CC BY
16
The database used is MySQL, this is an efficient database used in web applications, business application, technological applications and so on. Some of its characteristics are the following: Multi-layer server with independent modules, MySQL can be use multiple CPUs, high standard of compression and indexation, it uses a very fast algorithm to access memory and locate the information, it can be used for temporary tables and so on. [15]
The database uses the entity-relationship model of the Data Base designed. This is a part of the global design of the multi constellation vehicle tracking. This current designee developed to save the data such as id track that is the unique identifier of each vehicle, time in which the data is transmitted, latitude, longitude and speed or velocity of the vehicle gave by the receiver device also the altitude. This information will be transmitted every second
across the mobile network. The user can see the information in real time through the Internet in the cell phone or computer with a username and password. This information will be able always available when the user needs it.
Conclusions
The GNSS multi constellation receiver for vehicle tracking improves the accuracy, reliability and integrity to compute the current position of the vehicle. In near future, most of the GNSS satellite constellations will have global coverage and this will permit GNSS receivers to work with large number of satellites with significant advantages described in this paper. Finally, this system helps to minimize the time response of the Emergency center give the more precise position of the vehicle and doing some process described in the software, we pretend to improve the time response in 40 %.
REFERENCES
1. WIKIPEDIA. (2016). Vehicle tracking system [Online] Available from: https://en.wikipe-dia.org/wiki/Vehicle tracking system [Accessed: 10th April 2016]
2. SAE International. (2016). SAE J1939 Standards Collection. . [Online] Available from: http://subs.sae.org//j1939 dl/ [Accessed: 25th January 2016]
3. YU-HSUAN, CH., et al. Development of a Real-time GNSS Software Receiver for Evaluating RAIM in Multi-constellation [Online] Available from: http://gps.stanford.edu/papers/Chen_IO-NITM_2014_Multiraim.pdf [Accessed: 22th April 2016]
4. DEVELOPERSHOME. (2015). Introduction to AT Commands. [Online] Available from: http://www.de-velopershome.com/sms/atCommandsIntro.asp [Accessed: 2nd January 2 016]
5. SAE INTERNATIONAL. (2016) On-Highway Equipment Control and Communication Network [Online] Available from: http://store.sae.org/j193 9/contents/ [Accessed: 2nd January 2016]
6. NOVATEL. GLONASS. [Online] Available from: http://www.novatel.com/an-introduction-to-gnss/chapter-5-resolving-errors/multi-constellation-and-multi-frequency/ [Accessed: 8th March 2016].
7. WIKIPEDIA. (2015). Cellular network. [Online] Available from: https://en.wikipe-dia.org/wiki/Cellular_network [Accessed: 25th February 2016]
8. RAQUET, J., LACHAPELLE, G. (1996). Determination and Reduction of GPS Reference Station Multipath Using Multiple Receivers. [Online] Available from: http://plan.geomatics.ucalgary.ca/pa-pers/96gpsjor.pdf [Accessed: 27th January 2016]
УДК 621.396
Stepanova E. A., Shafran S. V., Kudryavtsev I. A.
Samara National Research University, Samara, Russia
GALILEO E5 RECEIVER FOR RELIABILITY IMPROVEMENT OF GNSS-BASED POSITIONING
The aim of the conducted research was to develop the part of Galileo E5 GNSS (Global Navigation Satellite System) signals receiver that will allow to estimate the position of the object with higher accuracy than receiver working with GPS signals. The task was to develop blocks for Galileo signals acquisition and tracking and to test them in order to show the operability of the developed blocks and the enhancement of the positioning accuracy. In Galileo constellation signals they introduced new type of modulation — Alternate Binary Offset Carrier modulation (AltBOC) [1] that provide highly accurate positioning under civilian control. Though GPS signal is available for civilian operation now it was initially meant for military purposes. The Galileo signal is meant for the civilian usage initially. Nowadays there is no fully operational Galileo receiver, only some blocks are developed by different researches, that is why this work is aiming at the development of such receiver.
Keywords:
Galileo signals, AltBOC modulation, acquisition, tracking, multipath
Introduction
The motivation for the development of the Galileo receiver is the growth of Galileo satellite constellation - now ESA (European Space Agency) has 11 operational satellites on-orbit and it is claimed that by the end of 2016 the constellation will enlarge up to 17 satellites [2]. This leads to the need of having the receiver that will be able to receive and process Galileo GNSS signals. The improvement of GNSS positioning will allow to use it more broadly in different areas, such as, airplane landing, car and trucks tracking, positioning in the emergency cases. Nowadays positioning error is not very good in some areas of the planet - it may be up to several tens of meters in urban areas or in forests, for example. In Galileo constellation the new modulation scheme [1] and the method of ionospheric corrections [3] are introduced to lessen the positioning error to the centimeters' level.
