Rate and Power Allocation for Discrete-Rate Link Adaptation

TL;DR

This paper introduces new discrete-rate link adaptation schemes with power control for fading channels, achieving near-Shannon capacity with limited codes and power levels, enhancing spectral efficiency.

Contribution

It proposes novel transmission schemes combining discrete codes and power adaptation, closely approaching Shannon limits with minimal complexity.

Findings

Four-code scheme achieves within 1 dB of Shannon capacity.

Power adaptation significantly improves spectral efficiency and transmission probability.

Discrete schemes with few codes and power levels are highly effective.

Abstract

Link adaptation, in particular adaptive coded modulation (ACM), is a promising tool for bandwidth-efficient transmission in a fading environment. The main motivation behind employing ACM schemes is to improve the spectral efficiency of wireless communication systems. In this paper, using a finite number of capacity achieving component codes, we propose new transmission schemes employing constant power transmission, as well as discrete and continuous power adaptation, for slowly varying flat-fading channels. We show that the proposed transmission schemes can achieve throughputs close to the Shannon limits of flat-fading channels using only a small number of codes. Specifically, using a fully discrete scheme with just four codes, each associated with four power levels, we achieve a spectral efficiency within 1 dB of the continuous-rate continuous-power Shannon capacity. Furthermore, when restricted to a fixed number of codes, the introduction of power adaptation has significant gains with respect to ASE and probability of no transmission compared to a constant power scheme.