Throughput analysis of hybrid single-packet and multiple-packet truncated type-II HARQ strategies with unreliable feedback channel

In this paper, we investigate different HARQ strategies with unreliable feedback channel. In classical approaches, retransmitted packets are different versions of the same user data. In order to improve HARQ performance, we propose to construct redundancy packets by jointly encoding several data packets. This strategy is referred to as HARQ Multiple Packet Incremental Redundancy (MP-IR). It can eliminate imperfect feedback effect on performance at medium to high Signal to Noise Ratio (SNR) values. On the other hand, classical HARQ Single Packet Incremental Redundancy (SP-IR) strategy is more robust at low SNR. This motivates us to introduce a hybrid SP-IR and MP-IR strategy. This strategy can benefit from SP-IR performance at low SNR and MP-IR performance at medium to high SNR. The throughput of the different schemes is analyzed using renewal theory and an appropriate Markov model representation. Simulation results confirming the proposed throughput analysis are also presented.