cell selection & reselection.ppt
DESCRIPTION
testTRANSCRIPT
1 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Selection and Reselection
5 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Selection and Reselection: Motivation
CM requestsNAS control radiomeasurements
PLMNselected
PLMNavailable
registrationarea changes
locationregistration
response
indicationto usermanual mode
locationregistratio
n
cell selectionand reselection
PLMN selectionand reselection
automatic mode
RRC tasks:• PLMN selection
and reselection;• Cell selection and
reselection; • Location
registration.
if the UE is in the RRC idle
mode
if the UE is in the RRC connected modestates:• CELL_FACH,• CELL_PCH, and• URA_PCH
9 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Operator controlled PLMN list
User controlled PLMN list
Last registered
PLMN
Home PLMN
Other PLMN‘s with RAT‘s the
UE is capable of
Switch on in automatic PLMN selection operation mode
PLMN Selection
HPLMN Search Period Timer6 .. 480 minutesDefault: 60 minutes
11 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reservations and Cell Restrictions
Cell- acceptable- suitable- barred- reserved
Access Class barred:(UE access classes 0..9 and
11..15)
BCCH: Cell Access Restriction
13 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reservations and Cell Restrictions
Cell Barred Cell reservedfor operator
Cell reservedfor future extension
Case
1
2
3
4
not barred
not barred
not barred
barred
not reserved not reserved
not reserved reserved
reserved ---
--- ---
suitable for selection and
reselection
suitable for AC 11 or 15 in HPLMN otherwise „barred“
Cell „barred“
Not suitable – not even for emergency call
15 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reservations and Cell Restrictions: Access Class
UE RRC idle
I ignore all Access Class related cell
access restrictions
when selecting a cell to camp
on
UE RRC connected
Access Class only relevant
for access
Access Class irrelevantfor access suitable cell
suitable cell
16 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reservations and Restrictions• WCEL: CellBarred
Defines whether the cell is barred or not. A barred cell is a cell where a UE is not allowed to camp on. This parameter is part of SIB 3.0 (Barred), 1 (Not barred); default: 1.
• WCEL: TBarredWhen the cell is barred, UE regards the cell barred condition valid for a number of seconds defined by the value of 'Cell barred period'. This parameter is part of SIB 3.[10, 20, 40, 80, 160, 320, 640, and 1280] seconds; default: 40 seconds.
• WCEL: Cell_ReservedDefines whether the cell is reserved for operator use. This parameter is part of SIB 3.0 (Reserved), 1 (Not reserved); default: 1.
• WCEL: IntraFreq_Cell_Reselect_IndDefines whether intra-frequency cell re-selection is allowed when the cell is barred.This parameter is part of SIB 3/4.0 (Allowed), 1 (Not allowed); default: 0.
19 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
States and State Transition in the RRC Idle Mode
Cell Selection Process
NAS controls
AS controlscorrespondentprocedures
NAS:
PLMNselection
• RAT(s) associated with the selected PLMN• forbidden registration areas• list of equivalent PLMNs
UE CN
AS:attempts to find suitable cells
21 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
States and State Transition in the RRC Idle Mode
1
InitialCell Selection
Campednormally
CellReselectionEvaluationProcess
no cell informationstored for the PLMN
cell informationstored for the PLMN
go here whenevera new PLMNis selected
no suitable cell found
suitable cell found suitable cell found
ConnectedMode
suitablecell found
no suitablecell found
nosuitable
cellfound
StoredInformation
Cell Selection
trigger
suitablecell selected
no suitablecell found
Cell Selectionwhen leaving
connectedmode
leaveidle mode
return toidle mode
NASregistration
rejected
(adopted from TS 25.305 V3.11.0 chap. 5.5.2)
23 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
States and State Transition in the RRC Idle Mode
Camped onAny Cell
Any CellSelection
ConnectedMode
(Emergencycalls only)
return toidle mode
go here when no USIM in the UE
USIM inserted1
leaveidle mode
no acceptable cell found
an acceptable cell found
Cell Selectionwhen leaving
connectedmode
acceptablecell found
suitablecell found
1
CellReselectionEvaluationProcess
trigger
acceptable
cell selected
no acceptablecell found
(adopted from TS 25.305 V3.11.0 chap. 5.5.2)
25 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Selection Criterion S (in the FDD mode)
Qqualmeas (dB)(CPICH Ec/N0)
Qrxlevmeas (dBm)CPICH RSCP
Qqualmin(–24...0)
Qrxlevmin(–115...–25)
Srxlev > 0
Pcompensation
Squal > 0 S-Criterionfulfiled
Squal >0 ANDSrxlev > 0
suitable
cell?
