A Novel Scheme for Code Tracking Bias Mitigation in Band-Limited Global Navigation Satellite Systems 


Vol. 32,  No. 10, pp. 1032-1041, Oct.  2007


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  Abstract

The global navigation satellite system (GNSS), which is the core technique for the location based service, adopts the direct sequence/spread spectrum (DS/SS) as its modulation method. The success of a DS/SS system depends on the synchronization between the received and locally generated pseudo noise (PN) signals. As a step in the synchronization process, the tracking scheme performs fine adjustment to bring the phase difference between the two PN signals to zero. The most widely used tracking scheme is the delay locked loop with early minus late discriminator (EL-DLL). In the ideal case, the EL-DLL is the best estimator among various DLLs. However, in the band-limited multipath environment, the EL-DLL has tracking bias. In this paper, the timing offset range of correlation function is divided into advanced offset range (AOR) and delayed offset range (DOR) centering around the correct synchronization time point. The tracking bias results from the following two reasons: symmetry distortion between correlation values in AOR and DOR, and mismatch between the time point corresponding to the maximum correlation value and the synchronization time point. The former and latter are named as the type Ⅰ and type Ⅱ tracking bias, respectively. In this paper, when the receiver has finite bandwidth in the presence of multipath signals, it is shown that the type Ⅱ tracking bias becomes a more dominant error factor than the type I tracking bias, and the correlation values in AOR are not almost changed. Exploiting these characteristics, we propose a novel tracking bias mitigation scheme and demonstrate that the tracking accuracy of the proposed scheme is higher than that of the conventional scheme, both in the presence and absence of noise.

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  Cite this article

[IEEE Style]

S. Yoo, S. Kim, S. Yoon, I. Song, S. Y. Kim, "A Novel Scheme for Code Tracking Bias Mitigation in Band-Limited Global Navigation Satellite Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 32, no. 10, pp. 1032-1041, 2007. DOI: .

[ACM Style]

Seungsoo Yoo, Sanghun Kim, Seokho Yoon, Iickho Song, and Sun Yong Kim. 2007. A Novel Scheme for Code Tracking Bias Mitigation in Band-Limited Global Navigation Satellite Systems. The Journal of Korean Institute of Communications and Information Sciences, 32, 10, (2007), 1032-1041. DOI: .

[KICS Style]

Seungsoo Yoo, Sanghun Kim, Seokho Yoon, Iickho Song, Sun Yong Kim, "A Novel Scheme for Code Tracking Bias Mitigation in Band-Limited Global Navigation Satellite Systems," The Journal of Korean Institute of Communications and Information Sciences, vol. 32, no. 10, pp. 1032-1041, 10. 2007.