Blind interference cancellation for the downlink of CDMA systems (original) (raw)
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Blind Interference Cancellation for the Downlink of CDMA Systems 1
Ciss, 2000
In this paper we propose a blind interference cancellation (IC) receiver for asynchronous direct-sequence code-division multiple-access (DS-CDMA) systems using a maximum mean energy (MME) optimization criterion. The simulation results show that this scheme offers performance gains over the well known blind receiver that is based on the minimum mean squared error (MMSE) optimization criterion. Our results show that the blind receiver is particularly effective in the presence of a few strong interferers as may be the case in the downlink of CDMA systems where intracell user transmissions are orthogonal.
Blind successive interference cancellation for DS-CDMA systems
IEEE Transactions on Communications, 2002
In this work we propose a blind successive interference cancellation receiver for asynchronous direct-sequence code-division multiple-access (DS-CDMA) systems using a maximum mean energy (MME) optimization criterion. The covariance matrix of the received vector is used in conjunction with the MME criterion to realize a blind successive interference canceler that is referred to as the BIC-MME receiver. Simulation results show that this scheme offers performance gains over the well known blind receiver that is based on the minimum mean squared error (MMSE) optimization criterion. Further, the BIC-MME receiver is particularly effective in the presence of a few strong interferers as may be the case in the downlink of DS-CDMA systems where intracell user transmissions are orthogonal. The receiver is also shown to perform well in the presence of estimation errors of the covariance matrix making it suitable for use in time-varying channels. An iterative implementation that results in reduced complexity is also studied WINLAB Proprietary i
Nonlinear adaptive blind interference cancellation for DS-CDMA systems
Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152), 2000
In this paper we propose a multistage nonlinear blind interference cancellation (MS-NL-BIC) receiver for directsequence code-division multiple-access (DS-CDMA) systems. The receiver uses higher order statistics of the received baseband signal. Specifically, we use the second and fourth moments of the received signal to determine a component of the received vector that has significant mean energy and low variability of the energy which are favorable characteristics for application in an interference cancellation scheme that uses hard decisions. The structure of the receiver is multidimensional and can be viewed as a matrix of receivers. Each row in the matrix consists of receivers that perform (hard decisions) cancellation of successive components that have significant mean energy and low variability of the energy. The columns of the matrix essentially resemble multistage receivers that iteratively refine performance from earlier stages. Simulation results show that unlike linear receivers, the MS-NL-BIC is exceptionally efficient in systems with strong and highly correlated interferers, as may be the case in overloaded DS-CDMA systems.
Blind adaptive interference suppression for direct-sequence CDMA
Proceedings of The IEEE, 1998
Direct sequence (DS) code division multiple access (CDMA) is a promising technology for wireless environments with multiple simultaneous transmissions because of several features: asynchronous multiple access, robustness to frequency selective fading, and multipath combining. The capacity of DS-CDMA systems is interference-limited and can therefore be increased by techniques that suppress interference. In this paper, we present recent developments in interference suppression using blind adaptive receivers that do not require knowledge of the signal waveforms and propagation channels of the interference, and that require a minimal amount of information about the desired signal. The framework considered generalizes naturally to include additional capabilities such as receive antenna diversity. The most powerful application of the methods described here is for linearly modulated CDMA systems with short spreading waveforms (i.e., spreading waveforms with period equal to the symbol interval), for which they provide substantial performance gains over conventional reception. Implications for future system design due to the restriction of short spreading waveforms and directions for further investigation are discussed.
Multistage Blind Interference Cancellation and Channel Estimation for DS-CDMA Systems
2001
In this paper we propose a blind interference cancellation and channel estimation receiver for direct-sequence code-division multiple-access (DS-CDMA) systems, which assumes knowledge of only the nominal desired user signature sequence. It is a multistage nonlinear blind interference cancellation and channel estimation receiver that uses higher order statistics (second and fourth moments) of the received baseband signal. Simulation results show that unlike linear receivers, the scheme is exceptionally efficient in systems with strong and highly correlated interferers, and is also able to jointly estimate channel response and perform interference cancellation.
