Research On Optimization Of CSMA Channel Access Technology

CSMA based access schemes have been usually adopted for wireless multi-access networks, such as WLAN, WSN and WPAN, due to the inherent flexibility of random access protocols. Based on analysis and comparison of current CSMA type schemes, this paper proposes two algorithms to improve the current IEEE 802.11 CSMA/CA (a variation of p-persistent CSMA) and IEEE 802.15.4 CSMA/CA (a variation of nonpersistent CSMA), respectively. Our works can be summarized as follows:First, we propose a deterministic backoff algorithm, namely PS-CS, to improve the delay performance of IEEE 802.11 CSMA/CA. We derive the system throughput of PS-CS, and further by simulation show that PS-CS can be designed to achieve the optimal capacity of p-persistent CSMA and enjoy significantly better delay performance than the optimal p-persistent CSMA.Second, we propose a mathematical framework for evaluating the throughput, delay and reliability of an IEEE 802.15.4 distributed wireless network when the system allows multi-packet reception in asynchronous operating mode and each node can access to the medium in a completely asynchronous way. Simulation results verify the accuracy of our analytical results, reveal the backoff window size that maximizes the throughput, and further indicate that asynchronous multi-packet reception indeed outperforms synchronous multi-packet reception in IEEE 802.15.4 CSMA/CA.