JP3471630B2 - Subscriber termination equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to subscriber termination equipment, and more particularly to window control.

[0002]

2. Description of the Related Art A variety of multimedia services (voice, video, data) are divided into fixed-length cells and integrated processing is possible (ATM).
de: Asynchronous transfer mode) technology and optical transmission equipment shared by multiple users to reduce system cost PO
N (Passive Optical Network)
An ATM-PON is an access communication system that makes use of both characteristics of the technology.

FIG. 7 is a diagram showing a network configuration of an ATM-PON. As shown in this figure, a subscriber terminal device (hereinafter, referred to as an OLT) 2 installed in a telephone station and a plurality of subscriber devices (hereinafter, referred to as ONU (Optic) in a building or a home are installed.
al NetworkUnit)) 4 # 1 to 4 # x are connected through an optical fiber by a splitter called a star coupler 6 which is a passive element.

Information is contained in an ATM cell and transferred in units of cells to which additional bytes necessary for communication on the PON of the optical transmission line are added. OLT2 to ONU4 # 1-4 # x
The downstream information to the ONU is transmitted by a continuous signal of the ATM cell, and each ONU communicates by receiving the information addressed to itself.

On the other hand, ONUs 4 # 1-4 # x to OLT2
As for the upstream signal to, the OLT 2 transfers a polling signal that grants a transmission right to a specific downstream ONU to perform polling, and one ONU 4 # i in one time slot.
The ONU 4 # i sets the ATM cell in the assigned time slot and transfers the information.

In ATM-PON, polling is
PLO to a specific location in a frame (eg 56 cells)
A cell dedicated to polling called an AM cell is prepared, and an identifier (for example, ONU serial number) of ONU4 # i which gives a transmission right to this PLOAM cell is set, and each ON
A method of transferring to U4 # j (j = 1 to x) or an ONU4 that gives a transmission right to the area preceding the header of each ATM cell
This is performed by a method of setting the ONU serial number of #i, etc., and transferring.

Then, OLT2 → ONU4 # i → OLT
2 round trip delays for all ONU4 # i
By making it constant with respect to (i = 1 to x), communication is performed while avoiding collision between upstream ATM cells.

FIG. 8 is a diagram showing a round trip delay of ATM-PON. But under normal conditions,
As shown in FIG. 8, the round trip delay Di differs depending on the distance from the OLT 2 to each ONU 4 # i and the processing in each ONU 4 # i. Therefore, the land trip delay D _max of the farthest ONU from the closest ONU 4 # i
By electrically inserting a delay Xi (= D _max -Di) in order to give the same land trip delay as above, the delay can be made the same for all subscribers.

Therefore, in the ATM-PON system,
It is necessary to measure the round trip delay Xi from the OLT 2 to each ONU 4 # i before the start of communication, and to electrically add a delay to each ONU 4 # i so as to be the same as the maximum allowable delay D _max . , This delay measurement is performed every time a new ONU is connected to the OLT.

FIG. 9 is a block diagram of a conventional OLT. FIG. 10 is a configuration diagram of the ONU in FIG. 7. FIG. 11 is a diagram showing conventional window control.

FIG. 12 is a diagram showing a conventional window opening timing. ONU band generator 8 # i (i = 1
~ X) are ONU4 # i according to the bandwidth of ONU4 # i.
To generate a polling signal that gives the upstream ATM cell a transmission right. The MUX 10 multiplexes the polling signal generated by the ONU band generation unit 8 # i to generate a FIFO (First In).
Write to First Out) 12. The read control unit 14 uses the FIF
The polling signal written in O12 is read out.

When measuring the delay of the ONU 4 #n, the window control unit 16 causes the read control unit 14 to receive the FIFO 14.
The read stop signal is activated from. Read control unit 14
When the read stop signal becomes active, the FIFO 14
Stop reading from.

The window control unit 16 includes a read control unit 14
After the read stop signal is made active for a certain period of time, the delay measuring polling signal generator 18 is instructed to generate the polling signal.

[0014] The fixed time means that a cell transmitted by a plurality of ONUs 4 # i which have the transmission right by the polling signal included in the time, and a cell which responds to the polling signal for delay measurement are transmitted by the ONU without delay. It refers to the time that does not arrive from D _min to D _max , based on the time of the above.

