JP6776320B2 - PAM4 symbol error addition device and method and error rate measurement device and method - Google Patents

Description

The present invention comprises a PAM4 symbol error adding device and method for adding an error to a symbol of a PAM4 signal, and a bit error rate (BER: Bit Error) by inputting the PAM4 signal as a test signal into a device under test (DUT). Rate) The error rate measuring device and method for measuring.

In standards such as 100G and 400G defined by IEEE, transmission by PAM4 signal is specified instead of transmission by PAM2 (NRZ) signal so far in order to respond to ultra-high speed of bit rate.

For the PAM4 signal, for example, as shown in Patent Document 1 below, after generating the most significant bit string signal MSB (Most Significant Bit) and the least significant bit string signal LSB (Least Significant Bit) using two signal sources, these By adding the signals, it can be generated as a four-value signal of 0 (00), 1 (01), 2 (10), and 3 (11).

By the way, when considering simulating a bit error due to the influence of signal deterioration in the physical layer, since the value transition is only 0 → 1, or 1 → 0 in the conventional NRZ signal, it is simply a signal generator. A bit error could be simulated by inverting the bit in the final stage.

JP-A-2018-033098

However, in the case of the PAM4 signal, there are two bits consisting of the most significant bit string signal MSB and the least significant bit string signal LSB. Therefore, if the four PAM4 symbols 0 (00), 1 (01), 2 (10), and 3 (11) are simply bit-inverted in the final stage, 0 (00) → 3 (11), 1 ( 01) → 2 (10), 2 (10) → 1 (01), 3 (11) → 0 (00), and it cannot be controlled to change to an arbitrary PAM4 symbol.

Further, in the above precondition of simulating the influence of signal deterioration in the physical layer, it is considered that the transition of the PAM4 symbol is one symbol, so it is necessary to change it to an arbitrary PAM4 symbol.

However, if the symbol to be uniquely transitioned is determined, the inserted error will be biased. For example, when fixed in the transition direction of 0 → 1, 1 → 2, 2 → 3, 3 → 2, an error that appears in the Upper Eye at the three eye pattern openings (Upper Eye, Middle Eye, Lower Eye) of the PAM4 signal. Will double the error that appears in the Middle Eye and Lower Eye.

Here, considering the occurrence of an error that may occur in the natural world, if ISI (Intersymbol interference) is evenly added, it is difficult to think that the error is inserted in a biased manner in some Eye. Therefore, it is desired that errors can be added evenly to Upper Eye, Middle Eye, and Lower Eye.

Therefore, the present invention has been made in view of the above problems, and is a PAM4 symbol error adding device and method capable of adding an error to each of the three eye pattern openings of the PAM4 signal with an equal probability, and an error rate. It is intended to provide measuring devices and methods.

In order to achieve the above object, the PAM4 symbol error adding device according to claim 1 of the present invention is a PAM4 symbol error adding device 2 that adds an error to a symbol of a PAM4 signal.
The first signal generation means 13 for generating the highest-order bit string signal, and
A second signal generation means 14 for generating the lowest bit string signal for generating the PAM signal by adding the highest bit string signal, and
Setting means 11 that defines a bit that allows error insertion and a bit that prohibits error insertion with different bit information, and sets symbol transition information indicating the transition destination of the four PAM4 symbols of the PAM4 signal.
1 in 3 clocks with respect to the symbol transition information set by the setting means so that the error occurrence probability when viewed at each of the three eye pattern openings in the amplitude direction of the PAM4 signal is 1/3. A transition destination changing means 12 that outputs symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed at a rate of one time, and
A mask generating means 15 that generates a mask pattern for each of the highest-order bit string signal and the lowest-order bit string signal based on the symbol transition information from the transition destination changing means.
It is provided with an error inserting means 16 for inserting an error based on the bit information of the mask pattern corresponding to each bit of the most significant bit string signal and the least significant bit string signal specified according to the symbol error rate. It is a feature.

The PAM4 symbol error addition method according to claim 2 is a PAM4 symbol error addition method for adding an error to a symbol of a PAM4 signal.
Steps to generate the highest bit string signal,
A step of generating the lowest bit string signal for generating the PAM signal by adding it to the highest bit string signal, and
A step of defining a bit that allows error insertion and a bit that prohibits error insertion with different bit information, and setting symbol transition information indicating the transition destination of the four PAM4 symbols of the PAM4 signal.
The rate of occurrence of an error when viewed at each of the three eye pattern openings in the amplitude direction of the PAM4 signal is 1/3 of the set symbol transition information at a rate of once every 3 clocks. A step of outputting symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed, and
A step of generating a mask pattern for each of the highest-order bit string signal and the lowest-order bit string signal based on the symbol transition information in which the transition destination of the PAM4 symbol is changed, and
It is characterized by including a step of inserting an error based on the bit information of the mask pattern corresponding to each bit of the most significant bit string signal and the least significant bit string signal specified according to the symbol error rate.

