JP2015082770A - Optical communication system, registration control method, and subscriber side optical line termination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a frequency of occurrence of collision of registration request signals which a station side optical line termination device receives from a plurality of subscriber side optical line termination devices on the condition that operation of the station side optical line termination device is made in accordance with a standard specification.SOLUTION: An optical communication system comprises a station side optical line termination device and a subscriber side optical line termination device connected with the station side optical line termination device via an optical communication path. The subscriber side optical line termination device comprises a registration request signal transmission control unit that determines whether or not a registration request signal to request registration of the station side optical line termination device by the station side optical line termination device should be transmitted to the station side optical line termination device according to a predetermined probability in response to reception of a registration request transmission control signal transmitted by the station side optical line termination device.

Description

  The present invention relates to an optical communication system, a registration control method, and a subscriber side optical line termination device.

  As one form of access network, PON (Passive Optical Network) is known. The PON is between an OLT (Optical Line Terminal) installed on the telecommunications carrier side and an ONU (Optical Network Unit: subscriber side optical line termination device) installed on the subscriber side. In the communication, the access network is configured to branch the optical signal into a plurality of parts by using a splitter which is a passive element without performing photoelectric conversion. In such a PON, since a single optical fiber can be shared by a plurality of users, an economical network can be constructed.

  Among the PONs, those in which the OLT and the ONU communicate with each other using an Ethernet (registered trademark, hereinafter the same) frame are referred to as EPON (Ethernet (registered trademark, the same hereinafter) PON).

  Among EPONs, GE-PON (Gigabit Ethernet PON) with a transmission speed of 1 Gbps is a high-speed and inexpensive FTTH (Fiber To The Home) configuration of an access optical communication network that directly draws optical fiber into a subscriber's home via a transmission line. System) service can be provided. For this reason, GE-PON is widely used especially in Japan. Recently, a standard specification of 10G-EPON having a transmission rate increased to 10 Gbps has been studied.

In recent years, studies have been made on optical repeaters for PON, and it has become possible to expand the standard and increase the number of branches. Specifically, conventional PONs were often used with 32 branches or less due to optical signal intensity restrictions, but multi-branch connections such as 1000 branches became possible.
In general, in PON, the direction of communication from the OLT to the ONU is referred to as the downstream direction, and the direction of communication from the ONU to the OLT is referred to as the upstream direction.

  In many PONs including EPON, upstream communication is performed by time division multiple access. By controlling the transmission timing of each ONU by the OLT, a plurality of ONUs can perform time division communication with the OLT. Similarly, 10G-EPON upstream communication is performed by time division multiple access. In 10G-EPON, a method in which a plurality of ONUs having different uplink transmission rates can be connected to one OLT is being studied. At this time, uplink communication is realized by time division multiple access even between ONUs of different speeds.

In many PONs in which uplink communication is performed by time-division multiple access, in order to efficiently use the uplink communication band, a band permitting uplink communication for each ONU is set as a communication status. It has a dynamic bandwidth allocation function that dynamically changes according to the frequency.
Here, the bandwidth for each ONU in the PON can be allocated, for example, by the OLT calculating a transmission permission amount for each ONU and securing the transmission time zone exclusively. The ONU transmits an upstream signal only in the time zone assigned by the OLT. For this reason, the waiting time for waiting for the assigned time zone is added to the transmission delay time.

  In EPON, a protocol called MPCP (Multi Point-Control Protocol) for controlling communication between a plurality of ONUs by one OLT is defined as a standard. As MPCP, there are known Discovery Processing for detecting an unregistered ONU and REPORT Processing / GATE Processing for controlling the transmission timing of an upstream signal transmitted by the ONU.

  In the EPON, when the ONU is connected to the PON, the OLT discovers the ONU, assigns an LLID (Logical Link ID) to the ONU, and automatically establishes a communication link. This function is called P2MP discovery (Point to multi-point Discovery). MPCP Discovery Processing is a protocol for realizing P2MP discovery.

