RU2214690C2 - Method reconstructing transmitted information signals after their passage through communication channel - Google Patents

Abstract

FIELD: exchange of discrete information with use of communication systems with various types of modulation. SUBSTANCE: technical result of invention consists in transmission to user of information on authenticity of signal belonging to specific signal region, on quality of through discrete communication channel, in optimization in process of reception of dimensions and configuration of uncertainty zones depending on quality of communication channel. In correspondence with invention method reconstructing transmitted information signals after passage through communication channel identifies signal regions, uncertainty zones and characteristic zones, signals received in analog form are divided into orthogonal components by correlation method, belonging of received signal to particular signal region, to uncertainty zone and characteristic zone is determined in the form of its numbered orthogonal components. EFFECT: transmission of authentic information to user. 4 dwg

Description

 A method of recovering transmitted information signals after passing them through a communication channel relates to the field of discrete information exchange using communication systems with various types of modulation.

 There is a method of recovering transmitted information signals while simultaneously receiving information about the signal quality, at which a plurality of phase-modulated digital symbols are received, the received symbols are identified by their belonging to the signal areas, and information is received on the quality of the received phase-modulated digital symbols (see RF patent 213061, MKI 6 H 04 L 27/22, publ. In BI 16.10.06.98)) [1].

 The disadvantage of this method is the impossibility of its use in relation to multi-position ensembles of signals with amplitude-phase shift keying (AFM), since all operations of the method are based on actions with phase estimates of the received symbols without taking into account their amplitude.

 There is also a method of recovering transmitted information signals with amplitude-phase modulation after they pass through a communication channel, which consists in the reception of signals transmitted through a communication channel, the signals received in the analog form are divided into orthogonal components by the correlation method, and they are converted from analog to digital form, determine the belonging of the received signal in the form of its digitized orthogonal components to a specific signal area (see RF patent 2054810, MKI 6 H 04 L 27/22, H 03 D 5/00, 1/00, publ. BI 5, 02.20.96)) [2].

 The disadvantages of this method are as follows.

 Firstly, according to the known method, the signal areas are determined based on a given signal to noise ratio. At the same time, in real communication systems, the conditions for transmitting information symbols and, accordingly, the signal-to-noise ratio can significantly differ from the nominal value and, in addition, change during a communication session. The known method does not allow to take this factor into account and, accordingly, to carry out optimal signal reception.

 Secondly, the known method does not allow the consumer to transmit information about the reliability of the identification of the signal by its belonging to a specific signal area, since, in particular, it does not involve the allocation of zones of uncertainties. Meanwhile, the determination and transmission to the consumer of information on the reliability (reliability) of a signal belonging to a specific area is a mandatory operation for most modern Viterbi convolutional decoders, which are widely used in information transmission systems [3].

 Of the known technical solutions, the closest to the patented method (prototype) is a method for recovering transmitted information signals after passing them through a communication channel, which consists in isolating a vector field within which reliable signal reception is possible, and sharing the selected field in accordance with the adopted scheme the location of the vectors of the transmitted signals in amplitude and phase to the signal areas, assign to each point of the signal area the same signal symbol that has The ctor of the transmitted signal around which the region is formed is allocated along the boundaries of the signal areas of the uncertainty zone, assigned to each point of these zones the first additional signal symbol, information signals transmitted through the communication channel are received, the signals received in analog form are divided into orthogonal components by the correlation method, determined their values in analog form, convert the values of the orthogonal components from analog to digital, by digitizing the analog quantities orthogonal components, determine the status of a received signal as its orthogonal components of the digitized signal to a particular area and the area of uncertainty is determined for correcting the amplitude of the received signal and the phase value, the identified signal is converted into a form suitable for consumer use (see. RF patent 2066926, MKI 6 H 04 L 27/22, publ. in BI 26.06.06.96) [8].

 The disadvantages of this method are as follows.

 1. The known method does not involve transmitting to the consumer information about the reliability of the identification of the signal, ie the reliability of the calculated membership of the signal in a specific signal area. Meanwhile, without such information, the functioning of Viterbi “soft” convolutional decoders [3], which is one of the main types of decoders in modern communication systems [4], is impossible.

