JP5733453B1 - Station side apparatus and power saving method in station side apparatus - Google Patents

Abstract

An optimal number of OSUs that can be started without excess or shortage is determined. A station side device used in an optical access network including a station side device having a plurality of termination devices and a plurality of subscriber side devices connected to the station side devices via an optical transmission line. A traffic information collecting means for collecting traffic information, a distributed accommodation means for distributing and accommodating subscriber-side apparatuses in a predetermined number of terminating devices, and a probability of congestion as a result of the distributed accommodation. Threshold value determining means for determining whether or not there is a terminal device having a threshold value or more, and a startup number setting means means. The number-of-start-up setting means increases the number of start-ups by one when there is a terminal device that is equal to or greater than the threshold as a result of the determination by the threshold value determination means, and decreases the number of start-ups by one when there is no end device. [Selection] Figure 1

Description

  The present invention relates to a station-side device used in an optical access network including a station-side device including a plurality of termination devices and a plurality of subscriber-side devices, and a power saving method in the station-side device.

  A communication network connecting a building (station) owned by a telecommunications carrier and a subscriber's house is called an access network. In response to the recent increase in communication capacity, optical access networks that enable transmission of an enormous amount of information by using optical communication are becoming mainstream.

  As one form of the optical access network, there is a passive optical network (PON: Passive Optical Network). The PON includes one station side device (OLT: Optical Line Terminal) provided in the station, a plurality of subscriber side devices (ONU: Optical Network Unit) provided in each subscriber's house, and an optical splitter. Is done. The OLT and the ONU and the optical splitter are connected by an optical fiber.

  A single-core optical fiber is used for connection between the OLT and the optical splitter. This single-core optical fiber is shared by a plurality of ONUs. The optical splitter is an inexpensive passive element. Thus, PON is excellent in economic efficiency and easy to maintain. For this reason, the introduction of PON is progressing rapidly.

  In PON, signals transmitted from each ONU to the OLT (hereinafter also referred to as upstream optical signals) are combined by an optical splitter and transmitted to the OLT. On the other hand, a signal sent from the OLT to each ONU (hereinafter also referred to as a downstream optical signal) is demultiplexed by the optical splitter and transmitted to each ONU. In order to prevent interference between the upstream optical signal and downstream optical signal, different wavelengths are assigned to the upstream optical signal and downstream optical signal, respectively.

  In PON, various multiplexing techniques are used. The multiplexing technology used in the PON includes time division multiplexing (TDM) technology in which a short interval on the time axis is assigned to each subscriber, wavelength division multiplexing (WDM) in which different wavelengths are assigned to each subscriber (WDM: Wave Division Division Multiplex). And code division multiplexing (CDM) technology that assigns different codes to each subscriber. Among these multiplexing techniques, TDM-PON using TDM is currently most widely used. In TDM-PON, TDMA (Time Division Multiple Access) is used. TDMA is a technique in which the OLT manages the transmission timing of each ONU so that upstream optical signals from different ONUs do not collide with each other.

Among the PON systems, those using the Ethernet (registered trademark) technology are referred to as Ethernet (registered trademark) -PON, and those using the Gigabit (1 × 10 ⁹ bits / sec) Ethernet (registered trademark) technology are used. -Called PON. GE-PON is standardized by IEEE 802.3ah.

  By the way, a PON system using both TDM and WDM (hereinafter also referred to as TDM / WDM-PON) has been proposed. In the TDM / WDM-PON, for example, the OLT has a plurality of terminal units (OSU: Optical Subscriber Unit).

  In TDM / WDM-PON, each OSU communicates with the ONU at a specific wavelength. And between each OSU-ONU, an upstream optical signal and a downstream optical signal are time-multiplexed and transmitted for each wavelength without overlapping each other. In TDM / WDM-PON, ONUs are distributed to a plurality of OSUs and managed, and the number of ONUs managed by one OSU can be reduced, thereby increasing the service bandwidth provided to subscribers.

