A.B. Zazulina, A.N. Lutkov

At automatic control of aircrafts there is a problem of information transfer about their condition, operating mode and commands transfer for big distances. It is particularly important to provide sufficient reliability of information's transfer at minimum costs on elaboration and on exploitation of wireless channels. Modern communication systems are constructed on the basis of digital technologies. The key parameter of digital wireless channel's quality is the bit error probability or bit error rate (BER). This parameter is one of initial for design. Complexity of radio channel's realization, in particular, complexity of channel coding algorithms, depend on admissible BER. Thus, adequate evaluation of admissible BER is required. The assessment of admissible probability erroneous message transfer is performed at the first stage of calculation. Admissibility of one message loss during transient of the most dynamic onboard automatic control system is chosen as the assessment criterion. This period of sampling shows the minimum possible time for message transfer, that corresponds to limiting and possible speed of data transmission in a communication system. The simplified BER calculation is executed from the received admissible erroneous message probability at the second stage. Neglect possibility by components with high degrees is put in the basis of BER calculation simplification. It is fair in the solution of equations for small values of probability admissible erroneous message transfer and allows us considerably to simplify calculation for messages with big sizes. The offered technique allows us to estimate a priori admissible probability of BER in the digital wireless channel with aircrafts system at early design stages of automatic control system when exact data of admissible messages losses are unknown, and to use the received probability as maximum initial task at development of the wireless channel.