JP3715555B2 - Transmission equipment - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a transmission apparatus, and more particularly to a transmission apparatus that performs digital transmission of ATM (Asynchronous Transfer Mode).
[0002]
[Prior art]
ATM is a connection-type communication method that provides multimedia communication consisting of data, voice, video, and the like on a single network in accordance with the speed and quality required by each, and has been standardized and developed.
[0003]
On the other hand, one of the ATM functional layers defined by ITU-T I.363 is AAL (ATM adaptation layer). AAL is a functional layer that converts data into cells and decells according to the characteristics of the transmission service. AAL1, which is one of the types of AAL, transmits CBR (Constant Bit Rate) audio and video data. Target.
[0004]
Here, the AAL1 transmission apparatus receives the CBR signal, performs necessary processing, and then reproduces and transmits the CBR signal again. In this case, the received CBR signal has a delay fluctuation due to a cross-connect device that passes through the ATM network, a cell loss, a cell misdistribution, or the like. For this reason, a CDV (Cell Delay Variation Allowable Value: Cell Delay Variation) absorption buffer that absorbs delay fluctuations is required for the transmission apparatus.
[0005]
In general, the transmission path has a redundant configuration, and when a failure occurs, data is guaranteed by switching without interruption. In this case, there is a large delay difference between the cell received from the 0 system and the cell received from the 1 system. Therefore, in order to perform uninterrupted switching when a failure occurs, the transmission apparatus also needs a cell arrival delay difference absorption buffer for absorbing a cell arrival delay difference.
[0006]
[Problems to be solved by the invention]
However, in the conventional transmission apparatus as described above, the capacity of the CDV absorption buffer is several ms, and the capacity of the cell arrival delay difference absorption buffer is several tens of ms. Therefore, very large memories are separately arranged at two locations. Therefore, there is a problem that the mounting area and the circuit scale increase.
[0007]
In addition, when the valid sequence count value attached to the cell cannot be received, the cells are continuously discarded, and an underflow occurs in the CDV absorption buffer. Conventionally, when the device is initialized or underflowed, efficient cell read control from the CDV absorption buffer has not been performed, and there has been a problem that malfunction may occur.
[0008]
Furthermore, when maintenance cells are continuous or when cells are continuously discarded, an RTS (Residual Time Stamp) value that is clock information cannot be received even though there is no line failure. Conventionally, there has been a problem that the maintainability is low because there is no function for detecting and notifying an abnormal state of acquisition of the RTS value.
[0009]
The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission apparatus that reduces the circuit scale and efficiently performs high-quality AAL transmission control.
[0010]
[Means for Solving the Problems]
In the present invention, in order to solve the above-described problem, in a transmission apparatus 10 that performs digital transmission as shown in FIG. 1, burst cells sent from a network are stored, delay fluctuations of burst cells, and redundant transmission lines A delay absorbing unit 11 that absorbs a cell arrival delay difference caused by the configuration and generates capacity information; a state transition monitoring unit 12 that monitors a state transition of the cell; Based on at least one of the cell fluctuation absorbing means 13 for absorbing fluctuations, the capacity information, the state transition, and the cell reading period in the cell fluctuation absorbing means 13, the delay absorbing means 11 performs cell read request control at a fixed speed. And a cell read request control means 14 for performing transmission.
[0011]
Here, the delay absorbing means 11 stores burst cells sent from the network, absorbs the delay fluctuation of the burst cells and the cell arrival delay difference caused by the redundant transmission path configuration, and generates capacity information. . The state transition monitoring unit 12 monitors cell state transitions. The cell fluctuation absorbing means 13 stores the cell and absorbs the cell fluctuation generated when the cell is decelerated. The cell read request control unit 14 performs cell read request control at a fixed speed from the delay absorbing unit 11 based on at least one of the capacity information, the state transition, and the cell read cycle in the cell fluctuation absorbing unit 13.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG.IsIt is a principle diagram of a feeding device. The transmission device 10 terminates the ATM AAL1 function and performs ATM digital transmission. The transmission device 10 is arranged in, for example, an exchange station, extracts information cells including video signals from ATM cells received from an ATM network, and transmits the information cells to a video device in the TV station.
