Dissertations / Theses on the topic 'Channel equalization'
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Shiao, Fu-Sheng. "Combined Channel Estimation and Turbo Equalization for Wireless Channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1189.
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Single-carrier linear modulation techniques combined with frequency-domain equalization provide a viable alternative to multicarrier techniques for combating multipath fading in channels with large delay spread. Such modulations tolerate frequency offset and have well controlled peak to average power ratio. They have comparable complexity to orthogonal frequency division multiplexing (OFDM) systems, and are more robust to synchronization errors. If error correction coding is used, then information can be iteratively passed between the equalizer and the decoder to improve performance. This is referred to as turbo equalization. To date, several turbo equalization schemes have been proposed, but little work has been done to address the problem of channel estimation for the turbo equalization process. The work in this thesis considers frequency-domain turbo equalization with imperfect channel state information (CSI) at the receiver for different wireless channels. A receiver structure incorporating joint frequency-domain turbo equalization and time- domain channel estimation is developed. The novelty of this scheme lies in the combination of time-domain channel estimation and frequency-domain turbo equalization, and in its extension to high level modulation formats. The performance of the system is investigated by a combination of analysis and computer simulation. It is found that the system performs well over a range of dispersive channels.
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Lu, Biao. "Wireline channel estimation and equalization /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004324.
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Çiftçi, Mahmut. "Channel equalization for chaotic communications systems." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15464.
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COSTA, BERNARDO RODRIGUES DA. "CHANNEL EQUALIZATION IN BLOCK TRANSMISSION SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11845@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA necessidade pela transmissão em altas taxas, por exemplo nos novos sistemas de TV Digital de alta definição, telefonia celular de terceira e quarta geração, DSL e etc, trazem consigo um problema: o aumento dos múltiplos percursos no canal de comunicações (principalmente nas interfaces áereas), dando origem ao fenômeno de interferência intersimbólica (IES). Este trabalho investiga o desempenho de sistemas de transmissão com uma única portadora (SC ou single-carrier) com equalização linear no domínio da freqüência. Diferentes algoritmos recursivos são apresentados para implementar estes filtros FIR. Além dos equalizadores lineares, uma estrutura não-linear é introduzida, onde decisões passadas do decisor de mínima distância são utilizadas para mitigar os efeitos da IES na detecção dos símbolos subseqüentes. Este arranjo é conhecido como equalização/filtragem com decisões realimentadas (DFE ou Decision Feedback Equalizers). Por último, os resultados obtidos com o sistema SC nas diferentes configurações de filtragem na recepção são comparados com os resultados do já estabelecido sistema OFDM. A transmissão OFDM se dá com múltiplas portadoras, onde as freqüências das sub-portadoras são ortogonais entre si, permitindo que a informação seja enviada de forma paralela. Resultados mostram que os sistemas SC-FDE tem desempenho superior aos sistemas OFDM.
The demand for high rate transmission systems, for example in HDTV, third and fourth generation cellular telephony, DSL and so on, causes the rise of a problem: The multipath communications channel (specially in wireless communications), which leads to intersymbol interference phenomenon (ISI). The present work investigates the performance of single-carrier (SC) transmission systems with frequency-domain linear equalization. Different recursive algorithms are presented in order to implement these FIR filters. Besides the linear equalizers, a non- linear structure is introduced, where the past decisions made by the detectors are used to mitigate the effect of ISI on the detection of the forthcoming symbols. This set is known as Decision Feedback Equalizers (DFE). Finally, the results of the aforementioned systems are compared to the well-known OFDM. OFDM transmission relies on sub-carriers, frequency orthogonal to each other, in which the data is sent in a parallel basis. The results obtained show that SC- FDE systems outperform OFDM systems.
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Gurrapu, Omprakash. "Adaptive filter algorithms for channel equalization." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19219.
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Equalization techniques compensate for the time dispersion introduced bycommunication channels and combat the resulting inter-symbol interference (ISI) effect.Given a channel of unknown impulse response, the purpose of an adaptive equalizer is tooperate on the channel output such that the cascade connection of the channel and theequalizer provides an approximation to an ideal transmission medium. Typically,adaptive equalizers used in digital communications require an initial training period,during which a known data sequence is transmitted. A replica of this sequence is madeavailable at the receiver in proper synchronism with the transmitter, thereby making itpossible for adjustments to be made to the equalizer coefficients in accordance with theadaptive filtering algorithm employed in the equalizer design. This type of equalization isknown as Non-Blind equalization. However, in practical situations, it would be highlydesirable to achieve complete adaptation without access to a desired response. Clearly,some form of Blind equalization has to be built into the receiver design. Blind equalizerssimultaneously estimate the transmitted signal and the channel parameters, which mayeven be time-varying. The aim of the project is to study the performance of variousadaptive filter algorithms for blind channel equalization through computer simulations.Uppsatsnivå: D
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Yao, Ning. "Iterative algorithms for channel estimation and equalization /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20YAO.
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Mheidat, Hakam. "Channel Estimation and Equalization for Cooperative Communication." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2852.
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The revolutionary concept of space-time coding introduced in the last decade has demonstrated that the deployment of multiple antennas at the transmitter allows for simultaneous increase in throughput and reliability because of the additional degrees of freedom offered by the spatial dimension of the wireless channel. However, the use of antenna arrays is not practical for deployment in some practical scenarios, e. g. , sensor networks, due to space and power limitations. A new form of realizing transmit diversity has been recently introduced under the name of user cooperation or cooperative diversity. The basic idea behind cooperative diversity rests on the observation that in a wireless environment, the signal transmitted by the source node is overheard by other nodes, which can be defined as "partners" or "relays". The source and its partners can jointly process and transmit their information, creating a "virtual antenna array" and therefore emulating transmit diversity.
Most of the ongoing research efforts in cooperative diversity assume frequency flat channels with perfect channel knowledge. However, in practical scenarios, e. g. broadband wireless networks, these assumptions do not apply. Frequency-selective fading and imperfect channel knowledge should be considered as a more realistic channel model. The development of equalization and channel estimation algorithms play a crucial element in the design of digital receivers as their accuracy determine the overall performance.
This dissertation creates a framework for designing and analyzing various time and frequency domain equalization schemes, i. e. distributed time reversal (D-TR) STBC, distributed single carrier frequency domain (D-SC-FDE) STBC, and distributed orthogonal frequency division multiplexing (D-OFDM) STBC schemes, for broadband cooperative communication systems. Exploiting the orthogonally embedded in D-STBCs, we were able to maintain low-decoding complexity for all underlying schemes, thus, making them excellent candidates for practical scenarios, such as multi-media broadband communication systems.
