Ambiguity analysis for a hybrid type II ARQ/FEC protocol on a fluctuating radio channel

Hybrid automatic-repeat-request/forward-error-correction (ARQ/FEC) schemes are commonly used to provide reliable transmission over noisy channels. At high channel error rate, hybrid type II ARQ/FEC strategies which do not discard packets in error, but combine them with suitable parity packets, have shown better performances. However it is usually assumed in the literature that the control is error free in both forward and backward directions. Without this assumption, a corrupted control makes the packet useless, which is then inevitably discarded. In this paper a hybrid type II ARQ/FEC scheme using a concatenated coding is proposed in a TDMA setting. This protocol is intended to operate under realistic conditions. To manage the reception of packets with corrupted control, an intelligent mechanism is introduced. Simulations have proven a gain in throughput when this mechanism is implemented.