JP6665911B1 - Master station device, wavelength assignment device, wavelength assignment program, wavelength assignment method, and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assign each scheduling information of a plurality of other systems on a wavelength axis to improve the uplink delay time and the power saving effect. A master station apparatus (OLT1) includes wavelength allocation processing means for allocating wavelengths for accommodating other systems based on scheduling information collected from a plurality of connected other systems, and the wavelength allocation processing means Based on the scheduling information, the similarity calculation unit that calculates the similarity of the uplink transmission period between other systems, and based on the similarity of the uplink transmission period between other systems, group the other systems by hierarchical cluster analysis. A cluster analysis unit that determines the number of used wavelengths according to the number of groups based on the hierarchical cluster analysis result, and assigns a used wavelength to each group obtained by the hierarchical cluster analysis result A wavelength allocation unit. [Selection diagram] Fig. 1

Description

  The present invention relates to a master station device, a wavelength assignment device, a wavelength assignment program, a wavelength assignment method, and an optical communication system.

  For example, in a fifth generation mobile communication system (5G), application of a PON (Passive Optical Network) system to a fronthaul is considered. Also, on 5G, it has been considered to configure and operate a system for each service on a virtual network. Therefore, unlike the conventional FTTH, in the PON system, it is assumed that various systems and virtual networks such as a wireless system and an IoT network are connected through an upper system and / or a lower system.

  When these various systems and virtual networks are connected to the PON system, it may not be necessary to calculate the required amount of uplink data in the PON system as in the related art. For example, there are wireless scheduling and data periodically transmitted by an IoT (Internet of Things) device. As an example of wireless communication, in LTE, scheduling is determined on the wireless system side 4 ms before uplink data transmission. When an IoT network is connected, the server on the cloud determines the uplink transmission cycle of the IoT device and the like.

  As described above, when the start time and the data amount of the uplink data passing through the PON section are known in advance outside the PON system, that is, when the scheduling information is known, the optical line terminal (OLT; Optical Line Terminal) sets them up. The data transmission start time in the PON section can be calculated based on the information.

  Here, if the scheduling information is known as described above, another system (such as a BBU or an IoT infrastructure system on the cloud) connected to the PON has determined the scheduling. It is desirable to transmit uplink data.

  However, even when the scheduling information is known, in the bandwidth allocation that calculates the bandwidth on the PON system side using a general report, it takes time to exchange the control message of Report and Gate, and the time is scheduled according to the time scheduled by another system. It is difficult to transmit uplink data, and a technology for reducing delay (in a PON section) is required for uplink.

  Therefore, as in Non-Patent Document 1 and Patent Document 1, techniques for reducing delay in a case where scheduling information is known, such as determining a Gate using a schedule of another system connected to the PON system, have been developed. .

JP 2017-50775 A JP-A-2005-50667

Go Yazawa et al., NTT Access Service Systems Laboratories, "Low-latency technology for applying TDM-PON to mobile fronthaul", IEICE Technical Report, IEICE Transactions, 2013, B- 8-38, PP.51-56

  However, since the techniques described in Non-Patent Document 1 and Patent Document 1 are techniques for reducing delay within one wavelength, when the transmission time of an uplink signal is received between other systems, the uplink signal of either system is It is necessary to shift the transmission time on the time axis, and there is a problem that an uplink delay time occurs.

  Therefore, the present invention proposes a master station apparatus, a wavelength allocating apparatus, a wavelength allocating program, and a wavelength allocating method for allocating scheduling information of a plurality of other systems on a wavelength axis to improve an uplink delay time and improve a power saving effect. , And an optical communication system.

In order to solve this problem, a master station device according to a first aspect of the present invention provides a master station device that optically communicates with a plurality of slave station devices at an assigned wavelength by: (1) requesting from each of a plurality of other systems to be connected; Scheduling information collecting means for collecting the assigned scheduling information; (2 ) wavelength allocation processing means for allocating wavelengths accommodating each other system; and (3) each wavelength allocated by the wavelength allocation processing means, Wavelength switching processing means for notifying the station apparatus and switching the wavelength, wherein the wavelength allocation processing means (2-1) determines a service between services provided by the other systems based on the scheduling information collected from the other systems . A similarity calculation unit that calculates the similarity of the uplink transmission period, which is the degree of overlap of the uplink signal transmission time, and (2-2) the similarity calculation unit that calculates the similarity between the other systems. (2-3) A cluster analysis unit that groups a plurality of other systems in ascending order of the similarity value of the transmission period, and determines the number of wavelengths used according to the number of groups grouped by the cluster analysis unit. a used wavelength number calculation unit, and having a (2-4) with respect to the grouped respective groups, the wavelength allocation unit for allocating a wavelength used.

According to a second aspect of the present invention, there is provided a wavelength assignment apparatus, in an optical communication system in which a master station apparatus and a plurality of slave station apparatuses optically communicate with each other at an assigned wavelength, scheduling information requested from each of a plurality of other connected systems. A wavelength allocating device for allocating a wavelength accommodating each other system based on the above , and (1) overlapping of uplink signal transmission times between services provided by the other systems based on each scheduling information collected from each other system. a similarity calculation means for calculating the similarity of the uplink transmission period is the degree, (2) a plurality of other systems in the ascending order of the similarity values of the uplink transmission period between calculated other systems similarity calculation means and cluster analysis means for grouping, (3) cluster analysis means used wavelength number calculation to determine the used wavelength number corresponding to the number of groups grouped by Means for each group (4) grouping, characterized in that it comprises a wavelength assignment means for assigning wavelength used.

In an optical communication system in which a master station device and a plurality of slave station devices optically communicate at an assigned wavelength, scheduling information requested by each of a plurality of other connected systems is provided. A wavelength allocation program for allocating a wavelength accommodating each other system based on the above-mentioned method, comprising the steps of: (1) transmitting an uplink signal between services provided by the other systems based on each scheduling information collected from each other system; multiple and similarity calculation means for calculating the similarity of the uplink transmission period is a degree of overlapping time, (2) having a small value of the similarity of the uplink transmission period between other systems calculated in the similarity calculation means sequentially and cluster analysis means for grouping the other system, used in accordance with the number of groups grouped by (3) cluster analysis means A wavelength number calculation unit used to determine the length number, and wherein (4) the relative grouped each group to function as a wavelength assignment means for assigning wavelength used.

