Work of Uplink Dedicated Physical Channel in WCDMA
There are two kinds of uplink dedicated physical channels, the Dedicated Physical Data Channel (DPDCH) and the Dedicated Physical Control Channel (DPCCH).
The DPDCH is used to carry the DCH transport channel. The DPCCH is used to carry the physical sub-layer control bits.
- Each DPCCH time slot consists of Pilot, TFCI，FBI，TPC
- Pilot is used to help demodulation
- TFCI: transport format control indicator
- FBI:used for the FBTD. (feedback TX diversity)
- TPC: used to transport power control command.
Uplink DPDCH and DPCCH are I/Q code division multiplexed (CDM) within each radio frame.
DPDCH carries data generated at Layer 2 and higher layer, the OVSF code is Cch,SF,SF/4, where SF is from 256 to 4.
DPCCH carries control information generated at Layer 1, the OVSF code is Cch,256,0.
Frame Structure of Uplink DPDCH/DPCCH
On the figure above, we can see the DPDCH and DPCCH time slot constitution. The parameter k determines the number of symbols per slot. It is related to the spreading factor (SF) of the DPDCH by this simple equation: SF=256/2k. The DPDCH SF ranges from 4 to 256. The SF for the uplink DPCCH is always 256, which gives us 10 bits per slot. The exact number of pilot, TFCI, TPC and FBI bits is configured by higher layers.
This configuration is chosen from 12 possible slot formats. It is important to note that symbols are transmitted during all slots for the DPDCH