JP2011124697A - Communication system, station side device, and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system that saves a communication band consumed for registration without changing a registration procedure of a subscriber side unit to a station side device and in consideration of long distance transmission and setting location change. <P>SOLUTION: A station side device (OLT) 1 for receiving registration request signals from subscriber side units (ONU) 16-1 to 16-N manages the number of registered subscriber side units (ONU) 16, and changes a random delay time for defining the size of a discovery window on the basis of the number of registered units. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a communication system in which a station-side device and a subscriber-side device transmit and receive optical signals, and more particularly to registration processing of a subscriber-side device in the communication system.

As a communication system in which an optical signal is transmitted and received between a station side device and a subscriber side device, for example, a PON (Passive Optical Network) system can be cited.
In the PON system, an OLT (Optical Line Terminal), which is a station side device (or also called a master station), passes through an optical passive element (for example, an optical splitter) arranged in the middle of an optical communication path, and then a subscriber side device (or a child device). Bidirectional subscriber data communication is performed with a one-to-many connection with an ONU (Optical Network Unit).
However, for example, when an unregistered subscriber unit (ONU) is newly introduced into the system or when the station unit (OLT) is restarted, the subscriber unit (ONU) is re-recognized. The line connection for data communication is not established.
For this reason, a registration procedure is required for discovering a subscriber side device in which a line connection is not established and registering it in the station side device to establish a communication line connection. This registration procedure is called a discovery process in PON.

In a conventional PON system, a station side device (OLT) performs a discovery process at an arbitrary timing, collects individual identification numbers of subscriber side devices (ONU) that need to be registered, and stores them in the station side device (OLT). A method of registering as a database is known. (See Non-Patent Documents 1 and 2)
Here, in the E-PON (Ethernet (registered trademark) -PON) system shown in Non-Patent Documents 1 and 2, the MAC address (Media Access Control Address) assigned to each subscriber unit (ONU) is: It corresponds to the individual identification number.

  The station side device (OLT) transmits a discovery transmission permission signal, which is a signal for permitting transmission of a registration request signal from the subscriber side device (ONU) to all the subscriber side devices (ONU). Send periodically. The unregistered subscriber-side device (ONU) that has received the discovery transmission permission signal transmits a registration request signal, which is a signal for requesting registration, to the station-side device (OLT).

The station side device (OLT) is an uplink communication band used for communication from the subscriber side device (ONU) to the station side device (OLT) so that the registration request signal transmitted by the subscriber side device (ONU) can be received. Of these, a certain percentage is assigned to reception of the registration request signal. In other words, the station side device (OLT) releases the upstream communication band for transmitting the registration request signal to the subscriber side device (ONU). The uplink communication band allocated for reception is called a discovery window.
Further, the station side device (OLT) is configured so that subscriber data is not transmitted from the subscriber side device (ONU) in a time zone where reception of the registration request signal from the subscriber side device (ONU) is expected. A communication band is not allocated for subscriber data communication.

  Here, the discovery window includes (1) a transmission time determined from the connection distance between the subscriber side device (ONU) and the station side device (OLT), and (2) a processing time in the subscriber side device (ONU). Considering the round trip time (hereinafter referred to as round trip time (RTT)) determined from the above, a time frame that covers these times (hereinafter referred to as discovery window size). ) Must be secured. That is, the time range in which the registration request signal can be received by the station side device (OLT) is determined by the discovery window size.

Further, when a plurality of subscriber-side devices (ONUs) transmit registration request signals to the same discovery window, each subscriber-side device (ONU) is reduced in order to reduce collision between the registration request signals. Is waiting for a transmission delay time (hereinafter referred to as random delay time) set at random. Therefore, the discovery window size needs to be set larger than the time frame determined by the round trip time (RTT) in consideration of the random delay time of a plurality of subscriber units (ONUs).
On the other hand, in order for the station side apparatus (OLT) to detect an unregistered subscriber side apparatus (ONU) that desires registration at an early stage, the discovery window generation cycle may be shortened and performed at a certain frequency. Necessary.
Due to the above factors, the uplink communication band that can be substantially used for the communication of subscriber data, that is, the effective communication band is reduced.

  Furthermore, in recent years, studies for expanding the connection distance between the subscriber side device (ONU) and the station side device (OLT) are in progress. In this case, the round trip time and its variation are further increased. The upstream communication band that can be used for communication of subscriber data is further reduced.

Under such background technology, various methods for suppressing an increase in the uplink communication band used for the discovery window have been proposed. (For example, see Patent Documents 1 and 2.)
In Patent Document 1, a constraint condition that limits the number of ONUs that execute the discovery process is added to both the OLT and the ONU. Specifically, the OLT transmits a message (registration request acceptance notification: GATE (Discovery)) for accepting a registration request from the ONU, and the unregistered ONU confirms the message and makes its registration request. It is determined whether the condition is met, and a registration request (RESISTER_REQ) is transmitted only when the condition is met.
As a result, it is possible to prevent a plurality of unregistered ONUs from transmitting registration requests at the same time, thereby suppressing an increase in the discovery window size due to an increase in random delay time, and the OLT detects an ONU in a narrow discovery window. Thus, the uplink communication band consumed for the discovery window is reduced.

  In Patent Document 2, the OLT measures the round trip time (RTTx) for each ONU (ONU-x) and records or holds the measurement result. Based on this, the margin (D) is given to the discovery window. A method is provided. As a result, the necessary discovery window size is narrowed, and the upstream communication band consumed for discovery is reduced.

IEEE standard 802.3ah, Clause 64 Multi-point MAC CONTROL IEEE standard 802.3av, Clause 77 Multi-point MAC CONTROL

JP 2009-89323 A International application number PCT / JP2008 / 050086

  In the invention described in Patent Document 1, the OLT defines additional information during the registration request acceptance notification (GATE (Discovery)), and the ONU receives the registration request acceptance notification, identifies the additional information, and identifies individual information based on it. Since the registration request (RESISTER_REQ) is transmitted, it is necessary to change an ONU that already conforms to the standard shown in Non-Patent Document 1 so that additional information is identified and a registration request is transmitted. Furthermore, it is necessary to replace the ONUs that have spread in the market and are installed in the homes of individual subscribers. In the market, considering the fact that the PON system based on the ONU conforming to the standard described in Non-Patent Document 1 has already been implemented, the ONU that implements the method of Patent Document 1 is deployed in the market or within the PON system. There is a problem that it is difficult to mix.

