RU2804937C1 - Method of jamming-resistant information transmission based on amplitude manipulation - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention is intended for use in jamming-resistant radio communication systems. In the method of jamming-resistant information transmission based on amplitude manipulation, the bit stream is additionally divided into information blocks of more than four bits, and the time cycle of transmitting the information block is divided into two time subcycles; the list of operating frequencies is formed based on the requirements for the permissible value of the minimum frequency spacing between neighbouring operating frequencies, and the number of operating frequencies is set equal to the number of combinations of information blocks, a unique combination of an information block is assigned to each operating frequency, a harmonic oscillation is generated with a nominal frequency equal to the nominal operating frequency corresponding to the transmitted combination of the information block. In the first time subcycle, the generated harmonic oscillation is emitted, in the second time subcycle, transmission is not carried out. When receiving a radio signal at all the operating frequencies in the first time subcycle, operating frequencies are selected with the level of the received signal exceeding the specified threshold value of amplitude detection, after which, from the selected operating frequencies, operating frequencies with the maximum difference in the levels of the received signal on in the first and second time subcycles, if two or more operating frequencies are determined, then the formation of an information block and its transmission to the message recipient is not carried out, but a decision is made to replace the list of operating frequencies, otherwise, based on the selected operating frequency, an information block is formed and transmitted to the message recipient.

EFFECT: improved noise immunity of signal reception under exposure to barrage noise and polyharmonic interference concentrated in a dedicated operating frequency band.

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Description

The invention relates to the field of radio engineering and is intended for use in noise-resistant radio communication systems.

The known “Method for transmitting discrete signals in the mode of software adjustment of the operating frequency with variable modulation parameters” (RF Patent No. 2770417, IPC H04B 1/713, published 04/18/2022. Bulletin No. 11).

In the known method, the primary signal S ( t ) is generated in a non-harmonic basis, a reference oscillation M ( t ) is formed, the frequencies of which ƒ ₁ , ƒ ₂ , ... are determined in accordance with a given pseudo-random code sequence O ₂ ( t ). The modulated signal S ^' ( t ) is multiplied with the reference oscillation M ( t ), the parameters of the generated signal are selected in accordance with a given pseudo-random code sequence O ₁ ( t ) synchronously with the change in the frequency of the reference oscillation M ( t ).

Synchronized with each change in reference frequencyM(t) form code words based on pseudo-random sequencesO ₁(t) AndO ₂(t). At the transmitting side, the frequency band of the voice channel is divided into two bands based on a frequency cut-off value, which is selected using a pseudo-random sequence codewordO ₁(t). The first and second code words are formed from the information sequence, based on the code sequenceO ₁(t) choose the order of the first, second, third, fourth wavelet functions. The elements of the first and second code words are replaced with radio pulses, which are obtained respectively from the first, second and third, fourth wavelet functions, and the length of the code words is determined based on the values of the bands formed in the channel band of the tone frequency and the order of the wavelet functions, and the elements of the first The code word is replaced by radio pulses of the first and second wavelet functions, the elements of the second code word are replaced by radio pulses of the third and quarter wavelet functions, the radio pulses of the second code word are inverted and the radio pulses are added. In this case, the pulses of the first code word are first summed, then the second, followed by their addition. Based on the received primary signalS(t) at an intermediate frequency form single sideband modulation signal.

The generated single-sideband signal is demodulated, and the carrier frequency during demodulation is chosen equal to the sum of the values of the intermediate frequency and the cutoff frequency value obtained in accordance with the codeword of the pseudo-random sequence O ₁ ( t ). Based on the demodulated signal at the operating frequency determined by the code word of the O ₂ ( t ) sequence, a single-sideband modulation signal is generated, which is emitted towards the correspondent. Then the frequency of the reference oscillation M ( t ) is changed in accordance with the algorithm for implementing the programmatic adjustment of the operating frequency.

On the receiving side, after selecting the operating frequency of oscillations M ( t ) in accordance with the code word of the sequence O ₂ ( t ), the single-sideband modulation signal is demodulated, and the radio pulses of the first and second code words are separated. In accordance with the code sequence O ₁ ( t ), radio pulses are replaced with logical elements of the information sequence, which is transmitted to the message recipient.

The disadvantage of this method is the low noise immunity under conditions of exposure to barrage noise and polyharmonic interference concentrated in the operating frequency band.

