UNDERWATER COMMUNICATIONS WITH ACOUSTIC STEGANOGRAPHY: RECOVERY ANALYSIS AND MODELING

In the modern warfare environment, communication is a cornerstone of combat competence. However, the increasing threat of communications-denied environments highlights the need for communications systems with low probability of intercept and detection. This is doubly true in the subsurface environment, where communications and sonar systems can reveal the tactical location of platforms and capabilities, subverting their covert mission set. A steganographic communication scheme that leverages existing technologies and unexpected data carriers is a feasible means of increasing assurance of communications, even in denied environments. This research works toward a covert communication system by determining and comparing novel symbol recovery schemes to extract data from a signal transmitted under a steganographic technique and interfered with by a simulated underwater acoustic channel. We apply techniques for reliably extracting imperceptible information from unremarkable acoustic events robust to the variability of the hostile operating environment. The system is evaluated based on performance metrics, such as transmission rate and bit error rate, and we show that our scheme is sufficient to conduct covert communications through acoustic transmissions, though we do not solve the problems of synchronization or equalization.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

Communication platform for inter-satellite links in distributed satellite systems

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Synchronization Performance in DVB-T2 system

The Digital Video Broadcasting (DVB) project has developed digital broadcasting system specifications which have been adapted worldwide. The family of DVB standards includes DVB-S for satellite, DVB-C for cable and DVB-T for terrestrial system. This DVB-T system has proven its capability and thus accepted as the standard for terrestrial system in most countries. DVB-T2 is the enhancement of DVB-T that will overcome the shortcomings of the previous standard and provide additional features. This thesis concentrates on synchronization performance in DVB-T2 systems. Synchronization is the most important task that the receiver has to perform in the beginning of its reception of the signal. DVB-T2 uses Orthogonal Frequency Division Multiplexing (OFDM) modulation method and has a special symbol, named P1 symbol, for performing initial synchronization tasks. This symbol is also used for detecting DVB-T2 signal, meaning that, if the receiver can detect the P1 symbol, then it can conclude that the channel contains DVB-T2 signal. Moreover, P1 symbol also transmits basic transmission parameters that the receiver needs in the first place in order to proceed for further processing. In this work, the DVB-T2 system model has been implemented including the P1 symbol and the performance of synchronization by P1 symbol has been analyzed extensively by simulations in different channel conditions. P1 symbol deals with the synchronization issues before performing Fast Fourier Transform (FFT). Therefore, P1 symbol based methods can achieve coarse timing synchronization and fine frequency synchronization. Also the detecting and decoding probabilities based on P1 symbol in different channels are presented in this thesis. /Kir0

Synchronization Performance in DVB-T2 system

The Digital Video Broadcasting (DVB) project has developed digital broadcasting system specifications which have been adapted worldwide. The family of DVB standards includes DVB-S for satellite, DVB-C for cable and DVB-T for terrestrial system. This DVB-T system has proven its capability and thus accepted as the standard for terrestrial system in most countries. DVB-T2 is the enhancement of DVB-T that will overcome the shortcomings of the previous standard and provide additional features. This thesis concentrates on synchronization performance in DVB-T2 systems. Synchronization is the most important task that the receiver has to perform in the beginning of its reception of the signal. DVB-T2 uses Orthogonal Frequency Division Multiplexing (OFDM) modulation method and has a special symbol, named P1 symbol, for performing initial synchronization tasks. This symbol is also used for detecting DVB-T2 signal, meaning that, if the receiver can detect the P1 symbol, then it can conclude that the channel contains DVB-T2 signal. Moreover, P1 symbol also transmits basic transmission parameters that the receiver needs in the first place in order to proceed for further processing. In this work, the DVB-T2 system model has been implemented including the P1 symbol and the performance of synchronization by P1 symbol has been analyzed extensively by simulations in different channel conditions. P1 symbol deals with the synchronization issues before performing Fast Fourier Transform (FFT). Therefore, P1 symbol based methods can achieve coarse timing synchronization and fine frequency synchronization. Also the detecting and decoding probabilities based on P1 symbol in different channels are presented in this thesis. /Kir0

Stacked Modulation Formats Enabling Highest-Sensitivity Optical Free-Space Communications

