had overs

Soc Classification level 1 © Nokia Siemens Networks Presentation / Author / Date

WCDMA Handovers


Handover types

Soft Handover

4

Hard/Inter-Frequency Handover

Inter-System Handover

Node B

Frequencyf1

Frequencyf1

Frequencyf1

Frequencyf2

UMTS GSM900/1800

Frequencyf1

Frequencyf1

RNC RNC

Iur

Iub Iub

Node B

Node B Node B

Node BNode B

Softer Handover

Sector 1f1

Sector 2f1

Sector 3f1

Sector 1

Sector 3

Node B

Node B BTS


Node B

UTRAN

RNC

UE

System Information [BCCH]

I am in the RRC idle mode

Node B

UTRAN

RNC

UE

System Information [BCCH]

I am in the CELL_FACH, CELL_PCH or

URA_PCH sub-state

Node B

UTRAN

RNC

UE

Measurement Control [DCCH]

I am in the CELL_DCH sub-state

SIB 3 & SIB 11

SIB 4 & SIB 12(SIB 3 & SIB 11)

• SIB 3 [4]: parameters for cell selection and re-selection [in the RRC connected mode]

• SIB 11 [12] : measurement control information [in the RRC connected mode]read and valid: idle, CELL_FACH, CELL_PCH, URA_PCH.(SIB 11/12 is also valid in the CELL_DCH.)

Measurement Control


UE RNC

Measurement Control [RLC-AM, DCCH]

UE RNC

Measurement Control [RLC-AM, DCCH]

[RLC-AM, DCCH] Measurement Control Failure

UE RNC

[RLC-UM/AM, DCCH] Measurement Report

There is a measurement

event!

Measurement Control and Measurement Report


UE IEs

Measurement IEs

PhyCH IEs

Measurement Identity

Measurement Command

Measurement Reporting Mode

CHOICE Measurement type

Additional measurements list

DPCH compressed mode status info

setup/modify/release

RLC AM/UM andperiodical reporting/event triggered

includes non-frequencyrelated cell info

UERNC

Measurement Control ( )

Measurement Control

Measurement Type Measurement Events

Part II Traffic Volume Measurement

4A, 4B

Part III

UE Internal Measurements

6A, 6B, 6C, 6D, 6E, 6F, 6G

Part IV

Quality Measurements 5A

Part V Intra-Frequency Measurements

1A, 1B, 1C, 1D, 1E, 1F

Part VI

Inter-Frequency Measurements

2A, 2B, 2C, 2D, 2E, 2F

Part VII

Inter-RAT Measurements 3A, 3B, 3C, 3D


Maximum number of neighbours

The maximum number of neighbours that can be defined in RNC database is

• ADJS: 31

– 31 neighbours + serving cell = 32 cells to measure

• ADJI: 32/carrier, total 48

• ADJG: 32


Soft Handover

HC supports the following measurement reporting events and features:

• Event 1A: A primary CPICH enters the reporting range (Ncell addition)

• Event 1B: A primary CPICH leaves the reporting range (Ncell deletion)

• Event 1C: A non-active CPICH becomes better than an active primary CPICH (Ncell replacement)

•Handover decision performed by RNC based on measurements and available resources

•Admission Control can reject the branch addition in case the maximum load is achieved in DL (threshold + offset), valid both for RT and NRT bitrates.

•Hard blocking may prevent branch addition


4

1A: A Primary CPICH Enters the Reporting Range

Strongest CPICH in AS

time

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

1

2

3

AdditionWindow

AdditionTime

AdditionReportingInterval

RNC

MeasurementReport

To theAS?