Furthermore, we propose and analyze various non-coherent and channel estimation algorithms to improve the quality and reliability of wireless communication networks. Specifically, we derive a non-coherent decoding rule which can be implemented in practice by a Viterbi-type algorithm. We demonstrate through the derivation of a pairwise error probability expression that the proposed non-coherent detector guarantees full diversity. Although this decoding rule has been derived assuming quasi-static channels, its inherent channel tracking capability allows its deployment over time-varying channels with a promising performance as a sub-optimal solution. As a possible alternative to non-coherent detection, we also investigate the performance of mismatched-coherent receiver, i. e. , coherent detection with imperfect channel estimation. Our performance analysis demonstrates that the mismatched-coherent receiver is able to collect the full diversity as its non-coherent competitor over quasi-static channels.
Finally, we investigate and analyze the effect of multiple antennas deployment at the cooperating terminals assuming different relaying techniques. We derive pairwise error probability expressions quantifying analytically the impact of multiple antenna deployment at the source, relay and/or destination terminals on the diversity order for each of the relaying methods under consideration.
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Jalali, Sammuel. "Wireless Channel Equalization in Digital Communication Systems." Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/cgu_etd/42.
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Our modern society has transformed to an information-demanding system, seeking voice, video, and data in quantities that could not be imagined even a decade ago. The mobility of communicators has added more challenges. One of the new challenges is to conceive highly reliable and fast communication system unaffected by the problems caused in the multipath fading wireless channels. Our quest is to remove one of the obstacles in the way of achieving ultimately fast and reliable wireless digital communication, namely Inter-Symbol Interference (ISI), the intensity of which makes the channel noise inconsequential.
The theoretical background for wireless channels modeling and adaptive signal processing are covered in first two chapters of dissertation.
The approach of this thesis is not based on one methodology but several algorithms and configurations that are proposed and examined to fight the ISI problem. There are two main categories of channel equalization techniques, supervised (training) and blind unsupervised (blind) modes. We have studied the application of a new and specially modified neural network requiring very short training period for the proper channel equalization in supervised mode. The promising performance in the graphs for this network is presented in chapter 4.
For blind modes two distinctive methodologies are presented and studied. Chapter 3 covers the concept of multiple "cooperative" algorithms for the cases of two and three cooperative algorithms. The "select absolutely larger equalized signal" and "majority vote" methods have been used in 2-and 3-algoirithm systems respectively. Many of the demonstrated results are encouraging for further research.
Chapter 5 involves the application of general concept of simulated annealing in blind mode equalization. A limited strategy of constant annealing noise is experimented for testing the simple algorithms used in multiple systems. Convergence to local stationary points of the cost function in parameter space is clearly demonstrated and that justifies the use of additional noise. The capability of the adding the random noise to release the algorithm from the local traps is established in several cases.
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Barron, Richard J. (Richard John). "Channel equalization for self-synchronizing chaotic systems." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38828.
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Song, Liying Tugnait Jitendra K. "Channel estimation and equalization for doubly-selective channels using basis expansion models." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Dissertation/Song_Liying_29.pdf.
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Aktas, Emre. "Channel estimation and equalization for wireless communication systems in frequency selective channels /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486546889382902.
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Leong, Sang-Yick. "Channel modeling, estimation and equalization in wireless communication." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4183.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 25, 2006) Vita. Includes bibliographical references.
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Abrar, Shafayat. "Blind channel equalization and instantaneous blind source separation." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540044.
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Wu, Hai. "A coherent optical equalization based on channel estimation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/MQ65528.pdf.
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NETO, AUREO SERRANO DE MARINS. "EQUALIZATION AND CHANNEL ESTIMATION IN OFDM TRANSMISSION SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7973@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORcrescimento dos sistemas de comunicações móveis celulares e dos sistemas de rádio difusão de sinais de áudio e vídeo tem despertado grande interesse na pesquisa de novos métodos para a transmissão de sinais nestas redes. A necessidade de se transmitir dados em altas taxas, com significante eficiência no uso da largura de faixa de freqüências disponível, e por meio de um canal de propagação ruidoso e variante no tempo, constitui o principal problema para o desenvolvimento de novas técnicas de trasmissão de sinais. Dentro deste contexto, esta dissertação trata do uso dos conceitos de transmissão digital e filtragem adaptativa para a demodulação de sinais OFDM (Orthogonal Frequency Division Multiplexing). A equalização de sinais antes e após o estágio de DFT (Discrete Fourier Transform) no receptor e as técnicas de estimação de canal são o objeto principal de estudo deste trabalho. Os resultados dos experimentos são analisados em termos da taxa de erro de bit média obtida e da convergência dos algoritmos empregados nas etapas de equalização e estimação de canal no receptor.
The growth of cellular mobile communication systems and audio and video broadcasting systems has stimulated great interest in the research of new methods for the signal transmission in these networks. The high rate data transmission, with significant efficiency in the use of the available bandwidth, in a noisy and time variant channel, constitutes the main problem for the development of new techniques for signal transmission. In this context, this dissertation deals with the use of the concepts of digital transmission and adaptive filtering for the demodulation of OFDM (Orthogonal Frequency Division Multiplexing) signals. The equalization pre and post DFT (Discrete Fourier Transform) in the receiver and the channel estimation techniques are the main object of study in this work. The results of the experiments are analyzed in terms of the mean bit error rate achieved and the convergence for the algorithms used in the stages of equalization and channel estimation in the receiver.
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Ma, Yi. "Channel estimation and equalization for wireless multicarrier transmissions." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414844.
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Fung, Carrson Chee-Ho. "Eigensystem based techniques for blind channel estimation and equalization /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20FUNG.
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Chesnutt, Elizabeth. "Novel Turbo Equalization Methods for the Magnetic Recording Channel." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6867.
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Novel Turbo Equalization Methods for the Magnetic Recording Channel
Elizabeth Chesnutt
95 Pages
Directed by Dr. John R. Barry
The topic of this dissertation is the derivation, development, and evaluation of novel turbo equalization techniques that address the colored noise problem on the magnetic recording channel. One new algorithm presented is the noise-predictive BCJR, which is a soft-output detection strategy that mitigates colored noise in partial-response equalized magnetic recording channels. This algorithm can be viewed as a combination of the traditional BCJR algorithm with the notion of survivors and noise prediction.
