On the optimal contention window size in IEEE 802.11 based WLANs under co-channel interference

Throughput in IEEE 802.11 based wireless local area networks (WLANs) significantly depends on the minimum contention window (CW) parameter of CSMA/CA medium access control protocol. The throughput-optimal value of the minimum CW is modeled by G. Bianchi for a single WLAN without considering co-channel interference as N√2T_c, where N is the number of contending nodes in the WLAN and T_c is the collision time in mini-slots [1]. In this paper, the throughput-optimal configuration of the minimum CWs of the CSMA/CA based WLANs is studied under co-channel interference via extensive simulations. From the simulation results, it is investigated that in a WLAN the optimal value of the minimum CW is 4% to 25% higher than the Bianchi optimal CW due to co-channel interference. However, in WLANs, the optimal throughput is very close to the throughput obtained at the Bianchi optimal CW. In WLANs, very close to the optimal throughput can be obtained by configuring each WLAN independently with the simple Bianchi model even when the co-channel interference is considered.