JP2015095756A - Pon system, olt and onu - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable avoiding collision between Register Request signals regardless of priority of ONUs, and thereby to shorten a time until communication link establishment of the ONUs.SOLUTION: An OLT 1 comprises: an information storage unit 111 that stores identification information on ONUs 4 and RTT information; an order determination unit 113 for determining establishment order so that Register Request signals will not collide with each other when communication links of the ONUs 4 are established at the same time on the basis of the stored information; and an OLT side transmission unit (a transmission control unit 114 and an optical transmission unit 122) that transmits a Discovery GATE signal to the ONUs 4 by unicast according to the determined order. Each ONU 4 comprises: an ONU side reception unit (a reception detection unit 411 and an optical reception unit 421) that receives the Discovery GATE signal; and an ONU side transmission unit (a transmission control unit 412 and an optical transmission unit 422) that transmits a Register Request signal to the OLT 1 without delay when the Discovery GATE signal is received.

Description

  The present invention relates to an optical communication network composed of a station-side terminal device (hereinafter referred to as OLT) and a plurality of subscriber-side terminal devices (hereinafter referred to as ONU), in particular, a PON (Passive Optical Network) system, It relates to OLT and ONU.

  In the PON system, one OLT and a plurality of ONUs are connected by a passive optical branching device such as an optical splitter, and a tree-like network having the OLT as a vertex is configured. A downstream signal from the OLT to the ONU is transmitted to the optical branch via one trunk optical fiber, branched by the optical branch, and then transmitted to all ONUs via the branch optical fiber. The upstream signal from the ONU to the OLT is transmitted from each ONU to each optical branching unit via each branch optical fiber, and is transmitted from the optical branching unit to one OLT via one trunk optical fiber. The control of the PON system is standardized by IEEE802.3.

  When a plurality of ONUs transmit signals regarding the upstream signal from the ONU to the OLT, the signals transmitted from the ONUs collide with each other, and the OLT cannot correctly receive the signals. In order to prevent such signal interference, an upstream signal transmitted from each ONU to the OLT needs to be transmitted in a time division manner within a limited band. Therefore, an identifier called LLID (Logical Link ID), which is a unique number for identifying each ONU, is assigned to each ONU in advance, and signal transmission timing is notified to each ONU using the LLID. In addition, in the case of a downlink signal transmitted from the OLT to each ONU, since it is branched from one trunk optical fiber by an optical branching unit and transmitted to all ONUs, each ONU uses a preamble of a frame to be transmitted. With reference to the stored LLID, if the LLID matches its own LLID, a frame is fetched. If the LLID does not match, the frame is discarded.

Here, in IEEE 802.3, the OLT always sends a Discovery GATE signal to all ONUs in a broadcast manner in preparation for discovering newly connected unregistered ONUs. The DiscoveryGATE signal is a signal for notifying the ONU to which no LLID is assigned, of the signal transmission timing. The ONU is set not to transmit a signal unless it receives a GATE signal (such as a Discovery GATE signal or a Grant GATE signal) from the OLT in order to prevent a collision between signals.
Then, the unregistered ONU that has received the DiscoveryGATE signal transmits a RegisterRequest signal at a random time, and requests a registration request, that is, granting an LLID.

Next, the OLT transmits a Register signal to the unregistered ONU and assigns an LLID. Further, the OLT individually notifies the corresponding ONU of the GrantGATE signal including the assigned LLID by the unicast method. The OLT notifies the transmission band and the transmission timing with a GrantGATE signal while checking the degree of data congestion with other ONUs.
Next, when the ONU receives the GrantGATE signal, the ONU transmits a RegisterAck signal to notify the OLT that the GrantGATE signal has been received.
Thus, the communication link between the OLT and the ONU is established.