Additionally, an alternative equalization architecture for magnetic recording is presented that addresses the shortcomings of the PRML approach, which dominates magnetic recording. Specifically, trellis-based equalizers are abandoned in favor of simple equalization strategies based on nonlinear filters whose complexity grows only linearly with their length. This research focuses on the linear-complexity SFE algorithm and on investigating the possibility of lowering the SFE filter calculation complexity. The results indicate that with using the proposed novel SFE method, it is possible to increase the information density on magnetic media without raising the complexity. The most important result presented is that partial-response equalization needs to be reconsidered because of the amount of noise enhancement problems that it adds to the overall system. These results are important for the magnetic recording industry, which is trying to attain a 1 Tb/cm2 information storage goal.
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Zhang, Wen Pian Paul. "Transmitter-induced cyclostationarity for blind channel identification and equalization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ49753.pdf.
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Nadakuditi, Rajesh Rao. "A channel subspace post-filtering approach to adaptive equalization." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87613.
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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2002.Includes bibliographical references (p. 151-154).
by Rajesh Rao Naduditi.
S.M.
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Williams, Ian E. "Channel Equalization and Spatial Diversity for Aeronautical Telemetry Applications." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605946.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaThis work explores aeronautical telemetry communication performance with the SOQPSK- TG ARTM waveforms when frequency-selective multipath corrupts received information symbols. A multi-antenna equalization scheme is presented where each antenna's unique multipath channel is equalized using a pilot-aided optimal linear minimum mean-square error filter. Following independent channel equalization, a maximal ratio combining technique is used to generate a single receiver output for detection. This multi-antenna equalization process is shown to improve detection performance over maximal ratio combining alone.
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Allander, Martin. "Channel Equalization Using Machine Learning for Underwater Acoustic Communications." Thesis, Linköpings universitet, Kommunikationssystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166643.
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Wireless underwater acoustic (UWA) communications is a developing field with various applications. The underwater acoustic communication channel is very special and its behavior is environment-dependent. The UWA channel is characterized by low available bandwidth, and severe motion-introduced Doppler effectcompared to wireless radio communication. Recent literature suggests that machine learning (ML)-based channel estimation and equalization offer benefits overtraditional techniques (a decision feedback equalizer), in UWA communications. ML can be advantageous due to the difficultly in designing algorithms for UWA communication, as finding general channel models have proven to be difficult. This study aims to explore if ML-based channel estimation and equalization as a part of a sophisticated physical layer structure can offer improved performance. In the study, supervised ML using a deep neural network and a recurrent neural network will be utilized to improve the bit error rate. A channel simulator with environment-specific input is used to study a wide range of channels. The simulations are utilized to study in which environments ML should be tested. It is shown that in highly time-varying channels, ML outperforms traditional techniques if trained with prior information of the channel. However, utilizing ML without prior information of the channel yielded no improvement of the performance.
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Lambotharan, Sangarapillai. "Algorithms and structures for adaptive blind equalization." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268038.
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Otnes, Roald. "Improved Receivers for Digital High Frequency Communications : Iterative Channel Estimation, Equalization, and Decoding (Adaptive Turbo Equalization)." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-86.
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We address the problem of improving the throughput and the availability of digital communications in the High Frequency (HF, 3-30 MHz) band. In standardized military waveforms, the data is protected by an error-correcting code (ECC), and the code bits are shuffled by an interleaver and mapped onto a signal constellation for modulation onto a single carrier. Training sequences are multiplexed into the stream of transmitted symbols to aid the receiver in tracking the channel variations. The channel imposes severe time-varying intersymbol interference (ISI) as well as additive noise. Conventional receivers for such a system would first perform adaptive equalization (to mitigate the ISI) and symbol demapping, deinterleave the received code bits, and finally perform decoding, where the redundancy of the ECC is used to make high-quality decisions on the transmitted data bits even when bit errors have been introduced by the channel. Such a receiver is suboptimal because the equalizer does not make use of the redundancy introduced by the ECC, and is outperformed by an iterative scheme called turbo equalization. In turbo equalization, a.k.a. iterative equalization and decoding, soft information on the code bits is fed back from the decoder to the equalizer in an iterative fashion, and by performing the equalization and decoding tasks several times the bit error rates become significantly smaller than for a conventional “single-pass” receiver. Since we are dealing with an unknown time-varying channel, we must also perform channel estimation. We include channel estimation in the iterative loop of the turbo equalizer, using soft information fed back from the decoder as “training sequences” between the ordinary transmitted training sequences. Then, the receiver performs iterative channel estimation, equalization, and decoding, which can also be called adaptive turbo equalization. We have proposed a receiver using adaptive turbo equalization, and performed simulations using the MIL-STD-188-110 waveform at 2400 bps, transmitted over an ITU-R poor channel (a commonly used channel to test HF modems). We find that the proposed receiver outperforms a conventional receiver by 2-3 dB in terms of required signal-to-noise ratio to achieve a certain bit error rate. In this dissertation, we give an introduction to the fields of HF communications and standardized HF waveforms, channel modelling, and turbo equalization. We present an analysis of measured channel data to motivate our research in turbo equalization. We then present our research contributions to the field of turbo equalization: A low-complexity soft-in soft-out equalizer for time-varying channels, a comparative study of channel estimation algorithms using soft information as the input signal, and an investigation of adaptive turbo equalization using a technique known as EXIT charts. Finally, we present our main practical result, which is our proposed receiver and the corresponding simulation results.
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Franz, Volker. "Turbo-detection for GSM-systems channel estimation, equalization and decoding /." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=96205772X.
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Yu, Jean Xiang-Qun. "Utilization of inherent diversity for channel coding and equalization algorithms." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149389.
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Choi, Jongsoo. "Recursive filtering approaches to channel equalization and estimation in communications." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29283.
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Communication poses challenges in the presence of interference channel environments. In order to attain performance gains, signal processing techniques at the receiver need to detect the most likely transmitted signal based on the knowledge of the received signal, the channel state information and the statistics of noise. This thesis develops such practical schemes based on a Kalman filter framework, assuming that the channel knowledge is unknown to the receiver. The communication contexts addressed in this thesis include the equalization of intersymbol interference (ISI) channels in single-transmit single-receive (STSR) systems and the channel estimation combined with the decoding of multiple-input multiple-output (MIMO) systems in fading channels. Signal processing based on a Bayesian filtering framework, built on a state-space model of the given communication system, plays a critical role in the equalization and the estimation of the channel.
