JP3015282B2 - Delay fluctuation absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a delay fluctuation absorbing device used for an ATM communication control device or the like.

[0002]

2. Description of the Related Art In recent years, in the field of information communication, as a communication system, an ATM transmission / exchange system for transmitting / exchanging information using fixed-length buckets called cells has been used. A
In the TM transmission / exchange method, even if cells are transmitted at regular intervals during transmission due to transmission delay during transmission or variation in exchange time during exchange, delay fluctuation occurs in which intervals between received cells vary. . For this reason, a device that receives a cell needs a delay fluctuation absorbing device that absorbs the delay fluctuation and returns the cell interval to the same interval as when transmitting.

FIG. 5 shows a configuration of a conventional delay fluctuation absorbing device. In FIG. 5, reference numeral 51 denotes a delay fluctuation absorbing buffer for storing received cells on a first-in first-out basis. The delay fluctuation absorbing buffer 51 includes a W terminal, an R terminal, and an RST.
The receiving cell 501 input while the W terminal is 1 is stored, and the cell stored while the R terminal is 1 is output as the transmitting cell 502.
When 1 is input to the terminal, the delay fluctuation absorbing buffer 51 is initialized and emptied. 52 is a delay fluctuation absorbing buffer 5
1 is a buffer read / write control unit that generates a cell write signal 504 based on a cell reception signal 503 and generates a read signal 506 based on a read timing signal 505. 53 is a buffer initialization means for generating an initialization signal 508 based on the alarm signal 507 and initializing the delay fluctuation absorption buffer 51 when an abnormality such as an instantaneous interruption occurs behind the delay fluctuation absorption device. It is.

FIG. 6 is a timing chart for explaining the operation of the conventional delay fluctuation absorbing device. FIG. 6A shows an example of cells at the time of transmission, which are output at equal intervals. FIG.
(B) is an example of a cell at the time of reception, and the cell interval varies due to delay fluctuation. The delay fluctuation absorbing device absorbs the delay fluctuation of the received cell and returns the cell interval to the same interval as when transmitting. Therefore, the received cell 501 (FIG. 6B) is temporarily stored in the delay fluctuation absorbing buffer 5.
1 is written, and after writing a certain amount, it is read from the delay fluctuation absorbing buffer 51 at the same interval as that at the time of transmission. In FIG. 6, reading is started after writing one cell into the delay fluctuation absorbing buffer 51. Thus, delay fluctuation is absorbed (FIG. 6E).

At this time, if a failure such as an instantaneous interruption occurs behind the delay fluctuation absorbing device and the cell cannot be received (third to fifth cells in FIG. 6B), the alarm signal 507 becomes 1. . At this time, the buffer initialization control means 53 determines that the delay fluctuation absorbing buffer 51 is to be initialized, and generates an initialization signal 508 to generate the delay fluctuation absorbing buffer 51.
Is initialized to be empty (FIG. 6D). And again,
After a certain amount of received cells are written in the delay fluctuation absorbing buffer 51, they are read out at the same intervals as during transmission to absorb delay fluctuations (from the eighth cell in FIG. 6 (e)).

As described above, even with the above-described conventional delay fluctuation absorbing device, the delay fluctuation of the received cell can be absorbed, and the cell interval can be returned to the transmission interval.

[0007]

However, in the above-mentioned conventional delay fluctuation absorbing device, a fault such as an instantaneous interruption occurring behind the delay fluctuation absorbing device is notified by an alarm signal, and the delay fluctuation absorbing buffer is initialized. At that time,
It takes several seconds from the occurrence of a failure until the alarm signal is received by the delay fluctuation absorber. Therefore, there is a first problem that the delay fluctuation absorbing buffer is initialized after a failure such as an instantaneous interruption is recovered and normal cells are received, and even normal cells are discarded.

The operation when the instantaneous interruption occurs will be described with reference to FIG. FIG. 6 shows an example in which the third to fifth cells are discarded due to an instantaneous interruption, and the alarm signal 507 is received by the delay fluctuation absorbing device after the seventh cell is received (the alarm signal 507 is received after the seventh cell is received). 1). In this case, since the instantaneous interruption is detected after the reception of the eighth cell, the normally received sixth to seventh cells are discarded.

