2G3G Interworking Final

1 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004

2G <-> 3G inter-working


2G <-> 3G inter working

Idle mode Connected mode

2G -> 3G reselection


2G -> 3G handover CS AMR

2G -> 3G handover PS

3G -> 2G handover CS AMR

3G -> 2G handover PS




Cell Reselection Cell Selection S-Criteria-

• The cell selection criteria S are defined as follows:

• The cell selection criterion S for a suitable cell is fulfilled when:

• Where:

Squal = Qqualmeas – Qqualmin

Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation

Squal > 0

Srxlev > 0

Squal Cell Selection quality value, (dB). Not applicable for TDD cells or GSM cells

Srxlev Cell Selection RX level value (dB)Qqualmeas Measured cell quality value. The quality of the

received signal expressed in CPICH Ec/N0 (dB) for FDD cells. Not applicable for TDD cells or GSM cells.

Qrxlevmeas Measured cell RX level value. This is received signal, CPICH RSCP for FDD cells (dBm), P-CCPCH RSCP for TDD cells (dBm) and RXLEV for GSM cells (dBm).

Qqualmin Minimum required quality level in the cell (dB). Not applicable for TDD cells or GSM cells.

Qrxlevmin Minimum required RX level in the cell. (dBm)Pcompensation max(UE_TXPWR_MAX_RACH – P_MAX, 0) (dB)UE_TXPWR_MAX_RACH

Maximum TX power level an UE may use when accessing the cell on RACH (read in system information), (dBm)

P_MAX Maximum RF output power of the UE, (dBm)

S-Criteria OKS-Criteria OK

Cells with Highest HCSPriorities &

H > 0


H > 0

BestR

BestR

Serving + measuredneighboring cells



BestR

BestR



Cells with Lower HCS

Priority than in Serving cell



BestR

BestR

Fast MS

If No Cellwith H>0accept allneighbors

HCS in use: HCS not in use:

-20dB

-115dBm

-115dBm -115dBm -104dBm

intra

inter

GSM

TS 25.304 5.2.3.1.2

TS 25.304 5.2.3.1.2


• If system info in the cell indicates that HCS is not used (UseOfHCS) then for intra-freq, inter-freq and inter-system the UE shall:

• If Squal > Sintrasearch, UE need not perform intra-frequency measurements. If Squal <= Sintrasearch, perform intra-frequency measurements.

• If Squal > Sintersearch, UE need not perform inter-frequency measurementsIf Squal <= Sintersearch, perform inter-frequency measurements.

• If Squal > SsearchRAT m, UE need not perform measurements on cells of RAT "m".If Squal <= SsearchRAT m, perform measurements on cells of RAT "m".

Cell Reselection


Cell Reselection

Sintrasearch

Sintersearch

SsearchRAT

WCDMACELL

1234

Sintrasearch = 4 dB: Equate to –16dB Ec/No

Sintersearch = 2 dB: Equate to –18dB Ec/No

SsearchRAT m, = 0dB: Equate to –20dB

Ec/No

Region Condition Neighbour cells to be measured

1 Squal > Sintrasearch None

2 Sintersearch < Squal Sintrasearch Intra-frequency cells

3 SsearchRATm < Squal Sintersearch Intra- and inter-frequency cells

4 Squal SsearchRATm Intra-, inter-frequency and inter-RAT cells


Cell Reselection• The following cell re-selection criteria is used for intra-freq, inter-freq &

inter-RAT:

Rs = Qmeas,s + Qhysts Rn = Qmeas,n - Qoffsetn

Rs = Qmeas,s + Qhysts Rn = Qmeas,n - Qoffsetn

QmeasQuality value. The quality value of the received signal expressed in CPICH_Ec/No or CPICH_RSCP_LEV for FDD cells as set by the Cell_selection_and_reselection_quality_measure information element, P-CCPCH_RSCP_LEV for TDD cells and RXLEV for GSM cells.

Where:

Qhyst1This specifies the hysteresis for serving cell that is of different radio access modes or technologies AND for serving FDD cell when cell_selection_and reselection-quality_measure is set CPICH RSCP..

Qoffset1This specifies the offset between the two cells when the neighbour cells that are of different radio access modes or technologies AND for neighbour FDD cells when cell_selection_and reselection-quality_measure is set CPICH RSCP

Qhyst2This specifies the hysteresis for serving FDD cell when the cell_selection_and reselection-quality_measure is set CPICH Ec/No.

Qoffset2This specifies the offset between the two cells when neighbour FDD cells when the cell_selection_and reselection-quality_measure is set CPICH Ec/No.


Cell Reselection

First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)

Rs = CPICH RSCP/GSM RSSI + Qhyst1Rn= CPICH_RSCP(n) or RXLEV(n) - Qoffset1


Rs = CPICH RSCP/GSM RSSI + Qhyst1Rn= CPICH_RSCP(n) or RXLEV(n) - Qoffset1

Rn higher in GSM cellRn higher in GSM cellYes No

Cell re-selection to GSM

Cell re-selection to GSM

Second ranking only for WCDMA cells based on CPICH Ec/No

Rs = CPICH Ec/No + Qhyst2Rn= CPICH Ec/No -Qoffset2

Second ranking only for WCDMA cells based on CPICH Ec/No

Rs = CPICH Ec/No + Qhyst2Rn= CPICH Ec/No -Qoffset2

Cell re-selection to WCDMA cell of highest

R value

Cell re-selection to WCDMA cell of highest

R value

Neighbour WCDMA or GSM cell calculation with offset

parameter


parameter

Serving WCDMA cell calculation, with

hysteresis parameter


hysteresis parameter

If a TDD or GSM cell is ranked as the best cell, then the UE must perform cell re-selection to that TDD or GSM cell.

If a FDD cell is ranked as the best cell and cell_selection_and_reselection-quality_measure is set to CPICH RSCP, the UE shall perform cell re-selection to that FDD cell.

If a FDD cell is ranked as the best cell and IE cell_selection_and_reselection-quality_measure is set to CPICH Ec/No, the UE shall perform a second ranking of the FDD cells according to the R criteria using the measurement quantity CPICH Ec/No calculating the R values of the FDD cells.


Cell Reselection Cell Reselection Process with S,H, and R Criteria-



H > 0


H > 0

BestR

BestR




BestR

BestR







BestR

BestR

Fast MSIf No Cellwith H>0accept allneighbors

HCS in use: HCS not in use:


Cell Reselection UE Measurements / HCS Used

• When serving cell belongs to a hierarchical cell structure, the UE use Squal for FDD cells and Srxlev for TDD cells as Sx

• Rules for intra- and inter-frequency measurements:• if (Srxlevs <= SsearchhHCS) OR (FDD and Sx <= Sintersearch)

• UE shall measure all intra- and inter-frequency cells• else if (Sx > Sintersearch)

• UE shall measure all intra and inter-frequency cells which have higher HCS priority than the serving cell.

Sintrasearch = 4dB, Sintersearch = 2dB, Slimit,

searchRAT = 2dBSsearch_RAT = 0dB, Ssearch_HCS = 1dB, SHCS_RAT = 1dB



Squal = Qqualmeas

–

Qqualmin

Srxlev = Qrxlevmeas

-

Qrxlevmin - Pcompensation

WCEL:UseOfHCS = 0 (HCS not used), 1 (HCS in use)WCEL:UseOfHCS = 0 (HCS not used), 1 (HCS in use)

HCS_PRIO = 0 … 7; 0 indicates lowest priority and 7 the highest priority

HCS_PRIO = 0 … 7; 0 indicates lowest priority and 7 the highest priority

TS 25.304 5.2.6.1

TS 25.304 5.2.6.1

-


• Rules for inter-RAT measurements:• if (Srxlevs <= SHCS,RATm) OR (FDD and Squal <= SSearchRATm)

UE shall measure all inter-RAT cells• else if (Sx > Slimit, SearchRATm)

UE need not to measure inter-RATm neighboring cells• else

UE shall measure all inter-RATm cells with have equal or higher HCS priority level than the serving cell.





Cell Reselection UE Measurements / HCS Used

TS 25.304 5.2.6.1

TS 25.304 5.2.6.1

• When serving cell belongs to a hierarchical cell structure, the UE use Squal for FDD cells and Srxlev for TDD cells as Sx

Squal = Q Qqualmin

Srxlev = Qrxlevmeas

-

Qrxlevmin - Pcompensation

qualmeas


Cell Reselection UE Measurements / HCS Used & fast moving UE

• If the number of cell reselections during time period TCRmax exceeds NCR, high-mobility has been detected.

• When the number of cell reselections during time period TCRmax no longer exceeds NCR, UE shall continue these measurements during time period TCrmaxHyst.

