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A GNSS Code Tracking Scheme Based in Slope Difference of Correlation Outputs  

Yoo, Seung-Soo (건국대학교 전자정보통신공학부)
Yoo, Seung-Hwan (건국대학교 전자정보통신공학부)
Chong, Da-Hae (성균관대학교 정보통신공학부)
Ahn, Sang-Ho (성균관대학교 정보통신공학부)
Yoon, Seok-Ho (성균관대학교 정보통신공학부)
Kim, Sun-Yong (건국대학교 전자정보통신공학부)
Publication Information
The Journal of Korean Institute of Communications and Information Sciences / v.33, no.6C, 2008 , pp. 505-511 More about this Journal
Abstract
The global navigation satellite system (GNSS) is using a direct sequence/spread spectrum (DS/SS) modulation. In order to recover the information data, the DS/SS system first performs a two-step synchronization process: acquisition and tracking. The acquisition process adjusts the phase difference between the received and locally generated acquisition sequences within ${\pm}T_c/2$ or less, where $T_c$ is the chip period. The tracking process performs fine synchronization. In this paper, we focus on the tracking issue. The single delta delay locked loop($\Delta$-DLL) is the optimal tracking scheme for a GNSS in the absence of multipath signals, where $\Delta$ means the spacing between the early and late correlation time offset. In the multipath environments, however, the $\Delta$-DLL suffers from huge estimation bias(denoted by $\beta$) caused by distorted correlation values. Although some modified schemes such as a $\Delta$-DLL with a narrow $\Delta$ and a double delta DLL (${\Delta}^{(2)}$-DLL) were proposed to reduce the estimation bias, they cannot remove the estimation bias completely and need more accurate acquisition process. This paper proposes a novel tracking scheme that can dramatically reduce the estimation bias, using the maximum slope change among the correlation outputs.
Keywords
Global Navigation Satellite System (GNSS); Direct Sequence/Spread Spectrum (DS/SS) System; Code Tracking; Slope Difference; Tracking Bias;
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