JP4611171B2 - PON system and communication method thereof - Google Patents

Description

  The present invention relates to a PON system and a communication method thereof, and more particularly to a technique for improving transmission quality using FEC processing and effectively using a transmission band in a GE PON system.

  In the conventional PON system and its communication method, a plurality of ONUs are subordinately connected to one OLT via the PON, and a frame from the OLT is transmitted to all the subordinate ONUs (downlink frames). ). For example, even when the OLT sends a frame addressed to one dependent ONU, that is, a unicast frame, this frame is not only transmitted to this one ONU but also to all ONUs including other ONUs ( Broadcast). Since the destination information is included in the frame, each ONU refers to this destination information, performs reception processing on the frame addressed to itself, and discards the frame not addressed to itself. If the frame from the OLT is a frame addressed to all ONUs, that is, a broadcast frame, all the ONUs receive this frame. When the frame from the OLT is a frame addressed to a predetermined group, that is, a multicast frame, ONUs belonging to this group perform reception processing of this frame, and other ONUs discard this frame.

  Further, in the conventional PON system and its communication method, the transmission quality is improved by restoring the frame using the FEC processing. In the FEC process, an error correction code called an FEC code is added in advance to a frame to be processed and transmitted, so that even if a failure occurs in a part of the frame due to a communication error or the like, it can be restored on the receiving side. To do. An example of a PON system using FEC processing and a communication method thereof is disclosed in, for example, Patent Document 1.

JP 2004-364059 A

  As described above, in the PON system and its communication method, the same frame is transmitted from the OLT to all subordinate ONUs. Therefore, when a frame is a broadcast frame or a multicast frame that is transmitted to a plurality of ONUs at once, a plurality of ONUs that perform reception processing of this frame have an FEC processing function and an FEC processing function. When things that do not have are mixed, or those that require FEC processing and those that do not require FEC processing, there is a problem of how to perform FEC processing.

  IEEE 802.3ah stipulates the application of FEC to the PON system, but there are a mixture of those that have FEC processing functions and those that do not have FEC processing functions in a plurality of ONUs subordinate to one OLT. In this case, control is not defined when there are a mixture of cases that require FEC processing and those that do not require FEC processing. Further, Patent Document 1 describes FEC processing in a case where ONUs that require FEC processing and ONUs that do not require FEC processing are mixed, but the case where the frame is a broadcast frame or a multicast frame is described. No mention is made.

  The present invention has been made to solve these problems, and it is an object of the present invention to provide a PON system capable of appropriately performing FEC processing in a broadcast frame and a multicast frame and a communication method therefor. is there.

  A PON system according to the present invention is a PON system having an ONU group including an OLT and a PON connected to the OLT and a plurality of ONUs connected to the OLT via the PON and subordinate to the OLT. The OLT is an ONU group. When the broadcast frame is transmitted to the ONU group, if all ONUs included in the ONU group are the first ONU having the FEC processing function and needing the FEC processing, the broadcast frame is FEC processed to the ONU group and transmitted collectively. When the first ONU is not included in the ONU group, the broadcast frame is transmitted to the ONU group without performing FEC processing. When the first ONU is partially included in the ONU group, the broadcast frame is transmitted to the ONU group. processing Transmitting a unicast frame having a second same content as the broadcast frame to the ONU obtained by removing a first ONU from the ONU group as well as collective transmission Te.

  A PON system according to the present invention is a PON system having an ONU group including an OLT and a PON connected to the OLT and a plurality of ONUs connected to the OLT via the PON and subordinate to the OLT. The OLT is an ONU group. When the broadcast frame is transmitted to the ONU group, if all ONUs included in the ONU group are the first ONU having the FEC processing function and needing the FEC processing, the broadcast frame is FEC processed to the ONU group and transmitted collectively. When the first ONU is not included in the ONU group, the broadcast frame is transmitted to the ONU group without performing FEC processing. When the first ONU is partially included in the ONU group, the broadcast frame is transmitted to the ONU group. processing Transmitting a unicast frame having a second same content as the broadcast frame to the ONU obtained by removing a first ONU from the ONU group as well as collective transmission Te. Therefore, the transmission quality can be improved as compared with a case where only broadcast frames are collectively transmitted without performing FEC processing. Also, the transmission band can be used more effectively than when only unicast frames are transmitted without performing batch transmission of broadcast frames.

