Comparison of PN code tracking digital DLL´s for direct sequence spread spectrum systems

Four different digital delay locked loops for PN code tracking in DS-CDMA systems are compared in this paper. Three of them, namely coherent, noncoherent and modified tracking schemes are well known. The fourth is the new scheme that we propose here as an alternative to the noncoherent (L2 norm) DLL. The new scheme is based on L1 norms of the early and late correlator output signals that are used to form an error signal. The error signal is used to control the local PN code delay. It has been shown that L1 norm based tracking offers similar performance in terms of tracking jitter to that of L2 norm tracking and as such is a viable candidate for implementation because it is computationally less demanding when implemented on DSPs.