This work is focused on the Galileo E5 GNSS signal as the signal with the new type of modulation that will provide the more reliable positioning in comparison with the GPS signals po-
sitioning. We develop the acquisition and tracking blocks of Galileo E5 receiver taking for the basis the code developed by Kai Borre for GPS Software defined radio [4]. The novelty of the developments is that we designed blocks for Galileo GNSS signals acquisition and tracking that may be developed further by introducing the block of navigation solution into the fully operational Galileo GNSS signals receiver.
Research method
The work deals with the complex modulation scheme firstly introduced in the Galileo E5 signals - AltBOC modulation. The properties of this modulation are discussed in details in [1,5]. In [6] the multipath error envelopes for Galileo signals are discussed. Simsky et el. showed that in comparison with GPS signals that the error envelopes for all Galileo signals modulations are all inside the error envelope for GPS CA-code. The smallest error was for the Galileo E5 AltBOC modulation - it was within 50 meters for multipath delay. The results of the research conducted by Simsky et el. showed that the Galileo E5 AltBOC modulation was superior to any other type of modulation in terms of positioning accuracy.
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The strategies for acquisition of Galileo E5 signal are described in [7]. It is shown in that work that the most efficient strategies are full-band independent code acquisition (in the case we work with E5a and E5b signals separately) and direct AltBOC acquisition (E5a and E5b are processed together). Besides, it is concluded that the early-late correlation method is optimal for the acquisition strategy of Galileo signals. This method was further used in the conducted work to acquire Galileo E5 GNSS signals.
The analysis of Galileo E5 GNSS signal tracking strategies and the design of phase-locked loop (PLL) and delay-locked loop (DLL) is provided in [8]. It is shown in this work that AltBOC modulation has a high resistance to mul-tipath delays and better code noise error. This makes signals modulated with AltBOC scheme suitable for high sensitive and robust applications. This is the reason, why in this work we decided to work with Galileo E5 GNSS signals that use AltBOC modulation scheme.
In our research we developed blocks for signals acquisition and tracking of Galileo E5 GNSS signals modulated with AltBOC modulation scheme. These blocks are developed by means of Matlab software [9]. For acquisition block it was chosen to use early-late correlation method with the accordance with the research conducted in [7]. The tracking block was developed on the basis of the results of [8], with the new code generators and longer minimum dwell time [4]. In this work we developed two block for Galileo E5 GNSS signals processing that are able to operate together. The results were compared with the GPS signals processing results and it was shown that positioning results obtained from Galileo E5 signals is more accurate than the positioning with GPS signals.
Experimental results
For acquisition block we used early-late correlation method that is the following: we take early and late replicas with an appropriate delay and combine them. Local replica for early-late method is generated in the following way:
t-T = C t-T • sc\ t-T
(1)
' t-T]
= c 11 - T- ^
• sc\ t- T--
In Galileo E5 signal AltBOC (15, 10) modulation is used, the delay for this type of modulation is 0.167 chips. The correlation forms for early, late and prompt replicas are shown in the Figure 1. It may be observed that the correlation peak is flat at the value of 0.167 chips and the correlation has the shape similar to BPSK correlation function.
Figure 1 - Early-late correlation for AltBOC(15, 10)
The developed block of acquisition was tested with real data samples which were recorded in Samara National Research University by the research group with the help of Javad antenna and receiver and SdrNav-40 front-end [10]. We compared the acquisition results of Galileo E5 signal and GPS signal with two levels of signal to noise ratio (SNR): -20dB and -30dB. The obtained auto correlation functions (for Galileo and GPS signals) are shown in Figure 2 (a, b), respectively. It can be seen that in case of SNR=-20dB acquisition of Galileo signals is much more reliable and provides better accuracy. This means that there is a possibility of acquiring the Galileo signals with higher levels of noise, like shown in Figure 2(b). It is evident that acquisition of GPS signal couldn't be successful, when SNR=-30dB, unlikely the one of Galileo signal and the introduction of Galileo signal will lead to more reliable positioning of the object.
Figure 2 - (a) ACF of GPS and Galileo signals comparison. SNR=-20dB; (b) ACF of GPS and Galileo
signals comparison. SNR=-30 dB
The results of acquisition (frequency-time mesh) are presented in the figure 3. It is possible to see the correlation peak which shows that the received signal and locally-generated signal replica are aligned and the satellite is acquired (i.e. present in the data record). During tracking, we estimate time shifts and Dop-pler shifts with higher accuracy. This results are used in phase-locked loop and delay-locked loop. The carrier signal is tracked using phase-locked loop (PLL). The code is tracked with a delay-locked loop, also called early-late track-
ing loop. Code delay tracking is extremely important as it provides pseudorange measurements and prompt code phases for PLL.
