A modified PN code tracking loop for direct-sequence spread-spectrum communication over arbitrarily correlated multipath fading channels

A modified fully-digital PN code tracking loop is proposed for direct-sequence spread-spectrum communication. By taking advantage of the inherent diversity, a modified code tracking loop is embedded into a RAKE receiver to avoid problems caused by unstable locked points of error signals. Such unsteadiness of locked points often occurs with a conventional code tracking loop because the error signals may be randomly biased by multipath fading. Thus, a robust pull-in capability can be provided over a time-variant fading channel where multiple propagation paths are arbitrarily correlated. Very attractive behaviors obtained using the proposed technique are verified.