RU2713507C1 - Method for increasing interference immunity and carrying capacity of an adaptive sw radio communication system - Google Patents

Abstract

FIELD: radio engineering and communication.

SUBSTANCE: invention relates to radio communication and can be used in construction of adaptive systems and complexes of SW radio communication. Method is based on step-by-step adaptation of a radio channel of a slave and a master station, performing route probing, interference environment testing, finding values of optimized parameters of a radio communication system, transmitting values of selected parameters to a master station, adjusting the receiving and transmitting paths to new optimized parameters, establishing and maintaining communication, wherein a second receiving channel is additionally introduced, consisting of identical to the first receiving channel of the receiving antenna, an antenna-feeder device and a high-frequency amplifier, as well as two-channel synchronous analogue-to-digital converter, which is connected in parallel to both receiving channels, in which amplified radio signals digitization is performed.

EFFECT: technical result consists in improvement of interference immunity and capacity of adaptive communication system with OFDM-signals under conditions of influence of narrow-band station and natural interference.

3 cl, 6 dwg

Description

The invention relates to the field of radio communications and can be used to increase the noise immunity and throughput of adaptive systems and HF radio systems using OFDM (Orthogonal frequency-division multiplexing) technology under the influence of narrow-band station and natural interference.

A known method and system of adaptive HF radio communication that provides protection against narrow-band interference described in (US Patent US9,008,594B2, IPC H04B 7/02, H04B L / 707, H04B 1/69, H04L 25/03, H04L 5/06, H04L 5/00 (2006.01). Method and adaptive radio communication system in the HF band, published on 04/14/2015), in which the influence of these interference is reduced by eliminating channels in which interference is present. The disadvantages of this method and system can indicate the complexity of the practical implementation, the impossibility of creating a separate device connected to the input of the receiving device, as well as the need to use filters with high selectivity (selection).

A known method of adaptation of HF radio communication using OFDM technologies (Patent 2639657 of the Russian Federation, IPC H04 5/00, H04L 27/26 (2006.01). Method of adaptation of HF radio system with OFDM signals; publ. 12/21/2017, bull. No. 36). In order to increase the throughput of an adaptive communication system with OFDM signals, the method additionally introduces a parameter — the frequency diversity value of neighboring OFDM signal subcarriers. Assessment of the state of the communication channel is carried out by the values of frequency and time scattering, as well as by the signal-to-noise ratio, which are measured in the process of receiving signals of path sounding. The values of the grouped pairs of optimized parameters of the communication system are determined by pre-prepared correspondence tables.

The disadvantages of this method include:

- low efficiency of establishing communication due to the complexity of the adaptation process associated with the calculation of conformity tables;

- lack of monitoring of the state of the communication channel in the process of communication;

- the lack of the ability to compensate for the effect of narrow-band station interference;

- the inability to transmit broadband signals, providing the ability to increase the bandwidth of the radio channel;

- lack of ability to maintain a constant average speed of information transfer.

A known method of adaptation of the HF radio communication system, implemented in the adaptive system "Redan-Pierce" (a set of technical means for adaptive data and speech transmission on HF radio channels of the modification "Redan-Pierce", https://www.rimr.ru/catalog/rzhd/avtomatizirovannyy -adaptivnyy-komp-leks-tekhnicheskikh-sredstv-redan-pirs /) based on the use of OFDM technologies. This method is the closest in technical essence to the claimed invention and is selected as a prototype. In this method, a multi-parameter adaptation is applied to the propagation conditions of the radio waves and the interference environment by purposefully changing the operating frequencies, the information transfer rate (within 300-9600 bit / s) and the code rate (from 0.4 to 0.8).

Due to active route sounding at all stages of communication, the parameters of the radio channel are evaluated (multipath analysis, estimation of the signal-noise situation and calculation of the number of errors detected by the code), as a result of which the optimal operating frequency is selected and a preliminary frequency schedule is compiled.

The disadvantages of this method include:

- the lack of the ability to compensate for the effect of narrow-band station interference;

- the lack of the ability to transmit broadband signals, providing increased throughput of the radio channel;

- lack of ability to maintain a constant average speed of information transfer.