The error rate measuring device according to claim 3 includes the PAM4 symbol error adding device 2 according to claim 1 and the error rate measuring device 2.
It is characterized by including an error measuring device 3 for measuring an error rate by receiving a signal from the measured object when the PAM4 signal generated by the PAM4 symbol error adding device is input to the measured object W.

The error rate measuring method according to claim 4 includes a step of inputting the PAM4 signal generated by the PAM4 symbol error adding method of claim 2 and the object to be measured W.
It is characterized by including a step of receiving a signal from the object to be measured and measuring an error rate accompanying the input of the PAM4 signal to the object to be measured.

According to the present invention, an error can be added to each of the three eye pattern openings of the PAM4 signal with an equal probability. As a result, it becomes possible to simulate an error in the physical layer in the PAM4 signal.

It is a block diagram which shows the schematic structure of the error rate measuring apparatus including the PAM4 symbol error addition apparatus which concerns on this invention. It is a figure which shows (a) the relationship between a clock signal and a symbol transition, and (b) is a figure which shows the error insertion probability of three eye pattern openings. It is a flowchart of the case where the PAM4 symbol error addition apparatus which concerns on this invention generates a PAM4 signal which inserted an error evenly. (A), (b) It is a figure which shows an example of the PAM4 signal before and after the error insertion in the PAM4 symbol error addition apparatus which concerns on this invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the attached drawings.

As shown in FIG. 1, the error rate measuring device 1 of the present embodiment is roughly configured with a PAM4 symbol error adding device (hereinafter abbreviated as an error adding device) 2 and an error measuring device 3, and has a known pattern. The PAM4 signal is input to the object to be measured (DUT: Device Under Test) as a test signal, and the bit error rate (BER) is measured.

As shown in FIG. 1, the error adding device 2 includes a setting means 11, a transition destination changing means 12, a first signal generating means 13, a second signal generating means 14, a mask generating means 15, an error inserting means 16, and a signal. The synthesis means 17 is roughly configured, and error insertion is controlled so as to have a designated PAM4 symbol to generate a PAM4 signal.

The setting means 11 sets the symbol error rate and the symbol transition information. This setting can be performed, for example, via a user interface on a setting screen of a display means (not shown).

The symbol transition information is information indicating the transition destination for each symbol of the four PAM symbols of the PAM4 signal when an error is inserted. For example, when simulating a bit error due to the influence of signal deterioration in the physical layer, symbol 0 (00) → symbol 1 (01), symbol 1 (01) → symbol 2 (10), symbol 2 (10) → The symbol transition information is set so that the PAM4 symbol transitions by only one symbol, such as symbol 1 (01), symbol 3 (11) → symbol 2 (10).

The symbol error rate and the symbol transition information can be stored in advance in a storage means (not shown) and can be appropriately selected and set by the setting means 11 via the user interface. Further, the symbol transition information is not limited to the transition of only one symbol, and can be set arbitrarily.

The transition destination changing means 12 is a setting means so that the error occurrence probability when viewed at each of the three eye pattern openings (Upper Eye, Middle Eye, Lower Eye) in the amplitude direction of the PAM4 signal is reduced to 1/3. With respect to the symbol transition information set in 11, the symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed at a rate of once every three clocks is output to the mask generation means 15.

Specifically, when the symbol transition information is set to symbol 0 → symbol 1, symbol 1 → symbol 2, symbol 2 → symbol 1, symbol 3 → symbol 2 in the setting means 11, FIG. 2A shows. As shown, the transition destination of the PAM4 symbol is not changed in the first clock and the second clock while the transition destination of the PAM4 symbol is set, and the transition destination of the symbol 1 is changed from symbol 1 to symbol 0 and the transition destination of the symbol 2 is changed to symbol 2 only in the third clock. → Change to symbol 3.

