Interference mitigation for a joint radar communication system based on the FrFT for automotive applications

In multi user scenarios to prevent interference between users that share the same bandwidth at the same time,each user has to transmit wave forms that are uncorrelated with those of other users. However, due to spectrum limitations, the uncorrelated property cannot always be satisfied meaning that interference is unavoidable. In order to alleviate the interference, a framework for interference mitigation is presented. The performance of the proposed framework is tested on simulated and real signals. The real signal is acquired in a controlled laboratory environment using a Software Defined Radio (SDR). The simulated and experimental results show that the proposed framework is capable of mitigating the interference from other users

Dual operative radar for vehicle to vehicle and vehicle to infrastructure communication

The research presented in this Thesis deals with the concepts of joint radar and communication system for automotive application. The novel systems developed include a joint radar and communication system based on the fractional Fourier transform (FrFT) and two interference mitigation frameworks. In the joint radar and communication system the FrFT is used to embed the data information into a radar waveform in order to obtain a signal sharing Linear Frequency Modulation (LFM) characteristics while allowing data transmission. Furthermore, in the proposed system multi user operations are allowed by assigning a specific order of the FrFT to each user. In this way, a fractional order division multiplexing can be implemented allowing the allocation of more than one user in the same frequency band with the advantage that the range resolution does not depend on the number of the users that share the same frequency band but only from the assigned of the FrFT. Remarkably, the predicted simulated radar performance of the proposed joint radar and communication system when using Binary Frequency Shift Keying (BFSK) encoding is not significantly affected by the transmitted data. In order to fully describe the proposed waveform design, the signal model when the bits of information are modulated using either BFSK or Binary Phase Shift Keying (BPSK) encoding is derived. This signal model will result also useful in the interference mitigation frameworks. In multi user scenarios to prevent mutual radar interference caused by users that share the same frequency band at the same time, each user has to transmit waveforms that are uncorrelated with those of other users. However, due to spectrum limitations, the uncorrelated property cannot always be satisfied even by using fractional order division multiplexing, thus interference is unavoidable. In order to mitigate the interference, two frameworks are introduced. In a joint radar communication system, the radar also has access to the communication data. With a near-precision reconstruction of the communication signal, this interference can be subtracted. In these two frameworks the interfering signal can be reconstructed using the derived mathematical model of the proposed FrFT waveform. In the first framework the subtraction between the received and reconstructed interference signals is carried out in a coherent manner, where the amplitude and phase of the two signals are taken into account. The performance of this framework is highly depend on the correct estimation of the Doppler frequency of the interfering user. A small error on the Doppler frequency can lead to a lack of synchronization between the received and reconstructed signal. Consequently, the subtraction will not be performed in a correct way and further interference components can be introduced. In order to solve the problem of the lack of the synchronization an alternative framework is developed where the subtraction is carried out in non-coherent manner. In the proposed framework, the subtraction is carried out after that the received radar signal and the reconstructed interference are processed, respectively. The performance is tested on simulated and real signals. The simulated and experimental results show that this framework is capable of mitigating the interference from other users successfully.The research presented in this Thesis deals with the concepts of joint radar and communication system for automotive application. The novel systems developed include a joint radar and communication system based on the fractional Fourier transform (FrFT) and two interference mitigation frameworks. In the joint radar and communication system the FrFT is used to embed the data information into a radar waveform in order to obtain a signal sharing Linear Frequency Modulation (LFM) characteristics while allowing data transmission. Furthermore, in the proposed system multi user operations are allowed by assigning a specific order of the FrFT to each user. In this way, a fractional order division multiplexing can be implemented allowing the allocation of more than one user in the same frequency band with the advantage that the range resolution does not depend on the number of the users that share the same frequency band but only from the assigned of the FrFT. Remarkably, the predicted simulated radar performance of the proposed joint radar and communication system when using Binary Frequency Shift Keying (BFSK) encoding is not significantly affected by the transmitted data. In order to fully describe the proposed waveform design, the signal model when the bits of information are modulated using either BFSK or Binary Phase Shift Keying (BPSK) encoding is derived. This signal model will result also useful in the interference mitigation frameworks. In multi user scenarios to prevent mutual radar interference caused by users that share the same frequency band at the same time, each user has to transmit waveforms that are uncorrelated with those of other users. However, due to spectrum limitations, the uncorrelated property cannot always be satisfied even by using fractional order division multiplexing, thus interference is unavoidable. In order to mitigate the interference, two frameworks are introduced. In a joint radar communication system, the radar also has access to the communication data. With a near-precision reconstruction of the communication signal, this interference can be subtracted. In these two frameworks the interfering signal can be reconstructed using the derived mathematical model of the proposed FrFT waveform. In the first framework the subtraction between the received and reconstructed interference signals is carried out in a coherent manner, where the amplitude and phase of the two signals are taken into account. The performance of this framework is highly depend on the correct estimation of the Doppler frequency of the interfering user. A small error on the Doppler frequency can lead to a lack of synchronization between the received and reconstructed signal. Consequently, the subtraction will not be performed in a correct way and further interference components can be introduced. In order to solve the problem of the lack of the synchronization an alternative framework is developed where the subtraction is carried out in non-coherent manner. In the proposed framework, the subtraction is carried out after that the received radar signal and the reconstructed interference are processed, respectively. The performance is tested on simulated and real signals. The simulated and experimental results show that this framework is capable of mitigating the interference from other users successfully

