Equalization Requirements for 30 Mbps Indoor Wireless Data Transmission

The next step in the evolution of wireless local area networks (LANs) is an increase in the data rate from the present rates of a few Mbps to tens of Mbps. As a result of the faster rates the normalized delay-spread increases and simple modulation and demodulation has to be augmented by adaptive equalization. This paper investigates the equalizer requirements of a 4-QAM based system operating at a data rate of 30 Mbps. Through a series of simulations, using a large set of randomly generated channels with ensemble-averaged rms delay spreads of τrms = 25 ns, 50 ns, 100 ns and 150 ns, the minimum number of taps necessary to guarantee 99% availability (1% outage) is reported. Additionally, the paper presents a discussion on the effects of changing the location of the reference tap (gain-tap) of the equalizer on the overall system performance.