Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

Since traditional radar signals are “unintelligent,” regarding the amount of information they convey on the bandwidth they occupy, a joint radar and wireless communication system would constitute a unique platform for future intelligent transportation networks effecting the essential tasks of environmental sensing and the allocation of ad-hoc communication links, in terms of both spectrum efficiency and cost-effectiveness. In this paper, approaches to the design of intelligent waveforms, that are suitable for simultaneously performing both data transmission and radar sensing, are proposed. The approach is based on classical phase-coded waveforms utilized in wireless communications. In particular, requirements that allow for employing such signals for radar measurements with high dynamic range are investigated. Also, a variety of possible radar processing algorithms are discussed. Moreover, the applicability of multiple antenna techniques for direction-of-arrival estimation is considered. In addition to theoretical considerations, the paper presents system simulations and measurement results of complete “RadCom” systems, demonstrating the practical feasibility of integrated communications and radar applications.

Waveform Design and Signal Processing Aspects for Fusion of Wireless Communications and Radar Sensing

Millimeter-wave (mmWave) radar is widely used in vehicles for applications such as adaptive cruise control and collision avoidance. In this paper, we propose an IEEE 802.11ad-based radar for long-range radar (LRR) applications at the 60 GHz unlicensed band. We exploit the preamble of a single-carrier physical layer frame, which consists of Golay complementary sequences with good correlation properties that make it suitable for radar. This system enables a joint waveform for automotive radar and a potential mmWave vehicular communication system based on the mmWave consumer wireless local area network standard, allowing hardware reuse. To formulate an integrated framework of vehicle-to-vehicle communication and LRR, we make typical assumptions for LRR applications, incorporating the full duplex radar operation. This new feature is motivated by the recent development of systems with sufficient isolation and self-interference cancellation. We develop single- and multi-frame radar receiver algorithms for target detection as well as range and velocity estimation for both single- and multi-target scenarios. Our proposed radar processing algorithms leverage channel estimation and time–frequency synchronization techniques used in a conventional IEEE 802.11ad receiver with minimal modifications. Analysis and simulations show that in a single-target scenario, a gigabits-per-second data rate is achieved simultaneously with cm-level range accuracy and cm/s-level velocity accuracy. The target vehicle is detected with a high probability (above 99.99 $\%$ ) at a low false alarm rate of 10 $^{-6}$ for an equivalent isotropically radiated power of 40 dBm up to a vehicle separation distance of about 200 m. The proposed IEEE 802.11ad-based radar meets the minimum accuracy/resolution requirement of range and velocity estimates for LRR applications.

IEEE 802.11ad-Based Radar: An Approach to Joint Vehicular Communication-Radar System

Wireless mediums, such as RF, optical, or acoustical, provide finite resources for the purposes of remote sensing (such as radar) and data communications. Often, these two functions are at odds with one another and compete for these resources. Applications for wireless technology are growing rapidly, and RF convergence is already presenting itself as a requirement for both users as consumer and military system requirements evolve. The broad solution space to this complex problem encompasses cooperation or codesigning of systems with both sensing and communications functions. By jointly considering the systems during the design phase, rather than perpetuating a notion of mutual interference, both system’s performance can be improved. We provide a point of departure for future researchers that will be required to solve this problem by presenting the applications, topologies, levels of system integration, the current state of the art, and outlines of future information-centric systems.

Survey of RF Communications and Sensing Convergence Research

The 6G vision of creating authentic digital twin representations of the physical world calls for new sensing solutions to compose multi-layered maps of our environments. Radio sensing using the mobile communication network as a sensor has the potential to become an essential component of the solution. With the evolution of cellular systems to mmWave bands in 5G and potentially sub-THz bands in 6G, small cell deployments will begin to dominate. Large bandwidth systems deployed in small cell configurations provide an unprecedented opportunity to employ the mobile network for sensing. In this paper, we focus on the major design aspects of such a cellular joint communication and sensing (JCAS) system. We present an analysis of the choice of the waveform that points towards choosing the one that is best suited for communication also for radar sensing. We discuss several techniques for efficiently integrating the sensing capability into the JCAS system, some of which are applicable with NR air-interface for evolved 5G systems. Specifically, methods for reducing sensing overhead by appropriate sensing signal design or by configuring separate numerologies for communications and sensing are presented. Sophisticated use of the sensing signals is shown to reduce the signaling overhead by a factor of 2.67 for an exemplary road traffic monitoring use case. We then present a vision for future advanced JCAS systems building upon distributed massive MIMO and discuss various other research challenges for JCAS that need to be addressed in order to pave the way towards natively integrated JCAS in 6G.

