Improved subspace-based channel estimation algorithm for DS/CDMA systems exploiting pulse-shaping information

An improved subspace-based channel estimation algorithm for DS/CDMA system is presented. The proposed algorithm is based on the Torlak/Xu algorithm for asynchronous DS/CDMA systems. The aim is to incorporate knowledge of the pulse-shaping filter into the Torlak/Xu subspace algorithm with the objective of reducing the variance of the channel estimates. The improved algorithm is developed from a system model of a DS/CDMA system where the output is oversampled with respect to the chip rate. By oversampling the received signal, knowledge of the pulse-shaping filter is incorporated into the proposed channel estimation algorithm. It is shown that the variance of the channel estimate for the proposed subspace algorithm is less than the Torlak/Xu algorithm that does not exploit pulse-shaping filter information. A mathematical expression of the mean square error of estimation for the improved algorithm is also derived. It is shown that the analytical expression provides a good approximation of the actual mean square error for high SNR signals.

[1]  John G. Proakis,et al.  Digital Communications , 1983 .

[2]  Lang Tong,et al.  A new approach to blind identification and equalization of multipath channels , 1991, [1991] Conference Record of the Twenty-Fifth Asilomar Conference on Signals, Systems & Computers.

[3]  F. Li,et al.  Performance analysis for DOA estimation algorithms: unification, simplification, and observations , 1993 .

[4]  S. V. Schell,et al.  Improved performance of blind equalization using prior knowledge of transmitter filter , 1994, Proceedings of MILCOM '94.

[5]  Eric Moulines,et al.  Subspace methods for the blind identification of multichannel FIR filters , 1995, IEEE Trans. Signal Process..

[6]  Behnaam Aazhang,et al.  Subspace-based channel estimation for code division multiple access communication systems , 1996, IEEE Trans. Commun..

[7]  Stefan Parkvall,et al.  DS-CDMA Synchronization in Time-Varying Fading Channels , 1996, IEEE J. Sel. Areas Commun..

[8]  Stefan Parkvall,et al.  Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems , 1996, IEEE Trans. Commun..

[9]  Murat Torlak,et al.  Blind multiuser channel estimation in asynchronous CDMA systems , 1997, IEEE Trans. Signal Process..

[10]  L. Tong,et al.  Multichannel blind identification: from subspace to maximum likelihood methods , 1998, Proc. IEEE.

[11]  Antti Toskala,et al.  WCDMA for UMTS: Radio Access for Third Generation Mobile Communications , 2000 .

[12]  Erik G. Ström,et al.  A maximum likelihood approach for estimating DS-CDMA multipath fading channels , 2000, IEEE Journal on Selected Areas in Communications.

[13]  Urbashi Mitra,et al.  Complexity reduction in subspace-based blind channel identification for DS/CDMA systems , 2000, IEEE Trans. Commun..

[14]  Eric Moulines,et al.  Blind identification of multipath channels: a parametric subspace approach , 2001, IEEE Trans. Signal Process..

[15]  Antti Toskala,et al.  Wcdma for Umts , 2002 .