• Then, UE shall revert to measure according to the threshold based measurement rules.

TCRmax = 60s, NCR = 8, TCRmaxHyst = 0s TCRmax = 60s, NCR = 8, TCRmaxHyst = 0s

TS 25.304 5.2.6.1

TS 25.304 5.2.6.1


Cell Reselection Neighbour measurements summary

SintrasearchSintersearchSsearchRAT m

No need to measure

neighbour cells

Intra-frequenc

y

Sx=Squal= Ec/No

Intra-frequency

Inter-freqencyInter-RAT

Higher HCS priorityIntra-frequencyInter-frequency

Intra-frequencyInter-frequency

HCS not used

HCS used

SlimitsearchRAT m

Intra-frequency

Inter-frequency

Intra-frequency

Inter-freqencyInter-RAT

Intra-frequency

Inter-frequency

Higher HCS

priority inter RAT


3G -> 2G cell reselection


3G -> 2G Cell Reselection

GSMncellHCSpriority

GSMncellHCSthreshold

GSMncellQrxlevMin

GSMncellPenaltyTime

GSMncellQoffset1

GSMncellTempOffset1

HOPGId


Nokia Strategy: reselect to GSM early Note: GSM cell could be 15 dB weaker

Qmeas (CPICH Ec/No)

t

Serving WCDMA Cell

Neighbour GSM Cell

Qhyst1=0 dBAdjgQoffset1=-15 dB

SsearchRAT= 2 (4 dB)

Rs

Qqualmin= -18 dB

SqualsRs

about -100 dBm level in GSM


• Parameter SummaryName Description Default

HCS_PRIO Defines the HCS priority level for a cell 0NCr Defines the maximum number of cell reselections 8

QHCS Quality threshold level for applying prioritised hierarchical cell re-selection for a cell WCDMA: -24

Qhyst1Qhyst1 is used for TDD and GSM cells, and for FDD cells when cell selection and re-selection quality measure is set to CPICH RSCP 4

Qhyst2Qhyst2 is used for FDD cells when cell selection and re-selection quality measure is set to CPICH Ec/No 4

QqualMin The minimum required quality level in the cell (Ec/No) -20

QrxlevMin The minimum required RX level in the cellWCDMA: -115GSM: -105

SHCS_RAT The RAT specific threshold for inter-RAT measurement rules 1

SintersearchThe threshold for inter-frequency measurements, and for the HCS measurement rules 2

SintrasearchThe threshold for intra-frequency measurements, and for the HCS measurement rules 4

Slimit_SearchRAT Threshold for skipping inter-RAT measurement rules in HCS 2

Ssearch_RAT The RAT-specific threshold for inter-RAT measurement rules 0SsearchHCS Threshold for intra- and interfrequency measurement rules in HCS 1TCrmax The duration for evaluating the allowed amount of cell reselections 60 secTCrmaxHyst Cell reselection hysteresis for reverting from UE high-mobility measurements 0 sec

TreselectionThe UE triggers the reselection of a new cell if the cell reselection criteria are fulfilled during the time interval Treselection 0

UseOfHCSIndicates whether the serving cell belongs to a Hierarchical Cell Structure (HCS), or not 0

Cell Reselection




Cell Reselection Parameters• Qsearch_I and Qsearch_P define thresholds. The threshold value also

indicates, when the measurements have to be initiated and performed. The measurements are either started, when the serving cell‘s RLA is below or above the threshold value. The default value is 15.

• FDD_Qoffset and FDD_GPRS_Offset define offset values, which have to be added to the RLA of the serving and non-serving GSM cells. The result is compared with the RSCP value of the WCDMA cell. The default parameter is 0.

• FDD_Qmin defines a minimum CPICH Ec/No threshold for WCDMA cell for cell re-selection.

• FDD_REP_QUANT defines the reporting quantity for UTRAN cell (1=Ec/No or 0=RSCP, default: 1).

• 3G_Search_PRIO is used to inidicate to the MS if 3G cells can be looked for when BSIC decoding is required. (0=no, 1=yes, default: 1)

The 3G Cell Reselection list is only used by multi-RAT MSs. The system information SI2quater and SI2ter can be used to provide 3G cell information. If the two system information messages carry 3G cell information, than their lists have to be combined in the UE‘s 3G Cell Reselection list, which may then hold up to 96 UMTS cells. Up to 8 carrier frequency bands can be stored in this list, too.


Cell Reselection MeasurementsCell Reselection for Circuit Switched Services (Packet Switched

Services)A multi-RAT mobile phone reads the (GPRS) 3G Cell Reselection list, which may

hold other RATs. The network controls the cell reselection measurements by the parameter Qsearch_I (Qsearch_P), which is broadcasted on the BCCH (PBCCH). The two parameters define thresholds, which tell the UE whether measurements have to be performed when the RLA_C (RLA_P) of the serving cell is below or above the threshold. GSM cell measurements are often conducted more frequently then inter-frequency measurements to save battery power.

The MS identifies and selects the best UTRAN cell, given in the (GPRS) 3G Cell Reselection list, within 30 seconds. This holds, too, when several UTRAN cells of the same frequency are listed. This time increases by 30 seconds for each additional UTRAN frequency band in the (GPRS) 3G Cell Reselection list. The time limits are only valid under good radio conditions.

In the packet transfer mode, a MS must sent the first access to the best new UTRAN cell at latest 10+x seconds. x stands for the time required to read the relevant cell system information. The time holds only, when no new GSM cell is activated and good radio conditions. The time increases by 5 seconds for each additional UTRAN carrier band listed in the GPRS 3G Cell Reselection list.


Cell Reselection AlgorithmAlgorithm for cell re-selection from GSM (GPRS) to the FDD mode in

UTRANPre-requisite for cell re-selection to UMTS is, that UTRAN carrier bands are

included in the (GPRS) 3G Cell Reselection list. If so, the MS must update • RLA_C (RLA_P) value for the serving cell and• at least 6 strongest non serving GSM cellsat least every 5 seconds. Thereafter, the MS can re-select a suitable UTRAN cell,

based on the S-Criterion. If an FDD cell is suitable, following two conditions must have been met:

• For a period of 5 seconds, the measured RSCP value must exceed the PLA_C (RLA_P) of the serving GSM and of all non-serving GSM cells by the value FDD_Qoffset (FDD_GPRS_Qoffset). Did a cell re-selection occur within the previous 15 seconds, the FDD_Qoffset value is increased by 5 dB.

• The measured Ec/No value of the FDD cell must be greater or equal than the broadcasted value FDD_Qmin.

• If the UE as performed a cell re-selection to UTRAN within the previous 5 seconds, a cell re-selection back to UTRAN is not allowed, when a suitable cell can be found within GSM.


GSM BCCH 2Quater / 2TerBCCH info


Cell Reselection Algorithm from GSM to FDD-WCDMA (cs)Cell Reselection List

GSM MS starts WCDMA measurements if :RLA_C< F(Qsearch_I) for 0<Qsearch_I<=7

orRLA_C> F(Qsearch_I) for 7<Qsearch_I<=15

If, for suitable UMTS cell & for a period of 5 s:

CPICH RSCP > RLA_C + FDD_Qoffset

CPICH Ec/No FDD_Qmin

no prioritiesbetween WCDMA

neighbours

Measurement Updates:• RLA_C value of the serving cell• + least 6 strongest non serving GSM cells

at least every 5 s

check

and

WCDMA cellreselection

BCCH: FDD_Qmin, FDD_Qoffset

Fdd_Qoffset: select allways (value is -infinity)

FDD_Qmin= -13 dB


Cell Re-selection Parameters • Range of Qsearch_I and Qsearch_P (either Below or Above values comp.

to RLA_C)• Recommended value is 7 (measure always)

• Range of FDD_Qoffset and FDD_GPRS_Offset• Recommended value is 0 (select always if acceptable)

00

-98-98

88

-78-78

11 22

-94 -94 -90-90

99 1010

-74-74 -70-70

33

-86-86

1111

-66-66

44

-82-82

1212

-62-62

55

-78-78

1313

-58-58

66 77

-74-74 AlwaysAlways

1414 1515

-54-54 NeverNever

R_Below

dBm

R_Upper

dBm

00

-Always-Always

88

00

11 22

-28 -28 -24-24

99 1010

44 88

33

-20-20

1111

1212

44

-16-16

1212

1616

55

-12-12

1313

2020

66 77

-8-8 -4-4

1414 1515

2424 2828

Range

dBm

Range

dBm


Cell Re-selection Parameters• Range of FDD_Qmin

• Recommended value is 7 (-13 dBm)

• FDD_REP_QUANT defines the reporting quantity for UTRAN cell (1=Ec/No or 0=RSCP, default 1)

• 3G_Search_PRIO parameter allows to extend the BSIC reporting interval from 10 s to 13s by checking the BSICs from non-serving BCCH carriers and also make WCDMA measurements as often as possible. Range is 0=no, 1=yes, default value 1

Defined in the SI2quater and PSI3quater if PBCCH is allocated.