Die vorliegende Arbeit befasst sich mit hochempfindlichen optischen Kommunikationssystemen, wie sie z.B. bei Intersatellitenlinks verwendet werden. Theoretische Überlegungen zur Steigerung der Empfängerempfindlichkeit werden mit Simulations- und Messergebnissen ergänzt und verifiziert. Auf Grund der steigenden Nachfrage nach optischen Links zwischen Satelliten stellt sich die Frage, was sind geeignete Eckparameter, um ein solches System zu beschreiben. Die gigantischen Datenmengen, die von diversen Messgeräten, wie z.B. hochauflösende Kameras auf einem Satelliten generiert werden, bringen die Kapazitäten klassischer HF-Datenlinks an ihre Grenzen. Hier können optische Kommunikationssysteme auf Grund ihrer hohen Trägerfrequenz im Infrarotbereich sehr hohe Datenraten im Terabit/s Bereich ermöglichen. Systeme mit Radiowellen im GHz Bereich als Trägerfrequenz sind hier deutlich limitierter. [7] Linkdistanz, verfügbare Leistung, Pointinggenauigkeit und verfügbare Antennengröße sind einige Parameter, die einen wichtigen Einfluss auf die Leistungsfähigkeit des Systems haben. Je größer die Distanz und desto kleiner die verfügbare Antennengröße sowohl am Sender als auch am Empfänger sind, desto weniger Signalleistung wird den Detektor erreichen. Nimmt man dann noch ungenaues Pointing hinzu, d.h. Sender und Empfänger sind nicht exakt aufeinander ausgerichtet, treten zusätzliche Verluste auf. [7] Ziel dieser Arbeit ist es, ein vereinfachtes System zu implementieren und zu testen, das mit möglichst wenigen Photonen pro Bit bei einer gegebenen Bitfehlerwahrscheinlichkeit bei einer möglichst hohen Datenrate arbeiten kann. Hierfür werden alle Freiheitsgrade einer optischen Welle zur Modulation verwendet, um mit sog. „Stapeln“ von Modulationsformaten eine Empfindlichkeitssteigerung zu erreichen. Die Amplitude des Signals wird durch Pulspositionsmodulation (PPM) moduliert, wobei das zeitlich variable Vorhandensein eines Pulses innerhalb des Symbols die Information enthält. Dieses Modulationsformat weist bis dato die höchste Empfindlichkeit in Literatur und Experimenten auf [4]. Je mehr Möglichkeiten es gibt, einen Puls in einem Symbol zu platzieren, desto höher ist die zu erwartende Empfindlichkeit des Systems. Mit anderen Worten: Steigert man die zeitliche Dauer eines PPM-Symbols, so wächst ebenfalls die Empfängerempfindlichkeit. Da bei diesem Ansatz die Datenrate sinkt, wird in dieser Arbeit eine andere Methode vorgestellt, die Empfindlichkeit eines Übertragungssystems zu steigern, ohne die Symbollänge unnötig in die Länge zu ziehen. Diese Arbeit befasst sich mit dem Stapeln (sog. „Stacking“) von Modulationsformaten, in dem neben der Amplitudenmodulation weitere Freiheitsgrade, wie die Frequenz, Phase und Polarisation geschickt genutzt werden. Bei der Frequenzumtastung (FSK) wird die optische Frequenz je nach Symbol um ein gewisses Maß verschoben. Bei der polarisations-geschalteten Quadratur-Phasenumtastung (PS-QPSK) werden sowohl die Phase, als auch die Polarisation der optischen Welle moduliert [12]. Als Endergebnis erhält man PPM-FSK-PS-QPSK als Modulationsformat mit hoher Empfindlichkeit. Gegenüber dem reinen PPM wird eine theoretische Empfindlichkeitssteigerung von mehr als 1 dB erreicht. Sowohl Simulations- als auch Messergebnisse bestätigen den Empfindlichkeitsgewinn

