RU167430U1 - A device for estimating the probability of error per bit for signals with eight-position phase modulation by four-position signals - Google Patents

Abstract

The utility model relates to the field of electro-radio engineering, namely to radio communication technology, and can be used in data transmission systems using signals with relative phase modulation to estimate the probability of error per bit. The technical result of the claimed utility model is to provide an estimate of the probability of error per bit for the increased multiplicity mode, namely for the mode of using signals with eight-position relative phase modulation, while in the mode of using signals with four-position relative phase modulation without introducing redundancy. The device comprises an analog-to-digital converter, a first accumulation unit, a demodulator, a phase difference determination unit, a symbol determination unit, a condition verification unit, an accumulation unit, an adder, a divider, a condition verification unit, a bit error probability estimation calculation unit, a decision storage unit. The technical result is achieved due to the fact that in the proposed device is counted the particular contact of the phase difference in certain sectors. An analytical expression was found that relates the probability of error per bit for signals with eight-position phase modulation with the probability of falling into these sectors. 1 ill.

Description

The utility model relates to the field of electro-radio engineering, namely to radio communication technology, and can be used in data transmission systems using signals with relative phase modulation without introducing redundancy to estimate the probability of error per bit for the increased multiplicity mode, namely, the mode of using signals with eight-position relative phase modulation, while in the mode of using signals with four-position relative phase modulation.

In the process of functioning of adaptive data transmission systems, the problem arises of choosing the modulation factor to ensure the maximum information data transfer rate. Often, various test or service signals are used for this. However, this leads to the need to interrupt the flow of useful information, which reduces the information transfer rate, therefore, it is necessary to apply approaches that allow you to form an estimate and make a decision on the information signal without using any tests. During the communication session, in order to increase the data transfer rate, there is a gradual transition from two-position phase modulation to four-position and then to eight-position. Then the problem arises of estimating the probability of an error per bit from signals with four-position phase modulation for signals with eight-position phase modulation.

Closest to the claimed technical solution is the RF patent for the invention No. 2434334 "Method for assessing the reliability of signal reception with multi-position relative phase modulation", which is adopted as a prototype. The method comprises a demodulator, a phase difference determination unit, a character determination unit, and a bit error probability determination unit. The proposed method does not allow to estimate the probability of an error per bit for signals with eight-position phase modulation if encoding is not used for data transmission, or the number of detected errors in the received code block is greater than a predetermined threshold.

The purpose of the utility model is to obtain an estimate of the probability of error per bit from information signals with four-position phase modulation for signals with eight-position phase modulation.

где

- величина, полученная со второго выхода второго блока проверки условия, а p₈ - искомая оценка вероятности ошибки на бит для восьмипозиционной фазовой модуляции, далее вычисленную оценку с выхода блока вычисления оценки вероятности ошибки на бит передают на второй вход блока хранения решения, получая, таким образом, искомую вероятность ошибки на бит для восьмипозиционной фазовой модуляции.This goal is achieved by the fact that in the device for estimating the probability of error per bit, containing a demodulator, a phase difference determination unit, a character determination unit, a calculation unit for estimating the probability of error per bit, the following are input: an analog-to-digital converter (ADC), the input of which is the input of the device, in which samples of the received signal with four-position phase modulation are received, which are transmitted from the output of the ADC to the input of the first accumulation unit, in which the signal samples are accumulated for the duration of two elementary packets , from the output of the first accumulation unit, the accumulated array of values is transmitted to the input of the demodulator, which is a series-connected phase difference determination unit and a symbol determination unit, and the demodulator input is simultaneously the input of the phase difference determination unit, in which the initial phase difference between two adjacent packages is determined according to the well-known principle described in [1], and the resulting difference is transmitted from the output of the phase difference determination unit to the input of the symbol determination unit, where the received the symbol, assuming that a signal is received with eight-position phase modulation and character arrangement in accordance with the Gray code [2], then the received character, consisting of three bits, is transmitted from the output of the character definition block, which is also the output of the demodulator, to the input of the first check block a condition in which it is checked whether the received symbol is equal to the symbol “000”, “110”, “101” or the symbol “011” and, if equal, then from the output of the first verification block the conditions are transferred to the input of the second accumulation block “1”, and if not equal, then transmit 0 ", while in the second accumulation block, the obtained values are accumulated over the duration of the analysis interval, the accumulated array of values from the output of the second accumulation block is transferred to the input of the adder, in which the resulting array of values is summed, the summation from the output of the adder is transmitted to the input of the divider, in which dividing the obtained value by the duration of the analysis interval, the division result from the output of the divider is transmitted to the input of the second unit for checking the condition in which it is checked that the obtained value is greater than 0.5 or earlier, and if the obtained value is greater than 0.5, then from the first output of the second test unit the conditions transfer a value of 0.5 to the first input of the decision storage unit, and if the obtained value is less than 0.5, then from the second output of the second test unit the conditions are transmitted the value at the input of the error probability estimate calculation unit per bit, in which the estimate of the error probability per bit is calculated in a tabular manner as a solution to the following equation:

Where

is the value obtained from the second output of the second condition checking unit, and p ₈ is the desired error probability per bit estimate for eight-position phase modulation, then the calculated estimate from the output of the error probability estimation calculation block per bit is transmitted to the second input of the decision storage unit, thus obtaining Thus, the sought probability of error per bit for eight-position phase modulation.

