RU2277760C2 - Method for transferring information in communication systems with noise-like signals and a software product - Google Patents

Abstract

FIELD: communications engineering, in particular, technology for transferring information in communication systems with noise-like signals.

SUBSTANCE: in accordance to method, during transfer, stream of transferred bits of information signal is split on a series of transferred symbols, each one of transferred symbols having given duration is transformed, to one of previously given noise-like signals of same duration; a series of noise-like signals is transferred; during receipt optimal receipt is performed by correlation maximum with appropriate one of previously given noise-like signals for selecting transferred signals, while during transfer in each one of transferred signals a combination of k bits, where 0≤k≤n, is transformed to given noise-like signal, while a combination of remaining n-k bits of this symbol is transformed to temporal delay, during receipt a combination of k bits of each transferred symbol is determined, which provides maximal correlation and optimal receipt of current transferred symbol, delay value between correlation maximums is determined in each pair of transferred symbols following one another, on basis of which combination of n-k bits is determined for first transferred symbols in aforementioned pair.

EFFECT: increased information transfer speed.

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Description

Field of Invention

The present invention relates to communication technology, in particular to a method for transmitting information in communication systems with noise-like signals.

The current level of technology

Currently, data transmission systems using noise-like signals (BSS) (or spread-spectrum signals) are widely used, i.e. signals in which:

- the frequency band is much wider than the minimum necessary for data transmission;

- the expansion of the spectrum is carried out using the so-called expanding (or code) signal, which does not depend on the transmitted information;

- restoration of the original data by the receiver (narrowing of the spectrum) is carried out by comparing the received signal with a synchronized copy of the spreading signal.

A known method of transmitting information in communication systems with noise-like signals, in which the data stream is converted into blocks that are encoded using a pseudo-noise sequence, while additional information is transmitted by superimposing or not superimposing a pseudo-noise sequence on the transmitted video image signal (EPO application No. 0999548, publ. 10.05.2000).

This method is very complex and requires the use of a single pseudo-noise sequence to transmit one bit of information.

The closest analogue of the present invention is a method of transmitting information in communication systems with noise-like signals (spread spectrum systems using the direct sequence method), which consists in the fact that when transmitting, the stream of transmitted bits of the information signal is divided into a sequence of transmitted symbols, each of which contains a group of n ( n≥1) the next successive bits of said stream; converting at least a portion of each of said transmitted symbols having a predetermined duration into one of predetermined noise-like signals of the same duration; transmitting the sequence of noise-like signals obtained by such a conversion as said sequence of transmitted symbols; upon reception, optimal reception is performed to the maximum correlation with the corresponding one of the aforementioned predetermined noise-like signals to highlight the transmitted characters (US patent No. 6353627, publ. 05.05.2002). The disadvantage of this method is that for the transfer of additional information, it is necessary to use additional pseudo-noise sequences.

SUMMARY OF THE INVENTION

The purpose of the present invention is to develop such a method of transmitting information in communication systems with noise-like signals, which would increase the speed of information transfer and (or) reduce the ratio of the energy of one bit to the spectral density of noise required for transmitting information without increasing the information required for transmitting information frequency bands.

To solve this problem and achieve the indicated technical result in a method of transmitting information in communication systems with noise-like signals, which consists in the fact that during transmission, the stream of transmitted bits of the information signal is divided into a sequence of transmitted symbols, each of which contains a group of n (n≥1) consecutive bits of said stream; converting at least a portion of each of said transmitted symbols having a predetermined duration into one of predetermined noise-like signals of the same duration; transmitting the sequence of noise-like signals obtained by such a conversion as said sequence of transmitted symbols; when receiving, optimal reception is performed to the maximum correlation with the corresponding one of the aforementioned predetermined noise-like signals to highlight the transmitted symbols, in accordance with the present invention, a combination of k bits (0≤k <n) at predetermined positions in each said group is used for transmission of n bits for said conversion of said portion of each transmitted symbol to a corresponding one of said predetermined noise-like signals; converting a combination of the remaining (n-k) bits in the same group of n bits in accordance with the selected encoding method into a time delay in transmitting the next transmitted symbol; upon reception, a combination of k bits of each transmitted symbol is determined corresponding to that of the aforementioned predetermined noise-like signals, which ensured the aforementioned maximum of correlation at the optimal reception of the given transmitted symbol; find the delay between the mentioned maximums of correlation in each pair of successive transmitted symbols; determined by the found delay in accordance with the method inverse to the selected encoding method, a combination of (n-k) bits for the first transmitted symbol in said pair.

