Sum-Rate and Power Scaling of Massive MIMO Systems with Channel Aging

TL;DR

This paper analyzes how channel aging affects the sum-rate and power scaling in massive MIMO systems, showing that aging does not alter the fundamental power scaling law but impacts the sum-rate performance.

Contribution

It provides tight lower bounds on sum-rate with aged CSI, examines the effects of channel prediction, and characterizes the impact on power scaling laws in massive MIMO systems.

Findings

Power of each user can be scaled down by 1/√M regardless of channel aging.

Channel prediction improves sum-rate but does not change power scaling law.

Aged CSI degrades sum-rate performance but does not affect the fundamental power scaling law.

Abstract

This paper investigates the achievable sum-rate of massive multiple-input multiple-output (MIMO) systems in the presence of channel aging. For the uplink, by assuming that the base station (BS) deploys maximum ratio combining (MRC) or zero-forcing (ZF) receivers, we present tight closed-form lower bounds on the achievable sum-rate for both receivers with aged channel state information (CSI). In addition, the benefit of implementing channel prediction methods on the sum-rate is examined, and closed-form sum rate lower bounds are derived. Moreover, the impact of channel aging and channel prediction on the power scaling law is characterized. Extension to the downlink scenario and multi-cell scenario are also considered. It is found that, for a system with/without channel prediction, the transmit power of each user can be scaled down at most by $1/\sqrt{M}$ (where $M$ is the number of BS antennas), which indicates that aged CSI does not degrade the power scaling law, and channel prediction does not enhance the power scaling law; instead, these phenomena affect the achievable sum-rate by degrading or enhancing the effective signal to interference and noise ratio, respectively.