JP2002009780A - Dynamic band assignment system and dynamic band assignment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome a problem such that a conventional dynamic band assignment system has statistically increased a transfer delay time of a cell and the burst performance of the cell. SOLUTION: When a consecutive number of valid cells received from network terminators 11a, 11b, 11c exceeds a prescribed threshold, a network unit 18 increases number of assigned cell slots to the network terminators 11a, 11b, 11c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an FSAN (Fu)
ll Service Access Network
k) and ITU-T (International T)
elecommunication Union-Te
communication Standardi
ATM-PON (Asynchronous Tr) whose international standardization is being carried out by Zoning Sector.
answer Mode-Passive Optical
al Network), the present invention relates to a dynamic band allocation system and a dynamic band allocation method for dynamically allocating a band with respect to an upstream band provided to a network device by a network terminating device.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing a conventional dynamic band allocation system disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-135502. In the figure, reference numerals 12a, 12b, and 12c denote user devices, 14a, 14b, and 14b. 14c is a transmission line, 15 is a distribution device, 16 is a transmission line, and 17 is a network device. The user devices 12a, 12b, 12c are connected to the transmission lines 14a, 14b, 14
The distribution device 15 is connected to the network device 17 via the transmission line 16. FIG.
(A) shows the network devices 17 to the user devices 12a, 12b, 1
8 shows the flow of a signal in the downward direction toward 2c.
(B) shows an upward signal flow from the user devices 12a, 12b, and 12c to the network device 17.

Next, the operation will be described. In FIG. 8 (A), the network device 17 sends out the frame identifier F, then the information a going to the user device 12a, and then the user device 12a.
The information b going to b and the information c going to the user device 12c are output to the transmission line 16. Information a, b, and c are stored in the network device 1.
7 is received from the communication network. Information a,
The network device 17 inserts destination user device information into b and c.

[0004] The distributor 15 outputs exactly the same signal to the transmission lines 14a, 14b, 14c. The user devices 12a, 12b, 12c are connected to the transmission lines 14a, 14b, 14
c, and receives information addressed to itself. Note that the frame identifier F in FIG.
In the upward direction in FIG. 8B, the user equipment 12a, 1
Information indicating time slots used by 2b and 12c in the next frame is inserted.

[0005] In FIG. 8B, user devices 12a,
Each of 12b and 12c recognizes a time slot in which the apparatus itself should output information from the frame identifier F in FIG. 8A, and outputs information a, b, and c to the time slot, respectively. Note that the user devices 12a, 12b, 12c
When it is desired to increase the number of time slots to be transmitted, information is transmitted to all of the allocated time slots. For the frame identifier F, for example, the user device 12a
Can be fixedly output.

[0006] The distribution device 15 outputs the information a, b, and c to the transmission line 16 in the same order. Transmission lines 14a, 14
When the transmission lines 16 b and 14 c and the transmission line 16 are optical fibers, an optical star coupler is used as the distribution device 15. The network device 17 receives the frame identifier F and the information a, b, c from the transmission line 16 and transfers the information a, b, c to the communication network.

Next, upon receiving all the information of one frame, the network device 17 determines, for each of the user devices 12a, 12b, and 12c, whether or not information has been inserted into all of the assigned time slots. If all are inserted, the time slot allocation of the user apparatus is increased. Otherwise, the time slot allocation is executed so as not to reduce or change the time slot allocation. The information is inserted into the frame identifier F of the direction. By doing so, it is possible to increase the time slot assignment to the user apparatus that wants to increase the uplink time slot assignment.

[0008]

Since the conventional dynamic band allocation system is configured as described above, the cell transfer delay time becomes statistically large and the cell burstiness becomes statistically high. There were issues such as.

The details are as follows. Here, the user device 12a will be described, but the same applies to the user devices 12b and 12c. FIG. 9 is an explanatory diagram showing the relationship between the allocation position of the time slot to the required band of the user apparatus 12a and the output information. In FIG. 9, frame 1 and frame 2 are frame names given for explanation. In the output information of the user device 12a, the output of the frame identifier F is omitted.

FIG. 9 shows an example in which the required bandwidth of the user apparatus 12a increases in the middle of the frame 1. Examples of services that increase or decrease the required bandwidth include video data transfer and computer data transfer services. In FIG. 9, since the increase of time slots is not requested before the required bandwidth increases, the output of information is stopped at the allocated time slots, and thereafter, the required bandwidth increases and information is transmitted to all of the allocated time slots. Output.

However, since no information was output in the assigned time slot in frame 1, the network device 17
Recognizes the time slot increase request of the user apparatus 12a when the last information of the user apparatus 12a is received in the frame 2, and further waits until the end of the frame 2 to increase the time slot of another user apparatus. Recognize the request and begin time slot reallocation. When the reallocation calculation is completed, the network device 17 inserts the time slot information into the downlink frame identifier F, and
Can receive the time slot information and output the information to the reallocated time slot from the next uplink frame.

