Friday, November 6, 2009

Downlink Physical Channels

SCH -> Synchronization Channels : 1) Used for Cell search 2) Two Subchannels : Primary and secondary SCH 3) Transmitted only during first 256 chips in each timeslot

CPICH -> Common Pilot Channels : 1) Fixed rate 30 kbps 2) Carried a predefined sequence 3) P-CPICH : SCH, Primary CCPCH, AICH and PICH 3) S-CPICH : Optional

P-CCPCH -> Primary Common control physical channel : 1) Fixed Rate 30 kbps 2) Carries BCH But not transmitted in First 256 chps of each slot

S-CCPCH-> Secondary Common Control Physical Channel : 1) Variable Rate 2) FACH and PCH, can be mapped to same/separate channels 3) Transmitted only when data is available

P-DSCH -> Physical Downlink Shared Channel : 1) Carries DSCH 2) This channel used in CELL-FACH state to transfer data 3) Allways associated with downlink DPCH, carries control info.

PICH -> Paging Indicator channel : Carries paging indicators, which indicates the present of paging message on PCH

AICH -> Acquisition Indicator Channel : Carries acquisition indicators. This carries signatures for random access procedures

HS-PDSCH -> High Speed- Physical Downlink Shared Channel : 1) QPSK or 16 QAM Modulation 2) Carreis HS-DSCH 3) Each frame is 2 ms with 3 slots 4) Spreading Factor is 16

HS-SCCH -> High Speed - Shared Control Channel for HS-DSCH : 1) Carries downlink signalling related to HS-DSCH transmission 2) Indicates when there is data on DSCH for UE 3) Fixed rate channel SF=128 i.e 60 kbps 4) UE monitors 4 HS-SCCH

IF PCPCH (If CPCH is not supported the below will not be present)

CPCH : Access preamble acquisition Indicator channel (AP-AICH). Carries AP acquisition indicator of associated CPCH

CSICH : CPCH Sttatus Indicator channel. This carries CPCH status information

CD/CA-ICH : Collision Detection/Channel Assignment Indicator channel

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