RU2362273C2 - Method of transmitting information using pseudonoise signals and device to this end - Google Patents

Abstract

FIELD: communication devices.

SUBSTANCE: invention relates to the technology of communication and transmitting data and can be used for transmitting discrete information using a broadband pseudonoise signal at low signal-to-noise ratio, in a signal transmission channel, including less than one. The method of transmitting information using pseudonoise signals (PNS) is characterised by that, on the transmitting side, there is modulation of the carrier wave with a periodic pseudonoise signal. Each alphabet symbol is encoded by a periodic pseudonoise signal with its own distinct repetition period T_i. On the receiving side the value of autocorrelation function Y(r) is calculated at points r = T_i and the received symbol is assigned that value for which the autocorrelation function is maximum. The device for transmitting information using pseudonoise signals contains a transmitter, communication line and receiver. The transmitter contains a carrier-frequency generator, balanced modulator, read-only memory, digital-to-analogue converter, smoothing low-pass filter, address generating device, frequency divider, and a unit for matching with the communication line. The receiver contains a unit for matching with the communication line, two multipliers, reference generator, phase changer, two low-pass filters, two analogue-to-digital converters, decision device, m structure-identical channels for processing received signal, each of which contains four multipliers, two memory elements, two adders, subtracter, two integrators and two module selection units.

EFFECT: increased noise immunity due to elimination of interfering components.

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Description

The invention relates to communication and data transmission techniques and can be used to transmit discrete information by a broadband noise-like signal with a low signal-to-noise ratio in the communication line, including less than one.

The known advantages of broadband noise-like signals (SHPS) [Sklyar, Bernard. Digital communication. Theoretical Foundations and Practical Application, 2nd Edition .: Per. from English - M.: Williams Publishing House, 1403. - 1104 p.: Ill. - Paral. tit. English 2003]. In common communication systems with SHPS, phase modulation (FM) or phase difference modulation (PRM) is widely used, as the most effective from the point of view of noise immunity [Okunev Yu.B. Digital transmission of information by phase-shifted signals. M .: Radio and communication, 91, - 196 p.]. The receiving part of such systems works according to the principle of a correlator, in which the scalar product of the received signal x (t) and some reference signal x _on (t) is calculated:

where T is the duration of the transmitted character.

The various methods for receiving and processing signals in a correlation receiver essentially differ in the way the reference signal x _on (t) is generated. In principle, coherent reception schemes have the best sensitivity when x _on (t) is generated in the receiver using a special generator, however, this method requires perfect synchronization, which is achieved either by increasing the transmission power, i.e. in fact, due to the deterioration of the same sensitivity, or due to a significant complication of the circuit. In addition, the system is very sensitive to distortion of the waveform in the communication line.

The task of receiving and processing SHPS is greatly simplified in the autocorrelation receiver, in which x _on (t) is formed from the received signal x (t) by delaying it for a certain interval τ.

A known method of transmitting information using phase-difference modulation on the transmitting side and autocorrelation reception on the receiving side [A.S. No. 177471 Rakhnovich L.M. A method for detecting phase-shifted signals transmitted by the method of double relative phase manipulation. M .: TsNIIIPI, 1966]. The disadvantage of this method is the presence of interference in the multiplication results preceding integration with the reset.

The known method [patent No. 2168869, Skripkin A.A., Scherbachev V.A. A method of demodulating signals with relative phase shift keying and a device for its implementation. 2001], which eliminated additional interference arising from the multiplication results preceding integration with the reset. The disadvantages of both methods include the impossibility of working with the m - dimensional alphabet, as well as the fact that the error in one received character extends to two adjacent characters.

A known autocorrelation method for transmitting digital information, called the Lange-Muller method and selected as a prototype [Lange F. Correlation electronics. Sudpromgiz 63. (Prototype method)]. In this method, the correlation-time modulation is used, according to which the output signal of the transmitter is formed as the sum of some BPS s (t) and its delayed copy s (t-τ), where

τ is the interval assigned to the transmitted character.

