共查询到20条相似文献,搜索用时 31 毫秒
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Zhi Ding Jing Liang 《Signal Processing, IEEE Transactions on》2001,49(2):325-333
Blind identification of discrete-time single-user FIR channels with nonminimum phase is studied here. Exploiting higher order cumulants of output signals of unknown channels, a new closed-form solution to the FIR channel impulse response is derived. The algorithm is simple and fast. It relies only on nullspace decomposition of some cumulant matrices. This method neither involves the difficult task of iterative global minimization of nonunimodal cost functions, nor does it require overparametrization, which poses consistency difficulties. It can be used either as the final channel estimate or as a good initial point in nonlinear cumulant matching techniques. The application of this identification method is broad and not limited to the use of any fixed-order cumulants. Its application in identifying data communication systems shows great potential and promise 相似文献
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We consider the design and analysis of quantizers for equal gain transmission (EGT) systems with finite rate feedback-based communication in flat-fading multiple input single output (MISO) systems. EGT is a beamforming technique that maximizes the MISO channel capacity when there is an equal power-per-antenna constraint at the transmitter, and requires the feedback of t-1 phase angles, when there are t antennas at the transmitter. In this paper, we contrast two popular approaches for quantizing the phase angles: vector quantization (VQ) and scalar quantization (SQ). On the VQ side, using the capacity loss with respect to EGT with perfect channel information at transmitter as performance metric, we develop a criterion for designing the beamforming codebook for quantized EGT (Q-EGT). We also propose an iterative algorithm based on the well-known generalized Lloyd algorithm, for computing the beamforming vector codebook. On the analytical side, we study the performance of Q-EGT and derive closed-form expressions for the performance in terms of capacity loss and outage probability in the case of i.i.d. Rayleigh flat-fading channels. On the SQ side, assuming uniform scalar quantization and i.i.d. Rayleigh flat-fading channels, we derive the high-resolution performance of quantized EGT and contrast the performance with that of VQ. We find that although both VQ and SQ achieve the same rate of convergence (to the capacity with perfect feedback) as the number of feedback bits B increases, there exists a fixed gap between the two 相似文献
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针对全盲条件下正交空时分组码(OSTBC)的正交性识别问题,提出一种基于高阶累积量的OSTBC识别方法.通过对接收信号白化,在不需要信道估计的情况下,消除信道对识别结果的干扰,既减少了算法复杂度,又提高了低信噪比条件下OSTBC的识别概率;考虑实际系统中噪声对识别结果的影响,利用高阶累积量(阶数大于2)的去噪声特性,消除噪声对于STBC正交特性识别的影响;分析了两种四阶累积量的OSTBC识别特性,选取了适用于OSTBC识别的四阶累积量作为特征参数.仿真结果表明,所提出方法对于OSTBC识别问题区分性能较好. 相似文献
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调制识别算法及性能分析 总被引:1,自引:0,他引:1
为了提高信号调制识别的性能,以信号的六阶和四阶累积量作为识别特征,研究了一种基于高阶累积量的调制识别算法.分析了最大似然调制识别算法和高阶累积量调制识别算法的性能.并在高斯信道和平衰落信道下对其性能进行了仿真,仿真表明,在一般通信环境下,基于累积量的调制识别算法具有较强的稳健性和实用性. 相似文献
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This paper employs a high resolution quantization framework to study the effects of finite-rate quantization of the channel state information (CSI) on the performance of MISO systems over correlated fading channels. The contributions of this paper are twofold. First, as an application of the general distortion analysis, tight lower bounds on the capacity loss of correlated MISO systems due to the finite-rate channel quantization are provided. Closed-form expressions for the capacity loss in high-signal-to-noise ratio (SNR) and low-SNR regimes are also provided, and their analysis reveals that the capacity loss of correlated MISO channels is related to that of i.i.d. fading channels by a simple multiplicative factor which is given by the ratio of the geometric mean to the arithmetic mean of the eigenvalues of the channel covariance matrix. Second, this paper extends the general asymptotic distortion analysis to the important practical problem of suboptimal quantizers resulting from mismatches in the distortion functions, source statistics, and quantization criteria. As a specific application, two types of mismatched MISO CSI quantizers are investigated: quantizers whose codebooks are designed with minimum mean square error (MMSE) criterion but the distortion measure is the ergodic capacity loss (i.e., mismatched design criterion), and quantizers with codebook designed with a mismatched channel covariance matrix (i.e., mismatched statistics). Bounds on the channel capacity loss of the mismatched codebooks are provided and compared to that of the optimal quantizers. Finally, numerical and simulation results are presented and they confirm the tightness of theoretical distortion bounds. 相似文献
