A wireless communication system provides for a random access channel (RACH) procedure for user equipment (UE) to request access to an uplink channel. From a physical layer perspective, an evolved Base Station (eNB) responds with a random access preamble and a random access response (RAR) of a fixed length message, such as 21 bits or 20 bits with a reserved bit for future extensions. In answer to a need that exists for an RAR to accommodate variations in system bandwidth, an approach to encoding a truncated resource block (RB) assignment of the RAR in manner in which the UE can interpret the RAR without loss of information. Thereby, needs for achieving RACH procedures and existing channel resources can be realized.