10 research outputs found

    Performance analysis of bandwidth efficient coherent modulation schemes with L-fold MRC and SC in Nakagami-m fading channels

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    This paper presents the average symbol error rates (SERs) of the 16-ary phase shift keying (16PSK), 16-ary amplitude phase shift keying (16APSK) and 16-ary quadrature amplitude modulation (16QAM) with L-fold maximal ratio combining (MRC) and selection combining (SC) space diversity receptions over Nakagami-m fading channels. Numerical results manifested error performance improvement when L-fold MRC and SC diversity receptions were employed. Error performance improvement attributed to an L=2 MRC diversity reception is comparable with that attributed to an L=4 SC diversity reception for the above three 16-ary modulation systems in a Nakagami-m fading channel with m of 5.published_or_final_versio

    Effect of negative spatial/temporal correlation on the performance of maximal ratio combining in a WCDMA cellular system

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    Please read the abstract in the section 00front of this documentDissertation (M Eng (Electronic Engineering))--University of Pretoria, 2005.Electrical, Electronic and Computer Engineeringunrestricte

    ЛИНЕЙНОЕ СУММИРОВАНИЕ СИГНАЛОВ РАВНОЙ МОЩНОСТИ, ПЕРЕДАВАЕМЫХ ПОСРЕДСТВОМ ОБОБЩЕННОГО КАНАЛА СВЯЗИ С ЗАМИРАНИЯМИ

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    We suggest the alternative approach based on definition of the moment generating function for the average signal-to-noise ratio (SNR) at the receiver output with the purpose to analyze performance of systems with equal gain combining over Nakagami-n (Rice) and Nakagami-q (Hoyt) fading channels under consideration of land, mobile and satellite telecommunication systems. We derive the exact closed-form mathematical expressions for average symbol error probability and outage probability using the Pade rational approximation to moment generating function of the SNR at the output of the combiner. We investigate the following important receiver performance such as the average SNR at the receiver output, fading, spectral effectiveness at weak input signals. Additionally, we study the rational Pade approximation of the moment generating function applying to the average SNR at the receiver output and evaluate bit error rate and the outage probability. Additionally, we investigate a possibility of modeling a Hoyt fading channel based on presentation Nakagami-m statistical model for evaluation of error performance under the use of equal gain combining technique. Учитывая важность статистических моделей, используемых при описании канала связи с замираниями, подчиняющимися таким законам распределения, как Накагами-n (распределение Райса) и Накагами-q (рас- пределение Хойта), при рассмотрении наземных, мобильных и спутниковых телекоммуникационных систем, мы представляем альтернативный подход, основанный на моментных функциях, для анализа характеристик приемных устройств с линейным суммированием сигналов равной мощности, передаваемых посредством каналов связи с замираниями, которые являются независимыми, но необязательно идентично распределенными в соответствии с законами Райса и Хойта. Получены точные математические выражения для моментных функций отношения сигнал/помеха на выходе сумматора приемного устройства. Исследуются важные критерии характеристик приемнго устройства, такие как среднее отношение сигнал/помеха на выходе приемного устройства, степень замираний, спектральная эффективность в режиме сигналов малой мощности. Кроме того, используя рациональную аппроксимацию Паде, то есть наилучшую рациональную аппроксимацию степенного ряда, применительно к производящей функции моментов отношения сигнал/помеха на выходе приемного устройства, оцениваются средняя вероятность ошибок на символ и вероятность нарушения связи. Мы также исследуем соответствие моделирования замираний в канале связи, описываемых распределением Хойта, с помощью выбранной должным образом модели распределения Накагами-m при условии, что рассматривается помехозащищенность, или коэффициент ошибок приемного устройства при линейном суммировании сигналов равной мощности.

