Dissertations / Theses on the topic 'Intersymbol Interference'
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Neeser, Fredy D. "Communication theory and coding for channels with intersymbol interference /." Zürich, 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10314.
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Long, Eric M. "Decision-aided sequential sequence estimation for intersymbol interference channels." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/15019.
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Lyman, Raphael J., and Qingsong Wang. "A DECOUPLED APPROACH TO COMPENSATION FOR NONLINEARITY AND INTERSYMBOL INTERFERENCE." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605571.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaTo achieve good efficiency in a space-based radio transmitter, its final amplifier must be operated near the saturation point, in its nonlinear region. Because of strict band limitations, this nonlinear operation is combined with the problem of intersymbol interference. Normally, these problems are addressed using a combination of equalization and power back-off, resulting in reduced power efficiency. Many proposed receiver-based methods, such as Volterra equalization, attempt to compensate for the nonlinearity and ISI in a single block before the detector, allowing higher efficiency operation, but introducing a great deal of complexity. We propose a receiver-based method in which the two effects are dealt with in separate blocks, an equalizer and a linearizer, resulting in considerable simplification. We go further and place the detector before the linearizer, achieving improved performance by eliminating the errors introduced by the linearizer. Simulation results compare favorably with the performance of a linear AWGN channel.
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Cheng, Taikun. "Equalization and coding for the two-dimensional intersymbol interference channel." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/t_cheng_113007.pdf.
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Sheen, Wern-Ho. "Performance analysis of sequence estimation techniques for intersymbol interference channels." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/13089.
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Li, Peter C. "Direct detection optical systems : intersymbol interference and electrical filter designs." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11848.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 182-184).
Peter Cheng-Lung Li.
Ph.D.
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Paterson, Gavin John. "Adaptive nonlinear equaliser structures for intersymbol and co-channel interference suppression." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436832.
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Gupta, Sunil 1966. "Intersymbol interference characterization and equalization for high density optical data storage." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278217.
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In optical data storage, intersymbol interference (ISI) is one of the limiting factors for high storage density. To reduce ISI, we need to understand its characteristics and use appropriate signal processing techniques. In this thesis, we characterize ISI for various data patterns and compare Signal to Noise Ratio (SNR) with and without ISI equalization. To characterize ISI, we sample the readback waveforms and use a computer program for data processing. To compare SNR with and without equalization, we record a pseudo random sequence and compare the detected marks with original marks. We also compute SNR using the additive interleaving detection (AID) technique without ISI equalization. From our studies, ISI is found to be more significant as mark widths become smaller. We also found that SNR can be increased by 3-9 db with equalization. More interestingly, we found that AID gives good SNR even without ISI equalization. This indicates the simplicity of using AID for higher storage density.
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Balaji, Bhashyam. "An adaptive, multirate method for eliminating intersymbol interference in non-ideal channel." Thesis, University of Ottawa (Canada), 2000. http://hdl.handle.net/10393/8604.
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In this thesis, an adaptive method for eliminating intersymbol interference (ISI) using multirate techniques, is presented. This is inspired by the work of Chevillat and Ungerboeck on the design of finite impulse response (FIR) 'multirate zero ISI filters' for data transmission over a band limited ideal channel. Their analysis is extended to the case when the channel is non-ideal. It is shown that there are infinitely many multi rate filters (dependent of the upsampling/downsampling factor Mc) that can eliminate ISI. As an illustration, two simple adaptive algorithms for computing the zero ISI filters are presented and applied to discrete multitone transmission (DMT) and discrete wavelet multitone transmission (DWMT) systems. It is found that even the minimum length, multirate zero ISI filters compare favourably (in terms of reduced complexity and performance) with other techniques, such as the cyclic prefix method.
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Abou, Faycal Ibrahim C. (Ibrahim Chafik). "An information theoretic study of reduced-complexity receivers for intersymbol interference channels." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8922.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 105-108).
The complexity of the optimal receiver for communications over a discrete-time additive Gaussian intersymbol interference channel typically grows exponentially with the duration of the channel impulse response. Consequently, practical sub-optimal receivers are often designed as though the channel impulse response were shorter than it is. While previous studies on the performance of such receivers have mainly focused on bit error rates in uncoded systems, this thesis takes a different approach to the problem. We adopt an information theoretic approach and study the rates that are achievable in the Shannon sense over the true channel with the given, possibly sub-optimal, decoding rule. One can establish that, under such mismatch conditions, the achievable rates are bounded in the Signal-to-Noise Ratio necessitating the use of a linear equalizer at the front end of the decoder. We derive the achievable rates for these schemes and optimize under complexity constraints the design of the equalizer and the receiver. Overall, two ensemble of codes are considered: the Independent Identically Distributed Gaussian ensemble and the "spherical" ensemble, where codewords are uniformly distributed over a sphere.
by Ibrahim C. Abou Faycal.
Ph.D.
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Peng, Yanjie. "Design and Implementation of Belief Propagation Symbol Detectors for Wireless Intersymbol Interference Channels." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-dissertations/410.