A wavelength assignment method according to a fourth aspect of the present invention is the optical communication system in which the master station device and the plurality of slave station devices perform optical communication at the assigned wavelengths, and the scheduling information requested by each of the plurality of other connected systems. A wavelength allocation method for allocating a wavelength accommodating each other system based on the above, wherein: (1) the similarity calculating means calculates a service between services provided by the other systems based on the scheduling information collected from the other systems; (2) The cluster analysis unit calculates the similarity of the uplink transmission period between the other systems, which is calculated by the similarity calculation unit, with a small value. A plurality of other systems are grouped in ascending order, and (3) the number-of-used-wavelength calculating means calculates the used wavelength according to the number of groups grouped by the cluster analysis unit. Determines, (4) wavelength assignment means for grouped each group, and allocates the operating wavelength.

An optical communication system according to a fifth aspect of the present invention is an optical communication system including one master station device and a plurality of slave station devices that optically communicate with the master station device at any wavelength. (1) scheduling information collecting means for collecting scheduling information requested from each of a plurality of other systems connected to the optical communication system; (2) wavelength allocation processing means for allocating a wavelength accommodating each other system; (2) wavelength switching processing means for notifying each wavelength assigned by the wavelength allocation processing means to each corresponding slave station device, wherein the wavelength allocation processing means (2-1) each wavelength collected from each other system based on the scheduling information, a similarity calculation unit which calculates the similarity of the uplink transmission period is a degree of overlapping of the uplink signal transmission time between services other system provides, (2- ) And cluster analysis unit for grouping a plurality of other systems in the ascending order of the value of the similarity of the uplink transmission period between other systems calculated in the similarity calculation unit, the grouping (2-3) cluster analysis unit has been the use wavelength number calculation unit uses to determine the number of wavelengths corresponding to the number of groups, and having a (2-4) with respect to the grouped respective groups, the wavelength allocation unit for allocating a wavelength used .

  ADVANTAGE OF THE INVENTION According to this invention, it can allocate each scheduling information of several other systems by a wavelength axis, can improve an uplink delay time and can improve the power saving effect.

FIG. 1 is a configuration diagram illustrating an overall configuration of an optical access system and a functional configuration of an OLT according to an embodiment. FIG. 4 is an explanatory diagram illustrating an example of scheduling information requested by a plurality of other systems to a PON system. FIG. 3 is an explanatory diagram illustrating a basic concept of setting scheduling information on a wavelength axis according to the embodiment. FIG. 4 is an explanatory diagram illustrating an overall flow of a wavelength / bandwidth assignment process according to the embodiment. 5 is a flowchart illustrating an entire process of a wavelength / band allocation process in the OLT according to the embodiment. 6 is a flowchart illustrating an operation of a wavelength allocation process in a wavelength allocation processing unit according to the embodiment. FIG. 9 is an explanatory diagram illustrating calculation of a similarity between services according to the embodiment. FIG. 11 is an explanatory diagram illustrating calculation of a similarity based on a relationship between scheduling information of a plurality of virtual NWs according to the embodiment. FIG. 9 is an explanatory diagram illustrating a process of a hierarchical cluster analysis according to the embodiment. It is an explanatory view showing a processing result of a hierarchical cluster analysis concerning an embodiment. It is a flowchart which shows the confirmation process of the bandwidth amount in the hierarchical cluster analysis which concerns on embodiment. FIG. 3 is an explanatory diagram for explaining an influence of overhead related to wavelength switching in the embodiment (part 1). FIG. 9 is an explanatory diagram illustrating an influence of overhead related to wavelength switching in the embodiment (part 2). 9 is a flowchart illustrating a process for determining a wavelength assigned to each cluster according to the embodiment.

(A) Main Embodiment Hereinafter, embodiments of a master station device, a wavelength assignment device, a wavelength assignment program, a wavelength assignment method, and an optical communication system according to the present invention will be described in detail with reference to the drawings.

(A-1) Basic Concept First, the basic concept of the wavelength assignment processing according to this embodiment will be described with reference to FIGS.

  For example, it is assumed that the PON system is connected to one or more other systems or virtual networks (hereinafter, referred to as “other systems”) as an upper system or a lower system. For example, another system transmits and receives a data signal using a PON system to provide a service.

  It is assumed that another system is scheduled for an uplink data transmission period, and requests the PON system for its scheduling information (that is, the uplink data transmission period).

  FIG. 2 is an explanatory diagram illustrating an example of scheduling information requested by a plurality of other systems to the PON system.

  In FIG. 2, the network provided by the PON system for each other system is referred to as a “virtual NW” for ease of explanation, and the PON system receives a request for scheduling information from each of the six other systems. An example is shown.

  For example, “virtual NW # 1” and “virtual NW # 3” are systems that collect sensor data from IoT devices, and include “virtual NW # 2”, “virtual NW # 4”, and “virtual NW # 6”. Is a wireless system, and "virtual NW # 5" is a system that requires a low delay of uplink data, such as automatic driving, telemedicine, and online games.

  In FIG. 2, scheduling information of “virtual NW # 1 and virtual NW # 2”, “virtual NW # 3 and virtual NW # 4”, and “virtual NW # 5 and virtual NW # 6” are temporally overlapped. Therefore, if the OLT schedules the uplink transmission period as it is based on the scheduling information requested from each of the virtual NWs # 1 to # 6, the uplink signals will collide.

  In order to avoid such collision of the uplink signal, a method of shifting any of the scheduling information overlapping in time on the time axis is considered. Specifically, this is a method of delaying any transmission time among “virtual NW # 1 and virtual NW # 2”.

  However, if the schedule information of the other systems overlapping in time is shifted on the time axis, the transmission time of the other system is delayed, and the uplink delay time increases.

  Therefore, in the present proposal, when the overlap of the scheduling information is known in advance, the uplink transmission time is not shifted on the time axis but shifted on the wavelength axis (wavelength allocation) as shown in FIG. To reduce. That is, in this proposal, a plurality of virtual NWs are accommodated in one wavelength, and adjustment is made so that the overlapping of the scheduling information of the virtual NWs is reduced within one wavelength.

