JP5722827B2 - Optical subscriber line termination device, optical network termination device, and optical network system - Google Patents

Description

  The present invention relates to an optical subscriber line termination device, an optical network termination device, and an optical network system that perform point-to-multipoint communication via an optical fiber transmission line.

  As an economical optical access system, there is a passive optical network (PON). As shown in FIG. 1, a PON is composed of a single optical subscriber line terminal (OLT) 300 and a plurality of optical network unit (ONU) 400 and an optical fiber transmission line 100 and a pair. This is a network that performs point-to-multipoint communication via k optical splitters 200 (k is a natural number). Typical standards for PON include gigabit class 1G-EPON (Ethernet (registered trademark) PON) standardized by IEEE 802.3 and 10 gigabit class 10G-EPON. These are collectively called EPON.

  FIG. 2 shows a functional block diagram of the ONU 400 in EPON. The upstream main signal flows to the PON-IF (PON Interface) port 44 via the UNI (User Network Interface) port 41, the queue management means 42, and the PON signal processing means 43. On the other hand, the downstream main signal flows to the UNI port 41 via the PON-IF port 44, the PON signal processing means 43, and the queue management means 42. The ONU 400 includes a queue for the upstream direction, and includes a queue monitoring unit 45 that monitors the amount of data in the queue. The PON signal processing unit 43 reports the amount of data in the queue to the OLT 300 by a REPORT message, receives an uplink bandwidth allocation result from the OLT 300 by a GATE message, an MPCP (Multi-Point Control Protocol) unit 43a, and the OLT 300 An OAM (Operations, Administration and Maintenance) unit 43b for exchanging control frames for maintenance monitoring is provided.

  FIG. 3 shows a functional block diagram of the OLT 300 in the EPON. The downlink main signal flows to the PON-IF port 31 via the SNI (Service Node Interface) port 34, the queue management means 33, and the PON signal processing means 32. On the other hand, the upstream main signal flows to the SNI port 34 via the PON-IF port 31, the PON signal processing means 32, and the queue management means 33. The PON signal processing unit 32 causes the ONU 400 to report the amount of data in the queue provided in the ONU by the REPORT message, and receives the allocation result of the upstream bandwidth from the ONU 400 by the GATE message and the MPCP unit 32a. The bandwidth allocation unit 32b monitors the amount of data in the queue in the ONU based on the reported message, and allocates the transmission order and the amount of data that can be transmitted to each ONU 400 using a dynamic bandwidth allocation (DBA) algorithm. And an OAM unit 32c for exchanging control frames for maintenance monitoring with the ONU.

  For communication services where the source ONU and destination ONU exist in the same PON, such as smart grid applications and peer-to-peer (P2P) applications, use OLT loopback (between ONUs) without using the core network It is known that end-to-end delay can be reduced by doing so. For example, in Non-Patent Document 1, delay reduction is achieved by using OLT loopback (between ONUs) in an optical wireless hybrid network using a WDM / TDM (Wavelength Division Multiplexing / Time Division Multiplexing) type PON. .

  In particular, it is known that the downlink throughput can be improved by up to 50% by applying the network coding (NC) process in the OLT to the bidirectional flow in the communication between ONUs. Non-Patent Document 2 discusses application forms of NC technology in PON.

  For example, FIG. 4 shows the concept of NC when bidirectional communication is performed between two ONUs connected to the same OLT in a TDM type PON represented by EPON. First, as shown in FIG. 4A, the ONU 1 and the ONU 2 notify the OLT of the amount of data in the queue by a REPORT message. When there is data for performing communication between ONUs, the destination information is also notified to the OLT at the same time. The bandwidth allocation unit of the OLT determines the uplink data transmission time and the bandwidth allocated to each ONU based on the data amount notified from the ONU, and notifies the ONU of such information by a GATE message. When the transmission time comes, ONU1 transmits data f1 addressed to ONU2 to the OLT, and ONU2 transmits data f2 addressed to ONU1 to the OLT.