[0013]
The delay absorbing means 11 stores ATM burst cells sent from the ATM network. Then, the delay fluctuation of the burst cell and the cell arrival delay difference caused by the redundant transmission line configuration including the 0 system and the 1 system are absorbed. Then, capacity information indicating how many cells are currently stored is generated.
[0014]
The state transition monitoring unit 12 monitors cell state transitions. The cell state transition will be described later with reference to FIG.
The cell fluctuation absorbing means 13 stores the cell and absorbs the cell fluctuation generated when the cell is decelerated. Details will be described later with reference to FIG.
[0015]
The cell read request control means 14 receives a fixed rate (hereinafter referred to as CBR) cell read request from the delay absorbing means 11 based on at least one of the capacity information, the state transition, and the cell read cycle in the cell fluctuation absorbing means 13. Take control.
[0016]
Next, cell state transition will be described. FIG. 2 is a diagram showing state transition. Cell states include Start, Out Of Sync, Sync, Out Of Sequence, and Invalid. Each cell is numbered one by one, and this number is called SC (Sequence Count).
[0017]
[S1] Start is a state at the time of initialization.
[S1a] When a cell is received at Start, if the cell is an invalid cell, it remains at Start. Then, the invalid cell is discarded.
[S1b] When a cell is received at the start, if the cell is a valid cell, transition is made to Out Of Sync (synchronization has not yet been achieved). The cell is discarded.
[0018]
[S2a] If a discontinuous SC is received by Out Of Sync, it stays at Out Of Sync. For example, if the cell is SC1 and the next received cell is SC4, the number sequence is not normal (two cells are missing), so it remains Out Of Sync. The cell is discarded.
[S2b] If an invalid SN is received during Out Of Sync, the process proceeds to Start. The cell is discarded.
[0019]
[S2c] At the time of Out Of Sync, if a continuous SC is received, transition is made to Sync. For example, if the cell SC is 0 (hereinafter referred to as SC0) and the next received cell is SC1, the sequence of numbers is normal (because synchronization is established), and transition is made to Sync. And the cell accepts.
[S3a] If a continuous SC is received by Sync, it stays at Sync. And the cell accepts.
[0020]
[S3b] If a discontinuous SC is received at the time of Sync, transition to Out Of Sequence. And the cell accepts. For example, when SC1, SC2, SC5, SC3, and SC4 are received, the SC becomes discontinuous at SC5, and the process shifts to Out Of Sequence. Here, it can be seen that SC5 is misdistributed.
[S3c] If an invalid SN is received at the time of Sync, transition to Invalid. And the cell accepts.
[0021]
[S4a] If an invalid SN is received during Out Of Sequence, the process proceeds to Start. The cell is discarded.
[S4b] At the time of Out Of Sequence, if a discontinuous SC is received, transition is made to Out Of Sync. The cell is discarded.
[S4c] At the time of Out Of Sequence, SN error estimation (SC / cell acceptance 2 larger than last valid cell), cell loss (contiguous SC with previous cell / dummy cell insertion and cell acceptance), cell misdistribution (last In the case of a valid cell and continuous SC / cell discard), transition to Sync.
[0022]
[S5a] When Invalid, if cell misdistribution or SN error estimation, transition to Sync.
[S5b] If an invalid SN is received during Invalid, the process proceeds to Start. The cell is discarded.
[S5c] If a discontinuous SC is received during Invalid, transition to Out Of Sync. The cell is discarded.
[0023]
Next, the configuration and operation of the transmission apparatus 10 will be described in detail. FIG. 3 is a diagram illustrating the configuration of the transmission apparatus 10.
