Intersymbol Decorrelating Detector for Asynchronous CDMA Networks with Multipath
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Intersymbol Decorrelating Detector for Asynchronous CDMA Networks with Multipath Gaonan Zhang School of Electrical and Electronic Engineering, Nanyang Technological University, Block S1, Singapore 639798 Email: [email protected]
Guoan Bi School of Electrical and Electronic Engineering, Nanyang Technological University, Block S1, Singapore 639798 Email: [email protected]
Qian Yu School of Electrical and Electronic Engineering, Nanyang Technological University, Block S1, Singapore 639798 Received 16 June 2003; Revised 16 March 2005; Recommended for Publication by Lawrence Yeung Most reported multiuser detection techniques for CDMA systems need the channel estimation including the delay spread and the parameters of the multipath channel of the desired user. This paper proposes an intersymbol decorrelating detector that makes use of the cross-correlation matrix constructed by the consecutively received symbols. The proposed detector is attractive for its simplicity because no channel estimation is required except for the synchronization of the desired user. Compared with other reported multiuser detectors, simulation results show that the proposed detector provides a good performance when the active users have significant intersymbol interference. Keywords and phrases: blind multiuser detection, cross-correlation matrix, multipath, decorrelating detector.
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INTRODUCTION
Blind multiuser detection for code-division multiple-access (CDMA) systems has flourished rapidly in recent years. The general ground work of blind multiuser detection was first reported in [1], in which it was assumed that the detector had no priori knowledge except for the signature waveform and timing of the desired user. Without considering the multipath, a blind minimum output energy (MOE) detector was proposed in [1], and later the canonical subspace representation of decorrelating detector and minimum mean square error (MMSE) detector were reported in [2]. In [3], a reducedrank MOE detector was proposed by using array processing techniques. However, these detectors would not work properly when the intersymbol interference (ISI) could not be ignored. In asynchronous CDMA systems, the ISI is generated by the delays and the multipath channels of the active users. In order to overcome the influence of the ISI, several approaches for channel estimation were developed in [4, 5, 6], This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
and a number of improved subspace detectors were proposed by exploiting the channel estimation in [7, 8, 9]. Since the channel estimation increases the computational complexity of the detectors substantively, a reduced computational constrained optimization solution was proposed with a sacrifice of the performance (inferior to MMSE detector) [10]. However, all these methods need to estimate the delay spread and the parameters of the multipath channel of the
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