An Enhanced Link Adaptation Strategy for IEEE 802.11 Wireless Ad Hoc Networks

The multi-rate capability provided by the IEEE 802.11 physical layer requires that the MAC layer adapts the transmission rate according to the receiver-side channel conditions. Many link adaptation schemes for a multi-hop wireless ad hoc network have been proposed so far where most of them probe the receiver's channel condition using RTS/CTS handshake and select the highest attainable data rate at which the receiver can decode successfully. A key problem with such schemes is that they do not consider the interference from hidden nodes in multi-hop and multi-rate environments, and hence, they may not work properly since the higher rate also increases the probability of interference. In this paper, we investigate the relation between interference and transmission rates and show that a transmitter can achieve higher performance by transmitting at the decreased rate in multi-hop ad hoc networks. Based on the observation, we present a new effective link adaptation scheme that integrates the receiver-based and sender- based techniques and determines the best transmission strategy taking the interference as well as the receiver's channel quality into consideration.