Transport channels provide for information transfer between the physical layer and the medium access control (MAC) layer in the three layer structure illustrated in Figure 1.
Figure 1. Layers
The following uplink transport channels are defined:
Random access channel (RACH)
Uplink shared channel (UL-SCH)
Uplink transport channels are mapped to uplink physical channels as shown in Figure 2.
Figure 2. Uplink Transport Channel Mapping
The random access channel processes incoming data as follows:
Adds control information
Adds the random access preamble
The uplink shared channel processes the incoming data as follows:
Adds the cyclic redundancy check (CRC) for error detection
Performs code block segmentation
Adds turbo encoding
Performs rate matching
Performs code block concatenation
Performs data and control multiplexing