JP4587981B2 - Cell transmission equipment - Google Patents

Description

  The present invention relates to a cell transmission apparatus, and more particularly to a cell transmission apparatus in which a cell disassembly unit equipped with a buffer for absorbing a cell delay when performing decelization is duplicated.

  FIG. 4 shows an ATM cell transmission system including the above cell transmission apparatus. The transmitting apparatus 100 of this system supplies the audio digital signal VS to the cell assembling units 120 and 130 which are duplexed as the active system and the non-active system by the distribution unit 110. Since this ATM cell transmission system transmits through an ATM network, the cell assembly units 120 and 130 perform ATM cell conversion. The audio signals formed into cells by the cell assembly units 120 and 130 are output to the duplexed ATM network NW via the line interfaces 140 and 150, respectively.

  On the other hand, in the receiving apparatus 200, the signal from the duplicated ATM network NW is STM terminated at the line interfaces 210 and 220, and then input to the cell disassembling units 230 and 240, respectively. In the cell disassembling units 230 and 240, after the network cell delay is absorbed in the CDV absorption buffer for absorbing the built-in cell delay, reading is also performed to the built-in decelization buffer. The read signal is level-converted into an audio signal, sent to the selector 250, and the system switching signal CS is used to switch the system between the cell decomposing units 230-240 as necessary to reproduce the audio digital signal VS.

  Part of the receiving device 200 in the ATM cell transmission system as described above is shown in detail as a cell transmission device in FIG.

  In the conventional example of this cell transmission apparatus, the selector 3 is connected to the cell disassembly units 1 and 2 that are duplicated as an active system or a non-active system, and one data is selected and output by the system switching signal CS. Has been. Cell decomposing units 1 and 2 monitor buffers (CDV absorption buffer: maximum cell accumulation number j [number of cells]) 11 and 21, respectively, and the cell accumulation numbers of CDV absorption buffers 11 and 21 for absorbing cell delay. In addition, when the cell accumulation number of the buffers 11 and 21 reaches the read threshold value j / 2 [cell number], the cell accumulation number monitoring units 12 and 22 that read cells from the buffers 11 and 21 and the CDV absorption buffers 11 and 21 It comprises buffers 13 and 23 for decelerating (cell decomposing) the read cells.

  The selector 3 includes a selection unit 31 that selects and outputs one of the decelerated data from the deceleration buffers 13 and 23 in the cell decomposing units 1 and 2 based on the system switching signal CS.

  In the operation of such a conventional example, the cell accumulation number monitoring units 12 and 22 constantly monitor the cell accumulation number of the buffers 11 and 21, respectively. When 2 is reached, the cells stored in the buffers 11 and 21 are read out, and the read cells are decelled in the decelization buffers 13 and 23 and sent to the selector 3. In the selector 3, the selection unit 31 selects and outputs one of the data in the decelization buffers 13 and 23 based on the system switching signal CS.

The cell signal terminated by the SN / SNP processing unit and the cell loss compensation signal from the delay fluctuation absorbing buffer are input to the data output creation unit of the structured data reproduction unit, and the internal OFS value from the internal OFS calculation unit is input. And the received OFS value are compared in the monitoring unit, the short frame detection unit that counts the short frame detection and the number of missing cells due to the missing cell, the long frame detection that is due to the erroneous insertion cell and the long frame count that counts the excess cell number ATM-STM comprising: a detection unit; and a cell request generation unit that cancels reading of the buffer when a short frame is detected and performs processing for complementing the number of missing cells and performs discard processing by continuous reading from the buffer when a long frame is detected There is a conversion device (see, for example, Patent Document 1).
JP 2002-354036 A

  In the cell transmission device according to the prior art as shown in FIG. 5, if the cell disassembly unit 1 of the duplicated cell disassembly units 1 and 2 is the active system and the cell disassembly unit 2 is the non-operational system, When the package of the cell disassembly unit 2 of the system is removed and reinserted (hereinafter referred to as “insertion / removal”), the cell disassembly unit 2 undergoes a power ON reset. Usually, the buffer 21 in the cell disassembly unit 2 of this non-operational system has its maximum cell accumulation number j [cell number or ms after power-on reset. (Hereinafter, this may be omitted.)] Is read out after accumulating up to half the cell accumulation number j / 2. This read cell accumulation number j / 2 is called a read threshold value, and cells are not read until this read threshold value j / 2.

  The buffers 11 and 21 having such a read threshold value j / 2 exhibit the operations shown in FIGS. [1] (1) to (3).