<Embodiment 1>
FIG. 1 is a schematic diagram showing a configuration of a GE (Gigabit Ethernet (registered trademark)) type PON (Passive Optical Network) system 100 according to the first embodiment. As shown in FIG. 1, the PON system 100 includes one OLT (Optical Line Terminal) 10 and eight ONUs (Optical Network Units) 21 to 28 subordinate to the OLT 10 via a PON 30 made of an optical fiber or the like. Consists of connected configurations. The OLT 10 is installed on the telecommunications carrier side, and the ONUs 21 to 28 are installed on each subscriber side. A downstream frame from the OLT 10 to the ONUs 21 to 28 is branched by the optical branching unit 31 of the PON 30. Upstream frames from the ONUs 21 to 28 to the OLT 10 are time-division multiplexed to each TS (Time Slot) in the optical branching unit 31 of the PON 30.

  In FIG. 1, it is assumed that ONUs 21 and 25 have an FEC (Forward Error Correction) processing function and require FEC processing. The ONUs 22 and 26 have FEC processing functions, but FEC processing is not necessary. The ONUs 23 and 27 do not have the FEC processing function, but the FEC processing is necessary. It is assumed that the ONUs 24 and 28 do not have an FEC processing function and do not require FEC processing. Further, the ONUs 21 to 24 constitute a multicast group 20 to which the same multicast frame is transmitted all at once. Hereinafter, with respect to the multicast group 20, a group consisting of all ONUs 21 to 28 subordinate to the OLT 10 is referred to as an ONU group, and the multicast group 20 and the ONU group are collectively referred to as a group. Whether or not FEC processing is necessary in each ONU is determined based on the distance between the ONU and the OLT, the quality of the communication line, and the like.

  FIG. 2 shows a table 40 that represents information about whether each of the ONUs 21 to 28 has an FEC processing function and information about whether each of the ONUs 21 to 28 requires FEC processing. In the following, those that have FEC processing functions and require FEC processing, such as ONUs 21 and 25, are referred to as first ONUs, and others (those that do not have FEC processing functions or do not require FEC processing functions) That is, the ONUs 22 to 24 and 26 to 28) are referred to as second ONUs. In addition, a process in which the ONU normally receives a frame addressed to itself (or to a group to which the ONU belongs) (that is, without discarding it) is referred to as a reception process.

  FIG. 3 is a block diagram showing functions of the OLT 10 shown in FIG. In FIG. 3, a user frame 51 and a control frame 52 generated by the control frame generation unit 12 are input to the frame identification unit 11 as downlink frames. The frame identification unit 11 reads destination information (such as a logical identifier and a MAC address) from the downstream frame and transmits it to the ONU information management unit 13. The ONU information management unit 13 holds in advance information about whether each of the ONUs 21 to 28 has an FEC processing function and information about whether each of the ONUs 21 to 28 requires FEC processing in the form of a table 40 or the like. Data is searched based on this information. Based on the search result from the ONU information management unit 13, the FEC control unit 14 determines for each frame whether or not to perform FEC processing. The speed adjustment unit 15 generates a speed adjustment control signal for inserting an FEC code for FEC processing according to the determination in the FEC control unit 14. The multiplexing unit 16 multiplexes the control frame and the user frame while referring to the speed adjustment signal generated by the speed adjustment unit 15. The frame multiplexed by the multiplexing unit 16 is input to the FEC encoding unit 18 after the TS insertion unit 17 performs TS insertion. The FEC encoding unit 18 performs FEC encoding on the input frame in accordance with information from the multiplexing unit 16 and then outputs the frame.

  Next, a communication method of the PON system 100 of FIG. 1 will be described using the flowchart of FIG.

  In step S1, the OLT 10 identifies the frame type by referring to the destination information in the frame to be transmitted. If the frame to be transmitted is a unicast frame, the process proceeds to step S2, and if it is a broadcast frame or a multicast frame, the process proceeds to step S5.

  In step S2, the OLT 10 refers to the above destination information (the transmission destination is one ONU because it is a unicast frame) and performs a search in the ONU information management unit 13, so that the ONU serving as the transmission destination is the FEC processing function. And whether FEC processing is required (that is, whether it is the first ONU).

  When the ONU that is the transmission destination is not the first ONU (that is, when the transmission destination is the second ONU such as the ONUs 22 to 24 and 26 to 28), the process proceeds to step S3 and the FEC process is not performed. When the ONU that is the transmission destination is the first ONU (that is, when the transmission destination is the ONUs 21 and 25), the process proceeds to step S4 and the FEC process is performed. As a result, it is possible to appropriately perform FEC processing, improve transmission quality, and effectively use the transmission band.

