Spatial Bandwidth of Bilateral Near-Field Channels for Linear Large-Scale Antenna Array System

TL;DR

This paper derives a closed-form expression for the spatial bandwidth of LoS channels in massive MIMO systems with linear large-scale antenna arrays, revealing conditions that maximize the effective degrees of freedom.

Contribution

It introduces a simple, accurate formula for spatial bandwidth and EDoF in bilateral near-field channels, enhancing understanding of array placement effects.

Findings

Closed-form expression for spatial bandwidth of LoS channels.

Maximum EDoF occurs when arrays are coplanar with specific orientation.

Analysis provides insights for optimal array placement in massive MIMO.

Abstract

This paper analyzes the spatial bandwidth of line-of-sight (LoS) channels in massive MIMO systems. For the linear large-scale antenna arrays (LSAA) of transceivers placed in random locations in 3D space, a simple but accurate closed-form expression is derived to characterize the spatial bandwidth. Subsequent analysis of the LSAA's spatial bandwidth properties is also provided, leading to the formulation of an approximate expression for the effective degrees of freedom (EDoF) of bilateral near-field channels. Interestingly, as proved in this work, when the transmit and receive arrays are coplanar, with the receive array positioned perpendicular to the axis joining the centroids of the transmit and receive arrays, the EDoF of the LoS channel is found to be approximately maximized.