  Here, in TDM / WDM-PON, an ONU may be registered in any of a plurality of OSUs. As already described, in TDM / WDM-PON, ONUs communicate with wavelengths according to the OSU, so each ONU communicates with any OSU as long as the transmittable and receivable wavelengths are variable. be able to. At this time, power consumption in the OLT can be reduced by controlling the number of OSU activations according to the communication amount of the entire network.

  For this reason, when there is an OSU whose average traffic exceeds the threshold, the number of OSUs activated is increased by one, and when there is no OSU, the number of OSUs activated is decreased by one to determine whether allocation is possible. In the case where allocation is possible, a technique has been proposed in which the number of OSUs activated is reduced by one (see, for example, Patent Document 1).

JP 2013-183331 A

  Here, when determining the number of OSUs to be activated in consideration of only the traffic average, there is a case where the optimum operation cannot be performed depending on the time distribution of traffic.

  For example, when the time dispersion of traffic is large, it is difficult to cope with an instantaneous increase in traffic and congestion is likely to occur. In addition, when the traffic time dispersion is small, the number of OSUs activated becomes excessive, which may waste power.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a station-side device that determines the optimal number of OSUs to be started without excess or deficiency, and a power saving method in the station-side device. Is to provide.

  In order to achieve the above-described object, a station-side device of the present invention includes a station-side device having a plurality of termination devices, and a plurality of subscriber-side devices connected to the station-side device via an optical transmission line. A station-side device used in the configured optical access network, a traffic information collecting unit that collects traffic information, a distributed accommodation unit that decentrally accommodates subscriber-side devices in a predetermined number of terminal devices; As a result of the distributed accommodation, the apparatus includes a threshold value determining unit that determines whether or not there is a terminal device having a congestion probability equal to or higher than a predetermined threshold value, and a startup number setting unit. The number-of-start-up setting means increases the number of start-ups by one when there is a terminal device that is equal to or greater than the threshold as a result of the determination by the threshold value determination means, and decreases the number of start-ups by one when there is no end device.

  The power saving method of the present invention is an optical access network including a station side device having a plurality of termination devices and a plurality of subscriber side devices connected to the station side device via an optical transmission line. A power-saving method used by a station-side device, which includes the following steps. First, in the decentralized accommodation process, subscriber-side devices are decentralized and accommodated in a predetermined number of terminal devices based on the collected traffic information. Next, in the threshold determination process, it is determined whether or not there is a terminal device having a probability of congestion exceeding a predetermined threshold as a result of the distributed accommodation. Next, as a result of the start determination, if there is a terminal device that is equal to or greater than the threshold value, the number of activated devices is increased by 1 in the process of adding activated devices. If there is no termination device equal to or greater than the threshold value as a result of the determination, the number of activated devices is reduced by one in the process of decreasing the number of activated devices. After performing the process of decreasing the number of activated units, the distributed accommodation process and the threshold value determining process are performed. If it does not exist, the process ends.

  According to the station-side device of the present invention and the power-saving method in the station-side device, it is determined whether or not there is a termination device having a probability of congestion equal to or higher than a predetermined threshold, and the termination device equal to or higher than the threshold If there is, the number of activated units is increased by one, and if not, the number of activated units is decreased by one. For this reason, in the case of a traffic distribution with a large time fluctuation, congestion is difficult. On the other hand, in the case of a traffic distribution with small time fluctuation, the number of terminal devices activated can be reduced, so that power consumption can be suppressed.

It is a schematic diagram of TDM / WDM-PON. It is a schematic diagram of OSU. It is a processing flowchart of a power saving method. It is a schematic diagram used for a comparison with a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the arrangement relationship of each component is merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

(TDM / WDM-PON)
The configuration of TDM / WDM-PON will be described with reference to FIG. FIG. 1 is a schematic diagram of TDM / WDM-PON.

  The TDM / WDM-PON 10 includes a station side device (OLT) 100 and L (L is an integer of 1 or more) subscriber side devices (ONU) 400-1 connected to the OLT 100 via the optical transmission line 300. To L.