The sequence diagram of FIG. 5 shows a communication procedure in P2MP discovery processing as Discovery Processing.
In the Discovery Processing, first, the OLT transmits a Discovery GATE frame, which is a GATE frame storing Discovery Information, to each ONU, and notifies the transmission timing (Step S1).
The GATE frame is a frame for notifying the ONU of control information related to transmission such as transmission timing, and the Discovery GATE frame is a frame for notifying the unregistered ONU of control information indicating the transmission timing of the REGISTER_REQ frame. The GATE frame is transmitted using Messages sent on broadcast cannel.

Next, unregistered ONU to the OLT receives a Discovery GATE frame after waiting a random waiting time (Random delay) _{T R} for collision avoidance, and transmits the REGISTER_REQ frame (step S2). The REGISTER_REQ frame is transmitted using Messages sent on broadcast cannel. The OLT sets the Discovery Window only for a time during which the REGISTER_REQ frame from the ONU may be received, and receives the REGISTER_REQ frame from each unregistered ONU during the set Discovery Window period.

Next, in response to reception of the REGISTER_REQ frame, the OLT newly registers an LLID that is an identifier of the ONU (or UNI port) that is the transmission source of the REGISTER_REQ frame. Then, the registered LLID is notified by a REGISTER frame (step S3). The REGISTER frame is transmitted using Messages sent on broadcast cannel.
In this way, when the LLID is notified from the OLT to the ONU, the OLT and the ONU can execute communication using the LLID. That is, a link is established between the OLT and the ONU.

Subsequently, the OLT notifies the uplink transmission timing by the GATE frame (step S4), and the ONU returns REGISTER_ACK according to the notified timing (step S5).
The P2MP discovery process is realized by the processes in steps S1 to S5. This GATE frame and REGISTER_ACK are transmitted using Messages sent on unicast cannels.
Thus, communication as Discovery Processing is executed between the OLT and the ONU (see, for example, Non-Patent Document 1).

The timing chart of FIG. 6 shows an example of transmission / reception timings of the Discovery GATE frame and the REGISTER_REQ frame in the P2MP discovery process. In correspondence with FIG. 5, transmission / reception of the Discovery GATE frame shown in FIG. 6 corresponds to step S1, and transmission / reception of the REGISTER_REQ frame corresponds to step S2.
Moreover, ONU200-k and ONU200-n shown by the figure each show one of several ONU. In the description of FIG. 6, a plurality of ONUs including the ONU 200-k and ONU 200-n are described as ONU 200 unless otherwise distinguished.

In FIG. 6, first, the OLT 100 transmits a Discovery GATE frame to each ONU 200 by broadcasting at time t0. Discovery GATE frame transmitted as described above, it includes a random wait time _{T R,} the information specifying the start time t1 of a random waiting time _{T R} as control information. The period of a random waiting time T _R shown in the figure indicates the maximum time as a random waiting time T _R.

Unregistered ONU200 in response to the reception of Discovery GATE frame, and transmits the REGISTER_REQ frame randomly within waiting time _{T R} designated by the Discovery GATE frame. If the communication distance of the ONU 200-n is the longest communication distance in the allowable range, the period T _D0 shown in FIG. 6 becomes the Discovery Window shown in FIG. Start timing of the period _{T D0} is the start time t1 in OLT 100, the end timing of the period _{T D0} is delayed according to the propagation time from the maximum time of the end time of the random waiting time _{T R} to OLT 100 in ONU 200-n It's time. That is, the period _T D0 indicates a period that may arrive REGISTER_REQ frame from ONU 200.

The Discovery Window period T _D0 is set based on the timing at which the OLT 100 transmits the Discovery GATE frame. Discovery Window is a period during which a REGISTER_REQ frame from an unregistered ONU 200 is preferentially received.
In the Discovery Window period T _D0 , the OLT performs control so that the registered ONU does not perform uplink transmission to the OLT.
For the EPON upstream communication, the OLT calculates the upstream transmission data amount of each ONU, and notifies the calculated transmission data amount, thereby performing bandwidth control so as to secure the transmission time for each ONU. . The Discovery Window period is a period during which a REGISTER_REQ frame from an unregistered ONU is received. In view of this, during the Discovery Window period, the OLT performs bandwidth control so that uplink transmission by registered ONUs is not performed. Thereby, it is possible to avoid a collision between a signal transmitted from a registered ONU and a REGISTER_REQ frame transmitted from an unregistered ONU.

