RU2791224C1 - Noise-like signals generating method - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio engineering and may be used in radio communication systems. The technical result is achieved by forming two quasi-orthogonal binary pseudorandom sequences (PRS) - a clock and information ones - that are phase-plotted with each other. Synchronizing PRS is periodic, and at each period of its repetition information PRS is cyclically shifted relative to the synchronizing PRS by the number of elements determined by the transmitted information symbol, element by element, summed with a delayed integer number of periods of the clock frequency synchronizing PSP and manipulated in the phase signal carrier frequency. The second carrier frequency signal phase shifted by ninety degrees is manipulated in phase by the synchronizing PSP or a periodic information PSP, depending on the level of the two-level signal coming from an additional information source. Both phase-manipulated signals are summed.

EFFECT: invention provides possibility to increase communication channels error-rate performance.

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Description

The invention relates to the field of radio engineering and can be used in radio communication systems with noise-like signals.

The main task that has to be solved in the design of such systems is to increase the data transfer rate while ensuring high reliability of their reception under the influence of both natural interference and interference from electronic countermeasures.

Most communication systems with noise-like signals described in scientific publications [1, 2, 3] and patents [4, 5] use binary signal alphabets for data transmission. Increasing the data transfer rate in such communication systems is possible only by reducing the duration of the signals, that is, reducing their base [3. page 5]. This leads to a decrease in the noise immunity of the communication system [3. p.6].

One of the ways to increase the noise immunity of a communication system at a high data rate is to use the alphabet of large volume signals [3. p.163].

Of the known methods for generating noise-like signals with a large volume of the alphabet, the closest in terms of the number of matching features to the claimed method is the method for generating noise-like signals described in [6].

According to this method, carrier and clock signals are generated. From the clock signal, two quasi-orthogonal or orthogonal binary pseudo-random sequences are formed, one of which is intended for synchronization (SP), and the second for information transmission (IP). The sequences are phased with each other, after which the IP is cyclically shifted relative to the SP by the number of elements determined by digital data coming from a high-speed information source in a time equal to the period of pseudo-random sequences. The cyclically shifted IP sequence is left unchanged or elementwise inverted depending on the value of the information bit coming from the low-speed information source. The resulting binary sequence is manipulated in phase with the carrier frequency signal. A second carrier frequency signal is formed, shifted relative to the first one in phase by ninety degrees, which is manipulated in phase by the SP sequence. The two phase-shift keyed carrier signals are summed.

The disadvantage of this prototype is the low noise immunity of data transmission from a low-speed information source.

Reception of information from a high-speed source is the determination of the magnitude of the cyclic shift of the IP sequence relative to the SP sequence. Receiving information from a low-rate source consists in determining whether the sequence with the found value of the cyclic shift was transmitted with inverted elements or with non-inverted ones.

Therefore, if the value of the cyclic shift of the IP sequence is incorrectly determined, the probability of an error in determining the value of a bit of information from a low-speed source is 0.5.

Thus, the probability of an error in receiving information from a low-speed source is only two times less than the probability of an error in receiving information from a high-speed source.

The aim of the invention is to improve the noise immunity of data transmission from a low-speed information source. The result achieved by using the invention is to increase the noise immunity of data transmission from a low-speed information source and expand its functionality.

To solve the problem posed in the invention in the method of generating noise-like phase-shift keyed signals, which consists in the fact that two carrier frequency signals are formed, shifted between themselves in phase by ninety degrees, and a clock frequency signal, from which two quasi-orthogonal binary pseudo-random sequences (PRS) are formed, phased with each other, synchronizing and informational, moreover, the synchronizing SRP is periodic, and on each period of its repetition, the information SRP is cyclically shifted relative to the synchronizing SRP by the number of elements determined by the transmitted information symbol, according to the invention, one of the carrier frequency signals is manipulated in phase by the sequence that is formed element-by-element addition modulo two of the cyclically shifted information SRP and the clock frequency of the synchronizing SRP delayed by an integer number of periods, in addition, a periodic information SRP is formed, phased with the synchronized and the second signal of the carrier frequency is manipulated in phase of the synchronizing SRP or periodic information SRP depending on the level of the two-level signal coming from the additional information source, and both phase-shift keyed signals are summed.