ParameterParameter

Name for Sys Info (SI)Name for

Sys Info (SI)

Qsearch_IQsearch_I

2quater2quater

Qsearch_PQsearch_PQsearch_PQsearch_P

2quater2quater 3quater3quater

FDD_QMinFDD_QMin

2ter2ter

FDD_(GPRS)Qoffset

FDD_(GPRS)Qoffset

2quater2quater

FDD_REP_QUANT

FDD_REP_QUANT

2ter2ter

00

-20-2011 22

-19 -19 -18-1833

-17-1744

-16-1655

-15-1566 77

-14-14 -13-13

Range

dBm

3G_search_PRIO

3G_search_PRIO

2(3)quarter(PBCCH)

2(3)quarter(PBCCH)

Fdd_Qmin mappingAif parameter 0 1 2 3 4 5 6 7Fdd_Qmin (old) [dB] -20 -19 -18 -17 -16 -15 -14 -13Fdd_Qmin (new) [dB] -20 -6 -18 -8 -16 -10 -14 -12

old

New mapping from 05.08 [late 2003]:

UEs have to support new parameter range !


Cell Re-selection ExampleNon GPRS case

t

Serving GSM Cell

Neighbour WCDMA Cell

Ec/NoRSCP/RLA_C

5 sec.

Cell re-selection to WCDMA

FDD_Qmin=0(-20 dB)

FDD_Qoffset =6 (-8 dB)

Qsearch_I=0 (-98 dBm)

RLA_C

Measurements starts (serving cell)

Minimum Quality Requirement for WCDMA Ec/N0

RSCP


Cell Re-selection Example GPRS case

t

Serving GSM Cell (Best)

Neighbour WCDMA Cell

Ec/NoRSCP/RLA_C

5 sec.

Cell re-selection to WCDMA

FDD_Qmin=-20 dB

FDD_GPRS_Qoffset =10 (8 dB)Qsearch_P=0(-98 dBm)

RLA_P

Measurements starts (serving cell)

Minimum Quality Requirement for WCDMA

Ec/N0

RSCP



Rs = CPICH RSCP + Qhyst1Rn= RXLEV(n) - Qoffset1

Rn higher in GSM cell

YesNo

Cell re-selection to GSM Second ranking only for

WCDMA cells


parameter


hysteresis parameterGSM cell measurements available If :

CPICH Ec/No-QqualMin < Ssearch_RAT

WCDMA-> GSM cell reselection


How to avoid ping pong ?• When phone is camped on 3G, GSM measurements can start when CPICH

Ec/Io of serving cell is below Ssearch_RAT + QqualMin.

• When phone is camped on GSM, cell reselection to 3G is possible if CPICH Ec/Io of the candidate is above FDD_Qmin.

• Therefore, to avoid ping pongs between 3G and GSM the following condition should be met:

FDD_Qmin >= QqualMin+Ssearch_RAT

QqualMin=-18 dB

Ssearch_RAT=4 dB

CPICH Ec/Io

FDD_Qmin >= -13 dB

QqualMin +Ssearch_RAT

t

Camping on 3G Camping on GSM Camping on 3G


3G -> 2G General handover procedure flow


ISHO Process Overview

HO Triggering Thresholds set in RNCHO Triggering Thresholds set in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

RNC commands selected UE(s) to startIF/IS measurements

RNC commands selected UE(s) to startIF/IS measurements

Measurements are done in Compressed Mode (CM)

Measurements are done in Compressed Mode (CM)

UE reports GSM cells withstrongest RSSI signals to RNC

UE reports GSM cells withstrongest RSSI signals to RNC

RNC makes HO decision andcommands UE to target cell

RNC makes HO decision andcommands UE to target cell

RSSI measurements and BSICverification for GSM cells

RSSI measurements and BSICverification for GSM cells

Different decision methods for IF HOOnly one decision method for IS HO

5 Coverage/Capacity HO Reasons

About 25 HO parameters

Reporting cells are active set cells (max 3) + max 6 IFHO, max 6 ISHO neighb.

Max 32 neighbours could be measured

(31 Intra-Freq neighbours)48 Inter-Freq neighbours 32 Inter-System neighbours can be measured


3G -> 2G Handover measurement triggering


IS Handover Triggering Reasons

1. DL DPCH approaches itsmaximum allowed powerFMCI: IFHOcauseTxPwrDLFMCG: GSMcauseTxPwrDL

2. Quality deterioration report from UL outer loop PCFMCI: IFHOcauseUplinkQualityFMCG: GSMcauseUplinkQuality

4. UE Tx power approaches itsmaximum allowed power, event 6A/6DFMCI: IFHOcauseTxPwrULFMCG: GSMcauseTxPwrUL

5 . Low measured absoluteCPICH RSCP, events 1E/1FFMCI: IFHOcauseCPICHrscp, FMCG: GSMcauseCPICHrscp

3. Low measured absolute CPICH Ec/No, event 1E/1F FMCI: IFHOcauseCPICHEcNoFMCG: GSMcauseCPICHEcNo

HO trigger

6 . Others (Not implemented in RAN 1.5): e.g. Traffic & load reason IS-HO, etc

Frequency Measuring Control for Inter-Frequency = FMCIFrequency Measuring Control for Inter-System (GSM) = FMCG


Measurement triggering: DL Coverage

Node BRNC

DCH Data Frame

IubUE

PO1TPCPilotbitsTFCI

Data 2 bitsData 1 bits

PO3PO2 DL_CODE_PWR – PowerOffsetDLdpcchPilot CPICH_POWER + MAX_DL_DPCH_TXPWR + DL_DPCH_TXPWR_THRESHOLD

Max Power on DPCH (e.g. 33 dBm)

Serving WCDMA cell time

It‘s time to triggerHO measurements

in the UE

e.g. Radio Link Measurement Report(e.g. Transmitted Code Power Value)

HHoMaxAllowedBitrateDL

Example Speech:Power Data Bits > 33dBm + (-3dB) + (-1dB)

Power Data Bits > 29 dBm (~1W)

Max Power on Channel


Measurement triggering: DL Coverage

• RNC orders UE to make IF/IS measurements when DL TX power of a single radio link reaches threshold defined as: DL_code_PWR -PowerOffsetDLdpcchPilot > CPICH Pwr + DL Tx Pwr + DL_TPCH_TXPWR_Threshold

• DL_CODE_PWR = measured DL code power • PowerOffsetDLdpcchPilot = power offset for the DPCCH pilot bits relative to the

DPDCHs power default = 3 dB, range 0...6 dB, step size 0.25 dB• DL Tx Pwr (DPCH) = measurement on DPCH Tx power, (reported by BTS)

• RLMeasRepPeriod (WBTS) / default=500ms, range 0..2000ms, step 100ms• CPICH Pwr = Tx power of the CPICH of an active cell

• PtxPrimaryCPICH (serving RNC) or AdjsCPICHTxPwr (drifting RNC)/33 dBm, range -10…50 dBm, step 0.1 dBm

• DL_TPCH_TXPWR_Threshold = depends on the service type• FMCI: InterfreqDLTxPwrThrAMR/CS/RtPS/NrtPS -1/-3/-3/-1 dB(range -10 dB..0,

step 0.5 dB)• FMCG: GSMDLTxPwrThrAMR/CS/RtPS/NrtPS -1/-3/-3/-1 dB(range -10 dB..0,

step 0.5 dB)• In Addition, the DL data rate allocated to the user must not exceed

• WCEL: HHoMaxAllowedBitrateDL/64 kbits/sNOTE: Either WCDMA or GSM will be measured, not both systems


Measurement triggering: UL QualityTarg

et

SIR

Max SIR target

Min SIR target

Actual SIR target

1st Quality deterioration report from PC to HC inside RNC

2nd Quality deterioration report (while the condition issatisfied the message is periodically repeated)

default 5s time

SIRSIR

RNC

ULQualDetRepThreshold (recommendation 2 s)

EnableULQualDetRepHHoMaxAllowedBitrateUL

RNC


Measurement triggering: UL Quality• RNC starts IF/IS measurements based on UL outer-loop power control

reports.• Enable reports from Outer-loop Power Control Controller to trigger

IF/IS HO, RNC:EnableULQualDetRep/default 0=no, 1=yes• Time duration for which BER/BLER target has not been reached,

despite SIR target at maximum level, RNC: ULQualDetRepThreshold/5 s, 0.5..5, step 0.5s

• Periodic report, every RNC: ULQualDetRepThreshold seconds, while BLER/BLER target is not reached.

