RU2804518C1 - Method of radio communication with mimo technology and pseudo-random tuning of operating frequencies - Google Patents

Abstract

FIELD: wireless communication systems.

SUBSTANCE: method of radio communication with MIMO technology and pseudo-random tuning of operating frequencies, characterized by the fact that, on the transmitting side, pairs of complex symbols transmitted in parallel are formed, the elements of the upper and the lower lines are transmitted through spatially separated antennas, the elements of the output matrices of the formed pairs of parallel transmitted modulated symbols are transmitted via subcarriers, subcarrier frequencies are formed in a pseudo-random manner, while information about the fading correlation frequency interval is supplied to the time-frequency matrix generator based on the results of ionospheric sounding with a periodicity not less than the duration of the stationarity interval of the decameter communication channel, radio exchange is carried out at the generated subcarrier frequencies for a time not exceeding the duration of the stationary interval of the decameter communication channel, after which the transition to the newly formed subcarrier frequencies is carried out.

EFFECT: enabled operation of a MIMO communication channel using pseudo-random tuning of operating frequencies to ensure immunity to interference.

2 cl, 4 dwg, 1 tbl

Description

The invention relates to wireless communication systems and, in particular, to methods for performing radio communication in systems with several spatially separated receivers and transmitters [H04B7/04, H04B7/06, H04B7/08].

A UNIFIED STRUCTURE AND CENTRALIZED PLANNING FOR DYNAMIC MODES SIMO, SU-MIMO and MU-MIMO WITH RL TRANSMISSIONS [RU2420880, publ. 12/10/2010]. A wireless communication method used in a wireless communication system, the method comprising the steps of: transmitting at least one power control reference signal from an antenna selected from a group of M antennas, where M is a positive integer; transmitting a power spectral density (PSD) offset from an antenna used to communicate the at least one power control reference signal, wherein the PSD offset is based on a reference PSD level for transmitting the at least one power control reference signal; and transmitting a pilot signal from each antenna in the set of M antennas to estimate a multiple-input multiple-output (MIMO) channel when M>1 and a single-input multiple-output (SIMO) channel when M=1.

The disadvantage of the analogue is the low throughput of the communication channel due to the fact that additional frequency resources are not used to transmit information.

Also known from the prior art is a METHOD FOR TRANSMITTING MULTI-USER MIMO IN WIRELESS COMMUNICATION SYSTEMS [RU2649856, publ. 04/05/2018], the method comprising the steps of: determining the energy per resource element (EPRE) ratio of a physical downlink shared channel (PDSCH) to the EPRE of a mobile device-specific reference signal based on the layer number; transmitting downlink control information including hybrid automatic retransmission request information, mobile device-specific reference signal information, modulation and coding scheme information for each transport block, and new data indicator information for each transport block; and transmitting data on the PDSCH based on the downlink control information.

The disadvantage of the analogue is the low throughput of the communication channel due to the fact that additional frequency resources are not used to transmit information.

Also known from the prior art is a METHOD FOR PARALLEL MULTI-FREQUENCY TRANSMISSION OF DIGITAL INFORMATION USING COMBINED MULTI-POSITION FREQUENCY AND PHASE MODULATION IN FREQUENCY SUB-CHANNELS [RU2574080, publ. 02/10/2016] in which data arrives at the input of the transmitting part of the communication system in two separate streams and is then transmitted through N parallel channels of a multi-frequency communication system, using the grouping of L individual frequency subchannels into N/L clusters (groups), in each of which digital data is displayed in the form of modulation symbols obtained by the combined modulation method sequentially in two stages: initially, according to the law of multi-tone multi-frequency modulation, a subset R of L active subcarriers is generated, displaying in each cluster the symbols of this modulation for the data of one of the information flows, displaying in a combination of R tone subcarriers the choice of modulation symbol, and then, at the second stage, the digital data of the second stream is modulated according to the law of phase modulation P from R active subcarriers and on the receiving side the demodulation process is performed respectively in each cluster sequentially in two stages: first, the received tone multifrequency modulation symbols are demodulated in an incoherent demodulator, by detecting R active subcarriers, the totality of which determines the values of the digital data carrier symbols of the first stream, and at the second stage, selecting from R phase-modulated subcarriers demodulated at the first stage, the data carrier symbols of the second stream are demodulated, characterized in that during transmission in the second stage in each cluster of R active subcarriers, defined according to the law of multi-tone multi-frequency modulation, part of the P subcarriers is modulated by the multi-position phase modulation method, and the remaining R-P active subcarriers, the positions of which within the cluster are uniquely determined by a given rule when transmitting in relation to P phase-keyed subcarriers, are used on the receiving side for the formation of reference oscillations necessary for coherent demodulation of symbols of the second information stream.

