RU2405253C1 - Transmitting and receiving method of discrete information in radio line with pseudo-random tuning of operating frequency - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: N-fold repetition of each information bit occurs on transmitting end of radio line, where N≥3, in K frequency positions, and transmitted radio signal is received on receiving end of radio line, probability of error of signal reception of p_er1 bit is calculated, values of single received bits are ranged in compliance with their error probabilities, then all ranged M-sequences of single received bits, where M=N, M=N-2,…, M=3, are decoded at one and the same time as per majority circuit and error probability of p_er(M) is calculated for each M value, obtained p_er(M) values are compared to each other and final decision is taken on the value of transmitted bit, which corresponds to minimum p_er(M) value.

EFFECT: increasing interference immunity of received discrete information.

4 cl, 8 dwg

Description

The invention relates to radio communications, and in particular to the transmission of discrete information by signals with pseudo-random tuning of the operating frequency (MFC).

The proposed method can be used for radio links with frequency hopping for long distances, for example on satellite links.

There is a method of transmitting discrete information in a radio line with pseudo-random tuning of the working part (see Gorshkov V.V., Kuksin O.V., Rubtsov S.L., Sukhov L.V. Military communication systems with pseudo-random tuning of the working frequency. Foreign electronics, 3, 1986, pp. 3-13), which also concludes that packets are formed from the information signal at the transmitting end, which modulate the respective carrier frequencies and radiates into space, at the receiving end of the radio link, the signal is received, converted to an intermediate frequency, demodulated, and per go to the terminal equipment.

The disadvantage of this method is the relatively low noise immunity due to the fact that when the frequencies of the subscriber’s reception coincide with the frequencies of the interfering stations, the probability of erroneous signal reception at this frequency increases sharply, which will lead to a deterioration in the quality of communication below the permissible level.

There is also a method of transmitting information to a radio line with a pseudorandom restructuring of the working part (see RF patent No. 2099886, class H04L 5/02, published in 1997), which consists in the fact that packets are formed from the information signal by means of which modulate the respective carrier frequencies and radiate into space. The carrier frequency is selected taking into account the interference situation at the frequencies specified by the pseudo-random sequence generators. Signal reception, its conversion to an intermediate frequency, demodulation is performed on all K channels. The conclusion on which of the channels the information was transmitted is made based on the analysis of the address of the received packet.

The disadvantage of this method is also the relatively low noise immunity. This is explained by the difference in the interference environment at the transmitting and receiving ends of the radio line, which is characteristic of long-distance radio lines, which can lead to the choice of the operating transmission frequency affected by interference at the receiving end, and, consequently, to a deterioration in communication quality below the permissible level.

The closest in technical essence to the claimed invention (prototype) is a method for transmitting discrete information in a radio line with a pseudo-random tuning of the operating frequency and a device that implements it (see RF patent No. 2178237, CL HB04 1/713, published in 2001, BI No. 10). The known method is that at the transmitting end the input signal is divided into blocks of a given length, the carrier frequency of the transmitter is tuned in accordance with the code of one of two or more pseudorandom sequences, modulated by the corresponding packet and emitted into space, receive the radio signal simultaneously at all frequencies according to the codes of pseudorandom sequences, select the frequency channel over which the transmission was carried out, convert the signal to an intermediate frequency, amplify, demodulate Decoded packet and the information signal supplied to the terminal device. At the receiving end of the radio line, simultaneously with the reception of the information signal, they receive at all frequencies corresponding to subsequent clock cycles of pseudorandom sequence codes, monitor the level of interference at these frequencies and, if there is interference at the controlled frequency of the work program, generate control information for tuning the correspondent transmitter to a frequency of least interference. Form information packets by attaching control information to the information signal blocks, modulate the carrier of their transmitter with a corresponding information packet, and emulate the modulated carrier into space. At the transmitting end, simultaneously with the radiation of the modulated carrier into space, an information signal is simultaneously received at all frequencies according to pseudo-random sequence codes. Select the frequency channel through which the transmission was carried out, convert the signal to an intermediate frequency, amplify and demodulate, decode the packet with the allocation of a block of the information signal received at the terminal device, and a block containing information on controlling its transmitter for its subsequent tuning to the frequency with the lowest optimal interference level for the receiving end.