  The optical transmission line 300 includes, for example, optical fibers 310 and 330 and an optical splitter 320. In the configuration example shown in FIG. 1, the optical fiber 310 connected to the multiplexer / demultiplexer 130 of the OLT 100 is branched by the optical splitter 320. The ONU 400 is connected to each of the branched optical fibers 330.

  Each of the ONUs 400-1 to 400-L generates an upstream optical signal based on the upstream data signal received from each of the user terminals 70-1 to 70-L and the upstream control signal for requesting the bandwidth, and transmits the upstream optical signal to the OLT 100.

  The OLT 100 generates a downstream optical signal based on the downstream data signal received from the upper network (NW) 50 and the downstream control signal for managing the ONU 400, and transmits the downstream optical signal to the ONU 400.

(Station equipment)
The OLT 100 includes a management unit 110, switching elements 120, M (M is an integer of 2 or more) termination units (OSU) 200-1 to M, and a multiplexer / demultiplexer 130.

  The switching element 120 sets a communication path between the upper NW 50 and each OSU 200. Based on the transmission plan notified from the management unit 110, the switching element 120 distributes and transmits the downlink data signal to each OSU 200 and transmits the uplink data signal transmitted from each OSU 200 to the upper NW 50. In addition, the management unit 110 is notified of information such as the destination and traffic of the downlink data signal transmitted from the upper NW 50.

  The multiplexer / demultiplexer 130 multiplexes downstream optical signals having different wavelengths transmitted from the respective OSUs 200 and transmits them to the ONU 400 via the optical transmission line 300. In addition, the time-multiplexed upstream optical signal sent from each ONU 400 via the optical transmission path 300 is demultiplexed for each wavelength and sent to the OSU 200 corresponding to the wavelength.

  The management unit 110 includes a traffic information collection unit 111, a distributed accommodation unit 113, a threshold determination unit 115, a startup number setting unit 117, and an OSU control unit 119.

The traffic information collecting unit 111 collects traffic information and stores the traffic information in any suitable storage unit (not shown) such as a RAM so as to be readable and rewritable. This traffic information is traffic information regarding each ONU in a certain period including a certain time t, and includes, for example, information on the average value Tave of traffic and time dispersion σ _T ² .

  The distributed storage means 113 distributes and stores ONUs in a predetermined number of OSUs. For distributed accommodation, it is desirable that the average traffic of each OSU be allocated so as to be equal.

  The threshold determination unit 115 determines whether or not there is an OSU having a congestion probability equal to or higher than a predetermined threshold Pth as a result of the distributed storage in the distributed storage unit 113.

For example, for a certain OSU traffic, the traffic is applied to a normal distribution. When the sum of the average value Tave and the standard deviation σ _T is about the maximum throughput, the probability of congestion is about 30%, and the sum of the average value Tave and twice the standard deviation σ _T is the maximum. In the case of throughput, the probability of congestion is approximately 5%.

  The number-of-start-up setting unit 117 increases the number of boots by one if there is an OSU whose congestion probability is equal to or higher than the threshold Pth as a result of the determination by the threshold judgment unit 115. Reduce one.

  The OSU control means activates the OSUs of the number of activated units set by the activated number setting means, and sets the other OSUs to the sleep state or the off state. The OSU in the sleep state or in the off state consumes less power than the OSU in the active state.

(Terminal equipment)
The configuration of the OSU 200 will be described with reference to FIG. FIG. 2 is a schematic diagram of an OSU.

  In this embodiment, the OSU 200 is configured to include an electrical signal processing unit 250 and an optical signal processing unit 270. The electrical signal processing unit 250 includes an interface 255, an electrical signal transmission unit 257, an electrical signal reception unit 259, and a control unit 261. The optical signal processing unit 270 includes an optical signal transmission unit 271, an optical signal reception unit 273, and a multiplexing / demultiplexing unit 275.

  The electrical signal transmission unit 257 generates a downlink electrical signal based on the downlink data signal received from the interface 255 and the downlink control signal received from the control unit 261. The downstream electrical signal is sent to the optical signal transmission unit 271.

