A Novel Cost-Effective MIMO Architecture with Ray Antenna Array for Enhanced Wireless Communication Performance

TL;DR

The paper addresses the hardware and energy challenges of scalable MIMO for 6G-scale high-frequency systems by introducing the ray antenna array (RAA), a phase-shifter-free architecture built from many low-cost elements organized into orientation-driven sULAs and controlled by a ray selection network. It develops a complete modeling and design framework, including an explicit array response model, orientation and spacing rules, and a cost-aware comparison to conventional ULAs. For communications, it proposes efficient joint beamforming and ray selection algorithms for uplink and downlink, using greedy MMSE and alternating optimization with MMSE/MRT and SOCP, achieving near-optimal performance with reduced complexity. Simulation results show significant uplink/downlink gains and substantial hardware savings, highlighting RAA as a practical, scalable solution for mmWave/THz MIMO and sensing in future networks, with prospective extensions to blockage and 3D implementations.

Abstract

This paper proposes a novel multi-antenna architecture, termed ray antenna array (RAA), which practically enables flexible beamforming and also enhances wireless communication performance for high frequency systems in a cost-effective manner. RAA consists of a large number of inexpensive antenna elements and a few radio frequency (RF) chains. These antenna elements are arranged in a novel ray like structure, where each ray corresponds to one simple uniform linear array (sULA) with a carefully designed orientation. The antenna elements within each sULA are directly connected, so that each sULA is able to form a beam towards a direction matching the ray orientation without relying on any analog or digital beamforming. By further designing a ray selection network (RSN), appropriate sULAs are selected to connect to the RF chains for subsequent baseband processing. Compared to conventional multi-antenna architectures such as the uniform linear array (ULA) with hybrid analog/digital beamforming (HBF), the proposed RAA enjoys three appealing advantages: (i) finer and uniform angular resolution for all signal directions; (ii) enhanced beamforming gain by using antenna elements with higher directivity, as each sULA is only responsible for a small portion of the total angle coverage range; and (iii) dramatically reduced hardware cost since no phase shifters are required, which are expensive and difficult to design in high-frequency systems such as mmWave and THz systems. To validate such advantages, we first present the input-output mathematical model for RAA-based wireless communications. Efficient algorithms for joint RAA beamforming and ray selection are then proposed for single-user and multi-user RAA-based wireless communications. Simulation results demonstrate that RAA achieves superior performance compared to the conventional ULA with HBF, while significantly reducing hardware cost.

Figures (13)

• Figure 1: MIMO architectures with $N_{\text{RF}}$ chains. (a) The conventional fully-connected HBF architecture based on phase shifters. (b) The proposed RAA architecture without any phase shifters.
• Figure 2: Uplink multi-user communications based on the proposed RAA architecture.
• Figure 3: The proposed RAA architecture is composed of $MN$ antenna elements, which are arranged into $N$ rays. Each ray corresponds to one $M$-element sULA with all antenna elements directly connected.
• Figure 4: Beam patterns $|f(\phi,\eta_n)|$ in (\ref{['steering_eff00']}) for $\eta_n=-0.3\pi$, $0$, and $0.3\pi$, where $M=8$ and $G(\zeta)=1$, $\forall \zeta$.
• Figure 5: Orientation design principle for adjacent sULAs in RAA, where $M=8$ and $G(\zeta)=1$, $\forall \zeta$.