A feature of the method of the present invention is that pseudo-random sequences can be used as noise-like signals.

Finally, the difference (n-k) can be selected depending on the signal-to-noise ratio in the transmission path of the communication system used.

The same task with the achievement of the same technical result is solved in a software product that is executed on a computer in a method for transmitting information in communication systems with noise-like signals, in which when transmitting, the stream of transmitted bits of the information signal is divided into a sequence of transmitted symbols, each of which contains a group of n (n≥1) consecutive successive bits of the stream; converting at least a portion of each of said transmitted symbols having a predetermined duration into one of predetermined noise-like signals of the same duration; transmitting the sequence of noise-like signals obtained by such a conversion as a sequence of transmitted symbols; and when receiving, optimal reception is performed to the maximum correlation with the corresponding one of the predetermined noise-like signals to highlight the transmitted characters, in accordance with the present invention, the software product provides the following method operations: when transmitting: using a combination of k bits (0≤k <n) at predetermined positions in each said group of n bits for said conversion of said part of each transmitted symbol to the corresponding one of said predetermined x noise-like signals; converting a combination of the remaining (n-k) bits in the same group of n bits in accordance with the selected encoding method into a time delay in transmitting the next transmitted symbol; upon reception: determining a combination of k bits of each transmitted symbol corresponding to that of the aforementioned predetermined noise-like signals, which provided the aforementioned maximum of correlation with the optimal reception of this transmitted symbol; finding the delay value between the aforementioned correlation maxima in each pair of successive transmitted symbols; determining, by the found delay value, in accordance with the method inverse to said selected coding method, a combination of (n-k) bits for the first transmitted symbol in said pair.

Moreover, a feature of the software product is that the difference (n-k) is selected depending on the signal-to-noise ratio in the transmission path of the communication system.

In the current level of technology, no sources of information have been identified that would contain information about objects of the same purpose with the specified set of distinctive features, which allows us to consider the method and software product of the present invention new and having an inventive step.

Brief Description of the Drawings

The present invention is illustrated by drawings in which the same or similar elements are denoted by the same reference numerals.

Figure 1 illustrates the signal generation using modulation pseudo-noise sequence.

Figure 2 shows the spectrum of the signal generated in accordance with figure 1.

Figure 3 is a block diagram of a known spread spectrum signal transmission system using the direct sequence method.

Figure 4 illustrates the signals in the circuit of figure 3.

5 is a block diagram of a signaling system in which the method of the present invention is embodied.

Fig.6 illustrates the signals in the circuit of Fig.5 when transmitting additional information in accordance with the proposed method.

Detailed Description of Preferred Embodiments

Figure 1 illustrates the signal generation using modulation pseudo-noise sequence. To simplify further consideration of the processes, we assume that the modulation of the carrier oscillation is carried out using binary phase shift keying (QPS). The carrier oscillation 1 and the original binary sequence 2 (information signal) are supplied to the corresponding inputs of the first multiplier 6, the output of which is formed by a narrow-band signal 3, obtained as a result of phase manipulation of the original binary sequence 2. The phase-manipulated signal 3 is fed to the first input of the second multiplier 7, on the second input of which is fed a pseudo-noise signal in the form of a pseudo-random sequence (PSP) 4 from the output of the generator 8 of the PSP. The resulting phase-shifted noise-like signal (BSS) 5 is removed from the output of the second multiplier 7. Figure 1 shows the duration T of the binary discharge, which is equal to the duration of the SRP 3, as well as the duration τ _about one element of the SRP 4.

The main characteristic of the NPS is the signal base B, defined as the product of the width F of its spectrum and the duration T of this signal: B = F · T.

In digital communication systems that transmit information in the form of binary characters, the duration T and the speed C of the message transfer are the inverse values: T = 1 / C. Therefore, the signal base B = F / C characterizes the expansion of the spectrum of the NPS relative to the spectrum of the transmitted message. For the case shown in figure 1, the base of the NPS is numerically equal to the number N = T / τ ₀ elements of the SRP. The spectrum of the generated signal 5 is shown in Fig.2.

For definiteness, we assume that the 13-bit Barker code is used as the SRP in the system example for implementing the method of the present invention, i.e. the signal base is 13.

Figure 3 presents a block diagram of a system that implements a known method for transmitting a signal with a spread spectrum, carried out by the direct sequence method [Sklyar Bernard. Digital communication. Theoretical foundations and practical application .: Per. from English - M.: Williams Publishing House, 2003. - 746 p.], I.e. by manipulating the carrier wave with an information signal (input data), followed by the manipulation of this manipulated carrier wave with a pseudo noise spreading signal PSP.