In the example shown in FIG. 6, although the normal 6th to 7th cells are discarded due to the initialization of the delay fluctuation absorbing buffer, it usually takes several seconds for the alarm signal to be received by the delay fluctuation absorbing device. Therefore, thousands of cells are discarded.

Further, in the conventional delay fluctuation absorbing device, it is necessary to increase the amount of delay fluctuation absorption in order to prevent the delay fluctuation absorption buffer from being emptied and initialized by delay fluctuation instead of instantaneous interruption. . For this reason, the second problem that the delay time in the delay fluctuation absorbing buffer increases.
There is a problem.

[0011] The present invention is to solve such a conventional problem.
An object of the present invention is to provide an excellent delay fluctuation absorbing device that can normally absorb delay fluctuation again without discarding normal cells.

[0012]

According to a first aspect of the present invention, there is provided:
In order to solve the first problem, the buffer initialization means included in the conventional delay fluctuation absorbing device counts the number of dummy cells output from the delay fluctuation absorbing buffer, and this value is set to a set threshold value. Is exceeded, it is determined that cell loss has occurred due to momentary interruption, etc., the delay fluctuation absorption buffer is initialized, and a certain amount of received cells are written again to the delay fluctuation absorption buffer, and then the same interval as when transmitting is used. In order to absorb delay fluctuations.

In order to solve the above-mentioned second problem, the second configuration of the present invention provides a buffer delay / absorption control device, a buffer read / write control unit, and a buffer initialization unit which are included in a conventional delay fluctuation absorbing device. A buffer amount counting means for counting the number of cells stored in the delay fluctuation absorbing buffer,
The buffer initialization means observes the output value of the buffer amount counting means after outputting the dummy cells from the delay fluctuation absorbing buffer, and if this value does not change from 0 within the set period, cell discard occurs due to instantaneous interruption or the like. Is determined, the delay fluctuation absorption buffer is initialized, and again,
After a certain amount of received cells are written in the delay fluctuation absorbing buffer, they are read out at the same interval as when transmitting to absorb the delay fluctuations.

[0014]

Therefore, according to the first configuration of the present invention, when the number of dummy cells output from the delay fluctuation absorbing buffer exceeds the set threshold value, cell discarding due to an instantaneous interruption or the like occurs in the buffer initialization means. Judge that it has occurred,
By initializing the delay fluctuation absorbing buffer, it is possible to prevent normal cells from being discarded.

According to the second configuration of the present invention, the buffer amount counting means counts the number of cells stored in the delay fluctuation absorbing buffer, and the buffer amount counting means separates the dummy cells from the delay fluctuation absorbing buffer. Observe the output value of the buffer amount counting means after the output, and if this value does not change from 0 within the set period, determine that cell loss has occurred due to an instantaneous interruption or the like, and initialize the delay fluctuation absorbing buffer. By doing so, even when the delay fluctuation absorption amount is set small, initialization is performed only when an instantaneous interruption occurs, and the number of normals discarded due to initialization of the delay fluctuation absorption buffer can be reduced.

[0016]

【Example】

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a delay fluctuation absorbing buffer for storing received cells on a first-in first-out basis. The delay fluctuation absorbing buffer 1 has a W terminal, an R terminal, and an RST terminal, and the reception cell 1 input while the W terminal is 1
01 is stored, and the stored cell is output while the R terminal is 1. When the delay fluctuation absorbing buffer 1 is empty, 1 is output from the E terminal, and when 1 is input to the RST terminal, the delay fluctuation absorbing buffer 1 is initialized to empty. Reference numeral 2 denotes a read start determination means for determining a timing at which reading of cells from the delay fluctuation absorbing buffer 1 is started, and is initialized by the initialization signal 110. 3
Is a buffer R / W (read / write) control means,
From the read start signal 103 output from the read start determining means 2, the empty signal 105 indicating that the delay fluctuation absorbing buffer 1 is empty, and the read timing signal 107 indicating the read timing, a cell for the delay fluctuation absorbing buffer 1 is obtained. The write signal 104 and the read signal 106 are generated, and the initialization signal 11
Initialized by 0. When the read timing signal 107 becomes 1 when the empty signal 105 is 1, the buffer R / W control means 3 determines that a dummy cell is to be output from the delay fluctuation absorbing buffer 1, and outputs the dummy cell insertion signal 108 as 1. . Numeral 4 denotes a dummy cell counting means for counting the number of times the dummy cell insertion signal 108 becomes 1 continuously, which is counted up by the dummy cell insertion signal 108 and reset by the read signal 106. Reference numeral 5 denotes a delay fluctuation absorbing buffer 1, a read start judging means 2, and a buffer R / P when the value counted by the dummy cell counting means 4 exceeds a set threshold value.
This is an initialization determination unit that generates an initialization signal 110 for initializing the W control unit 3.