(1) Before insertion / removal of cell disassembly unit In this case, since the active buffer 11 and the non-active buffer 21 are both operated with the same cell accumulation number a, the buffer cell accumulation number a [cell number] is j When the value becomes equal to / 2, even if the selector 31 of the selector 3 switches from the active system to the non-operating system, both of them output the same data, so the original source is reproduced and there is no problem.

(2) Immediately after insertion / removal of the non-operational cell disassembly unit In this case, in the active buffer 11, a part of the accumulated cell number a is output during insertion / removal of the non-operational buffer 21 and becomes the cell number b. In addition, the number c of cells is accumulated, and the non-operation buffer 21 is reset and the number of cells becomes zero.

(3) Time when cells are accumulated up to the non-operational readout threshold At this time, the operation buffer 11 outputs all the number of cells b in (2) above, and also outputs a state d in which some cells of the number of cells c are output. However, during this period, j / 2 cells are accumulated.

  On the other hand, since the non-operation buffer 21 starts from the reset state (2), the number of cells is accumulated up to j / 2.

  Accordingly, since the cell accumulation number d + e of the active buffer 11 is not equal to j / 2 at the reading time [3], the cell accumulation numbers of the buffers 11 and 21 are different from each other.

  Therefore, when the selector 31 of the selector 3 performs system switching from the cell disassembly unit 1 to the cell disassembly unit 2 based on the system switch signal CS, the start position of the buffer 11 and the start position of the buffer 21 are different. There is a problem that the data output from the selector 3 before and after switching is lost in continuity, and the original source cannot be reproduced.

  Therefore, according to the present invention, in a cell transmission apparatus in which a cell disassembly unit equipped with a buffer for absorbing cell delay when performing decellarization is duplicated, even if system switching is performed regardless of insertion / extraction of the cell disassembly unit, continuous data transfer is possible. The purpose is to make it possible to reproduce the original source by maintaining the characteristics.

  In order to achieve the above object, a cell transmission apparatus according to the present invention includes a buffer for absorbing cell delay and a cell accumulation number monitoring unit for monitoring the cell accumulation number of the buffer. In a cell transmission apparatus comprising: a cell disassembly unit serving as an active system; and a selector having a selection unit that selects and outputs one of the decelerated data from each cell disassembly unit as the active system, the selector includes the selector A switching protection circuit that prohibits system switching for the selection unit, and when the cell accumulation number monitoring unit of each cell decomposition unit determines that the own system is a non-operational system, cell storage of the other cell decomposition unit The cell accumulation number monitoring information from the number monitoring unit is fetched, and the non-operation buffer is read until the cell accumulation number of the own non-operation buffer reaches the read threshold with the cell accumulation number monitoring information as a read threshold. Stop Together, characterized in providing a system switching prohibition signal to said switching protection circuit.

  The operation principle of the present invention will be described below with reference to FIGS. 1 [2] (1) to (3).

(1) Before Insertion / Removal of Cell Decomposition Unit In this case, both the active system and the non-operating system are operated with the same cell accumulation number a as before the insertion / extraction in FIGS. 1 [1] (1). Therefore, no problem occurs even if the system is switched at this point.

(2) Immediately after insertion / removal of the non-operational cell disassembly unit In this case as well, immediately after insertion / removal of the non-operational system in FIGS. 1 [1] (2), some of the operation buffer (corresponding to the buffer 11 described above) The cell accumulation number is output during insertion / removal of the cell decomposing unit 21, becomes the cell accumulation number b, and the cells corresponding to the next cell accumulation number c are accumulated in the operational buffer 11. As a result, cells of the number b + c = p are accumulated in the buffer 11. At this time, the non-operational buffer (corresponding to the buffer 21 described above) is reset.

(3) Time at which cells are stored up to the non-operating system read threshold The number of stored cells b and c in the active buffer is between the number of cells p (until the time of insertion / extraction) since the start of cell storage in the non-operating buffer. Cells are output, and instead p [cell number] cells are accumulated.

  On the other hand, in the non-operation buffer, the cell number p of the operation buffer detected in the above (2) is taken as a read threshold, and the cell is not read out until the cells are accumulated by p [number of cells]. At this time, reading of the non-operational buffer is stopped and the switching protection circuit is stopped until the cell accumulation number of the own non-operational buffer reaches the read threshold using the cell accumulation number monitoring information as a read threshold. Thus, a system switching prohibition signal is provided so that the selector selection unit does not perform system switching.

  Therefore, after all the cells (b + c = p) remaining in the active buffer are swept out, reading of the cells with the cell accumulation number p in the non-active buffer is started, and the active buffer and the non-active buffer are started. The beginning of the data will match.

