Hybrid Precoding and Combining for Millimeter-Wave Full-Duplex Joint Radar and Communication Systems with Self-Interference Mitigation

Core Concepts

The paper proposes a hybrid precoder and combiner design for a full-duplex joint radar and communication system at millimeter-wave frequencies, aiming to maximize downlink spectral efficiency while guaranteeing radar performance and mitigating self-interference.

Abstract

The paper considers a full-duplex joint radar and communication (JRC) system operating at millimeter-wave frequencies, where the base station (BS) transmits data to a mobile station (MS) while concurrently using the same transceiver as a monostatic radar to detect targets in the environment.
The key challenges addressed are:

Providing a trade-off between communication and sensing performance while mitigating the self-interference (SI) caused by full-duplex operation.
Designing the precoders and combiners under the hardware limitations of a hybrid MIMO architecture.

The proposed approach involves:

Designing the precoder at the BS using a generalized eigenvalue-based solution that maximizes downlink spectral efficiency while suppressing SI and ensuring a minimum radar gain in the target direction.
Designing the analog combiner at the BS to further suppress the residual SI, while maintaining sufficient radar gain.
Employing OFDM-based radar processing to accurately estimate the range and velocity of the detected targets.

The numerical results demonstrate that the proposed architecture achieves the required radar gain and SI mitigation, with a small loss in downlink spectral efficiency compared to optimal precoding. The OFDM-based radar processing also shows highly accurate range and velocity estimates for the detected targets.

Stats

Pt = 20 dBm
σ2_BS = -93.8 dBm
ρ/σ2_BS = 80 dB
NBS = 32, NBS,RF = 4
NMS = 16, NMS,RF = 4
Ns = 4
M = 792, N = 14
Subcarrier spacing Δf = 120 kHz
OFDM symbol duration T = 8.92 μs

Quotes

"The primary challenge in FD systems lies in effectively reducing self-interference (SI). In the case of mmWave systems equipped with large arrays, SI suppression only through hardware design can be costly and challenging."
"Consequently, SI suppression should be a key consideration for the precoder/combiner design, even though many works in the integrated sensing and communication (ISAC) literature tend to overlook the SI constraint."

Key Insights Distilled From

Hybrid Precoding and Combining for mmWave Full-Duplex Joint Radar and Communication Systems under Self-Interference

by Mura... at arxiv.org 04-03-2024

https://arxiv.org/pdf/2311.14942.pdf

Deeper Inquiries

How can the proposed hybrid precoding and combining approach be extended to handle multiple downlink users and multiple targets simultaneously

The proposed hybrid precoding and combining approach can be extended to handle multiple downlink users and multiple targets simultaneously by incorporating multi-user and multi-target beamforming techniques. For multiple downlink users, the precoders at the base station can be designed to maximize the sum rate of all users while ensuring high radar gain and SI suppression. This can be achieved by formulating a joint optimization problem that considers the communication requirements of each user, the radar performance for multiple targets, and the hardware constraints. By solving this optimization problem iteratively, the precoders can be tailored to serve multiple users efficiently while maintaining radar capabilities.
Similarly, for multiple targets, the precoders and combiners can be optimized to provide high radar gain for each target while minimizing interference and maintaining communication performance. The design process would involve considering the spatial separation of the targets, their individual radar cross-sections, and the desired radar performance metrics. By incorporating these factors into the optimization framework, the hybrid precoding and combining approach can be extended to handle the complexities of multiple targets in a JRC system.

What are the potential tradeoffs between communication performance, radar performance, and hardware complexity in a full-duplex JRC system as the number of antennas and RF chains is scaled up

As the number of antennas and RF chains is scaled up in a full-duplex JRC system, several potential tradeoffs come into play.

Communication Performance: Increasing the number of antennas and RF chains can enhance the communication performance by enabling more spatial multiplexing and diversity. However, this improvement may come at the cost of increased hardware complexity and power consumption.

Radar Performance: More antennas and RF chains can improve the radar performance by providing higher resolution and accuracy in target detection and tracking. Nevertheless, the tradeoff lies in balancing the radar performance with the communication requirements, as allocating resources for one aspect may impact the other.

Hardware Complexity: Scaling up the number of antennas and RF chains can lead to increased hardware complexity in terms of calibration, synchronization, and signal processing. This complexity can introduce challenges in implementation, maintenance, and cost, requiring efficient algorithms and designs to manage the system effectively.

Power Consumption: With more antennas and RF chains, the power consumption of the system may rise, affecting energy efficiency. Balancing the power consumption with the desired performance levels is crucial to ensure sustainable operation and minimize energy wastage.

By carefully considering these tradeoffs and optimizing the hybrid precoding and combining techniques, a full-duplex JRC system can achieve a balance between communication performance, radar capabilities, and hardware complexity as the system scales up.

What are the implications of the proposed techniques for energy efficiency and power consumption in full-duplex JRC systems operating at millimeter-wave frequencies

The proposed techniques in the full-duplex JRC system operating at millimeter-wave frequencies have implications for energy efficiency and power consumption.

Energy Efficiency: The hybrid precoding and combining approach can enhance energy efficiency by optimizing the use of resources for both communication and radar functions. By efficiently allocating transmit power, minimizing interference, and maximizing radar gain, the system can achieve higher energy efficiency in transmitting and receiving signals.

Power Consumption: The use of advanced beamforming techniques and SI suppression methods can help reduce power consumption in the system. By optimizing the precoders and combiners to mitigate SI and enhance radar performance, the system can operate more efficiently, leading to lower overall power consumption.

Hardware Design: Efficient hardware design, such as using phase shifters for analog beamforming and digital processing for precoding, can contribute to lower power consumption. By leveraging the hybrid architecture and optimizing the hardware components, the system can achieve a balance between performance and power efficiency.

System Optimization: Overall system optimization, including algorithm design, signal processing, and hardware implementation, plays a crucial role in managing power consumption. By continuously refining the techniques and algorithms for hybrid precoding and combining, the system can achieve optimal energy efficiency while meeting the communication and radar requirements.

In conclusion, the proposed techniques have the potential to improve energy efficiency and reduce power consumption in full-duplex JRC systems operating at millimeter-wave frequencies, contributing to sustainable and effective wireless communication and sensing applications.