27 research outputs found

    Generalised differential golden code modulation: error performance analysis and bandwidth efficiency.

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    Doctoral Degree. University of KwaZulu-Natal, Durban.The receiver of a conventional differential modulation scheme performs detection without knowledge of the channel state information (CSI). This results in a 3dB performance loss compared to coherent modulation. In order to enhance this error performance, generalised differential modulation is utilised. This thesis firstly presents a generalised differential modulation scheme for the Golden code (GDMGC) based on quadrature amplitude modulation (QAM). The average bit error probability (ABEP) for the GDM-GC scheme is derived and simulations on bit error rates (BER) are carried out in order to verify the derived theoretical framework, where it is shown that BER results lie well within the derived bounds. In addition, compared to coherent GC with maximum likelihood (ML) detection both 16QAM and 64QAM GDM-GC result in approximately 0.4 dB performance loss for a frame length of L = 400. However, the computational complexity of the GDM-GC scheme is reduced significantly in comparison to the coherent ML detector. Secondly, this thesis extends the generalised differential modulation scheme to multiple input symbol Golden code and proposes a multiple input symbol generalised differential Golden code (MIS-GD-GC) scheme. This scheme not only boosts error performance in comparison to conventional differential multiple input symbol Golden code (MIS-GC), but it lso produces multiple diversity order compared to the conventional Golden code. The simulations on BER for the MIS-GD-GC scheme not only compare very well to the derived theoretical bounds but also show that the BER draws closer to that of coherent MIS-GC when the frame length is increased. For instance, at a frame length of L = 400 , the error performance gap between MIS-GD-GC and its coherent counterpart is only 0.4 dB. Finally, driven by the need to develop a scheme that can allow for transmission of more data to help meet the demands of modern wireless communication systems, this thesis seeks to improve the bandwidth efficiency of the GDM-GC scheme. An enhanced bandwidth efficient generalised differential Golden code (EBE-GD-GC) scheme based on QAM is proposed and its ABEP derived. The simulated BER results for the EBE-GD-GC scheme are shown to lie well within the derived ABEP and achieve almost the same error performance as GDM-GC at high signal-to-noise ratio (SNR) regions but with extra bit(s) of information sent in each transmitted space-time block code (STBC) compared to the typical GDM-GC scheme. In addition, compared to the conventional generalised differential Golden code, both 16QAM and 64QAM EBE-GD-GC result in < 1dB performance loss from a BER of 1 × 10−5

    Recent Advances in Wireless Communications and Networks

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    This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

    Povećanje informacionog kapaciteta i pouzdanosti u bežičnim optičkim komunikacijama primenom algoritama adaptivnog prenosa

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    This dissertation considers adaptive transmission algorithms and their influence towards increasing information capacity and system reliability. Theses algorithms are applied to optical wireless communications, as well as to radio-frequency system with diversity receiver. System of adaptive transmission is described in detail, and different algorithms of adaptation are applied: ORA, OPRA, CIFR, and TIFR. Derived probability density function combines influence of atmospheric turbulence, atmospheric losses and positioning errors that consist of laser pointing precision and jitter. FSO system without adaptation is also considered. For this case, bit-error rate and outage probability are determined when signal is exposed to different strengths of atmospheric turbulence, when there is atmospheric attenuation and positioning errors due to both main causes, when IM/DD and heterodyne detection are used. Power penalty is also determined for such system. Bit-error rate is also determined for the case when SIM is used in combination with binary modulation and quadrature amplitude modulation. Capacity analysis is given for the use of ORA, OPRA, CIFR and TIFR adaptive transmission algorithms, and for IM/DD and heterodyne detection cases. Algorithms used for transmitter power adaptation are additionally analyzed and improved with an aim to obtain realistic and functional systems. Based on analytical expression, simulation model is developed for adaptive transmission systems, which is used to validate numerical results. Approximate expressions are also given for used adaptive algorithms. Finally, adaptive transmission is considered also for a class of wireless RF systems. Fading model used is based on α-κ-μ distribution. Outage probability and amount of fading are given as representative performance measures. Besides adaptive transmission algorithms used in FSO systems, analysis of space diversity reception is also presented for the general case of using L antennas

    Uncoded space-time labeling diversity with three transmit antennas: symbol mapping designs and error performance analysis.