• In addition, the UL data rate allocated to the user must not exceed WCEL: HHoMaxAllowedBitrateUL/32 kbits/s


Measurement triggering: CPICH Ec/No

Reporting event: 1E: A P-CPICH exceeds an absolute threshold (triggered if one) 1F: A P-CPICH falls below an absolute threshold (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



• RNC starts IF/IS measurement when event 1F occurs for all cells in the active set: A Primary CPICH becomes less than an absolute threshold

• RNC stops IF/IS measurement when event 1E occurs for at least one cell of the active set : A Primary CPICH becomes better than an absolute threshold

• Note:IF/IS measurements can be stopped if event 1Fs are cancelled by events 1E only when IFHO/ISHO was not successful and only inside the time between CM measurements, specified by the time InterFreqMinMeasInterval GsmMinMeasInterval/default 10s, recommendation 2s .

• Filtering applied before event evaluation in the UE: • FMCS: EcNoFilterCoefficient/0= 200ms filtering period



• Event 1E parameters:• Triggering conditions: Active set cells• Hysteresis: not used in 1F• Threshold used frequency: FMCS : HHoEcNoCancel/ -20 dB• Time-to-trigger: FMCS: HHoEcNoCancelTime/ 1280 ms• Amount of reporting: infinity• Reporting interval: not applied.• Reporting cell status: max 3 active cells.

• Event 1F parameters:• Triggering conditions: Active set cells• hysteresis: not used in 1F• Threshold used frequency: FMCS : HHoEcNoThreshold / -

22 dB (range 0..-24 dB)• Time-to-trigger: FMCS: HHoEcNoTimeHysteresis / 640 ms

(range 0..5000ms)• Amount of reporting: infinity• Reporting interval: not applied.• Reporting cell status: max 3 active cells.


Reporting Events 6A, 6B and 6D

timetime totrigger

UE T

x P

ow

er

UE Transmitted Power Tx

Threshold

6B

6A

6D

min(UEtxPowerMaxDPCH, P_MAX)

6A: The UE Tx power exceeds an absolute threshold 6B: The UE Tx power falls below an absolute threshold 6D: The UE Tx power reaches its maximum value

InterfreqUETxPwrTimeHystGSMUETxPwrTimeHyst


Measurement triggering: UL Coverage

• RNC orders IF/IS measurements when one of the following event occurs:• Event 6A: The UE Tx power becomes larger than an absolute

threshold• Event 6D: The UE Tx power reaches its maximum value

• Also GSM measurements could be measured first depending on UE Tx power values in IFHO and ISHO parameters

• Only lower threshold is send to UE, so either WCDMA or GSM is measured first, but also other RAT could be measured if not good enough neighbour is found

• In addition, the UL data rate allocated to the user must not exceed WCEL: HHoMaxAllowedBitrateUL/32 kbits/s

• RNC calls off inter-frequency measurements when event 6B occurs: the UE Tx power becomes less than an absolute threshold.

• Filtering applied before event evaluation in the UE.• FMCI : InterfreqUETxPwrFilterCoeff/8=10ms (range 10..480ms)• FMCG: GSMUETxPwrFilterCoeff/8 =10ms (range 10..480ms)

• NOTE: Not all UE vendors support 6A event


Measurement triggering: UL Coverage

• Event 6A parameters:• Time-to-trigger: 0s• UE Transmitted Power threshold = min (UEtxPowerMaxDPCH,

Pmax) – UE_TX_POWER_threshold• UEtxPowerMaxDPCH is the maximum allowed UL tx power on

DPCH in the active cell (range -50..24 dBm, step 1, default 21 dBm), Pmax is the maximum RF output power

• UE_TX_POWER_Threshold depends on the type of service:• FMCI: InterfreqUETxPwrThrAMR/-3 dB (range -10..0, step1)• FMCI: InterfreqUETxPwrThrCS/-3 dB (same range and step)• FMCI: InterfreqUETxPwrThrNrtPS/-3 dB • FMCI: InterfreqUETxPwrThrRtPS/-3 dB • FMCG: GSMUETxPwrThrAMR/CS/NrtPS/RtPS -1/-3/-1/-3/ dB

• Event 6B parameters: time-to-trigger• FMCI: InterfreqUETxPwrTimeHyst/1280 ms • FMCG: GSMUETxPwrTimeHyst/1280 ms

• Event 6D parameter: time-to-trigger: 0s


Measurement triggering: CPICH RSCPReporting event: 1E: A P-CPICH exceeds an absolute threshold (triggered if one) 1F: A P-CPICH falls below an absolute threshold (triggered if all)

time

Cell 1 Cell 2

Cell 3

absolutethreshold

e.g

. P

-CP

ICH

Rscp

1E: HHoRscpCancel

1E: HHoRscpCancelTime

1F: HHoRscpThreshold

1F: HHoRscpTimeHysteresis


Measurement triggering: CPICH RSCP

• UE continually monitors pilot channels of BTSs in AS

• If RSCP of a Node B falls below threshold, HHoRscpThreshold, UE sends event 1F report

• RNC starts IF/IS measurements when event 1F occurs for all cells in AS

• RNC stops IF/IS measurements when event 1E occurs for at least one cell of AS

• Note:IF/IS measurements can be stopped if event 1Fs are cancelled by events 1E only when IFHO/ISHO was not successful and only inside the time between CM measurements, specified by the time InterFreqMinMeasInterval GsmMinMeasInterval/default 10s, recommendation 2s .

• UE filtering applied before event evaluation using HHoRscpFilterCoefficient (FMCS) /200ms, range 200…1600ms


Measurement triggering: CPICH RSCP• Event 1E (A primary CPICH exceeds an absolute threshold) parameters:

• Triggering conditions: Active set cells• hysteresis: not used in 1E• Threshold used frequency: (FMCS) : HHoRscpCancel/ - 100 dBm• Time-to-trigger: (FMCS): HHoRscpCancelTime/ 1280 ms• Amount of reporting: infinity• Reporting interval: not applied.• Reporting cell status: max 3 active cells.

• Event 1F (A primary CPICH falls below an absolute threshold) parameters:• Triggering conditions: Active set cells• Hysteresis: not used in 1F• Threshold used frequency: HHoRscpThreshold (FMCS)/ - 105 dBm• Time-to-trigger: HHoRscpTimeHysteresis (FMCS)/ 640 ms• Amount of reporting: infinity• Reporting interval: not applied.• Reporting cell status: max 3 active cells.


3G -> 2G Compressed Mode


Compressed Mode in Uplink

GSM BTS WCDMA BTS

DL

DL CM (this should be offwhen GSM is measured)

UL CM (needed to avoid interference)

During WCDMA transmissionsignal leakage will go to GSMRx also


Compressed Mode (CM)• CM was introduced to WCDMA to allow inter-frequency (system) handovers• CM is used to create idle periods (gaps) in the transmission during which ncell

measurements on another frequency can be made

• Gaps can be created using single or double frame approach (Nokia supports both)

• Because same data amount is sent in a shorter time more power is needed during CM (both in UE and BTS)

=> affects WCDMA coverage

• Fast Power control information might be lost during the gap => higher Eb/No=> affects WCDMA capacity

• Compressed frames may be lost if power control is not set correctly => affects WCDMA quality

• CM methods are Puncturing, Spreading Factor Halving and Higher Layer Scheduling

Normal frame Normal frame

Measurement gapMeasurement gapPower / Data Rate

CompressedMode

Normal frame


AssumptionAssumption Effect to the capacityEffect to the capacity

Required Eb/No is 1.5 dB higher during compressed frames

Required Eb/No is 1.5 dB higher during compressed frames1.5 dB = 41% more interference1.5 dB = 41% more interference

Every 3rd frame is compressedEvery 3rd frame is compressed41% /3 = 14% more interference41% /3 = 14% more interference

10% of the users are measured at the same time

10% of the users are measured at the same time14% /10 = 1.4% more interference14% /10 = 1.4% more interference

Capacity degradation < 2%

Performance of Compressed Mode: Capacity

Exact increase in Eb/N0 depends on service, multipath diversity, antenna diversity, mobile speed, uplink or downlink, measurement gap length, compressed mode method (spreading factor or puncturing), and 1.5 dB represents a typical value.

