Energy Efficient Topology Control for WLANs

Wireless LANs employing the IEEE 802.11a/b/g/n standard operate in the unlicensed frequency bands. Their deployment has seen an exponential growth since their introduction. It is very common to find a wireless LAN in most buildings and houses around the world. These infrastructure-based WLANs are deployed to meet certain connectivity requirements and are usually deployed randomly. This random deployment has made the networks to be collectively unmanaged leading to the existence of larger interference areas. Power is lost because the access points usually operate with their factory default configurations that use the maximum authorized power level. This leads the access points to cover an area beyond required leading to the formation of larger interference areas that affects the performance of the networks. In this paper we study the power control problem in these networks using computation geometry and coalition formation game theory. We first analyze a coalition formation game between two neighboring access points for transmit power optimization. Then we set the requirements for other access points to join the coalition and investigate if a stable coalition can be formed. We finally show that by forming a coalition of up to five access points an optimal radio range assignment scheme exists that minimizes the total transmit power in the network substantially while meeting the requirements of network coverage.