JP2010199861A - Station-side terminating device, optical communication system, band allocation control method and program of the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a station-side terminating device which can improve the followability of band allocation to the change of a required band and lowering the ratio of a control band occupied in an up band without the need of reporting a BUFFER storage amount; an optical communication system; a band allocation control method; and a program of the device. <P>SOLUTION: The station-side terminating device includes: a traffic analysis means for determining the change pattern of the required band for each band allocation unit of a subscriber-side terminating device; and a switching means for switching a band control method for each band allocation unit on the basis of the change pattern determined by the traffic analysis means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a station-side terminator, an optical communication system, and bandwidth allocation in a system in which subscriber-side terminators are connected by time division multiple access (TDMA) such as various PON (Passive Optical Network) systems. The present invention relates to a control method and an apparatus program.

  ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) Recommendation G983.4 defines SR (status reporting) and NSR (non-status reporting) methods as upstream bandwidth control methods for PON systems. ing.

In general, a PON system is configured by connecting a plurality of subscriber-side terminators (ONUs) to a station-side terminator (OLT; Optical Line Terminal).
As an upstream bandwidth control method for such a PON system, SR-type control is often adopted mainly because of the good followability of appropriate bandwidth assignment by OLT. The NSR method is used only when the ONU cannot report the amount of BUFFER stored in it (for example, when it does not have the REPORT notification function) and when it wants to perform dynamic bandwidth management using the OLT. It was done.

  In addition, as a related technique of the present invention, when the traffic load is high, the ONU increases the notification frequency as a notification opportunity multiple times per frame, and when the traffic load is low, the ONU notifies the notification frequency as a single notification opportunity over a plurality of frames. And performing dynamic bandwidth control by OLT by this notification (see, for example, Patent Document 1).

JP 2002-305544 A

However, in recent years, due to the expansion of the transmission band in the PON section, the maximum number of ONUs and the maximum number of TCONT (traffic container: bandwidth allocation unit) defined in the ONU are increasing, and a control band is required for each TCONT. In the SR method, the ratio of the total control bandwidth to the total uplink bandwidth is becoming difficult to ignore.
That is, the problem of the SR method is that a general data transmission band is wasted because of the control band in units of TCONT.

  In addition, the NSR method is a method for determining the bandwidth assignment by estimating the bandwidth required by the ONU based on the traffic received on the OLT side. Therefore, when the bandwidth allocated to the ONU at the time of detection is not sufficient, There is insufficient information to determine the amount of bandwidth increase in the next cycle. For this reason, a certain amount of time is required for the OLT to properly assign the necessary bandwidth required by the ONU.

  That is, the problem of the NSR system is that the followability of the appropriate band assignment is poor due to lack of information for band control. The fact that the bandwidth is not properly assigned means that the bandwidth for general data is naturally consumed, and the ratio is much larger than that in the SR method. Therefore, SR-type control is generally used.

  In the above-mentioned Patent Document 1, the OLT performs dynamic bandwidth control using information on the BUFFER accumulation amount transmitted from the ONU by the SR method described above, and information on the BUFFER accumulation amount from the ONU. It has not been considered to switch the control method without using, and combine the advantages of the two control methods of the SR method and the NSR method.

  The present invention has been made in view of such a situation, and does not require notification of the BUFFER accumulation amount, can improve the follow-up performance of band allocation to a change in necessary band, and is a control band that occupies the upstream band. It is an object of the present invention to provide a station-side terminal device, an optical communication system, a bandwidth allocation control method, and a device program capable of reducing the ratio of the above.

  In order to achieve such an object, the station-side terminating device according to the present invention is determined by a traffic analyzing unit that determines a required bandwidth change pattern for each bandwidth allocation unit of the subscriber-side terminating device, and the traffic analyzing unit. And switching means for switching a band control method for each of the band allocation units based on a change pattern.

  The optical communication system according to the present invention is characterized in that a plurality of subscriber-side terminators are connected to the above-mentioned station-side terminator according to the present invention via a transmission line.

  Further, the bandwidth allocation control method according to the present invention is based on a traffic analysis step of determining a required bandwidth change pattern for each bandwidth allocation unit of the subscriber-side terminal device, and a change pattern determined by the traffic analysis step, And a switching step of switching a band control method for each of the band allocation units.

  The station-side terminal device program according to the present invention is based on a traffic analysis process for determining a required bandwidth change pattern for each bandwidth allocation unit of the subscriber-side terminal device, and a change pattern determined by the traffic analysis process. And switching processing for switching the band control method for each of the band allocation units.

