Dissertations / Theses on the topic 'Decision feedback equalization'
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1
Rice, Michael, Gayatri Narumanchi, and Mohammad Saquib. "Decision Feedback Equalization for SOQPSK." International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581839.
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This paper investigates a fractionally-spaced decision-feedback equalization technique for Shaped Offset Quadrature Phase Shift Keying (SOQPSK). The kernel of the block-based feedback algorithm is to estimate the intersymbol interference and cancel it from the samples used to make the bit decisions. This process refines the bit estimates sequentially, thereby increasing the probability of obtaining accurate estimates. The simulated bit error rate performance of the decision-feedback technique shows a 1 dB improvement over MMSE-equalized SOQPSK-TG over channels derived from multipath channel measurements at Cairns Army Airfield, Ft. Rucker, Alabama and Edwards AFB, California.
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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.
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Kennedy, Rodney Andrew, and rodney kennedy@anu edu au. "Operational Aspects of Decision Feedback Equalizers." The Australian National University. Research School of Physical Sciences and Engineering, 1989. http://thesis.anu.edu.au./public/adt-ANU20050418.151329.
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The central theme is the study of error propagation effects in decision feedback equalizers (DFEs). The thesis contains: a stochastic analysis of error propagation in a tuned DFE; an analysis of the effects of error propagation in a blindly adapted DFE; a deterministic analysis of error propagation through input-output stability ideas; and testing procedures for establishing correct tap convergence in blind adaptation. To a lesser extent, the decision directed equalizer (DDE) is also treated.¶ Characterizing error propagation using finite state Markov process (FSMP) techniques is first considered. We classify how the channel and DFE parameters affect the FSMP model and establish tight bounds on the error probability and mean error recovery time of a tuned DFE. These bounds are shown to be too conservative for practical use and highlight the need for imposing stronger hypotheses on the class of channels for which a DFE may be effectively used.¶ In blind DFE adaptation we show the effect of decision errors is to distort the adaptation relative to the use of a training sequence. The mean square error surface in a LMS type setting is shown to be a concatenation of quadratic functions exposing the possibility of false tap convergence to undesirable DFE parameter settings. Averaging analysis and simulation are used to verify this behaviour on some examples.¶ Error propagation in a tuned DFE is also examined in a deterministic setting. A finite error recovery time problem is set up as an input-output stability problem. Passivity theory is invoked to prove that a DFE can be effectively used on a channel satisfying a simple frequency domain condition. These results give performance bounds which relate well with practice.¶ Testing for false tap convergence in blind adaptation concludes our study. Simple statistic output tests are shown to be capable of discerning correct operation of a DDE. Similar tests are conjectured for the DFE, supported by proofs for the low dimensional cases.
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Abdulrahman, Majeed Carleton University Dissertation Engineering Electrical. "Decision feedback equalization with cyclostationary interference for DSL." Ottawa, 1989.
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Wang, Rujiang. "Mitigating error propagation of decision feedback equalization in boradband communications." Doctoral thesis, Université Laval, 2008. http://www.theses.ulaval.ca/.
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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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Wang, Rujiang. "Mitigating Error Propagation of Decision Feedback Equalization in Broadband Communications." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25328/25328.pdf.
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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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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.
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McGinty, Nigel, and nigel mcginty@defence gov au. "Reduced Complexity Equalization for Data Communication." The Australian National University. Research School of Information Sciences and Engineering, 1998. http://thesis.anu.edu.au./public/adt-ANU20050602.122741.
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Optimal decision directed equalization techniques for time dispersive communication channels are often too complex to implement. This thesis considers reduced complexity decision directed equalization that lowers complexity demands yet retains close to optimal performance. The first part of this dissertation consists of three reduced complexity algorithms based on the Viterbi Algorithm (VA) which are: the Parallel Trellis VA (PTVA); Time Reverse Reduced State Sequence Estimation (TR-RSSE); and Forward-Backward State Sequence Detection (FBSSD). The second part of the thesis considers structural modifications of the Decision Feedback Equalizer (DFE), which is a special derivative of the VA, specifically, optimal vector quantization for fractionally spaced DFEs, and extended stability regions for baud spaced DFEs using passivity analysis are investigated.¶
For a special class of sparse channels the VA can be decomposed over a number of independent parallel trellises. This decomposition will be called the Parallel Trellis Viterbi Algorithm and can have lower complexity than the VA yet it retains optimal performance. By relaxing strict sparseness constraints on the channel a sub-optimal approach is proposed which keeps complexity low and obtains good performance.¶
Reduced State Sequence Estimation (RSSE) is a popular technique to reduce complexity. However, its deficiency can be the inability to adequately equalize non-minimum phase channels. For channels that have energy peaks in the tail of the impulse response (post-cursor dominant) RSSE's complexity must be close to the VA or performance will be poor. Using a property of the VA which makes it invariant to channel reversal, TR-RSSE is proposed to extend application of RSSE to post-cursor dominant channels.¶
To further extend the class of channels suitable for RSSE type processing, FBSSD is suggested. This uses a two pass processing method, and is suited to channels that have low energy pre and post-cursor. The first pass generates preliminary estimates used in the second pass to aid the decision process. FBSSD can range from RSSE to TR-RSSE depending on parameter settings.¶
The DFE is obtained when the complexity of RSSE is minimized. Two characterizing properties of the DFE, which are addressed in this thesis, are feedback and quantization. A novel fractionally spaced (FS) DFE structure is presented which allows the quantizer to be generalized relative to the quantizer used in conventional FS-DFEs. The quantizer can be designed according to a maximum a posteriori criterion which takes into account a priori statistical knowledge of error occurrences. A radically different quantizer can be obtained using this technique which can result in significant performance improvements.¶
Due to the feedback nature of the DFE a form of stability can be considered. After a decision error occurs, a stable DFE will, after some finite time and in the absence of noise, operate error free. Passivity analysis provides sufficient conditions to determine a class of channels which insures a DFE will be stable. Under conditions of short channels and small modulation alphabets, it is proposed that conventional passivity analysis can be extended to account for varying operator gains, leading to weaker sufficient conditions for stability (larger class of channels).
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Huang, Gillian. "Decision-feedback equalization and channel estimation for single-carrier frequency division multiple access." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551318.