The disadvantage of the analogue is low noise immunity due to the fact that the technology of spatial diversity of receiving and transmitting antennas is not used.

The closest in technical essence is TRANSMISSION DIVERSITY SCHEME WITH MULTIPLE ANTENNAS [RU2432683, publ. 27.10.2011]. A method for transmitting data, comprising the steps of: modulating the data to be transmitted into a plurality of modulated symbols; and transmitting a plurality of modulated symbols in accordance with an output matrix using a multi-antenna transmission space-frequency diversity scheme via a plurality of frequency subcarriers; wherein the first symbol and the second symbol are transmitted through the first antenna by the first frequency subcarrier and the second frequency subcarrier, respectively, the third symbol and the fourth symbol are transmitted through the second antenna by the third frequency subcarrier and the fourth frequency subcarrier, respectively, the inverse complex conjugate of the second symbol and the complex the conjugate value of the first symbol is transmitted through the third antenna by the first frequency subcarrier and the second frequency subcarrier, respectively, and the inverse complex conjugate value of the fourth symbol and the complex conjugate value of the third symbol are transmitted through the fourth antenna by the third frequency subcarrier and the fourth frequency subcarrier, respectively; and wherein the density of the resource elements used to transmit the reference signals through the third antenna and the fourth antenna is less than the density of the resource elements used to transmit the reference signals through the first antenna and the second antenna.

The main technical problem of the prototype is the low noise immunity of transmitted data due to the impossibility of sharing the technology of spatial diversity of transmitting and receiving antennas and pseudo-random tuning of operating frequencies.

The objective of the invention is to eliminate the shortcomings of the prototype.

The technical result of the invention is to enable the operation of a MIMO communication channel using pseudo-random tuning of operating frequencies to ensure noise immunity.

This technical result is achieved due to the fact that the method of radio communication with MIMO technology and pseudo-random tuning of operating frequencies, characterized by the fact that pairs of complex symbols transmitted in parallel are formed on the transmitting side, each generated pair of symbols is encoded with the space-time Alamouti code, forming an output matrix, elements of the upper and the lower rows of the output matrix from the formed pair of symbols are transmitted through space-spaced antennas, the elements of the output matrices of the formed pairs of parallel transmitted modulated symbols are transmitted through various subcarriers, the frequencies of the subcarriers are formed in a pseudo-random manner based on data from the columns of the time-frequency matrix, in which the frequencies of the subcarriers formed pairs of parallelly transmitted modulated symbols are orthogonal to each other and do not fall into the fading correlation frequency interval, while information about the fading correlation frequency interval is supplied to the time-frequency matrix generator based on the results of ionospheric sounding with a periodicity no less than the duration of the stationarity interval of the decameter communication channel, maintaining radio exchange at the formed subcarrier frequencies is carried out for a time not exceeding the duration of the stationary interval of the decameter communication channel, after which the transition to the newly formed subcarrier frequencies is carried out in accordance with the values in the columns of the time-frequency matrix.

In particular, the duration of the stationary interval of a decameter communication channel ranges from five minutes to one hour.

Brief description of the drawings.

In fig. Figure 1 shows a general diagram of the implementation of a method for transmitting and receiving data in a system with several spatially separated receivers and transmitters, and using the technology of pseudo-random tuning of operating frequencies.

In fig. Figure 2 shows the operating algorithm of the Alamouti encoder.

In fig. Figure 3 shows a typical method of transmitting data over a radio channel using MIMO technology with four transmit antennas on the same frequency.

In fig. Figure 4 shows an embodiment of a method for transmitting data over spatially separated radio transmitters with four transmitting antennas at two frequencies.

The figures indicate: 1 - data source; 2 - elements of the low-frequency radio transmitting path; 3 - serial-parallel converter; 4 - Alamouti space-time encoder; 5 - transmitter; 6-transmitting antenna; 7 - receiving antenna; 8-receiver; 9-space-time decoder Alamouti; 10 - parallel-serial converter; 11 - elements of the low-frequency radio receiving path; 12 - data receiver, 13 - generator of time-frequency matrices.

