JP5394949B2 - Transmission quality evaluation apparatus and transmission quality evaluation method - Google Patents

Description

    The present invention relates to an apparatus and method for evaluating transmission quality of a digital signal, and more particularly to an apparatus and method for evaluating the quality of a digital signal transmitted in units of frames.

  When transmitting a digital signal through a network, it is necessary to evaluate the quality of the transmitted digital signal in order to ensure the reliability of the transmitted digital signal.

Conventionally, a bit error rate has been used as a representative index for evaluating the quality of a transmitted digital signal.
In the first prior art, a reference pattern signal is transmitted to a communication device or a transmission path to be measured, and the bit pattern of the digital signal that has passed through the measurement target is compared with the bit pattern of the original reference pattern signal It is a measure of how many bit errors are present. FIG. 11 shows the configuration of the quality evaluation apparatus 6 used in the first prior art. The quality evaluation device 6 generates a reference pattern signal such as a pseudo random pattern (PRBS) signal, for example, and transmits the reference pattern signal to a communication device or transmission path 2 to be measured, A second pattern generation unit 64 that generates the same signal as the reference pattern signal generated by the pattern generation unit 61, a received digital signal obtained from the measurement target (transmission path) 2, and a reference pattern generated by the second pattern generation unit 64 A synchronization establishment unit 63 that synchronizes with a signal and an error detection unit 62 that includes, for example, an exclusive OR circuit and detects error bits. The quality evaluation apparatus 6 according to the first prior art performs exclusive OR of the received digital signal from the transmission path 2 and the reference pattern signal from the second pattern generation unit 64 synchronized with the received digital signal. Thus, the bit error rate is measured by detecting the bit in which an error has occurred in the transmission process and counting the bit (for example, Patent Document 1 and Patent Document 2).

  As a second conventional technique, there is a method of detecting a bit (error bit) in which an error has occurred using a check bit. This is because the check bits for the data to be transmitted are calculated in advance, the redundant check bits are added to the data and transmitted, and the syndrome of the received digital signal received from the transmission path is calculated using the check bits. The error bit is detected (Patent Document 3 and Patent Document 4).

JP 11-46184 A Patent No. 30588805 JP-A-5-327523 JP-A-8-255111

  By the way, in actual transmission, in many cases, a digital signal is transmitted and received in units of frames having a finite length, not as a continuous bit string. Therefore, in the evaluation of transmission quality, it is necessary to measure the frame error rate and the bit error rate as an evaluation index based on transmission in units of frames.

However, the above-described first conventional technique measures the bit error rate using a continuous bit signal. Therefore, the first prior art cannot be used for transmission quality evaluation in the case of transmitting a digital signal in units of frames because there is no frame recognition processing necessary for receiving frames.
In the first prior art, if the number of bits is increased or decreased by performing some processing in the transmission path, the reference pattern signal and the received digital signal are out of synchronization, and an error occurs. Bits cannot be detected. Therefore, when processing such as encoding and decoding is involved in the transmission process, the transmission quality cannot be evaluated by the first conventional technique.

  In the second prior art, it is necessary to calculate the check bits in advance according to the data used for transmission and add them. Further, since the number of error bits that can be detected has an upper limit determined by the inspection bit length, the number of error bits cannot be detected when the received digital signal includes many errors.

Accordingly, a first object of the present invention is to evaluate transmission quality in accordance with the actual situation of transmitting a digital signal in units of frames, and to provide a transmission quality evaluation index based on a frame configuration. is there.
A second object of the present invention is to make it possible to evaluate the transmission quality in units of frames even if there is no upper limit to the number of error bits that can be detected and the received digital signal contains many errors.

  In order to achieve the above-described object, a transmission quality evaluation apparatus according to the present invention generates a plurality of frames composed of a plurality of bits, and sends a signal including these frames to a transmission path. The signal transmitted from the frame generator is received via the transmission path, and a frame receiver that recognizes a frame from the received signal and generated by the frame generator for transmission to the transmission path. Based on the transmission frame and the received frame recognized by the frame receiving unit, an evaluation unit that calculates an evaluation index representing the transmission quality of the frame via the transmission path, and outputs the evaluation index calculated by the evaluation unit And an output unit.

  Here, the frame reception unit discards a frame including at least one bit error, and the evaluation unit counts the number of transmission frames counted by the transmission frame counting unit and the number of reception frames received by the frame reception unit. A first received frame count unit; a first number for calculating the number of discarded frames discarded by the frame receiving unit from a difference between the number of transmission frames and the number of received frames received by the frame receiving unit; The number of discarded frames calculation unit, and a ratio of the number of transmission frames and the number of discarded frames, a first ratio indicating a ratio of error frames transmitted through the transmission path and having an error to the transmission frames And a first frame error rate calculation unit that calculates the frame error rate as the evaluation index.

  The evaluation unit further includes, based on the first frame error rate, a first ratio indicating a ratio of error bits transmitted through the transmission path and having an error with respect to bits included in the transmission frame. You may comprise so that the 1st bit error rate calculation part which calculates a bit error rate as said evaluation parameter | index may be provided.

  The frame receiving unit discards only frames in which an error occurs in bits necessary for frame recognition, and the evaluation unit is received by the transmission frame counting unit that counts the number of transmission frames and the frame receiving unit. A second received frame counting unit that counts the number of received frames, and a difference between the number of transmitted frames and the number of received frames received by the frame receiving unit was not recognized as a frame by the frame receiving unit A second discarded frame number calculating unit for calculating the number of discarded frames, an error frame counting unit for counting the number of error frames in which errors have occurred among the received frames received by the frame receiving unit, and the discarded frames And the number of error frames and the ratio of the number of transmission frames to the transmission frame. The transmitted via the transmission path may be composed of a second frame error rate calculation unit for calculating a second frame error rate, the percentage of error frames an error occurs as the evaluation index Te.

  The evaluation unit further includes an error bit count unit that counts the number of error bits in which an error has occurred among bits constituting the reception frame received by the frame reception unit, and a reception frame received by the frame reception unit. Based on the number of error bits in which an error has occurred, the number of discarded frames, the number of transmission frames, and the frame length of the transmission frame, for the bits constituting the transmission frame, You may comprise so that the 2nd bit error rate calculation part which calculates the 2nd bit error rate which shows the ratio of the error bit which transmitted through the said transmission line and the error produced | generated as said evaluation parameter | index may be provided.

