Study on chaotic oscillator‐based algorithm for weak GLONASS signal acquisition

Abstract

According to the characteristics of the chaotic oscillator in detecting weak signals, an algorithm based on Duffing chaotic oscillator array was proposed for acquisition of weak GLONASS signals. By means of GLONASS intermediate frequency and Duffing chaotic oscillator models, Lyapunov exponent is adopted to judge the critical condition of phase track and decide whether GLONASS signals exist or not by the change of the critical condition, and numeric iteration procedure is used to calculate the exponent. Finally, the performance of algorithm is simulated using GLONASS intermediate frequency data. The results indicate that acquisition algorithm can satisfy the need of object positioning in low signal-to-noise ratio environment. K E Y W O R D S acquisition, chaotic oscillator, GLONASS, low signal-to-noise ratio 1 | INTRODUCTION Currently, the global navigation systems chiefly include GPS of the United States, BeiDou of China, GLONASS of Russia, and Galileo of the United Nation, in which the GPS is used most widely in the world, and its weak signal acquisition technique is undoubtedly the hot spot in relevant studies. Among the existing weak GPS signal acquisition algorithms, the accumulation time is prolonged in almost all the algorithms, to increase the signal processing gain and improve the detection sensitivity. The commonly used weak GPS signal acquisition methods include the coherent accumulation, noncoherent accumulation, coherent accumulation plus noncoherent accumulation, differential coherent accumulation, and various improved algorithm-based such methods. 1-4 As for the GLONASS system, because of economic reasons, Russia has never provided the high-accuracy positioning for its GLONASS system, which is fully distributed over the satellite constellation but unavailable for use by users from time to time, so few studies have been conducted on GLONASS signal acquisition, particularly weak GLONASS signal acquisition under the environment with low signal-to-noise ratio. In most of the existing weak GLONASS signal acquisition methods, the processing methods similar to those for weak GPS signals are still adopted, that is, by increasing the accumulation time to increase the signal processing gain 5-7 and improve the acquisition sensitivity of the receiver. However, the existing algorithms for acquisition of weak GPS signals and weak GLONASS signals show the limitations, that is, significantly increasing the signal processing time while prolonging the accumulation time and reducing the real-time capability of the receiver, particularly unsuitable for navigation positioning under the highly dynamic environment. With its economic recovery in recent years, Russia speeds up the network patching of the GLONASS system, which has the important realistic values on the studies on GLONASS

Double block zero padding differential coherent weak signal acquisition algorithm under ionospheric interference

“…On this basis, by optimizing the objective function, part of the calculation amount is reduced and the capture probability is improved, but it needs a large data storage space. Yu L et al proposed a chaotic oscillation model, which realized the capture of weak GLONASS signal under the condition of low signal-to-noise ratio [3]. Faqin G proposed an improved acquisition algorithm based on Doppler compensation, which combined with incoherent integration method to achieve the acquisition of GNSS weak signals, but the acquisition effect is not good in extremely weak environment [4].…”