A Multiuser, Multicarrier Link Adaptation Strategy for Fading Channels with PER Constraints

Link Adaptation (LA), adopted by many emerging standards, such as WCDMA, LTE and WiMAX is a key element for providing improved data rates and performance guarantees under specified Quality of Service (QoS) requirements. Link Adaptation can dynamically adjust a number of transmission parameters, most often modulation and coding, to reflect the characteristics of the wireless link to improve throughput and maintain link reliability. Most LA algorithms require only an estimate of the signal-to-noise ratio (SNR) to select an appropriate PHY mode, relying on the assumption of an AWGN channel. For channels experiencing frequency selective fading however, the conventional approach fails to accurately represent the stochastic variability across independent channels, resulting in inaccurate prediction of the current channel state and failure in selecting appropriate transmission parameters. A new channel quality metric is proposed in this paper that attempts to estimate the likelihood of packet errors in a fading channel and adjust Modulation and Coding Scheme (MCS) selection across each fading realisation independently. Results show improved mode selection efficiency over the conventional LA approach with added flexibility, as this approach is independent of the channel environment, providing a universal solution to LA.