However, in the OLT of the conventional PON system, the Discovery GATE signal is transmitted to all ONUs, and the LLID, the transmission band, and the transmission timing are notified according to the RegisterRequest signal that is randomly transmitted from the ONU. Therefore, when there are a large number of unregistered ONUs, there is a high possibility that the Register Request signals of the respective ONUs will collide with each other. As a result, there is a problem that it takes time to establish a communication link of the ONU, and it takes a long time to start service of the entire system.
Therefore, a PON system that shortens the time until the service of the entire system is started is known (for example, see Patent Documents 1 and 2).

  The PON system disclosed in Patent Document 1 is configured to preferentially establish a communication link for an ONU that provides a high priority service. In this case, first, when the OLT transmits a GATE signal to all the ONUs, each ONU transmits to the OLT an identifier for specifying a service provided by itself, together with a registration request. Next, the OLT identifies a service from the identifier transmitted from the ONU, refers to a priority table that defines the priority of the service, and assigns an LLID from the ONU that provides the service with a high priority.

  Further, in the PON system disclosed in Patent Document 2, a service with high priority can be provided by reducing processing necessary for establishing a communication link with an ONU that establishes a communication link with priority among a plurality of ONUs. A communication link with the ONU to be provided is established in a short time.

JP 2006-262129 A JP 2009-188519 A

As described above, in the conventional PON system, when there are a large number of unregistered ONUs, there is a high possibility that the Register Request signals of each ONU will collide with each other. There was a problem that it took a long time to start the service of the entire system.
On the other hand, in the methods disclosed in Patent Documents 1 and 2, processing necessary for establishing a communication link with respect to the ONU is performed by preferentially establishing a communication link with respect to an ONU that provides a high priority service. By reducing this, the time until the start of the service of the entire system is shortened. However, in these methods, there is a problem that a system with uniform priority cannot be expected to have an effect on shortening the time required for establishing communication links of all ONUs.

  The present invention has been made to solve the above-described problems, and can avoid collision between ONU Register Request signals regardless of the priority of the ONU, and shorten the time until the ONU communication link is established. It is an object to provide a PON system, an OLT, and an ONU that can perform the above.

  In the PON system according to the present invention, in the PON system including the OLT and a plurality of ONUs connected to the OLT, the OLT includes identification information for identifying the ONU and RTT information regarding a frame round-trip delay time between the ONU. Order determination for determining the communication link establishment order so that the Register Request signals from the ONU do not collide with each other when the ONU communication link is established based on the information storage unit to be stored and the information stored in the information storage unit And an OLT side transmission unit that transmits a DiscoveryGATE signal by unicast to the ONU according to the order determined by the order determination unit, and the ONU includes an ONU side reception unit that receives the DiscoveryGATE signal from the OLT, Discovery GATE by ONU side receiver If the issue is received, in which a ONU-side transmission unit that transmits RegisterRequest signal to OLT.

  According to the present invention, since it is configured as described above, collision between ONU Register Request signals can be avoided regardless of the priority of the ONU, and the time until the ONU communication link is established can be shortened.

It is a figure which shows the structure of the PON system which concerns on Embodiment 1 of this invention. It is a figure which shows the sequence of the communication link establishment of the PON system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the PON system which concerns on Embodiment 2 of this invention. It is a figure which shows the sequence of the communication link establishment of the PON system which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a diagram showing a configuration of a PON system according to Embodiment 1 of the present invention.
As shown in FIG. 1, the PON system includes an OLT 1 that is a station-side termination device, and a plurality of ONUs 4 that are subscriber-side termination devices connected to the OLT 1 via an optical fiber 2 and an optical splitter 3. And a monitoring control terminal 5 for monitoring the OLT 1.

  As shown in FIG. 1, the OLT 1 includes a PON control unit 11 and an optical transmission / reception unit 12.

  The PON control unit 11 controls the PON interface. The PON control unit 11 includes an information storage unit 111, an RTT measurement unit 112, an order determination unit 113, and a transmission control unit 114.

