An admission control algorithm for multi-hop 802.11e-based WLANs

Recently, wireless local area network (WLAN) hotspots have been deployed in many areas. The new IEEE 802.11e standard further provides quality of service (QoS) provisioning by grouping the applications into four different access categories. The coverage area of WLANs can be extended by allowing the neighboring mobile devices to relay data to the access points. This concept is known as multi-hop WLANs or wireless mesh networks. Due to the limited network capacity and the contention-based channel access mechanism, admission control is required to regulate the number of simultaneous flows to maintain QoS. The multi-hop extension of WLANs present further challenges for admission control design due to the location-dependent contention in the network. In this paper, we propose an admission control algorithm for multi-hop 802.11e-based WLANs. In our proposed admission control algorithm, we first use a contention graph to model the contention situation in the multi-hop WLAN. It is followed by an estimation of the capacity for each maximal clique in the contention graph. A new flow is admitted if the aggregated traffic load is less than the estimated network capacity. The proposed algorithm supports both stationary and mobile nodes, as well as handoff and new connections. Simulation results show that the proposed algorithm is effective in providing QoS guarantee to the existing voice and video flows while maintaining a good performance for best effort traffic.