Experimental evaluation of synchronization errors on the performance of smart antenna algorithms for CDMA

Official URL: http://risc01.sabanciuniv.edu/record=b1084500 (Table of Contents)

The CDMA and smart antennas are two promising approaches to increase system capacity and spectrum efficiency for mobile communication services. In a CDMA system, frequency offset between local oscillator and the carrier of impinging signal, timing offset between local generated PN sequence and received PN sequence, imperfect power control may exist and this degrades the performance of the smartantenna algorithms. In this thesis, the effects of frequency and timing offsets on smart antenna performance is presented. A smart antenna system has been set up to implement blind adaptive algorithms for W-CDMA in a laboratory environment. The blind adaptive algorithms implemented on the smart antenna system are Least- Squares Despread-Respread Multi Target Array (LS-DRMTA) and Least- Squares Despread-Respread Multi Target Constant Modulus Algorithm (LSDRMTCMA). Since both LS-DRMTA and LS-DRMTCMA algorithms utilize users PN sequence, they have several advantages compared to other blind adaptive algorithms for CDMA. BER and beamforming performances of LS-DRMTA and LSDRMTCMA algorithms in a two-user and two- element-antenna array system is evaluated for systems with timing offset and frequency offset. Experimental results show that frequency and timing offset degrades the performance, however they still give reasonable BER. In all test conditions LS-DRMTA and LS-DRMTCMA outperforms conventional receiver, moreover LS - DRMTCMA can generate deeper nulls and outperforms LS-DRMTA.