Abstract: According to the problem of timeliness for IEEE 802. 11's binary exponential backoff algorithm,which used maxmum transmitting times, a new delay-constrained binary exponential backoff algorithm was proposed, which used timcout threshold instead of maxmum transmitting times as the reference for packet dropping. It can increase system u- nitary effective throughput,and doesn't reduce system unitary throughput dramatically,which is fit for wireless Ad hoc networks demanding restrict delay. A Markov model was introduced to analyze system performance. The simulations validate the accuracy of model and the advantagement of IBC BEB over BEB.

Key words: Ad hoc, 802. 11, I3ackoff algorithm, Delay, Throughput