The “Method for noise-free transmission of discrete data based on single-sideband modulation” is known (RF Patent No. 2784030. IPC H04B 10/54, published 11/23/2022. Bulletin No. 33).

In the known method, a code with a constant weight is selected to encode the subcarriers of the generated radio signal in such a way that the bit depth of the code corresponds to the number of subcarriers available for transmission. The bit stream is divided into information blocks in accordance with the number of available code combinations that determine its alphabet, and each information block is assigned its own unique combination of code elements.

Signals are generated in the form of amplitude-manipulated oscillations for the duration of each transmitted symbol only on those subcarriers to which information units correspond, after which additive addition of the generated signals on all subcarriers is carried out. Demodulate the resulting frequency-shift keyed signal at subcarrier frequencies as independent frequency-spaced amplitude-shift keyed oscillations.

On the transmitting and receiving sides, the values of frequency and phase shifts are set, for which the frequency range from zero to two kilohertz and the phase change range from zero to three hundred and sixty degrees are divided into nine equal intervals. Each of them is assigned a numerical value that determines the corresponding nominal frequency or phase shift, and a numerical value equal to the sum of the initial boundary value of the interval and the value that determines its length. For each information block, a random binary sequence of ten elements is formed, on the basis of which the first and second random numbers are obtained.

Moreover, the first random number is obtained as a result of converting all elements of the generated binary random sequence into a decimal number, from the first element of which a second random number is obtained, which takes the value of zero or one, respectively. The range of values of the first random number is divided into nine integer uniform intervals, each of which is sequentially assigned the values of frequency and phase shifts.

The value of the radiation frequency is determined, for which the value of the frequency shift corresponding to the value of the first random number is added to the nominal operating frequency, if the second random number is equal to one, if the random number is equal to zero, then the frequency shift is subtracted.

On the transmitting side, at an intermediate frequency, the resulting frequency-shift keyed signal is formed, on the basis of which a single-sideband modulation radio signal is formed at the emission frequency. Moreover, the carrier phase of the single-sideband modulation signal is chosen equal to the phase shift corresponding to the value of the first random number, and a radio signal is emitted towards the correspondent.

At the receiving side, a radio signal is received at the emission frequency, the single-sideband modulation radio signal is demodulated to an intermediate frequency, and the carrier phase of the single-sideband modulation signal is taken equal to the value of the phase shift corresponding to the value of the first random number, then the resulting frequency-shift keyed signal is demodulated.

The disadvantage of this method is the low noise immunity under conditions of exposure to barrage noise and polyharmonic interference concentrated in the operating frequency band.

The closest in technical essence (prototype method) to the claimed one is “Method for transmitting and receiving information based on frequency-shift keyed signals” (RF Patent No. 2777280. IPC H04L 27/00, publ. 08/02/2022. Bulletin No. 22) .

In the prototype method, a code with a constant weight is selected for encoding subcarriers in such a way that the bit depth of the code corresponds to the number of subcarriers available for transmission. Then the bit stream is divided into information blocks in accordance with the number of available code combinations that determine its alphabet. Each information block is assigned its own unique combination of code elements with a constant weight, which determines the transmitted symbol. And signals are generated in the form of amplitude-manipulated oscillations for the duration of each transmitted symbol only on those subcarriers that correspond to information units determined by a combination of code elements with a constant weight.

Moreover, the resulting frequency-shift keyed signal is formed by additive addition of the oscillations of all subcarriers, and the resulting frequency-shift keyed signal is received at subcarrier frequencies as independent frequency-spaced amplitude-shift keyed oscillations. In this case, the quality of the signal on the subcarriers is assessed by comparing the calculated average value of the power of its spectral components within each of the subcarriers with the calculated average value of the signal power over the duration of the received symbol on all subcarriers. And the decision to transmit an information unit within each of the subcarriers is made if the calculated average power value of the spectral components within the subcarrier exceeds the calculated average power value for the duration of the received symbol on all subcarriers, otherwise a decision is made to transmit the information zero.

For transmission, a list of operating frequencies is selected, the number of which is specified by the product of the number of subcarriers for transmitting an information block by the number of combinations of the selected code with a constant weight, and the range of operating frequencies is divided into intervals so that the number of frequencies in the interval coincides with the number of subcarriers for transmitting the information block. Before transmitting each information block, unique combinations of elements of the selected code with a constant weight are assigned to frequency intervals according to a pseudo-random law, and the resulting frequency-shift keyed signal is formed at the operating frequencies of the interval corresponding to the assigned code combination with a constant weight of the transmitted information block.

