JP3125756B2 - Bit error rate measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a bit error rate measuring method in a data transmission system having different transmission speeds in the upstream and downstream directions.

[0002]

2. Description of the Related Art FIG. 7 is a schematic diagram illustrating a method of measuring a bit error rate (Bit Error Rate) by a conventional loopback method.

In a conventional digital subscriber line termination device in which the transmission rate in the up direction is equal to the transmission rate in the down direction, generally, a maintenance test device of the exchange transmits a loopback start command to the terminal, and the terminal performs a downlink operation. Is set to wrap the data in the upward direction. In addition, a test pattern for measuring a bit error rate (hereinafter, referred to as BER) is inserted into the downlink data from the maintenance test device, and the maintenance test device receives the uplink data returned by the terminal, and BER measurement was possible by checking the bits of the uplink data.

The BER measurement is a function for observing the line quality from an exchange, and is one of important maintenance functions for maintaining high quality data transmission.

[0005]

However, the transmission speed in the downstream (exchange → terminal) direction is different from the transmission speed in the upstream (terminal → exchange) direction, and the transmission speed in the downstream direction is higher than the transmission speed in the upstream direction. A subscriber line termination device, for example, ADSL (Asymmetric Di)
In the conventional method, the terminal cannot loop back all data in the downlink direction in the uplink direction, so that the BER is not obtained.
There was a problem that measurement could not be performed.

A main object of the present invention is to provide a bit error rate measurement method capable of performing BER measurement by loopback even in a digital subscriber line termination device in which the downstream transmission speed is higher than the upstream transmission speed. That is.

[0007]

According to the present invention, there is provided a bit error rate measuring method for a data transmission system in which a data transmission speed from an exchange to a terminal and a data transmission speed from a terminal to the exchange are different. Means for adding a synchronization pattern to the bit error rate measurement test pattern frame and inserting it into the payload of the line signal frame,
The terminal detects the synchronization pattern from a line signal frame transmitted from the exchange, and detects a CRC (Cyclic Redundancy) included in the line signal frame.
Check) bit is used to detect the presence or absence of a bit error in the payload of the line signal frame. If at least one bit error is detected, one or more bit errors are included. A means for turning back only the frame that is present in the exchange.

According to the present invention, only a line signal frame in which a bit error has occurred can be looped back. Therefore, even when the transmission rate of downlink data is higher than the transmission rate of uplink data, the BER measurement device can use the BER measurement apparatus. The number of occurrences of bit errors can be counted, and the line quality can be observed at the exchange.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a bit error rate measuring method according to the present invention. In the bit error rate measurement method shown in FIG. 1, the downlink (exchange 1 → terminal 2)
Direction) Data transmission speed increases (terminal 2 → exchange 1)
Direction) It is assumed that the transmission speed is higher than the data transmission speed.

The exchange 1 includes a BER measuring device 3, a digital subscriber line terminating device 4, and a maintenance test device 5. The BER measurement device 3 includes a BER test pattern generation circuit 6
And a BER test pattern comparison circuit 7.

The BER test pattern generation circuit 6 has a function of transmitting a BER measurement test pattern for performing BER measurement. As shown in FIG. 2, the BER measurement test pattern includes a BER test pattern synchronization pattern and a random pattern for enabling synchronization in the BER test pattern comparison circuit 7 in the BER measurement device 3. This random pattern is the same pattern for each frame.

In the digital subscriber line terminating device 4, B
The ER measurement test pattern is assembled into the line signal frame shown in FIG. The line signal frame includes a line signal synchronization pattern and a payload (BER measurement test pattern in the case of this embodiment) that carries transmission / reception data of the end user.
And CRC bits.

The CRC bit is well known in digital transmission, and is added in a frame for the purpose of detecting an error.

This line signal frame is further encoded,
The digital signal processing and the processing in the analog circuit are performed, and the signal is transmitted to the metallic line 15.

The maintenance test apparatus 5 has a function of inputting a control command for starting loopback at the terminal 2 and supplying a BER measurement start trigger signal to the BER measurement apparatus 3 to start BER measurement. .

The loopback start command is sent to the digital subscriber line termination unit 4, and this command is assigned to the overhead bit mapped on the line signal frame and transmitted to the terminal 2. This is, for example, ANSI (American National)
Standards Institutes) T1.6
Eoc (Embedded Op.
This is a method similar to the method according to (Erasure Channel).

