+7 (495) 957-77-43

Article-2_12-2018

Извините, этот техт доступен только в “Американский Английский”. For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

RESEARCH OF ACQUISITION ALGORITHMS FOR WEAK SPREAD SPECTRUM SIGNALS

Alexey S. Volkov, National Research University of Electronic Technology, Moscow, Russia, leshvol@mail.ru
Alexey V. Solodkov, National Research University of Electronic Technology, Moscow, Russia, solodkov_aw@mail.ru
Ilya V. Chugunov, National Research University of Electronic Technology, Moscow, Russia, ivchiginov2016@gmail.com

Abstract
In urban conditions the path loss of radio signals is much higher than in the case of propagation in free space and as a result of GNSS signal could be not detected, even if the satellite is in radio visibility. This degrades positioning accuracy with GNSS or even makes positioning impossible at low signal levels at the receiving point. Using of algorithms for the initial search of signals based on the increased correlation calculation time received signal and local replica of the spreading code allows to increase the probability of acquisition and to improve the basic consumer characteristics of the GPS receiver: the positioning accuracy and time of the cold start.
A lot of devices, that are capable to receive such signals, have limited resources (computing power, memory), comparable to the minimum required resources for the operation of these algorithms. That should be taken into account when choosing signal acquisition algorithm. In this work compares the developed mathematical models of algorithms for initial search of C/A signals of GPS system by the criteria of probability of correct acquisition of the signal using only one cold start and the time of the required post-processing.
A mathematical model of the received signal with impact of the Doppler shift and modulation by data is obtained. Both effects reduce the magnitude of the main peak of autocorrelation function. All the considered algorithms are focused on the increased of correlation interval the received signal and the reference replica of the spreading code, taking into account this model.
The measurement of the characteristics was carried out on the recorded sample of real signal with additional noise, simulating the attenuation of the signal power with its proper structure. The gain from using the considered algorithms is about 7 to 11 dB with the probability of successful detect and determining signals’ characteristics from the first run Pd=0,99, and the number of detected satellites increases on average by two times. The drawbacks of use researched algorithms are determined: the post-processing time of improved search algorithms is increased by 5-7 times, in addition, either more memory or more FFT calculations are required.

Keywords: GNSS, signal detection, PN signals, DSSS, GPS, coarse acquisition.

References

1. Ipatov V.P. (2007). Shirokopolosnye sistemy i kodovoe razdelenie signalov [Wideband and code division systems]. Moscow: Tekhnosfera. 488 p.
2. James Bao-Yen Tsui. (2004). Fundamentals of Global Positioning System Receivers: A Software Approach. Wiley-Interscience. 352 p.
3. Comparison of acquisition techniques for GNSS signal processing in geostationary orbit . The Institute of Navigation, Inc. 2018. URL: www.ion.org/publications/abstract.cfm?articleID=7114.
4. Dan Doberstein GPS Receivers: A Hardware Approach. Springer, 2014. 329 p.
5. Barinov V.V., Lebedev M.V., Kuznetsov V.S. (2006). Analysing correlated characteristics of spreading ensembles. Electrosvyaz’. No. 3, pp. 38-39.
6. Kuznetsov V.S. (2013). Teoriya mnogokanal’nykh shirokopolosnykh sistem sviazi [Theory of multi-channel broadband communication systems]. Moscow: Goriachaia liniia – Telekom. 200 p.
7. Kuznetsov V.S., Shevchenko I.V., Volkov A.S. (2017). Ensemble of Gold’s codes generation for direct-sequence spread spectrum. Trudy MAI. No. 96, p. 18. URL: http://trudymai.ru/published.php?ID=85813.
8. Kai Borre, Dennis M. Akos, Nicolaj Bertelsen, Peter Rinder, Soren Holdt Jensen. (2007). A Software-Defined GPS and Galileo Receiver. Birkhauser Áîñòîí. 189 p.
9. Jack K. (2007). Holmes. Spread Spectrum Systems for GNSS and Wireless Communications. Artech House. 855 p.
10. Thomas Pany. (2010). Navigation Signal Processing for GNSS Software Receivers (GNSS Technology and Applications). Artech House. 352 p
11. Ping Tang et al. (2017). A low-complexity algorithm for fast acquisition of weak DSSS signal in high dynamic environment. GPS Solutions. Vol. 21. N4 (10), pp. 1427-1441.
12. Luca Fanucci, Marco Luise, Filippo Giannetti, Massimo Rovini. (2011). An Experimental Approach to CDMA and Interference Mitigation: From System Architecture to Hardware Testing through VLSI Design. Springer. 274 p.
13. Nesreen I. Ziedan. (2006). GNSS Receivers forWeak Signals. Artech House, Inc. 250 p.
14. Bakhtin A.A., Omel’yanchuk E.V., Semenova A.Yu. (2017). Analiz sovremennykh vozmozhnostey organizatsii sverkhvysokoskorostnykh sputnikovykh radioliniy. Trudy MAI. No. 96. P. 18.
15. Bakhtin A.A., Belousov E.O., Lomovskaya K.M., Timoshenko A.G. (2015). Aktual’nyye zadachi postroyeniya sistem svyazi dlya naplanetnykh i orbital’nykh stantsiy. Izvestiya vysshikh uchebnykh zavedeniy. Elektronika. No. 5, pp. 74-81.

Information about authors:
Alexey S. Volkov, PhD, assistant professor of the Department of Telecommunications, National Research University of Electronic Technology, Moscow, Russia
Alexey V. Solodkov, lector of the Department of Telecommunications, National Research University of Electronic Technology, Moscow, Russia
Ilya V. Chugunov, bachelor of the Department of Telecommunications, National Research University of Electronic Technology, Moscow, Russia