On the MIMO Capacity with Residual Transceiver Hardware Impairments

TL;DR

This paper analyzes how residual hardware impairments in MIMO transceivers limit capacity, showing capacity saturation at high SNRs and the effects of large antenna arrays, with analytical capacity expressions derived.

Contribution

It provides a validated impairment model and derives analytical ergodic capacity expressions, revealing capacity saturation and the impact of antenna scaling on MIMO performance.

Findings

Capacity saturates at high SNR due to impairments

Impairments have a second-order impact at low SNR

Large-scale MIMO can mitigate capacity ceiling effects

Abstract

Radio-frequency (RF) impairments in the transceiver hardware of communication systems (e.g., phase noise (PN), high power amplifier (HPA) nonlinearities, or in-phase/quadrature-phase (I/Q) imbalance) can severely degrade the performance of traditional multiple-input multiple-output (MIMO) systems. Although calibration algorithms can partially compensate these impairments, the remaining distortion still has substantial impact. Despite this, most prior works have not analyzed this type of distortion. In this paper, we investigate the impact of residual transceiver hardware impairments on the MIMO system performance. In particular, we consider a transceiver impairment model, which has been experimentally validated, and derive analytical ergodic capacity expressions for both exact and high signal-to-noise ratios (SNRs). We demonstrate that the capacity saturates in the high-SNR regime, thereby creating a finite capacity ceiling. We also present a linear approximation for the ergodic capacity in the low-SNR regime, and show that impairments have only a second-order impact on the capacity. Furthermore, we analyze the effect of transceiver impairments on large-scale MIMO systems; interestingly, we prove that if one increases the number of antennas at one side only, the capacity behaves similar to the finite-dimensional case. On the contrary, if the number of antennas on both sides increases with a fixed ratio, the capacity ceiling vanishes; thus, impairments cause only a bounded offset in the capacity compared to the ideal transceiver hardware case.