Application of high rate coded modulation schemes to radio LANs

Radio LAN systems are being proposed for the transfer of ever higher data rates, for such applications as cordless telephony, work station interconnect, variable bit rate video, and multimedia systems, operating within the same building or the same office. There is also a convergence with picocellular personal communication systems, being proposed to operate in very similar environments and increasingly to offer similar services. As data rate increases the dispersion due to the multipath channel will become more significant. The most commonly proposed solution to this problem is the use of channel equalisation. Spread spectrum techniques with CDMA have also been proposed but in picocellular systems this is less bandwidth efficient than FDMA or TDMA. This paper presents an alternative approach: to reduce the symbol rate to within the coherence bandwidth or equivalently to increase the symbol period to greater than the delay spread. It proposes the use of high rate coded modulation techniques, having bandwidth efficiencies and hence symbol rates similar to those of QAM, but also a significant coding gain increasing robustness to interference