Exact increase in Eb/N0 depends on service, multipath diversity, antenna diversity, mobile speed, uplink or downlink, measurement gap length, compressed mode method (spreading factor or puncturing), and 1.5 dB represents a typical value.


Performance of Compressed Mode: Coverage

AssumptionAssumption Effect to the coverageof real time services

Effect to the coverageof real time services

Required Eb/No is 1.5 dB higher during compressed frames

Required Eb/No is 1.5 dB higher during compressed frames 1.5 dB reduced coverage1.5 dB reduced coverage

7-slot gap is used7-slot gap is used 10*log10(15/8) = 2.7 dB reduced coverage

10*log10(15/8) = 2.7 dB reduced coverage

Every 2nd frame is compressed with 20 ms interleaving (speech)

Every 2nd frame is compressed with 20 ms interleaving (speech) 4.2 dB / 2 = 2.1 dB reduced coverage 4.2 dB / 2 = 2.1 dB reduced coverage

Total coverage reduction 2.1 dB

Compressedmode

Mobile max. power

Frame error if mobile hitsits maximum power

2.7 dB + 1.5 dB more power is needed during compressed mode

• Non-real time services can reduce the bit rate during compressed frames no effect to coverage• Speech connection can switch to a lower AMR mode


Measurement Gap

Min transmitted TSs per Frame: 8

radio frame radio frame

TGL

Length of gap:3, 4, 5, 7 timeslots

Single-frame method

radio frame radio frame

TGL

Double-frame method

Length of gap:3, 4, 5, 7, 10, or 14 timeslots


Compressed mode methods • Puncturing for Speech in DL

• Reducing the physical channel bit amount (Channel Coding – Convolution Coding)

• More Tx power is needed if same QoS requirements have to be satisfied• Only if all DCHs have enough free puncturing capacity

• RNC: DLPuncturingLimit/0.68 =puncturing from coding rate 1/3 to coding rate 1/2.

• Halving Spreading Factor, SF/2 for RT and NRT services (UL and DL)

• Doubles temporarily the physical channel data rate, possible for all services• Needs 3 dB more UE power due to halved spreading ratio • If new channelization code is available from code tree in DL

• WCEL: AltScramblingCodeCM/0=used (def), 1=not used

• Higher Layer Scheduling, HLS (UL and DL) • Only possible for PS services (RT or NRT)• Does not cause extra load to the cell but reduces DCH user data• HLS ¾ data rate or HLS ½ data rate possible

Double frame is used in case of puncturing and HLS ¾ data rate

Single frame is used in case of spreading factor halving and HLS ½ data rate.


Compressed mode parameters• CM can be activated/deactivated by CMmasterSwitch (RNC) /0=in use (def) • HLS rate configurable using HLSModeSelection (RNC)/def 0=1/2 HSL ,

1=3/4 HSL

• Method used for voice:• HLS not possible• UL LowerULAMRmodeCM (RNC) /7.4 kbits/s defines AMR mode

corresponding to SF/2• DL selection bit puncturing and SF/2 based on MinDLAMRmodeCM

(RNC)/7.4 kbits/s (range 4.75...12.2 kbits/s)

• Method used for RT and NRT services • SF/2 is allowed if: UE DL Tx Power < Max_UE_DL_Tx_Pwr• PowerMarginCMcodeHalving (RNC)/3 dB (range 0..10, step 0.25)

• Maximum number of UEs in CM is controlled through MaxNumbUECMcoverHO (RNC)/16 (range 0..255)

• The number of UEs in DL CM depends on the PtxTotal value• The number of UEs in UL CM depends on the PrxTotal value


How many UEs in Compressed Mode ?

PtxTarget/PrxTarget

DL/ULtransmission power

Load

PtxOffset/PrxOffset

New UEs can be switched to CM when:Pxx_Total < Pxx_Target &

# of UEs in CM < MaxNumbUECMcoverHO

One new UE in CM can be allowedif the limit is not reached

No new UE can be in CM here


Applicable methods for related services

Service UL CM method DL CM Method

AMR SF/2, HLS SF/2, Puncturing

PS NRT SF/2, HLS SF/2, HLS

CS Data SF/2 SF/2

AMR+PS 1. If the PS bit rate >> AMR bit rate it is possible to create idle gaps by applying frame compression to just the PS DCH. In this case the CM method selection is as in the case of stand-alone PS NRT.2. If both DCHs must be ”compressed” then only the methods applicable to both can be used: i.e. in DL only SF/2 is possible

CM method Frame Mode

SF/2 Single Frame

½ HLS Single Frame

¾ HLS Double Frame

Puncturing Double Frame


Selection of DL CM Method

Channel coding>DLPuncturingLimit

Use puncturing(for AMR speech)

SF/2 code available Use SF/2 with thesame scrambling code

Reduce bit rate(for packet data)

DL CM is started with Puncturing instead of SF/2because puncturing needs less power, allow more puncturing if downlink capacity is orthogonal code limited

Link level powerlimit reached

Use SF/2 with anotherscrambling code

Yes

Yes

NoNo

Yes

AMR rate>MinDLAMRModeCM

Lower AMR rate (+ puncturing)

Yes

No

No

Alternative scrambling codeis used when the SF/2 codeis reserved

UL: LowerULAMRModeCMfor AMR rate


Compressed mode method in RAN 1.5.2

Id Compressed mode method

1 Puncturing (Not supported in RAN 1.5)

2 SF/2

3 SF/2 with alternative scrambling code

4 HLS 1/2

5 HLS 3/4

Compressed mode method in NRT PSTriggering reason: Too high UE Tx power

Parameter HHOMaxAllowedBitRateUL should be checkedCompressed mode method in Downlink (in priority order): 1,2,3,4,5Compressed mode method in Uplink (in priority order): 2,4,5

Triggering reason: Too high DL DCH power

Parameter HHOMaxAllowedBitRateDL should be checkedCompressed mode method in Downlink (in priority order): 4,5Compressed mode method in Uplink (in priority order): 2,4,5

Triggering reason: Low CPICH EcNo, Low CPICH RSCP, poor UL DCH

Compressed mode method in Downlink (in priority order): 2,3,4,5Compressed mode method in Uplink (in priority order): 2,4,5


CM Pattern Parameters

TG Pattern 1

TGPattern 2

TG Pattern 1

TGPattern 2

TGPattern 2

TG Transmission Gap TGL Transmission Gap Length (3,4,5,7,10,14 SL)TGPL Transmission Gap Pattern Length (1-144 Frames) TGD Transmission Gap start Distance (15-269 SL)TGSN Transmission Gap Starting slot Number (1-14 SL) TGPRC TG Pattern Repeat Count

TG Pattern 1 TG Pattern 2

TGPL1 TGPL2

TGSNTGL1 TGL2TGL1TGL2

TGD TGD

#1 #2 #3 #4 #TGPRC

TGCNF transmission gap pattern sequence

GapPositionSingleFrame

TGSN


3G -> 2G Measurements


Decision Algorithm

UE Tx Power (Event 6A)•Threshold:GsmUETxPwrThrXX •L3 filter: GsmUETxPwrFilterCoeff•Hysteresis margin: GsmUETxPwrTimeHyst•Data rate threshold HHOMAxAllowedBitrateUL

UL Quality•Timer:ULQualDetRepThreshold•Data rate threshold HHOMAxAllowedBitrateUL

DL DPCH power•Threshold: GsmDLTxPwrThrXX•Data rate threshold HHOMAxAllowedBitrateDL

(XX=AMR,CS,NrtPS,RtPS)

CPICH RSCP (Event 1F)

•Thresholds:HHoRscpThreshold HHoRscpCancelL3 filter: HHoRscpFilterCoefficient•Timers:HHoRscpTimeHysteresisHHoRscpCancelTime

CPICH Ec/Io (Event 1F)•Thresholds:HHoEcNoThresholdHHoEcNoCancel•L3 filter:Done already for SHO•Timers:HHoEcNoTimeHysteresisHHoEcNoCancelTime

AdjgTxPwrMaxTCHAdjgRxLevMinHO (n)GsmMeasAveWindow

GsmMeasRepIntervalGsmNcellSearchPeriodGsmMinMeasIntervalGsmMaxMeasPeriod

Handover Triggering

Handover Execution2G-to-3G back prevention

GsmMinHoInterval

GSM measurement reporting

ISHO parameters


ISHO measurements• After HO triggering message is sent to RNC, a RRC message

”Measurement Control” is sent to UE containing details of the measurement that the UE must execute. Measurement reporting is periodical. Max 6 GSM cells could be measured by UE and reported to RNC. No filtering in measurements by UE

• Upon reception of the measurements reported by the UE, RNC applies a sliding averaging window to the RXLEV measurements. The averaged levels are used as input to the IS-HO decision algorithm.

