共查询到20条相似文献,搜索用时 15 毫秒
1.
We approach the multiple input multiple output (MIMO) decision feedback equalization (DFE) problem in digital communications from an H/sup /spl infin// estimation point of view. Using the standard (and simplifying) assumption that all previous decisions are correct, we obtain an explicit parameterization of all H/sup /spl infin// optimal DFEs. In particular, we show that, under the above assumption, minimum mean square error (MMSE) DFEs are H/sup /spl infin// optimal. The H/sup /spl infin// approach also suggests a method for dealing with errors in previous decisions. 相似文献
2.
Halpern M.E. Bottema M.J. Moran W. Dasgupta S. 《Signal Processing, IEEE Transactions on》1998,46(9):2353-2358
This paper contains results on the design of optimum equalizers to eliminate intersymbol interference (ISI) in linear nonminimum phase channels conveying binary signals. The optimization is with respect to an open eye condition with a delay d. For causal stable channels with n c nonminimum phase zeros, we argue that this problem requires only the consideration of the nc-tap FIR modified channel that has all the nc nonminimum phase zeros of the original channel. We show that if this modified channel can be equalized to yield an equalized system that is open eye with delay d, then the optimizing equalizer is, in fact, (d-nc)-tap FIR with all zeros outside the unit circle. We also give a simple necessary and sufficient condition to determine if for a particular d, a given channel can be equalized to achieve an equalized response that is open eye with delay d 相似文献
3.
As an alternative to existing techniques and algorithms, we investigate the merit of the H∞ approach to the linear equalization of communication channels. We first give the formulation of all causal H∞ equalizers using the results of and then look at the finite delay ease. We compare the risk-sensitive H∞ equalizer with the MMSE equalizer with respect to both the average and the worst-case BER performances and illustrate the improvement due to the use of the H∞ equalizer 相似文献
4.
Equalization and semi-blind channel estimation for space-time block coded signals over a frequency-selective fading channel 总被引:6,自引:0,他引:6
Jinho Choi 《Signal Processing, IEEE Transactions on》2004,52(3):774-785
In this paper, we investigate the equalization and channel identification for space-time block coded signals over a frequency-selective multiple-input multiple-output (MIMO) channel. The equalization has been considered by taking into account the cyclostationarity of space-time block coded signals. The minimum mean square error (MMSE) solutions have been derived for the linear and decision feedback (DF) equalizers. The channel estimation is required for the equalization. With known symbols (as pilot symbols), MIMO channels can be estimated. In addition, due to the redundancy induced by space-time block code, it is possible to identify MIMO channels blindly using the subspace method. We consider both blind and semi-blind channel estimation for MIMO channels. It is shown that the semi-blind channel estimate has fewer estimation errors, and it results in less (bit error rate) performance degradation of the MMSE linear and DF equalizers. 相似文献
5.
Koga H. Yamamoto H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(4):1546-1555
This correspondence is concerned with asymptotic properties on the codeword length of a fixed-to-variable length code (FV code) for a general source {X/sup n/}/sub n=1//sup /spl infin// with a finite or countably infinite alphabet. Suppose that for each n /spl ges/ 1 X/sup n/ is encoded to a binary codeword /spl phi//sub n/(X/sup n/) of length l(/spl phi//sub n/(X/sup n/)). Letting /spl epsiv//sub n/ denote the decoding error probability, we consider the following two criteria on FV codes: i) /spl epsiv//sub n/ = 0 for all n /spl ges/ 1 and ii) lim sup/sub n/spl rarr//spl infin///spl epsiv//sub n/ /spl les/ /spl epsiv/ for an arbitrarily given /spl epsiv/ /spl isin/ [0,1). Under criterion i), we show that, if X/sup n/ is encoded by an arbitrary prefix-free FV code asymptotically achieving the entropy, 1/nl(/spl phi//sub n/(X/sup n/)) - 1/nlog/sub 2/ 1/PX/sup n/(X/sup n/) /spl rarr/ 0 in probability as n /spl rarr/ /spl infin/ under a certain condition, where P/sub X//sup n/ denotes the probability distribution of X/sup n/. Under criterion ii), we first determine the minimum rate achieved by FV codes. Next, we show that 1/nl(/spl phi//sub n/(X/sup n/)) of an arbitrary FV code achieving the minimum rate in a certain sense has a property similar to the lossless case. 相似文献
6.