  At this time, the cell accumulation number monitoring unit that has determined that the own system is the non-operational system reads the cell from the non-operational buffer by detecting that the cell accumulation number of the own system buffer has reached the read threshold. At the same time, the disconnection switching prohibition signal is released.

  In this way, the continuity of data is maintained when system switching is performed, so that the original source can be restored.

  When the cell accumulation number monitoring information indicates zero, the cell accumulation number monitoring unit that has determined that its own system is a non-operational system may determine that it is before path setting and continue normal processing.

  Further, each cell accumulation number monitoring unit can determine whether it is the own system, the active system, or the non-operating system based on the presence or absence of the power ON reset.

  According to the cell transmission apparatus of the present invention, the system switching is performed because the data at the head position of the buffer in the non-operational system and the operation system is always the same no matter how many times the non-operational cell disassembly unit is inserted / extracted. However, data can be reproduced normally.

  FIG. 2 shows a configuration example of a cell transmission apparatus according to the present invention. In this configuration example, the connection relationship of the cell accumulation number monitoring units 12 and 22 in the cell disassembly units 1 and 2 is different from the conventional example shown in FIG. That is, the cell accumulation number monitoring units 12 and 22 monitor the cell accumulation numbers of the buffers 11 and 21, respectively, and always give their own cell accumulation number monitoring information p to each other.

  Note that the cell accumulation number monitoring in the cell accumulation number monitoring units 12 and 22 is performed by incrementing a monitor counter (not shown) by converting to a reading time for one cell when one cell is accumulated in the buffers 11 and 21. Decrement by cell read. This is always done until the buffer is empty.

  In addition, the selector 3 is provided with a switching protection circuit 32 for canceling the prohibition of system switching for the selection unit 31 and connected so as to receive the system switching prohibition / cancellation signal IR from the cell accumulation number monitoring units 12 and 22. Has been.

  An operation example of each of the cell accumulation number monitoring units 12 and 22 in the configuration example shown in FIG. 2 is shown in the flowchart of FIG.

  First, the cell accumulation number monitoring units 12 and 22 mounted in the cell disassembling units 1 and 2 do not know whether they are active or non-operating. Therefore, when the package of the cell disassembly unit is inserted / removed, the buffer 11 or 21 is initialized and a power ON reset is applied.

  Accordingly, in the cell accumulation number monitoring unit 12 or 22, it is determined whether or not the buffer 11 or 21 has been subjected to power ON reset (step S1). If the power ON reset has not been performed, the own cell disassembly unit is operated. The system is recognized (step S2), and normal processing is continued (step S3).

  On the other hand, if a power-on reset is applied, the local system is recognized as a non-operating system (step S4). Here, it is assumed that the cell decomposition unit 1 is an active system and the cell decomposition unit 2 is a non-operational system. Even if the relationship is reversed, the operation is exactly the same.

  At this time, the non-operating cell accumulation number monitoring unit 22 constantly takes in the cell accumulation number monitoring information p [cell number] sent from the active cell accumulation number monitoring unit 12 (step S5). Note that this cell accumulation number monitoring information p is the number of cells that does not match the cell accumulation number in the non-operational CDV absorption buffer 21 unless the cells in the operation CDV absorption buffer 11 are completely read, and input / output to the buffer is not performed. Since it always occurs, it fluctuates.

  Next, it is determined whether or not the cell accumulation number monitoring information p from the active cell accumulation number monitoring unit 12 is “0” (step S6). As a result, when p = 0, the cell has not yet been set, and the normal process of accumulating cells up to the normal read threshold value j / 2 [number of cells] is continued (step S7). Since this operation is the same operation in the active system, there is no problem even if switching between the active system and the non-operating system is performed.

  On the other hand, when the cell accumulation number monitoring information p is not “0”, the non-operational cell accumulation number monitoring unit 22 sets the captured cell accumulation number monitoring information p as a read threshold and, for example, “H”. System switching prohibition / cancellation signal IR set to the level is given to the switching protection circuit 32 to prohibit the selection unit 31 of the selector 3 from switching from the active cell disassembly unit 1 to the non-operational cell disassembly unit 2 (Step S8).

  Thereafter, the non-operating cell accumulation number monitoring unit 22 determines whether or not the accumulated cell number has reached the read threshold value p (step S9), and if not, the cell accumulation number monitoring unit 22 Only cell accumulation is continued without reading cells (step S10).