IEEE std 802.3-2012 SECTION FIVE

If a REGISTER_REQ frame collision occurs in the P2MP discovery processing sequence, the collided REGISTER_REQ frame is discarded. In this case, for the ONU that is the source of the discarded REGISTER_REQ frame, the P2MP discovery sequence is not completed, and the link with the OLT is not established.
In this case, the ONU that is the transmission source of the collided REGISTER_REQ frame needs to perform registration processing again by the next P2MP discovery processing.
In particular, if the random wait time T _R is short and, the more frequently a collision occurs when an unregistered number ONU should establish links is large, enough to start ONU communicate with P2MP discovery process has completed May take a long time.

In a communication system, in general, the shorter the time from link establishment to communication start and the shorter the delay time, the higher the communication performance.
The interval at which the P2MP discovery process is executed in EPON is as long as about 0.1 to 1.5 seconds. For this reason, even if only one retry occurs in the P2MP discovery process, the influence on the delay is great. Furthermore, when the P2MP discovery process is executed simultaneously with a large number of ONUs, such as when the system is started up, the frequency of REGISTER_REQ frame signal collision increases. In such a state, there may be two or more retries, and the delay further increases.

  The present invention has been made in view of such circumstances, and after the operation of the station side optical line terminator conforms to the standard, the station side optical line terminator has a plurality of subscriber side optical line terminators. It is an object of the present invention to reduce the frequency of collision of registration request signals received from a device.

  One aspect of the present invention includes a station-side optical line terminator, and a subscriber-side optical line terminator connected to the station-side optical line terminator via an optical communication path. In response to reception of a registration request transmission control signal transmitted from the station side optical line terminator, the station of the registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator An optical communication system includes a registration request signal transmission control unit that determines whether transmission to a side optical network unit is possible according to a predetermined probability.

  One aspect of the present invention is the optical communication system described above, wherein the registration request signal transmission control unit includes a random number generation unit that generates a random number in a fixed numerical range, and the fixed numerical range corresponding to the probability. It is determined that a registration request signal should be transmitted when the random number is included in a predetermined numerical group selected from the above, and it is determined that a registration request signal should not be transmitted when the random number is not included in the numerical group A transmission permission / inhibition determining unit.

  One aspect of the present invention is an optical communication method in an optical communication system comprising a station side optical line termination device and a subscriber side optical line termination device connected to the station side optical line termination device via an optical communication path. The subscriber-side optical line terminator receives the registration request transmission control signal transmitted from the station-side optical line terminator, and receives the registration request transmission control signal from the station-side optical line terminator. A registration control method comprising a registration request signal transmission control step for determining whether or not a registration request signal for requesting registration can be transmitted to the station side optical network unit according to a predetermined probability.

  One aspect of the present invention is a subscriber-side optical line terminator connected to a station-side optical line terminator via an optical communication path, and a registration request transmission control signal transmitted from the station-side optical line terminator. In response to reception, whether or not to transmit a registration request signal for requesting registration of the station side optical network unit by the station side optical network unit to the station side optical network unit is determined according to a predetermined probability. A subscriber-side optical line termination device including a registration request signal transmission control unit.

  As described above, according to the present invention, the operation of the station side optical line terminator conforms to the standard, and the station side optical line terminator receives from a plurality of subscriber side optical line terminators. The effect of reducing the frequency of registration request signal collisions can be obtained.

It is a figure which shows the structural example of the optical communication system in this embodiment. It is a figure which shows an example of the transmission / reception timing of a Discovery GATE frame and a REGISTER_REQ frame in the P2MP discovery process in this embodiment. It is a figure which shows the structural example of ONU in this embodiment. It is a flowchart which shows the example of a process sequence which ONU in this embodiment performs in response to reception of a Discovery GATE frame. It is a sequence diagram which shows the example of a communication procedure in a P2MP discovery process. It is a figure which shows an example of the transmission / reception timing of a Discovery GATE frame and a REGISTER_REQ frame in a P2MP discovery process.

FIG. 1 shows a configuration example of an optical communication system in the present embodiment. The optical communication system shown in the figure corresponds to, for example, 10G-EPON.
The optical communication system shown in FIG. 1 includes one OLT (Optical Line Terminal) 100 and a plurality of ONUs (Optical Network Units: subscriber side optical line terminators) 200-1 to 200-n. Are connected via the optical communication path 500. The optical communication path 500 is formed with an optical splitter, an optical fiber or the like.
In the following description, the ONUs 200-1 to 200-n are described as ONUs 200 unless otherwise distinguished.

