A Novel Adaptive Antenna Array for DS/CDMA Code Acquisition

Equipped with an adaptive beamformer, existing adaptive array code acquisition still relies on the correlator structure. Due to the inherent property of the associated serial-search scheme, its mean acquisition time is large, especially in strong interference environments. In this paper, we propose a novel adaptive filtering scheme to solve the problem. The proposed scheme comprises two adaptive filters, an adaptive spatial and an adaptive temporal filter. With a specially designed structure, the spatial filter can act as a beamformer suppressing interference, while the temporal filter can act as a code-delay estimator. A mean squared error (MSE) criterion is proposed such that these filters can be simultaneously adjusted by a stochastic gradient descent method. The performance as well as the convergence behavior of the proposed algorithm are analyzed in detail. Closed-form expressions for optimum filter weights, optimum beamformer signal-to-interference-plus-noise ratio (SINR), steady-state MSE, and mean acquisition time are derived for the additive white Gaussian noise (AWGN) channel. Computer simulations show that the mean acquisition time of the proposed algorithm is much shorter than that of the correlator-based approach, and the derived theoretical expressions are accurate.

[1]  Kwang Bok Lee,et al.  Acquisition for DS/CDMA systems with multiple antennas in frequency-selective fading channels , 2002, 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333).

[2]  Savo Glisic,et al.  Two-dimensional code acquisition in time and angular domains , 2001, IEEE J. Sel. Areas Commun..

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

[4]  A.U.H. Sheikh,et al.  An adaptive filtering PN code acquisition scheme with improved acquisition based capacity in DS/CDMA , 1998, Ninth IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (Cat. No.98TH8361).

[5]  S. Haykin,et al.  Adaptive Filter Theory , 1986 .

[6]  Asrar U. H. Sheikh,et al.  Code acquisition of DS/SS signals in fading channels using an LMS adaptive filter , 1998, IEEE Communications Letters.

[7]  Joseph R. Cavallaro,et al.  On multipath channel estimation for CDMA systems using multiple sensors , 2001, IEEE Trans. Commun..

[8]  Andreas Polydoros,et al.  A Unified Approach to Serial Search Spread-Spectrum Code Acquisition - Part I: General Theory , 1984, IEEE Transactions on Communications.

[9]  Hyuck M. Kwon,et al.  PN code acquisition for DS-CDMA systems employing smart antennas .II , 2003, IEEE Trans. Wirel. Commun..

[10]  Hyuck M. Kwon,et al.  PN code acquisition using smart antenna for spread-spectrum wireless communications. I , 2003, IEEE Trans. Veh. Technol..

[11]  Gonzalo Seco.  EXPLOITING ANTENNA ARRAYS FOR SYNCHRONIZATION , 2008 .

[12]  Sofiène Affes,et al.  A new receiver structure for asynchronous CDMA: STAR-the spatio-temporal array-receiver , 1998, IEEE J. Sel. Areas Commun..

[13]  Erik G. Ström,et al.  An efficient code-timing estimator for DS-CDMA signals , 1997, IEEE Trans. Signal Process..

[14]  Todd K. Moon,et al.  Average acquisition time for SSMA channels , 1991, MILCOM 91 - Conference record.

[15]  Kwang Bok Lee,et al.  Utilization of multipaths for spread-spectrum code acquisition in frequency-selective Rayleigh fading channels , 2001, IEEE Trans. Commun..

[16]  Upamanyu Madhow,et al.  Acquisition in direct-sequence spread-spectrum communication networks: An asymptotic analysis , 1993, IEEE Trans. Inf. Theory.

[17]  Hyung-Rae Park,et al.  On the performance of a maximum-likelihood code-acquisition technique for preamble search in a CDMA reverse link , 1998 .

[18]  H. Vincent Poor,et al.  On parameter estimation in long-code DS/CDMA systems: Cramer-Rao bounds and least-squares algorithms , 2003, IEEE Trans. Signal Process..

[19]  Wen-Rong Wu,et al.  A novel adaptive code acquisition using antenna array for DS/CDMA systems , 2005, IWAT 2005. IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials, 2005..

[20]  Wen-Rong Wu,et al.  Multirate adaptive filtering for DS/CDMA code acquisition , 2003, Proceedings of the 3rd IEEE International Symposium on Signal Processing and Information Technology (IEEE Cat. No.03EX795).

[21]  Hui Liu,et al.  Low-complexity space-time processor for DS-CDMA communications , 2000, IEEE Trans. Signal Process..

[22]  Guisheng Liao,et al.  PN code acquisition and beamforming weight acquisition for DS-CDMA systems with adaptive array , 2003, 14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003..

[23]  Jian Li,et al.  An efficient code-timing estimator for receiver diversity DS-CDMA systems , 1997, Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136).

[24]  Scott L. Miller,et al.  Acquisition performance of an adaptive receiver for DS-CDMA , 1999, IEEE Trans. Commun..

[25]  Simon Haykin,et al.  Adaptive filter theory (2nd ed.) , 1991 .

[26]  Neil J. Bershad,et al.  On the probability density function of the LMS adaptive filter weights , 1989, IEEE Trans. Acoust. Speech Signal Process..

[27]  Kwang Bok Lee,et al.  Acquisition for DS/CDMA systems with multiple antennas in frequency-selective fading channels , 2003, IEEE Trans. Wirel. Commun..

[28]  Bijan Jabbari,et al.  Spreading codes for direct sequence CDMA and wideband CDMA cellular networks , 1998, IEEE Commun. Mag..

[29]  Jack Kenneth Holmes,et al.  Coherent Spread Spectrum Systems , 1982 .

[30]  A.U. Sheikh,et al.  Adaptive synchronization for spread spectrum systems , 1996, Proceedings of Vehicular Technology Conference - VTC.

[31]  Savo Glisic,et al.  Two-dimensional code acquisition in environments with a spatially nonuniform distribution of interference: algorithms and performance , 2004, IEEE Transactions on Wireless Communications.

[32]  J.E. Mazo,et al.  Digital communications , 1985, Proceedings of the IEEE.