 2. The known method does not allow calculating and transmitting to the consumer information on the quality of the communication channel, which in the general case is determined not only by the signal-additive white Gaussian noise ratio, but also by multiplicative noises such as phase noise of frequency converters, as well as impulse noise. Information about the quality of the communication channel, defined as the signal-to-noise ratio by instruments such as a spectrum analyzer, is incomplete because it does not take into account the state of the tracking systems used for receiving and demodulating, primarily the phase noise of the carrier frequency recovery system and the jitter of the clock synchronization system.

 Therefore, even the use of an operation external to the known method for calculating the signal-to-noise ratio does not give the consumer complete and reliable information about the quality of the communication channel, since the operations of the known method (separation of signals received in analog form into orthogonal components by the correlation method, conversion of the value of orthogonal components from analogue in digital form, determination for the received signal of correcting values for amplitude and phase) among other operations form a digital information transmission channel [5].

 3. The known method does not allow to optimize the process of receiving the value of the zones of uncertainty depending on the quality of the communication channel. Meanwhile, for the optimal implementation of the procedures for recovering transmitted information signals through the communication channel, the uncertainty zones should decrease (increase) while improving (deteriorating) the quality of the communication channel.

 4. The operations of digitizing the orthogonal components used in the known method several times during the duration of a time signal unit and the subsequent operations on the data received in each digitization cycle generally make sense (correct) only for unlimited (unfiltered) signals in band.

 Real communication systems, in which the level of inter-channel interference is strictly normalized, use not only effective band-pass filtering, but also special measures to form the most compact spectrum such as the use of predistortion filters. In addition, the well-known method itself involves limiting the signal over a frequency band (integration, integration with a reset, filtering in the low-pass filter), which is part of the operation of dividing analog signals into orthogonal components by the correlation method.

 Under these conditions (bandwidth limitation of the signal), the digitization of its quadrature components with a digitization cycle exceeding the normalized limit (established by Kotelnikov's theorem on counts) does not lead to any additional information about the signal or noise.

 In real communication systems, the influence of factors such as multipath signal propagation, its bandwidth restriction by filters with high squareness and intersymbol interference (MSI) generally lead to the fact that the trajectory of the signal point (until the decision is made) along the vector field becomes practically uninformative and at least not allowing to increase the reliability of the reception.

The technical result of the patented method is as follows:
a) transmitting to the consumer information on the reliability (reliability) of the signal belonging to a specific signal area (including the use of this information in the Viterbi soft decoder);
b) transmitting to the consumer information on the quality of the through discrete communication channel (which includes not only the quality of the physical channel for the distribution of radio waves, but also the quality of the conversion of the signal spectrum and tracking systems used in reception and demodulation);
c) optimization in the process of receiving sizes and configurations of uncertainty zones depending on the quality of the communication channel;
d) making optimal (according to the Kotelnikov-Siegert criterion) decisions on whether the received signal belongs to a specific signal area is invariant with respect to the degree of filtering of the spectrum of the transmitted and received signals.

The specified technical result is achieved by performing the following operations on the signal:
- allocate a vector field within which reliable signal reception is possible;
- share the selected field in accordance with the adopted arrangement of the vectors of the transmitted signals in amplitude and phase into signal areas;
- assign to each point of the signal region the same signal symbol, which according to the scheme has a vector of the transmitted signal around which the region is formed;
- allocate uncertainty zones along the boundaries of the signal areas;
- Assign to each point of these zones the first additional signal symbol;
- distinguish characteristic zones in signal areas;
- Assign to each point of these zones a second additional signal symbol;
- carry out the reception of information signals that have passed through the communication channel;
- divide the signals received in analog form into orthogonal components by the correlation method;
- determine their values in analog form;
- convert the values of the orthogonal components from analog to digital, by digitizing the analog values of the orthogonal components;
- determine the belonging of the received signal in the form of its digitized orthogonal components to a specific signal region, the uncertainty zone and the characteristic zone;
- determine the corrected value for the received signal in amplitude and phase;
- convert the identified signal into a form convenient for use by the consumer;
- the first additional signal symbol is transmitted to the consumer as information about the reliability of the signal belonging to a specific area;
- the second additional signal symbol is transmitted to the consumer as information about the quality of the communication channel, the average value of the second additional signal symbol is determined for all received information signals, the selected ambiguity zones are corrected depending on the average value of the second additional signal symbol.