As a result, as shown in FIG. 2B, the transition probability of symbol 0 → symbol 1 is 1/4, the transition probability of symbol 1 → symbol 0 is 1/12, the transition probability of symbol 1 → symbol 2 and symbol 2 → The transition probability of symbol 1 is 1/6, the transition probability of symbol 2 → symbol 3 is 1/12, and the transition probability of symbol 3 → symbol 2 is 1/4. Then, the probability of occurrence of an error when viewed at each of the three eye pattern openings (Upper Eye, Middle Eye, Lower Eye) in the amplitude direction is reduced to 1/3, and the three eye pattern openings (Upper Eye) in the amplitude direction are reduced. , Middle Eye, Lower Eye) It is possible to add an error with equal probability.

The above-mentioned change of symbol 1 (01) → symbol 0 (00) and symbol 2 (10) → symbol 3 (11) may be performed only in the first clock or only in the second clock. That is, it is rewritten only once every three clocks.

The first signal generating means 13 generates the most significant bit string signal MSB for generating the PAM4 signal by adding the least significant bit string signal LSB generated by the second signal generating means 14.

The second signal generation means 14 adds the most significant bit string signal MSB generated by the first signal generation means 13 to generate the least significant bit string signal LSB for generating the PAM4 signal.

The mask generating means 15 adds the corresponding bits of the most significant bit string signal MSB generated by the first signal generating means 13 and the least significant bit string signal LSB generated by the second signal generating means 14 to each other. Generates a PAM4 signal.

Further, the mask generating means 15 defines a bit that allows error insertion and a bit that prohibits error insertion with different bit information (0, 1), and is based on the symbol transition information input from the transition destination changing means 12. The mask pattern of the most significant bit string signal MSB and the mask pattern of the least significant bit string signal LSB are generated with bit information (0, 1), respectively. For example, as bit information, the bit that allows error insertion is defined as 0, and the bit that prohibits error insertion is defined as 1, and the mask pattern of the most significant bit string signal MSB is defined based on the symbol transition information input from the transition destination changing means 12. And the least significant bit string signal LSB mask pattern is generated. Then, the mask generating means 15 outputs the mask patterns of the most significant bit string signal MSB, the least significant bit string signal LSB, the most significant bit string signal MSB, and the least significant bit string signal LSB to the error inserting means 16.

The error inserting means 16 confirms the bit information of the mask pattern corresponding to each bit of the most significant bit string signal MSB and the least significant bit string signal LSB specified by the error insertion request information, and the bit information of the mask pattern inserts an error. Insert an error in that bit when allowing.

The error insertion request information is determined according to the symbol error rate set by the setting means 11, and is information that specifies which bit from the input the error is inserted and the bit for which the error insertion is requested. ..

The signal synthesizing means 17 outputs the PAM4 signal by adding the most significant bit string signal MSB and the least significant bit string signal LSB after the error is inserted by the error inserting means 16. This PAM4 signal is input to the object W as a test signal of a known pattern when measuring the error rate of the object W to be measured.

When the PAM4 signal is input to the object W as a test signal of a known pattern from the error addition device 2, the error measuring device 3 receives a signal returned from the object W to be measured in connection with the input of the PAM4 signal and makes an error. Measure the rate.

Next, in the error addition device 2 of the error rate measuring device 1 configured as described above, a method of controlling error insertion so as to have a designated PAM4 symbol to generate a PAM signal will be described with reference to FIG. To do. Here, a case where an error is inserted into the first and third bits from the input to generate a PAM4 signal will be described as an example.

The bit information when generating the mask pattern is defined as "0" for the bit that allows error insertion and "1" for the bit that prohibits error insertion.

First, the setting means 11 sets the symbol transition information. For example, symbol 0 (00) → symbol 1 (01), symbol 1 (01) → symbol 2 (10), symbol 2 (10) → symbol 1 (01), symbol 3 (11) → symbol 2 (10). As described above, the symbol transition information is set so that the PAM4 symbol transitions by only one symbol.

Further, the setting means 11 sets the symbol error rate (for example, 1 × 10 ^-5 ). For example, the symbol error rate is set so that the first and third bits from the input (the first and third bits from the right) are specified as the bits requesting error insertion.

When the above settings are completed and a PAM signal is generated, the first signal generation means 12 generates the most significant bit string signal MSB, and the second signal generation means 13 generates the least significant bit string signal LSB (ST1). ).

In the example of FIG. 1, the first signal generation means 12 generates "00202202" as the most significant bit string signal MSB. Further, the second signal generation means 13 generates "10111000" as the least significant bit string signal LSB.