  The electrical signal receiver 259 separates the upstream electrical signal received from the optical signal receiver 273 into an upstream data signal and an upstream control signal. The uplink data signal is sent to the upper NW 50 via the interface 255 and the switching element 120, and the uplink control signal is sent to the control unit 261.

  The optical signal transmission unit 271 converts each downstream electrical signal into a downstream optical signal. The optical signal transmission unit 271 includes any suitable electrical / optical conversion unit such as an LD (Laser Diode). The downstream optical signal is sent to the multiplexer / demultiplexer 130 via the multiplexer / demultiplexer 275.

  The optical signal receiving unit 273 converts the upstream optical signal transmitted through the multiplexing / demultiplexing unit 275 into an upstream electrical signal. The optical signal receiving unit 273 is configured to include any suitable photoelectric conversion element such as an optical receiver (PD: Photo Diode). The upstream electrical signal is sent to the electrical signal receiving unit 259.

  The multiplexer / demultiplexer 275 sends the downstream optical signal generated by the optical signal transmitter 271 to the multiplexer / demultiplexer 130 and transmits the upstream optical signal received from the multiplexer / demultiplexer 130 to the optical signal receiver 273. The multiplexing / demultiplexing unit 275 includes any suitable multiplexer / demultiplexer such as a WDM filter. In TDM / WDM-PON 10, light in different wavelength bands is used for downstream optical signals and upstream optical signals. Therefore, for example, an upstream optical signal and a downstream optical signal can be multiplexed and demultiplexed by using a WDM filter.

  Each OSU is used for a conventional PON except that the wavelength of the downstream optical signal generated by the optical signal transmission unit 271 and the wavelength of the upstream optical signal received by the optical signal reception unit 273 are different for each OSU. Since it can be configured in the same manner as an OLT, detailed description is omitted here.

(Subscriber equipment)
Again, the configuration of the ONU 400 will be described with reference to FIG.

  As shown in FIG. 1, in this embodiment, the ONU 400 includes a MAC (Media Access Control) 455, a wavelength variable transmitter 471, a wavelength variable receiver 473, and a multiplexer / demultiplexer 475.

  The variable wavelength transmitter 471 converts the upstream electrical signal received from the MAC 455 into an upstream optical signal. The wavelength tunable transmitter 471 includes any suitable electrical / optical conversion means capable of changing the wavelength, such as a TLD (Tunable Laser Diode). The wavelength of the upstream optical signal is set based on a notification from the MAC 455. The upstream optical signal generated by the wavelength tunable transmitter 471 is sent to the multiplexer / demultiplexer 475 and sent to the OSU 200 via the optical transmission line 300.

  The MAC 455 transmits and receives uplink data signals and downlink data signals to and from the user terminal 70. The MAC 455 has a function of generating an upstream electrical signal by placing a data signal received from the user terminal 70 on a frame used in TDM / WDM-PON. In addition, it has a function of extracting a downlink data signal from a frame that is a downlink electrical signal received from the OLT.

  The wavelength tunable receiver 473 converts the downstream optical signal transmitted through the multiplexer / demultiplexer 475 into a downstream electrical signal. The downstream electrical signal is sent to the MAC 455. The wavelength tunable receiver 473 includes a variable wavelength filter and any suitable photoelectric conversion element such as a PD. The PD is set to receive at least a downstream optical signal in a wavelength band that can be set by the OSU 200.

  The multiplexer / demultiplexer 475 combines and demultiplexes the upstream optical signal and downstream optical signal. The multiplexer / demultiplexer 475 is configured to include any suitable multiplexer / demultiplexer such as a WDM filter. As already described, in TDM / WDM-PON, light in different wavelength bands is used for downstream optical signals and upstream optical signals. Therefore, for example, an upstream optical signal and a downstream optical signal can be multiplexed and demultiplexed by using a WDM filter. In TDM / WDM-PON, the wavelengths of the upstream optical signal and downstream optical signal differ depending on the OSU accommodated. Therefore, by using the wavelength tunable transmitter 471 and the wavelength tunable receiver 473, the wavelength of the optical signal transmitted and received by each ONU can be changed.