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Long- Term Evolution (LTE) is standardized by the 3rd Generation Partnership Project (3GPP) to meet the customers' need of high data-rate mobile communications in the next 10 years and beyond. A popular technique, orthogonal frequency division multiple access (OFDMA), is employed in the LTE down link. However, the high peak- to-average ratio (PAPR) of OFDMA transmit signals leads to low power efficiency that is particular undesirable for power-limited mobile handsets. Single-carrier frequency division multiple access (SC-FDMA) is employed in the LTE uplink due to its inherent low-PAPR property, simple frequency domain equalization (FDE) and flexible resource allocation. Working within the physical (PHY) layer, this thesis focuses on decision- feedback equalization (DFE) and channel estimation for SC-FDMA systems. In this thesis, DFE is investigated to improve the equalization performance of SC- FDMA. Hybrid-DFE and iterative block decision-feedback equalization (IB-DFE) are considered. It is shown that hybrid-DFE is liable to error propagation, especially in channel-coded systems. IB-DFE is robust to error propagation due to the feedback (FB) reliability information. Since the FB reliability is the key to optimize the performance of IB-DFE, but is generally unknown at the receiver, FB reliability estimation techniques are presented. Furthermore, several transform-based channel estimation techniques are presented. Various filter design algorithms for discrete Fourier transform (DFT) based channel estimation are presented and a novel uniform-weighted filter design is derived. Also, channel estimation techniques based on different transforms are provided and a novel pre-interleaved DFT (PI-DFT) scheme is presented. It is shown that SC-FDMA employing the PI-DFT based channel estimator gives a close error rate performance to the optimal linear minimum mean square error (LMMSE) channel estimator but with a much lower complexity. In addition, a novel windowed DFT-based noise variance estimator that remains unbiased up to an SNR of 50dB is presented. Finally, pilot design and channel estimation schemes for uplink block-spread code division multiple access (BS-CDMA) are presented. It is demonstrated that the recently proposed bandwidth-efficient BS-CDMA system is a member of the SC-FDMA family. From the viewpoint of CDMA systems, novel pilot design and placement schemes are proposed and a channel tracking algorithm is provided. It is shown that the performance of the proposed schemes remain robust at a Doppler frequency of 500Hz, while the pilot block scheme specified in the LTE uplink fails to work in such a rapidly time-varying channel.
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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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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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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, CaliforniaMany 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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Guvensen, Gokhan Muzaffer. "Near Capacity Operating Practical Transceivers For Wireless Fading Channels." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610398/index.pdf.
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Multiple-input multiple-output (MIMO) systems have received much attention due to their
multiplexing and diversity capabilities. It is possible to obtain remarkable improvement
in spectral efficiency for wireless systems by using MIMO based schemes. However, sophisticated
equalization and decoding structures are required for reliable communication at
high rates. In this thesis, capacity achieving practical transceiver structures are proposed for
MIMO wireless channels depending on the availability of channel state information at the
transmitter (CSIT).
First, an adaptive MIMO scheme based on the use of quantized CSIT and reduced precoding
idea is proposed. With the help of a very tight analytical upper bound obtained for limited
rate feedback (LRF) MIMO capacity, it is possible to construct an adaptive scheme varying
the number of beamformers used according to the average SNR value. It is shown that
this strategy always results in a significantly higher achievable rate than that of the schemes
which does not use CSIT, if the number of transmit antennas is greater than that of receive
antennas.
Secondly, it is known that the use of CSIT does not bring significant improvement over
capacity, when similar number of transmit and receive antennas are usedon the other hand, it reduces the complexity of demodulation at the receiver by converting the channel into noninterfering subchannels. However, it is shown in this thesis that it is still possible to achieve a performance very close to the outage probability and exploit the space-frequency diversity benefits of the wireless fading channel without compromising the receiver complexity, even if the CSIT is not used. The proposed receiver structure is based on iterative forward and backward filtering to suppress the interference both in time and space followed by a spacetime decoder. The rotation of multidimensional constellations for block fading channels and the single-carrier frequency domain equalization (SC-FDE) technique for wideband MIMO channels are studied as example applications.
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Gulmez, Baskoy Ulku. "A Turbo Detection Scheme For Egprs." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1259415/index.pdf.
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Enhanced Data Rates for Global Evolution (EDGE) is one of the 3G wireless communication standards, which provides higher data rates by adopting 8-PSK modulation in TDMA system infrastructure of GSM. In this thesis, a turbo detection receiver for Enhanced General Packet Radio Services (EGPRS) system, which is the packet switching mode of EDGE, is studied. In turbo detection, equalization and channel decoding are performed iteratively. Due to 8-ary alphabet of EGPRS modulation, full state trellis based equalization, as usually performed in GSM, is too complex not only for turbo detection but even for conventional equalizationso suboptimum schemes have to be considered. The Delayed Decision Feedback Sequence Estimation (DDFSE) is chosen as suboptimal and less complex trellis based scheme and it is examined as a conventional equalization technique firstly. It is shown that the DDFSE has a fine tradeoff between performance and complexity and can be a promising candidate for EGPRS. Then it is employed to reduce the number of the trellis state in turbo detection. Max-log-MAP algorithm is used for soft output calculations of both SISO equalizer and SISO decoder. Simulation results illustrate that proposed turbo detection structure improves bit error rate and block error rate performance of the receiver with respect to the conventional equalization and decoding scheme. The iteration gain varies depending on modulation type and coding rate of Modulation Coding Scheme (MCS) employed in EGPRS.
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Wang, Cheng-Kang, and 王承康. "Minimum Relevant Error Decision Feedback Equalization." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/63987363145369401357.
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Kennedy, Rodney. "Operational Aspects of Decision Feedback Equalizers." Phd thesis, 1988. http://hdl.handle.net/1885/47458.
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The central theme is the study of error propagation effects in decision feedback equalizers (DFEs). The thesis contains: a stochastic analysis of error propagation in a tuned DFE; an analysis of the effects of error propagation in a blindly adapted DFE; a deterministic analysis of error propagation through input-output stability ideas; and testing procedures for establishing correct tap convergence in blind adaptation. To a lesser extent, the decision directed equalizer (DDE) is also treated.¶ ...
