Friday, November 6, 2009

Initial Cell Selection Procedure

S1) Search for Primary SCH : Here UE knows the SCH primary synch.code as this is common for all cells

S2) Timeslot Synchronization : P-SCH is sent in first 256 chips of each slot, From Here UE will achieve Time Slot synchronization

S3) Frame Synchronization : There are 64 combination group of S-SCH codes, getting the matching set which UE read with the standard 64 combinations UE achieves Frame Synchrnization

S4) Primary Scrambliing Code acquisition: Each code group has 8 possible scrambling codes , UE will find out the one by matching each one from the set which it achieved from Frame Synchronization. This gives Scrambling code. getts form CPICH of the cell.

CPICH carries predefined bit-sequence is primary scrambling code, this will be used to detech CCPCH

S5) Decoding SIB and get PLMN identity: Once primary scrambling code is found, it uses this code decode BCH , from BCH SIBs UE reads PLMN identity and validate the home n/w PLMN for camping

*In Roaming, when home PLMN is not found,, RRC has to report all available PLMNs.
*From Neighbouring cell list : UE gets frequency and primary scrambling codes. So that it can do fast descrambling CPICH. From descrambled CPICH, UE caliculates chipEnergy-to-Noise ratio(Rx Ec/No)

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