JP2016140011A - Optical network unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control periodic sleep so as to ensure power saving and a real time property.SOLUTION: An ONU 2 comprises: a buffer situation acquisition unit 25 for acquiring a buffer situation of a transmission buffer 21; a first determination unit 43 for performing determination on a connection state on first communication in a lower layer; a second determination unit 44 for performing determination on a connection state on second communication in a higher layer; and a sleep control unit 45 for making an optical reception unit 42 sleep periodically depending on the buffer situation. The sleep control unit 45 makes, depending on the buffer situation, a sleep time be equal to or shorter than a first sleep time when the first communication is in a connection state and the second communication is not in a connection state; makes the sleep time be a second sleep time shorter than the first sleep time when the second communication is in a connection state; and makes the sleep time be a third sleep time longer than the first sleep time when neither the first nor the second communication is in a connection state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a slave station apparatus in a passive optical network system, which performs periodic sleep control.

  Conventionally, in a passive optical network (PON) system, power consumption reduction of a slave station device (ONU: Optical Network Unit) has been an important issue. In 2013, the international standard IEEE1904.1 SIEPON (Service Interoperability in EPON) etc. stipulated basic power saving functions.

  In order to save such power, in an ONU in which there is no communication traffic, power supply to an optical transceiver or the like is suspended (sleep). Downstream received data that arrived at a master station device (OLT: Optical Line Terminal) during the sleep was buffered by the OLT, and was transmitted from the OLT to the ONU after the active period (receivable period). In such sleep control, in order to ensure real-time communication, a sleep period and an active period are periodically repeated in a short period (see, for example, Patent Document 1).

JP 2014-57192 A

  In periodic sleep such as cyclic sleep, in order to save power, it is required to increase the sleep time which is the length of the sleep period. On the other hand, in order to improve the real-time property, it is required to increase the active time which is the length of the active period.

  The present invention has been made in the situation as described above, and is an ONU in a PON system, which controls a periodic sleep so as to realize both power saving and real-time property securing. An object is to provide an apparatus.

  To achieve the above object, a slave station device according to the present invention is a slave station device in a passive optical network system in which a master station device and a plurality of slave station devices are connected by an optical communication path having a splitter, A transmission buffer for buffering data transmitted to the station device, an optical transmitter for transmitting the data buffered in the transmission buffer to the parent station device, and an optical receiver for receiving data transmitted from the parent station device A buffer status acquisition unit that acquires a buffer status related to a buffering status of data in the transmission buffer, data transmitted by the optical transmission unit, and data received by the optical reception unit, A first determination unit that determines a connection state related to the first communication in one layer, and data transmitted by the optical transmission unit. A second determination unit that determines a connection state related to the second communication in the second layer, which is a layer higher than the first layer, according to at least one of the data received by the optical reception unit, and a buffer A sleep control unit that periodically sleeps the optical reception unit according to the buffer status acquired by the status acquisition unit, wherein the sleep control unit sets the length of the sleep period in the periodic sleep to the first When the determination unit determines that the first communication is in a connected state, and the second determination unit determines that the second communication is not in a connected state, the buffer status acquired by the buffer status acquisition unit Accordingly, when the second determination unit determines that the second communication is in the connected state, the first sleep time is determined from the first sleep time. When the second sleep time is determined to be small, the first determination unit determines that the first communication is not in the connected state, and the second determination unit determines that the second communication is not in the connected state. The third sleep time is determined to be larger than the first sleep time.

  With such a configuration, when the first communication is in a connected state (for example, a state in which a TCP (Transmission Control Protocol) connection is established), even if there is no upstream transmission data, the user can Since uplink transmission data can be generated by performing the above operation, it is possible to improve the responsiveness to the occurrence of such uplink transmission data by setting the length of the sleep period to be equal to or shorter than the first sleep time. . Also, for example, when the first communication is transport layer communication, the length of the sleep period can be controlled according to the connection of the first communication regardless of the communication in the upper application layer. . Therefore, even when communication according to a new communication standard (protocol) is added in a layer higher than the first layer, if the communication is performed by the first communication, an appropriate sleep for the communication is performed. Control can be performed. In addition, when the second communication is in a connected state (for example, a state in which a session of SIP (Session Initiation Protocol) is established), it is generally considered that real-time property is required. Even if there is no communication delay, the delay of the communication can be prevented by setting the length of the sleep period to the second sleep time. Further, when the first and second communications are not performed, the length of the sleep period is set to the third sleep time, for example, in a situation where communication traffic hardly occurs at night or when there is no communication. Thus, it is possible to effectively save power.