The block diagram of the proposed device is shown in FIG.

The device for estimating the probability of error per bit contains an analog-to-digital converter 1 (ADC), the output of which is connected to the input of the first storage unit 2, the output of which is connected to the input of the demodulator 3, inside which there is a phase difference determination unit 3.1, the output of which is connected to the input of the determination unit characters 3.2. At the same time, the input of the demodulator is simultaneously the input of the phase difference determination unit 3.1, and the output of the symbol definition block 3.2 is simultaneously the output of the demodulator. In this case, the output of the demodulator 3 is connected to the input of the first condition checking unit 4, the output of which is connected to the input of the accumulation unit 5, the output of which is connected to the input of the adder 6. In this case, the output of the adder 6 is connected to the input of the divider 7, the output of which is connected to the input of the second verification unit condition 8, the first output of which is connected to the first input of the decision storage unit 10, and the second output is connected to the input of the error probability calculation unit for bit 9, the output of which is connected to the second input of the decision storage unit 10.

The proposed device can be used for adaptive communication systems using signals with phase modulation. A distinctive feature of the described device is the ability to estimate the probability of an error per bit after demodulation using information signals with four-position phase modulation for signals with eight-position phase modulation, without introducing redundancy. The presence of such a device makes it possible to abandon the use of test signals with eight-position phase modulation to assess the quality of the communication channel for the specified modulation frequency, if at present a four-position phase modulation is used. Moreover, the method allows to obtain the desired estimate, regardless of whether or not encoding of the transmitted information. In addition, the transmission time can be used completely to transfer useful data, which leads to an increase in the data transfer rate. The number of errors in the received bits does not affect the accuracy of the method.

The structure of the proposed device is obtained from the following assumptions.

As you know, one of the transmission modes is the four-position relative phase modulation (OFM-4). During the communication session, in order to increase the data transfer rate, there is a gradual transition from two-position phase modulation to four-position and then to eight-position. In this case, the probability of error per bit when using OFM with higher positioning can be estimated based on the following approach.

Consider the problem of estimating the probability of error per bit for signals with eight-position relative phase modulation (OFM-8). The transmission of characters 00, 01, 11 and 10 for OFM-4 signals is equivalent to the transmission of the characters "000", "110", "101" or the character "011" for signals with OFM-8 in accordance with the Gray code. Then the probability of an error per bit for signals with OFM-8 is related to the probability of the phase difference of the received signal getting into the sectors corresponding to the symbols “000”, “110”, “101” or the symbol “011”, taking into account the phase arrangement in accordance with the Gray code is described by the following equation:

(1-p ₈ ) ³ + 3p ₈ ² (1-p ₈ ) = P _match

where P _matched is the probability of the event that the phase of the received signal is in the sectors corresponding to the symbols "000", "110", "101" or "011", regardless of which symbol was transmitted, p ₈ is the probability of error per bit for signals from OFM-8.

можно использовать соответствующую частость, доступную для измерения:As an estimate

you can use the appropriate frequency available for measurement:

которая характеризуется некоторой погрешностью.where k ₈ is the number of hits of the phase of the received signal in the sectors corresponding to the symbols "000", "110", "101" or the symbol "011", N is the sample size. With such a replacement, it should be borne in mind that the solution to the new equation is no longer true, but an estimate of the probability of error per bit

which is characterized by some error.

Thus, in a fairly simple computational scheme, it is possible to obtain an estimate of the probability of error per bit for signals from OFM-8, while receiving useful information transmitted using signals from OFM-4. At the same time, it is easiest to store the solution to this equation in a tabular form so as not to waste time solving the equation during the operation of the communication system.

The operation of the device is as follows.

