Performance analysis of link adaptation in wireless personal communication systems

We analyze the link adaptation (LA) performance of a wireless personal communication system supporting two types of voice connections, full-rate and half-rate. Full-rate connections are used when the channel conditions are poor. When the channel conditions are good a full-rate connection is switched to a half-rate for improving spectral efficiency. For analysis simplicity, we consider flat uniform propagation conditions where, for a given propagation exponent, the received powers are determined by distances. Using this propagation model, users in the outer region of the cell will use full-rate channels while users in the proximity of the base station will use half-rate channels. The numerical results are extracted by forming a multi-dimensional Markov chain model of the proposed scheme and are compared with those obtained through a comprehensive computer simulation for call blocking probability, hand-off failure probability and carried traffic. A 42% increase in capacity is achieved when 75% of the users can use halfrate channels