  Specifically, virtual NWs are grouped by cluster analysis based on the scheduling information of known other systems so as to reduce the overlap, and wavelength allocation is performed for each group. At this time, the number of clusters is the number of wavelengths used. By using a threshold value, an attempt is made to improve the power saving effect while reducing the uplink delay time.

  The present proposal is a wavelength allocation method. As a general wavelength allocation method of TWDM-PON, for example, Patent Document 2 and the like are cited. However, the conventional wavelength allocation method focuses on the load distribution of a band or the like and the power saving effect, and is different from the wavelength allocation method for reducing the uplink delay time as in the present proposal.

(A-2) Configuration of Embodiment [Overall Configuration of Optical Access System]
FIG. 1 is a configuration diagram illustrating an overall configuration of an optical access system (optical communication system) and a functional configuration of an OLT according to an embodiment.

  It is assumed that the optical access system 10 according to the embodiment is, for example, a TWDM (Time and Wavelength Division Multiple) -PON system which is an ITU-T recommendation-compliant system. In this embodiment, the case where the optical access system 10 is a TWDM-PON is illustrated, but a PON other than the TWDM-PON conforming to the ITU-T recommendations may be used. The PON may be a PON conforming to the IEEE standard such as GE (Gigabit Ethernet (registered trademark))-PON or 10GE-PON.

  1, the optical access system 10 includes an OLT 1 as a master station device, an ONU 2 (2-1 to 2-m; m is an integer of 1 or more) as a slave station device, and an optical splitter 5.

  The optical splitter 5 distributes and aggregates an optical signal between the OLT 1 and each ONU (Optical Network Unit) 2. The optical splitter 5 distributes a downstream optical signal (hereinafter, also referred to as “downstream signal”) transmitted from the OLT 1 to each ONU 2, and transmits an upstream optical signal (hereinafter, “upstream signal”) transmitted from each ONU 2. ) Are collected and transmitted to the OLT 1.

  The OLT 1 is an optical line terminal on the office side. The OLT 1 relays the upstream signal of each ONU 2 to the host system 3 and relays the downstream signal received from the host system 3 to each ONU 1.

  Each ONU 2 is a subscriber-side optical line terminal. Each OLT 2 relays downstream communication from the OLT 1 to the lower system 4 and relays upstream communication received from the lower system 4 to the OLT 1.

  The OLT 1 and each ONU 2 regularly exchange messages called Gate and Report with a control protocol called MPCP (Multiple Control Protocol). Generally, a Gate message (hereinafter, simply referred to as “Gate”) is a message in which the OLT 1 instructs each ONU 2 to transmit, and a Report message (hereinafter, simply referred to as “Report”). , Each ONU 2 requests the OLT 1 to transmit uplink data (Data).

[Internal Configuration of OLT 1]
Next, a functional configuration of the OLT 1 according to the embodiment will be described with reference to FIG.

  In FIG. 1, the OLT 1 has a functional configuration of a scheduling information collecting unit (also referred to as a scheduling information collecting unit) 11, a wavelength assignment processing unit 12, a wavelength switching processing unit 13, a signal processing unit 14, a plurality of OSUs (Optical Subscribers). (Unit) processing units 15-1 to 15-n (n is an integer of 1 or more).

  The hardware configuration of the OLT 1 includes, for example, a CPU, a main storage device, an auxiliary storage device, and the like, and realizes various functions as the OLT 1 by executing a processing program by the CPU. The processing program of the OLT 1 (for example, a wavelength assignment program) may be constructed by being installed. Even in such a case, the processing program executed by the CPU has the functional configuration shown in FIG.

  The scheduling information collecting unit 11 collects scheduling information from another system or a virtual network connected to the optical access system 10. Further, the scheduling information collecting unit 11 calculates a data transmission start time in the PON section based on the scheduling information collected from another system or the like.

  For example, as another system or virtual network connected to the optical access system 10, one or a plurality of systems that provide services using the optical access system 10 can be applied. These other systems may be connected to the optical access system 10 as the upper system 3 connected to the OLT 1 and the lower system 4 connected to each ONU 2. Therefore, the scheduling information collecting unit 11 collects scheduling information from each of the other systems existing in the upper system 3 or the lower system 4.

  The scheduling information collecting unit 11 collects scheduling information determined by another system or the like at predetermined intervals. As a result, the latest scheduling information of another system or the like can be collected. The collection period of the scheduling information is not particularly limited, but may be, for example, a DBA (Dynamic Bandwidth Allocation) period. Further, the scheduling collection cycle may be determined according to the type of another system or the like.

  The wavelength assignment processing means 12 performs a wavelength assignment process based on the scheduling information of each other system collected by the scheduling information collection unit 11.

  As shown in FIG. 1, the wavelength assignment processing unit 12 uses a similarity calculation unit 121 for deriving a similarity required for cluster analysis, a cluster analysis unit 122 for performing hierarchical cluster analysis based on the similarity, and a cluster analysis result. The number-of-used-wavelength calculating unit 123 derives the number of used wavelengths (the number of clusters) in consideration of the power saving effect, and assigns the wavelength to each cluster in consideration of the influence of the overhead associated with wavelength switching of a plurality of ONUs belonging to each cluster. It has a wavelength switching influence calculator 124 for deriving the order of allocation, and a wavelength allocator 125 for allocating a wavelength to each cluster. A detailed description of the processing of the wavelength assignment processing means 12 will be given in the section of operation.

  The wavelength switching processing unit 13 performs a switching process to the wavelength assigned to each cluster by the wavelength allocation processing unit 12.

  The signal processing unit 14 analyzes the identification information (for example, LLID) of the downstream signal received from the host system 3 and the ONU 2 of the destination, and gives the downstream signal to the OSU processing unit 15 corresponding to the used wavelength of the ONU 2 of the destination. . Further, the signal processing unit 14 analyzes the identification information (for example, LLID) of the upstream signal received from each of the OSU processing units 15-1 to 15-n, and transmits the upstream signal to the upper system 3 as a transmission destination. Or

  The signal processing unit 14 also manages identification information of a plurality of other systems connected to the optical access system 10. For example, the signal processing unit 14 manages identification information of another system connected as the upper system 3 and identification information of the lower system 4 connected to each ONU 2. The signal processing unit 14 analyzes an upstream signal from each ONU 2 and recognizes which ONU 2 a data signal relating to which other system passes. That is, the signal processing unit 14 recognizes the correspondence between another system and each ONU 2. Each ONU 2 may be connected to one system or virtual network, or may be connected to a plurality of systems or virtual networks. Therefore, it recognizes from which ONU 2 an upstream data signal of each system or another system such as a virtual network is transmitted.

