JP2011176897A - Communication control method, station-side device and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a communication control method capable of avoiding decrease of user bands or increase of delay fluctuation with the execution of discovery procedures. <P>SOLUTION: The present invention relates to a communication control method in the case of implementing discovery procedures as procedures for an OLT 1 to detect an ONU to be newly connected in a PON system. The method includes: a transmission permission signal transmitting step for transmitting, from the OLT 1, a discovery transmission permission signal including mask information designating an individual number of an ONU allowed to respond and matching detection target bits of the individual number; and a registration request signal transmitting step of comparing, by an ONU which is not registered to the OLT 1 yet, the matching detection target bits of the individual number designated by the mask information with its own individual number based on the received transmission permission signal and, when matched, transmitting a registration request signal to the OLT 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a communication control method for executing a discovery procedure in a PON system.

  In a PON (Passive Optical Network) system, when an ONU (Optical Network Unit) that is a subscriber side device is connected, the individual number of the ONU is registered in an OLT (Optical Line Terminal) that is a station side device. Conventionally, the OLT collects the ONU individual number (corresponding to the MAC address in E-PON (Ethernet (registered trademark) PON)) by performing the discovery procedure at an arbitrary timing, and registers it in the OLT database ( Non-patent document 1).

  Further, when collecting the individual number of the ONU, the OLT does not allocate user data in a time zone in which the registration request signal from the ONU is expected to be received. This time zone is called a discovery window. The discovery window needs to be opened for a time that covers the round trip time with the installed ONU. However, if the window is enlarged to cover the round trip time, the usable user bandwidth is reduced.

  In the following Patent Document 1, a fixed delay is set for the ONU when a new ONU is installed, and the bandwidth consumed by the discovery window is saved by detecting the ONU in a narrow discovery window.

  On the other hand, the PON system is a system that provides optical access to subscribers economically by sharing an optical fiber with many subscribers, and the more subscribers that share the optical fiber, the higher the economic effect. Improvements are being made in the direction of further multi-branching and lengthening.

JP 2001-326666 A

IEEE 802.3ah Clause 64 Multi-point MAC Control

  However, in the prior art, for example, when multi-branching is performed in order to increase the number of subscribers sharing an optical fiber, there is a problem that it takes a lot of time to acquire the ONU individual number by executing the discovery procedure. It was. For example, the OLT transmits a transmission permission signal for discovery using a multicast address as a destination. Thereafter, a discovery window for receiving a registration request signal from the ONU is provided so that a user grant is not assigned to an ONU that is in an operating state. On the other hand, the ONU avoids signal collision by transmitting a registration request signal at a random timing within a time slot designated by the OLT when a transmission permission signal is received. On the other hand, by transmitting registration request signals at random timing, collision between ONU transmission signals can be reduced to some extent, but if the number of ONUs increases due to further multi-branching, the collision probability increases and discovery The number of trials increases, and the time required for the ONU to register with the OLT increases. As a result, the service start is delayed.

  Although it is possible to reduce the collision probability by expanding the time slot of the random delay, the expansion of the time slot leads to a decrease in the user band and an increase in delay fluctuation for the ONU transmission signal in the operation state, and as a result It will cause communication quality degradation.

  In the prior art, when the extension is performed to increase the number of subscribers sharing the optical fiber, the round trip time with the near-end ONU and the round trip time with the far-end ONU are reduced. Since it is necessary to provide a discovery window to cover, a larger discovery window is required. As a result, there is a problem that the usable user bandwidth is reduced.

  The present invention has been made in view of the above, and even when further multi-branching and lengthening are implemented in the PON system, the reduction in user bandwidth and the increase in delay fluctuation accompanying the execution of the discovery procedure are achieved. An object is to obtain an avoidable communication control method.

  In order to solve the above-described problems and achieve the object, the present invention provides mask information for the station-side device to specify the individual number of the subscriber-side device that permits the response and the match detection target bit of the individual number. Including a transmission permission signal transmitting step for transmitting a transmission permission signal for discovery, and the subscriber side device before registration in the station side device having the individual number specified by the mask information based on the received transmission permission signal. A registration request signal transmitting step of comparing the bit for coincidence detection with its own individual number and transmitting a registration request signal to the station side device if they match.

