Variable-delay tree-based searcher for spread-spectrum communication systems

Before a communication link is established, spread spectrum systems must synchronize by acquiring the spreading sequence. The choice of code-acquisition algorithms is dictated by the trade-off of complexity and performance. In this paper, a new tree-based search approach is proposed, which permits the testing of “multiple hypotheses” by utilizing the orthogonal property of the PN spreading sequence. By defining a delayed decision mechanism and a depth dependent threshold, in the proposed approach, it is possible to permit a trade-off between the computational time required for the maximum likelihood (ML) test and the robustness lost in pure tree search