  Also, in the transmission quality evaluation apparatus according to the present invention, the frame receiving unit includes a first frame receiving unit that discards a frame including at least one bit error, and a frame in which an error occurs in a bit necessary for frame recognition. A second frame receiving unit that discards only the transmission frame counting unit, and the evaluation unit counts the number of transmission frames received by the first frame receiving unit. A first discard frame discarded by the first frame reception unit based on a difference between the first reception frame count unit and the number of transmission frames and the number of reception frames received by the first frame reception unit; The transmission frame number is calculated from a first discard frame number calculation unit that calculates the number of frames, and a ratio between the number of transmission frames and the number of first discard frames. A first frame error rate calculation unit that calculates a first frame error rate that indicates a ratio of error frames that are transmitted through the transmission path and cause an error as a result of the evaluation, and the second frame error rate calculation unit. A second received frame counting unit that counts the number of received frames received by the frame receiving unit, and a difference between the number of transmitted frames and the number of received frames received by the second frame receiving unit, There is an error in a second discarded frame number calculating unit that calculates the number of second discarded frames that are not recognized as frames by the second frame receiving unit, and a received frame received by the second frame receiving unit. An error frame count unit that counts the number of error frames in which an error occurs, a sum of the number of second discarded frames and the number of error frames, and the transmission frame A second frame error that calculates a second frame error rate that indicates a ratio of error frames transmitted through the transmission path and having an error from the transmission frame as the evaluation index. A rate calculating unit comparing the first frame error rate and the second frame error rate, and based on the comparison result, the first frame error rate and the second frame error by the output unit And an output control unit that controls the output of the rate.

The evaluation unit further includes a first ratio indicating a ratio of error bits transmitted through the transmission path and having errors based on the bits included in the transmission frame based on the first frame error rate. A first bit error rate calculation unit that calculates a bit error rate of
An error bit count unit that counts the number of error bits in which an error has occurred among the bits constituting the reception frame received by the second frame reception unit, and a reception frame received by the second frame reception unit. Based on the number of error bits in which an error has occurred, the number of second discarded frames, the number of transmission frames, and the frame length of the transmission frame, the bits constituting the transmission frame And a second bit error rate calculating unit that calculates a second bit error rate indicating the rate of error bits transmitted through the transmission path and causing an error as the evaluation index.
The output control unit further compares the first bit error rate and the second bit error rate, and based on the comparison result, the first bit error rate and the first bit error rate in the output unit The output of the bit error rate of 2 may be controlled.

  In the transmission quality evaluation apparatus according to the present invention described above, the frame reception unit sets a frame including at least one bit error as a discard frame, and the first bit error rate calculation unit calculates the frame error rate R1 and the bit error. The bit error rate R2 may be calculated from the frame error rate R1 based on the equation (1) indicating the relationship between the rate R2 and the frame length n.

1- (1-R2) ⁿ = R1 (1)

  In addition, the bit error rate calculation unit is an expression indicating the relationship among the number C1 of transmission frames, the number C3 of discarded frames, the bit error rate R3 of discarded frames, and the number m of bits necessary for frame recognition. The bit error rate R3 of the discarded frame is calculated from (3), and the discarded frame calculated from the bit error rate R3 of the discarded frame, the number of discarded frames C3, and the frame length n is calculated according to the equation (4). The sum of the number of error bits included (C3 × n × R3) and the number of error bits C5 in which errors occur among the bits constituting the reception frame, and the total number of bits of the transmission frame (C1 × n) The bit error rate R2 may be calculated by obtaining the ratio of.

1- (1-R3) ^m = C3 / C1 (3)
R2 = {C5 + (C3 × n × R3)} / (C1 × n) (4)

  The transmission quality evaluation apparatus according to the present invention also includes a frame generation unit that generates a plurality of frames composed of a plurality of bits, the frame generated by the frame generation unit, and a codeword obtained by encoding the frame. An encoding unit to be transmitted to a transmission line; a decoding unit for receiving the codeword transmitted from the encoding unit via the transmission line; and decoding the received codeword into a frame; and the decoding unit A frame receiving unit for recognizing a frame from the digital signal decoded by the unit, a transmission frame generated by the frame generating unit for transmission to the transmission path, and a received frame recognized by the frame receiving unit An evaluation unit that calculates an evaluation index representing the transmission quality of the frame via the transmission path, and a previous calculation calculated by the evaluation unit. It can be configured to an output unit for outputting the evaluation index.

  Here, the evaluation unit determines a ratio of error frames including an error to the frame generated by the frame generation unit based on at least the number of transmission frames and the number of reception frames received by the frame reception unit. A frame error rate calculation unit for calculating a frame error rate (R1) indicating the number of bytes in error with respect to the total number of bytes of the codeword received by the decoding unit based on the frame error rate (R1) And a pre-decoding byte error rate calculation unit for calculating a pre-decoding byte error rate (R5) indicating a ratio of the number of bits, and the decoding unit with respect to the total number of bits included in the frame generated by the frame generation unit Bit error rate calculation unit for calculating a bit error rate (R2) indicating the ratio of the number of erroneous bits included in the frame decoded by It may be configured with.

  In the transmission quality evaluation apparatus according to the present invention, the encoding unit sends a k-byte code word to the transmission line, and the decoding unit detects errors up to q bytes (q <k) included in the code word. The pre-decoding byte error rate calculation unit calculates a pre-decoding byte error rate R5 based on the following equation (5), and the bit error rate calculation unit calculates the following equation (6): Based on this, the post-decoding byte error rate (R6) indicating the ratio of the number of erroneous bytes to the total number of bytes of the decoded frame is calculated, and the bit error rate is calculated based on the following equation (7) You may comprise so that (R2) may be calculated.

  According to the present invention, it is possible to measure a transmission quality evaluation index based on a frame configuration, instead of evaluating the quality of a signal as a simple bit string as shown in the first prior art. Can be evaluated. Also, since there is no upper limit to the number of error bits that can be detected, the transmission quality can be evaluated even when the received digital signal contains many errors.

