On Repetition Protocols and Power Control for Multiple Access Block-Fading Channels

TL;DR

This paper investigates how combining repetition protocols with power control and feedback in block-fading multiple access channels can significantly improve long-term throughput, especially at low to moderate SNR levels.

Contribution

It introduces a feedback-informed approach to optimize repetition and power control protocols, achieving near-capacity throughput with minimal feedback bits.

Findings

Remarkable throughput improvements at low/moderate SNR

Throughput close to ergodic capacity with few feedback bits

Power control is the main driver of throughput gains

Abstract

In this paper we study the long-term throughput performance of repetition protocols coupled with power control for multiple access block-fading channels. We propose to use the feedback bits to inform the transmitter about the decoding status and the instantaneous channel quality. We determine the throughput of simple and practically inspired protocols; we show remarkable throughput improvements, especially at low and moderate SNR, when compared to protocols where the feedback bits are used for acknowledgment only or for power control only; we show that the throughput is very close to the ultimate ergodic multi-user water-filling capacity for small number of feedback bits and/or retransmissions. For symmetric Rayleigh fading channels, numerical results show that the throughput improvement is mainly due to the ability to perform a power control, rather than to retransmit.