JPH01183245A - Appearance probability distribution measurement method for soft decision data - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a measurement method for measuring the probability of appearance of soft decision data used for error correction in S-star digital communications, etc., this purpose is to investigate the cause when a desired error rate cannot be obtained. The purpose is to send transmission data to a transmission path through a modulator and a transmitter, receive the modulated transmission data via the transmission path by a receiver, and then demodulate it by a demodulator to obtain received data and soft decision data. In a digital communication system, a soft-decision data detector detects whether the soft-decision data matches/disagrees with a desired measurement data pattern inputted from the outside, and a coincidence detection output pulse of the soft-decision data detector is counted for a certain period of time. and an appearance probability counter that displays the appearance probability.

[Industrial application field]

The present invention relates to a method for measuring appearance probability distribution of soft decision data,
In particular, the present invention relates to a soft-decision data appearance probability distribution measurement method for measuring the appearance probability of soft-decision data used for error correction in satellite digital communications and the like.

[Conventional technology]

In digital signal transmission, data errors occur due to the introduction of noise during transmission, so error correction is essential to improve data reliability. Particularly in satellite digital communications, the transmission path is extremely long and is susceptible to the effects of climate, atmosphere, etc., and a large amount of M sound (white noise) is generated on the transmission path. For this reason, in satellite digital communications, a soft decision method for received data is often adopted as an error correction method in order to improve error correction capability.

This soft-decision method divides the amplitude of the data waveform into multiple parts, and depending on which division range the level of the actual received data waveform falls within, soft-decision data of multiple bits (3 bits when the number of divisions is 8) is used. For example, if one bit of transmitted data is “0”,
The theoretical value of the appearance probability of 3-bit soft decision data obtained by transmitting `` and receiving it on the receiving side is as shown in the following table, and the distribution diagram at that time is shown in Figure 3. , The following table shows the values when Es/Nv is 0.5 cB, where the energy of one symbol (bit) is Es and the noise distribution density is No.

Table 1 In addition, in FIG. 3, P0 to P7 are P in the above table.

Corresponding to ~P1, when the transmission data is 6゛0'', the probability Po of the appearance of 3-bit soft decision data ``000'' indicating the minimum level is maximum, and the 3-bit soft decision data ``111'' indicating the maximum level appears. ” appears, the probability P7 is the minimum.

In addition, the threshold value of the hard decision method, which determines "1'' when the level of the received data waveform is above a predetermined threshold value, and O" when the level is below, is between P3 and P4 in Figure 3. is set to

When correcting errors in received data, more accurate error correction can be performed by also referring to the above-mentioned soft decision data.

(Problem to be Solved by the Invention) However, when the theoretical value obtained by the above-mentioned soft-decision method is supplied directly to the error corrector without passing through the modulator/demodulator, a predetermined theoretical value can be obtained. However, if it is received and then demodulated by a demodulator and then supplied to an error corrector, the theoretical value may vary due to non-linearity of the transmission system or a phase shift between the demodulator's recovered clock and recovered carrier wave. There was something different.

Although this variation in the appearance probability distribution of soft-decision data is a factor that directly affects (degrades) the bit error rate characteristics, conventionally there has been no method for measuring the appearance probability distribution of soft-decision data.

The present invention has been made in view of the above points, and it is possible to measure the appearance probability distribution of soft decision data when desired characteristics cannot be obtained in measuring bit error rate characteristics. The purpose is to provide a distribution measurement method.

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention. In the figure, 1 is a modulator, 2 is a transmitter, 3 is a satellite as a transmission path, 4 is a receiver, and 5 is a demodulator. counter 7
is provided.

The soft decision data detector 6 detects coincidence/mismatch between the soft decision data and a desired measurement data pattern inputted from the outside. The appearance probability counter 7 displays the appearance probability.

[Effect]

The transmission data modulated by the modulator 1 is transmitted from the antenna 2a of the transmitter 2 to the transmission path t! The signal is transmitted to the 17th star 3 and further received via this satellite 3 by a receiver 4 having an antenna 4a. The modulated transmission data taken out from the receiver 4a is demodulated by the demodulator 5 to become received data and also generates soft decision data.

This soft decision data is supplied to the soft decision data detector 6,
Here, it is detected whether or not it matches a desired measurement data pattern input from the outside, and a match detection pulse is output every time there is a match. This coincidence detection pulse is supplied to an appearance probability counter 7, where the number of coincidence detection pulses within a certain period of time is regulated.

Therefore, the appearance probability of soft decision data that is the same as the desired measurement data pattern can be measured by the count value of the appearance probability counter 7.