As described above, when the required bandwidth of the user equipment increases and the user equipment requests an increase in the bandwidth, the network equipment 17 starts reallocation of the time slot two frame time after one frame. . Generally, the user apparatus stores information in a buffer memory while a required time slot is not allocated. For this reason, the slower the reallocation of the time slot becomes, the larger the required amount of buffer memory becomes and the larger the amount of information to be stored becomes, so that the transfer delay time becomes longer. Also, if the amount of cells stored in the buffer is large, the burstiness of the cells increases. In general, a device in a communication network requires a large amount of buffer memory for transferring information having a high burst property, and therefore, a device in a communication network desirably transfers information having a low burst property.

Next, FIG. 10 shows a case where the required bandwidth in the user equipment 12a increases and the required bandwidth continues.
FIG. 6 is an explanatory diagram showing the number of assigned time slots of a and the amount of output information of the user apparatus 12a. In FIG. 10, the delay time from when the user apparatus 12a issues a time slot increase request to when the information is output in the actually increased time slot is X time, and the user apparatus 12a stops the time slot increase request. From the above, assuming that a delay time until information is output in the actually reduced time slot is Y time,
When the required bandwidth of the user device 12a increases, the assigned time slot of the user device 12a increases after X hours, and the output information amount of the user device 12a also increases.

Here, for the sake of simplicity, it is assumed that the increased time slot bandwidth is greater than the required bandwidth of the user equipment 12a. In addition, in the case where information is not output to all of the allocated time slots, the description will be made on the assumption that the time slot allocation is always reduced.

Thereafter, the user device 12a loses the information stored in the buffer memory, and does not output information to all of the assigned time slots.
Next, the network device 17 determines that the assignment of the time slot of the user device 12a may be reduced, and decreases the number of assigned time slots of the user device 12a after Y time. As a result, the amount of output information of the user device 12a is reduced, and the information is stored again in the buffer memory.
This state is repeated until the required bandwidth of a decreases. When information is accumulated in the buffer memory, the delay time increases. In the above situation, a transfer state with a large amount of information and a transfer state with a small amount of information are alternately present, and the burst property of the cell is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a dynamic delay that can statistically reduce the cell transfer delay time and statistically reduce the cell burstiness. It is an object to obtain a band allocation system and a dynamic band allocation method.

[0017]

A dynamic bandwidth allocation system according to the present invention is arranged such that when the number of consecutive valid cells received from a network terminating device exceeds a predetermined threshold, the network device allocates a cell slot to the network terminating device. Is to increase.

A dynamic bandwidth allocation system according to the present invention comprises:
When the number of valid cells received from the network terminating device within the determination cycle falls below a predetermined threshold, the network device reduces the allocation of cell slots to the network terminating device.

A dynamic band allocation system according to the present invention comprises:
When the number of valid cells received from the network terminating device within the determination cycle exceeds a predetermined threshold, the network device increases the allocation of cell slots to the network terminating device.

A dynamic band allocation system according to the present invention comprises:
The threshold value is set according to the total number of cells received by the network device within the determination cycle.

In the dynamic bandwidth allocation method according to the present invention, when the number of consecutive valid cells received from the network terminating device exceeds a predetermined threshold, the number of cell slots allocated to the network terminating device is increased.

In the dynamic bandwidth allocating method according to the present invention, when the number of valid cells received from the network terminating device within the determination period falls below a predetermined threshold, the allocation of cell slots to the network terminating device is reduced. Things.

In the dynamic bandwidth allocating method according to the present invention, when the number of valid cells received from the network terminating device within the determination period exceeds a predetermined threshold, the number of cell slots allocated to the network terminating device is increased. Things.

In the dynamic band allocation method according to the present invention, a threshold value is set according to the total number of cells received within a determination cycle.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a configuration diagram showing a dynamic bandwidth allocation system according to Embodiment 1 of the present invention.
11a, 11b, and 11c are network terminating devices that transmit cells to the network device 18 in cell slots allocated by the network device 18, 12a, 12b, and 12c are user devices, and 13a,
13b and 13c are transmission lines, 14a, 14b and 14c are transmission lines, 15 is a distribution device, 16 is a transmission line, and 18 is the number of consecutive valid cells received from the network terminating devices 11a, 11b and 11c exceeding a predetermined threshold. And the network terminating devices 11a and 11
While increasing the number of cell slots allocated to b and 11c, while the number of valid cells received from the network terminating devices 11a, 11b and 11c within the determination cycle falls below a predetermined threshold,
This is a network device that reduces the assignment of cell slots to the network terminating devices 11a, 11b, 11c.

The determination of cell slot increase / decrease may be made for each frame or for several frames. In the following, 1
The description will be made on the assumption that the determination of the increase / decrease of the cell slot is made for each frame. The user devices 12a, 12b, and 12c in FIG. 8 described in the related art are the network terminating device 11a and the user device 12a, and the network terminating device 11b and the user device 12 in FIG.
b, in a form separated into a network termination device 11c and a user device 12c. The reason is that, in the ATM-PON, the first embodiment is currently in practical use. The network terminating devices 11a, 11b, and 11c are provided on the carrier network side, and provide a user-network interface to the user devices 12a, 12b, and 12c.