no

ActiveSetWeightingCoefficient


CoreNetwor

k

ACTIVE SET UPDATE

Addition A-I

Handover

Control

RADIO LINK ADDITION REQUEST

NBAPNBAP

RADIO LINK ADDITION RESPONSE NBAPNBAP

ALCAP ALCAPERQ

ECFALCAP ALCAP

Uplink SyncFP FP

FP FPDownlink SyncRequired for soft handover

Cell 1 Cell 2

RRC RRCMEASUREMENT CONTROL

RRCRRC MEASUREMENT REPORT (DCCH): e1a

Active AMR Call ongoing

Admission Control

RRC RRCACTIVE SET UPDATE

RRC RRC ACTIVE SET UPDATE

COMPLETE

RRC RRCMEASUREMENT CONTROL

New Cell has been Added and Neighbour lists are updated


Strongest CPICH in AS

time

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

1

2

3

DropWindow

DropTime

MeasurementReport

1B: A Primary CPICH Leaves the Reporting Range

Remove the

reported cell from the AS


SHO_e1b

UE BTS RNC

Handover tresholds fulfilled (MEHO)- Event 1B is triggered

RRC: Active Set Update Request

RRC Measurement Report

RRC: Active Set Update Complete

NBAP: Radio Link Deletion Request

NBAP: Radio Link Deletion Response

RRC: Measurement Control


time

weakest CPICH3 in AS

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

P CPICH 4

AS has 3 cells

ReplacementReportingInterval3

1

2

ReplacementWindow

ReplacementTime

MeasurementReport

RNC

ASupdate?

no

1C: A non-active CPICH becomes better than an active primary CPICH


SHO_e1c

UE BTS RNC

Handover tresholds fulfilled (MEHO)- Event 1C is triggered

RRC: Active Set Update Request

RRC: Measurement Report

NBAP:Radio Link Addition Response

NBAP: Radio Link Addition Request

RRC: Active Set Update Complete

NBAP: Radio Link Deletion Request

NBAP: Radio Link Deletion Response



Cell 5

Cell 6 Cell 7 Cell 8

Cell 9Cell 10

Cell 11

Cell 12

Cell 1 Cell 2 Cell 3 Cell 4

Neighbour List Cell 6:

•Cell 2•Cell3•Cell 7•Cell 11•Cell 10•Cell 5

Neighbour List Cell 7:

•Cell 3•Cell4•Cell 8•Cell 12•Cell 11•Cell 6

Cell 3

Cell11

Cell 3

Cell11

Neighbour cells which are common to Cell 6 and Cell 7 Cell 4

Cell 8

Cell 12

Cell 6

Cell 4

Cell 8

Cell 12

Cell 6

Neighbour cells defined only for

Cell 7

Cell 2

Cell7

Cell 10

Cell 5

Cell 2

Cell7

Cell 10

Cell 5

Neighbour cells defined only for

Cell 6

Two Cells in the Active Set

Neighbourhood List Combination for Intra-frequency HOs


Cell 2

Cell 5

Cell 7

Cell 9

Cell 11

Cell 15

Cell 48

Cell 4

Cell 41

Cell 6

..

...

Cell 43

Cell 2

Cell 5

Cell 7

Cell 9

Cell 11

Cell 15

Cell 48

Cell 4

Cell 41

Cell 6

..

...

Cell 43

Cell 15

Cell 21

Cell 2

Cell 7

Cell 37

Cell 51

Cell 49

Cell 9

Cell 10

Cell 56

…

...

Cell 25

Cell 15

Cell 21

Cell 2

Cell 7

Cell 37

Cell 51

Cell 49

Cell 9

Cell 10

Cell 56

…

...

Cell 25

Cell 1

Cell 2

Cell 3

Cell 7

Cell 11

Cell 50

Cell 9

Cell 13

Cell 10

Cell 22

…

...

Cell 33

Cell 1

Cell 2

Cell 3

Cell 7

Cell 11

Cell 50

Cell 9

Cell 13

Cell 10

Cell 22

…

...

Cell 33

Neighbour Cells Lists

Step 1Step 1

Three Cells in the Active Set

Cell2

Cell 7

Cell 9

Cell2

Cell 7

Cell 9

Common to 3 Neighbour Lists

Step 2Step 2

Cell 11

Cell 15

Cell 10

Cell 11

Cell 15

Cell 10Cell 37

Cell 41

Cell 49

…..

…

Cell 22

Cell 37

Cell 41

Cell 49

…..

…

Cell 22

Max 32

Cells

Neighbour Cells defined for only 1

Neighbour list: best Ec/No first Step 4Step 4

Common to 2

Neighbour Lists

Step 3Step 3

Neighbourhood List Combination for Intra-frequency HOs


Intersystem Handovers


3G 2G interworking

• Handover from GSM to WCDMA or vice-versa is an inter-RAT HHO

• Interworking is also possible in Idle Mode when making cell selection

• Handover reasons are mainly based on coverage in WCDMA and load in GSM

• Compressed Mode is used in WCDMA for inter-RAT neighbour measurements before handover decision

• Service downgrade / upgrade might be needed during inter-RAT handover

• GSM to WCDMA initiated by the GSM radio network

• WCDMA to GSM initiated by the WCDMA radio network (UTRAN)


• The problem: A CS call takes place. The UE is in the CELL_DCH sub-state. There is a continuous transmission both in the uplink and downlink direction. UTRAN wants the UE to perform inter-frequency and inter-RAT measurements to support inter-frequency handovers.