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    Doctoral Degrees. University of KwaZulu-Natal, Durban.Abstract available in PDF.Publications on page iii

    Error performance analysis of cross QAM and space-time labeling diversity for cross QAM.

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    Doctoral Degrees. University of KwaZulu-Natal, Durban.Abstract available in the PD

    Phase distribution and correlated statistics in wireless environments : theory and experimental validation

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    Orientador: Michel Daoud YacoubTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Esta tese propõe, investiga e valida estatísticas de primeira e segunda ordens para canais com desvanecimento em ambientes sem fio. A caracterização estatística contempla tanto a obtenção de modelos teóricos quanto investigações práticas através de campanhas de medições de campo. Os modelos probabilísticos analisados aqui, chamados ?-µ e a-µ, foram recentemente propostos com o intuito de prover uma análise mais realista do canal rádio-móvel. Por apresentarem um grau de liberdade a mais do que as distribuições tradicionais, uma maior flexibilidade é alcançada. Mais especificamente, as contribuições desta tese são: a obtenção da distribuição conjunta da envoltória e da fase para canais em desvanecimento ?-µ e a validação do seu modelo de fase. Além disso, e sem menos importância, a distribuição a-µ é validada amplamente. Suas funções de distribuição cumulativa, correlação cruzada, autocorrelação e espectro de potência da envoltória, estas últimas encontradas em formulações fechadas, bem como a taxa de cruzamento de nível, são investigadas na prática através do uso de um sistema de medição de campo construído especialmente para este fim. Comparações entre o modelo de canal a-µ e os modelos tradicionais da literatura são realizadas e um excelente ajuste entre os dados teóricos e experimentais é encontradoAbstract: This thesis proposes, investigates and validates first and second order statistics of fading channels in wireless environments. The statistical characterization includes both theoretical models and practical investigations through field measurements. The investigated channel models, namely ?-µ and a-µ, have recently been proposed in order to provide a more realistic analysis of the propagated signal. Because these fading models have one more degree of freedom than the traditional distributions, a greater flexibility is achieved. More specifically, the contributions of this thesis are: the ?-µ phase-envelope joint distribution derivation and its phase model validation. Furthermore, the distribution a-µ is fully validated. Its cumulative distribution, cross-correlation, autocorrelation and power spectrum functions of the envelope, these latter obtained in closed-form expressions, and the level crossing rate, are investigated in practice by using a field measurement system, specifically built for this purpose. Comparisons between the a-µ channel model and the traditional distributions are performed and excellent fits between the theoretical and experimental data are foundDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

    Application of cognitive radio based sensor network in smart grids for efficient, holistic monitoring and control.