It is a figure which shows the structure of the transmission quality evaluation apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the evaluation part of the transmission quality evaluation apparatus which concerns on 1st Embodiment. It is a figure which shows an example of the hardware constitutions of the transmission quality evaluation apparatus which concerns on 1st Embodiment. It is a figure which shows the structure of the transmission quality evaluation apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the evaluation part of the transmission quality evaluation apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the transmission quality evaluation apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the evaluation part of the transmission quality evaluation apparatus which concerns on 3rd Embodiment. It is a figure which shows the structure of the transmission quality evaluation apparatus which concerns on the 4th Embodiment of this invention. It is a figure explaining the relationship between transmission of a frame, and encoding and decoding by a Reed-Solomon code. It is a figure which shows the structure of the evaluation part of the transmission quality evaluation apparatus which concerns on 4th Embodiment. It is a figure explaining the 1st conventional technique.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the transmission quality evaluation apparatus 1 according to the first embodiment of the present invention digitally receives a frame generator 11 and a signal transmitted from the frame generator 11 via a transmission line 2. A frame receiving unit 12 for recognizing a frame, an evaluation unit 13 for calculating an evaluation index representing transmission quality of the frame via the transmission path 2, and an output unit for outputting the evaluation index calculated by the evaluation unit 13 14.

  The frame generator 11 generates a plurality of frames and sends a signal including these frames to the transmission path 2. A frame generated by the frame generator 11 is a digital signal having a finite length composed of a plurality of bits.

  A typical example of such a frame is an Ethernet (registered trademark) frame. The Ethernet frame is composed of four parts: “preamble”, “MAC header”, “data”, and “FCS (frame check sequence)”. Here, the “preamble” added to the beginning of the frame is a special bit string indicating the start of the frame. Further, “FCS” added to the end of the frame is also called a value (“FCS value”) for checking whether there is an error (error) in the MAC header or data portion preceding this, and as an example, Is the sum of all bits of.). This FCS is calculated and added at the frame transmitting side when a frame is created. On the receiving side, when the preamble is detected, the same calculation as the calculation of the FCS value is performed, and if the calculation result matches the FCS value of the frame, the transmitted digital signal is recognized as a frame and received. .

  The frame receiving unit 12 recognizes a frame from the digital signal received via the transmission path 2 and receives the frame. For convenience of explanation, in the first embodiment, the frame receiving unit 12 recognizes the start of a frame from the received digital signal, recognizes the start of the frame, and a series of digital data constituting this frame. If there is no error in any bit of the signal, this series of digital signals is recognized as one frame and received. Therefore, in the present embodiment, the frame receiving unit 12 does not recognize (ie, discard) a frame in which at least one bit error has occurred as a result of being transmitted via the transmission path 2 as a frame. ).

Such a frame receiver 12 includes, for example, a pattern generator that generates the same bit pattern as the frame generated in the frame generator 11 and a synchronization establishment unit that detects a preamble from the received digital signal and establishes synchronization. The bit pattern generated in the pattern generation unit and the received digital signal are synchronized and each bit is compared, and only when all the bits match, the received series of digital signals is converted into one frame. Recognize and receive.
If the frame to be transmitted is an Ethernet frame, the start of the frame is detected to recognize the start of the frame, and if the FCS is correct, the received series of digital signals are recognized as one frame. You may make it receive.

  The evaluation unit 13 receives a frame (hereinafter referred to as “transmission frame”) A generated by the frame generation unit 11 for transmission to the transmission path 2 and a frame recognized by the frame reception unit 12 (hereinafter referred to as “reception”). An evaluation index representing the transmission quality of the frame via the transmission path 2 is calculated based on “frame”.) B.

In the present embodiment, the evaluation unit 13 includes a transmission frame count unit 131, a reception frame count unit 132, a discarded frame number calculation unit 133, a frame error rate calculation unit 134, and a bit error rate calculation unit 135, as shown in FIG. I have.
The transmission frame count unit 131 receives a frame from the frame generation unit 11 and transmits the number of transmission frames A sent by the frame generation unit 11 to the transmission path 2 (hereinafter referred to as “transmission frame number”, which is expressed as “C1”). .)
The reception frame counting unit 132 receives the reception frame B recognized and received by the frame reception unit 12 from the frame reception unit 12, and refers to the number of reception frames B (hereinafter referred to as “the number of reception frames”, “C2”). Count).

  The discard frame number calculation unit 133 receives the number of transmission frames (C1) and the number of reception frames (C2) counted by the transmission frame count unit 131 and the reception frame count unit 132, respectively, and receives a reception frame from the number of transmission frames (C1). The number (C2) is subtracted to calculate the number of discarded frames (hereinafter referred to as “discarded frame number”, expressed as “C3”) (C3 = C1−C2). This “number of discarded frames” represents the number of frames that have been sent from the frame generation unit 11 to the transmission path 2 but have not been recognized and received as frames by the frame receiving unit 12, that is, the number of discarded frames. .

  Based on the number of transmission frames (C1) counted by the transmission frame count unit 131 and the number of discarded frames (C3) calculated by the number of discarded frames calculation unit 133, the frame error rate calculation unit 134 (Hereinafter referred to as “R1”). The “frame error rate (R1)” is a ratio of frames (hereinafter referred to as “error frames”) in the transmission frame A in which errors (errors) are transmitted through the transmission path.

In the first embodiment, as described above, since a frame in which an error has occurred even with one bit is discarded, all frames including an error become a discarded frame. Therefore, since the frame error rate (R1) is equal to the frame discard rate (R0), the frame error rate calculation unit 134 divides the number of discarded frames (C3) by the number of transmitted frames (C1) to obtain the frame discard rate ( R0 = C3 / C1) is calculated as the frame error rate (R1).
The frame error rate (R1 = R0) obtained in this way is output from the output unit 14 as an evaluation index indicating the transmission quality of the frame via the transmission path 2, and is also sent to the bit error rate calculation unit 135.

  The bit error rate calculation unit 135 calculates a “bit error rate” (hereinafter referred to as “R2”) based on the frame error rate (R1 = R0) calculated by the frame error rate calculation unit 134. The “bit error rate (R2)” refers to a bit (hereinafter referred to as “error bit”) in which an error occurs due to transmission through the transmission path 2 with respect to the bit included in the transmission frame A. It is a ratio.

  In this embodiment, as described above, all frames with errors are discarded, so that the bit error rate (R2) is determined when there is an error of 1 bit or more in n bits of the frame. Can be calculated by solving the equation (1) indicating the relationship between the frame error rate (R1 = R0) and the bit error rate (R2) in the case of error (discarding) as a bit error rate (R2). .