On the transmitting side, the carrier wave generator 10 is connected to the first input of the first phase modulator 11, to the second input of which a bit stream of transmitted data 12 is supplied. The output of the first phase modulator 11 is connected to the first input of the second phase modulator 13, the second input of which is connected to the output of the PSP generator 14 Barker. The output of the second phase modulator 13 is connected to the transmitting antenna 15. The clock input of the SRP generator 14 is connected to the output of the clock generator 16, which is also connected to the input of the frequency divider 17, the output of which is connected to the synchronization input of the SRP generator 14.

On the receiving side, the receiving antenna 20 is connected through a series-connected amplifier 21 and a matched filter 22 to the input of the carrier oscillator 23 and the first input of the multiplier 24, the second input of which is connected to the output of the carrier oscillator 23. The output of the multiplier 24 is connected to the input of the threshold block 25. The output of the threshold block 25 is the output of the system.

All the blocks shown in figure 3, can be performed in the same way as in the closest analogue (US patent No. 6353627).

The operation of the system of figure 3 is illustrated by diagrams in figure 4. The signal from the carrier oscillation generator 10 is supplied to the first phase modulator 11, to the other input of which the input data 12 is also supplied as modulating signals (Fig. 4, a). From the output of the first phase modulator 11, the phase-shifted signal is fed to the second phase modulator 13, the other input of which receives a pseudo-random sequence (Barker code in this case) from the PSP generator 14 (Fig. 4, b). The operation of the generator 14 SRP is clocked by signals from the clock generator 16, and the frequency divider 17 provides a division of the frequency of these signals by the value of base B (in this example, B = 13). The output signal of the frequency divider 17 serves as a clock signal to start the generator 14 of the SRP. It should be noted that this invention does not address the timing of the timing of the SRP generator 14 with the input data, as well as the timing and synchronization of the transmitting and receiving sides of the system used. These issues are resolved by any method well known in the art, for example, in the same way as is done in the closest prior art (US Pat. No. 6,353,627).

The output of the second phase modulator 13 generates an output noise-like signal (Fig. 4, c) of the transmitting side (similar to the signal 5 in Fig. 1), which is transmitted to the antenna 15 of the transmitting side. At the receiving side, this signal enters the antenna 20, amplifies in the amplifier 21, and enters the matched filter 22. The impulse response of the matched filter 22 is a mirror image of the noise-like signal on the transmitting side. The signal compressed in the matched filter 22 (Fig. 4, d) is a pulsed radio signal, the high-frequency filling phase of which is set by the input information signal. Therefore, the signal from the output of the matched filter 22 is fed to the inputs of the multiplier 24 and the carrier oscillator 23. The carrier oscillation restored in the extractor 23 is also supplied to the multiplier 24. From the output of the multiplier 24, a pulse signal with a variable polarity (Fig. 4, e), determined by the high-frequency filling phase, enters the threshold unit 25 with a threshold voltage equal to zero. The decision to transmit 1 or 0 is made by the sign of the signal at the output of the threshold device 25 at the time of the end of the received signal.

The method of the present invention can be implemented with a system whose block diagram is shown in FIG. In this system, compared to the well-known system of the prior art (Fig. 3), a frequency divider 17 is excluded, and a bitstream of input data 12 is supplied to the information input of encoder 18, the clock input of which is connected to the output of the clock generator 16, and the output is connected to the synchronization input generator 14 PSP. For definiteness, we choose that the encoding method in this particular example consists in generating a time delay directly proportional to the digital code arriving at the encoder. In this case, the encoder 18 can be implemented similarly to the methods used in time-pulse digital-to-analog converters [Kukush V.D. Electro-radio measurements: Textbook for universities. - M .: Radio and communications, 1985. - 104 p.]. On the receiving side, to the output of the multiplier 24, in addition to the threshold block 25, the output of which is the first output of the system, the input of the decoder 26 is also connected, the output of which is the second output of the system. The block decoder is designed to determine the value of the transmitted characters in accordance with the selected encoding method and in the example considered in the application is intended to measure the time interval between each pair of successive pulses, which is proportional to the transmitted code. The decoder can be implemented similarly to that considered in [Shlyandin V.M. Digital measuring devices: Textbook for high schools. - 2nd ed., Revised. and add. - M .: Higher. school, 1981. - 162 p.] a digital meter of time intervals.

