On the Effectiveness of OTFS for Joint Radar Parameter Estimation and Communication

We consider a joint radar parameter estimation and communication system using orthogonal time frequency space (OTFS) modulation. The scenario is motivated by vehicular applications where a vehicle (or the infrastructure) equipped with a mono-static radar wishes to communicate data to its target receiver, while estimating parameters of interest related to this receiver. Provided that the radar-equipped transmitter is ready to send data to its target receiver, this setting naturally assumes that the receiver has been already detected. In a point-to-point communication setting over multipath time-frequency selective channels, we study the joint radar and communication system from two perspectives, i.e., the radar parameter estimation at the transmitter as well as the data detection at the receiver. For the radar parameter estimation part, we derive an efficient approximated Maximum Likelihood algorithm and the corresponding Cramér-Rao lower bound for range and velocity estimation. Numerical examples demonstrate that multi-carrier digital formats such as OTFS can achieve as accurate radar estimation as state-of-the-art radar waveforms such as frequency-modulated continuous wave (FMCW). For the data detection part, we focus on separate detection and decoding and consider a soft-output detector that exploits efficiently the channel sparsity in the Doppler-delay domain. We quantify the detector performance in terms of its pragmatic capacity, i.e., the achievable rate of the channel induced by the signal constellation and the detector soft-output. Simulations show that the proposed scheme outperforms concurrent state-of-the-art solutions. Overall, our work shows that a suitable digitally modulated waveform enables to efficiently operate joint radar parameter estimation and communication by achieving full information rate of the modulation and near-optimal radar estimation performance. Furthermore, OTFS appears to be particularly suited to the scope

Пространственное линейное кодирование сигналов в совместной системе радиолокации и многоадресной радиосвязи

Introduction. This paper presents optimization methods for the amplitude-phase distribution in a transmitting antenna array in a system with a common signal for multicast data transmission and radar sensing in a given sector of space. Two approaches are considered for the choice of an objective function for the optimization problem. The first approach involves minimizing the transmitted power for a given quality of user service and radar surveillance. The second approach involves optimizing the quality of service for the worst radar and communication channel under a given power budget. The value that determines the quality of service is the signal-to-noise ratio, for both communication and radar.Aim. Тo solve the optimization problem of spatial linear coding of signals in a joint multicast radar and communication system, which shares a common signal.Materials and methods. Optimization of spatial linear coding in a joint radio radar and communication system was carried out by the methods of statistical theory and optimization theory using the numerical solution of optimization problems. The performance characteristics of the system were analyzed by Monte Carlo simulation. Statistical simulation was performed in the MATLAB environment using standard tools, as well as the CVX package for the numerical solution of convex optimization problems.Results. Optimization problems were formulated based on the criteria of the minimum radiated power and the maximum signal-to-noise ratio in the worst channel. A limitation on the radiated power of individual antenna channels was used for both cases. Optimization problems were approximately reduced to convex problems with semidefinite constraints, which could be solved using the wellknown interior point algorithm with polynomial complexity. The performed statistical simulation produced optimal performance characteristics of a joint system, including the total power versus the threshold signal-to-noise ratio and the signal-to-noise ratio for the worst channel versus the power budget.Conclusion. The proposed numerical optimization methods for spatial linear coding in a transmitting antenna array can be recommended when designing joint radar communication systems.Введение. В статье решается актуальная задача разработки методов оптимизации амплитудно-фазового распределения в передающей антенной решетке в системе, в которой используется общий сигнал для многоадресной передачи данных и радиолокационного зондирования в заданном секторе пространства. Выбор целевой функции для оптимизационной задачи основывается на двух подходах. Первый подход заключается в минимизации излучаемой мощности при заданном качестве обслуживания пользователей и радиолокационного наблюдения. Второй подход основан на оптимизации качества обслуживания в наихудшем канале передачи данных и радиолокационного наблюдения при заданном бюджете мощности. Величиной, определяющей качество обслуживания, является отношение сигнал/шум как для передачи данных, так и для радиолокации.Цель работы. Решение задачи оптимизации пространственного линейного кодирования сигналов в совместной системе многоадресной радиосвязи и радиолокации, в которой используется общий временной сигнал.Материалы и методы. Оптимизация пространственного линейного кодирования в совместной системе радиосвязи и радиолокации основывается на методах статистической теории и методах теории оптимизации с использованием численного решения оптимизационных задач. Характеристики системы анализируются с помощью математического моделирования на основе метода Монте-Карло. Статистическое моделирование выполняется в среде MATLAB с использованием стандартных средств, а также пакета CVX для численного решения выпуклых оптимизационных задач.Результаты. Сформулированы оптимизационные задачи на основе критериев минимума излучаемой мощности и максимума отношения сигнал/шум в наихудшем канале. В обоих случаях используется ограничение на излучаемую мощность отдельными антенными каналами. Оптимизационные задачи приближенно сводятся к выпуклым задачам с полуопределенными условиями, которые решаются с помощью хорошо известного алгоритма внутренней точки, имеющего полиномиальную сложность. Проведено статистическое моделирование, в результате которого получены оптимальные характеристики совместной системы, а именно зависимости излучаемой мощности от порогового отношения сигнал/шум и зависимости отношения сигнал/шум в наихудшем канале от бюджета мощности.Заключение. Предложены методы оптимального линейного кодирования в антенной решетке, основанные на численном решении оптимизационных задач, которые рекомендуется использовать при разработке совместной системы многоадресной радиосвязи и радиолокации

A Comprehensive Overview on 5G-and-Beyond Networks with UAVs: From Communications to Sensing and Intelligence

Due to the advancements in cellular technologies and the dense deployment of cellular infrastructure, integrating unmanned aerial vehicles (UAVs) into the fifth-generation (5G) and beyond cellular networks is a promising solution to achieve safe UAV operation as well as enabling diversified applications with mission-specific payload data delivery. In particular, 5G networks need to support three typical usage scenarios, namely, enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC). On the one hand, UAVs can be leveraged as cost-effective aerial platforms to provide ground users with enhanced communication services by exploiting their high cruising altitude and controllable maneuverability in three-dimensional (3D) space. On the other hand, providing such communication services simultaneously for both UAV and ground users poses new challenges due to the need for ubiquitous 3D signal coverage as well as the strong air-ground network interference. Besides the requirement of high-performance wireless communications, the ability to support effective and efficient sensing as well as network intelligence is also essential for 5G-and-beyond 3D heterogeneous wireless networks with coexisting aerial and ground users. In this paper, we provide a comprehensive overview of the latest research efforts on integrating UAVs into cellular networks, with an emphasis on how to exploit advanced techniques (e.g., intelligent reflecting surface, short packet transmission, energy harvesting, joint communication and radar sensing, and edge intelligence) to meet the diversified service requirements of next-generation wireless systems. Moreover, we highlight important directions for further investigation in future work.Comment: Accepted by IEEE JSA