Further, in the slave station device according to the present invention, the sleep control unit transmits the sleep request to the master station device by the optical transmission unit and transmits from the master station device in response to the transmission of the sleep request when the optical receiver is put to sleep. When the received sleep permission is received by the optical receiving unit, the optical receiving unit may be caused to sleep periodically.
With such a configuration, when the sleep is permitted also in the master station device, periodic sleep is performed, and more reliable sleep control can be performed.

In the slave station device according to the present invention, the sleep control unit may also cause the optical transmission unit to sleep according to the buffer status acquired by the buffer status acquisition unit.
With such a configuration, not only the optical receiving unit but also the optical transmitting unit can be the target of sleep control, and the power consumption in the slave station device can be further reduced.

In the slave station device according to the present invention, the sleep control unit may cause the optical transmission unit to sleep when there is no data to be transmitted according to the buffer status.
With such a configuration, in a situation where there is no uplink transmission data, the optical transmission unit that performs the transmission is set to sleep, so that power saving can be achieved while reducing the influence on the transmission of the uplink transmission data. become.

  In the slave station apparatus according to the present invention, the buffer status may be at least one of a data arrival interval and a buffer amount.

  According to the slave station apparatus according to the present invention, periodic sleep can be controlled so as to realize both power saving and real-time property securing.

The block diagram which shows the structure of the PON system by embodiment of this invention The block diagram which shows the structure of OLT by the embodiment The block diagram which shows the structure of ONU by the same embodiment A flowchart showing the operation of the OLT according to the embodiment A flowchart showing the operation of the ONU according to the embodiment The figure for demonstrating the sleep control by the embodiment The figure for demonstrating the sleep time by the embodiment Diagram for explaining TCP connection start Diagram for explaining TCP connection termination Diagram for explaining generation and disconnection of SIP session

  Hereinafter, the PON system of the present invention will be described using embodiments. In the following embodiments, components and steps denoted by the same reference numerals are the same or equivalent, and repetitive description may be omitted. The PON system according to the present embodiment controls periodic sleep time in the ONU.

  FIG. 1 is a block diagram showing a configuration of a PON system (passive optical network system) according to the present embodiment. The PON system according to the present embodiment includes an OLT (master station device) 1 and a plurality of ONUs (slave station devices) 2-1, 2-2,. 2-N (N is an integer of 2 or more). Note that the ONUs 2-1 2-2,. The OLT 1 is sometimes referred to as a station-side optical terminator, and the ONU 2 is sometimes referred to as a subscriber-side optical terminator. The optical signal transmitted from the OLT 1 through the optical fiber is branched by the splitter 3 and reaches each ONU 2. The optical signal transmitted from each ONU 2 via the optical fiber reaches the OLT 1 via the splitter 3. Note that the OLT 1 controls the transmission timing of each ONU 2 so that data transmitted from the ONU 2 does not collide with data transmitted from other ONUs 2. A server, a network, and the like are connected to the upstream side of the OLT 1. A PC and other user terminals are connected to the downstream side of the ONU 2.

  FIG. 2 is a block diagram showing a configuration of the OLT 1 in the PON system. In FIG. 2, the OLT 1 includes a transmission buffer 11, a reception buffer 12, an optical transmission / reception unit 13, a WDM 14, a buffer status acquisition unit 15, a control unit 16, and an interface 17. The optical transmission / reception unit 13 includes an optical transmission unit 31 and an optical reception unit 32. The control unit 16 has a sleep determination unit 33.

  In the transmission buffer 11, downlink transmission data transmitted to the ONU 2 is buffered for each ONU 2. In the reception buffer 12, the uplink reception data transmitted from the ONU 2 is buffered. The optical transmission unit 31 of the optical transmission / reception unit 13 transmits the data buffered in the transmission buffer 11 to the ONU 2. In the transmission, the optical transmission unit 31 converts electrical signal data into an optical signal and transmits the optical signal. The optical receiver 32 of the optical transmitter / receiver 13 receives data transmitted from the ONU 2. In the reception, the optical receiver 32 receives the optical signal and converts it into electrical signal data. A WDM (Wavelength Division Multiplexing) 14 multiplexes or separates optical signals having different wavelengths. An optical signal from the optical transmission unit 31 is transmitted by an optical fiber via the WDM 14, and an optical signal from the optical fiber is input to the optical reception unit 32 via the WDM 14.

  The buffer status acquisition unit 15 acquires a buffer status related to the data buffering status in the transmission buffer 11. The buffer status may be, for example, at least one of a data arrival interval and a buffer amount. The buffer amount is the amount of data accumulated in the transmission buffer 11. The buffer status may be an average value according to the latest predetermined period.