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Yih-Ming, Tsuie, and 崔義明. "Adaptive Decision Feedback Equalization: Applications and Performance Analysis." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/76678401109798022006.
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博士國立交通大學
電信工程系
89
In digital communication systems, intersymbol interference (ISI) is one of the main causes degrading system performance. The decision feedback equalizer (DFE) has been considered a simple yet effective remedy for this problem. This thesis consists of three parts. In the first part, we consider the performance analysis of adaptive DFE. Analysis of the DFE error probability is known to be a difficult problem. This is primarily due to the nonlinear operation involved in the decision process. The problem is further complicated if the DFE is operated in a time-varying channel. In this case, an adaptive algorithm must be used to track the channel variation. Then, a decision error not only propagates through the feedback filter affecting the future outputs, but also through the adaptive algorithm updating the tap weights toward a wrong direction. We specifically take this effect into account and analyze the error probability of the DFE under the slowly fading channels. We consider the most widely used adaptive algorithm, namely, the least mean square (LMS) algorithm. Closed-form expressions are derived for the training mode as well as the decision-directed mode. The validity of the theoretical results are verified through computer simulations. Although the LMS algorithm is simple, its convergence is slow. As a result, it is not suitable for DFE adaptation in fast varying channels. In the second part of the thesis, we then propose an extended multiple-training LMS algorithm accelerating the convergence process. The convergence properties of the multiple-training LMS algorithm are also analyzed. We prove that the multiple-training LMS algorithm can converge regardless its initial value and derive closed-form expressions for the weight error vector power. We then apply this algorithm to the IS-136 system. Taking advantage of the IS-136 downlink slot format, we divide a slot into two subslots. Bi-directional processing is then applied to each individual subslot. The proposed LMS-based DFE has a low computational complexity and is suitable for real-world implementation. Simulations with a 900MHz carrier show that our algorithm can meet the 3% bit error rate (BER) requirement for mobile speeds up to 100 km/hr. Another commonly used equalization method is called the maximum likelihood sequence estimator (MLSE). The MLSE can outperform the DFE, however, its computational complexity is higher. The MLSE is usually implemented by the Viterbi algorithm (VA). The computational complexity of the VA grows exponentially with the length of the channel response. With some performance reduction, a decision-feedback equalizer (DFE) can be used to shorten the channel response reducing the computational requirement for the VA. However, for many real-world applications, the complexity of the DFE/MLSE approach may be still too high. In the third part of the thesis, we propose a constrained DFE further reducing the computational complexity of the VA. The basic idea is to pose some constraints on the DFE such that the postcursors of the shortened channel response have only discrete values. As a result, the multiplication operations can be replaced by shift operations making the VA almost multiplication free. This will greatly facilitate the real world applications of the MLSE algorithm. Simulation results show that while the proposed algorithm remains almost the original MLSE performance, the VA is much more efficient than the conventional approach. Finally, we consider the delayed decision-feedback sequence estimation (DDFSE) for detection of the trellis coded modulation (TCM) signal in presence of the intersyombol interference (ISI). We use the constrained DFE to shape the channel response such that the post cursors have discrete values. This greatly reduces the implementation complexity of the VA involved in the DDFSE.
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Hasnie, Shazia. "Modified decision feedback equalization techniques for data communications." Phd thesis, 1999. http://hdl.handle.net/1885/148083.
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Wiedmann, Ralf. "An adaptive all-pass filter for decision feedback equalization." Thesis, 1997. http://hdl.handle.net/1957/34252.
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Increasing densities on magnetic data storage devices leads to problems of
severe intersymbol interference (ISI), additive noise and non-linearities. Advanced
detection strategies for magnetic recording channels fall into two categories: partial
response equalization with maximum likelihood decoding and decision feedback
equalization. This study focuses on doing an adaptive all-pass forward filter for
the decision feedback channel. The decision feedback channel can be equalized by
a low-order continuous-time filter, and does not require a transversal filter with
high-precision multiplication. This results in considerable savings in both power
consumption and chip die area. One problem that has yet to be addressed is how to
adaptively set the coefficients of the all-pass filter. This thesis examines the design
and performance of an adaptive all-pass filter.
The performances in terms of the mean-squared error (MSE) of a first- and
second-order all-pass are evaluated. They are compared to a conventional FIR filter
design of various lengths. An adaptive algorithm based on the least mean-squared
(LMS) error is developed and characterized over a range of storage densities. Since
this does not require sampling of the filter input or any states of the forward filter, the system could be realized in continuous-time up to the decision device.
Numerical simulations for various data densities and noise variances are done to verify the theoretically expected performance and the adaptation behavior of the all-pass.Graduation date: 1997
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Lin, Chiou Huei, and 林秋輝. "Multichannel Maximum Likelihood Decision Feedback Equalization for GMSK signals." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/27899328983568911807.
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碩士元智大學
電機與資訊工程研究所
87
This thesis investigates multichannel maximum likelihood decision feedback equalization for GMSK signals. The sequence-based Maximum Likelihood Sequence Estimation (MLSE) can be simplified by incorporating feedback decisions. On the other hand, the symbol-based decision feedback equalizer (DFE) can be improved to realize maximum likelihood decisions. We designe RS-ML-DFE and DF-RS-MLSE algorithm for GSM antenna array system. We also tested several methods and compare their bit error rate and computation time. Multichannel decision feedback reduced phase states MLSE (DF-RS-MLSE) appears to be a promising method both in terms of bit error rate and computation complexity.
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Lee, Chi-Hsin, and 李啟新. "Underwater Data Transmission Using Blind Adaptive Decision Feedback Equalization." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/96370419415938525710.
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碩士國立海洋大學
電機工程學系
89
Underwater acoustic communications have been the focus of underwater technology researches in recent years. However, the propagation of acoustic wave in water is extremely complicated. The underwater acoustic channel is characterized as a time-varying multipath environment, which in addition to possible Doppler effect make developing an underwater communication system a very challenging task. Research work for improving the quality of underwater communication systems has been pursed constantly. In this thesis, the blind adaptive decision feedback equalizer (BADFE) is employed to enhance the performance of the receiver. The BADFE has advantages of the decision feedback equalizer (DFE) and blind equalizer, and it can overcome the transmission difficulties in severely time-varying underwater channel. With the same computational complexity, the BADFE exhibits the same convergence speed, steady-state MSE, and bit-error rate as the trained conventional DFE, but it requires no training. Consequently, the BADFE can improve the transmission efficiency and increase bandwidth efficiency. A SONY SIR 1000W Data Recorder is also used to record the transmitted signal for off-line analysis. The experimental results show that the BADFE is particularly suitable for underwater acoustic communication applications.