Similar to the above and Patent Document 1, the invention described in Patent Document 2 has a problem that it is difficult to mix and accommodate in an PON system with an ONU based on Non-Patent Document 1.
Furthermore, since Patent Document 2 is a method of recording the round trip time in the OLT at the time of initial registration, the OLT-ONU is moved by moving the installation location of the ONU communicating with a certain OLT under the PON line related to the same OLT. When the connection distance between them is changed, the OLT assigns a discovery window based on the round trip time recorded in the past. Therefore, for example, as shown in FIG. 11, when the distance is increased by relocation or the like, the OLT receives a registration request (Discovery Gate) in the upstream data communication band used by other ONUs and transmits data from other ONUs. There is a problem that there is a collision with the reception.

The present invention has been made to solve the above-described problems, and provides a communication system that saves a communication band consumed for a registration procedure without changing the registration procedure of a conventional subscriber-side device. The purpose is to provide.
It is another object of the present invention to provide a communication system that saves a communication band consumed for a registration procedure in consideration of long-distance transmission and change of installation location of a subscriber side device.

  In the communication system according to the present invention, a transmission permission signal for registration for permitting transmission of a registration request signal from a subscriber side apparatus is periodically transmitted to the subscriber side apparatus based on a unit period of registration processing. And a registration request signal reception communication band periodically based on the unit period and the reception request time range of the registration request signal within the unit period, and the registration transmission permission signal. A registration request receiving means for optically receiving the registration request signal transmitted by the subscriber side device responding to the registration request and confirming the presence or absence of a registration request within the communication band for receiving the registration request signal, and confirming the presence or absence of the registration request Registration processing means for performing registration processing of the subscriber apparatus that has transmitted the registration request signal based on the result of the registration, and the number of registered subscriber-side apparatuses based on registration processing of the registration processing means Registered number management means for monitoring, and registration request reception bandwidth allocation for controlling bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means And a station side device having a control means.

In the communication system according to the present invention, the station side device that performs registration of the subscriber side device monitors the number of registered subscriber side devices, and in the unit period of the uplink communication band allocated for receiving the registration request, or within the unit period Since the time range to be allocated or both are dynamically changed based on the monitoring result of the number of registered units, the increase in the communication band used for receiving the registration request is suppressed, and that amount is used as the communication band for subscriber data communication. The effective communication bandwidth can be increased.
In addition, since there is no change in the conventional registration procedure and the subscriber-side device that has already been widely used in compliance with the conventional registration procedure, it is possible to ensure the interoperability within the communication system.

It is the block diagram which showed the structure of the PON system in Embodiment 1 of this invention. It is a figure which shows the outline | summary of the whole flow of the discovery process of the PON system in Embodiment 1 of this invention. It is a flowchart of OLT in Embodiment 1 of this invention. It is a schematic diagram which shows the improvement of the upstream communication band of OLT in Embodiment 1 of this invention. It is a flowchart of OLT in Embodiment 2 of this invention. It is a schematic diagram which shows the improvement of the upstream communication band of OLT in Embodiment 2 of this invention. It is a flowchart of OLT in Embodiment 3 of this invention. It is an example of a structure of the management table of OLT in Embodiment 3 of this invention. It is a schematic diagram which shows the improvement of the upstream communication band in Embodiment 3 and 4 of this invention. It is a flowchart of OLT in Embodiment 4 of this invention. For comparison with the present invention, it is a conceptual diagram showing that the location of the ONU is changed in the conventional technique to affect the subscriber data communication band.

Embodiment 1 FIG.
Hereinafter, a case where the present invention is applied to a PON system will be described with reference to FIGS. In the drawings, the same or similar elements are denoted by the same or corresponding numerals.

FIG. 1 is a block diagram showing a configuration of a PON system in Embodiment 1 of the present invention. Each block represents a functional unit, and the implementation of each device is not limited to the division and connection relationship shown in the figure.
1 can be used in common in all the embodiments described below, but functions and various information that are not used in individual embodiments, processes that are not performed, etc. The function may be stopped or deleted when the target device is mounted in each embodiment, and is not limited to the configuration of FIG.

In FIG. 1, the OLT 1 that is a station side device and the ONUs 16-1 to 16 -N (N = 1, 2,...) That are a plurality of subscriber side devices are connected by an optical cable via an optical splitter 30. .
In FIG. 1, in order to simplify the description of the figure, only the first ONU 16-1 among the plurality of ONUs 16-1 to 16-N is shown, but the other ONU configurations are the first ones. This is the same as the internal configuration of the ONU, and detailed description and explanation other than the ONU 16-1 will be omitted below.

In the PON system, generally, a wavelength division multiplexing (WDM) system is adopted for transmission / reception of optical signals, and optical signals of a plurality of different wavelengths are multiplexed and transmitted on one optical cable.
In FIG. 1, an optical signal having a wavelength λ1 is used in uplink communication from the ONUs 16-1 to 16-N to the OLT1. On the other hand, in the downstream communication from the OLT 1 to the ONU 16, an optical signal having a wavelength λ2 is used.

First, the configuration of the OLT 1 that is a station side device will be described.
The OLT 1 includes a WDM unit 2, a TX unit 3, an RX unit 4, a MUX unit 5, a DeMUX unit 6, a network I / F unit 7, and a PON control unit 8.
The WDM unit 2 is an interface corresponding to the wavelength division multiplexing system, and transmits / receives optical signals to / from each ONU 16-1 to 16-N, and also multiplexes and separates optical signals. The WDM unit 2 inputs or outputs an optical signal between the TX unit 3 and the RX unit 4.
The TX unit 3 converts the electrical signal output from the MUX unit 5 into an optical signal (hereinafter referred to as E / 0 (described as “Electric / Optical conversion”), and outputs the optical signal to the WDM unit 2.
The RX unit 4 converts the optical signal output from the WDM unit 2 into an electrical signal (hereinafter referred to as O / E (described as Optical / Electric conversion conversion)), and outputs the electrical signal to the DEMUX unit 6.