  Assume that the OLT receives data f1 and data f2 in this order. When the NC process is not applied, as shown in FIG. 4B, the OLT transmits the data f1 that has arrived first to the ONU 2, and then transmits the data f2 to the ONU 1. ONU1 receives data f2 transmitted from ONU2, and ONU2 receives data f1 transmitted from ONU1.

  On the other hand, when the NC processing is applied, as shown in FIG. 4C, when the OLT identifies that the data f1 and the data f2 are two-way communication closed by the PON, the encoding processing is performed using the data f1 and the data f2. I do. For example, an exclusive OR (XOR: eXclusive OR) operation is performed on the data f1 and the data f2. The encoded data f3 output as a result is multicast transferred to ONU1 and ONU2. If the ONU 1 holds the data f1 sent by itself until the data f3 arrives, the data f2 transmitted by the ONU 2 can be decoded by the XOR operation of these data. If the ONU 2 keeps the data f2 sent by itself until the data f3 arrives, the data f1 transmitted by the ONU 1 can be decoded by the XOR operation of these data. In this case, since only the data f3 is multicast in the downlink direction, the downlink bandwidth is reduced by 50% compared to the unicast case. In general, when bidirectional communication is performed between r (r: natural number) ONUs, when the NC processing is performed, the downstream band is (r -1) / r.

  FIG. 5 shows an example of uplink bandwidth allocation in EPON. In a sensor / actuator network, a large amount of data is periodically generated from a terminal at the same time. The generated data is first transmitted to the ONU, and the ONU reports the amount of data in the queue to the OLT by a REPORT message. The OLT collects information related to uplink data from all ONUs for each DBA cycle, and determines an uplink band to be allocated to each ONU by a DBA algorithm in a band allocation unit. The OLT notifies the permitted upstream band by a GATE message. When performing NC processing, if there is data addressed to an ONU connected to the same OLT, information for identifying the destination ONU is written in the REPORT message. For identification of the destination ONU, for example, an LLID (Logical Link Identifier), an IP (Internet Protocol) address, and a MAC (Medium Access Control) address can be used. In the GATE message, an identifier for notifying the ONU whether or not to perform NC processing is written. The ONU decides whether to hold the transmitted data for a certain period of time based on the identifier information. This holding time is set to a value larger than the maximum value of the queuing time in the OLT for performing NC processing. For example, if it is assumed that NC processing is performed only when two-way communication is detected within one DBA cycle, the holding time needs to be set to a value sufficiently larger than the sum of the DBA cycle and the OLT-ONU round-trip transmission delay. is there.

  The bandwidth allocation unit also schedules time slots allocated to each ONU. For example, as shown in FIG. 6, a method of randomly assigning slots to all ONUs is called an RS (Random Scheduling) method. For example, consider performing NC processing only when two-way communication is detected within one DBA cycle. Assuming that the ONU 7 and the ONU 15 are ONUs that transmit a flow to be subjected to NC processing, the data transmitted from the ONU 15 waits for data arrival from the ONU 7 in the OLT. At this time, it is necessary to wait in the OLT for the data transmitted from the ONU 15 by the queuing delay dq. Here, a delay from the beginning of the DBA cycle to the start of NC processing is defined as a scheduling delay ds.

Yan Li, Jiangping Wang, Chunging Qiao, Ashwin Gumaste, Yun Xu, Yinlong Xu, “Integrated fiber-wireless (FiW) access network stakes. 28, no. 5, pp. 714-724, March 2010. Kerim Fouli, Martin Maier, Muriel Medard, "Network coding in next-generation passive networks", IEEE Communications Magazines. 49, no. 9, pp. 38-46, September 2011.

  As described above, since it is necessary to synchronize data in order to apply the NC processing capable of reducing the downlink bandwidth, a problem arises that a queuing delay occurs in the OLT and a large-capacity buffer must be provided. was there.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an OLT that can perform NC processing but eliminates the need for a large-capacity buffer in the OLT and reduces queuing delay. And an optical network system provided with them.