The method for generating noise-like phase-shift keyed signals consists in sequentially performing the following operations:

- Form two signals of the carrier frequency, shifted between themselves in phase by ninety degrees.

- Form a clock signal.

- From the clock signal form two quasi-orthogonal binary pseudo-random sequences (RRP), in phase with each other, synchronizing and information.

- Synchronizing PSP is periodic, and the information PSP on each repetition period of the synchronizing PSP is cyclically shifted relative to the synchronizing PSP by the number of elements determined by the transmitted information symbol.

- The synchronizing PR is delayed by an integer number of clock cycles and elementwise sum modulo two with the cyclically shifted information PR.

- The received binary sequence is manipulated in phase by one of the carrier signals.

- Form a periodic information SRP, phased with the synchronizing SRP.

- The second carrier frequency signal is manipulated in phase of the synchronizing SRP or periodic information SRP depending on the level of the two-level signal coming from the additional information source.

- Sum two phase-shift keyed signals.

Thus, to transmit information from different sources, different quadrature components of the signal are used. Information from one source is transmitted by an alphabet of quasi-orthogonal signals, the volume of which m is equal to the number of different transmitted information symbols. Additional source information is transmitted in an alphabet containing two quasi-orthogonal signals.

As shown in [3, p.162], the probability of error when receiving m orthogonal signals is proportional to (m - 1). If binary information is received from an additional source, and the duration of one bit is equal to the PRS period, and the powers of the quadrature components of the signal are the same, then the error probability when receiving one bit of information from the additional source is (m - 1) times less than the error probability when receiving one symbol of information.

Thus, compared with the prototype, the noise immunity of data transmission from an additional source of information is significantly increased.

In addition, the additional source information may be out of sync with the PR repetition period, and may also be non-binary. For example, an additional source of information may be a pulse-width modulator [3, p.174].

Another advantage is that the reception of information from both sources can be done in a non-coherent way. This is of great importance for radio channels, in which tracking the carrier frequency of the signal in the receiver is impossible or technically difficult. In addition, with a large volume of the alphabet of signals, the noise immunity of incoherent and coherent reception of information differ slightly [3, p.163, fig. 7.6].

The introduction of modulo two summation of a cyclically shifted information PRS and a clock frequency delayed by an integer number of periods, synchronizing the PRS, makes it possible to increase the noise immunity of receiving information symbols in radio channels with multipath signal propagation due to the decorrelation of signals with different time delays.

An example of a technical implementation of a device that generates noise-like signals by the considered method is shown in Fig. 1.

The device contains:

1 – carrier and clock signal generator (LPFC);

2 - counter modulo N,Where N- amount of elements

synchronizing PSP;

3 – modulo N adder;

4 - parallel register;

5, 6 - Read Only Memory (ROM);

7 - switch;

8 – modulo two adder;

9, 10 - multiplier;

11 - phase shifter;

12 - adder.

The device works as follows. The clock signal generated by LPTF 1 is supplied to the clock inputs of the counter modulo N 2, at the output of which a periodic sequence of multi-digit binary numbers [0, 1, 2, ..., N-1] is formed. The signals from the multi-bit output of the modulo N 2 counter are fed to the address inputs of the three-bit ROM 5. One of the bits of the ROM 5 contains the values of the elements of the synchronizing PSP, the other - the information PSP, and the third - the cyclically shifted synchronizing PSP. At the outputs of the ROM 5 are formed periodic PSP - synchronizing, informational and delayed by an integer number of periods of the clock frequency synchronizing.

Periodic synchronizing PSP and information PSP from the outputs of the ROM 5 are fed to the inputs of the switch 7, the control input of which receives a two-level signal from an additional source of information (AI). The output of the switch 7 is switched either synchronizing PSP, or informational PSP, depending on the level of the AI signal.