RNCRRC: ”Measurement control ” message (GSM RSSI measurements)

UE

RNC

RXLEV measurements are reported through”Measurement report” messages

UE

RRC: ”Measurement report”

RRC: ”Measurement report”

The first measurement report has info from the best GSM cell:

BCCH freq & RSSI, no filteringused in UE

GsmMeasRepInterval (default 0.5s)


Measurement Control Parameters: FMCG

• GSMMeasRepInterval: 0.5 seconds• This is the interval between measurement reports, which are sent to

BTS• This parameter should be kept to 0.5 seconds. Increasing the

reporting interval would increase the IS-HO process delay.

• GSMMinMeasInterval:10 s• This is Minimum Measurement Interval, wait time when the following

CM starts. In case of an unsuccessful IS-HO attempt, the network will deactivate compressed mode for a time period given by this parameter, thus better value will be 2 s to speed up the reactivation of CM.

• GSMMeasAveWindow: 6• This is Measurement Averaging Window size, sliding window is used

• GSMMaxMeasPeriod: 20 reports• This is Maximum Measurement Period which determines the

maximum allowed duration of the inter-sytem measurement• If the RNC is not able to execute an inter-system handover, it shall

stop the inter-system measurements after the UE has sent the predefined number of measurement reports to the RNC.


Measurement Control Parameters: FMCG

• Maximum allowed duration of the inter-system measurement is calculated:

• GSMMeasRepInterval * GSMMaxMeasPeriod (=0.5*20s) =10s, • This seems to be too long time, because based on field

measurements BSIC and RSSI delays are about 3 seconds, so it makes senses to reduce the value of this parameter to some value about 3 seconds, otherwise, if the BSIC or RSSI measurements fail or if the IS-HO execution is not possible to due low GSM RSSI levels, the network will not deactivate compressed mode until the timer of 10 seconds has expired. Thus, decreasing the parameter value will allow the UE/network to initiate a new IS-HO attempt. Proposed value for GSMMaxMeasPeriod is 6

• GSMNcellSearchPeriod: 0 • This is neighbour cell search period parameter, ISHO is not

allowed until the are enough measurement reports given by this parameter

• O means that only 1 measurement result is enough for decision making

• Duration of the cell search period is calculated: • GSMRepInterval * GSMNcellSearchPeriod).


ISHO: BSIC Verification• After the selection of the target GSM cell, the RNC sends to UE the RRC

message "Measurement control” which includes details to measure ”BSIC” .

• UE stops RSSI measurements and updates the transmission gap pattern to the pattern used for BSIC decoding. The measurement reports are sent periodically to RNC.

• If the UE is unable to decode the BSIC during the given period, the BSIC measurement operation is aborted.

RNC

RRC: ”Measurement control ” message (BSIC decoding)

WCDMA

IS-HO trigger Target Cell found IS-HO command

RSSI meas. BSIC verification

•Numbers of GSM cells in the neighbour cell list•Reporting interval•Sliding averaging window•Transmission gap pattern for RSSI measurements

TBSIC depends on :

•Transmission gap pattern for BSIC decoding

TRSSI depends on


3G -> 2G Handover decision


On this page, you find conditions, which have to be satisfied, before an inter-frequency handover can be conducted. The best neighbouring cell must fulfil following criterion („best“ according to Ec/No): AVE_RXLEV_NCell(n)

> GSMncellRxLevMinHO(n) + max(0, GSMncellTxPwrMaxTCH(n) - P_max)where

• AVE_RXLEV _Ncell(n) is the averaged GSM carrier RSSI value of the GSM neighbour cell(n), averaging done directly from dBm values (no linear averaging); GSMMeasAveWindow / 6, 1…32 meas report.

• GSMncellRxLevMinHO(n) determines the minimum Required RSSI (dBm) level of the neighbour cell(n).

• GSMncellTxPwrMaxTCH(n) indicated the maximum Tx power level (dBm) an UE may use in GSM neighbour cell(n).

• P_MAX is the maximum UE power capability.

• If several GSM cells fulfils the equation above, cells are ranked based on HOPG: GSMncellPriorityCoverage/0, range 0…7

• A cell is ranked higher than another cell if it has a higher priority level even though its signal strength condition was worse

• Inter-system HO could be forbidden during the first measurements reports from the UE, to let the UE report all the candidate inter-system cells in its neighbourhood.

• FMCG FMCGNcellSearchPeriod / 0

Inter-RAT HO Decision


AdjgRxLevMinHO(n)

max(0, AdjgTxPwrMaxTCH(n) - P_max)

AVE_RXLEV_NCell(n) > AdjgRxLevMinHO(n) + max(0, AdjgTxPwrMaxTCH(n) - P_max)

GSM cell

ISHO Decision


• For UE with multi-service, 4 parameters are used:• FMCG: GsmHandoverAMR (Yes/No/Priority, def =yes)• FMCG: GsmHandoverCS (Yes/No/Priority, def=yes)• FMCG: GsmHandoverNrtPS (Yes/No, def=No)• FMCG: GsmHandoverRtPS (Yes/No/Priority, def=No)

• If GsmHandover X = No (X=AMR/CS/NrtPS/RtPS), HO is not allowed for the corresponding type of service, whatever the value of the others parameters

• If GsmHandover X = yes (X=AMR/CS/NrtPS/RtPS), HO is allowed for the corresponding type of service. Handover must be allowed for each type of service, before handover is allowed.

• If GsmHandover X = Priority (X=AMR/CS), HO is allowed for the corresponding type of service, whatever the value of the others parameters.

• If both voice and CS data are prioritised, priority is then based on Allocation/retention priority parameter.

Inter-System handovers - Multi-service


Inter-System handovers - Multi-service

• Example: UE with voice and PS NRT services

GsmHandoverAMR GsmHandoverNrtPS HO allowed yes Yes HO for voice and

PS Nrt allowed Yes No No HO allowed No Yes/No No HO allowed Priority Yes HO for voice and

PS Nrt allowed Priority No HO for voice only


3G -> 2G Handover signalling


GSM

GSMBSS

NMS

WCDMA 1RAN

(1) Handover triggering thresholdsare set from NMS to RNC

(1) Handover triggering thresholdsare set from NMS to RNC

Iu interface A interfaceCorenetwork

WCDMA Service gap 80-100ms

IS measurement

Compressed mode

(3) RNC commands selected UE(s) to start IS-measurements

(3) RNC commands selected UE(s) to start IS-measurements

(6) RNC selects target cell => IS-HO command to UE

(6) RNC selects target cell => IS-HO command to UE

(2) HO trigger fulfilled in RNC(=load/service/coverage reason)

Any penalty timer (RAN2) ?

(2) HO trigger fulfilled in RNC(=load/service/coverage reason)

Any penalty timer (RAN2) ?

(4) UE in CM• neighbor list• CM pattern

(4) UE in CM• neighbor list• CM pattern

(5) UE reports measurement resultback to RNC

(5) UE reports measurement resultback to RNC

(7) UE waits until last TTI with data

(7) UE waits until last TTI with data

(8) service gap(8) service gap

Handover Nokia WCDMA to GSMRAN1/ph1.5


ISHO 3G->2G Signalling

CS voice handover-RAN part


AMR Handover procedure overview (1)

RRC connection setup

ISUP signalling

Parameters for HO event triggere1e, e1f, e6a,e6b



ISUP signalling

Mobility management; several AS cell add & cell drops



Compressed Mode Parameters

Measurement report to trigger CM

Mobility management; several AS cell add & cell drops



RNC sends updated GSM NB listUE sends inter RAT meas. ResultsRNC commands UE to verify BSIC ofbest reported cellTarget cell BSIC verifiedRNC triggers HO to GSM target cellTiming advance informationUE ends HHO - procedure UE is handed over to GSM

2G signalling


Physical Channel reconfigurationRRC: Physical Channel reconfiguration


Measurement Control new RAT NB list

[..]

new inter RAT NB listMeasurement info

RRC: Measurement Control


UE Measurement Report GSM cells-RSSI measurements

measured best cell by ARFCN

measured 2nd best cell by ARFCN

measured 3rd best cell by ARFCN

measured 4th best cell by ARFCN



RRC: Measurement Report


Measurement Control carrying target cell info

RRC: Measurement Control

UE shall stop measuring RSSI of RAT NB list and focus on best cell´s BSIC verification


UE Measurement Report target GSM cell-BSIC verification

RRC: Measurement Report

UE reports verified BSIC of best cell to RNC


Handover from UTRAN command

RRC: HO from UTRAN command


Handover command GSM signalling

L3: Handover command

2G cell information (RF&configuration)

