CCTrCH [Under UMTS]
» Phy layer
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Multiplexing and Channel coding (FDD) - 25.212 «
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UE radio transmission and reception (FDD) - 25.101 «
PHY multiplexes multiple and related transport channels (like number of DCHs, PCH and FACH) to form a single binary stream. The single binary stream is CCTrCH (Coded Composite TRaffic CHannel). CCTrCH is then sent over one or several physical channels.
At receiving side, the process is reversed. Transport Format Combination Indicator (TFCI) will be required to demultiplex transport channels back at receiving side. TFCI is carried in corresponding physical control channel. Yes, PHY layer has its control channel. In addition to TFCI, it may carry (fast) power control bits called Transmit Power Control (TPC) bits.
What UMTS has done by having TF and CCTrCH is that: it has given freedom and separation to physical layer to carry out physical layer procedures. Though controlled by RRC, PHY layer can effectively do power control and take care of other CDMA PHY specific challenges.
Below diagram shows CCTrCH models at UE for UL and DL respectively (TDD specific channels not considered).
References: UMTS by Sanchez and Thioune, and WCDMA for UMTS by Holma and Toskala.
| Copyright © Samir Amberkar 2010 | § |
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