To address these shortcomings, the claimed invention is directed “A method for increasing the noise immunity and bandwidth of an adaptive HF radio communication system”, the technical task of which is to increase the noise immunity and bandwidth of an adaptive communication system with OFDM signals, in the conditions of narrow-band station and natural interference.

The implementation of the task allows to achieve the following total technical result:

- the ability to provide a given noise immunity in the HF radio channel at low signal-to-noise ratios in the conditions of narrow-band station and natural interference;

- the ability to transmit broadband signals (more than 40 kHz) to provide an increased information transfer rate;

- the ability to maintain a constant average speed of information transfer.

To achieve the indicated technical result, a “Method for increasing the noise immunity and throughput of an adaptive HF radio communication system” is proposed, using OFDM technology based on phased adaptation of the radio channel of the slave and master stations, performing routing sounding procedures, testing the interference environment, finding values of optimized parameters of the radio communication system, transmission values of the selected parameters to the master station, tuning the receiving and transmitting paths to new optimized ny parameters, establishing and maintaining communication.

The fundamental difference between the claimed invention and the prototype is that an additional receiving channel is additionally introduced into the receiving path, consisting of a receiving antenna (antenna-feeder device) identical to the first receiving channel and a high-frequency amplifier, and also a two-channel synchronous input connected to both receiving channels is additionally introduced An analog-to-digital converter, in which the amplified radio signals are digitized synchronously. Next, spatial-correlation processing of the signals is performed in the signal processing unit of the computing device, where the cross-correlation of the signals represented by the parallel code is carried out, carrying information about individual symbols with a sample size equal to the length of the Barker code. Next, an information sequence represented by a parallel code is generated by comparing the calculated cross-correlation values with a threshold number. Moreover, in the signal generation block of the computing device, each bit of information coming from the terminal is encoded with a Barker noise-like binary code sequence having an autocorrelation function close to a delta function that increases the noise immunity of the radio channel. Next, perform the procedure of intersymbol interleaving. In addition, testing with test signals No. 1-3 is carried out to assess the state of the radio channel. Further, according to the results of testing in the adaptive radio channel control unit of the computing device to maintain a given radio channel capacity, the frequency-code structure of the OFDM signal is adapted by frequency distribution of the OFDM signal subcarriers.

Introduction to the receiving path of the second receiving channel and a two-channel synchronous analog-to-digital converter allow spatial-correlation processing of signals in a computing device, providing increased noise immunity of the radio channel.

To perform spatial correlation processing of the signals in the claimed method, the distance between the receiving antennas should be at least half the wavelength (λ / 2) from each other.

To adapt the frequency-code design of the OFDM signal, OFDM signal subcarriers are excluded, where a large number of test errors occur and where the interference level exceeds the average noise level in the entire test signal band by more than 30%, with the affected subcarriers being transferred to the edges of the original OFDM -signal within the extended band of the test signal.

The proposed method is implemented in a device containing a pairing unit 1, connected in series with the information output of the terminal, the output of which is connected in series with the information input of the signal conditioning unit 2.1 of computing device 2.

The signal output of the signal conditioning unit 2.1 of the computing device 2 is connected in series with a broadband power amplifier 3.1 of the transmission path 3, the output of which is connected in series with the antenna of the transmission path 3.

Both antennas of the receiving path 4 are connected in series with the corresponding signal inputs of high-frequency amplifiers 4.1.1 and 4.2.1 of the receiving channels 4.1 and 4.2 of the receiving path 4, the signal outputs of which are connected in series with the signal inputs of a two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4. Signal the outputs of the two-channel synchronous analog-to-digital converter 4.3 are connected in series with two inputs of the signal processing unit 2.3 of the computing device 2, and the information output the signal processing unit 2.3 of the computing device 2 is connected in series with the interface unit 1. Next, the output of the interface unit 1 is connected in series with the information input of the terminal.

Additionally, the signal processing unit 2.3 of the computing device 2 is connected in series through the control input and output to the adaptive control unit of the radio channel 2.2 of the computing device 2. Also, the adaptive control unit of the radio channel 2.2 of the computing device 2 is connected in series through the control output to the signal generation unit 2.1 of the computing device 2.