 The problem is achieved in that in the method of recovering transmitted information signals after passing them through the communication channel, a vector field is isolated, within which reliable signal reception is possible, the selected field is divided in accordance with the accepted arrangement of the vectors of the transmitted signals in amplitude and phase into signal areas, assign to each point of the signal region the same signal symbol, which according to the scheme has a vector of the transmitted signal around which the region is formed, the boundaries of the signal areas of the uncertainty zone, assign a first additional signal symbol to each point of these zones, receive information signals transmitted through the communication channel, divide the signals received in the analog form into the orthogonal components by the correlation method, determine their values in the analog form, and convert the values of the orthogonal components from analogue in digital form, by digitizing the analog values of the orthogonal components, determine the ownership of the received signal in in the form of its digitized orthogonal components to a specific signal region and uncertainty zone, a correction value for the received signal in amplitude and phase is determined and the identified signal is converted into a form convenient for use by the consumer.

 According to the invention, when implementing the method, characteristic zones are additionally distinguished in the signal areas, a second additional signal symbol is assigned to each point of these zones, the belonging of the received signal in the form of its digitized orthogonal components to a specific characteristic zone is determined, the first additional signal symbol is transmitted to the consumer as information on the reliability of belonging signal to a specific area, the second additional signal symbol is transmitted to the consumer as quality information the communication channel, determine the average value of the second additional signal symbol for all received information signals, carry out the correction of the selected zones of uncertainty depending on the average value of the second additional symbol.

 In FIG. 1 shows a selected vector field with signal vectors located on it, divided into signal areas; figure 2 shows a vector field divided into signal areas with highlighted areas of uncertainty; figure 3 shows the principle of allocation of characteristic zones; Fig 4. shows the relationship between areas of uncertainty and characteristic zones.

и т. д., соответствующих применяемому в системе связи М-позиционному ансамблю сигналов, где m= log₂M - число битов информации, передаваемых одним сигнальным вектором. Разделяют выделенное поле на сигнальные области (см. фиг.1) в соответствии с принятой схемой расположения векторов

передаваемых сигналов на векторном поле, при этом присваивают каждой точке сигнальной области то же значение, которое имеет по схеме вектор передаваемого сигнала, вокруг которого образована эта область. На фиг.1. приведен пример наиболее распространенного в системах связи 4-позиционного ансамбля фазоманипулированных сигналов ФМ-4 и показано присвоение сигнальным областям значений S_A, S_B, S_C, S_D. При этом М=4; m=2. По границам сигнальных областей выделяют зоны неопределенности (размеры которых зависят от первоначально заданного соотношения сигнал/шум, вида и уровня помех) и присваивают каждой точке зоны неопределенности первый дополнительный символ S¹, отличающий эти точки от других точек данного сигнального поля (см. фиг.2, где каждой точке зоны неопределенности, соответствующей сигнальной области, присваивают сигнальные символы S¹ _A S¹ _B, S¹ _C, S¹ _D. В пределах сигнальных областей выделяют характерные зоны независимо от выделенных зон неопределенности (см. фиг.3, где каждой точке характерной зоны присвоен второй дополнительный сигнальный символ S² _A, S² _B S² _C, S² _D). Соотношение между зонами в пределах одной сигнальной области (на примере области вектора

иллюстрирует фиг.4. Поскольку в общем случае оптимальный М-позиционный ансамбль сигналов строится путем решения задачи наиболее плотной укладки М сфер одинакового радиуса в М-мерном пространстве или задачи наиболее плотной укладки М окружностей на плоскости [6,7], то мажорирующим фактором помехоустойчивости такого ансамбля является минимальное расстояние между центрами окружностей этого М-позиционного ансамбля d_min. Следовательно, характерные зоны для i-й сигнальной области, которые должны нести информацию о качестве канала связи, целесообразно строить в виде множества точек S² _i так, что:
S $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ ∪S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ = S_i;
S $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ ⊂S_i; S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ ⊂S_i
S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ ∩S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ = ⌀;
i - номер сигнальной области; i={А, D, С...};
S_i - полное множество точек i-й сигнальной области
S³ _i - окружность с радиусом

