Direct sequence spread spectrum radio LANs

The performance of direct sequence spread spectrum (DSSS) ISM (2.4-2.5 GHz) band radio local area networks (RLANs) using BPSK modulation and matched filter receivers is investigated. Short and long pseudonoise (PN) spreading sequences, a Barker code and an M-sequence, have been employed in both differential and coherent systems operating in a Rayleigh fading multipath channel with different delay spreads. A channel estimator was designed to perform the system synchronisation and control the receiver in order to mitigate the multipath fading and time-dispersion effects by using various multipath diversity techniques. It is found that with low delay spreads the short sequence leads to much better system performance than the long one. It is also shown that use of coherent instead of differential techniques increases the maximum tolerable delay spread