The signal s (t) + s (t-τ) thus obtained is transmitted over the communication line. On the receiving side, this signal is delayed for a time τ, and then a pair of signals s (t) + s (t-τ) and s (t-τ) + s (t-2τ) are used to calculate autocorrelation:

The obtained value of Y (τ) is compared with the threshold and, in case of exceeding, a decision is made that a symbol corresponding to this τ has been transmitted.

By comparing different information symbols with different values of τ, the above method can be extended to the transmission of alphabet symbols of the required dimension m.

энергии принятого сигнала, тогда как его полная энергия равна:This prototype method has a number of disadvantages. First, in expression (2), only the second term gives a useful effect, while the rest are in the nature of interfering noise, and this noise component is not connected in any way with extraneous noise, but is generated by the signal itself. Secondly, only a part is used on the receiving side

energy of the received signal, while its total energy is equal to:

The technical result of the proposed invention is to increase the noise immunity due to the exclusion of interference components generated in the prototype method by the signal itself, as well as due to more complete use of the energy of the received signal.

, т.е. модулируемым параметром является период ШПС. Соответственно, на приемной стороне вычисляют совокупность значений автокорреляцииThe technical result is achieved by the fact that the transmitted symbol a _i is represented by a periodic pseudo-noise sequence obtained by n _i - multiple repetition of SHPS, and the repetition period T _i is equal to

, i.e. the modulated parameter is the BSC period. Accordingly, at the receiving side, a set of autocorrelation values is calculated

Next, the obtained values of Y (T _i ) are compared with each other to find the maximum value of Y (T _i ) _max = Y (T _j ) and decide that the character a _j corresponding to the found T _j was transmitted.

We show that the proposed method is devoid of the disadvantages noted in the prototype method. Indeed, if the symbol a _j was transmitted, which corresponds to the repetition period T _j , then on the receiving side there will be a maximum Y (T _j ), which will take the value:

Comparing expressions (4) and (2), it is easy to see that in the proposed method there are no spurious noise components, and the energy of the received signal is used almost completely if the number of repetitions n _j is large enough.

The proposed method has other advantages. Firstly, the repetition period of a complex signal is a parameter that is least affected by any kind of distorting factors in the communication line. Secondly, the detection of a periodic signal against a background of noise is a technical problem that can be easily solved by modern computing means. Thirdly, the proposed method allows without reconfiguring the communication system to gain the necessary energy of the symbol by simply increasing the number of repeats SHPS. Finally, the proposed communication method easily fits into the most advanced transmission schemes over the communication line using a high-frequency carrier signal, such as transmission with a suppressed carrier or even single-band transmission.

There are communication devices that implement autocorrelation reception and processing of digital information [A.S. No. 451166, Schelkunov K.N., Okunev Yu.B., Babel E.S., Goncharov V.N. Communication system with phase difference modulation of the first order. M .: TsNIIIPI, 1975; A.S. No. 543194, Schelkunov K.N., Babel E.S., Goncharov V.N. Communication system with phase difference modulation of the first order. M .: TsNIIIPI, 1977; Patent No. 2168869, Skripkin A.A., Scherbachev V.A. A method of demodulating signals with relative phase shift keying and a device for its implementation 2001. (Prototype device)]. They operate in a carrier mode, the initial phase of which is modulated by a digital information signal so that it changes from symbol to symbol, but within the duration of one symbol, T remains unchanged. Usually use binary phase shift keying with a phase value of 0 and π. The disadvantage of the device described in A.S. No. 451166, is not sufficiently high noise immunity to additive noise due to the deterioration of energy ratios due to the need to process only half of information messages. This disadvantage is eliminated in the device described in A.S. No. 543194, however, it contains interference in the results of multiplication prior to integration with the reset. These interference are eliminated in the device described in patent No. 2168869, which is the closest to the proposed device and is selected by us as a prototype.

