Local Frequency Folding Method for Fast PN-Code Acquisition

Wenquan FENG  Xiaodi XING  Qi ZHAO  ZuLin WANG  

Publication
IEICE TRANSACTIONS on Communications   Vol.E97-B   No.5   pp.1072-1079
Publication Date: 2014/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.1072
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
Keyword: 
PN-code acquisition,  local frequency folding,  detection probability,  mean acquisition time,  

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Summary: 
The large Doppler offset that exists in high dynamic environments poses a serious impediment to the acquisition of direct sequence spread spectrum (DSSS) signals. To ensure acceptable detection probabilities, the frequency space has to be finely divided, which leads to complicated acquisition structures and excessively long acquisition time at low SNR. A local frequency folding (LFF) method designed for combined application with established techniques dedicated to PN-code synchronization is proposed in this paper. Through modulating local PN-code block with a fixed waveform obtained by folding all frequency cells together, we eliminate the need for frequency search and ease the workload of acquisition. We also analyze the performance of LFF and find that the detection performance degradation from folding can be compensated by FFT-based coherent integration. The study is complemented with numerical simulations showing that the proposed method has advantages over unfolding methods with respect to detection probability and mean acquisition time, and the advantage becomes obvious but limited if the folded number gets larger.