  The present invention reduces the amount of data buffered in the OLT by continuously allocating slots to ONUs (NC group ONUs) that transmit NC flow when allocating uplink transmission slots to each ONU. It was decided.

Specifically, the OLT according to the present invention is an optical subscriber line terminator (OLT) that performs point-to-multipoint communication with a plurality of optical network terminators (ONUs) via an optical fiber transmission line.
A bandwidth allocation unit that allocates a transmission order and a transmittable data amount for each ONU based on a bandwidth request from the ONU, and an NC that performs network coding (NC) processing on data transmitted and received between the ONUs And comprising
The bandwidth allocating unit is characterized in that the transmission order of the ONUs belonging to one NC processing target applied by the NC unit is continued.

  By continuously assigning slots to the NC group ONU, data waiting for communication between ONUs in the OLT can be reduced. For this reason, the buffer amount of the OLT can be reduced, and the queuing delay can be reduced. Therefore, the present invention can provide an OLT that can perform NC processing but eliminates the need for a large-capacity buffer in the OLT and can reduce queuing delay.

  The bandwidth allocating unit of the OLT according to the present invention is characterized in that a transmission order s (s: natural number) is continued in a range of s ≦ n with respect to the ONU belonging to one NC processing target applied by the NC unit. And However, the number of ONUs connected to the OLT is n (n: natural number), and the number of ONUs belonging to one NC processing target performed by the NC unit is r (r: natural number, but belongs to NC processing target) If the ONU does not exist, r = 1).

  When scheduling is performed with n time slots allocated to each ONU as one cycle, the presence / absence of the NC group ONU is confirmed every cycle, and when there is an NC group ONU, the time slots allocated to the ONU are continued. By scheduling in this way, the time slots assigned to each ONU become fair, so that it is possible to ensure the fairness of delay between flows that are subjected to NC processing and flows that are not subjected to NC processing.

  The bandwidth allocation unit of the OLT according to the present invention has a priority m (m: a natural number, r ≦ m ≦ n), and transmits the ONU belonging to one NC processing target applied by the NC unit. The order s is continuous in the range of s ≦ m.

  When NC technology is applied to periodically occurring flows such as sensor data in a control communication network, a time slot that is behind in one cycle is specified by scheduling, and end-to-end delay increases. There was a problem that there was. Therefore, in the present invention, the scheduling delay is reduced by preferentially allocating the slot near the head to the NC group ONU, thereby reducing the end-to-end delay.

  The bandwidth allocation unit of the OLT according to the present invention sets the transmission order s of the ONUs belonging to one NC processing target applied by the NC unit to a (a: a natural number, a ≦ (n−r + 1) or a ≦ ( It may be randomly assigned in the range of r natural numbers that are continuous from m−r + 1)) to a + r−1.

  The bandwidth allocation unit of the OLT according to the present invention may dynamically determine m according to at least one of n and r.

  The bandwidth allocating unit of the OLT according to the present invention is configured such that the priority m is a delay time of a frame transmitted from each ONU, a bandwidth allocated to each ONU, and a bandwidth actually used by each ONU. It may be determined dynamically according to at least one of the following.

  In the present invention, delay fairness can be improved by adaptively determining the priority m according to the number of registered ONUs n, the number of NC group ONUs r, the delay time, and the like.

An ONU according to the present invention is an ONU connected to the OLT,
A message transmission unit for notifying information of the destination ONU to the OLT at the same time as a bandwidth request when there is data addressed to another ONU connected to the OLT;
A restoration unit that holds data scheduled to be subjected to NC processing for a certain period of time and restores data addressed to itself from the data and data subjected to NC processing by the NC unit of the OLT;
It is characterized by providing.

  The optical network system according to the present invention is characterized in that the OLT and the plurality of ONUs are connected in a point-to-multipoint manner via an optical fiber transmission line and communicate with each other.

