We develop a new technique for a dual-function system with joint radar and communication platforms. Sidelobe control of the transmit beamforming in tandem with waveform diversity enables communication links using the same pulse radar spectrum. Multiple simultaneously transmitted orthogonal waveforms are used for embedding a sequence of LB bits during each radar pulse. Two weight vectors are designed to achieve two transmit spatial power distribution patterns, which have the same main radar beam, but differ in sidelobe levels towards the intended communication receivers. The receiver interpretation of the bit is based on its radiated beam. The proposed technique allows information delivery to single or multiple communication directions outside the mainlobe of the radar. It is shown that the communication process is inherently secure against intercept from directions other than the pre-assigned communication directions. The employed waveform diversity scheme supports a multiple-input multiple-output radar operation mode. The performance of the proposed technique is investigated in terms of the bit error rate.

Dual-Function Radar-Communications: Information Embedding Using Sidelobe Control and Waveform Diversity

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

In this paper, we introduce a radar information metric, the estimation rate, that allows the radar user to be considered in a multiple-access channel enabling performance bounds for joint radar-communications coexistence to be derived. Traditionally, the two systems were isolated in one or multiple dimensions. We categorize new attempts at spectrum-space-time convergence as either coexistence, cooperation, or co-design. The meaning and interpretation of the estimation rate and what it means to alter it are discussed. Additionally, we introduce and elaborate on the concept of “not all bits are equal,” which states that communications rate bits and estimation rate bits do not have equal value. Finally, results for joint radar-communications information bounds and their accompanying weighted spectral efficiency measures are presented.

Radar-Communications Convergence: Coexistence, Cooperation, and Co-Design

The last decade witnessed a growing demand on radio frequency that is driven by technological advances benefiting the end consumer but requiring new allocations of frequency bandwidths. Further, higher data rates for faster communications and wireless connections have called for an expanded share of existing frequency allocations. Concerns for spectrum congestion and frequency unavailability have spurred extensive research efforts on spectrum management and efficiency [1]-[4] within the same type of service and have led to cognitive radio [5] and cognitive radar [6]. On the other hand, devising schemes for coexistence among different services have eased the competition for spectrum resources, especially for radar and wireless communication systems [7]-[14]. Both systems have been recently given a common portion of the spectrum by the Federal Communications Commission.

Signaling strategies for dual-function radar communications: an overview

Mobile network is evolving from a communication-only network towards the one with joint communication and radio/radar sensing (JCAS) capabilities, that we call perceptive mobile network (PMN). Radio sensing here refers to information retrieval from received mobile signals for objects of interest in the environment surrounding the radio transceivers. In this paper, we provide a comprehensive survey for systems and technologies that enable JCAS in PMN, with a focus on works in the last ten years. Starting with reviewing the work on coexisting communication and radar systems, we highlight their limits on addressing the interference problem, and then introduce the JCAS technology. We then set up JCAS in the mobile network context, and envisage its potential applications. We continue to provide a brief review for three types of JCAS systems, with particular attention to their differences on the design philosophy. We then introduce a framework of PMN, including the system platform and infrastructure, three types of sensing operations, and signals usable for sensing, and discuss required system modifications to enable sensing on current communication-only infrastructure. Within the context of PMN, we review stimulating research problems and potential solutions, organized under eight topics: mutual information, waveform optimization, antenna array design, clutter suppression, sensing parameter estimation, pattern analysis, networked sensing under cellular topology, and sensing-assisted secure communication. This paper provides a comprehensive picture for the motivation, methodology, challenges, and research opportunities of realizing PMN. The PMN is expected to provide a ubiquitous radio sensing platform and enable a vast number of novel smart applications.

Enabling Joint Communication and Radio Sensing in Mobile Networks -- A Survey

A compact double-layer Bowtie antenna optimized for medical diagnosis is presented in this paper. This on-body antenna is matched to the human body to allow more energy to be radiated into the human body to obtain stronger reflections for image processing. By using a Bowtie antenna with double layers as well as a folded structure and meandered microstrip lines at the bottom of the antenna, a small size of 30 × 30 mm2 with a size reduction of 40% is achieved, compared to the reference antenna of 50 × 50 mm2 within the same operational frequency range. After the optimization of the antenna parameters, the antenna is characterized from 0.5 to 2 GHz, where the low frequencies enable a high penetration into human body and the large frequency range contributes to a high bandwidth and hence a fine range resolution. The simulated and measured results are shown with respect to the impedance matching, near-field pattern, gain and SAR distributions. With features such as a very small size, very low operational frequency, high front-to-back ratio, this design shows a high potential for use in medical diagnosis of stroke, breast cancer and water accumulation detection in the human body.

A Compact Double-Layer On-Body Matched Bowtie Antenna for Medical Diagnosis

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

This paper presents a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) joint radar-communication (RadCom) system and explores its tolerance toward mutual interference. Since OFDM signals are weak toward subcarrier misalignment caused by frequency offsets, some form of interference cancellation will definitely be required for operation in real scenarios. A simple and flexible system level interference cancellation algorithm is proposed, which is to be employed when the radar estimation is no longer reliable. For the proof-of-concept verification, the MIMO RadCom node is implemented on universal software radio peripherals to take hardware imperfections and propagation losses into account. Real-time measurements are also presented to prove the 2D+velocity estimation capability as well as the effectiveness of the interference cancellation algorithm. With this system concept, the dual functions of the RadCom node will be possible in a realistic automotive scenario for vehicle-to-vehicle and vehicle-to-infrastructure communication with the aim of enhancing overall road safety by making driving a collaborative effort instead of an individual one.

On Mutual Interference Cancellation in a MIMO OFDM Multiuser Radar-Communication Network

This paper presents an overview of the OFDM joint radar and communication system concept which has been developed for automotive radar applications. Using an OFDM- based signal, the range and Doppler estimation algorithm are independent of the payload data and overcomes the typical drawbacks of correlation-based processing. The derivation of parameters for the operation at 24 GHz suited for automotive applications are then shown. The system concept is then verified with MATLAB simulation and measurement. A brief description of the on-going work to adapt this system to a realistic multipath- multiuser environment along with simulation results are also presented.

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The OFDM Joint Radar-Communication System: An Overview

In this paper an extension of the OFDM joint radar and communication system concept to cope in a multipath and multiuser environment is explored. A realistic multipath propagation channel model is built with an established ray-tracing algorithm and incorporated into the radar system simulation and one additional user/interferer is then introduced into the scenario for the observation of the radar's performance. From a theoretical point of view as well as from measurement results, the interferer causes a severe degradation of the radar's dynamic range, thus requiring an interference cancellation scheme to remove the traces of the interferer. Inherent to the interference cancellation scheme is the phase and frequency offset estimation algorithm for the high fidelity reconstruction of the interferer signal for subtraction from the radar signal which are explored in this paper. The result of the end-system and the improvement to the radar's dynamic range are then presented.

Yoke Leen Sit

Papers

A Compact Double-Layer On-Body Matched Bowtie Antenna for Medical Diagnosis

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

On Mutual Interference Cancellation in a MIMO OFDM Multiuser Radar-Communication Network

The OFDM Joint Radar-Communication System: An Overview

Extension of the OFDM joint radar-communication system for a multipath, multiuser scenario