Multilevel modulation and coding for indoor radio channels

The indoor radio channel provides the essential physical transmission medium for the implementation of radio LANs. We consider two alternative techniques for the mitigation of intersymbol interference due to multipath on indoor radio channels: the use of narrower signalling pulses (duty cycle less than 100%), and the use of FEC coding. Using the GWSSUS channel model, and assuming an exponential power-delay profile, the effect of intersymbol interference on the irreducible BER is calculated for both techniques, both for Rayleigh fading, and for a non-fading line-of-sight path. In the non-fading case, narrowing the signalling pulse is more effective than coding, but less robust in the presence of thermal noise, while in the fading case coding is more effective. The appropriate technique allows a maximum data rate, normalised to 1/(delay spread), of 0.62 in the non-fading case and 0.32 in Rayleigh fading, for irreducible BER 10^-6