Recently, a novel approach for PN code acquisition of direct sequence code division multiple-access (DS-CDMA) systems in Rayleigh fading multipath channel was proposed in . The authors considered a combination of adaptive thresholding constant false alarm rate (CFAR) and smart antennas to increase the system capacity and consequently enhance the detection performance. This paper considers still the problem of PN code acquisition for DS-CDMA communication systems over Rayleigh fading channels under the presence of multipath and multiple-access interference (MAI) signals. We propose and analyze an adaptive array acquisition system, which integrates an adaptive thresholding technique based on ordered data variability (ODV) index constant false alarm rate (ODVCFAR) and digital beamforming where a low complexity least mean square (LMS) algorithm is used to calculate the optimal weighting coefficients. This approach is expected to mitigate interferences caused by the presence of multiple access interference and multipath. Unlike other approaches based on a fixed censoring point when the number of interferences is assumed known, ODV-CFAR processing does not require prior knowledge about the number of interferences. The simulation results show a robust performance of the proposed system in varying mobile communication channels.
2. Polydoros, A. and C. L. Weber, "A unified approach to serial search spread-spectrum code acquisition --- Part I: General theory," IEEE Transactions on Communications, Vol. 32, No. 5, 542-549, 1984.
3. Linatti, J., "On the threshold setting principles on code acquisition of DS-SS signals," IEEE Journal on Selected Areas in Communications, Vol. 18, No. 1, 62-72, 2000.
4. Kim, C. J., H. J. Lee, and H. S. Lee, "Adaptive acquisition of PN sequences for DSSS communications," IEEE Transactions on Communications, Vol. 46, No. 8, 993-996, 1998.
5. Kim, C. J., "Adaptive acquisition of PN code in multipath fading mobile channels," Electronics Letters, Vol. 38, No. 2, 135-137, 2002.
6. Benkrinah, S. and M. Barkat, "An adaptive acquisition using order statistic CFAR in DS-CDMA serial search for a multipath Rayleigh fading channel," Proceedings of the Third IEEE International Conference on Systems, Signals and Devices, 2005.
7. Finn, H. M. and R. S. Johnson, "Adaptive detection mode with threshold control as a function of spatially sampled clutter level estimates," RCA Review, Vol. 29, 414-464, 1968.
8. Barkat, M., Signal Detection and Estimation, 2nd Ed., Artech House, Boston, MA, 2005.
9. Kedia, D., "Comparative analysis of peak correlation characteristics of non-orthogonal spreading codes for wireless systems," International Journal of Distributed and Parallel Systems (IJDPS), Vol. 3, No. 3, 63-74, 2012.
10. Zhang, X., X. Gao, and Z. Wang, "Blind paralind multiuser detection for smart antenna CDMA system over multipath fading channel," Progress In Electromagnetics Research, Vol. 89, 23-38, 2009.
11. Godara, L. C., Smart Antennas, 1st Ed., CRC Press LLC, New York, NY, 2004.
12. Wang, B. and H. M. Kwon, "PN code acquisition using smart antenna for spread-spectrum wireless communications ---| Part I," IEEE Transactions on Vehicular Technology, Vol. 52, No. 1, 142-149, 2003.
13. Wang, B. and H. M. Kwon, "PN code acquisition for DS-CDMA systems employing smart antennas --- Part II," IEEE Transactions on Wireless Communications, Vol. 2, No. 1, 108-117, 2003.
14. Gandhi, P. P. and S. A. Kassam, "Analysis of CFAR processors in nonhomogeneous background," IEEE Transactions on Aerospace and Electronic Systems, Vol. 24, No. 4, 427-445, 1988.
15. Alhariqi, N., M. Barkat, and A. Sofwan, "Serial PN acquisition using smart antenna and censored mean level CFAR adaptive thresholding for a DS/CDMA mobile communication," 14th IEEE International Conference on High Performance Computing and Communications (HPCC 2012), 1193-1198, 2012.
16. Rickard, J. T. and Adaptive detection algorithms for multiple-target situations, "Adaptive detection algorithms for multiple-target situations," IEEE Transactions on Aerospace and Electronic Systems, Vol. 13, No. 4, 338-343, 1977.
17. Ritcey, J. A., "Performance analysis of the censored mean-level detector," IEEE Transactions on Aerospace and Electronic Systems, Vol. 22, No. 4, 443-454, 1986.
18. Smith, M. E. and P. K. Varshney, "Intelligent CFAR processor based on data variability," IEEE Transactions on Aerospace and Electronic Systems, Vol. 36, No. 3, 837-847, 2000.
19. Himonas, S. D. and M. Barkat, "Automatic censored CFAR detection for nonhomogeneous environments," IEEE Transactions on Aerospace and Electronic Systems, Vol. 28, No. 1, 286-304, 1992.
20. Barboy, B., A. Lomes, and E. Perkalski, "Cell-averaging CFAR for multiple-target situations," IEE Proceedings --- Radar, Sonar and Navigation, Vol. 133, No. 2, 176-186, 1986.
21. Barkat, M., S. D. Himonas, and P. K. Varshney, "CFAR detection for multiple target situations," IEE Proceedings | Radar, Sonar and Navigation, Vol. 136, No. 5, 193-209, 1989.
22. Prastitis, L. A., J. Frank, and S. D. Himonas, "Automatic censored cell averaging CFAR detector in nonhomogeneous clutter," 1992 International Radar Conference, 218-221, 1992.
23. LehtomÄaki, J., J. Vartiainen, M. J. Juntti, and H. Saarnisaari, "CFAR outlier detection with forward methods," IEEE Transactions on Signal Processing, Vol. 55, No. 9, 4702-4706, 2007.
24. Liu, P.-Z. and C.-Z. Han, "Distributed automatic censored cell-averaging CFAR detector," Acta Automatica Sinica, Vol. 35, No. 7, 903-910, 2009.
25. Proakis, J. G., Digital Communications, 3rd Ed., McGraw-Hill, New York, 1995.
26. Song, Y. S., H. M. Kwon, and B. J. Min, "Computationally effcient smart antennas for CDMA wireless communications," IEEE Transactions on Vehicular Technology, Vol. 50, No. 6, 1613-1628, 2001.
27. Buehrer, R. M., Code Division Multiple Access (CDMA), 1st Ed., Morgan & Claypool, Blacksburg, Virginia, US, 2006.
28. Yang, L.-L. and L. Hanzo, "Serial acquisition of DS-CDMA signals in multipath fading mobile channels," IEEE Transactions on Vehicular Technology, Vol. 50, No. 2, 617-628, 2001.
29. Shin, O. S. and K. B. Lee, "Utilization of multipath for spread-spectrum code acquisition in frequency-selective Rayleigh fading channels," IEEE Transactions on Communication, Vol. 49, No. 4, 734-743, 2001.
30. Berbra, K., M. Barkat, and B. Atrouz, "Analysis of the CMLD in K-distributed clutter for fully correlated/uncorrelated texture," Proceedings of the 1999 International Radar Conference, 1999.
31. Rohling, H., "Radar CFAR thresholding in clutter and multiple target situations," IEEE Transactions on Aerospace and Electronic Systems, Vol. 19, No. 4, 608-621, 1983.