An Improved Double Delta Correlator for BOC Signal Tracking in GNSS Receivers
Multipath is one of main error sources in code tracking in global navigation satellite system. One of the first approaches to mitigate multipath is called Double Delta Correlator (DDC). This technique originally applied to Global Positioning System signal
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Abstract Multipath is one of main error sources in code tracking in global navigation satellite system. One of the first approaches to mitigate multipath is called Double Delta Correlator (DDC). This technique originally applied to Global Positioning System signals (C/A signals) which are Binary Phase ShiftKeying ones and have a single–peak autocorrelation function. Latter, it also applied to new GNSS signals which are binary offset carrier (BOC) modulated ones. It shows a good code multipath performance for mid-delayed and long-delayed multipath in both cases. For short-delayed multipath, there is still remaining error. This paper presents an Improved DDC that could reduce the error for short-delayed multipath signals. This improved DDC method is proposed for BOC signals. The simulation results show a better performance of proposed method than conventional DDC. Keywords BOC signal
Double delta correlator Multipath mitigation
1 Introduction Currently, binary offset carrier (BOC) modulation has been recommended to some new navigation signals such as Galileo L1OS (OS for Open Service), Global Positioning System (GPS) future L1C (New Civilian L1) [1]. The BOC (m, n) signal is created by modulating a sine wave carrier with the product of a spreading code and a square wave subcarrier. The parameter m stands for the ratio between the subcarrier frequency and the reference frequency f0 ¼ 1:023 MHz, and n stands for the ratio between the code rate and f0 .
P.-V. Hung (&) D.-N. Chien N.-V. Khang School of Electronics and Telecommunications, Hanoi University of Science and Technology, Hanoi, Vietnam e-mail: [email protected]
J. J. (Jong Hyuk) Park et al. (eds.), Multimedia and Ubiquitous Engineering, Lecture Notes in Electrical Engineering 240, DOI: 10.1007/978-94-007-6738-6_144, Ó Springer Science+Business Media Dordrecht(Outside the USA) 2013
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The most common multipath mitigation techniques are based on tracking loop structure which contains carrier phase locked loop (PLL) and code delay locked loop (DLL) [2]. Conventionally, two correlators spaced at one chip from each other are used in delay estimator. It tries to track the delay of the direct signal by correlating the down-converted received signal with replicas of local generating codes in the receiver. However, the classical estimator fails to estimate the multipath error envelope (MEE) accurately. Thus several evolutions have been introduced in the literature in order to mitigate the influence of MP signals, especially in short delayed multipath scenarios. Examples of these are Narrow Correlator [3], DDC [4], early/late slope technique, Early1/Early2 tracker [5]. Initially, these techniques were proposed to GPS signals which are Binary Phase Shift Keying (BPSK) ones and have triangular autocorrelation function. Among these above mentioned MP mitigation techniques, DDC have the best code multipath performance for medium-to-long delayed MP [4]. However, DDC are still not good enough for short-delayed MP environment su
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