Bandwidth Allocation and Tradeoffs of Source Coding, Channel Coding and Spreading in CDMA Systems
Author: Qinghua Zhao
Publisher:
Published: 2004
Total Pages: 290
ISBN-13:
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Cross-layer Design of Wideband CDMA Systems and Cooperative Diversity for Wireless Ad Hoc Networks
Author: Ramesh Annavajjala
Publisher:
Published: 2006
Total Pages: 145
ISBN-13:
DOWNLOAD EBOOKSome of the challenges in the design of next generation wireless systems are providing high data rate multimedia services, increasing user capacity, improving reliability and range, terminal mobility, robustness to interference, limited spectrum availability, and transmission power constraints. The approaches that we take in this dissertation to address some of the aforementioned issues are cross-layer design and user cooperation. In the first part of the dissertation, on a wideband CDMA channel with a finite transmission bandwidth constraint, we consider the problem of optimal bandwidth allocation for source coding, channel coding and spread-spectrum modulation. For analytical tractability, we assume a memoryless Gaussian source with an optimum quantizer, a convolutional encoder with a soft-decision decoder, and a spread spectrum modulator with random spreading codes and a RAKE receiver. In the presence of both multiple access interference (MAI) and narrowband interference (NBI), for frequency-selective Nakagami fading channels, we derive upper and lower bounds on the end-to-end average source distortion. Since an exact expression for the average distortion is difficult to derive, we seek to obtain the three-tuple (i.e., source coding rate, channel coding rate, and spreading factor) that optimizes the upper and lower bounds on the average distortion. Under various channel conditions and interference levels, we numerically computed the optimum three-tuple, and verify the accuracy with system-level simulations. For small values of spreading factor, we show that the system performance is hurt by the self-interference of the user-of-interest, thus cautioning against aggressive channel coding. Since a multi-carrier DS-CDMA (or, simply MC-CDMA) system is more robust to NBI, we propose to employ an MC-CDMA system to improve the distortion performance on channels with severe NBI. For a fixed channel code rate, we then quantify the tradeoff between source coding and spreading for an MC-CDMA system. In the second part of the dissertation, we consider a parallel relay channel wherein the relay nodes help the source transmissions to provide improved reliability at the destination. With multiple relay nodes, we design and analyze robust noncoherent amplify-and forward receivers for use on rapidly varying Rayleigh fading channels with unknown instantaneous channel knowledge. Next, with a sum power constraint, we consider the problem of optimal transmit power allocation when only statistical knowledge, in terms of the average fading power, of the channel is available at the transmitting nodes. We quantify the improvements in both outage probability performance and asymptotic cooperation gain of various relaying protocols with optimal power allocation.
Signal Processing for Wireless Communication Systems
Author: H. Vincent Poor
Publisher: Springer Science & Business Media
Published: 2006-01-19
Total Pages: 299
ISBN-13: 0306473224
DOWNLOAD EBOOKSignal Processing for Wireless Communication Systems brings together in one place important contributions and up-to-date research results in this fast moving area. The Contributors to this work were selected from leading researchers and practitioners in this field. The book's 18 chapters are divided into three areas: systems, Networks, and Implementation Issues; Channel Estimation and Equalization; and Multiuser Detection. The Work, originally published as Volume 30, Numbers 1-3 of the Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology, will be valuable to anyone working or researching in the field of wireless communication systems. It serves as an excellent reference, providing insight into some of the most challenging issues being examined today.
Coding-Spreading Tradeoff in CDMA Systems
Author: Eduardo J. Bolas
Publisher:
Published: 2002-09-01
Total Pages: 111
ISBN-13: 9781423507512
DOWNLOAD EBOOKIn this thesis we investigate the usage of low rate codes primarily to provide the total bandwidth expansion required for a CDMA system. Comparing different combinations of coding and spreading with a traditional DS-CDMA, as defined in the IS-95 standard, allows the criteria to be defined for the best coding-spreading tradeoff in CDMA systems. The analysis of the coding-spreading tradeoff is divided into two parts. The first part is dedicated to the study of the deterministic components of the problem. This includes the different factors with non-random behavior that the system's designer can determine. The processing gain, the code characteristics and the number of users are well- defined variables that can determine the overall performance and can consequently affect the tradeoff. The second part of the study is dedicated to analyzing different combinations of coding and spreading with no ideal channel estimation and interference reduction techniques. Small-scale fading channel conditions are emulated through Nakagami-m distribution. Large-scale path loss was incorporated through the extended Hata model while Lognormal shadowing considered the fluctuations on the received power at points with the same distance to the transmitter. We assessed the performance of different combinations of coding and spreading considering in two cases: a worst-case scenario in which the mobile user was located at the corner of a hexagon cell in a seven-cell cluster and a more realistic scenario in which the user could be physically located anywhere in the cell, following a uniform probability distribution function. Furthermore, we investigated the improvement in performance generated by interference reduction techniques, such as sectoring and power control.