The disadvantage of the closest analogue is the relatively low noise immunity, since the control of the law of tuning the frequency of the transmitter in radio lines with a long communication range is inefficient due to the significant excess of the propagation time of the signal through the feedback channel for the duration of the signal at this frequency position. In addition, the control of the law of tuning the frequency of the transmitter is ineffective in conditions of deliberate interference, when the period of tuning in the frequency of the interference coincides with the period of pseudo-random tuning of the operating frequency of the radio line.

The aim of the present invention is to develop a method for transmitting and receiving discrete information in a radio line with a pseudo-random tuning of the operating frequency, which improves the noise immunity of receiving discrete information due to majority decoding and the use of error probability values for a single bit reception.

This goal is achieved by the fact that in the known method of transmitting and receiving discrete information in a radio line with pseudo-random tuning of the operating frequencies, information packets are formed at the transmitting end of the radio line by dividing the information signal into blocks of a given length, the carrier frequency of the transmitter is tuned to the frequency corresponding to the pseudo-random sequence code, modulate the carrier frequency of the transmitter and emit a radio signal, and at the receiving end of the radio line receive the transmitted radio signal, convert it o at an intermediate frequency, amplify and demodulate. At the transmitting end of the radio link, information packets are formed in the form of blocks of a given length with N-fold repetition of each information bit, where N≥3. At the receiving end, each bit of the information signal is received N times at K frequency positions corresponding to the pseudo-random sequence code. At each frequency position, the error probability of a single bit reception is calculated, for which the power of the mixture of the received signal and the interference P _{c + n} are measured and stored at the frequency of the nth step of the pseudo-random tuning of the operating frequency. In the time interval of the (n-1) -th cycle at the frequency of the n -th cycle of the pseudo-random tuning of the operating frequency, the interference power R _{p is} measured and stored. Then, according to the obtained data, the signal power P _{c is} calculated as the difference between the power of the signal mixture and the interference P _{s + p} and the interference power P _p . Next, h ^{2 is} calculated as the ratio of the signal power P _c to the interference power R _p and, knowing the type of signal modulation, the error probability of the one-time received bit p _osh1 = f (h ² ) at the nth step of the pseudo-random tuning of the operating frequency is found. The values of the one-time received bit and the corresponding error probability value _{psh1 are stored} . The values of the once received bits are ranked in accordance with the error probabilities p _osh1 . Then, simultaneously, for ranked M-sequences of once-received bits, where M = N, M = N-2, M = N-4, ..., M = 3, majority decoding is applied, in which the value of the transmitted bit is received that is more times contained in a sequence of M once received bits. At the same time, for each value of M, the probability of error p _osh (M) is calculated by the formula

- число сочетаний из М по i; q_kj - вероятность правильного приема (1-р_ош1)_k или ошибки р_{ош 1k} k-го однократно примятого бита в j-м сочетании i неверно принятых битов в М - последовательности.where M is the number of repetitions of the information bit;

- the number of combinations from M to i; q _kj - the probability of correct reception (1-p _{osh1) k} or p errors _{err 1k} k-th bit in the flattened once j-th combination i incorrectly received bits in M - sequences.

Compare values obtained p _err (M) for each M is selected between itself and the decision on the transmitted bit, which corresponds to the minimum value of p _err (M).

Owing to a new set of essential features, the method implements the principle of selective majority decoding according to the probability of receiving errors N times the repeated information bit and making the final decision on the transmitted bit after comparing the calculated error probabilities p _os (M) with each other for all ranked M-sequences of once received bits This is what improves the noise immunity of receiving discrete information in a radio line with a pseudo-random tuning of the operating frequency.

