Optimizing Communication-Radar Coexistence with STAR-RIS: Analysis and Algorithms

Core Concepts

The core message of this work is to propose a STAR-RIS-assisted communication radar coexistence system that can suppress mutual interference, enhance communication performance, and provide full space coverage by optimizing the STAR-RIS passive beamforming and the radar beamforming.

Abstract

This work proposes a STAR-RIS-assisted communication radar coexistence system to address the mutual interference between the communication and radar systems. The key highlights are:

The proposed system utilizes a STAR-RIS, which can simultaneously transmit and reflect signals, to improve communication performance while suppressing interference and providing full space coverage.

The authors derive closed-form expressions for the achievable spectral efficiencies (SEs) at the radar and communication receiver side, considering correlated Rayleigh fading channels.

An alternating optimization (AO) framework is developed to optimize the STAR-RIS passive beamforming and the radar beamforming. The STAR-RIS optimization is performed using a projected gradient ascent algorithm (PGAM) that can simultaneously optimize the amplitudes and phase shifts.

The proposed optimization based on statistical channel state information (CSI) can be performed less frequently compared to instantaneous CSI, reducing overhead and complexity.

Simulation results demonstrate the superior performance of the proposed STAR-RIS-assisted architecture over the conventional RIS counterpart. A benchmark full instantaneous CSI-based design is also provided, showing higher sum-rate but with increased overhead.

Stats

The radar transmit power budget is limited by Pmax.
The SINR threshold for the radar is denoted as γr.

Quotes

"The required improvement in wireless transmission capacity can be achieved in two ways. The first key way concerns the move to a higher spectrum such as millimeter wave or even terahertz transmission [2], [3]. The second promising direction includes sharing of the frequency bandwidth among different systems."
"To cover these gaps, integrated sensing and communication (ISAC) has emerged as a promising solution that can improve wireless capacity and collect sensing data simultaneously [4], [5]."

Key Insights Distilled From

STAR-RIS-Assisted Communication Radar Coexistence: Analysis and Optimization

by Anastasios P... at arxiv.org 04-26-2024

https://arxiv.org/pdf/2404.16394.pdf

Deeper Inquiries

How can the proposed STAR-RIS-assisted communication radar coexistence system be extended to incorporate more advanced communication and radar techniques, such as non-linear precoding or advanced radar signal processing

The proposed STAR-RIS-assisted communication radar coexistence system can be extended to incorporate more advanced communication and radar techniques by integrating non-linear precoding and advanced radar signal processing methods. Non-linear precoding techniques, such as dirty paper coding or Tomlinson-Harashima precoding, can be applied to optimize the communication performance by mitigating interference and enhancing signal quality. These techniques can help in achieving higher data rates and improved spectral efficiency in the presence of interference from the radar system.
On the radar side, advanced signal processing algorithms, such as adaptive beamforming, space-time adaptive processing (STAP), and waveform diversity, can be implemented to enhance radar detection capabilities. Adaptive beamforming techniques can help in focusing the radar beam towards the target of interest while suppressing interference from other directions. STAP algorithms can mitigate clutter and interference in radar signals, improving target detection in complex environments. Waveform diversity techniques can enhance radar performance by transmitting multiple waveforms to improve target detection and tracking accuracy.
By incorporating these advanced techniques into the STAR-RIS system, the coexistence of communication and radar functionalities can be further optimized, leading to improved overall system performance and efficiency.

What are the potential challenges and limitations in deploying a practical STAR-RIS system for communication-radar coexistence, considering factors like hardware impairments, calibration, and real-world deployment scenarios

Deploying a practical STAR-RIS system for communication-radar coexistence poses several challenges and limitations that need to be addressed for successful implementation in real-world scenarios:

Hardware Impairments: Practical implementation of STAR-RIS systems may face challenges related to hardware impairments, such as phase noise, non-linearities, and calibration errors. These impairments can affect the accuracy and reliability of the phase shifts and amplitude control of the RIS elements, leading to performance degradation in communication and radar operations.

Calibration and Synchronization: Ensuring accurate calibration and synchronization of the RIS elements is crucial for the proper functioning of the system. Any discrepancies in the phase shifts or timing among the RIS elements can result in signal distortion, interference, and reduced system efficiency. Robust calibration techniques and synchronization mechanisms need to be developed to address these challenges.

Real-World Deployment Scenarios: In real-world deployment scenarios, factors such as environmental conditions, multipath propagation, and dynamic channel variations can impact the performance of the STAR-RIS system. Adapting the system to varying environmental conditions and optimizing the RIS configuration in dynamic scenarios is essential for maintaining reliable communication and radar operations.

Power Consumption and Cost: Implementing a large-scale STAR-RIS system with a high number of reconfigurable elements can lead to increased power consumption and cost. Balancing the trade-off between system complexity, power efficiency, and cost-effectiveness is a key consideration in the deployment of practical STAR-RIS solutions.

Addressing these challenges through advanced hardware design, calibration techniques, adaptive algorithms, and efficient system integration can help overcome limitations and enable the successful deployment of STAR-RIS systems for communication-radar coexistence.

Beyond the communication-radar coexistence application, how can the STAR-RIS technology be leveraged to enable other integrated sensing and communication use cases, such as joint localization and communication or multi-functional sensing

Beyond the communication-radar coexistence application, STAR-RIS technology can be leveraged to enable other integrated sensing and communication use cases, such as joint localization and communication or multi-functional sensing applications. Some potential applications include:

Joint Localization and Communication: STAR-RIS systems can be utilized for joint localization and communication tasks in wireless networks. By integrating localization algorithms with communication protocols, the RIS can assist in accurate positioning of devices while enabling efficient data transmission. This can be beneficial for applications like indoor navigation, asset tracking, and location-based services.

Multi-Functional Sensing: STAR-RIS technology can be extended to support multi-functional sensing applications, where the same RIS elements are used for both communication and sensing purposes. By reconfiguring the RIS elements to act as sensors, the system can perform tasks such as environmental monitoring, object detection, and surveillance in addition to communication functions. This multi-functional approach enhances the versatility and utility of the STAR-RIS system.

Smart Infrastructure and IoT: Integrating STAR-RIS technology into smart infrastructure and Internet of Things (IoT) systems can enable intelligent communication networks with enhanced sensing capabilities. By deploying RIS-enabled devices in smart cities, industrial IoT environments, and critical infrastructure, the system can facilitate efficient data exchange, real-time monitoring, and adaptive control based on sensor data and communication requirements.

By exploring these diverse applications, STAR-RIS technology can unlock new opportunities for integrated sensing and communication systems, paving the way for innovative solutions in various domains.