1- (1-R2) ⁿ = R1 (1)
Here, n represents the frame length.

The left-hand side of this equation (1) is the probability (1-R2) an error in any of the n bits is not generated for a frame by subtracting from 1 a ^n, represents the probability that an error occurs in one of the bit Equation (1) shows that this probability is equal to the frame error rate (R1).

  The bit error rate (R2) calculated in this way is output from the output unit 14 as an evaluation index representing the transmission quality of the frame via the transmission path 2, similarly to the frame error rate (R1).

The transmission quality evaluation apparatus according to this embodiment described above is realized by installing a transmission quality evaluation program in a computer. FIG. 3 shows an outline of the hardware configuration of the computer. As hardware resources, a central processing unit (CPU) 101, an internal storage device 102 such as a ROM and a RAM, and various interface devices (I / F) 104 and 105 are connected to each other via a bus 103. An external device (for example, an external storage device such as an HDD or an input / output device such as a keyboard or a display) is connected to the I / F 104.
The transmission quality evaluation program is taken into the internal storage device 102 from the external storage device 106 via the I / F 104 or via the network. Under the control of the transmission quality evaluation program, the CPU 101, the internal storage device 102, and the I / Fs 104 and 105 cooperate to function as the frame generation unit 11, the frame reception unit 12, the evaluation unit 13, and the output unit 14 described above. Realize.

  According to the transmission quality evaluation apparatus according to the present embodiment, it is possible to measure the frame error rate and bit error rate of all transmission frames A including discarded frames, and to evaluate the transmission quality with high accuracy in units of frames. it can.

  Further, the evaluation unit may simply take an exclusive OR of each bit of the transmission frame A and the reception frame B, and transmit a signal in which the error bit is 1 and the non-error bit is 0 to the output unit. In that case, how the error occurs can be recognized in time series, and there are effects of reducing the power consumption, downsizing, reducing the price, and increasing the speed of the apparatus. Alternatively, the total number of 1s representing error bits may be output, and the error type may be a continuous error (an error that continues for L bit or more with L as a threshold) or a discontinuous error (an error that does not continue for L bit or more with L as a threshold). ) Etc. may be determined and output.

Further, in order to investigate the occurrence state of various levels of errors, an attenuator may be inserted in the transmission line, and an error may be intentionally inserted in the frame.
The frame transmission method may be either continuous transmission with an idle signal inserted between frames or burst transmission in which no signal is transmitted between frames.

[Second Embodiment]
Next, a transmission quality evaluation apparatus according to the second embodiment of the present invention will be described.
In addition, about the structure which is common in the transmission quality evaluation apparatus which concerns on 1st Embodiment mentioned above, suppose that the same code | symbol is used and the description is abbreviate | omitted suitably.

FIG. 4 shows the configuration of the transmission quality evaluation apparatus according to the second embodiment.
Compared with the transmission quality evaluation apparatus 1 according to the first embodiment described above, the transmission quality evaluation apparatus 1a according to the present embodiment has a common frame generation unit 11 and output unit 14, while the frame reception unit 12a. The evaluation unit 13a is different in the following points.

  That is, the present embodiment is different from the first embodiment described above in that the frame receiving unit 12a recognizes and receives a frame based on some bits of the frame rather than the entire frame. Therefore, even if an error (error) is included in a frame transmitted via the transmission path 2, if there is no error in a predetermined bit necessary for recognition as a frame, an error is included in other bits. Even if it is recognized as a frame. In the case of an Ethernet frame, as the above-described “predetermined bits necessary for recognition as a frame”, for example, a preamble added to the beginning of the frame may be used.

  Further, the evaluation unit 13a that calculates the evaluation index, as shown in FIG. 5, causes an error (error) that is transmitted through the transmission path as the frame reception unit 12a has the characteristics described above. An error frame count unit 236 that counts the number of frames (hereinafter referred to as “number of error frames”, referred to as “C4”), and the number of error bits (hereinafter referred to as “number of error bits”, expressed as “C5”). And an error bit count unit 237 for counting.

  Specifically, the error frame count unit 236 and the error bit count unit 237 are both the bits included in the transmission frame A generated by the frame generation unit 11 and the reception frame B recognized and received by the frame reception unit 12a. Is compared with each bit included in. Then, if there is a bit different between the two, the error bit count unit 237 counts this as an error bit to obtain the error bit number C5. Further, if even one error bit is included in the received frame B, the error frame count unit 236 counts that frame as an error frame and obtains the number of error frames including the error bit (number of error frames (C4)). .

In the present embodiment, the calculation of the frame error rate and the bit error rate in the frame error rate calculation unit 234 and the bit error rate calculation unit 235 is as follows.
<Calculation of frame error rate>
The frame error rate calculation unit 234 calculates the frame error rate (R1) based on the number of transmission frames (C1), the number of discarded frames (C3), and the number of error frames (C4), for example, according to the following equation (2).

  R1 = (C3 + C4) / C1 (2)

  Here, (C3 + C4) is the number of frames that have been transmitted through the transmission path 2 and have bits in which errors (errors) have occurred regardless of whether or not they are predetermined bits necessary for recognition as a frame. Therefore, the value obtained by dividing this by the number of transmission frames (C1) is “the ratio of frames in the transmission frame A that are transmitted through the transmission path and in which an error (error) occurs, that is, the frame error rate (R1)”. It becomes.

<Calculation of bit error rate>
The bit error rate calculation unit 235 obtains, for example, the bit error rate (hereinafter referred to as “R3”) of the discarded frame from the following equation (3), and then the bits included in the transmission frame A from the equation (4). In contrast, a bit error rate (R2) indicating the ratio of error bits transmitted through the transmission path 2 and causing errors (errors) is calculated.

1- (1-R3) ^m = C3 / C1 (3)
R2 = {C5 + (C3 × n × R3)} / (C1 × n) (4)
Here, m is the number of bits of “predetermined bits necessary for recognizing a digital signal received by the frame receiving unit 12a via the transmission path 2 as a frame”, and n is the frame length (the number of bits constituting the frame). ) (M <n). For example, when the frame receiving unit 12a recognizes the frame by detecting the 64-bit preamble at the head of the frame, the value of m is 64.