The delay measuring polling signal generator 18 is
The polling signal for delay measurement of ONU4 # n is generated. This polling signal is transferred from OLT2 to ONU4 # n. When the ONU 4 #n receives the polling signal for delay measurement through the WDM coupler 22 at the receiving unit 24, the control unit 26 generates an ATM cell for delay measurement response, and the transmitting unit 28 outputs the WDM coupler 22 to the ONU 4 #n. Through O
Transfer to LT2.

The OLT 2 calculates the delay time Dn from the arrival time when the ONU with no delay responds to the arrival of the delay measurement response ATM cell, and (D _max -Dn) as the delay inserted by the ONU 4 #n. Is set in the downlink ATM cell and is notified to the ONU 4 # n.

As shown in FIG. 11, while the delay time of the ONU 4 # n is being measured, in order to avoid collision, the uplink A
The transfer of TM cells has to be stopped. The stop time is, for example, 0 to 2 from the distance from OLT2 to ONU.
If it is 0 km, a delay variation of (D _max −D _min ) = about 200 μs is considered, and during that time (for example, 155.52 M).
In the case of bps, 73 cells) and the transfer of upstream ATM cells is stopped.

Therefore, the distance to ONU2 # n is 0 to 2
When only the distance between 0 km is known, the delay measurement area (window) is opened during the upstream communication of another ONU as shown in FIG. 11 to measure the delay. In order to check the accuracy of the delay measurement, etc., the measurement is performed 2 to 5 times, and after confirmation,
Communication is started by electrically delaying the difference from the maximum distance delay time.

[0019]

[Problems to be Solved by the Invention]
If delay measurement is required, a polling signal for delay measurement is transferred, and communication of other ONUs is stopped while the window is opened. The cells in the meantime are accumulated in the transmission waiting buffer 30 in the ONU and the delay becomes large. Furthermore,
If it is performed 2 to 5 times in succession, the delay is further accumulated and the delay is likely to increase. Moreover, as shown in FIG. 12, this window was opened periodically.

In ATM, there are a service class such as a CBR service such as a telephone having a limited delay time and a service class such as a UBR service in which some delay is allowed such as data communication. Therefore, if the delay measurement window is opened 2 to 5 times in a row, the cell from the ONU to the OLT is delayed, and there is a problem that the delay variation of a service with a limited delay time such as the CBR service becomes large.

The present invention has been made in view of the above circumstances, and a subscriber terminal device capable of avoiding the problem of ATM cell delay by controlling the influence of a window so that it does not remain in the next window. It is intended to be provided.

[0022]

FIG. 1 shows the principle of the present invention. As shown in this figure, according to the present invention, a plurality of subscriber devices (for example, ONUs, hereinafter referred to as ONUs) 31 # i (i = 1 to x) are accommodated and a specific ONU 3 is accommodated.
In the subscriber terminating device 22 which gives the transmission right to 1 # j,
A plurality of band generating means 32 # i (i = 1 to x) for generating a first polling signal that gives the ONU 31 # i a transmission right according to the band of each ONU 31 # i, and the band generating means 3
A FIFO storing the first polling signal generated by 2 # i
When O33 and the read inhibit signal are inactive, the FIF
Read control means 34 for reading the first polling signal from O33 and stopping the reading of the first polling signal from the FIFO 33 when the read inhibit signal is active, and polling signal generating means 35 for generating the second polling signal.
After the polling signal generating means 35 generates the second polling signal, if the first polling signal accumulated in the FIFO 33 becomes equal to or less than a predetermined number, the read inhibit signal is activated and the polling signal generating means 35 receives the first polling signal. 2 Polling control means 36 for instructing generation of a polling signal
There is provided a subscriber terminating device comprising:

According to the above configuration, the plurality of band generation means 32 # i (i = 1 to x) give the transmission right to the ONU 31 # i according to the band of each ONU 31 # i. Generate a signal. This first polling signal is F
The data is sequentially stored in the IFO 33. Polling control means 36
If the number of the first polling signals in the FIFO 33 is equal to or less than a certain number after the polling signal generating means 35 generates the second polling signal for delay measurement or the like, it means that the second polling signal was generated last time. ONU31 # i
It is judged that the influence of the transmission delay from is suppressed.