The OLT 100 is an optical line terminating device installed on the telecommunications carrier side. A host network 300 is connected upstream of the OLT 100. The host network 300 includes various servers that exist on the Internet, for example.
The OLT 100 performs, for example, signal conversion between an electrical signal and an optical signal or multiplexing of signals in communication between the host network 300 and the optical communication path 500.

  The ONU 200 is an optical line terminating device installed on the subscriber side. A lower network 400 (400-1 to 400-N) is connected to the downstream side of the ONU 200 (200-1 to 200-n). The lower network 400 includes network devices such as a personal computer used at a subscriber's home.

In the optical communication system configured as described above, the ONU 200 that is not registered on the OLT 100 side cannot communicate with the OLT 100 because a link with the OLT 100 is not established. Therefore, for the ONU 200 that is not registered in the OLT 200, it is necessary to establish a link with the OLT 100 to enable communication.
For this purpose, a P2MP discovery process according to the procedure shown in FIG. 5 is executed between the OLT 100 and the unregistered ONU 200.

  The OLT 100 broadcasts a Discovery GATE frame to the ONU 200 in step S1 of FIG. When the REGISTER_REQ frame is normally received in step S2 in FIG. 5, for example, the processing after step S3 in FIG. 5 is executed according to the procedure according to the standard.

ONU200, when transmitting the REGISTER_REQ frame, as described with reference to FIG. 6, for collision avoidance, and after waiting a random waiting time _{T R} to send the REGISTER_REQ frame. However, collision avoidance by random waiting time _{T R} is not a thorough, reception period of the plurality of REGISTER_REQ frames overlap at OLT 100, there is a possibility that REGISTER_REQ frame collides. In particular, when the random wait time T _R or if not registered short ONU200 is such a large number, the frequency of occurrence of a collision is high.
FIG. 6 shows an example in which the REGISTER_REQ frame (R1) transmitted from the ONU 200-k and the REGISTER_REQ frame (R2) transmitted from the ONU 200-n collide with each other.

  When a collision occurs in the REGISTER_REQ frame, the signal of the collision part is discarded because sufficient reliability cannot be secured. When the REGISTER_REQ frame is discarded in this way, the ONU 200 that is the transmission source of the collided REGISTER_REQ frame is not registered in the OLT 100, and therefore communication for retry is executed in the next P2MP discovery process. Such a retry causes a delay in communication time, which causes a deterioration in communication performance in an optical communication system, for example.

  Therefore, in the present embodiment, the ONU 200 performs the following processing in association with the transmission of the REGISTER_REQ frame as step S2 in FIG. 5, thereby reducing the frequency of occurrence of REGISTER_REQ frame collisions.

The timing chart of FIG. 2 shows an example of transmission / reception timings of the Discovery GATE frame (registration request transmission control signal) and the REGISTER_REQ frame (registration request signal) in the P2MP discovery process in the present embodiment.
The OLT 100 transmits a Discovery GATE frame to each ONU 200 by broadcasting at time t0. Discovery GATE frame includes information specifying the maximum wait _{T R,} a start time t1 of a random waiting time _{T R.} Instead of the random waiting time _{T R,} for example, the waiting time such that the random between ONU 200, may be fixedly set for each ONU 200.
The transmission of the Discovery GATE frame by the OLT 100 corresponds to step S1 in correspondence with FIG.

After transmitting the Discovery GATE frame, the OLT 100 sets a Discovery Window based on the period T _D0 with the start time t1 as the start time as shown in FIG. The OLT 100 accepts reception of a REGISTER_REQ frame during the Discovery Window period.

The ONU 200 compliant with the standard specification always transmits a REGISTER_REQ frame in response to the reception of the Discovery GATE frame, as shown in step S2 of FIG.
On the other hand, the ONU 200 according to the present embodiment does not necessarily transmit the REGISTER_REQ frame in response to the reception of the Discovery GATE frame. That is, the ONU 200 according to the present embodiment may or may not transmit the REGISTER_REQ frame even when receiving the Discovery GATE frame.