  According to the present invention, since the number of subscriber side devices that respond simultaneously can be limited, even when further multi-branching or lengthening is performed, registration request signals can be generated without expanding the discovery window. There is an effect that the probability of collision can be reduced. In addition, since the number of discovery attempts can be reduced by reducing the signal collision probability, it is possible to shorten the time until the service starts.

FIG. 1 is a diagram showing a configuration example of a PON system capable of realizing the communication control method according to the present invention. FIG. 2 is a diagram illustrating an example of a format of a discovery transmission permission signal. FIG. 3 is a diagram illustrating an example of the format of the registration request signal. FIG. 4 is a flowchart illustrating the communication control method according to the first embodiment. FIG. 5 is a diagram illustrating an example of a discovery transmission permission signal. FIG. 6 is a diagram showing an outline of discovery in the second embodiment. FIG. 7 is a diagram illustrating an example of a correspondence between an OLT-ONU distance and an ONU MAC address. FIG. 8 is a flowchart illustrating the communication control method according to the second embodiment. FIG. 9 is a diagram showing an outline of discovery in the third embodiment. FIG. 10 is a flowchart illustrating the communication control method 3 according to the embodiment.

  Embodiments of a communication control method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to these embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a PON system capable of realizing the communication control method according to the present invention. The PON system of FIG. 1 includes an OLT 1, ONUs 10-1 to 10 -N (N = 1, 2,...), And a splitter 50, and the devices are connected by optical cables. The PON system employs wavelength division multiplexing (hereinafter referred to as WDM (Wavelength Division Multiplexing)) and multiplexes and transmits optical signals of a plurality of different wavelengths on an optical cable. Each ONU transmits an upstream burst optical signal having a wavelength λ1 to the OLT 1. The OLT 1 transmits a downstream optical signal having a wavelength λ2 to each ONU.

  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 PON control unit 7, a network I / F unit 8, and a database 9. ing. The WDM unit 2 is an interface compatible with the wavelength division multiplexing method, and transmits and receives optical signals. The TX3 unit performs E / O (Electric / Optical) conversion of the electrical signal output from the MUX unit 5 into an optical signal. The RX unit 4 performs O / E (Optical / Electric) conversion of the optical signal output from the WMD unit 2 into an electrical signal. The MUX unit 5 multiplexes the downlink PON control signal and user data. The DeMUX unit 6 separates the upstream PON control signal and user data. The PON control unit 7 generates a PON control signal and outputs it to the MUX unit 5, and analyzes the PON control signal output from the DeMUX unit 6. The network I / F unit 8 transmits and receives user data. The database 9 stores information related to the ONU in the operational state obtained by executing the discovery procedure, information necessary for executing the discovery procedure, and the like. The operational state refers to a state in which the ONU is connected to the PON system and activated.

  The ONUs 10-1 to 10-N include a WDM unit 11, an RX unit 12, a TX unit 13, a DeMUX unit 14, a MUX unit 15, a PON control unit 16, and a user I / F unit, respectively. 17. The WDM unit 11 is an interface compatible with the wavelength division multiplexing method, and transmits and receives optical signals. The RX unit 12 O / E converts the optical signal output from the WMD unit 11 into an electrical signal. The TX unit 13 E / O converts the electrical signal output from the MUX unit 15 into an optical signal. The DeMUX unit 14 separates the downstream PON control signal from the user data. The MUX unit 15 multiplexes the uplink PON control signal and user data. The PON control unit 16 generates a PON control signal and outputs it to the MUX unit 15 and analyzes the PON control signal output from the DeMUX unit 14. The user I / F unit 17 transmits and receives user data.

  FIG. 2 is a diagram illustrating an example of a format of a discovery transmission permission signal generated by the PON control unit 7 of the OLT 1. In this example, a discovery transmission permission signal is defined in a GATE message defined by IEEE 802.3ah. “Destination Address” (hereinafter referred to as “destination address”) 301 is an ONU individual number, and in IEEE 802.3ah, the MAC address of the ONU is set. Furthermore, in this embodiment, “Address Mask (hereinafter, address mask)” 302 is defined in the GATE message. The PON control unit 7 of the OLT 1 designates an ONU that permits transmission of a registration request signal using the destination address 301 and the address mask 302.