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    Doctoral Degree. University of KwaZulu-Natal, Durban.This thesis is directed towards the application of cognitive radio based sensor network (CRSN) in smart grid (SG) for efficient, holistic monitoring and control. The work involves enabling of sensor network and wireless communication devices for spectra utilization via the capability of Dynamic Spectrum Access (DSA) of a cognitive radio (CR) as well as end to end communication access technology for unified monitoring and control in smart grids. Smart Grid (SG) is a new power grid paradigm that can provide predictive information and recommendations to utilities, including their suppliers, and their customers on how best to manage power delivery and consumption. SG can greatly reduce air pollution from our surrounding by renewable power sources such as wind energy, solar plants and huge hydro stations. SG also reduces electricity blackouts and surges. Communication network is the foundation for modern SG. Implementing an improved communication solution will help in addressing the problems of the existing SG. Hence, this study proposed and implemented improved CRSN model which will help to ultimately evade the inherent problems of communication network in the SG such as: energy inefficiency, interference, spectrum inefficiencies, poor quality of service (QoS), latency and throughput. To overcome these problems, the existing approach which is more predominant is the use of wireless sensor network (WSNs) for communication needs in SG. However, WSNs have low battery power, low computational complexity, low bandwidth support, and high latency or delay due to multihop transmission in existing WSN topology. Consequently, solving these problems by addressing energy efficiency, bandwidth or throughput, and latency have not been fully realized due to the limitations in the WSN and the existing network topology. Therefore, existing approach has not fully addressed the communication needs in SG. SG can be fully realized by integrating communication network technologies infrastructures into the power grid. Cognitive Radio-based Sensor Network (CRSN) is considered a feasible solution to enhance various aspects of the electric power grid such as communication with end and remote devices in real-time manner for efficient monitoring and to realize maximum benefits of a smart grid system. CRSN in SG is aimed at addressing the problem of spectrum inefficiency and interference which wireless sensor network (WSN) could not. However, numerous challenges for CRSNs are due to the harsh environmental wireless condition in a smart grid system. As a result, latency, throughput and reliability become critical issues. To overcome these challenges, lots of approaches can be adopted ranging from integration of CRSNs into SGs; proper implementation design model for SG; reliable communication access devices for SG; key immunity requirements for communication infrastructure in SG; up to communication network protocol optimization and so on. To this end, this study utilized the National Institute of Standard (NIST) framework for SG interoperability in the design of unified communication network architecture including implementation model for guaranteed quality of service (QoS) of smart grid applications. This involves virtualized network in form of multi-homing comprising low power wide area network (LPWAN) devices such as LTE CAT1/LTE-M, and TV white space band device (TVBD). Simulation and analysis show that the performance of the developed modules architecture outperforms the legacy wireless systems in terms of latency, blocking probability, and throughput in SG harsh environmental condition. In addition, the problem of multi correlation fading channels due to multi antenna channels of the sensor nodes in CRSN based SG has been addressed by the performance analysis of a moment generating function (MGF) based M-QAM error probability over Nakagami-q dual correlated fading channels with maximum ratio combiner (MRC) receiver technique which includes derivation and novel algorithmic approach. The results of the MATLAB simulation are provided as a guide for sensor node deployment in order to avoid the problem of multi correlation in CRSN based SGs. SGs application requires reliable and efficient communication with low latency in timely manner as well as adequate topology of sensor nodes deployment for guaranteed QoS. Another important requirement is the need for an optimized protocol/algorithms for energy efficiency and cross layer spectrum aware made possible for opportunistic spectrum access in the CRSN nodes. Consequently, an optimized cross layer interaction of the physical and MAC layer protocols using various novel algorithms and techniques was developed. This includes a novel energy efficient distributed heterogeneous clustered spectrum aware (EDHC- SA) multichannel sensing signal model with novel algorithm called Equilateral triangulation algorithm for guaranteed network connectivity in CRSN based SG. The simulation results further obtained confirm that EDHC-SA CRSN model outperforms conventional ZigBee WSN in terms of bit error rate (BER), end-to-end delay (latency) and energy consumption. This no doubt validates the suitability of the developed model in SG

    A Novel Diversity Receiver Structure for Severe Fading and Frequency Offset Conditions

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    This paper presents a novel diversity receiver of MPSK signal in fading channel in the presence of the carrier frequency offset. As a part of this receiver, a new algorithm for the estimation of the combining coefficients (ECC algorithm) is introduced. Having in mind that the QPSK modulation is one of the most used modulation formats in many wireless communication standards (LTE, WiFi, WiMax), the performance of the proposed receiver is analyzed in more detail for the QPSK modulation. In the presence of Rayleigh fading, representing the most severe fading condition, this algorithm shows significantly better performance comparing to the same receiver structure that uses conventional constant modulus algorithm (CMA1 or CMA2). The proposed diversity receiver structure with ECC algorithm operates within a wide carrier frequency offset range with a very small variation of the performance. For this reason, it can be applied in 4G mobile communication systems

    Analysis and Simulation of MRC Diversity Reception in Correlated Composite Nakagami-Lognormal Fading Channels

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    The physical meaning of the composite Nakagami-lognormal fading model is not well understood by many researchers using the model. The signal power transfer and transform at the interface between the global lognormal shadowing sub-channels and the local Nakagami multipath sub-channels in the presence of correlation between these diversity sub-channels is rather complex. This is the main reason why a thorough analysis or a simulation model is absent to date for the case of correlated composite Nakagami-lognormal diversity channels. This paper presents a novel technique for the estimation of the probability density function (PDF) of the signal-to-noise (SNR) at the output of a maximum ratio combining (MRC) receiver operating in correlated composite diversity fading channels. The PDF is estimated using the recently proposed two-point lossless moment generating function (MGF) matching technique and a closed-form expression for the bit-error rate (BER) for QPSK signal is consequently presented using the Gauss-Hermite polynomial approximation. The paper also presents the complex Monte-Carlo simulation model for the MRC reception and BER counting in correlated composite Nakagami-lognormal fading channels
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