Multipath aided rapid acquisition

Abstract

Spread-spectrum systems with large transmission bandwidth present significant challenges from the standpoint of achieving synchronization before communication commences. This research investigates a rapid acquisition procedure that exploits the multipath to aid the synchronization. In particular, we consider a class of serial search strategies and determine the optimal search procedure for the uncertainty space consisting of N[sub]s total cells and N[sub]Q correct cells. We derive closed-form expressions for both the minimum and maximum mean acquisition times (MATs) and the conditions for achieving these limits. We prove that the fixed-step serial search (FSSS), with the step size N[sub]Q, achieves the near-optimal MAT. We also prove that the conventional serial search, in which consecutive cells are tested sequentially, and the FSSS with the step size N[sub]s - 1 should be avoided as they result in the maximum MAT. Analytical tools used in the research include Markov chain diagrams, the transformation of feasible spaces, and convexity theory. Our results apply to all signal-to-noise ratio values, regardless of the detection-layer decision rule and the fading distribution. The impact of this research is significant for the design, implementation, and deployment of spread-spectrum systems.