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1
Senol, Sinan. "Performance Comparison Of Adaptive Decision Feedback Equalizer And Blind Decision Feedback Equalizer." Master's thesis, METU, 2004. http://etd.lib.metu.edu/upload/1023746/index.pdf.
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The Decision Feedback Equalizer (DFE) is a known method of channel equalization which has performance superiority over linear equalizer. The best performance of DFE is obtained, commonly, with training period which is used for initial acquisiton of channel or recovering changes in the channel. The training period requires a training sequence which reduces the bit transmission rate or is not possible to send in most of the situations. So, it is desirable to skip the training period. The Unsupervised (Blind) DFE (UDFE) is such a DFE scheme which has no training period. The UDFE has two modes of operation. In one mode, the UDFE uses Constant Modulus Algorithm (CMA) to perform channel acquisition, blindly. The other mode is the same as classical decision-directed DFE. This thesis compares the performances of the classical trained DFE method and the UDFE. The performance comparison is done in some channel environments with the problem of timing error present in the received data bearing signal. The computer aided simulations are done for two stationary channels, a time-varying channel and a frequency selective Rayleigh fading channel to test the performance of the relevant equalizers. The test results are evaluted according to mean square error (MSE), bit-error rate (BER), residual intersymbol interference (RISI) performances and equalizer output diagrams. The test results show that the UDFE has an equal or, sometimes, better performance compared to the trained DFE methods. The two modes of UDFE enable it to solve the absence of training sequence.
2
Wickert, Mark, Shaheen Samad, and Bryan Butler. "AN ADAPTIVE BASEBAND EQUALIZER FOR HIGH DATA RATE BANDLIMITED CHANNELS." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604050.
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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California<br>Many satellite payloads require wide-band channels for transmission of large amounts of data to users on the ground. These channels typically have substantial distortions, including bandlimiting distortions and high power amplifier (HPA) nonlinearities that cause substantial degradation of bit error rate performance compared to additive white Gaussian noise (AWGN) scenarios. An adaptive equalization algorithm has been selected as the solution to improving bit error rate performance in the presence of these channel distortions. This paper describes the design and implementation of an adaptive baseband equalizer (ABBE) utilizing the latest FPGA technology. Implementation of the design was arrived at by first constructing a high fidelity channel simulation model, which incorporates worst-case signal impairments over the entire data link. All of the modem digital signal processing functions, including multirate carrier and symbol synchronization, are modeled, in addition to the adaptive complex baseband equalizer. Different feedback and feed-forward tap combinations are considered as part of the design optimization.
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Brooks, Duncan John. "Adaptive algorithms for low complexity equalizers in mobile communications." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312445.
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Woodward, Graeme Kenneth. "Adaptive detection for DS-CDMA." Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27691.
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Adaptive techniques for detection of direct sequence code division multiple access (DS—CDMA) signals are
investigated. The goal is to improve CDMA system performance and capacity relative to conventional systems
by reducing interference between users. The techniques considered are adaptive versions of multiuser
receiver structures. Most multiuser receivers proposed to date suffer from overly high computational complexity
or impractical levels of assumed system knowledge. Adaptive techniques may be used to improve the
feasibility of certain classes of multiuser receivers. Receivers estimate system and environmental conditions
in lieu of having such knowledge a priori. Multiuser receiver structures are catalogued, concentrating on the
important class of minimum mean squared error (MMSE) receivers which are particularly suited to adaptive
implementation. A major limitation is their poor performance in non—stationary channel environments. One
motivation of this work is to explore ways to alleviate this. Transform domain techniques are considered as
an adjunct to current adaptive techniques and may be used for data pre—conditioning or complexity reduction
of receiver algorithms. Lattice structures are presented as a means of implementing such transforms. A combination
of time division multiple access and CDMA is investigated. This has the advantage of increasing the
CDMA chip rate while allowing smaller spreading gain. Improved tracking in fading channels and reduced
complexity filter structures result. This facilitates increased system capacity. The linear MMSE structure is
extended to non-linear decision feedback techniques. Under ideal conditions the multiuser MMSE decision
feedback filter is an ideal interference canceller. Its structure is amenable to adaptive implementation, for
which numerous algorithms are studied. Adaptive multiuser decision feedback structures are capable of
suppressing unknown sources of interference while simultaneously performing cancellation of known sources
of interference. Decision feedback is further extended to multistage multiuser decision feedback structures,
which are demonstrated to be capable of achieving greater increases in system capacity.
5
Xiaoqi, Han. "Nonlinear Equalization Based on Decision Feedback Equalizer for Optical Communication System." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1386170540.
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Nassr, Husam, and Kurt Kosbar. "PERFORMANCE EVALUATION FOR DECISION-FEEDBACK EQUALIZER WITH PARAMETER SELECTION ON UNDERWATER ACOUSTIC COMMUNICATION." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626999.
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This paper investigates the effect of parameter selection for the decision feedback equalization (DFE) on communication performance through a dispersive underwater acoustic wireless channel (UAWC). A DFE based on minimum mean-square error (MMSE-DFE) criterion has been employed in the implementation for evaluation purposes. The output from the MMSE-DFE is input to the decoder to estimate the transmitted bit sequence. The main goal of this experimental simulation is to determine the best selection, such that the reduction in the computational overload is achieved without altering the performance of the system, where the computational complexity can be reduced by selecting an equalizer with a proper length. The system performance is tested for BPSK, QPSK, 8PSK and 16QAM modulation and a simulation for the system is carried out for Proakis channel A and real underwater wireless acoustic channel estimated during SPACE08 measurements to verify the selection.
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Chandramouli, Soumya. "A Novel Analog Decision-Feedback Equalizer in CMOS for Serial 10-Gb/sec Data Transmission Systems." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19847.
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This dissertation develops an unclocked receiver analog decision-feedback equalizer (ADFE) circuit architecture and topology and implements the circuit in 0.18-um CMOS to enable 10-Gb/sec serial baseband data transmission over FR-4 backplane and optical fibre. The ADFE overcomes the first feedback-loop latency challenge of traditional digital and mixed-signal DFEs by separating data re-timing from equalization and also eliminates the need for clock-recovery prior to decision-feedback equalization.
The ADFE enables 10-Gb/sec decision-feedback equalization using a 0.18-um CMOS process, the first to do so to the author s knowledge. A tuneable current-mode-logic (CML) feedback-loop is designed to enable first post-cursor cancellation for a range of data-rates and to have external control over loop latency over variations in process, voltage and temperature. CML design techniques are used to minimize current consumption and achieve the required voltage swing for decision-feedback to take place. The all-analog equalizer consumes less power and area than comparable state-of-the art DFEs.
The ADFE is used to compensate inter-symbol interference (ISI) for 20 inches of FR-4 backplane and 300 m of multi-mode fibre at 10-Gb/sec. The ADFE also extends the reach of single-mode fibre at 10-Gb/sec to 120 km. The work described in this dissertation advances the state-of-the-art in equalization solutions for multi-Gb/sec serial data transmission and can find applications in several of the 10-Gb/sec Ethernet standards that have been approved recently. The contributions of this work toward future research are also discussed.
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Michaelides, John Frixou. "Nonlinear adaptive filtering for echo cancellation and decision feedback equalization." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66261.
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Adnan, Rubyet. "Blind Equalization for Tomlinson-Harashima Precoded Systems." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1130.