A radio signal is emitted, a radio signal is received at all operating frequencies, and at each frequency interval the combination of elements of the selected code obtained on the basis of receiving a frequency-shift keyed signal is compared with the combination assigned to a given frequency interval. A frequency interval with the maximum coincidence of combinations is selected, based on the combination of elements of the selected code assigned to the selected frequency interval, an information block is formed and transmitted to the message recipient.

At a given transmission duration, the total number of mismatched received code elements is counted; if the ratio of the number of mismatched elements to the total number of transmitted code elements at a given time interval exceeds the permissible value, a decision is made to replace the list of operating frequencies.

The disadvantage of the prototype method is the insufficient noise immunity of reception under conditions of exposure to barrage noise and polyharmonic interference concentrated in the operating frequency band.

The objective of the invention is to combine methods for encoding with information bits the variable operating frequency of the generated signal and the correlation-energy difference between the signal and interference concentrated in the operating frequency band.

The technical result of the invention is to increase the noise immunity of signal reception under conditions of exposure to barrage noise and polyharmonic interference concentrated in a dedicated operating frequency band

The technical result in a method of noise-resistant information transmission based on amplitude manipulation, which consists in the fact that the bit stream is divided into information blocks, a list of operating frequencies is selected for transmission, a radio signal is generated and emitted, a radio signal is received at all operating frequencies, an information block is formed and transmitted to the recipient messages, make a decision to replace the list of operating frequencies, while the bit stream is additionally divided into information blocks of more than four bits, and the time cycle of transmitting the information block is divided into two time subcycles, the list of operating frequencies is formed based on the requirements for the permissible value of the minimum frequency separation between neighboring nominal operating frequencies, and the number of operating frequencies is set equal to the number of combinations of information blocks, a unique combination of an information block is assigned to each operating frequency, a harmonic oscillation is formed with a nominal frequency equal to the nominal operating frequency corresponding to the transmitted combination of information block, in the first time subcycle the generated harmonic oscillation, in the second time subcycle the radiation is not carried out, when receiving a radio signal at all operating frequencies in the first time subcycle, operating frequencies are selected with the level of the received signal exceeding the specified threshold value of amplitude detection, after which, from the selected operating frequencies, operating frequencies with the maximum difference in the levels of the received signal are determined signal in the first and second time subcycles, if two or more operating frequencies are determined, then the formation of an information block and its transmission to the message recipient is not carried out, but a decision is made to replace the list of operating frequencies, otherwise, based on the selected operating frequency, an information block is formed and transmitted to its message recipient.

Thanks to a new set of essential features, the proposed method, based on the implementation of a simpler type of modulation compared to the prototype method, combines methods for encoding radio signal parameters with information bits and correlating differences in the energy parameters of the signal and interference acting in a dedicated operating frequency band.

Let us explain the possibility of achieving the specified technical result.

In the prototype method, a permutation modulation signal is generated at frequency intervals at several operating frequencies within a selected frequency interval. The proposed method uses the simplest analogue of this signal at one operating frequency, which determines an increase in noise immunity, and according to (Borisov V.I., Zinchuk V.M., Limarev A.E. Noise immunity of radio communication systems by expanding the spectrum of signals by the method of pseudo-random tuning of the operating frequency // edited by V.I. Borisov; 2nd edition, revised and supplemented - M.: RadioSoft, 2008. - 512 pp.) noise immunity indicators compared to the prototype method. Additionally, the frequency band occupied by the radio signal spectrum in the prototype method is several times higher than the frequency band of the signal generated at the operating frequency in the inventive method, which leads to improved noise immunity properties.

In addition, the proposed method implements a change in the signal level during the transmission cycle of a side of information bits. Considering that the random process of changing the level of interference affecting the operating frequency band, in most practical cases is not correlated with a change in the signal level during the transmission cycle (see, for example , D.D. Klovsky. Theory of signal transmission. Textbook - M. 1973), it can be assumed that in the proposed method the correlation difference between the energy parameters of the signal at the operating frequency and interference is realized. If this criterion is not met, then the list of operating frequencies is changed. These operations provide increased noise immunity under conditions of interference in the allocated operating frequency band in the inventive method.

The claimed method is illustrated by drawings, which show:

fig. 1 - signal at the formation stage based on the bit block 0011010 at the first operating frequency;

fig. 2 - signal at the stage of receiving bit block 0011010 at the first operating frequency when exposed to noise interference.

