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MMSE equalization of downlink CDMA channel utilizing unused orthogonal spreading sequences

IEEE TRANSACTIONS ON SIGNAL PROCESSING 2003年第5期51卷 1390-1402页

作者： Choi, J Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW Australia

For the code division multiple access (CDMA) downlink channel, the chip-level equalization has been considered in this paper. There is no interference after despreading if all spreading codes are orthogonal, as in IS-95. However, it cannot be true for a frequency-selective fading channel. In this case, the chip-level equalization can be applied to restore the orthogonality. We investigate the chip-level equalization using finite impulse response (FIR) equalizers for the mobile station with multiple receive antennas. A blind approach and the minimum mean square error (MMSE) approach with cod.e-multiplexed pilot are considered. A generalized MMSE equalization, which combines the MMSE and blind approaches together, is also investigated;It is shown that the generalized MMSE equalizer can effectively increase the number of samples to track the variation of channel and thereby performs better when the coherence time is small. In addition, we derive closed-form solutions of the blind, MMSE, and generalized MMSE equalizers for given channels.

关键词： adaptive algorithm blind algorithm CDMA chip-level equalizer IS-95 time-variant frequency-selective fading

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blind adaptive carrier phase recovery for QAM systems

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DIGITAL SIGNAL PROCESSING 2016年 49卷 65-85页

作者： Abrar, Shafayat Zerguine, Azzedine Nandi, Asoke K. COMSATS Inst Informat Technol Islamabad 44000 Pakistan King Fahd Univ Petr & Minerals Dhahran 31261 Saudi Arabia Brunel Univ London Uxbridge UB8 3PH Middx England Tongji Univ Shanghai 200092 Peoples R China

This paper provides a study of adaptive phase recovery in quadrature amplitude modulation (QAM) based communication systems. Here, we modify the traditional fourth-power phase recovery algorithm (FP-PRA) to propose three improved algorithms, and analyze their performances in the presence of additive white Gaussian noise, phase noise, frequency-offset, and inter-symbol interference. We demonstrate that it is possible to obtain the optimal values of step-sizes (or loop-gains) in closed-form in the presence of phase noise and/or frequency-offset. In particular, we discuss two methods to improve FP-PRA. The first method involves utilizing the idea of partitioning the QAM constellation into QPSK-like and not-QPSK-like annular regions. The phase synchronizer is allowed to update only when a derotated QAM symbol lies in QPSK-like region;otherwise, the update process is stopped. The second method exploits an evolving idea of QAM-to-QPSK transformation, and uses transformed symbols to estimate phase mismatch. We provide a new interpretation of this transformation method and relate it to the quadrant-wise centroid of the rotated constellation. Furthermore, we discuss the feasibility of this method for both square and cross-QAM, and, identify and verify numerically the existence of false-locks in the case of cross-QAM. To the best of our knowledge, the ideas of constellation partitioning and constellation transformation have not appeared earlier in the context of adaptive phase recovery. We discuss adaptive blind estimation of optimal step-sizes in the presence of phase noise and frequency-offset. Finally, we discuss the modification of the proposed stochastic gradient methods to transform them into batch processing algorithms so as to make them more suitable for higher data rate systems. Numerical experiments indicate that the proposed algorithms can outperform the traditional FP-PRA algorithm for a number of practical QAM sizes under different mismatch conditions, and that o

关键词： Adaptive receiver design blind algorithm Carrier phase recovery Quadrature amplitude modulation Quadrature phase shift keying Mean square deviation

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Two blind algorithms of MMSE Filter Based on Second-Order Statistics in MIMO Systems with Multiple Interferences

Two Blind Algorithms of MMSE Filter Based on Second-Order St...

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2011年无线通信与信号处理国际会议(WCSP 2011)

作者： Bo Hu Xu Wang Tao Yang Fan He Rueywen Liu E.E. Dept. of Fudan University Shanghai 200433 China University of Notre Dame Notre Dame IN USA

In this paper, we consider an MIMO system with multiple interferences. The minimum mean-square error (MMSE) criterion is the best trade off between the rejection of interference and the preservation of user signal in terms of bit error rate (BER). The solution of MMSE filter is known but it requires channel state information which is to be estimated by pilot signals. The estimation tends to be inaccurate or time consuming when the interferences are large. As such, an accurate blind algorithm under heavy interferences would be an attractive alternative approach. In this paper two blind algorithms are presented, one for strong signal and one for strong interferences. The deviation of the mean-square error (MSE) between the ideal MMSE filter and the estimated MMSE filter by the blind algorithms are shown by simulation to be within 0.001.

