Comparison of two ARQ protocols in a Rayleigh fading channel

Go-back-N (GBN) and selective repeat (SR) protocols for automatic repeat request (ARQ) are compared in a frequency-nonselective Rayleigh fading channel. Protocols implemented in software are used in a computer-simulated fading channel to study the throughput of these protocols as a function of fading parameters, such as the mean signal-to-noise ratio (SNR), maximum Doppler frequency number of diversity branches, time-out period and round-trip delay. The purpose is to complement well-documented theoretical work in (1) providing some design considerations and (2) investigating quantitatively whether data communications combining detection-only coding, diversity, and basic ARQ protocols can offer reasonable throughput in a fading channel. Although based on a set of assumptions, the following conclusions remain valid: (1) SR is significantly superior to GBN when the fading rate is high; this advantage decreases as fading becomes slower; and (2) error detection combined with ARQ and diversity selection can provide reliable data communications in a Rayleigh fading channel