The method of transmitting information of the present invention is carried out in the system of figure 5 as follows.

The input data, which is a stream of transmitted bits of an information signal, is divided into a sequence of transmitted symbols, each of which contains a group of n (n≥1) next successive bits of this stream. This separation is carried out by any method known in the art, for example by means of a series-parallel converter in the form of a shift register. In each group of n bits, a combination of k bits (0≤k <n) is selected at predetermined positions. For definiteness, let n = 4, and k = 1 and this single bit is the fourth in each group of four bits (in each transmitted character of the sequence). For this case, the encoder 18 can be made in the form of a three-digit counter, to the installation inputs of which the bits from the first to the third in each incoming symbol are supplied. The subtraction input of this counter is the clock input of the encoder 18, and the output of the encoder 18 is the zeroing output of this counter.

The fourth bit of each transmitted symbol is fed directly to the first phase modulator 11 (Fig. 6, a), and its processing in blocks 11 and 13 is no different from the operations described above in Figs. 3 and 4. Similarly to that considered, the SRP is generated in the generator 14 SRP, but the beginning of this formation now depends on which combination of (nk) bits is written to the counter of encoder 18. Formation of the SRP in the generator 14 of the SRP starts only after the counter of the encoder 18 counts to 0, i.e. after receipt of the number of clock pulses at its subtracting input, which corresponds to the combination of (nk) bits recorded in it. As a result, the generation of the SRP will begin with a delay determined by this combination, which in each transmitted symbol may be different from the others. Therefore, pauses will appear in the signal from the output of the PSP generator 14 (Fig. 6, b), which will be transferred to the resulting signal of the transmitting side (Fig. 6, c), and the duration of each such pause will be Δt = τ ₀ · m, where m - the information contained in the combination of (nk) bits of the transmitted symbol.

The processing at the receiving side remains almost the same as for the well-known system (Figs. 3 and 4), but in addition to the threshold block 25, which decides what is the size of the fourth (in this example) bit in the transmitted symbol, the signal from the multiplier 24 also enters the decoder 26, which determines the additional delay in the arrival of the next transmitted symbol upon receipt of each pair of consecutive symbols. According to the present invention, the time of occurrence of a signal compressed in a matched filter is not known in advance and depends on the value of the transmitted information in bits one through three in the transmitted symbol. From the theory of optimal signal detection, an algorithm for optimal detection is known [Lezin Yu.S. Introduction to the theory and technique of radio systems: A textbook for universities. - M .: Radio and communications, 1986. - 57s]. The threshold device 25 (Fig. 5) is part of an optimal signal detector and is a decisive circuit that generates a voltage at the output, indicating that a decision is made on the presence of a signal at a given time if the voltage at its input exceeds the threshold voltage. The threshold voltage value is selected based on the characteristics of the signal and interference. As a threshold device, a comparator can be used [Titze U., Schenk K. Semiconductor circuitry: Reference manual. Per. with him. - M .: Mir, 1982. - 188 pp.], Which switches the output voltage level when the input signal continuously changing in time becomes lower than a certain negative level or above a positive certain level (threshold). The switching moment of the comparator fixes the time of appearance of the signal at the output of the matched filter, and the sign of the signal at this point in time at the input of the comparator determines the value of the transmitted bit 0 or 1.

In this example, as a decoder, you can also use a counter that starts after time T (the duration of the SRP signal) after the appearance of a pulse at the output of the threshold device 25 and counts the clock pulses until a signal from the output of the threshold device 25 arrives at its inhibitory input Then, the counting result in this counter of decoder 26 will be the information that was encoded on the transmitting side by a delay in the formation of the SRP. This combination of bits, together with the bit from the output of the threshold device, is that group of n bits formed during transmission.

It is easy to understand that the considered particular example is generalized to the case when k> 1, and a combination of (nk) bits does not necessarily follow in a row. It is clear that when transmitting to convert a part of k bits of each transmitted symbol, one of 2 ^k predetermined noise-like signals must be used. The combination of the remaining (nk) bits in the same group of n bits is converted into a time delay in transmitting the next transmitted symbol in accordance with the selected encoding method. At reception, a combination of k bits of each transmitted symbol is determined that corresponds to that of a predetermined noise-like signal that provides maximum correlation with the optimal reception of this transmitted symbol (this can be done by parallel switching on k matched filters, each of which has an impulse response corresponding to one of selected noise-like signals). After that, between the adjacent correlation maxima (in each pair of transmitted symbols following each other), the delay value is found and a combination of (nk) bits for the first transmitted symbol in this pair is determined in accordance with the method inverse to the encoding method selected during transmission.

