A robust code acquisition architecture for non-coherent systems using dual digital matched filters

In this paper, we are proposing a new noncoherent PN code acquisition method for CDMA mobile communication systems. The proposed method employs two digital matched filters, and the code acquisition is based on a double dwell process. Through serial cascading of the dual matched filters, the proposed code acquisition method keeps track of the incoming sequence, until it eliminates the possibility of false alarms through the verification process. This unique feature imparts to our design much desired stability. Moreover, the use of two matched filters in parallel increases the acquisition speed which is of prime importance in the currently emerging wide-band CDMA technology such as IMT2000. Our performance analysis show that the proposed acquisition technique can achieve code acquisition within 35 ms at -10 dB input chip SNR. This is many times faster than the conventional active correlation technique. In this analysis, we have considered the minimum expected acquisition time as the condition for optimality. At this minimized acquisition time, we have analyzed the threshold values required for optimal performance and have derived the probability of detection and false alarm. The worst case acquisition time for the proposed system is 850 ms and the best case is 21 ms. The probability of false alarm for our system is of the order of 3.7^×10^-4