RU2573586C2 - System for transmitting data via multi-beam communication link - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method comprises generating, emitting and receiving information in packets consisting of two parts - a synchronising part and an information part. Data transmission precedes transmission of the synchronising part, having the form of a certain number of signals which are modulated by whole periods of a maximum-length sequence (M-sequence). The information part is a sequence of a certain number of signals which are modulated by Hadarmad functions, which are element-by-element modulo-2 summed with the M-sequence.

EFFECT: high noise-immunity and reliability of transmitting data in conditions for signal propagation in a multi-beam communication link on the condition that interference is equal to or greater than the signal.

3 dwg

Description

The invention relates to marine engineering, and in particular to the field of signal transmission in the marine environment, and can be used to transmit information via a hydroacoustic communication channel, characterized by multipath propagation due to refraction due to the distribution of the speed of sound in depth, and the presence of sound reflecting the water surface and bottom seas.

A radio-acoustic device is known for remotely disconnecting an underwater product and controlling its location on the sea surface (patent RU 2297641 C1, publ. 04/20/2007), which contains a radiation channel for hydro-acoustic encoded broadband control signals and a channel for receiving control signals. The control signal emission channel comprises a modulating code generator, a master oscillator, a phase manipulator, a power amplifier, and a hydroacoustic emitter. The channel for receiving control signals contains a hydrophone, an amplifier, a demodulator, two decoders, an electromagnetic relay. As hydroacoustic encoded control signals, complex signals with phase shift keying are used.

A known system of secretive hydroacoustic communication (patent RU No. 2397915 C1, publ. 08/27/2010), containing a transmitting path configured to generate and emit a broadband frequency-modulated (frequency-manipulated) signal, and a receiving path including an antenna , noise-like signal limiter amplifier, high and low frequency amplifiers, frequency detector, diver's telephone. The receiving path is configured to receive a signal from an amplifier-limiter of a noise-like signal to an amplitude detector without carrier recovery, and after it to a high-pass bandpass filter tuned to a frequency of twice the frequency-modulated (frequency-manipulated) carrier frequency, and then to this amplifier double carrier frequency.

From radio communication, systems for transmitting data via broadband / noise-like signals (BPS) are known, which have increased stealth and noise immunity. Examples of such systems are given in the book of L. Varakin. “Communication systems with noise-like signals”, ed. “Radio and communications”, Moscow, 1985. One of the applied modulation methods for noise-like signals is phase modulation or phase shift keying (FM). As a prototype, a block diagram of a communication system with phase-shifted ShPS is adopted, which is given in the book of L. Varakin. on page 18, fig. 1.9. A prototype feature is the use of an information signal as a source of synchronizing data.

A common drawback of these technical solutions is the decrease in the reliability of data transmission in the case of signal reception in multipath propagation.

The objective of the present invention is to provide a data transmission system via a multipath communication channel with improved characteristics - noise immunity and reliability. Improving the noise immunity and reliability of data transmission is achieved due to the formation, emission and reception of information in packages consisting of two parts - synchronizing and information.

To this end, in a data transmission system via a multipath communication channel, comprising a transmitting path configured to generate and emit a broadband phase-modulated / phase-shifted (FM) signal, and a receiving path including an electro-acoustic receiver, a signal preparation unit, a mixer (demodulator), a correlator and a synchronizer, into a transmission path, configured to generate a synchronizing part of the package, consisting of a number of FM signals, modulated / manipulated During the periods of the M-sequence by means of the M-sequence generator, an information part forming unit has been introduced, containing a Hadamard function generator connected in series, a synchronization-information switch, an element-wise adder modulo two signals and M-sequences. After the signal preparation unit, demodulator, correlator and synchronizer, connected in series with the signal output from the correlator to the weighted accumulation device, and after it to the threshold device and then to the maximum delay determinant and the controlled delay device, are introduced into the receiving path receiving the information part of the package, which includes a series-connected correlator the envelope of the signal is a matrix of Hadamard functions, the determinant of the shift of the maximum of the function cross-correlation and a memory unit, as well as an M-sequence generator and an element-wise adder modulo two signals and M-sequences, configured to receive a signal from the output of the controlled delay device to one input and from the output of the M-sequence generator to another input, and applying an output signal to the input of the correlator.

The information part is a sequence of a number of signals modulated / manipulated by Hadamard functions, element-wise summed modulo two with an M-sequence.

