Opportunistic Relaying without CSI: Optimizing Variable-Rate HARQ

TL;DR

This paper investigates how variable-rate HARQ can significantly improve throughput in opportunistic relaying over block-fading channels without CSI, using dynamic programming for optimization.

Contribution

It introduces a novel approach to optimize variable transmission rates in HARQ relaying without CSI, enhancing throughput over fixed-rate schemes.

Findings

Variable-rate HARQ outperforms fixed-rate in throughput.

Optimization via double-recursive dynamic programming is effective.

Simplified methods reduce computational complexity.

Abstract

We analyze the opportunistic relaying based on HARQ transmission over the block-fading channel with absence of channel state information (CSI) at the transmitter nodes. We assume that both the source and the relay are allowed to vary their transmission rate between the HARQ transmission rounds. We solve the problem of throughput maximization with respect to the transmission rates using double-recursive Dynamic Programming. Simplifications are also proposed to diminish the complexity of the optimization. The numerical results confirm that the variable-rate HARQ can increase the throughput significantly comparing to its fixed-rate counterpart.