DS/SS code acquisition with joint detection of multiple correct cells using locally optimum test statistics in Rayleigh fading channels

Abstract

A new PN code acquisition scheme is proposed based on the joint detection of correct cells (H-1 cells) at which the code phase offset between the locally generated and received PN codes is within a desired small offset. Most of the acquisition schemes which have been proposed assume that there exists one and only one H-1 cell over the uncertainty region. However, in practical systems, there exist multiple H-1 cells. In this paper, using the locally optimum test statistic, the joint decision rule of two H-1 cells is derived for nonselective Rayleigh fading channels. Then, with the proposed acquisition scheme based on the joint decision rule, a closed-form expression of the mean acquisition time is obtained with the state diagram, and the probabilities of detection, missing, and false alarm are derived. The mean acquisition time performance of the proposed acquisition scheme is compared with that of a conventional acquisition scheme in which only an H-1 cell is used for detection at each step. The numerical results show that the proposed scheme not only has better performance but also is more robust to the residual code phase offset variation than the conventional scheme. (C) 2002 Elsevier Science B.V. All rights reserved.