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"In modern wireless communication systems, intersymbol interference (ISI) introduced by frequency selective fading is one of the major impairments to reliable data communication. In ISI channels, the receiver observes the superposition of multiple delayed reflections of the transmitted signal, which will result errors in the decision device. As the data rate increases, the effect of ISI becomes severe. To combat ISI, equalization is usually required for symbol detectors. The optimal maximum-likelihood sequence estimation (MLSE) based on the Viterbi algorithm (VA) may be used to estimate the transmitted sequence in the presence of the ISI. However, the computational complexity of the MLSE increases exponentially with the length of the channel impulse response (CIR). Even in channels which do not exhibit significant time dispersion, the length of the CIR will effectively increase as the sampling rate goes higher. Thus the optimal MLSE is impractical to implement in the majority of practical wireless applications. This dissertation is devoted to exploring practically implementable symbol detectors with near-optimal performance in wireless ISI channels. Particularly, we focus on the design and implementation of an iterative detector based on the belief propagation (BP) algorithm. The advantage of the BP detector is that its complexity is solely dependent on the number of nonzero coefficients in the CIR, instead of the length of the CIR. We also extend the work of BP detector design for various wireless applications. Firstly, we present a partial response BP (PRBP) symbol detector with near-optimal performance for channels which have long spanning durations but sparse multipath structure. We implement the architecture by cascading an adaptive linear equalizer (LE) with a BP detector. The channel is first partially equalized by the LE to a target impulse response (TIR) with only a few nonzero coefficients remaining. The residual ISI is then canceled by a more sophisticated BP detector. With the cascaded LE-BP structure, the symbol detector is capable to achieve a near-optimal error rate performance with acceptable implementation complexity. Moreover, we present a pipeline high-throughput implementation of the detector for channel length 30 with quadrature phase-shift keying (QPSK) modulation. The detector can achieve a maximum throughput of 206 Mb/s with an estimated core area of 3.162 mm^{2} using 90-nm technology node. At a target frequency of 515 MHz, the dynamic power is about 1.096 W. Secondly, we investigate the performance of aforementioned PRBP detector under a more generic 3G channel rather than the sparse channel. Another suboptimal partial response maximum-likelihood (PRML) detector is considered for comparison. Similar to the PRBP detector, the PRML detector also employs a hybrid two-stage scheme, in order to allow a tradeoff between performance and complexity. In simulations, we consider a slow fading environment and use the ITU-R 3G channel models. From the numerical results, it is shown that in frequency-selective fading wireless channels, the PRBP detector provides superior performance over both the traditional minimum mean squared error linear equalizer (MMSE-LE) and the PRML detector. Due to the effect of colored noise, the PRML detector in fading wireless channels is not as effective as it is in magnetic recording applications. Thirdly, we extend our work to accommodate the application of Advanced Television Systems Committee (ATSC) digital television (DTV) systems. In order to reduce error propagation caused by the traditional decision feedback equalizer (DFE) in DTV receiver, we present an adaptive decision feedback sparsening filter BP (DFSF-BP) detector, which is another form of PRBP detector. Different from the aforementioned LE-BP structure, in the DFSF-BP scheme, the BP detector is followed by a nonlinear filter called DFSF as the partial response equalizer. In the first stage, the DFSF employs a modified feedback filter which leaves the strongest post-cursor ISI taps uncorrected. As a result, a long ISI channel is equalized to a sparse channel having only a small number of nonzero taps. In the second stage, the BP detector is applied to mitigate the residual ISI. Since the channel is typically time-varying and suffers from Doppler fading, the DFSF is adapted using the least mean square (LMS) algorithm, such that the amplitude and the locations of the nonzero taps of the equalized sparse channel appear to be fixed. As such, the channel appears to be static during the second stage of equalization which consists of the BP detector. Simulation results demonstrate that the proposed scheme outperforms the traditional DFE in symbol error rate, under both static channels and dynamic ATSC channels. Finally, we study the symbol detector design for cooperative communications, which have attracted a lot of attention recently for its ability to exploit increased spatial diversity available at distributed antennas on other nodes. A system framework employing non-orthogonal amplify-and-forward half-duplex relays through ISI channels is developed. Based on the system model, we first design and implement an optimal maximum-likelihood detector based on the Viterbi algorithm. As the relay period increases, the effective CIR between the source and the destination becomes long and sparse, which makes the optimal detector impractical to implement. In order to achieve a balance between the computational complexity and performance, several sub-optimal detectors are proposed. We first present a multitrellis Viterbi algorithm (MVA) based detector which decomposes the original trellis into multiple parallel irregular sub-trellises by investigating the dependencies between the received symbols. Although MVA provides near-optimal performance, it is not straightforward to decompose the trellis for arbitrary ISI channels. Next, the decision feedback sequence estimation (DFSE) based detector and BP-based detector are proposed for cooperative ISI channels. Traditionally these two detectors are used with fixed, static channels. In our model, however, the effective channel is periodically time-varying, even when the component channels themselves are static. Consequently, we modify these two detector to account for cooperative ISI channels. Through simulations in frequency selective fading channels, we demonstrate the uncoded performance of the DFSE detector and the BP detector when compared to the optimal MLSE detector. In addition to quantifying the performance of these detectors, we also include an analysis of the implementation complexity as well as a discussion on complexity/performance tradeoffs."
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Chan, Albert M. (Albert Michael) 1975. "A class of batch-iterative methods for the equalization of intersymbol interference channels." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/8809.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 187-194).
A class of nonlinear receivers is proposed to equalize intersymbol interference (ISi) channels in a batch-iterative fashion. The iterated-decision or multipass equalizer uses symbol decisions made during the previous iteration to cancel out both precursor and postcursor ISi during the current iteration. With each successive pass of the equalizer, the probability of symbol error decreases. Eventually, after relatively few iterations, the symbol error rate converges. The structure of the equalizer makes it attractive to use in combination with channel coding, since equalization and coding become largely separable issues. The multipass equalizer is optimized according to a maximum signal-to-interference+noise ratio (SINR) criterion, and, unlike the decision-feedback equalizer, the multipass equalizer is optimized assuming that decisions used for ISi cancellation can be erroneous. Furthermore, even under such an assumption, the performance of the iterated-decision equalizer can still be readily evaluated in the severe-ISi case. With a complexity comparable to the linear equalizer and the decision-feedback equalizer, the multi pass equalizer is shown in theory and in simulations to perform significantly better than either equalizer when the ISi is severe. In particular, for the long channel impulse responses we consider, the iterated-decision equalizer requires 2.507 dB less transmit power at high SNR to achieve the same probability of error as the minimum mean-square error decision-feedback equalizer (MMSE-DFE). Even more remarkably, the iterated-decision equalizer performs at high SNR as if the severeISi channel has been transformed into an ideal bandlirnited additive white Gaussian noise channel (AWGN) with the same receiver SNR. An adaptive version of the multipass equalizer is also proposed, which does not require a priori knowledge of the channel characteristics. Simulations show that only a modest amount of training data is required for the performance of the adaptive equalizer to be comparable to its non-adaptive counterpart. The adaptive equalizer is easily modified into a fractionally spaced adaptive equalizer, which can compensate for a wider range of amplitude and phase distortion. The fractionally spaced equalizer is also generalized to the case of multichannel communication.
by Albert M. Chan.
S.M.
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Law, Eugene. "Effect of Group Delay Variations on Bit Error Probability." International Foundation for Telemetering, 1993. http://hdl.handle.net/10150/611879.
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International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, NevadaGroup delay variations are a potential problem in many communication systems. This paper is slanted towards the effects of group delay variations in analog magnetic recorder/reproducer systems but the results are applicable in general. Because it is difficult to get an arbitrary group delay profile at the output of a recorder/reproducer, a method of generating arbitrary group delays for bit error probability (BEP) testing was developed. A 32-bit pattern in which all five-bit sequences appear with equal probability was selected as the test signal. The amplitude and phase of the discrete Fourier components were calculated for both non-return-to-zero-level (NRZ-L) and biphase-level (BI -L) waveforms. Filtering and group delay variations were computer generated by varying the amplitude and phase of the Fourier components. The modified signals were then programmed into an arbitrary waveform generator. Noise was added and the composite signal was applied to a bit synchronizer and bit error detector. BEPs were measured for various noise levels and group delay profiles.
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Kanprachar, Surachet. "Modeling and Analysis of the Effects of Impairments in Fiber Optic Links." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35245.
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In digital communication systems, several types of impairments may be introduced
to the signal. These impairments result in degraded system performance; for example,
high bit-error-rate or power penalty. For optical communication systems, in this thesis,
these impairments are categorized into four types; that is, thermal noise, shot noise,
signal-dependent noise, and intersymbol interference (ISI). By using a Gaussian approximation,
effects of the first three impairments are analyzed. It is shown that signal-dependent noise
introduces an error floor to the system and the bit-error-rate is considerably degraded
if a nonzero-extinction ratio is applied to the system. It is shown that if the decision
threshold at the decision circuit is set improperly, more received power is required to
keep the bit-error-rate constant.
