A new Z search method is proposed which can significantly improve mean acquisition time when compared with the best previous Z search strategy. The codephase search starts from a position offset from centre of a range which has been determined from a priori information. The proposed search method includes previous Z search strategies as special cases. The distribution and mean of acquisition time have been developed for the proposed search strategies. With minimum mean acquisition time as objective, optimization of the starting position offset has been investigated.

The paper presents a time-domain approach to the analysis of the code phase acquisition process in direct sequence spread spectrum receivers. This approach is suitable for a variety of search and verification/lock strategies. The time-domain approach is more direct than the unified z transform-domain approach and permits computation of the acquisition time distribution. The paper also provides equations for calculating the mean acquisition time under various search and verification/lock strategies. The usefulness of the approach is demonstrated by application to a specific nontrivial case of practical significance.

Serial search spread-spectrum code acquisition is analyzed. A modified flow graph is presented. It permits the use of a generalized lock strategy and allows the false alarm time to be treated as a random variable. The distribution of acquisition time is obtained directly by using an extended generalization of Bernoulli trials. Compared to recent work which uses a fixed penalty false alarm time, the analysis is more general and requires fewer assumptions and approximations. The analysis is suitable for both single dwell and multidwell systems. Examples are presented to show the effect on the acquisition time distribution of sequence length and normalized detection threshold.>

The authors evaluate a robust framing technique which incorporates sufficient memory to simultaneously evaluate all bits in a candidate synchronizing codeword. Three performance measures are identified and the distribution function and mean value are developed in closed form for each measure. Predicted search and maintenance time distributions have been verified by measurements on a laboratory model. The authors present graphs of search time distributions which illustrate the effect of system parameters and variations in the channel error rate.>

Serial digital transmission requires reliable frame synchronization at the receiver in order to demultiplex and recover the transmitted signals. This paper proposes a faster and more robust method of detecting frame synchronization. A large serial memory is used to store sufficient received history to include all bits of the synchronizing codeword. Equations have been developed which predict the search and "in frame" performance. These equations have been verified with laboratory models. Using, for example, the well-known D3 PCM system, the reframe time is improved from 48 to 3 ms. With an error rate of 1 percent, the predicted "in frame" time is improved from 1.9 s to several centuries! Techniques for hardware implementation are suggested and application to the extended framing format is discussed.