AMC and HARQ: How to Increase the Throughput

TL;DR

This paper explores how layer-coded HARQ (L-HARQ) combined with adaptive modulation and coding (AMC) can significantly improve throughput in block fading channels, especially at high signal-to-noise ratios.

Contribution

The paper introduces L-HARQ as a novel approach that separates AMC and HARQ, simplifying encoding/decoding and enhancing throughput over traditional methods.

Findings

L-HARQ outperforms conventional HARQ in throughput.

Numerical results show significant gains with L-HARQ.

Practical implementation with turbo codes confirms real-world benefits.

Abstract

In this work, we consider transmissions over block fading channels and assume that adaptive modulation and coding (AMC) and hybrid automatic repeat request (HARQ) are implemented. Knowing that in high signal-to-noise ratio, the conventional combination of HARQ with AMC is counterproductive from the throughput point of view, we adopt the so-called layer-coded HARQ (L-HARQ). L-HARQ allows consecutive packets to share the channel and preserves a great degree of separation between AMC and HARQ; this makes the encoding and decoding very simple and allows us to use the available/optimized codes. Numerical examples shown in the paper indicate that L-HARQ can provide significant throughput gains compared to the conventional HARQ. The L-HARQ is also implemented using turbo codes indicating that the throughput gains also materialize in practice.