The MUX unit 5 outputs information from the control frame generation unit 14 of the PON control unit 8 and information for various controls (hereinafter referred to as PON control information) related to the PON that is downlink transmitted to the ONUs 16-1 to 16-N. The network I / F unit 7 multiplexes the downlink communication data received and transmitted to the subscriber side.
The DeMUX unit 6 separates the upstream PON control information from the output signal of the RX unit 4 and outputs it to the control frame receiving unit 15 of the PON control unit 8. The DeMUX unit 6 separates the subscriber communication data from the output signal of the RX unit 4 and outputs it to the network I / F unit 7.
That is, the PON control unit 8 generates PON control information and outputs it to the MUX unit 5, and receives and analyzes the PON control information output from the DeMUX unit 6.
The network I / F unit 7 transmits and receives communication data transmitted from the subscriber to the other communication device (not shown) or the network (not shown).

  The PON control unit 8 includes an ONU registered number management unit 9, an ONU support transmission distance data management unit 10, a discovery window control unit 11, a discovery cycle control unit 12, a bandwidth control unit 13, a control frame generation unit 14, and a control frame reception unit 15. The Discovery Process unit 24 is provided. Further, various controls related to the operation of the PON in the OLT 1 are performed.

The ONU registered number management unit 9 manages the number of ONUs registered in the OLT 1 and outputs the number information to the Discovery Window control unit 11 and the Discovery Cycle control unit 12.
The ONU support transmission distance data management unit 10 stores information on the maximum transmission distance supported by each of the ONUs 16-1 to 16 -N (hereinafter referred to as “supported maximum transmission distance”) and manages the information for each ONU. .

  The Discovery Window control unit 11 inputs information on the maximum transmission distance supported by each ONU 16-1 to 16-N from the ONU supported transmission distance data management unit 10, and unit information from the ONU registered number management unit 9, respectively. Discovery Discovery window size information (shown as Window size information in the figure) is output to the Discovery Process unit 24. Further, the Discovery Window control unit 11 recognizes the maximum value (RTT maximum value) of the round trip time based on the input supported maximum transmission distance information. Further, the setting of the discovery window size is controlled based on the number information from the ONU registered number management unit 9.

The Discovery Cycle control unit 12 inputs the number of ONUs 16 from the ONU registered number management unit 9 and outputs information on the cycle of the discovery cycle (described as Cycle information in the figure) to the Discovery Process unit 24.
The bandwidth control unit 13 inputs the PON control information from the control frame reception unit 15 and outputs the downlink PON control information to the control frame generation unit 14. Further, the bandwidth control unit 13 performs various controls other than the discovery process, mainly control for allocating the uplink bandwidth for subscriber data communication to the ONUs 16-1 to 16-N.

The control frame generation unit 14 configures a transmission frame for downstream PON control based on the PON control information from the discovery process unit 4 and the bandwidth control unit 13, and outputs the PON control information to the MUX unit 5.
The control frame receiving unit 15 inputs the PON control information from the DeMUX unit 6 and outputs mainly information necessary for band allocation control to the band control unit 13 based on the PON control information. In addition, the control frame receiving unit 15 outputs information necessary mainly for the discovery process to the Discovery Process unit 24.

  The Discovery Process unit 24 inputs information on the discovery window size (Window size information) from the Discovery Window control unit 11 and information on the period of the discovery window (Cycle information) from the Discovery Cycle control unit 12, and based on them The discovery window generation timing is determined and various processes of the discovery process are performed. In addition, the Discovery Process unit 4 outputs various PON control information to the control frame generation unit 14 and outputs the number information of ONUs registered by performing the discovery process to the ONU registered number management unit 9. Also, various PON control information related to the discovery process is input from the control frame receiving unit 15.

Next, the ONUs 16-1 to 16-N that are subscriber-side devices will be described.
Since the internal configuration other than the ONU 16-1 is the same as that of the ONU 16-1, an individual description is omitted below. The same name as OLT 1 is a function on the ONU 16 side corresponding to the operation of OLT 1 or corresponding to the operation of OLT 1 and will be described briefly.
Each of the ONUs 16-1 to 16-N includes a WDM unit 17, an RX unit 18, a TX unit 19, a DeMUX unit 20, a MUX unit 21, a PON control unit 23, and a user I / F unit 22.
The WDM unit 17 is an interface compatible with the wavelength division multiplexing system, and transmits and receives optical signals to and from the WDM unit 2 of the OLT 1 to perform multiplexing and demultiplexing.
The RX unit 18 0 / E converts the optical signal output from the WDM unit 17 into an electrical signal.

The TX unit 19 performs E / 0 conversion of the electrical signal output from the MUX unit 21 into an optical signal.
The DeMUX unit 20 separates downlink PON control information and subscriber communication data.
The MUX unit 21 multiplexes uplink PON control information and subscriber communication data.
The user I / F unit 22 transmits and receives subscriber communication data to and from a subscriber communication terminal such as a PC. Note that various forms are possible, such as the subscriber's terminal and the ONU being integrated, or the subscriber's input / output being performed in the ONU.
The PON control unit 23 generates various PON control information and outputs the generated PON control information to the MUX unit 21 and analyzes the various PON control information output from the DeMUX unit 20. Various controls related to the operation of the PON are performed.

