Li, Xiaofan
(Center for Spatial Information Science, The University of Tokyo)
,
Manandhar, Dinesh
(GNSS Technologies Inc and Center for Spatial Information Science, The University of Tokyo)
,
Shibasaki, Ryosuke
(Center for Spatial Information Science, The University of Tokyo)
Acquisition is to detect the presence of the GPS signal. Once the signal is detected, the estimated frequency and code phase are passed to a tracking loop to demodulate the navigation data. In order to detect the weak signal, multiple length of data integration is always needed. In this paper, we pr...
Acquisition is to detect the presence of the GPS signal. Once the signal is detected, the estimated frequency and code phase are passed to a tracking loop to demodulate the navigation data. In order to detect the weak signal, multiple length of data integration is always needed. In this paper, we present five different acquisition approaches based on circular correlation and Fast Fourier Transform (FFT), using coherent as well as non-coherent integration techniques for the multiple length of collected GPS satellite signal. Moreover a general approach of determining the acquisition threshold is introduced based on noise distribution which has been proved effective, and independent of the hardware. In the end of this paper, the processing speed and acquisition gain of each method are illustrated, compared, and analyzed. The results show that coherent approach is much more time consuming compared to noncoherent approaches, and in the case of multiple length of data integration from 2ms to 8ms, the processing times consumed by the fastest non-coherent acquisition method are only 25.87% to 1.52% in a single search, and 34.76% to 1.06% in a global search of those in the coherent acquisition. However, coherent acquisition also demonstrates its better performance in the acquisition gain, and in the case of 8ms of data integration it is 4.23 to 4.41 dB higher than that in the non-coherent approaches. Finally, an applicable scheme of combining coherent and non-coherent acquisition approaches in the development of a real-time Software GPS receiver in the University of Tokyo is provided.
Acquisition is to detect the presence of the GPS signal. Once the signal is detected, the estimated frequency and code phase are passed to a tracking loop to demodulate the navigation data. In order to detect the weak signal, multiple length of data integration is always needed. In this paper, we present five different acquisition approaches based on circular correlation and Fast Fourier Transform (FFT), using coherent as well as non-coherent integration techniques for the multiple length of collected GPS satellite signal. Moreover a general approach of determining the acquisition threshold is introduced based on noise distribution which has been proved effective, and independent of the hardware. In the end of this paper, the processing speed and acquisition gain of each method are illustrated, compared, and analyzed. The results show that coherent approach is much more time consuming compared to noncoherent approaches, and in the case of multiple length of data integration from 2ms to 8ms, the processing times consumed by the fastest non-coherent acquisition method are only 25.87% to 1.52% in a single search, and 34.76% to 1.06% in a global search of those in the coherent acquisition. However, coherent acquisition also demonstrates its better performance in the acquisition gain, and in the case of 8ms of data integration it is 4.23 to 4.41 dB higher than that in the non-coherent approaches. Finally, an applicable scheme of combining coherent and non-coherent acquisition approaches in the development of a real-time Software GPS receiver in the University of Tokyo is provided.
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문제 정의
The purpose of this paper is to test and evaluate five common GPS C/A code acquisition algorithms. The speed and output signal-to-threshold ratio of each method are compared and evaluated.
가설 설정
3. Locally generate ca(t) and repeat it for n periods.
제안 방법
The purpose of this work is to analyze their performance and provide a best scheme for the development of a real-time C/A code Software-based GPS receiver in the University of Tokyo.
This paper presents five different acquisition approaches and a practical threshold determination method which is respectively calculated for each approach and independent from hardware configuration. The purpose of this work is to analyze their performance and provide a best scheme for the development of a real-time C/A code Software-based GPS receiver in the University of Tokyo.
이론/모형
In considering the frequency resolution, 1KHz is not enough for a successful tracking. Thus refining the frequency is achieved by applying either amplitude comparison method [3], or coherent FFT method [4].
성능/효과
6. Circular processing of 13 Doppler frequency components will be done, and the peak absolute value of totally 13 X 16368=212784 complex outputs will be compared to the predetermined threshold. The satellite is evaluated as visible if the former surpasses the latter.
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