Three main components in the system (i.e., transmitter, optical fiber, and receiver)
are modeled as Butterworth filters. ISI from this model is determined by computer simulation.
A high ISI is from a small system bandwidth. It is shown that a minimum power penalty can be
achieved if the transmitter and receiver bandwidths are matched and fixed, and the ratio of
fiber bandwidth to bit rate is 0.85. Comparing ISI from this model to ISI from raised cosine-
rolloff filters, it is shown that at some particular bandwidths ISI from raised cosine-rolloff
filters is much lower that that from this model. However, if the transmitter and receiver
bandwidths are not matched and are not equal to these bandwidths, ISI from this model is lower
than ISI from raised cosine-rolloff filters.Master of Science
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See, Chong Meng Samson. "Space-time processing for wireless mobile communications." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/25284.
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Intersymbol interference (ISI) and co-channel interference (CCI) are two major obstacles to high speed data transmission in wireless cellular communications systems. Unlike thermal noise, their effects cannot be removed by increasing the signal power and are time-varying due to the relative motion between the transmitters and receivers. Space-time processing offers a signal processing framework to optimally integrate the spatial and temporal properties of the signal for maximal signal reception and at the same time, mitigate the ISI and CCI impairments. In this thesis, we focus on the development of this emerging technology to combat the undesirable effects of ISI and CCL We first develop a convenient mathematical model to parameterize the space-time multipath channel based on signal path power, directions and times of arrival. Starting from the continuous time-domain, we derive compact expressions of the vector space-time channel model that lead to the notion of block space-time manifold, Under certain identifiability conditions, the noiseless vector-channel outputs will lie on a subspace constructed from a set. of basis belonging to the block space-time manifold. This is an important observation as many high resolution array processing algorithms Can be applied directly to estimate the multi path channel parameters. Next we focus on the development of semi-blind channel identification and equalization algorithms for fast time-varying multi path channels. Specifically. we develop space-time processing algorithms for wireless TDMA networks that use short burst data formats with extremely short training data. sequences. Due to the latter, the estimated channel parameters are extremely unreliable for equalization with conventional adaptive methods. We approach the channel acquisition, tracking and equalization problems jointly, and exploit the richness of the inherent structural relationship between the channel parameters and the data sequence by repeated use of available data through a forward- backward optimization procedure. This enables the fuller exploitation of the available data. Our simulation studies show that significant performance gains are achieved over conventional methods. In the final part of this thesis, we address the problem identifying and equalizing multi path communication channels in the presence of strong CCl. By considering CCI as stochasic processes, we find that temporal diversity can be gained by observing the channel outputs from a tapped delay line. Together with the assertion that the finite alphabet property of the information sequences can offer additional information about the channel parameters and the noise-plus-covariance matrix, we develop a spatial temporal algorithm, iterative reweighting alternating minimization, to estimate the channel parameters and information sequence in a weighted least squares framework. The proposed algorithm is robust as it does not require knowledge of the number of CCI nor their structural information. Simulation studies demonstrate its efficacy over many reported methods.
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Zhu, Ying. "Signal detection on two-dimensional intersymbol interference channels correlated sources and reduced complexity algorithms /." [Pullman, Wash.] : Washington State University, 2008. http://www.dissertations.wsu.edu/Dissertations/Fall2008/y_zhu_081408.pdf.
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Thesis (Ph. D.)--Washington State University, December 2008.Title from PDF title page (viewed on Sept. 23, 2008) "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 83-90).
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Chen, Brian. "Efficient communication over additive white Gaussian noise and intersymbol interference channels using chaotic sequences." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40151.
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Vrahas, Antonios Costa 1967. "Bit error rate computations for both noise and intersymbol interference considerations in optical communications." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278277.
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Bit error rate computation for optical communication systems incorporating equalizers and under both noise and intersymbol interference (ISI) is discussed. An accurate method based on a saddlepoint approximation is used for the computation. Previous work based on saddlepoint approximation has considered only the use of basic integration-and-dump detection. When ISI is strong, this simple detection method is unsatisfactory. Instead, a raised-cosine filtering is often used to achieve minimal ISI. This thesis considers both integration-and-dump and raised-cosine equalizers. The use of equalizers other than integration-and-dump complicates the computation because of the complexity of the moment generating function involved. Two different input pulses are considered to study the effect of ISI. Results show that when intersymbol interference is strong, the use of raised-cosine equalizers can reduce intersymbol interference and improve the performance of the system significantly.
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Ma, Hannan. "Iterative row-column algorithms for two-dimensional intersymbol interference channel equalization complexity reduction and performance enhancement /." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Summer2010/h_ma_062110.pdf.
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Thesis (M.S. in electrical engineering)--Washington State University, August 2010.Title from PDF title page (viewed on July 28, 2010). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 51).
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He, Shabai. "Simulation of wireless communications in underground tunnels." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-11409.
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The new released 4G standard wireless communication reminds us that higher transmission data rate and more reliable service are required urgently. However, to fulfill the demand can face problems in a complex environment like mines. In this thesis, characterization of underground tunnel mines with the idea of combating intersymbol interference effect is presented. Ray tracing simulation method is applied to characterize channel impulse response in different positions of an underground tunnel. From this channel impulse response, we can obtain how intersymbol interference affects different wireless systems. Intersymbol interference occurs due to multipath propagation of time dispersion channel. Adaptive Equalization is the most effective way to compensate intersymbol interference. Adaptive filter adapts filter coefficients to compensate the channel so that the combination of the filter and channel offers a flat frequency response and linear phase. The bit error rate performance without using adaptive equalization is compared with using equalizer. Moreover, adaptive equalization approaches using RLS and LMS algorithms are compared with each other. The tradeoff between convergence rate, computation cost instability and ensemble averaged minimum squared errors are analyzed to determine how to select the optimum adaptive equalizer.
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Zaizouni, Mostafa. "Récepteurs à détection différentielle avec égalisation non cohérente pour le système de radiocommunication DECT." Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/f0ae3ced-fe2f-4018-9322-a56120a5869c.