On the other hand, the terminal 2 comprises a driver / receiver 8, a digital circuit 9, a BER test pattern synchronization detection circuit 10
, A CRC error detection circuit 11, a framer circuit 12, a selector 13, and a test pattern latch circuit 14.

The driver / receiver 8 amplifies and filters the line signal sent from the digital subscriber line terminating device 4 and performs A / D conversion and a D / A conversion function.
It has a transmission function to perform conversion, filtering, and amplification.

The line signal received by the driver / receiver 8 is transmitted to a digital circuit 9, which performs waveform equalization, signal judgment, and synchronous detection of a line signal frame.

The signal output from the digital circuit 9 is
BER test pattern synchronization detection circuit 10, framer circuit 12
Is transmitted to the CRC error detection circuit 11.

The BER test pattern synchronization detection circuit 10 detects the synchronization pattern of the BER measurement test pattern shown in FIG. 2 and pulls in the frame synchronization of the BER measurement test pattern.

The framer circuit 12 has a function of generating a line signal frame transmitted by the terminal 2 and transmitting a line signal frame transmitted by the terminal 2 to the selector 13 in synchronization with the transmission timing of the terminal 2.

The CRC error detection circuit 11 compares a CRC bit in the line signal frame received from the digital circuit 9 with a CRC operation result calculated from the payload, and compares at least one of the CRC bits in the payload of the frame.
It has a function of detecting the presence or absence of one or more bit errors, and transmits the detection result to the test pattern latch circuit 14 and the selector 13.

The synchronization timing signal of the BER measurement test pattern detected by the BER test pattern synchronization detection circuit 10 and the line signal frame sent from the digital subscriber line termination device 4 via the BER test pattern synchronization detection circuit 10 This is sent to the test pattern latch circuit 14.

In the test pattern latch circuit 14, the BER
From the synchronization timing signal of the measurement test pattern, the line signal frame and the CRC error detection result, the payload of the line signal frame in which no CRC error has occurred, that is, the BER
It has a function to latch the measurement test pattern frame.
The BER measurement test pattern frame having no latched CRC error is transmitted to the framer circuit 12.

The selector 13 has a line signal frame transmitted from the framer circuit 12 and a BER having no CRC error.
A function of receiving a measurement test pattern frame and selecting one of the line frame signal and a BER measurement test pattern frame having no CRC error based on a result of a detection signal indicating the presence or absence of a bit error detected in the CRC error detection circuit 11. Have.

The frame selected by the selector 13 is sent to the digital circuit 9, after performing desired digital signal processing, sent to the metallic line 15 via the driver / receiver 8, and looped back to the exchange 1. Is configured to be possible.

Next, the operation of the embodiment of the present invention will be described. First, an operation of returning data in the downlink direction to data in the uplink direction will be described with reference to the configuration diagram of FIG.

In order to activate the loopback operation at the terminal 2, a loopback activation command is input from the maintenance test device 5 in the exchange 1 to the digital subscriber line termination device 4. Upon receiving this command, the digital subscriber line termination unit 4 assigns this command to the overhead bit mapped on the line signal frame and transmits it to the terminal 2.

On the other hand, in the line signal received by the terminal 2 via the metallic line 15, a loopback start command is detected in the digital circuit 9 via the driver / receiver 8, and the loopback operation in the terminal 2 is performed. I do.

This method is similar to the loop-back starting operation by the eoc message as specified in ANSI T1.601, and is a well-known method.

Next, the operation of the BER measurement method will be described with reference to FIGS. FIG. 3 and FIG. 4 are diagrams showing data return in loopback when a CRC error is detected on the terminal side.

The BER measurement is performed by a BER measuring device 3 provided in the exchange 1 shown in FIG. The test pattern output from the BER test pattern generation circuit 6 in the BER measuring device 3 is transmitted to the terminal 2 via the digital subscriber line terminating device 4, and is looped back by the terminal 2 to the exchange 1. Sent to the BER test pattern comparing device 7 via the digital subscriber line terminating device 4,
The BER test pattern comparison device 7 detects the presence or absence of a bit error and counts the number of bit errors by comparing the test pattern sent from the BER test pattern generation circuit 6 with the test pattern folded back at the terminal 2. It is. The principle of this measuring method is the same as the conventional method.

After the above setting, the BER test pattern generation circuit 6 inserts the BER measurement test pattern frame shown in FIG. 2 into the payload of the line signal frame of the digital subscriber line terminal 4. The BER measurement test pattern frame includes a BER test pattern synchronization pattern and a random pattern, and each frame is the same test pattern frame. The line signal frame of the digital subscriber line terminating device 4 includes a line signal synchronization pattern, a payload, and a CRC bit for detecting the presence or absence of a bit error on the terminal side.

