MMSE PN Code Tracking in Frequency Selective Fading Channels

M. El-Tarhuni (UAE) and A. Ghrayeb (Canada)


PN code tracking, adaptive filtering, CDMA, multipath fading.


Code tracking is very crucial in the successful operation of any direct sequence spread spectrum communication system. A small error in code timing would degrade their Bit Error Rate (BER) performance. The performance of conventional tracking loops, such as the delay-locked loop (DLL), has been shown to degrade significantly in the presence of multipath fading, especially when the multipath components are within a few chips apart. In this paper, we propose a new code tracking algorithm that uses a finite impulse response (FIR) adaptive filter to mitigate the multipath interference. We show that the root mean-square tracking error of the proposed scheme in the presence of two adjacent paths is less than one-eighth of a chip, which is deemed adequate for most applications. We also study the sensitivity of the proposed scheme with respect to various parameters, including the Doppler frequency and adaptation speed.

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