Specifically, when receiving the Discovery GATE frame, the ONU 200 according to the present embodiment determines whether or not to transmit the REGISTER_REQ frame in response to the Discovery GATE frame received this time, according to a predetermined probability.
If you decide that it should send a REGISTER_REQ frame, ONU 200 transmits the REGISTER_REQ frame upon waiting a random waiting time _{T R.}
On the other hand, when it is determined that the REGISTER_REQ frame should not be transmitted, the ONU 200 does not transmit the REGISTER_REQ frame in response to the reception of the current Discovery GATE frame.

In FIG. 2, as a result of determining whether transmission is possible according to a predetermined probability as described above, the ONU 200-k determines that the REGISTER_REQ frame should not be transmitted, and the ONU 200-n determines that the REGISTER_REQ frame should be transmitted. Is shown.
According Such determination result, in the figure, ONU 200-k is not transmitting REGISTER_REQ frame even after random wait time _{T R.} On the other hand, ONU 200-n are transmitted to REGISTER_REQ frame after a random waiting time _{T R.} As a result, as can be seen in comparison with FIG. 6, only the REGISTER_REQ frame (R2) transmitted by the ONU 200-n during the Discovery Window period is received by the OLT, and the REGISTER_REQ frame (R1) and The state where no collision has occurred is shown.

By operating the ONU 200 in this manner, the ONU 200 that transmits the REGISTER_REQ frame in response to one Discovery GATE frame transmission from the OLT 100 is almost equal to the predetermined probability value of all the unregistered ONUs 200. Limited to the corresponding number.
As an example, if the probability is ¼ (= 0.25), the number of ONUs 200 that transmit REGISTER_REQ frames in response to one Discovery GATE frame transmission is approximately the number of all unregistered ONUs 200. Limited to ¼.

That is, in the present embodiment, the number of unregistered ONUs 200 that transmit the REGISTER_REQ frame in response to the transmission of the Discovery GATE frame can be made smaller than the number of all the unregistered ONUs 200.
Thereby, in the present embodiment, it is possible to reduce the frequency of occurrence of collision of REGISTER_REQ frames received by the OLT 100, and to effectively suppress the deterioration of communication performance due to retry. As a result, the time until normal reception on the OLT 100 side of REGISTER_REQ frames transmitted from all unregistered ONUs 200 is shortened. That is, the time until all unregistered ONUs 200 complete the registration request process is shortened, and deterioration of communication quality can be suppressed.

  Note that the OLT 100 according to the present embodiment repeatedly executes the transmission of the Discovery GATE frame at a predetermined timing although it is regular or irregular. Thus, in the process of repeatedly executing the discovery GATE frame transmission, all the unregistered ONUs 200 are transmitted with the REGISTER_REQ frame, and all the ONUs 200 can be registered.

  A configuration example of the ONU 200 of the present embodiment will be described with reference to FIG. The ONU 200 shown in the figure includes a wavelength multiplexer / demultiplexer 201, an optical receiving unit 202, a control unit 203, a user data transmission unit 204, and an optical transmission unit 205.

  The optical communication system according to the present embodiment employs a wavelength division multiplexing method in which different wavelengths are assigned to the upstream and downstream optical signals to simultaneously transmit and receive upstream and downstream optical signals using a single optical fiber. According to such a configuration, the ONU 200 of this embodiment includes a wavelength multiplexer / demultiplexer 201. The wavelength multiplexer / demultiplexer 201 includes a wavelength filter corresponding to the wavelength of each optical signal in the upstream direction and the downstream direction.

The wavelength multiplexer / demultiplexer 201 extracts the optical signal transmitted from the OLT 100 by separating the wavelength corresponding to the downstream optical signal from the optical signal transmitted by the optical fiber, and outputs the optical signal to the optical receiving unit 202.
The wavelength multiplexer / demultiplexer 201 synthesizes an optical signal having a wavelength corresponding to the upstream direction output from the optical transmission unit 205 into an optical signal transmitted by an optical fiber, and transmits the optical signal to the OLT 100.

  The optical receiving unit 202 demodulates the optical signal input from the wavelength multiplexer / demultiplexer 201 into a data signal and outputs the data signal to the control unit 203.

