Capture effects of wireless CSMA/CA protocols in Rayleigh and shadow fading channels

Abstract

We investigate the capture effects for a wireless local area network (LAN) system in the presence of multipath, shadowing, and near-far effects. The performance of wireless media access control (MAC) protocols with Rayleigh fading, shadowing, and capture effect are analyzed. We consider carrier-sense multiple-access/collision-avoidance (CSMA/CA) protocols as the wireless MAC protocols, since CSMA/CA protocols are based on the standard for wireless LAN's IEEE 802.11. We analyze and compare the channel throughput and packet delay for three types of CSMA/CA protocols: basic CSMA/CA, stop-and-wait automatic repeat request (SW ARQ) CSMA/CA, and four-way handshake (4-WH) CSMA/CA. We calculate the capture probability of an access point (AP) in a channel with Rayleigh fading, shadowing, and near-far effects, and we derive the throughput and packet delay for the various protocols. We have found that the performance of CSMA/CA in a radio channel model is 50% less than in an error-free channel model in low-traffic load, while the throughput and packet delay of CSMA/CA in a radio channel model show better performance than in an error-free channel model in high-traffic load. We also found that the 4-WH CSMA/CA protocol is superior to the other CSMA/CA protocols in high-traffic load.