Use of smart antenna system in universal mobile communications systems (UMTS)

Smart antenna technology is gaining more and more interest in the wireless community. The smart antenna, compared to conventional antenna, significantly improves channel capacity, spectral efficiency, and coverage area. In a direct sequence-code division multiple access (DS-CDMA) system, since all users share the same frequency, the interference reduction is a major criterion to improve capacity and performance. In this study, we focus on adaptive beamforming algorithms with smart antenna at the CDMA base station for interference reduction and multipath suppression in the up (reverse) link. Two algorithms, least squares de-spread re-spread multitarget array (LS-DRMTA) and least squares de-spread re-spread multitarget constant modulus algorithm (LS-DRMTCMA) are examined and compared. Results show that a smart antenna using these algorithms provides nulls in all directions of the interferers even under extremely low signal-to-interference (SIR) ratio. The LS-DRMTA has several advantages over the LS-DRMTCMA. The LS-DRMTCMA can offer a much better bit error rate performance compared to the LS-DRMTA, but at the expense of additional complexity.

[1]  Zhigang Rong,et al.  Simulation of Adaptive Array Algorithms for CDMA Systems , 1996 .

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

[3]  Theodore S. Rappaport,et al.  Simulation of multitarget adaptive array algorithms for wireless CDMA systems , 1997, 1997 IEEE 47th Vehicular Technology Conference. Technology in Motion.

[4]  J. Capon High-resolution frequency-wavenumber spectrum analysis , 1969 .

[5]  B. Agee Blind separation and capture of communication signals using a multitarget constant modulus beamformer , 1989, IEEE Military Communications Conference, 'Bridging the Gap. Interoperability, Survivability, Security'.

[6]  Theodore S. Rappaport,et al.  Smart Antennas for Wireless Communications: Is-95 and Third Generation Cdma Applications , 1999 .

[7]  S. Applebaum,et al.  Adaptive arrays , 1976 .

[8]  John Litva,et al.  Digital beamforming in wireless communications , 1996 .

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

[10]  B. G. Agee,et al.  The least-squares CMA: A new technique for rapid correction of constant modulus signals , 1986, ICASSP '86. IEEE International Conference on Acoustics, Speech, and Signal Processing.