Hui Wu Tierno J.A. Pepeljugoski P. Schaub J. Gowda S. Kash J.A. Hajimiri A. 《Solid-State Circuits, IEEE Journal of》2003,38(12):2131-2137
Intersymbol interference (ISI) caused by intermodal dispersion in multimode fibers is the major limiting factor in the achievable data rate or transmission distance in high-speed multimode fiber-optic links for local area networks applications. Compared with optical-domain and other electrical-domain dispersion compensation methods, equalization with transversal filters based on distributed circuit techniques presents a cost-effective and low-power solution. The design of integrated distributed transversal equalizers is described in detail with focus on delay lines and gain stages. This seven-tap distributed transversal equalizer prototype has been implemented in a commercial 0.18-/spl mu/m SiGe BiCMOS process for 10-Gb/s multimode fiber-optic links. A seven-tap distributed transversal equalizer reduces the ISI of a 10-Gb/s signal after 800 m of 50-/spl mu/m multimode fiber from 5 to 1.38 dB, and improves the bit-error rate from about 10/sup -5/ to less than 10/sup -12/. 相似文献
7.
《Vehicular Technology, IEEE Transactions on》2008,57(5):2766-2778
8.
We propose a novel blind equalization method based on subgradient search over a convex cost surface. This is an alternative to the existing iterative blind equalization approaches such as the Constant Modulus Algorithm (CMA), which often suffer from the convergence problems caused by their nonconvex cost functions. The proposed method is an iterative algorithm called SubGradient based Blind Algorithm (SGBA) for both real and complex constellations, with a very simple update rule. It is based on the minimization of the l/sub /spl infin// norm of the equalizer output under a linear constraint on the equalizer coefficients using subgradient iterations. The algorithm has a nice convergence behavior attributed to the convex l/sub /spl infin// cost surface as well as the step size selection rules associated with the subgradient search. We illustrate the performance of the algorithm using examples with both complex and real constellations, where we show that the proposed algorithm's convergence is less sensitive to initial point selection, and a fast convergence behavior can be achieved with a judicious selection of step sizes. Furthermore, the amount of data required for the training of the equalizer is significantly lower than most of the existing schemes. 相似文献
9.
MMSE analysis of certain large isometric random precoded systems 总被引:1,自引:0,他引:1
Debbah M. Hachem W. Loubaton P. de Courville M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(5):1293-1311
Linear precoding consists in multiplying by an N/spl times/K matrix a K-dimensional vector obtained by serial-to-parallel conversion of a symbol sequence to be transmitted. In this paper, new tools, borrowed from the so-called free probability theory, are introduced for the purpose of analyzing the performance of minimum mean-square error (MMSE) receivers for certain large random isometric precoded systems on fading channels. The isometric condition represents the case of precoding matrices with orthonormal columns. It is shown in this contribution that the signal-to-interference-plus-noise ratio (SINR) at the equalizer output converges almost surely to a deterministic value depending on the probability distribution of the channel coefficients when N/spl rarr/+/spl infin/ and K/N/spl rarr//spl alpha//spl les/1. These asymptotic results are used to analyze the impact of orthogonal spreading as well as to optimally balance the redundancy introduced between linear precoding versus classical convolutional coding, while preserving a simple MMSE equalization scheme at the receiver. 相似文献
10.
Xiaofeng Lin Sooping Saw Jin Liu 《Solid-State Circuits, IEEE Journal of》2005,40(3):593-602
This paper presents a CMOS 0.25-/spl mu/m continuous-time 6-tap FIR filter that is used as a fractionally spaced receiver equalizer for 1-Gb/s data transmission. Each tap of the FIR filter delay line is realized with a second-order low-pass filter. Simulations show that the tap delay can be tuned from 100 ps to 300 ps while keeping a constant group delay within the bandwidth of 2.1 GHz and 800 MHz correspondingly. Experimental results show that the FIR filter can successfully recover a 1-Gb/s differential digital signal that has been transmitted over a 220-inch PCB trace which causes -31.48-dB attenuation at the symbol rate frequency of 1 GHz. The measured bit error rate after equalization is less than 10/sup -12/ over a 750-ps sampling range, compared to a 10/sup -2/ bit-error rate before equalization. Also presented are the measurement results comparing the horizontal and the vertical openings of the signals before and after equalization for PCB traces with different length. The chip dissipates 45 mW from a 2.5-V supply and occupies 0.33/spl times/0.27 mm/sup 2/ in a 0.25-/spl mu/m CMOS process. 相似文献
11.
Schwartz D.F. Allen J.C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2004,51(7):364-368
This paper presents the first implementation of Helton's H/sup /spl infin// approach to wide-band impedance matching. The prototypical problem is to maximize the transducer power gain uniformly over an operating band for a load connected to a generator by a lossless two-port. The H/sup /spl infin// approach computes the maximum transducer power gain attainable by any lossless two-port uniformly over the operating band. This maximum gain is computed for Fano's classic RLC circuit and an high-frequency antenna represented by measured reflectance data. 相似文献
12.
