19]. In more recent years, the trend has been to accomplish the variation of the time difference between the incoming and local PN waveforms by a dis- crete stepping process wherein the phase of the local PN code is, at uniform increments in time, advanced (or retarded) by a fixed amount (typically a fraction of a chip). This time-discrete sweep of the uncertainty region can be accomplished by a uniform (unidirectional) search from one end of the region to the other, as in the case of no a priori information about the received PN code phase, or by a non-uniform search typically starting in the region of highest code phase certainty and expanding as a function of time to regions of lesser certainty. Such expanding window serial search strate- gies [20]-[24], or the simpler z-type search strategies [24], are well suited to applications where the length of code makes it not feasible to search the whole code and thus some a priori information about the code phase must be provided by other means. Continuing our subclassification of search strategies, we can distinguish two different philosophies with regard to the time elapsed before reaching the final acquisition state. In one case, the search is allowed to proceed as long as is necessary to achieve acquisition with the given fidelity criterion, although it is clearly desirable to accomplish this state as fast as possible. Such serial search techniques are classified as having non-limited permitted acquisition time and are typically employed in applications where informa- tion modulation is always present in the received waveform. Serial search strategies with limited permitted acquisition time are characteristic of DS/SS systems where information modulation commences to be transmitted only after PN code acquisition has been ensured. In such applications, a fixed time is usually allotted to achieve code acquisition, and furthermore this achieve- ment must be accomplished with high probability. The final classification of serial search strategies is in accordance with