Implementation of the proposed method in accordance with Fig. 1, fig. 2 is carried out as follows.

1. The bit stream is divided into information blocks of more than four bits (seven bits, see Fig. 1, Fig. 2).

The implementation of this procedure is similar to the prototype method, with the exception of the requirement for a block length of at least four bits. This requirement is determined by the value of the base of the generated noise-protected signal, which must exceed the value of ten (Borisov V.I., Zinchuk V.M., Limarev A.E. Noise immunity of radio communication systems by expanding the spectrum of signals by the method of pseudo-random tuning of the operating frequency // edited by V. I. Borisov, 2nd edition, revised and supplemented - M.: RadioSoft, 2008. - 512 pp.), (D. D. Klovsky. Theory of signal transmission. Textbook - M. 1973).

Indeed, when transmitting a block of one symbol, it is sufficient to allocate one operating frequency per transmission cycle. In this case, the value of the signal base is equal to one. When transmitting two symbols, four frequencies are required (determined by the number of combinations of bits in the information block), therefore, the base value is four. For a signal base value greater than ten, at least four bits of the information block are required.

2. The time cycle of transmitting an information block is divided into two time subcycles.

This procedure is organizational. It is necessary to take into account that the duration of the transmission cycle should be determined by the statistical properties of the radio communication channel, see, for example, (D.D. Klovsky. Theory of signal transmission. Textbook - M. 1973), (Military radio communication systems. Part I / Ed. V.V. Ignatova. - L.: VAS, 1989. - 386 pp.), (Integral model of noise-immune radio communication lines / Dvornikov S.V., Pshenichnikov A.V., Manaenko S.S., Glukhikh I.N. // Radio industry, 2018, Vol. 28, No. 4, pp. 8-14). In this case, the durations of the subcycles are chosen to be equal.

3. For transmission, a list of operating frequencies f ₁ ... f _M is formed (see Fig. 1, Fig. 2) based on the requirements for the permissible value of the minimum frequency separation (Δ f _min , see Fig. 1) between adjacent nominal operating frequencies , and the number of operating frequencies M is set equal to the number of combinations of information blocks.

The formation of a list of operating frequencies is carried out similarly to the prototype method, with the exception of the requirements for the minimum frequency spacing between adjacent nominal operating frequencies and the number of operating frequencies.

The minimum frequency spacing must be greater than the width of the spectrum of the amplitude-shift keying signal, which will be formed due to the emission of the radio signal only in the first time subframe (see clause 6). The signal spectrum width is determined, for example, in (Franks L. Theory of signals / Translated from English - M.: Sov. Radio, 1974. - 344 p.), (D.D. Klovsky. Theory of signal transmission. Textbook - M 1973).

In the prototype method, the coding of blocks of information sequence was carried out in frequency intervals. In the proposed method, information blocks are encoded by frequencies, which determines the requirements for the number of operating frequencies equal to the number of combinations of information blocks of at least four bits (see clause 1).

4. Each operating frequency is assigned a unique combination of an information block (for example, combination 0011010 is assigned to the first operating frequency, see Fig. 1, Fig. 2).

This operation is organizational and similar to the prototype method, except that the combination of the information block in the prototype method was assigned to the frequency interval, and in the claimed method to the operating frequency.

5. A harmonic oscillation ( Uc , Fig. 1) is formed with a nominal frequency f equal to the nominal operating frequency corresponding to the transmitted combination _of the information block (Fig. 1, frequency f ₁ , combination 0011010).

The procedure for generating a harmonic oscillation with the required frequency is known and is implemented in frequency synthesizers (see, for example, a frequency grid synthesizer based on a PLL circuit with fractional noise compensation (RF Patent No. 2491713. IPC H03L 7/00, published on August 27, 2013. Bulletin . No. 24) or exciter R-170 V. In this case, the frequency of the generated harmonic oscillation is determined by the combination of the transmitted information block.

6. In the first time subcycle, the generated harmonic oscillation is emitted; in the second time subcycle, the emission is not carried out.

This operation is organizational and is actually equivalent to the procedure for generating an amplitude manipulation signal. The procedure for generating this signal is well-known and is given, for example, in (Franks L. Theory of Signals / Translated from English - M.: Sov. Radio, 1974. - 344 p.), (D.D. Klovsky. Theory of Signal Transmission Textbook - M. 1973). Implemented, for example, in the exciter R-170 V.