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In this paper, we propose a downlink transmission and receiving scheme for interleave-division multiple access (IDMA) system based on time-division duplexing (TDD) mode and time-reversal (TR) technique. The proposed scheme uses the time-reversed version of the channel impulse responses (CIR) obtained from the transmitted signal at base uplink to pre-process the station. By exploiting the weak correlations of fading channels for different user ends (UE), it is helpful to alleviate the multi-user interference (MUI) and co-channel interference (CCI). Moreover, the application of the TR technique in a multiple input-single output (MISO) configuration can reduce the delay spread of the channel impulse response, and mitigate inter-symbol interference (ISI). The UE can be simplified by canceling the iteration operation. Thus the data detection of the proposed scheme is rather simple as compared with the traditional IDMA, the complexity and computational load of UE is decreased substantially, and the proposed scheme provides a great deal of privacy and security to mobile users. 相似文献
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Konstantinos Diamantaras Theophilos Papadimitriou 《Journal of Signal Processing Systems》2011,65(3):525-534
In this paper we present a new blind identification and source separation method for linear Multi Input Single Output (MISO)
convolutive systems driven by PAM sources. Our method is based on the estimation of the output difference distribution for
pairs of outputs. We show that the most likely differences (not counting the zero difference) are the ones corresponding to
the columns of the mixing matrix (upto a sign). The columns can be arranged in the correct order by using the block-Toeplitz
property of the transfer matrix. Thus the problem is transformed into the density estimation problem. The method is conceptually
simple and can work with relatively small data sets although it is exponentially complex with the channel length or the number
of input signals. 相似文献
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Exact and general analysis of the capacity for multiple-input single-output (MISO) correlated Rayleigh fading channels in
the presence of both correlated Rayleigh co-channel interference and additive Gaussian noise is not available in the literature,
although its counterpart with Gaussian noise alone has been thoroughly investigated. The difficulty arises from the quadratic
form of interference term. In this paper, we obtain exact solutions to the ergodic and outage capacity for MISO systems with
and without channel state information at the transmitter. Numerical results are also presented for illustration. 相似文献
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通过对FSK/PSK混合调制雷达信号脉内特征的分析,提出了一种FSK/PSK混合调制信号多参数估计方法。利用快速四阶循环累积量算法、时频脊线分析与小波变换相结合的方法,实现了跳频频率和码速率等参数的高精度估计。仿真表明,该方法可在较低信噪比下得到该混合调制信号的多参数高精度估计,具有较高的工程应用价值。 相似文献
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Chuxiang Li Guosen Yue Khojastepour M.A. Xiaodong Wang Madihian M. 《Communications, IEEE Transactions on》2008,56(3):485-496
We treat the problem of designing low-density parity-check (LDPC) codes to approach the capacity of relay channels. We consider an efficient analysis framework that decouples the factor graph (FG) of a B-block transmission into successive partial FGs, each of which denotes a two-block transmission. We develop design methods to find the optimum code ensemble for the partial FG. In particular, we formulate the relay operations and the destination operations as equivalent virtual MISO and MIMO systems, and employ a binary symmetric channel (BSC) model for the relay node output. For AWGN channels, we further develop a Gaussian approximation for the detector output at the destination node. Jointly treating the relay and the destination, we analyze the performance of the LDPC-coded relay system using the extrinsic mutual information transfer(EXIT) chart technique. Furthermore, differential evolution is employed to search for the optimum code ensemble. Our results show that the optimized codes always outperform the regular LDPC codes with a significant gain; in the AWGN case, when Protocol-II is employed and the relay is close to the source, the optimized code performs within 0.1dB to the capacity bound. 相似文献
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We treat the performance analysis and optimization of an interleave-division-multiplexing (IDM) multiple-input-single-output (MISO) system with partial channel state information (CSI) at the transmitters and an iterative (turbo) receiver. We propose a general methodology to analyze and evaluate the performance of such an IDM-MISO system. In particular, an SNR tracking method is proposed to calculate the output SNR of the soft-input soft-output IDM detector. The extrinsic mutual information transfer chart technique is employed to analyze the performance of the entire system. More specifically, the repetition decoder and the low-density parity check decoder are considered for the uncoded IDM system and the coded IDM system, respectively. Furthermore, based on the above analytical framework, we present the optimal transmit strategy for the IDM-MISO system with an imperfect CSI at the transmitter. Extensive simulations are performed to demonstrate the performance of the proposed IDM schemes under the MISO channels with different correlation statistics. Our results show that the proposed IDM-MISO scheme can outperform the existing space-time block code schemes in the low-rate transmission scenario 相似文献