/pdf/joint-design-of-communication-and-sensing-for-beyond-5g-and-346b2apj40.pdf

Joint Design of Communication and Sensing for Beyond 5G and 6G Systems

A modification of the classical orthogonal frequency division multiplexing signals is discussed that allows for the creation of a set of perfectly orthogonal transmit signals sharing the same bandwidth. These signals can be employed for performing radar measurements with multiple transmitters being simultaneously active, for example, in radar networks or multi-input multi-output radar applications. Since all the signals of the individual transmitters occupy the full available bandwidth, no deterioration of the achievable range resolution occurs. This study comprises both the theoretical considerations as well as the verification simulations and measurements. A particular focus is on the requirements regarding the frequency and time synchronisation of the individual signals and their impact on the achievable performance. The influence of possible Doppler shifts is also considered. Finally, a performance comparison with classical code-based multiple user access techniques is provided. The achieved results demonstrate that the proposed multi-carrier waveforms clearly outperform the classical code-based approach under realistic assumptions of synchronisation accuracy.

Spectrally interleaved multi-carrier signals for radar network applications and multi-input multi-output radar

The design process of a joint radar and communication system employing OFDM is analyzed. In particular, the question on how to choose OFDM modulation parameters such as carrier distance, guard interval length, frame length or pilot design is studied. Such systems use the same OFDM frames to transmit data and image the surroundings, so both radar and communication are affected by the choice of these parameters. The main design criteria for the radar component are accuracy of distance and speed measurements, whereas the communication subsystem needs to be designed such that it transmits robustly through a mobile communication channel. As these design criteria often are antipodal, arguments for choosing a particular set of modulation parameters are discussed. The presented design process is applied to the case of a vehicular (car-to-car) communication, in which moving participants communicate in the 24 GHz range.

/pdf/parametrization-of-joint-ofdm-based-radar-and-communication-kk0wkvkduq.pdf

Parametrization of joint OFDM-based radar and communication systems for vehicular applications

A distance and speed estimation algorithm for OFDM based radar is analysed statistically. The maximum likelihood estimator is derived and compared to previous results. A connection to spectral analysis is drawn, simplifying the analysis of the estimator in question. Finally, a method to evaluate the performance of the algorithm is presented and conclusions for the structure of the OFDM signals are drawn. It is shown that the estimation algorithm works well above an SNR threshold, but rapidly degrades below.

/pdf/maximum-likelihood-speed-and-distance-estimation-for-ofdm-2mul5e71cu.pdf

Maximum likelihood speed and distance estimation for OFDM radar

In this paper a recently proposed novel processing approach for OFDM radar is verified with measurements. This processing algorithm directly calculates a radar image from the transmitted and received modulation symbols that compose the OFDM signal without the need for performing correlation operations. The implementation of a suitable system setup is described. The measurement results confirm that with this approach a very high dynamic range can be obtained. Moreover, the SNR in the measured radar images is investigated. The results prove that the proposed algorithm provides high processing gain.

Performance verification of symbol-based OFDM radar processing

In this paper an approach will be presented that allows for estimating the velocity of multiple reflecting objects with standard OFDM communication signals. The proposed technique does not require any specific coding of the transmit signal and provides high dynamic range and low sidelobe levels. This allows for an efficient acquisition of velocity information in joint communication and radar systems. The paper discusses the developed algorithm and a possible OFDM system concept for automotive applications. Measurement results are provided that prove the operability in practical scenarios.

Martin Braun

Papers

Spectrally interleaved multi-carrier signals for radar network applications and multi-input multi-output radar

Parametrization of joint OFDM-based radar and communication systems for vehicular applications

Maximum likelihood speed and distance estimation for OFDM radar

Performance verification of symbol-based OFDM radar processing

A multiple target doppler estimation algorithm for OFDM based intelligent radar systems