Попадание сигнальной точки в характерную зону несет важную информацию о качестве канала связи: чем чаще сигнальные точки попадают в множество точек S² _i, тем хуже качество канала связи.A method of recovering transmitted information signals after passing through a communication channel consists of the following actions. Preliminarily, depending on the type and condition of the telecommunication channel and the equipment used, the sizes of the vector field are determined, within which reliable signal reception is possible. The data transmission and reception scheme provides for a certain organization of the arrangement of signal vectors

etc., corresponding to the M-position ensemble of signals used in the communication system, where m = log ₂ M is the number of information bits transmitted by one signal vector. The selected field is divided into signal areas (see Fig. 1) in accordance with the accepted arrangement of vectors

transmitted signals on a vector field, at the same time, each point of the signal region is assigned the same value as the vector of the transmitted signal, around which this region is formed, according to the scheme. In figure 1. an example of the most common 4-position ensemble of phase-shifted FM-4 signal ensembles in communication systems is given and the assignment of S _A , S _B , S _C , S _D values to signal areas is shown. Moreover, M = 4; m = 2. Uncertainty zones (the sizes of which depend on the initially specified signal-to-noise ratio, type and level of interference) are distinguished along the boundaries of the signal regions and each first point of the uncertainty zone is assigned the first additional symbol S ¹ distinguishing these points from other points of the given signal field (see Fig. 2, where each point of the uncertainty zone corresponding to the signal area is assigned signal symbols S ¹ _A S ¹ _B , S ¹ _C , S ¹ _D. Within the signal areas, characteristic zones are distinguished regardless of the allocated zones indefinitely 3 (where each point of the characteristic zone is assigned a second additional signal symbol S ² _A , S ² _B S ² _C , S ² _D ). The relationship between the zones within the same signal region (for example, the vector region

Figure 4 illustrates. Since in the general case the optimal M-position ensemble of signals is constructed by solving the problem of the most dense packing of M spheres of the same radius in the M-dimensional space or the problem of the most dense packing of M circles on the plane [6,7], the minimum distance is the major factor in the noise immunity of such an ensemble between the centers of the circles of this M-position ensemble d _min . Therefore, the characteristic zones for the i-th signal region, which should carry information about the quality of the communication channel, it is advisable to build in the form of a set of points S ² _i so that:
S $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ ∪S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ = S _i ;
S $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ ⊂S _i ; S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ ⊂S _i
S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ ∩S $\genfrac{}{}{0ex}{}{\text{3}}{\text{i}}$ = ⌀;
i is the number of the signal region; i = {A, D, C ...};
S _i - the full set of points of the i-th signal region
S ³ _i - circle with radius

A signal point entering a characteristic zone carries important information about the quality of the communication channel: the more often the signal points fall into the set of points S ² _i , the worse the quality of the communication channel.

Moreover, the cases of falling into the zones of points S ² _i fundamentally differ from the case of falling into the zones of points 8 ¹ _i (see Fig. 3). So, the hit of a signal point in the subzone F in this case does not lead to an error in determining the area A, moreover, this determination occurs with high reliability (the points F are guaranteed not to fall into the zone of uncertainty).

косвенно свидетельствует о высокой вероятности ошибок в других случаях. В самом деле, если бы вектор

оказался направленным в сторону области D (вектор

на фиг.3), произошла бы ошибка в символе, причем в этом случае не было бы даже установлено ненадежное определение области S_d, поскольку точка не попала бы в зону неопределенности.However, due to the uniform effect of noise in all directions of the signal field, such a magnitude of the noise vector

indirectly indicates a high probability of errors in other cases. In fact, if the vector

turned out to be directed towards the region D (vector

3), an error would occur in the symbol, in which case an unreliable determination of the region S _d would not even be established, since the point would not fall into the zone of uncertainty.

In general, we can assume that the symbol S ¹ _i carries information about the reliability of this symbol, and the average value of S ² _i - about the quality of the communication channel for the duration of the entire session (both due to averaging and due to a significant excess of the area of the zone S ² _i over the area of the zone S ¹ _i ).

In Fig. 4, horizontal hatching marks the points S ² _A belonging to the characteristic zone; vertical shading - points S ¹ _A belonging to the zone of uncertainty; both types of hatching indicate that the point belongs to two zones simultaneously.

 Based on the method for determining the zones of uncertainty and characteristic zones, four cases of belonging of signal points are possible (see table).

 For definiteness, we assume that the assignment of a point to the first or second additional signal symbol means that the value of the corresponding attribute of the point (additional signal symbol) is 1, otherwise it is 0. The implementation of these actions is carried out, for example, using a storage device with the required amount of memory, whose memory cells contain the necessary number of bits that provide the ability to perform these actions.