и полученные две пары НЧ сигналов подают на дальнейшую обработку в двух квадратурных корреляторах. Далее выходные сигналы корреляторов поступают на схему, реализующую алгоритм приема ФРМ второго порядка, которая формирует сигнал для решающего устройства с учетом n-й, (n-1)-й и (n-2)-й информационных посылок. В целом, приемник устройства-прототипа содержит восемь перемножителей, опорный генератор, фазовращатель на

, пять элементов памяти на половину длительности посылки Т, два интегратора со сбросом, три сумматора, решающее устройство, устройство синхронизации, два фильтра нижних частот (ФНЧ), вычитающее устройство.In this device, the transmitter performs first-order phase difference manipulation (PRM1), and in the receiver, the received signal is decomposed using the reference generator into in-phase and quadrature components relative to the center frequency of the input signals, then these components are filtered in the low frequency band, and then they are shifted by

and the obtained two pairs of low-frequency signals are fed for further processing in two quadrature correlators. Next, the output signals of the correlators are fed to a circuit that implements a second-order FRM reception algorithm, which generates a signal for the solver taking into account the nth, (n-1) th and (n-2) th information parcels. In General, the receiver of the prototype device contains eight multipliers, a reference generator, a phase shifter on

, five memory elements for half the duration of sending T, two integrators with a reset, three adders, a solver, a synchronization device, two low-pass filters (low-pass filters), a subtracting device.

The advantage of the prototype device is that, firstly, it provides stability to the instability of the signal frequency, and secondly, by lowering the frequency in the input part of the receiver, it allows digital processing of the received signal using a modern digital signal processor (DSP).

The disadvantage of the prototype device is that the receiver has many multipliers connected in series, which negatively affects the dynamic range, given the limited capabilities of existing computing tools. The second drawback is that the error in one received character extends to two adjacent characters. In addition, the prototype device has limited functionality: the device only works with binary characters and cannot be used in the case of the m - dimensional alphabet, and also cannot be directly used for the proposed method of character encoding by modulating the repetition period of the NPC.

The technical result of the proposed device is the expansion of the dynamic range, increasing the resistance to distortion of the waveform in the communication line, reducing the likelihood of symbolic errors, as well as expanding the functionality of the prototype: the ability to work with the m - dimensional alphabet, the possibility of using ShPS, the ability to transmit with a suppressed carrier, or even single-band transmission, the ability to use the proposed method for modulating the repetition period of the NPS

The technical result is achieved by the fact that a permanent memory device (ROM) is introduced into the transmitter, which contains a pseudo-random sequence (PSP), the output of which is connected through a digital-to-analog converter (DAC) and a smoothing low-pass filter to the second input of the balanced modulator, while the first input of the balanced modulator connected to a carrier frequency generator, as well as an address generation device, the clock input of which through a frequency divider is connected to the output of the same carrier frequency generator, and the information the input is connected to the source of the transmitted characters, while the output of the address generation device is connected to the address input of the ROM, while the output of the balanced modulator through the matching device is connected to the communication line.

The receiving part of the proposed device is implemented by a circuit comprising a matching unit with a communication line, where the signal is picked up from the communication line, amplified by an amplifier equipped with an automatic gain control circuit (AGC) and filtered from interference located outside the signal band, the output of the matching unit is connected to the first inputs of two multipliers, the second inputs of which are connected to a common reference generator, while the second input of the first multiplier is directly connected to the reference generator, and the second input of the second of a resident through a phase shifter, the output of the first multiplier through a series-connected low-pass filter and an analog-to-digital converter is connected to common-mode inputs, and the output of the second multiplier through a second low-pass filter and a second analog-to-digital converter to quadrature inputs of processing channels m-identical in structure signal, each of which includes four multiplier, two memory elements at a duration T _i, adder, subtractor and two integrators, with the in-phase input of i-th channel by for prison directly to first inputs of first and third multipliers channel quadrature input i-th channel is directly connected to first inputs of the second and fourth multipliers channel, whereas the second inputs of the first and second multipliers channel connected to in-phase input channel through a common memory element over the duration T _i and the second inputs of the third and fourth channel multipliers are connected to the quadrature channel input through the second memory element for the duration T _i , the outputs of the first and fourth channel multipliers la through an adder are connected to the input of the first channel integrator, and the outputs of the second and third channel multiplier through a subtracter are connected to the input of the second channel integrator. According to the invention, the receiving part of the device contains m channels tuned for different delays T _i , and not integrators with reset, but integrators with a sliding window are used in each channel, the outputs of the integrators are connected to the second adder of the channel through the module selection blocks, and the output of the second adder is an output i-th channel and connected to the corresponding input of the deciding device.