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At a communications receiver the observed signal is a corrupted version of the transmitted signal. This distortion in the received signal is due to the physical characteristics of the channel, including multipath propagation, the non-idealities of copper wires and impulse noise. Equalization is a process to combat these distortions in order to recover the original transmitted signal. Roughly stated, the equalizer tries to implement the inverse transfer function of the channel while taking into account the channel noise. The equalizer parameters can be tuned to this inverse transfer function using an adaptive algorithm. In many cases, the algorithm uses a training sequence to drive the equalizer parameters to the optimum solution. But, for time-varying channels or multiuser channels the use of a training sequence is inefficient in terms of bandwidth, as bandwidth is wasted due to the periodic re-transmission of the training sequence. A blind equalization algorithm is a practical method to eliminate this training sequence. An equalizer adapted using a blind algorithm is a key component of a bandwidth efficient receiver for broadcast and point-to-multipoint communications. The initial convergence performance of a blind adaptive equalizer depends on the higher-order statistics of the transmitted signal. In modern digital systems, Tomlinson-Harashima precoding (THP) is often used for signal shaping and to mitigate the error propagation problem of a decision feedback equalizer (DFE). The concept of THP comes from pre-equalization. In fact, it is a nonlinear form of pre-equalization, which bounds the higher-order statistics of the transmitted signal. But, THP and blind equalization are often viewed as incompatible equalization techniques. In this research, we give multiple scenarios where blind equalization of a THP-encoded signal might arise. With this motivation we set out to answer the question, can a blind equalizer successfully acquire a THP-encoded signal? We investigate the combination of a Tomlinson-Harashima precoder on the transmitter side and a blind equalizer on the receiver side. By bounding the kurtosis of the THP-encoded signal, we show that THP actually aids the initial convergence of blind equalization. We find that, as the symbol constellation size increases, the THP-encoded signal kurtosis approaches that of a uniform distribution, not a Gaussian. We investigate the compatibility of blind equalization with THP-encoded signals for both SISO and MIMO systems. In a SISO system, conventional blind algorithms can be used to counter the distortions introduced in the received signal. However, in a MIMO system with multiple users, the other users act as interferers on the desired user's signal. Hence, modified blind algorithms need to be applied to mitigate these interferers. For both SISO and MIMO systems, we show that the THP encoder ensures that the signal distribution approaches a non-Gaussian distribution. Using Monte Carlo simulations, we study the effects of Tomlinson-Harashima precoding on the performance of Bussgang-type blind algorithms and verify our theoretical analysis. The major contributions of this thesis are: • A demonstration that a blind equalizer can successfully acquire a THP-encoded signal for both SISO and MIMO systems. We show that THP actually aids blind equalization, as it ensures that the transmitted signal is non-Gaussian. • An analytical quantification of the effects of THP on the transmitted signal statistics. We derive a novel bound on the kurtosis of the THP-encoded signal. • An extension of the results from a single-user SISO scenario to multiple users and a MIMO scenario. We demonstrate that our bound and simulated results hold for these more general cases. Through our work, we have opened the way for a novel application of training sequence-less equalization: to acquire and equalize THP-encoded signals. Using our proposed system, periodic training sequences for a broadcast or point-to-multipoint system can be avoided, improving the bandwidth efficiency of the transceiver. Future modem designs with THP encoding can make use of our advances for bandwidth efficient communication systems.
10
Liu, Yizhou. "ELECTRICAL EQUALIZATION FOR MULTIMODE FIBER SYSTEMS." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1484004535118825.
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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).
12
Ziebart, Brian D. "Modeling Purposeful Adaptive Behavior with the Principle of Maximum Causal Entropy." Research Showcase @ CMU, 2010. http://repository.cmu.edu/dissertations/17.
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Predicting human behavior from a small amount of training examples is a challenging machine learning problem. In this thesis, we introduce the principle of maximum causal entropy, a general technique for applying information theory to decision-theoretic, game-theoretic, and control settings where relevant information is sequentially revealed over time. This approach guarantees decision-theoretic performance by matching purposeful measures of behavior (Abbeel & Ng, 2004), and/or enforces game-theoretic rationality constraints (Aumann, 1974), while otherwise being as uncertain as possible, which minimizes worst-case predictive log-loss (Gr¨unwald & Dawid, 2003).
We derive probabilistic models for decision, control, and multi-player game settings using this approach. We then develop corresponding algorithms for efficient inference that include relaxations of the Bellman equation (Bellman, 1957), and simple learning algorithms based on convex optimization. We apply the models and algorithms to a number of behavior prediction tasks. Specifically, we present empirical evaluations of the approach in the domains of vehicle route preference modeling using over 100,000 miles of collected taxi driving data, pedestrian motion modeling from weeks of indoor movement data, and robust prediction of game play in stochastic multi-player games.
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Gunning, Dan, and Pontus Jernberg. "Estimation of Inter-Cell Interference in 3G Communication Systems." Thesis, Linköpings universitet, Reglerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-71156.
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In this thesis the telecommunication problem known as inter-cell interference is examined. Inter-cell interference originates from users in neighboring cells and affects the users in the own cell. The reason that inter-cell interference is interesting to study is that it affects the maximum data-rates achievable in the 3G network. By knowing the inter-cell interference, higher data-rates can be scheduled without risking cell-instability. An expression for the coupling between cells is derived using basic physical principles. Using the expression for the coupling factors a nonlinear model describing the inter-cell interference is developed from the model of the power control loop commonly used in the base stations. The expression describing the coupling factors depends on the positions of users which are unknown. A quasi decentralized method for estimating the coupling factors using measurements of the total interference power is presented. The estimation results presented in this thesis could probably be improved by using a more advanced nonlinear filter, such as a particle filter or an Extended Kalman filter, for the estimation. Different expressions describing the coupling factors could also be considered to improve the result.
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Deyneka, Alexander. "Metody ekvalizace v digitálních komunikačních systémech." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-218963.
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Tato práce je psaná v angličtině a je zaměřená na problematiku ekvalizace v digitálních komunikačních systémech. Teoretická část zahrnuje stručné pozorování různých způsobů návrhu ekvalizérů. Praktická část se zabývá implementací nejčastěji používaných ekvalizérů a s jejich adaptačními algoritmy. Cílem praktické části je porovnat jejich charakteristiky a odhalit činitele, které ovlivňují kvalitu ekvalizace. V rámci problematiky ekvalizace jsou prozkoumány tři typy ekvalizérů. Lineární ekvalizér, ekvalizér se zpětnou vazbou a ML (Maximum likelihood) ekvalizér. Každý ekvalizér byl testován na modelu, který simuloval reálnou přenosovou soustavu s komplexním zkreslením, která je složena z útlumu, mezisymbolové interference a aditivního šumu. Na základě implenentace byli určeny charakteristiky ekvalizérů a stanoveno že optimální výkon má ML ekvalizér. Adaptační algoritmy hrají významnou roli ve výkonnosti všech zmíněných ekvalizérů. V práci je nastudována skupina stochastických algoritmů jako algoritmus nejmenších čtverců(LMS), Normalizovaný LMS, Variable step-size LMS a algoritmus RLS jako zástupce deterministického přístupu. Bylo zjištěno, že RLS konverguje mnohem rychleji, než algoritmy založené na LMS. Byly nastudovány činitele, které ovlivnili výkon popisovaných algoritmů. Jedním z důležitých činitelů, který ovlivňuje rychlost konvergence a stabilitu algoritmů LMS je parametr velikosti kroku. Dalším velmi důležitým faktorem je výběr trénovací sekvence. Bylo zjištěno, že velkou nevýhodou algoritmů založených na LMS v porovnání s RLS algoritmy je, že kvalita ekvalizace je velmi závislá na spektrální výkonové hustotě a a trénovací sekvenci.