  The signal processing unit 14 gives the scheduling information received from another system as the upper system 3 or the lower system 4 to the scheduling information collection unit 11.

  The signal processing unit 14 groups (clusters) other systems (for example, virtual NWs) connected to the optical access system 10 by cluster analysis by the wavelength allocation processing unit 12 and obtains information (wavelengths) assigned to each cluster. Allocation information).

  Based on the wavelength allocation information of each cluster, the signal processing unit 14 provides the OSU processing units 15-1 to 15-n corresponding to the allocated wavelength of each cluster with the wavelength allocation information destined for the ONU 2 belonging to each cluster. Notify.

  The signal processing unit 14 receives the wavelength switching signal from the wavelength switching processing unit 13 for the ONU 2 that needs to switch the wavelength used, and sends the wavelength switching signal to the OSU processing unit 15 for the switching destination wavelength of the ONU 2. Signal the signal.

  Different wavelengths (λ1 to λn) are fixedly assigned to the respective OSU processing units 15-1 to 15-n, and are connected to the respective ONUs 2 via the optical splitter 5. Therefore, the downstream signal input to each of the OSU processing units 15-1 to 15-n is transmitted to the destination ONU 2 at a fixedly assigned wavelength. The upstream signal transmitted from each ONU 2 is wavelength-separated by the optical splitter 5 and received by each of the OSU processing units 15-1 to 15-n.

  Each of the OSU processing units 15-1 to 15-n performs a process related to a control signal that is periodically exchanged with each of the ONUs 2. In other words, the OSU processing units 15-1 to 15-n create Gates to be transmitted to each ONU 2 and read Reports received from each ONU 2. The OSU processing units 15-1 to 15-n perform band allocation processing, grant generation, and report reading.

  Each of the OSU processing units 15-1 to 15-n acquires the wavelength allocation information and the scheduling information of each cluster from the signal processing unit 14, and based on the scheduling information of a plurality of other systems (virtual NWs) belonging to each cluster, A signal including the transmission time of the uplink data signal is transmitted to each ONU 2.

  In addition, each of the OSU processing units 15-1 to 15-n transmits a wavelength switching signal including the switching destination wavelength and the like to the ONU 2 that needs to switch the used wavelength.

(A-3) Operation of Embodiment Next, the operation of the wavelength assignment processing according to this embodiment will be described in detail with reference to the drawings.

(A-3-1) Overall Flow of Wavelength / Band Allocation Processing in System FIG. 4 is an explanatory diagram illustrating the overall flow of wavelength / band allocation processing according to this embodiment.

  The OLT 1 is notified of scheduling information from each of one or a plurality of other systems connected to the optical access system 10.

  For example, when the other system is the host system 3, the OLT 1 is notified of the scheduling information determined by the host system 3. Further, for example, when the other system is the lower system 4 of the ONU # 2, the scheduling information determined by the lower system 4 is notified to the OLT 1 via the ONU # 2. The scheduling information includes, for example, identification information for identifying a system or a virtual network, a transmission cycle of an uplink signal of the system or the virtual network, and the like.

  The OLT 1 performs a wavelength allocation process and a bandwidth allocation process for reducing the uplink delay time for each DBA_t cycle based on the scheduling information notified from the plurality of other systems, and outputs the wavelength allocation process result and the bandwidth allocation process result to each ONU 2. Notify.

  For example, known scheduling information will be implemented in the future to some extent (eg, after a few ms). That is, when the content of the scheduling information of a certain other system is known, each ONU 2 transmits the uplink data signal at a transmission cycle of the uplink data signal of the scheduling information after a predetermined time (for example, several ms). I do. In other words, the OLT 1 performs the wavelength allocation process and the band allocation process by the predetermined time so that the uplink signal can be communicated by the scheduling information after the predetermined time, and determines the wavelength allocation process result and the band allocation process result by the predetermined time. Each ONU 2 is notified.

  Therefore, each ONU 2 switches to the wavelength notified from the OLT 1 at the time notified from the OLT 1 (the corresponding time in the future), and then transmits the upstream data signal to the OLT 1 in accordance with the band allocation information notified from the OLT 1.

  The OLT 1 and each ONU 2 perform the above-described exchange at every DBA_t period. Accordingly, the wavelength switching timing of each ONU 2 comes every DBA_t cycle. This wavelength switching process is performed during the λ-tuning period, for example, as shown in ONU # 2 in FIG.

  However, not all ONUs 2 necessarily execute the wavelength switching processing. When it becomes necessary for the ONU 2 to transmit an uplink data signal at a wavelength different from the wavelength used for transmitting the immediately preceding uplink data signal, a wavelength switching process is required. FIG. 4 illustrates a case where ONU # 2 performs a wavelength switching process and transmits an uplink data signal during the λ-tuning period, whereas ONU # 1 performs a wavelength switching process. The case where an uplink signal is transmitted without performing it is illustrated.

  In this embodiment, it is assumed that the time length of λ-tuning, which is the wavelength switching time of each ONU 2, is smaller than the time length of the DBA_t cycle, and the cycle of λ-tuning is shorter than the DBA_t cycle. explain.

  As the time length of λ-tuning, a known length may be used, or a time obtained by averaging wavelength switching times required in the past in each ONU 2 or a time obtained by performing statistical processing may be used. You may do so.

  Regarding the correspondence between the ONU 2 and another system, a plurality of other systems (for example, another system and a virtual network) may be accommodated in one ONU 2. An uplink data signal may be generated individually for each. Also in this case, the one ONU 2 transmits an uplink data signal of each other system at a wavelength assigned to each other system using cluster analysis described later.

(A-3-2) Overall Operation of Wavelength / Band Allocation Processing in OLT FIG. 5 is a flowchart showing overall processing of wavelength / band allocation processing in the OLT 1 according to this embodiment.

  When the scheduling information is notified to the OLT 1 from the OSU processing units 15-1 to 15-n or the upper system 3, or when the OLT 1 collects the scheduling information from the upper system 3 or the lower system 4, the scheduling information collecting unit 11 The scheduling information of the system is held (step S1).

