Idle Mode and Common Channel Behavior Functions PLMN
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 If Not Available 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 d. Bm in random order 6. Other PLMN where RSCP <= -95 d. Bm in descending order If Not Available *In case HPLMN was not available for selection, it will be tried again in 30 min. during national roaming (default)
Cell Search P-CCPCH (PSC + SSC + BCH) 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, Super-frame synchronization determined ------> UE adjusts transmit timing to match timing of BS + 1. 5 Chips Cell Synchronization complete
Cell Selection These 2 parameters allow the carrier to reserve or limit access to the cells in the network; Cell. Reserved ; Not Reserved (If Reserved, there will be no service to UEs) Access. Class. NBarred an Access Class) [0 -65535] (Each bit corresponds to
Cell Selection • Cell selection criteria: IF – Squal > 0 AND – Srxlev > 0 » then cell selection criteria are met CPICH Ec/No [d. B] measured by UE Sent on SIB 3 Squal = Qqualmeas – q. Qual. Min Srxlev = Qrxlevmeas – q. Rx. Lev. Min - Pcompesation CPICH RSCP [d. Bm] measured by UE max(max. Tx. Power. Ul - P, 0)
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) + q. Hyst(s) R (neighbour) = Qmeas(n) - q. Offset(s, n) q. Hyst 1 CPICH RSCP q. Hyst 2 CPICH Ec/No q. Offset 1 sn CPICH RSCP q. Offset 2 sn CPICH Ec/No QMeas can be either RSCP or Ec/No depending on the value of parameter Qual. Meas. Quantity. For GSM cells it always is RSCP. For WCDMA it is Ec/No by default
Cell Reselection WCDMA Measurement Quantity Serving cell ranking QHyst 1 1 Camp on Neigbour 1 1 2 Neighbour 1 2 Qoffset 1 sn Neighbour 2 3 3 3 tre. Selection Same idea as in GSM, serving cells are favored while neighbors are penalized
Measurements in Idle Mode • UE starts Intra-frequency measurements if : Squal<=s. Intra. Search [2 d. B] • UE starts Inter-Frequency measurements if : Squal<=s. Inter. Search [2 d. B] • UE starts GSM measurements if : Squal<=s. RATSearch [2 d. B] And/or Srxlev<=s. Hcs. Rat [2 d. B]
Cell Reselection IRAT tre. Selection (2 sec. )
Ie. F & IRAT Measurements in Cell_FACH mode Measurements are controlled by 2 parameters in Cell_FACH mode; inter. Freq. Fdd. Meas. Indicator: TRUE or FALSE depending on presence of Ie. F neighbors TRUE UE will perform measurements and evaluate cell reselection criteria on Ie. F cells FALSE UE will not perform measurements and will not evaluate cell reselection criteria on Ie. F cells fach. Meas. Occa. Cyc. Len. Coeff = 4 with this setting the UE will leave the FACH channel every 16 th frame to perform measurements on Ie. F or IRAT neighbors (2 fach. Meas. Occa. Cyc. Len. Coeff = 24 = 16 (Ie. F or IRAT) or 23=8 (Ie. F and IRAT) )
Mobility Management Registrations ØLocation / Routing Area Update ØA new cell w/ different LAC/RAC ØPeriodic Registration ØLU is controlled by T 3212 sent on BCCH ØRU is controlled by T 3312 (CN parameter) ØIMSI attach/detach ØDuring 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 Idle Mode Paging PCH is only decoded when PICH indicates that there is a paging for UEs paging group DRX (Discontinuous Reception) is used to limit battery consumption in idle mode t. PICH • • • S-CCPCH • • • Frame with PI Indicator • • • Associated S-CCPCH frame • • •
Master / System Information Blocks The UE reads the system information on the BCCH when the following events occur: Ø UE is powered up Ø UE changes cell in Idle mode or in state CELL_FACH Ø UE is informed of a change of System Information, when the UE is in Idle mode or state CELL_FACH Ø UE moves from dedicated mode to common mode Ø Timer expires for SIBs ØThe SIBs contain all information necessary for UEs to work properly in both Idle and Connected mode Master Information Block Ø Each SIB contains different kinds of information System Information Block 1 System Information Block 3 System Information Block n ØEach SIB has its own repetition period (sibx. Rep. Period) ØThe MIB has a fixed, predefined repetition rate equal to 80 ms
Mapping of System Information onto MIB and SIBs Contents MIB PLMN Identity x SIB 1 Cell selection and reselection parameters SIB 3 SIB 5 SIB 7 x SIB 12 x x Paging parameters Measurement management x Cell and common channel configuration x Timers and counters in Idle mode x Power Control on common channel x Location and routing updating SIB Scheduling Information SIB 11 X X x
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