Optimal Transmitter Design and Pilot Spacing in MIMO Non-Stationary Aging Channels

TL;DR

This paper develops an analytical framework for optimizing transmitter design and pilot spacing in MIMO systems over non-stationary, aging channels, accounting for spatial correlation and channel variation to maximize sum-capacity.

Contribution

It introduces a novel beamforming and pilot spacing optimization method for MIMO systems considering channel aging and spatial correlation effects.

Findings

Optimal pilot spacing improves sum-capacity under channel aging.

Beamforming vectors tailored to spatial correlation enhance performance.

Simulation confirms the method's superiority over previous approaches.

Abstract

This work considers an uplink wireless communication system where multiple users with multiple antennas transmit data frames over dynamic channels. Previous studies have shown that multiple transmit and receive antennas can substantially enhance the sum-capacity of all users when the channel is known at the transmitter and in the case of uncorrelated transmit and receive antennas. However, spatial correlations stemming from close proximity of transmit antennas and channel variation between pilot and data time slots, known as channel aging, can substantially degrade the transmission rate if they are not properly into account. In this work, we provide an analytical framework to concurrently exploit both of these features. Specifically, we first propose a beamforming framework to capture spatial correlations. Then, based on random matrix theory tools, we introduce a deterministic expression that approximates the average sum-capacity of all users. Subsequently, we obtain the optimal values of pilot spacing and beamforming vectors upon maximizing this expression. Simulation results show the impacts of path loss, velocity of mobile users and Rician factor on the resulting sum-capacity and underscore the efficacy of our methodology compared to prior works.