An adaptive hybrid FEC/ARQ protocol using turbo codes

This paper describes a type-II adaptive hybrid FEC/ARQ protocol using turbo codes. Both voice and data services are considered. Recently, a powerful family of error correcting codes using parallel concatenated convolutional codes is introduced. Near-Shannon-limit is achievable by such codes. For example, a bit error rate of 10^-5 ; can be achieved at E_b/N_o 0.7 dB using a rate 1/2 code or at about 2.5 dB if fewer iterations are used in decoding. Given the promising performance of the codes, it is expected that the performance of an adaptive FEC/ARQ protocol employing turbo codes will be better than protocols using other error correcting codes. For real-time services, the number of retransmissions is limited to one so as to limit the delay. For data services, the number of retransmissions is unlimited to provide a reliable communication link. Results in terms of throughput are obtained through analysis and approximation using the performance curves