Idle Mode and Common Channel Behavior
Dec 30, 2015
Idle Mode and Common Channel Behavior
Functions
PLMN Selection
Cell Selection / Reselection
LA / RA Update
Paging
System Information
Automatic PLMN Selection
1. Last registered PLMN
2. Home PLMN
3. PLMN priority List from “user controlled” USIM
4. PLMN priority List from “operator controlled” USIM
5. Other PLMN where RSCP > -95 dBm in random order
6. Other PLMN where RSCP <= -95 dBm in descending order
If NotAvailable
If NotAvailable
If NotAvailable
If NotAvailable
If NotAvailable
*In case HPLMN was not available for selection, it will be tried again in 30min. during national roaming (default)
Initiate Cell Synchronization
UE monitors Primary SCH code, detects peak in matched filter output
Slot Synchronization Determined ------>
UE monitors Secondary SCH code, detects SCG and frame start time offset
Frame Synchronization and Code Group Determined ------>
UE determines Scrambling Code by correlating all possible codes in group
Scrambling Code Determined ------>
UE monitors and decodes BCH data
BCH data, Super-frame synchronization determined ------>
P-CCPCH
(PSC + SSC + BCH)
UE adjusts transmit timing to match timing of BS + 1.5 Chips
Cell Synchronization complete
Cell Search
Cell Selection
These 2 parameters allow the carrier to reserve or limit access to the cells in the network;
CellReserved Reserved ; Not Reserved (If Reserved, there will be no service to UEs)
AccessClassNBarred [0-65535] (Each bit corresponds to an Access Class)
• Cell selection criteria:IF
– Squal > 0
AND
– Srxlev > 0
» then cell selection criteria are met
Squal = Qqualmeas – qQualMin
Srxlev = Qrxlevmeas – qRxLevMin - Pcompesation
Cell Selection
CPICH Ec/No [dB] measured by UE
Sent on SIB3
CPICH RSCP [dBm] measured by UE max(maxTxPowerUl - P, 0)
Cell Reselection
Cell Reselection happens;• When the UE is camped normally has found a better neighbouring cell than the cell on which it is
camping
• When the cell on which it is camping is no longer suitable
– The cells to camp on are ranked based on R criteria;
R (serving) = Qmeas(s) + qHyst(s)R (neighbour) = Qmeas(n) - qOffset(s,n)
qHyst1 CPICH RSCP qOffset1sn CPICH RSCPqHyst2 CPICH Ec/No qOffset2sn CPICH Ec/No
QMeas can be either RSCP or Ec/No depending on the value of parameter QualMeasQuantity. For GSM cells it always is RSCP. For WCDMA it is Ec/No by default
Cell Reselection WCDMA
Serving cell
Neighbour 1
Neighbour 2
QHyst1
Qoffset1sn
3
2
1
treSelection
Measurement Quantity
ranking ranking ranking
2
1
21
3
3
Camp on Neigbour1
Same idea as in GSM, serving cells are favored while neighbors are penalized
Measurements in Idle Mode
• UE starts Intra-frequency measurements if :Squal<=sIntraSearch [2 dB]
• UE starts Inter-Frequency measurements if :Squal<=sInterSearch [2 dB]
• UE starts GSM measurements if :Squal<=sRATSearch [2 dB]
And/or
Srxlev<=sHcsRat [2 dB]
Cell Reselection IRAT
treSelection (2 sec.)
IeF & IRAT Measurements in Cell_FACH mode
Measurements are controlled by 2 parameters in Cell_FACH mode;
interFreqFddMeasIndicator: TRUE or FALSE depending on presence of IeF neighborsTRUE UE will perform measurements and evaluate cell reselection criteria on IeF cellsFALSE UE will not perform measurements and will not evaluate cell reselection criteria on IeF cells
fachMeasOccaCycLenCoeff = 4 with this setting the UE will leave the FACH channel every 16th frame to perform measurements on IeF or IRAT neighbors(2fachMeasOccaCycLenCoeff = 24 = 16 (IeF or IRAT) or 23=8 (IeF and IRAT) )
Mobility Management Registrations
Location / Routing Area UpdateA new cell w/ different LAC/RAC
Periodic RegistrationLU is controlled by T3212 sent on BCCHRU is controlled by T3312 (CN parameter)
IMSI attach/detachDuring Switch on & off
Paging
UEs can be paged on;
•Idle Mode (Type I) via PICH & PCH [S-CCPCH]•Cell_FACH Mode (Type II) via DCH•Cell_DCH Mode (Type II) via DCH
Frame withPI Indicator
AssociatedS-CCPCH frame• • •
• • • • • •
• • •
PICH
S-CCPCH
PICH
PCH is only decoded when PICH indicates that there is a paging for UEs paging groupDRX (Discontinuous Reception) is used to limit battery consumption in idle mode
Idle Mode Paging
Master / System Information Blocks
Master Information
Block
System Information
Block 1
System Information
Block 3
System Information
Block n
The SIBs contain all information necessary for UEs to work properly in both Idle and Connected mode
Each SIB contains different kinds of information
Each SIB has its own repetition period (sibxRepPeriod)
The MIB has a fixed, predefined repetition rate equal to 80 ms
The UE reads the system information on the BCCH when the following events occur:
UE is powered up UE changes cell in Idle mode or in state CELL_FACH UE is informed of a change of System Information, when the UE is in Idle mode or state CELL_FACH UE moves from dedicated mode to common mode Timer expires for SIBs
Mapping of System Information onto MIB and SIBs
Contents MIB SIB1 SIB3 SIB5 SIB7 SIB11 SIB12
PLMN Identity xCell selection and
reselection parameters x x
Paging parameters xMeasurement management x x
Cell and common channel configuration x
Timers and counters in Idle mode x
Power Control on common channel x
Location and routing updating X
SIB Scheduling Information X