Equation (3) is the ratio of the number of discarded frames to the number of transmitted frames, that is, the frame discard rate (R0 = C3 / C1) when one frame out of m bits is discarded if there is an error. This shows the relationship with the bit error rate (R3) of the frame.
Further, the expression (4) indicates that the sum of the number of error bits (C5) of the received frame B and the number of error bits (C3 × n × R3) in the discard frame (that is, the frame other than the received frame B) is transmitted. The bit error rate (R2) is calculated by dividing by the total number of bits (C1 × n) of frame A.
Note that the bit error rate (R3) of the discard frame may be a fixed value. For example, when the bit error rate (R3) of the discarded frame is sufficiently small, the number of error bits in the discarded frame is assumed to be 1 bit, and the bit error rate (R3) of the discarded frame is used as the frame length (n). The inverse of may be used.

The frame error rate (R1) and the bit error rate (R2) calculated in this way are output from the output unit 14.
As described above, even when frame recognition / reception is performed based on some bits of the frame, the frame error rate (R1) and the bit error rate (R2) are used as evaluation indexes representing the transmission quality of the frame. Can be sought.

  If it can be assumed that the error exists uniformly in the frame, the evaluation unit may substitute the bit error rate (R3) of the discarded frame obtained by the equation (3) for the bit error rate (R2). good.

[Third Embodiment]
The transmission quality evaluation apparatus according to the third embodiment of the present invention includes both the evaluation unit 13 in the first embodiment and the evaluation unit 13a in the second embodiment substantially described above, The output of the evaluation index is controlled by comparing the evaluation indices by these two evaluation units.

FIG. 6 shows the overall configuration of the transmission quality evaluation apparatus according to the present embodiment, and FIG. 7 shows the configuration of the evaluation unit 13b. In addition, about the structure which is common in the transmission quality evaluation apparatus which concerns on the 1st and 2nd embodiment mentioned above, suppose that the same code | symbol is used and the description is abbreviate | omitted suitably.
As shown in FIG. 6, the transmission quality evaluation apparatus 1b according to the present embodiment includes two frame reception units, that is, a first frame reception unit 12 and a second frame reception unit 12a. The frame is recognized and received and the received frame B and the received frame B ′ are output by the method described in the embodiments and the second embodiment.
In FIG. 7, the first received frame count unit 132, the first discarded frame number calculation unit 133, the first frame error rate calculation unit 134, and the first bit error rate calculation unit 135 are each described in the first embodiment. The same processing as that of the received frame count unit 132, the discarded frame number calculation unit 133, the frame error rate calculation unit 134, and the bit error rate calculation unit 135 is performed. In addition, the second received frame count unit 232, the second discarded frame number calculation unit 233, the second frame error rate calculation unit 234, and the second bit error rate calculation unit 235 are the received frames described in the second embodiment. The same processing as that of the counting unit 232, the discarded frame number calculating unit 133, the frame error rate calculating unit 234, and the bit error rate calculating unit 235 is performed.

  Therefore, the transmission frame count unit 131, the first reception frame count unit 132, the first discard frame number calculation unit 133, the first frame error rate calculation unit 134, and the first bit error rate calculation unit 135 are the same as those in the first implementation described above. The evaluation unit 13 (hereinafter referred to as a “first evaluation unit”) in the form of the transmission frame count unit 131, the second reception frame count unit 232, the second discard frame number calculation unit 233, the second The frame error rate calculation unit 234, the error frame count unit 236, the error bit count unit 237, and the second bit error rate calculation unit 235 are the evaluation unit 13a in the second embodiment described above (hereinafter referred to as “second "Evaluation part").

  The evaluation index calculated by the first evaluation unit 13, that is, the first frame error rate (R11) and the first bit error rate (R21) calculated by the first frame error rate calculation unit 134 (hereinafter referred to as "Evaluation result (Q1)") and the evaluation index calculated by the second evaluation unit 13a, that is, the second frame error rate (R12) calculated by the second frame error rate calculation unit 234. The second bit error rate (R2 2) (hereinafter collectively referred to as “evaluation result (Q2)”) is input to the output control unit 138.

The output control unit 138 compares the evaluation result (Q1) by the first evaluation unit 13 and the evaluation result (Q2) by the second evaluation unit 13a, and determines whether or not to output them. For example, the difference between two evaluation results is obtained, and when the difference is equal to or less than a certain threshold T1 (| Q1-Q2 | ≦ T1), it is determined that the evaluation results are reliable, and these are output to the output unit 14. If it is output and is larger than the threshold value T1 (| Q1-Q2 |> T1), it may be determined that the evaluation result is unreliable and not output.
Here, as specific examples of | Q1-Q2 |, the magnitude of the difference between two frame error rates | R11-R12 | and the magnitude of the difference between two bit error rates | R21-R2 | .

  In the first evaluation unit 13 and the second evaluation unit 13a, the bit to be noted when recognizing the frame from the digital signal received via the transmission path 2 is the entire frame in the former, whereas in the latter, This is different in that it is a predetermined partial bit of a frame, for example, a preamble. On the other hand, in the transmission via the transmission path 2, if the probability that an error occurs is uniform regardless of the position of the bits constituting the frame (that is, the position in the frame), the evaluation result (Q1 ) And the evaluation result (Q2) should be the same. Therefore, when the difference between the evaluation result (Q1) and the evaluation result (Q2) is large, the evaluation result may be output as suspicious, or the user may be able to output that the evaluation result is unreliable. .

As described above, in the first to third embodiments, the output unit 14 has been described as outputting both the frame error rate (R1) and the bit error rate (R2). May be output only.
Further, although the evaluation units 13, 13a, and 13b have been described as having both a configuration for calculating the frame error rate and a configuration for calculating the bit error rate, the frame error rate (R1) and the bit error are described. When only one of the rates (R2) is output, only the configuration for calculating the output evaluation index may be provided.

  Further, a new evaluation index may be calculated and output from the frame error rate (R1) and the bit error rate (R2). For example, the output unit 14 divides the frame error rate (R1) by the bit error rate (R2), and the result (R1 / R2 = R4) is equal to or less than a certain threshold value (T2) (R4). ≦ T2), it is determined that there are error bits in some frames, and if they are large (R4> T2), the difference in the number of error bits included in each frame is small (the error bits are uniformly present). And the result of the determination may be output. Such an index (R4) can be used to determine whether or not an error has occurred due to a sudden phenomenon.