  The control unit 16 performs OLT side control based on the PON protocol, and includes a sleep determination unit 33. The control unit 16 accumulates the downlink transmission data received via the interface 17 in the transmission buffer 11, reads the buffered downlink transmission data, and transmits it to the ONU 2 via the optical transmission / reception unit 13. In addition, the control unit 16 receives the uplink reception data transmitted from the ONU 2 via the optical transmission / reception unit 13, accumulates it in the reception buffer 12, reads out the buffered uplink reception data, and reads the interface 17. To the upstream device or network. Moreover, the control part 16 controls those optical communications so that the uplink data transmitted from each ONU2 may not collide. Note that the processing of the control unit 16 other than the sleep determination unit 33 is known in the conventional PON system, and detailed description thereof is omitted.

When the OLT 1 receives a sleep application transmitted from the ONU 2, the sleep determination unit 33 determines whether the ONU 2 that transmitted the sleep application may sleep using the acquired buffer status. If the result of the determination is that sleep is allowed, the sleep determination unit 33 transmits a sleep permission to the ONU 2 that transmitted the sleep application. On the other hand, as a result of the determination, if it is not good to go to sleep, the sleep determination unit 33 may transmit a sleep non-permission to the ONU 2 that has transmitted the sleep application, or nothing is transmitted. May be. Further, the sleep request may be included in the sleep request transmitted from the ONU 2. When the sleep request includes the sleep time, the sleep determination unit 33 determines that the sleep time determined using the buffer status is shorter than the sleep time included in the sleep request. The sleep permission including the sleep time may be transmitted. Details of the processing of the sleep determination unit 33 will be described later.
The interface 17 implements an interface function with an upstream device or network.

  FIG. 3 is a block diagram showing the configuration of the ONU 2 in the PON system. In FIG. 3, the ONU 2 includes a transmission buffer 21, a reception buffer 22, an optical transmission / reception unit 23, a WDM 24, a buffer status acquisition unit 25, a control unit 26, and an interface 27. The optical transmitter / receiver 23 includes an optical transmitter 41 and an optical receiver 42. The control unit 26 includes a first determination unit 43, a second determination unit 44, and a sleep control unit 45.

  In the transmission buffer 21, uplink transmission data transmitted to the OLT 1 is buffered. In the reception buffer 22, downlink reception data transmitted from the OLT 1 is buffered. The optical transmission unit 41 of the optical transmission / reception unit 23 transmits the data buffered in the transmission buffer 21 to the OLT 1. In the transmission, the optical transmission unit 41 converts electrical signal data into an optical signal and transmits the optical signal. The optical receiver 42 of the optical transmitter / receiver 23 receives the data transmitted from the OLT 1. In the reception, the optical receiver 42 receives the optical signal and converts it into electrical signal data. The optical transmitter / receiver 23 receives only the data destined for its own ONU 2 among the received downlink data, and discards the data destined for the other ONU 2. The WDM 24 multiplexes or separates optical signals having different wavelengths. An optical signal from the optical transmission unit 41 is transmitted by an optical fiber via the WDM 24, and an optical signal from the optical fiber is input to the optical reception unit 42 via the WDM 24.

  The buffer status acquisition unit 25 acquires a buffer status related to the data buffering status in the transmission buffer 21. The buffer status may be at least one of a frame arrival interval and a buffer amount, for example. The buffer amount is the amount of data accumulated in the transmission buffer 21. The buffer status may be an average value according to the latest predetermined period.

  The control unit 26 performs control on the ONU side based on the PON protocol, and includes a first determination unit 43, a second determination unit 44, and a sleep control unit 45. The control unit 26 accumulates the uplink transmission data received via the interface 27 in the transmission buffer 21, reads the buffered uplink transmission data, and transmits it to the OLT 1 via the optical transmission / reception unit 23. Further, the control unit 26 receives the downlink reception data transmitted from the OLT 1 via the optical transmission / reception unit 23, accumulates it in the reception buffer 22, and reads the buffered downlink reception data to read the interface 27. To the downstream device or network. Further, the control unit 26 controls the uplink transmission data to be transmitted according to the instruction from the OLT 1 so that the uplink data transmitted from each ONU 2 does not collide. Note that the processes of the control units 26 other than the first and second determination units 43 and 44 and the sleep control unit 45 are known in the conventional PON system, and detailed description thereof is omitted.

  The first determination unit 43 determines the connection state related to the first communication in the first layer according to at least one of the data transmitted by the optical transmission unit 41 and the data received by the optical reception unit 42. . The determination is a determination regarding whether or not the first communication is in a connected state. In the present embodiment, the case where the first layer is a transport layer and the first communication is TCP communication will be mainly described. However, the first communication includes the establishment of communication and the end of communication. Any existing communication may be used, and the communication is not limited to TCP communication. Further, the first layer may be other than the transport layer.

