Implementation Aspects of a Transmitted-Reference UWB Receiver

In this paper, we discuss the design issues of an ultra wide band (UWB) receiver targeting a single-chip CMOS implementation for low data-rate applications like ad hoc wireless sensor networks. A non-coherent transmitted reference (TR) receiver is chosen because of its small complexity compared to other architectures. After a brief recapitulation of the UWB fundamentals and a short discussion on the major differences between coherent and non-coherent receivers, we discuss issues, challenges and possible design solutions. Several simulation results obtained by means of a behavioral model are presented, together with an analysis of the trade-off between performance and complexity in an integrated circuit implementation

Generalized Code-Multiplexing for UWB Communications

Code-multiplexed transmitted reference (CM-TR) and code-shifted reference (CSR) have recently drawn attention in the field of ultra-wideband communications mainly because they enable noncoherent detection without requiring either a delay component, as in transmitted reference, or an analog car- rier, as in frequency-shifted reference, to separate the reference and data-modulated signals at the receiver. In this paper, we propose a generalized code-multiplexing (GCM) system based on the formulation of a constrained mixed-integer optimization problem. The GCM extends the concept of CM-TR and CSR while retaining their simple receiver structure, even offering better bit-error-rate performance and a higher data rate in the sense that more data symbols can be embedded in each transmitted block. The GCM framework is further extended to the cases when peak power constraint is considered and when inter-frame interference exists, as typically occurs in high data-rate transmissions. Numerical simulations performed over demanding wireless environments corroborate the effectiveness of the proposed approach

Implementation of a coded-reference ultra-wideband system

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2011.Thesis (Master's) -- Bilkent University, 2011.Includes bibliographical references leaves 60-64.Coded-reference ultra-wideband (CR UWB) systems provide orthogonalization of the reference and data signals in the code domain to facilitate communications without the need for complex channel estimation and have significant advantages over the previous techniques in terms of performance and/or implementation complexity. This thesis presents a UWB testbed as a general experimental platform to explore pulse-based UWB communications and discusses design and implementation issues. A testbed is built as a flexible solution for hardware implementation of a CR UWB system.Gürlevik, OsmanM.S

Receiver Design and Security for Low Power Wireless Communications Systems

This dissertation focuses on two important areas in wireless communications: receiver design and security. In the first part of this dissertation we consider low data rate receiver design for ultra-wideband (UWB), a wideband radio technology that promises to help solve the frequency allocation problem that often inhibits narrowband systems. Reference-based receivers are promising candidates in the UWB regime, because the conventional rake receiver designs suffers from complexity limitations and inaccuracies in channel estimation. Many reference-based systems have arisen as viable solutions for receivers. We unify these systems as well as other systems into the general framework for performance analysis to suggest the optimal system for varying constraints. We improve the performance of frequency-shifted reference (FSR-UWB) for an average power constraint by halving the frequency offset and employing a sample-and-hold approach across the frame period. Also, we introduce a novel peak mitigation technique; tone reservation, for the multi-differential (MD) version of FSR-UWB, to reduce the high peak-to-average power ratio observed as the data carriers increase. The next part of this dissertation is about wireless security which is ubiquitous in modern news. Cryptography is widely use for security but it assumes limited computational abilities of an eavesdropper, is based on the unproven hardness of the underlying primitives, and allows for the message to be recorded and decrypted later. In this dissertation we consider an information-theoretic security approach to guaranteeing everlasting secrecy. We contribute a new secrecy rate pair outage formulation, where an outage event is based on the instantaneous rates of the destination and the eavesdropper being below and above desired thresholds, respectively. In our new secrecy rate pair outage formulation, two new unaccounted outage events emerge: secrecy breach, where the eavesdropper is above the targeted threshold; unreliable, where the destination is unable to successfully decode the message. The former case must be carefully avoided, while for the latter case we can exploit automatic retransmissions (ARQ) while maintaining the eavesdropper intercept probability below the target threshold. We look at both ``simple\u27\u27 receivers and also complex receivers that use a buffer to store previous messages to maximally combine signal-to-noise ratio (SNR). Then we extend these results to the two-hop case where we maximize the end-to-end secure throughput by optimizing the intercept probability at each eavesdropper given a total end-to-end intercept constraint. Lastly, we consider the difficult case in information-theoretic security: the near eavesdropper case, where we contribute an optimal power allocation algorithm that leverages nearby chatter nodes to generate noise to reduce the probability of intercept by the eavesdropper while minimally impeding the source-to-destination communication. As shown in both one-hop and two-hop cases, allowing a slight outage at the destination for cases of when the eavesdropper is above a specific threshold greatly improves secrecy performance