  When cells are accumulated up to the read threshold value p, the cell accumulation number monitoring unit 22 starts reading the cells. At this time, the cell accumulation number monitoring unit 22 resets the system switching prohibition / cancellation signal IR to “L” level and cancels the system switching prohibition operation for the switching protection circuit 32 (step S11).

  As a result, the switching protection circuit 32 causes the number of stored cells in the buffers 11 and 21 to reach the read threshold value p as shown in FIGS. 1 [2] (3), and data discontinuity occurs even when switching between both systems is performed. The system switching prohibition release signal IR is given to the selection unit 31 as not to be performed. Accordingly, after this, the selection unit 31 can perform system switching upon receiving the system switching CS.

  By doing so, the head information and the capacities of the active and non-operating CDV absorption buffers match, and the original source can be reproduced even if the system is switched.

It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that various modifications can be made by those skilled in the art based on the description of the scope of claims.

(Appendix 1)
A cell disassembly unit that has a buffer for absorbing cell delay and a cell accumulation number monitoring unit that monitors the cell accumulation number of the buffer, and each becomes an active system and a non-operating system, and deceleration from each cell decomposition unit In a cell transmission apparatus comprising a selector having a selection unit that selects and outputs one of the data as an active system,
The selector further includes a switching protection circuit for prohibiting system switching for the selection unit;
When the cell accumulation number monitoring unit of each cell disassembly unit determines that its own system is a non-operational system, it takes in cell accumulation number monitoring information from the cell accumulation number monitoring unit of the other cell decomposition unit, and the cell accumulation number monitoring information Until the number of cells stored in the non-operating buffer of the own system reaches the reading threshold, and reading of the non-operating buffer is stopped and a system switching prohibition signal is given to the switching protection circuit. Characteristic cell transmission equipment.
(Appendix 2) In Appendix 1,
When the cell accumulation number monitoring unit that has determined that the local system is a non-operational system detects that the cell storage number of the local non-operational buffer has reached the read threshold, it starts reading cells from the non-operational buffer. And a cell transmission apparatus that cancels the system switching prohibition signal.
(Appendix 3) In Appendix 1 or 2,
The cell transmission number monitoring unit that has determined that its own system is a non-operational system determines that the path has not been set and continues normal processing when the cell storage number monitoring information indicates zero. apparatus.
(Appendix 4) In Appendix 1,
Each cell accumulation number monitoring unit determines whether the own system is an active system or a non-operating system based on the presence or absence of power ON reset of the buffer of the own system.

It is a schematic sequence diagram for demonstrating the difference of the operation principle of a prior art example and this invention. It is the block diagram which showed one structural example of the cell transmission apparatus which concerns on this invention. It is the flowchart figure which showed the operation example of the cell accumulation number monitoring part in the cell transmission apparatus which concerns on this invention. 1 is a block diagram showing an ATM cell transmission system to which a cell transmission apparatus according to the present invention and a conventional example is applied. FIG. It is the block diagram which showed the cell transmission apparatus by a prior art example.

Explanation of symbols

1, 2 Cell disassembly
11, 21 CDV absorption buffer
12, 22 Cell storage count monitoring unit
13, 23 Decelized buffer
3 Selector
31 Selection section
32 Switching protection circuit In the figure, the same reference numerals indicate the same or corresponding parts.

Claims (3)

A cell disassembly unit that has a buffer for absorbing cell delay and a cell accumulation number monitoring unit that monitors the cell accumulation number of the buffer, and each becomes an active system and a non-operating system, and deceleration from each cell decomposition unit In a cell transmission apparatus comprising a selector having a selection unit that selects and outputs one of the data as an active system,
The selector further includes a switching protection circuit for prohibiting system switching for the selection unit;
When the cell accumulation number monitoring unit of each cell disassembly unit determines that its own system is a non-operational system, it takes in cell accumulation number monitoring information from the cell accumulation number monitoring unit of the other cell decomposition unit, and the cell accumulation number monitoring information Until the number of cells stored in the non-operating buffer of the own system reaches the reading threshold, and reading of the non-operating buffer is stopped and a system switching prohibition signal is given to the switching protection circuit. Characteristic cell transmission equipment. In claim 1,
When the cell accumulation number monitoring unit that has determined that the local system is a non-operational system detects that the cell storage number of the local non-operational buffer has reached the read threshold, it starts reading cells from the non-operational buffer. And a cell transmission apparatus that cancels the system switching prohibition signal. In claim 1 or 2,
The cell transmission number monitoring unit that has determined that its own system is a non-operational system determines that the path has not been set and continues normal processing when the cell storage number monitoring information indicates zero. apparatus.

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