The digital subscriber line signal frame in which the BER measurement test pattern frame is inserted is sent to the terminal 2 via the metallic line 15, and the driver / receiver 8 in the terminal 2 and the digital circuit 9 perform desired processing. After that, the BER measurement test pattern frame shown in FIG. 2 is extracted.

The extracted BER measurement test pattern frame is sent to the BER test pattern synchronization detection circuit 10 while detecting the BER test pattern synchronization pattern shown in FIG.
Establish R measurement test pattern frame synchronization. This BE
The R test pattern synchronization pattern is determined in advance, and it is assumed that the terminal 2 expects to receive this synchronization pattern. When the BER measurement test pattern frame synchronization is established, a random pattern in the BER measurement test pattern frame in FIG. 2 can be detected.

On the other hand, the CRC error detection circuit 11 of FIG. 1 detects a CRC bit from the line signal frame of FIG. 2 extracted and performs a CRC operation on the payload, and there is no bit error in the target line signal frame. In this case, the random pattern detected by the BER test pattern detection circuit 10 is
Hold in. That is, the test pattern latch circuit 1
4 holds the same data as the data output from the BER test pattern generation circuit 6 which does not include a bit error.

When the same operation is performed and at least one bit error is detected in the target line signal frame, the selector 13 in the terminal 2 detects the BER test pattern synchronization detection via the framer circuit 12. Control is performed so that data from the circuit 10 is output.

That is, the data containing at least one bit error appears in the output of the selector 13.

Referring to FIG. 3, a description will be given of a method of returning the downlink data in the upward direction when a bit error is detected and when it is not detected. CRC error detection circuit 1
1, when a CRC error is detected, the BER is controlled via the framer circuit 12 under the control of the selector 13.
Payload containing at least one or more bit errors output from the test pattern synchronization detection circuit 10, ie, BE
Control is performed so that the R test pattern + random pattern is turned up.

When a CRC error is not detected, control is performed such that the payload, which does not include the bit error, held by the test pattern latch circuit 14 appears at the output of the selector 13 via the framer circuit 12. By this operation, all payloads including at least one bit error can be looped back as uplink data.

A bit error counting method in the BER measuring device 3 in the exchange 1 will be described with reference to FIG.
The upstream data returned by the terminal 2 is subjected to required processing by the digital subscriber line terminating device 4 and then the payload, that is, the BER test pattern synchronization pattern + random data including at least one bit error is extracted. The BER test pattern comparison circuit 7 receives the BER test pattern. BER
The test pattern comparison circuit 7 compares the payload output from the BER test pattern generation circuit 6 with the payload including the bit error returned by the terminal 2 and counts the number of mismatched bits.

In this case, since the downlink data transmission rate is faster than the uplink data transmission rate, the downlink data capacity minus the uplink data capacity is equal to B as shown in FIG.
The data output from the BER test pattern generation circuit 6 in the ER test pattern comparison circuit 7 may be directly added to the uplink payload as dummy data and compared (in this case, bit errors are not counted).

The data transmission speed in the downstream direction, that is,
As long as the total number of bits of the payload transmitted from the BER test pattern generation circuit is held, the comparison and error count processing may be stopped for a portion having no uplink payload.

After performing these processes, BER measurement can be performed by calculating (bit error count value / total number of bits transmitted from the BER test pattern generation circuit).

As described above, in the loopback test control method according to the present invention, in a transmission system in which the downlink data transmission rate is faster than the uplink data transmission rate, all bit errors occurring on the line can be received. , BER measurement can be performed.

Next, the basic configuration is as described above.
FIG. 5 shows a configuration of another embodiment in which a payload including all bit errors can be looped back to the exchange when more bit errors occur. In the system shown in FIG. 5, a buffer 16 is provided between the BER test pattern synchronization detection circuit 10 and the framer circuit 12 in the configuration diagram shown in FIG.

The buffer 16 is used for the CRC error detection circuit 1
1 has a function of temporarily holding payload data containing a CRC error when the CRC error is detected. By increasing the depth of the buffer 16, the payload including the bit error temporarily increases, and when it is necessary to loop back the payload exceeding the data transmission capacity in the upstream direction, the payload including the bit error held in the buffer 16 is stored. Can be sequentially transmitted in accordance with the data transmission capacity in the upward direction.

