1 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004 2G <-> 3G inter-working
1 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
2G <-> 3G inter-working
2 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
2G <-> 3G inter working
Idle mode Connected mode
2G -> 3G reselection
3G -> 2G reselection
2G -> 3G handover CS AMR
2G -> 3G handover PS
3G -> 2G handover CS AMR
3G -> 2G handover PS
3 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
3G -> 2G reselection
4 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
Cells with Highest HCSPriorities &
H > 0
BestR
BestR
Serving + measuredneighboring cells
Serving + measuredneighboring cells
S-Criteria OKS-Criteria OK
BestR
BestR
Serving + measuredneighboring cells
Serving + measuredneighboring cells
Cells with Lower HCS
Priority than in Serving cell
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
5 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
• 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
6 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
7 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
8 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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
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
Neighbour WCDMA or GSM cell calculation with offset
parameter
Serving WCDMA cell calculation, with
hysteresis parameter
Serving WCDMA cell calculation, with
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.
9 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
Cell Reselection Cell Reselection Process with S,H, and R Criteria-
S-Criteria OKS-Criteria OK
Cells with Highest HCSPriorities &
H > 0
Cells with Highest HCSPriorities &
H > 0
BestR
BestR
Serving + measuredneighboring cells
Serving + measuredneighboring cells
S-Criteria OKS-Criteria OK
BestR
BestR
Serving + measuredneighboring cells
Serving + measuredneighboring cells
Cells with Lower HCS
Priority than in Serving cell
Cells with Lower HCS
Priority than in Serving cell
BestR
BestR
Fast MSIf No Cellwith H>0accept allneighbors
HCS in use: HCS not in use:
10 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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
-
11 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
• 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.
Sintrasearch = 4dB, Sintersearch = 2dB, Slimit,
searchRAT = 2dBSsearch_RAT = 0dB, Ssearch_HCS = 1dB, SHCS_RAT = 1dB
Sintrasearch = 4dB, Sintersearch = 2dB, Slimit,
searchRAT = 2dBSsearch_RAT = 0dB, Ssearch_HCS = 1dB, SHCS_RAT = 1dB
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
12 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
13 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
14 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
3G -> 2G cell reselection
15 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
3G -> 2G Cell Reselection
GSMncellHCSpriority
GSMncellHCSthreshold
GSMncellQrxlevMin
GSMncellPenaltyTime
GSMncellQoffset1
GSMncellTempOffset1
HOPGId
16 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
17 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
• 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
18 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
2G -> 3G reselection
19 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
20 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
21 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
22 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
GSM BCCH 2Quater / 2TerBCCH info
23 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
24 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
25 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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 !
26 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
27 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
28 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)
Rs = CPICH RSCP + Qhyst1Rn= RXLEV(n) - Qoffset1
Rn higher in GSM cell
YesNo
Cell re-selection to GSM Second ranking only for
WCDMA cells
Neighbour WCDMA or GSM cell calculation with offset
parameter
Serving WCDMA cell calculation, with
hysteresis parameterGSM cell measurements available If :
CPICH Ec/No-QqualMin < Ssearch_RAT
WCDMA-> GSM cell reselection
29 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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3G -> 2G General handover procedure flow
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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
32 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
3G -> 2G Handover measurement triggering
33 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
34 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
35 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
36 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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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
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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
39 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
Measurement triggering: CPICH Ec/No
• 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
40 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
Measurement triggering: CPICH Ec/No
• 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.
41 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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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
43 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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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
45 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
46 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
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3G -> 2G Compressed Mode
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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
49 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
50 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
51 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
52 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
53 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
54 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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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
56 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
57 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
58 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
59 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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3G -> 2G Measurements
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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
62 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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)
63 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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.
64 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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).