The output signal of the switch 7 is fed to one of the inputs of the multiplier 9, the second input of which is supplied with a carrier frequency signal from the output of the LPTF 1. In the multiplier 7, the phase keying of the carrier frequency signal of the synchronizing PRS or information PRS is performed depending on the signal level of the IS.

The formation of the second quadrature component of the signal is carried out as follows.

The signal from the output of the transfer of the counter modulo N 2 corresponding in time to the last element of the next repetition period of the synchronizing SRP is fed to an external data transmission device (EDD). In the UPD, a binary code of the next transmitted information symbol is generated, which enters the information input of the parallel register 4 and is written into it by a signal from the counter transfer output modulo N 2.

The binary code of the information symbol from the output of parallel register 4 is fed to one of the multi-bit inputs of the adder modulo N 3, the second input of which receives a sequence of multi-bit binary numbers [0, 1, 2, ..., N-1] from the output of the counter modulo N 2. In the adder modulo N 3 there is a cyclic shift of this sequence by the number of elements, the binary representation of which is equal to the binary code of the information symbol.

The multi-bit output signal of the adder modulo N 3 is supplied to the address input of the ROM 6, which contains the information PSP. At the output of the ROM 6, an information PSP is formed, cyclically shifted relative to the synchronizing PSP by the number of elements, the binary representation of which is equal to the binary code of the transmitted information symbol.

The cyclically shifted information PSP from the output of ROM 6 is fed to one of the inputs of the adder modulo two 8, the second input of which receives the synchronizing PSP delayed by an integer number of periods of the clock frequency from the output of the third bit of ROM 5. At the output of the adder modulo two 8, a sequence of sums is formed modulo two elements of the cyclically shifted information SRP and the delayed synchronizing SRP.

The output signal of the adder modulo two 8 is fed to one of the inputs of the multiplier 10, the second input of which is supplied with a carrier frequency signal from the output of the LPTF 1, shifted in phase by ninety degrees in the phase shifter 11. In the multiplier 10, phase manipulation of the carrier frequency signal shifted along phase by ninety degrees, a sequence of sums modulo two of the elements of the cyclically shifted information SRP and the delayed synchronizing SRP. The output signals of the multipliers 9, 10 are summed in the adder 12.

SOURCES OF INFORMATION

1. Sklyar B. Digital communications. Theoretical foundations and practical application. Ed. 2nd, corrected: Per. from English. - M .: Williams Publishing House, 2004. - 1104 pp., pp. 733-819.

2. Borisov V. I. et al. Noise immunity of radio communication systems with the expansion of the spectrum of signals by modulation of the carrier pseudo-random sequence - M .: Radio and communication, 2003. - 641 p.

3. Varakin L.E. Communication systems with noise-like signals. - M .: Radio and communication, 1985. - 384 p.

4. Patent RU 2646 353 C1. Transmitter of increased structural and energy secrecy. Published on 02.03.2018. Bull. No. 7.

5. Patent RU 2127 486 C1. Method and device for transmitting messages by broadband signals. Published 03/10/1999.

6. Patent RU 2279 183 C2. A method for transmitting information in a communication system with broadband signals. Published on 06/27/2006. Bull. No. 18.

Claims (1)

A method for generating noise-like signals, which consists in the fact that two carrier frequency signals are formed, shifted between themselves by ninety degrees in phase, and a clock frequency signal, from which two quasi-orthogonal binary pseudo-random sequences (PRS) are formed, phased with each other, synchronizing and informational, moreover, the synchronizing SRP is periodic, and at each period of its repetition, the information SRP is cyclically shifted relative to the synchronizing SRP by the number of elements determined by the transmitted information symbol, characterized in that one of the carrier frequency signals is manipulated in phase by a sequence that is formed by element-by-element addition modulo two cyclically shifted information SRP and delayed by an integer number of periods of the clock frequency of the synchronizing SRP, in addition, a periodic information SRP is formed, phased with the synchronizing SRP, and the second carrier signal is manipulated in the sync phase onizing PSP or periodic information PSP, depending on the level of a two-level signal coming from an additional source of information, and both phase-shift keyed signals are summed.

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