  When the first communication is TCP, a state in which a TCP connection is established is a connection state. In TCP, communication is established as shown in FIG. 8A (3-way handshake). First, apparatus A transmits a SYN packet to apparatus B. When the device B receives the SYN packet, the device B transmits a SYN + ACK packet to the device A accordingly. When device A receives the SYN + ACK packet, device A transmits an ACK packet indicating the start of connection to device B, and TCP communication is performed between devices A and B. In TCP, communication is terminated as shown in FIG. 8B. First, when there is no data to be transmitted from the device A to the device B, the device A transmits a FIN packet to the device B. When apparatus B receives the FIN packet, apparatus B transmits an ACK packet to apparatus A accordingly. Thereafter, when there is no more data to be transmitted from the device B to the device A, the device B transmits a FIN packet to the device A. When device A receives the FIN packet, device A transmits an ACK packet to device B accordingly. In this way, TCP communication between the devices A and B is completed. Note that TCP communication may be terminated as shown in FIG. 8B, but this may not be the case. For example, the communication is ended also when the power of the device B is turned off during the communication. Even in such a situation, apparatus A determines that the connection with apparatus B has been established because it has not performed connection termination processing. Therefore, in TCP, it is possible to confirm that communication is in an established state by periodically transmitting and receiving keep alive packets. That is, when the power of the device B is turned off, the device A has terminated the connection with the device B because the keep-alive packet does not arrive or there is no response to the keep-alive packet. Can know. Needless to say, the connection start process may be performed from the apparatus B side, and the connection end process may be performed from the apparatus B side.

  For example, when the first determination unit 43 observes uplink transmission data and downlink reception data and detects that a three-way handshake process has been performed, the first communication is in a connected state ( That is, it may be determined that a TCP connection has been established. Further, for example, when the first determination unit 43 observes uplink transmission data and downlink reception data and detects that connection termination processing has been performed, the first communication is no longer in a connected state (ie, It may be determined that the TCP connection is released. In addition, the first determination unit 43 observes uplink transmission data and downlink reception data, for example, and when it is determined that the first communication is in a connected state, the first determination unit 43 performs keep alive for a predetermined time or more. When the transmission / reception is not performed, it may be determined that the first communication is no longer connected (that is, the TCP connection is released). The predetermined time may be, for example, 30 seconds, may be longer than 1 minute, 5 minutes, 30 minutes, etc., or may be 10 seconds shorter than 30 seconds. . The time may be set manually by the user, or may be automatically set based on a transmission interval of keepalives that are periodically transmitted. In addition, the first determination unit 43 may make a determination regarding the first communication by observing only uplink or downlink data. For example, when one of the SYN packet or SYN + ACK packet is observed, it may be determined that the TCP connection is established, and when the FIN packet is observed, it may be determined that the TCP connection is terminated. .

  The second determination unit 44 determines whether the second layer is a higher layer than the first layer, according to at least one of the data transmitted by the optical transmission unit 41 and the data received by the optical reception unit 42. A connection state relating to the second communication is determined. The determination is a determination regarding whether or not the second communication is in a connected state. In the second communication, communication other than the first communication is performed in the first layer. For example, when the first communication is TCP communication in the transport layer, the second communication may be UDP (User Datagram Protocol) communication in the transport layer. In the present embodiment, the case where the second layer is an application layer and the second communication is SIP communication using UDP will be mainly described. However, the second communication is communication establishment and communication termination. Is not limited to SIP communication. The second layer may be other than the application layer as long as it is higher than the first layer.

  When the second communication is SIP, the connection state is a state in which a SIP session is established. In SIP, communication is established and disconnected as shown in FIG. 8C. First, the calling side transmits an INVITE message to the called side. In response to the transmission of the INVITE message, 100 Trying, which is a provisional response notifying that INVITE is being executed, is transmitted. The called party that has received the INVITE message performs a calling process such as ringing a ringing tone and transmits 180 Ringing, which is a provisional response notifying the calling party that the calling is in progress. On the called side, if there is a user process such that the handset goes off-hook according to the ringing tone, 200 OK is transmitted from the called side to the calling side accordingly. In response to the reception of the 200 OK, the calling side transmits an ACK that acknowledges the establishment of the session, and as a result, a SIP session is established between the calling side and the called side. As a result, voice data and the like are exchanged between the two, and a call state is established. In the case of disconnecting the connection, for example, when one user performs processing such as putting the handset on hook, a BYE message is transmitted from the user to the other party. Then, when the other party transmits 200 OK in response to receiving the BYE message, the SIP session is disconnected and the call is terminated. Although FIG. 8C shows a case where the BYE message is transmitted from the calling side, it goes without saying that the BYE message may be transmitted from the called side.