We develop adaptive channel equalization techniques utilizing recurrent neural networks and Kalman filters for ISI cancellation in STSR systems, which include nonlinear distortions, additive white Gaussian noise and additive white non-Gaussian impulsive noise. In uncoded systems, the extended Kalman filter (EKF) and the unscented Kalman filter (UKF) are used to train the recurrent neural equalizers and achieve the performance improvement in terms of bit error rate and convergence rate, with a shorter training sequence over the conventional equalization schemes.
The integration of semiblind channel estimation into a turbo receiver, the so-called turbo-BLAST1, is developed for narrowband MIMO wireless channels. For quasi-static MIMO channels, we present iterative channel estimation schemes based on adaptive filtering algorithms such as least-mean square, recursive least-squares and the Kalman filter. The iterative strategy with adaptive filtering leads to a computationally efficient solution to iterative channel estimation, compared to the conventional snapshot approaches. For time-varying MIMO channels, we present the use of particle filtering in order to track the time variations of the channels. The improved performance by the particle filtering channel tracking is demonstrated for both Gaussian and non-Gaussian noise environments.
1BLAST: Bell-labs LAyered Space-Time architectures.
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Waseem, Athar, and A. H. M. Sadath Hossain. "MIMO Channel Equalization and Symbol Detection using Multilayer Neural Network." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2345.
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In recent years Multiple Input Multiple Output (MIMO) systems have been employed in wireless communication systems to reach the goals of high data rate. A MIMO use multiple antennas at both transmitting and receiving ends. These antennas communicate with each other on the same frequency band and help in linearly increasing the channel capacity. Due to the multi paths wireless channels face the problem of channel fading which cause Inter Symbol Interference (ISI). Each channel path has an independent path delay, independent path loss or path gain and phase shift, cause deformations in a signal and due to this deformation the receiver can detect a wrong or a distorted signal. To remove this fading effect of channel from received signal many Neural Network (NN) based channel equalizers have been proposed in literature. Due to high level non-linearity, NN can be efficient to decode transmitted symbols that are effected by fading channels. The task of channel equalization can also be considered as a classification job. In the data (received symbol sequences) spaces NN can easily make decision regions. Specifically, NN has the universal approximation capability and form decision regions with arbitrarily shaped boundaries. This property supports the NN to be introduced and perform the task of channel equalization and symbol detection. This research project presents the implementation of NN to be use as a channel equalizer for Rayleigh fading channels causing ISI in MIMO systems. Channel equalization has been done using NN as a classification problem. The equalizer is implemented over MIMO system of different forms using Quadrature Amplitude Modulation scheme (4QAM & 16QAM) signals. Levenberg-Marquardt (LM), One Step Secant (OSS), Gradient Descent (GD), Resilient backpropagation (Rprop) and Conjugate Gradient (CG) algorithms are used for the training of NN. The Weights calculated during the training process provides the equalization matrix as an estimate of Channel. The output of the NN provides the estimate of transmitted signals. The equalizer is assessed in terms of Symbol Error Rate (SER) and equalizer efficiency.
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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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Stranges, Anthony G. "Blind equalization and fading channel signal recovery of OFDM modulation." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5740.
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Approved for public release; distribution is unlimited.Algorithms for blind equalization and data recovery of orthogonal frequency-division multiplexed (OFDM) signals transmitted through fading channels are implemented and simulated in this thesis. The channel is estimated without knowledge of the transmitted sequence (i.e., blindly) using a least mean squares (LMS) adaptive filter and filter bank precoders. This method was used to estimate channel characteristics using both binary and quadrature phase-shift keying signals. Additionally, the method was analyzed for robustness with a poor initial estimate of channel characteristics, with the addition of white Gaussian noise to the signal, and with non-stationary channel conditions. In addition, it is shown that the proposed method is particularly suited in situations with deep fading channels, where some of the subcarriers have a very low SNR. Simulations for both aspects of this thesis were conducted using MATLAB, and the results are presented.
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Kuchler, Ryan J. "Comparison of channel equalization filtering techniques in underwater acoustic communications." Thesis, Monterey California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/5887.
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In this thesis, underwater acoustic communications signal processing techniques, which are used to equalize the distortional effects associated with the ocean as a communications channel, are investigated for a shallow water ocean environment. The majority of current signal processing techniques employ a Finite Impulse Response (FIR) filter. Three equalization filters were investigated and presented as alternatives; they were the passive time-reversed filter, the inverse filter, and the Infinite Impulse Response (IIR) filter. The main advantage of the passive time-reversed filter and the inverse filter is simplicity of design. Bit error rates for the time-reversed filter were consistently around 10-1 and those for the inverse filter were greater than 10-1. However, inability of the passive time-reversed filter to completely eliminate multipath components and the ill-conditioned nature of the inverse filter made it difficult to achieve Probability of Error results below 10-1. Research into the development of an array receiver using a time-reversed filter should improve calculated bit error rates. Simulations of the IIR filter were conducted with limited success. The main advantage of an IIR filter is that fewer parameters are required in the design of the filter. However, the potential for instability in the filter is a significant limitation. Probability of Error results were found to be on the order of those for current FIR filters at close ranges. Unfortunately, instability issues arose for receivers as range from the source increased. This research on the IIR filter is still in the embryonic stage, whereas research using FIR filters is relatively highly developed. Further research is needed to address the issue of instability in IIR filters in order to make them an effective signal processing technique employable in underwater acoustic communications.
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Nawaz, Rab. "Low complexity channel shortening and equalization for multi-carrier systems." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56060/.
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A new time domain blind adaptive channel shortening algorithm for Discrete Multi Tone (DMT)-based multicarrier systems is first proposed. It is computationally less expensive, and more robust to non- Gaussian impulsive noise environments than a recently reported Sum squared Autocorrelation Minimization (SAM) algorithm. A "left" initialization scheme is also suggested for Carrier Serving Area (CSA) loop Asymmetric Digital Subscriber Line (ADSL) channels. Simulation studies show that by a proper selection of the learning parameter i.e., the step size, the bit rates achieved by the SAM algorithm when operating in an environment contaminated by Additive White Gaussian Noise (AWGN) can be further improved. Next a novel time domain low complexity blind adaptive channel short ening algorithm called Single Lag Autocorrelation Minimization (SLAM) is introduced. The algorithm is totally blind in the sense that it does not require a prior knowledge about the length of the channel impulse response. The proposed novel stopping criterion freezes the adaptation of the SLAM algorithm when the maximum amount of Inter Symbol Interference (ISI) is cancelled. As such, the stopping criterion can also be used with SAM. An attractive alternate frequency domain equalization approach for multicarrier systems is Per Tone Equalization (PTEQ). This scheme en- ables true signal-tonoise ratio optimization to be implemented for each tone and it always achieves higher bit rates than Time domain Equalizer (TEQ) based channel shortening schemes but at the price of increased computational complexity and higher memory requirements. A low complexity (PTEQ) scheme is, therefore, finally proposed. The com plexity of the PTEQ can be traded off with the complexity of the timing synchronization within the system. In particular, it is shown that the use of more than one difference terms and hence a long equalizer in the PTEQ scheme is generally redundant. The PTEQ scheme assumes knowledge of the channel impulse response. In this case synchronization is trivial and it is possible to use only a length two PTEQ equalizer and attain essentially identical bit rate performance to a PTEQ equalizer with length matched to the cyclic prefix. This observation allows for a substantial reduction in computational complexity of the PTEQ scheme in both initialization and data transmission modes. For a reasonable range of values of synchronization error, <5, around the optimal value of 5 = 0, the performance of this length two equalizer is shown to remain relatively constant. For positive synchronization errors, however, the required PTEQ equalizer length is proportional to the synchronization error. A low complexity blind synchronization method is ultimately suggested which is based on the construction of the difference terms of the PTEQ scheme.
