JP2015192221A - Olt, pon system, program, and communication band allocation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excess uplink data transmission delay from occurring due to dynamic band allocation even if a DBA cycle is longer than a TDM cycle, and further to control reduction in downlink band utilization efficiency even if the DBA cycle is shortened or the number of ONUs subordinate to an OLT has increased.SOLUTION: An OLT comprises: a band allocation amount calculation unit 3 that calculates uplink transmission start timing and the amount of uplink transmission data allocated to each LLID on the basis of an uplink band request per LLID received from each ONU; a gate signal generating unit 5 that generates a single gate message specifying a broadcast LLID as a destination LLID on the basis of the calculated uplink transmission start timing and the amount of uplink transmission data and information on an ONU in connection; and a notification unit 9 that transmits the single gate message to all ONUs in connection per DBA cycle.

Description

  The present invention relates to a technology for allocating an upstream communication band to a subscriber-side terminal device (ONU: Optical Network Unit) constituting a passive optical network (PON) system.

  2. Description of the Related Art Conventionally, a passive optical network (PON) system (hereinafter referred to as a “PON system”) in which a plurality of subscriber connection devices share an optical transmission line is known. FIG. 4 is a diagram showing an outline of the PON system. An OLT (Optical Line Terminal) and each ONU (Optical Network Unit) -1 to ONU-3 are connected by an optical fiber. In downstream Donwstream, a packet with a destination address is transmitted from the OLT to each ONU via the branching device in a time division manner. Each ONU recognizes the destination address and extracts only the packet addressed to itself.

  On the other hand, in Upstream, which is upstream, packets transmitted from each ONU are bundled by the branching device and reach the OLT. Here, if each ONU transmits a packet at random, the packet will collide and interfere with communication. Therefore, the OLT controls the packet transmission timing for each ONU and avoids packet collision. Yes.

  FIG. 5 is a sequence chart showing an operation example of the conventional PON system. The OLT transmits a Gate message notifying the transmission timing of the ONU to each ONU at a DBA (Dynamic Bandwidth Allocation) cycle. First, when the OLT transmits a Gate message to the ONU (Step T1), the ONU transmits a Report message (Step T2). At first, since the upstream data does not reach the ONU, the report is not particularly meaningful. Next, when the OLT transmits a Gate message (step T3) and the ONU transmits a report for notification of transmitting uplink data (step T4), the OLT transmits a Gate message including control information regarding the uplink data. (Step T5). The ONU transmits uplink data according to the Gate message (step T6), and transmits a Report message (step T7). In this manner, packet collision in the upstream is avoided by transmitting and receiving the Gate message and the Report message between the OLT and the ONU.

  For example, Patent Document 1 discloses a technique for reducing communication delay in a PON system. In order to shorten the upstream communication delay from some ONUs, this technology ensures at least a certain fixed bandwidth each time for some ONUs when the OLT allocates bandwidths to subordinate ONUs. The configuration to be assigned to is adopted.

JP 2011-146780 A

  However, in the conventional technique, when the DBA (Dynamic Bandwidth Allocation) cycle is longer than the TDM (Time Division Multiplexing) cycle, an extra uplink data transmission delay due to dynamic band allocation occurs. That is, as shown in FIG. 5, when the ONU receives an uplink data signal immediately after transmitting a Report message to the OLT in Step T2, it next transmits a Report message including a request to transmit the uplink data. In addition, it takes time to receive a Gate message for the Report message from the OLT and transmit uplink data according to the Gate message.

  Such “generation of latency” also occurs in the technique disclosed in Patent Document 1. That is, as shown in FIG. 6, even if there is a transmission timing by fixed band allocation in the ONU, if the upstream data signal (Data # 2) is received by the ONU immediately after the end of the transmission timing, the next transmission is performed. An interval is left until the timing, and “Latency” occurs.

  In the prior art, since a unicast LLID is specified as a destination LLID (Logical Link ID / Logical Link Identifier), it is necessary to transmit Gate messages by the number of logical links for each Grant period. For example, when N ONUs are connected under the OLT and each ONU uses M logical links, as shown in FIGS. 7 and 8, the IEEE 802.3 frame preamble, SFD (Start It is necessary to transmit N × M Gate messages including a frame delimiter), a destination address, a source address, and the like every Grant period. In the example shown in FIG. 7, a maximum of four uplink data transmission slots are designated by one Gate message. For this reason, as the DBA cycle is shortened or the number of ONUs under the OLT is increased, the downlink bandwidth utilization efficiency is lowered.