  For example, when the second determination unit 44 observes uplink transmission data and downlink reception data and detects that the SIP session establishment process is performed by UDP, the second communication is in a connected state. (That is, it may be determined that a SIP session has been established). The second determination unit 44 observes uplink transmission data and downlink reception data, for example, and detects that the connection termination process has been performed, that is, the second communication is no longer connected (that is, The SIP session may be disconnected). In addition, the second determination unit 44 may determine whether or not the second communication other than SIP is in a connected state. That is, the second determination unit 44 may make a determination for one type of second communication, or may make a determination for a plurality of types of second communication. In addition, the second determination unit 44 may make a determination regarding the second communication by observing only uplink or downlink data. For example, when an INVITE message is observed, or when a series of transmissions performed in the order of 100 Trying, 180 Ringing, and 200 OK is observed, it may be determined that a SIP session has been established. If observed, or if no communication is observed for a certain period after 200 OK is observed, it may be determined that the SIP session has ended.

  The sleep control unit 45 causes the light reception unit 42 to sleep periodically according to the buffer status acquired by the buffer status acquisition unit 25. That is, the sleep control unit 45 determines that the optical reception unit 42 is set to the sleep mode (power saving mode) when the buffer condition satisfies the sleep condition regarding reception, and the optical reception unit 45 when the sleep condition regarding reception is not satisfied. It may be determined that 42 is not in the sleep mode. The sleep control unit 45 may cause the optical transmission unit 41 to sleep according to the buffer status acquired by the buffer status acquisition unit 25. That is, the sleep control unit 45 determines that the optical transmission unit 41 is set to the sleep mode when the buffer condition satisfies the sleep condition regarding transmission, and sets the optical transmission unit 41 to the sleep mode when the sleep condition regarding transmission is not satisfied. You may decide not to. The optical receiving unit 42 is in the sleep mode when the optical receiving unit 42 periodically sleeps. This is because downlink received data from the OLT 1 can be received with a short delay. On the other hand, when the optical transmission unit 41 enters the sleep mode, the optical transmission unit 41 may periodically sleep or may sleep instead of periodically. This is because, in the case of the optical transmission unit 41, the sleep can be canceled appropriately according to the generation of uplink transmission data. Also, the sleep condition related to reception and the sleep condition related to transmission may be the same or different. In the present embodiment, both are the same, and the case where the sleep control unit 45 causes the optical transmission unit 41 and the optical reception unit 42 to sleep simultaneously will be mainly described. That is, in the present embodiment, a case where cyclic sleep (cyclic sleep) that is periodic TRx sleep is performed will be mainly described. Note that the sleep of the optical transmission unit 41 and the optical reception unit 42 means that power supply to the optical transmission unit 41 and the optical reception unit 42 is stopped. Thus, power consumption can be reduced by stopping the power supply. In addition, the periodic sleep means that a sleep state and an active state that is a state of not sleeping are alternately repeated. When the period of the sleep state is called a sleep period and the period of the active state is called an active period, in the periodic sleep, the sleep period and the active period are alternately repeated. The time length of the sleep period is called sleep time (Ts), the time length of the active period is called active time (Ta), and the time obtained by adding the sleep time and the active time is a period (Tp). ). That is, Ts + Ta = Tp. In periodic sleep, the period (Tp) may be constant or not. In the latter case, the active time (Ta) is constant, and the period (Tp) may change according to the fluctuation of the sleep time (Ts).

