.

Tslow: time for UE slow speed decision Time window for UE slow speed

decision

Nslow: threshold for UE slow speed decision Threshold for UE slow speed

decision

Periodic timer for slow speed decision: The length of the periodic timer is set to

Period of UE slow speed decision.

Handover procedures:

(1) The UE slow speed decision is triggered after the periodic timer for slow speed

decision is expired.

(2) The UE is decided in slow speed if the number of changes of best cells for the

UE is below Threshold for UE slow speed decision within Time window for

UE slow speed decision

Parameters:


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Parameter Name Time window for UE slow speed decision

Parameter ID TSLOWSPDEST

GUI Range 0–511

Physical Range& Unit 0–511. Unit: s

Default Value 240



SET HCSHO

Description:

Statistic duration for UE slow speed decision

Parameter Name Threshold for UE slow speed decision

Parameter ID NSLOWSPDEST

GUI Range 1–16

Physical Range& Unit 1–16

Default Value 3



SET HCSHO

Description:

Threshold of the number of best cell changes during [TSlowSpdEst] for UE slow

speed decision. UE is considered in slow state when the number of the best cell

changes during [TSlowSpdEst] is smaller than [NSlowSpdEst].

Configuration Rule and Restriction:


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Number of the best cell changes for the unit time duration of fast state must not be

less than that of slow state, that is,

Threshold for UE fast speed decision / Time window for UE fast speed

decision

≥

Threshold for UE slow speed decision / Time window for UE slow speed

decision

Parameter Name Period of UE slow speed decision

Parameter ID TCYCLESLOW

GUI Range 0–255

Physical Range& Unit 0–255. Unit: s

Default Value 60



SET HCSHO

Description:

Cycle of UE slow state decision. Whether the UE is in slow state is judged at the

end of [TcycleSlow].

III. Anti-Pingpong 1D Recording

During a given period of time, intra-frequency handover may be performed back and

forth across two or three cells, resulting in several event 1Ds of the same cell in the

statistic queue and thus inaccurate UE speed estimation.

Therefore, a mechanism is used for anti-pingpong 1D recording. During the recent

period Related length for 1D records, 1D event with repeated cell would not be

recorded.


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Parameter Name Related length for 1D records

Parameter ID TRELATELENGTH

GUI Range 0–120

Physical Range& Unit 0–120. Unit: s.

Default Value 10



SET HCSHO

Description:

During a given period of time, intra-frequency handover may be performed back

and forth across two or three cells, resulting in several event 1Ds of the same cell

in the statistic queue and thus inaccurate UE speed estimation. During the latest

[TRelateLength], if more than one event 1D of a certain cell occurs, the event 1D

record is restored to the state when the first event 1D occurs during the latest

[TRelateLength].

19.4.4 HCS Handover Based on Speed Estimation

I. Fast Inter-Hierarchy Handover

When the RNC decides that the UE is in fast speed, this UE is handed over from the

cell of high priority to the cell of low priority.

If the UE is located at the converged part between the cell of high priority and the cell

of low priority, the blink handover is initiated.

The target cell can be a UMTS cell or a GSM cell. The priority of intra-system inter-

frequency blind handover is higher than that of inter-system blind handover. If the

neighboring cell for blind handover is not configured or the blind handover fails, the

measurement is initiated for cells of low priority. The target cell is decided based on

the measurement report from the UE.

II. Slow Inter-Hierarchy Handover

When the RNC decides that the UE is in slow speed, this UE is handed over from the

cell of low priority to the cell of high priority.

Because the coverage of high priority cells is smaller than that of low priority cells,

slow speed inter-hierarchy handover algorithm needs to initiate the measurement for


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cells of high priority, and then decides the target cell based on the measurement

report from the UE.

19.4.5 Signaling Procedure for HCS Handover

The signaling procedure for HCS handover is the same as that for inter-frequency

handover and inter-system handover. For detailed information, see section "inter-

frequency handover" and "inter-system handover."