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Chou, Huang-Kuan, and 周鍠坤. "Block adaptive decision-feedback equalization techniques for wireless communications." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/51603218945240078967.
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碩士國立清華大學
電機工程學系
85
Equalization is one of the most important parts in a time division multipleaccess (TDMA) wireless mobile communication system. Its purpose is to combatintersymbol interference caused by multipath fading channel during thetransmission process. In this thesis, we present a new equalization approach,called bi-directional linear extrapolation equalization (BDLEE) for thedown-link transmission in a TDMA-based mobile communication. Unlike theconventional bi- directional equalization (BDE) technique which updates theequalizer's coefficients based on a fixed adaptive algorithm throughput theinterval of data symbols, the BDLEE technique adopts two different strategiesfor updating the equalizer's coefficients; the coefficients are determinedbased on an adaptive algorithm before the channel fading exceeds a specifiedlevel, and are determined by a simple extrapolation scheme after that. It isclear that a BDLEE-based equalizer requires less computational complexity andless power than a BDE-based equalizer, especially for applications where acomplicated adaptive algorithm is required. This is an attractive feature forthe mobile station design of a TDMA-based wireless system. To demonstrate theperformance of the proposed approach, computer simulations based on a blockadaptive decision-feedback equalization scheme are performed for the NorthAmerican IS-54 (or IS-136) digital cellular system under the worst casetwo-ray Rayleigh fading channel. The simulation results show that the BDLEEtechnique reaches better bit error rate (BER) performance than the BDEtechnique when the speed of the mobile station is more than 60 Km/hour; whenthe speed lower than 60Km/hour, both systems have comparable BER performance.Besides, the performance exceeds the requirements of the IS-54 system greatly.To further reduce the computational complexity, the fixed bi- directionallinear extrapolation equalization (FBDLEE) which comes from BDLEE has fixedcomplexity but worse performance. If we just want to achieve the requirementof IS-54, we can select the suitable parameters of FBDLEE by computersimulations to achieve the BER specification of IS-54. Besides IS-54 system, these two proposed equalization methods can also be applied to all TDMA-basedcommunications.
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"Mitigating Error Propagation of Decision Feedback Equalization in Broadband Communications." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25328/25328.pdf.
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Yang, Che-shih, and 楊哲詩. "Using Reduced Decision-Feedback Chebyshev FLANN Structure in Channel Equalization." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/67276038704057439198.
Full textAbstract:
碩士國立雲林科技大學
電機工程系碩士班
94
The design of a channel equalizer in digital communication systems is discussed in this thesis. Among the various methods for realizing channel equalizers, we have chosen Chebyshev functional link artificial neural networks (CFLANN) for the implementation. The design has been successfully applied to digital communication systems transmitting 4QAM modulated signals. The CFLANN structure has the advantage of being able to expand the lower dimensional signal space onto a higher dimensional hypersurface by using nonlinear functional approximation. This expansion can convert the linear inseparable problem into a separable one, which makes the CFLANN have pretty simple network structure and low computational complexity. Because the CFLANN does not need the hidden layers, which are existed in most MLP-based equalizers, it generally exhibits high speed of convergence. Moreover, in order to further improve the performance of CFLANN, we have proposed a reduced decision-feedback Chebyshev functional link artificial neural networks (RDF-CFLANN) for the design of a nonlinear channel equalizer in digital communication systems. In this RDF-CFLANN we add a local feedback signal to the input layer directly from the output. This new architecture not only preserves the advantages of the traditional CFLANN, but also significantly saves the hardware cost. Besides, the decision feedback mechanism utilized in the RDF-CFLANN structure can greatly speed up the convergence of network settings during the training process. As it can easily meet the real-time processing requirement of modern communication systems, the RDF-CFLANN is more suitable for implementing a nonlinear channel equalizer than CFLANN. Simulation results show that the error performance of RDF-CFLANN can be up to 3 to 5 dB better than CFLANN. By the way, as it has less functionally expanded terms than DF-CFLANN, the RDF-CFLANN is more suitable for realization with parallel processing.
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Engelbrecht, Linda M. "A DAC and comparator for a 100MHz decision feedback equalization loop." Thesis, 1996. http://hdl.handle.net/1957/34236.
Full textAbstract:
Decision Feedback Equalization (DFE) in a data recovery channel filters
the bit decision in the current symbol period in generating the sample at the
comparator in the subsequent clock period. The operations of sampling,
comparing, filtering the decision bits into a feedback signal, and subtraction of
that feedback signal are cascaded, thereby establishing the critical timing path.
Thus, this system, though simple, requires its components to have large
bandwidths in order to achieve the high-speed response necessary to perform
the described feedback function. For the entire system to run at speeds
comparable to those of competing technologies (100MHz to 250MHz), the
components must have bandwidths greater than 100MHz, and work together to
provide a loop bandwidth of at least 100MHz.
A 300MHz latching comparator and a 125MHz 6-bit current-DAC were
designed in a 5V, 1 um CMOS n-well process for use in a DFE loop. Both blocks
are fully differential and achieve an accuracy of 1/2 LSB (10uA) over a differential
signal range of 1.28mA. This is true for their operations at speed, in isolated
simulation and as contiguous blocks. The DAC power consumption is relatively
high at 23mW, due to internal switching circuits which require a static current,
but the comparator's power consumption is minimal at 5mW.Graduation date: 1997
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Chun-Chieh, Chen. "Adaptive Decision-Feedback Equalization for Unique-Word Based Single Carrier Systems." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709315021.
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Shih-HungChang and 張士浤. "Frequency-Domain Iterative Block Decision Feedback Equalization for SC-FDMA Systems." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/xhyny2.