The fundamental difference between the claimed invention and the prototype is that the device uses two identical receive channels connected to a two-channel synchronous analog-to-digital converter, which allows performing spatial-correlation signal processing.

Such a constructive solution of the invention due to the distinguishing features gave new technical effects:

1. Improving noise immunity in the HF radio channel under conditions of natural interference and fading occurring in the ionospheric radio channel due to the interleaving of the symbols of the information signal, expanding the signal base and the use of spatial correlation signal processing. The alternation of the symbols of the information signal scatters the grouping errors that occur in the ionospheric HF radio channel, which allows the use of correction codes with minimal redundancy, thereby ensuring maximum channel and information speed in the radio channel. The expansion of the signal base and spatial-correlation signal processing can further increase the noise immunity of the radio channel, providing the ability to receive a signal with a given noise immunity at a signal to noise ratio.

2. Improving noise immunity in the HF radio channel under the influence of narrow-band station interference by using the spatial correlation method of signal processing and ensuring the uniformity of the interference field spectrum of the station interference within the receive path band by adapting the parameters of the radio channel to the interference situation in the HF band based on the exclusion of subcarriers frequencies "struck" by narrow-band interference. The “affected” subcarrier frequencies are excluded when the level of narrow-band interference exceeds the average level of the remaining narrow-band interference by more than 30% and where the largest number of errors is observed when testing the interference environment.

3. Maintaining the average information transmission rate due to the constant number of subcarriers in the OFDM signal by transferring the frequency subcarriers "affected" by narrow-band interference to the edges of the "unaffected" sections of the extended spectrum of the OFDM signal within the entire receiving path band.

The claimed method is illustrated by drawings, which depict:

FIG. 1. Functional diagram of a device for transmitting and receiving an OFDM signal in a HF radio channel.

FIG. 2. Typical dependence of the cross-correlation coefficient of station interference on the passband of the receive path.

FIG. 3. The spectrum of a typical OFDM signal.

FIG. 4. Spectra of sequentially transmitted signals used to test signal levels and interference (test signal No. 2).

FIG. 5. The principle of forming the optimal frequency-code design of the OFDM signal:

a) an explanation of the analysis of the interference environment in the tested frequency band;

b) an explanation of the transfer of the affected frequency sections of the OFDM signal.

FIG. 6. An explanation of the formation of a test signal for evaluating the temporal scattering in the radio channel (test signal No. 3).

For the implementation of the claimed method requires the presence of two identical in composition of stations A and B.

In FIG. 1 shows a functional diagram of a device for transmitting and receiving HF radio signals.

The diagram shows:

Station A consisting of:

1. The interface unit.

2. Computing device.

2.1. Signal conditioning unit.

2.2. Adaptive radio channel control unit.

2.3. Signal processing unit.

3. The transmission path.

3.1. Broadband power amplifier.

Antenna (antenna feeder device).

4. The receiving path.

4.1. The first receiving channel.

4.1.1. High frequency amplifier.

Antenna.

4.2. The second receiving channel.

4.2.1. High frequency amplifier.

Antenna.

4.3. Two-channel synchronous analog-to-digital converter.

Station B.

All structural elements in the interface unit 1, in the computing device 2, in the signal conditioning unit 2.1, in the adaptive control unit of the radio channel 2.2, in the signal processing unit 2.3, in the broadband power amplifier 3.1 of the transmitting path 3, in the high-frequency amplifiers 4.1.1 of the first receiving channel 4.1 and 4.2.1 of the second receiving channel 4.2, in a two-channel synchronous analog-to-digital Converter 4.3 of the receiving path 4 are connected by electrical connections.

In FIG. 2. A typical dependence of the cross-correlation coefficient of the interference field of narrow-band station interference (ρ _na ) on the passband of the receive path (Δƒ) obtained as a result of experimental studies is presented. The experimental results showed the possibility of reducing the mutual correlation of station interference falling into the band of the processed signals, with the expansion of the passband of the receiving path. This allows you to compensate for the effect of narrow-band station interference when using spatial-correlation signal processing, providing the ability to transmit information in a wide frequency band against interference with a given noise immunity.