The user devices 12a, 12b, 12c are connected to the network terminating devices 11a, 11b via transmission lines 13a, 13b, 13c.
11b and 11c, respectively.
a, 11b and 11c are connected to a distribution device 15 via transmission lines 14a, 14b and 14c, and the distribution device 15 is connected to a network device 18 via a transmission line 16. FIG. 1 (A)
FIG. 1B shows a downstream signal flow from the network device 18 to the user devices 12a, 12b, and 12. FIG. 1B shows an upstream signal flow from the user devices 12a, 12b, and 12c to the network device 18. Is shown. In the prior art, the symbols a, b, and c in the frame in FIG. 1 have been described as information. However, in the ATM-PON, information is transferred by a fixed-length packet called a cell. In the description of 1, the symbols a,
Description will be made assuming that b and c are cells.

Next, the operation will be described. In FIG. 1A, a network device 18 is a PL-OAM (Physical).
Layer-Operation and Main
transmission) cell P, and then the network terminating device 11
A cell a going to a, a cell b going to the network terminator 11b, and a cell c going to the network terminator 11c next
Output to The cells a, b, and c are received by the network device 18 from the communication network, and the destination user device information is inserted in the cells a, b, and c.

The distributor 15 outputs the same signal as this signal to the transmission lines 14a, 14b and 14c. The network terminators 11a, 11b, 11c are connected to the transmission lines 14a, 14b, 14
c, and receives information addressed to itself. The network terminating devices 11a, 11b, and 11c connect the cells a, b, and c to the user devices 12a, 12b, and 12 respectively.
c.

Note that the PL-OAM cell P in FIG. 1A has information indicating the cell slot position used by the network terminating devices 11a, 11b, and 11c in the upstream direction in FIG. 1B from the next frame. Is inserted. In the conventional technology, the cell slot is a time slot. However, since the ATM-PON uses a cell, the cell slot is used as a cell slot. Although the PL-OAM cell is output once in one frame in FIG. 1, it is actually output a plurality of times in one frame, and the PLOAM cell at the head of the frame is the information inserted in the cell. Can be identified as the PL-OAM cell at the head of the frame.

In FIG. 1B, the user devices 12a and 12a
b, 12c connect the cells a, b, c to the network terminating devices 11a, 11b.
b, 11c. Network terminating devices 11a, 11b, 1
In step 1c, the own apparatus recognizes a cell slot from which information is to be output from the PL-OAM cell in FIG. 1A, and outputs cells a, b, and c to the cell slot. In addition, the band of the cell received from the user devices 12a, 12b, and 12c and the band of the cell transmitted to the distribution device 15 are equal for a long period, but there is a difference in a short period.

The network terminating devices 11a, 11b and 11c store cells therein for a short period of time to absorb the difference between the band of the cells received from the user devices 12a, 12b and 12c and the band of the cells transmitted to the distribution device 15. It is necessary to have a buffer memory for storing, and while cells are stored in the buffer memory, valid cells are transmitted to all assigned cell slots. When no cells are left in the buffer memory, idle cells are output to the assigned cell slots. Idle cells are in the form of cells, but do not transmit information.

The distribution device 15 outputs the cells a, b and c to the transmission line 16 in the same order. Transmission lines 14a, 14
When the transmission lines 16 b and 14 c and the transmission line 16 are optical fibers, an optical star coupler is used as the distribution device 15. The network device 18 receives the cells a, b, and c from the transmission line 16 and transfers the cells a, b, and c to the communication network. Note that, in the upward direction, PL-O
Although the AM cell is not described, in the ATM-PON, the network device measures the delay amount of the upstream frame with respect to the downstream frame in advance, and determines the PL-OA at the head of the downstream frame.
A cell that arrives after the delay time after transmitting the M cell is treated as a head cell of an upstream frame, so that a frame identifier is not required.

Next, upon receiving all the information of one frame, the network device 18 monitors the received cells for each of the network terminating devices 11a, 11b, and 11c, allocates cell slots, and performs the uplink in FIG. The information is inserted into the PM-OAM cell in the direction. Next, details of cell slot assignment will be described. Hereinafter, the user equipment 12a and the network terminating equipment 11
Although a will be described, the user device 12b and the network termination device 11b and the user device 12c and the network termination device 11c perform the same operation.

The case where the band of the cell output from the user apparatus 12a is increased will be described. When the bandwidth of the cell output from the user equipment 12a increases, the required bandwidth in the upstream direction of the network terminating equipment 11a increases. FIG. 2 shows a network termination device 11a.
FIG. 6 is an explanatory diagram showing a relationship between a required band of the network termination device, a cell slot position allocated to the network termination device 11a, and output information of the network termination device 11a.

