Soft-decision decoding applied to the generalized type-II hybrid ARQ scheme

A generalized hybrid automatic-repeat-request (GH-ARQ) scheme using hard-decision decoding and variable depth (redundancy) for adaptive error control in digital communications systems has recently been proposed by S.D. Morgera and H. Krishna (see Digital Signal Processing over Finite Fields: Applications to Communications and Algebraic Coding Theories. New York: Academic, 1988). An important feature of the GH-ARQ scheme is that variable depth and, consequently, variable minimum distance, is possible with a single encoder/decoder configuration. The present authors use binary PSK signaling, an additive white Gaussian noise (AWGN) channel, and several relevant code parameter choices in computer simulations to illustrate the improvement in throughput efficiency when soft-decision decoding is used in the GH-ARQ method. From the computational complexity standpoint, the use of GH-ARQ soft-decision decoding is feasible, since the code lengths used are relatively short. Comparison of simulation results is also made to the soft-decision ARQ scheme of G. Benelli (see ibid., vol.COM-33, p.285-8, Mar. 1985)