Statistical approach to the code acquisition problem in direct-sequence spread-spectrum communication systems

In direct-sequence spread-spectrum (DS/SS) communication, users' original signals are modulated into higher frequencies with the users' codes. DS/SS communication has the attractive property that multiple users' signals can be simultaneously transmitted; however, communication cannot be performed without synchronization of users' spread-spectrum (SS) signal. Synchronization is typically performed in two steps, i.e. code acquisition and tracking. This paper gives a statistical solution to the question as to how code acquisition can be performed effectively and precisely. First, properties of matched-filter outputs of SS signal are discussed. Second, a theoretical method of code acquisition is proposed according to statistical decision theory. The method uses all matched-filter outputs for code acquisition. Third, matched-filter outputs are dichotomized with a threshold value and the dichotomous outputs are used for code acquisition. A simple and effective method for code acquisition is proposed. Numerical simulations are also given to illustrate the effectiveness of the proposed method. Finally, a further discussion and conclusion to this study are provided.