Then, the polling control means 36 activates the read inhibit signal, and the polling signal generation means 3 is activated.
5 is instructed to generate the second polling signal. This causes the ONU by generating the second polling signal.
It is possible to suppress the delay variation of the transmission signal from 31 # i.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 2 is a configuration diagram of an OLT according to the first embodiment of the present invention.

As shown in this figure, the OLT includes an interface unit 42, a band setting unit 44, and an ONU band generating unit 46.
#I (i = 1 to x), MUX 48, FIFO 50, read control unit 52, window request unit 54, window control unit 56, empty flag 58, window prohibition flag 6
0, delay measurement polling signal generator 62, selector 6
4, a PLOAM cell generator 66, a FIFO 68, a frame generator 70, and a selector 72.

The interface section 42 receives the band of each ONU 82 # i (i = 1 to x) instructed by the control system 40, outputs it to the band setting section 44, and sends it to the control system 40 and the band setting section 44. It controls the interface between. The control system 40 notifies the bandwidth of each ONU 82 # i to the interface unit 42 of the OLT.

The timing at which the band is notified to the interface unit 42 is set when each ONU 82 # i joins or when the ONU 82 # i joins.
This is when there is an incoming / outgoing call to 82 # i. If the band is notified when the ONU 82 # i joins, for example, ONU
This is a case where the band of 82 # i is used by PVC (Permanent Virtual Call), and the control system 40 is a center device of the exchange. The case where the band is notified to the ONU 82 # i at the time of making or receiving a call is, for example, SVC (Signaling Vertual).
Call) (for example, telephone service), and the control system 40 is an exchange.

The band setting unit 44 is the interface unit 42.
By receiving the band information of the ONU 82 # i, the band is set in the ONU band generator 46 # i. The ONU band generation unit 46 # i synchronizes with the clock CLK, and according to the band of the ONU 82 # i set by the band setting unit 44, a polling signal (for example, if the band is 1 Mbps, the ONU 82 # i is set to 1 Mbps). (Giving a transmission right so that the ATM cell can be transferred at the transmission speed)
It is output to X48.

The MUX 48 has each ONU band generator 46 #.
The polling signal output from i is stored in a buffer, multiplexed, and then written in the FIFO 50. The FIFO 50 is a FIFO that stores a polling signal.
O memory.

When the read inhibit signal is active, the read control unit 52 stops reading the polling signal from the FIFO 50, and when the read inhibit signal is inactive, it reads the polling signal from the FIFO 50 at a constant speed and sends it to the selector 64. It is what is output. The read control unit 52
When the FIFO 50 becomes empty, the empty flag 58 is turned on (“1”), and when the polling signal is accumulated in the FIFO 50, the empty flag 58 is turned off.

The window request unit 54 requests the window control unit 56 to open a window. The window request automatically searches for the ONU serial number of an unspecified ONU newly connected to the OLT, and
To give an ON-ID, a new connection is made and PON-
This is the case, for example, to measure the delay of the ONU 82 # n to which the ID is assigned, and to measure the delay of the ONU 82 # i again when the OLT is restarted. For these reasons, window requests are made at regular intervals. Below,
The case of delay measurement will be described as an example. Window control unit 5
6 has the following functions.

When the window request signal becomes active, when the window prohibition flag 60 is off, the window prohibition flag 60 is turned on (“1”), the read prohibition signal is made active for a certain time, and then the generation instruction signal is made active. To do. After that, the read inhibit signal is made inactive.

When the window request signal becomes active, when the window prohibition flag 60 is on, wait until the window prohibition flag 60 is turned off, and then
The window prohibition flag 60 is turned on, the read prohibition signal is made active for a certain time, and then the generation instruction signal is made active. After that, the read prohibition prohibition signal is made inactive.

When the window prohibition flag 60 is on,
When the empty flag 58 is turned on, the window prohibition flag 60 is turned off. Whether or not the empty flag 58 is turned on may be periodically monitored by an interval timer or the like, and when the empty flag 58 is turned on, an interrupt signal may be sent to the window controller 56. .