The delay absorbing buffer 11a corresponds to the delay absorbing means 11, and is a buffer in which a conventional CDV absorbing buffer and a cell arrival delay difference absorbing buffer are combined into one. The delay absorbing buffer 11a outputs an ATM cell C1 that has been converted to CBR based on the cell read request signal Rc.
[0024]
The delay absorption buffer 11a outputs capacity information indicating its own buffer capacity state, and outputs an underflow notification signal U1 when underflow occurs. An OAM (Operation And Maintenance) cell detection means 15 uses OAM cells (VP / VC-AIS cell, VP / VC-RDI cell, VP / VC) as maintenance cells from the ATM cell C1 output from the delay absorption buffer 11a. VC-CC cell, in-device monitoring cell, etc.) are detected, and the detected OAM cell is transmitted to the maintenance control side, and user ATM cells other than the OAM cell are transmitted to the SN / SNP processing means 12a.
[0025]
SN (Sequence Number) / SNP (SN Protection) processing means 12a includes state transition monitoring means 12, and the cell validity using SN field and SNP field of SAR-PDU header shown in ITU-T I.363.1・ Determine cell loss / misplacement by invalidity determination or SC continuity monitoring, monitor state transition, and output a state notification signal. Then, the user ATM cell is output to the decellization buffer 13a together with the write enable WN. The RTS value, which is clock information, is also acquired from the CSI bit in the user ATM cell.
[0026]
If cell loss compensation is required, a cell complement signal is output to the decellization buffer 13a, and the read trigger is turned off (cell read request control means 14 prohibits cell read requests). During normal operation, the read trigger is ON (a cell read request is permitted to the cell read request control means 14).
[0027]
The decelerating buffer 13a includes a cell fluctuation absorbing unit 13, and absorbs small fluctuations of several cells generated by the decelling process such as the removal of the OAM cell by the OAM cell detecting unit 15 and the discard of invalid cells / misplaced cells. Then, the CBR signal is output. Also, clock transfer from the network clock to the regenerated RTS clock based on the RTS value is performed. The output CBR signal is transmitted to, for example, a video apparatus.
[0028]
Further, the decelerating buffer 13a outputs a read cycle signal for notifying the read cycle of the CBR signal and an underflow notification signal U2 indicating that at the time of underflow.
[0029]
  The RTS control means 16, KuCorresponding to the lock information control means, an RTS value in which the reception period fluctuation caused by cell fluctuation is absorbed is output. The clock regenerated from the RTS value is used as the clock for the CBR signal.
[0030]
Here, even if the ATM cell C1 read from the delay absorption buffer 11a is controlled to CBR, the RTS reception cycle also fluctuates due to fluctuation due to cell discard. Therefore, the RTS control means 16 absorbs fluctuation due to the reception cycle by the buffer installed inside. In this case, a large buffer of several ms unit as in the conventional circuit is not necessary, and only about 140 μs is actually required.
[0031]
In addition, when the valid cell cannot be received, the RTS control unit 16 cannot acquire the RTS value, and therefore instructs the switching to the free-running RTS clock generated inside the apparatus. In this case, as a trigger for the switching request, the switching instruction is turned ON when either the state notification signal (at least one of Start and Out Of Sync) or the underflow notification signal U2 is active. Further, when the RTS value cannot be received, an abnormality is notified to the outside by an alarm signal K1.
[0032]
When the AAL1 state notifying unit 17 recognizes that the state of Start or Out Of Sync is continuous by the state notification signal, the AAL1 state notifying unit 17 notifies the abnormality of the state transition of AAL1 to the outside by the alarm signal K2.
[0033]
Based on the capacity information from the delay absorption buffer 11a, the cell read request control means 14 reads ATM cells from the delay absorption buffer 11a in accordance with the speed (recognized by the read cycle signal) for reading the CBR signal from the deceleration buffer 13a. Thus, the cell read request signal Rc is created.
[0034]
Further, when the delay absorption buffer 11a is initialized or when an AAL1 abnormality is detected, a cell read request signal Rc is generated so that the cell accumulation amount of the delay absorption buffer 11a maintains the center value.
