A study of the impact of frequency selectivity on link adaptive wireless LAN systems

Wireless local area networks (WLANs) supporting broadband multimedia communication are being developed and standardized around the world. The HIPERLAN/2, 802.11a and HiSWANa standards provide channel adaptive data rates between 6 and 54 Mbps in the 5GHz radio band. The link adaptation mechanism is not specified in the standards. In this paper the performance of the HIPERLAN/2 system is evaluated in terms of throughput in a range of test channels with different degrees of frequency selectivity. On this basis, the impact of frequency selectivity on system performance is evaluated and the implications for the design of a link adaptation strategy are discussed. The issue of link adaptation for time bounded applications is also considered. The resulting conclusions are generally applicable to all three 5 GHz WLAN standards.