• But how can the UE make measurements on other frequency carriers except for the serving frequency carrier, when it has to receive continuously data?

• There are two ways to overcome the problem: •Either the UE has a dual receiver, or •The compressed mode is applied.

Compressed Mode (= Slotted Mode)


radio frame radio frame

TGL

3, 4, 5, 7, timeslots

radio frame radio frame

TGL

Single-frame method

Double-frame method

transmitted TSs: 8

Compressed Mode: Transmission Gap Methods


TGPL1 TGPL2

TG Pattern 1

TGPattern 2

TG Pattern 1

TGPattern 2

TGPattern 2

TG Transmission Gap TGL Transmission Gap LengthTGPL Transmission Gap Pattern Length TGD Transmission Gap start DistanceTGSN Transmission Gap Starting slot Number TGPRC TG Pattern Repeat Count

TG Pattern 1 TG Pattern 2

TGSNTGL1 TGL2TGL1TGL2

TGD TGD

#1 #2 #3 #4 #TGPRC

TGCNF transmission gap pattern sequence

Compressed Mode (Slotted Mode)


Handover Triggering Thresholds set in RNC

Handover Triggering Thresholds set in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

RNC commands the UE to start IS measurements periodically

RNC commands the UE to start IS measurements periodically

Measurements are done in Compressed Mode (CM)

Measurements are done in Compressed Mode (CM)

UE reports best GSM cells having strongest RSSI results back to RNCUE reports best GSM cells having

strongest RSSI results back to RNC

RNC makes HO decision andcommands UE to target cell

RNC makes HO decision andcommands UE to target cell

RSSI measurements and verification for GSM cellsRSSI measurements and verification for GSM cells

Inter System Handover 3G -> 2G Procedure

•ISHO measurements can be triggered for different reasons•To measure GSM frequencies, 3G UE needs (a) dual receiver or (b) Compressed Mode capability

• CM to ‘create’ gap during which BCCH frequencies on the 2G network can be measured•CM introduces a delay which depends on the measurement reason and pattern used

•Two types of CM measurements; GSM RSSI & GSM BSIC verification (verification is not normally done for NRT)

•Methods for implementing CM are (i) High Layer Scheduling (HLS), (ii) Spreading Factor Halving (SF/2)

•Handover decision driven by RNC using measurements made by UE•Compressed Mode affects 3G coverage, capacity and quality

!


Downlink DPCH powerDownlink DPCH power UL Quality deteriorationUL Quality

deterioration UE Tx powerUE Tx power CPICH RSCPCPICH RSCP CPICH Ec/I0CPICH Ec/I0

RAN Internal measurements Configured UE measurements

Initiate Compressed ModeConfigure GSM measurements


GSM cellmeets HO condition ?

GSM cellmeets HO condition ?

Initiate HandoverInitiate Handover



UE Reports GSM BSIC measurements

UE Reports GSM BSIC measurements

UE Reports GSM RSSI measurements

UE Reports GSM RSSI measurements

No

Yes

Is BSCI verificationrequired?

Is BSCI verificationrequired?

No

Yes

Inter System Handover 3G -> 2G Procedure


1. Measurement trigger CPICH Ec/No

Reporting event: 1E: A P-CPICH exceeds an absolute threshold 1F: A P-CPICH falls below an absolute threshold

(HO triggered if all)

time

Cell 1 Cell 2

Cell 3

absolutethreshold

e.g

. P

-CP

ICH

Ec/N

o

1E: HHoEcNoCancel

1E: HHoEcNoCancelTime

1F: HHoEcNoThreshold

1F: HHoEcNoTimeHysteresis


Compressed Mode Procedure

•RNC informs UE of CM pattern and 2G neighbour list in RRC: Measurement Control message

•3GPP states that the UE must be capable of recording a minimum number of GSM RSSI measurement samples per transmission gap

•GSM RSSI measurements are made without acquiring GSM synchronisation

•UE reports on strongest 6 GSM neighbours at periodic interval defined by GSMMeasRepInterval

•RNC applies a sliding averaging window to the measurements provided by the UE

•RNC instructs UE to perform BSIC verification (AMR=always, PS=as required) using new CM pattern