  Various methods can be applied to the method of obtaining the scheduling information of the OLT 1 as long as the OLT 1 can obtain the scheduling information from another system, and is not particularly limited. For example, the other system may notify the OLT 1 of the scheduling information, or the OLT 1 may issue a request for acquiring the scheduling information to the other system, and the OLT 1 may acquire the scheduling information. In any case, the scheduling information of each other system is collected and held by the scheduling information collecting unit 11.

  The wavelength assignment processing unit 12 performs a wavelength assignment process based on the scheduling information collected by the scheduling information collection unit 11 (Step S2). A detailed description of the wavelength allocation processing in the wavelength allocation processing means 12 will be described later.

  The result of the wavelength allocation processing by the wavelength allocation processing means 12 is notified to the wavelength switching processing means 13. The wavelength switching processing means 13 performs the wavelength switching processing for each ONU 2 by the same method as the existing wavelength switching processing. The wavelength switching processing unit 13 provides the signal processing unit 14 with information including wavelength information on the switching destination wavelength (wavelength assigned to the ONU 2) for the ONU 2 that needs to switch wavelengths. Then, the signal processing unit 14 notifies the OSU processing unit 15 of the corresponding wavelength of a wavelength switching signal destined for the ONU 2 based on the information from the wavelength switching processing unit 13.

Each of the OSU processing units 15-1 to 15-n is notified of the wavelength allocation information and the scheduling information, and each of the OSU processing units 15-1 to 15-n is notified of the wavelength allocation information, the scheduling information and , The associated ONU information is changed at the corresponding time, and a bandwidth allocation process is performed (step S 3 ). This band allocation process may use an existing method disclosed in Non-Patent Document 1, Patent Document 1, or the like.

  Then, the OSU processing units 15-1 to 15-n notify the corresponding ONU 2 of a wavelength switching signal including the corresponding wavelength information (step S4).

  Each ONU 2 is notified of the wavelength allocation information and the band allocation information. Then, based on the wavelength allocation information and the band allocation information, each ONU 2 switches to the allocated wavelength and transmits an uplink signal at a corresponding time. Thereby, the OLT 1 receives the upstream signal from each ONU 2 (Step S5).

(A-3-3) Wavelength allocation processing Next, the operation of the wavelength allocation processing according to this embodiment will be described. The goal of the wavelength assignment processing according to this embodiment is to determine a group of ONUs 2 with less overlap in scheduling (transmission period of an uplink data signal) based on known scheduling information.

  This is a problem of optimal combination, and as the number of services and the number of ONUs increase, the calculation cost for finding the optimal solution increases exponentially. In this case, cluster analysis, which is a heuristic analysis method with a low computation cost, is effective.

  Thus, in this embodiment, as shown in FIG. 3B, a group (that is, a cluster) is divided into a plurality of pieces of scheduling information by cluster analysis so that the uplink delay time in the group is reduced.

However, applying the cluster analysis to the TWDM-PON requires solving the following three problems.
(1) Since the cluster analysis requires an index of the similarity between elements, it is necessary to newly define the similarity between services. (2) In the cluster analysis, grouping is performed based on only the similarity. Clusters that are not applicable to the current network may be created. Specifically, a cluster exceeding the band capacity can be created. (3) It is necessary to associate the analysis result cluster with the used wavelength.

  In this embodiment, for the problem (1), the number of slot overlaps between the schedulings is defined as the similarity between the services. To solve the problem (2), a check mechanism for checking whether the bandwidth capacity is exceeded when creating a cluster is introduced. With respect to the problem (3), an assignment process that reduces the influence of wavelength switching has been devised.

  FIG. 6 is a flowchart showing the operation of the wavelength assignment processing in the wavelength assignment processing means 12 according to this embodiment.

[Step S11]
As a first step of the wavelength allocation process, the similarity calculating unit 121 calculates the similarity between the services based on the scheduling information of each service (that is, the service provided by each other system).

  In this embodiment, the overlapping time of the scheduling information between the services is defined as the similarity between the services. The value of the similarity is increased as the overlapping time of the transmission time of the uplink signal between the services is longer, and the value of the similarity is decreased as the overlapping time is shorter. Hereinafter, the similarity between services is also referred to as a distance between services or an overlapping distance. The relationship between the similarity and the distance is such that the smaller the value of the similarity is, the shorter the distance is, and the larger the value of the similarity is, the longer the distance is.

  For example, in this embodiment, a predetermined unit time set in advance is set to one slot time, and the similarity calculation unit 121 obtains the number of slots of the overlapping time of the scheduling information of a plurality of services (that is, the transmission time of the uplink signal). Then, a case where the number of slots is set as the value of the similarity is illustrated.

  FIG. 7 is an explanatory diagram illustrating calculation of the degree of similarity between services according to the embodiment. For example, FIG. 7 illustrates the calculation of the similarity between the virtual NW # 1 providing the wireless system and the virtual # 2 providing the IoT system. As shown in FIG. 7, the uplink signal transmission time of the virtual NW # 1 and the uplink signal transmission time of the virtual NW # 2 overlap in the time from time t1 to t2, and the overlap time is 5 slots. It is assumed that In this case, the similarity calculation unit 121 calculates the value of the similarity between the virtual NW # 1 and the virtual # 2 as “5”.

  FIG. 8 is an explanatory diagram illustrating the calculation of the similarity based on the relationship between the scheduling information of the plurality of virtual NWs # 0 to # 8 according to the embodiment.

  For example, it is assumed that the scheduling information of nine virtual NWs # 0 to # 8 is illustrated in FIG. Here, for ease of explanation, all uplink signal transmission times are assumed to be 10 slots.

  In this case, the similarity calculation unit 121 calculates a 9 × 9 distance matrix as illustrated in FIG. 8B. In the distance matrix of FIG. 8B, for example, the first row (the top horizontal row) indicates the similarity between the virtual NW # 0 and the virtual NW # 0 to the virtual NW # 8. The leftmost element in the first row indicates the similarity between the virtual NW # 0 and the virtual NW # 0. Since the similarity is the virtual NW # 0 itself, the value of the similarity is “0”. . The second element from the left in the first row is the similarity between the virtual NW # 0 and the virtual NW # 1, and the overlap time is 10 slots, so the value of the similarity is “10”. The other elements in the first row indicate the similarity between the virtual NW # 0 and the virtual NW # 2 to NW # 8 as described above.