  In step S5, the OLT 10 is set to be addressed to the above destination information (ONU belonging to the ONU group (ie, ONUs 21 to 28 in the broadcast frame), and ONU (ie, ONU 21) belonging to the multicast group 20 in the multicast frame. 24) is set, and the ONU information management unit 13 performs a search, and a group (transmission destination group) that is a transmission destination has an FEC processing function and performs FEC processing. It is determined whether a required ONU (first ONU) exists. In broadcasting, since the transmission destination group is an ONU group, when the first ONU exists in the ONUs 21 to 28, the process proceeds to step S6, and otherwise, the process proceeds to step S7. In multicast, since the destination group is the multicast group 20, if the first ONU exists in the ONUs 21 to 24, the process proceeds to step S6, and otherwise, the process proceeds to step S7 (FIG. 1). In this case, since ONUs 21 and 25 are the first ONUs, the process proceeds to step S6).

  In step S6, the OLT 10 refers to the destination information and performs a search in the ONU information management unit 13 to determine whether all ONUs in the transmission destination group have an FEC processing function and require FEC processing ( That is, whether or not it is the first ONU) is determined. In broadcasting, since the destination group is an ONU group, if all of the ONUs 21 to 28 are first ONUs, the process proceeds to step S8, and otherwise, the process proceeds to step S9. In multicast, since the destination group is the multicast group 20, when all of the ONUs 21 to 24 are the first ONU, the process proceeds to step S8, and otherwise, the process proceeds to step S9. (In FIG. 1, since ONUs 22 to 24 and 26 to 28 are second ONUs, the process proceeds to step S9 for both broadcast and multicast).

  In step S7, since there is no first ONU in the transmission destination group, no FEC processing is performed.

  In step S8, since all the ONUs included in the transmission destination group are the first ONUs, only the FEC process is performed.

  In step S9, since the first ONU is partially included in the transmission destination group, the FEC process is partially performed. That is, FEC processing is performed on the broadcast frame or multicast frame (for batch transmission), and a unicast frame having the same contents as the broadcast frame or multicast frame is generated (multiple copy) (for transmission to the second ONU) ). Hereinafter, the FEC processing in this case will be described in detail.

  In the broadcast, among the ONUs 21 to 28 belonging to the ONU group, the ONUs 22 to 24 and 26 to 28 are second ONUs. Accordingly, the FEC process is performed on the broadcast frame and transmitted collectively (ONUs 21 and 25 perform the reception process), and a unicast frame having the same contents as the broadcast frame is generated, and the ONUs 22 to 24 are not performed without performing the FEC process. , 26 to 28 (ONUs 22 to 24 and 26 to 28 perform reception processing). Thereby, reception processing is performed in all ONUs 21 to 28 belonging to the ONU group.

  In the multicast, among the ONUs 21 to 24 belonging to the multicast group 20, the ONUs 22 to 24 are second ONUs. Accordingly, the FEC process is performed on the multicast frame and transmitted in a batch (ONU 21 performs the reception process), and a unicast frame having the same contents as the multicast frame is generated and sent to each of the ONUs 22 to 24 without performing the FEC process. Transmit (ONUs 22 to 24 perform reception processing). As a result, reception processing is performed in all the ONUs 21 to 24 belonging to the multicast group 20.

  As described above, when the first ONU and the second ONU are mixed in the transmission destination group, the PON system 100 and the communication method according to the present embodiment perform FEC processing on the broadcast frame or the multicast frame and perform batch transmission. Then, the first ONU is subjected to reception processing, and a unicast frame having the same content as the broadcast frame or multicast frame is transmitted without FEC processing, and is received by each second ONU.

  Therefore, it is possible to improve the transmission quality as compared with the case where only the broadcast frame or multicast frame that is not subjected to the FEC process is collectively transmitted.

  In addition, the transmission band can be effectively used as compared with the case where only the transmission of the unicast frame (multiple copy) is performed without performing the batch transmission of the broadcast frame or the multicast frame.

1 is a schematic diagram illustrating a configuration of a PON system according to Embodiment 1. FIG. It is a figure which shows the table showing the information regarding ONU which concerns on Embodiment 1. FIG. 3 is a block diagram illustrating functions of the OLT according to the first embodiment. FIG. 3 is a flowchart illustrating a communication method of the PON system according to the first embodiment.