The claimed method is illustrated by drawings, which show:

figure 1 - N-fold repetition of the information bit when it is transmitted at different frequency positions;

figure 2 - the probability of error with a single reception of a bit;

figure 3 - ranking of decisions about a once transmitted bit depending on the probability of error;

4 is a complete N-selection of decisions about a once transmitted bit for majority decision making;

5 is a selection of (N-2) -x best decisions about a once transmitted bit for a majority decision;

6 is a selection of the three best decisions about a once transmitted bit for majority decision making;

Fig.7 - the total sample length and the probability of error of the final decision on the value of the transmitted bit;

Fig is a General view of the dependence of p _OSh from h ² .

The possibility of implementing the inventive method is explained as follows. In the presence of natural or deliberate interference, to improve the noise immunity of the radio line, signals with a pseudo-random tuning of the operating frequency with a controlled law of tuning are used. In long-distance radio lines, for example, in satellite communication lines, the interference situation at its transmitting and receiving ends varies greatly, and the length of time a radio signal with frequency hopping at one frequency position is significantly shorter than its propagation time. In this case, in the presence of natural or deliberate interference, the control of the pseudo-random tuner of the working frequency using the feedback channel is not effective. This contradiction is eliminated in the inventive method by adapting in probability of error the majority decision scheme at the receiving end of the radio link.

When working with frequency hopping signals, a random sequence generator generates commands for tuning the operating frequency (carrier) according to an equally probable pseudo-random law.

Known methods are when, at the transmitting end of a radio link, a sequence of information bits is divided into blocks of a given length (packets). Each packet is transmitted and received N times at the K frequency positions corresponding to the pseudo-random sequence code (Fig. 1). Moreover, each information bit is transmitted and received N times, which allows the use of a majority decision scheme at the receiving end of the radio link.

In real radio links, the probability of a mistake in a single bit reception at different frequency positions is different (Fig. 2). In this case, the significance of single decisions in the majority decoding scheme is different, which is not taken into account in the known analogues and prototype.

It is known that to increase the fidelity of majority decoding, it is advisable to exclude one-time decisions about the transmitted bit with a high probability of error (see Smirnov P.V., Dunin-Barkovsky I.V. Course in probability theory and mathematical statistics for technical applications, 2nd ed. - M .: Nauka, 1965, p. 63-67).

Thus, the proposed method proposes:

1) to rank decisions on a once transmitted bit depending on the probability of error (Fig. 3);

2) generate ranked once received bits, each time discarding 2 single decisions with a maximum error probability, where M = N (full sample, FIG. 4), M = N-2 (FIG. 5), M = N-4, ..., M = 3 (minimum sample, Fig.6);

3) simultaneously, for all ranked M-sequences, apply majority decoding, in which the value of the transmitted bit is received, which is contained more than once in the sequence of M once received bits;

4) at the same time, solving the exhaustive problem, for all ranked M-sequences, calculate the probability of error p _osh (M) according to the formula

- число сочетаний из М по i; q_kj - вероятность правильного приема (1-р_ош1)_k или ошибки р_{ош 1k} k-го однократно принятого бита в j-м сочетании i неверно принятых битов в M-последовательности.where M is the number of repetitions of the information bit;

- the number of combinations from M to i; q _kj - the probability of correct reception (1-p _{osh1) k} or p errors _{err 1k} k-th bit in the received single j-th combination i incorrectly received bits in the M-sequence.

For example, when M = 3, the probability of erroneous reception of a bit during majority decoding is determined by the expression:

_ROSH (3) = _{ROSH1 ROSH2 ROSH3} + (1- _ROSH1 ) _{ROSH2 ROSH3} + _ROSH1 (1- _ROSH2 ) _ROSH3 + _{ROSH1 ROSH2} (1- _OSH3 ).

5) compare the values obtained p _err (M) for each of M and choose between a final decision on the transmitted bit, which corresponds to the minimum value of p _err (M) (Figure 8).