[0035]
Here, when a state transition abnormality is detected, the cell read request control means 14 issues a cell read request with a free-running RTS clock so that the delay absorption buffer 11a does not underflow.
[0036]
Further, the cell read request control means 14 does not make a cell read request when an abnormality in the state transition is detected and it is determined from the capacity information that the capacity is small. Further, the cell read request control unit 14 can set a cell read request mode from the outside. For example, a mode in which cell reading is not performed until the cell accumulation amount reaches the vicinity of the center value can be set from the outside.
[0037]
Next, the cell read request control means 14 will be described. 4 and 5 are time charts showing the operation of cell read request control. Note that the capacity monitoring in the figure represents the capacity state of the decelerating buffer 13a.
[0038]
luckDuring use, the delay absorption buffer 11a absorbs the delay difference between burst-like ATM cells transmitted from the 0-system and 1-system, and also absorbs CDV generated on the network, and the buffer capacity is near the center value. Accumulated to be. Control for keeping the capacity of the delay absorption buffer 11a near the center value is performed by the cell read request control means 14, and an example of the operation is shown in the figure.
[0039]
Further, in the figure, the capacity of the decelerating buffer 13a is 5 stages and the threshold value is 3. A threshold value of 3 means that reading of the CBR signal is started after writing three cells in the decelerating buffer 13a. The buffer capacity and the threshold are values determined by the transmission frequency of the network, the clock frequency of the CBR signal, and the margin for overflow / underflow, and can be variably set.
[0040]
[S10] The capacity of the delay absorbing buffer 11a and the decelerating buffer 13a immediately after the reset is released is empty. Therefore, the capacity information of the delay absorbing buffer 11a is also L. This capacity information is a signal that becomes H when the accumulated amount of the delay absorption buffer 11a exceeds the center value, and becomes L when the amount is below the center value. While this signal is L, a cell read request from the delay absorption buffer 11a is not performed, and the cell waits for cells to be accumulated in the delay absorption buffer 11a.
[S11] When the capacity information changes from L to H, a cell read request is started, and cell read requests are continuously made until the decelization buffer 13a exceeds the threshold value.
[0041]
In the example in the figure, in response to the first cell read request, the cell 1 read from the delay absorption buffer 11a is discarded because the SC is not yet synchronized by the SN / SNP processing means 12a, and the state transition is started. Transition from to Out Of Sync.
[0042]
From the next cell 2, the SN / SNP processing means 12a accepts all of them because the SC is synchronized. Then, when the threshold value of 3 cells of the decelerating buffer 13a is reached, the decelerating buffer 13a starts reading the CBR signal.
[S12] The cell read request control means 14 determines the period of the CBR signal read from the decelization buffer 13a and the number of cells to be written to the decelization buffer 13a when the SN / SNP processing means 12a determines that it is valid. From the monitoring result of (only payload), the accumulation amount of the decelization buffer 13a is grasped. When the accumulation amount becomes 3, a cell read request is made, and when it becomes 4 or more, the cell read request is not made. Thereby, the cell interval read from the delay absorbing buffer 11a can be set to CBR.
[0043]
FIG. 6 is a time chart showing the operation of cell read request control. This is a case of absorbing fluctuations caused by cell discard, and shows a case of the Fast-SN algorithm.
[S20] If the cell read from the delay absorbing buffer 11a is an erroneously delivered cell, the state transition of the SN / SNP processing means 12a transits from Sync to Out Of Sequence. Cannot be judged. For example, in the figure, it is not possible to determine whether a cell received after cell 5 (misplaced cell) is misdelivered until cell 6 is received. In the case of the Fast-SN algorithm, this misdistributed cell is written in the decelerating buffer 13a.
[S21] The capacity of the decelerating buffer 13a is increased to 4 cells, which is the same as usual. Then, when the next cell 6 is received, it can be determined that the previous cell was an erroneously delivered cell. In the case of the Fast-SN algorithm, this cell 6 is discarded.
