Towards Dual-functional Radar-Communication Systems: Optimal Waveform Design (1711.05220v1)

Abstract: We focus on a dual-functional multi-input-multi-output (MIMO) radar-communication (RadCom) system, where a single transmitter communicates with downlink cellular users and detects radar targets simultaneously. Several design criteria are considered for minimizing the downlink multi-user interference. First, we consider both the omnidirectional and directional beampattern design problems, where the closed-form globally optimal solutions are obtained. Based on these waveforms, we further consider a weighted optimization to enable a flexible trade-off between radar and communications performance and introduce a low-complexity algorithm. The computational costs of the above three designs are shown to be similar to the conventional zero-forcing (ZF) precoding. Moreover, to address the more practical constant modulus waveform design problem, we propose a branch-and-bound algorithm that obtains a globally optimal solution and derive its worst-case complexity as a function of the maximum iteration number. Finally, we assess the effectiveness of the proposed waveform design approaches by numerical results.

• The paper introduces globally optimal waveform strategies that minimize multi-user interference while maintaining robust radar target detection.
• It develops trade-off optimization algorithms that balance radar sensing with communication performance using weighted objective functions.
• A branch-and-bound method for constant modulus waveform design achieves computational efficiency comparable to traditional zero-forcing precoding.

Optimal Waveform Design for Dual-functional Radar-Communication Systems

The paper "Towards Dual-functional Radar-Communication Systems: Optimal Waveform Design" by Fan Liu et al. explores the design of dual-functional multi-input-multi-output (MIMO) systems that simultaneously support radar and communication functionalities. The research focuses on a configuration where a single transmitter serves both radar target detection and communication with downlink cellular users. Specifically, the paper addresses waveform optimization to minimize multi-user interference (MUI) whilst maintaining radar performance.

Key Contributions

1. Waveform Design Approaches: The paper introduces several waveform design strategies for dual-functional radar-communication (RadCom) systems. These include:
   • Omnidirectional beampattern design for initial probing.
   • Directional beampattern design aligned with desired target directions.

Both designs are formulated as optimization problems that yield closed-form globally optimal solutions.

1. Trade-off Optimization: The research also considers a weighted optimization problem to balance radar and communication performance. This approach employs a low-complexity algorithm to achieve a globally optimal solution, allowing an adjustable compromise between radar detection and communication efficiency.
2. Constant Modulus Waveform Design: To address practical implementation challenges, the paper explores waveform design under constant modulus constraints. A branch-and-bound algorithm is developed to efficiently solve this non-convex problem, ensuring globally optimal solutions over conventional methods, like the Successive Quadratic Constrained Quadractic Programming Refinement (SQR).
3. Computational Efficiency: Remarkably, the computational costs of the proposed solutions are comparable to traditional zero-forcing precoding, making the approaches viable for real-time applications.

Numerical Results and Implications

The paper presents numerical evaluations demonstrating that the proposed methods significantly outperform zero-forcing in terms of communication sum-rate while preserving radar functionality. The trade-off optimization enables improved communication performance with minimal radar degradation. Furthermore, the constant modulus design outperforms existing algorithms like SQR, closely approaching convex relaxation bounds.

Theoretical and Practical Implications

The integration of radar and communication functionalities into a single system represents a substantial contribution to the efficient use of spectrum resources. By optimizing waveform design, this research advances the development of systems capable of performing radar sensing and data transmission concurrently without compromising on performance.

The theoretical insight provided by the optimal trade-off between radar and communication functions fosters an understanding of how shared resources can be managed dynamically. Practically, the algorithms developed could lead to more robust and cost-effective implementations of dual-functional RadCom systems in real-world scenarios, where spectrum scarcity is a growing concern.

Future Directions

The paper paves the way for further exploration into adaptive systems that can dynamically adjust to varying operational demands in complex environments. Future research could focus on extending these concepts to more intricate scenarios, including multi-target tracking and high-mobility communications. Additionally, real-world testing and integration with emerging technologies such as 5G could offer valuable insights and enhancements to these systems.

In conclusion, this paper provides a comprehensive framework for optimizing dual-functional RadCom systems, balancing spectrum efficiency with operational performance. Its contributions are crucial for both theoretical advancements and practical implementations in communication and radar applications.