Figure 1 shows the structural diagram of a transmission device, and figure 2 - receiving device, with which the proposed method of transmitting information is implemented.

According to the proposed method:

, где Т - длительность передачи одного символа.1. The transmitted character a _i represent a periodic pseudo-noise sequence obtained by n _i - multiple repetition of the NPS, and the repetition period T _i equal

where T is the transmission duration of one character.

2. The symbol thus formed is transmitted over the communication line.

3. At the receiving side, the signal is amplified and filtered in the desired frequency band.

4. For the amplified and filtered signal, a set of autocorrelation values is calculated

5. The obtained values of Y (T _i ) are compared and find the maximum of them Y (T _i ) _max

6. Assign to the received symbol the value of a _j for which Y (T _j ) turned out to be maximum.

A device that implements the proposed method for transmitting information, contains a transmitting (figure 1) and a receiving part (figure 2).

On the transmitting side (see Fig. 1), a permanent storage device 1 is introduced into the transmitter, containing a pseudo-random digital sequence, the output of which is connected through the DAC 2 and the smoothing low-pass filter 3 to the second input of the balanced modulator 4, while the first input of the balanced modulator is connected to the generator carrier frequency 5, as well as a device for generating address 6, the clock input of which through a frequency divider 7 is connected to the output of the same generator of carrier frequency 5, and the information input is connected to the source x characters, while the output of the address generation device 6 is connected to the address input of the ROM 1, while the output of the balanced modulator through the matching device 8 is connected to the communication line.

The receiving part of the proposed communication device is implemented by a circuit comprising a matching unit with a communication line 9, the output of which is connected to the first inputs of two multipliers 10, 11, the second inputs of which are connected to a common reference generator 12, while the second input of the multiplier 10 is directly connected to the reference generator, and the second input of the multiplier 11 through the phase shifter 13, the output of the multiplier 10 through the sequentially connected low-pass filter 14 and the ADC 15 is connected to common-mode inputs, and the output of the multiplier 11 through the low-pass filter 16 and the ADC 17 to the quadrature input am m-identical in structure to the channels for processing the received signal, each of which contains two memory elements 18, 19 for a duration T _i , four multipliers 20, 21, 22, 23, a subtractor 24, an adder 25, and two integrators 26, 27, and in-phase the input of the i-th channel is connected directly to the first inputs of the multipliers 20, 22, the quadrature input of the i-th channel is connected directly to the first inputs of the multipliers 21, 23, while the second inputs of the multipliers 12 and 13 are connected to the common-mode input of the channel through a common memory element 10 on duration T _i, and the second Rin rows of the multipliers 20 and 21 are connected to a quadrature input channel via the second memory element 19 at a duration T _i, the outputs of multipliers 20 and 23 through the adder 25 are connected to the input of the first channel integrator 26, and the outputs of multipliers 21 and 22 via the subtractor 24 are connected to the input of the second integrator channel 27. According to the invention, the receiving part of the device contains m channels tuned for different delays T _i , and not integrators with reset, but integrators with a sliding window, outputs of integrators through blocks are used in each channel allocations of module 28.29 are connected to the second adder of channel 30, and the output of adder 30 is the output of the ith channel and is connected to the corresponding input of the resolver 31.

Consider the operation of the device blocks in the transmission of characters. On the transmitting side, a pseudo-random digital sequence is stored in ROM 1. The information symbol a _i to be transmitted is fed to the input of the address generating device 6, which reads from the ROM 1 a fragment of the memory bandwidth of the corresponding length, and re-reads this fragment the corresponding number of times n _i .