Next, the operation of the delay fluctuation absorbing device in this embodiment will be described with reference to the timing chart of FIG. The received cell 101 (FIG. 2A) receives a write signal 104 (FIG. 2A) output from the buffer R / W control means 3.
(C)) is written into the delay fluctuation absorbing buffer 1. The cell reception signal 102 (FIG. 2 (b)) is a signal which becomes 1 only during cell reception, and the buffer R / W control means 3
Outputs this signal as a write signal 104. The read start determining means 2 counts the number of times that the cell received signal 102 becomes 1 in order to absorb the delay fluctuation of the reception cell 101, and after this value reaches the set delay fluctuation absorption amount, the delay fluctuation absorption buffer A read start signal 103 indicating that the cell may be read from 1 is output as 1 (FIG. 2D). The read start signal 103 (FIG. 2)
(D)) is a timing chart when the delay fluctuation absorption amount is set to 2 cells. The buffer R / W control means 3
When the read start signal 103 is 1 and the delay fluctuation absorbing buffer 1 is not empty, the read timing signal 107 (FIG. 2E) is output as a read signal 106 for reading cells from the delay fluctuation absorbing buffer 1 (FIG. 2).
(F)). When the delay fluctuation absorbing buffer 1 becomes empty and the empty signal 105 becomes 1 when the cell is discarded due to an instantaneous interruption or the like, the read timing signal 107 is not output as the read signal 106, and the delay fluctuation absorbing buffer 1 is not output. Is output as a dummy cell as it is (the hatched portion in FIG. 2 (h)), and the dummy cell insertion signal 10 is output.
8 is output as 1 (FIG. 2 (i)).

The dummy cell counting means 4 counts the number of times the dummy cell insertion signal 108 becomes 1 (FIG. 2 (j)).
This value is output to the initialization determination means 5. When the value output from the dummy cell counting means 4 exceeds the set threshold value, the initialization judging means 5 judges that cell discard has occurred due to an instantaneous interruption or the like, and outputs the initialization signal 110 as 1 (FIG. 2 (k)). FIG. 2 (k) shows an example in which the threshold value in the dummy cell counting means 4 is set to 2.

When the initialization signal 110 becomes 1, the delay fluctuation absorbing buffer 1, the read start determining means 2 and the buffer R / W control means 3 are initialized, and the operation of absorbing the delay fluctuation is performed again from the beginning. Therefore, after this, the delay fluctuations are normally absorbed, and the cells in which the delay fluctuations have been absorbed are output (the eighth and subsequent cells in FIG. 2 (h)).

As described above, according to the first embodiment,
When the number of dummy cells counted by the dummy cell counting means 4 exceeds the set threshold value, the initialization judging means 5 judges that cell discard has occurred due to an instantaneous interruption or the like, and the delay fluctuation absorbing buffer 1 and the read start judging means By initializing the buffer 2 and the buffer R / W control means 3 and absorbing the delay fluctuation again, it is possible to prevent normal cells from being discarded due to the initialization of the delay fluctuation absorbing buffer.

