A Fast Time-Recursive Correlator for DSSS Communications

Direct sequence spread spectrum (DSSS) correlators synchronize received signals with locally generated replicas. They can be implemented either in time or frequency domains. Time-domain correlators are more flexible in multimode operations, and they are typically preferred in hardware-based implementations. Frequency-domain approaches are more computationally efficient, which makes them attractive for software-based solutions. As an alternative to frequency-domain methods, this letter derives computationally-fast time-domain algorithm using the pseudorandom and binary structure of widely used DSSS signals. Our approach is multiplication-free and accurate, it is efficient for multimode operations requiring limited number of correlator outputs, and no constraints are imposed on sequence lengths.