V.N. Kharisov, P.M. Golovin
Modernization of global navigation satellite systems (GNSS) GLONASS and GPSspent now, and also creation and expansion of GNSS Galileo are based on use of new navigation signals, in particular signals with BOC modulation
The great popularity of signals with BOC modulation is caused by that they provide advantages in accuracy of measurement of a delay in comparison with signals with traditional way of modulation of BPSK. However, it is considered that BOC-signalshave an essential shortcoming – complication of search procedure.
By analogy to reception of BPSK signals for BOC signals it is necessary to choose . As a result the number of correlators for BOC signals essentially (in 4m/n) increases concerning number of correlators for BPSK signals with the same duration of a symbol. It leads to proportional complication of hardware, or increase in time of signal search.
From literature methods of search of the BOC signals, numbers of correlators not demanding such increase as the traditional optimum approach demands are known. Feature of these methods is that after detection of a signal and an assessment of a delay of a code, it is necessary to carry out the second stage of detection – permission procedure, that is search of the central peak of AKF of BOC-signal in an interval corresponding to the chip of a code.
Known methods are reasonable engineering solutions of a problem of simplification of asearch, however they don't follow from the theory. The problem of receiving the optimum or near optimal algorithm simplifying realization of search of BOC signals of rather traditional optimum algorithm is actual.
On the basis of a method of an additional variable the simplified optimum algorithm of search of signals with BOC modulation is synthesized. Advantage of algorithm in comparison with known is simultaneous definition of a delay of a code of a signal and an assessment of a phase of the meander forming a BOC signal that allows to exclude completely usual for the simplified algorithms of search the second stage serving for definition of true peak of autocorrelation function of formed on an exit of the block of correlators of the search scheme.