The operation of the address generating device 6 is clocked through the frequency divider 7 by the carrier generator 5 itself, thereby providing an integer number of carrier frequency periods f ₀ during the repetition period of the expanding BSS T _i .

The digital BSS from the output of the ROM is converted into analog form using the DAC 2, filtered by a smoothing low-pass filter 3 and fed to the second input of the balanced modulator 4, the first input of which is supplied with a carrier frequency oscillation from the same generator 5. Thus, the signal at the output of the balanced modulator has view:

where A (t) is a periodic pseudo-noise sequence with a period T _i . This signal is transmitted to the communication line through the device matching with the communication line 8.

When passing through the communication line, the signal may experience distortion, so the signal at the input of the receiver has the form:

where B (t) is generally different from A (t). It is important, however, that B (t) retains the same periodicity.

Since the initial phase φ does not play a role in autocorrelation reception, we assume that it is equal to zero for simplicity of further calculations.

At the receiving side, the signal (6) passes through a matching device with a communication line 9, in which the noise located outside the signal band is filtered, and the working band is amplified by an amplifier with AGC. Then the signal goes to the analog multipliers 10, 11. At the second inputs of the multipliers, oscillations are generated by the generator 12 and the phase-shifting circuit 13. The oscillation frequency is approximately equal to ω ₀ , and the phase is shifted by a quarter of the oscillation period, relative to each other:

2cos (ω ₀ + Δω)) t

2sin (ω ₀ + Δω)) t

Δω is the difference between the carrier frequency and the frequency of the reference oscillator.

At the output of multipliers 10, 11 we obtain the following signals:

Next, the blocks 14, 16 of the analog filters filter out vibrations with a double frequency, and at their outputs the signals can be written as:

B (t) cosΔωt

From the output of the low-pass filter 14, 16, the signals arrive at the ADC 15, 17, where they are converted to digital form, and further processing takes place digitally. The digitized signals (8) are fed to the inputs of m autocorrelation reception channels of the same structure, each of which is configured for its delay time T _i .

The signals (8) received by the channel are delayed in it using memory elements 18, 19, and then the received two pairs of signals (direct and delayed) are fed to the inputs of multipliers 20-23. All further expressions refer to the channel tuned to the transmitted character a _i .

at 20

at 21

at 22

at 23

After summing and subtracting the corresponding blocks 25, 24 we get

In the following blocks 26, 27, the results are integrated over time (T-T _i ):

where E _S is the energy of the symbol.

Blocks 28, 29 perform the operation of finding the module, and block 30 summarizes the values of the modules. The output signal of the block 30 Y (T _i ) is the result of processing the received symbol by the i-th channel. If we take into account that Е _S , characterizing energy, is always positive, we can write:

, при любых Δω - сдвигах между частотой, несущей на предающей стороне, и частотой опорного генератора на приемной стороне.that is, at the output of the channel tuned to the symbol a _i , the processing result is equal to the signal energy multiplied by a periodic function, the minimum value of which is 1, and the maximum

, for any Δω - shifts between the frequency of the carrier on the transmitting side and the frequency of the reference oscillator on the receiving side.

The outputs of all channels are connected to the inputs of the resolver 31, which compares all Y (T _i ) with each other and assigns to the received symbol the value of a _j that corresponds to the channel with the maximum response.

To ensure clock synchronization, the solving device needs to know the value of the autocorrelation function Y (T _i ) at each time point. This is ensured by the use of integrators with a sliding window, which greatly simplifies the solution of the clock synchronization problem.

At the time of filing an application, a model of a device that transmits a signal modulated by an information sequence according to the proposed method to a communication line and a device for receiving and demodulating this signal from the communication line, the algorithm following the blocks 15 and 17, is implemented in digital form in the MATLAB environment. The experiments confirmed an increase in noise immunity compared to the Lange-Muller method, as well as the invariance of the data transmission method to the carrier frequency offset, the ability to work with the signal-to-noise ratio in the communication line is less than unity.