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention. In FIG. 3, reference numeral 31 denotes a delay fluctuation absorbing buffer for storing received cells on a first-in first-out basis. The delay fluctuation absorbing buffer 1 has a W terminal, an R terminal,
It has a terminal and an RST terminal, and stores cells input while the W terminal is 1, and outputs the stored cells while the R terminal is 1. When the delay fluctuation absorbing buffer 31 is empty, 1 is output from the E terminal, and
When 1 is input to the RST terminal, the delay fluctuation absorbing buffer 31 is initialized and emptied. Reference numeral 32 denotes a read start determining means for determining a timing at which a cell is read from the delay fluctuation absorbing buffer 31, and is initialized by an initialization signal 310. Reference numeral 33 denotes a buffer R / W (read / write) control unit, which includes a read start signal 303 output from the read start determination unit 32 and an empty signal 305 indicating that the delay fluctuation absorbing buffer 31 is empty.
And a read timing signal 307 indicating a read timing, a write signal 304 and a read signal 306 of the cell with respect to the delay fluctuation absorbing buffer 31 are generated and initialized by an initialization signal 310. When the buffer R / W control unit 33 determines that a dummy cell is to be output from the delay fluctuation absorbing buffer 31,
The dummy cell insertion signal 308 is output as “1”. Numeral 34 denotes a buffer amount counting means for counting the number of cells stored in the delay fluctuation absorbing buffer 31.
4 and is counted down by the read signal 306. 35 is a delay fluctuation absorbing buffer 31, a read start determining means 32, and a buffer R / W
This is an initialization determining means for initializing the control means 33. The output value of the buffer amount counting means 34 after outputting the dummy cells from the delay fluctuation absorbing buffer 31 is observed, and this value changes from 0 within a set period. If not, it is determined that cell discard has occurred due to an instantaneous interruption or the like, and the initialization signal 310 is output as 1.

Next, the operation of the delay fluctuation absorbing device in this embodiment will be described with reference to the timing chart of FIG. The received cell 301 (FIG. 4A) has a write signal 304 (FIG. 4A) output from the buffer R / W control unit 33.
(C)) is written into the delay fluctuation absorbing buffer 31. The cell reception signal 302 (FIG. 4B) is a signal that becomes 1 only during cell reception, and the buffer R / W control unit 33 outputs this signal as a write signal 304. The read start determining means 32 counts the number of times that the cell received signal 302 becomes 1 in order to absorb the delay fluctuation of the reception cell 301, and after this value reaches the set delay fluctuation absorption amount, the delay fluctuation absorption A read start signal 303 indicating that a cell may be read from the buffer 31 is output as 1 (FIG. 4D). Read start signal 3
03 (FIG. 4D) is a timing chart when the delay fluctuation absorption amount is set to 2. When the read start signal 303 becomes 1 and the delay fluctuation absorbing buffer 31 is not empty, the buffer R / W control means 33 converts the read timing signal 307 (FIG. 4E) to read cells from the delay fluctuation absorbing buffer 31. It is output as a read signal 306 (FIG. 4F). When a cell loss occurs due to an instantaneous interruption or the like and the delay fluctuation absorbing buffer 31 becomes empty and the empty signal 305 becomes 1, the read timing signal 307 is not output as the read signal 306 and the delay fluctuation absorbing buffer is not output. The output value of 1 is output as it is as a dummy cell (the hatched portion in FIG. 4H), and the initialization determination unit 35 sets the dummy cell insertion signal 308 to 1
(FIG. 4 (i)).

The buffer amount counting means 34 counts the number of cells stored in the delay fluctuation absorbing buffer 31 based on the write signal 304 and the read signal 306, and outputs this value to the initialization judging means 35. Initialization determination means 35
Observes the buffer amount count value 309 after the dummy cell insertion signal 308 becomes 1, and determines that cell discard has occurred due to an instantaneous interruption or the like if the buffer amount count value 309 does not change from 0 within the set period. Then, the initialization signal 310 is output as 1. FIG. 4 shows an example in which the period is set to 8 cell hours. In FIG. 4, since the buffer amount count value 309 after the insertion of the dummy cell does not change from 0, it is determined that cell discard has occurred due to an instantaneous interruption or the like, and the initialization signal 310 is output as 1.

When the initialization signal 310 becomes 1, the delay fluctuation absorbing buffer 31, the read start determining means 32, and the buffer R / W control means 33 are initialized, and the operation of absorbing the delay fluctuation is performed again from the beginning. Therefore, after this, the delay fluctuation is normally absorbed, and the cell in which the delay fluctuation has been absorbed is output (from the eleventh cell in FIG. 4H).