In FIG. 2, before the required bandwidth of the network termination device 11a increases, no cells are left in the buffer of the network termination device 11a and idle cells are output. Thereafter, the band of the cell output from the user apparatus 12a increases, and the valid cells are output continuously. Here, assuming that the threshold of the number of consecutive valid cells corresponding to the total number of cells received by the network termination device 11a at the time of determining the increase of the cell slot for the network termination device 11a is S cell, the valid cell is S + in FIG.
Since one cell is continuous and exceeds the threshold S cell, the network device 18 starts increasing the cell slot allocation of the network terminating device 11a. Here, the above threshold is used for increasing the number of cell slots, and is therefore called an increase threshold. The increase of other network terminating devices is determined in the same manner.

Since a valid cell or an idle cell of the network termination device 11a is always inserted into the cell slot allocated to the network termination device 11a, the value of the number of cell slots allocated in one frame of the network termination device 11a is , After a certain delay time, the network device 18 receives from the network termination device 11a 1
This is the value of the total number of cells in the frame. The threshold for increasing the number of consecutive valid cells is set in accordance with the total number of cells received in one frame. If the total number of received cells changes,
This increase threshold also changes.

The counting of the total number of received cells and the number of valid cells will be described. After transmitting the PL-OAM at the head of the downstream frame, the network device 18 recognizes the cell arriving after the delay time measured in advance as the upstream frame head cell, and allocates the cell to the network terminating device 11a. Since the position of the cell slot in the frame is recognized, the network device 18 can recognize the cell time at which the cell is received from the network terminating device 11a.

At the time of receiving a cell from the network terminating device 11a, the network device 18 counts the total number of cells and the number of valid cells, for example, as follows. First, the counter for the total number of cells of the network termination device 11a is counted up. Next, ATM
If the cell header is a valid cell in view of the cell header, the network termination device 1
What is necessary is just to count up the valid cell number counter of 1a.

It is necessary to allocate cell slots at equal intervals as much as possible in order to reduce the burstiness of cells. In this case, the allocation of the cell slot of the network termination device is set to K cells, and the increase threshold of the number of consecutive valid cells of the network termination device at the time of the cell slot increase determination is L.
Assuming a cell, when the required band of the network terminating device increases, the probability that the increase of the cell slot can be determined at the end of the frame is about L / K.

In the prior art, since the increase of the cell slot is always determined at the end of the next frame, the time from the increase in the required bandwidth of the network termination device to the determination of the increase in the network device is stochastically reduced. You can do it. For example, K
If L = 50 and L = 50, the probability that the network device can determine the increase of the cell slot at the end of the frame after the required bandwidth of the network terminating device increases is about 1/2. If the network equipment cannot determine the increase of the cell slot at the end of the frame after the required bandwidth of the network termination equipment has increased, the network equipment determines the increase of the cell slot at the end of the next frame. After the required bandwidth of the device has increased,
The average time required for the network device to determine an increase in cell slots is 1.0 frame time when K = 100 and L = 50.

In the prior art, the increase is determined two frames after one frame, so that it takes 1.5 frames on average. Therefore, in the first embodiment, the time is reduced by an average of 0.5 frame compared to the conventional technique. This effect is K
The effect increases as the value of / L decreases. However, effective cells may be continuous due to fluctuations of cells output by the user equipment, and cannot be extremely reduced. Therefore, the increase threshold is determined by the characteristics of the cell of the user equipment and the number of cell slots to be increased with respect to the network termination equipment. Is determined in consideration of the above parameters.

As is apparent from the above, according to the first embodiment, the time from the increase in the required bandwidth of the network terminating devices 11a, 11b and 11c to the determination of the increase in the cell slot in the network device 18 is stochastically determined. Therefore, the number of cells stored in the buffer memories of the network terminating devices 11a, 11b, 11c can be statistically reduced, the cell transfer delay time can be statistically reduced, and the burstiness of the cells can be statistically reduced. This has the effect of being able to be reduced.

Next, the case where the band of the cell output from the user apparatus 12a is reduced will be described. FIG. 3 shows the required bandwidth of the network terminating device 11a, the number of allocated cell slots in one frame of the network terminating device 11a, the total number of cells in one frame received from the network terminating device 11a in the network device 18, and the 1 of the network terminating device 11a. Number of output effective cells in frame and network device 1
8 is an explanatory diagram showing the relationship between the number of effective cells in one frame received from the network terminating device 11a in FIG.

In FIG. 3, the initial value is the network terminating device 11
a, the number of allocated cell slots in one frame is “100”;
In the network device 18, the total number of cells in one frame received from the network terminating device 11a is “100”, the number of valid output cells in one frame of the network terminating device 11a is “80”,
In the following description, it is assumed that the number of effective cells in one frame received from the network terminating device 11a is "80". For the sake of simplicity, the description will be made on the assumption that the number of cell slots allocated to the network terminating device 11a has only two values of 100 cells and 50 cells in one frame. Of course, in reality, the number of cell slots to be allocated can be defined instead of binary values.