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Mendes, Filho João. "Sobre equalizadores autodidatas de decisão realimentada aplicados a sistemas multiusuário." Universidade Presbiteriana Mackenzie, 2007. http://tede.mackenzie.br/jspui/handle/tede/1450.
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Previous issue date: 2007-01-24<br>Fundo Mackenzie de Pesquisa<br>Due to the growing demand for mobile communications, adaptive equalizers play an important role for enhancing the efficiency of data transmission. In this scenario, the Decision Feedback Equalizer (DFE) stands out. It presents a favorable tradeoff between computational cost and efficient behavior, mainly when compared to Linear Transversal Equalizer. In this work, the blind adaptation of DFE is investigated for the single and multiuser cases. In the single user case, the perfect equalization conditions for the DFE are revisited, considering the absence of noise and feedback of correct decisions. Assuming the joint blind adaptation of the DFE's feedforward and feedback filters, two stochastic gradient algorithms are also revisited. The first is based on the Constant Modulus cost function, subjected to a constraint to avoid degenerate solutions. The second considers the minimization of a cost function that takes into account the probability density function of the equalizers's output. This latter, known in the literature as the Soft Decision-Directed (SDD) algorithm, was proposed for the recovery of signals based on the Quadrature Amplitude Modulation (QAM). From the division of the complex plane into regions containing 4-QAM type constellations, we propose a modification in the SDD algorithm based on the centers of these regions. The resulting algorithm presents a more favorable tradeoff between convergence rate and computational cost. Moreover, in order to mitigate the steady-state mean-square error, we consider concurrent algorithms based on the previous mentioned. As a core of this dissertation, the perfect equalization conditions and the remarked algorithms are extended to the multiuser case. Simulation results point out that the Modified SDD algorithm and its concurrent adaptation with the constrained Constant Modulus Algorithm present advantages in terms of convergence rate for the blind adaptation of DFE in the recovering of QAM signals.<br>Devido à crescente demanda por comunicações móveis, equalizadores adaptativos autodidatas desempenham um importante papel na melhoria da eficiência da transmissão de dados. Nesse cenário, destaca-se o equalizador de decisão realimentada (DFE - Decision Feedback Equalizer), que apresenta um compromisso favorável entre custo computacional e comportamento eficiente, principalmente quando comparado ao equalizador linear transversal. Neste trabalho, a adaptação autodidata do DFE é investigada tanto no caso mono quanto no multiusuário. Considerando o caso monousuário, revisitam-se as condições de equalização perfeita com o DFE, assumindo realimentação de decisões corretas e ausência de ruído. Revisitam-se também dois algoritmos do gradiente estocástico para adaptação autodidata conjunta dos filtros direto e de realimentação do DFE. O primeiro é baseado na função custo do Módulo Constante com uma restrição imposta, a fim de se evitar soluções degeneradas. O segundo considera a minimização de uma função custo que leva em conta a função densidade de probabilidade do sinal de saída do equalizador. Este último, conhecido na literatura como algoritmo de Decisão Direta Suave (SDD - Soft Decision-Directed), foi proposto para recuperação de sinais com modulação do tipo QAM (Quadrature Amplitude Modulation). A partir da divisão do espaço complexo em regiões contendo constelações do tipo 4-QAM, é proposta uma modificação ao algoritmo SDD baseada nos centros dessas regiões. O algoritmo resultante apresenta uma relação mais favorável entre velocidade de convergência e complexidade computacional. Ainda com o intuito de mitigar o erro quadrático resultante da adaptação autodidata, considera-se a utilização de algoritmos concorrentes baseados nos algoritmos supracitados. Como cerne desta dissertação, as condições de equalização perfeita e os algoritmos abordados são estendidos para o caso multiusuário. Resultados de simulações evidenciam que o algoritmo SDD modificado e sua adaptação concorrente com o algoritmo do Módulo Constante com restrição apresentam vantagens em termos de velocidade de convergência para adaptação autodidata do DFE na recuperação de sinais do tipo QAM.
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McLucas, Alan Charles Civil Engineering Australian Defence Force Academy UNSW. "An investigation into the integration of qualitative and quantitative techniques for addressing systemic complexity in the context of organisational strategic decision-making." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Civil Engineering, 2001. http://handle.unsw.edu.au/1959.4/38744.
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System dynamics modelling has been used for around 40 years to address complex, systemic, dynamic problems, those often described as wicked. But, system dynamics modelling is not an exact science and arguments about the most suitable techniques to use in which circumstances, continues. The nature of these wicked problems is investigated through a series of case studies where poor situational awareness among stakeholders was identified. This was found to be an underlying cause for management failure, suggesting need for better ways of recognising and managing wicked problem situations. Human cognition is considered both as a limitation and enabler to decision-making in wicked problem environments. Naturalistic and deliberate decision-making are reviewed. The thesis identifies the need for integration of qualitative and quantitative techniques. Case study results and a review of the literature led to identification of a set of principles of method to be applied in an integrated framework, the aim being to develop an improved way of addressing wicked problems. These principles were applied to a series of cases in an action research setting. However, organisational and political barriers were encountered. This limited the exploitation and investigation of cases to varying degrees. In response to a need identified in the literature review and the case studies, a tool is designed to facilitate analysis of multi-factorial, non-linear causality. This unique tool and its use to assist in problem conceptualisation, and as an aid to testing alternate strategies, are demonstrated. Further investigation is needed in relation to the veracity of combining causal influences using this tool and system dynamics, broadly. System dynamics modelling was found to have utility needed to support analysis of wicked problems. However, failure in a particular modelling project occurred when it was found necessary to rely on human judgement in estimating values to be input into the models. This was found to be problematic and unacceptably risky for sponsors of the modelling effort. Finally, this work has also identified that further study is required into: the use of human judgement in decision-making and the validity of system dynamics models that rely on the quantification of human judgement.
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Chen, Kuan-Yu, and 陳冠宇. "Design of 20Gbps Adaptive Linear Equalizer and Decision Feedback Equalizer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/rc2864.
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碩士<br>國立臺灣大學<br>電子工程學研究所<br>105<br>Nowadays, the SerDes (Serializer-to-Deserializer) topology is increasingly popular in the wireline communication systems for the reduced I/O pads and also the low fabrication cost. However, the aggregate bandwidth of the data traffic is strictly limited by the channel characteristics. The limited bandwidth of the channel will induce large inter-symbol interference (ISI), and also deteriorate the bit-error-rate (BER) performance. Thus, the equalization is more and more important in the wireline systems. Moreover, the channel attenuation greatly varies with materials and lengths, and hence the adaptation techniques for the equalizer are required in most applications.
In this thesis, the most common equalizers in the receiver are designed, analyzed, and verified. The first part shows a 20Gbps linear equalizer with the proposed adaptation method. Fabricated in 40nm CMOS technology, this adaptive linear equalizer can well compensate the channel loss under 18.3dB attenuation. Only 2.68us is required for the adaptation procedure and 4.9mW is consumed by the adaptation logics.
The second part presents a 20Gbps infinite impulse response decision feedback equalizer (IIR-DFE). To enhance the power efficiency of the IIR-DFE, the charge-steering logic (CSL) is utilized in this work. Besides, the quarter-rate topology and some circuit merging techniques are adopted. Fabricated in 40nm CMOS technology, the power efficiency of 0.31mW/Gbps can be obtained.