(Embodiment) FIG. 2 shows a block diagram of an embodiment of the main part of the system of the present invention. In the figure, the same components as in FIG. 1 are given the same reference numerals. In FIG. 2, 9 is a random data generator, 10 is an output terminal, 11 is a reproduced clock input terminal, 12a to 12
c is an input terminal for each pit of 3-bit soft decision data, 1
3 is an adder constituted by an antagonistic OR circuit, 14 is a delay circuit for time synchronization, 15 is a coincidence comparator, and 16 is a switch for setting a measurement data pattern.

The 1-bit random data generated by the random data generator 9 is supplied to the modulator 1 via an output terminal 10 as transmission data. This transmission data is transmitted and received based on the standard digital communication method, and the demodulator 5 generates 3-bit soft decision data, which is input to the input terminals 12a to 12c, and the reproduced clock is input to the input terminal 11. is input.

The above 3-bit soft decision data is sent to the soft decision data detector 6.
In order to simplify the configuration, the signals are input to the input terminals 12a to 12c in a folded binary format. The relationship between this soft decision data and folded binary is as shown in the numerical table.

Table 2 Of the above 3-bit folded binary, the MSB (most significant bit) is supplied to the adder 13, where a delay circuit 14 converts the transmission data from the input terminal of the modulator 1 to the output of the demodulator 5. It is added to the original transmission data (this is 1 bit) that was delayed by the time until reaching the end and time-aligned, and if the two match, it is "0", and if they do not match, it is returned as "0". “It is considered to be a 1-pa signal.

The output signal of this adder 13 and the input terminal 12b.

The 12G input signals are each supplied to a negative number comparator 15,
Here, it is compared with a desired measurement data pattern input via the measurement data pattern setting switch 16.

For example, when measuring the maximum appearance probability Pa, the input measurement data pattern is a folded binary maximum appearance probability value "o i i ". Therefore, at this time, when the transmission data is "0", the adder 13 and the input terminal 1
For the 3-bit data from 2b and 12c, "011" appears most often and is matched with the above measurement data pattern by the match comparator 15. Even when the transmitted data is 1",
Since '011' appears most often in the 3-bit data from the adder 13 and the input terminals 12b and 12c, the above measurement data pattern and the above match are obtained.

When measuring the other appearance probabilities P1 to P7, they are input in folded binary as described above. In this way, −
The number comparator 15 compares soft decision data replaced with data similar to the case where all "0"s are transmitted as the transmission data and a desired measurement data pattern set in advance ("o o o" to "
111''), and each time a coincidence is detected, a coincidence detection pulse is generated and supplied to the appearance probability counter (error rate measuring device) 7.

The appearance probability counter calculates the ratio between the number of reproduced clocks within a certain period of time and the number of coincidence detection pulses from the soft decision data detector 6, and displays the appearance probability. In this case, an error rate measuring device can be used for the occurrence probability counter 7. That is,
Counting the number of errors for soft-decision data set to all °O' by using an error rate measuring device is equivalent to counting the number of coincidence detection pulses.

Therefore, the error rate displayed on the error rate measuring device directly becomes the probability of appearance of the set measurement data pattern, and the normality/abnormality of the appearance probability distribution of the soft decision data can be confirmed by comparing it with the logical value of the garment 1.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to measure the appearance probability of soft decision data that is the same as a desired measurement data pattern from the count value of the appearance probability counter, so that it is possible to obtain the desired error rate when measuring the error rate. This method has the advantage of being able to confirm whether the probability of occurrence of soft decision data, which is one of the causes of error rate deterioration, is normal or abnormal when the error rate is not correct, thereby reducing the time devoted to troubleshooting.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the main part of the present invention, and Fig. 3 is the appearance of 3-bit soft decision data when °゛0'' is the transmission data. It is a probability distribution diagram. In the figure, 1 is a modulator, 2 is a transmitter, 3 is a satellite, 4 is a receiver, 5 is a demodulator 6 is a soft decision data detector, and 7 is an appearance probability counter. Patent application People Fujitsu Su19kawa Co., Ltd./1 埒01 PRO-N2

Claims (1)

[Claims] Transmission data is sent to a transmission path (3) through a modulator (1) and a transmitter (2), and modulated transmission data that has passed through the transmission path (3) is received by a receiver (4). In a digital communication system in which the soft decision data is demodulated by a demodulator (5) to obtain received data and soft decision data, the soft decision data is demodulated by a demodulator (5) to detect whether the soft decision data matches/disagrees with a desired measurement data pattern inputted from the outside. a judgment data detector (6); and an appearance probability counter (6) that counts the coincidence detection output pulses of the soft judgment data detector (6) for a certain period of time and displays the appearance probability.
7) A method for measuring appearance probability distribution of soft decision data.