Due to the independent operation of the transmitter and receiver in reception during cyclic filling, a mismatch in the initial address of the buffer with the beginning of the data block may occur. For the correct reception of information, it is required that the entire data block be in the memory buffer, that is, a synchronization signal is required.

Data transmission is preceded by the transmission of the synchronizing part, having the form of a certain number of signals, modulated / manipulated by entire periods of the sequence of maximum length (M-sequence).

First, a synchronizing signal is received, it is optimally processed in the correlator, and a weighted accumulation of the correlator output is performed. The accumulation result is compared with a threshold. If the threshold is exceeded, a decision is made on the presence of a signal. In the accumulated output of the correlator, the largest of the maxima is determined, that is, the maximum corresponding to the beam of the highest intensity is searched. Weighted accumulation and development of the synchronizer for the largest of the maxima of the cross-correlation function (FVC) provides an increase in the reliability of data transmission.

The maximum offset is determined and transmitted to the controlled delay device. After the delay time has elapsed, the data are fed into the multichannel correlator, which performs optimal processing of the information part of the signal. At the output of the correlator there is a maximum, its abscissa is determined, which is the transmitted data. The abscissa is written to the memory block. When the entire specified number of data is placed in the memory unit, the data is provided to the recipient of the information.

The essence of the invention is illustrated by drawings, where:

- in FIG. 1 is a block diagram of a transmission path,

- in FIG. 2 shows a block diagram of a receiving path,

- in FIG. 3 shows diagrams of time and cross-correlation functions of the M-sequence (synchronization) and Hadamard functions (information).

The numbers in the drawings indicate:

in FIG. one

1 - source of information,

2 - generator of M-sequences,

3 - carrier oscillator,

4 - phase manipulator (modulator),

5 - power amplifier,

6 - electro-acoustic emitter,

7 - block forming the information part of the package,

8 - source level "logical zero"

9 - generator of Hadamard functions,

10 - synchronization-information switch,

11 - element-wise adder modulo two;

in FIG. 2

12 - electro-acoustic receiver,

13 - block signal preparation,

14 - demodulator

15 - correlator envelope signal - M-sequence,

16 - recipient of information,

17 - synchronizer,

18 - synchronization-information switch,

19 is a device for weighted accumulation,

20 - threshold device

21 is a determinant of maximum delay,

22 - controlled delay device,

23 - block receiving the information part of the package,

24 - generator of the M-sequence,

25 - element-wise adder modulo two,

26 - correlator envelope of the signal is a matrix of Hadamard functions,

27 - determinant of the maximum displacement of the FVC,

28 - memory block;

in FIG. 3

3.1 is an M-sequence diagram before synchronization,

3.2 is a diagram of the output of the cross correlator signal - M-sequence before synchronization,

3.3 is an M-sequence diagram after synchronization,

3.4 is a diagram of the output of the cross correlator signal - M-sequence after synchronization,

3.5 is a diagram of a Hadamard function,

3.6 - output diagram of the mutual correlator signal - matrix of Hadamard functions.

The operation of the data transmission system via a multipath communication channel is as follows.

In the transmitting path after receiving from the source of information 1 data intended for transmission, the synchronization-information switch 10 is set to the "synchronization" position. This ensures the supply from the source of the logic zero level 8 to the input of the element-wise adder modulo two 11, due to which the elements of the M-sequence from the generator of M-sequences 2 without changing the values (diagram 3.3 of Fig. 3) are fed to the upper input of the phase manipulator ( modulator) 4, to the other input of the phase manipulator (modulator) 4 a signal is supplied from the carrier oscillator 3.

Next, the synchronization-information switch 10 is set to the “information” position and the data received from the information source 1 is sent to the Hadamard function generator 9 of the order corresponding to the incoming number (diagram 3.5 of Fig. 3). The Hadamard function through the synchronization-information switch 10 is supplied to one of the inputs of the element-wise adder modulo two 11, to the other input of the element-wise adder modulo two 11 the element-wise values of the M-sequence are received from the M-sequence generator 2.

Serially connected, the Hadamard function generator 9, the synchronization-information switch 10 and the element-wise adder modulo two 11 form a block for forming the information part of the packet 7.

The total signal is fed to the input of the phase manipulator / modulator 4, the signal from the carrier oscillation generator 3 is fed to the other input of the phase manipulator / modulator 4. The FM signal passes the power amplifier 5 and is radiated into the aqueous medium by means of an electro-acoustic emitter 6.