The control unit 203 executes control related to communication with the OLT 100 and communication with the lower network 400.
The user data transmission unit 204 receives user data transmitted from the lower network 400 to the ONU 200 and passes it to the control unit 203. In addition, the user data transmission unit 204 transmits the user data transferred from the control unit 203 to the lower network 400.
The optical transmission unit 205 inputs the transmission signal (user data, REPORT frame, REGISTER_REQ frame, etc.) output from the transmission signal storage unit 234 of the control unit 203, converts it to an optical signal having a wavelength corresponding to the upstream direction, The converted optical signal is supplied to the wavelength multiplexer / demultiplexer 201 and transmitted to the OLT 100.

  Next, a configuration example of the control unit 203 will be described with reference to the same FIG. The control unit 203 shown in the figure includes a signal discrimination unit 231, a registration request signal transmission control unit 232, a registration request signal generation unit 233, a transmission signal storage unit 234, a transmission control unit 235, and a REPORT frame generation unit 236.

The signal discriminating unit 231 discriminates the signal input from the light receiving unit 202.
In the signal transmitted from the OLT, a signal to be transmitted to each ONU is multiplexed. The signal discriminating unit 231 determines whether or not the received signal (frame) is addressed to itself. Here, the signal addressed to itself is a signal transmitted by broadcast from the OLT 100, or a signal whose LLID (Logical Link ID) stored in the frame matches its own LLID. In the case of a signal transmitted by broadcast, a predetermined address corresponding to broadcast is stored in the destination address (DA). The signal discriminating unit 231 can determine whether or not the signal is transmitted by broadcasting by referring to the destination address (DA).

Furthermore, when the received signal is a signal transmitted to itself, the signal discriminating unit 231 determines the type of the received signal.
For example, when the type of information stored in the frame of the signal transmitted by broadcasting indicates that it is a Discovery GATE frame, the signal discriminating unit 231 determines that the received signal is a Discovery GATE frame.
When determining that the Discovery GATE frame has been received, the signal discriminating unit 231 outputs the received Discovery GATE frame to the registration request signal transmission control unit 232 and the transmission control unit 235.

In addition, the signal discriminating unit 231 determines that the received signal is a GATE frame when the type information stored in the received signal frame indicating that it is a GATE frame (other than the Discovery GATE frame). To do.
In this case, the signal discriminating unit 231 outputs the received GATE frame to the transmission control unit 235.

  The signal discriminating unit 231 determines that the received signal is user data when the type of information stored in the received signal frame addressed to the user indicates user data. In this case, the signal discriminating unit 231 transmits the received user data from the user data transmission unit 204 to the lower network 400.

In response to receiving the Discovery GATE frame transmitted from the OLT 100, the registration request signal transmission control unit 232 determines whether or not the REGISTER_REQ frame that requests registration of the ONU 200 by the OLT 100 can be transmitted to the OLT 100 according to a predetermined probability.
For this purpose, the registration request signal transmission control unit 232 includes a random number generation unit 232a and a transmission permission / inhibition determination unit 232b as an example.
The random number generation unit 232a generates a random number within a certain numerical range.
The transmission permission / inhibition determining unit 232b determines that a REGISTER_REQ frame should be transmitted when a random number is included in a predetermined numerical group selected from a predetermined numerical range corresponding to a preset probability. On the other hand, the transmission permission / inhibition determining unit 232b determines that the registration request signal should not be transmitted when a random number is not included in the numerical value group.

The registration request signal generation unit 233 generates a REGISTER_REQ frame when the transmission request determination unit 232b of the registration request signal transmission control unit 232 determines that the registration request signal should be transmitted.
The REGISTER_REQ frame generated as described above is accumulated in the transmission signal accumulation unit 234 and then output to the optical transmission unit 205 under the control of the transmission control unit 235 and transmitted from the wavelength multiplexer / demultiplexer 201 to the OLT 100. The

On the other hand, if the registration request signal generation unit 233 determines that the registration request signal should not be transmitted by the transmission permission determination unit 232b of the registration request signal transmission control unit 232, the registration request signal generation unit 233 responds to the Discovery GATE frame received this time A REGISTER_REQ frame is not generated. Also, the transmission control unit 235 discards the Discovery GATE frame received this time, and does not execute transmission control according to the Discovery GATE frame received this time.
In this case, the REGISTER_REQ frame corresponding to the Discovery GATE frame received this time is not transmitted to the OLT 100.
As described above, in the present embodiment, the registration request signal transmission control unit 232 controls the transmission of the REGISTER_REQ frame in response to the reception of the Discovery GATE frame according to the predetermined probability.

