Optimal Power Allocation for Hybrid ARQ With Chase Combining in I.i.d. Rayleigh Fading Channels
The authors consider the optimization of Chase Combining (CC)-based Hybrid-Automatic Repeat reQuest (HARQ) schemes with a limit on the maximum number of retransmissions. They formulate two optimization problems: minimizing the Packet Drop Probability (PDP) under a total average transmits power constraint, and minimizing the average transmits power under a fixed PDP constraint. Towards solving these equivalent optimization problems, they provide a closed-form expression for the outage probability of a CC-HARQ scheme. They then show that solving the optimization problems using an exact expression of the outage probability becomes complex with an increase in the maximum number of retransmissions.