  The second line indicates the similarity between the virtual NW # 1 and the virtual NW # 0 to the virtual NW # 8. The leftmost element in the second row is the similarity between the virtual NW # 1 and the virtual NW # 0. Since the overlap time is 10 slots, the value of the similarity is “10”. The other elements in the second row indicate the similarity between the virtual NW # 0 and the virtual NW # 2 to NW # 8, as described above. The same applies to the other rows.

  As described above, the similarity calculation unit 121 calculates the similarity between services of all other systems (virtual NWs) connected to the optical access system 10. Note that the similarity calculation unit 121 may combine the scheduling of all services to which a certain ONU 2 is connected into one scheduling. That is, the similarity between services may be calculated based on the scheduling information of all services to which a certain ONU 2 is connected.

[Step S12]
Next, the cluster analysis unit 122 performs a hierarchical cluster analysis using the distance matrix calculated by the similarity calculation unit 121.

  This hierarchical cluster analysis is a method of grouping elements having short distances based on the distance between the elements. The hierarchical cluster analysis may use an existing method.

  FIG. 9 is an explanatory diagram illustrating the processing of the hierarchical cluster analysis according to this embodiment. For example, when the cluster analysis unit 122 performs a hierarchical cluster analysis using the distance matrix of FIG. 9A, a hierarchical cluster analysis result as shown in FIG. 9B is obtained. The horizontal axis in FIG. 9B indicates the index (virtual NW number) of the virtual NW, and the vertical axis indicates the overlapping distance (similarity).

In the hierarchical cluster analysis result of FIG. 9B, virtual NW # {8, 2, 5}, virtual NW # {6, 0, 3}, and virtual NW # {7, 1, 4} are collected as a cluster. ing. Generally, when a hierarchical cluster analysis is performed, a tree structure as shown in FIGS. 9B and 10 is obtained. FIG. 10 shows a result of hierarchical cluster analysis using a distance matrix obtained by calculating the similarity between 100 virtual NWs. The general hierarchical cluster analysis is a method of grouping (clustering) in order from the most similar combination in order . In the present embodiment , combinations having smaller similarity values (those having shorter distances) are grouped in order. It will become.

  The cluster analysis unit 122 determines the number of clusters using, for example, the hierarchical cluster analysis result of the tree structure in FIG. 9B or FIG.

  For example, the number of clusters becomes “4” when grouped by the solid line in FIG. 10, and the number of clusters becomes “3” when grouped by the dotted line. For example, when the number of clusters is "4", four wavelengths (that is, four OSU processing units 15) are used, and when the number of clusters is "3", three wavelengths (that is, three OSU processing units 15) are used. ) Will be used.

  The clustering algorithm is not particularly limited. For example, a method based on the maximum distance, a method based on the total distance between the elements in the cluster, and the like can be applied.

  FIG. 11 is a flowchart illustrating a band amount confirmation process in the hierarchical cluster analysis according to the embodiment.

  In the hierarchical cluster analysis, the cluster analysis unit 122 checks whether or not the amount of bandwidth is exceeded when grouping clusters. Thus, it is possible to prevent the total value of the bandwidth amounts used by the plurality of virtual NWs belonging to one grouped cluster from exceeding the preset upper limit value of the bandwidth amount.

  When grouping elements (that is, virtual NWs) or clusters, the cluster analysis unit 122 performs a bandwidth amount confirmation process.

First, in the hierarchical cluster analysis processing, the cluster analysis unit 122 determines one grouping target, searches for a cluster having the smallest similarity value, and groups the clusters into one cluster.

The cluster analysis unit 122 determines one cluster or element x to be grouped (step S121), and determines one cluster or element t having the smallest similarity to x (step S122).

  The cluster analysis unit 122 determines whether or not the total bandwidth of x and y exceeds a preset upper limit of the bandwidth (step S123). For example, when x or y is an element (that is, a virtual NW), the used bandwidth of the virtual NW is used. If x or y is a cluster, the sum is the total used bandwidth of all the virtual NWs belonging to the cluster.

  When the total bandwidth of x and y does not exceed the preset upper limit of the bandwidth, the cluster analysis unit 122 groups x and y into one cluster (step S124).

On the other hand, when the total bandwidth amount of x and y exceeds the preset upper limit value of the bandwidth amount, the cluster analysis unit 122 determines whether there is a cluster or an element having the next smaller similarity value for x. Is determined (step S126). Next, when there is a cluster or an element having a smaller similarity value , the cluster or the element is set to y (step S127), and the process proceeds to step S123. Next, when there is no cluster or element having the smaller similarity value, the process proceeds to step S125 (step S126).

  Then, the cluster analysis unit 122 checks whether there are any other clusters or elements that can be grouped (step S125). If there are any other clusters or elements that can be grouped, the process proceeds to step S121; otherwise, the process ends.

[Step S13]
Upon completion of the hierarchical cluster analysis by the cluster analysis unit 122, the used wavelength number calculation unit 123 determines the number of used wavelengths.

  As described above, in this embodiment, the number of clusters determined by the hierarchical cluster analysis affects the number of wavelengths used and the number of OSU processing units 15 used. For example, if the number of used wavelengths is increased, the number of OSU processing units 15 to be used is also increased, so that the power saving effect is reduced. However, since the number of ONUs 2 accommodated in one wavelength is reduced, the delay time of the upstream signal is reduced. can do. On the other hand, when the number of wavelengths used is small, the number of OSU processing units 15 used is reduced, so that the power saving effect is improved. However, the number of ONUs 2 accommodated in one wavelength increases, and the delay time of the upstream signal may increase. .

  Therefore, a threshold θ regarding the delay time of the uplink signal is set, and the minimum number of clusters that does not exceed the threshold θ is set as the number of used clusters (= the number of used wavelengths). The method of determining the number of clusters may be determined as appropriate according to the operation of the optical access system 10.

[Step S14]
Next, the wavelength switching influence calculator 124 and the wavelength allocator 125 determine a wavelength to be allocated to each cluster.

  By the processing of steps S11 to S13, it is possible to create a cluster set with an improved power saving effect while reducing the uplink delay time. However, since a wavelength is not assigned to each cluster, the wavelength switching influence calculating unit 124 and the wavelength assigning unit 125 assign a wavelength to each cluster.