  The present invention has been made in view of such circumstances, and avoids the occurrence of an extra uplink data transmission delay due to dynamic bandwidth allocation even when the DBA period is longer than the TDM period. Provided are an OLT, a PON system, a program, and a communication bandwidth allocation method capable of reducing a decrease in downlink bandwidth utilization efficiency even when the DBA cycle is shortened or the number of ONUs under LT is increased. For the purpose.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the OLT of the present invention is an OLT (Optical Line Terminal) that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units). Based on an uplink bandwidth request for each LLID (Logical Link ID) received from the ONU, a bandwidth allocation calculation unit for calculating an uplink transmission start timing and an uplink transmission data amount to be assigned to each LLID, and the calculated uplink transmission start timing A Gate signal generation unit that generates a single Gate message that designates a broadcast LLID as a destination LLID based on the amount of uplink transmission data and information of the connected ONU, and the single Gate message is represented by DBA (Dynamic (Bandwidth Allocation) A notification unit that transmits to all connected ONUs every cycle Characterized in that it obtain.

  In this way, a single Gate message specifying the broadcast LLID as the destination LLID is generated, and the single Gate message is transmitted to all connected ONUs every DBA cycle, so the DBA cycle is longer than the TDM cycle. Even if it is long, it avoids the occurrence of extra uplink data transmission delay due to dynamic bandwidth allocation, and even if the DBA cycle is shortened or the number of ONUs under OLT increases, It is possible to reduce a decrease in bandwidth utilization efficiency.

  (2) In the OLT of the present invention, the number of subordinate ONUs is N, the number of logical links used by each ONU is M, and the number of transmission slots allocated in one DBA cycle is assigned to one logical link number. When K is set, the Gate signal generation unit specifies N × M × K uplink data transmission slots in the single Gate message.

  In this way, since N × M × K uplink data transmission slots are designated in a single Gate message, it is not necessary to designate the uplink data transmission slots many times as in the prior art. It is possible to specify in times.

  (3) In the OLT of the present invention, the single Gate message indicates that the destination address is a broadcast address and conforms to the MAC (Media Access Control) frame format defined in IEEE 802.3. Features.

  In this way, the single Gate message has a broadcast address as the destination address and conforms to the MAC (Media Access Control) frame format defined in IEEE 802.3. Without adding, it becomes possible to implement the present invention only by updating the software.

  (4) The PON system according to the present invention includes an OLT (Optical Line Terminal) according to any one of (1) to (3), a plurality of ONUs (Optical Network Units), the OLT, and each ONU. And an optical fiber connecting the two.

  With this configuration, a single Gate message specifying a broadcast LLID as a destination LLID is generated, and a single Gate message is transmitted to all connected ONUs every Grant period, so the DBA period is longer than the TDM period. Even if it is long, it avoids the occurrence of extra uplink data transmission delay due to dynamic bandwidth allocation, and even if the DBA cycle is shortened or the number of ONUs under OLT increases, It is possible to reduce a decrease in bandwidth utilization efficiency.

  (5) The program of the present invention is an OLT (Optical Line Terminal) program that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units). Then, based on an upstream bandwidth request for each LLID (Logical Link ID) received from each ONU, a process of calculating an upstream transmission start timing and an upstream transmission data amount to be assigned to each LLID, and the calculated upstream transmission start A process for generating a single Gate message specifying a broadcast LLID as a destination LLID based on the timing, the amount of uplink transmission data, and information of the ONU being connected, and the single Gate message is converted into a DBA (Dynamic Bandwidth Allocation Allocation). ) Processing to send to all connected ONUs every cycle, and a series of processing And characterized by causing a computer to execute.

  In this way, a single Gate message specifying the broadcast LLID as the destination LLID is generated, and the single Gate message is transmitted to all connected ONUs every DBA cycle, so the DBA cycle is longer than the TDM cycle. Even if it is long, it avoids the occurrence of extra uplink data transmission delay due to dynamic bandwidth allocation, and even if the DBA cycle is shortened or the number of ONUs under OLT increases, It is possible to reduce a decrease in bandwidth utilization efficiency.

  (6) The communication band allocation method of the present invention is applied to a PON (Passive Optical Network) system, and an OLT (Optical Line Terminal) that allocates an upstream communication band to a plurality of ONUs (Optical Network Units). Communication bandwidth allocation method according to claim 1, wherein the uplink transmission start timing and uplink transmission data amount allocated to each LLID are calculated based on an upstream bandwidth request for each LLID (Logical Link ID) received from each ONU; Generating a single Gate message specifying a broadcast LLID as a destination LLID based on the calculated upstream transmission start timing and upstream transmission data amount, and information of the ONU being connected; and the single Gate message, Sending to all connected ONUs every DBA cycle, at least It is characterized by including.