A selection signal for selecting either the output of the FIFO 50 or the polling signal for delay measurement is output to the selector 64. Empty flag 58
Is a flag that is turned on by the read control unit 52 when the FIFO 50 is empty. The window prohibition flag 60 is turned on when prohibiting opening a window.

Here, the window prohibition flag 60 is turned on when the polling signal for opening the window is transferred, and is turned off when the OLT is started up and the polling signal for opening the window is turned on. It is when the empty flag 58 is turned on after the transfer.

As described above, in the next window, since the FIFO 50 is empty (the bandwidth of all the ONUs 82 # i is secured) after opening the previous window, another window due to the opening of another window is displayed. It is possible to suppress delay fluctuations in ONU cell transmission.

In the present embodiment, the next window is opened because the FIFO 50 becomes empty, but the next window is opened when the number of the polling signals of the FIFO 50 becomes a certain number or less. You can

The polling signal generator 62 for delay measurement is
When the generation request signal becomes active, a delay measurement polling signal is generated. The selector 64 selects the output of the FIFO 50 or the delay measurement polling signal according to the selection signal. The PLOAM cell generation unit 66 generates a PLOAM cell from the polling signal output from the selector 64. Here, the polling signal is transferred by the PLOAM cell, but the polling signal may be transferred in another format.

The FIFO 68 is a FIFO memory for storing a main signal (downstream cell). Read control unit 67
Is to read the downlink main signal from the FIFO 68 at a constant speed. The frame generator 70 uses the clock CLK
In synchronism with the above, a selection signal for selecting a PLOAM cell and a main signal cell is generated in accordance with a prescribed frame format. The selector 72 selects the PLOAM cell or the main signal according to the selection signal.

FIG. 3 is a time chart of FIG. The operation of FIG. 2 will be described below. (A) Band Generation The band of each ONU 82 # i (i = 1 to x) is applied at the time of contract and is notified from the control system 40 to the band setting unit 44 via the interface unit 42. Alternatively, each ONU
82 # i (i = 1 to x) by SVC, control system 40
Is notified to the band setting unit 44 via the interface unit 42.

The band setting unit 44 is the interface unit 42.
Then, the band of each ONU 82 # i (i = 1 to x) is input and set in the ONU band generator 46 # i. The ONU band generation unit 46 # i synchronizes with the clock CLK so that the ONU 82 has a bit rate equal to the set band.
Upstream polling signal for #i (for example, ONU8
2 # i serial number) and output to the MUX 48.

The MUX 48 is an ONU band generator 46 # i.
After inputting the polling signal from the buffer into the buffer, the signals are multiplexed and written into the FIFO 50. Read control unit 5
2 is the FIFO if the read inhibit signal is inactive
The polling signal is read from 50 and output to the selector 64. If the read inhibit signal is active, the FIFO 5
The reading of the polling signal is stopped from 0. Also, F
If the IFO 50 is empty, the empty flag 58
Is turned on, and if not empty, the empty flag 58 is turned off.

(B) Window request The window request unit 54 is a newly connected unspecified ON
Obtain the ONU serial number of U82 # n, and then
Since the ID is automatically assigned, the window request signal is periodically activated as shown in FIG. 3 in order to measure the delay time of the ONU 82 # n to which the PON-ID has been assigned.

(C) Window control FIGS. 4 and 5 are flowcharts of the window control section in FIG. In step S2 in FIG. 4, it is checked whether or not there is a window request from the window request part 54, and if there is a window request, step S4
If there is no window request, the process waits in step S2.

In step S4, it is checked whether or not the window prohibition flag 60 is on. If the window prohibition flag 60 is on, then wait in step S4,
If the window prohibition flag 60 is off, step S6
Proceed to.

For example, at the times Ta and Tc when the window request is made in FIG. 3, the window prohibition flag 60 is off, so the routine proceeds to step S6. At time Tb, the window prohibition flag 60 is on, so that the window is prohibited at step S4. It will wait until the flag 60 is turned off.

In step S6, the window prohibition flag 60 is turned on. In step S8, the read inhibit signal is activated as shown in FIG. In step S10, it is checked whether or not a fixed time has elapsed. If the fixed time has not elapsed, the process waits until the fixed time elapses. When the fixed time elapses, the process proceeds to step S12. When the read inhibit signal becomes active, the read control unit 52 stops reading the polling signal from the FIFO 50.