 Carry out the reception of information signals that have passed through the communication channel in accordance with the adopted scheme.

When receiving information signals, synchronize the operation of transmitting and receiving systems. Synchronization is carried out on service signals that are transmitted at the beginning and (or) during transmission in accordance with the adopted scheme. The received information signal S _p is the transmitted information signal S _p distorted when passing through the communication channel. In turn, the transmitted information signal S _p is a signal with a sending duration T and modulated in amplitude and phase in accordance with the selected scheme. The signal received in analog form is divided into orthogonal components by the correlation method and the values of the analog projections X _pr , Y _{pr are} determined. Next, the received signals are converted from analog to digital form X _c , Y _c , digitizing the analog values of X _pr , Y _p orthogonal components of the signal.

According to the obtained values of the orthogonal components in digital form, X _c , Y _c determine the identity of the signal to specific
- signal area;
- zone of uncertainty;
- characteristic zone.

After converting the signal to a convenient form (transcoding by a manipulation code, pairing of electrical interfaces), the consumer receives not only information about the transmitted signal S _p , but also data on the reliability of the demodulation performed (the first additional signal symbol S ¹ _i ) and the quality of the communication channel (second additional signal symbol S ² _i ). Moreover, the value of S ¹ _i = 1 means a low confidence probability of the performed identification of the symbol, and the value of S ¹ _i = 0 is high.

The current value of S ² _i = 1 means low current quality of the communication channel, and the value. S ² _i = 0 - high. The average value of S ² _i ; for all information signals during the communication session, we obtain the average value of S ² _cp , depending on the size of which the dimensions of the uncertainty zones are changed.

 At the same time, in the general case, the received signal is corrected for amplitude and phase. Check correction is carried out on service signals, which are agreed in advance, in accordance with the applicable scheme, the magnitude of the amplitude, phase and duration of the symbol.

Sources of information
1. RF patent 2113061, MKI 6 H 04 L 27/22, publ. in BI on 10.16.06.98

 2. RF patent 2054810, MKI 6 H 04 L 27/22, H 03 D 5/00, 1/00, publ. in BI 5 02/20/96

 3. Clark J., Jr., Kane J. Coding with error correction in digital communication systems. - M .: Radio and communications, 1987.- C. 231-233.

 4. Feer K. Wireless digital communications. Modulation and spreading methods. - M.: Radio and Communications, 2000. - C. 287.

 5. Calculation of noise immunity of discrete message transmission systems: Handbook / Ed. L.M. Finca. - M .: Radio and communication, 1981. - C. 4.

 6. Noise immunity and efficiency of information transmission systems / Ed. A.G. Zyuko. - M .: Radio and communications, 1985.- 272 p.

 7. Radio engineering information transmission systems / Ed. V.V. Kalmykova. - M .: Radio and communications, 1990. - C. 97-99.

 8. RF patent 2066926, MKI 6 H 04 L 27/22, publ. in BI 26.06.06.96, the prototype.

Claims (1)

 A method of recovering transmitted information signals after passing them through a communication channel, which consists in allocating a vector field within which reliable signal reception is possible, dividing the selected field in accordance with the accepted arrangement of the vectors of the transmitted signals in amplitude and phase into signal areas, assign at each point of the signal region, the same signal symbol that has a vector of the transmitted signal, around which the region is formed, is allocated along the boundaries of the signal areas of the zone of uncertainty, assign to each point of these zones the first additional signal symbol, receive information signals that have passed through the communication channel, divide the signals received in the analog form into the orthogonal components by the correlation method, determine their values in the analog form, and convert the values of the orthogonal components from the analog to digital form, digitizing the analog values of the orthogonal components, determine the membership of the received signal in the form of its digitized orthogonal components to a specific signal region and the uncertainty zone, determine the correcting value for the received signal in amplitude and phase, convert the signal into a form convenient for use by the consumer, characterized in that characteristic zones are distinguished in the signal regions, and each second point of these zones is assigned a second additional signal symbol, determine the belonging of the received signal in the form of its digitized orthogonal components to a specific characteristic zone, the first additional signal the second symbol is transmitted to the consumer as information about the reliability of the signal belonging to a specific signal area, the second additional signal symbol is transmitted to the consumer as information about the quality of the communication channel, the average value of the second additional signal symbol is determined for all received information signals, the selected uncertainty zones are adjusted depending on the value average value of the second additional character.

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