Link adaptation policies for wireless broadband networks

Wireless broadband access is becoming increasingly popular in the telecommunications market due to the projected demand for high data-rate connections. Given the inherent volatility of the wireless channel, the accurate estimation of channel conditions and the adoption of sophisticated adaptation techniques is required, so that transmission parameters are selected based on link quality, and user throughput is maximized. We consider a simple wireless link monitoring method, which is based on counting positive and negative acknowledgments (ACKs and NACKs), and we investigate the class of adaptation policies that correspond to this method. The policy that maximizes the long-term throughput efficiency of a user is shown to be of threshold type. Due to inherent difficulties in realization of this policy, a suboptimal heuristic method to perform link adaptation is provided. Our results indicate a considerable improvement in link throughput under such adaptive techniques.