Power Allocation in HARQ-based Predictor Antenna Systems

TL;DR

This paper analyzes power allocation strategies in HARQ-based predictor antenna systems on vehicles, deriving optimal power schemes and demonstrating significant power savings through HARQ feedback at various vehicle speeds.

Contribution

It introduces closed-form solutions for power allocation in predictor antenna systems considering spatial mismatch and evaluates HARQ protocols' impact on power efficiency.

Findings

HARQ feedback significantly reduces power consumption.

Closed-form expressions enable accurate power allocation.

Higher vehicle speeds benefit more from HARQ-based power control.

Abstract

In this work, we study the performance of predictor antenna (PA) systems using hybrid automatic repeat request (HARQ). Here, the PA system is referred to as a system with two sets of antennas on the roof of a vehicle. In this setup, the PA positioned in the front of the vehicle can be used to predict the channel state information at the transmitter (CSIT) for data transmission to the receive antenna (RA) that is aligned behind the PA. Considering spatial mismatch, due to the vehicle mobility, we derive closed-form expressions for the optimal power allocation and the minimum average power of the PA systems under different outage probability constraints. The results are presented for different types of HARQ protocols and we study the effect of different parameters on the performance of PA systems. As we show, our proposed approximation scheme enables us to analyze PA systems with high accuracy. Moreover, for different vehicle speeds, we show that HARQ-based feedback can reduce the outage-limited power consumption of PA systems by orders of magnitude.