Efficient approaches to robust and cooperative wireless network design

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 181-200).In wireless networks, relaying and user cooperation offer several attractive benefits such as higher throughput, better power efficiency, and larger coverage. As a result, cooperative networks are regarded as one of the most promising enabling technologies able to meet the increasingly high rate demands and quality of service requirements in wireless networks. In this dissertation, we investigate the efficient design of cooperative wireless networks from the perspectives of robust resource allocation, wideband communications, and energy efficiency. Given that the primary resource to be allocated is the relay node's transmission power, we propose robust and efficient relay power allocation algorithms when the global channel state information is subject to uncertainty. In addition, we propose practical algorithms that do not require frequent tracking of the global channel state information. This work reveals that ignoring global channel state information uncertainties and solving the relay power optimization problems often lead to poor performance, highlighting the importance of robust algorithm designs in practical wireless networks. Wideband cooperative networks allow for both higher data rate and higher resistance to interference. Since the gains achieved by using cooperation come at the cost of higher node complexity and substantial coordination overhead, it is important to study practical low-complexity signaling and receiver schemes suitable for wideband networks. In particular, we consider transmitted-reference signaling schemes and provide a unified performance analysis in terms of bit error rate. Since wideband networks are expected to coexist with many existing narrowband systems, it is important to characterize the effect of narrowband interference. We further extend the performance analysis of transmitted-reference signaling schemes to include the effect of narrowband interference..(cont) Finally, we conclude by studying the benefits of cooperation in a wireless sensor network, which aims at detecting the presence or absence of a certain physical phenomenon of interest using geographically dispersed sensor nodes. We propose a consensus flooding protocol and analyze its average energy consumption. We investigate the tradeoff between the detection reliability and the energy efficiency when nodes are allowed to cooperate. By addressing the above design challenges, this dissertation will be useful for obtaining insight into the theory and application of cooperative networks in future communication systemsby Tony Q.S. Quek.Ph.D

Contribution à l'étude de la détection des signaux UWB. Etude et implémentation d'un récepteur ad hoc multicapteurs. Applications indoor de localisation

Cette thèse s inscrit dans le projet de communication à proximité aux départements Electronique et Physique et Communications, Images et Traitement de l Information de l Institut Télécom Sud Paris. Le projet comporte la mise au point d un récepteur basé sur une méthode de détection pseudo-cohérente des signaux Ultra Large Bande à double impulsion (TR-UWB), méthode désignée par Time Delayed Sampling and Correlation (TDSC). La première partie de ce document comporte la réalisation d une plate-forme modulaire de communication UWB basée sur le système de détection TDSC. Cette plate-forme comporte une puce CMOS 0.35 m conçue précédemment au laboratoire EPH. Elle offre la possibilité d enregistrer des signaux TR-UWB réels et de réaliser des tests de fonctionnement. La deuxième partie est une étude approfondie du récepteur utilisant la méthode TDSC. La détection des signaux UWB et la procédure de synchronisation sont évalués en utilisant les signaux réels acquis à partir de la plate-forme. Un ensemble de tests ont été menés avec des signaux en bande de base et des signaux transposés en fréquence, dans les deux cas en transmission sur câble puis par radio. Les résultats ont permis de valider la détection et le principe de la synchronisation. La troisième partie est une proposition d estimation de la distance entre deux dispositifs d un réseau radio UWB utilisant un récepteur TDSC, pour une localisation en intérieur. L étude fait la synthèse de plusieurs propositions et expérimentations et conduit à la définition des meilleurs critères pour une mesure du temps d arrivée (TOA) et son implémentation pratique sur un récepteur TDSCThis thesis is part of the Electronics and Physics (EPH) department s research work at Institut Telecom SudParis in collaboration with the Information, Images and Information Processing (CITI) Department. The project included the development of a receiver architecture called Time Delayed Sampling and Correlation (TDSC) that works with Transmitted Reference Ultra Wideband signals (TR-UWB), and which could achieve a good performance without channel estimation. The first part of this work included the design of a modular UWB communication system based on the TDSC method. This platform uses a 0.35 m CMOS chip conceived by the EPH laboratory. This gives the possibility to record real TR-UWB signals and to achieve functional tests. A second part of the thesis was to deepen the use of the TDSC method for detection of UWB signals and the synchronization procedure of the receiver using real signals acquired by the platform. A series of tests were conducted in this regard by using baseband signals as well as frequency translated signals, through cable channels and radio transmission. The results let us validate the TDSC detection and the synchronization procedure. Finally, a third line of work was the study and development of a distance estimation proposal based on the time of arrival (TOA) of TR-UWB signals, for indoor localization purposes. The study included a synthesis of several proposals and experimental works. Simulations were made and compared with other methods. Experimental results and their good convergence with the simulations let conclude that the proposal is a feasible solution to the measurement of the TOA, based on a TR-UWB receiver with low-complexity architectureEVRY-INT (912282302) / SudocSudocFranceF