关键词： Autocorrelation function MMSE filter blind algorithm Linear MIMO system

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blind-based demodulation scheme for virtual massive MIMO systems

Blind-based demodulation scheme for virtual massive MIMO sys...

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International Symposium on Antennas and Propagation (ISAP)

作者： Takahashi, Sota Watanabe, Issei Nishimori, Kentaro Taniguchi, Ryotaro Murakami, Tomoki Niigata Univ Ikarashi Grad Sch Sci & Technol Nishi Ku Ikarashi 2 Nocho 8050 Niigata 9502181 Japan NTT Corp Access Network Serv Syst Labs 1-1 Hikari No Oka Yokosuka Kanagawa 2390847 Japan

ISBN: (纸本)9784885523267

In beyond-fifth-generation (B5G) networks, massive multiple-input-multiple-output (MIMO) systems using a large number of base station antennas have attracted significant attention. As the number of antennas increases, the hardware scale of massive MIMO systems is complicated. In recent years, a virtual massive (VM)-MIMO system which performs MIMO transmission by using virtual antenna arrays creating a single antenna element has been investigated. In this paper, we propose a blind-based demodulation scheme for a VM-MIMO system to cancel the interference with oversampling. In our proposed scheme, as a signal whose level is less than a certain power threshold cannot be used in the high-order modulation scheme with oversampling, we apply filtering wherein signals with the noise power level are removed. Through this procedure, multi-level modulation signals can be utilized in VM-MIMO. Moreover, our simulation evaluations show that the bit error rate improves considerably by using our proposed scheme on the uplink commutation environment including up to ten users.

关键词： Virtual Massive MIMO blind algorithm Unsynchronous sampling

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A blind SNR ESTIMATOR FOR DIGITAL BANDPASS SIGNALS

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Journal of Electronics(China) 2008年第1期25卷 7-13页

作者： Sui Dan Ge Lindong Institute of Information Engineering Information Engineering University Zhengzhou 450002 China

A subspace-based blind Signal-to-Noise Ratio (SNR) estimation algorithm for digital bandpass signals in Additive White Gaussian Noise (AWGN) channel is discussed. The lower bounds of the mean and variance of the estimation are derived, and simulations are performed for the commonly used digital bandpass signals, such as MPSK (M=2, 4, 8), MFSK (M=2, 4) and MQAM (M=16, 64, 128, 256) signals. Theoretical analyses and simulation results indicate that the proposed algorithm is ef- fective even when the SNR is below 0dB. Furthermore, the algorithm can provide a blind estimator in that it needs neither the parameters of the received signals, such as the carrier frequency, symbol rate and modulation scheme, nor the synchronization of the system.

关键词： Signal-to-Noise Ratio (SNR) estimation blind algorithm Performance analysis Bandpass signals Subspace projection

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A semi-blind approach for MMSE equalization in downlink CDMA channel 8

A semi-blind approach for MMSE equalization in downlink CDMA...

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8th International Conference on Communication Systems

作者： Choi, JH Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia

ISBN: (纸本)0780375106

We investigate the chip-level equalization using finite impulse response (FIR) equalizers for the mobile station of code division multiple access (CDMA) systems with single and multiple receive antennas. As a semi-blind method, a generalized minimum mean square error (MMSE) equalization, which combines the MMSE and blind approaches together, is investigated. It is shown that the generalized MMSE equalizer can effectively increase the number of samples to track the variation of channel and thereby performs better when the coherence time is small. In addition, we derive a closed-form solution of the. MMSE and generalized MMSE equalizers for given channels.

关键词： CDMA IS-95 chip-level equalizer blind algorithm adaptive algorithm time-variant frequency-selective fading

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Hybrid Time/Frequency Domain Compensator for RF Impairments in OFDM Systems

Hybrid Time/Frequency Domain Compensator for RF Impairments ...

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22nd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Kiayani, Adnan Anttila, Lauri Zou, Yaning Valkama, Mikko Tampere Univ Technol Dept Commun Engn FI-33101 Tampere Finland