As described above, according to the present invention, the notification of the BUFFER accumulation amount is not required, the followability of the band allocation to the change in the necessary band can be improved, and the ratio of the control band to the upstream band is reduced. Can do.
For this reason, more efficient bandwidth control can be performed.

It is a block diagram which shows the structural example and downstream frame of a PON system. It is a block diagram which shows the structural example of a PON system, and an uplink direction frame. 3 is a block diagram showing a configuration around a band allocation control unit 109. FIG. It is a figure which shows the band allocation time change at the time of SR. It is a figure which shows the band allocation time change 1 at the time of NSR. It is a figure which shows the band allocation time change 2 at the time of NSR. It is a figure which shows the time change by the control by embodiment of this invention. 5 is a flowchart illustrating a bandwidth allocation control method according to an embodiment of the present invention.

  Next, an embodiment in which a station-side terminal device, an optical communication system, a bandwidth allocation control method, and a device program according to the present invention are applied to a PON system will be described in detail with reference to the drawings.

First, an outline of the present embodiment will be described.
In the present embodiment, as an upstream bandwidth control method using OLT, more efficient upstream bandwidth allocation control is performed by simultaneously incorporating the advantages of the SR method and the NSR method defined in ITU-T recommendation G983.4. This is the main feature.

  The advantage of the SR method is that an actual bandwidth assignment can be quickly adjusted with respect to the required bandwidth required by the ONU, and the disadvantage is that a dedicated bandwidth for bandwidth control is required.

  An advantage of the NSR method is that an uplink control band is not required, and a disadvantage is that it is difficult to adjust the ONU to allocate an appropriate band.

  In this embodiment, by analyzing the change pattern of the upstream traffic, the SR method and the NSR method are selectively used as the upstream bandwidth control method of the PON system, the shortcomings of each bandwidth control method are improved, and efficient bandwidth control is realized. To do.

Next, the configuration of the PON system as the present embodiment will be described with reference to FIGS.
FIG. 1 explains the configuration of the PON system and the state of downlink frame transmission. The PON system includes an OLT 101 arranged in a station (not shown), first to N- _th ONUs 102 ₁ to 102 _n arranged in an end user's home, and an optical splitter (branching means) for branching or joining signals between them. 103, which are connected by an optical transmission line using an optical fiber.

A personal computer (not shown) at each end user's house is connected to an upper network (not shown) via any _one of the ONUs 102 _{1 to} 102 _n , the optical splitter 103 and the OLT 101. A plurality of TCONTs 104 are defined in each ONU 102, and transmission / reception of frames is performed in units of TCONTs.

In the PON, an upstream signal and a downstream signal are transmitted by wavelength multiplexing through a bidirectional single-core optical fiber. As shown in FIG. 1, the downstream signal is transmitted from the OLT 101 to all the ONUs 102 ₁ to 102 _n simultaneously. In this case, the ONUs 102 _{1 to} 102 _n check all the destinations of the transmitted frames, and take in only the destination frames to any TCONT of the own apparatus.

FIG. 2 is a diagram for explaining a state of uplink frame transmission in the PON system having the same configuration as FIG.
The upstream frames from the ONUs 102 _{1 to} 102 _n join at the optical splitter 103. Therefore, it is necessary to prevent the frames from overlapping each other at the position of the optical splitter 103 and causing a signal collision. For this reason, time division multiplex communication is performed so that frames transmitted from the ONUs 1021 to 102n do not overlap in time.

The frame transmission timing is controlled by the OLT 101 for each TCONT defined in the ONU. The OLT 101 calculates the transmission time based on the distance between the OLT 101 and each ONU 102, determines the timing for all the TCONTs for which an output request has been made, and gives a transmission permission signal (BWMAP). A transmission permission signal from the OLT 101 is given in units of TCONTs 104 _{A to} 104 _Z defined for each ONU.

  The transmission permission signal from the OLT 101 includes information on a transmission start time and a transmission stop time that enables transmission of frames stored in the destination TCONT. Each TCONT transmits frames accumulated in the BUFFER in the ONU during this specified time. If all accumulated frames remain to be transmitted after transmission, The IDLE frame is transmitted for the remaining time. In other words, when the OLT 101 receives an IDLE frame from the ONU 102, the OLT has excessively assigned a band that is higher than the transmission source TCONT requires.

  As a method for the OLT 101 to determine the transmission permission signal, the ITU-T G984.3 standard defines two types of SR method and NSR method. Here, an SR method, which is a method for determining the time for transmission by the TCONT using an output request (REPORT) in units of TCONT, will be described first.

