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It has been believed that the simultaneous use of multiple channels in 802.11 wireless local area networks (WLANs) can improve network performance. Many efforts have been done to better exploit multiple non-overlapped channels. However, due to the limited number of orthogonal channels in IEEE 802.11 b/g standards, using only non-overlapping channels cannot completely eliminate the interference. Recent studies indicate that we can improve the full-range channel utilization and the network throughput by properly utilizing the partially overlapping channels. However, there are only limited studies of channel assignment algorithms for partially overlapping channels. In this paper, we investigate the problem of partially overlapping channel assignment to improve the performance of 802.11 wireless networks based on SINR model. Using the SINR model, we deduce a direct relationship between maximizing system throughput and minimizing total interference when partially overlapping channels are employed. After that, we propose a greedy method to minimize the total interference for throughput maximization. We evaluate our algorithm through extensive simulations and compare its performances with those of the state-of-the-art.

In this paper, we discuss the issue of unicast routing in dynamic CR networks. The problem of our concern is: given a set of CR nodes with geographical positions and temporarily available channels, how to design a protocol so that the average number of transmissions per packet for a unicast transmission is minimized. We propose a novel distributed protocol where packets are transmitted through successively geographic closer intermediate destination nodes, until eventually destination is reached. The intermediate destination nodes are within a twohop neighborhood and locally chosen by a heuristic algorithm we develop. A priority-based opportunistic routing method is adopted to forward the packets between two nearby intermediate destination nodes. Extensive simulations are conducted to show the performance of our protocol.

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