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La mise en œuvre de nouvelles applications demande un développement continu des normes standardisées de la seconde génération de systèmes de radiocommunication avec les mobiles. En particulier l'utilisation du système DECT (Digital European Cordless Telecommunications), conçu au départ pour les communications à l'intérieur des bâtiments, dans certaines nouvelles applications comme les points d'accès multiples. Des études récentes ont révélé une forte dégradation des performances du récepteur standard, basé sur une détection différentielle ou bien à limiteur-discriminateur, dans les milieux de propagation associés à ces applications. Ces derniers sont caractérisés principalement par des dispersions moyennes des retards dont les valeurs maximales sont typiquement comprises entre 200 et 250 ans. En vue de garantir une qualité de transmission acceptable, nous étudions d'abord l'impact des diverses distorsions introduites par le canal radio mobile sur la détection différentielle. A cet effet nous développons les modèles du canal radio mobile et en particulier ceux associés aux nouvelles applications du système DECT. Nous évaluons ensuite les performances de la détection différentielle dans ces canaux. Les résultats de simulation montrent que la dégradation de taux d'erreur par bit est liée principalement aux interférences inter-symboles dues à la dispersion moyenne des retards de ces derniers. Pour réduire l'impact des interférences inter-symboles, nous proposons une nouvelle structure de récepteur basée sur la détection différentielle suivie d'une égalisation à retour de décision et d'un seuil de décision optimal. Cette structure à l'avantage d'être très peu sensible d'une part aux fluctuations de l'indice de modulation, et, d'autre part, aux dérives de la fréquence de l'oscillateur local. Nos résultats montrent que les performances obtenues avec ce nouveau récepteur dans les divers milieux de propagation sont très satisfaisantes et similaires à celles obtenues avec une structure plus complexe (détecteur différentiel suivi d'un égaliseur de Viterbi). La structure proposée permet ainsi d'obtenir un bon compromis entre performances et complexité de mise en œuvreOwing to the emergence of a demand for Cordless outdoor and large indoor services, there have been various attempts to characterise the performances of the standard Digital European Cordless Telephone (DECT) receiver in dispersive channels. Such channels are likely to arise in any Telepoint application, large public areas, microcellular up to 200 m, and are link performance with this standard DECT receiver, which consists in a non-coherent receiver (differential phase detector or limiter-discriminator detector), will not be adequate for such large indoor and outdoor environments and is at best capable of handling delay spreads up to 90 ns. In order to guarantee acceptable link performance in such dispersive channels, we propose a new non-coherent receiver based on a simple one-tap decision feedback equaliser using the correlation properties of the training sequence for channel estimation and an optimised threshold. Software simulation is used to investigate the effect of the channel on system performance , mainly the impact of delay spread. Our BER simulation results show that this simple Non-Coherent Equaliser yields acceptable performance in the delay range of the outdoor DECT channels (100 to 250 ns) while it is much less sensitive to both modulation index drifts and frequency offsets. Furthermore BER comparison with the more complex Viterbi equaliser indicate very similar performance improvement
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Guzeev, Andrew. "Use of equalization and echo canceling on circuit board wires." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1466.
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Advances in CMOS technology have resulted in increased clock fre-quencies, even exceeding 3GHz. At the same time, frequencies on most board wires are 125-800MHz. It is especially problematic in modern computer mem-ory buses and high speed telecommunication devices, such as switches and routers operating at 10Gb/s on its ports. It is believed that circuit board buses can be used up to about 20GHz, but there is a problem with Intersymbol Inter-ference (ISI) causing distortion of transmitted symbols by multiple reflections.
Actually, the circuit board bus behaves like a passive low pass filter with unknown (perhaps changing) transfer characteristic. The problem of ISI was solved some time ago in the telecommunication area. With use of adaptive equalizers it is possible to increase throughput of a long distance communication channel dramatically.
But the microprocessor bus has certain differences from telecommunica-tion devices such as modems. First of all, the clock frequency on a bus is much higher than in modems. Secondly, a bus has a much more complex structure than a telecommunication channel. At the same time, we can’t use a lot of re-sources for bus maintaining.
The aim of the thesis work is to investigate the possibility of using adap-tive equalization on a bus, and the construction of a reasonable mathematical model of such an equalizer. Also limits of equalizationare examined and de-pendencies are derived.
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McGinty, Nigel, and nigel mcginty@defence gov au. "Reduced Complexity Equalization for Data Communication." The Australian National University. Research School of Information Sciences and Engineering, 1998. http://thesis.anu.edu.au./public/adt-ANU20050602.122741.
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Optimal decision directed equalization techniques for time dispersive communication channels are often too complex to implement. This thesis considers reduced complexity decision directed equalization that lowers complexity demands yet retains close to optimal performance. The first part of this dissertation consists of three reduced complexity algorithms based on the Viterbi Algorithm (VA) which are: the Parallel Trellis VA (PTVA); Time Reverse Reduced State Sequence Estimation (TR-RSSE); and Forward-Backward State Sequence Detection (FBSSD). The second part of the thesis considers structural modifications of the Decision Feedback Equalizer (DFE), which is a special derivative of the VA, specifically, optimal vector quantization for fractionally spaced DFEs, and extended stability regions for baud spaced DFEs using passivity analysis are investigated.¶
For a special class of sparse channels the VA can be decomposed over a number of independent parallel trellises. This decomposition will be called the Parallel Trellis Viterbi Algorithm and can have lower complexity than the VA yet it retains optimal performance. By relaxing strict sparseness constraints on the channel a sub-optimal approach is proposed which keeps complexity low and obtains good performance.¶
Reduced State Sequence Estimation (RSSE) is a popular technique to reduce complexity. However, its deficiency can be the inability to adequately equalize non-minimum phase channels. For channels that have energy peaks in the tail of the impulse response (post-cursor dominant) RSSE's complexity must be close to the VA or performance will be poor. Using a property of the VA which makes it invariant to channel reversal, TR-RSSE is proposed to extend application of RSSE to post-cursor dominant channels.¶
To further extend the class of channels suitable for RSSE type processing, FBSSD is suggested. This uses a two pass processing method, and is suited to channels that have low energy pre and post-cursor. The first pass generates preliminary estimates used in the second pass to aid the decision process. FBSSD can range from RSSE to TR-RSSE depending on parameter settings.¶
The DFE is obtained when the complexity of RSSE is minimized. Two characterizing properties of the DFE, which are addressed in this thesis, are feedback and quantization. A novel fractionally spaced (FS) DFE structure is presented which allows the quantizer to be generalized relative to the quantizer used in conventional FS-DFEs. The quantizer can be designed according to a maximum a posteriori criterion which takes into account a priori statistical knowledge of error occurrences. A radically different quantizer can be obtained using this technique which can result in significant performance improvements.¶
Due to the feedback nature of the DFE a form of stability can be considered. After a decision error occurs, a stable DFE will, after some finite time and in the absence of noise, operate error free. Passivity analysis provides sufficient conditions to determine a class of channels which insures a DFE will be stable. Under conditions of short channels and small modulation alphabets, it is proposed that conventional passivity analysis can be extended to account for varying operator gains, leading to weaker sufficient conditions for stability (larger class of channels).