[Fourth Embodiment]
The transmission quality evaluation apparatus according to the fourth embodiment of the present invention is an apparatus that evaluates transmission quality when a frame is encoded and transmitted and decoded on the reception side. The transmission quality evaluation device 4 is obtained by adding an encoding unit 45 and a decoding unit 46 to the transmission quality evaluation device according to the first to third embodiments described above.

Specifically, as shown in FIG. 8, the transmission quality evaluation apparatus 4 according to the present embodiment encodes a frame generator 41 that generates a plurality of frames, and a frame generated by the frame generator 41. The encoding unit 45 that sends the obtained code word to the transmission path 2, and the code word sent from the encoding section 45 is received via the transmission path 2, and the received code word is decoded into a frame. Decoding unit 46, frame receiving unit 42 for recognizing a frame from the digital signal decoded by decoding unit 46, transmission frame A generated by frame generating unit 41 and frame receiving unit 42 Based on the received frame B, an evaluation unit 43 that calculates an evaluation index representing the transmission quality of the frame via the transmission path 2, and the evaluation unit 43 calculates And an output unit 14 for outputting the evaluation index is.
Here, the configuration and operation of the output unit 14 are the same as those of the output unit in the first to third embodiments described above, and thus detailed description thereof is omitted.

  The frame generation unit 41 in the present embodiment corresponds to the frame generation unit 11 in the first to third embodiments described above. The frame receiving unit 42 in the present embodiment corresponds to the frame receiving units 12 and 12a in the first to third embodiments described above. The evaluation unit 43 corresponds to the evaluation units 13, 13a, and 13b in the first to third embodiments.

The encoding unit 45 receives the transmission frame A generated by the frame generation unit 41, encodes a Reed-Solomon code (h, k), for example, and transmits the codeword α to the transmission path. The decoding unit decodes the codeword β received from the transmission path using, for example, a Reed-Solomon code (h, k), and transmits the decoded codeword β to the frame receiving unit 42.
H and k are integers representing the number of bytes (h <k), and Reed-Solomon sends and receives a h-byte signal with a redundant signal of p (p = k−h) bytes. In this encoding, the error included in the k-byte signal is corrected to the number of bytes obtained by multiplying p by 0.5 (referred to as q).

Here, the relationship between frame transmission and Reed-Solomon encoding / decoding will be described with reference to FIG.
The transmission frame A (frame length n bits (FIG. 9 (a))) generated by the frame generation unit 41 is added by the encoding unit 45 with a redundant signal of p (p = k−h) bytes for every h bytes. Then, it is encoded into a k-byte code word α (FIG. 9B). In many cases, when such a code word α is transmitted through the transmission line 2, an error occurs in the transmission process, and the code word β including the error is received by the decoding unit 46 (see FIG. 9 (c)). However, when the code word β including this error is decoded by the decoding unit 46, a digital signal in which all errors generated in the transmission process are corrected (if it is within q bytes) is obtained (FIG. 9). (D)). The frame receiving unit 42 recognizes a frame having a frame length of n bits by detecting a preamble from the digital signal.

  As illustrated in FIG. 10, the evaluation unit 43 includes an error including an error with respect to the frame generated by the frame generation unit 41 based on at least the number of transmission frames and the number of reception frames received by the frame reception unit. A frame error rate calculation unit 434 that calculates a frame error rate (R1) indicating the ratio of frames, and an error relative to the total number of bytes of the codeword received by the decoding unit 46 based on the frame error rate (R1) Based on the pre-decoding byte error rate calculation unit 436 for calculating the pre-decoding byte error rate (R5) indicating the ratio of the number of certain bytes, and the pre-decoding byte error rate (R5), the frame generation unit 41 The division of the number of erroneous bits contained in the frame decoded by the decoding unit 46 to the total number of bits contained in the generated frame. Composed of the bit error rate calculation unit 435 Metropolitan for calculating the bit error rate (R2) indicating the.

If the frame error rate (R1) is obtained by the frame error rate calculation unit 434, the pre-decoding byte error rate (R5) and the bit error rate (R2) are calculated according to the following relational expressions (5) to (7). it can.
Note that “ _k C _t ” in the expressions (5) and (6) represents a combination function.

First, the pre-decoding byte error rate calculation unit 436 calculates the pre-decoding byte error rate (R5) according to the equation (5) based on the frame error rate (R1). Since this equation (5) cannot correct an error (error) exceeding q bytes depending on the Reed-Solomon code, the probability of occurrence of an error only in an arbitrary t byte (q + 1 ≦ t ≦ k) (R5 ^t (1− R5) ^(kt) ) is calculated for each of (q + 1) bytes to k bytes, and the sum of them is equal to the frame error rate (R1), so that the byte error rate (R5) before decoding is calculated. It is. The frame error rate (R1) has the same meaning as the frame error rate (R1) described in the first embodiment.

Also, the bit error rate calculation unit 435 calculates the byte error rate (R6) of the frame after decoding by the decoding unit 46 from the pre-decoding byte error rate (R5) according to the equation (6). The bit error rate (R2) is calculated from the error rate (R6) according to the equation (7).
In general, the byte error rate is obtained by dividing the number of bytes in which an error (error) exists even in one bit (this is expressed as “B1”) by the total number of bytes (this is expressed as “B2”). (B3 = B1 / B2).

Here, Equation (6) is an equation representing the relationship between the pre-decoding byte error rate (R5) and the decoded frame byte error rate (R6). This equation (6) is the code (R5 ^t (1−R5) ^(kt) ) with the probability (R5 ^t (1−R5) ^(kt) ) that an error (error) occurs in any t bytes (q + 1 ≦ t ≦ k) of k-byte code words. The ratio (t / k) of error bytes (t) to the total bytes (k) of the word is weighted, and the sum of those between (q + 1) bytes and k bytes, which is the number of bytes that cannot be corrected by decoding, is taken. This value is equal to the ratio of error bytes included in all codewords to the total number of bytes of all codewords, that is, the byte error rate (R6) of the encoded frame.
In general, the relationship between the byte error rate and the bit error rate is expressed by equation (7).

  As described above, according to the present embodiment, when a codeword obtained by encoding a frame is transmitted through a transmission path, the transmission quality of the frame is determined by observing the decoded frame. A frame error rate and a bit error rate can be calculated as an evaluation index representing. Therefore, even when a digital signal is encoded and transmitted, the transmission quality can be evaluated on the premise of the frame configuration.