In FIG. 3. presents a spectrum of a typical OFDM signal using a Barker code to expand the signal base.

In FIG. 4. Spectra of sequentially transmitted signals used for testing signal levels and interference are presented (test signal No. 2).

In FIG. 5: the principle of generating the optimal frequency-code design of the OFDM signal is presented, with an explanation of the analysis of the interference situation in the tested frequency band and the method of transferring the affected frequency sections of the OFDM signal.

In FIG. 6. shows the principle of formation of test signal No. 3, used to estimate the temporal scattering in the radio channel.

The implementation of the method

To implement the claimed method, the outgoing information signal from the terminal enters the interface unit 1, in which it is converted into the format of the computing device 2.

Next, in the signal conditioning unit 2.1 of the computing device 2, the following operations are sequentially performed:

- coding of each bit of information with a noise-like binary Barker code sequence;

- excessive coding corrective code;

- intersymbol scrambling (interleaving) of information code combinations;

- the formation of the OFDM signal with the established frequency spacing of the subcarriers and the frequency-code design (Fig. 3).

The generated OFDM signal is fed to a broadband power amplifier 3.1 of the transmission path 3, after amplification in which it is fed to an antenna-feeder device that emits electromagnetic waves in the direction of the receiving station (Fig. 1).

The received radio signal arrives at two identical antennas, spatially spaced at least half the wavelength (d> λ / 2) from each other, positioned orthogonally to the transmitting station. The radio signal from the antenna outputs is fed to two identical high-frequency amplifiers 4.1.1 and 4.2.1 of the receiving channels 4.1 and 4.2 of the receiving path 4, after amplification in which the radio signal is fed to the inputs of the two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4. The two-channel synchronous analog- the digital Converter 4.3 of the receiving path 4 digitizes the amplified radio signals that are fed to the two inputs of the signal processing unit 2.3 of the computing device 2, in which when receiving information signals after ovatelno operations are performed:

- demodulation of the OFDM signal;

- calculation of cross-correlation of demodulated signals on the interval of the Barker code;

- the formation of an information sequence by comparing the calculated sum of the cross-correlation values with a threshold value;

- descrambling of the received information sequences in the reverse order of intersymbol interleaving;

- decoding received redundant code combinations with the correction of detected errors.

The received information signal is fed to the interface unit 1, in which the information signal is converted to the terminal operation format.

When testing the temporal dispersion of the signal in the radio channel in the signal processing unit 2.3 of the computing device 2, the amplitude-modulated test signal No. 3 is demodulated.

To establish the optimal parameters of the radio channel at the stages of establishing and maintaining communication, the adaptive control unit of radio channel 2.2 of computing device 2 is used, which performs the functions of:

- route sounding of the radio channel;

- testing of jamming conditions.

A phased adaptation of the channel parameters of the slave and master stations is carried out in the radio channel.

When parameters are adapted by the slave station, all stages of testing are performed: route sounding of the radio channel and testing of the jamming environment.

For testing, test signals No. 1, No. 2 and No. 3 are used.

. Использование узкополосного тестового сигнала обосновано снижением влияния на работу других станций в процессе трассового зондирования. Тестовый сигнал №1 формируется путем подачи кодовой комбинации «11111…1» с блока адаптивного управления радиоканалом 2.2 на блок формирования сигнала 2.1 вычислительного устройства 2, в котором выполняется его OFDM-модуляция.Test signal No. 1 represents narrowband OFDM signal containing all subcarriers $$\Delta f_{\text{test1}}=0.25\Delta f_{\text{OFDM}}$$

. The use of a narrow-band test signal is justified by a decrease in the effect on the operation of other stations in the process of path sounding. Test signal No. 1 is generated by applying the code combination “11111 ... 1” from the adaptive control unit of radio channel 2.2 to the signal conditioning unit 2.1 of computing device 2, in which its OFDM modulation is performed.