The information storage unit 111 is a database that stores identification information (such as a MAC address of the ONU 4) that identifies the ONU 4 connected to the OLT 1 and RTT information related to a frame round trip delay time (hereinafter referred to as RTT: Round Trip Time).
The information storage unit 111 can be accessed from the monitoring control terminal 5. Then, the maintenance person performs a registration operation of the identification information and RTT information of the ONU 4 via the monitoring control terminal 5, and the information storage unit 111 stores these pieces of information as initial information in advance according to the registration operation. Further, when the RTT measurement unit 112 measures the RTT between the OLT 1 and the ONU 4, the information storage unit 111 updates the corresponding RTT information based on the measurement result.

  The RTT measurement unit 112 periodically measures the RTT between the OLT 1 and the ONU 4.

The order determination unit 113 determines the communication link establishment order based on the information stored in the information storage unit 111 so that the Register Request signals from the ONU 4 do not collide when the ONU 4 establishes the communication link. is there.
The transmission control unit 114 performs transmission control of a Discovery GATE signal transmitted to the ONU 4 by unicast according to the order determined by the order determination unit 113.

The optical transceiver 12 transmits and receives signals to and from the ONU 4. The optical transmission / reception unit 12 includes an optical reception unit 121, an optical transmission unit 122, and a WDM unit 123.
The optical receiving unit 121 receives an upstream signal from the ONU 4.
The optical transmitter 122 transmits a downstream signal to the ONU 4.
The WDM unit 123 combines the upstream signal received by the optical receiver 121 and the downstream signal transmitted by the optical transmitter 122.
Here, the transmission control unit 114 and the optical transmission unit 122 correspond to “an OLT-side transmission unit that transmits a DiscoveryGATE signal by unicast to the ONU according to the order determined by the order determination unit” of the present invention. .

On the other hand, the ONU 4 includes a PON control unit 41 and an optical transmission / reception unit 42 as shown in FIG. In FIG. 1, the internal configuration is shown only for ONU # A, but the other ONUs 4 (ONU # B, ONU # C) are configured similarly.
The PON control unit 41 controls the PON interface. The PON control unit 41 includes a reception detection unit 411 and a transmission control unit 412.

The reception detection unit 411 detects reception of a DiscoveryGATE signal by the optical transmission / reception unit 42 (an optical reception unit 421 described later).
The transmission control unit 412 controls transmission of the RegisterRequest signal when the reception detection unit 411 detects reception of the DiscoveryGATE signal.

The optical transceiver 42 transmits and receives signals to and from the OLT 1. The optical transmission / reception unit 42 includes an optical reception unit 421, an optical transmission unit 422, and a WDM unit 423.
The optical receiving unit 421 receives a downstream signal from the OLT 1.
The optical transmission unit 422 transmits an uplink signal to the OLT 1.
The WDM unit 423 combines the downlink signal received by the optical reception unit 421 and the uplink signal transmitted by the optical transmission unit 422.
Here, the reception detection unit 411 and the optical reception unit 421 correspond to the “ONU-side reception unit that receives the DiscoveryGATE signal from the OLT” of the present invention. The transmission control unit 412 and the optical transmission unit 422 correspond to an “ONU side transmission unit that transmits a RegisterRequest signal to the OLT when a DiscoveryGATE signal is received by the reception unit”.

Next, in the PON system configured as described above, the operation when the ONU 4 establishes a communication link will be described with reference to FIG.
When establishing a communication link for the ONU 4, first, the order determination unit 113 of the PON control unit 11 of the OLT 1 refers to the identification information and RTT information of the ONU 4 stored in the information storage unit 111. Here, the longer the RTT is set, the longer the distance between the OLT 1 and the ONU 4 is. For example, if the distance between the OLT 1 and the ONU 4 is 20 km (kilometers) or less, the RTT takes a maximum of about 200 μs (microseconds) considering each processing time in the OLT 1 and the ONU 4 and an optical transmission time of 20 km.

  Then, the order determination unit 113 determines the communication link establishment order based on the referred information so that the Register Request signals from the ONU 4 do not collide when the ONU 4 establishes the communication link. That is, the OLT 1 determines the optimal order in which LLIDs can be assigned in the shortest time to all ONUs 4 connected to the OLT 1 based on the RTT information.