[0044]
For this reason, since the cell 6 is not written to the decellization buffer 13a, the next cell is immediately requested to the delay absorption buffer 11a. As described above, when a misdistributed cell is received, a fluctuation of ± 1 cell occurs, but it can be easily absorbed by the decelerating buffer 13a.
[S22] On the other hand, when the read cells from the delay absorption buffer 11a are continuous OAM cells, the cells are discarded by the OAM cell detection means 15. As shown in the figure, even in the case of an OAM cell, the next cell is immediately requested to the delay absorption buffer 11a, and the re-request is repeated until the capacity of the decellization buffer 13a exceeds the threshold value of 3 cells.
[0045]
In the example shown in the figure, the re-request is performed four times, and thereafter the CBR cell interval is restored. As described above, when the OAM cells are continuous, fluctuations of several cells occur. Actually, OAM cells continuously occur at the time of failure, and in normal operation, if the capacity of the decelerating buffer 13a is sufficient to withstand fluctuations of several cells, it can be sufficiently absorbed.
[0046]
Next, an operation at the time of detecting an abnormality in the RTS value will be described. FIG. 7 is a time chart showing an operation at the time of detecting an abnormality in RTS value acquisition. The read timing in the figure is the read timing from the RTS control means 16 and the write timing is the write timing to the RTS control means 16. The RTS acquisition status is normal for L and abnormal for acquisition.
[0047]
First, it is monitored whether or not there is a write timing (RTS value reception timing) to the RTS control means 16 within one RTS period of the clock frequency of the CBR signal reproduced from the RTS value. If there is, no RTS value is received. In this case, the RTS value is counted as not received. If the count continues for the number of times of protection, an abnormality in acquiring the RTS value is detected. In the figure, as an example, a case where the number of protection times is 3 is shown.
[0048]
  FIG. 8 is a time chart showing the operation at the time of canceling the acquisition abnormality of the RTS value.. nWhen n RTS values can be acquired within the RTS cycle, it is canceled. That is, here, when the RTS value for the protection count is received within the RTS cycle for the clock protection count, the cancellation is made.
[0049]
This is because when the RTS abnormality is recovered, the cell reception cycle is expected to be unstable without becoming CBR. Take it. For this reason, the number of receptions within the nRTS period corresponds to an unstable reception period.
[0050]
The figure shows a case where the number of times of protection is two. In the case of two stages of protection times, there are release timings A and B and RTS reception times A and B, and a period shifted by 1 RTS with respect to the 2 RTS period of the monitoring period is monitored.
[0051]
If the RTS reception timing is within the release timing period, the RTS reception count is incremented, and the RTS acquisition abnormality is canceled when the count reaches the protection count. In the figure, A is released at the release timing A because RTS is received twice earlier.
[0052]
Next, cell read request control when AAL1 is abnormal will be described. 9 and 10 are time charts showing the operation of cell read request control. The figure is an example in which the state transition of the SN / SNP processing means 12a is Sync and the cells having invalid SNs are continuously received from the normal state and the AAL1 abnormality is detected.
[0053]
First, simultaneously with the detection of the AAL1 abnormality, the cell read request mode is switched to a mode that follows the buffer capacity of the delay absorption buffer 11a. When the capacity information is H at the reference timing of the capacity information, the cell read request signal Rc is output, and when it is L, it is not output. As a result, it is possible to prevent the capacity of the delay absorbing buffer 11a from decreasing (underflow) when AAL1 is abnormal.
[0054]
Next, cell loss detection will be described. There are two controls for the buffer control of the decelerating buffer 13a: Robust-SN or Fast-SN.
FIG. 11 is a conceptual diagram showing a difference in control between the case of Robust-SN and the case of Fast-SN. For example, in the cell loss detection, since the cell C7 comes immediately after the cell C3 with respect to the input cell in the figure, three cell losses occur continuously during this period.