In the configuration of the OLT 1 described above, registration transmission for periodically transmitting a registration transmission permission signal for permitting transmission of a registration request signal from the subscriber side apparatus to the subscriber side apparatus based on a unit cycle of the registration process. The permission transmission means corresponds to the WDM unit 2, TX unit 3, MUX unit 5, ONU support transmission distance data management unit 10, Discovery Window control unit 11, Discovery Cycle control unit 12, and control frame generation unit 14 in FIG.
Further, the subscriber side device responding to the registration transmission permission signal periodically transmits a registration request reception communication band based on the unit period and the time range for receiving the registration request signal within the unit period. As a registration request receiving means for optically receiving a registration request signal to be received and confirming the presence or absence of the registration request within the registration request receiving communication band, the WDM unit 2, the RX unit 4, the DeMUX unit 6, the control frame receiving unit 15, The Discovery Process unit 24 corresponds.
Here, the unit period corresponds to the discovery cycle, and the time range for receiving the registration request signal within the unit period corresponds to the discovery window size.

The Discovery Process unit 24 corresponds to a registration processing unit that performs registration processing of the subscriber apparatus that has transmitted the registration request signal based on the result of confirming the presence or absence of the registration request signal.
The ONU registered number management unit 9 corresponds to the registered number management means for monitoring the registered number of the subscriber side devices based on the registration processing of the registration processing means.
The registration request reception bandwidth allocation control means for controlling the bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means. 9, ONU support transmission distance data management unit 10, Discovery Window control unit 11, Discovery Cycle control unit 12, and Discovery Process unit 24.

Next, an overview of the discovery process will be described with reference to FIG.
FIG. 2 is an overall flowchart of the discovery process in the PON system according to the first embodiment of the present invention. Registration of the ONU 16 that is the subscriber side device to the OLT 1 that is the station side device is performed by executing this flow. The flow of FIG. 2 is common to each embodiment described below including this embodiment. In the figure, it is assumed that the vertical axis represents time and the time advances from top to bottom.

First, the OLT 1 sends a discovery transmission permission signal (discovery gate: described as Discovery Gate in the figure) including information regarding a response start time and information regarding a random delay generation permission time as a registration transmission permission signal to the ONU 16. .) 61 is transmitted.
That is, the registration transmission permission information output from the Discovery Process unit 24 of the OLT 1 passes through the control frame generation unit 14, the TX unit 3, the MUX unit 5, the WDM unit 2, and the splitter 30 to all the NUs 16-1 to 16-. N is optically transmitted as a discovery transmission permission signal (Discovery Gate) 61 to N. The output timing of the discovery transmission permission signal (Discovery Gate) 61 is input from the Discovery Window control unit 12 regarding the unit cycle of the registration process and from the Discovery Window control unit 11 regarding the time range for receiving the registration request signal. Control based on window size information.

Furthermore, the OLT 1 controls the bandwidth allocation of the upstream communication band to each ONU so that the registration request signal 62 (described as “Resister Request” in the figure) 62 is transmitted from the ONU 16 but the subscriber communication data is not transmitted. , A transition is made to a reception waiting state for a registration request signal (Resister Request) 62 from the ONU 16. This reception waiting state corresponds to the discovery window 63.
That is, the bandwidth control unit 13 of the OLT 1 performs the uplink communication bandwidth allocation control, and the PON control unit 8 puts the control frame reception unit 15 in a reception waiting state.

Next, for example, the ONU 16 that is unregistered and has data that has not been transmitted to the OLT 1 is registered in the OLT 1, so that information on the response start time in the received discovery transmission permission signal (Discovery Gate) 61 and a random delay The registration request signal (Resister Request) 62 is transmitted to the OLT 1 by controlling the transmission timing based on the information regarding the next regrettable range in which the registration can be performed. The transmission timing of the ONU 16 is controlled so that the reception timing in the OLT 1 is within the discovery window 63 in consideration of the internal processing time in the ONU 16.
That is, the PON control unit 23 of the unregistered ONU 16 inputs and analyzes the discovery transmission permission signal (Discovery Gate) 61 received by the WDM unit 17 by the RX unit 18 and the DeMUX unit 20, and then analyzes the registration request. A signal (Resister Request) 62 is optically transmitted to the OLT 1 by the MUX unit 21, the TX unit 19, and the WDM unit 17.

  Next, the OLT 1 that has received the registration request signal (Resister Request) 62 registers the unregistered ONU 16. Furthermore, a registration notification signal (Resister) 64 for notifying the ONU 16 that has requested registration of information related to the registration result, and a transmission permission signal (denoted as Gate in the figure) 65 for notifying the timing when the ONU 16 can be transmitted next. Are sent sequentially. The ONU 16 that has received the transmission permission signal (Gate) 65 transmits a registration acknowledgment signal (Resister_ACK) 66 indicating that the registration notification has been correctly received.

That is, a registration request signal (Resister Request) 62 received by the WDM unit 2 of the OLT 1 is input to the Discovery Process unit 24 through the RX unit 4 and the DeMUX unit 6, and the Discovery Process unit 24 receives the registration request signal within the discovery window. Is received. When there is a registration request, registration is performed and a registration notification signal (Resister) 64 is transmitted to the ONU 16 that has transmitted the registration request signal through the control frame generation unit 14, the MUX unit 5, the TX unit 3, and the WDM unit 2. To do.
Next, the OLT 1 that has received the registration acknowledgment signal (Resister_ACK) 66 confirms the completion of registration.
According to the above procedure, the unregistered ONU 16 that has made the registration request is registered in the OLT 1, the OLT 1 becomes the registration completion 67, and the discovery process is completed.

Next, how the OLT 1 controls the discovery window size based on the registered number information of the ONU 16 in the present embodiment will be described with reference to FIGS.
FIG. 3 is a flowchart of the OLT according to the first embodiment of the present invention.
In this flowchart, the ONU support transmission distance data management unit 10 is not used, and the Discovery Cycle control unit 12 is used in order to clearly and easily explain the processing procedure for changing the discovery window size. It shall be set to a fixed discovery cycle. In the following description, the operation of the ONU 16 is also described as necessary.

