Near-Field Perturbation Effect on Constellation Error in Beam-Space MIMO

TL;DR

This paper investigates how near-field interactions impact the constellation error in beam-space MIMO systems, especially with higher-order modulations, highlighting the need for revised decoding strategies in practical scenarios.

Contribution

It extends previous studies by analyzing the effects of near-field perturbations on higher-order modulation schemes in beam-space MIMO, emphasizing the importance of decoding adjustments.

Findings

Near-field perturbations distort constellation points in beam-space MIMO.

Error vector magnitude increases with proximity to the user model.

Reconsideration of decoding methods is necessary for practical deployment.

Abstract

Beam-space MIMO has recently been proposed as a promising solution to enable transmitting multiple data streams using a single RF chain and a single pattern-reconfigurable antenna. Since in a beam-space MIMO system radiation pattern of the transmit antenna is exploited as extra dimension for encoding information, near-field interaction of the transmit antenna with its surrounding objects affects spatial multiplexing performance of the system. Through numerical simulations in the previous work, it has been concluded that under BPSK signaling beam-space MIMO is not more vulnerable to near-field coupling than its conventional counterpart. In this work, we extend the study to the case of higher-order modulation schemes, where the presence of external perturbation also affects the data constellation points transmitted by a beam-space MIMO antenna. To this aim, the error vector magnitude of the transmitted signal is evaluated when placing a QPSK beam-space MIMO antenna in close proximity to a hand model of the user. The obtained results emphasize the importance of reconsidering the decoding approach for beam-space MIMO systems in practical applications.