(фиг. 4).Test signal No. 2 is alternating subcarriers and free frequency bands. They are formed on the basis of two inverse code combinations "01010101 ... 1" and "1010101 ... 10" with a length exceeding 1.25 times the number of subcarriers of the OFDM signal (Fig. 4). These code combinations enter the signal generation block 2.1 of computing device 2, on the basis of which sequentially transmitted test signals are synthesized, as a result of which test signal No. 2 is generated, the spectrum of which is two offset sequences of subcarriers and free frequency bands in the common band of the tested signal $$\Delta f_{\text{test}}$$

 (Fig. 4).

.Test signal No. 3 is a sequence of amplitude-modulated pulses with a high duty cycle (Fig. 6), the duration of which is determined by the spectral width of the test signal

.

Track sounding performs the following operations of adaptation of the radio channel:

- selection of a sub-band of operating frequencies according to the conditions of passage of HF radio waves: maximum and lowest applicable frequencies (MFC - NFC);

- determination of the optimal operating frequency and frequency dispersion in the selected sub-range of operating frequencies;

- selection of the optimal frequency spacing of the subcarriers of the OFDM signal according to the results of the estimation of the temporal scattering of the test signal.

In order to reduce the influence of the radio channel on the work of other stations during route sounding the determination of the operating frequency sub-range is carried out after preliminary calculation of the long-term frequency prediction according to the coordinates of the stations using known programs (for example, VOACAP (http://www.voacap.com/). According to the results of the long-term forecast (MFR - LFN), the test signal No. 1 is sequentially emitted in an extended operating frequency range, starting from the highest frequency equal to 1.3 MFP to the LFN, which corresponds to the minimum signal-to-noise ratio. To do this, in the adaptive control unit of the radio channel 2.2 of the computing device 2, test signal No. 1 is used, which is transmitted to the signal generation block 2.1 of the computing device 2. In this block, OFDM modulation of the test signal No. 1 is carried out at sequentially changing operating frequencies. These generated test signals are sequentially transmitted to the broadband power amplifier 3.1 of the transmission path 3, after amplification in which these signals are fed to the antenna-feeder device, from which the radio signal is emitted in the direction of the slave station.

In the receiving path of the slave station, a probing test signal No. 1 is received in one of the channels of the receiving path. After amplification and digitization of the test signal in the high-frequency amplifier 4.1.1 of the first receiving channel 4.1 of the receiving path 4 and in the connected two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4, the received probe signal is fed to one input of the signal processing unit 2.3 of the computing device 2, where the measurement of signal levels at all subcarrier frequencies of a narrowband OFDM signal. The results of measurements of signal levels in all sub-bands are received in the adaptive control unit of radio channel 2.2 of computing device 2, which determines the current operating frequency range (MFC - NPC). MUF is determined by the presence of a signal at the highest frequency (Cherenkova E.L., Chernyshev O.V. Propagation of radio waves. - M: Radio and communications, 1984, 272 p.), And MUF is determined by the minimum signal level corresponding to the known sensitivity of the receiver . Information about the selected range of operating frequencies is transmitted to the master station via a feedback channel at the corresponding sensing frequencies of the HF subbands. This information is stored in the memory of the adaptive control blocks of the radio channel 2.2 of the computing device 2 of each station.

Determination of the optimal operating frequency and frequency scattering of the signal is carried out by sequentially sensing the selected sub-range of operating frequencies in the range from MFP to LF. To do this, in the adaptive control unit of the radio channel 2.2 of the computing device 2, a test signal No. 2 is generated, which is transmitted to the signal conditioning unit 2.1 of the computing device 2. In the signal conditioning unit 2.1 of the computing device 2, OFDM modulation of the test signal No. 2 is performed at successively changing operating frequencies with step of the frequency grid equal to the width of the spectrum of the test signal No. 2 (Fig. 4).

Modulated test signals at different operating frequencies are fed to a broadband power amplifier 3.1 of the transmission path 3, after amplification in which these signals are fed to an antenna-feeder device, from which the radio signal is emitted in the direction of the slave station.