7. A radio signal is received at all operating frequencies f ₁ ... f _M , while in the first time subcycle, operating frequencies are selected with the level of the received signal exceeding the specified amplitude detection threshold value ( U _thr , Fig. 2).

Reception of radio signals at all operating frequencies is similar to the prototype method and is based on the implementation of multi-channel radio receivers. In this case, the amplitude detection prorog can be selected similarly to the method described in (Franks L. Theory of Signals / Translated from English - M.: Sov. Radio, 1974. - 344 p.), (D.D. Klovsky. Transmission Theory signals. Textbook - M. 1973) or presented in the method of transmitting information over a short-wave communication channel using frequency-shift keyed signals, see (RF patent No. 2705357. IPC H04L 27/22, publ. 07.11.19. Bull. No. 31), or, for example, implemented in the radio receiver of the R-170P series.

8. From the selected operating frequencies, the operating frequencies with the maximum difference in the levels of the received signal in the first and second time subcycles are determined; if two or more operating frequencies are determined, then the formation of an information block and its transmission to the message recipient is not carried out, but a decision is made to replace the list of operating frequencies , otherwise, based on the selected operating frequency, an information block is formed and transmitted to the message recipient.

Determination of the amplitude difference at selected frequencies is based on measuring the amplitudes at the first and second time subcycles. This operation is well-known and is implemented, for example, in a device for measuring the amplitude and phase of a radio signal, see (USSR patent No. 1485851. IPC G01V 3/12, publ. 06/27/95) or in a device for receiving quadrature amplitude-shift keying signals, see ( RF patent No. 2756906. IPC H04L 27/34, published 10/06/2021. Bulletin No. 28).

After determining the amplitude level, the frequency with the maximum difference in the amplitude difference in the first and second time subcycles is determined. This operation is formal and logical-arithmetic and can be implemented in software on digital processors. The choice of digital processors and their interface with radio link elements is presented, for example, in patent No. 2273099 H04 B 15/00, publ. 03/27/2006. Bull. No. 9).

If more than two frequencies are selected, this means the presence of interference ( U _pom , Fig. 2) with the same correlation-energy parameters as the signal in the operating frequency band. In this case, the list of operating frequencies is replaced. Replacing the list of operating frequencies is carried out similarly to the prototype method. If one frequency is selected, then, similarly to the prototype method, information bits are generated and transmitted to the message recipient.

The results of the simulation of the transmission of binary bits in the MatLAB environment based on the developed method showed a significant reduction in the probability of error in receiving a signal element compared to the prototype method under the influence of interference from electronic devices localized in the operating frequency band (on average by two orders of magnitude).

Thus, in the claimed technical solution, when implemented, noise-free transmission of information is ensured based on amplitude manipulation, under conditions of interference concentrated at operating frequencies, which indicates the achievement of the claimed technical result and the objective of the invention.

Claims (1)

A method of noise-resistant information transmission based on amplitude manipulation, which consists in dividing the bit stream into information blocks, selecting a list of operating frequencies for transmission, generating and emitting a radio signal, receiving a radio signal at all operating frequencies, forming an information block and transmitting it to the message recipient, receiving decision to replace the list of operating frequencies, characterized in that the bit stream is divided into information blocks of more than four bits, and the time cycle of transmission of the information block is divided into two time subcycles; the list of operating frequencies is formed based on the requirements for the permissible value of the minimum frequency spacing between neighboring ones at nominal value operating frequencies, and the number of operating frequencies is set equal to the number of combinations of information blocks, a unique combination of an information block is assigned to each operating frequency, a harmonic oscillation is formed with a nominal frequency equal to the nominal operating frequency corresponding to the transmitted combination of the information block, in the first time subcycle the generated harmonic oscillation is emitted oscillations, in the second time subcycle no emission is carried out, when receiving a radio signal at all operating frequencies in the first time subcycle, operating frequencies are selected with the level of the received signal exceeding the specified threshold value of amplitude detection, after which, from the selected operating frequencies, operating frequencies with the maximum difference in the levels of the received signal are determined in the first and second time subcycles, if two or more operating frequencies are determined, then the formation of an information block and its transmission to the message recipient is not carried out, but a decision is made to replace the list of operating frequencies, otherwise, based on the selected operating frequency, an information block is formed and transmitted to the recipient of the message.