[0055]
In such a case, the Robust-SN is a control for outputting a CBR signal such as S31 from the decelerating buffer 13a. Fast-SN is control for outputting a CBR signal such as S32 from the decelerating buffer 13a.
[0056]
FIG. 12 is a time chart showing the operation of cell loss detection. The time chart in the case of Robust-SN is shown. The cell is composed of a header and a payload, and the SC in the header circulates from 0 to 7. Hereinafter, the data number of the payload is expressed as a cell number. For example, the cell of payload D6 is expressed as cell C6.
[0057]
For the input cell shown in the figure, cell C13 (here Out Of Sequence) appears next to cell C6 (up to here SYNC), followed by cell C14 (hereafter SYNC), valid empty cell, and so on. Therefore, it can be seen that 6 cells are continuously lost between the cell C6 and the cell C13 (the cell C6 and the cell C13 are connected by the cell C13 and the cell C14 after the reception of the cell C6. Recognizes the occurrence of cell loss).
[0058]
The loss information output is output in a waveform as shown in the figure, whereby SC 6 held by SC is extended to the start position of the payload of cell C15. The SSC hold is a signal obtained by retiming the SC hold and has the same phase as the count value of the SCR counter that counts 0 to 7 SCs.
[0059]
The shift register shifts the payload of the input cell for a predetermined time from the SSC holding and SCR counter signals. The storage FF latches the output from the shift register at intervals as shown in the figure. Then, the write timing to the decelization buffer 13a is written in the storage FFs D4, D5, and D6 at the timings shown in the figure, and the write is disabled while the loss information output is “H”, and then the D13 of the storage FFs. , D14 is written at the timing shown in the figure.
[0060]
FIG. 13 is a time chart showing the operation of cell loss detection. The time chart in the case of Fast-SN is shown. From the input cell to the shift register waveform is the same as in FIG. In addition, the write timing to the decellization buffer 13a is such that the payloads D5, D6, and D13 of the input cells are written at the timing shown in the figure, and the write information is disabled while the loss information output is “H”. D14 and the payload of the input cell after D15 are written at the timing shown in the figure.
[0061]
Next, cell misdelivery detection will be described. FIG. 14 is a time chart showing the operation of cell misdelivery detection. The time chart in the case of Robust-SN is shown.
With respect to the input cell shown in the figure, a misplaced cell of SC7 appears next to the cell C3, followed by a cell C4, a cell C5,. The state transition changes in the phase shown in the figure in the order of SYNC → Out Of Sequence → SYNC. The SC hold has a phase as shown in the figure, and the SSC hold is a signal obtained by retiming the SC hold and has the same phase as the count value of the SCR counter that counts 0 to 7 SCs. In addition, the count value 4 of the SCR counter extends across SSC holdings 7 and 4.
[0062]
The shift register shifts the input cell for a predetermined time from the SSC holding and SCR counter signals. The storage FF latches the output from the shift register at intervals as shown in the figure. As for the write timing to the decelerating buffer 13a, the D1, D2, and D3 of the storage FFs are written at the timing as shown in the figure, the write is disabled at the misplaced portion, and then the D4 and D5 of the storage FFs are shown in the figure. Write at such timing.
[0063]
FIG. 15 is a time chart showing the operation of cell misdelivery detection. The time chart in the case of Fast-SN is shown. From the input cell to the shift register waveform is the same as in FIG. The decelization buffer 13a is written at the input cell payloads D2 and D3 and the misdelivery payload at the timing shown in the figure, and the period shown in the figure is disabled, and then the input cell payload D5 is written. , D6 and later are written at the timing shown in the figure.
[0064]
Next, error estimation of the SN error protection function will be described. FIG. 16 is a time chart showing an error estimation operation of the SN error protection function. The time chart in the case of Robust-SN is shown.
[0065]
With respect to the input cell shown in the figure, the cell of SC7 and payload D4 (referred to as SN error cell) appears next to cell C3, followed by cell C5, cell C6... (After reception of cell C3, SC7 and payload By following the cell D4 and the cell C5, it is recognized that the SC7 and payload D4 cells are SN error cells).