Next, in the mask generating means 14, the corresponding bits of the most significant bit string signal MSB generated by the first signal generating means 12 and the least significant bit string signal LSB generated by the second signal generating means 13 are used. Are added together to generate a PAM4 signal (ST2).

In the example of FIG. 1, since the most significant bit string signal MSB is “00202202” and the least significant bit string signal LSB is “10111000”, “10313202” is generated as a PAM4 signal as shown in FIG. 4A.

Then, the transition destination changing means 12 masks the symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed at a rate of once every three clocks with respect to the symbol transition information set by the setting means 11. Output to means 15. Specifically, as shown in FIG. 2A, the transition destination of the PAM4 symbol is not changed in the first clock and the second clock, and symbol 0 → symbol 1, symbol 1 → symbol 2, symbol 2 → symbol 1 , Symbol 3 → symbol 2 is output to the mask generation means 14 as symbol transition information, and the transition destination of symbol 1 is changed from symbol 1 to symbol 0 and the transition destination of symbol 2 is changed from symbol 2 to symbol 3 only at the third clock. The transition information is output to the mask generation means 14 (ST3).

Then, the mask generating means 14 generates a mask pattern of the most significant bit string signal MSB and a mask pattern of the least significant bit string signal LSB based on the symbol transition information changed by the transition destination changing means 12 (ST4).

For example, in FIG. 1, focusing on the first bit (the first bit from the right) from the input of the PAM4 signal “10313202”, the PAM4 symbol is the symbol 2 (10). Then, since the symbol transition information input from the transition destination changing means 12 at the first clock is symbol 2 (10) → symbol 1 (01), it is the most significant to make the symbol 2 (10) transition to the symbol 1 (01). It is necessary to insert an error in the first bit of the upper bit string signal MSB and the least significant bit string signal LSB. Therefore, both the mask pattern of the most significant bit string signal MSB and the first bit of the mask pattern of the least significant bit string signal LSB are information "0" that allows error insertion.

Further, in FIG. 1, focusing on the third bit (third bit from the right) from the input of the PAM4 signal “10313202”, the PAM4 symbol is the symbol 2 (10). Then, since the symbol transition information input from the transition destination changing means 12 at the third clock is symbol 2 (10) → symbol 3 (11), it is the most significant to make the symbol 2 (10) transition to the symbol 3 (11). The third bit of the upper bit string signal MSB does not insert an error, and it is necessary to insert an error into the third bit of the least significant bit string signal LSB. Therefore, the third bit of the mask pattern of the most significant bit string signal MSB is the information "1" that prohibits error insertion, and the third bit of the mask pattern of the least significant bit string signal LSB is the information that allows error insertion. It becomes "0".

Then, in the example of FIG. 1, the mask pattern of the most significant bit string signal MSB is generated as "01101110" and the mask pattern of the least significant bit string signal LSB is generated as "00000000000" based on the symbol transition information from the transition destination changing means 12. ..

Next, the error inserting means 15 confirms the bit information of the mask pattern corresponding to each bit of the most significant bit string signal MSB and the least significant bit string signal LSB specified by the error insertion request information. Then, if the bit information of the mask pattern is information that allows error insertion, an error is inserted into that bit (ST5).

In the example of FIG. 1, since the bits specified by the error insertion request information are the first and third, the first and third bit information of the mask patterns of the most significant bit string signal MSB and the lowest bit string signal are confirmed. As for the most significant bit string signal MSB, the first bit information of the mask pattern is the information "0" that permits error insertion, and the third bit information is the information "1" that prohibits error insertion. Insert an error only in the bits of. As for the least significant bit string signal LSB, since the first and third bit information of the mask pattern is the information "0" that allows error insertion, an error is inserted in both the first and third bits.

Next, when an error is inserted by the error inserting means 15, the signal synthesizing means 16 adds the corresponding bits of the most significant bit string signal MSB and the least significant bit string signal LSB and outputs a PAM4 signal (ST6).

In the example of FIG. 1, the most significant bit string signal MSB after error insertion is "00202200" and the least significant bit string signal LSB is "10111101". Therefore, as shown in FIG. 4B, "10313301" is PAM4 after error insertion. Output as a signal.

As described above, in the above-described operation, as shown in FIGS. 4 (a) and 4 (b), an error is added to the first and third bits of the same symbol 2 from the input, but the first from the input. While symbol 2 of the bit has transitioned to symbol 1, symbol 2 of the third bit from the input has transitioned to symbol 3, and it can be confirmed that the transition destination is different even for the same symbol.