  By combining with the OLT, it is possible to provide an ONU and an optical network system that can perform NC processing but eliminate the need for a large-capacity buffer in the OLT and reduce queuing delay.

  The present invention can provide an OLT that can perform NC processing but does not require a large-capacity buffer in the OLT and reduce queuing delay, an ONU accommodated in the OLT, and an optical network system including the OLT. .

It is a figure explaining the structure of PON. It is a figure explaining the structure of ONU. It is a figure explaining the structure of OLT. It is a figure explaining the concept of NC. (A) is a figure explaining an upstream signal. (B) is a figure explaining the downstream signal when NC is not applied. (C) is a figure explaining the downstream signal at the time of applying NC. It is the figure which showed the example of the uplink band allocation in EPON. It is the figure which showed the example of the scheduling (RS system) of the time slot allocated to ONU. It is a figure explaining OLT concerning the present invention. It is a figure explaining ONU concerning the present invention. It is the figure which showed the example of the scheduling (GRS system) of the uplink transmission slot which OLT which concerns on this invention performs. It is the figure which showed the example of the scheduling (GPS system) of the uplink transmission slot which OLT which concerns on this invention performs.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  The functions of the OLT and ONU according to the present invention will be described by taking 1G-EPON and 10G-EPON, which are IEEE standard EPONs, as an example.

  A functional configuration example of the OLT 301 of the present embodiment is shown in FIG. The OLT 301 is an OLT that performs point-to-multipoint communication with a plurality of ONUs 401 via the optical fiber transmission line 100. The OLT 301 performs network coding (NC) processing on data transmitted / received between the ONUs 401 and a bandwidth allocation unit 32b that allocates a transmission order and a data amount that can be transmitted for each ONU based on a bandwidth request from the ONUs 401. NC section 35, and band allocation section 32b makes the transmission order of ONUs 401 belonging to one NC processing target performed by NC section 35 continuous.

  The downlink main signal flows to the PON-IF port 31 via the SNI (Service Node Interface) port 34, the queue management means 33, and the PON signal processing means 32. On the other hand, the upstream main signal flows to the SNI port 34 via the PON-IF port 31, the PON signal processing means 32, and the queue management means 33. Further, the ONU communication main signal for performing the loopback communication in the OLT 301 flows through the PON-IF port 31, the PON signal processing means 32, and the queue management means 33, and is buffered until the NC processing is started in the queue management means 33. After the NC processing is performed, it flows to the PON-IF port 31 via the PON signal processing means 32.

  The PON signal processing means 32 reports to the ONU 401 the data amount in the queue provided in the ONU and the information of the destination ONU for communication between the ONUs by the REPORT message, and the GATE signal indicates the result of the upstream bandwidth allocation and the presence or absence of NC processing. The data amount of the queue in the ONU is monitored based on the MPCP unit 32a that notifies the ONU by a message and the report message received from the ONU 401, and the order of transmission and the amount of data that can be transmitted are allocated to each ONU 401 by the DBA algorithm. A bandwidth allocating unit 32b and an NC unit 35 that performs NC processing on communication data between ONUs are provided.

  In the bandwidth allocation unit 32b, an uplink transmission slot is allocated to all ONUs 401 connected to the OLT 301 within one DBA cycle. Further, the NC unit 35 has a function of buffering ONU communication data in the queue management means 33 until the NC processing is started. In the NC processing in the OLT 301, for example, encoding using an XOR operation is performed.

  An example of the functional configuration of the ONU 401 of this embodiment is shown in FIG. When there is data addressed to another ONU 401 connected to the OLT 301, the ONU 401 has a message transmission unit that notifies the OLT 301 of information about the destination ONU 1 at the same time as a bandwidth request, and data that is to be subjected to NC processing. Is stored for a certain period, and the restoration unit restores the data addressed to itself from the data and the data subjected to the NC processing by the NC unit 35 of the OLT 301.

