# The method of discrete information transmission in a radio link with a pseudorandom operating frequency tuning

The invention relates to communication technology and can be used in the computer network with pseudorandom change the operating frequency. The technical result is to increase the noise immunity of communication. The length of the binary vector of the block of the input signal selected in accordance with the number of frequency channels form two binary pseudorandom vector sequences by simultaneous parallel recording information from various bits of the shift register, the transmitter rebuild sequentially on two carrier frequencies in accordance with the codes and the reception in the presence of the signal in each frequency channel demodulator and shape the signal into a binary vector that represents the number of the frequency channel. 4 C.p. f-crystals, 2 Il. The invention relates to the field of radio communications and computing, and more particularly to methods and devices for data transmission in the computer network by radio with pseudorandom change the operating frequency.Known methods of discrete information transmission in a radio link with pseudorandom change the operating frequency (see, for example, [1] pages 19-35 and request for izobreteny who eat modulation package information signal frequency of the transmitter, carrier which reconstruct the pseudo law.The closest to the technical nature of the claimed method is a method described in the application 99123808/09 from 10.11.1999. Prototype method includes dividing an input signal at the transmitting end in units, restructuring of the carrier frequency of the transmitter in accordance with the code of one of the two or more pseudo-random sequences generated by shift register with feedback, modulation of the carrier frequency of the transmitter corresponding package and subsequent radiation in space, the signal at the receiving end of the radio link simultaneously at all frequencies according to the codes of pseudo-random sequences, the selection of the frequency channel on which the transfer was made, converting the signal to an intermediate frequency, amplification, demodulation, decoding package and submission of the information signal on the target device.However, the prototype method has a drawback. Despite the fact that the carrier frequency of the transmitter is reconstructed in accordance with the pseudo-random code sequence, the communication system is unstable with active intrusion, since it is ensured timely determination of the frequency of radiation Nala. This is because if the structure of the shift register having n-bits, and linear or nonlinear feedback known, upon receiving the n symbols of pseudo-random sequence by recording the emitted frequency of the transmitter, open the structure of the pseudo-random sequence, and the status register at the relevant point in time [3] p. 93. If the structure of the shift register with linear feedback is unknown, upon receiving the 2n-character pseudo-random sequence for a few seconds may be determined by the location of the taps, the number of adders included in the feedback circuit, and the status register at the relevant point in time [3] p. 94.The possibility of creating sighting frequency noise or interference in the multiple frequency channels to reduce interference immunity radio communication with pseudorandom change the operating frequency.The invention aims to improve the noise immunity of communication.This is achieved by the known method of discrete information transmission in a radio link with pseudorandom change the operating frequency, which consists in dividing the input signal at the transmitting end in units form the om binary vector of pseudo-random sequences, created by a shift register with feedback, frequency modulation transmitter and the subsequent emission of a signal in space, the signal at the receiving end of the radio link simultaneously at all frequencies, converting the signal to an intermediate frequency, amplification, demodulation and signal is applied to the target device, according to the invention the length of the binary vector of the block of the input signal selected in accordance with the number of frequency channels form two binary pseudorandom vector sequences by simultaneous parallel recording information from various bits of the shift register, while the length of each binary vector pseudo-random sequence is chosen equal to the length of the binary vector of the block of the input signal, and the transmitter rebuild sequentially on two frequencies in accordance with the codes, which form in the form of binary vectors by adding modulo two bits of each binary vector pseudo-random sequence of bits of the binary vector of the block of the input signal, and at the receiving side when the presence of a signal in the frequency channel after its demodulation form the signal as a binary vector, which corresponds to sequence what Inoi sequence and produce a binary vector of the block of the input signal by adding modulo two bits of the signal, appearing first in one frequency channel, the bits of the first binary vector pseudo-random sequence, and by adding modulo two bits of the binary vector signal arising in another frequency channel, the bits of the second binary vector pseudo-random sequence, compare binary vectors for the two frequency channels and at their coincidence submit one of them to the target device, when the presence of signals in more than two frequency channels filter out false signals by sequential analysis of the signal in one frequency channel in combination with signals in other frequency channels.In the combination of features of the proposed method under a binary vector refers to the signal as a sequence of zeros and a single bit corresponding to the representation of a number in binary.Listed set of essential features provides high noise immunity because the carrier frequency of the transmitter is not modulated by the information signal, the sequence of adjustment of the carrier frequencies of the transmitter will not be opened even when the opening of the pseudo-random sequence, and in the design is Ktorov pseudo-random sequence. The establishment of the sighting frequency interference does not lead to the loss of the information signal, as the latter is formed by means of the signal in the corresponding frequency channel. Because the sequence of adjustment of the carrier frequencies of the transmitter is determined by the sum of the values of the binary vector information signal and the binary vectors of the pseudo-random sequence, then the possibility of opening a pseudo-random sequence when fixing the frequency of the radiation transmitter in each cycle of the radio link, which does not allow to create an effective false information signals.The possibility of technical realization of the inventive method is explained as follows.If the number of frequency channels is 2