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Liao, Sheng-Hui, and 廖盛惠. "Soft Decision Approaches for Blind Adaptive Decision Feedback Equalizer." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/60781162149955816270.
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碩士<br>國立臺灣海洋大學<br>電機工程學系<br>93<br>Because of multi-path and Doppler effect, the development of the underwater acoustic communication system is a challenging task. The optimum equalization and appropriate signal processing technique are needed to improve the quality of communications.
In this thesis, the implementation algorithms based on the blind adaptive decision feedback equalization (BADFE), whose function can be automatically adjusted according to variations of channel, are investigated. The soft decision is combined with the BADFE to get a modified equalization scheme. The proposed method combines decision feedback, blind adaptive scheme, and the soft decision method at the same time. Therefore it can combat the distortion occurred
in underwater communication channels without the need of the training sequence. The bit error rates and the transmission efficiency are improved. Computer simulation results indicate that the performances of the proposed method always has better convergence speed and lower bit error rate even in the bad channel and low SNR.
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Lin, Yuan-Fu, and 林元莆. "5~20 Gb/s Adaptive Linear Equalizer and Decision-Feedback Equalizer." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13812443680406086957.
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碩士<br>國立臺灣大學<br>電子工程學研究所<br>102<br>In recent years, in addition to the fast growing in data rate, wide-range data is also required in the applications of various multimedias and portable devices. As the data rate keeps rising, many significant problems appear. One is that the bandwidth is limited compared to the data rate. It will result a significant inter symbol interference (ISI) to degrade the bit error rate (BER). In order to deal with ISI, equalizers are widely adopted. However, the length or the material of the communication channel may be different depending on the application. Therefore, an adaptive algorithm with the equalizer is more popular in recent communication systems. In wide-range data rate application, power efficiency issue is also concerned.
This thesis is mainly divided into two parts. In Chapter 2, a 5-20 Gb/s power scalable adaptive continuous-time linear equalizer (CTLE) architecture is proposed. We use a power scalable technique to improve the power efficiency for slow data rate. We also propose an adaptive algorithm using edge counting. This circuit is implemented in 40-nm CMOS process.
A 5-20 Gb/s adaptive charge-steering decision-feedback equalizer (DFE) is presented in chapter 3. To lower power consumption of the system, charge-steering logic circuit is adopted in this design. We use sign-sign least mean square (SSLMS) algorithm to adjust the DFE’s taps adaptively. This circuit is implemented in 40-nm CMOS process.
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SHI, JUN-DIAN, and 施君典. "Adaptive decision feedback equalizer for tdma mobile radio receiver." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/97955454574045569248.
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Chen, Nancy Fang-Yih. "High-Performance Adaptive Decision Feedback Equalizer Designs for Ethernet Systems." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1307200416371500.
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李智偉. "Improvements in convergence of the blind adaptive decision feedback equalizer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/71009722495584364480.
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碩士<br>國立海洋大學<br>電機工程學系<br>90<br>In the field of underwater acoustic communications, digital communications systems generally use binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) signaling. The multipath effects and Doppler frequency shift can be overcome by an adaptive trained decision feedback equalizer (DFE). Unfortunately, the trained DFE is inefficient, unless it is periodically retrained, for digital communications through a water channel. But it will reduce effective capacity.
The blind adaptive decision feedback equalization (BADFE) exhibits good convergence rate and symbol-error rate (SER) as the conventional trained decision feedback equalizer (DFE) does, but it requires no training. In this thesis, a new method for BADFE is discussed. An recursive-least-square (RLS) algorithm is employed for updating the parameters of the recursive whitening filter in BADFE during the starting period, and the revised structure is called BADFE(RLS). BADFE(RLS) can speed up the convergence rate and get better tracking capabilities. This will improve the quality of communication and increase the capacity.
Because of the advantages of the reliable, programmable and model of the DSP system, we complier the BADFE program based on TMS320C6711 DSK. The testing system uses a QPSK modulation with 12 kbps data rate and the carrier frequency is 36 kHz.
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Chen, Nancy Fang-Yih, and 陳方玉. "High-Performance Adaptive Decision Feedback Equalizer Designs for Ethernet Systems." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/w56wtg.
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碩士<br>國立臺灣大學<br>電子工程學研究所<br>92<br>As the applications and prevalence of the world wide web (WWW) flourish over the past decade, the demand for higher bandwidth and data rate is skyrocketing. In August 2002, the IEEE 802.3ae task force finalized the 10-Gigabit Base LX4 Ethernet Standard. However, under multi-gigabit data rates, fiber is no longer an ideal transmission medium. This is especially the case for multi-mode fiber (MMF) used in 10G Base LX4 Ethernet systems, because it suffers from differential mode dispersion (DMD). However, conventional adaptive decision feedback equalizers (ADFE) cannot attain the bit error rate (BER) requirement of 10-12 in 10G Base LX4 Ethernet systems, because hard decision of slicers causes error propagation in the feedback loop. Soft threshold multi-layer adaptive decision feedback equalizer (STM-ADFE) designs are adopted to solve this problem. Our system simulation environment includes three representative channel impulses responses, trans-impedance amplifier (TIA), analog equalizer (AEQ), analog/digital converter (ADC), and STM-ADFE. Integration with the analog front end reduces the filter tap numbers needed in STM-ADFE. VLSI architectures of STM-ADFE are also presented. With low hardware overhead, STM-ADFE not only lowers the BER, but also reduces the bit resolution needed in the ADC from 8 to 6.
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Xiang, Yihai. "Design of high-speed adaptive parallel multi-level decision feedback equalizer." Thesis, 1997. http://hdl.handle.net/1957/34362.
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Multi-level decision feedback equalization (MDFE) is an effective technique to remove inter-symbol interference (ISI) from disk readback signals, which uses the simple architecture of decision feedback equalization. Parallelism which doubles the symbol rate can be realized by setting the first tap of the feedback filter to zero.
A mixed-signal implementation has been chosen for the parallel MDFE, in which coefficients for the 9-tap feedback filter are adapted in the digital domain by 10-bit up/ down counters; 6-bit current mode D/A converters are used to convert digital coefficients to differential current signals which are summed with the forward equalizer (FE) output, and a flash A/D is used to make decisions and generate error signals for adaptation.
In this thesis, a description of the parallel structure and the adaptation algorithm are presented with behavioral level verification. The circuit design and layout were carried out in HP 1.2um n-well CMOS process. The design of the high-speed counter and the current-mode D/A are discussed. HSPICE simulations show that a symbol rate of 100Mb/s for the feedback equalizer is readily achieved.<br>Graduation date: 1997
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Yang, Meng-Da, and 楊孟達. "Efficient VLSI Design of Adaptive Decision Feedback Equalizer for Gigabit Ethernet." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/61001349691646492395.
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碩士<br>國立臺灣大學<br>電機工程學研究所<br>90<br>Abstract
The IEEE 802.3ab task force finalizes the 1000-BASE-T standard, which increases the data rate even further to 1Gb/s for copper wiring over distances of 100m minimum[1]-[3]. 1000-BASE-T employs full duplex baseband transmission over four pair of Category 5 cabling. In order to achieve a target bit error rate (BER) of less than , the receiver corresponding to a wire pair must operate under the sever channel impairment such as the Intersymbol Interference (ISI), echo, Near-end Cross Talk(NEXT), and Far-end Cross Talk(FEXT). Hence, the DSP techniques can be applied to overcome the above problems. For example, the adaptive equalizer, the adaptive echo and NEXT cancellers can be employed to compensate the ISI, Echo, and NEXT, respectively. Moreover, the Trellis-coded Modulation (TCM) is also applied to improve the noise margin. The Decision Feedback Equalizer (ADFE) is employed to compensate the ISI here. In this thesis, we will focus on the VLSI design of ADFE. Here, we will propose two VLSI design of ADFE. In the one design of ADFE we will design a low-cost/low-power ADFE for 1000BASE-T and 100BASE-T applications by various techniques from the system level, the architecture level and the circuit level. In the another design of the ADFE, we will apply our proposed Predicted Parallel Branch Slicer scheme to design a high-performance/high-throughput rate pipelined ADFE. Finally, we will implement these two designs of the ADFE by the Avanti standard cell library in order to verify our VLSI design of the ADFE.
