An Adaptive Hybrid FEC/ARQ Protocol Using Turbo Codes for Multi-Media Transmission of ATM over Wireless Networks

Abstract

This paper describes a type-II adaptive hybrid FEC/ARQ protocol using turbo codes for both voice and data services.Recently, a powerful family of error correcting codes using parallelconcatenated convolutional codes is introduced. Near-Shannon-limitis achievable by such codes. For example, a bit error rateof $10^{-5}$ can be achieved at $E_b/N_o =$ 0.7~dB using a rate1/2 code or at about 2.5~dB if fewer iterations are used in decoding.Given the promising performance of the codes, it is expected thatthe performance of an adaptive FEC/ARQ protocol employingturbo codes will be better than protocols using other error correcting codes.Rate compatible turbo codes are used in the protocol. Extra parity bitscorresponding to a lower rate turbo code will betransmitted if the previous transmission leads to a decoding error.For real-time services, the number of retransmissions is limited to one soas 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 for the adaptive FEC/ARQ protocol using compatible rate 1/2 and rate 1/4 turbo codes.