Proposed WCDMA receiver structure based on smart antennas system.

Alaa Jasim Mosa Al-Joubory
Dr. Samir S. Al-Attar
Dr. Fawzi M . Al-Naima

Abstract: Smart antennas systems (SAS’s) have gained a lot of interest due to the explosive growth in demand for mobile communications in the last few years to overcome practical challenges in providing the service. The main benefit of the SAS technology lies in its ability to exploit the spatial domain, on top of the temporal and frequency domains, to improve the transceiver performance. Uniform Circular Arrays (UCA’s) are of interest because of their natural ability to provide a full azimuth (i.e. 360°) coverage found in typical scenarios for sensor array applications, such as radar, sonar and wireless communications. In this dissertation, a unified study of Davies linear transformation technique as a UCA preprocessing technique is carried out. This transformation yields a mathematically more convenient form –the Vandermonde form– for the array steering vector. The purpose of this transformation is to adapt array processing techniques such as Direction Of Arrival (DOA) estimation and beampattern synthesis naturally suited for ULA’s to be applied to UCA’s New DOA algorithm for UCA arrays is proposed based on merging the Davies transformation technique with an improved version of the well known Root-MUSIC algorithm. The proposed method has many advantages over the conventional Root-MUSIC algorithms: (i) it can estimate the DOA angles of coherent sources, (ii) the algorithm does not require any forward/backward spatial smoothing, (iii) the proposed algorithm can estimate the DOA of (N-1) sources in comparison with (N/2) sources in the case of the conventional algorithm, and (iv) the computation load is significantly reduced due to the fact that the proposed algorithm doesn’t need to calculate the covariance matrix of the received signals, whereas the conventional algorithm does. In addition to these advantages, the simulation results show that the proposed algorithm provides superior DOA estimation resolution using fewer array elements and outperforms the conventional MUSIC algorithms by about 10 dB gain in SNR to achieve the same RMSE performance at RMSE=1o. A general smart antennas system (SAS) is developed based on exploiting the spatial domain by beamforming the uplink and downlink signals according to the DOA information estimated from the uplink signals. Simulation results of the SAS are presented to demonstrate the performance of the proposed SAS. In addition to the algorithm level studies, the application of the developed SAS to WCDMA, the RF link of 3G networks, is investigated. The performance of WCDMA link is evaluated in terms of BER improvement using a simple multi-user approach. Simulation is carried out assuming the multipath propagation environments of COST259 channel model. The final results showed significant improvement in the system performance as compared to the case without using SAS.