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Lin, Yu-Chun, and 林育羣. "High Throughput Concurrent Adaptive Decision Feedback Equalizer for 2-PAM Systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/43751081341932125009.
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博士<br>國立中央大學<br>電機工程學系<br>101<br>Adaptive Decision Feedback Equalizers (ADFEs) are widely used to reduce the inter-symbol interferences (ISIs) caused by channels in communication systems since ADFEs are better than Adaptive Linear Equalizers (ALEs) in both signal-to-noise ratio (SNR) and hardware complexity points of views. However, the data rate of an ADFE is limited due to the feedback path in both the coefficients update part and the data equalization part. In theorem, to do lookahead and then parallel can eliminate the limitation of data rate and the data lookahead scheme is usually used. Data lookahead scheme requires calculating all-possible results; hence the hardware complexity grows quickly with the parallelism and the tap-number of the ADFE.
In this dissertation, we propose the coefficients-lookahead scheme for the ADFEs in the receivers of 2-level Pulse Amplitude Modulation (2-PAM) systems, that is, to find out the coefficients for lookahead scheme. Based on the coefficients-lookahead scheme, the self-lookahead filter and the high speed architecture are proposed. The proposed architecture has almost the same SNR with conventional ADFE and has hardware complexity growing slowly with parallelism. In coefficients adaption, we propose a slow updating method, Batch Mode Coefficients Update (BMCU) algorithm to fit the requirement for channel tracking and high data rate. Besides, to avoid noise enhancement at the feed-forward filter (FFF), a FFF noise-suppression ADFE (FNS-ADFE) architecture is proposed which has 2 dB better SNR or 1% less bit error rate than that of a conventional ADFE.
The test-chip has been fabricated in a 40nm CMOS-GP technology with the core size as 275 μm × 275 μm (or 28.5k equivalent gates count), and dissipates 2.3 pJ/ bit at 10 Gbps with low-supply voltage (0.75 V), 3.5 pJ/bit at 13 Gbps with normal-supply voltage (0.9 V) and 5.8 pJ/bit at 16 Gbps with high-supply voltage (1.2 V).
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Lin, Chi-Shiung, and 林志雄. "Design and Implementation of Multi-Giga Bit Parallel Adaptive Decision Feedback Equalizer." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/36653261716961171331.
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碩士<br>國立中央大學<br>電機工程研究所<br>94<br>Internet and data transmission technique are going to grow fast, the trend of recent Ethernet system will make a high effort to provide high data rate services. According to the related standard about high speed wire-lined communication system, the data rate is more than gigabits per second, even several gigabits per second.
Hence, for the high transmitted data rate, the Inter-Symbol Interference (ISI) effect always exists, and it is serious and dominant for the signal distortion. The design of Adaptive Decision Feedback Equalizer (ADFE) is very important because it determines the system performance, such as Bit Error Rate (BER) and data rate. The computation cost of ADFE is also large for hardware implementation.
The conventional ADFE and the Least-Mean-Square (LMS) algorithm inherently have feedback inside the data flow and the operating frequency is limited by the feedback structures. The internal feedback or recursive in the architecture algorithms makes it difficult to implement systems concurrency in the form of either pipelined or paralleled processing. This thesis provides a high speed equalizer design, and it is suitable for the 10GBase-LX4 Ethernet system in IEEE 802.3ae standard (IEEE 802.3ae Ad-hoc database). We design and implement an all digital 3.5Gbps blind ADFE based on the TSMC 0.13 μm CMOS technology. The implementation shows that the chip area is 1.55 × 1.55 mm2 with operation up to 3.5 Gbps using 1.2-V supply and dissipates 110 mW.
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Tu, Chi-Chieh, and 杜啟傑. "Design and Analysis of an Adaptive Decision Feedback Recurrent Neural Network Equalizer." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/94017234188494698959.
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碩士<br>國立雲林科技大學<br>電機工程系碩士班<br>101<br>The goal of this thesis is mainly focused on the analysis and design of a decision feedback recursive neural network (DFRNN) equalizer for communications over nonlinear channels. We have proposed a recursive formula for the DFRNN real-time recurrent learning (RTRL) algorithm. The equalizer is applied to and verified by a binary transmission system. System performance is majorly compared with those of two commonly used architectures, that is, the recurrent neural network (RNN) and DFRNN with least mean square (LMS) algorithm. Although it requires slightly larger amount of computations, DFRNN(RTRL) exhibits faster speed of convergence and lower bit error rate (BER) than DFRNN(LMS) and RNN. Simulation results show that, for a BER of 10-4, DFRNN(RTRL) is about 2 dB better than DFRNN(LMS) under a severe intersymbol interference (ISI) environment. While in such a harsh environment, RNN presents a totally intolerable performance.
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Wang, Bor-Ming, and 王博民. "Dynamic Power-Saving Adaptive Decision Feedback Equalizer Design for High-Speed Communication Systems." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/65828061187282662550.
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碩士<br>國立臺灣大學<br>電子工程學研究所<br>91<br>In this thesis, we design a high-speed Adaptive Decision Feedback Equalizer (ADFE) with dynamic power saving mechanism. Our target is to provide ADFE architectures for high-speed communication systems.
We propose two high-speed ADFE architectures named Type-I and Type-II Partial Unrolled Pipelined ADFE (PUP-ADFE) respectively in Chapter 4 . Furthermore, we also propose a dynamic power saving strategy for ADFE design in Chapter 5 .
All the ideas are verified from algorithm to physical implementation. Finally, we list our implementation results to show the achievements of our design.
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Ng, Chee-Kit, and 吳智傑. "A 50Gb/s 115mW All-Digital Adaptive Decision Feedback Equalizer with Noise-Suppression Filter." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/23ej26.
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碩士<br>國立交通大學<br>電機資訊國際學程<br>102<br>Next generation wire-line communication system operate at multi-Gbps data rates becomes more demanding, the need for high-speed low power equalizers that can compensate on highly dispersive channels loss significantly increases. Adaptive Decision Feedback Equalizers (ADFEs) are widely used due to its superior performance to reduce the inter-symbol interferences (ISIs) caused by channels in communication systems and provide high signal-to-noise ratio (SNR). However, the data throughput rate of ADFEs is limited due to the feedback loops in the coefficients update part and data equalization part. Therefore, Noise-Suppression Extended Incremental Coefficients-Lookahead ADFEs (NS-EICL ADFEs) has been proposed.
NS-EICL ADFEs uses the coefficients-lookahead scheme followed by parallelism to eliminate the limitation of data rate. Based on the coefficients-lookahead scheme, a high-throughput self-lookahead filter, and extended filter (feedback filter) are realized. Together with the slow update rate Batch Mode Coefficients Update (BMCU) unit and Noise-Suppression Filters (NSFs), an unlimited data rate and better output SNR ADFE is achieved. However, the number of delay elements grows quickly in the feedback loop with high parallelism of the ADFEs. Therefore, the hardware area and power are increased.