In step S12, the generation request signal is activated. Delay measurement polling signal generator 6
When the generation request signal becomes active, 2 generates a delay measurement polling signal and outputs it to the selector 64.

In step S14, the read inhibit signal is made inactive. When the read inhibit signal becomes inactive, the read control unit 52 causes the FIFO 5 to operate at a constant speed.
The polling signal is read from 0.

Further, the window control unit 56 sends a delay measurement polling signal if the read inhibit signal is active, and the FIFO 5 if the read inhibit signal is inactive.
A selection signal is output to the selector 64 so as to select the output of 0.

The selector 64 receives the FI signal according to the selection signal.
The output of the FO 50 or the polling signal for delay measurement is selected and output to the PLOAM cell generator 66. PLOAM
The cell generator 66 outputs the PLOAM from the output of the selector 64.
A cell is generated and output to the selector 72.

On the other hand, the window control unit 56 periodically sends the empty flag 5 in step S20 in FIG.
8 is monitored, and if the empty flag 58 is on, the window prohibition flag 60 is turned off, and if the empty flag 58 is off, the process ends.

As a result, once the window is opened, the next window is not opened until the empty flag 58 is turned on. Therefore, at the time of opening the next window, the cell delay due to the opening of the previous window is delayed. Fluctuation is less.

(D) The ATM cell, which is the main transfer signal of the ATM cell, is accumulated in the FIFO 68. The read control unit 67 reads the downlink cell from the FIFO 68 at a constant speed and outputs it to the selector 72. The frame generator 70 outputs the output of the FIFO 68 or a selection signal for selecting a PLOAM cell according to the defined frame format.

The selector 72 receives the FI signal in accordance with the selection signal.
Select the output of FO 68 or PLOAM cell. The cell selected by the selector 72 is converted into an optical signal by an electric / optical converter (not shown), and is passed through the coupler 80 to the ONU.
82 # i (i = 1 to x).

(E) When the cell sending ONU 82 # n receives a polling signal that matches its own PON-ID, it generates a delay measuring cell,
For example, after a lapse of time defined by the time slot number from the upstream head frame, the frame is transferred to the OLT.

The OLT is an ONU when the delay time is zero.
The delay time Dn from the time when the delay measurement cell is received to the time when the delay measurement cell is actually received is measured. The measurement of the delay time Dn is repeated several times, the average value is calculated, and ( _Dmax- Dn) is notified to the ONU 82 # n. At the time of communication, the ONU 82 # n displays (D _max
-Dn) outputs an upstream cell with an electrical delay.

According to the first embodiment described above, once the window is opened, the next window is not opened until the empty flag 58 is turned on.
It is possible to suppress delay variation of M cells.

Second Embodiment FIG. 6 is a block diagram of an OLT according to a second embodiment of the present invention, in which elements substantially the same as the elements in FIG. 2 are designated by the same reference numerals.

The difference between the OLT according to the second embodiment and the OLT according to the first embodiment is that a delay due to opening a window is applied to a band of a CBR service class whose delay time is limited (hereinafter referred to as CBR band). For the bandwidth of the UBR service class (hereinafter referred to as the UBR bandwidth) in which fluctuations are suppressed and delay is allowed to some extent such as in data communication, when there is a margin in the bandwidth, that is, the polling signal and delay measurement for the CBR bandwidth. That is, the polling signal for the UBR band is generated when the polling signal for communication is not transferred.

In the first embodiment, a single polling signal of a combined band of the CRR band and the UBR band is stored in one FIFO.
Since it was stored in 50, the total bandwidth of these is large,
This is because when the free band is small, the polling signal is accumulated in the FIFO 50, the FIFO 50 is less likely to be empty, and the transfer of the delay measurement polling signal or the like may be delayed.

As shown in this figure, the OLT includes an interface unit 42, a band setting unit 44, an ONUCBR band generating unit 90 # i (i = 1 to x), a MUX 48, and a FIFO 5.
0, read control unit 93, window request unit 54, window control unit 56, empty flag 58, window prohibition flag 60, delay measurement polling signal generation unit 62, selector 64, PLOAM cell generation unit 66, read control unit 6
7, FIFO 68, frame generator 70, selector 7
2, ONUUBR band generator 92 # i (i = 1 to x),
It comprises a MUX 94, a FIFO 96, a read control unit 98 and a selector 100.

