Fair relaying and cooperation in multi-rate 802.11 networks

We consider a multi-rate WLAN using the 802.11 technology. Previous work advocated the use of relay nodes to alleviate the 802.11 anomaly effect, however the role of relay is a thankless one. Here, we propose two relay strategies that aim at giving relay nodes some incentives for their roles, while at the same time enhancing the overall network performances. The first strategy involves the implementation of two LLC queues at each station: one handles ´local´ traffic, the other collects relay traffic from other stations. This solution does not require any modification to current 802.11 cards. The second strategy relies on the 802.11e EDCA capabilities. It gives better performance with respect to the previous one, but its implementation depends on the availability of the 802.11e technology. Our strategies apply to infrastructured as well as ad hoc networks. Results show that they significantly improve system performances, both in terms of throughput and fairness.