•BSIC verification needs synchronisation to GSM frame

RNC commands the selected UEs to enter compressed

mode and provides compressed mode parameters

and neighbour list

During the DL reception gap UE can make measurements

from 2G network

UE measures RSSI of GSM neighbours and reports these

to RNC periodically

RNC makes HO decision

RNC commands UE to decode BSIC of cell with strongest

RSSI

RNC sends handover command to UE

WCDMA

IS-HO trigger Target Cell found IS-HO command

RSSI measurements

BSIC verification

TRSSI TBSIC


ISHO 3G -> 2G - AMR Signaling Flow

BSIC verification always performed for AMR calls – no interrupt in voice call

CNUE

Node B

RNC



NBAP: Radio Link Reconfiguration PrepareNBAP: Radio Link

Reconfiguration ReadyNBAP: Radio Link Reconfiguration CommitRRC: Physical Channel

ReconfigurationRRC: Physical Channel Reconfiguration Complete NBAP: Compressed Mode

Command



NBAP: Compressed Mode Command



RRC: Handover from UTRAN Command

GSM BSIC Identification

GSM RSSI Measurement

ISHO triggering (5 reasons are possible)

Initial Compressed Mode Configuration

RANAP: Relocation Required

RANAP: Relocation Command

RANAP: IU Release Command

RANAP: IU Release Complete


In most cases BSIC verification is not required (data interrupt as UE moves to 2G)PS makes use of RRC: CELL CHANGE ORDER FROM UTRAN message

UE

Node B

RNC



NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete



RRC: Measurement Control GSM RSSI Measurement



CN

RANAP: SRNS Context Request

RANAP: SRNS Context Response



RRC: Cell Change Order from UTRAN

RANAP: SRNS Data Forward Command

ISHO 3G -> 2G - PS Signaling Flow


Handover Decision


CoreNetwor

k

Inter System Handover - I

MEASUREMENT CONTROL (DCCH)RRCRRC

RRC RRCMEASUREMENT REPORT (DCCH): Event 1f for first cell in Active Set

RRC RRCMEASUREMENT REPORT (DCCH): Event 1f for last cell in Active Set

Reporting event 1f triggers for first Cell

in Active set

Reporting event 1f triggers for last Cell

in Active set

Decision to activate inter-RAT measurements. Determination of CM-pattern

RL RECONFIGURATION PREPARE

NBAPNBAP

RL RECONFIGURATION READY

NBAPNBAP

RL RECONFIGURATION COMIT NBAPNBAP

RRC RRCPHYSICAL CHANNEL RECONFIGURATION (DCCH)

RRC RRCPHYSICAL CHANNEL RECONFIGURATION COMPLETE (DCCH)

COMPRESSED MODE COMMAND (CFN, TGPSI2)

NBAPNBAP


ISHO triggering


MEASUREMENT CONTROL (DCCH): RSSI, CFN, TGPSI2RRCRRC

RRC RRCMEASUREMENT REPORT (DCCH): GSM RSSI, BCCH ARFCN

RRC RRCMEASUREMENT REPORT (DCCH): GSM RSSI, BCCH ARFCN


CoreNetwor

kCOMPRESSED MODE

COMMAND (CFN, TGSPI3)NBAPNBAP


MEASUREMENT CONTROL (DCCH): BSIC, CFN, TGPSI3RRCRRC

RRC RRCMEASUREMENT REPORT (DCCH): BSIC, GSM Cell index)

RELOCATION REQUIRED RANAPRANAP

RELOCATION COMMAND RANAPRANAP

IU RELEASE COMMAND RANAPRANAP

IU RELEASE COMPLETE RANAPRANAP

RRC RRCHANDOVER FROM UTRAN COMMAND

UE is now on 2G and 3G resources have been released

RADIO LINK DELETION REQUEST

NBAPNBAP

RADIO LINK DELETION RESPONSE

NBAPNBAP

RELEASE REQUESTALCAP ALCAP

RELEASE RESPONSEALCAP ALCAP

RELEASE REQUESTALCAP ALCAP

RELEASE RESPONSEALCAP ALCAP

CoreNetwor

k

BSC

A - Interface

Handover Request BSSMAPBSSMAP

Handover Request Acknowledge

BSSMAPBSSMAP

Handover AccessRIL3-RR RIL3-RR

Inter System Handover - II

Handover Detect BSSMAPBSSMAP

Handover Complete BSSMAPBSSMAP

Handover Complete RIL3-RRRIL3-RR


ISHO 3G -> 2G - AMR Signaling Flow

BSIC verification always performed for AMR calls – no interrupt in voice call

CNUE

Node B

RNC



NBAP: Radio Link Reconfiguration PrepareNBAP: Radio Link

Reconfiguration ReadyNBAP: Radio Link Reconfiguration CommitRRC: Physical Channel

