Performance Analysis of Multi-Channel MAC Schemes Based on 802.11

In order to improve the throughput performance of medium access control (MAC) schemes in wireless communication networks, some researchers proposed to split the single shared channel into two sub-channels: a control sub-channel and a data sub-channel. The control sub-channel is used for access reservation to the data sub-channel over which the data packets are transmitted. In this paper, an analytical framework is presented to evaluate the maximum achievable throughput of a class of generic multi-channel MAC schemes that are based on the RTS/CTS (ready-to-send/clear-to-send) dialogue and on the backoff contention resolution mechanism proposed in 802.11 DCF(distributed coordination function). By making use of a discrete Markov chain model for the backoff mechanism, the interval time of successfully transmitted RTS/CTS on the control sub-channel is obtained, and then it is applied to derive the saturation throughput of the multi-channel MAC schemes, which is closely related to the bandwidth allocation ratio between the control sub-channel and the data sub-channel. Moreover, the influence of the number of stations, the packet size, and the minimum contention window on the optimal bandwidth allocation ratio is investigated. Compared with the performance of the corresponding single channel MAC scheme that sends RTS/CTS packets and DATA packets on a single shared channel, the experiment results show that the multi-channel MAC schemes can only bring some performance enhancement. But under the condition that RTS/CTS are transmitted in full channel rate, the single channel MAC scheme can out-perform the multi-channel MAC schemes.