Integrated Sensing and Communication Signals Toward 5G-A and 6G: A Survey

Integrated sensing and communication (ISAC) has the advantages of efficient spectrum utilization and low hardware cost. It is promising to be implemented in the fifth-generation-advanced (5G-A) and sixth-generation (6G) mobile communication systems, having the potential to be applied in intelligent applications requiring both communication and high-accurate sensing capabilities. As the fundamental technology of ISAC, ISAC signal directly impacts the performance of sensing and communication. This article systematically reviews the literature on ISAC signals from the perspective of mobile communication systems, including ISAC signal design, ISAC signal processing algorithms and ISAC signal optimization. We first review the ISAC signal design based on 5G, 5G-A and 6G mobile communication systems. Then, radar signal processing methods are reviewed for ISAC signals, mainly including the channel information matrix method, spectrum lines estimator method and super resolution method. In terms of signal optimization, we summarize peak-to-average power ratio (PAPR) optimization, interference management, and adaptive signal optimization for ISAC signals. This article may provide the guidelines for the research of ISAC signals in 5G-A and 6G mobile communication systems.Comment: 25 pages, 13 figures, 8 tables. IEEE Internet of Things Journal, 202

Novel Multi-User Chirp Signaling Schemes for Future Aviation Communication Applications

Many wireless communication systems will need to accommodate a larger number of users in the future. One application in particular in which this is critical is low data rate, long range communication links with very large numbers of nodes, such as the internet of things (IoT), possibly the internet of flying things (IoFT), etc. These systems demand advanced multi-access techniques with minimal multiple access interference (MAI). They should also be robust to multiple impairments, including multipath channel distortions, Doppler spreading, and interference. Chirp waveforms are one type of waveform set that can satisfy future system demands in the presence of these impairments. When the constant amplitude variety of chirp is used, this exhibits a desirable very low peak to average power ratio (PAPR). The ridge-shaped ambiguity function of chirp signals can also be useful for radar and channel modeling (sounding) applications. Hence chirps are promising candidates for many such applications. Chirps are specified in the IEEE 802.15.4a standard as chirp spread spectrum (CSS). Another growing application area requiring advanced communications is aviation. In particular, unmanned aircraft systems (UAS), also known as unmanned aerial vehicles (UAVs), and “drones,” will in the future operate within airspace along with commercial, cargo, and other piloted aircraft. The command and control (C2), or control and non-payload communications (CNPC) link must provide highly reliable safety critical information for the control of the UAV both in terrestrial-based line of sight conditions and in satellite communication links. Chirp signaling features make chirp signal sets good candidates to meet CNPC link requirements. In this dissertation, we investigate multi-user chirp signaling for future aviation communication and channel sensing systems. We describe the basics of chirp signaling, chirp sounding, and investigate via mathematical analysis, computer simulations, and some experiments, the effects of aviation channel-induced non-idealities such as Doppler and asynchronism on the chirp signaling schemes. We also describe a hybrid design where the system is not only a communication entity but also does channel estimation (sounding). We describe methods to increase spectral efficiency and how to avoid multiple access interference among users (and intersymbol interference for a given user). We also conducted experiments on chirp channel sounding using a small drone and software defined radios, and provide some channel characterization results. The majority of this work, and our major contributions, pertain to detailed evaluation of performance of multi-user chirp spread spectrum systems under a variety of conditions. We find, analytically, new expressions for bit error rate performance of binary coherent and noncoherent chirp spread spectrum signals, and we compare and validate numerical and analytical results with simulations. These error probability expressions are general, and can be used for any multi-user chirp signaling set. We also design more practical sets of chirp signals that out-perform existing chirp signal sets when synchronization is imperfect, a condition we term quasi-synchronous. These new practical chirp designs employ nonlinear trajectories in the time-frequency plane. Our new chirp designs also outperform existing schemes in the presence of Doppler shifts. We provide examples of air to ground link performance with empirical channel models to illustrate the superior performance of our proposed designs