The interface section 42, the band setting section 44,
MUX 48, FIFO 50, window request unit 54, window control unit 56, empty flag 58, window prohibition flag 60, delay measurement polling signal generation unit 6
2, the selector 64, the PLOAM cell generator 66, the read controller 67, the FIFO 68, the frame generator 70, and the selector 72 are substantially the same as the elements in FIG.

ONUCBR band generator 90 # i (i = 1
Up to x) generate a polling signal according to the CRR band of the ONU 82 # i. The ONUUBR band generation unit 92 # i (i = 1 to x) is the UR of the ONU 82 # i.
A polling signal is generated according to the R band.

The read controller 93 is the read controller 5 shown in FIG.
In addition to the function similar to 2, the read control unit 9 is used when the read inhibit signal is inactive and the FIFO 50 is empty.
8. A function for activating the read permission signal to 8 and outputting a selection signal to the selector 100 so as to select the output of the FIFO 96 when the read permission signal is active and to select the output of the FIFO 50 when the read permission signal is inactive. Have.

The MUX 94 has the ONU 82 # i (i = 1 to 1).
The UBR band polling signal of x) is input to the buffer, multiplexed, and then written in the FIFO 96. When the read enable signal is active, the read control unit 98 synchronizes with the clock CLK and the FIFO at a constant speed.
The UBR band polling signal is read from 96, and FI
When the free space of the FO 96 falls below a certain level and overflow may occur, the ONUUBR band 92 # i (i = 1 to 1)
The bandwidth of x) is reduced or the generation of the bandwidth is temporarily prohibited. The selector 100 selects the outputs of the FIFOs 50 and 96 according to the selection signal.

The operation of FIG. 6 will be described below. (A) Bandwidth The bandwidth of each ONU 82 # i (i = 1 to x) is C at the time of contract.
BR band, UBR band and application for each service class,
The control system 40 notifies the band setting unit 44 of each service class via the interface unit 42. Alternatively,
The SVC to each ONU 82 # i (i = 1 to x) notifies the band setting unit 44 from the control system 40 via the interface unit 42 for each service class.

The band setting unit 44 is the interface unit 42.
Input the band for each service class of each ONU 82 # i (i = 1 to x), set the CBR band in the ONUCBR band generation unit 90 # i, and set the UBR band in the ONUUBR band generation unit 92 # i. .

(B) CBR band generation The ONUCBR band generation unit 90 # i generates an upstream polling signal for the ONU 82 # i (for example, the serial number of the ONU 82 # i) so that the bit rate becomes equal to the CBR band. And outputs it to the MUX 48. CB
Information indicating that the service class is CBR may be added to the polling signal in the R band. MUX
48 inputs the polling signal from the ONUCBR band generation unit 90 # i into the buffer, multiplexes it, and then FI
Write in FO50.

If the read inhibit signal is inactive, the read controller 93 reads the polling signal from the FIFO 50 at a constant speed and outputs it to the selector 100. If the read inhibit signal is active, the read control unit 93 reads the polling signal from the FIFO 50. Stop. Further, the read control unit 93
If the read inhibit signal is inactive and the FIFO 50 is empty, the read enable signal is made active in the read control unit 98, and otherwise the read enable signal is made inactive.

(C) UBR band generation The ONUUBR band generation unit 92 # i generates an upstream polling signal for the ONU 82 # i (for example, the serial number of the ONU 82 # i) so that the bit rate becomes equal to the UBR band. And outputs it to the MUX 94. UB
Information indicating that the service class is UBR may be added to the polling signal in the R band. MUX
94 inputs the polling signal from the ONUUBR band generation unit 92 # i to the buffer, multiplexes it, and
I write it in FO96.

The read controller 98 reads the polling signal of the UBR band from the FIFO 96 at a constant speed if the read enable signal is active, and stops the read from the FIFO 96 if the read enable signal is inactive.

The read enable signal becomes active and the UBR
The band polling signal is output when there is no CBR band polling signal and the window is not open, and cell delay variation in the UBR band may occur. However, in the UBR band, delay variation occurs. There is no problem because it is greatly permitted.

