A modified PN code tracking loop for direct-sequencespread-spectrum communication over arbitrarily correlated multipathfading channels

摘要

A modified fully digital pseudonoise code tracking loop isnproposed for direct-sequence spread-spectrum communication. By takingnadvantage of the inherent diversity, a modified code tracking loop isnembedded into a RAKE receiver in order to avoid problems caused bynunstable locked points of error signals. Such unsteadiness of lockednpoints often occurs with a conventional code tracking loop because thenerror signals may be randomly biased by multipath fading. Thus, a robustnpull-in capability can be provided over a time-variant fading channelnwhere multiple propagation paths are arbitrarily correlated.nFurthermore, an effective multipath interference regeneration andncancellation technique is also proposed to improve the errorncharacteristics of the proposed technique. Analytical expressions of thenerror characteristics and error signals are derived and then confirmednby means of extensive computer simulation results. In addition, severalnsimulation results for the timing jitter and the mean time to lose locknare also presented. The very attractive behavior obtained using thenproposed technique is verified