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Fan, Tiange, Kung Yao, and Don Whiteman. "ADAPTIVE EQUALIZATION FOR OQPSK THROUGH A FREQUENCY SELECTIVE FADING CHANNEL." International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/606497.
Full textAbstract:
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaSpectral sidelobes of QPSK, OQPSK, IJF-OQPSK, and SQAM modulated signals after nonlinear amplification are compared. It is known that OQPSK has lower spectral sidelobes than QPSK. However, in the presence of frequency selective fading, a decision-feedback adaptive equalizer is able to equalize the QPSK signal but not the OQPSK signal. By using phase pre-distortion on the OQPSK waveform before nonlinear amplification, not only is the adaptive equalizer able to equalize this signal, its spectral sidelobes are also reduced. Simulations are presented to confirm these results.
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Kuchler, Ryan J. "Comparison of channel equalization filtering techniquies in underwater acoustic communications." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FKuchler.pdf.
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Charalabopoulos, Grigorios. "Radial basis function neural networks for channel equalization and co-channel interference cancellation in OFDM." Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416116.
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Luschi, Carlo. "Probabilistic techniques for equalization of the mobile radio channel in the presence of co-channel interference." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/12489.
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This thesis studies the problem of soft-output equalization of the mobile radio channel in interference-limited environments, where it is often difficult to obtain an accurate statistical model of the (non-Gaussian) disturbance. The first part of the thesis proposes a new technique for single-channel MAP trellis equalization in the presence of multipath and non-Gaussian interference. The approach is based on the non-parametric estimation of the density function of the overall disturbance by means of kernel smoothing. The work considers the problem of density estimation with limited volume of data, and addresses the use of a whitening filter in the presence of coloured interference. As an application, simulation results are provided for the GSM system, showing a significant performance improvement with respect to the trellis equalizer based on the Gaussian assumption. The second part of the thesis considers the case of an antenna array receiver, and studies a simple method to derive the reliability information at the output of a deterministic decision-feedback least-squares space-time equalizer. Computer simulations for the Enhanced Data Rates for GSM Evolution (EDGE)/Enhanced General Packet Radio Service (EGPRS) system show that the receiver performance can be significantly improved by a soft-output calculation based on short-term statistics of the equalizer output error. The thesis also addresses the additional use of soft-decision feedback, which provides further robustness to the proposed soft-output equalizer. The study shows the relevance of probabilistic processing for robust equalization of the wireless channel in the presence of non-Gaussian interference, and emphasizes the advantages of strategies that do not rely on a statistical model of the disturbance.
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Deleu, Thibault. "Digital predistortion and equalization of the non-linear satellite communication channel." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209212.
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In satellite communications, non-linear interference is created by the non-linear power amplifier aboard the satellite. Even in the case of a memoryless power amplifier, the channel is a non-linear system with memory due to the presence of linear filters on ground and aboard the satellite. The non-linear interference degrades the system performance, especially when considering high-order modulations or in case of several signals being amplified by the same power amplifier. In this thesis, we have proposed algorithms at the transmitter and at the receiver to digitally compensate this interference. In particular, a new predistortion algorithm has been proposed, which significantly improves state-of-the-art algorithms. Since the complexity of this algorithm is an issue, low-complexity algorithms have also been proposed and achieve almost the same performance as the initial algorithm. We have also proposed joint predistortion and turbo-equalization algorithms to further improve the system performance. / En communications par satellite, de l’interférence non-linéaire est créée par l’amplificateur de puissance non-linéaire à bord du satellite. Même si l’amplificateur peut être considéré comme sans mémoire, le canal est malgré tout un système non-linéaire avec mémoire de par la présence de filtres linéaires au sol ou à bord du satellite. L'interférence non-linéaire dégrade les performances du système, en particulier lorsqu’on considère des modulations d’ordre élevé ou plusieurs signaux amplifiés par le même amplificateur de puissance. Dans cette thèse, nous avons proposé des algorithmes à l’émetteur et au récepteur pour compenser numériquement cette interférence. En particulier, nous avons proposé un nouvel algorithme de prédistorsion qui améliore de façon significative les algorithmes de l’état-de-l’art. La complexité de l’algorithme étant très élevée, nous avons proposé des algorithmes de plus faible complexité atteignant pratiquement les mêmes performances par rapport à l’algorithme initial. Nous avons aussi proposé des algorithmes de prédistorsion et d’égalisation conjointes, permettant d'atteindre des performances plus élevées qu'avec la prédistorsion seule.Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Kalla, Sai Chandra Kumari. "Neural networks for optical channel equalization in high speed communication systems." Master's thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/67796.