(Power saving method)
A power saving method will be described with reference to FIG. FIG. 3 is a processing flowchart of the power saving method.

  This power saving method is periodically executed. This power saving method determines the number of OSU activation N [t + 1] at time t + 1 after the elapse of one cycle with respect to the number of OSU activation N [t] at the current time t. The OLT collects and holds traffic information for each ONU.

  In step (hereinafter, step is indicated by S) 10, the number N of OSUs started is defined as the number N [t] of startups at time t.

Next, in S20, based on the traffic information collected by the traffic information collection unit 111, the distributed accommodation unit 113 distributes and accommodates the ONUs currently performing communication in the OSUs with the number N of startups. This distributed accommodation can be performed using any suitable conventionally known method. It is desirable that the traffic congestion probability be allocated so as to be uniform among OSUs. The probability of congestion can be calculated by fitting the traffic of individual ONUs to a normal distribution and comparing the average value Tave and standard deviation σ _T with the maximum throughput of the OSU. For example, when the sum of the average value Tave and the standard deviation σ _T is about the maximum throughput for a certain OSU traffic, the probability of congestion is about 30%, which is twice the average value Tave and the standard deviation σ _T. Is about the maximum throughput, the probability of congestion is about 5%.

  Next, in S <b> 30, the threshold determination unit 115 determines whether there is an OSU having a congestion probability equal to or higher than a predetermined threshold Pth. This threshold value Pth is determined in consideration of, for example, network communication quality and power saving effect. When high quality is required, the threshold value Pth may be set low, and when a power saving effect is required, the threshold value Pth may be set high.

  If there is an OSU greater than or equal to the threshold value Pth, the number-of-start-up setting unit 117 adds one start-up number N [t + 1] of OSUs at time t + 1 after the elapse of one cycle to the number of start-up N in S40. As a result, N + 1 is assigned as the ONU, and the process is terminated. In this case, the startup number N [t + 1] after one cycle has elapsed is given by N [t + 1] = N [t] +1 with respect to the startup number N [t] at the current time t.

  If there is no OSU equal to or greater than the threshold value Pth, in S50, the number-of-start-up setting unit 117 reduces the number of booted N of OSUs by one from the number of booted N [t] at time t, so that N [t] −1. To do.

  Next, in S60, the distributed accommodation unit 113 again distributes and accommodates the ONUs currently performing communication in the OSUs of the number N of startups. This S60 is performed in the same manner as S20.

  Next, in S70, the threshold determination unit 115 determines whether there is an OSU having a congestion probability equal to or higher than a predetermined threshold Pth. This S70 is performed in the same manner as S30.

  If there is an OSU greater than or equal to the threshold value Pth, in S80, the number-of-start-up setting unit 117 increases the number of start-ups N [t + 1] of OSUs at time t + 1 after one cycle has elapsed by one from N, and N [t + 1 ] = N + 1 = (N [t] −1) + 1 = N [t], an ONU is assigned and the process is terminated.

  If there is no OSU equal to or greater than the threshold value Pth, the process is terminated. In this case, the number of OSUs activated N [t + 1] at time t + 1 after the elapse of one cycle is N = N [t] −1.

  After these processes are completed, the OSU control unit 119 sets the number of OSUs set by the startup unit setting unit 117 to the active state and sets the other OSUs to the sleep state or the off state.

  Referring to FIG. 4, the power saving method of the present invention is compared with the conventional example. FIG. 4 is a schematic diagram used for comparison with a conventional example. 4A to 4D show the traffic distribution as a normal distribution, the horizontal axis indicates the traffic magnitude, and the vertical axis indicates the distribution frequency in arbitrary units. 4A shows an embodiment when the time dispersion is small, FIG. 4B shows an embodiment when the time dispersion is large, and FIG. 4C shows a conventional case where the time dispersion is small. An example is shown, and FIG. 4D shows a conventional example when time dispersion is large.

