Serial search acquisition system with adaptive threshold and optimal decision for spread spectrum systems

摘要

A PN code acquisition system for Code Division Multiple Access (CDMA) Direct Sequence Spread Spectrum (DSSS) systems, with automatic decision threshold, is based on the combination of the Maximum Likelihood (ML) and Serial Search (SS) acquisition approaches. In contrast to the conventional SS acquisition system, the disclosed system adaptively estimates optimal threshold by exploiting the statistics of the signal and noise, and makes an optimal decision based on the threshold. The system estimates the threshold by employing ML estimation and applies the threshold as in SS acquisition and makes a decision by comparing the updated threshold with the current signal strength. Together with post detection verification logic, this approach will increase detection probability and reduce false alarm probability significantly. An optimum system parameter design approach and the advantages of this approach as compared to conventional approaches (ML or SS acquisition) are demonstrated.