As described above, according to the second embodiment,
The buffer amount counting means 34 counts the number of cells stored in the delay fluctuation absorbing buffer 31, and the initialization judging means 35 observes the output of the buffer amount counting means 34 after the dummy cell is inserted, and this value is set. If it does not change from 0 within the specified period, it is determined that cell discard has occurred due to an instantaneous interruption or the like, the delay fluctuation absorbing buffer 31, the read start determining means 32, and the buffer R / W control means 33 are initialized, and the delay fluctuation is again performed. , It is possible to reduce the number of normal cells discarded due to the initialization of the delay fluctuation absorbing buffer.

[0026]

As is apparent from the first embodiment, the present invention provides a conventional delay fluctuation absorbing device with a dummy cell counting means for counting the number of dummy cells output from the delay fluctuation absorbing buffer, Initialization judgment means for judging whether or not cell discard due to an instantaneous interruption or the like has occurred based on the threshold value set by the value counted by the dummy cell counting means in the initialization judgment means. If it exceeds, it is determined that cell discard has occurred due to an instantaneous interruption, etc., the delay fluctuation absorbing buffer and the read start determining means are initialized, and the delay fluctuation is absorbed again,
There is an effect that normal cells can be prevented from being discarded by initializing the delay fluctuation absorbing buffer.

According to the present invention, as is apparent from the second embodiment, the conventional delay fluctuation absorbing apparatus includes buffer amount counting means for counting the number of cells stored in the delay fluctuation absorbing buffer, Initialization judgment means for judging whether or not cell loss due to disconnection has occurred. The initialization judgment means observes the output value of the buffer amount counting means after the dummy cell is inserted, and Does not change from 0 within the set period, it is determined that cell discard has occurred due to an instantaneous interruption or the like, the delay fluctuation absorbing buffer, the read start determining means, and the buffer R / W control means are initialized, and the delay fluctuation is again performed. By performing the absorption, the number of normal cells discarded due to the initialization of the delay fluctuation absorption buffer can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a delay fluctuation absorbing device according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the delay fluctuation absorbing device in the first embodiment.

FIG. 3 is a block diagram showing a configuration of a delay fluctuation absorbing device according to a second embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the delay fluctuation absorbing device in the second embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional delay fluctuation absorbing device.

FIG. 6 is a timing chart for explaining the operation of the conventional delay fluctuation absorber.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 delay fluctuation absorbing buffer 2 reading start determining means 3 buffer R / W controlling means 4 dummy cell counting means 5 initialization determining means 31 delay fluctuation absorbing buffer 32 reading start determining means 33 buffer R / W controlling means 34 buffer amount counting means 35 initial Determination means 51 delay fluctuation absorption buffer 52 read start determination means 53 buffer R / W control means

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuyuki Yamazaki, Inventor, International Telegraph and Telephone Corporation, 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo (56) References JP-A-7-95208 (JP, A JP-A-1-175433 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (2)

(57) [Claims] 1. A delay fluctuation absorbing device for absorbing a delay fluctuation of a received cell, a delay fluctuation absorbing buffer for storing a received cell and absorbing the delay fluctuation,
Read start determining means for determining the timing to start reading a cell from the delay fluctuation absorbing buffer; and a buffer for generating a write signal and a read signal for the delay fluctuation absorbing buffer based on a result of the determination by the read start determining means. Read / write control means, dummy cell counting means for counting the number of dummy cells output from the delay fluctuation absorbing buffer, and cell discarding when the value counted by the dummy cell counting means exceeds a set threshold value A delay fluctuation absorbing device, comprising: 2. A delay fluctuation absorbing device for absorbing a delay fluctuation of a received cell, comprising: a delay fluctuation absorbing buffer for storing the received cell and absorbing the delay fluctuation;
Read start determining means for determining the timing to start reading a cell from the delay fluctuation absorbing buffer; and a buffer for generating a write signal and a read signal for the delay fluctuation absorbing buffer based on a result of the determination by the read start determining means. Read / write control means, buffer amount counting means for counting the number of cells stored in the delay fluctuation absorbing buffer, and outputting a dummy cell when the delay fluctuation absorbing buffer becomes empty, and thereafter receiving the cell The delay fluctuation absorbing device further comprising: an initialization judging means for judging that cell discard has occurred when the value output from the buffer amount counting means does not change from 0 within a set period.