ReconfigurationRRC: Physical Channel Reconfiguration Complete NBAP: Compressed Mode

Command






RRC: Handover from UTRAN Command





RANAP: Relocation Required

RANAP: Relocation Command




In most cases BSIC verification is not required (data interrupt as UE moves to 2G)PS makes use of RRC: CELL CHANGE ORDER FROM UTRAN message

UE

Node B

RNC



NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete



RRC: Measurement Control GSM RSSI Measurement



CN

RANAP: SRNS Context Request

RANAP: SRNS Context Response



RRC: Cell Change Order from UTRAN

RANAP: SRNS Data Forward Command

ISHO 3G -> 2G - PS Signaling Flow


Different CPICH EcNo thresholds were used with setting 3:

IS-HO performance at threshold values of –11 dB and –12 dB is very similar.

Routes EcNo (IS-HO Success) % IS-HO

Threshold /(Attempts) success rate

Route 2 -11 12/12 100%-12 12/12 100%-14 3/9 33.3%

Route 4 -11 7/9 77.7%-12 8/9 88.8%-14 7/9 77.7%

Route 6 -11 13/16 81.25%-12 13/16 81.25%-14 9/20 45%-11 32/37 86.50%

Total -12 33/37 89.20%-14 19/38 50%

Inter System Handover 3G -> 2G TuningEc/No

Threshold, AMR

Ec/No Threshold,

AMR


Routes RSCP (IS-HO Success) % IS-HO

Threshold /(Attempts) success rate

-105 9/9 100%Route 2 -106 9/9 100%

-107 8/9 88%Route 3 -105 10/10 100%

-106 14/15 93.3%-107 11/15 73.3%-105 8/9 88%

Route 4 -106 8/9 88%-107 6/9 66%-105 21/25 84%

Route 6 -106 16/20 80%-107 -- ---105 48/53 90.5%

Total -106 47/53 88.7%-107 25/33 75.8%



Inter System Handover 3G -> 2G TuningRSCP

Threshold, AMR

RSCP Threshold,

AMR


2G -> 3G Handover


GSMGSM

GSMGSM

Load and Coverage Reason Handover

GSMGSM

GSM highloaded

WCDMA lowloaded

GSMGSM GSMGSM

WCDMAWCDMA WCDMAWCDMA

Load reason handover for speech and for HSCSD

Load reason handover for speech and for HSCSD

WCDMAWCDMA GSMGSM

Load reason handover

Coverage reason handover

WCDMA can be usedto relieve GSM overload

GSM can be used to extend WCDMA coverage area

WCDMA can be usedto relieve GSM overload

GSM can be used to extend WCDMA coverage area

Mobile moving


Load based handover GSM -> WCDMA

100%

80%

0%

Load reason handoversfor speech

Load of GSM cell

Packet Data to WCDMAregardless of GSM load

Packet Data to WCDMAregardless of GSM load

Speech to WCDMAonly with high GSM load

Speech to WCDMAonly with high GSM load

Higher bit ratesfor data users

Higher bit ratesfor data users

More capacity for speech

More capacity for speech


Inter-System handover procedure to WCDMA

Inter-RAT measurements starts in case the RXLEV of the serving cell is above or

below the given threshold Qsearch_C, (threshold for Multi-RAT MS)

Inter-RAT measurements starts in case the RXLEV of the serving cell is above or

below the given threshold Qsearch_C, (threshold for Multi-RAT MS)

Handover decision is done in case ofload of the serving cell > load_Threshold

and CPICH Ec/No (MET) > Min Ec/No threshold

Handover decision is done in case ofload of the serving cell > load_Threshold

and CPICH Ec/No (MET) > Min Ec/No threshold

MS selects the target UTRAN cell based on measurement results

MS selects the target UTRAN cell based on measurement results

Handover command is send to MSCHandover command is send to MSC

Load threshold = 80% (default)Load reporting interval= 20 s (default)

Qsearch_C= always (default)


ISHO L3 Signalling 2G->3G

had overs

Documents

mode sib

d soc classification

cell selection

dch substate ue rnc

dcch rlc

rnc database

pch substate ue rnc

ue rlcumam