  Next, a method for determining the sleep time will be described. When the first determination unit 43 determines that the first communication is in the connected state and the second determination unit 44 determines that the second communication is not in the connected state, the sleep control unit 45 In accordance with the buffer status acquired by the buffer status acquisition unit 15, the sleep time is determined to be equal to or shorter than the first sleep time (Ts1). In addition, when the second determination unit 44 determines that the second communication is in the connected state, the sleep control unit 45 sets the sleep time to a second sleep time (Ts2) that is smaller than the first sleep time. ). The sleep control unit 45 also determines that the first determination unit 43 determines that the first communication is not in a connected state, and the second determination unit 44 determines that the second communication is not in a connected state. The sleep time is determined as a third sleep time (Ts3) that is larger than the first sleep time. The first sleep time Ts1 may be a time included in the range of 100 to 800 (ms), for example. Further, the second sleep time Ts2 may be a time included in a range of 10 to 100 (ms), for example. The third sleep time may be, for example, a time included in a range of 800 (ms) or more and less than 1 (s). Further, the period Tp may be 1 (s), for example. Note that the first to third sleep times and cycles may be other than the times described above as long as Ts2 <Ts1 <Ts3. However, in the current PON standard, in order to maintain reliable link connectivity between the OLT 1 and the ONU 2, the line connection is disconnected when there is no communication traffic for 1 (s) or more, and the period Tp is set to 1 ( It is preferable that communication be performed at least during an active period included in the cycle. Needless to say, the period Tp exceeding 1 (s) may be used when the international standard regarding the time for disconnecting the line is revised or when the time can be expanded in operation. Further, as described above, the active time Ta may be constant and Ta + Ts may be changed. However, even in this case, the period Tp = Ta + Ts is constant during the period in which the sleep time Ts does not change. . Also, the first and second sleep times may be fixed values or not. The case where the second sleep time can be changed will be described later. The third sleep time is usually a fixed value.

  Here, when the first determination unit 43 determines that the first communication is in the connected state and the second determination unit 44 determines that the second communication is not in the connected state, the sleep control unit 45. A brief description will be given of how to determine the sleep time. In such a case, for example, the sleep control unit 45 may determine the sleep time such that the shorter the data arrival interval indicated by the buffer status, the shorter the sleep time, and the buffer amount indicated by the buffer status. The sleep time may be determined so that the sleep time becomes shorter as the number of times increases, or a combination of both may be used. In any case, as described above, it is assumed that the sleep time determined by the sleep control unit 45 is equal to or shorter than the first sleep time. Note that a lower limit value greater than 0 may be set for the sleep time, or not. In the latter case, it may be considered that the lower limit value is zero.

  The sleep control unit 45 transmits the sleep request to the OLT 1 by the optical transmission unit 41 when the optical reception unit 42 is put to sleep, and the sleep permission transmitted from the OLT 1 in response to the transmission of the sleep application is the optical reception. When received by the unit 42, the optical receiving unit 42 may be shifted to the sleep mode. The sleep application may include the determined sleep time. The sleep permission may include a sleep time that is finally set. When the sleep time is included in the sleep permission, the sleep control unit 45 may control the sleep using the sleep time included in the sleep permission. That is, the sleep control may be performed such that the sleep period corresponding to the sleep time included in the sleep permission and the active period are repeated. The sleep time included in the sleep permission may be the same as or different from the sleep time included in the sleep application. In the latter case, the sleep time included in the sleep permission is usually shorter than the sleep time included in the sleep application. This is because it is preferable to employ the shorter sleep time of the sleep time determined by the ONU 2 and the sleep time determined by the OLT 1. Note that when the sleep permission does not include the sleep time, the sleep control unit 45 may control the sleep using the sleep time determined by itself. On the other hand, when the sleep permission is not transmitted from the OLT 1 in response to the transmission of the sleep application, or when the sleep non-permission transmitted from the OLT 1 is received by the light receiving unit 42, the sleep control unit 45 The optical receiver 42 and the like do not have to be shifted to the sleep mode. Note that after shifting to the sleep mode, the sleep control unit 45 controls the power supply to the optical transmission / reception unit 23 so that the sleep for each set sleep time is repeated. Further, in order to notify the OLT 1 that the ONU 2 is in the active period in the sleep mode, for example, the ONU 2 may transmit the fact that the active period has been reached to the OLT 1 at the start of the active period. It does not have to be.

  The interface 27 implements an interface function with downstream devices and networks. Note that a plurality of interfaces 27 may exist when there are a plurality of downstream devices and the like.

