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blind adaptive beamformer for cyclostationary sources with application to CDMA systems

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2004年第5期E87A卷 1258-1269页

作者： Miyajima, T Ibaraki Univ Dept Syst Engn Hitachi Ibaraki 3168511 Japan

In this paper, a simple blind algorithm for a beamforming antenna is proposed. This algorithm exploits the property of cyclostationary signals whose cyclic autocorrelation function depends on delay as well as frequency. The cost function is the mean square error between the delay product of the beamformer output and a complex exponential. Exploiting the delay greatly reduces the possibility of capturing undesired signals. Through analysis of the minima of the non-quadratic cost function, conditions to extract a single signal are derived. Application of this algorithm to code-division multiple-access systems is considered, and it is shown through simulation that the desired signal can be extracted by appropriately choosing the delay as well as the frequency.

关键词： cyclostationarity DS/CDMA adaptive array antenna blind algorithm higher-order statistics

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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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Pre- Calibration Techniques for Transmitter-Side RF Imbalance and Spectrum Distortion 95

Pre- Calibration Techniques for Transmitter-Side RF Imbalanc...

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IEEE 95th Vehicular Technology Conference: (VTC-Spring)

作者： Deng, Juinn-Horng Prasad, Pavan Vatal Shankar Huang, Wei-Cheng Ku, Meng-Lin Yuan Ze Univ Dept Elect Engn 135 Yuan Tung Rd Chungli Taiwan Natl Cent Univ Dept Commun Engn 300 Zhong Da Rd Chungli Taiwan

ISBN: (数字)9781665482431

ISBN: (纸本)9781665482431

In this paper, we study the cascaded pre-calibration techniques to overcome the coexisting problems of RF IQ imbalance (IQI) and RF spectrum distortion, which can improve the performance of a single package mmWave IC. The calibration techniques are designed separately. We first pre-compensate the IQI effect by using a single-tone signal with a blind algorithm to estimate the impairment parameters and calculate the precalibration weighting coefficients. After that, we adopt quadrature wideband training sequences to estimate the RF distorted responses and calculate the pre-calibration filters via the deconvolution techniques. The above calibration schemes are realized in the digital pre-processing domain and can perform better than the conventional RF calibration circuit design. Both the computer simulation results and the mmWave software defined radio (SDR) platform measurement results confirm that the proposed techniques can pre-calibrate the cascaded RF IQI and RF spectrum distortion problems.

关键词： Separated calibration procedures RF IQ imbalances RF spectrum distortion digital pre-calibration blind algorithm deconvolution technique mmWave software defined radio platform.

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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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blind Adaptive Arrays with Subcarrier Transmission Power Assignment for Spectrum Superposing

Blind Adaptive Arrays with Subcarrier Transmission Power Ass...

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Asia-Pacific Microwave Conference Proceedings

作者： Maruta, Kazuki Mashino, Jun Sugiyama, Takatoshi NTT Corp NTT Access Network Serv Syst Labs 1-1 Hikarino Oka Yokosuka Kanagawa 2390847 Japan NTT Corp NTT Network Innovat Labs Yokosuka Kanagawa 2390847 Japan

ISBN: (纸本)9784902339314

This paper proposes an extension scheme of blind adaptive arrays for spectrum superposing in cognitive radio networks. Though Maximal Ratio Combining (MRC) and Power Inversion (PI) are known as one of the blind adaptive array algorithms, MRC strongly receives a desired signal when SIR (at the antenna input)>0dB while PI appropriately suppresses interference signal when SIR<0dB. With the proposed method, the secondary transmitter intentionally provides a level difference between subcarriers. At the receiver side, MRC is applied to the received signals of subcarrier assigned higher power and PI is applied to ones assigned lower power. Computer simulation results show that the proposed scheme can suppress interference around SIR=0dB while improving operational SIR for the primary system over 5dB. Our initial study revealed the validity of the proposed scheme for spectrum superposing.

关键词： Adaptive Array Subcarrier Transmission Power Assignment blind algorithm Maximal Ratio Combining (MRC) Power Inversion (PI) Spectrum Superposing

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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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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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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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Constant Modulus and Kurtosis based blind Adaptive Array Interference Suppression: Comparisons and New Approach 18

Constant Modulus and Kurtosis based Blind Adaptive Array Int...

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18th International Symposium on Communications and Information Technologies (ISCIT)

作者： Maruta, Kazuki Nishimori, Kentaro Ahn, Chang-Jun Chiba Univ Grad Sch Engn Chiba Japan Niigata Univ Grad Sch Sci & Technol Niigata Japan

ISBN: (纸本)9781538684580

This paper presents performance comparison of interference suppression on blind adaptive array algorithms. Co-channel interference becomes more extensive due to frequency resource exhaustion and small cell deployment which had been triggered by mobile traffic explosion. Multi-antenna signal processing is an effective means for such co-channel interference suppression. Strict approach is to utilize a priori information of channel state by estimating it via known training sequences. It gratuitously consumes radio resource and thus overhead inflates according to the increase of interference source to be suppressed. In addition, training sequence cannot be shared between wireless communication systems employing different transmission schemes. Here we focus on blind adaptive array where any channel estimation is not required. algorithms of interest in this study are based on constant modulus and independent component analysis (ICA) criteria. We present fundamental observation of their interference suppression performance compared in terms of modulation order, number of interference sources, and degree of freedom, then derive the most stable approach using ICA incorporated with beamspace pre-processing.

关键词： Adaptive array blind algorithm Interference suppression Constant modulus Independent component analysis

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