In the figure 4(a) the output of DLL correlator is presented. It shows the signals for early, prompt and late replicas of the signal. It is seen that prompt replica is higher than early and late ones - the signal is tracked correctly. In the figure 4(b) the output of PLL indicating the tracking error is presented. In the beginning errors were up to 15 meters, in 1 second errors are reduced and remained fluctuating near zero.
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Conclusions
In the result of the conducted research were developed blocks for Galileo E5 GNSS signals acquisition and tracking. These blocks were developed in Matlab software and tested on the real samples of data. Also, the comparison with GPS signals acquisition results was conducted. It was shown that Galileo E5 signals perform better in the higher noise conditions and it is more reliable than GPS signal. Galileo E5 signal may be used, for example, in urban conditions and give more accurate results of object positioning. Testing on real samples of data, recorded by the research group, showed that the developed blocks perform well - the satellites that present in data record are acquired and tracked properly.
Figure 3 - Time-frequency meshes
Figure 4
output of DLL correlator; (b) output of PLL correlator
On the next stage of the research it is necessary to develop navigation solution block in order to have operational Galileo E5 receiver.
After that it is supposed to optimize the algorithm of the receiver operation for its faster work and to implement it on FPGA.
REFERENCES
1. Galileo Open Service Signal In Space Interface Control Document (OS SIS ICD), Issue 1.2, November 2015. European Union 2015.
2. European GNSS Service Centre. Constellation Information. [Online] Available from: http://www.gsc-europa.eu/system-status/Constellation-Information [Accessed: 5th November 2015].
3. Ionospheric Correction Algorithm for Galileo Single Frequency Users, Issue 1.1, June 2015. European Union 2015.
4. Borre, K. A Software-Defined GPS and Galileo Receiver/K. Borre.- Boston: Birkhauser, 2007. -
176 p.
5. Shivaramaiah, N. C., Dempster A. G. The Galileo E5 AltBOC: Understanding the Signal Structure/ N. C. Shivaramaiah. - International Global Navigation Satellite Systems Society. IGNSS Symposium 2009. Holiday Inn Surfers Paradise, Qld, Australia 1 - 3 December, 2009.
6. Simsky A., Mertens D., Sleewaegen J., Hollreiser M., Crisci M. (2008) Experimental Results for the Multipath Performance of Galileo Signals Transmitted by GIOVE-A Satellite. International Journal of Navigation and Observation Volume 2008, Article ID 416380
7. Shivaramaiah, N. C., Dempster A. G. An Analysis of Galileo E5 Signal Acquisition Strategies/ N. C. Shivaramaiah. - Proc. of the European Nav. Conf., ENC GNSS 2008, April 23-25, 2008, Toulouse, France.
8. Tawk, Y., Bollerun, C., Jovanovic, A., Farinc, P. Analysis of Galileo E5 and E5ab code tracking./ Y. Tawk. - Springer-Verlag 2011.
9. MathWorks. [Online] Available from: http://www.mathworks.com. [Accessed: 10th October 2015].
10. Самарский университет. Материальная база. НИЛ-98. [Online] URL: http://www.ssau.ru/mat-baza/11/ [Accessed: 25th December 2015]
YHK 621.396
Tabatabaei1 A. , Mosavi1 M. R., Khavari1 A., Shahhoseini1 H.Sh., Shafran2 S.V.
1Iran University of Science and Technology, Narmak, Iran
2Samara National Research University, Samara, Russia
RELIABILITY ADVANTAGES OF IMPROVED FUZZY WLS METHOD FOR GPS AND GLONASS COMBINED RECEIVER IN JAMMING SCENARIOS
One of the important concerns in Global Positioning System (GPS) receivers is interference and jamming. Received signals in GPS receivers are very weak. So, they are vulnerable to interference which cause losing the satellite signals and thus impairs the positioning availability and accuracy. In this paper, the integration of GPS with Russian Global Navigation Satellite System (GLONASS) as the second world-wide satellite-based navigation system is proposed to overcome this problem. Increasing the number of visible satellites is a significant benefit of this compound system. We also introduce an improved fuzzy weighted least-square method to weight the information according to its system reliability and its satellite properties such as its impress on positioning and horizontal dilution oof precision. Experimental results show that the final solution has been improved to 32% in defined figure of merit parameter.
Key words:
GPS, GLONASS, Integrated Receiver, Jamming, Reliability, Fuzzy Weighted Least Square