  FIG. 3 is a diagram illustrating an example of a format of a registration request signal generated by the PON control unit 16 of the ONU. In this example, a registration request signal is defined in a RegisterRequest message defined by IEEE 802.3ah. “Source Address” (hereinafter referred to as source address) 401 is its own individual number, and sets the MAC address of the ONU as described above. The PON control unit 16 of the ONUs 10-1 to N receives the discovery transmission permission signal shown in FIG. 2, and notifies the OLT 1 of the own individual number with the registration request signal shown in FIG. 3 when the conditions are matched. When the registration request signal is normally received, the OLT 1 stores the ONU individual number and other information in the database 9.

  Next, the communication control method of the first embodiment will be described in detail with reference to the drawings. FIG. 4 is a flowchart showing the operation of the ONU. First, the ONU checks whether or not a discovery transmission permission signal has been received (step S1). When the discovery transmission permission signal is received (step S1: Yes), the PON control unit 16 determines whether the received signal is unicast transmission based on the value of the destination address 301 (step S2). For example, in the case of unicast transmission (step S2: Yes), the destination address 301 and the address mask 302 are referred to, and the value of the bit position specified by the address mask 302 is checked against its own MAC address. (Step S3).

  When the designated bit in the destination address 301 matches the own MAC address in the process of step S3 (step S3: Yes), the ONU PON control unit 16 sets its own MAC address to the source address 401. Is created and transmitted to the OLT 1 as a registration request signal (step S4). At this time, transmission may be performed with a random delay conventionally performed.

  If it is determined in step S2 that the transmission is multicast transmission (step S2: No), the PON control unit 16 of the ONU transmits a registration request signal to the OLT 1 according to a conventional procedure (step S4). In addition, when the process does not match in the process of step S3 (step S3: Yes), the PON control unit 16 of the ONU repeatedly executes the process of steps S1 to S3 until they match.

  On the other hand, the PON control unit 7 of the OLT 1 that has received the registration request signal determines that the ONU having the MAC address set in the source address 401 is in the operating state and registers it in the database 9.

  FIG. 5 is a diagram illustrating an example of a discovery transmission permission signal in a case where transmission of a registration request signal is permitted to an ONU whose least significant bit of the MAC address is “0”. For example, when permitting transmission of a registration request signal only to an ONU having the least significant bit of the MAC address “0”, the OLT 1 sets only the least significant bit of the address mask 302 to “1” as shown in FIG. A discovery transmission permission signal instructing a match search of only the least significant bit is transmitted to the ONU. Only the ONU for which the match of the least significant bit is confirmed transmits a registration request signal to the OLT 1. In the figure, x is an arbitrary value of 0 or 1. In FIG. 5, the case of instructing the search for matching the least significant bit is described. However, the present invention is not limited to this, and a search for matching more bits may be instructed. As a result, the number of collisions can be further reduced.

  As described above, in this embodiment, when transmitting the discovery transmission permission signal in the PON system, a part of the ONU individual number is masked. As a result, the number of ONUs that respond simultaneously can be limited, so that the probability of registration request signals colliding with each other without expanding the discovery window can be reduced even when further multi-branching or lengthening is implemented. Can do. In addition, since the number of discovery attempts can be reduced by reducing the signal collision probability, it is possible to shorten the time until the service starts.

  In this embodiment, the ONU's individual number and address mask are included in the transmission permission signal for discovery to limit simultaneously responding ONUs. However, without specifying the ONU's individual number, The bit value may be directly specified in the address mask. In this embodiment, the individual number of the ONU is a MAC address, but a serial number, a manufacturing number, or the like may be used.

Embodiment 2. FIG.
In the first embodiment, a part of the ONU individual number is masked and the number of ONUs that can respond at the same time is limited to avoid collision between registration request signals without expanding the discovery window. In this embodiment, by associating the ONU's individual number and the distance between OLT and ONU, even if the extension is further extended, registration request signals from the ONU can be received without expanding the discovery window. And Note that the PON system of the present embodiment has the same configuration as that of FIG. 1 of the first embodiment described above.