  The OLT 101 requests all the TCONTs 104 in the connected state to perform a TCONT state report by REPORT. This REPORT includes information on the state of the buffer memory queue storing the frames to be transmitted in each TCONT unit, that is, information on the queue length. For this reason, the OLT 101 can confirm the frame transmission time required for each TCONT, that is, the requested upstream bandwidth, by the REPORT processing unit 105 shown in FIG.

  The band calculation unit 106 shown in FIG. 3 performs calculation according to the report value and priority information set in each TCONT based on information from each TCONT 104, creates a transmission permission signal (BWMAP), and sends it to each TCONT. Send to. As described above, in the SR method, since the OLT 101 performs calculation based on a specific request value from the ONU, it is possible to perform bandwidth assignment accurately and quickly.

Next, the NSR method, which is a method for determining the time for transmission by the TCONT based on the traffic received by the OLT 101, will be described.
The OLT 101 uses the traffic analysis unit 107 shown in FIG. 3 to count the number of IDLE frames during transmission time for each TCONT unit. The bandwidth calculation unit 106 collects the results in units of TCONT, and if the IDLE frame is 0, performs allocation larger than the previous bandwidth for the corresponding TCONT. When IDLE frames are counted, a ratio of the number of IDLE frames in all bands is calculated, and band allocation smaller than the previous band is performed according to the ratio.

  In this embodiment, an SR / NSR switching control unit 108 for selecting the above-described SR method and NSR method is mounted on the OLT 101. This SR / NSR switching control unit 108 transmits an instruction to the band calculation unit 106 so as to operate in the NSR system for all TCONTs in the normal state. In addition, an instruction is transmitted to the bandwidth calculation unit 106 so that the operation as the SR method is performed only for the TCONT whose IDLE count number by the traffic analysis unit 107 is zero. However, if the upstream band is in a congested state, that is, if a large number of TCONT requests assignment higher than the current band and there is no room to increase the current band of each TCONT, the operation in the NSR system is instructed. To do.

  As described above, in this embodiment, as shown in FIG. 3, the SR / NSR switching control unit 108 is provided in the band allocation control unit 109, and the band control method is changed to the SR method and the NSR according to the change pattern of the upstream traffic. It is characterized in that uplink bandwidth control is efficiently performed by switching to any of the methods.

Next, an upstream bandwidth allocation operation in the PON system will be described.
First, FIG. 4 shows an example in which bandwidth control is performed using only the SR method. FIG. 4 shows a time change of a band required for a certain TCONT by a dotted line, and a band actually allocated from the OLT 101 is shown by a bar graph.

  In the case of the SR method, the band that requires TCONT is always reported to the OLT 101 in a certain time unit, so even if the band necessary for TCONT varies greatly with time, the OLT 101 is matched to that band. Can quickly assign the bandwidth required for the ONU.

  Here, when a plurality of TCONT requests a bandwidth, it may be impossible to assign a bandwidth corresponding to the request to all TCONTs. In this case, the bandwidth calculation unit 106 performs bandwidth assignment corresponding to the priority of each TCONT, but the calculation algorithm is not related to the main features of the present embodiment, and thus the description thereof is omitted. In the following description, it is assumed that there is sufficient bandwidth that can be assigned to the TCONT request.

  Next, FIG. 5 shows an example in which bandwidth control is performed using only the NSR method. Similarly, in FIG. 5, the time change of the band required by a certain TCONT is shown by a dotted line, and the band actually allocated from the OLT 101 is shown by a bar graph.

  In the NSR system, since the REPORT notification is not sent from the ONU, it is necessary for the OLT to estimate the necessary bandwidth based on the traffic received from the TCONT. A general method for this estimation method is to count the number of IDLE frames in the traffic of the TCONT. For example, for an OLT bandwidth assignment of 100 Mbps, if the IDLE frame occupying the upstream traffic of the TCONT is 50%, the next bandwidth assignment is 50 Mbps.

  When the required bandwidth is estimated by this method, when the required bandwidth of the ONU in FIG. 5 is reduced, it is relatively easy for the OLT to adjust the bandwidth assignment to the required bandwidth of TCONT. Even when compared with the SR method shown in FIG. 5, the proper values have been assigned in step (6), and there is almost no difference in performance.

  However, when the necessary bandwidth in TCONT is increasing, the difference in performance appears greatly. Since the necessary bandwidth is insufficient in this increased section, naturally the IDLE frame is not transmitted from TCONT, and the count value in the OLT is always zero. In this case, OLT understands that TCONT requires a larger band than the current band, but cannot determine how much it can increase with respect to the current band. For this reason, in order for the necessary bandwidth of TCONT and the actual assignment bandwidth to be appropriate, a considerable amount of time is required as compared with the SR method. 4 and 5, the SR mode shown in FIG. 4 has an appropriate value in step (11), and the NSR mode shown in FIG. 5 has an appropriate value in step (14).

