Optimum sub-packet transmission for turbo-coded hybrid ARQ systems

Turbo codes are popular for their near-Shannon capacity of bit-error-rate (BER) at low signal-to-noise ratio (SNR) with long packet lengths. They have been proposed in automatic-repeat-request (ARQ) systems as the forward-error correction (FEC) codes. Although sub-packet schemes were proposed in ARQ systems, optimum sub-packet transmission is more effective to maximize throughput in a dynamic channel. Sub-packet schemes can provide additional error correction capability with iterative turbo decoding algorithms. An efficient method is proposed to estimate the optimum number of sub-packets, and adaptive sub-packet schemes, i.e., that enables a system to employ different optimum numbers of sub-packets under variable conditions, are suggested to achieve the maximum throughput of the system. Simulations show that the adaptive sub-packet scheme is effective at moderate SNR, e.g. from 2.6 dB to 5.0 dB, and can provide higher throughput than conventional packet schemes.