A radio communication system that implements a method of transmitting data over spatially separated radio transmitters is characterized by the fact that on the transmitting side there is a data source 1, the output of which is connected to the functional elements of the low-frequency radio transmitting path 2, at least one of which is connected to a serial-parallel converter 3. In series The parallel converter 3 is configured to convert a sequence of consecutive symbols from the output of the low-frequency radio transmitting path 2 into a finite set of pairs of symbols formed at the parallel outputs of the serial-parallel converter 3. In an embodiment, each generated pair contains adjacent symbols from the original sequence . Each output of the serial-parallel converter 3 is connected to a space-time Alamouti encoder 4. Each space-time Alamouti encoder 4 has two outputs, each of which is connected to a separate transmitter 5. Each output of the transmitter 5 is connected to a transmitting antenna 6.

On the receiving side of the radio communication system there is a finite set of receiving antennas 7, each of which is connected to a receiver 8. The outputs of each pair of receivers 8 are connected to a space-time Alamouti decoder 9. A pair of receivers 8 is connected to a specific space-time Alamouti decoder 9 in such a way that ensure decoding of the corresponding pair of symbols transmitted, through a pair of transmitters 5 connected to the corresponding space-time Alamouti encoder 4, at the corresponding transmission frequency (subcarrier). The outputs of the space-time Alamouti decoders 4 are connected to the inputs of the parallel-serial converter 10. The parallel-serial converter 10 is configured to convert 9 pairs of symbols arriving in parallel from the space-time Alamouti decoders into a single sequence of consecutive symbols. The output of the parallel-to-serial converter 10 is connected to other functional elements of the low-frequency radio receiving path 11, at least one of which is connected to the data receiver 12.

Also, each of the transmitters 5 on the transmitting side is configured to adjust the transmission frequency, respectively, each of the receivers 8 on the receiving side is also configured to adjust the receiving frequency. Receivers 8 and transmitters 5 are made with the ability to change transmission and reception frequencies synchronously according to time-frequency matrices. Time-frequency matrices are formed by time-frequency matrix generators 13, which can be implemented in the form of hardware and software systems. Formators of time-frequency matrices are located on both the receiving and transmitting sides and are connected to the corresponding transmitters 5 and receivers 8.

The method of transmitting data over spatially dispersed radio transmitters is characterized by the fact that when transmitting data from data source 1, they are processed in accordance with known (from the prior art) digital algorithms for processing transmitted (via radio channels) information. This processing is carried out due to the presence of functional elements of the low-frequency radio transmitting path 2. In particular, the following functional elements can be used: data converter into binary sequences; various blocks implementing noise-resistant coding and interleaving algorithms; digital modulator (carrying out modulation of data to be transmitted and conversion of binary sequences into complex values, in accordance with a given digital modulation method) and other functional elements (depending on the specifics of the specific implementation of the low-frequency transmitting path). At the output of one of the functional elements of the low-frequency radio transmitting path 2 that sequentially process the data, a plurality of modulated complex symbols of the message transmitted via the radio channel is formed. In this case, the symbols are arranged in the form of a sequence in which they are arranged sequentially one after another in accordance with the time of their formation (z ₁,z ₂, z ₃,_...,z _i,...,z _n). Next, the generated sequence of symbols is sent to serial-parallel converter 3, where they are split into pairs (the first pair includes symbolsz ₁,z ₂; the second pair includes charactersz ₃,z ₄; … the j-th pair includes charactersz _n-1,z _n). Thus, pairs can be formed from adjacent symbols, and the set of all pairs of formed symbols includes the entire set of transmitting symbols (in the case of an odd number of the set of transmitting symbols, an additional non-information symbol is added to create the pair). The number of simultaneously generated pairs of symbols corresponds to the number of outputs of the serial-parallel converter 3, and at the same time, the number of simultaneously generated pairs of symbols is half that of the number of transmitting antennas 6.