  In this way, a single Gate message specifying the broadcast LLID as the destination LLID is generated, and the single Gate message is transmitted to all connected ONUs every DBA cycle, so the DBA cycle is longer than the TDM cycle. Even if it is long, it avoids the occurrence of extra uplink data transmission delay due to dynamic bandwidth allocation, and even if the DBA cycle is shortened or the number of ONUs under OLT increases, It is possible to reduce a decrease in bandwidth utilization efficiency.

  According to the present invention, even when the DBA period is longer than the TDM period, an extra uplink data transmission delay caused by dynamic bandwidth allocation is avoided, and when the DBA period is shortened, Even when the number of ONUs increases, it is possible to reduce the decrease in downlink bandwidth utilization efficiency.

It is a block diagram which shows schematic structure of OLT applied to the TDM-PON system of this embodiment. It is a flowchart which shows operation | movement of the Gate signal generation part which concerns on this embodiment. It is a figure which shows an example of the Gate message produced | generated by the Gate signal production | generation part. It is a figure which shows the outline | summary of a PON system. It is a sequence chart which shows the operation example of the conventional PON system. It is a sequence chart which shows the operation example of the conventional PON system. It is a figure which shows the conventional Gate message format. 2 illustrates an IEEE 802.3 MAC frame format.

  The present inventors pay attention to the fact that when the DBA cycle is longer than the TDM cycle, an extra uplink data transmission delay due to dynamic bandwidth allocation occurs, and when the DBA cycle is shortened or under the OLT. If the number of ONUs increases, it will be noted that the downstream bandwidth utilization efficiency will decrease, and the Gate message will be rewritten to make the contents uniform for all ONUs, and this will be broadcast and distributed, so that excess uplink data transmission The inventors have found that it is possible to avoid the occurrence of delay and the decrease in downstream bandwidth utilization efficiency, and have come to the present invention.

  That is, the OLT of the present invention is an OLT (Optical Line Terminal) that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units). Based on an uplink bandwidth request for each LLID (Logical Link ID) received from the ONU, a bandwidth allocation calculation unit for calculating an uplink transmission start timing and an uplink transmission data amount to be assigned to each LLID, and the calculated uplink transmission start timing And a Gate signal generation unit that generates a single Gate message that specifies a broadcast LLID as a destination LLID based on the amount of uplink transmission data and information of the ONU that is connected, and the single Gate message for each DBA cycle. And a notification unit that transmits to all ONUs currently connected.

  As a result, the present inventors avoid the occurrence of an extra uplink data transmission delay due to dynamic band allocation even when the DBA period is longer than the TDM period, and further reduce the DBA period. Even when the number of ONUs under the OLT increases, it is possible to reduce the decrease in downlink bandwidth utilization efficiency. Embodiments of the present invention will be specifically described below with reference to the drawings.

  In this embodiment, by specifying a broadcast LLID as the destination LLID, one Gate message is transmitted every Grant period regardless of the number of logical links under the OLT. As a result, it is possible to complete the preamble, SFD, destination address, source address, etc. of the IEEE 802.3 frame that has been transmitted N × M times per Grant period in the past, thereby improving the downstream bandwidth usage efficiency. can do.

  Conventionally, as shown in FIG. 5, up to four uplink data transmission slots are specified by one Gate message, but in this embodiment, N × M × K uplinks are specified by one Gate message. Specify the data transmission slot. Here, K is the number of transmission slots assigned to one logical link in the Grant period. In the present embodiment, by setting “K <4”, it is possible to reduce an extra uplink data transmission delay due to dynamic band allocation as compared with the conventional technique.

  FIG. 1 is a block diagram showing a schematic configuration of an OLT applied to the TDM-PON system of the present embodiment. In the OLT 10, the bandwidth request extraction unit 1 extracts the upstream bandwidth request information for each LLID used by the ONU from the Report signal from each ONU. The bandwidth allocation amount calculation unit 3 calculates the upstream transmission start timing and the upstream transmission data amount assigned to each LLID based on the upstream bandwidth request information. In the connected ONU database (DB) 11, information (ONU number and LLID value used by each ONU) of ONUs connected under the OLT is recorded.

  The Gate signal generation unit 5 generates a Gate message based on the output of the bandwidth allocation amount calculation unit 3 and the information of the connected ONU DB 11. The memory 7 temporarily stores information being processed in the Gate signal generation unit 5. The notifying unit 9 notifies the subordinate ONU of the Gate message generated by the Gate signal generating unit 5.