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La demande future de bande passante pour les données dépassera les capacités des systèmes de communication optique actuels, qui approchent de leurs limites en raison des limitations de la bande passante électrique des composants de l’émetteur. L’interférence intersymbole (ISI) due à cette limitation de bande est le principal facteur de dégradation pour atteindre des débits de données élevés. Dans ce mémoire, nous étudions plusieurs techniques de réseaux neuronaux (NN) pour combattre les limites physiques des composants de l’émetteur pilotés à des débits de données élevés et exploitant les formats de modulation avancés avec une détection cohérente. Notre objectif principal avec les NN comme égaliseurs de canaux ISI est de surmonter les limites des récepteurs optimaux conventionnels, en fournissant une complexité évolutive moindre et une solution quasi optimale. Nous proposons une nouvelle architecture bidirectionnelle profonde de mémoire à long terme (BiLSTM), qui est efficace pour atténuer les graves problèmes d’ISI causés par les composants à bande limitée. Pour la première fois, nous démontrons par simulation que notre BiLSTM profonde proposée atteint le même taux d’erreur sur les bits(TEB) qu’un estimateur de séquence à maximum de vraisemblance (MLSE) optimal pour la modulation MDPQ. Les NN étant des modèles pilotés par les données, leurs performances dépendent fortement de la qualité des données d’entrée. Nous démontrons comment les performances du BiLSTM profond réalisable se dégradent avec l’augmentation de l’ordre de modulation. Nous examinons également l’impact de la sévérité de l’ISI et de la longueur de la mémoire du canal sur les performances de la BiLSTM profonde. Nous étudions les performances de divers canaux synthétiques à bande limitée ainsi qu’un canal optique mesuré à 100 Gbaud en utilisant un modulateur photonique au silicium (SiP) de 35 GHz. La gravité ISI de ces canaux est quantifiée grâce à une nouvelle vue graphique des performances basée sur les écarts de performance de base entre les solutions optimales linéaires et non linéaires classiques. Aux ordres QAM supérieurs à la QPSK, nous quantifions l’écart de performance BiLSTM profond par rapport à la MLSE optimale à mesure que la sévérité ISI augmente. Alors qu’elle s’approche des performances optimales de la MLSE à 8QAM et 16QAM avec une pénalité, elle est capable de dépasser largement la solution optimale linéaire à 32QAM. Plus important encore, l’avantage de l’utilisation de modèles d’auto-apprentissage comme les NN est leur capacité à apprendre le canal pendant la formation, alors que la MLSE optimale nécessite des informations précises sur l’état du canal.The future demand for the data bandwidth will surpass the capabilities of current optical communication systems, which are approaching their limits due to the electrical bandwidth limitations of the transmitter components. Inter-symbol interference (ISI) due to this band limitation is the major degradation factor to achieve high data rates. In this thesis, we investigate several neural network (NN) techniques to combat the physical limits of the transmitter components driven at high data rates and exploiting the advanced modulation formats with coherent detection. Our main focus with NNs as ISI channel equalizers is to overcome the limitations of conventional optimal receivers, by providing lower scalable complexity and near optimal solution. We propose a novel deep bidirectional long short-term memory (BiLSTM) architecture, that is effective in mitigating severe ISI caused by bandlimited components. For the first time, we demonstrate via simulation that our proposed deep BiLSTM achieves the same bit error rate (BER) performance as an optimal maximum likelihood sequence estimator (MLSE) for QPSK modulation. The NNs being data-driven models, their performance acutely depends on input data quality. We demonstrate how the achievable deep BiLSTM performance degrades with the increase in modulation order. We also examine the impact of ISI severity and channel memory length on deep BiLSTM performance. We investigate the performances of various synthetic band-limited channels along with a measured optical channel at 100 Gbaud using a 35 GHz silicon photonic(SiP) modulator. The ISI severity of these channels is quantified with a new graphical view of performance based on the baseline performance gaps between conventional linear and nonlinear optimal solutions. At QAM orders above QPSK, we quantify deep BiLSTM performance deviation from the optimal MLSE as ISI severity increases. While deep BiLSTM approaches the optimal MLSE performance at 8QAM and 16QAM with a penalty, it is able to greatly surpass the linear optimal solution at 32QAM. More importantly, the advantage of using self learning models like NNs is their ability to learn the channel during the training, while the optimal MLSE requires accurate channel state information.
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Nguyen, Hoang. "The expectation-maximization Viterbi algorithm for blind channel identification and equalization /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Kho, Yau Hee. "MIMO Receiver Structures with Integrated Channel Estimation and Tracking." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/1264.
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This thesis looks at the problem of channel estimation and equalization in a multiple-input multiple-output (MIMO) dispersive fading environments. Two classes of MIMO receiver structure are proposed with integrated channel estimation and tracking. One is a symbol-by-symbol based receiver using a MIMO minimum mean square error (MMSE) decision feedback equalizer (DFE), and the other is a sequence-based receiver using a partitioned Viterbi algorithm (PVA) which approaches the performance of maximum likelihood sequence estimation (MLSE). A MIMO channel estimator capable of tracking the time and frequency selective channel impulse responses, known as the vector generalized recursive least squares (VGRLS) algorithm, is developed. It has comparable performance and a similar level of complexity as the optimum Kalman filter. However, it does not require any knowledge of the channel statistics to operate and as such it can be employed in a Rician fading channel readily. A reduced complexity form of the estimator, known as the vector generalized least mean squares (VGLMS) algorithm, is also developed. This is achieved by replacing the online recursive computation of the VGRLS algorithm's 'intermediate' Riccatti matrix with an offline pre-computed matrix. This reduces the complexity of the algorithm by an order of a magnitude, but at the expense of degraded performance. The estimators are integrated with the above-mentioned equalizers in a decision directed mode to form a receiver structure that can operate in continuously time-varying fading channels. Due to decision delays, the outputs from the equalizer are delayed and this then produces 'delayed' channel estimates. A simple polynomial-based channel prediction module is employed to provide up-to-date channel estimates required by the equalizers. However, simulation results show that the channel prediction module may be omitted for a very slowly fading channel where the channel responses do not vary much. In the case of the PVA- receiver, the zero-delay tentative decisions are used as feedback to the channel estimators with negligible loss.
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Kongara, Gayathri. "Space-Frequency Equalization in Broadband Single Carrier Systems." Thesis, University of Canterbury. Electrical and Computer engineering, 2009. http://hdl.handle.net/10092/4421.
Full textAbstract:
Broadband wireless access systems can be used to deliver a variety of high data
rate applications and services. Many of the channels being considered for such
applications exhibit multipath propagation coupled with large delay spreads. Cur-
rently, orthogonal frequency division multiplexing is employed in these channels
to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc-
tion with frequency-domain equalization (FDE) at the receiver has been shown to
be a practical alternate solution as it has lower peak to average power ratio and is
less sensitive to frequency offsets and phase noise compared to OFDM. The effect
of multipath propagation increases with increasing data rate for SC systems. This
leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca-
pacity of SC-broadband systems depends on their ability to accommodate multiple
signal transmissions in the same frequency band, which results in co-channel inter-
ference (CCI) when detecting the desired data stream. The effects of CCI and ISI
are more pronounced at high data rates. The objective of this research is to investi-
gate and a develop low-complexity frequency domain receiver architectures capable
of suppressing both CCI and ISI and employing practical channel estimation.
