B.V. Sultanov - Dr. Sc. (Eng.), Professor, Department «Information security of systems and technologies», Penza State University. E-mail: bv_sultanov@mail.ru N.B. Zhukova - Post-graduate Student, Engineer, Department «Information security of systems and technologies», Penza State University. E-mail: zhukova-nb@yandex.ru S.L. Zefirov - Ph. D. (Eng.), Associate Professor, Head of Department «Information security of systems and technologies», Penza State University. E-mail: sergeizefirov@mail.ru V.V. Doroshkevich - Assistant, Department «Information security of systems and technologies», Penza State University. E-mail: ibst@pnzgu.ru

Possible algorithms of the initial synchronization (acquisition) in fast frequency hopping systems, possessing potentially high speed and based on recurrent measurement of instant frequency of an input signal are considered. This frequency unequivocally defines a phase of the pseudo-random sequence setting the law of a frequency change in the received signal. However in a real situation exact measurement cannot be carried out owing to influence of noise. Therefore fixed in a linear feedback shift register (LFSR) of the receiver the code proportional to this frequency, is determined on the basis of L (L the number of digits in the register) consistently carried out estimations of frequency hopping duration Tс, and from each binary number corresponding the next estimation is used only one most sig-nificant bit (MSB). In paper is shown, that upon termination of L jumps of frequency, i.e. later time tс = LTс, in LFSR of the receiver there is recorded a code, taken place tс seconds ago in LFSR the transmitter. After reception of this number in LFSR the receiver and a delay received the signal for a while tс, is carried out testing correctness of the received result, sold with use of the correlator. There are various methods of measurement of frequency at presence of noise, but any of them does not guarantee correct determi-nation of all MSB. At a wrong estimation even one MSB, the result of testing appears negative, and the described procedure of recurrent acquisition should be executed repeatedly, that magnifies its total duration. Thus the greatest contribution to magnifying of duration of acquisition brings necessity of performance of new testing as time spent for check of the made estimation of digits, more than on the order surpasses time spent for a estimation. In paper algorithms of the recurrent acquisition, allowing to find out presence of incorrect or not reliable estimations MSB up to a stage of testing and by that to exclude necessity of performance of this stage at high probability of reception of negative result are considered and offered. Results of an estimation of efficiency of the considered and offered algorithms, received on the basis of imitating simulation analysis are brought.

 

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