Impact of Fading Correlation and Unequal Branch Gains on the Capacity of Diversity Systems

We investigate the eeect of fading correlation and branch gain imbalance on the Shannon capacity of diversity systems in conjunction with adaptive transmission techniques. This capacity provides the theoretical upper bound for the spectral eeciency of adaptive transmission schemes. We obtain closed-form expressions for this capacity for Rayleigh fading channels under four adaptation policies: optimal power and rate adaptation (opra), optimal rate adaptation with constant power (ora), truncated channel inversion with xed rate (tifr), and complete channel inversion with xed rate (cifr). We give numerical examples illustrating the main trends and ooer comparisons on the behavior of opra, ora, tifr, and cifr under variation of diierent parameters.