  Further, in the NSR method, the time until the appropriate band is reached is considered even if the band is increased gradually as shown in FIG. 6 instead of gradually increasing the band as shown in FIG. Although the procedure up to the procedure (12) in FIG. 6 can be somewhat shortened, a useless bandwidth is largely assigned in the procedures (9) and (10).

  As described above, in a system using only the NSR system, it is difficult to control when the necessary bandwidth for TCONT is increasing, and communication frame transmission delay due to insufficient assignment bandwidth or useless bandwidth due to excessive bandwidth assignment is likely to occur.

Next, the uplink bandwidth allocation operation by the OLT 101 of this embodiment will be described with reference to FIGS.
Based on the characteristics of the SR method and the NSR method described above, the OLT 101 according to the present embodiment, as shown in FIG. 7, shows a case where there is no change in the necessary band for TCONT or a decreasing tendency (when IDLE count> 0). The band control of the TCONT is performed by the method. Further, when the required bandwidth is increasing (when IDLE count = 0), a REPORT request is made only to the corresponding TCONT so that control is performed by the SR method.

For this reason, the OLT 101 of the present embodiment performs the following control as shown in FIG.
When the traffic analysis unit 107 determines that the IDLE count is 1 or more for the TCONT to be analyzed (step S2; No), the SR / NSR switching control unit 108 does not change or tends to decrease in the necessary bandwidth for TCONT. Instructs the bandwidth calculation unit 106 to perform bandwidth control of the TCONT by the NSR method (step S5).

  Further, when the traffic analysis unit 107 determines that IDLE count = 0 for the TCONT to be analyzed (step S2; Yes), the required bandwidth of the TCONT tends to increase, so the uplink bandwidth can be increased with respect to the TCONT. If it is determined by the traffic analysis unit 107 (step S3; Yes), the SR / NSR switching control unit 108 instructs the bandwidth calculation unit 106 to perform bandwidth control of the TCONT by the SR method. (Step S4).

However, when the traffic analysis unit 107 determines that the upstream bandwidth processing is congested and the bandwidth cannot be increased any more (step S3; No), the SR / NSR switching control unit 108 determines that the IDLE count = 0. Even so, the bandwidth calculation unit 106 is instructed to perform bandwidth control by the NSR method (step S5).
Then, the switching control in steps S2 to S5 described above is sequentially performed on each TCONT (steps S1, S6, and S7).

As described above, the present embodiment has the following effects.
The first effect is that when there is no change in the required band of TCONT or there is a tendency to decrease, the band control is performed by the NSR system, so there is no need for an upstream control band in units of TCONT. It can be used as a communication frame band.

  The second effect is that when the required bandwidth of TCONT is increasing, the bandwidth control by the SR method is performed, so that the bandwidth required by TCONT can be assigned quickly, and the wasteful bandwidth and transmission delay can be suppressed. is there.

  As described above, by performing the uplink bandwidth allocation control method using the OLT according to the present embodiment, it is possible to reduce the proportion of the control bandwidth in the uplink bandwidth while maintaining the bandwidth followability similar to that of the SR method. For this reason, more efficient bandwidth control can be performed.

  Each of the above-described embodiments is a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, the present invention is not limited to being applied only to the upstream bandwidth control of the PON system as in the above-described embodiment, and is similarly applied to a communication device that shares a bandwidth between subscribers in a time division manner. Is possible.

In addition, by recording the processing procedure for realizing the OLT as each embodiment described above on a recording medium as a program, the above-described functions according to each embodiment of the present invention can be performed by a program supplied from the recording medium. It can be realized by causing a CPU of a computer constituting the apparatus to perform processing.
In this case, the present invention can be applied even when an information group including a program is supplied to the output device from the above recording medium or from an external recording medium via a network.
That is, the program code itself read from the recording medium realizes the novel function of the present invention, and the recording medium storing the program code and the signal read from the recording medium constitute the present invention. It will be.
As this recording medium, for example, flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, non-volatile Sex memory cards, ROM, etc. may be used.

  According to the program according to the present invention, each function in the above-described embodiment can be realized in the OLT or PON system controlled by the program.