[0066]
The state transition changes in the phase shown in the figure in the order of SYNC → Out Of Sequence → SYNC. The SC hold has a phase as shown in the figure, and the SSC hold is a signal obtained by retiming the SC hold and has the same phase as the count value of the SCR counter that counts 0 to 7 SCs. The shift register shifts the input cell for a predetermined time from the SSC holding and SCR counter signals. The storage FF latches the output from the shift register at intervals as shown in the figure. .., And D1 to D6... Of the storage FFs are written at the phase timing as shown in the figure.
[0067]
FIG. 17 is a time chart showing the error estimation operation of the SN error protection function. The time chart in the case of Fast-SN is shown. From the input cell to the shift register waveform is the same as in FIG. As for the write timing to the decellization buffer 13a, the payloads D2 to D7... Of the input cells are written at the phase timing as shown in the figure.
[0068]
  As explained above, LegendSince the transmission apparatus 10 is configured to absorb the delay fluctuation of the burst cell and the difference in cell arrival delay by the single delay absorption buffer 11a, the circuit can be reduced in size.
[0069]
Further, the cell read request control means 14 can efficiently read cells while managing the buffer capacity of the delay absorption buffer 11a. Furthermore, when an abnormality occurs in the acquisition state of the RTS value, the abnormality can be notified to an external operator, so that maintenance efficiency can be improved.
[0070]
In the above description, the application of the present invention to the received burst ATM cell has been mainly described. However, the present invention can also be applied to other burst signals other than the ATM cell.
[0071]
(Supplementary note 1) In a transmission apparatus for digital transmission,
A delay absorbing means for storing burst cells sent from the network, absorbing delay fluctuations of the burst cells and a cell arrival delay difference caused by a redundant transmission path configuration, and generating capacity information;
State transition monitoring means for monitoring cell state transition;
Cell fluctuation absorbing means for storing the cells and absorbing cell fluctuations generated when the cells are decelerated;
Cell read request control means for performing read request control of the cell at a fixed speed from the delay absorbing means, based on at least one of the capacity information, the state transition and the cell read cycle in the cell fluctuation absorbing means; ,
A transmission apparatus comprising:
[0072]
(Supplementary note 2) The transmission apparatus according to supplementary note 1, wherein the cell read request control means makes a read request of the cell with a free-running clock when an abnormality of the state transition is detected.
[0073]
(Additional remark 3) The said cell read request control means does not perform the read request of the said cell, when abnormality of the said state transition is detected and it judges that the capacity | capacitance is small from the said capacity | capacitance information. The transmission device described.
[0074]
(Supplementary Note 4) The cell read request control means restores the capacity of the delay absorbing means to the center value after initializing the delay absorbing means or after the underflow of the delay absorbing means is canceled. The transmission apparatus according to supplementary note 1, wherein the cell read request is not performed until the above.
[0075]
(Supplementary note 5) The transmission apparatus according to supplementary note 1, further comprising clock information control means for receiving clock information from the network and absorbing a reception period variation of the clock information caused by the cell fluctuation.
[0076]
(Supplementary note 6) The transmission apparatus according to supplementary note 5, wherein the clock information control means issues a switching instruction to switch to a free-running clock when the clock information cannot be received.
[0077]
(Supplementary note 7) When the state in which one or more pieces of clock information cannot be acquired in N clock cycles in the period of one clock information continues N times, the clock information control unit determines that the clock information acquisition is abnormal and notifies the clock information. The transmission apparatus according to appendix 5, which is characterized.
[0078]
(Supplementary note 8) The transmission according to supplementary note 5, wherein the clock information control means cancels the acquisition abnormality notification of the clock information when n pieces of clock information can be obtained within an n clock information period. apparatus.