    Design and analysis of wireless diversity system

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    Ph.DDOCTOR OF PHILOSOPH

    Razvoj metoda i algoritama za procenu performansi komunikacionih sistema primenom aproksimacija specijalnih funkcija

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    The intensive development of wireless communication systems has been accompanied by the need to develop methods and algorithms for implementing appropriate approximations of special functions in order to efficiently estimate the corresponding performance of these services through their application. In order to evaluate the behavior of digital communications systems, it is necessary to estimate standard performance measures for the observed wireless communications systems, various modulation types application, detection types, as well as channel models, and observe relations between performance and key values of system parameters. The analysis of the average bit error rate at reception for the applied modulation format is one of the tools for assessing service performance, that describes the nature of the wireless communication system in the best manner. In order to analytically evaluate the average bit error rate for the applied modulation format, it is necessary to perform the most accurate implementation of the approximation of special functions erfc(x), erf (x), Marcum Q, in the widest input range values. The dissertation will present composite methods of the special functions’ approximations. In addition to the simplicity of realization in approximating the observed functions, the aspect of robustness of approximations absolute and relative error values in a wide range of input parameters values will be considered. The advantages of the proposed solutions will be highlighted by direct comparison with the absolute and relative errors obtained by using the known special functions’ approximations from the literature. Furthermore, when transferring information through fading communication channels, for cases of application of proposed special functions’ approximations, it will be proved that system performance can be determined more easily by applying solutions proposed in the dissertation. In this way, it would be easier to determine the probability of the error of communication systems due to different types of fading existance in the channel. By comparing predicted values of the average bit error rate at reception, when transmitting signals through various communication channels medias, for cases of application of existing, previously proposed special functions’ approximations, with the average bit error rate at reception obtained by calculation based on the proposed approximation solutions, it will be shown that communication performances can be calculated more precisely. Proposed approximations could also be used in the source coding of the signal and could simplify design and realization of the quantizers

    Some fundamental issues in receiver design and performance analysis for wireless communication

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    Ph.DDOCTOR OF PHILOSOPH

    Uticaj nesavršene ekstrakcije referentnog nosioca na performanse diverziti prijemnika digitalno fazno modulisanih signala u kanalu sa fedingom

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    The results of the research, presented in this dissertation, refer to the analysis of imperfect reference signal recovery influence on performance of digital systems with BPSK and QPSK modulation and diversity at the reception applied. In order to make the content easy for understanding, the theoretical basics, necessary for calculations performed in the following chapters, has been presented at the beginning. In the analysis of the imperfect reference signalrecovery influence on the performance of single channel systems for BPSK and QPSK signal detection two cases have been considered. The analysis has been performed for Hoyt and composite Kg fading channel. ..

    Low complexity MIMO detection algorithms and implementations

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    University of Minnesota Ph.D. dissertation. December 2014. Major: Electrical Engineering. Advisor: Gerald E. Sobelman. 1 computer file (PDF); ix, 111 pages.MIMO techniques use multiple antennas at both the transmitter and receiver sides to achieve diversity gain, multiplexing gain, or both. One of the key challenges in exploiting the potential of MIMO systems is to design high-throughput, low-complexity detection algorithms while achieving near-optimal performance. In this thesis, we design and optimize algorithms for MIMO detection and investigate the associated performance and FPGA implementation aspects.First, we study and optimize a detection algorithm developed by Shabany and Gulak for a K-Best based high throughput and low energy hard output MIMO detection and expand it to the complex domain. The new method uses simple lookup tables, and it is fully scalable for a wide range of K-values and constellation sizes. This technique reduces the computational complexity, without sacrificing performance and the complexity scales only sub-linearly with the constellation size. Second, we apply the bidirectional technique to trellis search and propose a high performance soft output bidirectional path preserving trellis search (PPTS) detector for MIMO systems. The comparative error analysis between single direction and bidirectional PPTS detectors is given. We demonstrate that the bidirectional PPTS detector can minimize the detection error. Next, we design a novel bidirectional processing algorithm for soft-output MIMO systems. It combines features from several types of fixed complexity tree search procedures. The proposed approach achieves a higher performance than previously proposed algorithms and has a comparable computational cost. Moreover, its parallel nature and fixed throughput characteristics make it attractive for very large scale integration (VLSI) implementation.Following that, we present a novel low-complexity hard output MIMO detection algorithm for LTE and WiFi applications. We provide a well-defined tradeoff between computational complexity and performance. The proposed algorithm uses a much smaller number of Euclidean distance (ED) calculations while attaining only a 0.5dB loss compared to maximum likelihood detection (MLD). A 3x3 MIMO system with a 16QAM detector architecture is designed, and the latency and hardware costs are estimated.Finally, we present a stochastic computing implementation of trigonometric and hyperbolic functions which can be used for QR decomposition and other wireless communications and signal processing applications