Full textAbstract:
碩士國立成功大學
電腦與通信工程研究所
102
The single-carrier frequency-division multiple access (SC-FDMA) system suffers from severe inter-symbol interference (ISI) in multi-path channels. In order to mitigate this problem, we apply the equalization methods that are originally developed for the single-carrier block transmission (SCBT) systems to the SC-FDMA system. Because of the poor performance of the linear equalizers, we focus on the non-linear iterative block decision feedback equalizer (IBDFE) in this thesis. The IBDFE with hard detection (HD-IBDFE) eliminates the residual ISI by using the hard detected data from previous iteration as the input of the feedback filter, but using the wrongly detected data for feedback might result in performance degradation. To overcome this drawback, the IBDFE with soft detection (SD-IBDFE) feeds back only the detected data that are deemed reliable. Simulation results show that SD-IBDFE not only improves the performance of HD-IBDFE, but also reduces the complexity of parameter estimation. In the thesis, we also investigate the effect of imperfect channel estimation on the performance of IBDFE. Simulation results show that the minimum mean square error (MMSE) channel estimator leads to the best bit-error-rate performance; however, the drawbacks of MMSE estimator include the higher complexity and requiring the knowledge of the channel statistics.
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Chen, Chun-Chieh, and 陳俊杰. "Adaptive Decision-Feedback Equalization for Unique-Word Based Single Carrier Systems." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/37595848807117114309.
Full textAbstract:
碩士國立清華大學
通訊工程研究所
94
Unique word based single carrier (UW-SC) systems have been proposed as an alternative to orthogonal frequency division multiplexing (OFDM) systems. UW-SC not only avoids the peak-to-average power ratio problem that plagues OFDM but also supplies the known information of unique words for additional purposes. Although UW-SC is very robust to frequency selective fading in a multipath environment, it is sensitive to the time selective in wireless channel that corrupts the orthogonality of the channel matrix in the frequency domain. In this thesis, we first derive a low-complexity time-domain block minimum mean-squared error (MMSE) solution as a feedforward filter for UW-SC systems in the presence of inter-symbol interference (ISI) caused by doubly selective channel. For residual ISI reduction, we also present a decision feedback filter after the feedforward filter to form a new decision feedback equalizer adapted by unique word. Simulation results and complexity comparisons are given to show that the proposed method has considerably satisfactory performance and lower complexity than linear MMSE and iterative MMSE.
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Zhang, Zeyang. "Coarsely quantized Massive MU-MIMO uplink with iterative decision feedback receiver." Thesis, 2020. http://hdl.handle.net/1828/11719.
Full textAbstract:
Massive MU-MIMO (Multiuser-Multiple Input and Multple Output) is a promising technology for 5G wireless communications because of its spectrum and energy efficiency. To combat the distortion from multipath fading channel, the acquisition of channel state information is essential, which generally requires the training signal that lowers the data rate. In addition, coarse quantization can reduce the high computational energy and cost, yet results in the loss of information.
In this thesis, an iterative decision feedback receiver, including iterative Channel Estimation (CE) and equalization, is constructed for a Massive MU-MIMO uplink system. The impact of multipath distortion and coarse quantization can be gradually reduced due to the iterative structure that exploits extrinsic feedback to improve the CE and data detection, so that the data rate is improved by reducing training signals for CE and by using low precision quantization. To observe and evaluate the convergence behaviour, an Extrinsic Information Transfer (EXIT) chart method is utilized to visualize the performance of the iterative receiver.Graduate
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Shiu, Jen Kang, and 徐振康. "Adaptive decision-feedback equalization of multipath fading channels in coded modulation systems." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/68162726332158020083.
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Huang, Chun-Wei, and 黃俊威. "4-QAM Decision feedback equalization using Evoluation based multi-layer perceptron structures." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/17006511886587685435.
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Cheng, Yuan Yu, and 鄭元佑. "Performance Analysis of Decision Feedback Equalization for Asynchronous CDMA in Wireless Communications." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/53267112576718286196.
Full textAbstract:
碩士輔仁大學
電子工程學系
97
In CDMA systems, besides the additivity white Gaussian noise(AWGN), the system may suffer from intersymbol interference(ISI), interchip interference(ICI) and multiple access interference(MAI). ISI and ICI were caused by multipath fading channel. In many research of communication system, RAKE receiver has been proposed to combat multipath fading by using the path diversity, however MAI was not considered in this scheme. In other words, as users of the system increase, the performance of system which used RAKE receiver will decay. When fading channel’s delay time is less than chip time, will be very difficult to evaluate the correct channel parameter, especially in uplink condition. In order to solve this problem, using decision feedback equalizer can not only suppression ISI, ICI and MAI. Therefore this paper main discussion the performance analysis of using decision feedback equalization for asynchronous CDMA in wireless communications.
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Lo, Chen-Chi, and 羅振吉. "Finite-Length Decision Feedback Equalization for Space-Time Block Coded Communication Systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42919895705043359630.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
95
Decision feedback equalization (DFE) is a well-established intersymbol interference mitigating technique for linear, noise, and dispersive channels. In this thesis, we discuss the finite length decision feedback equalization and present a new solution for the receiver based on the signal-to-interference and noise ratio (SINR) criterion. We also extend the DFE receiver concepts to space-time block-coded transmission over frequency-selective multi-input multi-output (MIMO) channels. The focus lies on Alamouti''s space-time block code with two transmit and only one receive antenna. Combined equalization and decoding scheme is presented under the constraint of linear processing complexity (no trellis search) at the receiver. Simulation is made over several channels including typical EDGE channels, and significant gains can be observed compared with a single-input single-output DFE scheme.
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Hsu, Yuan-Po, and 許淵博. "Performance Analysis of Decision-feedback Equalization over Mobile Radio Channels with CCI." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/58686617631271076543.
Full textAbstract:
碩士輔仁大學
電子工程學系
94
In mobile communications, the decision-feedback equalizer (DFE) is a most powerful and popular technology. Hence, the performance analysis of the finite-tap DFE is fairly important. This thesis presents the analysis of quadrature amplitude modulation (QAM) using optimum diversity combining with a finite-length DFE in the presence of co-channel interference (CCI) over frequency selective fading channels. Precise CCI model with the random time and phase offsets between the desired signal and co-channel interference is considered. The optimal diversity scheme can be developed while CCI is treated as a wide-sense stationary process (WSS). We derive the formula of the DFE with finite taps in the presence of ISI, CCI and noise. The simulation results can provide the designer to decide the required number of taps for his applications. In calculating the accurate average error probability, an efficient method namely Gaussian Quadrature Rules (GQR) is used.