The receiving path is in a state of waiting for a communication signal, that is, the electro-acoustic receiver 12 (Fig. 2) is affected only by sea noises. When the acoustic signal from the transmitting tract acts on the electro-acoustic receiver 12, the electric signal will arrive at the signal preparation unit 13. The signal preparation unit 13 includes amplification, bandpass filtering, and analog-to-digital conversion devices. The signal from the signal preparation unit 13 is supplied to a demodulator 14, which performs the multiplication of the signal by a sinusoidal reference signal of the same frequency as the carrier oscillation, and averaging the products. Via the synchronization-information switch 18, available in the synchronizer 17, the signal envelope is transmitted to the signal envelope correlator - the M-sequence 15, where the FVC of the signal envelope with the matrix - the circulant of the M-sequence is determined.

In the weighted storage device 19, a weighted accumulation of the FVC values is performed, which in the threshold device 20 are compared with the threshold. If the threshold is not exceeded, then the continuation of the wait state follows.

Exceeding the threshold indicates the presence of a signal; in this case, a reference is made to the maximum delay determinant 21, where the maximum delay of the FVC is determined, which consists in determining the number of the memory cell where the maximum is placed and subtracting from this number the starting address of the buffer allocated for storing the FVC.

Diagrams 3.1, 3.2 (Fig. 3) show, as an example, a synchronization signal having one signal maximum and an abscissa offset of 30.

The delay value is recorded in the controlled delay device 22, which is necessary for tuning to the maximum beam, the synchronization-information switch 18 switches the signal to the controlled delay device 22. After the delay in the controlled delay device 22, the synchronization signal has the form shown in diagrams 3.3, 3.4 ( Fig. 3), where the offset is zero. Thus, synchronism is achieved, and in the controlled delay device 22, data transmission to the reception unit of the information part of the packet 23 begins.

In the adder modulo two 25 modulo summation is performed on the two signals coming through the controlled delay device 22, and the M-sequence generated by the M-sequence generator 24. This operation has the value of data recovery before receiving information.

The information part is received by the correlator, the envelope of the signal — the Hadamard function matrix 26, the maximum displacement determiner of the FVC 27 and the memory unit 28. In the correlator, the signal envelope — the Hadamard function matrix 26, which is the second correlator, is determined by the FVC of the signal envelope and the Hadamard function matrix.

Diagram 3.5 (Fig. 3) shows a sample of the 50-order Hadamard function, diagram 3.6 shows the FVC of the same function, in which the maximum abscissa is also 50, which indicates the correct recognition of the data.

The maximum displacement of the FVC is the data received from the communication channel. These data are stored in the memory unit 28, from where they are issued to the recipient of information 16.

The technical solutions outlined ensure the operability of a data transmission system via a multipath communication channel with a signal to noise ratio equal to or greater than minus 6 dB.

The proposed data transmission system via a multipath communication channel can be used for communication with autonomous seismic-hydroacoustic observation stations, with self-propelled uninhabited underwater vehicles - carriers of high-resolution equipment, as well as for providing full-scale tests of marine objects detection equipment for the purpose of transmitting control commands and data on the state of the equipment to drive target ships to the sonar beacon.

Claims (1)

A multi-beam communication system for transmitting data, comprising a transmitting path configured to generate and emit a broadband phase-modulated / phase-shifted signal, and a receiving path including an electro-acoustic receiver, a signal preparation unit, a mixer (demodulator), a correlator and a synchronizer, characterized in that in the transmission path, configured to generate a synchronizing part of the package, consisting of a number of phase-modulated / phase-manipulated s of the signals modulated / manipulated by entire periods of the M-sequence by means of the M-sequence generator, an information part formation unit is introduced, containing a Hadamard function generator connected in series, a synchronization-information switch, an element-wise adder modulo two signals and M-sequences, into the receiving path after sequentially connected signal preparation unit, demodulator, correlator and synchronizer, configured to receive a signal from the output of the correlate and to the weighted accumulation device, and after it, to the threshold device and then to the maximum delay determinant and the controlled delay device, a block for receiving the information part of the package is introduced, which includes a series-connected correlator the envelope of the signal — the matrix of Hadamard functions, the determinant of the maximum offset of the mutual function correlations and a memory unit, as well as an M-sequence generator and an element-wise adder modulo two signals and M-sequences, configured to receive a signal and output devices controlled delay at one input and output from the M-sequence generator - to the other input, and supplying to the input of the correlator output.

Images