  Here, when assigning a wavelength to each cluster, in this embodiment, the wavelength is assigned to each cluster in such a manner that the influence of the overhead related to wavelength switching is minimized.

  FIG. 12 and FIG. 13 are explanatory diagrams illustrating the influence of the overhead related to wavelength switching in the embodiment.

  For example, as described with reference to FIG. 4, the ONU 2 that needs to switch the wavelength used for transmitting the uplink signal performs the switching process of the wavelength used during the wavelength switching time (λ-tuning time). Transmission will be performed.

  As shown in FIG. 12A, when the wavelength switching time (λ-tuning time) and the scheduling information overlap in the ONU 2, the ONU 2 needs to perform the wavelength switching, so that the ONU 2 performs the λ-tuning time. Cannot send an upstream signal. Therefore, as shown in FIG. 12B, the ONU 2 transmits an uplink signal after the elapse of the λ-tuning time. That is, the upstream signal is transmitted with a delay due to the influence of the overhead related to wavelength switching.

  As described above, in order to reduce the influence of the overhead due to the wavelength switching, it is desired that the ONU 2 having the scheduling information overlapping with the λ-tuning is not targeted for the wavelength switching as much as possible.

  For example, as shown in FIG. 13, it is assumed that the scheduling information of the virtual NW # 1 overlaps the λ-tuning time, but the scheduling information of the virtual NW # 2 does not overlap the λ-tuning time. In the case of this example, if the ONU # 1 belonging to the virtual NW # 1 is a wavelength switching target, the uplink signal will be transmitted with a delay due to the influence of the overhead, as described above. On the other hand, even if ONU # 2 belonging to virtual NW # 2 is set as a wavelength switching target, the scheduling information of virtual NW # 2 does not overlap with the λ-tuning time, so that there is no delay of the uplink signal.

  Therefore, in this embodiment, ONUs 2 having scheduling information overlapping with λ-tuning are not targeted for wavelength switching as much as possible.

  FIG. 14 is a flowchart illustrating a process for determining a wavelength to be allocated to each cluster according to this embodiment.

  First, for all clusters, the wavelength switching influence calculation unit 124 selects ONU_k0 having the greatest influence of wavelength switching from each cluster k (step S141).

  Various methods can be used to select the ONU_k0 that has the greatest influence of wavelength switching. For example, comparison is made based on the number of slots within the λ-tuning time, and the ONU that has a greater influence is selected as the number of slots is larger. Can be used.

  As another method, for example, a method of biasing the magnitude of the influence by the priority of the service can be considered. For example, there are virtual NWs that provide a low-delay service such as telemedicine and automatic driving, and other virtual NWs that require an uplink delay but can tolerate some delay compared to the low-delay service described above. Therefore, the priority regarding the delay of the service of the virtual NW may be set in advance, and the ONU belonging to the service having the higher priority (requiring a smaller delay) may be selected.

  Next, the wavelength switching influence calculator 124 compares the influence of the wavelength switching of the ONU_k0 selected from each cluster k, selects the ONU_k0 having the greatest influence of the wavelength switching, and determines the wavelength in order from the cluster to which the ONU_0 belongs. (Step S142). That is, the influence of wavelength switching between ONU_k0s selected from each cluster is compared, and the cluster to which ONU_k0 having the largest wavelength switching influence belongs is regarded as having the largest wavelength switching influence. The wavelength is determined in advance.

  First, the wavelength allocating unit 125 sets the currently used wavelength of the ONU_k0 belonging to the cluster to the wavelength λ_k0 for the cluster having the largest influence of the wavelength switching, and the wavelength allocating unit 125 allocates the wavelength λ_k0 to another cluster. It is determined whether or not it has been performed.

  If the wavelength λ_k0 has not been allocated to another cluster, the wavelength allocating unit 125 sets the wavelength λ_k0 as the used wavelength of the cluster (step S144).

  For example, in the case of the first cluster for which the wavelength switching is to be determined (the cluster having the largest influence of the wavelength switching), since the used wavelength has not been allocated to the other clusters, ONU_k0 is currently set to the relevant cluster. The used wavelength λ_k0 is assigned as the used wavelength.

  If the wavelength assignment has not been completed for all the clusters, the process returns to S142 and repeats the process.

  Next, the wavelength assigning unit 125 sets the currently used wavelength of the ONU_k0 belonging to the cluster to the wavelength λ_k0 for the cluster that has the second largest influence of the wavelength switching, and this wavelength λ_k0 has already been assigned to another cluster. It is determined whether or not.

  For example, if the currently used wavelength λ_k0 of the ONU_k0 belonging to the cluster having the second largest influence of wavelength switching is the same as the wavelength assigned to the first cluster having the largest influence of wavelength switching, the process proceeds to S145. Otherwise, the process proceeds to S144.

  If the wavelength λ_k0 has already been allocated to another cluster, the wavelength allocating unit 125 selects the ONU_ki having the next largest influence of the wavelength switching in the cluster, sets this ONU_ki as ONU_k0, and proceeds to S143 (step S145). ). That is, when the ONU of the cluster that has the greatest influence of the wavelength switching has the currently used wavelength λ_k0 assigned to another cluster, the ONU that has the next greatest influence in the cluster is selected, and It is determined whether or not the used wavelength is assigned to another cluster.

  Then, wavelengths are allocated in order from the cluster having the largest influence of wavelength switching, and when the wavelength allocation is completed for all clusters, the process ends.

  As described above, by assigning a wavelength to each cluster, it is possible to reduce the influence of the uplink delay associated with wavelength switching.

(A-4) Effects of Embodiment As described above, according to this embodiment, the uplink delay time is improved and the power saving effect is improved by allocating each piece of scheduling information of a plurality of other systems on the wavelength axis. Can be done.

  In this embodiment, based on the scheduling information collected from other systems connected to the optical communication system, the overlap time of the uplink transmission time is defined as the similarity of the cluster analysis, and those having similar similarities are grouped. I made it. As a result, even when many other systems are connected to the optical communication system, the grouping can be performed while suppressing the calculation cost.

  According to this embodiment, when performing the cluster analysis, the grouping is performed while determining whether the total bandwidth amount of the cluster or the element to be grouped exceeds the upper limit value, so that the bandwidth amount does not exceed the upper limit value. You can group by range.

