Methods and apparatus are provided for a User Equipment (UE) to transmit signals in response to the reception of a Downlink Control Information (DCI) format transmitted from a base station of a communication system. The DCI format may provide only the frequency resources for the transmission of signals by the UE, while other parameters associated with the transmission of signals by the UE may be either predetermined or known to the UE through other signaling from the base station. The frequency resources used for the transmission of signals by the UE may be a sub-set of the frequency resources indicated by the DCI format and the determination of this sub-set by the UE may be either deterministic or pseudo-random.