  When the time dispersion is small, in the conventional example in which the number is determined based on the average value of traffic, there is room for adding ONUs as shown in FIG. In this state, the number of OSUs activated in the conventional example is excessive.

  On the other hand, in the embodiment in which the number is determined based on the probability of congestion, as shown in FIG. 4A, the number of ONUs accommodated with respect to the maximum throughput can be increased compared to the conventional example. As a result, the number of OSUs activated can be reduced.

  Further, when time dispersion is large, in the conventional example in which the number is determined based on the average value of traffic, as shown in FIG. 4D, the probability of congestion increases and high-quality communication cannot be performed. On the other hand, in the embodiment in which the number is determined based on the probability of congestion, as shown in FIG. 4B, the probability of congestion can be suppressed below a threshold value.

  According to the power saving method described above, the number of OSUs activated is determined in consideration of not only the average value of traffic but also time dispersion. For this reason, in the case of a traffic distribution with a large time dispersion, the number of ONUs accommodated in one OSU is reduced and the number of OSUs activated is increased. On the other hand, in the case of a traffic distribution with small time dispersion, ONUs are accommodated until the maximum throughput is approached, so the number of OSUs activated can be reduced and power consumption can be reduced.

10: TDM / WDM-PON
100: Station side device (OLT)
110: Management unit 111: Traffic information collecting unit 113: Distributed accommodating unit 115: Threshold determining unit 117: Number of activated units setting unit 119: OSU control unit 120: Switching element 130: MUX / DEMUX 200: Termination unit (OSU)
250: Electric signal processing unit 255: Interface 257: Electric signal transmission unit 259: Electric signal reception unit 261: Control unit 270: Optical signal processing unit 271: Optical signal transmission unit 273: Optical signal reception unit 275, 475: Multiplexing / demultiplexing Unit 300: optical transmission line 310, 330: optical fiber 320: optical splitter 400: subscriber unit (ONU)
455: MAC
471: Variable wavelength transmitter 473: Variable wavelength receiver

Claims (4)

A station-side device used in an optical access network including a station-side device having a plurality of termination devices and a plurality of subscriber-side devices connected to the station-side device via an optical transmission line. ,
Traffic information collecting means for collecting traffic information;
A decentralized accommodation means for decentrally accommodating subscriber-side devices in a predetermined number of activated terminal devices;
As a result of distributed accommodation, threshold determination means for determining whether or not there is a terminal device having a congestion probability equal to or higher than a predetermined threshold;
As a result of the determination, if there is a terminating device equal to or greater than a threshold value, the number of activated units is increased by one, and if there is not, the number of activated units setting means for reducing the number of activated units by one;
A station side device comprising: The station-side apparatus according to claim 1, wherein the threshold determination unit estimates a probability of congestion by applying a traffic distribution to a normal distribution based on the traffic information. Performed by the station-side device used in an optical access network including a station-side device having a plurality of termination devices and a plurality of subscriber-side devices connected to the station-side device via an optical transmission line A power saving method,
Based on the collected traffic information, a decentralized accommodation process in which subscriber-side devices are decentralized and accommodated in a predetermined number of activated terminal devices,
As a result of distributed accommodation, a threshold determination process for determining whether or not there is a terminal device having a probability of congestion of a predetermined threshold or more;
As a result of the determination, if there is a terminal device that is equal to or greater than a threshold value, a startup number addition process for increasing the startup number by one;
As a result of the determination, when there is no termination device equal to or higher than a threshold value, a startup number reduction process for reducing the startup number by one is provided.
After performing the number-of-starts-decreasing process, performing the distributed accommodation process and the threshold value determining process, and if there is a terminal device exceeding the threshold value, performing the number-of-start-up addition process, exceeding the threshold value The power saving method is characterized in that the processing is terminated when there is no terminating device. The power saving method according to claim 3, wherein the probability of congestion is estimated by applying a traffic distribution to a normal distribution based on the traffic information.

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