19.4.6 HCS Handover and Other Features

The section describes the cooperation between HCS handover and other handover,

including:

The Cooperation between HCS Handover and Intra-Frequency

Handover

The Cooperation between HCS Handover and Inter-Frequency

Handover

The cooperation between HCS handover and inter-RAT handover

I. The Cooperation between HCS Handover and Intra-Frequency Handover

If HCS handover measurement is initiated when intra-frequency cell measurement is

ongoing and the intra-frequency handover is required, the HCS handover

measurement is not interrupted in the process of intra-frequency handover. After the

intra-frequency handover, if the best cell remains, the inter-hierarchy measurement

continues; and if the best cell changes, the fast speed estimation for the UE is

triggered.

For more information about intra-frequency handover, see section "intra-frequency

handover".

II. The Cooperation between HCS Handover and Inter-Frequency Handover

The causes to trigger inter-frequency handover include the follows:

Report of 2D event

Imbalanced load between inter-frequency cells

Estimation decision for UE speed in HCS

Where, the report of 2D event indicates that the inter-frequency handover based on

coverage is triggered, which is of high priority to be processed.

If the HCS handover algorithm is performing inter-frequency measurement when the

2D event is reported, the measurement control of inter-frequency measurement will

be updated according to the algorithm of inter-frequency handover based on

coverage.


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If the RNC is performing inter-frequency measurement after the 2D event is reported,

that is, the inter-frequency measurement based on coverage, HCS handover will not

be processed.

When the inter-frequency handover based on load is required to be triggered due to

imbalanced load between inter-frequency cells, this handover will not be triggered if

the HCS handover algorithm is performing inter-frequency inter-hierarchy

measurement.

On the other hand, when the RNC is performing inter-frequency measurement for

handover based on load, the HCS handover cannot be initiated even the speed

estimation algorithm decides that the UE is in fast speed or in low speed.

For more information about inter-frequency handover, see section "inter-frequency

handover".

III. The cooperation between HCS handover and inter-RAT handover

It is strongly recommended that the inter-RAT handover to 2G is not used in HCS

handover.

To disable this procedure, make configurations as follows:

Disable HCS priority setting for GSM neighboring cells. For more details about

HCS priority settings, refer to Chapter 2 "UE Behaviors in Idle Mode."

For the UMTS layer whose HCS priority is next-higher to GSM layer, use

maximum value for Threshold for UE fast speed decision so that the fast inter-

hierarchy handover (from UMTS to GSM) will not be triggered.

For the UMTS layer whose HCS priority is next-lower to GSM layer, use

minimum value for Threshold for UE slow speed decision so that the slow

inter-hierarchy handover (from UMTS to GSM) will not be triggered.

19.5 Specifications

None.

19.6 Implementation

19.6.1 Enabling HCS

I. Hardware Installation

This feature does not need extra hardware because the algorithm module for the

HCS handover is integrated in the RNC.

II. License Update

To enable the HCS handover, you need to purchase a license for HCS handover from

Huawei Technologies Co., Ltd., and then perform the following steps:


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2) Obtain a new license.

3) Download the file through FTP to the BAM directory "BAM installation directory\

FTP \license".

4) On the M2000 or RNC LMT, run this new License.

III. Data Configuration

To configure the parameters for the HCS handover, perform the following steps:

5) Execute the MML command ADD CELLHCS to set the HCS attributes of this

cell.

6) Execute the MML command SET CORRMALGOSWITCH to set RNC oriented

HCS speed estimation handover switch.

7) Execute the MML command SET HCSHO to set RNC oriented HCS speed

estimation handover algorithm parameters.

8) Execute the MML command ADD CELLHCSHO to set cell oriented HCS speed

estimation handover algorithm parameters.

Note:

Step 4 is optional.

If step 4 is not included, adopt the parameters in step 3.

IV. Enabling the HCS

To enable the HCS handover, perform the following step:

9) Execute the MML command LST CELLHCS to check whether the parameter

UseOfHcs is USED.

10) Execute the MML command LST CORRMALGOSWITCH to check whether the

parameter HCS_SPD_EST_SWITCH is 1.

11) Execute the MML command LST CELLHCSHO to check whether the parameter

SpdEstSwitch is ON.

