Abstract
In [1], a novel approach using smart antenna with adaptive thresholding constant false alarm rate (CFAR) in pseudo-noise (PN) code acquisition for direct sequence code division multiple access (DS/CDMA) communication systems in Rayleigh slowly fading multipath channel was proposed. In this paper, we consider the use of the censored mean level detector constant false alarm rate (CMLD-CFAR) algorithm as an adaptive threshold processor for DS/CDMA in multiuser signals situations. Under mobile communication environments, multipath signals and other users' signals affect the performance of the PN code acquisition. Fixed threshold techniques are unable to adapt to these varying environments. Accordingly, a high false alarm rate and/or a low detection probability may result, and thus, adaptive thresholding techniques are essential. A smart antenna is an array of antenna elements that can modify the array pattern adaptively to minimize the effect of noise, multiple access interference (MAI) of other users, and multipath. The proposed system still considers PN code serial acquisition by using the smart antenna, but an adaptive threshold value based on a reference window of CMLD-CFAR processing. We derive an exact expression for the probability of false alarm for the proposed system, while the detection performance of the system is studied in terms of computer simulations under various parameters. The simulation results show that the system proposed is robust in a MAI environment.