A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2001

Wide Band Code Division Multiple Access (WCDMA) has been selected as the main air interface standard for the third generation cellular systems. WCDMA facilitates the development of new wireless wideband multimedia applications, providing advanced services such as high-quality sound and video services for users. In a Code Division Multiple Access (CDMA) system, the code synchronization is a key task to be performed in the receiver. Conventionally this is accomplished by using the well known sliding correlator or the matched filter based code synchronization methods. However, the sliding correlator suffers from many drawbacks especially m an environment where the multiple access interference is high and the channel is fading rapidly. The performance of a CDMA system can drastically be improved by improving the synchronization sub-module of the system. Thus in this thesis, the applicability of a more advanced code acquisition scheme to the WCDMA system has been investigated. Subspace-based code acquisition schemes have been studied previously for the narrow band CDMA systems under simple channel conditions. In this research work the performance of a subspace-based code acquisition scheme is analysed for a WCDMA system under more practical channel conditions. The performance is analysed under a relatively fast fading channel condition and the code acquisition process is investigated for a Rake receiver structure where each finger of the Rake receiver is synchronized to one of the multipath components. The probability of acquisition error of the subspace-based code acquisition scheme is analysed with reference to the conventional sliding correlator code acquisition method for different parameter settings. Simulation results show that the subspace based code acquisition scheme gives better performance than the conventional sliding correlator when the system operates under heavy multiple access interference (MAI) conditions. Even though the complexity of the receiver is increased by the subspace-based code acquisition scheme, with the use of present state technology, it will not be a major drawback compared to the improvement of performance guaranteed by this method.