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Book

Synchronization Techniques for Digital Receivers

TL;DR: The Principles, Methods and Performance Limits of Carrier Frequency Recovery with Linear Modulations and Timing Recovery with CPM Modulations are presented.
Abstract: Introduction. Principles, Methods and Performance Limits. Carrier Frequency Recovery with Linear Modulations. Carrier Frequency Recovery with CPM Modulations. Carrier Phase Recovery with Linear Modulations. Carrier Phase Recovery with CPM Modulations. Timing Recovery in Baseband Transmission. Timing Recovery with Linear Modulations. Timing Recovery with CPM Modulations. Index.
Citations
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Journal ArticleDOI
TL;DR: Numerical results show that by optimizing the trajectory of the relay and power allocations adaptive to its induced channel variation, mobile relaying is able to achieve significant throughput gains over the conventional static relaying.
Abstract: In this paper, we consider a novel mobile relaying technique, where the relay nodes are mounted on unmanned aerial vehicles (UAVs) and hence are capable of moving at high speed. Compared with conventional static relaying, mobile relaying offers a new degree of freedom for performance enhancement via careful relay trajectory design. We study the throughput maximization problem in mobile relaying systems by optimizing the source/relay transmit power along with the relay trajectory, subject to practical mobility constraints (on the UAV’s speed and initial/final relay locations), as well as the information-causality constraint at the relay. It is shown that for the fixed relay trajectory, the throughput-optimal source/relay power allocations over time follow a “staircase” water filling structure, with non-increasing and non-decreasing water levels at the source and relay, respectively. On the other hand, with given power allocations, the throughput can be further improved by optimizing the UAV’s trajectory via successive convex optimization. An iterative algorithm is thus proposed to optimize the power allocations and relay trajectory alternately. Furthermore, for the special case with free initial and final relay locations, the jointly optimal power allocation and relay trajectory are derived. Numerical results show that by optimizing the trajectory of the relay and power allocations adaptive to its induced channel variation, mobile relaying is able to achieve significant throughput gains over the conventional static relaying.

1,079 citations

Journal ArticleDOI
13 Aug 2007
TL;DR: The goal of this paper is to provide a comprehensive survey of the latest results in the field of synchronization for OFDMA systems, with tutorial objectives foremost.
Abstract: Orthogonal frequency division multiple access (OFDMA) has recently attracted vast research attention from both academia and industry and has become part of new emerging standards for broadband wireless access. Even though the OFDMA concept is simple in its basic principle, the design of a practical OFDMA system is far from being a trivial task. Synchronization represents one of the most challenging issues and plays a major role in the physical layer design. The goal of this paper is to provide a comprehensive survey of the latest results in the field of synchronization for OFDMA systems, with tutorial objectives foremost. After quantifying the effects of synchronization errors on the system performance, we review some common methods to achieve timing and frequency alignment in a downlink transmission. We then consider the uplink case, where synchronization is made particularly difficult by the fact that each user's signal is characterized by different timing and frequency errors, and the base station has thus to estimate a relatively large number of unknown parameters. A second difficulty is related to how the estimated parameters must be employed to correct the uplink timing and frequency errors. The paper concludes with a comparison of the reviewed synchronization schemes in an OFDMA scenario inspired by the IEEE 802.16 standard for wireless metropolitan area networks.

731 citations

Book
02 Nov 2007
TL;DR: This book is intended as an introduction to the entire range of issues important to reconfigurable computing, using FPGAs as the context, or "computing vehicles" to implement this powerful technology.
Abstract: The main characteristic of Reconfigurable Computing is the presence of hardware that can be reconfigured to implement specific functionality more suitable for specially tailored hardware than on a simple uniprocessor. Reconfigurable computing systems join microprocessors and programmable hardware in order to take advantage of the combined strengths of hardware and software and have been used in applications ranging from embedded systems to high performance computing. Many of the fundamental theories have been identified and used by the Hardware/Software Co-Design research field. Although the same background ideas are shared in both areas, they have different goals and use different approaches.This book is intended as an introduction to the entire range of issues important to reconfigurable computing, using FPGAs as the context, or "computing vehicles" to implement this powerful technology. It will take a reader with a background in the basics of digital design and software programming and provide them with the knowledge needed to be an effective designer or researcher in this rapidly evolving field. · Treatment of FPGAs as computing vehicles rather than glue-logic or ASIC substitutes · Views of FPGA programming beyond Verilog/VHDL · Broad set of case studies demonstrating how to use FPGAs in novel and efficient ways

531 citations

Journal ArticleDOI
03 Jan 2006
TL;DR: The paper provides a tutorial overview of the DVB-S2 system, describing its main features and performance in various scenarios and applications.
Abstract: DVB-S2 is the second-generation specification for satellite broad-band applications, developed by the Digital Video Broadcasting (DVB) Project in 2003. The system is structured as a toolkit to allow the implementation of the following satellite applications: TV and sound broadcasting, interactivity (i.e., Internet access), and professional services, such as TV contribution links and digital satellite news gathering. It has been specified around three concepts: best transmission performance approaching the Shannon limit, total flexibility, and reasonable receiver complexity. Channel coding and modulation are based on more recent developments by the scientific community: low density parity check codes are adopted, combined with QPSK, 8PSK, 16APSK, and 32APSK modulations for the system to work properly on the nonlinear satellite channel. The framing structure allows for maximum flexibility in a versatile system and also synchronization in worst case configurations (low signal-to-noise ratios). Adaptive coding and modulation, when used in one-to-one links, then allows optimization of the transmission parameters for each individual user,dependant on path conditions. Backward-compatible modes are also available,allowing existing DVB-S integrated receivers-decoders to continue working during the transitional period. The paper provides a tutorial overview of the DVB-S2 system, describing its main features and performance in various scenarios and applications.

