Power Allocation for Discrete-Input Non-Ergodic Block-Fading Channels

TL;DR

This paper analyzes power allocation strategies for fixed-rate transmission over Nakagami-m non-ergodic block-fading channels with discrete inputs, highlighting the benefits of long-term constraints and proposing practical sub-optimal schemes.

Contribution

It demonstrates the application of existing optimal schemes, characterizes the SNR exponent, and introduces low-complexity sub-optimal power allocation algorithms.

Findings

Optimal short-term scheme's SNR exponent equals the Singleton bound.

Long-term power constraints significantly improve outage performance.

Proposed sub-optimal schemes achieve near-optimal outage probabilities.

Abstract

We consider power allocation algorithms for fixed-rate transmission over Nakagami-m non-ergodic block-fading channels with perfect transmitter and receiver channel state information and discrete input signal constellations under both short- and long-term power constraints. Optimal power allocation schemes are shown to be direct applications of previous results in the literature. We show that the SNR exponent of the optimal short-term scheme is given by the Singleton bound. We also illustrate the significant gains available by employing long-term power constraints. Due to the nature of the expressions involved, the complexity of optimal schemes may be prohibitive for system implementation. We propose simple sub-optimal power allocation schemes whose outage probability performance is very close to the minimum outage probability obtained by optimal schemes.