  The upstream main signal flows to the PON-IF port 44 via the UNI port 41, the queue management means 42, and the PON signal processing means 43. On the other hand, the downstream main signal flows to the UNI port 41 via the PON-IF port 44, the PON signal processing means 43, and the queue management means 42. The ONU 401 includes a queue for the upstream direction, and includes a queue monitoring unit 45 that monitors the amount of data in the queue. Further, the queue monitoring unit 45 includes a queue for buffering data scheduled to be subjected to NC processing for a certain period of time.

  The PON signal processing unit 43 reports to the OLT 301 the amount of data in the queue and the information of the destination ONU of the communication between ONUs by a REPORT message, and receives an uplink bandwidth allocation result from the OLT by a GATE message; An NC unit 46 is provided that restores data addressed to its own ONU from data subjected to NC processing in the OLT 301. In the NC process in the ONU 401, for example, decoding using an XOR operation is performed. The message transmission unit corresponds to the MPCP unit 43a, and the restoration unit corresponds to the NC unit 46.

Example 1
When the number of ONUs 401 connected to the OLT 301 is n (n: natural number) and the number of ONUs belonging to one NC processing target applied by the NC unit 35 is r (r: natural number, but there is no ONU belonging to the NC processing target) When r = 1), the bandwidth allocation unit 32b continues the transmission order s (s: natural number) in a range of s ≦ n with respect to ONUs belonging to one NC processing target performed by the NC unit 35.

  In the first embodiment, as illustrated in FIG. 9, the OLT 301 implements a GRS (Grouped Random Scheduling) scheme as a scheduling scheme for uplink transmission slots in the band allocating unit 32 b. Here, the “ONU belonging to one NC processing target performed by the NC unit 35” is an ONU that transmits a flow to be subjected to the NC processing, and hereinafter, the set of the ONU is described as “NC group”. There are things to do. In the GRS system, continuous transmission slots are assigned to ONUs belonging to the NC group. That is, if the number of ONUs connected to the OLT 301 is n (n: natural number), the transmission order s (s: natural number) is continuously assigned to ONUs belonging to the NC group in the range of s ≦ n.

  For example, when three or more ONUs belong to the NC group, the transmission order between the ONUs belonging to the NC group can be arbitrarily determined. Also, the transmission order between the NC group and the non-NC group can be arbitrarily determined. For example, the transmission order is determined randomly. For example, as shown in FIG. 9, when considering a case where ONU 7 and ONU 15 are ONUs belonging to the NC group among the ONUs connected to OLT 301, consecutive slots are assigned to ONU 7 and ONU 15.

平均スケジューリング遅延ｄｓが

となる。ただし、ｒはＮＣグループに属するＯＮＵの数である。一方、ＧＲＳ方式を用いた場合には、平均キューイング遅延ｄｑが

平均スケジューリング遅延ｄｓが

となる。例えば、ｎ＝１６、ｒ＝８、ｐ＝１ｍｓとすると、キューイング遅延ｄｑは、ＲＳ方式の場合４００μｓ程度であるが、ＧＲＳ方式の場合２００μｓ程度となる。 The queuing delay dq in the OLT 301 can be reduced by assigning continuous transmission slots to ONUs belonging to the NC group using the GRS method. For example, assuming that n ONUs 401 are connected to the OLT 301, the DBA cycle is p, and the bandwidth allocated to each ONU 401 is equal, the slot interval s is a constant value p / n. When the RS method is used, the average queuing delay dq is

Average scheduling delay ds is

It becomes. Here, r is the number of ONUs belonging to the NC group. On the other hand, when the GRS method is used, the average queuing delay dq is

Average scheduling delay ds is

It becomes. For example, if n = 16, r = 8, and p = 1 ms, the queuing delay dq is about 400 μs for the RS method, but about 200 μs for the GRS method.

  Further, the scheduling delay ds is about 900 μs in the case of the RS method, but is about 700 μs in the case of the GRS method. As described above, by using the GRS method, the queuing delay dq and the scheduling delay ds can be reduced, and as a result, the buffer capacity of the OLT and the end-to-end delay for the ONU communication data are reduced.