In the receiving path of the slave station, a probing test signal No. 2 is received in one of the channels of the receiving path. After amplification and digitization of the test signal in the high-frequency amplifier 4.1.1 of the first receiving channel 4.1 of the receiving path 4 and in the connected two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4, the received probe signal is fed to one input of the signal processing unit 2.3 of the computing device 2, where demodulation of the OFDM test signal is performed. Next, the demodulated signal enters the adaptive control unit of channel 2.2 of computing device 2, where its frequency scattering is evaluated and the received code sequence is compared with the known test signal No. 2, which determines the number of errors in the received code sequence. The results of the frequency scattering estimation and the number of errors at all operating frequencies of the tested frequency sub-range are stored in the memory of the adaptive control unit of the radio channel 2.2 of computing device 2. Next, to minimize the frequency scattering and the number of errors, the best operating frequencies are selected that provide the highest bandwidth and noise immunity of the radio channel. According to this criterion, a rating distribution of operating frequencies is made. In this case, the operating frequency is optimal, with the least number of errors and the minimum frequency scattering.

After the rating distribution, the best operating frequency is selected as the primary, and the remaining ones as backup frequencies. The reserve frequencies are used in accordance with the long-term forecast of frequencies and in cases of changing interference in the rating order. Information about the primary and backup optimal operating frequencies is transmitted to the master station via a feedback channel at all sensing frequencies within the selected frequency sub-band. This information is stored in the memory of the adaptive control unit of the radio channel 2.2 of the computing device 2.

The optimal frequency spacing of the subcarriers of the OFDM signal is selected by probing with test signal No. 3 at the optimal operating frequency. For this, in the adaptive control unit of the radio channel 2.2 of the computing device 2, a sequence of single pulses with a high duty cycle is generated, which is transmitted to the signal conditioning unit 2.1 of the computing device 2. In the signal conditioning unit 2.1 of the computing device 2, the amplitude modulation of test signal No. 3 is performed, which after amplification in broadband power amplifier 3.1 of the transmission path 3 is fed to the antenna-feeder device, from which the radiation of the radio signal in the direction slave station.

In the receiving path of the slave station, a sounding signal is received in one of the channels of the receiving path. After amplification and digitization of the test signal in the high-frequency amplifier 4.1.1 of the first receiving channel 4.1 of the receiving path 4 and in the connected two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4, the received probe signal is fed to one input of the signal processing unit 2.3 of the computing device 2, where demodulation of amplitude-modulated test signal No. 3 is performed. Next, the demodulated signal enters the adaptive control unit of channel 2.2 of computing device 2, where the time scattering is estimated, which determines the maximum spectral width of the subcarrier frequency.

Next, the optimal frequency spacing of the OFDM signal subcarriers is determined from the results of the frequency and time scattering estimation.

Information about the optimal frequency separation of the OFDM signal is transmitted to the slave station through a feedback channel at the optimal operating frequency. This information is stored in the memory of the adaptive control blocks of the radio channel 2.2 of the computing device 2 of each station.

As a result of performing path sounding in the radio channel in the direction from the master to the slave station, the optimal operating frequency and the subcarrier spacing of the OFDM signal are established.

Interference Testing It is carried out after trace sounding and during the transmission of information to form the optimal frequency-code design of the OFDM signal. To do this, at the selected optimal operating frequency in the adaptive control unit of the radio channel 2.2 and the signal generation unit 2.1 of the computing device 2, a test signal No. 2 is generated.

The generated test signal enters the broadband power amplifier 3.1 of the transmission path 3, after amplification in which it is fed to the antenna-feeder device, followed by radiation into the air.

In the receiving path 4 of the slave station during testing, one of the channels of the receiving gain path is used. After amplification and digitization of the test signal in the high-frequency amplifier 4.1.1 of the first receiving channel 4.1 of the receiving path 4 and in the connected two-channel synchronous analog-to-digital converter 4.3 of the receiving path 4, the received probe signal is fed to one input of the signal processing unit 2.3 of the computing device 2, where demodulation and measurement of interference levels are performed at all subcarrier frequencies of the test signal. The demodulated test signal and the results of measurements of noise levels are received in the adaptive control unit of radio channel 2.2 of computing device 2.

(фиг. 5 а).In the adaptive control unit 2.2 of the computing device 2, the received signal is compared with a known test signal, based on which errors are determined at the corresponding subcarrier frequencies of the test signal. This block also evaluates the average level of interference on all subcarriers of the test signal and the allocation of subcarriers of frequencies whose level exceeds the average level of interference in the entire passband of the receive path $$U_i{}_{\text{raised}}\text{> 1}\text{, 3}{\overline{\text{U}}}_{\text{test}}$$

(Fig. 5 a).