In this thesis, a linear and a non-linear receiver architecture are developed in the
frequency domain for use in highly dispersive channels employing multiple input
multiple output (MIMO) antennas. The linear receiver consists of parallel branches
each corresponding to a transmit data stream and implements linear equalization
and demodulation. Frequency domain joint CCI mitigation and ISI equalization is
implemented based on estimated channel parameters and is called space-frequency
Broadband wireless access systems can be used to deliver a variety of high data
rate applications and services. Many of the channels being considered for such
applications exhibit multipath propagation coupled with large delay spreads. Cur-
rently, orthogonal frequency division multiplexing is employed in these channels
to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc-
tion with frequency-domain equalization (FDE) at the receiver has been shown to
be a practical alternate solution as it has lower peak to average power ratio and is
less sensitive to frequency offsets and phase noise compared to OFDM. The effect
of multipath propagation increases with increasing data rate for SC systems. This
leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca-
pacity of SC-broadband systems depends on their ability to accommodate multiple
signal transmissions in the same frequency band, which results in co-channel inter-
ference (CCI) when detecting the desired data stream. The effects of CCI and ISI
are more pronounced at high data rates. The objective of this research is to investi-
gate and a develop low-complexity frequency domain receiver architectures capable
of suppressing both CCI and ISI and employing practical channel estimation.
In this thesis, a linear and a non-linear receiver architecture are developed in the
frequency domain for use in highly dispersive channels employing multiple input
multiple output (MIMO) antennas. The linear receiver consists of parallel branches
each corresponding to a transmit data stream and implements linear equalization
and demodulation. Frequency domain joint CCI mitigation and ISI equalization is
implemented based on estimated channel parameters and is called space-frequency
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Ketonen, J. (Johanna). "Equalization and channel estimation algorithms and implementations for cellular MIMO-OFDM downlink." Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789514298578.
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Abstract The aim of the thesis is to develop algorithms and architectures to meet the high data rate, low complexity requirements of the future mobile communication systems. Algorithms, architectures and implementations for detection, channel estimation and interference mitigation in the multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) receivers are presented. The performance-complexity trade-offs in different receiver algorithms are studied and the results can be utilized in receiver design as well as in system design. Implementation of detectors for spatial multiplexing systems is considered first. The linear minimum mean squared error (LMMSE) and the K-best list sphere detector (LSD) are compared to the successive interference cancellation (SIC) detector. The SIC algorithm was found to perform worse than the K-best LSD when the MIMO channels are highly correlated. The performance difference diminishes when the correlation decreases. With feedback to the transmitter, the performance difference is even smaller, but the full rank transmissions still require a more complex detector. A reconfigurable receiver, using a simple or a more complex detector as the channel conditions change, would achieve the best performance while consuming the least amount of power in the receiver. The use of decision directed (DD) channel estimation is also studied. The 3GPP long term evolution (LTE) based pilot structure is used as a benchmark. The performance and complexity of the pilot symbol based least-squares (LS) channel estimator, the minimum mean square error (MMSE) filter and the DD space-alternating generalized expectation-maximization (SAGE) algorithm are studied. DD channel estimation and MMSE filtering improve the performance with high user velocities, where the pilot symbol density is not sufficient. With DD channel estimation, the pilot overhead can be reduced without any performance degradation by transmitting data instead of pilot symbols. Suppression of co-channel interference in the MIMO-OFDM receiver is finally considered. The interference and noise spatial covariance matrix is used in data detection and channel estimation. Interference mitigation is applied for linear and nonlinear detectors. An algorithm to adapt the accuracy of the matrix decomposition and the use of interference suppression is proposed. The adaptive algorithm performs well in all interference scenarios and the power consumption of the receiver can be reducedTiivistelmä Tämän väitöskirjatyön tavoitteena on kehittää vastaanotinalgoritmeja ja -arkkitehtuureja, jotka toteuttavat tulevaisuuden langattomien tietoliikennejärjestelmien suuren datanopeuden ja pienen kompleksisuuden tavoitteet. Työssä esitellään algoritmeja, arkkitehtuureja ja toteutuksia ilmaisuun, kanavaestimointiin ja häiriönvaimennukseen monitulo-monilähtötekniikkaa (multiple-input multiple-output, MIMO) ja ortogonaalista taajuusjakokanavointia (orthogonal frequency division multiplexing, OFDM) yhdistäviin vastaanottimiin. Algoritmeista saatavaa suorituskykyhyötyä verrataan vaadittavaan toteutuksen monimutkaisuuteen. Työn tuloksia voidaan hyödyntää sekä vastaanotin- että järjestelmäsuunnittelussa. Lineaarista pienimmän keskineliövirheen (minimum mean square error, MMSE) ilmaisinta ja listapalloilmaisinta (list sphere detector, LSD) verrataan peräkkäiseen häiriönpoistoilmaisimeen (successive interference cancellation, SIC). SIC-ilmaisimella on huonompi suorituskyky kuin LSD-ilmaisimella radiokanavan ollessa korreloitunut. Korrelaation pienentyessä myös ilmaisimien suorituskykyero pienenee. Erot suorituskyvyissä ovat vähäisiä silloinkin, jos järjestelmässä on takaisinkytkentäkanava lähettimelle. Tällöinkin korkean signaali-kohinasuhteen olosuhteissa LSD-ilmaisimet mahdollistavat tilakanavoidun, suuren datanopeuden tiedonsiirron. Radiokanavan muuttuessa uudelleenkonfiguroitava vastaanotin toisi virransäästömahdollisuuden vaihtelemalla kompleksisen ja yksinkertaisen ilmaisimen välillä. Kanavaestimointialgoritmeja ja niiden toteutuksia vertaillaan käyttämällä lähtökohtana nykyisen mobiilin tiedonsiirtostandardin viitesignaalimallia. Tutkittavat algoritmit perustuvat pienimmän neliösumman (least squares, LS) ja pienimmän keskineliövirheen menetelmään, sekä päätöstakaisinkytkettyyn (decision directed, DD) kanavaestimointialgoritmiin. DD-kanavaestimaattori ja MMSE-suodatin parantavat vastaanottimen suorituskykyä korkeissa käyttäjän nopeuksissa, joissa viitesignaaleiden tiheys ei ole riittävä. DD-kanavaestimoinnilla datanopeutta voidaan nostaa viitesignaaleiden määrää laskemalla vaikuttamatta suorituskykyyn. Työssä tarkastellaan myös saman kanavan häiriön vaimennusta. Häiriöstä ja kohinasta koostuvaa kovarianssimatriisia käytetään ilmaisuun ja kanavaestimointiin. Työssä esitetään adaptiivinen algoritmi matriisihajoitelman tarkkuuden ja häiriön vaimennuksen säätämiseen. Algoritmi mahdollistaa hyvän suorituskyvyn kaikissa häiriötilanteissa vähentäen samalla virrankulutusta
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Baddour, Kareem Emile. "Analysis of optimum diversity combining and equalization for dispersive fading channel communications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/MQ36001.pdf.
