Protocol design and throughput analysis of frequency-agile multi-channel medium access control

Time-varying channel conditions, due to multipath fading, present a unique challenge for wireless network design. In this paper, we take a cross-layer approach to study frequency-agile medium access control design for ad hoe networks. Specifically, building on the IEEE 802.11 standard, we propose an opportunistic multi-channel MAC protocol (OMC-MAC), with three key features: 1) by exploiting the channel variations across multiple channels, OMC-MAC achieves selection diversity gain in an opportunistic and distributed manner; 2) the size of the contention window is adjusted adaptively based on the estimate of the number of competing stations, which is obtained via using a Sequential Monte Carlo technique; and 3) OMC-MAC achieves "resource pooling" and thus improves the stability of the network. Analysis results reveal that OMC-MAC in wireless LANs achieves significant throughput gain, even under heavy traffic conditions. Extensive simulation studies show that OMC-MAC can achieve efficient channel utilization for each Added channel, compared with the standard 802.11 MAC protocol and other multichannel protocols such as DCA and MMAC [1], [2]. Finally, we show via examples that the sequential Monte Carlo method is effective for the adaptation of the contention window size.