THROUGHPUT PERFORMANCE OF AN FHMA SYSTEM WITH VARIABLE-RATE CODING

In this paper, we compare throughput bounds for a frequency-hopped mul tiple-access (FHMA) system employing variable rate as well as fixed ra te coding (FRC), Nonfading as well as Rayleigh-fading channels are exp lored. The throughput bounds for the variable rate coding (VRC) scheme s are based on the assumption that the number of active users in the s ystem, m, is known at any time while the bounds for the FRC scheme ass umes that the fixed code rate is optimized for the user population mea n, lambda, where the population is assumed Poisson distributed. We pre sent bounds for theoretical ''perfect'' codes which achieve capacity a s well as bounds for Reed-Solomon (RS) codes of practical, block lengt hs, Finally, we show the dependence of a VRC scheme upon the accuracy of the estimates of m and present a general comparison of the gains of using VRC versus a realistic FRC scheme.