(Example 2)
The bandwidth allocation unit 32b has a priority m (m: natural number, r ≦ m ≦ n), and sets the transmission order s of ONUs belonging to one NC processing target performed by the NC unit 35 to s ≦ m. Continue in a range.

  As shown in FIG. 10, a GPS (Grouped Priority Scheduling) method is implemented as a scheduling method for uplink transmission slots in the bandwidth allocation unit of the OLT. When a set of ONUs that transmit a flow subjected to NC processing is defined as an NC group, in the GPS system, consecutive transmission slots are allocated to ONUs belonging to the NC group, and further before the mth (m: natural number). The transmission slots are assigned so that the transmission order becomes. The priority m is set to be not less than the number of ONUs belonging to the NC group and not more than the number of ONUs connected to the OLT. That is, the transmission order s is assigned to ONUs belonging to the NC group so as to be in the range of s ≦ m.

  For example, for the r ONUs belonging to the NC group, the transmission order s is randomly set within a range of r natural numbers that are continuous from a (a: natural number, a ≦ (m−r + 1)) to a + r−1. Can be assigned. For example, as shown in FIG. 10, in the case of ONUs connected to the OLT, ONU7 and ONU15 are ONUs belonging to the NC group, and ONU7 and ONU15 are continuous to the mth. The previous slot is assigned.

平均スケジューリング遅延ｄｓが

となる。一方、ＧＰＳ方式を用いた場合には、平均キューイング遅延ｄｑが

平均スケジューリング遅延ｄｓが

となる。例えば、ｎ＝１６、ｒ＝８、ｐ＝１ｍｓ、ｍ＝８とすると、キューイング遅延ｄｑは、ＲＳ方式の場合４００μｓ程度であるが、ＧＰＳ方式の場合２００μｓ程度となる。 The queuing delay dq in the OLT can be reduced by assigning continuous transmission slots to ONUs belonging to the NC group using the GRS method. For example, assuming that n ONUs are connected to the OLT, the DBA cycle is p, and the bandwidth allocated to each ONU is equal, the slot interval s is a constant value p / n. When the RS method is used, the average queuing delay dq is

Average scheduling delay ds is

It becomes. On the other hand, when the GPS method is used, the average queuing delay dq is

Average scheduling delay ds is

It becomes. For example, if n = 16, r = 8, p = 1 ms, and m = 8, the queuing delay dq is about 400 μs for the RS system, but about 200 μs for the GPS system.

  Further, the scheduling delay ds is about 900 μs in the case of the RS method, but is about 400 μs in the case of the GPS method. As described above, by using the GPS method, the queuing delay dq and the scheduling delay ds can be reduced. As a result, the buffer capacity of the OLT and the end-to-end delay for the ONU communication data are reduced.

ｍは自然数であるため、仮の優先度ｍ’から優先度ｍを求める。 The priority m can be dynamically determined according to the number n of ONUs connected to the OLT and / or the number r of ONUs belonging to the NC group. For example, when it is desired to improve the delay fairness by making the average scheduling delay of data transmitted from ONUs belonging to the NC group equal to the average scheduling delay of data transmitted from ONUs not belonging to the NC group, the following equation is assumed. The priority m ′ is determined.

Since m is a natural number, the priority m is obtained from the provisional priority m ′.

  The calculation for obtaining the priority m from the provisional priority m ′ may be any of rounding off the decimal point, rounding up the decimal point, and rounding down the decimal point. For example, when n = 16, r = 8, and p = 1 ms, the priority m ′ is 12.5, and the priority m is 13 by rounding off. At this time, the average scheduling delay ds of the data transmitted from the ONU belonging to the NC group is about 600 μs. The average scheduling delay ds of data transmitted from ONUs not belonging to the NC group is also about 600 μs, and the fair scheduling delay is high compared to the average scheduling delay ds when m = 8 is set to about 700 μs. .

