Abstract:Signal modulation is an essential design factor of a positioning system, which directly impacts the system’s potential performance. Chirp compressions have been widely applied in the fields of communication, radar, and indoor positioning owing to their high compression gain and good resistance to narrowband interferences and multipath fading. Based on linear chirp, we present a modulation method named chirped pseudo-noise (ChPN). The mathematical model of the ChPN signal is provided with its auto-correlation f… Show more
“…The characteristics of the second and third data sets are the same as the first one. Note that although various techniques have been accomplished to meet the requirements of GPS indoors (Liu et al, 2018; Liu et al, 2019a), as Figures 10 and 11 show, the scenarios considered here for the results of the proposed ISBC method and the traditional methods are concerned with the characteristics of urban areas such as tall buildings, trees, and etc. Figure 10.Setup for recording real data around Iran University of Science and Technology.Figure 11.Recording real data in front of the IUST School of Electrical Engineering laboratory building where the view to the sky is blocked by buildings and trees.…”
The presence of code Doppler and navigation bit sign transitions means that the acquisition of global positioning system (GPS) signals is difficult in weak signal environments where the output signal-to-noise ratio (SNR) is significantly reduced. Post-correlation techniques are typically utilised to solve these problems. Despite the advantages of these techniques, the post-correlation techniques suffer from problems caused by the code Doppler and the navigation bit sign transitions. We present an improved semi-bit differential acquisition method which can improve the code Doppler and the bit sign transition issues in the post-correlation techniques. In order to overcome the phenomenon of navigation bit sign transitions, the proposed method utilises the properties of the navigation bit. Since each navigation bit takes as long as 20 ms, there would be 10 ms correlations duration integration time between the received signal and the local coarse/acquisition (C/A) code in which the navigation bit sign transitions will not occur. Consequently, this problem can be cancelled by performing 10 ms correlations in even and odd units separately. Compensation of the code Doppler is also accomplished by shifting the code phase of the correlation results. To validate the performance of our suggested method, simulations are performed based on three data sets. The results show that the quantity of required input SNR to detect at least four satellites in the proposed method is − 48·3 dB, compared with − 20 dB and − 9 dB, respectively, in traditional differential and non-coherent methods.
“…The characteristics of the second and third data sets are the same as the first one. Note that although various techniques have been accomplished to meet the requirements of GPS indoors (Liu et al, 2018; Liu et al, 2019a), as Figures 10 and 11 show, the scenarios considered here for the results of the proposed ISBC method and the traditional methods are concerned with the characteristics of urban areas such as tall buildings, trees, and etc. Figure 10.Setup for recording real data around Iran University of Science and Technology.Figure 11.Recording real data in front of the IUST School of Electrical Engineering laboratory building where the view to the sky is blocked by buildings and trees.…”
The presence of code Doppler and navigation bit sign transitions means that the acquisition of global positioning system (GPS) signals is difficult in weak signal environments where the output signal-to-noise ratio (SNR) is significantly reduced. Post-correlation techniques are typically utilised to solve these problems. Despite the advantages of these techniques, the post-correlation techniques suffer from problems caused by the code Doppler and the navigation bit sign transitions. We present an improved semi-bit differential acquisition method which can improve the code Doppler and the bit sign transition issues in the post-correlation techniques. In order to overcome the phenomenon of navigation bit sign transitions, the proposed method utilises the properties of the navigation bit. Since each navigation bit takes as long as 20 ms, there would be 10 ms correlations duration integration time between the received signal and the local coarse/acquisition (C/A) code in which the navigation bit sign transitions will not occur. Consequently, this problem can be cancelled by performing 10 ms correlations in even and odd units separately. Compensation of the code Doppler is also accomplished by shifting the code phase of the correlation results. To validate the performance of our suggested method, simulations are performed based on three data sets. The results show that the quantity of required input SNR to detect at least four satellites in the proposed method is − 48·3 dB, compared with − 20 dB and − 9 dB, respectively, in traditional differential and non-coherent methods.
“…In the previous research process, the principle of pseudolite [16][17][18][19][20][21][22][23][24][25] has been briefly introduced. The pseudolite generates a local intermediate frequency signal under the control of the same clock.…”
At present, pseudosatellite navigation and positioning technology is the only positioning technology compatible with GNSS navigation signals and applied to indoors. This technology can realize continuous indoor and outdoor positioning services for mobile terminals and dedicated terminals. At the same time, the indoor application of pseudolite technology also faces some problems. Aiming at the large-area networking problem of pseudolites in indoor space, this paper uses the existing indoor array pseudolite technology to propose a technique for constructing a network using the characteristics of pseudolite signals in indoor space. By making full use of the signal’s multiple access classification characteristics and the signal’s Doppler, interstation delay, and other characteristics, a multilevel grid segmentation and networking scheme for indoor space based on pseudolites is realized. This method combines the existing experimental foundation and experience accumulation, has the feasibility of realizing large-area networking indoors, can solve the problems faced in the current indoor pseudolite networking process, and provides guarantee for the application of pseudolite networking in indoor environments.
“…These methods change some of the filter parameters according to the conditions, and yet not all of the parameters change at the same time. There are other methods based on the use of pseudolites that can be useful in indoor situations (Liu et al, 2018, 2019b). All of the methods described above are based on scalar tracking methods where one satellite is tracked separately from another satellite.…”
Global satellite navigation systems (GNSS) are nowadays used in many applications. GNSS receivers experience limitations in receiving weak signals in a degraded environment. Hence, tracking weak GNSS signals is a topic of interest to researchers in this field. Different methods have been proposed to address this issue, each of which has advantages and disadvantages. In this paper, a method based on the vector tracking method is proposed for weak signal tracking. This method has been developed based on a strong Kalman filter instead of the extended Kalman filter used in conventional vector tracking methods. In order to adjust important parameters of this filter, the fuzzy method is used. The results of tests performed with both simulated data and real data demonstrate that the proposed method performs better than previous ones in weak signal tracking.
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