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Lo, Chen-Chi. "Finite-Length Decision Feedback Equalization for Space-Time Block Coded Communication Systems." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0407200716135700.
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McGinty, Nigel. "Reduced Complexity Equalization for Data Communication." Phd thesis, 1998. http://hdl.handle.net/1885/47801.
Full textAbstract:
Optimal decision directed equalization techniques for time dispersive communication channels are often too complex to implement. This thesis considers reduced complexity decision directed equalization that lowers complexity demands yet retains close to optimal performance. The first part of this dissertation consists of three reduced complexity algorithms based on the Viterbi Algorithm (VA) which are: the Parallel Trellis VA (PTVA); Time Reverse Reduced State Sequence Estimation (TR-RSSE); and Forward-Backward State Sequence Detection (FBSSD). The second part of the thesis considers structural modifications of the Decision Feedback Equalizer (DFE), which is a special derivative of the VA, specifically, optimal vector quantization for fractionally spaced DFEs, and extended stability regions for baud spaced DFEs using passivity analysis are investigated. ¶ ...
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Yasotharan, Hemesh. "Equalization of Integrated Optical Photodiodes using an Infinite Impulse Response Decision Feedback Equalizer." Thesis, 2011. http://hdl.handle.net/1807/29649.
Full textAbstract:
This thesis examines the challenges in creating a fully integrated optical receiver. Due to the nature of silicon, 850nm light exhibits a poor impulse response when directed at an on-die photodiode. Using a modified decision feedback equalizer with an infinite impulse response filter in the feedback path allows to eliminate the long tail of post-cursor ISI that is generated by the photodiode. Due to silicide depositions over the photodiodes, making them opaque, the receiver was tested using an electrical cable with similar frequency roll-off as that of a photodiode. A data rate of 3.7 Gbps was achieved and only limited by the amount of input reflections at the transimpedance amplifier. The receiver occupies an area of 0.23 mm^2 and consumes 51.3mW.
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Bai, Yun-kai, and 白雲凱. "Block-based Bayesian Decision Feedback Equalization for ZP-OFDM Systems with Semi-Blind Channel Estimation." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/khv96f.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
95
Orthogonal frequency division multiplexing (OFDM) modulator with redundancy has been adopted in many wireless communication systems for higher data rate transmissions. The introduced redundancy at the transmitter allows us to overcome serious inter-block interference (IBI) problems due to highly dispersive channel. However, the selection of redundancy length will affect the system performance and spectral efficiency, and is highly dependent on the length of channel impulse response. In this thesis, based on the pseudorandom postfix (PRP) OFDM scheme we propose a novel block-based OFDM transceiver framework. Since in the PRP-OFDM system the PRP can be employed for semi-blind channel estimation with order-one statistics of the received signal. Hence, for sufficient redundancy case the PRP-OFDM system with the Bayesian decision feedback equalizer (DFE) is adopted for suppressing the IBI and ISI simultaneously. However, for the insufficient redundancy case (the length of redundancy is less than the order of channel), we first propose a modified scheme for channel estimation. To further reduce the complexity of receiver, the maximum shortening signal-to-noise-ratio time domain equalizer (MSSNR TEQ) with the Bayesian DFE is developed for suppressing the IBI and ISI, separately. That is, after knowing the channel state information (CSI) and removing the effect of IBI with MSSNR TEQ, the Bayesian DFE is applied for eliminating the ISI. Via computer simulation, we verify that performance improvement, in terms of bit error rate (BER), compared with the conventional block-based minimum mean square error (MMSE)-DFE can be achieved.
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Hsieh, Chih-nung, and 謝志農. "Block-Based Equalization Using Nonorthogonal Projector with Bayesian Decision Feedback Equalizer for CP-OFDM Systems." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/34663153613079932526.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
94
All digital communication channels are subject to inter-symbol interference (ISI). To achieve the desired system performance, at receiver end, the effect of ISI must be compensated and the task of the equalizer is to combat the degrading effects of ISI on the transmission. Due to the demand of high data transmission rate, the multicarrier modulation (MCM) technique implemented with the orthogonal frequency division multiplexing (OFDM) has been adopted in many modern communications systems for block transmission. In block transmission systems, transmitter-included redundancy using finite-impulse response (FIR) filterbanks can be utilized to suppress inter-block-interference (IBI). However, the length of redundancy will affect the system performance, which is highly dependent on the length of channel impulse response. To deal with the effect of ISI, many equalizing schemes have been proposed, among them the FIR zero-forcing (ZF) equalizer with the non-orthogonal projector provides a useful transceiver design structure for suppressing the IBI and ISI, simultaneously. In this thesis, we propose a new equalizing scheme; it combines the FIR-ZF equalizer with non-orthogonal projector as well as the Bayesian decision feedback equalizer (DFE) for IBI and ISI suppression. The Bayesian DFE is known to be one of the best schemes to achieve the desired performance for eliminating ISI. It can be employed to achieve the full potential of symbol-by-symbol equalizer. That is, after removing the effect of IBI with the non-orthogonal projector, the Bayesian DFE is employed for eliminating the ISI, simultaneously. For comparison, the system performance, in term of bit error rate (BER) is investigated, and compared with the minimum mean square error (MMSE)-IBI-DFE. The advantage of the new proposed equalizing scheme is verified via computer simulation under condition of insufficient redundancy.
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Gao, Hairong. "Design of high-speed summing circuitry and comparator for adaptive parallel multi-level decision feedback equalization." Thesis, 1997. http://hdl.handle.net/1957/34282.
Full textAbstract:
Multi-level decision feedback equalization (MDFE) is an effective sampled signal processing technique to remove inter-symbol interference (ISI) from disk read-back signals. Parallelism which doubles the symbol rate can be realized by utilizing the characteristic of channel response and decision feedback equalization algorithm.
A mixed-signal IC implementation has been chosen for the parallel MDFE. The
differential current signals from the feedback equalizer are subtracted from the forward
equalizer output at the summing node to cancel the non-causal ISI. A high-speed
comparator with 6 bit resolution is used after the cancellation to detect the signal which
contains no ISI.