    Analiza i načini poboljšanja performansi bežičnih optičkih telekomunikacionih sistema u uslovima atmosferske turbulencije

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    Since contemporary radio-frequency (RF) communication systems are characterized by overcrowded and licensed spectrum, limited bandwidth and relatively low transmission data rates, the use of these technologies does not provide a series of new demands that future generations of telecommunications systems have to realize. Although optical fiber systems allow more bandwidth and higher transmission rates, they are characterized by complicated and expensive implementation. As one possible solution for the "last mile" problem, Free Space Optics (FSO) technology has gained importance since it provides simultaneously the optical fibre systems data rates and the flexibility of wireless communications. The optical signal at the reception is converted into an electrical one by photodiode after transmission via the atmospheric channel. Commercial FSO systems generally use intensity modulation (IM) with OOK scheme at the transmitting part of the system, while direct detection (DD) is performed at the reception. The FSO system employing IM/DD with OOK scheme and PIN photodiode at the receiver is analyzed in the thesis. The outage probability and error rate expressions are presented, which are used to examine the effect of atmospheric turbulence and pointing errors. The FSO systems with subcarrier intensity modulation (SIM) employing various modulations in electrical domain (phase shift keying (PSK), differential phase shift keying (DPSK) and quadrature amplitude modulation (QAM)) are analyzed in the continuation of the thesis. The error rate expressions are derived. The SIM-PSK and SIM- DPSK FSO system analysis is performed considering more general case when the hardware imperfections of the receiver electrical part are taken into account. The ergodic and outage capacity analysis is also presented, taking into consideration the probability of the optical signal blockage due to random obstacles. Based on the derived results, the FSO link optimization is done in order to achieve better system performance. Furthermore, the analysis of FSO systems with avalanche (APD) photodiode at the reception is presented. The bit error rate expressions for the FSO systems employing IM/DD with OOK scheme, SIM-PSK and SIM-BDPSK are derived. Based on the presented results, the APD gain optimization is performed in order to achieve minimal values of the error rate. The use of relaying technology is investigated as a method to improve system performance. The mixed RF/FSO systems with fixed and variable AF (Amplify and Forward) relays are analyzed. Beside the noise-limited scenario, the more general case, when the relay is affected by noise and interference, is also considered. The outage probability and error rate expressions are presented, which are utilized to determine the effects of the RF and FSO link conditions on system performance. The determination of a variable gain is performed based on instantaneous channel state information (CSI), which is happened to be outdated in practical scenario. Therefore, the analytical expressions for the outage probability and error rate are derived, considering the RF/FSO system with variable AF relay based on outdated CSI. Further improvement of the system performance is achieved by using diversity combining techniques in the RF domain by multiple parallel relaying. The analytical expressions for the system performance are derived for the RF/FSO system with partial relay selection based on outdated CSI. The RF/FSO system with fixed AF relays is considered, as well as the RF/FSO system with variable AF relays when the amplification gain is determined by the same outdated CSI used for relay selection. The effect of RF channel state is examined, as well as the influence of atmospheric conditions, pointing errors and FSO aperture design on the system performance. A developed simulation model is utilized to confirm the numerical results obtained by the analytical expressions presented in the dissertation thesis
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