Real-Time Localization Using Software Defined Radio

Service providers make use of cost-effective wireless solutions to identify, localize, and possibly track users using their carried MDs to support added services, such as geo-advertisement, security, and management. Indoor and outdoor hotspot areas play a significant role for such services. However, GPS does not work in many of these areas. To solve this problem, service providers leverage available indoor radio technologies, such as WiFi, GSM, and LTE, to identify and localize users. We focus our research on passive services provided by third parties, which are responsible for (i) data acquisition and (ii) processing, and network-based services, where (i) and (ii) are done inside the serving network. For better understanding of parameters that affect indoor localization, we investigate several factors that affect indoor signal propagation for both Bluetooth and WiFi technologies. For GSM-based passive services, we developed first a data acquisition module: a GSM receiver that can overhear GSM uplink messages transmitted by MDs while being invisible. A set of optimizations were made for the receiver components to support wideband capturing of the GSM spectrum while operating in real-time. Processing the wide-spectrum of the GSM is possible using a proposed distributed processing approach over an IP network. Then, to overcome the lack of information about tracked devices’ radio settings, we developed two novel localization algorithms that rely on proximity-based solutions to estimate in real environments devices’ locations. Given the challenging indoor environment on radio signals, such as NLOS reception and multipath propagation, we developed an original algorithm to detect and remove contaminated radio signals before being fed to the localization algorithm. To improve the localization algorithm, we extended our work with a hybrid based approach that uses both WiFi and GSM interfaces to localize users. For network-based services, we used a software implementation of a LTE base station to develop our algorithms, which characterize the indoor environment before applying the localization algorithm. Experiments were conducted without any special hardware, any prior knowledge of the indoor layout or any offline calibration of the system

NB-IoT via non terrestrial networks

Massive Internet of Things is expected to play a crucial role in Beyond 5G (B5G) wireless communication systems, offering seamless connectivity among heterogeneous devices without human intervention. However, the exponential proliferation of smart devices and IoT networks, relying solely on terrestrial networks, may not fully meet the demanding IoT requirements in terms of bandwidth and connectivity, especially in areas where terrestrial infrastructures are not economically viable. To unleash the full potential of 5G and B5G networks and enable seamless connectivity everywhere, the 3GPP envisions the integration of Non-Terrestrial Networks (NTNs) into the terrestrial ones starting from Release 17. However, this integration process requires modifications to the 5G standard to ensure reliable communications despite typical satellite channel impairments. In this framework, this thesis aims at proposing techniques at the Physical and Medium Access Control layers that require minimal adaptations in the current NB-IoT standard via NTN. Thus, firstly the satellite impairments are evaluated and, then, a detailed link budget analysis is provided. Following, analyses at the link and the system levels are conducted. In the former case, a novel algorithm leveraging time-frequency analysis is proposed to detect orthogonal preambles and estimate the signals’ arrival time. Besides, the effects of collisions on the detection probability and Bit Error Rate are investigated and Non-Orthogonal Multiple Access approaches are proposed in the random access and data phases. The system analysis evaluates the performance of random access in case of congestion. Various access parameters are tested in different satellite scenarios, and the performance is measured in terms of access probability and time required to complete the procedure. Finally, a heuristic algorithm is proposed to jointly design the access and data phases, determining the number of satellite passages, the Random Access Periodicity, and the number of uplink repetitions that maximize the system's spectral efficiency

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Design and FPGA implementation of a SISO and a MIMO wireless system for software defined radio

MIMO (Multiple-input Multiple-output) technology combined with space time coding techniques provides significant increase in performance and capacity over an equivalent SISO (Single-input Single-output) system while maintaining the same bandwidth and transmission power. MIMO has emerged as the major breakthrough in recent communication technologies. To migrate from SISO to MIMO system, multiple RF (Radio Frequency) front ends and additional signal processing are required. Software defined radio (SDR) allows MIMO and other evolving techniques to be added to current systems through software update instead of hardware replacement. SDR provides a flexible and economic solution to the system upgrade and migration. In this thesis, an SDR based SISO system using QPSK modulation scheme is implemented on FPGA. The system produces signal with an intermediate frequency of 25 MHz and throughput of 12.5 Mbps. One carrier recovery and two symbol timing recovery algorithms (Gardner and Maximum Likelihood) are investigated and implemented. A 2x1 MIMO system using Alamouti scheme and CORDIC based carrier recovery is designed as well. The SDR based SISO system can be easily incorporated to the MIMO design. Throughout this thesis, detailed design information is presented along with both computer simulation results and real hardware performance. The comparisons of different algorithms and component structures are also provided. Based on these comparisons, the suitable algorithm or structure according to specific implementation considerations and system requirement can be selected. The design and implementation are processed based on a system-level design flow. System modeling and simulation are performed using Xilinx's System Generator for DSP and Simulink. After it is mapped to HDL (Hardware Description Language) netlist, the design is synthesized and implemented by Xilinx's ISE tool. The generated bit-stream is then downloaded to target FPGA to program the device. The hardware performance is measured by BER (Bit Error Rate) tester, oscilloscope and spectrum analyzer. This thesis is an initial project for future work of Wireless Design Laboratory at Concordia University. The system realized in this project can be viewed as a base of future MIMO implementation with different number of antennas and advanced signal processing techniques

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks