This letter presents a simple but accurate analytical model to evaluate the throughput of IEEE 802.11 distributed coordination function in non-saturated conditions. The influence of offered load on the throughput of both basic and RTS/CTS access mechanisms are analyzed and compared. It's shown that basic access scheme can achieve the same maximal throughput as that of RTS/CTS mechanism in non-saturated conditions while the latter is robust to the number of contending stations compared to basic mechanism. The analytical results are validated by extensive simulations.

Supporting quality-of-service (QoS) of multimedia communications over IEEE 802.11 based ad hoc networks is a challenging task. This paper develops a simple 3-D Markov chain model for queuing analysis of IEEE 802.11 MAC layer. The model is applied for performance analysis of voice communications over IEEE 802.11 single-hop ad hoc networks. By using the model, we finish the performance optimization of IEEE MAC layer and obtain the maximum number of voice calls in IEEE 802.11 ad hoc networks as well as the statistical performance bounds. Furthermore, we design a fully distributed call admission control (CAC) algorithm which can provide strict statistical QoS guarantee for voice communications over IEEE 802.11 ad hoc networks. Extensive simulations indicate the accuracy of the analytical model and the CAC scheme.