V. Examples

//(1) Obtain License

Download the file through FTP to the BAM directory "BAM installation

directory\FTP\license"

//(2) Activate the LICENSE

ACT LICENSE: FN="Filename";


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//(3) Execute the DSP LICENSE command to check whether the RNC gets the

authorization of HCS handover

DSP LICENSE:;

//(4) Set cell HCS attributes

ADD CELLHCS: CELLID=1000, USEOFHCS=USED, HCSPRIORITYLEVEL=3, SSEARCHHCS=0,

SHCSRAT=0, QHCS=20, TCRMAX=D60, CRMAXNUM=8, TCRMAXHYST=D20,

SLIMITSEARCHRAT=0;

//(5) Set RNC oriented HCS speed estimation handover switch

SET CORRMALGOSWITCH: HoSwitch=HCS_SPD_EST_SWITCH-1;

//(6) Set RNC oriented HCS speed estimation handover algorithm parameters

SET HCSHO: TFastSpdEst=180, NFastSpdEst=15, TCycleSlow=60,

TSlowSpdEst=240, NSlowSpdEst=3, TRelateLength=10;

//(7) Set cell oriented HCS speed estimation handover algorithm parameters

ADD CELLHCSHO: CellId=1000, SpdEstSwitch=ON, TFastSpdEst=180,

NFastSpdEst=15, TCycleSlow=60, TSlowSpdEst=240, NSlowSpdEst=3,

TRelateLength=10;

//(8) Query the status of RNC oriented HCS speed estimation handover

switch

LST CORRMALGOSWITCH: LstFormat=VERTICAL;

Where, the parameter HCS_SPD_EST_SWITCH is 1.

19.6.2 Reconfiguring HCS Parameters

I. Parameter Reconfiguration

The commands for reconfiguring HCS handover fall into the following categories:

Table 19-1 shows the commands for reconfiguring speed estimation algorithm

parameters.

For information about commands for reconfiguring handover algorithm

parameters based on non-coverage, see section "inter-frequency handover" and

"inter-system handover."


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Table 19-1 Commands for reconfiguring speed estimation algorithm parameters

Function Command

Reconfigure RNC

oriented speed

estimation algorithm

parameters

Query RNC oriented

speed estimation

algorithm parameters

LST HCSHO

Set RNC oriented speed


parameters

SET HCSHO

Reconfigure cell oriented

speed estimation


Query cell oriented

speed estimation


LST CELLHCSHO

Set cell oriented speed


parameters

MOD CELLHCSHO

Reconfigure cell

hierarchical attributes

and hierarchical priority

Query cell hierarchical

attributes and

hierarchical priority

LST CELLHCS

Set cell hierarchical

attributes and

hierarchical priority

MOD CELLHCS

Reconfigure RNC

oriented speed


switch

Query connection

oriented algorithm switch

LST

CORRMALGOSWITCH

Set connection oriented

algorithm switch

SET

CORRMALGOSWITCH

Reconfigure cell oriented

speed estimation

algorithm switch

Query cell oriented

speed estimation

algorithm switch

LST CELLHCSHO

Set cell oriented speed


switch

MOD CELLHCSHO

II. Verification of Parameter Reconfiguration

To verify the parameter reconfiguration, perform the following steps:


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12) Execute the MML command LST CELLHCS query the parameters Use of HCS

and HCS priority Level.

13) Execute the MML command LST CORRMALGOSWITCH to query the

parameter HCS_SPD_EST_SWITCH.

14) Execute the MML command LST HCSHO to query the RNC oriented

reconfigured parameters.

15) Execute the MML command LST CELLHCSHO to query cell oriented

reconfigured parameters.

For information about verification of reconfiguring handover algorithm parameters

based on non-coverage, see section "inter-frequency handover" and "inter-system

handover."

III. Examples

//Reconfigure cell hierarchical attribute and hierarchical priority

//(1) Query cell hierarchical attribute and hierarchical priority

LST CELLHCS: CellId=10101, LstFormat=VERTICAL;

//(2) Set cell hierarchical attribute and hierarchical priority

MOD CELLHCS: CELLID=10101, USEOFHCS=USED, HCSPRIORITYLEVEL=3;

//(3) Execute the LST CELLHCS command to check whether cell hierarchical

attribute and hierarchical priority are reconfigured.

