Performance of hybrid ARQ schemes for the fading channel

We define and use a general method for evaluating and comparing the performance of different hybrid ARQ schemes for the fading channel, whose evolution is assumed to be represented by a finite state Markov chain (FSMC). To obtain an unbiased comparison of different ARQ schemes a theoretical viewpoint is adopted. More precisely, the sphere-packing bound is used to evaluate the best possible performance of a hybrid ARQ scheme. To assess the correctness and the accuracy of the analysis, some simulation results, based on the use of turbo codes, are also presented. The results highlight the relative merits and drawbacks of the investigated hybrid ARQ schemes, some of which are under evaluation for the Universal Mobile Telecommunications System (UMTS) standard.