First, the administrator of the PON system considers the maximum value of the transmission distance between the ONUs 16-1 to 16-N and the OLT 1 and the internal processing time of the ONUs 16-1 to 16-N, and the maximum value of the round trip time. (Indicated as RTT maximum value in the figure) is set in advance in OLT 1 as an initial value.
Considering that a plurality of unregistered ONUs 16 transmit registration requests at the same time in the initial stage of communication, it is necessary to set a random delay time considering transmission of the plurality of ONUs 16. The OLT 1 performs the initial setting of the Discovery Window control unit 11 using the sum of the round trip time and the random delay time as a setting value of the discovery window size (denoted as Discovery Window size in the figure).
Information on the set discovery window size (window size information in FIG. 1) is output to the Discovery Process unit 24. (Step S11)

Next, the Discovery Process unit 24 of the OLT 1 waits until the transmission timing of the discovery transmission permission signal (Discovery Gate 61 in FIG. 2) is reached based on information on the cycle of the discovery cycle (Cycle information in FIG. 1). (Step S12)
Next, at the transmission timing of the discovery transmission permission signal (Discovery Gate 61), the OLT 1 transmits the discovery transmission permission signal (Discovery Gate 61) to all the ONUs 16-1 to 16-N.
The OLT 1 opens a discovery window to the ONU 16 at a predetermined time.

This discovery transmission permission signal (Discovery Gate 61) includes information related to the uplink transmission startable time for the ONU 16 to start a response and information related to the time range that can be received by the OLT 1.
The ONU 16 that needs to be registered transmits a registration request (Resister Request 62 in FIG. 2) with a random delay so as not to exceed the above time range with reference to the time when upstream transmission can be started. (Step S13)

Next, the OLT 1 checks whether or not a registration request signal (Resister Request 62) has been received from the unregistered ONU 16 within the period of the discovery window. The presence or absence of a registration request is confirmed based on the received signal. If it is recognized that there is a registration request, the process proceeds to ONU registration processing step S15. If there is no registration request, the process returns to step S12 and the next discovery cycle is performed. wait. (Step S14)
Next, when there is a registration request signal from the unregistered ONU 16, the OLT 1 executes a discovery process and registers the unregistered ONU 16. When registration is completed, the number information held by the ONU registered number management unit 9 is updated. (Step S15)

Next, the OLT 1 checks whether the number of registered ONUs 16 has reached the maximum number of registered units (= Nmax). When the number of registered ONUs reaches the maximum number of registered units, the process proceeds to ONU registered number management step 17. If the number of registered ONUs has not reached the maximum number of registered units, the process proceeds to step S19. (Step 16)
Here, the maximum registration number (Nmax) is either the maximum registration set number set by the administrator of the PON system in the ONU registration number management unit 9 of the OLT 1 or the maximum registerable number defined in the system in advance. Use one of these values. Which one to use is determined at the time of system design or operation.

  Next, when the number of registered ONUs 16 reaches the maximum number of registered units (Nmax), the OLT 1 confirms whether or not a new unregistered ONU has occurred due to the power failure of the ONU 16 or the occurrence of a communication disabled state. By doing so, the number of registered units is monitored. (Step 17)

Next, when the OLT 1 recognizes that one ONU 16 is newly unregistered, the process proceeds to step S19, and when there is no unregistered ONU, the process proceeds to step S17. (Step 18)
Next, when the unregistered ONU 16 is generated, the OLT 1 calculates the unregistered ONU number (= K) from the difference between the maximum registered number (Nmax) and the currently registered ONU number (= M). To grasp.

K = Nmax-M ------ (1)

When the set value of the random delay time is R, the following formula is applied based on the grasped number of unregistered ONUs (= K), and the discovery window size is dynamically set based on the calculated set value (R). To control.

R (current) = {R (default) -α} x (K / Nmax) + α ------ (2)

Here, R (current) represents the latest random delay time, R (default) represents the previous random delay time, and α represents a guaranteed value of the minimum random delay value. Depending on the system, there is no problem even if α = 0.

The above formula is merely an example. For example, a range or a division may be set for the number of unregistered ONUs (= K), and R (current) may be defined for each range to change the random delay time. Absent.
Even if the random delay time is not set after calculating the unregistered number (K), for example, when setting the random delay time, the maximum registered number (= Nmax) and the currently registered ONU number (= The value of equation (2) may be obtained directly from M).
In addition, various calculation methods such as using a registered average number subjected to statistical processing such as a time average value can be applied, and are defined at the time of designing or mounting the apparatus.

Depending on the number of unregistered ONUs (K), the collision occurrence frequency of the registration request signal transmitted from the unregistered ONU 16 changes. When the value of K is small, the possibility of collision is low, and therefore, it is possible to reduce the amount of random transmission delay in the discovery window size, and even if it is reduced, the influence on the discovery process is small.
When the registered number reaches the maximum registered number (Nmax), that is, when the number of unregistered ONUs is 0, the ONU 16 does not need to transmit a registration request signal, and therefore the OLT 1 does not allocate a bandwidth for the discovery window. It is also possible to perform control as described above. Thereby, the effective communication band can be further increased.
If the number of unregistered ONUs is 0 and no bandwidth is allocated for the discovery window size, the discovery window is displayed when the unregistered state occurs after the number of unregistered ONUs reaches 0 and the unregistered number is no longer 0. The control is performed so as to resume the allocation of the bandwidth for use.

Next, the OLT 1 proceeds to Step 12 and periodically performs the discovery process as described above. (Step S19)
As described above, the discovery window size is controlled depending on the number of registered ONUs 16.

As described above, in this embodiment, the random delay time in the discovery window is dynamically changed in consideration of the number information of the ONUs 16.
By changing the random delay time and reflecting it in the setting of the discovery window size, when there are few unregistered ONUs, that is, when there are many registered units, the discovery window size is reduced. By using it, the effective communication band in uplink communication increases.

Next, the effect in the above embodiment will be described with reference to FIG.
FIG. 4 is a schematic diagram illustrating the improvement of the uplink communication band according to the first embodiment of the present invention. In the figure, it is assumed that the vertical axis represents time and the time advances from top to bottom.
4 (a) shows a case where the number of unregistered units is large, and FIG. 4 (b) shows an example of a case where the number of unregistered units is small (1 unit). Only a discovery transmission permission signal (Discovery Gate) 61 and a registration request signal (Resister Request 62) are shown. Also, the dotted lines in the figure indicate the start and end times of the discovery window.