According to this embodiment, even if a large number of errors occur in a burst, the payload including all bit errors can be looped back to the exchange, so that the accuracy of the measured BER value is further improved. It has the effect of doing.

In the above-described embodiment, even when a large number of bit errors occur in a burst, all the payloads including bit errors are transmitted by passing the data through the buffer 16 when returning the downstream data to the upstream data. Although the function and effect of being able to be folded in the direction are obtained, similar effects can be obtained by changing the configuration of the BER measurement test pattern frame transmitted from the BER test pattern generation circuit 6 in the exchange.

FIG. 6 shows a configuration for this purpose. FIG. 6 is a diagram showing a relationship between a line signal frame and a BER measurement test pattern frame according to still another embodiment of the present invention. In this system, the digital subscriber line termination device 4
A plurality of BER measurement test pattern frames are inserted into the line signal frame. This test pattern frame is shown in FIG.
As in the embodiment shown in FIG. 7, the BER test pattern synchronization pattern and the random pattern are used, and each random pattern is the same data.

If the frame length of the BER test measurement pattern inserted into the payload is long, and even if a bit error occurs in even one bit in the payload, the entire payload is folded back at the terminal, and the number of bits to be folded increases. When the BER test measurement pattern frame length is shortened, it is possible to reduce the number of bits to be turned back as compared with the case where the frame length is long. This has a synergistic effect that the buffer depth shown in the embodiment of FIG. 5 can be reduced.

[0054]

As described above, according to the present invention, when performing BER measurement for monitoring the line quality in a transmission system in which the data transmission rate in the downlink direction is faster than the data transmission rate in the uplink direction, all the downlinks are measured. Since the data in the direction is not looped back in the upstream direction, only the frame containing at least one bit error in the signal frame is looped back in the upstream direction according to the check result of the CRC error. All errors can be received by the exchange, and B
ER measurement becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a bit error rate measurement system according to the present invention.

FIG. 2 is a diagram illustrating a relationship between a line signal frame and a BER measurement test pattern frame.

FIG. 3 is a diagram showing data return in loopback when a CRC error is detected on the terminal side.

FIG. 4 is a diagram showing data return in loopback when a CRC error is detected on the terminal side.

FIG. 5 is a configuration diagram showing another embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a line signal frame and a BER measurement test pattern frame according to still another embodiment.

FIG. 7 is a configuration diagram showing a conventional bit error rate measurement method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 exchange 2 terminal 3 BER measuring device 4 digital subscriber line termination device 5 maintenance test device 6 BER test pattern generation circuit 7 BER test pattern comparison circuit 8 driver / receiver 9 digital circuit 10 BER test pattern synchronization detection circuit 11 CRC error detection circuit 12 Framer circuit 13 Selector 14 Test pattern latch circuit 15 Metallic circuit 16 Buffer

Claims (6)

(57) [Claims] 1. A bit error rate measurement method for a data transmission system in which a data transmission rate from an exchange to a terminal and a data transmission rate from a terminal to an exchange are different, wherein the exchange generates a bit error rate measurement test pattern frame. Means for adding a synchronization pattern to the payload of the line signal frame and inserting the synchronization pattern into the payload of the line signal frame, the terminal detects the synchronization pattern from the line signal frame transmitted from the exchange, and detects a bit error in the payload of the line signal frame. A bit error rate measurement method comprising: means for detecting the presence / absence and, when at least one bit error is detected, returning only a frame including one or more bit errors to an exchange. 2. The apparatus according to claim 1, wherein when at least one bit error is detected in the payload of the line signal frame transmitted from the exchange, the terminal temporarily stores a payload data containing the error. The bit error rate measurement method according to claim 1, further comprising: 3. A method according to claim 1, wherein a plurality of bit error rate measurement test pattern frames are inserted into a payload of one line signal frame transmitted from said exchange.
Or the bit error rate measurement method according to 2. 4. The bit error rate measuring method according to claim 1, wherein a data transmission speed from said exchange to the terminal is faster than a data transmission speed from the terminal to the exchange. 5. A loopback control method applied to measurement of a bit error rate from an exchange, wherein only frames containing at least one bit error at the terminal among the data from the exchange to the terminal are returned to the exchange. A loopback control method characterized in that a bit error rate measurement can be performed by using the method. 6. The loopback control method according to claim 5, wherein a data transmission speed from the exchange to the terminal is faster than a data transmission speed from the terminal to the exchange.