  FIG. 2 is a flowchart showing the operation of the Gate signal generator according to this embodiment. FIG. 3 is a diagram illustrating an example of a Gate message generated by the Gate signal generation unit. First, the Gate signal generator initializes the memory (step S1), and writes “Destination Address to Number of grants” as “Destination Address = broadcast address” in the memory (step S2). Next, “i = 1” is set (step S3), and “j = 1” is set (step S4). Next, “Target LLID = jth LLID in ONU # 1” is additionally written into the memory (step S5). Then, “Grant #j Start time” and “Grant #j Length” are additionally written in the memory from the result of the bandwidth allocation amount calculation unit (step S6).

  Next, it is determined whether or not “j = number of LLIDs per ONU (M)” (step S7). If not “j = number of LLIDs per ONU (M)”, “j = j + 1” (Step S8), the process proceeds to Step S5. On the other hand, if “j = number of LLIDs per ONU (M)” in step S7, it is determined whether or not “i = number of connected ONUs (N)” (step S9). If it is not “ONU number being connected (N)”, “i = i + 1” is set (step S10), and the process proceeds to step S4. On the other hand, if “i = number of connected ONUs (N)” in step S9, “Pad / Reserved” is additionally written in the memory (step S11), the FCS value is calculated, and is additionally written in the memory. (Step S12) The contents of the memory are set as a Gate message, and SPD to FCS are added to the head to form an IEEE 802.3 MAC frame (LLID = broadcast LLID value) (Step S13), and the process ends.

  Thereby, a Get message as shown in FIG. 3 is generated. By broadcasting this from the OLT to each ONU, it is possible to complete a single notification. As a result, it is possible to avoid the occurrence of “Latency” in uplink data transmission and to eliminate the need to transmit the preamble over and over, thereby improving the efficiency of downlink band utilization.

1 Bandwidth request extraction unit 3 Bandwidth allocation calculation unit 5 Gate signal generation unit 7 Memory 9 Notification unit 10 OLT
11 Connected ONU database

Claims (6)

An OLT (Optical Line Terminal) that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units),
A bandwidth allocation calculation unit that calculates an uplink transmission start timing and an uplink transmission data amount to be allocated to each LLID based on an uplink bandwidth request for each LLID (Logical Link ID) received from each ONU;
A Gate signal generation unit that generates a single Gate message specifying a broadcast LLID as a destination LLID, based on the calculated uplink transmission start timing and uplink transmission data amount, and information of a connected ONU;
An OLT comprising: a notifying unit that transmits the single Gate message to all ONUs connected at every DBA (Dynamic Bandwidth Allocation) period.   When the number of subordinate ONUs is N, the number of logical links used by each ONU is M, and the number of transmission slots allocated in one DBA cycle for one logical link number is K, the Gate signal generator The OLT according to claim 1, wherein N × M × K uplink data transmission slots are designated in the single Gate message.   3. The single Gate message according to claim 1, wherein a destination address is a broadcast address and conforms to a MAC (Media Access Control) frame format defined in IEEE802.3. OLT. An OLT (Optical Line Terminal) according to any one of claims 1 to 3,
Multiple ONUs (Optical Network Units)
A PON (Passive Optical Network) system comprising the OLT and an optical fiber connecting the ONUs. An OLT (Optical Line Terminal) program that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units),
Based on the upstream bandwidth request for each LLID (Logical Link ID) received from each ONU, processing for calculating the upstream transmission start timing and the upstream transmission data amount to be allocated to each LLID;
A process of generating a single Gate message specifying a broadcast LLID as a destination LLID based on the calculated uplink transmission start timing and uplink transmission data amount, and information of the ONU being connected,
A program that causes a computer to execute a series of processes of transmitting the single Gate message to all connected ONUs every DBA (Dynamic Bandwidth Allocation) period. An OLT (Optical Line Terminal) communication band allocation method that is applied to a PON (Passive Optical Network) system and allocates an upstream communication band to a plurality of ONUs (Optical Network Units),
Calculating an uplink transmission start timing and an uplink transmission data amount to be assigned to each LLID based on an uplink bandwidth request for each LLID (Logical Link ID) received from each ONU;
Generating a single Gate message specifying a broadcast LLID as a destination LLID based on the calculated uplink transmission start timing and uplink transmission data amount, and information of the ONU being connected;
Transmitting at least one single Gate message to all connected ONUs every DBA (Dynamic Bandwidth Allocation) period.

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