In this dissertation, we propose a Dual Data-paths Self-Lookahead Filters (DD-SLFs) which is the modified version of previous SLFs design and is named (Dual Data-paths NS-EICL ADFE). DD-SLFs architecture have better energy efficiency and hardware area than SLFs architecture due to the number of delay elements in the feedback loop reduced. Based on the DD-SLFs architecture, two set of extended filters are used to determine the tentative decision data. Therefore, DD-SLFs have no performance degradation as is compared to SLFs architecture. Furthermore, gated clock technique with the design idea of register file architecture is used to replace pipelined delay elements to save power. Besides, in order to achieve an optimal energy efficiency ADFEs, an intelligent SNR-power management skill is proposed to optimize the overall power usages with required performance.
Two test chips have been fabricated in 40 nm CMOS GP technology process and operates at 1 GHz system clock rate. The measurement result verify that with a 40 parallelism factor, 40 Gbps NS-EICL ADFE with core size 500 µm x 500 µm (or 292.5k equivalent gates count), and dissipates 3.75 pJ/bit at 40 Gbps with low-supply voltage (0.87 V), 4.19 pJ/bit at 48 Gbps with normal-supply voltage (0.9 V) and 5.86 pJ/bit at 58 Gbps with high-supply voltage (1.04 V) in -25 dB channel. On the other hand, with a 50 parallelism factor, dual data-paths architecture, and power management (PM) is taped out. The core size is 653 µm x 653 µm (or 345.81k equivalent gates count). It dissipates 2.3 pJ/bit at best channel (-6 dB) and 2.74 pJ/bit at worst channel (-23.5 dB) under 0.9 V supply voltage at 50 Gbps throughput rate, respectively.
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Chuang, Ssu-Han, and 莊思涵. "Whitening Filters in Adaptive Blind Decision Feedback Equalizers." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/89433130350628701800.
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碩士<br>輔仁大學<br>電機工程學系碩士班<br>102<br>This thesis proposes the use of a recursive zero-pole whitening filter (ZPWF) to replace an all-pole whitening filter (APWF) and an all-zero whitening filter (AZWF) in the adaptive blind fractionally-spaced decision feedback equalizer (FS-DFE) for the single input multiple output (SIMO) system, and both the APWF and the AZWF are special cases of the proposed ZPWF. The rationale for proposing the ZPWF in adaptive blind FS-DFE may be explained as follows. Any arbitrary non-minimum phase channel may be approximated by the following three different types of channel: the moving-average (MA) channel, the autoregressive (AR) channel and the autoregressive-moving-average (ARMA) channel. Both the MA channel and the AR channel may be more effectively approximated by the ARMA channel with a much smaller total (numerator and denominator) number of coefficients. From the perspective of channel equalization, the proposed ZPWF employed in the adaptive blind FS-DFE may suit most channels in general. Computer simulation results demonstrated that the adaptive blind FS-DFE employing the ZPWF yielded the fastest convergence speed than that employing both the APWF and the AZWF when the ARMA channel was used. For the AR and the MA channels, simulation results showed that the proposed adaptive blind FS-DFE employing the ZPWF still outperformed that employing the APWF and the AZWF, respectively.
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Chang, Wei-Chieh, and 張維傑. "Adaptive Blind Decision Feedback Equalizers Using Whitening Filters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/tmr4hm.
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博士<br>輔仁大學<br>應用科學與工程研究所博士班<br>106<br>The trained channel equalization technique is known to reduce the effective information rate since its bandwidth is occupied by a training sequence. In contrast, the blind channel equalization technique does not require a training sequence, and therefore it can be used as an alternative technique to eliminate the intersymbol interference (ISI). However, when the blind equalization technique is applied to the classical adaptive decision feedback equalization (DFE), the effect of error propagation may likely prevent the blind adaptation from achieving an “eye-opening” condition in the presence of severe multipath channel, such as underwater acoustic communication channels, and terrestrial digital television (DTV) channels. Furthermore, another disadvantage of the blind equalization technique is its slow convergence, owing to the fact that convergence trajectory of the blind adaptation may be attracted by saddle point(s) in a multimodal cost function.
Motivated by these issues, this dissertation develops novel adaptive blind DFEs employing the whitening filters (WFs) in the single-input multiple-output (SIMO) multichannel systems, where the two-mode scheme (i.e., a starting mode and a tracking mode) is adopted to mitigate the error propagation. The use of the WF preceding the blind equalizer (BE), referred to as the pre-whitening scheme, is used in the starting mode in order to increase the curvature of the cost function of the BE, thus accelerating the convergence speed of the proposed adaptive blind DFE. Additionally, a robust modified pseudolinear regression (MPLR) algorithm was proposed for the WFs to prevent the adaptive blind DFE from becoming unstable when severe multipath channels have zeros close to the unit circle. Our analytical results give insight into how the use of the pre-whitening scheme may help the proposed adaptive blind DFE achieve convergence rapidly in the starting mode. Moreover, the adaptive blind DFE employing the pre-whitening scheme along with the Newton method (called Newton-like adaptive blind DFE) has been developed and analyzed, and simulation results confirmed that the proposed adaptive blind DFE significantly outperformed the existing adaptive blind DFEs.
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Denis and 黃育民. "Design and Implementation of an Adaptive Decision Feedback Equalizer for High Speed Wireless Local Area Network System." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/73813101816148877589.
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碩士<br>國立中正大學<br>電機工程研究所<br>87<br>The design and implementation of an Adaptive Decision Feedback Equalizer(ADFE) applicable to the receiver of the HIPERLAN(High Performance Radio LAN) system is investigated. computer simulations are used to design the parameters of the proposed equalizer architecture, including number of taps, step size, and the word length of input signal and coefficients of equalizer, from the standpoint of HIPERLAN physical layer performance. In addition, SPW(Signal Processing WorkSystem) is employed to verify the equalizer algorithm and architecture, and then the RTL codes are optimized and transferred by VA(Visual Architect) for the gate level circuit implementation of equalizer from a hardware standpoint.
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Patel, Shefalirani. "Interference Suppression in WCDMA with Adaptive Thresholding based Decision Feedback Equaliser." Thesis, 2013. http://ethesis.nitrkl.ac.in/5157/1/211EC4108.pdf.
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WCDMA is considered as one of the 3G wireless standards by 3GPP. Capacity calculation shows that WCDMA systems have more capacity compared to any other multiple access technique such as time division multiple access (TDMA) or frequency division multiple access (FDMA). So it is widely used. Rake receivers are used for the detection of transmitted data in case of WCDMA communication systems due to its resistance to multipath fading. But rake receiver treat multiuser interference (MUI) as AWGN and have limitation in overcoming the effect of multiple access interference (MAI) when the SNR is high. A de-correlating matched filter has been used in this thesis, which eliminates and improves system performance. But the given receiver works well only in the noise free environment. A DFE, compared to linear equaliser, gives better performance at severe ISI condition. The only problem in this equalisation technique is to select the number of symbols that are to be fed back. This thesis gives an idea on multiple symbol selection, based on sparity where an adaptive thresholding algorithm is used that computes the number of symbols to feedback. Simulated results show a significant performance improvement for Regularised Rake receiver along with thresholding in terms of BER compared to a rake receiver, de-correlating rake receiver and regularised rake receiver. The performance of the receiver in different channels is also analysed.