The read control unit 98, when the free space of the FIFO 96 becomes less than or equal to the lower limit, the ONUUBR band generation unit 92.
#I UBR band is temporarily reduced, or ONU
The UBR band generation unit 92 # i is instructed to temporarily stop the generation of the UBR band. As a result, by opening the window, the generation of the UBR band is suppressed, and F
Even if the UBR polling signal continues to be accumulated in the IFO 96, the FIFO 96 does not overflow.

The selector 100 outputs the F signal according to the selection signal.
The outputs of the IFOs 50 and 96 are selected and output to the selector 64. (D) Window request The window request unit 54 is a newly connected unspecified ON
Obtain the ONU serial number of U82 # n, and then
In order to automatically assign the ID, in order to measure the delay time of the ONU 82 # n to which the PON-ID has been assigned, a window request is periodically issued to the window control unit 56.

(E) Window control The window control unit 54 operates in the same manner as in the first embodiment, and when the window prohibition flag 60 is off, the read prohibition signal is made active for a fixed time, and then the delay measurement for delay measurement is performed. The delay measurement polling signal generation unit 62 is instructed to generate the polling signal. As a result, in the CBR band, the cell delay variation due to the opening of the window can be minimized and the delay variation of opening the delay measurement window can be minimized.

(F) The ATM cell, which is the main transfer signal of the ATM cell, passes through the coupler 80 through the ONU 82 # i (i = 1 to 1) as in the first embodiment.
x).

(G) When the cell sending ONU 82 # n receives a polling signal that matches its own PON-ID, it generates a delay measuring cell,
For example, it is transferred to the OLT after a lapse of time defined by the time slot number from the downlink head frame.

The OLT is an ONU when the delay time is zero.
The delay time Dn from the time when the delay measurement cell is received to the time when the delay measurement cell is actually received is measured. The delay time Dn from the transmission of the polling signal to the reception of the delay measurement cell is measured.

Repeat this measurement of the delay time Dn several times
And calculate the average value,_max-Dn) ONU82
Notify #n. During communication, ONU82 # n
(D _max-Dn) with an electrical delay, and the upstream cell
Is output.

In addition, a polling signal causes an upward ATM
The ONU 82 # i, which has obtained the cell transmission right, prioritizes cells in the CBR band according to the priority order of cell transmission,
Send a cell. When a service class is set in the polling signal, a cell that matches the set service class may be transmitted.

According to the second embodiment described above, the AT
You can do polling corresponding to each service of M,
The delay variation that opens the window for delay measurement can be minimized.

[0085]

As described above, according to the present invention,
After the second polling signal is generated, the second polling signal is generated when the number of the first polling signals accumulated in the FIFO is equal to or less than a certain number. Therefore, in the ONU by generating the second polling signal. It is possible to suppress variation in transmission delay.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an OLT according to the first exemplary embodiment of the present invention.

FIG. 3 is a time chart of FIG.

FIG. 4 is a flowchart of a window control unit in FIG.

5 is a flowchart of a window control unit in FIG.

FIG. 6 is a configuration diagram of an OLT according to a second embodiment of the present invention.

FIG. 7 is a network configuration diagram of an ATM-PON.

FIG. 8 is a diagram showing a round trip delay.

FIG. 9 is a configuration diagram of a conventional OLT.

10 is a configuration diagram of an ONU in FIG. 7.

FIG. 11 is a diagram showing conventional window control.

FIG. 12 is a diagram showing a timing of opening a conventional window.

[Explanation of symbols]

31 # i (i = 1 to x) ONU 32 # i (i = 1 to x) Band generation means 33 FIFO 34 Read Control Means 35 Polling signal generating means 36 Polling control means