2G cell information (Security)

2G cell information (PC)


GSM signalling

Physical synchronisation Information

Handover complete message

L3: Physical Information

L3: Handover complete


ISHO 3G->2G Signalling CS voice handover-3G Core part


ISHO Signalling on Iu-CS interface

RNC sends relocation request to MSC

source = 3G cell

target = 2G cell

RNC -> MSC via MGW

XX

XX


ISHO Signalling on Iu-CS interface

MSC -> RNC via MGW

RNC -> MSC via MGW

MSC -> RNC via MGW

..Iu resources released, UE left 3G world


ISHO Signalling 3G->2GPS Cell change order-RAN part

If two GSM neighbours with same ARFCN in

RRC: Measurement Control,BSIC verification is performed


ISHO Signalling 3G->2GPS Cell change order-3G core part


ISHO L3 Signalling 3G->2GMulti RAB


12b. Cancel Location

12c. Cancel Location Ack

12d. Insert Subscriber Data

16. TMSI Reallocation Complete

12f. Update Location Ack

13. Location Update Accept

15. Routeing Area Update Complete

14. Routeing Area Update Accept

8. Cancel Location

8. Cancel Location Ack

6. Update PDP Context Response

6. Update PDP Context Request

7. Update Location

10. Update Location Ack

12a. Update Location

11. Location Update Request

2. SGSN Context Response

3. Security Functions

2. SGSN Context Request

1. Routeing Area Update Request

9. Insert Subscriber Data

9. Insert Subscriber Data Ack

12e. Insert Subscriber Data Ack

MS BSS GGSN old SGSN new SGSN HLR

new MSC/VLR

old MSC/VLR

5. Forward Packets

4. SGSN Context Acknowledge

C3

C2

C1

Service interruption during Inter-System handover

(3G->GPRS)The data interruption time is defined in this report as the total time that the data connection (IP connection) is lost due to the switching from 3G to GPRS. The gap is defined as the time that the “Cell change order from UTRAN” message is sent to UE until the first IP datagram (UL or DL) is sent between UE and the GPRS network. The below dataflow, shows the more relevant signalling for our interest.

GPRS data transmission

Cell change order from UTRAN (3G)

Channel required (RR)

Location update request (MM)

Routing area update request (GMM)

First IP datagram (GPRS)

3G data transmission

Total interruption time P. channel required (RR)

Location update accepted (MM)

Routing area up. Req Acc (GMM)

Immmediate assignment (RR)

When network mode is set to 1, UE startscombined RUA/LUA procedure, as shownin the right figure. Thus data interruption should be smaller.

This message is sent in FTP session but not in streaming.


2G -> 3G Handover


ISHO L3 Signalling 2G->3GMulti RAB RAN part


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

RAN1/ph1.5 and BSS10.5


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

Packet BCCH parameters can be usedto push GPRS mobiles to WCDMA

Packet BCCH parameters can be usedto push GPRS mobiles to WCDMA

BSS10.5


Handover Process incl. RAN 1.5

Handover Triggering Thresholds set in BSCHandover Triggering Thresholds set in BSC

Inter-RAT measurements when: The RXLEV of the serving cell is above or

below the given threshold Qsearch_C

Inter-RAT measurements when: The RXLEV of the serving cell is above or


Handover Decision is done in case of• Load of the serving cell > Load_Threshold• and CPICH Ec/No> min Ec/No Threshold

Handover Decision is done in case of• Load of the serving cell > Load_Threshold• and CPICH Ec/No> min Ec/No Threshold

MS reports best UTRAN cell based on measurement results

MS reports best UTRAN cell based on measurement results

Handover command is send to MSCHandover command is send to MSC

Latest after 5 s(one WCDMA band)

However in S10.5 MS is measuring the UTRAN cells continuously if they are defined as a neighbour, measurements are done during idle periods


ISHO and Cell Reselection in RAN1.5The maximum number of reported cells is BSS10.5 is 6, the number of WCDMA

cells depends on the parameter FDD_MULTIRAT_REPORTING. Then the number of GSM neighbour reported could be 3-6 depending on the set value of parameter FDD_MULTIRAT_REPORTING. With Enhanced Measurement report (in BSS11) the maximum number of reported cells is 12 adjacent cells in case MS is reporting more than 6 neighbours !

In RAN1.5 the target WCDMA cell is identified by the MCC + MNC + LAC + RNC + Cell ID + SAC. Because the MCC + MNC are included, handover from the BSC in the PLMN_1 to the RNC in the PLMN_2 is possible, i.e. an inter-PLMN handover from GSM to WCDMA is supported.

Load threshold parameters are defined for • Speech Calls & Transparent Data• Non-Transparent Data • The load is measured in the cell level by comparing the occupied TCHs to the

available TCHs (20 s interval used)Parameters & defaults• LOAD_THRESHOLD_FOR_SC_IS_HO (range 0-100% , default 80%)• LOAD_THRESHOLD_FOR_NON_TPC_IS_HO (range, 0-100% default 0%)After a successful handover new handover for the same connection is not

allowed in 30 seconds. After an unsuccessful handover attempt it is not allowed to initiate a new handover attempt to the same cell within time defined by the parameter MIN_INTERVAL_BETWEEN_UNSUCC_ISHO_ATTEMPT.

The Network Controlled Cell Re-Selection (NCCRS) is done from GPRS, to WCDMA with Packet Cell Change Order message. For NCCRS load thresholds for following classes in GPRS cells exist: Interactive 1 traffic class, Interactive 2 traffic class, Interactive 3 traffic class, and Background traffic class.


GSM ISHO in RAN1.5: Example

• Load Threshold for Speech Calls inter-RAT Handover• LOAD_THRESHOLD_FOR_SC_IS_HO= 80%

• Min Ec/No threshold for a handover to the UTRAN adjacent cell• MIN_ECNO_THRSHOLD = -15 dB

• Qsearch_c = 15 (if Qsearch_c = 15, the mobile is not allowed to measure UTRAN adjacent cells and therefore the BSS does not send the Measurement Information message to the mobile at all)

1 Load of the serving cell = 45% and the measured Ec/No = - 20 dB --> Handover to the UTRAN not possible due to low load and low

Ec/No

2 Load of the serving cell = 45% and the measured Ec/No = - 10 dB --> Handover to the UTRAN not possible due to low load

3 Load of the serving cell = 95% and the measured Ec/No = -10 dB --> Handover to the UTRAN possible

Handover example (speech/Transparent data)-


Measurements Capabilities for Multi-Rat MSs„A multi-RAT MS is able to monitor 64 UTRAN cells, divided into (depending on

the MS capability):• FDD cells on up to 3 FDD frequencies, with a maximum of 32 cells per

frequency; and/or• TDD cells on up to 3 TDD frequencies with a maximum of 32 cells per

frequency, and/or• CDMA2000 cells.“ (TS 45.008 V5.8.0)

In case of a conflict with GSM tasks, the GSM tasks take precedence.

Measurement quantities in GSM for UTRAN FDDFor UTRAN FDD cells, the measurement quantities to be used are • CPICH Ec/No,• CPICH RSCP and • RSSI. RSCP must be used for the cell re-selection ranking criteria. Ec/No is used for a

minimum quality requirement. On the BCCH, SACCH, PBCCH and/or PACCH, the reporting quantity parameter for the FDD mode FDD_REP_QUANT is transmitted. It informs the MS, whether the RSCP or the Ec/No is used for measurement reporting. It is also possible to add a frequency in the neighbour cell list, without adding a scrambling code. If this is the case, the Ms must report the RSSI for this UTRA carrier band. (The measured value will then replace the RXLEV in the measurement report.)


Handover MeasurementThe Network controls the identification and the measurements of cells, which

belong to other radio access technologies, by the parameter Qsearch_C. This parameter is sent on the SACCH. If this parameter is not made available there, the MS uses the parameter Qsearch_C_Initial, which is sent on the BCCH. The parameter Qsearch_C has the same meaning as the parameter Qsearch_I. The MS can use search frames, which are required for BSIC decoding, to perform the required measurements. The parameter 3G_SEARCH_PRIO indicates to the MS, whether is can use up to 25 search frames per 13 seconds without BSIC decoding in these frames.

At latest 5 seconds after it had been activated, The MS must report the best UTRAN cell. The time only holds, when no new GSM cell is activated at the same time, and there are good radio conditions. The allowed reporting time increases by 5 seconds for each additional UTRAN carrier band.

Then the MS has „only“ a signalling connection on a SDCCH, the MS can use all TDMA frames for measurements, which are not allocated or used for GSM signal strength measurements. The MS then must report the best UTRAN cell within 1.7 seconds, given the same assumptions as above.