27 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Selection Criterion S
Pcompensation= max(UE_TXPWR_MAX_RACH – P_MAX, 0)
Cell size defining parameters:• Qrxlevmin• Qqualmin
I am outside
I am inside,
but have not
enough power
-50 .. 33 dBm
29 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
(Initial) Cell Selection Process
Initial Cell Selection
(scan RF channel)
Stored Information Cell Selectionor
I have to find a
suitable cell
Squal = Qqualmeas – Qqualmin > 0Srxlev = Qrxlevmeas - Qrxlevmin – Pcompensation > 0
Once a suitable cell is found this cell is selected
31 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Selection When Leaving the RRC Connected Mode
• active set cells as candidates for cell selections; if not, then
• Stored information cell selection Squal > 0Srxlev > 0
32 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Selection• WCEL: QrxlevMin
The minimum required RX level in the cell. This parameter is part of SIB 3.[-115 ... –25] dBm, step 2 dBm; default: -115 dBm.
• WCEL: QqualMin The minimum required quality level in the cell (Ec/No). This parameter is part of SIB 3.[-24 ... 0] dB, step 1 dB, default: -20 dB.
• WCEL: UEtxPowerMaxPRACHThis parameter defines the maximum transmission power level a UE can use on PRACH. The value of the parameter also effects the cell selection and reselection procedures. The value of the parameter is sent to UE in the Cell selection and re-selection of SIB 3 and 4 of the serving cell.[..]
35 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection in the RRC Idle and RRC Connected Mode
S-Criterionfulfilled
cells with highest HCSPriorities &H > 0
measurementthresholds
cells with lower HCS
priority than in serving cell
If No Cellwith H>0accept allneighbors
HCS in use: HCS not in use:
S-Criterionfulfilled
measurementthresholds
H-Criterionfor fast
moving UEsfor slow
moving UEs
R-Criterioncell ranking
R-Criterioncell ranking
R-Criterioncell ranking
37 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement Rules with no HCS
SintrasearchSintersearchSsearchRAT m
No need to measure
neighbour cells
Intra- frequency
Sx=Squal (in FDD mode)
Intra-frequencyInter-frequency
serving cell
Example: Nokia Sintrasearch = 4dB, Sintersearch = 2dB,Ssearch_RAT = 0dB
Where to perform measurements
Intra-frequency
Inter-freqencyInter-RAT
38 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part I)• WCEL: UseOfHCS
This parameter indicates whether the serving cell belongs to a Hierarchical Cell Structure (HCS). This parameter is part of SIB 11/12.0 (HCS not used), 1 (HCS in use); default: 0.
• WCEL: SintrasearchThe threshold for intra-frequency measurements, and for the HCS measurement rules. This parameter is part of SIB 3.[0 ... 20] dB, step 2 dB, default: 4 dB.
• WCEL: Sintersearch The threshold for inter-frequency measurements, and for the HCS measurement rules. This parameter is part of SIB 3.[0 ... 20] dB, step 2 dB, default: 2 dB.
• WCEL: Ssearch_RATThe RAT-specific threshold for inter-RAT measurement rules. This parameter is part of SIB 3.[0 ... 20] dB, step 2 dB, default: 0 dB.
41 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement Rules with HCS
SintrasearchSintersearchSsearchRAT m
Higher HCS priorityIntra-
frequencyInter-
frequency
SlimitsearchRAT m
Intra-frequencyInter-frequency
Equal &higher HCS
priorityIntra-
frequency
Inter-frequenc
y
Sx=Squal (in FDD mode)
Srxlevs <= SsearchHCSif
if
Example: Nokia Sintrasearch = 4dB, Sintersearch = 2dB,Ssearch_RAT = 0dB,SsearchHCS = 1dB
Srxlevs > SsearchHCS
43 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement Rules with HCS
SintrasearchSintersearchSsearchRAT m
Higher HCS priorityIntra-
frequencyInter-
frequency
SlimitsearchRAT m
Intra-frequencyInter-frequency
Intra-frequency
Inter-freqencyInter-RAT
Intra-frequenc
y,Inter-
frequency, &
Equal and higher HCS
priority inter RAT
Equal &higher HCS
priorityIntra-
frequency
Inter-frequenc
y
Sx=Squal (in FDD mode)
if Srxlevs <= SHCS,RATm measure on all Inter-RAT cells
ifSrxlevs > SHCS,RATm
Example: Nokia Sintrasearch = 4dB, Sintersearch = 2dB,Ssearch_RAT = 0dB, Slimit, searchRAT = 2dB SsearchHCS = -1dB, SHCS_RAT = 1dB
44 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part II)• WCEL: SHCS_RAT
The RAT specific threshold for inter-RAT measurement rules. This parameter is part of SIB 3.[-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).
