Theoretical Analysis of Near-Field MIMO Channel Capacity and Mid-Band Experimental Validation

TL;DR

This paper provides a theoretical analysis and experimental validation of near-field MIMO channel capacity, highlighting the impact of array size and distance on capacity in 6G wireless systems.

Contribution

It introduces a detailed electromagnetic-based near-field channel model and derives closed-form capacity expressions for UPA arrays, supported by experimental measurements.

Findings

Channel capacity decreases with increasing distance.

Large-scale MIMO offers significant capacity gains in near-field.

Small antenna arrays at the receiver limit capacity improvements.

Abstract

With the increase of multiple-input-multiple-output (MIMO) array size and carrier frequency, near-field MIMO communications will become crucial in 6G wireless networks. Due to the increase of MIMO near-field range, the research of near-field MIMO capacity has aroused wide interest. In this paper, we focus on the theoretical analysis and empirical study of near-field MIMO capacity. First, the near-field channel model is characterized from the electromagnetic information perspective. Second, with the uniform planar array (UPA), the channel capacity based on effective degree of freedom (EDoF) is analyzed theoretically, and the closed-form analytical expressions are derived in detail. Finally, based on the numerical verification of near-field channel measurement experiment at 13 GHz band, we reveal that the channel capacity of UPA-type MIMO systems decreases continuously with the communication distance increasing. It can be observed that the near-field channel capacity gain is relatively obvious when large-scale MIMO is adopted at both receiving and transmitter ends, but the near-field channel capacity gain may be limited in the actual communication system with the small antenna array at receiving end. This work will give some reference to the near-field communication systems.