^{k}then the length of the binary vector of the block of the input signal is chosen equal to k bits. For example, for 16 frequency channels length binary vector of the block of the input signal should be 4 bits.The formation of pseudo-random sequences of maximum length, containing 2

^{n}-1 character, can be done by using a linear shift register having n bits, the feedback which predelay] on pages 74-75.The formation of each binary vector pseudo-random sequence of length K bits can be done by removing information from various bits of the shift register numbers that can be defined by the value of the entered security key (seed bits of the shift register). For example, by defining a generating element of l

_{0}K(modq), if l

_{0}<2, l

_{0}= 2, and calculate the number of digit of the shift register according to the formula l

_{1}= l

_{0}, l

_{i}l

_{0}l

_{i-1}(modq), i = 1, K, where the value of q is selected from the primes and to the shift register, has 256 bits, q=257, and shift register having 128 bits, q= 127. In this case, due to the exponentiation of the parent number of l

_{0}we will move from one element of the field Fq to another. In this case, as shown in [3] pages 44, if l

_{0}- an element of order m, then all elements of l

_{0}l

_{0}

^{2}l

_{0}

^{3},... , l

_{0}

^{m-1}will be different.Code generation K

_{1}for adjustment of the transmitter at a first carrier frequency can be done by adding modulo two characters of the first binary vector pseudo-random sequence (for example, 1 is Ala (for example, 01117)K

_{1}=111115, and generate code To

_{2}for adjustment of the transmitter on the second carrier frequency can be done by adding modulo two characters of the second binary vector pseudo-random sequence (e.g., 00113) with the binary vector of the block of the input signal (01117)K

_{2}=01004 In accordance with the generated codes, the transmitter will emit a signal on the carrier 15 frequency channel and carrier 4 frequency channel.The decoding of the packet at the receiving side can be performed as follows. When the signal is present in 4, 6 and 15 frequency channels will be formed of 3 binary vector corresponding to the numbers

40100

60110

151111

Are the combinations for the first number (4 and 6) (4, 15). For each combination of folded modulo two characters of the binary vector of the first number (4) characters of the first binary vector of pseudorandom sequence number (8), and the symbols of the binary vector of another number (6) �2D/img_data/66/663201.gif">

Because these numbers are not equal, then check all other combinations of numbers.For the combination (4 and 15)

For the combination (6 and 4)

For the combination (6 and 15)

For the combination (15 and 4)

For the combination (15 and 6)

Analysis of all combinations shows that the coincidence of two binary vectors is obtained at the output of the fifteenth and the fourth frequency channels, a false signal at the output 6 channel filtered. Because of the coincidence of the binary vectors is performed for the combination (4 and 15), and (15) and 4), then choose the combination (15 and 4), because the signal at the output 15 frequency channel corresponds to the first carrier frequency of the transmitter and appears earlier signal 4 frequency channel, which corresponds to the second carrier frequency of the transmitter.The proposed method can be implemented using the devices represented by the flowchart in Fig.1, where

unit 1 - the signal source;

unit 2 - the first shift register;

unit 3 - the encoder;

unit 4 - the frequency synthesizer;

block 5 - modulator;

unit 6 - transmitter;

baterista,

and by the flowchart of Fig.2, where the blocks 11-16 bits 1-6 of the shift register and the block 7 - modulo two.For ease of description of the operation of the device will use small numbers. We assume that the shift register is 6 bits (the length of the security key 6 bits), and the number of frequency channels 16, then to transfer one block of the input signal can be used a binary vector of length 4 bits.To define the structure of the shift register is chosen primitive polynomial of the sixth degree, for example

^{6}+

^{5}+1

For the selected primitive polynomial structural diagram of the shift register with feedback will be of the form shown in Fig.2. Generated by the random number generator security key length of 6 bits