ただし、Ｋはゲイン、ｄ１はＮＣグループに属さないＯＮＵから送信されるデータの平均スケジューリング遅延、ｄ２はＮＣグループに属するＯＮＵから送信されるデータの平均スケジューリング遅延である。ゲインＫは任意の実数を設定する。 Further, in addition to the number of ONUs n connected to the OLT and / or the number of ONUs belonging to the NC group, the priority m is assigned to the delay time of the frame transmitted from each ONU and / or to each ONU. It can be determined dynamically according to the bandwidth and / or the bandwidth actually used. For example, even when the amount of uplink bandwidth allocated to each ONU by the bandwidth allocation unit is different, the average scheduling delay of data transmitted from the ONU belonging to the NC group and the data transmitted from the ONU not belonging to the NC group When it is desired to improve the delay fairness by equalizing the average scheduling delay, the provisional priority m ′ is determined by the following equation.

Here, K is a gain, d1 is an average scheduling delay of data transmitted from ONUs not belonging to the NC group, and d2 is an average scheduling delay of data transmitted from ONUs belonging to the NC group. The gain K is set to an arbitrary real number.

  For example, d1 and d2 can be calculated using an exponential moving average. Since m is a natural number, the priority m is obtained from the provisional priority m ′. The calculation for obtaining the priority m from the provisional priority m ′ may be any of rounding off the decimal point, rounding up the decimal point, and rounding down the decimal point.

The following is a summary of the OLT, ONU, and optical network system of this embodiment.
(1)
An OLT in an optical network in which one optical subscriber line termination unit (OLT) performs point-to-multipoint communication with a plurality of optical network termination units (ONUs) via an optical fiber transmission line,
A bandwidth allocation function for allocating the transmission order and the amount of data that can be transmitted for each ONU based on a bandwidth request from the ONU connected to the OLT, and data transmitted and received between the ONUs connected to the OLT It has an encoding function to perform network coding (NC) processing for
The number of ONUs connected to the OLT is n (n: natural number), and the number of ONUs that are going to transmit data to be subjected to NC processing is r (r: natural number, but NC processing is scheduled to be performed). When there is no ONU that is trying to transmit the data of r = 1),
The band allocation function continues the transmission order s (s: natural number) in a range of s ≦ n for r ONUs that are to transmit data scheduled to be subjected to NC processing by the encoding function. OLT characterized by assigning.

(2)
In the OLT described in (1) above,
When the priority is m (m: natural number, r ≦ m ≦ n),
The OLT according to claim 1, wherein the bandwidth allocation function allocates the transmission order s of ONUs that are about to transmit data scheduled to be subjected to NC processing by the encoding function to be in a range of s ≦ m.

(3)
In the OLT described in (2) above,
For r ONUs that are to transmit data scheduled to be subjected to NC processing, the transmission order s is changed to a continuous r from a (a: natural number, a ≦ (m−r + 1)) to a + r−1. An OLT that is randomly assigned within a range of natural numbers.

(4)
In the OLT according to the above (2) to (3),
The bandwidth allocation function dynamically changes the priority m according to the number n of ONUs connected to the OLT and / or the number r of ONUs that intend to transmit data scheduled to be subjected to NC processing. OLT characterized by determining.

(5)
In the OLT according to any one of (2) to (4) above,
The bandwidth allocation function dynamically determines the priority m according to a delay time of a frame transmitted from each ONU and / or a bandwidth allocated to each ONU and / or a bandwidth actually used. Characteristic OLT.

(6)
An ONU connected to the OLT according to any one of (1) to (5) above,
A function of notifying the OLT of information of the destination ONU simultaneously with the bandwidth request when there is data addressed to another ONU connected to the OLT;
An ONU having a decoding function that holds data scheduled to be subjected to NC processing for a certain period and restores data addressed to the ONU from the data and data encoded by the encoding function of the OLT.

(7)
The OLT according to any one of (1) to (5) above and the ONU according to (6) above are connected in a point-to-multipoint manner via an optical fiber transmission line and communicate with each other. A featured optical network system.