After the process of splitting the sequence of symbols, each of the generated pairs of symbols comes from the outputs of the serial-parallel converter 3 to the inputs of the space-time Alamouti encoders 4, where their space-time encoding is carried out in accordance with the known algorithm (an example is shown for the characters z _i , z _{i+ 1} ):

where G ₁ is the designation of the output matrix;

A ₁ - symbols generated from the first output of the space-time encoder Alamouti 4;

A ₂ - symbols generated from the second output of the space-time encoder Alamouti 4;

τ ₁ ,τ ₂ - the first and second clock cycles of the Alamouti 4 space-time encoder.

At the output of each space-time Alamouti encoder 4, an output matrix is formed, consisting of two rows, each of which contains information about one of two weakly correlated signals arriving at the inputs of transmitters 5.

In the high-frequency radio transmission paths of the transmitters 5, subcarrier frequencies are formed for transmitting the generated symbols; transferring the information signal (containing transmission symbols) to a corresponding subcarrier; amplification of the signal to the required (for transmission) power through the operation of power amplifiers, etc., then high-frequency signals are supplied to transmitting antennas 6, where they are radiated into free space. Thus, the upper and lower rows of the output matrix from the generated pair of symbols are transmitted through separate transmitting antennas 6.

The high-frequency paths of the transmitters 5 are configured in such a way that pairs of transmitters 5, the inputs of which are connected to the outputs of one space-time Alamouti encoder 4, form subcarriers at a particular time at the same transmission frequency, different from other pairs of transmitters 5 (the inputs of which are connected to the outputs of other space-time Alamouti coders 4) ( f ₁ , f ₂ , f ₃ ,… f _n ,). In this case, the subcarrier frequencies generated by each pore of the transmitters 5 at a particular time are orthogonal to all other subcarrier frequencies generated by other pairs of transmitters 5, united by common space-time Alamouti encoders 4.

The formation of transmission frequencies at a specific point in time is implemented by means of a time-frequency matrix generator 13, which initially contains a redundant set of operating frequencies orthogonal to each other (suitable for radio communications), at the same time, information about the state of the channel is sent to the time-frequency matrix generator 13 communication between the receiving and transmitting sides - based on the results of ionospheric sounding with a frequency no less than the stationary time of the communication channel between subscribers. The generated time-frequency matrices are organized as follows: each column of the time-frequency matrix represents a set of orthogonal transmission frequencies that are relevant for a period of time shorter than the stationary period of the communication channel. The generator of time-frequency matrices 13 operates as follows: immediately before organizing radio exchange, based on information from the results of ionospheric sounding (or based on statistics of work with a specific radio direction), the period of stationarity of the communication channel between the receiving and transmitting sides is determined. Next, based on information from the results of ionospheric sounding, frequencies (frequency ranges) of the HFCM range are determined that are not suitable for operation during the period of stationarity of the communication channel (fading frequency correlation intervals). Next, a column of the time-frequency matrix is formed, consisting of pre-established and pseudo-randomly selected frequencies orthogonal to each other, while frequencies that are unsuitable for operation (falling into the frequency correlation interval of fading) are excluded and replaced with others. Initially, specific frequencies within the current column are selected based on algorithms based on the selection of frequencies in accordance with a pseudo-random sequence of numbers, characteristic of communication systems with pseudo-random tuning of the operating frequency. Next, information about operating frequencies for the next time interval is transmitted synchronously to transmitters 5 and receivers 6. Then, during the operating time interval, radio exchange is carried out at the generated subcarrier frequencies. At the same time, the next column of operating frequencies is formed in the frequency-time matrix generator 13 - for the next operating time interval; similar to the previous iteration - initially the column is formed from frequencies orthogonal to each other, different from the frequencies formed in the column in the previous working time interval within one row. Next, from the generated column based on the results of ionospheric sounding, the values of unsuitable frequencies are replaced by the values of suitable orthogonal frequencies. After that, the updated values of the column of the time-frequency matrix are supplied to receivers 8 and transmitters 5, after which radio exchange is carried out at frequencies according to the current column of the time-frequency matrix. Next, the operation of changing frequencies is repeated. Thus, radio exchange is organized using MIMO technology with pseudo-random tuning of operating frequencies.

Thus, during radio exchange, the generator of time-frequency matrices 13 generates transmission and reception frequencies based on a pre-established bank of orthogonal frequencies, taking into account information obtained from ionospheric sounding during the period of stationary communication channel between subscribers.

