А. B. Tkachev, A. S. Bogdanov

In modern global navigation satellite systems (GNSS) the important problem is noise stability maintenance by transfer of the navigating data. GNSS signals have rather more difficult structure, than signals of communication systems, hence, at application in GNSS signals of methods of noiseproof coding it is necessary to consider features of transfer of the navigating information. The present work is devoted to the research of efficiency of methods of noiseproof coding in GNSS signals taking into account features of construction of navigating systems and to offer the ways of their modernization. Various ways of coding of navigating messages taking into account features of structure of the transferred information are considered. The comparative analysis of a noise stability of transfer of the navigating message with the use of a code of Hamming (32,26) with detection and correction of errors is carried out. The received results show that decoding with correction of errors allows to raise a power system effectiveness approximately twice. However because of properties of an applied code, the basic problem for GPS and GLONASS signals is the high probability of rejections of decoding. One of possible solutions in the modernized GLONASS system is a transition from block codes to convolution codes. The imitating modelling of a communication system spent by authors with the use of convolution code (g1 = 1+X+X2+X3+X6; g2 =1+X2+X 3+X 5+X 6), Viterbi decoded on algorithm, and the comparative analysis of the received results has shown that the coding scheme on the base of the convolution code, provides a noise stability of transfer of the navigating messages, considerably exceeding noise stability with the use of block coding. Besides, using the offered scheme of coding of the navigating information, it is possible to increase a transmission frequency of health bits, formed onboard the satellite bearing the information on reliability of onboard equipment.