Then, the PAM4 signal generated from the signal generator 2 as described above is input to the object W to be measured as a known test signal when measuring the error rate. When the PAM4 signal is input to the object W to be measured, the error measuring device 3 receives a signal returned from the object W to be measured with the input of the PAM4 signal to the object W to measure the error rate.

By the way, in the above-described embodiment, a mask pattern is generated by defining a bit that allows error insertion as "0" and a bit that prohibits error insertion as "1" as bit information indicating the permission and prohibition of error insertion. However, the definition may be reversed. That is, a mask pattern can be generated by defining a bit that allows error insertion as "1" and a bit that prohibits error insertion as "0".

As described above, according to the present embodiment, it is possible to transition to an arbitrary symbol by controlling the bit error, and assuming that the probability of occurrence of each symbol is uniformly 25%, Upper Eye / Middle Eye / The probability of error occurrence when viewed in each of the Lower Eyes is uniformly 1/3, and errors occur with equal probability in each of the three eye pattern openings (Upper Eye, Middle Eye, and Lower Eye) in the amplitude direction of the PAM4 signal. Can be added. As a result, it becomes possible to simulate an error in the physical layer in the PAM4 signal.

The best mode of the PAM4 symbol error addition device and method and the error rate measuring device and method according to the present invention has been described above, but the present invention is not limited by the description and drawings in this form. That is, it goes without saying that all other forms, examples, operational techniques, and the like made by those skilled in the art based on this form are included in the scope of the present invention.

1 Error rate measuring device 2 Error adding device (PAM4 symbol error adding device)
3 Error measuring instrument 11 Setting means 12 Transition destination changing means 13 First signal generating means 14 Second signal generating means 15 Mask generating means 16 Error inserting means 17 Signal synthesizing means WDUT (object to be measured)

Claims (4)

A PAM4 symbol error addition device (2) that adds an error to a PAM4 signal symbol.
The first signal generation means (13) for generating the highest-order bit string signal, and
A second signal generation means (14) for generating the lowest bit string signal for generating the PAM signal by adding the highest bit string signal to the signal.
A setting means (11) that defines a bit that allows error insertion and a bit that prohibits error insertion with different bit information, and sets symbol transition information indicating the transition destination of the four PAM4 symbols of the PAM4 signal.
1 in 3 clocks with respect to the symbol transition information set by the setting means so that the error occurrence probability when viewed at each of the three eye pattern openings in the amplitude direction of the PAM4 signal is 1/3. A transition destination changing means (12) that outputs symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed at a rate of one time, and
A mask generating means (15) that generates a mask pattern for each of the highest-order bit string signal and the lowest-order bit string signal based on the symbol transition information from the transition destination changing means.
An error inserting means (16) for inserting an error based on the bit information of the mask pattern corresponding to each bit of the most significant bit string signal and the least significant bit string signal specified according to the symbol error rate is provided. A PAM4 symbol error addition device characterized by this. This is a PAM4 symbol error addition method that adds an error to the PAM4 signal symbol.
Steps to generate the highest bit string signal,
A step of generating the lowest bit string signal for generating the PAM signal by adding it to the highest bit string signal, and
A step of defining a bit that allows error insertion and a bit that prohibits error insertion with different bit information, and setting symbol transition information indicating the transition destination of the four PAM4 symbols of the PAM4 signal.
The rate of occurrence of an error when viewed at each of the three eye pattern openings in the amplitude direction of the PAM4 signal is 1/3, so that the symbol transition information set is once every three clocks. A step of outputting symbol transition information in which the transition destinations of the four PAM4 symbols of the PAM4 signal are changed, and
A step of generating a mask pattern for each of the highest-order bit string signal and the lowest-order bit string signal based on the symbol transition information in which the transition destination of the PAM4 symbol is changed, and
PAM4 includes a step of inserting an error based on the bit information of the mask pattern corresponding to each bit of the most significant bit string signal and the least significant bit string signal specified according to the symbol error rate. How to add a symbol error. The PAM4 symbol error addition device (2) of claim 1 and
It is provided with an error measuring device (3) for measuring an error rate by receiving a signal from the measured object when the PAM4 signal generated by the PAM4 symbol error adding device is input to the measured object (W). A featured error rate measuring device. A step of inputting the PAM4 signal generated by the PAM4 symbol error addition method of claim 2 and the object to be measured (W), and
A method for measuring an error rate, which comprises a step of receiving a signal from the object to be measured and measuring an error rate accompanying the input of the PAM4 signal to the object to be measured.

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