более чем на 30 %.Based on the test results, the optimal frequency-code design of the OFDM signal is formed by eliminating subcarriers on which a greater number of testing errors occur and in the carrier frequency bands, where the interference level exceeds the average level of these interference in the entire test signal band $$\Delta f_{\text{test}}$$

more than 30%.

To maintain the average information transfer rate, the “affected” subcarriers are uniformly transferred to the edges of the original OFDM signal, within the extended band of the test signal (Fig. 5 b). Information about the optimal frequency-code design is transmitted at the optimal operating frequency via the feedback channel in the direction of the slave station. As a result, information about the frequency-code design is stored in the adaptive control units of radio channel 2.2 of the computing device 2 of both stations. After that, at both stations, the adaptive control units of the radio channel 2.2 of computing device 2. sets the corresponding frequency-code signal design, before the next test.

After adapting the parameters of the slave and master stations, information is exchanged, during which periodic testing is performed in order to maintain the required noise immunity of the radio channel. To do this, use the procedure for testing the interference environment, according to which the adaptation of the frequency-code structure of the OFDM signal is performed. In cases where it is impossible to form a full frequency-code structure of the OFDM signal at the current operating frequency, when the interference environment or the conditions of propagation of radio waves are changed, in order to maintain the average information transfer rate, a transition to the reserve operating frequencies is performed, at which the optimal frequency-code structure of the OFDM signal is determined . If it is impossible to form a complete code structure at all reserve frequencies, the radio channel switches to the sequential mode of performing routing sounding and testing the jamming environment.

Thus, the claimed "Method for improving the noise immunity and bandwidth of an adaptive HF radio communication system" is a new way to increase the noise immunity and bandwidth of an adaptive communication system with OFDM signals, in the conditions of narrow-band station and natural interference.

The claimed method is industrially applicable, since its implementation uses widespread components and products of the radio industry and computer technology.

Claims (3)

1. A method of increasing the noise immunity and throughput of an adaptive HF radio communication system using OFDM technology, based on the phased adaptation of the radio channel of the slave and master stations, performing routing sounding procedures, testing interference conditions, finding the values of optimized parameters of the radio communication system, transmitting the values of the selected parameters to the master station , restructuring the receiving and transmitting paths to new optimized parameters, establishing and maintaining communications, characterized in that a second receiving channel is additionally introduced into the receiving path, consisting of a receiving antenna identical to the first receiving channel, an antenna-feeder device and a high-frequency amplifier, and a two-channel synchronous analog-to-digital converter is simultaneously introduced in parallel with both receiving channels, in which they digitize synchronously amplified radio signals, then perform spatial-correlation signal processing in the signal processing unit of the computing device, where you perform calculating the cross-correlation of signals represented by a parallel code carrying information about individual symbols with a sample size equal to the length of the Barker code, then the information sequence represented by the parallel code is formed by comparing the calculated cross-correlation values with a threshold number; at the same time, in the signal generation block of the computing device, each bit of information coming from the terminal is encoded with a Barker noise-like binary code sequence having an autocorrelation function close to a delta function that increases the noise immunity of the radio channel; then perform the procedure of intersymbol interleaving; in addition, testing with test signals No. 1-3 is carried out to assess the state of the radio channel; Further, according to the results of testing in the adaptive radio channel control unit of the computing device to maintain a given radio channel throughput, the frequency-code structure of the OFDM signal is adapted by frequency distribution of the OFDM signal subcarriers. 2. The method according to p. 1, characterized in that the distance between the receiving antennas make at least half the wavelength (λ / 2) from each other. 3. The method according to p. 1, characterized in that to adapt the frequency-code design of the OFDM signal exclude subcarriers of the OFDM signal, which cause a large number of errors during testing and where the interference level exceeds the average noise level in the entire test signal band more than by 30%, with the transfer of the affected subcarriers to the edges of the original OFDM signal within the extended band of the test signal.

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