  Here, the sleep condition will be described. The sleep condition may be, for example, that the buffer amount is less than the buffer amount threshold, the data arrival interval may be greater than the arrival interval threshold, or both. Good. When the buffer amount is equal to the threshold value, it may be determined that the buffer amount is less than the threshold value or not. Further, when the data arrival interval is equal to the threshold value, it may be determined that the data arrival interval is larger than the threshold value, or not. The same applies to the comparison with the threshold value performed in OLT 1 described later. The buffer amount threshold value may be, for example, a predetermined value or a value corresponding to the sleep time. In the former case, the threshold may be zero. In that case, the absence of buffered uplink transmission data is a necessary condition for shifting to the sleep mode. The latter case will be described. If the periodic sleep cycle is Tp (s), the sleep time is Ts (s), and the data transmission rate in the active period is R1 (b / s), the amount of data (bits) that can be transmitted in one cycle is , (Tp−Ts) × R1. Then, the sleep control unit 45 may calculate the data amount (Tp−Ts) × R1 by using the sleep time Ts when the mode is shifted to the sleep mode, and may use it as a buffer amount threshold. This is because if the buffer amount is equal to or less than the threshold value, the buffered uplink transmission data can be transmitted in one active period, so that it is considered that there is no problem even if it sleeps. The transmission rate R1 may be set in advance or measured. Further, the threshold value of the data arrival interval may be a predetermined value, for example, or may be a value corresponding to the sleep time. In the latter case, the longer the sleep time, the longer the arrival interval threshold may be set. In this case, the threshold value of the arrival interval may be calculated using, for example, an increasing function using the sleep time as an argument, or may be specified using a table that associates the sleep time with the threshold value. Further, the buffer status used in determining whether or not the sleep condition is satisfied may be information corresponding to a predetermined time, for example, or information corresponding to a time corresponding to the sleep time. Good. In the latter case, for example, when the sleep time is long, the determination may be made using the buffer status corresponding to the longer time. For example, when the sleep time is Ts2, the determination may be performed according to the buffer status for 1 second, and when the sleep time is Ts3, the determination may be performed according to the buffer status for 50 seconds. . As described above, when the buffer status corresponding to different times is used, the buffer status acquisition unit 15 can acquire the buffer status corresponding to the different times (for example, the buffer status per second). Etc.) may be acquired in advance, and the buffer status corresponding to the desired time may be acquired using the information. Further, when a sleep time is necessary in determining a sleep condition or the like, the sleep time when shifting to the sleep mode at that time may be used. The method for calculating the sleep time is as described above. Although an example of the sleep condition used by the ONU 2 has been described, it goes without saying that the sleep condition may be other than the above description. For example, sleep conditions that are already known may be used.

  Next, the sleep conditions used in OLT 1 and the sleep time calculated in OLT 1 will be described. The sleep condition may be, for example, that the buffer amount is smaller than the buffer amount threshold, the data arrival interval may be larger than the arrival interval threshold, as in the case of ONU2, or Or both. The buffer amount threshold value may be, for example, a predetermined value or a value corresponding to the sleep time, as in the case of the ONU 2. The buffer amount threshold may be calculated by (Tp−Ts) × R2. The R2 is a transmission rate (b / s) from the OLT 1 to the ONU 2 in the active period. The arrival interval threshold may be the same as in the case of ONU2. As the sleep time Ts, the sleep time included in the sleep application may be used. Note that the sleep determination unit 33 may determine whether there is a sleep time that satisfies the sleep condition when it is determined that the sleep condition is not satisfied using the sleep time included in the sleep application. Then, when there is a sleep time that satisfies the sleep condition, it may be determined that the sleep condition is satisfied. For example, it is assumed that the condition regarding the data arrival interval is satisfied and the condition regarding the buffer amount is not satisfied. Assuming that the buffer amount is B (bit), if B / R2 is shorter than the period Tp, the condition regarding the buffer amount can be satisfied by shortening the sleep time. Therefore, when B / R2 <Tp is satisfied, the sleep determination unit 33 may determine that the sleep condition is satisfied. Then, when the sleep time included in the sleep application is Tp-B / R2 or more, the sleep determination unit 33 determines the sleep time as the sleep time included in the sleep application, and is not so. In this case, the sleep time may be determined as a sleep time equal to or less than Tp-B / R2. Then, the sleep permission including the determined sleep time may be transmitted to the ONU 2. On the other hand, when B / R2 <Tp is not satisfied, the sleep determination unit 33 may perform control so that sleep disapproval is transmitted so that the ONU 2 does not enter the sleep mode. Here, determining whether B / R2 <Tp is satisfied is the same as determining whether the buffer amount is less than Tp × R2. Although an example of the sleep condition used by the OLT 1 has been described, it goes without saying that the sleep condition may be other than the above description. For example, sleep conditions that are already known may be used.

  In addition, data transmitted and received in the PON system is usually a frame. Therefore, the above-described transmission data and reception data may be considered as a transmission frame and a reception frame. Note that data other than frames may be transmitted and received.

