[Paper Review] Hybrid Beamforming in mmWave Dual-Function Radar-Communication Systems: Models, Technologies, and Challenges

Ziyang Cheng, Linlong Wu+4 more|arXiv (Cornell University)|Sep 10, 2022

Antenna Design and Optimization4 citations

TL;DR

This paper proposes hybrid beamforming (HBF) for millimeter-wave dual-function radar-communication (DFRC) systems to balance high spectral/energy efficiency with reduced hardware cost. By integrating radar sensing and communication via shared hardware and signaling, HBF enables multi-user communication and target detection using limited RF chains and phase shifters, achieving a favorable trade-off between performance and complexity in 6G networks.

ABSTRACT

As a promising technology in beyond-5G (B5G) and 6G, dual-function radar-communication (DFRC) aims to ensure both radar sensing and communication on a single integrated platform with unified signaling schemes. To achieve accurate sensing and reliable communication, large-scale arrays are anticipated to be implemented in such systems, which brings out the prominent issues on hardware cost and power consumption. To address these issues, hybrid beamforming (HBF), beyond its successful deployment in communication-only systems, could be a promising approach in the emerging DFRC ones. In this article, we investigate the development of the HBF techniques on the DFRC system in a self-contained manner. Specifically, we first introduce the basics of the HBF based DFRC system, where the system model and different receive modes are discussed with focus. Then we illustrate the corresponding design principles, which span from the performance metrics and optimization formulations to the design approaches and our preliminary results. Finally, potential extension and key research opportunities, such as the combination with the reconfigurable intelligent surface, are discussed concisely.

Motivation & Objective

• Address the high hardware cost and power consumption of large-scale arrays in mmWave dual-function radar-communication (DFRC) systems.
• Investigate hybrid beamforming (HBF) as a solution to reduce RF chains while maintaining radar and communication performance.
• Develop system models and design principles for HBF-based DFRC with unified signal processing for sensing and communication.
• Identify key challenges in joint optimization of digital and analog beamformers under practical constraints.
• Explore future extensions such as integration with reconfigurable intelligent surfaces (RIS) and OTFS modulation.

Proposed method

• Propose a system model for HBF-based DFRC with Nt transmit and Nr receive antennas, using Nt_RF and Nr_RF RF chains, respectively.
• Implement three analog beamforming architectures: full, partial, and dynamic connection, each with distinct hardware and performance trade-offs.
• Formulate optimization problems based on performance metrics such as radar beampattern directivity, communication rate, and energy efficiency.
• Integrate low-resolution ADCs/DACs into the HBF design to reduce power and cost, analyzing their impact on system performance.
• Explore joint active (HBF) and passive (RIS) beamforming for RIS-assisted DFRC systems to enhance beam accuracy and coverage.
• Investigate HBF design for OTFS-modulated DFRC systems to mitigate Doppler spread and intercarrier interference in high-mobility scenarios.

Experimental results

Research questions

• RQ1 How can hybrid beamforming be modeled in DFRC systems to jointly optimize radar sensing and communication performance?
• RQ2 What is the impact of analog beamformer architecture (full, partial, dynamic) on system performance and hardware efficiency in HBF-DFRC?
• RQ3 How do low-resolution ADCs/DACs affect the performance-EE trade-off in mmWave HBF-DFRC systems?
• RQ4 What are the challenges and opportunities in integrating reconfigurable intelligent surfaces (RIS) with HBF-DFRC for enhanced beamforming and coverage?
• RQ5 How can HBF be adapted for OTFS-modulated DFRC systems to address Doppler spread and intercarrier interference in high-mobility environments?

Key findings

• HBF in DFRC systems achieves a favorable trade-off between system performance and hardware cost by using a limited number of RF chains and phase shifters.
• The dynamic connection architecture in analog beamforming offers a better balance between performance and energy efficiency compared to full and partial connections.
• Low-resolution ADCs/DACs in HBF-DFRC systems can achieve comparable performance to ideal-quantized systems at low SNR, improving energy efficiency.
• Joint optimization of HBF and low-resolution ADCs/DACs is critical for achieving optimal performance-EE trade-offs, though this remains underexplored.
• RIS-assisted HBF-DFRC systems can enhance beam accuracy and spatial diversity, but require advanced optimization due to coupling between active and passive beamforming.
• OTFS-based HBF-DFRC systems face strong coupling between digital and analog beamformers due to wideband operation, necessitating low-complexity design for large delay-Doppler blocks.