Information sources

1. Sklyar, Bernard. Digital communication. Theoretical Foundations and Practical Application, 2nd Edition .: Per. from English - M.: Williams Publishing House, 1403. - 1104 p.: Ill. - Paral. tit. English 2003.

2. Okunev Yu.B. Digital transmission of information by phase-shifted signals. M .: Radio and communication, 91, - 196 p.

3. A.S. No. 177471, Rakhnovich L.M. A method for detecting phase-shifted signals transmitted by the method of double relative phase manipulation. M .: TsNIIIPI, 1966.

4. Patent No. 2168869, Skripkin A.A., Scherbachev V.A. A method for demodulating signals with relative phase shift keying and a device for its implementation, 2001. (Prototype device).

5. Lange F. Correlation Electronics. Sudpromgiz 63. (Prototype method).

6. A.S. No. 451166, Schelkunov K.N., Okunev Yu.B., Babel E.S., Goncharov V.N. Communication system with phase difference modulation of the first order. M .: TsNIIIPI, 1975.

7. A.S. No. 543194, Schelkunov K.N., Babel E.S., Goncharov V.N. Communication system with phase difference modulation of the first order. M .: TsNIIIPI, 1977.

Claims (2)

1. A method of transmitting information using noise-like signals, including modulating the carrier wave with a noise-like signal on the transmitting side, transmitting the modulated signal through the communication line, finding the autocorrelation function Y (τ) of the signal on the receiving side and deciding on the value of the transmitted symbol by comparative analysis of Y values (τ) calculated for various τ, characterized in that a periodic pseudo-noise sequence is used as a modulating noise-like signal, each Creed α _i alphabet encode periodic noise-like signal (NLS) with its different from other repetition period T _i, and on the reception side calculated values of the autocorrelation function Y (τ) at the points τ = T _i and assign the received symbol, the value α _j, for which Y (τ = T _j ) turned out to be maximum. 2. A device for transmitting information using noise-like signals, consisting of a transmitter, a communication line and a receiver, in which the transmitter contains a carrier frequency generator, a balanced modulator, a matching device with a communication line, and the output of the balanced modulator is connected to the communication line through a matching device with a communication line , the first input of the balanced modulator is connected to the output of the carrier frequency generator, while the receiver contains a second matching device with a communication line, the output of which is connected to the first inputs of the multipliers, the second inputs of which are connected to a common reference oscillator, with the second input of the first multiplier connected directly to the reference generator, and the second input of the second multiplier connected through a phase shifter, the output of the first multiplier through a low-pass filter connected in series and an analog-to-digital converter inputs, and the output of the second multiplier through the second low-pass filter and the second analog-to-digital converter is connected to quadrature inputs m-identical in the channel of the processing of the received signal, the outputs of which are connected to the resolver, while
each channel contains four multipliers, two memory elements, an adder, a subtractor and two integrators, the in-phase input of the i-th channel connected directly to the first inputs of the first and third channel multipliers, the quadrature input of the i-channel connected directly to the first inputs of the second and fourth channel multiplier, while the second inputs of the first and second channel multiplier are connected to the common-mode channel input through a common memory element for the duration T _i , and the second inputs of the third and fourth multipliers the channel is connected to the quadrature channel input through the second common memory element for the duration T _i , the outputs of the first and fourth channel multipliers through the adder are connected to the input of the first channel integrator, and the outputs of the second and third channel multipliers through the subtractor are connected to the input of the second channel integrator, characterized in that a permanent storage device is introduced into the transmitter, the output of which is connected to the second input through a digital-to-analog converter and a smoothing low-pass filter a balanced modulator, as well as an address generation device, the clock input of which through a frequency divider is connected to the output of the carrier frequency generator, and integrators with a sliding window are used in the receiver in each channel, the outputs of the channel integrators are connected to the second channel adder through the module selection blocks, and the output of the second the channel adder is connected to the corresponding input of the deciding device.