A response interframe space (RIFS) time period may be adapted in a communication system. The RIFS time period may be determined based, at least in part, on a processing time used by a receiving device to process a received physical layer transmission from a transmitting device. The RIFS may be optimized in consideration of channel conditions for a particular communications channel, capabilities of a receiving device, and/or characteristics of a particular physical layer transmission. For example, the RIFS may be dependent on characteristics of a final transmission symbol used to transmit a physical layer transmission. The RIFS may depend on a processing time associated with decoding forward error correction (FEC) encoded blocks that end in the final transmission symbol. The RIFS may depend on a quantity of decoding iterations in a communication system that uses iterative decoding of FEC encoded blocks.