A system and method is provided for communicating in a wireless communication system which supports link adaptation or link adaptation and incremental redundancy. The invention provides link adaptation at multiple code rate by dividing fixed length RLC blocks into coded sub-blocks. CRC code may be appended to the RLC blocks for error detection. The sub-blocks are then grouped into transmission units for transmission. The number of sub-blocks in each group is varied to provide multiple code rates. Headers are used to identify the transmission units being transmitted. In the case of retransmission, the transmission units may be expressly identified through extended headers. One or more of the originally transmitted sub-blocks are dropped and replaced by the extended headers in the retransmission. Accordingly, the present invention provides for a retransmission code rate which may be different from the code rate at which the transmission units were originally transmitted.