Ahmed S. Lambotharan S. Jakobsson A. Chambers J.A. 《Communications, IEEE Transactions on》2005,53(2):219-223
We consider estimation of frequency offset (FO) and equalization of a wireless communication channel, within a general framework which allows for different frequency offsets for various multipaths. Such a scenario may arise due to different Doppler shifts associated with various multipaths, or in situations where multiple basestations are used to transmit identical information. For this general framework, we propose an approximative maximum-likelihood estimator exploiting the correlation property of the transmitted pilot signal. We further show that the conventional minimum mean-square error equalizer is computationally cumbersome, as the effective channel-convolution matrix changes deterministically between symbols, due to the multiple FOs. Exploiting the structural property of these variations, we propose a computationally efficient recursive algorithm for the equalizer design. Simulation results show that the proposed estimator is statistically efficient, as the mean-square estimation error attains the Crame/spl acute/r-Rao lower bound. Further, we show via extensive simulations that our proposed scheme significantly outperforms equalizers not employing FO estimation. 相似文献
13.
本文通过对非线性信道模型的分析,构造了一种新的、关联模型的自适应均衡器。分析表明,与一般的基于Volterra级数的非线性扩展关联模型相比,新结构的权数大为减少。模拟实验证实,当信道噪声较小时,新结构以较高的精度收敛于最佳解。而且无论对最小相位或非最小相位信道,该均衡器均表现出良好的收敛特性和误码性能。 相似文献
14.
Masoomzadeh-Fard A. Pasupathy S. 《Selected Areas in Communications, IEEE Journal on》1996,14(3):512-520
A nonlinear decision-based adaptive equalizer compatible with differentially coherent phase shift keying (PSK) is proposed for frequency-selective fading channels. This equalization scheme is appropriate whenever conventional equalizers are not capable of tracking phase variations in selective fading channels. The received signal is first converted to a baseband signal and then sent through a differential detector. A nonlinear processor before the equalizer generates the needed nonlinear terms that are weighted and summed in the equalizer. Nonlinear intersymbol interference at the output of the differential detector is dealt with by minimizing an error signal between the output of the equalizer and the detected data. The adaptation algorithm can be any algorithm currently used for conventional equalizers. Our simulation results confirm that for channels with spectral nulls, equalization is achieved successfully with the proposed scheme, whereas, linear equalizers, either with coherent or noncoherent detection, fail 相似文献
15.
16.
In some estimation or identification techniques, a forgetting factor /spl rho/ has been used to improve the tracking performance for time-varying systems. However, the value of /spl rho/ has been typically determined empirically, without any evidence of optimality. In our previous work, this open problem is solved using the framework of H/sub /spl infin// optimization. The resultant H/sub /spl infin// filter enables the forgetting factor /spl rho/ to be optimized through a process noise that is determined by the filter Riccati equation. This paper seeks to further explain the previously derived H/sub /spl infin// filter, giving an H/sub /spl infin// interpretation of its tracking capability. Additionally, a fast algorithm of the H/sub /spl infin// filter, called the fast H/sub /spl infin// filter, is presented when the observation matrix has a shifting property. Finally, the effectiveness of the derived fast algorithm is illustrated for time-variant system identification using several computer simulations. Here, the fast H/sub /spl infin// filter is shown to outperform the well known least-mean-square algorithm and the fast Kalman filter in convergence rate. 相似文献
17.
《Signal Processing, IEEE Transactions on》2008,56(11):5555-5566
18.
Faa-Jeng Lin Tzann-Shin Lee Chih-Hong Lin 《Industrial Electronics, IEEE Transactions on》2003,50(3):456-470
In this paper, a robust controller design with H/sub /spl infin// performance using a recurrent neural network (RNN) is proposed for the position tracking control of a permanent-magnet linear synchronous motor. The proposed robust H/sub /spl infin// controller, which comprises a RNN and a compensating control, is developed to reduce the influence of parameter variations and external disturbance on system performance. The RNN is adopted to estimate the dynamics of the lumped plant uncertainty, and the compensating controller is used to eliminate the effect of the higher order terms in Taylor series expansion of the minimum approximation error. The tracking performance is ensured in face of parameter variations, external disturbance and RNN estimation error once a prespecified H/sub /spl infin// performance requirement is achieved. The synthesis of the RNN training rules and compensating control are based on the solution of a nonlinear H/sub /spl infin// control problem corresponding to the desired H/sub /spl infin// performance requirement, which is solved via a choice of quadratic storage function. The proposed control method is able to track both the periodic step and sinusoidal commands with improved performance in face of large parameter perturbations and external disturbance. 相似文献
19.
20.
We present a reinitialization scheme for blind equalizers adapted via the constant modulus algorithm (CMA) when an all-pole prefilter is included to whiten the received signal. The mechanism exploits the special structure of the minimum mean squared error (MMSE) equalizers and their relation with CMA equalizers. A heuristic rule for blind determination of the best equalization delay is also provided. Using these guidelines, the equalizer is capable of finding the optimal setting in an online and computationally efficient fashion. In particular, estimation and inversion of the channel output autocorrelation matrix is not needed, in contrast with previous approaches 相似文献