  In the control unit 203, the transmission signal accumulation unit 234 is a buffer that temporarily accumulates transmission signals waiting to be transmitted. The transmission signal accumulated by the transmission signal accumulation unit 234 is generated by, for example, user data transmitted from the lower network 400 via the user data transmission unit 204, a REGISTER_REQ frame generated by the registration request signal generation unit 233, and a REPORT frame generation unit 236. For example, a REPORT frame.

  The transmission control unit 235 performs transmission control according to the band (data transmission amount) notified by the GATE frame and the transmission timing. That is, the transmission control unit 235 transmits the transmission signal of the data transmission amount notified by the GATE frame among the transmission signals accumulated by the transmission signal accumulation unit 234 at the transmission timing notified by the GATE frame. To output. Thereby, the transmission signal of the transmission amount notified by the GATE frame is transmitted to the OLT 100 at the transmission timing notified by the GATE frame.

The REPORT frame generation unit 236 generates a REPORT frame. The REPORT frame is a frame for notifying the OLT 100 from the ONU 200 of the data amount of the transmission signal waiting for transmission stored in the transmission signal storage unit 234.
The REPORT frame generation unit 236 generates a REPORT frame storing data amount information indicating the data amount of transmission signals waiting to be transmitted that are accumulated in the transmission signal accumulation unit 234.
The generated REPORT frame is temporarily stored in the transmission signal storage unit 234 and then transmitted to the OLT 100 under the control of the transmission control unit 235.

The OLT 100 that has received the REPORT frame, based on the data amount indicated by the data amount information stored in the REPORT frame and the data amount of the ONU other than the REPORT frame transmission source, should be assigned to the ONU 200 that is the transmission source of the REPORT frame. Bandwidth (data transmission amount) and transmission timing are calculated. The transmission timing calculated here is the start time t1 of a random waiting time T _R shown such as in FIG.
The OLT 100 generates a GATE frame storing information on the calculated data transmission amount and transmission timing, and transmits the GATE frame to the ONU 200 that is the transmission source of the REPORT frame.

  The GATE frame received by the ONU 200 is output to the transmission control unit 235 in the control unit 203 as described above, and the transmission control unit 235 performs transmission based on the data transmission amount and the transmission timing indicated by the input GATE frame. Transmission control is performed on transmission signals waiting for transmission stored in the signal storage unit 234.

  Next, an example of a processing procedure executed by the ONU 200 that is not registered in the OLT 100 in response to receiving the Discovery GATE frame will be described with reference to the flowchart of FIG. Note that the processing shown in the figure corresponds to the case where the probability set in advance in the registration request signal transmission control unit 232 is 1/4 (= 0.25).

In the ONU 200, the signal discriminating unit 231 waits for a Discovery GATE frame to be received (step S101—NO). That is, the signal discriminating unit 231 waits until a discrimination result indicating that it is a Discovery GATE frame is obtained as a discrimination result for the received signal.
In response to the reception of the Discovery GATE frame (step S101—YES), the random number generation unit 232a in the registration request signal transmission control unit 232 sets the random number r within a numerical range of 0 or more and less than 1 (0 ≦ r <1). Generate (step S102).
Next, the transmission permission / inhibition determining unit 232b determines whether or not the random number r generated in step S102 is included in the numerical value group in the numerical value range of 0 or more and less than 0.25 (0 ≦ r <0.25). (Step S103).

  Here, the numerical value group corresponding to the numerical value range of 0 ≦ r <0.25 is selected from the numerical value range of 0 ≦ r <1 corresponding to the predetermined probability being ¼. is there. That is, the occupation ratio of the numerical range of 0 ≦ r <0.25 with respect to 0 ≦ r <1, which is the numerical range of values that can be taken as the random number r, is ¼. Therefore, the probability that the random number r is included in the range of 0 ≦ r <0.25 is also ¼.