• WCEL: Slimit_SearchRATThreshold for skipping inter-RAT measurement rules in HCS. Above this RAT specific threshold in the serving UTRA cell, the UE does not need to perform any inter-RATm measurements. This parameter is part of SIB 3.[0 ... 20] dB, step 2 dB, default: 2 dB.
• WCEL: SsearchHCSThreshold for intra- and inter-frequency measurement rules in HCS. Below this limit in the serving cell, the UE initiates measurements of all intra and inter-frequency neighbouring cells of the serving cell. This parameter is part of SIB 3. [-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).
47 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Measurement Rules with HCS and fast moving UEs
NCR = cell reselection threshold (default: 8)TCRmax = time period
NCR/TCRmax
fast moving UE
time
TCrmaxHyst
measurement rule for fast moving UEs
measures neighbouring cells with equal or lower
HCS priority
priorizes cells with lower HCS priority for
re-selection
Example: Nokia TCRmax = 60s,NCR = 8,TCRmaxHyst = 0s
measurement rules forslow moving UEs
measurement rules forslow moving UEs
48 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part III)• WCEL: NCr
This parameter defines the maximum number of cell reselections. If the number of cell reselections during the TCrmax time period exceeds the value of NCr, high mobility has been detected. Not used if TCrmax equals 'not used‚ This parameter is part of SIB 3.[1 ... 16], default: 8.
• WCEL: TCrmaxThe duration for evaluating the allowed amount of cell reselections. If the number of cell reselections during the time period defined by Tcrmax exceeds Ncr, high mobility has been detected. This parameter is part of SIB 3.[0 (= not used), 30, 60, 120, 180, 240] seconds, default: 60 seconds.
• WCEL: TCrmaxHystCell reselection hysteresis for reverting from UE high-mobility measurements. The additional time period before UE reverts to low-mobility measurements. This parameter is part of SIB 3. [0, 10, 20, 30, 40, 50, 60, 70] seconds, default: 0 seconds.
53 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: H-Criterion (slow moving UE)
S-Criterionfulfilled
only cells with
highest HCSpriorities &
H > 0
measurementthresholds
cells with lower HCS
priority than in serving cell
H-Criterionfor fast
moving UEsfor slow
moving UEs
R-Criterioncell ranking R-Criterion
cell ranking
Hs = Qmeas,s – Qhcss
Hn = Qmeas,n - Qhcsn – TOn * Ln
accept allneighbours
cells withH>0
R-Criterioncell ranking
no cells withH>0
54 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Qmeas,n - Qhcsn
0time
TOn TOn
PENALTY_TIMEn PENALTY_TIMEn
TOn = 0 TOn = 0
StartTn
StartTn
StopTn
Hs = Qmeas,s – Qhcss
Hn = Qmeas,n - Qhcsn – TOn * Ln
Example:HCS_PRIOn <> HCS_PRIOs
=> Ln = 1 TOn = TEMP_OFFSETn * W(PENALTY_TIMEn – Tn)
Cell Reselection: H-Criterion (slow moving UE) and TOn
55 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part IV)• WCEL: HCS_PRIO
This parameter defines the HCS priority level for a cell. Value 0 indicates the lowest HCS priority and value 7 indicates the highest HCS priority.[0 ... 7], default: 0.
• WCEL: QHCSQuality threshold level for applying prioritised hierarchical cell re-selection for a cell. Part of HCS Serving cell information (Qhcss). This parameter is part of SIB 3. [-24 ... 0] dB, step 0.5 dB, default: -24 dB.
• HOPS: AdjsHCSthresholdDefines the threshold level which must be exceeded by the CPICH Ec/No of the intra-frequency neighbouring cell before the hierarchical cell re-selection becomes possible (Qhcsn).[-24 ... 0] dB, step 0.5 dB, default: -24 dB. HOPI: AdjiHCSthreshold: [-24 ... 0] dB, step 0.5 dB, default: -24 dB. HOPG: AdjgHCSthreshold: [-110 ... -37] dBm, default: -110 dBm.
