On the performance of HARQ-IR over Nakagami-m fading channels in mobile Ad Hoc networks

In this paper, outage performance of hybrid automatic repeat request (HARQ) with incremental redundancy over Nakagami-m fading channels in a mobile ad hoc network is analyzed. Different from prior analyses, both interlink interference and random distribution of the nodes are considered, which makes the analysis practical and challenging. Based on an orthogonal polynomial approximation, the probability distribution of the product of multiple shifted signal-to-interference-and-noise ratios (SINRs) and the outage probability are derived in closed forms. The impacts of various system parameters including the intensity of source nodes, the number of retransmissions and the packet rate on the outage probability are then studied thoroughly. The closed-form outage probability enables further analysis of a wide range of performance metrics and delay limited throughput (DLT) is particularly discussed here. It is found that a limited number of retransmissions is sufficient to achieve the maximum DLT. With the analytical results, the optimal packet rate tomaximize the DLT is also found. To characterize the performance of the whole network, network DLT (NDLT), which is the maximum achievable aggregated DLT in a unit area under a certain outage constraint, is finally introduced. The scaling law of NDLT over the network density is revealed. Specifically, the NDLT scales linearly with the network density λ when the network is sparse, while it follows the (1 - α/2 ) power law over the network density where α is the path loss exponent when the network is dense.