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Ghrayeb, Ali A. "ON SYMBOL TIMING RECOVERY IN ALL-DIGITAL RECEIVERS." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609698.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaSandia National Laboratories (SNL) currently achieves a bandwidth efficiency (h ) of 0.5 to 1.0 bps/Hz by using traditional modulation schemes, such as, BPSK and QFSK. SNL has an interest in increasing the present bandwidth efficiency by a factor of 4 or higher with the same allocated bandwidth (about 10 MHz). Simulations have shown that 32- QAM trellis-coded modulation (TCM) gives a good bit error rate (BER) performance, and meets the requirements as far as the bandwidth efficiency is concerned. Critical to achieving this is that the receiver be able to achieve timing synchronization. This paper examines a particular timing recovery algorithm for all-digital receivers. Timing synchronization in a digital receiver can be achieved in different ways. One way of achieving this is by interpolating the original sampled sequence to produce another sampled sequence synchronized to the symbol rate or a multiple of the symbol rate. An adaptive sampling conversion algorithm which performs this function was developed by Floyd Gardner in 1993. In the present work, his algorithm was applied to two different modulation schemes, BPSK and 4-ary PAM. The two schemes were simulated in the presence of AWGN and ISI along with Gardner’s algorithm for timing recovery, and a fractionally spaced equalizer (T/2 FSE) for equalization. Simulations show that the algorithm gives good BER performance for BPSK in all the situations, and at different sampling frequencies, but unfortunately poor performance for the 4-ary PAM scheme. This indicates that Gardner’s algorithm for sampling conversion is not suitable for multi-level signaling schemes.
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Wilbrod, Jean-Hubert. "Variations spectrales de lasers semiconducteurs multimodes longitudinaux : Incidences sur les bilans de liaison." Saint-Etienne, 1987. http://www.theses.fr/1987STET4007.
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Laser employé dans des systèmes de télécommunication par fibres optiques. Dégradation dues à l'interférence intersymbole, au glissement spectral, au bruit de partition en continu, au bruit de partition sur les impulsions. Intérêt de la modulation externe du laser par rapport à la modulation par le courant
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Bicen, Ahmet Ozan. "Fundamentals of molecular communication over microfluidic channels." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55009.
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The interconnection of molecular machines with different functionalities to form molecular communication systems can increase the number of design possibilities and overcome the limited reliability of the individual molecular machines. Artificial information exchange using molecular signals would also expand the capabilities of single engineered cell populations by providing them a way to cooperate across heterogeneous cell populations for the applications of synthetic biology and lab-on-a-chip systems. The realization of molecular communication systems necessitates analysis and design of the communication channel, where the information carrying molecular signal is transported from the transmitter to the receiver. In this thesis, significant progress towards the use of microfluidic channels to interconnect molecular transmitter and receiver pairs is presented. System-theoretic analysis of the microfluidic channels are performed, and a finite-impulse response filter is designed using microfluidic channels. The spectral density of the propagation noise is studied and the additive white Gaussian noise channel model is developed. Memory due to inter-diffusion of the transmitted molecular signals is also modeled. Furthermore, the interference modeling is performed for multiple transmitters and its impact on the communication capacity is shown. Finally, the efficient sampling of the signal transduction by engineered bacterial receivers connected to a microfluidic channel is investigated for the detection of the pulse-amplitude modulated molecular signals. This work lays the foundation for molecular communication over microfluidic channels that will enable interconnection of engineered molecular machines.
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Matcha, Chaitanya Kumar, Mohsen Bahrami, Shounak Roy, Shayan Garani Srinivasa, and Bane Vasic. "Generalized belief propagation based TDMR detector and decoder." IEEE, 2016. http://hdl.handle.net/10150/622831.
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Two dimensional magnetic recording (TDMR) achieves high areal densities by reducing the size of a bit comparable to the size of the magnetic grains resulting in two dimensional (2D) inter symbol interference (ISI) and very high media noise. Therefore, it is critical to handle the media noise along with the 2D ISI detection. In this paper, we tune the generalized belief propagation (GBP) algorithm to handle the media noise seen in TDMR. We also provide an intuition into the nature of hard decisions provided by the GBP algorithm. The performance of the GBP algorithm is evaluated over a Voronoi based TDMR channel model where the soft outputs from the GBP algorithm are used by a belief propagation (BP) algorithm to decode low-density parity check (LDPC) codes.
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Kelly, Owen Ernest. "Intersymbol interference equalization by universal likelihood." Thesis, 1997. http://hdl.handle.net/1911/19173.
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Codelength based inference is used to decode binary symbols distorted by an inter-symbol interference (ISI) channel with additive noise. The transmitted signals are antipodal waveforms constructed from $\pm$1 valued signature sequences. The receiver adapts to the unknown channel by training on a known preamble sequence. The training sequence is quantized to a small alphabet and the resulting discrete valued sequence is used to train a context-tree model of the combined data-source and ISI channel. In additive white Gaussian noise, the context tree equalizer has a probability of error slightly larger than an adaptive decision feedback equalizer (DFE). The difference corresponds to approximately 1 dB loss of signal-to-noise ratio. However, a context tree equalizer performs equally well in the presence of heavy-tailed noise for which the adaptive DFE essentially fails. An empirical classification result of Gutman is extended to Markov processes of alphabet size two and unknown Markov order.
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Zerik, Ali. "Discrete spectral factorization in intersymbol interference problems." 1989. http://hdl.handle.net/1993/16920.
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Xiong, Fuqin. "Sequential sequence estimation for channels with intersymbol interference." 1989. http://hdl.handle.net/1993/16946.
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LEE, MING-LUN, and 李明倫. "Analysis of intersymbol interference for indoor wireless communications." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/87669575603770360989.
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碩士國立臺灣大學
電機工程學系
85
In indoor wireless communications, the effects of multpath result in not only frequency selective fading and amplitude fading but also intersymbol interference (ISI) in high data rates. In demand of high data rates in small indoor radio environments, how to resolve the influence of multipaath is the most important thing. This thesis uses 3D ray tracing to model the radio propagation in indoor environments and proposes a good approximation to calculate the outage probabilities in different areas. In order to increase the data rate and reduce ISI, performance enhancement techniques such as diversity, equalization, coding, and spread spectrum have been studied. This thesis focuses on external diversity including space diversity, polarization diversity, and sector antennas. It is shown that using sector antennas is the most effective approach to minimize ISI.
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Dai, Qingyuan. "Sequence estimation for Rayleigh fading channels with intersymbol interference." 1993. http://hdl.handle.net/1993/17548.
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Chou, Ching-Chang, and 周慶彰. "Characteristics Of Intersymbol Interference Over Optical Wireless Diffuse Channels." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/28553321881553196261.
