Adaptive techniques for code acquisition with receive diversity and constant false alarm rate schemes

Abstract

Recently, the use of multiple antennas in direct-sequence code division multiple access (DS/CDMA) systems has been widely recognized as a useful means to enhance the signal-to-noise ratio and increase the capacity of wireless systems. Nonetheless, the performance improvement of initial synchronization (i.e., code acquisition and tracking) using multiple antennas has rarely been considered. In DS/CDMA systems, acquisition of pseudonoise (PN) code should be performed first before the transmitted information can be retrieved. Since conventional acquisition systems have a fixed threshold value, they are unable to adapt themselves to varying mobile communication environments. An attractive class that can be used to overcome such problems is the class of constant false alarm rate (CFAR) schemes used widely in radar systems. In this dissertation, we address the cell averaging (CA), greatest of (GO), and smallest of (SO) CFAR processors for code acquisition in homogeneous and nonhomogeneous environment. The performance characteristics of the CA, GO, and SO processors are analyzed and compared when receiving antenna diversity is employed in the PN code acquisition of DS/CDMA systems. From the simulation results, it is observed that the GO CFAR scheme has the best performance in nonhomogeneous environment, and has almost the same performance as the CA CFAR scheme in homogeneous environment.