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Sebald, Daniel J. "Nonlinear signal processing for digital communications using support vector machines and a new form of adaptive decision feedback equalizer." 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.
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HSU, PO-SEN, and 許栢森. "Implementation of Adaptive Blind Decision Feedback Equalizers by Using Software-Defined Radios." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/42v2hw.
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碩士<br>輔仁大學<br>電機工程學系碩士班<br>105<br>This work implements an existing blind system structure which includes a transmitter and a blind receiver on software defined radio (SDR) platforms. The receiver of the blind system structure employs an adaptive blind fractionally-spaced decision feedback equalizer (FS-DFE), which is functioning alongside a zero-pole whitening filter (ZPWF) followed by a second-order phase-locked loop (PLL), referred to herein as the FS-DFE-ZPWF-PLL, in order to suppress both the carrier phase offset and the intersymbol interference (ISI) caused by practical time-varying channels. The indoor and outdoor experimental results show that the implemented blind system markedly outperformed its trained counterpart, and, moreover, the former system may save considerable bandwidth required by the latter system. Additionally, the implemented blind system may achieve outstanding experimental performance in terms of both the rate of convergence and the tracking capability.
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Liu, Che-Wei, and 劉哲維. "A 5 Gb/s Adaptive Infinite-Impulse-Response Decision-Feedback Equalizer with Infinite-Impulse-Response DFE and Discrete-Time DFE Techniques." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/33398034302649637111.
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碩士<br>國立中央大學<br>電機工程學系<br>105<br>As the data rate increasing, the signal integrity of high speed data transmission is worse since the limiting bandwidth of channel. Therefore, receivers generally adopt an equalizer to compensate for the signal attenuation caused by the channel. This study presents a 5 Gb/s adaptive infinite-impulse-response decision-feedback equalizer with infinite-impulse-response decision-feedback equalizer (IIR-DFE) and discrete-time decision-feedback equalizer (DT-DFE) Techniques, and takes USB 3.0 specification as reference material.
As the data rate increases, the channel loss increase linearly. Therefore, the channel loss should not be underestimated in the high speed serial link system. The power consumption becomes prohibitive if the equalizer fully adopts the DT-DFE technique for this larger channel loss. On the contrary, the feedback signal is easily affected by the process and temperature variations which cause the over compensation and under compensation if the equalizer fully adopts the IIR-DFE technique. In this thesis, the DT-DFE and the IIR-DFE are simultaneously controlled. This method can make the IIR-DFE get the best eye width under the process and temperature variation, by determining the both weights of two mechanisms to get the widest eye width at the first-post cursor position. This test chip was implemented by TSMC 90 nm (TN90GUTM) 1P9M CMOS process with 1 V supply voltage. The data rate is 5 Gbps and the DFE is operating at 5 GHz. When channel loss is 24 dB, the peak-to-peak jitter of equalized data is 45.78 ps, the root mean square (RMS) jitter of equalized data is 8.60 ps. When channel loss is 14 dB, the peak-to-peak jitter of equalized data is 30.22 ps, the RMS jitter of equalized data is 6.05 ps. When channel loss is 7 dB, the peak-to-peak jitter of equalized data is 24 ps, the RMS jitter of equalized data is 4.50 ps. The total power consumption of this work is 9.8 mW under 24 dB channel loss, and the power consumption of DFE and adaptive mechanism are 5.4 mW and 4.4 mW, respectively. The chip area is 0.868 mm2 and the core area is 0.037 mm2.
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Lan, Yi-Yang, and 藍義陽. "Volterra-based Decision Feedback Equalizer." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/77614132011693728845.
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碩士<br>國立交通大學<br>電信研究所<br>81<br>The advantages of a conventional decision feedback equa-
lizer(CDFE) is its simplicity in design and in implementa-
tion. However, the feedback part of CDFE is a linear equa-
lizer and, hence,the decision regions in the signal space are
delimited by hyperplanes. This property limits the performance
of the system. In the articles, we propose a new adaptive
nonlinear equalizer, called Volterra-based decision feedback
equalizer, which is capable of forming nonlinear decision
boundaries in the signal space. As a result, the performance
limit in the CDFE can effectively be overcome. Especially, it
has outstanding performance whenever the transmission channel
is nonlinear. Moreover, conventional adaptation algorithms can
be directly applied to the new structure. The simulation result
demonstrate that the new structure can be an effective
alternative in contrast to the CDFE.
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Chih-Hsiu, Lin. "High-performance Decision Feedback Equalizer Algorithms and Architectures." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2706200513551300.
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Lin, Chih-Hsiu, and 林志修. "High-performance Decision Feedback Equalizer Algorithms and Architectures." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/87741163492734933340.
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博士<br>國立臺灣大學<br>電子工程學研究所<br>93<br>An adaptive equalizer plays a key role at the receiver in modern digital transmission systems. The design of this equalizer is important since it determines the transmission quality attainable. Also, the equalizer occupies a high portion of the computational complexity in implementing the demodulator. Theses properties have made it the focus of much analytical and practical design. Recently, many researches of interest in communication systems are to increase transmission rate and recording density. However, with the increase of transmission rate and recording density, the signals propagating the channel suffer from serious channel distortion, which causes intersymbol interference (ISI). Hence, to design a robust and high-speed equalizer becomes important and necessary.
A decision feedback equalizer (DFE) is an efficient scheme to suppress this ISI. However, most cost-effective DFE implementations suffer from the phenomenon of error propagation, which degrades system performance in the sense of bit error rate (BER) or signal-to-noise ratio (SNR). In this thesis, we propose a soft-threshold-based multi-layer DFE (STM-DFE) algorithm to suppress the error propagation. Simulation results show that the proposed STM-Algorithm can efficiently reduce the BER and burst error length (BEL). When being applied to a practical Lorentzian channel and channels of different eigenvalue spread, the STM algorithm even outperforms the ideal DFE (IDFE) system (in an IDFE, symbols are assumed to be correctly fed back without propagation errors).
In VLSI implementations of the STM-DFE, the hardware overhead is negligible compared with a conventional DFE. The direct implementation can be applied to low-speed application such as magnetic data storage systems. In addition, for high-speed applications, we propose a two-stage precomputation scheme to lower the hardware overhead. A new adaptive algorithm to update for a DFE with precomputation scheme is also proposed so that both hardware complexity and power consumption can be saved. Finally, we consider the application of the STM-DFE to 10GBase-LX4 systems. With the help of the STM-DFE, we can perform effective EQ, and the required bit number of ADC can be reduced from 8 to 6. That is, STM-DFE can help to ease the ADC precision requirement, and help to save the silicon cost in implementing the receiver ICs.
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Chen, Qiong Zhang, and 陳瓊璋. "Distance-based decision feedback equalizer with cluster technique." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/24618178756238443020.
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LAI, KUN-CAI, and 賴坤財. "A decision-aided adaptive equalizer with simplified implementation." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/76901894192424203090.
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Kuo, Ching-Yu, and 郭經昱. "A Correlation-Aided Complementary Code Keying Decision-Feedback Equalizer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/05634360204453028349.