Cross-layer Bandwidth Allocation and Delay Allocation for Video Transmission Over Wireless Channels
Author: Yushi Shen
Publisher:
Published: 2006
Total Pages: 146
ISBN-13:
DOWNLOAD EBOOKThis dissertation proposes both coding schemes and system design strategies for video wireless communications. Video coding can benefit greatly from the development of algorithms for optimal intra/inter mode switching within a rate-distortion framework. We propose an algorithm to optimally switch between intra-coding and inter-coding modes for a video coder that operates on a packet-switched network with fixed-length packets. This optimal mode selection algorithm is integrated with an efficient channel encoder. And the framework is further extended to operate on a time-varying tandem wiredline-wireless channel with feedback information from the receiver. We then discuss a cross-layer optimization scheme for the system design of a wireless video communications system. We present a video transmission scheme with adaptive bandwidth allocation over wired and wireless CDMA networks. We derive the statistics of the received signal, as well as a theoretical bound on the packet drop rate at the receiver. Based on these results, an algorithm for efficient bandwidth allocation among source coding, channel coding and spreading is derived at the packet level, which incorporates the effects of both the changing channel characteristics and the source content. Another fundamental tradeoff in the cross-layer design of a communications system that we study is how to optimize the system when there is a delay constraint imposed by the application. The key elements in this tradeoff are the queuing delay in the source encoder output buffer, the delay caused by the interleaver, and the delay caused by channel decoding.
Bandwidth and Rate Allocation Tradeoffs of Source
Author: Suayb S. Arslan
Publisher:
Published: 2012
Total Pages: 159
ISBN-13: 9781267259677
DOWNLOAD EBOOKA conventional approach to the design of wireless multimedia communications is the layered approach, in which the network layers function independent of each other. This kind of layered approach is inspired partly by Shannon's separation theorem in which the optimization of each block is equivalent to optimization of the overall source-channel coding operation. However, the separation theorem is valid only in a point-to-point communication scenario in the case of asymptotically long block lengths of data and assumes huge amounts of processing power and delay. Therefore, current practical communication systems strive to jointly design building blocks of a multimedia system for better performance. The focus of this dissertation is therefore to present various joint designs for different channel models and systems, although limited by physical constraints such as bandwidth, power and complexity. First, a robust coded scheme for progressive multimedia transmission is considered for an additive white Gaussian noise channel, a Rayleigh fading channel, and a frequency selective channel using in combination different unequal protection methods. We investigate the judicious use of the limited bandwidth through the combination and optimization of a progressive source coder, a rate compatible punctured convolutional code and a hierarchical modulation. Next, we investigate a novel packet formatting scheme for progressive sources using interleavers and various channel codes. The source coder is combined with a concatenated block coding mechanism to produce a robust transmission system for embedded bit streams. The objective is to create embedded codewords such that, for a particular information block, the necessary protection is obtained via multiple channel codings, contrary to the conventional methods which use a single code rate per information block. We show that near capacity performance can be achieved using the proposed scheme in conjunction with low density parity check codes in a binary symmetric channel scenario. We initially focus on coding strategies for multimedia where the channel state information is missing. A generalized Digital Fountain (DF) code is proposed to provide efficient universal forward error correction solution for lossy packet networks with increased unequal error protection and unequal recovery time properties. We propose a progressive source transmission system using this generalized code design. We apply the generalized DF code to a progressive source and show that it has better unequal protection and recovery time properties than other published results.
Code Division Multiple Access (CDMA)
Author: R. Michael Buehrer
Publisher: Morgan & Claypool Publishers
Published: 2006
Total Pages: 192
ISBN-13: 1598290401
DOWNLOAD EBOOKThis book covers the basic aspects of Code Division Multiple Access or CDMA. It begins with an introduction to the basic ideas behind fixed and random access systems in order to demonstrate the difference between CDMA and the more widely understood TDMA, FDMA or CSMA. Secondly, a review of basic spread spectrum techniques are presented which are used in CDMA systems including direct sequence, frequency-hopping and time-hopping approaches. The basic concept of CDMA is presented, followed by the four basic principles of CDMA systems that impact their performance: interference averaging, universal frequency reuse, soft handoff, and statistical multiplexing. The focus of the discussion will then shift to applications. The most common application of CDMA currently is cellular systems. A detailed discussion on cellular voice systems based on CDMA, specifically IS-95, is presented. The capacity of such systems will be examined as well as performance enhancement techniques such as coding and spatial filtering. Also discussed are Third Generation CDMA cellular systems and how they differ from Second Generation systems. A second application of CDMA that is covered is spread spectrum packet radio networks. Finally, there is an examination of multi-user detection and interference cancellation and how such techniques impact CDMA networks. This book should be of interest and value to engineers, advanced students, and researchers in communications.
OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting
Author: Lajos L. Hanzo
Publisher: Wiley-IEEE Press
Published: 2005-01-28
Total Pages: 1014
ISBN-13: 0470861800
DOWNLOAD EBOOKOrthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels at different frequencies. CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimising the use of available bandwidth. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. Multi-Carrier (MC) CDMA is a combined technique of Direct Sequence (DS) CDMA (Code Division Multiple Access) and OFDM techniques. It applies spreading sequences in the frequency domain. Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality. This technical in-depth book is unique in its detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into three main parts: Part I provides a detailed exposure of OFDM designed for employment in various applications Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink Portrays the entire body of knowledge currently available on OFDM Provides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMA Considers the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examples Converts the lessons of Shannon’s information theory into design principles applicable to practical wireless systems Combines the benefits of a textbook with a research monograph where the depth of discussions progressively increase throughout the book This all-encompassing self-contained treatment will appeal to researchers, postgraduate students and academics, practising research and development engineers working for wireless communications and computer networking companies and senior undergraduate students and technical managers.