где

- величина, полученная со второго выхода второго блока проверки условия 8, а p₈ - искомая оценка вероятности ошибки на бит для восьмипозиционной фазовой модуляции. Далее с выхода блока вычисления оценки вероятности ошибки на бит 9 вычисленную оценку передают на второй вход блока хранения решения 10, получая, таким образом, искомую вероятность ошибки на бит для восьмипозиционной фазовой модуляции.The received signal is fed to an analog-to-digital converter 1 (ADC), which is the input of the device, in which samples of the received signal with four-position phase modulation are received, which are then transmitted from the output of the ADC to the input of the first storage unit 2, in which the signal samples are accumulated for two elementary premises. From the output of accumulation unit 2, an accumulated array of values is transmitted to the input of demodulator 3, which is a series-connected phase difference determination unit 3.1 and symbol determination unit 3.2. At the same time, the input of demodulator 3 is at the same time the input of the phase difference determination unit 3.1, in which the initial phase difference between two adjacent packages is determined, and the resulting difference is transmitted from the output of the phase difference determination unit 3.1 to the input of the symbol determination unit 3.2, where the received symbol is determined , on the assumption that a signal with eight-position phase modulation and character arrangement in accordance with the Gray code is received. Next, the received symbol, consisting of three bits, is transmitted from the output of the symbol definition block 3.2, which is also the output of the demodulator 3, to the input of the first condition verification block 4, in which it is checked whether the received symbol is equal to the symbols "000", "110", " 101 "or the symbol" 011 ". If the symbol is equal, then pass further to the input of the second accumulation block 5 “1”, and if not equal, then transmit “0”. In this case, in the second accumulation block 5, the obtained values are accumulated over the duration of the analysis interval, and the accumulated array of values from the output of the second accumulation block is transmitted to the input of the adder 6, in which the obtained array of values is summarized. The result of the summation from the output of the adder 6 is transmitted to the input of the divider 7, in which the obtained value is divided by the duration of the analysis interval, and the result of the division from the output of the divider 7 is transmitted to the input of the second condition verification unit 8. In the second verification unit of condition 8, it is checked whether there are more than 0 , 5 or less, the obtained value, and if the obtained value is greater than 0.5, then from the first output of the second condition checking unit 8, the value 0.5 is transmitted to the first input of the decision storage unit 10, and if the obtained value is less than 0.5, then from the second exit torogo condition check unit 8 to transmit the obtained value calculating unit estimates the bit error rate calculation portion 9. In the evaluation of the error probability per bit 9 tabular manner calculated estimate the bit error rate as a solution of the following equation:

Where

is the value obtained from the second output of the second block of checking condition 8, and p ₈ is the desired estimate of the probability of error per bit for eight-position phase modulation. Further, from the output of the error probability estimation calculation unit for bit 9, the calculated estimate is transmitted to the second input of the decision storage unit 10, thus obtaining the desired error probability per bit for eight-position phase modulation.

The proposed device in comparison with the prototype has the following advantages:

- provides an estimate of the probability of error per bit for signals with eight-position phase modulation, regardless of whether encoding is used or not when transmitting data;

- provides an estimate of the probability of error per bit for signals with eight-position phase modulation, regardless of the number of errors in the received signal with four-position phase modulation.

Literature

1. Phase and relative phase telegraphy. Digest of articles. M .: "Communication", 1967, p. 138.

2. Sklyar, Bernard. Digital communication. Theoretical foundations and practical application. M .: "Williams", 2003, p. 261.

Claims (1)

A device for estimating the probability of error per bit for signals with eight-position phase modulation by four-position signals, comprising a demodulator, a phase difference determination unit, a character determination unit, a calculation unit for estimating the probability of error per bit, characterized in that: an analog-to-digital converter, the input of which is the input of the device in which the samples of the received signal with four-position phase modulation are received, which are then transmitted from the output to the input of the first storage unit, in which the signal samples are taken for the duration of two chips, and from the output of the first accumulation block they transfer the accumulated array of values to the input of the demodulator, which is a series-connected block for determining the phase difference and the block for determining symbols, and the input of the demodulator is also the input of the block for determining the phase difference, in which the initial phase difference between two adjacent packages is determined, and the resulting difference is transmitted from the output of the phase difference determination unit to the input of the character determination unit, where determine the received symbol, on the assumption that a signal is received with eight-position phase modulation and the arrangement of the symbols in accordance with the Gray code, then the received symbol, consisting of three bits, is transmitted from the output of the symbol definition block, which is also the output of the demodulator to the input of the first condition check block , in which they check whether the received symbol is equal to the symbol "000", "110", "101" or the symbol "011" and, if equal, then pass on to the input of the second accumulation block "1", and if not equal, then transmit "0", while in Tue The rum accumulation block accumulates the obtained values over the duration of the analysis interval, and the accumulated array of values from the output of the second accumulation block is passed to the input of the adder, in which the resulting array of values is summed, and the summation result from the output of the adder is transmitted to the input of the divider, in which the obtained value is divided by the duration of the analysis interval, and the result of the division from the output of the divider is transmitted to the input of the second verification unit of the condition under which the result is greater than 0.5 or less, and if the obtained value is greater than 0.5, then from the first output of the second test block the conditions transfer the value 0.5 to the first input of the decision storage block, and if the obtained value is less than 0.5, then from the second output of the second test block the conditions transfer the received value to the block input computing estimates of the probability of error per bit, in which a tabular method calculates the estimate of the probability of error per bit as a solution to the following equation:

where

is the value obtained from the second output of the second condition checking unit, and p ₈ is the desired error probability per bit estimate for eight-position phase modulation, then the calculated estimate from the output of the error probability estimation calculation block per bit is transmitted to the second input of the decision storage unit, thus obtaining Thus, the sought probability of error per bit for eight-position phase modulation.