Performance Analysis of Two Multichannel Fast Retransmission Schemes for Delay-Sensitive Flows

This paper presents a Multiradio multichannel Fast Automatic-Repeat-reQuest (MF ARQ) scheme and an MF Hybrid ARQ (MF HARQ) scheme intended for transporting delay-sensitive flows in a multichannel environment. The proposed schemes are designed to allow the retransmission(s) only once using one or multiple channels simultaneously, unlike other ARQ/HARQ schemes where the retransmission(s) of a link packet can only be in one channel and continue until it is successfully received. By using the application throughput as the objective, the optimal retransmission policy can be determined based on the estimated channel quality and the size of the application-layer protocol data unit. For these two schemes, we show their improvement of the link packet delay and derive formulas of the application throughput, which are then validated via simulations. In addition, a cost analysis for systems adopting the proposed schemes is included. Next, the optimized MF ARQ/HARQ schemes are shown to be able to achieve better effective throughput (goodput) than similar multichannel ARQ/HARQ schemes in various Nakagami-m fading environments. Analytical and simulation results show, when optimized, that the MF HARQ scheme has much better throughput performance than the MF ARQ scheme in highly unreliable environments. We thus conclude that both the MF ARQ scheme and the MF HARQ scheme are excellent ARQ candidates for real-time multimedia transport in the multiradio multichannel environment.