ISBN: (纸本)9781457713484

I/Q signal processing based communication systems suffer from analog front-end (FE) imperfections such as in-phase and quadrature-phase (I/Q) imbalance and carrier frequency offset (CFO). These impairments are commonly encountered in all practical implementations, and severely degrade the obtainable link performance. Moreover, orthogonal frequency division multiplexing (OFDM)-based systems are particularly sensitive to radio frequency (RF) impairments. In this paper, we analyze the impact of transmitter and receiver I/Q imbalance together with channel distortion and CFO error on an ideal transmit signal, and propose low-complexity DSP algorithms and compensation structure for coping with such imperfections. Based on our proposed estimation/compensation structure, we are able to decouple the impairments and process them individually with rather low-complexity. More specifically, we first apply a blind algorithm for receiver I/Q imbalance compensation, followed by an efficient time domain CFO estimator and compensator. The transmitter I/Q imbalance and channel are then equalized jointly, in the frequency domain, with maximum-likelihood (ML) or zero-forcing (ZF) schemes, respectively. The applied algorithms are either blind working without aid of any training symbol or use only one OFDM symbol for impairments estimation, providing an efficient alternative solution with reduced complexity. The computer simulation results indicate a close to ideal performance of ZF scheme, and sugget that additional performance improvement due to frequency diversity can be obtained when ML estimation technique is employed.

关键词： CFO error Channel estimation Estimation I/Q signal processing based communication system Joints ML estimation OFDM OFDM modulation OFDM symbol OFDM system OFDM-based system RF impairment Radio transmitters Receivers ZF scheme analog front-end imperfection blind algorithm carrier frequency offset channel distortion communication complexity diversity reception estimation-compensation structure frequency diversity frequency domain compensator in-phase imbalance link performance low-complexity DSP algorithm maximum likelihood estimation maximum-likelihood scheme orthogonal frequency division multiplexing quadrature-phase imbalance radio frequency impairment radio receivers radio transmitters receiver I/Q imbalance time domain CFO estimator time domain compensator transmitter I/Q imbalance wireless channels zero-forcing scheme

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Mathematical Model for an Autonomous Vehicle to Fulfill the Closed Area 6

Mathematical Model for an Autonomous Vehicle to Fulfill the ...

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6th International Conference on Imaging, Signal Processing and Communications (ICISPC)

作者： Namngam, Kampanat Chitsakul, Pakkinee Satthamsakul, Sutham King Mongkuts Inst Technol Ladkrabang KMITL Dept Math Sch Sci Bangkok Thailand King Mongkuts Inst Technol Ladkrabang KMITL Sch Engn Dept Instrumentat & Control Engn Bangkok Thailand

ISBN: (纸本)9781665454803

This research presents the mathematical model to roam an autonomous vehicle in a closed region with minor coincident areas. This model is blind algorithm, no literature that concern on mathematical model. It is essential for agricultural technology, for example, shoveling soil for planting, spraying liquid fertilizer, harvesting agricultural products, to control the movement of the vehicle with the redundant path is as less as possible is benefited to decrease the working hours and also the burning oil and more for cost-saving without any expensive hardware. The almost wholly filled farmland depends on the shape, the size of the area, and the vehicle dimension.

关键词： mathematical model low-cost autonomous vehicle blind algorithm quadrilateral

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Splicebuster: a new blind image splicing detector

Splicebuster: a new blind image splicing detector

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IEEE International Workshop on Information Forensics and Security(WIFS)

作者： Cozzolino, Davide Poggi, Giovanni Verdoliva, Luisa Univ Naples Federico II DIETI Naples Italy

ISBN: (纸本)9781467368025

We propose a new feature-based algorithm to detect image splicings without any prior information. Local features are computed from the co-occurrence of image residuals and used to extract synthetic feature parameters. Splicing and host images are assumed to be characterized by different parameters. These are learned by the image itself through the expectation-maximization algorithm together with the segmentation in genuine and spliced parts. A supervised version of the algorithm is also proposed. Preliminary results on a wide range of test images are very encouraging, showing that a limited-size, but meaningful, learning set may be sufficient for reliable splicing localization.

关键词： Image forensics forgery detection and localization local image descriptors blind algorithm

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Noisesniffer: a Fully Automatic Image Forgery Detector Based on Noise Analysis 9

Noisesniffer: a Fully Automatic Image Forgery Detector Based...

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9th International Workshop on Biometrics and Forensics (IWBF)

作者： Gardella, Marina Muse, Pablo Morel, Jean-Michel Colom, Miguel Univ Paris Saclay Ctr Borelli CNRS ENS Paris Saclay Gif Sur Yvette France Univ Republica Fac Ingn IIE Montevideo Uruguay

ISBN: (纸本)9781728195568

Images undergo a complex processing chain from the moment light reaches the camera's sensor until the final digital image is delivered. Each of these operations leave traces on the noise model which enable forgery detection through noise analysis. In this article we define a background stochastic model which makes it possible to detect local noise anomalies characterized by their number of false alarms. The proposed method is both automatic and blind, allowing quantitative and subjectivity-free detections. Results show that the proposed method outperforms the state of the art.

关键词： image forensics automatic forgery detection noise residual blind algorithm

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