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ABSTRACT: We consider blind signal detection in an asynchronous code-division multiple-access (CDMA) system employing short spreading sequences in the presence of unknown multipath fading. This approach is capable of countering the presence of multiple-access interference (MAI) in CDMA fading channels. The proposed blind multiuser detector is based on an independent component analysis (ICA) to mitigate both MAI and noise. This algorithm has been utilised in blind source separation (BSS) of unknown sources from their mixtures. It can also be used for estimating the basis vectors of BSS. The aim is to include an ICA algorithm within a wireless receiver in order to reduce the level of interference in wideband systems. This blind multiuser detector requires no training sequence compared with the conventional multiuser detection receiver. The proposed ICA blind multiuser detector is made robust with respect to knowledge of signature waveforms and the timing of the user of interest. Several experiments are performed in order to verify the validity of the proposed ICA algorithm
IEE Proceedings - Communications 11/2006; · 0.32 Impact Factor
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ABSTRACT: We address in this paper a method for blind source separation of multi-microphone signals. The multi-microphone is modelled as a nonlinear mapping system, the nonlinear characteristic takes into consideration the sensor effect and natural phenomena. The observations (recorded signals) are modelled as post nonlinear mixtures. The proposed nonlinear algorithm is a generalization of serial gradient algorithm, cross-correlations, and Gram-Charlier series, which is extended in two ways: (1) to deal with nonlinear mapping, and (2) to be able to adapt to the actual statistical distributions of the sources by estimating the kernel density distribution at the output signals. The theory of the proposed learning algorithm is discussed. Simulations show that the algorithm is able to find the underlying sources from the post-nonlinear mixture observations
Machine Learning for Signal Processing, 2005 IEEE Workshop on; 10/2005
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ABSTRACT: We present experimental results of the blind separation of independent sources from their nonlinear mixtures. The proposed EKENS (equivariant kernel nonlinear separation) algorithm is a generalization of a natural gradient algorithm and the Gram-Charlier series, which is extended in two ways: (1) to deal with nonlinear mapping; (2) to be able to adapt to the actual statistical distributions of the sources by estimating the kernel density distribution at the output signals. The observations are modelled based on nonlinear generative multilayer perceptron analysis. The theory of the EKENS learning algorithm is discussed. Simulations show that the EKENS algorithm is able to find the underlying sources from the observation, even though the data generating mapping is nonlinear and unknown.
Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP '05). IEEE International Conference on; 04/2005 · 4.63 Impact Factor
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ABSTRACT: We propose an equivariant kernel nonlinear separation (EKENS) learning algorithm to extract independent sources from their nonlinear mixtures. Generally, unmixing signals from the nonlinear model in an unsupervised manner is very complicated, because both the nonlinear mapping and the sources distribution are not-known apriori, and should be learned from the observations. The observations are modelled based on nonlinear generative multilayer perceptrons analysis. The theory of the EKENS learning algorithm is discussed. In simulations with artificial data, the EKENS algorithm is able to find the underlying sources from the observation only, even though the data generating mapping is strongly nonlinear and flexible
Communications Theory Workshop, 2005. Proceedings. 6th Australian; 03/2005
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ABSTRACT: We propose and investigate a code-division multiple-access (CDMA) communication system using independent component analysis (ICA) for blind signal detection purposes. The proposed blind ICA based CDMA systems employ short spreading sequences in the presence of Rayleigh fading channels. This approach is capable of countering the presence of multiple access interference (MAI) in CDMA fading channels. The aim of the blind system is to include the ICA algorithm within a wireless receiver in order to reduce the level of multiuser interference in communication systems. Unlike the conventional MMSE receiver, the proposed ICA blind multiuser detector is made robust with no-training sequences and perfect knowledge of signature waveforms. It has achieved nearly the same performance of the conventional training based MMSE receiver. Several comparisons and experiments are performed based on examining bit error rate (BER) performance in AWGN and Rayleigh fading channels in order to verify the validity of the proposed blind ICA multiuser detector
Communications Theory Workshop, 2005. Proceedings. 6th Australian; 03/2005
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ABSTRACT: This paper introduces a blind multiuser detection algorithm for MIMO channels. The receiver is required to separate and recover the information signal of the desired user(s) based on independent component analysis (ICA) of the received sequence. The received sequence is assumed to be independent identically distributed. Experimental results show that the proposed blind ICA multiuser detection works well with a short symbol sequence, even if the channel time span is not accurately estimated. It is concluded that the proposed blind multiuser detection performs better than the conventional matched filters in a noisy environment.
Communications and Information Technology, 2004. ISCIT 2004. IEEE International Symposium on; 11/2004
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ABSTRACT: This paper investigates the performance of EASI algorithm and the proposed EKENS algorithm for linear and nonlinear mixtures. The proposed EKENS algorithm is based on the modified equivariant algorithm and kernel density estimation. Theory and characteristic of both the algorithms are discussed for blind source separation model. The separation structure of nonlinear mixtures is based on a nonlinear stage followed by a linear stage. Simulations with artificial and natural data demonstrate the feasibility and good performance of the proposed EKENS algorithm.
Communications and Information Technology, 2004. ISCIT 2004. IEEE International Symposium on; 11/2004
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ABSTRACT: This paper investigates the performance analysis of separation of mutually independent sources in nonlinear models. The nonlinear mapping constituted by an unsupervised linear mixture is followed by an unknown and invertible nonlinear distortion, are found in many signal processing cases. Generally, blind separation of sources from their nonlinear mixtures is rather difficult. We propose using a kernel density estimator incorporated with equivariant gradient analysis to separate the sources with nonlinear distortion. The kernel density estimator parameters of which are iteratively updated to minimize the output independence expressed as a mutual information criterion. The equivariant gradient algorithm has the form of nonlinear decorrelation to perform the convergence analysis. Experiments are proposed to illustrate these results.
Communications and Information Technology, 2004. ISCIT 2004. IEEE International Symposium on; 11/2004
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ABSTRACT: spread spectrum is a technique that the transmitted signal is spreaded over a broader portion of the radio frequency band, by means of a code independent of the data. This technique will however allow a better performance over a fading channel, inherent privacy, and immunity to narrowband interference. FCC has restricted the commercial use of the technology due to the increased frequency space it occupies. Therefore, step has to be taken to overcome the co-existence of wireless devices over this radio band. In this paper, we propose to adopt blind source separation techniques for interference mitigation in ISM band. These techniques strive to separate a mixture of N independent non-Gaussian signals received on an array of sensors and as such produce a signal with reduced jammer contamination. With the jammer mostly mitigated through the separation process, the SS system required smaller spreading gain and transmission bandwidth than the case if no separation is performed. Simulation results including other algorithms are provided to illustrate the effectiveness of the proposed approach.
Information, Communications and Signal Processing, 2003 and the Fourth Pacific Rim Conference on Multimedia. Proceedings of the 2003 Joint Conference of the Fourth International Conference on; 01/2004