  Next, the transmission control unit 114 of the PON control unit 11 performs transmission control of a Discovery GATE signal that is transmitted by unicast to each of all ONUs 4 according to the order determined by the order determination unit 113. Then, the optical transmission unit 122 transmits the DiscoveryGATE signal to the ONU 4 by unicast according to the control by the transmission control unit 114.

Next, the optical receiving unit 421 of the ONU 4 receives the DiscoveryGATE signal from the OLT 1, and the reception detection unit 411 detects this.
Next, the transmission control unit 412 performs transmission control of the RegisterRequest signal in response to the reception detection of the DiscoveryGATE signal by the reception detection unit 411. Then, the optical transmission unit 422 transmits a RegisterRequest signal to the OLT 1 according to the control by the transmission control unit 412.

As shown in FIG. 2, the OLT 1 uniquely determines the transmission order of the Discovery GATE signal for the ONU 4 and transmits it by unicast. The ONU 4 receives the signal and then returns the Register Request signal to return the Register Request signal. Is not coincident with other ONUs 4. Therefore, it is possible to prevent collision between Register Request signals with other ONUs 4.
As a result, it is possible to shorten the time until the communication link of the ONU 4 is established.

  Since the RTT measurement unit 112 periodically measures the RTT between the OLT 1 and the ONU 4, the RTT information stored in the information storage unit 111 is updated accordingly.

Further, when the link disconnection or power supply disconnection of the ONU 4 occurs, the OLT 1 updates the RTT information storage unit 7 based on the latest RTT information of the ONU 4. When the ONU 4 tries to establish a re-communication link next time, the same operation as described above is repeated with reference to the information in the updated RTT information storage unit 7.
Here, when a link disconnection or power supply disconnection occurs in one ONU 4 and re-registration is attempted, a RegisterRequest signal is transmitted at a random time (delayed) after receiving the DiscoveryGATE signal in the prior art. Therefore, some delay will inevitably occur. On the other hand, in the present invention, even when one ONU 4 tries to re-register, the Register Request signal is sent without delaying the random time, so that the occurrence of delay can be avoided. For example, when a plurality of ONUs 4 (for example, ONU # A and ONU # B) perform re-registration with a time difference, the reception time of the RegisterRequest signal from ONU # A with reference to the information in the RTT information storage unit 7 Then, the timing for transmitting a unicast DiscoveryGATE signal to ONU # B is controlled.

  As described above, according to the first embodiment, the OLT 1 uniquely determines the transmission order of the Discovery GATE signal to the ONU 4 based on the RTT and transmits it in unicast. After receiving the signal in the ONU 4, Since the Register Request signal is returned, it is possible to avoid a collision between the Register Request signals. As a result, regardless of the priority of the ONU 4, it is possible to suppress variations in the rise time when establishing the communication link with the ONU 4, and to shorten the time until the communication link of the ONU 4 is established.

Embodiment 2. FIG.
FIG. 3 is a diagram showing the configuration of the PON system according to Embodiment 2 of the present invention. The PON system according to the second embodiment shown in FIG. 3 is obtained by adding the same RTT determination unit 115 to the PON control unit 11 of the PON system according to the first embodiment shown in FIG. Further, among the ONUs 4, n (n is the maximum number of ONUs 4 to which 2 to OLT 1 can be connected) ONUs 4 are assumed to be equidistant from the OLT 1 and have the same line conditions (in FIG. The case where #B, ONU # C, and ONU # D are equidistance and equiline conditions is shown). Other configurations are the same, and the same reference numerals are given and only different portions will be described.

The same RTT determination unit 115 determines whether there are a plurality of ONUs 4 having the same RTT based on the information stored in the information storage unit.
Further, when the same RTT determination unit 115 determines that there are a plurality of ONUs 4 having the same RTT, the order determination unit 113 arbitrarily determines the communication link establishment order for the plurality of ONUs 4 having the same RTT.

