Pre-repeat go-back-n ARQ with error prediction in fading channel

A novel go-back-n (GBN) ARQ scheme using the pre-repeat (PR) technique is proposed and its efficiency is investigated by computer simulations. It is efficient in digital cordless-phone systems using TDMA-TDD under slow fading environments. In those systems, transmission errors are mainly caused by Rayleigh fading. Since the fading changes the signal level very slowly compared to the TDMA-TDD frame period, transmission errors in the up-link channel match those in the down-link channel. In the proposed technique, this correlation is utilized to predict errors occurring in the transmitted slots. Using the predicted error, retransmission is made before the request from the receiver is received. By using the PR-GBN scheme only at the transmitter, the data throughput is improved over conventional GBN. In this paper, the throughput efficiency of PR-GBN and conventional GBN are calculated and compared under PHS (Personal Handy-phone System) conditions. As a result, the proposed scheme is shown to improve the throughput efficiency; the gain in Eb/No is 4.2 dB at the throughput of 0.9