  FIG. 6 is a diagram showing an overview of discovery in the present embodiment. Here, as an example, it is assumed that the ONUa-OLT distance is short (no discovery window offset) and the ONUb-OLT distance is long (discovery window offset). For example, when searching for a newly connected ONU, OLT does not provide a discovery window that covers the distance to all ONUs, but uses a narrow discovery window to perform discovery for short distances and discovery for long distances. Implement separately. When performing discovery for short distance, set the discovery window so that ONUb at a long distance does not react. When performing discovery for long distance, set the discovery window so that ONUa at a short distance does not react. Set.

  FIG. 7 is a diagram illustrating an example of a correspondence between an OLT-ONU distance and an ONU MAC address. Here, the 4 bits of BIT7 to BIT4 in the fourth octet correspond to the distance from the OLT. That is, when the distance from the OLT is “0 to 10 km”, the 4 bits of BIT7 to BIT4 of the fourth octet of the MAC address are set to “0000”. Similarly, when the distance from the OLT is “10 to 20 km”, “20 to 30 km”, and “30 to 40 km”, the 4 bits of BIT7 to BIT4 of the fourth octet are set to “0001” and “0010”, respectively. , “0011”. Also, here, 4 bits of the address mask corresponding to 4 bits of BIT 7 to BIT 4 of the fourth octet of the MAC address are set to “1111”, and an ONU that permits transmission of the registration request signal is designated. In the figure, x is an arbitrary value of 0 or 1. The correspondence relationship is not limited to this, and other bit ranges and other bits may be associated with each other.

  Next, the communication control method according to the second embodiment will be described in detail with reference to the drawings. FIG. 8 is a flowchart showing the operation of the OLT.

  First, the PON control unit 7 of the OLT 1 searches for an ONU whose distance from itself is in the range of 0 to 10 km (step S11). Specifically, the MAC address (fourth octets b7 to b4 = 0000) corresponding to 0 to 10 km in FIG. 7 is set as the destination address, the discovery window offset is set to 0 μs, and the discovery window width is set to 100 μs. A transmission permission signal is transmitted.

  Thereafter, the PON control unit 7 of the OLT 1 checks the presence / absence of a registration request signal sent from the ONU side as a response to the process of step S11 (step S12). For example, when a registration request signal is received (step S12: Yes), the PON control unit 7 of the OLT 1 determines that the ONU having the MAC address set as the source address is in the operating state and registers it in the database 9. (Step S19).

  In the processing of steps S11 and S12, when registration of all ONUs existing in the range of 0 to 10 km is completed and registration request signals cannot be received (step S12: No), the PON control unit 7 of the OLT 1 Next, an ONU existing in a range of 10 to 20 km from itself is searched (step S13). Specifically, the MAC address (fourth octets b7 to b4 = 0001) corresponding to 10 to 20 km of FIG. 7 is set as the destination address, the discovery window offset is set to 100 μs, and the discovery window width is set to 100 μs. A transmission permission signal is transmitted.

  Thereafter, the PON control unit 7 of the OLT 1 checks whether or not there is a registration request signal sent from the ONU side as a response to the process of step S13 (step S14). For example, when a registration request signal is received (step S14: Yes), the PON control unit 7 of the OLT 1 determines that the ONU having the MAC address set as the source address is in the operating state and registers it in the database 9. (Step S19).

  In the processing of steps S11 to S14, when registration of all ONUs existing in the range of 0 to 20 km is completed and registration request signals cannot be received (step S14: No), the PON control unit 7 of the OLT 1 Next, an ONU existing in a range of 20 to 30 km from itself is searched (step S15). Specifically, the MAC address (fourth octets b7 to b4 = 0010) corresponding to 20 to 30 km in FIG. 7 is set as the destination address, the discovery window offset is set to 200 μs, and the discovery window width is set to 100 μs. A transmission permission signal is transmitted.

  Thereafter, the PON control unit 7 of the OLT 1 checks the presence / absence of a registration request signal sent from the ONU side as a response to the process of step S15 (step S16). For example, when a registration request signal is received (step S16: Yes), the PON control unit 7 of the OLT 1 determines that the ONU having the MAC address set as the source address is in an operating state and registers it in the database 9. (Step S19).