101 OLT (station side terminal equipment)
102 ONU (Terminal on the subscriber side)
103 Optical splitter (branching means)
104 TCONT (bandwidth allocation unit)
105 REPORT Processing Unit 106 Band Calculation Unit 107 Traffic Analysis Unit 108 SR / NSR Switching Control Unit 109 Band Allocation Control Unit

Claims (16)

Traffic analysis means for determining a required bandwidth change pattern for each of the bandwidth allocation units of the subscriber-side termination device;
A station-side terminating device comprising switching means for switching a bandwidth control method for each of the bandwidth allocation units based on a change pattern determined by the traffic analysis means.   2. The station side termination device according to claim 1, wherein the traffic analysis unit determines the change pattern based on the number of IDLE frames during transmission time from the band allocation unit. The traffic analysis means includes
When the number of IDLE frames in the transmission time from the bandwidth allocation unit is 0, it is determined that the change pattern has a tendency to increase the necessary bandwidth,
3. The station side according to claim 1, wherein when the number of IDLE frames during the transmission time from the band allocation unit is 1 or more, it is determined that the change pattern is a tendency to decrease a required band or no change. Termination device.   The switching means switches the bandwidth control method for each of the bandwidth allocation units to either an SR (status reporting) method or an NSR (non-status reporting) method. The station-side termination device according to claim 1. The switching means is
When the traffic analysis unit determines that the change pattern is a necessary bandwidth increase tendency, the bandwidth control method for the bandwidth allocation unit that is the determination target is switched to an SR (status reporting) method,
When the traffic analysis unit determines that the change pattern has a required bandwidth decrease tendency or no change, the bandwidth control method for the bandwidth allocation unit to be determined is switched to an NSR (non-status reporting) method. The station-side termination device according to any one of claims 1 to 3.   6. An optical communication system comprising a plurality of subscriber-side terminal devices connected to the station-side terminal device according to claim 1 through a transmission line. A traffic analysis step of determining a required bandwidth change pattern for each bandwidth allocation unit of the subscriber-side termination device;
A bandwidth allocation control method comprising: a switching step of switching a bandwidth control method for each of the bandwidth allocation units based on a change pattern determined by the traffic analysis step.   8. The bandwidth allocation control method according to claim 7, wherein, in the traffic analysis step, the change pattern is determined based on the number of IDLE frames during the transmission time from the bandwidth allocation unit. In the traffic analysis step,
When the number of IDLE frames in the transmission time from the bandwidth allocation unit is 0, it is determined that the change pattern has a tendency to increase the necessary bandwidth,
The band allocation according to claim 7 or 8, wherein when the number of IDLE frames in the transmission time from the band allocation unit is 1 or more, it is determined that the change pattern has a tendency to decrease a required band or no change. Control method.   The bandwidth switching method for each of the bandwidth allocation units is switched to either an SR (status reporting) method or an NSR (non-status reporting) method in the switching step. The bandwidth allocation control method according to claim 1. In the switching step,
When the change pattern is determined to be a necessary bandwidth increase tendency by the traffic analysis step, the bandwidth control method for the bandwidth allocation unit to be determined is switched to an SR (status reporting) method,
When the traffic analysis step determines that the change pattern is a trend toward a required bandwidth decrease or no change, the bandwidth control method for the bandwidth allocation unit that is the determination target is switched to an NSR (non-status reporting) method. The bandwidth allocation control method according to any one of claims 7 to 9. A traffic analysis process for determining a required bandwidth change pattern for each bandwidth allocation unit of the subscriber-side terminating device;
And a switching process for switching a bandwidth control method for each of the bandwidth allocation units based on a change pattern determined by the traffic analysis process. program.   13. The program for a station-side terminal device according to claim 12, wherein, in the traffic analysis process, the change pattern is determined based on the number of IDLE frames during the transmission time from the band allocation unit. In the traffic analysis process,
When the number of IDLE frames in the transmission time from the bandwidth allocation unit is 0, it is determined that the change pattern has a tendency to increase the necessary bandwidth,
14. The station side according to claim 12 or 13, wherein when the number of IDLE frames in the transmission time from the band allocation unit is 1 or more, it is determined that the change pattern has a tendency to decrease a required band or no change. Termination device program.   15. The switching process according to claim 12, wherein in the switching process, a bandwidth control method for each of the bandwidth allocation units is switched between an SR (status reporting) method and an NSR (non-status reporting) method. A program for a station-side terminal device according to claim 1. In the switching process,
When the traffic analysis process determines that the change pattern is a necessary bandwidth increase tendency, the bandwidth control method for the bandwidth allocation unit that is the determination target is switched to an SR (status reporting) method,
When it is determined by the traffic analysis process that the change pattern has a required bandwidth decrease tendency or no change, the bandwidth control method for the bandwidth allocation unit that is the determination target is switched to an NSR (non-status reporting) method. The program of the station side termination apparatus of any one of Claim 12 to 14.

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