After the signals are emitted into free space, they propagate through the formed radio channels and fall on the receiving antennas 7 of the receivers 8. During the processing of radio signals, the high-frequency paths of the receivers 8 are configured in such a way that pairs of receivers 8, the outputs of which are connected to the inputs of one space-time Alamouti decoder 9 , at a particular moment in time, only signals are received on the corresponding subcarriers ( f ₁ , f ₂ , f ₃ , ... f _n ,), corresponding to the generated subcarriers on the transmitting side. The time-frequency matrix generator 13 ensures that the reception and transmission frequencies coincide in time on the transmitting and receiving sides.

Thus, for the described method there is always a pair of transmitters 5 on the transmitting side (united by a common space-time Alamouti encoder 4), operating at the subcarrier frequencyf _i and a pair of receivers 8, on the receiving side, receiving at the same subcarrier frequencyf _i. That is, if a pair of characters is transmittedz ₁,z ₂ on a subcarrierf ₁. through two transmitters 5, then on the receiving side there are receivers 8 configured to receive symbolsz ₁,z ₂ on a subcarrierf ₁. After high-frequency processing of radio signals in receivers 8, low-frequency signals are sent to space-time Alamouti decoders 9, where the process of restoring the original symbols is implementedz _i,z _i+1. After which the pairs of 10 reconstructed symbols simultaneously arriving at the inputs of the parallel-serial converter are converted into a single sequence, where the symbols follow one after another in a sequence corresponding to the time of their formation (z ₁,z ₂, z ₃, ...,z _i,...,z _n). Character sequencez ₁,z ₂, z ₃, ...,z _i,...,z _nis transmitted to the functional elements of the low-frequency radio receiving path 11, where it is processed (digital demodulation (detection), extracting the information part from message packets, noise-resistant decoding, etc.) after which the information signal is converted into data in the form required by the recipient, which is received to the data recipient 12.

When organizing radio traffic by implementing the claimed method, transmitting antennas 6 operating on the same subcarrier f _i (and transmitting different rows of the output matrix from the generated pair of symbols) are located from each other at a distance not less than the value of the spatial fading correlation interval, which for decameter range is from 10 m to 200 m [1] .

The declared technical result - enabling the functioning of a MIMO communication channel using pseudo-random tuning of operating frequencies to ensure noise immunity - is achieved through the operation of serial-parallel 2 and parallel-serial 10 converters, which form pairs of simultaneously transmitted symbols and restore the information sequence of data from pairs of received symbols . In this case, during transmission, each pair of symbols is encoded using the Alamouti code and transmitted to the inputs of the corresponding pair of transmitters 5. Formator of frequency-time matrices 13 based on a preloaded set of frequencies orthogonal to each other and information about unusable frequencies (falling into the frequency correlation interval of fading) to conduct radio exchange while the communication channel is stationary, it forms the next column of the time-frequency matrix with reception and transmission frequencies and transmits information to pairs of transmitters 5 and receivers 8, the inputs (outputs) of which are connected to the outputs of a certain space-time Alamouti encoder 4 (Alamouti decoder 9) over a time interval not exceeding the stationary time of the communication channel. After a working time interval less than or equal to the stationary time of the communication channel, the time-frequency matrix generator 13 generates a new column of the time-frequency matrix with new values of operating frequencies. Next, this process is repeated for the duration of the radio exchange, thereby providing radio exchange with pseudo-random tuning of operating frequencies and using MIMO technology. The condition of orthogonality of the frequencies of the subcarriers of all pairs of transmitters 5 (all elements of the column of the time-frequency matrix consisted of orthogonal frequencies) ensures the preservation of a given level of noise immunity, due to the absence of frequency correlation in the operating time interval. The condition that the frequencies of the subcarriers of all pairs of transmitters 5 do not fall within the range of prohibited frequencies also ensures that the specified level of noise immunity is maintained, due to the fact that radio exchange is not carried out at frequencies at which the frequency response of the channel has extremely low values. The requirement that for a specific pair of transmitters 5 a new transmission frequency be formed after each working period of time ensures noise immunity of data transmission by changing the transmission frequency after each working time interval.

The frequency of receipt of information to the generator of time-frequency matrices 13 about the result of ionospheric sounding is selected based on the stationary time of the decameter communication channel. In accordance with studies [2-5], the stationary interval of the decameter channel ranges from five minutes to one hour.

An example of achieving a technical result.