In this thesis, a description of the parallel MDFE structure and decision feedback
equalization algorithm are presented. The design of a high-speed summing circuitry and
a high-speed comparator are discussed. The same comparator design is used for the flash
analog-to-digital converter (ADC) which generates error signals for adaptation.The
circuits design and layout were carried out in an HP 1.2-��m n-well CMOS process.Graduation date: 1998
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Xu, Qian-Jia, and 許乾甲. "A new joint echo cancellation and decision feedback equalization for baseband two-wire full-duplex data transmission." Thesis, 1986. http://ndltd.ncl.edu.tw/handle/56181412333030523383.
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Liang-SyunHuang and 黃亮勳. "Equalization for Single-Carrier Block Transmission in Fast-Varying Multipath Fading Channels Using Iterative Block Decision Feedback." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/03347947088553459868.
Full textAbstract:
碩士國立成功大學
電腦與通信工程研究所
101
In doubly-selective channels, single-carrier block transmission suffers from not only inter-symbol interference (ISI) but also virtual inter-carrier interference (virtual ICI) because channel variation within a transmitted block can no longer be neglected. In this case, the detection performance deteriorates considerably if the equalizer does not account for time selectivity. In the literature, equalization algorithms that cope with time-varying channels include time-domain minimum mean squared error linear equalizer (MMSE-LE) and minimum mean squared error successive interference cancellation (MMSE-SIC). The latter has a better error-rate performance, but the former has a much lower complexity. In hopes of achieving a better trade-off between performance and complexity, we extend the low-complexity iterative block decision feedback equalizer (IBDFE), originally designed for frequency-selective channels only, to doubly-selective channels. To deal with the virtual ICI, the matrix feedback filter is adopted. We assume correct decisions to derive the equalizer coefficients; however, we feed back the actual decisions in simulations. Simulation results show that the proposed algorithm achieves a better performance than MMSE-LE with only a slight increase in complexity. Compared with MMSE-SIC, the proposed algorithm has a poorer performance, but a much lower complexity.
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YANG, YUNG-HAO, and 楊庸豪. "Performance Analysis for SC-FDMA Using SIMO with Hybrid-Domain Decision Feedback Equalization over Rayleigh Fading Channel." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/hrb65u.
Full textAbstract:
碩士輔仁大學
電機工程學系碩士班
106
This thesis analyzes the performance of the single carrier frequency division multiplexing access (SC-FDMA) using diversity combining receiver with the Hybrid-domain decision feedback equalization (HD-DFE) over frequency-selective Rayleigh fading channel. The SC-FDMA is capable of using the Single-Carrier Frequency Domain Equalization (SC-FDE) techniques to combat the frequency selective nature of the channel. The proposed HD-DFE uses the frequency-domain feedforward filter (FD-FFF) to eliminate the post diversity-combining pre-cursor inter-symbol interference (ISI), and leaves the post-cursor inter-symbol interference (ISI) to be eliminated by the time-domain feedback filter (TD-FBF). The SC-FDMA has lower peak-to-average power ratio (PAPR) as compared with the OFDMA and has frequency diversity benefit from the different allocation scheme. Two channel allocation schemes, namely localized allocation scheme (LAS) and distributed allocation scheme (DAS) are considered in our analysis. Since using average method to calculate the accurate error probability is extremely time-consuming, we calculated fast and precisely using Gauss quadrature rule (GQR) method to approximate the error probability.
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Luo, Yuan-Hong, and 羅元鴻. "Accurate Performance Analysis of Optimum Space Diversity Combing and Finite-Length Decision-Feedback Equalization in Terrestrial Microwave Communication Systems." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41428055017921242098.
Full textAbstract:
碩士輔仁大學
電子工程學系
95
This research provides the performance analysis of QAM modulation with optimum space diversity combining and finite-length linear and decision-feedback equalization (DFE) in terrestrial microwave communications using minimum mean-square-error (MMSE) criterion. In our Monte Carlo simulation, the accurate error rate for each time-varying channel is obtained by using the Gauss quadrature rules (GQR) instead of the direct averaging method. The GQR algorithm can always provide precise results as well as considerable saving of simulation time when level of ISI is high. The number of taps to approach the optimum performance will be investigated. A comparison of the linear and the decision-feedback equalizer is also presented.
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Fang, Hung-Wen, and 方泓文. "Development and Accurate Performance Analysis of Optimum Diversity Combining and Decision-feedback Equalization over Mobile Radio Channel with CCI." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/95422852084040642397.
Full textAbstract:
碩士輔仁大學
電子工程學系
93
This research presents the analysis of optimum diversity combining Equalizations with quadrature amplitude modulation (QAM) in the presence of co-channel interference (CCI) over frequency-selective fading channels. Precise CCI model with the random time and phase offsets between the desired signal and co-channel interferers are considered. Having these two random-valued offsets, CCI can be treated as wide-sense stationary process (WSS) and therefore an optimal diversity can be developed. Diversity reception along with a post-combiner equalizer, either using a linear or decision-feedback scheme can be employed to simultaneously eliminate ISI and CCI. Since the accurate error probability estimation is very time exhaustive. We use Gaussian Quadrature Rule (GQR) method which is fast and accurate in evaluating average error probability.
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Hsu, Chen-Chu, and 徐禎助. "Multi-Stage Weighted Interference Cancellation and Decision Feedback Equalization with User Sorting and Receiver Diversity for MIMO CDMA Systems." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/56896359398282570921.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
91
Conventional multi-stage multi-user detectors (MUD) such as parallel interference cancellation (PIC) suffer from error propagation. In this thesis, unified signal models are introduced for general MIMO systems (including DS-CDMA and MC-CDMA). We propose several generalized multi-stage equalizers with receiver diversity, in which reliability weighting factors and user decision ordering are applied to reduce error propagation. Two flavors -- the parallelizable and nonparallelizabe — are presented in this thesis. An algorithm is next derived for the joint determination of the reliability weighting factors and weightings for linear diversity combining. Two selection diversity schemes are also presented as lower-complexity alternatives to linear diversity combining. Finally, sorting algorithms for determining the user decision order are also proposed. Simulation results show that the proposed multistage equalizers achieve very good performance. For Eb/N0<20 dB in DS-CDMA, using just a few stages certain variations of the proposed multistage equalizers almost achieve the single user bound with one antenna when the number of active users is smaller than 50 and with two antennas when the number of users is smaller than 30.