65 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
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3G -> 2G Handover decision
67 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
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
68 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
AdjgRxLevMinHO(n)
max(0, AdjgTxPwrMaxTCH(n) - P_max)
AVE_RXLEV_NCell(n) > AdjgRxLevMinHO(n) + max(0, AdjgTxPwrMaxTCH(n) - P_max)
GSM cell
ISHO Decision
69 © NOKIA / OS-PS CE Nokia Expert Club ISHO / 18.10.2004
• 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
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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
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3G -> 2G Handover signalling
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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
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ISHO 3G->2G Signalling
CS voice handover-RAN part
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AMR Handover procedure overview (1)
RRC connection setup
ISUP signalling
Parameters for HO event triggere1e, e1f, e6a,e6b
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AMR Handover procedure overview (2)
ISUP signalling
Mobility management; several AS cell add & cell drops
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AMR Handover procedure overview (3)
Compressed Mode Parameters
Measurement report to trigger CM
Mobility management; several AS cell add & cell drops
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AMR Handover procedure overview (4)
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
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Physical Channel reconfigurationRRC: Physical Channel reconfiguration
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Measurement Control new RAT NB list
[..]
new inter RAT NB listMeasurement info
RRC: Measurement Control
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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
measured 5th best cell by ARFCN
measured 6th best cell by ARFCN
RRC: Measurement Report
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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
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UE Measurement Report target GSM cell-BSIC verification
RRC: Measurement Report
UE reports verified BSIC of best cell to RNC
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Handover from UTRAN command
RRC: HO from UTRAN command
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Handover command GSM signalling
L3: Handover command
2G cell information (RF&configuration)
2G cell information (Security)
2G cell information (PC)
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GSM signalling
Physical synchronisation Information
Handover complete message
L3: Physical Information
L3: Handover complete
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ISHO 3G->2G Signalling CS voice handover-3G Core part
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ISHO Signalling on Iu-CS interface
RNC sends relocation request to MSC
source = 3G cell
target = 2G cell
RNC -> MSC via MGW
XX
XX
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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
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ISHO Signalling 3G->2GPS Cell change order-RAN part
If two GSM neighbours with same ARFCN in
RRC: Measurement Control,BSIC verification is performed
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ISHO Signalling 3G->2GPS Cell change order-3G core part
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ISHO L3 Signalling 3G->2GMulti RAB
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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.
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2G -> 3G Handover
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ISHO L3 Signalling 2G->3GMulti RAB RAN part
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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
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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
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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
below the given threshold Qsearch_C
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
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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.
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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)-
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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.)
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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.
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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
below the given threshold Qsearch_C
Inter-RAT measurements starts in case The RXLEV of the serving cell is above or
below the given threshold Qsearch_C
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
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2G -> 3G packet cell reselection (1)
GPRS traffic
UE reads 3G BCCH info& reselects to 3G
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2G -> 3G packet cell reselection (2)
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
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2G -> 3G packet cell reselection (3)
RAN radio resources rel.
PDP context release req.
PS detach request
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2G -> 3G packet cell reselection details
RRC connection setup request cause
Routing area update accept
New LAC / RAC
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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
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IMSI based handover
RAN ´04 feature
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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
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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
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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
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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
Operator A user path Operator B user path
WCDMA WCDMA
Separate neighbour lists for different IMSI ranges (different PLMN users)
GSM
GSM
WCDMA
GSM
GSM
Based on IMSI, load and service-based inter-
system HOs to their own GSM network in shared
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
Based on IMSI, users are handed over to their own
GSM networks when WCDMA coverage ends
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Case 3: IMSI Based Handover andMobile Virtual Network Operator
GSM GSM
GSM GSM
WCDMA WCDMA
Separate neighbour lists for different IMSI ranges (different PLMN users)
GSM
GSM
Operator A GSM cell
Operator A controlled WCDMA cell
Operator B GSM 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
Based on IMSI, users are handed over to their own
GSM networks when WCDMA coverage ends
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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
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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
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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
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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
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Thank you !