[0079]
【The invention's effect】
  As described above, the transmission apparatus of the present invention includes delay absorbing means for generating capacity information by absorbing delay fluctuations and cell arrival delay differences of burst cells, and includes capacity information of the delay absorbing means, cell state transitions and Based on at least one of the cell reading cycles in the cell fluctuation absorbing means, a fixed speed cell reading request control is performed from the delay absorbing means. This makes it possible to reduce the circuit scale because it is not necessary to place very large memories at multiple locations as in the prior art, and to perform efficient read request control of cells, so that high-quality transmission control is performed. Is possible.
The clock information control means of the transmission apparatus can detect and notify an abnormality in the acquisition of clock information, and at the timing when the protection count is reached the fastest among a plurality of release timing sequences in which the protection count is set. Therefore, even when the clock information has an unstable reception cycle, it is possible to recognize the recovery of the acquisition abnormality appropriately and quickly cancel the acquisition abnormality notification.
[Brief description of the drawings]
[Figure 1]BiographyIt is a principle diagram of a feeding device.
FIG. 2 is a diagram showing state transition.
FIG. 3 is a diagram illustrating a configuration of a transmission apparatus.
FIG. 4 is a time chart showing an operation of cell read request control.
FIG. 5 is a time chart showing an operation of cell read request control.
FIG. 6 is a time chart showing the operation of cell read request control.
FIG. 7 is a time chart showing an operation at the time of detecting an abnormality in acquisition of an RTS value.
FIG. 8 is a time chart showing an operation at the time of canceling the acquisition abnormality of the RTS value.
FIG. 9 is a time chart showing an operation of cell read request control.
FIG. 10 is a time chart showing an operation of cell read request control.
FIG. 11 is a conceptual diagram showing a difference in control between the case of Robust-SN and the case of Fast-SN.
FIG. 12 is a time chart showing an operation of cell loss detection.
FIG. 13 is a time chart showing an operation of cell loss detection.
FIG. 14 is a time chart showing an operation of cell misdelivery detection.
FIG. 15 is a time chart showing an operation of cell misdelivery detection.
FIG. 16 is a time chart showing an error estimation operation of the SN error protection function;
FIG. 17 is a time chart showing an error estimation operation of the SN error protection function.
[Explanation of symbols]
10 Transmission equipment
11 Delay absorption means
12 State transition monitoring means
13 Cell fluctuation absorption means
14 Cell read request control means

Claims (4)

In a transmission device that performs digital transmission,
A delay absorbing means for storing burst cells sent from the network, absorbing delay fluctuations of the burst cells and cell arrival delay differences caused by a redundant transmission path configuration, and generating capacity information;
State transition monitoring means for monitoring cell state transition;
Cell fluctuation absorbing means for storing the cells and absorbing cell fluctuations that occur when the cells are decelerated;
Cell read request control means for performing read request control of the cell at a fixed speed from the delay absorbing means, based on at least one of the capacity information, the state transition and the cell read cycle in the cell fluctuation absorbing means; ,
When clock information is received from the network, fluctuations in the reception period of the clock information caused by the cell fluctuation are absorbed, and one or more clock information cannot be acquired within one clock information period N times Is determined to notify that the clock information has been acquired abnormally, and when canceling the acquisition abnormality notification, it is determined whether or not the clock information having been protected n times can be acquired within the n clock information period. A plurality of release timing sequences are shifted by a predetermined period, a clock information control means for canceling the acquisition abnormality notification at the timing at which the protection count is reached fastest among the plurality of release timing sequences,
A transmission apparatus comprising:   2. The transmission apparatus according to claim 1, wherein said cell read request control means makes a read request of said cell with a free-running clock when said state transition abnormality is detected.   2. The transmission according to claim 1, wherein the cell read request control unit does not perform the cell read request when an abnormality of the state transition is detected and it is determined that the capacity is small from the capacity information. apparatus.   The cell read request control means, after the delay absorbing means is initialized or after the underflow of the delay absorbing means is canceled, until the capacity of the delay absorbing means recovers to the center value. The transmission apparatus according to claim 1, wherein no read request is made.

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