Since a valid cell or an idle cell of the network terminating device 11a is always inserted into the cell slot allocated to the network terminating device 11a, a cell is transmitted by the network terminating device 11a and then the network device 18 transmits the cell. Assuming that a delay time until a cell is detected is Z time, the value of the number of allocated cell slots in one frame of the network termination device 11a is delayed by Z time.
At 8, the value of the total number of cells in one frame received from the network terminating device 11a. Similarly, the network terminating device 11a
The number of valid cells in one frame becomes the value of the number of valid cells in one frame received from the network terminating device 11a in the network device 18 with a delay of Z time. In the graph of the number of valid cells in one frame received from the network terminating device 11a in the network device 18, a decrease threshold used for decreasing the cell slot assignment is described. The decrease threshold is the network device 1
8, the number changes in accordance with the total number of cells in one frame received from the network terminating device 11a.

When the bandwidth of the cell output from the user equipment 12a decreases, the required bandwidth of the network termination device 11a decreases, and the number of output effective cells in one frame of the network termination device 11a decreases. In FIG. 3, the number of output effective cells in one frame is “80”.
To "45". Accordingly, the network device 1
In 8, the number of valid cells in one frame received from the network terminating device 11a also changes from "80" to "45" after Z hours.

In the network device 18, the network terminating device 11
The reduction threshold value is “70” when the total number of cells in one frame received from “a” is “100”. In FIG.
The number of available cells in one frame of the network terminating device 11a decreases, and the number of valid cells in one frame received from the network terminating device 11a in the network device 18 becomes equal to or less than the decrease threshold, and the number of allocated cell slots decreases. Assuming that the delay time until the network termination device 11a outputs a cell in the actually reduced cell slot is Y time, the number of effective output cells in one frame of the network termination device 11a decreases to "45". After Y time, the number of allocated cell slots in one frame of the network termination device 11a decreases. In FIG. 3, the number is reduced to "50" and this state continues thereafter.

In the network device 18, the network terminating device 11
When the total number of cells received from “a” is “50”, the decrease threshold is “35”, but the number of valid cells received is “35”.
Since the number of cell allocation slots in one frame is limited to "50" and "100" even under the following conditions, the number of cell allocation slots in one frame of the network termination device 11a is reduced. do not do. Further, the decrease threshold is determined in consideration of the characteristics of the cell of the user apparatus and parameters such as the number of cell slots to be increased with respect to the network terminating apparatus.

Next, a case where the band of the cell output from the user apparatus 12a increases and the increased state continues will be described. FIG. 4 shows the required bandwidth of the network termination device 11a, the number of allocated cell slots in one frame of the network termination device 11a,
8, the total number of cells in one frame received from the network terminating device 11a, the number of valid cells output in one frame of the network terminating device 11a, and the number of valid cells in one frame received from the network terminating device 11a in the network device 18. It is explanatory drawing which shows a relationship. Each relationship is the same as that described in FIG.

In FIG. 4, the initial value is the network terminating device 11
a, the number of allocated cell slots in one frame of “a” is “50”, the total number of cells in one frame received from the network terminating device 11 a in the network device 18 is “50”, and the output valid cells in one frame of the network terminating device 11 a. It is assumed that the number is “40” and the number of effective cells in one frame received from the network terminating device 11a in the network device 18 is “40”.

When the band of the cell output from the user equipment 12a increases and the increase continues, the network termination equipment 11a
Required band increases, and the increased state continues. When the required bandwidth of the network termination device 11a increases, the number of output effective cells in one frame increases to the number of allocated cell slots. In FIG. 4, the number of output effective cells in one frame is "50".

In FIG. 4, when the number of available cells in one frame of the network termination device 11a rises to the number of allocated cell slots, the number of consecutive valid cells received from the network termination device 11a at the time of the determination naturally exceeds the increase threshold. Therefore, according to the principle described above, the number of allocated cell slots in one frame of the network termination device 11a increases. At this time, the network termination device 1
After the number of output effective cells in one frame of 1a increases,
Assuming that a delay time until a cell is output in the actually increased cell slot is X time, one frame of the network termination device 11a after X time after the number of output effective cells in one frame of the network termination device 11a increases. , The number of available cell slots within one frame of the network terminating device 11a increases. After Z hours, the network device 1
8, the total number of cells in one frame received from the network termination device 11a and the network device 18 also increase the number of valid cells in one frame received from the network termination device 11a.

In FIG. 4, it is assumed that the number of allocated cell slots and the number of output effective cells in one frame of the network termination device 11a have become "100". In the network device 18, the total number of cells and the number of valid cells in one frame received from the network terminating device 11a also become "100" after Z hours. Further, in the network device 18, when the total cells in one frame received from the network terminating device 11a are 100 cells, the reduction threshold is set to 80 cells.

Next, when there are no more cells stored in the buffer memory in the network termination unit 11a, the number of valid output cells in one frame of the network termination unit 11a decreases, and the network unit 18 receives the cells from the network termination unit 11a. If the number of valid cells in one frame does not fall below the decrease threshold, the number of allocated cell slots does not decrease, and this state continues thereafter. In the figure, the number of available cells in one frame of the network termination device 11a becomes 80 cells, and the number of valid cells in one frame received from the network termination device 11a in the network device 18 after Z time is eight.
Since the number of cells is 0, which is equal to or greater than the reduction threshold, this state continues thereafter.