As is known, the main goal of introducing MIMO technology is to increase spectral efficiency in conditions of increased demand for frequency resources.

The essence of MIMO technology is the use of multiple transmitting antennas and several receiving antennas to organize a radio channel on one carrier frequency in inhomogeneous environments of radio wave propagation, causing signal fading at the receiving point.

The implementation of reception in such conditions is based on ensuring diversity in one or several simultaneous parameters - space, polarization or time.

A positive effect in MIMO channels can be:

- increasing the channel capacity relative to channels with one receiving and one transmitting antennas;

- increasing noise immunity in fading channels;

- spatial multiplexing of different subscribers;

- ensuring spatial selectivity due to the formation of a radiation pattern.

MIMO technology has been actively developed in high-frequency communication systems, such as WiFi, LTE, etc. One of the problematic issues of using MIMO in decameter range channels is the difficulty in building antenna systems that ensure uncorrelated fading on different antennas due to the need for a large separation (more than 100 meters ), determined by the wavelength. This problem is especially acute in the case of organizing a channel between moving objects. Along with the above problem, the issue of increasing the capacity of a MIMO communication channel in the decameter range also causes great difficulties due to the large redundancy in coding the symbols arriving at the input of the MIMO encoder when the number of receiving and transmitting antennas is more than two.

The claimed method uses a space-time encoder 4 and an Alamouti decoder 9, while the Alamouti code is the simplest space-time code that implements the encoding process in accordance with FIG. 2. This code is designed to work on two transmitting antennas 6, using which two complex information symbols are transmitted in two clock intervals. Thus, this code has a speed, which is understood as the ratio of the number of transmitted symbols to the number of clock intervals:

.

It has been proven that the Alamouti code is unique according to the so-called rank criterion, i.e. it has maximum diversity order and has speed . Codes for a larger number of antennas, providing maximum diversity order, have a speed , except for a few codes for the number of transmitting antennas 6 And , which have code speed . Thus, increasing noise immunity is achieved by reducing throughput. For example, the code for the number of transmitting antennas is 6 and four transmitted symbols has the following form (Fig. 3):

In accordance with the stated method, it is proposed, subject to the availability of free frequencies organize the transfer as follows: Before the space-time code, a serial-parallel converter 3 is added, which splits the serial stream of information symbols according to the following scheme (an example for replacing the space-time code for and 4 transmitted characters):

The four antennas are divided in pairs. Each pair of antennas has its own space-time encoder that implements the Alamouti code (Fig. 4). Then for the first pair of antennas operating at the frequency , the following matrix is supplied:

and to the second pair of antennas operating at the frequency , the matrix is supplied:

Under the condition of orthogonality of frequencies And , the first and second matrices will be transmitted without mutual influence.

In this case, a reduction in the number of clock intervals for transmitting 4 symbols from 8 is implemented (for the code , fig. 3) to 2 (Fig. 4), provided that the maximum transmission spacing is maintained (2 by antennas and 2 by frequency), which is equivalent to increasing the capacity of the general multi-frequency MIMO radio channel by 4 times.

At the same time, to ensure noise immunity, within the framework of the claimed method, it is proposed to use pseudo-random tuning of operating frequencies. At the initial moment of time before radio exchange based on a pseudo-random algorithm, orthogonal frequencies of 10375 Hz and 13645 Hz were selected by the shaper of the time-frequency matrix 13 on the receiving side. However, based on the information received from the results of ionospheric sounding, the frequencies fall into the frequency correlation interval of fading. In this connection, the frequency of 13645 Hz was classified as prohibited by the hardware and software complex and was replaced by a frequency of 13450 Hz (which is also orthogonal to the frequency of 10375 Hz). After the column of the time-frequency matrix was generated, the frequency information was transmitted via a separate (service) communication channel to the time-frequency matrix generator 13 on the transmitting side to synchronize the reception and transmission frequencies. Next, radio exchange during a working time interval of 10 seconds was carried out at the indicated frequencies. After which the generator of frequency-time matrices 13 produced new frequencies of 11325 Hz and 14625 Hz, orthogonal to each other and not forbidden. As a result, after 30 frequency changes (5 minutes - the time of stationarity of the communication channel), updated data on ionospheric sounding arrived, and for the next period of stationarity the frequency correlation interval changed. The next 30 columns of the time-frequency matrix were formed taking this into account. An example of the generated time-frequency matrix is presented in Table 1.