Handover Parameters:• Qsearch_C_Initial identifies the Qsearch value to be used in connected mode

before Qsearch_C is received. 0 = use Qsearch_I, 1 = always. Default value = use Qsearch_I.

• Qsearch_C specifies the signal threshold to search for 3G cells (see Qsearch_I). Default value is 7.

• FDD_MULTIRAT_REPORTING gives the number of cells (0..3) from the access technology/mode FDD that the UE has to include in the list of strongest cells or in the measurement report.

• Min Ec/No Threshold gives the minimum CPICH Ec/No value for a UTRAN cell before a handover is possible. Reporting range: - 24..0 dB (step size 0.5 dB). Default value -15 dB.


Load based Handover Process: GSM-> WCDMA

Handover Triggering Thresholds set in BSCHandover Triggering Thresholds set in BSC

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


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


Handover Decision is done in case ofLoad of the serving cell > Load_Threshold and CPICH Ec/No> min Ec/No Threshold

Handover Decision is done in case ofLoad of the serving cell > Load_Threshold and CPICH Ec/No> 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

In the S10.5 MS is measuring the UTRAN cells continuously if they are defined as a neighbour,

The number of GSM neighbour reported could be 3-6 depending on the set value of parameter FDD_MULTIRAT_REPORT (0,1,2=def,3).

The load is measured in the cell level by comparing the occupied TCHs to the available TCHs (20 s interval used)

Load Threshold for Speech Calls or Transparent Data inter-RAT Handover:utranHoThScTpdc (Min Traffic Load TDHO), default = 80%minEcnoThreshold (Min CPICH EC/NO Threshold), default –15 dB

Parameters are sent from the BSC to the mobilein the Measurement Information message


2G -> 3G packet cell reselection (1)

GPRS traffic

UE reads 3G BCCH info& reselects to 3G



3G access

CS NAS signallingPS NAS signalling

GMM security

MM security

GMM security

RAN radio resources

PS NAS signalling comp.

CS NAS signalling comp.

RAN radio resources



RAN radio resources rel.

PDP context release req.

PS detach request


2G -> 3G packet cell reselection details

RRC connection setup request cause

Routing area update accept

New LAC / RAC


Service interruption during inter-system handover (GPRS->3G):

The below diagram describes the signalling during the inter-system handover process and the delays that were measured. Only the most relevant messages are shown in the signalling:

GPRS data transmission

Last IP (GPRS)

RRC: RRC connection request

MM: Routing area update request (3G)

MM: Routing area update accepted (3G)

First IP datagram (3G)

3G data transmission

Total delay

Delay (seconds)

0.3

1.8

~0.3

Location update request

Radio bearer reconf/accepted

Location update accepted

0.6

0.8

Streaming=1,Web/FTP =1.6

Streaming=0.9Web/FTP=2.6


IMSI based handover

RAN ´04 feature


IMSI Based Handover – Solution Overview

• IMSI based handover is feature candidate in RAN’04.

• The purpose of the IMSI specific handover feature is that a mobile subscriber in a visited network can be commanded to measure selectively only specified PLMN cells and to make handover accordingly to those specified (home or authorised) PLMNs. The input for the selective measurement control is the PLMN id that is included in the IMSI of the subscriber.

IMSI = MCC + MNC + MSIN

PLMN idIMSI International Mobile Subscriber IdentityMCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Subscriber Identification NumberPLMN Public Land Mobile Network


IMSI Based Handover – Example Cases

• IMSI-based handover can be used in different network sharing cases

• case 1: geographical sharing• case 2: common shared RAN with gateway core• case 3: mobile virtual network operator (MVNO)

• Based on IMSI, users of each operator can be handed over to their home or authorised WCDMA network from the shared area, when coverage becomes available (cases 1 and 2)

• Based on IMSI, inter-system handovers (coverage/quality, load and service based handovers) to the user’s home or authorised GSM network can be performed in the shared area (all cases)

- inter-frequency HO to home or authorised WCDMA cell

- inter-system HO to home or authorised GSM network

IMSI-based handovers from the shared area:

Different neighbour cell definitions in RNC for different IMSI ranges


Case 1: IMSI Based Handover andGeographical Sharing

GSM GSM GSM

GSM

WCDMA

GSM GSM GSM

WCDMA WCDMA WCDMA

WCDMA WCDMA WCDMA WCDMA

GSM GSM GSM GSM GSM

Operator A GSM cell

Operator A own WCDMA cellOperator A controlled sharedWCDMA cell

Operator B GSM cell

Operator B own WCDMA cellOperator B controlled shared WCDMA cell

Operator A user path Operator B user path

Based on IMSI, load and service-based inter-

system HOs to their own GSM network in shared

area

Separate neighbour lists for different IMSI ranges (different PLMN users)

Based on IMSI, operator A user is handed over to its

own WCDMA network when coverage

becomes available

GSM

GSMBased on IMSI, operator B user

is handed over to its own WCDMA network when

coverage becomes available

Based on IMSI, users are handed over to their own

GSM networks when WCDMA coverage ends


Case 2: IMSI Based Handover andCommon Shared RAN

GSM GSM GSM

WCDMA

WCDMA

GSM GSM GSM

Operator A GSM cell

Operator A own WCDMA cell

Common shared WCDMA cell

Operator B GSM cell

Operator B own WCDMA cell


WCDMA WCDMA


GSM

GSM

WCDMA

GSM

GSM



area

Based on IMSI, operator A user is handed over to its

own WCDMA network when coverage

becomes available

Based on IMSI, operator B user

is handed over to its own WCDMA network when

coverage becomes available




Case 3: IMSI Based Handover andMobile Virtual Network Operator

GSM GSM

GSM GSM

WCDMA WCDMA


GSM

GSM

Operator A GSM cell

Operator A controlled WCDMA cell

Operator B GSM cell




area




IFHO / ISHO Measurements• The measurement control parameters IMSIbasedIFHO and

IMSIbasedGsmHo indicate whether the IMSI based inter-frequency and inter-RAT (GSM) handovers are enabled in the cell

• When the IMSI based inter-frequency and/or inter-RAT handover is enabled, the RNC shall select only those neighbouring cells into the inter-frequency or inter-RAT (GSM) neighbour cell list whose PLMN identifier is included in the list of authorised PLMNs or which have the same PLMN identifier as the subscriber

• The PLMN Id of an inter-frequency neighbour cell is controlled by the parameters AdjiMCC and AdjiMNC, and the PLMN identifier of a GSM neighbour cell is controlled by the parameters AdjgMCC and AdjgMNC


Structure of the Authorised PLMN lists

• A list of authorised PLMNs shall contain the maximum of ten PLMN identifiers

• The radio network database shall have ten separate authorised PLMN lists

#0

Authorised PLMNs (max. 10)List #

#1

#2

…

#9

…

• 'All' in the list #9 indicates that all PLMNs are considered authorised PLMNs (RNC shall combine the neighbour cell list for the inter-frequency or inter-RAT (GSM) measurement from all neighbouring cells regardless of their PLMN identifiers)

• It is not necessary to add the home PLMN Id of the subscriber to the list of authorised PLMNs

PLMN 3 PLMN 4 …

PLMN 7

PLMN 1 PLMN 2

PLMN 1 PLMN 3

PLMN 5 PLMN 6

All

PLMN10


Selecting the List of Authorised PLMNs

• The RNC shall select the desired list of authorised PLMNs for the selective measurement control on the basis of the PLMN Id that is included in the IMSI of the subscriber

• The RNC links the PLMN id of the subscriber with the desired list of authorised PLMNs by means of an index table

0

1

2

…

127

123 12 1

123 34 0

123 45 2

… …

PLMN id List #

PLMN 123 45

Authorised PLMN list #2

• If the PLMN identifier of the subscriber does not match with the PLMN identifiers in the index table, the RNC shall select the list #9 of authorised PLMNs for the measurement control


Intra-Frequency Measurements• IMSI based handover does not have an effect on the sending

of intra-frequency neighbour cell lists on the DCCH• The RNC shall not select the neighbouring cells for the

intra-frequency measurement on the basis of the PLMN of the subscriber or neighbouring cell.

• The measurement control parameter IMSIbasedSHO indicates whether the IMSI based intra-frequency handover is enabled in the cell

• When the IMSI based intra-frequency handover is enabled in the cell, the PLMN identifier of the monitored cell (that has triggered the reporting event 1A or 1C) must be part of the list of authorised PLMNs or it must have the same PLMN Id as the subscriber or an active set cell before the RNC may add the monitored cell into the active set


Thank you !

Documents

2G3G Interworking Final