When the random number r is included in the numerical value group in the range of 0 to less than 0.25 (0 ≦ r <0.25) (step S103—YES), the transmission availability determination unit 232b determines that the REGISTER_REQ frame should be transmitted. (Step S104).
In response to the determination result in step S104, the registration request signal generation unit 233 generates a REGISTER_REQ frame (step S105). The generated REGISTER_REQ frame is stored in the transmission signal storage unit 234.
Then, the transmission control unit 235 executes control for transmitting the REGISTER_REQ frame stored in the transmission signal storage unit 234 to the OLT 100, for example, at a timing according to the notification of the GATE frame (step S106).

On the other hand, when the random number r is 0.25 or more and not included in the numerical value group in the range of 0 or more and less than 0.25 (0 ≦ r <0.25) (step S103—NO), the transmission permission / inhibition determining unit 232b , REGISTER_REQ frame is determined not to be transmitted (step S107).
In response to the determination result of step S107, the transmission control unit 235 discards the Discovery GATE frame received corresponding to step S101 (step S108).
In this case, the registration request signal generation unit 233 does not generate a REGISTER_REQ frame, and the transmission control by the transmission control unit 235 corresponding to the Discovery GATE frame received corresponding to step S101 is not executed. That is, transmission of the REGISTER_REQ frame in response to the Discovery GATE frame received in step S101 is not executed.

By executing such processing, the ONU 200 of the present embodiment can transmit a REGISTER_REQ frame according to a predetermined probability in response to reception of the Discovery GATE frame.
When each ONU 200 executes such processing, the number of unregistered ONUs 200 that transmit the REGISTER_REQ frame in response to one Discovery GATE frame transmission is smaller than all the unregistered ONUs 200. . As a result, the frequency of occurrence of REGISTER_REQ frame collision can be further reduced to improve communication performance.

In such a configuration, since whether or not to transmit the REGISTER_REQ frame is determined according to a predetermined probability in the ONU 200, the OLT 100 may transmit a Discovery GATE frame according to a standard specification.
That is, the OLT 100 according to the present embodiment can be used as it is based on the standard.

Note that the OLT 100 and the ONU 200 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function is recorded on a computer-readable recording medium, and the program recorded on this recording medium is read into a computer system and executed, whereby each operation of the OLT 100 and the ONU 200 is realized. May be. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  100 OLT, 200 ONU, 201 wavelength multiplexer / demultiplexer, 202 optical receiver, 203 controller, 204 user data transmitter, 205 optical transmitter, 231 signal discriminator, 232 registration request signal transmission controller, 232a random number generator , 232b transmission enable / disable determination unit, 233 registration request signal generation unit, 234 transmission signal storage unit, 235 transmission control unit, 236 REPORT frame generation unit, 300 upper network, 400 lower network, 500 optical communication path

Claims (4)

A station-side optical line terminator, and a subscriber-side optical line terminator connected to the station-side optical line terminator via an optical communication path,
The subscriber side optical line terminator is:
In response to reception of a registration request transmission control signal transmitted from the station side optical line terminator, the station side light of a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator An optical communication system including a registration request signal transmission control unit that determines whether transmission to a line terminating device is possible according to a predetermined probability. The registration request signal transmission control unit,
A random number generator for generating random numbers in a certain numerical range;
When the random number is included in a predetermined numerical group selected from the certain numerical range corresponding to the probability, it is determined that a registration request signal should be transmitted, and the random number is not included in the numerical group The optical communication system according to claim 1, further comprising: a transmission permission / inhibition determining unit that determines that a registration request signal should not be transmitted. A registration control method in an optical communication system comprising: a station side optical line termination device; and a subscriber side optical line termination device connected to the station side optical line termination device via an optical communication path,
The subscriber side optical line terminator is:
In response to reception of a registration request transmission control signal transmitted from the station side optical line terminator, the station side light of a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator A registration control method comprising a registration request signal transmission control step for determining whether transmission to a line terminating device is possible according to a predetermined probability. A subscriber side optical line terminator connected to a station side optical line terminator via an optical communication path,
In response to reception of a registration request transmission control signal transmitted from the station side optical line terminator, the station side light of a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator A subscriber-side optical line terminator comprising a registration request signal transmission control unit that determines whether or not transmission to a line terminator is possible according to a predetermined probability.

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