(effect)
The OLT, ONU, and optical network system according to the present embodiment continuously slot an ONU (NC group ONU) that transmits a flow to be subjected to NC processing when an uplink transmission slot is assigned to each ONU. Can reduce the queuing delay and end-to-end delay in the OLT. Further, the end-to-end delay can be reduced by preferentially assigning the slot close to the head in the DBA cycle to the NC group ONU. Furthermore, delay fairness between a flow subjected to NC processing and a flow not subjected to NC processing by adaptively determining the order of transmission slots according to the number of registered ONUs, the number of NC group ONUs, delay time, and the like Can be secured.

  In this embodiment, the case of 1G-EPON and 10G-EPON, which are IEEE standard EPONs, has been described. However, other PONs such as B-PON and G-PON, XG-PON conforming to the ITU-T recommendation, It is clear that the present invention can also be applied to a bandwidth allocation unit in WDM / TDM-PON.

31: PON-IF port 32: PON signal processing unit 32a: MPCP unit 32b: bandwidth allocation unit 32c: OAM unit 33: queue management unit 34: SNI port 35: NC unit 41: UNI port 42: queue management unit 43: PON Signal processing means 43a: MPCP section 43b: OAM section 44: PON-IF port 45: queue monitoring means 46: NC section 100: optical fiber transmission line 200: splitter 300, 301: OLT
400, 401: ONU

Claims (8)

An optical subscriber line terminator (OLT) that performs point-to-multipoint communication with a plurality of optical network terminators (ONUs) via an optical fiber transmission line,
A bandwidth allocation unit that allocates a transmission order and a transmittable data amount for each ONU based on a bandwidth request from the ONU;
An NC unit that performs network coding (NC) processing on data transmitted and received between the ONUs;
With
The OLT characterized in that the bandwidth allocating unit makes the transmission order of the ONUs belonging to one NC processing target performed by the NC unit continuous. The number of ONUs is n (n: a natural number), and the number of ONUs belonging to one NC processing target applied by the NC unit is r (r: a natural number, but if there is no ONU belonging to the NC processing target, r = When 1)
2. The bandwidth allocation unit according to claim 1, wherein the transmission order s (s: natural number) is continued in a range of s ≦ n for the ONUs belonging to one NC processing target applied by the NC unit. OLT as described.   The bandwidth allocating unit has a priority m (m: a natural number, r ≦ m ≦ n), and sets the transmission order s of the ONUs belonging to one NC processing target performed by the NC unit to s ≦ m The OLT according to claim 2, wherein the OLT is continuous in a range of.   The bandwidth allocating unit determines the transmission order s of the ONUs belonging to one NC processing target performed by the NC unit from a (a: a natural number, a ≦ (n−r + 1) or a ≦ (m−r + 1)). 4. The OLT according to claim 2, wherein the OLT is randomly assigned within a range of r natural numbers that are continuous up to a + r-1.   5. The OLT according to claim 3, wherein the bandwidth allocation unit dynamically determines m according to at least one of n and r.   The bandwidth allocation unit sets the priority m to at least one of a delay time of a frame transmitted from each ONU, a bandwidth allocated to each ONU, and a bandwidth actually used by each ONU. The OLT according to claim 3, wherein the OLT is dynamically determined according to claim 3, claim 4 quoting claim 3, or claim 5. An ONU connected to the OLT according to claim 1,
A message transmission unit for notifying information of the destination ONU to the OLT at the same time as a bandwidth request when there is data addressed to another ONU connected to the OLT;
A restoration unit that holds data scheduled to be subjected to NC processing for a certain period of time and restores data addressed to itself from the data and data subjected to NC processing by the NC unit of the OLT;
An ONU characterized by comprising:   The one OLT according to any one of claims 1 to 6 and the plurality of ONUs according to claim 7 are connected in a point-to-multipoint manner via an optical fiber transmission line and communicate with each other. A featured optical network system.

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