BeiDou signal bit synchronization algorithm based on long-time differential correlation and maximum likelihood

Affiliation of Author(s):自动化学院

Journal:Zhongguo Guanxing Jishu Xuebao

Abstract:BeiDou navigation message is modulated with a secondary code of NH code of 1 kbps, and the frequent bit jumps limit the coherent integration time to be 1 ms. So a bit synchronization algorithm is necessary to obtain bit edge and NH code phase information. In order to realize bit synchronization for weak signals with large frequency error and solve the problem that the frequent bit jumps and large frequency errors affect the performance of traditional bit synchronization algorithm, a bit synchronization algorithm based on long-time difference correlation and maximum likelihood is proposed. Firstly, the difference correlation is used to remove the effect of residual frequency error, and the differential delay time is set to be integer of bit cycle to remove the influence of NH code. Secondly, based on coherent and non-coherent integration, the maximum likelihood function detection can improve the detection probability of weak signals. Finally, the Monte Carlo simulation is used to analyze the detection performance of this algorithm comparing with traditional algorithm under the carrier-to-noise ratio of 20-40 dB·Hz and different frequency errors. Simulation results show that, under the condition that the frequency error is 50 Hz, the proposed algorithm presents a good detection performance, while the traditional method does not work. This algorithm can effectively remove the effect of BeiDou NH code, weaken the influence of frequency error, and realize bit synchronization of weak signals based on coherent and non-coherent integration. It is suitable for BeiDou weak signal bit synchronization with large frequency error. © 2017, Editorial Department of Journal of Chinese Inertial Technology. All right reserved.

ISSN No.:1005-6734

Translation or Not:no

Date of Publication:2017-12-01

Co-author:Han, Zhi-Feng,li rongbing,wyp

Correspondence Author:ljy

Date of Publication:2017-12-01