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碩士國立高雄第一科技大學
電腦與通訊工程所
91
Wireless indoor infrared transmission systems offer the potential to provide broadband mobile communications. Non-directed infrared light transmission with intensity modulation and direct detection(IM/DD) is a candidate for these indoor high-speed systems, which offers several advantages over radio as a medium for indoor wireless networks, including as immense window of unregulated bandwidth, immunity to multipath fading, and a lack of interference from one room to another. Non-LOS(Line-Of-Sight) link design increases link robustness and ease of use, allowing the link to operate even when barriers, such as people or cubicle partitions, stand between the transmitter and receiver. The greatest robustness and ease of use are achieved by the nondirected, non-LOS link design, which is often referred to as a diffuse link. The diffuse channels alleviate the need for a LOS(line-of-sight) path by relying on reflections from a large diffuse reflector, such as ceiling. While infrared diffuse channels are immune to multipath fading, the existence of multiple propagation paths does lead to temporal dispersion, potentially causing intersymbol interference in digital links with signaling rates greater than about 10Mbaud. The temporal dispersion can be expressed by delay spread, which limits the performance of wireless infrared systems. On the other hand, the environment, where the wireless infrared systems operate, contains intense ambient infrared radiation which also hampers the performance. In this thesis, we will use eyediagrams which are produced by our simulation program to evaluate the ability of different pulse shapes alleviating the impacts of delay spread . Also, a comparisons of ISI (intersymbol interference) performance for several pulse shapes in the environment with noise is presented. Finally, their performance for various dispersion conditions are presented in bit error rate(BER).
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Peng, Yu-Hao, and 彭于豪. "Simulation and Measurement of Intersymbol Interference for Indoor Wireless Communications." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/52256482225794761033.
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碩士國立臺灣大學
電機工程學系
86
The effects of multipath arise frequency selective fading, amplitude fading, and, especially in high data rates, intersymbol interference(ISI). In demand of high data rates, how to reduce the influence of multipath phenomenon is the most important thing in indoor wireless communications. This thesis uses ray tracing to model the radio propagation characteristics, and spectrum analyzer to measure the radio propagation mechanism in complicated environments. The purpose of this study includes the discussion about influence of different receiving antenna pattern on the transmission performance, and how to suitably place the base-station for increasing data rate. Finally, an easy EVM measurement which is another assessment method beside bit error rate is made.
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林佳賢. "Some Designs for communication systems on channels with intersymbol interference." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/38002403205663571316.
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碩士國立臺灣大學
電信工程學研究所
90
Abstract In this thesis, two systems which integrate the design of equali- zation and channel coding are investigated. The first system employs Tomlinson-Harashima precoding. Generalized Low Density (GLD) codes and Turbo codes are used in this system. GLD codes can be considered as the generalization of Low Density Parity Check (LDPC) codes. The performance of GLD codes is comparable to that of Turbo codes. Similar to Turbo codes, iterative algorithms (BCJR, SOVA) are used in the decoding of GLD codes. In the precoding system, the received data is a periodic extension of the transmitted data constellation, plus the white noise. Thus the decoding algorithms used in the AWGN channel can not be directly applied to this system. To compensate for this problem, we make a little modification on the original BCJR algorithm. In addition, an approach for reducing the average transmitted power in Tomlinson -Harashima precoding is proposed. Through simulation, we find that the bit error rate (BER) of the power-reduced system can achieve a gain about 0.2~0.5dB. A complexity-reduced approach for power reduction is also considered. The complexity can be greatly reduced with little loss in performance. The second system is Turbo Equalization that uses GLD codes as its coding scheme. Both conventional and low-complexity approaches for joint Turbo Equalization and GLD codes are considered.
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ZHENG, SHOU-ZHI, and 鄭守志. "Use of precoding technique to combat intersymbol interference on HDSL." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/93825021386357957210.
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"LMS electrical filters to reduce intersymbol interference in direct detection optical systems." Massachusetts Institute of Technology, Laboratory for Information and Decision Systems], 1994. http://hdl.handle.net/1721.1/3356.
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Rajatheva, R. M. A. P. "Demodulation for intersymbol interference channels in the presence of colored Gaussian noise." 1991. http://hdl.handle.net/1993/17398.
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Viswanathan, Rajendran Atheindhar. "INTERSYMBOL INTERFERENCE (ISI) MITIGATION SCHEMES IN IR-UWB SYSTEMS EMPLOYING ENERGY DETECTION RECEIVER." Thesis, 2013. http://hdl.handle.net/10222/21852.
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Ultra-Wideband (UWB) is an emerging wireless technology that has attracted many applications in modern day communications. Its ability to provide high data rates at very low complexity makes the system attractive for many indoor high-speed wireless communications. UWB signal can be transmitted by either impulse radio (IR) or multicarrier techniques. Impulse radio technique in particular, is a carrier less technology using pulses in the range of nanoseconds or less providing a low complexity, low power and low interference susceptible wireless system. These features motivate the usage of energy detection based receiver structures that operates at very low power.
With the recent developments in UWB technology, a promising feature of this system is to provide high data rate with transceivers operating at very low power. High data rate on the other hand can be achieved only by using a complex modulation schemes that requires more transmitted power. As a limitation in the spectral emission associated with UWB, only low-level modulation technology can be used in UWB systems. Hence, in order to achieve high data rates using low-level modulation schemes, the Inter-symbol interference (ISI) becomes unavoidable.
Decision feedback equalization (DFE) is one of the signal process techniques that can be used to mitigate the effects of ISI. This thesis proposes an energy subtraction algorithm combining with the principles of DFE to mitigate the effects of ISI in an impulse radio UWB system employing energy detection receiver. Computer simulations have been performed to verify the operation of the new proposed algorithm under UWB channel characteristics and relevant comparisons have been made with the basic energy detection receiver. Simulation results show that the ISI can be effectively mitigated with low system complexity.
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"Efficient communication over additive white Gaussian noise and intersymbol interference channels using chaotic sequences." Research Laboratory of Electronics, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/4155.
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Brian Chen.Also issued as Thesis (M. S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.
Includes bibliographical references (p. 103).
Supported in part by the Dept. of the Navy, Office of the Chief Naval Research. N0014-93-1-0686 Supported in part by the Advanced Research Projects Agency's RASSP program. N00014-95-1-0834 Supported in part by a National Defence Science and Engineering Graduate Fellowship.
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Tsai, Tzung-Hua, and 蔡宗樺. "Performance Analysis of Differential Transmitted-Reference Systems over Ultra-Wideband Channels with Intersymbol Interference." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/06087715950997915306.
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碩士國立清華大學
通訊工程研究所
98
The UWB system is a promising technology that can provide high-data rate and robustness to multipath fading. However, because of the difficulty in analyzing the UWB channel models adopted by the IEEE UWB 802.15.3a Task Group, previous analytical works regarding transmitted-reference systems are based on simplified channel models or computer simulations. Besides, the symbol duration is assumed to be sufficiently large so that the effect of intersymbol interference (ISI) can be ignored. In this thesis, the exact evaluation of the signal-to-interference-plus-noise ratio for differential transmitted-reference systems over the IEEE 802.15.3a channel structure is derived regarding the effect of ISI. A simplified formula is also provided for ease of the following system analysis. In particular, the optimal integration time for different symbol durations and channel models is studied. Some special phenomena due to ISI and a universal rule to approach the maximum SINR can hence be characterized. Compared with the previous methodology, our analytical results provide a more efficient and insightful way to receiver design and optimization.
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Chia-chen, Hsieh. "Single Carrier Modulation with Frequency Domain Equalization for Intensity Modulated-Direct Detection Channels with Intersymbol Interference." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2607200609383500.