To implement the proposed method, it is necessary to know the probability of a mistake in a single reception of a bit for each frequency position or, what is the same, for each clock cycle of a signal with frequency hopping. It is known that the error probability of a single reception of bit r _osh1 for a given type of modulation of the radio signal is uniquely determined by the value of h ² _—the ratio of the signal power P _c to the interference power R _p at the input of the demodulator (Fig. 8) (see B. Sklyar. Digital Communication. Theoretical fundamentals and practical application, 2nd ed .: Translated from English - M .: Williams Publishing House, 2003, p.146-158).

To calculate h ² on the duration and frequency of the nth step of the pseudo-random tuning of the operating frequency, the power of the mixture of the received signal and the interference P _{s + n} are measured and stored. The interference power P _p for a given frequency position is measured immediately before the signal jumps on it. That is, the interference power is measured on the time interval of the (n-1) -th cycle at the frequency of the n -th cycle of the pseudo-random tuning of the operating frequency and the obtained value of P _{p is} stored. Then, according to the obtained data, the signal power P _{c is} calculated as the difference between the power of the signal mixture and the interference P _{s + p} and the interference power P _p . Next, h ^{2 is} calculated as the ratio of the signal power P _c to the interference power P _p .

Thus, due to selective majority decoding according to the probability of receiving errors N times the repeated information bit and making the final decision on the transmitted bit after comparing the calculated error probabilities p _os (M) for all ranked M-sequences of once received bits, an increase in the noise immunity of receiving discrete information in a radio line with pseudo-random tuning of the operating frequency and, therefore, the formulated technical result is realized.

Claims (4)

1. The method of transmitting and receiving discrete information in a radio line with a pseudo-random tuning of the operating frequency, namely, that information packets are formed at the transmitting end of the radio line by dividing the information signal into blocks of a given length, the carrier frequency of the transmitter is tuned to the frequency corresponding to the pseudo-random sequence code, modulate the carrier frequency of the transmitter and emit a radio signal, and at the receiving end of the radio line receive the transmitted radio signal, convert it to an intermediate often y, amplify and demodulate, characterized in that at the transmitting end of the radio line information packets are formed in the form of blocks of a given length with N-fold repetition of each information bit, where N≥3 and emit at K frequency positions corresponding to the pseudo-random sequence code, and at the receiving at the end, each bit of the information signal is received N times at K frequency positions, and after demodulation of the received signal, the probability of erroneous reception of each once received bit is calculated, for which the power is measured and stored v mixture received signal and interference P _{p + with} a frequency and duration of the n-th clock cycle of the working pseudo-random frequency hopping, where n = 1, 2, 3, ..., N, the time interval (n-1) th stroke and frequency n th pseudorandom working stroke frequency adjustment is measured and stored interference power P _n, after which the received data signal power P is calculated _with the difference as a power signal and noise mixture P _{c + n} and the interference power P _n, h ² as the ratio of the signal power P _c and interference power R _p , probability of error r _{os1 of a} single reception of a bit at the nth step of the pseudo tea tuning of the operating frequency, remember the values of the one-time received bit and the corresponding error probability value p _os1 , the values of the once-received bits are ranked in accordance with their error probabilities, then all the ranked M-sequences of the once-received bits are simultaneously, where M = N, M = N -2, ..., M = 3, decode according to the majority scheme and calculate, for each value of M, the probability of error p _os (M), compare the obtained values of p _os (M) with each other and make the final decision on the value of the transmitted bit, which e represents the minimum value of p _err (M). 2. The method according to claim 1, characterized in that for each once received bit, the probability of its erroneous reception is calculated and the values of the once received bits are ranked in accordance with their error probabilities. 3. Method no. 1, characterized in that the probability of error p _osh (M) of majority decoding is calculated for each M sequence of ranked once received bits, where M = N, M = N-2, ..., M = 3, according to the formula

,
where M is the number of repetitions of the information bit;

- the number of combinations from M to i; q _kj is the probability of the correct reception of (1-p _{error 1} ) _k or the error р error _{1k of the} kth once received bit in the jth combination of i incorrectly received bits in the M-sequence. 4. The method according to claim 1, characterized in that they make the final decision on the value of the transmitted bit, which corresponds to the minimum probability of majority decoding error p _osh (M).

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