 variance, ACQ, both of which come at a considerable savings in computation. Since, historically, the evaluation of TACQ and ACQ for the single dwell system preceded the evaluation of the probability of successful acquisition for this system, we shall follow the same pattern in our discus- sions. In this way, the reader is first afforded the insight into the nature of 7t is convenient to assume that Tu is (or is bounded by) an integer multiple of the code time period Pseudonoise Code Acquisition in Direct-Sequence Receivers the acquisition process itself which is allowed by computation of the simpler performance parameters TACO and ACO, before being thrust into the com- plex mathematical developments needed to compute acquisition probability. Furthermore, to make matters even simpler at first, we shall assume that no code Doppler is present in the received PN signal and that the detection probability PD is constant (time invariant), the latter being equivalent to assuming that only one cell corresponds to a "correct" code alignment. Since the PN code correlation function is triangular over an interval of plus and minus one chip (-T,, for a search in increments of T/2, as is typical, there are, in reality, four8 cells which correspond to non-zero code correlation. Clearly, the cell corresponding to the largest of these code correlations (near- est to the peak of the triangular correlation curve) would be the one yield- ing the "correct" code alignment. However, because of the constant PD assumption, we must appropriately modify the results to be presented based on this assumption SO as to apply to the true situation as described above. A discussion of how this is done, based upon a worst case correlation error assumption, will be given in Section 1.2.5. Later on in the chapter, we pre- sent a more exact accounting of the effects of having multiple cells with non- zero code correlation. 1.2.2 Single Dwell Acquisition Time Performance in the Absence of Code Doppler In the absence of a priori knowledge concerning the