On the performance of a link-adaptive cellular system

We present a simple analytical approach to characterize the performance of a link adaptive wireless packet data system. We use this approach to compare the performance of an EDGE (enhanced data rates for global evolution) receiver (Ariyavisitakul, S.L. et al., 1999) that has two antennas with the performance of a receiver that uses a single antenna. It is shown that a receiver with two-antenna spatial diversity can offer over 50 kbps increase in the 50th percentile average throughput and 15% reduction in retransmission rates in a typical urban environment. Comparison with system simulation shows that the ARQ mechanism afforded by the EDGE RLC layer is quite robust in combating random wireless losses, except at low SINRs, where excessive delays at the RLC layer trigger TCP time-outs and lead to areas with very poor performance. One of the major benefits of receive spatial diversity is the alleviation of such cellular "dead spots" for data services.