As is clear from the above, according to the first embodiment, unlike the prior art, if the number of output cells in one frame of the network termination device 11a is equal to or greater than the reduction threshold, the output of the network termination device 11a Since the number of effective cells does not repeatedly increase or decrease, the accumulation of cells in the buffer memory is reduced, the cell transfer delay time can be statistically reduced, and the cell burstiness is statistically reduced. Can be done.

FIG. 5 is a flowchart showing a dynamic bandwidth allocation method according to the first embodiment. In this flowchart, N network terminating devices are connected to the network device 18 via the distribution device 15. And First, the update of cell slot assignment is started after the end of one frame (step ST1). Next, for the first network termination device, whether or not the number of consecutive valid cells received at the time of the determination exceeds an increase threshold value corresponding to the total number of cells received in one frame from the network termination device. Is confirmed (steps ST2 and ST3).

If Yes, a request is made to increase the cell slot allocation of the first network termination device (step ST4). In the case of No, it is confirmed whether or not the number of valid cells received in one frame is equal to or less than a decrease threshold set in accordance with the total number of cells received in one frame from the network terminating device (step ST5). In the case of Yes, a request is made to reduce the cell slot allocation of the first network termination device (step ST6). If No, a request is made not to change the cell slot assignment of the first network termination device (step ST7). The above process is performed for the N network terminating devices (step ST8), and when it is completed, the cell slot assignment of each network terminating device is updated according to the request of each network terminating device (step ST9).

The operation of the network terminating device includes a buffer memory inside, a cell received from the user device is written into the buffer memory, a cell is read out and output from the allocated cell slot, and the allocated cell slot is read. When there is no cell in the buffer memory, an operation of outputting an idle cell may be performed.

Embodiment 2 In the second embodiment, the network device 18 determines that the number of valid cells received from the network terminating device within the determination cycle exceeds a threshold set in accordance with the total number of cells received from the network terminating device within the decision cycle. For the terminating device, the cell slot allocation is increased, and the number of valid cells received from the network terminating device within the determination cycle is equal to or less than a threshold set in accordance with the total number of cells received from the network terminating device within the decision period. To reduce the cell slot assignment to the other network terminating device.

With respect to the thresholds set in accordance with the total number of cells received from the network terminating device within the determination cycle, the threshold for increasing cell slots is increased, and the threshold for decreasing cell slots is decreased. Let's call it the threshold.
The determination of cell slot increase / decrease may be made for each frame or every several frames. In the following, a description will be given assuming that the determination of increase / decrease of the cell slot is made for each frame. FIG. 1 is also used in the present embodiment. The operation is performed by the user device 12a.
Are the same as those in the first embodiment, except that the bandwidth of the cell output by the user equipment 12a increases. Therefore, the case where the bandwidth of the cell output by the user apparatus 12a increases will be described, and the other will be omitted.

The case where the band of the cell output from the user apparatus 12a increases will be described. In the following, the user device 12a and the network termination device 11a will be described, but the user device 12b and the network termination device 11b and the user device 1
2c and the network termination device 11c perform the same operation.

FIG. 6 shows the required bandwidth of the network termination device 11a, the number of allocated cell slots in one frame of the network termination device 11a, the total number of cells in one frame received from the network termination device 11a in the network device 18, and the network termination device. 11a, the number of output effective cells in one frame and the network device 18
FIG. 9 is an explanatory diagram showing a relationship between the number of valid cells in one frame received from FIG. Each relationship is the same as that described in FIG. For simplicity of explanation, the network terminating device 11a
Is 100 in one frame.
The description will be made on the assumption that there are only two values, cell and 50 cells. Of course, in reality, the number of cell slots to be allocated can be defined instead of binary values.

In FIG. 6, the initial value is the network terminating device 11
a, the number of allocated cell slots in one frame of “a” is “50”, the total number of cells in one frame received from the network terminating device 11 a in the network device 18 is “50”, and the output valid cells in one frame of the network terminating device 11 a. It is assumed that the number is “40” and the number of effective cells in one frame received from the network terminating device 11a in the network device 18 is “40”. In the network device 18, when the total number of cells in one frame received from the network terminating device 11a is "50" and "100", the increase thresholds are "45" and "95", respectively.

When the band of the cell output from the user equipment 12a increases and the increase continues, the network termination equipment 11a
Required band increases, and the increased state continues. When the required bandwidth of the network terminating device 11a increases, the number of output effective cells in one frame increases to the number of allocated cell slots. FIG.
In this case, the number of output valid cells in one frame becomes "50", and after Z time, the number of valid cells in one frame received from the network terminating device 11a in the network device 18 becomes "50" and exceeds the increase threshold. , The network device 18 is the network terminating device 11
a, the number of allocated cell slots in one frame of the network termination device becomes “10” after X hours.
Increase to 0 ".

When the number of allocated cell slots in one frame of the network terminating device increases to "100", the number of output effective cells in one frame of the network terminating device 11a increases to "100". , The total number of cells in one frame received from the network terminating device 11a also becomes “100”, and the number of valid cells in one frame received from the network terminating device 11a in the network device 18 also becomes “100”.