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Hsieh, Chia-chen, and 謝佳辰. "Single Carrier Modulation with Frequency Domain Equalization for Intensity Modulated-Direct Detection Channels with Intersymbol Interference." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/02984940746478630027.
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碩士國立臺灣大學
電信工程學研究所
94
In this thesis, we examine single carrier modulation with frequency domain equalization (SC-FDE) for optical communication systems using intensity modulation with direct detection (IM/DD) in the presence of additive white Gaussian noise. SC-FDE is a technique whose processing is quite similar to that of OFDM. Unlike OFDM, however, SC-FDE is compatible with IM/DD channels because it does not require the transmission of a strong dc. For an IM/DD channel, at high data rate regime, the effect of intersymbol interference (ISI) starts to dominate system performance. Inthis paper, we examine the use of SC-FDE and pulse position modulation (PPM) to combat ISI for IM/DD channels. Such a system enjoys the average power efficiency of PPM and the low complexity equalization of SC-FDE. We analyze the bit error performance of SC-FDE and compare it with a few known techniques.
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Evans, Andrew John. "Design, implementation, and measurements of a high speed serial link equalizer." 2012. http://hdl.handle.net/2152/19981.
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The advancements of semiconductor processing technology have led to the ability for computing platforms to operate on large amounts of data at very high clock speeds. To fully utilize this processing power the components must have data continually available for operation upon and transport to other system components. To enable this data requirement, high speed serial links have replaced slower parallel communication protocols. Serial interfaces inherently require fewer signals for communication and thus reduce the device pin count, area and cost. A serial communication interface can also be run at a higher frequency because the clock skew between channels is no longer an issue since the data transmitted on various channels is independent. Serial data transmission also comes with a set of drawbacks when signal integrity is considered. The data must propagate through a channel that induces unwanted effects onto the signals such as intersymbol interference. These channel effects must be understood and mitigated to successfully transmit data without creating bit errors upon reception at the target component. Previously developed adaptive equalization techniques have been used to filter the effects of intersymbol interference from the transmitted data in the signal. This report explores the modeling and implementation of a system comprised of a transmitter, channel, and receiver to understand how intersymbol interference can be removed through a decision-feedback equalizer realized in hardware. The equalizer design, implementation, and measurements are the main focus of this report and are based on previous works in the areas of integrated circuit testing, channel modeling, and equalizer design. Simulation results from a system modeled in Simulink are compared against the results from a hardware model implemented with an FPGA, analog to digital converter and discrete circuit elements. In both the software and hardware models, bit errors were eliminated for certain amounts of intersymbol interference when a receiver with decision-feedback equalization was used instead of a receiver without equalization.text
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Emad, Amin. "Effects of interference on carrier tracking in fading and symbol synchronization." Master's thesis, 2009. http://hdl.handle.net/10048/720.
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Thesis (M. Sc.)--University of Alberta, 2009.Title from PDF file main screen (viewed on Dec. 14, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Electrical and Computer Engineering, University of Alberta." Includes bibliographical references.
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Anoh, Kelvin O. O., G. Okorafor, B. Adebisi, A. Alabdullah, Steven M. R. Jones, and Raed A. Abd-Alhameed. "Full-Diversity QO-STBC Technique for Large-Antenna MIMO Systems." 2017. http://hdl.handle.net/10454/12065.
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YesThe need to achieve high data rates in modern telecommunication systems, such as 5G standard, motivates the study and development of large antenna and multiple-input multiple-output (MIMO) systems. This study introduces a large antenna-order design of MIMO quasi-orthogonal space-time block code (QO-STBC) system that achieves better signal-to-noise ratio (SNR) and bit-error ratio (BER) performances than the conventional QO-STBCs with the potential for massive MIMO (mMIMO) configurations. Although some earlier MIMO standards were built on orthogonal space-time block codes (O-STBCs), which are limited to two transmit antennas and data rates, the need for higher data rates motivates the exploration of higher antenna configurations using different QO-STBC schemes. The standard QO-STBC offers a higher number of antennas than the O-STBC with the full spatial rate. Unfortunately, also, the standard QO-STBCs are not able to achieve full diversity due to self-interference within their detection matrices; this diminishes the BER performance of the QO-STBC scheme. The detection also involves nonlinear processing, which further complicates the system. To solve these problems, we propose a linear processing design technique (which eliminates the system complexity) for constructing interference-free QO-STBCs and that also achieves full diversity using Hadamard modal matrices with the potential for mMIMO design. Since the modal matrices that orthogonalize QO-STBC are not sparse, our proposal also supports O-STBCs with a well-behaved peak-to-average power ratio (PAPR) and better BER. The results of the proposed QO-STBC outperform other full diversity techniques including Givens-rotation and the eigenvalue decomposition (EVD) techniques by 15 dB for both MIMO and multiple-input single-output (MISO) antenna configurations at 10−3 BER. The proposed interference-free QO-STBC is also implemented for 16×NR and 32×NR MIMO systems, where NR≤2. We demonstrate 8 x 16 and 32 transmit antenna-enabled MIMO systems with the potential for mMIMO design applications with attractive BER and PAPR performance characteristics.
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McGinty, Nigel. "Reduced Complexity Equalization for Data Communication." Phd thesis, 1998. http://hdl.handle.net/1885/47801.
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Optimal decision directed equalization techniques for time dispersive communication channels are often too complex to implement. This thesis considers reduced complexity decision directed equalization that lowers complexity demands yet retains close to optimal performance. The first part of this dissertation consists of three reduced complexity algorithms based on the Viterbi Algorithm (VA) which are: the Parallel Trellis VA (PTVA); Time Reverse Reduced State Sequence Estimation (TR-RSSE); and Forward-Backward State Sequence Detection (FBSSD). The second part of the thesis considers structural modifications of the Decision Feedback Equalizer (DFE), which is a special derivative of the VA, specifically, optimal vector quantization for fractionally spaced DFEs, and extended stability regions for baud spaced DFEs using passivity analysis are investigated. ¶ ...
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Asif, Rameez, Tahereh S. Ghazaany, Raed A. Abd-Alhameed, James M. Noras, Steven M. R. Jones, Jonathan Rodriguez, and Chan H. See. "MIMO discrete wavelet transform for the next generation wireless systems." 2013. http://hdl.handle.net/10454/9617.
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NoStudy is presented into the performance of Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) and MIMO-DWT with transmit beamforming. Feedback loop has been used between the equalizer at the transmitter to the receiver which provided the channel state information which was then used to construct a steering matrix for the transmission sequence such that the received signals at the transmitter can be combined constructively in order to provide a reliable and improved system for next generation wireless systems. As convolution in time domain equals multiplication in frequency domain no such counterpart exist for the symbols in space, means linear convolution and Intersymbol Interference (ISI) generation so both zero forcing (ZF) and minimum mean squared error (MMSE) equalizations have been employed. The results show superior performance improvement and in addition allow keeping the processing, power and implementation cost at the transmitter which has less constraints and the results also show that both equalization algorithms perform alike in wavelets and the ISI is spread equally between different wavelet domains.
