Design Guidelines for Training-based MIMO Systems with Feedback

TL;DR

This paper investigates optimal training and data transmission strategies for block fading MIMO systems with feedback, providing insights into power allocation, training length, and practical near-optimal solutions for different feedback types.

Contribution

It offers a comprehensive analysis of training strategies in MIMO systems with feedback, including optimal power allocation and training length, applicable to both CGF and CCF systems.

Findings

Optimal solutions for CGF systems without delay match non-feedback systems.

Training length for CCF systems can be less than the number of transmit antennas.

Proposed near-optimal transmission strategy for CCF systems.

Abstract

In this paper, we study the optimal training and data transmission strategies for block fading multiple-input multiple-output (MIMO) systems with feedback. We consider both the channel gain feedback (CGF) system and the channel covariance feedback (CCF) system. Using an accurate capacity lower bound as a figure of merit, we investigate the optimization problems on the temporal power allocation to training and data transmission as well as the training length. For CGF systems without feedback delay, we prove that the optimal solutions coincide with those for non-feedback systems. Moreover, we show that these solutions stay nearly optimal even in the presence of feedback delay. This finding is important for practical MIMO training design. For CCF systems, the optimal training length can be less than the number of transmit antennas, which is verified through numerical analysis. Taking this fact into account, we propose a simple yet near optimal transmission strategy for CCF systems, and derive the optimal temporal power allocation over pilot and data transmission.