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Λιόνας, Ιωάννης. "Τεχνικές συμπιεσμένης καταγραφής για εκτίμηση και ισοστάθμιση αραιών καναλιών." Thesis, 2011. http://hdl.handle.net/10889/4995.
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Κανάλια με αραιή κρουστική απόκριση εμφανίζονται πάρα πολύ συχνά σε εφαρμογές ασύρματων κυρίως τηλεπικοινωνιακών συστημάτων. Παραδείγματα τέτοιων εφαρμογών είναι η εκπομπή HDTV (HighDefinitionΤelevision) ή εκπομπή μέσω υποθαλλάσιων ακουστικών καναλιών. Σε όλες αυτές τις εφαρμογές η μορφή του καναλιού διαμορφώνεται από το φαινόμενο της πολυδιόδευσης. Συνεπώς ο δέκτης λαμβάνει έναν περιορισμένο αριθμό από διαφορετικές εκδοχές του εκπεμπόμενου σήματος καθεμία με διαφορετική εξασθένιση και καθυστέρηση. Ως εκ τούτου η συνάρτηση της κρουστικής απόκρισης ενός τέτοιου καναλιού αποτελείται από ελάχιστα μη μηδενικά στοιχεία σε συγκριση με το μήκος της, καθένα από τα οποία αντιστοιχεί σε ένα από τα μονοπάτια πολυδιόδευσης. Για την ισοστάθμιση αυτών των καναλιών έχουν προταθεί διάφορες τεχνικές, πολλές από τις οποίες εκμεταλλεύονται την ιδιαίτερη αυτή μορφή της κρουστικής απόκρισης. Πολλοί από τους προτεινόμενους ισοσταθμιστές καναλιών απαιτούν την παρεμβολή ακολουθίων εκμάθησης ανάμεσα στην ακολουθία δεδομένων, οι οποίες είναι εκ των προτέρων γνωστές στον δέκτη. Χρησιμοποιούνται δε προκειμένου ο αλγόριθμος εκτίμησης του καναλιού να συγκλίνει όσο το δυνατόν ταχύτερα στην επιθυμητή τιμή. Μειονέκτημα αυτών των μεθόδων είναι η επιβάρυνση του ωφέλιμου εύρους ζώνης που συνεπάγεται. Ωστόσο η εκ των προτέρων γνώση της αραιής μορφής της κρουστικής απόκρισης εχει δώσει αφορμή για την σχεδίαση ισοσταθμιστών με περιορισμένο μήκος αλλά εξίσου καλή απόδοση. Οι συμβατικές τεχνικές εκτίμησης καναλιών, όπως η Least Square μέθοδος, δεν εκμεταλλεύονται αυτή την γνώση. Οι πρόσφατες δε εξελίξεις στην ανακατασκευή αραιών σημάτων μέσω τεχνικών συμπιεσμένης καταγραφής (compressed sensing) έχουν οδηγήσει στην μελέτη της εφαρμογής τέτοιων τεχνικών στο πρόβλημα της εκτίμησης καναλιού. Η μέθοδος της συμπιεσμένης καταγραφής στηρίζεται στη δυνατότητα ανακατασκευής αραιών σημάτων από πλήθος δειγμάτων αισθητά κατώτερο από αυτό που προβλέπει το θεωρητικό όριο του Nyquist. Έχει αποδειχθεί ότι η ανακατασκευή αυτή είναι δυνατή όταν το σήμα ή έστω κάποιος μετασχηματισμός του περιέχει λίγα μη μηδενικά στοιχεία σε σχέση με το μήκος του. Οι εφαρμογές αυτών των τεχνικών εκτείνονται και σε άλλα πεδία όπως η επεξεργασία εικόνας, η μαγνητική τομογραφία, η ανάλυση γεωφυσικών δεδομένων, η επεξεργασία εικόνας radar, η αστρονομία κ.α. Στα πλαίσια αυτής της εργασίας παρουσιάζονταιοι βασικές αρχές που διέπουν την ανακατασκευή αραιών σημάτων μέσω της επίλυσης υποορισμένων συστημάτων γραμμικών εξισώσεων. Παράλληλα παρουσιάζονται οι κυριότεροι αλγόριθμοι που έχουν προταθεί για την υλοποίηση της και εξετάζονται ως προς την απόδοση και την υπολογιστική πολυπλοκότητα τους. Εν συνεχεία εξετάζεται η εφαρμογή αυτών των αλγορίθμων στο πρόβλημα της εκτίμησης αραιών καναλιών. Προτείνονται δε ισοσταθμιστές αραιών καναλιών βασισμένοι σε εκτιμητές απόκρισης που χρησιμοποιούν τεχνικές συμπιεσμένης καταγραφής.Channels with sparse impulse response are very common in wireless telecommunications systems applications. Example of such channel is HDTV channel where multipath distribution of the transmitted signal results in a sparse form of the channel impulse response. Several different versions of the same signal are received, each one with its own gain and delay. As a result, channel impulse response has a few non zero taps compared to its length, its one corresponding to a different distribution path. Several techniques for estimating and equalizing such channels have been proposed, most of them taking advantage of this sparse form of the impulse response. The transmission of a training sequence known to the receiver is required for this purpose. It is used so that the channel estimation algorithm at the receiver converges faster. The disadvantage of the use of a training sequence is the fact that the useful bandwidth is reduced. However the a priori knowledge of the sparse form of the training sequence has led to the design of equalizers that require short training sequences but have satisfactory performance. Channel estimation techniques based on least square method do not take advantage of this idea. On the other hand recent progress on sparse signal reconstruction using compressed sensing techniques has led scientists to research the potential use of such algorithms in channel estimation. Compressed sensing is based on the idea of reconstructing a sparse signal using less samples that those predicted by Nyquist theorem. It has been proved that such a reconstruction is feasible if the reconstructed signal is sparse enough. In this dissertation several sparse signal reconstruction algorithms are presented and their performance and complexity are evaluated. Then the application of these algorithms on channel estimation equalization problem is analyzed.
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Fernandes, Telmo Gabriel Simões. "Time-Interleaved BWB-OFDM with Iterative FDE." Master's thesis, 2015. http://hdl.handle.net/10316/40550.
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