  In the process of steps S11 to S16, when registration of all ONUs existing in the range of 0 to 30 km is completed and the registration request signal cannot be received (step S16: No), the PON control unit 7 of the OLT 1 Next, an ONU existing in a range of 30 to 40 km from itself is searched (step S17). Specifically, the MAC address (fourth octets b7 to b4 = 0011) corresponding to 30 to 40 km in FIG. 7 is set as the destination address, the discovery window offset is set to 300 μs, and the discovery window width is set to 100 μs. A transmission permission signal is transmitted.

  Thereafter, the PON control unit 7 of the OLT 1 checks the presence / absence of a registration request signal sent from the ONU side as a response to the process of step S17 (step S18). For example, when a registration request signal is received (step S18: Yes), the PON control unit 7 of the OLT 1 determines that the ONU having the MAC address set as the source address is in the operating state and registers it in the database 9. (Step S19).

  Thereafter, the PON control unit 7 of the OLT 1 periodically and repeatedly performs the operation (No in step S18) until the registration of all ONUs existing in the range of 0 to 40 km is completed in the processes in steps S11 to S18. .

  In the above example, the ONU search is performed in order of increasing distance from the OLT 1, but the search may be performed in a different order. The width of the discovery window is not limited to this.

  As described above, in this embodiment, the ONU individual number and the distance between the OLT and the ONU are associated with each other, and the OLT registers an ONU existing in a specific distance range by one discovery, The entire distance range was covered with a narrow discovery window while shifting the start timing of the discovery window. As a result, the discovery window can be prevented from expanding even when the extension is further extended.

Embodiment 3 FIG.
In Embodiments 1 and 2, the method of limiting ONUs that can respond when the OLT registers ONUs has been described. In this embodiment, the round trip time of the ONU in which discovery has been performed is retained, and the discovery window is set based on the retained time for the ONU in which discovery has been performed once. Note that the PON system of the present embodiment has the same configuration as that of FIG. 1 of the first embodiment described above.

  In the present embodiment, for example, as shown in FIG. 9, the OLT 1 performs two types of discovery. One is an initial discovery for detecting an ONU that has never registered an individual number. The other is to detect ONUs that have been discovered in the past and have their individual numbers registered, but are once in a non-operational state, such as when the power is turned off. Discovery after registration.

  FIG. 9 is a diagram showing an outline of discovery in the present embodiment. In the first discovery, the destination address is multicast, and the discovery window width is Wmax, which is a size that can cover the registration request signal from the farthest end ONU-x. When the registration request signal is received by this initial discovery, the OLT 1 holds the ONU-x individual number and the round trip time (RTTx) in the database 9. In addition, the OLT 1 performs discovery after registration for the ONU-x that is in a non-operational state after the initial discovery is performed. Here, a transmission permission signal for discovery in which the MAC address of the ONU-x is set as the destination address is transmitted. In addition, the discovery window when performing discovery after registration is a narrow window width with a margin D before and after the round trip time (RTTx) held in the database 9.

  Next, the communication control method 3 according to the embodiment will be described in detail with reference to the drawings. FIG. 10 is a flowchart showing the operation of the OLT.

  First, the PON control unit 7 of the OLT 1 starts an initial discovery (step S31). Specifically, first, the discovery transmission permission signal is transmitted with the destination address as a multicast address, the discovery window offset as 0 μs, and the discovery window width as Wmax (μs).

  Next, the PON control unit 7 of the OLT 1 checks the presence / absence of a registration request signal sent from the ONU side as a response to the process of step S31 (step S32). For example, if there is a registration request (step S32: Yes), the ONU having the MAC address set as the source address is determined to be in the operating state and registered in the database 9 (step S33). Further, the round trip time (RTT) of the ONU is registered in the database 9 (step S33).

  After completion of the registration process in step S33 or when there is no registration request in the process of step S32 (step S32: No), the PON control unit 7 of the OLT 1 is next registered from the database 9 and is in a non-operating state. Search for ONUs (step S34). When the corresponding ONU is searched (step S34: Yes), the PON control unit 7 of the OLT 1 performs discovery after registration for the searched ONU (step S35). Here, the destination address is the MAC address of the searched ONU (designated ONU), the discovery window start offset is “designated ONU RTT-D (μs)”, and the margin for providing the discovery window width before and after the RTT A transmission permission signal for discovery is transmitted as a total of 2D (μs) of D.

