Uplink Physical Channels

There are two dedicated channels and one common channel for the uplink. User data is transmitted on one of these channels, the Dedicated Physical Data Channel (DPDCH), as is the control information. The Random Access Channel is a common access channel.
 

The Dedicated Physical Control Channel (DPCCH) is needed to transmit pilot symbols for coherent reception, power signaling bits, and rate information for rate detection. The two basic solutions for multiplexing physical control and data channels are time multiplexing and code multiplexing. A combined IQ and code multiplexing solution (dual-channel QPSK) is used in the WCDMA uplink and to avoid Electromagnetic Compatibility (EMC) problems with Discontinuous Transmission (DTX).
There is a major drawback of a time multiplexed control channel, that is where there are EMC problems that arise when DTX is used for data transmission. Figure 31 shows an example of DTX during normal speech transmission. During periods when there is silence there is no need for information bits to be transmitted. This results in pulsed transmission of the of the control data that has to be transmitted.