<

_{6},

_{5},

_{4},

_{3},

_{2},

_{1}>

where

_{1}= 0,

_{2}= 0,

_{3}= 0,

_{4/}= 1,

_{5}= 1,

_{6}= 1 ply 5 and 6 digits of the shift register are received in each cycle at the input of the adder 17 modulo two, and from the output of the modulo two symbol=

_{5}

_{6}proceed to input the first digit of the shift register (block 11). The status bits for each measure in the process of the shift register are determined by the expression

If characters will be removed from the sixth discharge

_{6}then the binary pseudo-random sequence, the maximum period will be

{1110000010000110001010011110100011100100101101110110011010101111}

Note that the period of this sequence is any non-zero set of six digits 0 and 1 occurs only once.If the binary number will be removed from 1, 2, 3 and 4 digits of the shift register (blocks 11, 12, 13, 14) and at each step of the shift register and with a set of <

_{1},

_{2},

_{3},

_{4}> will map the binary vector (number) x =

_{1}+2

_{2}+2

^{2}

_{3}+2

^{3}

_{4}the sequence of binary numbers in the process p, , 12, 8, 1, 2, 5, 10, 4, 9, 3, 7, 15, 14, 13, 10, 4, 8, 1, 3, 7, 14, 12, 9, 2, 4, 9, 2, 5, 11, 6, 13, 11, 7, 14, 13, 11, 6, 12, 9, 3, 6, 13, 10, 5, 10, 5, 11, 7, 15, 15, 15, 14, 12,...}

If the binary number will be removed simultaneously with 1, 2, 5, 6 bits of the shift register (blocks 11, 12, 15, 16) and at each stage of the shift register with a set of <

_{6},

_{5},

_{2},

_{1}> will match the number in the form y =

_{6}+2

_{5}+2

^{2}

_{2}+2

^{3}

_{1}the sequence of binary numbers in the process of the shift register can be viewed as a sequence of symbols y{0, 1, 2,...,15} as

the= { 3, 3, 1, 8, 4, 0, 0, 2, 9, 12, 4, 0, 2, 11, 5, 8, 4, 2, 9, 14, 13, 12, 6, 11, 7, 3, 1, 10, 13, 12, 4, 2, 11, 7, 1, 8, 6, 9, 12, 6, 9, 14, 15, 5, 10, 15, 7, 1, 10, 15, 5, 8, 6, 11, 5, 10, 13, 14, 13, 14, 15, 7, 3,...}

Analysis of the generated sequences x and y shows that in the interval corresponding to a period equal to 63 cycles of operation of the shift register, each of the symbols { 1, 2,... 15} occurs exactly four times. The symbol for zero in both sequences, occurs exactly three times, and the sequence x and y can not be obtained from one another by cutting the uniformity of the characters used.The generated pseudo-random sequence of symbols x and y in the form of binary vectors received in the encoder 3, which form codes for adjustment of the carrier frequency of the transmitter by adding modulo two characters of the binary vectors pseudo-random sequence with characters of the binary vector of the block of the input signal.Similarly, on the receiving side are formed characters x, y in the block 8 and the symbols x and y in a decoding device 9 to recover the transmitted message.Thus due to the modulation of the carrier frequencies of the transmitter error-correcting code (e.g., Barker), it is possible not only to increase the robustness of communication, but also the secrecy of the transmission, and by changing the order of reading data or the number of bits of the shift register during the formation of binary vectors of pseudo-random sequence in each session precluded the opening of a pseudo-random sequence with the attacks on the basis of known or chosen source.If the shift register is passed the bars of his work, for which the generated binary vector of pseudorandom sequences coincide, provided statistical reunionese statistical methods of cryptanalysis to break the pseudorandom sequence.Implementation of the proposed method is straightforward, since all the blocks and units included in the device that implements the method, well-known and widely described in the technical literature.Sources of information

1. C. I. Borisov, V. M. Zinchuk, A. E. Lirnarev, N. P. Mukhin, V. I. Shestopalov. The immunity of radio communication systems with expansion of the range of signals, the method of pseudo-random adjustment of the operating frequency, Radio and communications", M., 2000.2. The method of discrete information transmission in a radio link with pseudorandom change the operating frequency and the device for its implementation. The application for the invention 99123808/09 from 10.11.1999 - MPK7 N 04 1/713.3. B. N. Voronkov, V. I., Tupot. Methodological guide for the development of the protection of information in computer networks. Voronezh, Voronezh State University, 2000.

Claims

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