Channel Assignment in Multi-Rate 802.11n WLANs

As the latest IEEE 802.11 standard, 802.11n allows a maximum physical data rate as high as 600Mbps, making it a desirable candidate for wireless local area network (WLAN) deployment. In WLANs, access points (APs) are often densely deployed, and thus neighboring APs should be assigned with orthogonal channels to avoid performance degradation caused by interference. It is challenging to find the optimal channel assignment strategy, as the number of channels is very limited. Many channel assignment schemes have been proposed for WLANs in the literature. However, most of them were not designed for 802.11n WLANs, and did not consider the challenges from the new channel bonding and frame aggregation mechanisms. Moreover, the impact of multi-rate clients on channel assignment is not fully investigated yet. In this paper, we study channel assignment in multi-rate 802.11n WLANs, aiming at maximizing the network throughput. We first present a network model and an interference model, and estimate the client throughput based on them. We then formulate the channel assignment problem into a throughput optimization problem. As the formulated problem is NP-hard, we propose a distributed channel assignment algorithm to provide practical solutions. We have conducted extensive simulations to evaluate the proposed algorithm and the results show that the network throughput can be significantly improved compared with existing schemes.