In the present embodiment, the encoding unit 45 and the decoding unit 46 have been described as being implemented on one piece of hardware together with the evaluation unit 43 and other components. The encoding unit 46 may be realized by independent hardware as an “encoding device” and a “decoding device”, respectively, and may be installed in a physically different place from the transmission quality evaluation device including the evaluation unit 43 and the like.
In the present embodiment, the encoding unit and the decoding unit are added to the transmission quality evaluation apparatus, but it goes without saying that a signal processing unit other than the encoding and decoding may be added as appropriate.

  The present invention can be used in the transmission field, particularly in digital transmission.

  DESCRIPTION OF SYMBOLS 1, 1a, 1b, 4 ... Transmission quality evaluation apparatus, 2 ... Transmission path, 11 ... Frame generation part, 12, 12a ... Frame reception part, 13, 13a, 13b, 43 ... Evaluation part, 14 ... Output part, 131 ... Transmission frame count unit, 132 ... reception frame count unit, 133 ... discard frame number calculation unit, 134, 234, 434 ... frame error rate calculation unit, 135, 235, 435 ... bit error rate calculation unit, 236 ... error frame count unit 237, error bit count unit, 138, output control unit, 45, encoding unit, 46, decoding unit, 436, pre-decoding byte error rate calculation unit.

Claims (10)

Generating a plurality of frames composed of a plurality of bits and sending a signal including these frames to a transmission path;
Receiving the signal transmitted from the frame generator via the transmission path, and recognizing a frame from the received signal;
Based on the transmission frame generated by the frame generation unit and the reception frame recognized by the frame reception unit for transmission to the transmission line, an evaluation index representing the transmission quality of the frame via the transmission line is calculated. An evaluation unit;
An output unit that outputs the evaluation index calculated by the evaluation unit ,
The frame receiver discards only the frame in which an error has occurred in bits necessary for frame recognition,
The evaluation unit is
A transmission frame count unit for counting the number of the transmission frames;
A second received frame counting unit for counting the number of received frames received by the frame receiving unit;
A second discarded frame number calculating unit that calculates the number of discarded frames discarded by the frame receiving unit from the difference between the number of transmission frames and the number of received frames received by the frame receiving unit;
An error frame count unit that counts the number of error frames in which errors have occurred among the received frames received by the frame reception unit;
The ratio of the sum of the number of discarded frames and the number of error frames and the number of transmission frames indicates the ratio of error frames that have been transmitted through the transmission path and have errors. A second frame error rate calculation unit for calculating a second frame error rate as the evaluation index;
A transmission quality evaluation apparatus comprising: In the transmission quality evaluation apparatus according to claim 1 ,
The evaluation unit further includes:
An error bit count unit for counting the number of error bits in which an error has occurred among the bits constituting the reception frame received by the frame reception unit;
Based on the number of error bits in which an error has occurred among the bits constituting the reception frame received by the frame reception unit, the number of discarded frames, the number of transmission frames, and the frame length of the transmission frame, A second bit error rate calculation unit that calculates, as the evaluation index, a second bit error rate indicating a ratio of error bits that are transmitted through the transmission path and have an error with respect to the bits constituting the transmission frame A transmission quality evaluation apparatus comprising: In the transmission quality evaluation apparatus according to claim 1,
The frame reception unit includes a first frame reception unit that discards a frame including at least one bit error, and a second frame reception unit that discards only a frame in which an error occurs in bits necessary for frame recognition. Have
The evaluation unit is
A transmission frame count unit for counting the number of the transmission frames;
A first received frame counting unit for counting the number of received frames received by the first frame receiving unit;
A first number of frames discarded by the first frame receiver is calculated from a difference between the number of transmission frames and the number of received frames received by the first frame receiver. A discard frame number calculation unit;
A first frame error rate indicating a ratio of error frames transmitted through the transmission path and causing an error to the transmission frame based on a ratio between the number of the transmission frames and the number of the first discard frames. A first frame error rate calculation unit that calculates the evaluation index as the evaluation index;
A second received frame counting unit for counting the number of received frames received by the second frame receiving unit;
From the difference between the number of transmission frames and the number of received frames received by the second frame receiving unit, the number of second discarded frames that are not recognized as frames by the second frame receiving unit is calculated. A second discard frame number calculation unit;
An error frame count unit for counting the number of error frames in which an error has occurred among the received frames received by the second frame reception unit;
From the ratio of the sum of the number of the second discarded frames and the number of the error frames and the number of the transmission frames, an error frame that is transmitted to the transmission frame via the transmission path and has an error. A second frame error rate calculation unit for calculating a second frame error rate indicating a ratio as the evaluation index;
The first frame error rate is compared with the second frame error rate, and the output of the first frame error rate and the second frame error rate by the output unit is controlled based on the comparison result And a transmission quality evaluation apparatus. In the transmission quality evaluation apparatus according to claim 3 ,
The evaluation unit further includes:
Based on the first frame error rate, a first bit error rate indicating a ratio of error bits transmitted through the transmission path and having an error to bits included in the transmission frame is determined as the evaluation index. A first bit error rate calculator that calculates as:
An error bit count unit for counting the number of error bits in which an error has occurred among the bits constituting the reception frame received by the second frame reception unit;
The number of error bits in which an error has occurred among the bits constituting the received frame received by the second frame receiver, the number of the second discarded frames, the number of the transmitted frames, and the frame length of the transmitted frames Based on the above, a second bit error rate indicating a ratio of error bits transmitted through the transmission path and having an error with respect to bits constituting the transmission frame is calculated as the evaluation index. A bit error rate calculation unit of
The output control unit further includes:
Comparing the first bit error rate and the second bit error rate, and controlling the output of the first bit error rate and the second bit error rate in the output unit based on the comparison result A transmission quality evaluation apparatus. In the transmission quality evaluation apparatus according to claim 4 ,
The first bit error rate calculation unit calculates the bit error rate R2 from the frame error rate R1 based on the equation (1) indicating the relationship among the frame error rate R1, the bit error rate R2, and the frame length n. A characteristic transmission quality evaluation device.
1- (1-R2) ⁿ = R1 (1) In the transmission quality evaluation apparatus according to claim 2 or 4 ,
The frame receiving unit sets a frame in which an error occurs in bits necessary for frame recognition as a discard frame,
The bit error rate calculation unit calculates the relationship between the number C1 of transmission frames, the number C3 of discarded frames, the bit error rate R3 of discarded frames, and the number m of bits necessary for frame recognition (3 ) To calculate the bit error rate R3 of the discarded frame, and is included in the discarded frame calculated from the bit error rate R3 of the discarded frame, the number C3 of discarded frames, and the frame length n according to Equation (4). The ratio of the sum of the number of error bits (C3 × n × R3) and the number of error bits C5 in which errors occur among the bits constituting the received frame to the total number of bits (C1 × n) of the transmission frame A bit error rate R2 is calculated by obtaining the transmission quality evaluation apparatus.
1- (1-R3) ^m = C3 / C1 (3)
R2 = {C5 + (C3 × n × R3)} / (C1 × n) (4) A frame generator for generating a plurality of frames composed of a plurality of bits;
An encoding unit that encodes the frame generated by the frame generation unit and sends the obtained codeword to a transmission line;
A decoding unit that receives the codeword sent from the encoding unit via the transmission line and decodes the received codeword into a frame;
A frame receiving unit for recognizing a frame decoded by the decoding unit;
Based on the transmission frame generated by the frame generation unit and the reception frame recognized by the frame reception unit for transmission to the transmission line, an evaluation index representing the transmission quality of the frame via the transmission line is calculated. An evaluation unit;
An output unit that outputs the evaluation index calculated by the evaluation unit ,
The evaluation unit is
A frame error rate (R1) indicating a ratio of error frames including an error to a frame generated by the frame generation unit based on at least the number of transmission frames and the number of reception frames received by the frame reception unit ) To calculate a frame error rate,
Based on the frame error rate (R1), a pre-decoding byte error rate (R5) indicating a ratio of the number of erroneous bytes to the total number of bytes of the codeword received by the decoding unit is calculated. A pre-decoding byte error rate calculator,
Based on the pre-decoding byte error rate (R5), the total number of bits included in the frame generated by the frame generation unit is compared with the number of erroneous bits included in the frame decoded by the decoding unit. A transmission quality evaluation apparatus comprising: a bit error rate calculation unit that calculates a bit error rate (R2) indicating a ratio of numbers . In the transmission quality evaluation device according to claim 7 ,
The encoding unit sends a k-byte code word to the transmission line,
The decoding unit corrects errors up to q bytes (q <k) included in the codeword;
The pre-decoding byte error rate calculation unit calculates a pre-decoding byte error rate R5 based on the following equation (5):
The bit error rate calculation unit calculates a post-decoding byte error rate (R6) indicating a ratio of the number of bytes having errors to the total number of bytes of the decoded frame based on the following equation (6): And the bit error rate (R2) is calculated based on the following equation (7).