  Next, the PON control unit 7 of the OLT 1 checks the presence / absence of a registration request signal sent from the designated ONU as a response to the process of step S35 (step S36). For example, if there is a registration request (step S36: Yes), the database 9 is updated by determining that the operation state has been reached again (step S37). Thereafter, the PON control unit 7 of the OLT 1 periodically repeats the operations of steps S31 to S37.

  If the corresponding ONU is not searched in step S34 (step S34: No), or if there is no registration request in step S36 (step S36: No), the PON control unit 7 of the OLT 1 again performs the first time. Transition to the discovery process.

  As described above, in the present embodiment, the round trip time of the ONU once discovered is stored. In addition, when performing discovery again for an ONU that has been in a non-operational state after discovery has been performed once, the minimum necessary discovery window will be opened based on the previously stored round trip time. . As a result, the bandwidth consumed for the discovery window can be significantly reduced.

  In the present embodiment, the case where the initial discovery and the discovery after registration are alternately performed has been described. However, either frequency may be increased. In addition, when discovery after registration fails for a predetermined number of times, it may be determined that the ONU has stopped and deleted from the database.

  As described above, the communication control method according to the present invention is useful for a PON system, and is particularly suitable as a communication control method when implementing multi-branching or lengthening in a PON system.

1 OLT
2 WDM part 3 TX part 4 RX part 5 MUX part 6 DeMUX part 7 PON control part 8 Network I / F part 9 Database 10-1 to 10-N ONU
11 WDM section 12 RX section 13 TX section 14 DeMUX section 15 MUX section 16 PON control section 17 User I / F section 50 Splitter

Claims (5)

In the PON system, a communication control method for performing a discovery procedure, which is a procedure for detecting a subscriber side device to which a station side device is newly connected,
The station-side device transmits a transmission permission signal for discovery including a multicast address that permits responses from all subscriber-side devices, and can receive registration request signals from all subscriber-side devices. A first discovery step for setting a discovery window in the band;
A registration request signal transmission step in which the subscriber side device before registration to the station side device transmits a registration request signal as a response to the received transmission permission signal;
The station side device that has received the registration request signal holds the individual number and round trip time of the subscriber side device that has transmitted the registration request signal;
The station-side device transmits a transmission permission signal including the individual number of the subscriber-side device that has been in a non-operational state once discovery has been performed, and further, at the round trip time held in the past discovery. A second discovery step for setting a discovery window in a time zone in which a registration request signal from the subscriber side device can be received,
The communication control method characterized by including. The second discovery step is repeatedly executed a predetermined number of times, and when there is no response from the non-operating subscriber side device, the held individual number and round trip time of the subscriber side device are deleted. The communication control method according to claim 1, wherein: In the PON system, a station side device that performs a discovery procedure that is a procedure for detecting a newly connected subscriber side device,
A station-side PON control means for generating and transmitting a transmission permission signal for discovery;
When receiving a registration request signal from a subscriber side device before registration that has received the transmission permission signal, holding means for holding the individual number and round trip time of the subscriber side device that has transmitted the registration request signal;
With
The station PON control means is
A discovery transmission permission signal including a multicast address that allows responses from all subscriber side devices is transmitted, and a discovery window is set in a time zone in which registration request signals from all subscriber side devices can be received. A first discovery function to
Transmits a transmission permission signal including the individual number of a subscriber side device that has been in a non-operating state after discovery has been performed, and further, the subscriber side device based on the round trip time held in the past discovery A second discovery function for setting a discovery window in a time zone in which a registration request signal from can be received;
A station side device characterized by comprising: The second discovery function is repeatedly executed a predetermined number of times, and when there is no response from the non-operating subscriber side device, the held individual number and round trip time of the subscriber side device are deleted. The station side apparatus according to claim 3, wherein The station side device according to claim 3 or 4,
When not registered in the station side device, a subscriber side device that transmits a registration request signal as a response to the received transmission permission signal; and
A communication system comprising:

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