56 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part IV)• HOPS: AdjsTempOffset1
This parameter is used in the cell ranking between cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. [3, 6, 9, 12, 15, 18, 21, 100 (Infinity)] dB, default: 3 dB. HOPI: AdjiTempOffset1, HOPG: AdjgTempOffset1
• HOPS: AdjsTempOffset2This parameter is used in the cell ranking between WCDMA cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. [2, 3, 4, 6, 8, 10, 12, 100 (Infinity)] dB, default: 2 dB. HOPI: AdjiTempOffset2
• HOPS: AdjsPenaltyTimeDefines the time period during which the Temporary Offset 1/2 is applied in the cell re-selection procedure for the intra-frequency neighbour cell in question.[0 ... 60] seconds, step 10 seconds, default: 0.HOPI: AdjiPenaltyTime, HOPG: AdjgPenaltyTime
59 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Qmeas,n – Qoffsets,n
PENALTY_TIMEnPENALTY_TIMEn
TOn = 0 TOn=0Start
Tn Start
Tn StopTn
Rs = Qmeas,s + Qhysts
Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)
Example:HCS_PRIOn = HCS_PRIOs
=> Ln = 0 TOn = TEMP_OFFSETn * W(PENALTY_TIMEn – Tn)
Cell Reselection: R-Criterion and TOn
Qmeas,s
temp. offset only used with HCS
TOn
TOn
60 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Rs = Qmeas,s + Qhysts
Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)
Cell Reselection: R-Criterion
Qmeas,n
Qmeas,s
Qm
eas
Rs
Rn
Qoffsets,n
Qhysts
Rn > Rs =>„cell reselection“
Example:HCS_PRIOn <> HCS_PRIOs
=> Ln = 1
Treselection
61 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Nokia Parameters for Cell Reselection (Part V)• WCEL: Qhyst1 (Qhyst2)
Qhyst1 is used for TDD and GSM cells, and for FDD cells when cell selection and re-selection quality measure is set to CPICH RSCP (CPICH Ec/No) (Qhyst1s/ Qhyst2s). This parameter is part of SIB 3.[0 ... 40] dB, step 2 dB, default: 4 dB.
• HOPS: AdjsQoffset1 (AdjsQoffset2) This parameter is used in the cell re-selection and ranking between WCDMA cells. The value of this parameter is subtracted from the measured CPICH RSCP (CPICH Ec/No) of the intra-frequency neighbour cell before the UE compares the quality measure with the cell re-selection/ranking criteria.[-50 ... 50] dB, default: 0 dB. HOPS: AdjsQoffset1 (AdjsQoffset2), HOPG: AdjgQoffset1, (AdjgQoffset2)
• WCELL: TreselectionThe UE triggers the reselection of a new cell if the cell reselection criteria are fulfilled during the time interval Treselection. This parameter is part of SIB 3.[0 ... 31] seconds, default: 0 seconds.
The remaining parameters were already specified under Nokia Parameters for Cell Reselection (Part IV).
63 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement Requirements – Serving CellDRXcycle
Nserv
S
S
S S
start measurement on all neighbouring cells
12 seconds
if still no suitable cells
UE initiates cell selection procedures for the
selected PLMN
UE “out of service area”
At least one• CPICH Ec/Io
measurement• CPICH RSCP
measurement• S criterion
evaluation
DRX cycle
if UE RRC idle
if UE in CELL_FACH, CELL_PCH or URA_PCH
65 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement – Intra-frequency Cells
At least one• CPICH Ec/Io
measurement, orCPICH RSCP measurement
TmeasureFDD cycle
3 dB
Serving cellIntra-frequency cell
time
UE is capable of evaluating that an intra-frequencycell has become better ranked (if Treselection = 0)
within TmeasureFDD
67 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement– Inter-frequency Cells
At least one• CPICH Ec/Io
measurement orCPICH RSCP measurement
(Ncarrier-1) * TmeasureFDD cycle
3 dB for CPICH Ec/Io 5 dB for CPICH RSCP
Serving cellInter-frequency cell
time
UE is capable of evaluating that an inter-frequencycell has become better ranked (if Treselection = 0)
within (Ncarrier -1) * TmeasureFDD
69 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Measurement Requirements + GSM Cells
DRX cyclelength [s]
Nserv [number ofDRX cycles]
TmeasureFDD [s](number ofDRX cycles)
TevaluateFDD [s](number ofDRX cycles)
TmeasureGSM [s](number ofDRX cycles)
0.08 4 0.64 (8 DRX cycles)2.56 (32 DRX cycl)2.56 (32 DRX cycl)
0.16 4 0.64 (4) 2.56 (16) 2.56 (16)
0.32 4 1.28 (4) 5.12 (16) 5.12 (16)
0.64 4 1.28 (2) 5.12 (8) 5.12 (8)
1.28 2 1.28 (1) 6.4 (5) 6.4 (5)
2.56 2 2.56 (1) 7.68 (3) 7.68 (3)
5.12 1 5.12 (1) 10.24 (2) 10.24 (2)
In idle mode, UE supports DRX cycles lengths 0.64, 1.28, 2.56 and 5.12 s
Each GSM neighbour
• GSM BCCH carrier RSSI
TmeasureGSM
BSIC at least every 30 seconds for each of the 4 strongest GSM BCCH carriers
30 seconds
+
(DRX cycle length table source: TS 25.133 V3.11.0 chap. 4.2.2.1)
71 © NOKIA topic: cell selection & reselection/ July 2003 /Markus Wimmer
Cell Reselection: Maximum Interruption in Paging Reception
50 ms
50 ms
50 ms
TSI
TBCCH
intra-frequency
inter-frequency
inter-RAT