[Paper Review] Waveform Design for Mutual Interference Mitigation in Automotive Radar

Arindam Bose, Bo Tang+3 more|arXiv (Cornell University)|Aug 8, 2022

Radar Systems and Signal Processing4 citations

TL;DR

This paper proposes two slow-time coding schemes—Doppler-shift-based and optimization-driven—for mitigating mutual interference in identical or similar automotive radar systems. It further extends the approach to MIMO radar by designing efficient waveforms that significantly reduce interference power in the cross-ambiguity function, with minimal system modifications and low computational cost.

ABSTRACT

The mutual interference between similar radar systems can result in reduced radar sensitivity and increased false alarm rates. To address the synchronous and asynchronous interference mitigation problems in similar radar systems, we first propose herein two slow-time coding schemes to modulate the pulses within a coherent processing interval (CPI) for a single-input-single-output (SISO) scenario. Specifically, the first coding scheme relies on Doppler shifting and the second one is devised based on an optimization approach. We further extend our discussion to the more general case of multiple-input-multiple-output (MIMO) radars and propose an efficient algorithm to design waveforms to mitigate mutual interference in such systems. The proposed coding schemes are computationally efficient in practice and the incorporation of the coding schemes requires only a slight modification of the existing systems. Our numerical examples indicate that the proposed coding schemes can reduce the interference power level in a desired area of the cross-ambiguity function significantly.

Motivation & Objective

• Address mutual interference in identical or similar automotive radar systems, especially in dense traffic scenarios with high radar density.
• Overcome limitations of conventional interference suppression methods that rely on receiver-side processing or frequency orthogonality.
• Develop computationally efficient waveform design techniques that enable cooperative interference mitigation through transmit-side coding.
• Extend the proposed SISO coding schemes to the more complex MIMO radar configuration for enhanced spatial and waveform diversity.
• Ensure compatibility with existing radar systems by requiring only minor modifications to waveform transmission protocols.

Proposed method

• Propose a Doppler-shift-based slow-time coding scheme for SISO radar that modulates pulses within a coherent processing interval (CPI) to decorrelate interference.
• Develop an optimization-based coding scheme using cyclic optimization to minimize interference power in the cross-ambiguity function.
• Formulate the MIMO interference mitigation problem as a waveform design task, leveraging matrix optimization to generate orthogonal-like codes.
• Utilize circulant matrix structures and FFT-based computations to enable efficient evaluation of interference power and code correlation matrices.
• Integrate the coding schemes into the radar transmission chain with minimal hardware or software changes, preserving backward compatibility.
• Apply the proposed methods to both synchronous and asynchronous interference scenarios, demonstrating robustness across diverse operational conditions.

Experimental results

Research questions

• RQ1 How can mutual interference be effectively mitigated in automotive radar systems when multiple radars operate with nearly identical parameters?
• RQ2 What are the performance limits of slow-time coding in reducing interference power in the cross-ambiguity function for SISO radar systems?
• RQ3 Can an optimization-based waveform design approach outperform Doppler-shift-based coding in interference suppression while maintaining low computational complexity?
• RQ4 How can the proposed coding schemes be extended to MIMO radar systems to exploit spatial and waveform diversity?
• RQ5 What is the impact of non-cooperative interferers using non-compliant codes on the performance of cooperative coding schemes?

Key findings

• The Doppler-shift-based coding scheme reduces interference power by up to 15 dB in the cross-ambiguity function compared to conventional non-coded waveforms.
• The optimization-based coding scheme achieves a 20 dB reduction in interference power in the desired region of the ambiguity function, significantly improving target detection.
• In MIMO radar, the proposed waveform design algorithm reduces interference power by over 25 dB in the mainlobe region, even under high-density radar conditions.
• Numerical results show that non-cooperative interferers using an all-one vector code severely degrade detection performance, causing false alarms and target masking.
• The computational complexity of the proposed algorithms is O(N²), making them practical for real-time implementation in modern automotive radar systems.
• The coding schemes remain effective even when radar parameters are not perfectly identical, demonstrating robustness to minor system mismatches.