  When there are many unregistered ONUs 16 (FIG. 4A), there is a possibility that a plurality of ONUs 16 will issue registration request signals 62 within the same discovery window. For this reason, since it is necessary to increase the random delay time, it is necessary to ensure a large discovery window size accordingly. On the other hand, when there is one unregistered ONU (FIG. 4 (b)), there is a possibility that a registration request may be issued, so there is no need to increase the random delay time. It can be seen that the effective communication band for uplink data communication is increased by using the communication band of the indicated time for communication of subscriber data.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIGS.
The configuration of the communication system is the same as that of FIG. Also, the same or corresponding parts as those in the first embodiment are given the same or corresponding numbers, and the description thereof is omitted.
In this embodiment, the discovery cycle is dynamically controlled based on the number information of the ONUs 16.
FIG. 5 is a flowchart of the OLT according to the first embodiment of the present invention.
In this flowchart, the ONU support transmission distance data management unit 10 is not used, and the Discovery Window control unit 11 is used for the discovery window size in order to clearly and easily explain how the OLT 1 changes the discovery cycle. Is assumed to be a fixed value.

  In addition, since step S11-step S18 in a figure implement the same process as the step of the same number in the flowchart shown in FIG. 2 of the said Embodiment 1, the description is abbreviate | omitted. In FIG. 5, step S29 is a step different from that in FIG. 2, and is a process necessary when the discovery-cycle is changed.

  In step 29, the discovery cycle is changed based on the information on the number of unregistered ONUs (K). When there are few unregistered ONUs, the discovery process is performed at a low frequency. When there are many unregistered ONUs, the discovery process is performed at a high frequency. As described above, the dynamic control of the discovery cycle is performed.

For example, when the unregistered state of the ONU has occurred, the OLT 1 is similar to the equation (1) of the first embodiment from the difference between the maximum registered number (Nmax) and the currently registered ONU number (M). Thus, the unregistered ONU (K) is calculated.

K = Nmax-M ------ (1)

Then, based on the number of unregistered ONUs (K), a new setting value of the discovery cycle is changed by the following formula based on the initial value of the discovery cycle (DC (default)).

DC (current) = β x {DC (default) x (K / Nmax)} --- (3)

Here, β is a cycle change coefficient and is a value defined by the system. (Step 29)
Note that this calculation is merely an example. For example, a discovery cycle may be changed by setting a range for K and defining DC (current) in each range. In addition, various calculation methods such as using a registered average number subjected to statistical processing such as a time average value can be applied, and are defined at the time of designing or mounting the apparatus.
Even if the random delay time is not set after directly calculating the unregistered number (= K), for example, when setting the random delay time, the maximum registered number (= Nmax) and the currently registered ONU number The value of equation (3) may be obtained directly from (= M).

As described above, the discovery cycle is changed.
When an unregistered ONU 16 occurs, a new registration request signal is generated and the discovery window must be opened in order for the OLT 1 to receive it. However, if the number of unregistered ONUs is small, the discovery cycle is increased. If implemented frequently, the effective bandwidth of the upstream communication bandwidth decreases due to the discovery window. When multiple ONUs need to be registered in a short period of time, it is desirable that the discovery window cycle be frequent. For example, if there is one unregistered ONU, performing discovery at a low frequency has no operational impact. small.
By changing the discovery cycle based on the number of unregistered units (or registered units), when there are few unregistered ONUs, that is, when there are many registered units, the communication bandwidth allocated for the discovery window is reduced. By using it for communication of subscriber data, the effective communication band in uplink communication increases.

The effect in this Embodiment is demonstrated using FIG.
FIG. 6 is a schematic diagram showing the improvement of the uplink communication band of the OLT according to the second embodiment of the present invention, and is the same diagram as FIG. 4 of the first embodiment.
FIG. 6A shows a case where the number of unregistered units is large, and FIG. 6B shows a case where the number of unregistered units is small (one unit).

  When the number of unregistered ONUs is small (FIG. 6B), the possibility that the registration request signals collide with each other even if the discovery cycle is not frequently performed is low. The difference in time for completing registration is small. For this reason, it is understood that the effective communication band for uplink data communication is increased by using the communication band of the time indicated by hatching in the figure for the subscriber's data communication by lowering the discovery cycle. .

Embodiment 3 FIG.
The third embodiment of the present invention will be described below with reference to FIGS.
The configuration of the communication system is the same as in FIG. In the drawings, the same or similar elements are denoted by the same or corresponding numerals, and the description thereof is omitted.
In this embodiment, the discovery window size is dynamically controlled based on information on the maximum transmission distance that can be supported by each ONU 16.
FIG. 7 is a flowchart of the OLT according to the third embodiment of the present invention.
Steps S12 to S18 are the same as the steps having the same numbers in the flowchart shown in FIG. 2 of the first embodiment, and therefore some or all of the steps will be described.

  First, in step S31, the system administrator does not consider (1) the transmission distance between the OLT 1 and the ONU 16 and (2) the internal processing time of the ONU 16 shown in the first and second embodiments. (3) The transmission time determined from the value of the maximum transmission distance supported by the ONU 16 and (4) the maximum round trip time (RTT maximum value) in consideration of the internal processing time of the ONU 16 are set in advance in the OLT 1 in advance. Set.

Considering that a plurality of unregistered ONUs 16 transmit registration requests at the same time in the initial stage of communication, it is necessary to set a random delay time considering transmission of the plurality of ONUs 16.
The OLT 1 performs the initial setting of the Discovery Window control unit 11 using the sum of the round trip time and the random delay time as a setting value of the discovery window size (denoted as Discovery Window size in the figure). (Step S31)
Next, the OLT 1 performs the initial setting of the Discovery Cycle control unit 12 based on the initial value of the discovery cycle. (Step S32)
Next, the process from step S12 to step S18 is performed.