Next, when the cells stored in the buffer memory in the network termination device 11a are exhausted, the network termination device 11a
, The number of output effective cells in one frame decreases. Here, it is assumed that 90 cells have been reached. Since the increase threshold when the total number of cells in one frame received from the network termination device 11a in the network device 18 is "100" is "95", the assigned cell slot in one frame of the network termination device 11a is also considered from the threshold value. Although the number does not increase, it is assumed that the number of cell allocation slots in one frame is only two values of "50" and "100". Therefore, even if the total number of received cells exceeds "95", the network termination device 11a Does not increase the number of allocated cell slots in one frame. Further, the decrease threshold is determined in consideration of the characteristics of the cell of the user apparatus and parameters such as the number of cell slots to be increased with respect to the network terminating apparatus.

When the band of the cell output from the user apparatus 12a is reduced, the operation is the same as in the first embodiment, and the description is omitted. Also, in the case where the band of the cell output from the user apparatus 12a increases and the increased state continues, the determination method for increasing the allocated cell slot in one frame of the network terminating apparatus 11a has been described in the second embodiment. Other than the above, the method is the same as that of the first embodiment, and the same result as that of the first embodiment can be obtained.

For this reason, when the band of the cell output from the user equipment 12a increases and the increased state continues, unlike the prior art, the number of output effective cells in one frame of the network termination device 11a is reduced by the decrease threshold. If so, the network terminating device 11
Since the number of output cells a does not repeatedly increase and decrease, the accumulation of cells in the buffer memory decreases, so that the cell transfer delay time can be statistically reduced, and
Statistically, the burstiness of cells can be reduced.
Further, in the second embodiment, the increase threshold value and the decrease threshold value are both set in the network device 18 in accordance with the total number of cells in one frame received from the network terminating device. Reduction is possible.

FIG. 7 is a flowchart showing a dynamic bandwidth allocation method according to the second embodiment. In this flowchart, N network terminating devices are connected to the network device 18 via the distribution device 15. And First, the update of the cell slot assignment is started after the end of one frame (step ST11). Next, for the first network termination device, the network device 18 sets the number of effective cells received in one frame from the network termination device in accordance with the total number of cells received in one frame from the network termination device. It is confirmed whether or not the threshold value is exceeded (steps ST12 and ST13).

If Yes, a request is made to increase the cell slot allocation of the first network termination device (step ST14). In the case of No, it is confirmed whether or not the number of valid cells received in one frame is equal to or less than a decrease threshold set in accordance with the total number of cells received in one frame from the network terminating device (step ST15). In the case of Yes, a request is made to reduce the cell slot allocation of the first network termination device (step ST16). If No, a request is made not to change the cell slot assignment of the first network termination device (step ST17). The above process is performed for the N network terminating devices (step ST18), and when it is completed, the cell slot assignment of each network terminating device is updated according to the request of each network terminating device (step ST19).

The operation of the network terminating device includes a buffer memory therein, a cell received from the user equipment is written into the buffer memory, a cell is read out and output from the allocated cell slot, and the allocated cell slot is output. When there is no cell in the buffer memory, an operation of outputting an idle cell may be performed.

[0073]

As described above, according to the present invention, when the number of consecutive valid cells received from the network terminating device exceeds a predetermined threshold, the network device increases the allocation of cell slots to the network terminating device. With the configuration, there is an effect that the transfer delay time of the cell can be statistically reduced and the burstiness of the cell can be statistically reduced.

According to the present invention, when the number of valid cells received from the network terminating device within the determination cycle falls below a predetermined threshold, the network device reduces the number of cell slots allocated to the network terminating device. This has the effect of statistically reducing the cell transfer delay time and statistically reducing the cell burstiness.

According to the present invention, when the number of valid cells received from the network terminating device within the determination cycle exceeds a predetermined threshold, the network device increases the number of cell slots allocated to the network terminating device. This has the effect of statistically reducing the cell transfer delay time and statistically reducing the cell burstiness.

According to the present invention, the threshold value is set in accordance with the total number of cells received by the network device within the determination cycle. Therefore, there is an effect that the standard for increasing or decreasing the cell slot can be optimized. .

According to the present invention, when the number of consecutive valid cells received from the network terminating device exceeds a predetermined threshold, the number of cell slots allocated to the network terminating device is increased. This has the effect that the burstiness of the cells can be statistically reduced.

According to the present invention, when the number of valid cells received from the network terminating device within the determination period falls below a predetermined threshold, the number of cell slots allocated to the network terminating device is reduced, so that cell transfer is performed. There is an effect that the delay time can be statistically reduced and the burstiness of the cell can be statistically reduced.

According to the present invention, when the number of valid cells received from the network terminating device within the determination cycle exceeds a predetermined threshold, the number of cell slots allocated to the network terminating device is increased. There is an effect that the delay time can be statistically reduced and the burstiness of the cell can be statistically reduced.

According to the present invention, the threshold value is set in accordance with the total number of cells received within the determination cycle, so that there is an effect that the standard for increasing or decreasing the cell slot can be optimized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a dynamic bandwidth allocation system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a required band of the network termination device, a cell slot position allocated to the network termination device, and output information of the network termination device.