Multifunction Transceiver Architecture and Technology for Future Wireless Systems

RÉSUMÉ Depuis la toute première transmission sans fil, les ondes radiofréquences ont été progressivement mises en valeur et exploitées dans un nombre de plus en plus important d'applications. Parmi toutes ces applications, la détection et la télécommunication sont sans doute les plus indispensables de nos jours. Il existe un grand nombre d’utilisations des radiofréquences, incluant les transports intelligents pour lesquels les véhicules doivent être équipés à la fois de radars et de dispositifs de communication afin d’être capables de détecter l'environnement ainsi que de réaliser la communication avec d'autres unités embarquées. La technologie émergente 5G est un autre exemple pour lequel plusieurs capteurs et radios devraient être capables de coopérer de manière autonome ou semi-autonome. Les principes de fonctionnement des systèmes radars et radio sont toutefois différents. Ces différences fondamentales peuvent entraîner l'utilisation de différentes architectures de traitement du signal et d'émetteur-récepteur, ce qui peut poser des problèmes pour l'intégration de toutes les fonctions requises au sein d'une seule et même plate-forme. En dehors de cela, certaines applications requièrent plusieurs fonctions simultanément dans un même dispositif. Par exemple, les systèmes de détection d'angle d'arrivée 2D nécessitent d'estimer l'angle d'arrivée (AOA) du faisceau entrant dans les plans horizontal et vertical simultanément. La communication radio multi-bandes et multi-modes est un autre exemple pour lequel un système radio doit être capable de communiquer dans plusieurs bandes de fréquences et dans plusieurs modes, par exemple, un duplexage en fonction de la fréquence ou du temps. À première vue, on peut penser que l'assemblage de plusieurs dispositifs distincts n'est pas la meilleure solution en ce qui concerne le coût, la simplicité et la fonctionnalité. Par conséquent, une direction de recherche consiste à proposer une architecture d'émetteur-récepteur unifiée et compacte plutôt qu’une plate-forme assemblant de multiples dispositifs distincts. C’est cette problématique qui est spécifiquement abordée dans ce travail. Selon les fonctions à intégrer dans un seul et unique système multifonctionnel, la solution peut traiter plusieurs aspects simultanément. Par exemple, toute solution réalisant l'intégration de fonctions liées au radar et à la radio devrait traiter deux aspects principaux, à savoir : la forme d'onde opérationnelle et l'architecture frontale RF.----------ABSTRACT Since the very early wireless transmission of radiofrequency signals, it has been gradually flourished and exploited in a wider and wider range of applications. Among all those applications of radio technology, sensing and communicating are undoubtedly the most indispensable ones. There are a large number of practical scenarios such as intelligent transportations in which vehicles must be equipped with both radar and communication devices to be capable of both sensing the environment and communication with other onboard units. The emerging 5G technology can be another important example in which multiple sensors and radios should be capable of cooperating with each other in an autonomous or semi-autonomous manner. The operation principles of these radar and radio devices are different. Such fundamental differences can result in using different operational signal, distinct signal processing, and transceiver architectures in these systems that can raise challenges for integration of all required functions within a single platform. Other than that, there exist some applications where several functions of a single device (i.e. sensor or radio) are required to be executed simultaneously. For example, 2D angle-of-arrival detection systems require estimating the angle of arrival (AOA) of the incoming beam in both horizontal and vertical planes at the same time. Multiband and multimode radio communication is another example of this kind where a radio system is desired to be capable of communication within several frequency bands and in several modes, e.g., time or frequency division duplexing. At a first glance, one can feel that the mechanical assembling of several distinct devices is not the best solution regarding the cost, simplicity and functionality or operability. Hence, the research attempt in developing a rather unified and compact transceiver architecture as opposed to a classical platform with assembled multiple individual devices comes out of horizon, which is addressed specifically in this work. Depending on the wireless functions that are to be integrated within a single multifunction system, the solution should address multiple aspects simultaneously. For instance, any solution for integrating radar and radio related functions should be able to deal with two principal aspects, namely operational waveform and RF front-end architecture. However, in some other above- mentioned examples such as 2D DOA detection system, identical operational waveform may be used and the main challenge of functional integration would pertain to a unification of multiple mono-functional transceivers

