Sidekick: AP aggregation over partially overlapping channels

Abstract

The uncoordinated deployment of many high-bandwidth 802.11a/g/n access points (APs) in urban areas offers the potential for WLANs to be a strong complement to cellular networks in providing ubiquitous connectivity. However, given that the bandwidth of the backhaul links connected to these APs is often an order-of-magnitude lower than that of the WLAN channel, aggregating the throughput from multiple APs is often necessary in order for the client to achieve an acceptable level of network performance. In this paper, we present Sidekick — a simple and novel AP aggregation protocol that exploits effective communication between 802.11a/g/n nodes on partially overlapping channels to attain high aggregate throughput in the face of dynamic WLAN and backhaul link conditions. Sidekick is built upon Aileron, which provides an extremely reliable and low-overhead control channel over which the APs and clients can coordinate the aggregation process. The use of such a control channel over partially overlapping channels enables Sidekick to quickly respond to varying bandwidth availability and probe for new transmission opportunities with little overhead. Our evaluation results indicate that Sidekick can make more than 30% improvement in throughput over FatVAP in a variety of situations.