383 citations

Proceedings ArticleDOI
06 Apr 2003
TL;DR: This tutorial overviews the state-of-the-art UWB in channel modeling, transmitters, and receivers of UWB radios, and outlines the research directions and challenges that needs to be overcome.
Abstract: Summary form only given. Ultra-wideband (UWB) refers to bandwidths in excess of 2 GHz, whose utilization by radar systems dates back to the late '60s. The renewed and rapidly growing interest for UWB was sparked by the spectral mask released by FCC in February 2002, and is well motivated by the attractive features UWB brings to commercial communications: low-power carrier-free transmissions, ample multipath diversity, enhanced penetration capability, low-complexity transceivers, ability to overlay existing systems, and a potential for increase in capacity. This article outlines features and challenges unique to UWB, with emphasis on timely signal processing issues that focus on synchronization, channel estimation, multiple access, and suppression of interference UWB systems cause to (and suffer from) co-existing narrowband systems. Application areas include shortrange indoor wireless links at home, and in the workplace for low-cost multimedia communications and storage, as well as secure connectivity for ranging, and covert communications.

363 citations

References
More filters
01 Jun 1993

19 citations

Patent
16 Jan 1988
TL;DR: In this paper, the authors proposed a timing error detector for timing synchronization with a receiver for synchronous data transmission, in which low-pass filtered in-phase components and quadrature components of the product of the received signal and the output signal from the carrier oscillator are passed, along with the signal terms suppressed by the double frequency, to the signal error detector in the form of a demodulated received signal.
Abstract: Timing error detector for timing synchronization a receiver for synchronous data transmission. Low-pass filtered in-phase components and quadrature components of the product of the received signal and the output signal from the carrier oscillator are passed, along with the signal terms suppressed by the double frequency, to the timing error detector in the form of a demodulated received signal. The output signal acts as a control signal (uTI) for the timing generator, and the timing error detector contains two band-passes, powered by the demodulated received signal, and a combinatorial circuit. Said circuit generates the control signal from the complex band-pass output signals, and is characterized by the fact that a further circuit (VF) generates a control signal (uf) from the complex output quantities of the band-passes (BP+), for controlling the frequency of the carrier oscillator.

9 citations

Book ChapterDOI
01 Jan 1997
TL;DR: In this article, the authors distinguish between two major cases: (1) the offset is much smaller than 1/T, and (2) it compensates for this offset by counter-rotating the received waveform at an angular speed 2πv.
Abstract: A frequency recovery system accomplishes two basic functions: (i) it derives an estimate v of the carrier frequency offset; (ii) it compensates for this offset by counter-rotating the received waveform r(t) at an angular speed 2πv. In the ensuing discussion we distinguish between two major cases [1]: (i) the offset is much smaller than 1/T, (ii) the offset is on the order of the symbol rate 1/T.

4 citations

Book ChapterDOI
01 Jan 1997
TL;DR: This chapter investigates timing recovery in PAM baseband transmission and additional features that arise with modulated signals will be explored in Chapters 8 and 9 for PAM and CPM modulations, respectively.
Abstract: In this chapter we investigate timing recovery in PAM baseband transmission. Additional features that arise with modulated signals will be explored in Chapters 8 and 9 for PAM and CPM modulations, respectively. The reason for first concentrating on baseband signals is motivated by the need of avoiding any distractions caused by modulation matters. As we shall see in the later chapters, such matters are easily taken into account when the basic concepts relevant to baseband systems are understood.

3 citations

Book ChapterDOI
01 Jan 1997
TL;DR: This chapter lays the groundwork for the material in the book and addresses three major themes: synchronization functions in a digital receiver, maximum likelihood parameter estimation theory, and limits to the performance of practical synchronizers.
Abstract: This chapter lays the groundwork for the material in the book and addresses three major themes. Section 2.2 describes synchronization functions in a digital receiver and indicates methods to pinpoint design limits on the synchronization errors. Section 2.3 is an overview of maximum likelihood parameter estimation theory, with emphasis on synchronization applications. A distinction is made between wanted and unwanted parameters, the former being those of interest in a given situation and with respect to which the maximum of a likelihood function is to be sought. The computation of likelihood functions for wanted parameters is investigated. Section 2.4 establishes limits to the performance of practical synchronizers. The most popular limit is the Cramer-Rao bound to the variance of unbiased estimators. It is argued that this limit is difficult to compute in most practical cases. A simpler limit is the modified Cramer-Rao bound, which is used as a benchmark in performance evaluations throughout the book.

3 citations