Green Holographic MIMO Communications With A Few Transmit Radio Frequency Chains

TL;DR

This paper explores energy-efficient holographic MIMO systems using few transmit RF chains, proposing a novel modulation scheme to maximize capacity and leverage spatial degrees-of-freedom without increasing RF hardware.

Contribution

It introduces non-uniform holographic pattern modulation (NUHPM) for capacity achievement with limited RF chains in holographic MIMO systems.

Findings

NUHPM achieves capacity limits in high SNR regimes.

Increasing antenna aperture size enhances capacity without more RF chains.

Numerical results confirm significant performance gains.

Abstract

Holographic multiple-input multiple-output (MIMO) communications are widely recognized as a promising candidate for the next-generation air interface. With holographic MIMO surface, the number of the spatial degrees-of-freedom (DoFs) considerably increases and also significantly varies as the user moves. To fully employ the large and varying number of spatial DoFs, the number of equipped RF chains has to be larger than or equal to the largest number of spatial DoFs. However, this causes much waste as radio frequency (RF) chains (especially the transmit RF chains) are costly and power-hungry. To avoid the heavy burden, this paper investigates green holographic MIMO communications with a few transmit RF chains under an electromagnetic-based communication model. We not only look at the fundamental capacity limits but also propose an effective transmission, namely non-uniform holographic pattern modulation (NUHPM), to achieve the capacity limit in the high signal-to-noise (SNR) regime. The analytical result sheds light on the green evaluation of MIMO communications, which can be realized by increasing the size of the antenna aperture without increasing the number of transmit RF chains. Numerical results are provided to verify our analysis and to show the great performance gain by employing the additional spatial DoFs as modulation resources.