Link availability prediction enhanced IEEE 802.11-based cooperative MAC with mobile relays

One of the most challenging issues in cooperative wireless networks at the medium access control (MAC) layer is to select a good helper (relay node) to start cooperation. The helpers' information is often stored in a CoopTable and updated via overhearing of the helpers' traffic. However, when the helpers are transmitting data infrequently or having random mobility, the cooperation may suffer from the out-of-date information in the CoopTable, since the source cannot gather enough timely information to make a good cooperation decision. In this paper, we propose to use link availability prediction to address such out-of-date information problem at the MAC layer. Making use of the possibly out-of-date information, our proposed solution does not introduce any additional signalling overhead but enables the source node to estimate the probability that the helper may appear in each cooperation zone. As such, the source node is able to make an intelligent decision even with the out-of-date information and benefit from a successful cooperation. The simulation results well demonstrate the source throughput improvement even when the helpers are less active in transmission and experiencing random walk mobility.