FIG. 3 shows the required bandwidth of the network termination device, the number of allocated cell slots in one frame of the network termination device, the total number of cells in one frame received from the network termination device in the network device, and the output in one frame of the network termination device. FIG. 4 is an explanatory diagram showing a relationship between the number of valid cells and the number of valid cells in one frame received from a network terminating device in the network device.

FIG. 4 shows the required bandwidth of the network termination device, the number of allocated cell slots in one frame of the network termination device, the total number of cells in one frame received from the network termination device in the network device, and the output in one frame of the network termination device. FIG. 4 is an explanatory diagram showing a relationship between the number of valid cells and the number of valid cells in one frame received from a network terminating device in the network device.

FIG. 5 is a flowchart showing a dynamic bandwidth allocation method according to the first embodiment.

FIG. 6 shows the required bandwidth of the network termination device, the number of allocated cell slots in one frame of the network termination device, the total number of cells in one frame received from the network termination device in the network device, and the output in one frame of the network termination device. FIG. 4 is an explanatory diagram showing a relationship between the number of valid cells and the number of valid cells in one frame received from a network terminating device in the network device.

FIG. 7 is a flowchart showing a dynamic bandwidth allocation method according to the second embodiment.

FIG. 8 is a configuration diagram showing a conventional dynamic band allocation system.

FIG. 9 is an explanatory diagram showing the relationship between the allocation position of time slots to the required bandwidth of the user apparatus and output information.

FIG. 10 is an explanatory diagram showing the number of time slots allocated to a user device and the amount of output information of the user device.

[Description of Signs] 11a, 11b, 11c Network Terminating Equipment, 12a, 12
b, 12c user device, 13a, 13b, 13c transmission line, 14a, 14b, 14c transmission line, 15 distribution device, 16 transmission line, 18 network device.

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[Procedure amendment]

[Submission date] June 14, 2001 (2001.6.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction contents]

Next, when the cells stored in the buffer memory in the network termination device 11a are exhausted, the network termination device 11a
, The number of output effective cells in one frame decreases. Here, it is assumed that 90 cells have been reached. The increase threshold when the total number of cells in one frame received from the network terminating device 11a in the network device 18 is "100" is "95". Although the number does not increase, it is assumed that the number of cell allocation slots in one frame takes only two values, "50" and "100". Therefore, even when the total number of received cells exceeds "95", the network termination device 11a Does not increase the number of allocated cell slots in one frame. Further, the increase threshold is determined in consideration of the characteristics of the cell of the user apparatus and parameters such as the number of cell slots to be increased with respect to the network terminating apparatus.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 8

[Correction method] Change

[Correction contents]

FIG. 8

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 9

[Correction method] Change

[Correction contents]

FIG. 9

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Asashiba 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Seiji Ozaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo No. Mitsubishi Electric Co., Ltd. (72) Inventor Tetsuya Yokotani 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. CB06 CC01 DA15 DB04

Claims (8)

[Claims] 1. A dynamic bandwidth allocation system comprising: a network device for allocating a cell slot; and a network terminating device for transmitting a cell to the network device in the cell slot allocated by the network device. A dynamic bandwidth allocation system for increasing the number of cell slots allocated to the network terminating device when the number of consecutive valid cells received from the network terminating device exceeds a predetermined threshold. 2. A dynamic bandwidth allocation system comprising: a network device for allocating a cell slot; and a network terminating device for transmitting a cell to the network device in the cell slot allocated by the network device. A dynamic bandwidth allocation system, wherein when the number of valid cells received from the network terminating device within a determination cycle falls below a predetermined threshold, the number of cell slots allocated to the network terminating device is reduced. 3. A dynamic bandwidth allocation system comprising: a network device for allocating a cell slot; and a network terminating device for transmitting a cell to the network device in the cell slot allocated by the network device. A dynamic bandwidth allocation system for increasing the number of cell slots allocated to the network terminating device when the number of valid cells received from the network terminating device within a determination cycle exceeds a predetermined threshold. 4. The network device according to claim 1, wherein the threshold value is set according to the total number of cells received within the determination cycle.
The dynamic bandwidth allocation system according to any one of claims 1 to 3. 5. A network device receives a cell transmitted from the network terminating device, and when the number of consecutive valid cells received from the network terminating device exceeds a predetermined threshold, allocates a cell slot to the network terminating device. Dynamic bandwidth allocation method to increase. 6. A network device receives a cell transmitted from the network terminating device, and when the number of valid cells received within a determination period from the network terminating device falls below a predetermined threshold value, a cell for the network terminating device. A dynamic bandwidth allocation method that reduces slot allocation. 7. A network device receives a cell transmitted from the network terminating device, and when the number of valid cells received from the network terminating device within a determination cycle exceeds a predetermined threshold value, a cell for the network terminating device. A dynamic bandwidth allocation method that increases slot allocation. 8. The dynamic band allocation method according to claim 5, wherein a threshold is set according to the total number of cells received within the determination cycle.