LST CELLHCS: CellId=10101 LstFormat=VERTICAL;

// The output results indicate that the parameters are reconfigured

//Reconfigure RNC oriented speed estimation algorithm switch

//(1) Query RNC oriented speed estimation algorithm switch


//(2) Set RNC oriented speed estimation algorithm switch

SET CORRMALGOSWITCH: HOSWITCH=HCS_SPD_EST_SWITCH-1;

//(3)Execute the LST CORRMALGOSWITCH command to check whether RNC oriented

speed estimation algorithm switch are reconfigured.


//The output results indicate that the parameters are reconfigured

//Reconfigure RNC oriented HCS speed estimation algorithm parameters

//(1)Query RNC oriented HCS speed estimation algorithm parameters

LST HCSHO: LstFormat=VERTICAL;

//(2) Set RNC oriented HCS speed estimation algorithm parameters

SET HCSHO: TFastSpdEst=180, NFastSpdEst=15, TCycleSlow=60,

TSlowSpdEst=240, NSlowSpdEst=3, TRelateLength=10;

//(3) Execute the LST HCSHO command to check whether RNC oriented HCS

speed estimation algorithm parameters are reconfigured.


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LST HCSHO: LstFormat=VERTICAL;


//Reconfigure cell oriented HCS speed estimation algorithm parameters

//(1) Query cell oriented HCS speed estimation algorithm parameters

LST CELLHCSHO: CellId=10101, LstFormat=VERTICAL;

//(2) Set cell oriented HCS speed estimation algorithm parameters

MOD CELLHCSHO: CellId=10101, TFastSpdEst=180, NFastSpdEst=15,

TCycleSlow=60, TSlowSpdEst=240, NSlowSpdEst=3, TRelateLength=10;

//(3)Execute the LST CELLHCSHO command to check whether cell oriented HCS

speed estimation algorithm parameters are reconfigured

LST CELLHCSHO: CellId=10101 LstFormat=VERTICAL;


19.6.3 Disabling HCS Handover

I. Method of Disabling HCS handover

To disable the HCS handover, perform the following commands:

16) Execute the MOD CELLHCSHO command to disable cell oriented HCS

handover.

17) Execute the SET CORRMALGOSWITCH command to disable RNC oriented

HCS handover.

II. Verification of the disabled feature

18) Execute the LST CELLHCSHO command to check whether cell oriented HCS

handover is disabled.

19) Execute the LST CORRMALGOSWITCH command to check whether RNC

oriented HCS handover is disabled.

III. Examples

//(1) Disable cell oriented HCS handover

ADD CELLHCSHO: CellId=10101, SpdEstSwitch=OFF;

//(2) Execute the LST CELLHCSHO command to check whether the SpdEstSwitch

is OFF

LST CELLHCSHO: CellId=10101, LstFormat=VERTICAL;

//The output results show that the SpdEstSwitch is OFF.

//(3) Deactivate RNC oriented HCS handover

SET CORRMALGOSWITCH: HOSWITCH=HCS_SPD_EST_SWITCH-0


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//(4) Execute the LST CORRMALGOSWITCH command to check whether RNC

oriented HCS_SPD_EST_SWITCH is 0


//The output results show that the HCS_SPD_EST_SWITCH is 0

19.7 Maintenance Information

19.7.1 MML commands

ADD CELLHCS

This command is executed to set the attributes of HCS in UMTS cell.

ADD GSMCELL

This command is executed to set the attributes of HCS in GSM cell.

SET HCSHO

This command is executed to set RNC oriented algorithm parameters for HCS

handover.

ADD CELLHCSHO

This command is executed to set cell oriented algorithm parameters for HCS

handover.

19.7.2 Alarms

None.

19.7.3 Counters

None.

19.8 References

3GPP TS 23.331 "Radio Resource Control (RRC); protocol specification".

3GPP TS 25.304 "User Equipment (UE) procedures in idle mode and

procedures for cell reselection in connected mode".


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Documents

19 HCS Handover