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The case where third-order cumulants of stationary ionic-channel current fluctuations (SICFs) are nonzero, and where SICFs are corrupted by an unobservable additive colored Gaussian noise that is independent of SICFs is considered. First, a virtual synthesizer that yields an output whose third-order cumulants are equivalent to those of SICFs on a specific slice is constructed. The synthesizer output is expressed by the sum of N s-1 first-order differential equation systems, where N s denotes the number of states of single ionic channels. Next, discretizing the synthesizer output, a discrete autoregressive [AR(N s-1)] process driven by the sum of N s-1 moving average (MA(N s -2)) processes is derived. Then the AR coefficients are explicitly related to the kinetic parameters of single ionic channels, implying that the kinetic parameters can be estimated by identifying the autoregressive moving-average coefficients using the third-order cumulants. In order to assess the validity of the proposed modeling and the accuracy of parameter estimates, Monte Carlo simulation is carried out in which the closed-open and closed-open-blocked schemes are treated as specific examples 相似文献
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Wei Li Wan-Chi Siu 《Signal Processing, IEEE Transactions on》2000,48(4):1144-1153
In this paper, we address the problem of identifying the parameters of the nonminimum-phase FIR system from the cumulants of noisy output samples. The system is driven by an unobservable, zero-mean, independent and identically distributed (i.i.d) non-Gaussian signal. The measurement noise may be white Gaussian, colored MA, ARMA Gaussian processes, or even real. For this problem, two novel methods are proposed. The methods are designed by using higher order cumulants with the following advantages. (i) Flexibility: method 1 employs two arbitrary adjacent order cumulants of output, whereas method 2 uses three cumulants of output: two cumulants with arbitrary orders and the other one with an order equal to the summation of the two orders minus one. Because of this flexibility, we can select cumulants with appropriate orders to accommodate different applications. (ii) Linearity: both the formulations in method 1 and method 2 are linear with respect to the unknowns, unlike the existing cumulant-based algorithms. The post-processing is thus avoided. Extensive experiments with ARMA Gaussian and three real noises show that the new algorithms, especially algorithm 1, perform the FIR system identification with higher efficiency and better accuracy as compared with the related algorithms in the literature 相似文献
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Different performance measures are an important mean in order to analyze and design wireless communications systems. Examples of common performance measures are the ergodic capacity, the outage capacity, and the average mean-square error (MSE). In this work, we study the delay-limited capacity (DLC). The DLC depends on the properties of the fading channel, e.g. on the spatial correlation and on the line-of-sight (LOS) component. In this letter, we derive the DLC for the general class of parallel fading channels, including the multiple antenna channels under moment and long-term power constraint. We prove that the DLC is Schur-concave with respect to the spatial correlation in single-input multiple-output (SIMO), and multiple-input single-output (MISO). Bounds for the DLC of multiple-input multiple-output (MIMO) and parallel fading channels are derived and the impact of the the mean component and spatial correlation on these bounds is characterized. 相似文献
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We proposed new solutions for distributed realization of the quasi orthogonal space-time block coding (QOSTBC), which is designed for 8 × 1 multiple input–single output (MISO) system. The first proposed solution assumes that base station and relay stations are equipped with 2 antennas, while for the second solution base station is equipped with 4 antennas and relay stations are with one antenna. In both scenarios mobile unit is equipped with single antenna. The proposed solutions are compared with distributed QOSTBC which is used for 4 × 1 MISO system. The simulation results show BER performances improvements provided with the proposed solutions in comparison with distributed QOSTBC designed for 4 × 1 MISO. It was shown that the first proposed scheme provides lower BER values than the second solution. Also, beside ideal channel estimation, influence of real estimation errors on BER performances is considered. 相似文献
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In frequency-division duplex (FDD) systems, channel-state information (CSI) is estimated by the receiver and then fed back to the transmitter through a feedback link, which inevitably requires additional bandwidth and power. In this letter, we jointly study optimal bandwidth allocation between the data channel, modeled as a flat-fading multiple-input single-output (MISO) channel, and the feedback channel for maximum average throughput in the data channel using a beamforming scheme. We consider two models of the partial CSI at the transmitter (CSIT): the noisy CSIT, modeled as jointly Gaussian with the actual channel state, and the quantized CSIT. In the first model, we use distortion-rate theory to relate the CSIT accuracy to the feedback-link bandwidth. In the second model, we derive a lower bound on the achievable rate of the data channel based on the ensemble of a set of random quantization codebooks. We show that in the MISO flat-fading channel case, beamforming based on feedback CSI can achieve an average rate larger than the capacity without CSIT under a wide range of mobility conditions. 相似文献
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