Here, when there are a plurality of ONUs 4 having the same distance from the OLT 1 and the same line conditions, the RTTs are the same. Therefore, there are a plurality of patterns of communication link establishment orders in which Register Request signals from the ONU 4 do not collide with each other when the communication link is established with the ONU 4.
Therefore, when there are a plurality of ONUs 4 having the same RTT, the order determination unit 113 determines an arbitrary order for these ONUs 4 based on the storage order in the information storage unit 111 and the like.
Then, as shown in FIG. 4, the transmission control unit 114 performs transmission control of a DiscoveryGATE signal that is transmitted in unicast according to the arbitrarily determined order, for a plurality of ONUs 4 having the same RTT.

  As described above, according to the second embodiment, since the signal transmission is performed by determining an arbitrary order for the ONUs 4 having the same RTT, it is possible to avoid the collision between the RegisterRequest signals. As a result, regardless of the priority of the ONU 4, it is possible to suppress variations in the rise time when establishing the communication link with the ONU 4, and to shorten the time until the communication link of the ONU 4 is established.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 OLT, 2 optical fiber, 3 optical splitter, 4 ONU, 5 supervisory control terminal, 11, 41 PON control unit, 12, 42 optical transmission / reception unit, 111 information storage unit, 112 RTT measurement unit, 113 order determination unit, 114 , 412 Transmission control unit, 115 Same RTT determination unit, 121, 421 Optical reception unit, 122, 422 Optical transmission unit, 123, 423 WDM unit, 411 Reception detection unit.

Claims (6)

In a PON system including an OLT and a plurality of ONUs connected to the OLT,
The OLT is
An information storage unit that stores identification information for identifying the ONU and RTT information regarding a frame round-trip delay time with the ONU;
An order determination unit that determines a communication link establishment order so that RegisterRequest signals from the ONU do not collide with each other when establishing a communication link with the ONU based on information stored in the information storage unit;
An OLT-side transmitter that transmits a DiscoveryGATE signal in unicast to the ONU according to the order determined by the order determiner;
The ONU is
An ONU-side receiving unit that receives a DiscoveryGATE signal from the OLT;
A PON system comprising: an ONU-side transmitter that transmits a RegisterRequest signal to the OLT when a DiscoveryGATE signal is received by the ONU-side receiver. The OLT is
Based on the information stored in the information storage unit, the same RTT determination unit for determining whether there are a plurality of ONUs having the same frame round-trip delay time,
The order determination unit arbitrarily determines a communication link establishment order for the plurality of ONUs having the same frame round-trip delay time when the same RTT determination unit determines that there are a plurality of ONUs having the same frame round-trip delay time. The PON system according to claim 1, wherein: The PON system according to claim 1, wherein the information storage unit stores the identification information and the RTT information in advance according to a registration operation by a maintenance person. The OLT is
An RTT measurement unit for periodically measuring a frame round-trip delay time with the ONU;
The PON system according to claim 3, wherein the information storage unit updates the corresponding RTT information based on a measurement result by the RTT measurement unit. In OLT connected to multiple ONUs,
An information storage unit for storing identification information for identifying the ONU and RTT information indicating a frame round-trip delay time with the ONU;
An order determination unit that determines a communication link establishment order so that RegisterRequest signals from the ONU do not collide with each other when establishing a communication link with the ONU based on information stored in the information storage unit;
An OLT comprising: an OLT-side transmitting unit that transmits a DiscoveryGATE signal by unicast to the ONU according to the order determined by the order determining unit. In multiple ONUs connected to the OLT,
When the ONT establishes a communication link based on identification information for identifying the ONU and RTT information indicating a frame round-trip delay time with the ONU, the Register Request signals from the ONU may collide with each other. The communication link establishment order is determined so that there is no ONU side receiving unit that receives the DiscoveryGATE signal transmitted in unicast according to the order;
An ONU comprising: an ONU-side transmitter that transmits a RegisterRequest signal to the OLT when a DiscoveryGATE signal is received by the ONU-side receiver.

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