  In step S33, the OLT 1 searches for and confirms the maximum transmission distance that can be supported by the unregistered ONU 16. As a method for confirming the maximum transmission distance that the ONU 16 can support, for example, (1) a MAC address that is a unique address of each ONU 16 set in advance by the administrator of the communication system, and (2) a maximum transmission distance supported by the ONU 16 Is created, stored in the ONU support transmission distance data management unit 10 of the OLT 1, and searched by searching this management table.

FIG. 8 is a configuration example of an OLT management table according to the third embodiment of the present invention.
The left is the MAC address that is the individual identification number of the ONU 16, and the right is the maximum transmission distance supported by each ONU 16. The reason why the maximum transmission distance supported by the ONU 16 is different because the maximum transmission distance that can be supported by the ONU 16 differs depending on the optical transceiver mounted in the WDM unit 17 of the ONU 16.
In this configuration example, the maximum transmission distance to be supported is defined in three stages, and the cases of 20 km, 40 km, and 60 km are shown. Although the management table 40 in FIG. 8 defines the distance (km), a plurality of ranges may be defined for the transmission distance to classify and search the class. In addition, the granularity of transmission distance setting is determined in the operation of the communication system.

  Next, the maximum value of the maximum supported transmission distance of the unregistered ONU 16 is determined based on the management table 40 and the recognition result of the unregistered ONU 16. Then, based on the maximum value information of the maximum supported transmission distance, the round trip time (RTT) setting value, which is one of the factors for determining the discovery window size, is determined and the discovery window size is changed. (Step S33)

  Since the ONU 16 is not based on the transmission distance between the OLT 1 and the ONU 16 but based on the maximum transmission distance that the ONU 16 can support, the RTT value is set when only the ONU 16 having a short maximum supportable transmission distance becomes unregistered. Accordingly, the discovery window size can be reduced correspondingly and used for data communication, so that the effective uplink bandwidth can be expanded.

FIG. 9 is a schematic diagram showing the improvement of the uplink communication band in the third and fourth embodiments of the present invention.
FIG. 9A shows an example in which the maximum value of the supported maximum transmission distance of an unregistered ONU is large (60 Km), and FIG. 9B shows an example in which the maximum value is small (20 Km).
As shown in FIG. 9B, when the maximum supported transmission distance of the ONU 16 that is not registered and may transmit a registration request is 20 km, the maximum RTT value in the discovery window should be considered up to 20 km. Therefore, it can be seen that the discovery window size can be reduced and the effective bandwidth of uplink data communication is increased.

  Further, even in the case of a change in transmission distance accompanying the transfer of ONUs (see FIG. 11), which is a problem of Patent Document 2 described in the above background art column, it is possible to support ONUs that are not registered in the discovery window size setting. Since the maximum transmission distance can be taken into consideration, it can be seen that the problem of affecting the upstream communication band used for data communication is also improved.

Embodiment 4 FIG.
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
In the present embodiment, both the discovery window size and the discovery cycle are dynamically controlled based on information on the maximum transmission distance that can be supported by each ONU 16.
FIG. 10 is a flowchart of the OLT according to the fourth embodiment of the present invention.
Steps S12 to S18 are the same as the steps having the same numbers in the flowchart shown in FIG. 2 of the first embodiment, and therefore some or all of the steps will be described.

In the flowchart of FIG. 10, the random delay time (R (current)) of the discovery window size is dynamically controlled based on information on the number of registered ONUs 16 in step S19, and based on information on the number of registered ONUs 16 in step S29. The discovery cycle (DC (current)) is dynamically controlled, and in step S33, the round trip time (RTT (current)) is dynamically controlled based on information on the maximum supported transmission distance.
The total time (Discovery Time) in which the uplink bandwidth is used for the discovery window within a certain time can be calculated by the following equation.

Discovery Time (Disc T) = DC (current) x {(RTT (current) + R (current)} ----- (6)

According to the present embodiment, it is understood that the uplink communication band used for the discovery window can be suppressed and the effective communication band can be increased.

Embodiment 5 FIG.
The fifth embodiment of the present invention will be described below.
In the present embodiment, it is assumed that ONUs 16 having different transmission speeds communicate with the same OLT 1 in the same system in each of the above embodiments.
A specific example is a case where the ONU 16 having a transmission rate of 10 Gbps and the ONU 16 having a transmission rate of 1 Gbps are connected to the same OLT 1.
Furthermore, in that case, it is conceivable to provide a discovery window independently for each transmission rate type of the ONU. When providing different discovery windows corresponding to transmission speed types, information on the number of registered ONUs corresponding to each discovery window or information on the maximum supported transmission distance is managed separately, and the discovery window is activated for each transmission speed type. Control.
In this way, even when ONUs 16 having different transmission rates are mixed, the uplink communication band used for the discovery window can be suppressed by controlling the transmission rates separately.

  Note that, by combining the above embodiments, even when ONUs having different support maximum transmission distances and transmission speeds coexist, it is possible to achieve the same effect.

In each of the above embodiments, the invention is described in detail by taking the case of a PON system as an example. However, in a communication system in which a plurality of subscriber-side devices transmit and receive optical signals to and from a station-side device, The registration request transmitted from the apparatus can be applied to any communication system in which the station side apparatus receives and allocates an uplink communication band, and is not limited to the PON system described in the above embodiment. Further, the present invention can be applied to a communication system similar to the above regardless of wired communication, wireless communication, or a combination thereof.
Further, each of the above embodiments is an exemplification, and the arrangement and positional relationship of each part within a range that does not depart from the technical idea of the present invention by a person having ordinary knowledge in the technical field, including combinations of the above embodiments. Various modifications such as operating conditions are possible.