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-336143 (JP, A) JP-A-9-233103 (JP, A) JP-A-11-17685 (JP, A) Satoshi Ezawa, Yutaka Ueda ， Kawaho Kawaguchi ， Kuniharu Hirose ， Kiyoshi Yokota ， Discussion of data traffic accommodation technology in ATM access system ， Technical report of IEICE ， Japan ， IEICE ， June 23, 1997 ， CS97－ 28 Satoshi Karasawa, Satoshi Furusawa, A study on ONU control method in ATM-PON system, Proc. Of IEICE General Conference 1996, The Institute of Electronics, Information and Communication Engineers, March 11, 1996, B-978 Miyabe Masayoshi, Tomohiro Shinomiya, Masamichi Kasa, Haruo Yamashita, ATM-PON Dynamic Bandwidth Allocation Method, 1997 IEICE If Conference Proceedings, Japan, Institute of Electronics, Information and Communication Engineers, March 6, 1997, B-8-53 (58) investigated the field (Int.Cl. ^7, DB name) H04L 12/44 H04L 12/56 H04B 10/20

Claims (7)

(57) [Claims] 1. A subscriber terminating device that accommodates a plurality of subscriber devices and gives a transmission right to a particular subscriber device, wherein the transmission right is given to the subscriber devices according to a band of each of the subscriber devices. A plurality of band generation means for generating a given first polling signal, a FIFO for storing the first polling signal generated by the plurality of band generation means, and a first read-out signal from the FIFO when the read inhibit signal is inactive. A polling signal is read, and when the read inhibit signal is active, read control means for stopping the reading of the first polling signal from the FIFO and a second polling signal for instructing a response to the particular subscriber unit are generated. Polling signal generation means, and the first polling signal generation means stores the first polling signal in the FIFO after generating the second polling signal. Polling control means for activating the read inhibit signal and instructing the polling signal generation means to generate the second polling signal when the number of polling signals is less than a predetermined number. Termination device. 2. A subscriber terminating device that accommodates a plurality of subscriber devices and gives a transmission right to a particular subscriber device according to a first band of a first service class of each of said subscriber devices. A plurality of first band generation means for generating a first polling signal for giving a transmission right to the subscriber device of the first service class; and a first FIFO for storing the first polling signal generated by the first band generation means. When the read inhibit signal is inactive, the first FIFO
Read the polling signal from the first FIFO, and when the read inhibit signal is active, first read control means for stopping the reading of the polling signal from the first FIFO, and a second polling signal for instructing a response to the specific subscriber unit. And a first polling signal generating means for generating the second polling signal after the polling signal generating means generates the second polling signal.
When the number of polling signals is less than a certain number, the read inhibit signal is activated, and polling control means for instructing the polling signal generation means to generate the second polling signal, and the second service of each subscriber device. A plurality of second band generation means for generating a third polling signal for giving a transmission right to the subscriber device of the second service class in accordance with the second band of the class; and a plurality of second band generation means. A second FIFO for storing the third polling signal, the read inhibit signal being inactive, and the first FIFO
And a second reading means for reading the second polling signal from the second FIFO when O is empty. 3. The second read means is the second FIFO.
3. The subscriber terminal device according to claim 2, wherein the plurality of second band generation means are instructed to suppress or stop the generation of the third polling when the free capacity of the above becomes less than a certain value. 4. The first FIFO based on a selection signal.
And a selection unit for selecting an output of the second FIFO, wherein the first reading unit outputs the selection signal.
A subscriber termination device as described. 5. The polling control means further comprises requesting means for periodically requesting the generation of the second polling signal, wherein the polling control means causes the polling signal generating means to perform the second polling on the basis of the request from the requesting means. 3. The subscriber terminal device according to claim 1, which instructs generation of a signal. 6. A first flag, a second flag, and if the first polling signal is not present in the FIFO, the first flag is turned on, and if the first polling signal is present in the FIFO, the first flag is turned on. First flag setting means for turning off a first flag; and a second flag for turning on the second flag when the second polling signal is generated and for turning off the second flag when the first flag is on. 2. The subscriber terminal device according to claim 1, further comprising setting means, wherein the polling control means instructs the polling signal generating means to generate the second polling signal when the second flag is off. 7. A first flag, a second flag, and, if the first polling signal is not present in the first FIFO, the first flag is turned on and if the first polling signal is present in the first FIFO. First flag setting means for turning off the first flag, and turning on the second flag when the second polling signal is generated, and turning off the second flag when the first flag is on 3. The subscriber terminal device according to claim 2, further comprising: 2 flag setting means, wherein the polling control means instructs the polling signal generating means to generate the second polling signal when the second flag is off. .