Explanation of symbols

1 OLT, 11 frame identification unit, 12 control frame generation unit, 13 ONU information management unit, 14 FEC control unit, 15 rate adjustment unit, 16 multiplexing unit, 17 TS insertion unit, 18 FEC encoding unit, 20 multicast group, 21 ~ 28 ONU, 30 PON, 31 optical splitter, 40 tables, 51 user frame, 52 control frame, 100 PON system.

Claims (7)

An OLT (Optical Line Terminal), a PON (Passive Optical Network) connected to the OLT, and an ONU group including a plurality of ONUs (Optical Network Units) connected to the OLT via the PON and subordinate to the OLT A PON system,
In the case where the OLT transmits a broadcast frame to the ONU group,
When all ONUs included in the ONU group are first ONUs having FEC (Forward Error Correction) processing functions and requiring FEC processing, FEC processing broadcast frames to the ONU group and collectively transmitting
When the ONU group does not include the first ONU at all, a broadcast frame is sent to the ONU group without performing FEC processing,
When the first ONU is partially included in the ONU group, the broadcast frame is FEC-processed and transmitted to the ONU group in a batch, and the broadcast is sent to the second ONU formed by removing the first ONU from the ONU group. A PON system that transmits a unicast frame having the same content as a frame. A PON system having an ONU group including an OLT and a PON connected to the OLT and a plurality of ONUs connected to the OLT via the PON and subordinate to the OLT;
The ONU group includes a multicast group including a plurality of ONUs,
In the case where the OLT transmits a multicast frame to the multicast group,
When all ONUs included in the multicast group are first ONUs having FEC processing functions and requiring FEC processing, multicast frames are FEC-processed to the multicast group and collectively transmitted,
When the first ONU is not included in the multicast group, a multicast frame is sent to the multicast group without performing FEC processing,
When the first ONU is partially included in the multicast group, the multicast frame is FEC-processed to the multicast group and transmitted collectively, and the multicast is sent to the second ONU excluding the first ONU from the multicast group. A PON system that transmits a unicast frame having the same content as a frame. The PON system according to claim 1 or 2, wherein
In the case where the OLT transmits a unicast frame to a predetermined ONU,
When the predetermined ONU is the first ONU, a unicast frame is FEC processed and transmitted to the predetermined ONU,
A PON system that transmits a unicast frame to the predetermined ONU without FEC processing when the predetermined ONU is not the first ONU. A PON system according to any one of claims 1 to 3,
The OLT is
An ONU information management unit that holds information about whether each of the plurality of ONUs constituting the ONU group has an FEC processing function and information about whether each of the plurality of ONUs constituting the ONU group requires FEC processing When,
A PON system comprising: an FEC control unit that determines for each frame whether or not to perform FEC processing based on the information held by the ONU information management unit. A communication method of a PON system having an ONU group including an OLT and a PON connected to the OLT and a plurality of ONUs connected to the OLT via the PON and subordinate to the OLT,
When all ONUs included in the ONU group are first ONUs having FEC processing functions and requiring FEC processing, the OLT performs FEC processing of broadcast frames to the ONU group and collectively transmits the ONU group;
When the ONT group does not include the first ONU at all, the OLT transmits a broadcast frame to the ONU group without performing FEC processing;
When the first ONU is partially included in the ONU group, the OLT FEC-processes the broadcast frame to the ONU group and transmits it in a batch, and removes the first ONU from the ONU group. Transmitting a unicast frame having the same content as the broadcast frame to
A communication method for a PON system comprising: A communication method of a PON system having an ONU group including an OLT and a PON connected to the OLT and a plurality of ONUs connected to the OLT via the PON and subordinate to the OLT,
The ONU group includes a multicast group including a plurality of ONUs,
When all ONUs included in the multicast group are first ONUs having an FEC processing function and requiring FEC processing, the OLT performs FEC processing of multicast frames to the multicast group and collectively transmits;
When the OLT does not include the first ONU in the multicast group, the OLT transmits the multicast frame to the multicast group without performing FEC processing; and
When the first ONU is partially included in the multicast group, the OLT FEC-processes the multicast frame to the multicast group and transmits it in a batch and removes the first ONU from the multicast group. Transmitting a unicast frame having the same content as the multicast frame;
A communication method for a PON system comprising: A communication method for a PON system according to claim 5 or 6,
When the predetermined ONU is the first ONU, the OLT FEC-processes and transmits a unicast frame to the predetermined ONU;
Transmitting the unicast frame to the predetermined ONU without FEC processing when the predetermined ONU is not the first ONU;
A PON system communication method further comprising:

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