Optimum Power and Rate Allocation for Coded V-BLAST

TL;DR

This paper develops an analytical framework for optimizing power and rate allocation in coded V-BLAST systems, introducing a fractional waterfilling algorithm that enhances capacity and outage performance.

Contribution

It introduces a novel fractional waterfilling algorithm for optimal power and rate allocation in coded V-BLAST, with closed-form solutions and practical near-optimal uniform allocation strategies.

Findings

Fractional waterfilling optimizes capacity and outage probability.

Uniform power allocation is near optimal at moderate to high SNR.

Results are applicable to multiuser detection and channel equalization.

Abstract

An analytical framework for minimizing the outage probability of a coded spatial multiplexing system while keeping the rate close to the capacity is developed. Based on this framework, specific strategies of optimum power and rate allocation for the coded V-BLAST architecture are obtained and its performance is analyzed. A fractional waterfilling algorithm, which is shown to optimize both the capacity and the outage probability of the coded V-BLAST, is proposed. Compact, closed-form expressions for the optimum allocation of the average power are given. The uniform allocation of average power is shown to be near optimum at moderate to high SNR for the coded V-BLAST with the average rate allocation (when per-stream rates are set to match the per-stream capacity). The results reported also apply to multiuser detection and channel equalization relying on successive interference cancelation.