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He, Shuangchi. "Doubly-selective channel estimation and equalization using superimposed training and expansion models." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/HE_SHUANGCHI_5.pdf.
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Zhuge, Qunbi. "Channel equalization and phase estimation for reduced-guard- interval CO-OFDM systems." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107851.
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Reduced-guard-interval (RGI) coherent optical (CO) orthogonal frequency-division multiplexing (OFDM) is a potential candidate for next generation 100G beyond optical transports, attributed to its advantages such as high spectral efficiency and high tolerance to optical channel impairments. First of all, we review the coherent optical systems with an emphasis on CO-OFDM systems as well as the optical channel impairments and the general digital signal processing techniques to combat them. This work focuses on the channel equalization and phase estimation of RGI CO-OFDM systems. We first propose a novel equalization scheme based on the equalization structure of RGI CO-OFDM to reduce the cyclic prefix overhead to zero. Then we show that intra-channel nonlinearities should be considered when designing the training symbols for channel estimation. Afterwards, we propose and analyze the phenomenon of dispersion-enhanced phase noise (DEPN) caused by the interaction between the laser phase noise and the chromatic dispersion in RGI CO-OFDM transmissions. DEPN induces a non-negligible performance degradation and limits the tolerant laser linewidth. However, it can be compensated by the grouped maximum-likelihood phase estimation proposed in this work.Le multiplexage à répartition en fréquence orthogonale (MRFO) optique à la détection cohérente avec intervalle à protection réduite (IPR) est un candidat potentiel pour la prochaine génération des systèmes de transport optique au-delà de 100G. Cette méthode démontre un rendement spectral élevé et une grande tolérance aux dégradations du canal optique. En premier lieu, nous présentons un bilan sur les systèmes optiques à la détection cohérente avec l'emphase sur MRFO, les dégradations du canal optique, et ainsi les techniques générales de traitement numérique du signal pour corriger ces dégradations. Ce travail se concentre sur l'égalisation du canal et l'estimation de phase des systèmes MRFO optique à la détection cohérente avec IPR. Nous commençons par proposer une nouvelle façon d'égalisation basée sur MRFO optique à la détection cohérente avec IPR pour réduire la marge de la préfixe cyclique à zéro. Ensuite, nous présentons que les non-linéarités intra-canal devrait être considérées pendant la conception des symboles de référence pour l'estimation du canal. Prochainement, nous proposons et analysons le phénomène du bruit de phase à la dispersion améliorée (BPDA) qui est causée par l'interaction entre le bruit de phase du laser and la dispersion chromatique dans les transmissions MRFO optique à la détection cohérente avec IPR. Le BPDA entraîne une dégradation de performance non-négligeable et limite la tolérances de la largeur spectrale du laser. Cependant, le BPDA peut être compensé par l'estimation de phase groupée à la vraisemblance maximum proposée dans ce travail.
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莊文仲. "channel equalization based on evolutionary algorithms." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/22621231007409904984.
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Li, zeyou, and 李則佑. "Applying PSO-SVM For Channel Equalization." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/21964865425522112791.
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碩士國立宜蘭大學
電機工程學系碩士班
100
The support vector machine (SVM) is a powerful tool for solving problems with high dimensional, nonlinearly, and is of excellent performance in classification. In this study, we propose SVM as channel equalization. To reconstruct the signal that has the inter symbol interference (ISI) and white Gaussian noise which in high speed communications environments. The SVM parameters will affect the identification of the result. Therefore, we use particle swarm optimization (PSO) to find the suit parameters in SVM. To obtain the channel equalization model and reconstruct the signal. The PSO-SVM equalizer to realize the Bayesian equalizer solution can be achieved efficiently. The performance degradation was nearly 1dB at SNR increased.
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Hsieh, Tsung-Da, and 謝宗達. "Channel Estimation and Equalization for OFDM Communication Systems." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/79163754713381504755.
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碩士樹德科技大學
電腦與通訊研究所
91
Following communication technology progress, from wired communication to wireless communication, in order to save the limited bandwidth resource, provide high quality communication service and resist frequency selective fading channel, OFDM technique is presented to solve many problems. There are a lot of interference exist in wireless channel. In order to enhance the system efficiency, a good channel estimator is necessary. In this thesis, we exploit pilot assisted channel estimation. Firstly, Pilot symbols are inserted into transmitted signal by periodic. In receiver, channel frequency response is obtained by utilizing least square method, and use interpolation method to get channel frequency response of subchannel and exact restore signal. In simulation, we make use of this method to traditional equalizer and compare efficiency which is presented by scholar of Won Gi Jeon , Kyung Hi Chang and Yong Soo Cho.
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Tsai, Wern-Fong, and 蔡文豐. "Adaptive Equalization for Fast Time-Varying Fading Channel." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/16180690768348297413.
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碩士國立中正大學
電機工程學系
86
Both symbol-by-symbol and sequence equalization of digital signaling on the time-varying multipath fading channels are investigated here. Two methods for symbol-by- symbol equalization, namely, Bayesian equalizer with decision feedback (Bayesian DFE)and Bayesian equalizer with recursive algorithm and one method for sequence equalization,namely, maximum likelihood sequence estimation(MLSE) equalizer have been considered inthis thesis. These equalizers in conjunction with an adaptive channel estimator consisting of a lest mean square(LMS) estimator are considered. In this thesis, we also consider a bi-directional adaptive equalization technique, which uses information in the adjacent time slot in a TDMA system and is able to estimate the location of a deep fade within a time slot, to improve the overall digital transmission systems performance over time varying land mobile radio channels.
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Yang, Hsiang-An, and 陽湘安. "Channel Estimation and Equalization for LTE Downlink System." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/98752110946449516179.
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碩士國立中央大學
通訊工程學系在職專班
104
This thesis introduces the orthogonal frequency division multiplexing technology、space frequency block code、LTE/LTE-A downlink system、spatial channel model、additive white gaussian noise、channel estimation and equalization，and reference to LTE/LTE-A downlink system specifications for channel estimation and equalization，compared the performance of different channel estimation techniques for different channels and different number of antennas。