Multistage Nonlinear Blind Interference Cancellation for DS-CDMA Systems
Information Technology: Transmission, Processing and Storage, 2002
In this paper we propose a multistage nonlinear blind interference cancellation (MS-NL-BIC) receiver for direct-sequence code-division multiple-access (DS-CDMA) systems. The receiver uses higher order statistics of the received baseband signal. Specifically, we use the second and fourth moments of the received signal to determine a component of the received vector that has significant mean energy and low variability of the energy, both of which are favorable characteristics for application in an interference cancellation scheme that uses hard decisions. The structure of the receiver is multidimensional and can be viewed as a matrix of receivers. Each row in the matrix consists of receivers that perform (hard decisions) cancellation of successive components that have significant mean energy and low variability of the energy. The columns of the matrix essentially resemble multistage receivers that iteratively refine performance from earlier stages. Simulation results show that unlike linear receivers, the MS-NL-BIC is exceptionally efficient in systems with strong and highly correlated interferers, as may be the case in overloaded DS-CDMA systems.
2006 IEEE Ninth International Symposium on Spread Spectrum Techniques and Applications, 2006
In this work we propose an adaptive blind linear parallel interference canceller (PIC) for direct-sequence code division multiple access (DS-CDMA) systems in frequency selective fading channels. A code-constrained constant modulus (CCM) design criterion based on constrained optimization techniques is proposed for PIC detectors in scenarios subject to multipath, and computationally efficient blind adaptive stochastic gradient (SG) and recursive least squares (RLS) algorithms are described for estimating both the receiver and channel parameters. Simulation results for an uplink scenario assess the algorithms, the proposed blind adaptive PIC detectors against existing receivers and evaluate the effects of error propagation of the new cancellation techniques.
Blind Adaptive Successive Interference Cancellation for Multicarrier DS-CDMA
ArXiv, 2011
A new adaptive receiver design for the Multicarrier (MC) DS-CDMA is proposed employing successive interference cancellation (SIC) architecture. One of the main problems limiting the performance of SIC in MC DS-CDMA is the imperfect estimation of multiple access interference (MAI), and hence, the limited frequency diversity gain achieved in multipath fading channels. In this paper, we design a blind adaptive SIC with new multiple access interference suppression capability implemented within despreading process to improve both detection and cancellation processes. Furthermore, dynamic scaling factors derived from the despreader weights are used for interference cancellation process. This method applied on each subcarrier is followed by maximum ratio or equal gain combining to fully exploit the frequency diversity inherent in the multicarrier CDMA systems. It is shown that this way of MAI estimation on individual subcarrier provides significantly improved performance for a MC DS-CDMA s...
IEEE Transactions on Wireless Communications, 2004
The paper deals with the problem of blind mitigation of intersymbol interference (ISI) as well as multiple-access interference (MAI) in asynchronous high data-rate direct-sequence code-division multiple-access systems. A blind adaptive multiuser receiver based on the constant-modulus algorithm (CMA) is proposed, which demodulates each desired user by exploiting only the knowledge of its spreading code, without requiring estimation of the users's channels and timings. In order to overcome the CMA interference capture problem, which arises in a multiuser scenario, a two-stage adaptive receiver is adopted: In the first stage, partial MAI and ISI suppression is blindly achieved by exploiting the desired user signature structure properties; in the second stage, the residual MAI and the ISI are removed by using the CMA, and the information symbols of the desired user are reliably recovered. Theoretical analysis and simulation results show that the first stage is an effective blind adaptive strategy which allows the CMA detector in the second stage to lock on the desired-user symbol, at a particular delay. The proposed blind receiver achieves a significant performance gain in comparison with existing blind methods.