The goal of this to investigate the impact of contention window size on the performance of the IEEE 802.11 MAC protocol. IEEE 802.11 specification requires all nodes to choose a random back off interval between zero and CW (contention window), and wait for the chosen number of slot times before trying to access the channel-The goal of this is to investigate the impact of contention window size on the performance of the IEEE 802.11 MAC protocol. IEEE 802.11 specification requires all nodes to choose a random back off interval between zero and CW (contention window), and wait for the chosen number of slot times before trying to access the channel