The deep space network, volume 15

The DSN progress is reported in flight project support, TDA research and technology, network engineering, hardware and software implementation, and operations. Topics discussed include: DSN functions and facilities, planetary flight projects, tracking and ground-based navigation, communications, data processing, network control system, and deep space stations

Wireless propagation studies in highly resonant and dynamic environments

This thesis develops efficient tools for modelling wireless communications within highly resonant environments. The aim of these tools is to augment analysis of wireless systems inside closed metallic cavity environments. The primary application for these systems is within the aerospace industry where weight and space are restricted and robustness is critical. The use of ever-advancing wireless communication options would offer significant weight and cost savings and increase safety through supplementing or the replacement of wired systems. The use of a low power wireless system offers the greatest advantage in terms of flexibility and weight. Accordingly, the most suitable applications of the wireless systems are discussed in terms of existing avionic systems. The electromagnetic properties of the aircraft environment and parameters to characterise both the properties of the environment and the wireless signal are introduced. Efficient models are then developed, which characterise the resonant and associated multipath nature of the cavity based on an equivalent circuit approach. The efficiency of these models permits the use of a statistical modelling approach, akin to reverberation chamber measurement techniques, in order to generalise the results for typically non-constant modal structures. Finally, a fractional boundary placement model is developed to augment the transmission line modelling method and permit boundary placement at non-integer positions within a structured mesh. The technique provides a semi-conformal capability with no deleterious impact on the modelling time step. This is then extended to a dynamic model for modelling structural variations during the simulation. A subset of wireless communication approaches is presented and the effectiveness and suitability of such systems are discussed. The developed models are applied to characteristic environments and a selection of the wireless communication methodologies in order to provide examples of their use and an insight into the effect of these environments upon a wireless system

Dual-Use Space Technology Transfer Conference and Exhibition

This document contains papers presented at the Dual-Use Space Technology Transfer Conference and Exhibition held at the Johnson Space Center February 1-3, 1994. Possible technology transfers covered during the conference were in the areas of information access; innovative microwave and optical applications; materials and structures; marketing and barriers; intelligent systems; human factors and habitation; communications and data systems; business process and technology transfer; software engineering; biotechnology and advanced bioinstrumentation; communications signal processing and analysis; new ways of doing business; medical care; applications derived from control center data systems; human performance evaluation; technology transfer methods; mathematics, modeling, and simulation; propulsion; software analysis and decision tools systems/processes in human support technology; networks, control centers, and distributed systems; power; rapid development perception and vision technologies; integrated vehicle health management; automation technologies; advanced avionics; ans robotics technologies. More than 77 papers, 20 presentations, and 20 exhibits covering various disciplines were presented b experts from NASA, universities, and industry