A frame generation step of generating a plurality of frames composed of a plurality of bits from a frame generation unit and sending a signal including these frames to a transmission line;
A frame receiving step of receiving the signal transmitted from the frame generating unit by a frame receiving unit via the transmission path, and recognizing a frame from the received signal;
Based on the transmission frame generated by the frame generation unit and the reception frame recognized by the frame reception unit for transmission to the transmission line, an evaluation index representing the transmission quality of the frame via the transmission line is calculated. An evaluation step;
An output step for outputting the evaluation index calculated by the evaluation step;
The evaluation step includes
A transmission frame counting step for counting the number of the transmission frames;
A received frame counting step for counting the number of the received frames;
From the difference between the number of transmission frames and the number of received frames, a discard frame number calculating step for calculating the number of discarded frames that are not recognized as frames by the frame receiving unit;
Based on the ratio between the number of transmission frames and the number of discarded frames, a first frame error rate indicating a ratio of error frames transmitted through the transmission path and causing an error to the transmission frames is evaluated. Based on the first frame error rate calculation step calculated as an index and the frame error rate, the ratio of error bits transmitted through the transmission path and having errors to bits included in the transmission frame is indicated. a first bit error rate possess a first bit error rate calculation step of calculating, as the evaluation index,
The evaluation step further comprises:
An error frame counting step of counting the number of error frames in which an error occurs in the received frames;
The ratio of the sum of the number of discarded frames and the number of error frames and the number of transmission frames indicates the ratio of error frames that have been transmitted through the transmission path and have errors. A second frame error rate calculating step of calculating a second frame error rate as the evaluation index;
An error bit counting step of counting the number of error bits in which errors occur among the bits constituting the received frame;
Based on the number of error bits in which errors occur in the bits constituting the reception frame, the number of discarded frames, the number of transmission frames, and the frame length of the transmission frame, the bits constituting the transmission frame On the other hand, a second bit error rate calculating step of calculating, as the evaluation index, a second bit error rate indicating a ratio of error bits transmitted through the transmission path and causing an error;
The first frame error rate and the second frame error rate, and the first bit error rate and the second bit error rate are respectively compared, and the evaluation index in the output step is based on the comparison result A transmission quality evaluation method comprising: an output control step for controlling the output of the transmission. A frame generation step for generating a plurality of frames composed of a plurality of bits from the frame generation unit;
An encoding step of encoding the frame generated by the frame generator and sending the obtained code word to a transmission line;
Receiving the codeword via the transmission path, and decoding the received codeword;
A frame receiving step for recognizing a frame from the decoded signal;
An evaluation step for calculating an evaluation index representing the transmission quality of the frame via the transmission path based on the transmission frame generated in the frame generation step and the reception frame recognized in the frame reception step;
An output step for outputting the calculated evaluation index,
The evaluation step includes
A frame error rate (R1) indicating a ratio of error frames including an error to a frame generated by the frame generation unit based on at least the number of transmission frames and the number of reception frames recognized in the frame reception step. ) To calculate a frame error rate;
Based on the frame error rate (R1), a pre-decoding byte error rate (R5) indicating a ratio of the number of erroneous bytes to the total number of bytes of the codeword received in the decoding step is calculated. A pre-decoding byte error rate calculation step;
Based on the pre-decoding byte error rate (R5), the total number of bits included in the frame generated by the frame generation unit is compared with the number of erroneous bits included in the frame decoded in the decoding step. And a bit error rate calculating step of calculating a bit error rate (R2) indicating a ratio of the number.

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