Channel quality estimation and adaptive trellis-coded modulation with macrodiversity
Adaptive trellis-coded modulation with the aid of macrodiversity is proposed for slowly Rayleigh fading channels with lognormal shadowing. We propose also the use of differences between the partial Euclidean distance metrics (or a suitable modification) of the best trellis path and the second best path averaging along the surviving path as channel quality measures. Simulation shows that the channel quality estimation could give us a packet-by-packet estimation of channel signal-to-noise ratio (SNR) estimation with an error within 1 dB. The estimation could be used in our adaptive trellis-coded modulation with macrodiversity scheme to choose the best signal from three nearby base stations (BS) and also be used to adjust the data rate of the transmitters. Simulation results show that a system with such an estimation technique, using macrodiversity in adaptive trellis-coded modulation scheme could bring nearly 30% throughput improvement and at higher average SNR situation, it could also bring a reduction in bit-error-rate (BER) bounds up to one order of magnitude.