As noise-like signals, it is possible to use pseudo-random sequences (SRP), as in the above example.

The considered method can be implemented not only in hardware, but also with the help of appropriate software, which, when executed on a computer (in the processor), provides the execution of the operations of this method associated with at least the choice of a combination of k bits (where 0≤k < n) at predetermined positions, converting the combination of the remaining (nk) bits in the same group of n bits in accordance with the selected encoding method into a time delay in the transmission of the next transmitted symbol, determining the combination and k bits of each transmitted symbol corresponding to that of the predetermined noise-like signals that provided maximum correlation at the optimal reception of the given transmitted symbol, finding the delay value between the correlation maxima in each pair of successive transmitted symbols, and determining by the found delay value in in accordance with the method opposite to the selected encoding method, a combination of (nk) bits for the first transmitted symbol in a pair. A specific program can be compiled by the programmer in the desired programming language.

Thus, the method of the present invention allows additional information to be transmitted without expanding the required bandwidth. In the above example, it is possible to increase the information transfer rate by almost three times. Of course, the payment for such an increase in the transmission rate is the requirement to increase the signal-to-noise ratio in the information receiving path.

The information transfer method of the present invention can be used in communication systems where the noise and interference levels can change over time. With a high level of interference, such a communication system works like a conventional communication system, for example, in the IEEE 802.11 standard. As the interference environment improves, the transmission speed can be increased by introducing a delay between successive transmitted symbols (SRP transmissions).

Industrial applicability

The present invention can be used in communication systems with noise-like signals.

The scope of this invention is not limited to the examples given in the description, which are merely illustrative, but is determined by the appended claims, which should be considered with regard to possible equivalents.

Claims (4)

1. A method of transmitting information in communication systems with noise-like signals, which consists in the fact that: when transmitting, the stream of transmitted bits of the information signal is divided into a sequence of transmitted symbols, each of which contains a group of n≥1 consecutive successive bits of the stream; converting each of the transmitted symbols having a predetermined duration into one of predetermined noise-like signals of the same duration; transmitting the sequence of noise-like signals obtained by such a conversion; when receiving, optimal reception is performed to the maximum correlation with the corresponding one of the predetermined noise-like signals to highlight the transmitted characters, characterized in that when transmitting in each of the transmitted symbols, a combination of k bits, where 0≤k <n, at predetermined positions is converted into one of the predetermined noise-like signals; a combination of the remaining n-k bits of the same transmitted symbol in accordance with the selected encoding method is converted into a time delay when generating a noise-like signal; when receiving, a combination of k bits of each transmitted symbol is determined, corresponding to that of the predetermined noise-like signals, which provided maximum correlation at the optimal reception of the given transmitted symbol; determining the delay between the correlation maxima in each pair of successive transmitted symbols, which determines, in accordance with the method inverse to the selected encoding method, a combination of n-k bits for the first transmitted symbol in the said pair. 2. The method according to claim 1, characterized in that the difference n-k is selected depending on the signal-to-noise ratio in the transmission path of the communication system. 3. A software product that is executed on a computing device in a method for transmitting information in communication systems with noise-like signals, in which when transmitting, the stream of transmitted bits of the information signal is divided into a sequence of transmitted symbols, each of which contains a group of n≥1 consecutive successive bits of the stream; converting each of the transmitted symbols having a predetermined duration into one of predetermined noise-like signals of the same duration; transmitting the sequence of noise-like signals obtained by such a conversion; when receiving, optimal reception is performed to the maximum correlation with the corresponding one of the predetermined noise-like signals to highlight the transmitted characters, characterized in that when transmitting in each of the transmitted symbols a combination of k bits, where 0≤k <n, at predetermined positions are converted into one of the predetermined noise-like signals; a combination of the remaining n-k bits of the same transmitted symbol in accordance with the selected encoding method is converted into a time delay when generating a noise-like signal; when receiving, a combination of k bits of each transmitted symbol is determined, corresponding to that of the predetermined noise-like signals, which provided maximum correlation at the optimal reception of the given transmitted symbol; determining the delay between the correlation maxima in each pair of successive transmitted symbols, which determines, in accordance with the method inverse to the selected encoding method, a combination of n-k bits for the first transmitted symbol in the said pair. 4. The software product according to claim 3, characterized in that the difference n-k is selected depending on the signal-to-noise ratio in the transmission path of the communication system.

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