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碩士<br>國立交通大學<br>電信工程系<br>90<br>Complementary code Keying (CCK) is employed as the modulation method for the high-rate scheme of the IEEE 802.11b WLAN system which provides 5.5Mbps and 11Mbps for high data rate transmission. The 8 chips within a CCK symbol have certain correlation properties and thus CCK performs better than conventional QPSK modulation in a AWGN channel. The WLAN system is operated in a wireless environment which will introduce time dispersion of the signal, thus techniques that combat the multipath interference are needed. In this thesis we discuss the equalizers that combat the intersymbol interference (ISI) and the decision-feedback equalizer (DFE) is commonly used in communication systems because it performs well and is simple for implementation. However, when applied in CCK scheme the silcer or hard-decision device in the DFE will destroy the correlation between chips in the same CCK symbol when the chip decision is not correct. Thus, a correlation-aided DFE is proposed that utilizes the detected symbols from the modified FWT block as the input of the feedback filter. That is, detection is done for symbols instead of chips to mitigate the detection error. Simulation results show that the modified DFE mitigates the detection error and thus perform better than the conventional DFE.
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Wen, Shao-Min, and 溫紹閔. "An Overlap-Cut Frequency Domain Equalizer with Decision Feedback." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/27290735396335554768.
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碩士<br>國立臺灣海洋大學<br>通訊與導航工程系<br>96<br>To overcome the effects of multipath fading in the wireless communication systems, equalizer is adopted at the receiver. Equalizers can be classified into two types : one is Frequency Domain Equalizer(FDE) and the other is Time Domain Equalizer(TDE). Transmitter inserts the guard interval (GI) to avoid inter-block interference (IBI) for the FDE receiver. However, system capacity will be reduced for the insertion of the GI.
In this paper, we propose a FDE without GI, i.e., Overlap-Cut(OC) FDE with decision feedback. The proposed FDE adopts the OC method to avoid the IBI and exploits the decision feedback to improve the BER performance. Without inserting the GI, the proposed FDE is more compatible to frame structure of the existing communication systems.
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Shih, I.-Hao, and 施義浩. "Design and Analysis in Decision Feedback Equalizer of OFDM System." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/90924484934069381681.
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碩士<br>國立交通大學<br>電信工程系所<br>94<br>Due to the reflection and diffraction of the EM wave, the wireless channels have the multipath fading effects. These influences reduce the system performance and the bit error rates of transmission raise. Therefore, we use the equalizer at the receiver to compensate the multipath channel influences and suppress the noise effect. The architecture and algorithms of equalizers are different, and in which, the decision feedback equalizer can remove the multipath interference effectively without enhancing the noise.
In this thesis, we design the architecture and the algorithms of decision feedback equalizer which originally belonged to the single carrier system for OFDM system. We will compare the performances of our architecture and the linear equalizer. Furthermore, different equalization systems have different influences when they have channel estimation errors or with channel coding systems, so we will take these influences into account in the simulations which is in the end of this thesis.
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Lin, Hsin-Lei, and 林心蕾. "Design of a Decision Feedback Equalizer for IEEE 802.11b WLAN System." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/82725817885192451197.
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碩士<br>國立中興大學<br>電機工程學系<br>90<br>In this thesis, design of a decision feedback equalizer (DFE) based on IEEE 802.11b protocol is presented. It has dual 6-tap feed-forward filters with 6-bit input and an 8-tap feedback filter with 2-bit input, that all the filters are implemented using the finite impulse response (FIR) filter. The output of the DFE is sliced into two levels by detector for CCK (8-chip complementary code keying) modulation. The least mean square (LMS) algorithm is used for updating the coefficients in the parallel DFE architecture. The data elapse time in the critical path is 19.46 nsec. The DFE is implemented using the TSMC 0.35 m CMOS 1p4m technology. The total gate count is 58624. The power consumption is 25.087 mW operating under a 3.3 V supply voltage.
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Yi-TingLi and 李依庭. "Frequency-Domain Iterative Block Decision Feedback Equalizer with Soft Decision for Single-Carrier Block Transmission." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/e35cfz.
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碩士<br>國立成功大學<br>電腦與通信工程研究所<br>105<br>Single-carrier block transmission (SCBT) with frequency-domain linear equalizer suffers from considerable performance degradation in severely frequency-selective fading channels. Nonlinear decision-feedback equalization (DFE), such as iterative block DFE with hard decision (HD-IBDFE), was proposed to tackle this problem. For simplicity, HD-IBDFE always uses the hard decisions from the previous iteration as the input of the feedback filter (FBF), but low-reliability decisions entering FBF limits the performance. In addition, the design of equalizer coefficients needs parameter estimation, which incurs additional complexity. To overcome these drawbacks of HD-IBDFE, we propose IBDFE with various soft decision devices (SD-IBDFE), by extending the idea of IBDFE with null zone (NZ-IBDFE) in the literature, which uses the thresholds to keep low-reliability decisions from being used for decision feedback. We propose several kinds of SD-IBDFE, such as IBDFE with erasure zone (EZ-IBDFE), IBDFE with linear clipper (LC-IBDFE) and IBDFE with conditional mean (CM-IBDFE). When the equalized signal falls between certain thresholds (i.e., falling in the erasure interval), EZ-IBDFE will use the intermediate value of the erasure interval for feedback, while LC-IBDFE will map through a linear function to determine the feedback value. CM-IBDFE uses the minimum mean square error estimate of the symbol (i.e., the conditional mean) as the input of FBF. In the thesis, we also propose a new parameter estimation method for HD-IBDFE and EZ-IBDFE that is simpler and yet more accurate than the conventional one. Simulation results show that the proposed SD-IBDFE has a better performance than HD-IBDFE.
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Huang, Yi-Jung, and 黃一容. "Applications of the ATSC DTV Systems Using the Modified Decision Feedback Equalizer." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/73540436273317931783.
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碩士<br>國立雲林科技大學<br>電子與資訊工程研究所<br>93<br>A complete study of the transceiver design for ATSC DTV is presented in this thesis. Since the performance of the ATSC DTV receiver mainly depends on the equalizer, several adaptive filtering algorithms, including LMS, RLS, SAG, CMA, and the proposed modified SAG are investigated for compact for compact the signal distortion.
To further improve the decision quality, a modified Viterbi decoder is used to be the decision device in the decision feedback equalizer. Computer simulation demonstrates that the proposed modified SAG algorithm and new DFE architecture can achieve performance improvement in the ATSC DTV system.
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yang, cheng-song, and 楊盛松. "Multilayer perceptron decision feedback equalizer in complex signals based on evolutionary algorithms." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/35062438890905889163.
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Wang, Wen-Lung, and 王文隆. "The Analyses of the activation function of Multilayer Perceptron Decision Feedback Equalizer." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/6hx6cp.
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碩士<br>國立臺北科技大學<br>電資碩士在職專班研究所<br>100<br>In digital communication system, digital signal will distort while the signal is sent to the receiver through the channels because all the communication channels in nature are not ideal. Generally, reasons causing distortion include Inter-Symbol Interference (ISI), Co-Channel Interference (CCI), Noise, Multi-path Interference (MAI), etc.
Traditionally, to lessen interferences, an equalizer is installed on the receiver to improve the distortion. On the other hand, to reduce ISI and Noise, and make channel features more stable, Adaptive Filters is applied as it will self-adjust to fit the situation of channel keeping changing all the time and with algorithm, different equalizer structure results in different improvement.
Multilayer perceptron decision feedback equalizer (MLP-DEF) of Neural Networks structure makes the interferences better improved. Although most of the MLP-DEF output layers, using fixed activation function, performs well, this article is trying to address a different idea in the light of this activation function to accelerate system convergence rate by adjusting the parameter, , and to explore how Bit Error Rate (BER) changes. Furthermore, we want to know the effect on this convergence rate and BER under the condition of different SNR (Signal Noise Ratio), by way of discussing the simulation experiments of formula, and comparison between before and after the adjustment.