Table 1 Working time intervals
(each interval according to the example is 10 seconds) 1 2 3 4 5 ... thirty 31 f ₁ 10375 11325 11750 12340 15600 ... 17540 13550 f ₂ 13450 14625 14825 13450 10375 ... 9580 14450

Thus, the declared technical result is achieved: increasing noise immunity due to pseudo-random tuning of operating frequencies; maintaining a high level of noise immunity is also achieved due to the receipt of information on the results of ionospheric sounding at least once during the period of stationarity of the HFCM communication channel and the use of orthogonal and non-forbidden frequencies in the time-frequency matrix.

An example of technical implementation of the claimed method

Data source 1 transmits information over a distance of R = 2000 km from northern latitudes to the middle zone from the area where radio receivers are located to the area where radio transmitters are located. The communication system is organized in accordance with four transmitting 6 and four receiving 7 antennas. In the area where radio transmitters are located and the area where radio receivers are located, antennas operating at different frequencies f ₁ , f ₂ are spaced 150 m apart from each other. Antennas operating at the same frequencies are spaced 5 m apart from each other. To implement functional elements Low-frequency radio transmitting 2 and radio receiving 11 paths use modernized modem equipment developed by ANO "IIF", implemented on the basis of domestically produced digital signal processors with a transmission speed of 3.6 kbit/s and an original communication protocol with increasing redundancy of noise-resistant coding and with adaptation to transmission speed data during a communication session. Separate hardware-software computing devices integrated into the low-frequency radio transmitting and radio receiving paths. As transmitters 5, standard PKM-5 radio transmitters with integrated power amplifiers and frequency synthesizers are used; standard radio receivers R-160P (R-170) are used as receivers 8; Inclined dipole antennas D2x40 are used as transmitting 6 and receiving 7 antennas. Integration of low-frequency and high-frequency paths is realized through software and hardware devices with analog-to-digital and digital-to-analog converters.

List of sources used

1. Pashintsev V.P., Koval S.A., Tsimbal V.A., Toiskin V.E., Senokosov M.A., Skorik A.D. Structural multipath approach to the development of a spatiotemporal model of a single-mode decameter communication channel with diffuse multipath. Journal of Radioelectronics [electronic journal]. 2022. No. 6. https://doi.org/10.30898/1684-1719.2022.6.3

2. Alpert Ya.L. Radio wave propagation and the ionosphere. M.: Publishing House of the USSR Academy of Sciences, 1960.

3. Alimov V.A. On the stationarity of the process of scattering short radio waves in the ionosphere // News of universities. Radiophysics. 1974. T. 17. No. 19.

4. ICKR. Documents of the XI Plenary Assembly. Oslo, 1966. T. 2 M.: Communication, 1969.

5. Chernov Yu.A. Special issues of radio wave propagation in communication and broadcasting networks. M.: Tekhnosphere, 2018. - 688 p. ISBN 978-5-94836-503-9.

Claims (2)

1. A method of radio communication with MIMO technology and pseudo-random tuning of operating frequencies, characterized by the fact that on the transmitting side pairs of complex symbols transmitted in parallel are formed, each generated pair of symbols is encoded with the space-time Alamouti code, forming an output matrix, elements of the upper and lower rows of the output matrix from the formed pair of symbols is transmitted through spatially separated antennas, the elements of the output matrices of the formed pairs of parallel transmitted modulated symbols are transmitted via different subcarriers, the frequencies of the subcarriers are formed in a pseudo-random manner based on data from the columns of the time-frequency matrix, in which the frequencies of the subcarriers of the formed pairs of parallel transmitted modulated symbols are orthogonal each other and do not fall into the fading frequency correlation interval, while information about the fading correlation frequency interval is supplied to the time-frequency matrix generator based on the results of ionospheric sounding with a frequency no less than the duration of the stationarity interval of the decameter communication channel, radio exchange is carried out at the generated subcarrier frequencies for a time not exceeding the duration of the stationary interval of the decameter communication channel, after which the transition to the newly formed subcarrier frequencies is carried out in accordance with the values in the columns of the time-frequency matrix. 2. The method according to claim 1, characterized in that the duration of the stationary interval of the decameter communication channel is from five minutes to one hour.