  According to this embodiment, by determining the number of wavelengths to be used based on the result of the hierarchical cluster analysis, it is possible to determine the number of wavelengths to be used while considering the delay time of the uplink signal and the power saving effect.

  According to this embodiment, since the used wavelength is allocated to each cluster while considering the influence of the wavelength switching of the ONUs belonging to each cluster, it is possible to reduce the overhead related to the wavelength switching processing in the ONU.

(B) Other Embodiments In the above-described embodiment, the case where the overlap of the uplink transmission times is defined as the similarity and the predetermined number of slots is set as the similarity has been exemplified. However, the absolute value of the uplink transmission time, that is, the overlap time itself may be used as the similarity.

  Reference Signs List 10 optical access system, 1 OLT, 2 (2-1 to 2-m) ONU, 3 upper system, 4 lower system, 5 optical splitter, 11 scheduling information collection unit, 12 wavelength assignment processing Means: 121: similarity calculation unit; 122: cluster analysis unit; 123: used wavelength number calculation unit; 124: wavelength switching influence calculation unit; 125: wavelength allocation unit; 13: wavelength switching processing unit; 15 (15-1 to 15-n)... OSU processing unit.

Claims (7)

In a master station device that performs optical communication with a plurality of slave station devices at an assigned wavelength,
Scheduling information collecting means for collecting scheduling information requested from each of a plurality of other systems to be connected;
Wavelength allocation processing means for allocating a wavelength accommodating each of the other systems,
Wavelength switching processing means for notifying each of the wavelengths allocated by the wavelength allocation processing means to each of the corresponding slave station apparatuses and performing wavelength switching,
The wavelength assignment processing means,
Based on the scheduling information collected from each of the other systems, based on the scheduling information, a similarity calculation unit that calculates the similarity of the uplink transmission period, which is the degree of overlap of uplink signal transmission times between services provided by the other systems,
A cluster analysis unit that groups the plurality of other systems in ascending order of similarity values of the uplink transmission periods between the other systems calculated by the similarity calculation unit;
A use wavelength number calculation unit that determines the use wavelength number according to the number of groups grouped by the cluster analysis unit,
And a wavelength allocating unit that allocates a use wavelength to each of the grouped groups.   When the cluster analysis unit groups the plurality of other systems, the total bandwidth of the target cluster or element and the other cluster or element having a small similarity value is an upper limit of a predetermined bandwidth. The master station device according to claim 1, wherein the master station devices are grouped so as not to exceed. The cluster analysis unit further includes a wavelength switching influence calculation unit that selects, from among the slave station devices belonging to each of the plurality of groups, the one that has the greatest effect on wavelength switching, for each of the groups,
The said wavelength allocation part allocates a use wavelength in order from the group which has an influence on wavelength switching based on the said slave station apparatus for every group selected by the said wavelength switching influence calculation part, or 3. The master station device according to 2. In an optical communication system in which a master station device and a plurality of slave station devices optically communicate at an assigned wavelength, a wavelength accommodating each of the other systems based on scheduling information requested from each of a plurality of other systems to be connected. Wavelength assigning apparatus for assigning
Based on the respective scheduling information collected from the respective other systems, based on the respective scheduling information, a similarity calculating unit that calculates a similarity of an uplink transmission period, which is a degree of overlap of uplink signal transmission times between services provided by the other systems,
Cluster analysis means for grouping the plurality of other systems in ascending order of similarity value of the uplink transmission period between the other systems calculated by the similarity calculation means,
Use wavelength number calculation means for determining the use wavelength number according to the number of groups grouped by the cluster analysis means,
Wavelength assigning means for assigning a use wavelength to each of the grouped groups. In an optical communication system in which a master station device and a plurality of slave station devices optically communicate at an assigned wavelength, a wavelength accommodating each of the other systems based on scheduling information requested from each of a plurality of other systems to be connected. A wavelength assignment program that assigns
Computer
Based on the respective scheduling information collected from the respective other systems, based on the respective scheduling information, a similarity calculating unit that calculates a similarity of an uplink transmission period, which is a degree of overlap of uplink signal transmission times between services provided by the other systems,
Cluster analysis means for grouping the plurality of other systems in ascending order of similarity value of the uplink transmission period between the other systems calculated by the similarity calculation means,
Use wavelength number calculation means for determining the use wavelength number according to the number of groups grouped by the cluster analysis means,
A wavelength assignment program for causing each of the grouped groups to function as wavelength assignment means for assigning a use wavelength. In an optical communication system in which a master station device and a plurality of slave station devices optically communicate at an assigned wavelength, a wavelength accommodating each of the other systems based on scheduling information requested from each of a plurality of other systems to be connected. A wavelength assignment method for assigning
The similarity calculating unit calculates a similarity of an uplink transmission period, which is a degree of overlap of uplink signal transmission times between services provided by the other systems, based on the scheduling information collected from the other systems,
Cluster analysis means, grouping the plurality of other systems in ascending order of the value of the similarity of the uplink transmission period between the other systems calculated by the similarity calculation means ,
The used wavelength number calculating means determines the used wavelength number according to the number of groups grouped by the cluster analysis unit,
A wavelength allocating method, wherein the wavelength allocating means allocates a used wavelength to each of the grouped groups. In an optical communication system including one master station device and a plurality of slave station devices optically communicating with the master station device at any wavelength,
The master station device,
Scheduling information collecting means for collecting requested scheduling information from each of a plurality of other systems connected to the optical communication system,
Wavelength allocation processing means for allocating a wavelength accommodating each of the other systems,
Wavelength switching processing means for notifying each wavelength allocated by the wavelength allocation processing means to each of the corresponding slave station devices,
The wavelength assignment processing means,
Based on the scheduling information collected from each of the other systems, based on the scheduling information, a similarity calculation unit that calculates the similarity of the uplink transmission period, which is the degree of overlap of uplink signal transmission times between services provided by the other systems,
A cluster analysis unit that groups the plurality of other systems in ascending order of similarity values of the uplink transmission periods between the other systems calculated by the similarity calculation unit;
A use wavelength number calculation unit that determines the use wavelength number according to the number of groups grouped by the cluster analysis unit,
An optical communication system, comprising: a wavelength allocating unit that allocates a use wavelength to each of the grouped groups.

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