An enhanced link adaptation for the MB-OFDM UWB system

In the paper, an improved link adaptation scheme is proposed for the WiMedia MB-OFDM UWB system, in which quality of service (QoS) support is provided. The proposed scheme consists of three functional blocks: link quality indicator (LQI) calculator, frame error rate (FER) estimator, and transmitter (TX) parameter selector. Instead of using the average receive SNR (ASNR) as LQI, a new LQI metric is defined based on a union bound analysis to capture the effects of both path loss and frequency selectivity of an instantaneous UWB channel. How to calculate LQI for each rate mode is investigated by analyzing the distribution of soft bit information. With the calculated LQI, the FER performance of each rate mode can be accurately estimated with a look-up table method, which is suitable for practical implementation. Using the estimated FERs, TX parameter selector can optimize TX rate mode to improve the communication throughput under QoS constraints. It is shown the proposed scheme can significantly improve the throughput while maintaining the required QoS compared to conventional ASNR based link adaptation schemes.