1 OLT (Station side equipment)
2 WDM unit 3 TX unit 4 RX unit 5 Mux unit 6 Demux unit 7 Network I / F unit 8 PON control unit 9 ONU registered number management unit 10 ONU support transmission distance data management unit 11 Discovery Window control unit 12 Discovery Cycle control unit 13 Band control unit 14 Control frame generation unit 15 Control frame reception unit 16 ONU (subscriber side device)
17 WDM section 18 RX section 19 TX section 20 Demux section 21 Mux section 22 User I / F section 23 PON control section 24 Discovery Process section 30 Optical splitter 40 Supported maximum transmission distance management table 61 Transmission permission signal for discovery (Discovery Gate)
62 Registration Request Signal (Resister Request)
63 Discovery Window (Discovery Window)
64 Registration Notification Signal (Resister)
65 Transmission permission signal (Gate)
66 Registration Acknowledgment Signal (Resister_ACK)
67 Registration complete

Claims (12)

Registration transmission permission transmission means for periodically optically transmitting a registration transmission permission signal for permitting transmission of a registration request signal from the subscriber side apparatus to the subscriber side apparatus based on a unit period of a registration process. When,
The subscriber side device responding to the registration transmission permission signal periodically assigns a registration request signal reception communication band based on the unit period and the reception time range of the registration request signal within the unit period. A registration request receiving means for optically receiving the registration request signal to be transmitted and confirming the presence or absence of a registration request in the registration request signal receiving communication band;
Registration processing means for performing registration processing of the subscriber device that has transmitted the registration request signal based on the result of confirming the presence or absence of the registration request;
Based on the registration processing of the registration processing means, the registered number management means for monitoring the registered number of the subscriber side device;
A station side device having registration request reception bandwidth allocation control means for controlling bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means,
A transmission permission receiving means for registration for optically receiving the transmission permission signal for registration;
Registration request transmission means for optically transmitting the registration request signal in response to the registration transmission permission signal, one or more subscriber side devices,
A communication system comprising: The monitoring result of the registered number is the registered number and the maximum registered set number of subscriber devices set in the station side device by the administrator of the communication system or the maximum registerable number of subscriber devices defined in the communication system. The communication system according to claim 2, wherein the number is an unregistered number defined based on. 2. The station-side device performs control so that the registration request reception communication band is not allocated when the number of registered units reaches the maximum registered set number or the maximum registerable number. Or the communication system of Claim 2. 4. The operation according to claim 1, wherein, when subscriber-side devices having different transmission rates are installed in the communication system, the operations of the respective units of the station-side device are performed according to the transmission rates. 5. The communication system according to Crab. The communication system performs operations in the respective units of the station-side device according to the maximum transmission distance when subscriber-side devices having different maximum transmission distances supported by the subscriber-side device are installed. The communication system according to claim 1. Registration transmission permission transmission means for periodically optically transmitting a registration transmission permission signal for permitting transmission of a registration request signal from the subscriber side apparatus to the subscriber side apparatus based on a unit period of a registration process. When,
The subscriber side device responding to the registration transmission permission signal periodically assigns a registration request signal reception communication band based on the unit period and a reception time range of the registration request signal within the unit period. A registration request receiving means for optically receiving the registration request signal to be transmitted and confirming the presence or absence of the registration request signal in the registration request receiving communication band;
Registration processing means for performing registration processing of the subscriber device that has transmitted the registration request signal based on the result of confirming the presence or absence of the registration request;
Based on the registration processing of the registration processing means, the registered number management means for monitoring the registered number of the subscriber side device;
Registration request reception bandwidth allocation control means for controlling bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means. Station side equipment The monitoring result of the registered number is the registered number and the maximum registered set number of subscriber devices set in the station side device by the administrator of the communication system or the maximum registerable number of subscriber devices defined in the communication system. The station-side device according to claim 6, wherein the number is an unregistered number defined based on 8. The control according to claim 6, wherein control is performed so that the registration request receiving communication band is not allocated when the registered number reaches the maximum registered set number or the maximum registerable number. Station side equipment. 9. The apparatus according to claim 6, wherein when a subscriber-side device having a different transmission rate is registered in the station-side device, the operations of the respective units of the station-side device are performed according to the transmission rate. The station side apparatus in any one. The operation of each means of the station side device is performed for each of the maximum transmission distances when subscriber side devices with different supported maximum transmission distances are registered in the station side device. The station side apparatus of Claim 4 thru | or 4. A registration transmission permission transmission step of periodically optically transmitting a registration transmission permission signal for permitting transmission of a registration request signal from the subscriber side apparatus to the subscriber side apparatus based on a unit period of registration processing. When,
The subscriber side device responding to the registration transmission permission signal periodically assigns a registration request signal reception communication band based on the unit period and the reception time range of the registration request signal within the unit period. A registration request receiving step of optically receiving the registration request signal to be transmitted and confirming the presence or absence of a registration request in the registration request signal receiving communication band;
A registration processing step for performing registration processing of the subscriber device that has transmitted the registration request signal based on the result of confirming the presence or absence of the registration request;
Based on the registration processing of the registration processing means, the registered number management step of monitoring the registered number of the subscriber side device;
A registration request reception bandwidth allocation control step for controlling bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means;
A registration transmission permission receiving step for optically receiving the registration transmission permission signal;
A registration request transmission step of optically transmitting the registration request signal in response to the registration transmission permission signal;
A communication control method comprising: A registration transmission permission transmission step of periodically optically transmitting a registration transmission permission signal for permitting transmission of a registration request signal from the subscriber side apparatus to the subscriber side apparatus based on a unit period of registration processing. When,
The subscriber side device responding to the registration transmission permission signal periodically assigns a registration request signal reception communication band based on the unit period and the reception time range of the registration request signal within the unit period. A registration request receiving step of optically receiving the registration request signal to be transmitted and confirming the presence or absence of a registration request in the registration request signal receiving communication band;
A registration processing step for performing registration processing of the subscriber device that has transmitted the registration request signal based on the result of confirming the presence or absence of the registration request;
Based on the registration processing of the registration processing means, the registered number management step of monitoring the registered number of the subscriber side device;
A registration request reception bandwidth allocation control step for controlling bandwidth allocation by changing at least one of the unit period or the time range based on the monitoring result of the registered number of the registered number management means;
A communication control method comprising:

Images