Adaptive coding for fading channels using outdated channel estimates

The development of adaptive trellis coded modulation schemes for communication systems operating over time-varying Rayleigh fading channels is considered. If the system employs a single outdated noiseless channel estimate and is able to achieve perfect interleaving of the coded symbols, substantial throughput gains are observed over non-adaptive trellis coded modulation schemes for systems with low user mobility. Next, the effect of noise in the channel estimates is shown to be an important consideration, even at the relatively high signal-to-noise ratios considered here. Finally, a bound to the pairwise error probability between two paths in the trellis of the adaptive scheme is derived analytically for the case where the coded symbols are imperfectly interleaved; this result suggests that adaptive signaling may be a strong candidate for systems operating in an environment that has limited diversity available.