A ROBUST RATE-ADAPTIVE HYBRID ARQ SCHEME FOR FREQUENCY-HPPED SPREAD-SPECTRUM MULTIPLE-ACCESS COMMUNICATION-SYSTEMS

This paper considers the application of rate-adaptive coding (RAC) to a spread spectrum multiple access (SSMA) communication system. Specifi cally, RAC using a variable rate Reed-Solomon (RS) code with a single decoder is applied to frequency-hopped SSMA. We show that this combina tion can accommodate a larger number of users compared to that with co nventional fixed-rate coding. This increase is a result of a reduction in the channel interference from other users. The penalty for this im provement in most cases is a slight increase in the delay (composed of propagation and decoding delay). The throughput and the undetected er ror probability for a Q-ary symmetric channel are analyzed, and perfor mance results are presented.