Distributed multichannel MAC protocol for IEEE 802.11 ad hoc wireless LANs

The IEEE 802.11 standard supports several independent and equal-capacity communication channels, which can be shared simultaneously and accessed by mobile stations in existing wireless local area networks (WLANs). However, under the restriction of one transceiver per network adapter, these mobile stations can only access one of these communication channels and, thus, the remainder channels are wasted inevitably. A multichannel carrier sense multiple access (CSMA) protocol, multichannel multiple access (MMA) protocol, is proposed in the paper for supporting parallel transmissions under the above single transceiver constraint. The MMA protocol enables mobile stations to contend for access of multiple data-transferring channels through the use of a dedicated service channel during each contention reservation interval (CRI). After granting the access right of these channels, these mobile stations can transmit data frames over different channels by using a pre-defined channel scheduling algorithm (CSA) in a distributed manner. The time complexity of the proposed heuristic CSA is O(|X|log|X|+|X|×M²) where |X| and M denote the number of successful requests in the CRI and the number of available channels, respectively. An improved MMA⁺ protocol with extending reserved transmission opportunities is also introduced and the goal is to maximize the channel utilization further. Simulation results show that the proposed MMA with CSA achieves a much higher throughput than conventional IEEE 802.11 WLAN with single channel. Simulation results also indicate that the achievable peek network throughput is not linearly proportional with the number of channels because of the native collision problem caused by single transceiver.