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Πούλος, Αθανάσιος. "VLSI αρχιτεκτονική χαμηλής κατανάλωσης για συγχρονισμό σε Multi-band UWB ασύρματα δίκτυα." 2006. http://nemertes.lis.upatras.gr/jspui/handle/10889/468.
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Η ΒΥΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της.Τα ψηφιακά συστήματα UWB (Ultra Wide-Band) παρέχουν τη δυνατότητα ασύρματης μετάδοσης σε πολύ υψηλό ρυθμό. Λόγω του μεγάλου εύρους ζώνης, το κανάλι εισάγει πολλαπλές ανακλάσεις οι οποίες φέρουν μεγάλο ποσοστό της ωφέλιμης ενέργειας του μεταδιδόμενου σήματος. Η ικανότητα του δέκτη για σύλληψη όσο το δυνατόν περισσότερης ωφέλιμης ενέργειας έχει αντίκτυπο στη συνολική απόδοση του συστήματος. Η χρήση της τεχνικής διαμόρφωσης με πολύπλεξη συχνότητας ορθογωνίων φερουσών (OFDM), που στην συγκεκριμένη περίπτωση (UWB) συνδυάζεται με πολυζωνική (Multi-band) μετάδοση, απλοποιεί τη διαχείριση του συνολικού φάσματος συχνοτήτων. Όμως η διαμόρφωση OFDM παρουσιάζει ιδιαίτερη ευαισθησία σε προβλήματα τόσο διασυμβολικής παρεμβολής (ISI) όσο και διακαναλικής παρεμβολής (ICI), λόγω του έντονου διασκορπιστικού χαρακτήρα του καναλιού καθώς επίσης και τυχόν αποκλίσεων που εμφανίζονται στους ταλαντωτές πομπού-δέκτη. Τα παραπάνω επιβάλλουν τη χρήση σύνθετων αλγορίθμων συγχρονισμού και συντονισμού (time and frequency synchronization) μεταξύ πομπού και δέκτη για την ομαλή λειτουργία. Στα πλαίσια της διπλωματικής αυτής θα πραγματοποιηθεί επιλογή κατάλληλων αλγορίθμων για τα προαναφερθέντα προβλήματα, οι οποίοι θα πρέπει να πληρούν τις προδιαγραφές του υπό διαμόρφωση διεθνούς προτύπου 802.15.3α και θα αναπτυχθούν βέλτιστες αρχιτεκτονικές VLSI, με στόχο τόσο το χαμηλό κόστος υλοποίησης όσο και την χαμηλή κατανάλωση ισχύος.
In this project have been studied the low power VLSI architecture for synchronization algorithms in Multi-band UWB Wireless systems. The main issues are timing and frequency synchronization algorithms.
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Χριστοδούλου, Κωνσταντίνος. "Δέκτες χωροχρονικής κωδικοποίησης για συχνοτικά επιλεκτικά συστήματα." Thesis, 2010. http://nemertes.lis.upatras.gr/jspui/handle/10889/3669.
Full textAbstract:
Η χωροχρονική μπλοκ κωδικοποίηση (STBC) αποτελεί μία αποδοτική και ευρέως διαδεδομένη τεχνική διαφορετικότητας μετάδοσης για την αντιμετώπιση του φαινομένου της εξασθένησης στις ασύρματες επικοινωνίες. Χαρακτηριστικό παράδειγμα είναι ο ορθογώνιος κώδικας του σχήματος Alamouti, ο οποίος με δύο κεραίες μετάδοσης επιτυγχάνει τη μέγιστη χωρική διαφορετικότητα στο μέγιστο δυνατό ρυθμό μετάδοσης, για οποιονδήποτε (πραγματικό ή μιγαδικό) αστερισμό συμβόλων. Ωστόσο, το σχήμα Alamouti έχει σχεδιαστεί για συχνοτικά επίπεδα κανάλια. Στην παρούσα εργασία μελετούμε την εφαρμογή STBC σε κανάλια συχνοτικά επιλεκτικής εξασθένησης. Εστιάζουμε κυρίως στο συνδυασμό του σχήματος Alamouti με τεχνικές εξάλειψης της διασυμβολικής παρεμβολής, εξετάζοντας τα σχήματα OFDM-STBC, FDE-STBC και TR-STBC, που έχουν προταθεί στη βιβλιογραφία. Επιπρόσθετα των συμβατικών δεκτών, για τα δύο τελευταία σχήματα περιγράφουμε και προσαρμοστικούς δέκτες, οι οποίοι παρακολουθούν τις μεταβολές του καναλιού, χωρίς να απαιτούν την ακριβή εκτίμησή του. Η έρευνα πάνω στα προηγούμενα σχήματα οδήγησε σε ορισμένα αξιόλογα αποτελέσματα. Κατ’ αρχήν, αποδεικνύουμε ότι τα σχήματα FDE-STBC και TR-STBC είναι ισοδύναμα, μολονότι καθένα εφαρμόζει διαφορετική κωδικοποίηση στα μεταδιδόμενα δεδομένα. Επίσης, σχεδιάζουμε έναν νέο δέκτη για το σχήμα TR-STBC, τον οποίο αναπτύσσουμε και σε προσαρμοστική μορφή. Βασικό πλεονέκτημα του προτεινόμενου δέκτη είναι ότι εκμεταλλεύεται τους κυκλικούς πίνακες συνέλιξης για τη μείωση της πολυπλοκότητας αποκωδικοποίησης. Τέλος, η απόδοση κάθε σχήματος και δέκτη αξιολογείται σε διάφορες συνθήκες εξασθένησης μέσω προσομοιώσεων σε υπολογιστικό περιβάλλον.Space-time block coding (STBC) is an effective and widely used transmit diversity technique to combat multipath fading in wireless communication systems. A prominent example of STBC is the orthogonal code of Alamouti scheme, which achieves full spatial diversity at full transmission rate for two transmit antennas and any (real or complex) signal constellation. However, Alamouti scheme has been designed only for frequency-flat channels. In this thesis we study the application of STBC in frequency-selective channels. We mainly focus on combining Alamouti scheme with techniques for mitigating intersymbol interference, by studying several schemes (OFDM-STBC, FDE-STBC and TR-STBC) that have been proposed in literature. In addition to the conventional receivers, for FDE-STBC and TR-STBC we describe adaptive receivers too, which have the ability of tracking channel variations, without requiring explicit channel estimation. Research made upon the above schemes has come to some remarkable results. First, we prove that TR-STBC and FDE-STBC are equivalent, although each one encodes differently the transmitted data. Then, we design a new receiver for TR-STBC, which exploits the circulant convolution matrices, in order to reduce decoding complexity and we, also, develop an adaptive structure for the proposed receiver. At last, we evaluate the performance of all the described schemes and receivers in different fading conditions, by using computer simulations.