  Next, the relationship between the first and second communications and the relationship between the connection state of the first and second communications and the sleep time will be described with reference to FIGS. If communication such as a session or connection is in a connected state between the OLT 1 and the ONU 2, even if the data is not transmitted / received, there is a high possibility that the data will be transmitted / received after that. From the viewpoint of securing real-time properties, it is preferable not to increase the sleep time. Further, when determining whether or not the communication is in a connected state, more communication can be covered if it is determined by the first communication in the lower layer. For example, as shown in FIG. 6, communication such as HTTP (Hypertext Transfer Protocol) and FTP (File Transfer Protocol) can be covered by determining whether TCP communication is in a connected state. On the other hand, when only the connection state of the first communication is determined, UDP communication is leaked. Therefore, in the present embodiment, UDP communication is individually determined by higher layer SIP, other communication establishing a session such as a video conference, and the like. Note that, for example, SIP is communicable with TCP according to the standard, but when SIP based on TCP is performed, it is included in the first communication. Further, the main reason why SIP, video conference, and the like communicate using UDP instead of TCP is to improve real-time performance. Therefore, normally, the second communication can be considered to have a higher real-time requirement than the first communication. Therefore, as shown in FIG. 7, when the second communication is in a connected state, The sleep time is set to the shortest second sleep time. In addition, although the second communication is not performed, as a situation in which the first communication is performed, for example, a case where a user is browsing a website and HTTP communication is performed is considered. . In such a case, when the user frequently changes the browsing destination, it is considered that the responsiveness of the user is higher when the responsiveness is better. On the other hand, when the user does not change the browsing destination so much, even if the responsiveness is not good, it is considered that the quality of experience of the user is not lowered. Therefore, in a situation where the second communication is not performed but the first communication is performed, the user can control the sleep time so as to be equal to or less than the first sleep time according to the buffer status. As long as the quality of experience is not impaired, the effect of suppressing power consumption can be enhanced. Controlling the sleep time according to the buffer status means that the sleep time is controlled so that the communication is more frequent depending on the buffer status, and the communication is not frequent (sparse). May be controlled so as to have a longer sleep time. On the other hand, when the first and second communications are not in a connected state, communication such as a session or a connection is not in a connected state between the OLT 1 and the ONU 2, so that the user goes out when there is no data transmission / reception. It can be considered that there is virtually no communication, such as during sleeping or sleeping. Therefore, in the sleep mode in such a situation, the sleep time is set to the longest third sleep time, and the power consumption is further reduced. In this way, it is possible to appropriately realize both real-time performance and reduced power consumption according to the communication status.

  Next, the operation of the OLT 1 will be described using the flowchart of FIG. Note that the flowchart of FIG. 4 shows the processing of the OLT 1 related to sleep control, and the processing related to optical communication between the OLT 1 and the ONU 2 is performed separately from the processing shown in this flowchart.

  (Step S101) The buffer status acquisition unit 15 determines whether it is time to acquire the buffer status. If it is time to acquire the buffer status, the process proceeds to step S102; otherwise, the process proceeds to step S106. Note that the buffer status acquisition unit 15 may periodically determine, for example, that it is time to acquire the buffer status.

  (Step S102) The buffer status acquisition unit 15 acquires the buffer status for each ONU 2.

  (Step S103) The sleep determination unit 33 determines whether there is an ONU 2 that is currently in the sleep mode. And when it exists, it progresses to step S104, and when that is not right, it returns to step S101. In this step, information indicating whether each ONU 2 is in the sleep mode and managed by the OLT 1 may be used.

  (Step S104) The sleep determination unit 33 determines whether the sleep condition is satisfied for the ONU 2 that is currently in the sleep mode, using the buffer status acquired in step S102. If the sleep condition is satisfied, the process returns to step S101. If the sleep condition is not satisfied, the process proceeds to step S105.

  (Step S105) The sleep determination unit 33 performs control so that a sleep release instruction (wake-up instruction) is transmitted for the ONU 2 that has determined that the sleep condition is not satisfied. The sleep cancellation instruction is transmitted via the optical transmission unit 31 when the ONU 2 in the sleep mode enters the active period.

  If it is determined in step S103 that two or more ONUs 2 are in the sleep mode, the processing in steps S104 and S105 is performed for each ONU 2.

  (Step S106) The sleep determination unit 33 determines whether or not the sleep application transmitted from the ONU 2 has been received by the optical reception unit 32. If the sleep application is received, the process proceeds to step S107. If not, the process returns to step S101.

  (Step S107) The sleep determination unit 33 determines whether the ONU 2 satisfies the sleep condition by using the latest buffer status regarding the ONU 2 that has transmitted the sleep application. If the sleep condition is satisfied, the process proceeds to step S108. If the sleep condition is not satisfied, the process proceeds to step S111. For example, as described above, the sleep determination unit 33 may determine that the sleep condition is not satisfied when B / R2 <Tp is not satisfied.

  (Step S108) The sleep determination unit 33 determines whether or not the sleep time included in the sleep application is appropriate by using the latest buffer status regarding the ONU 2 that transmitted the sleep application. If it is appropriate, the process proceeds to step S109; otherwise, the process proceeds to step S110. For example, as described above, the sleep determination unit 33 may determine that the sleep time is not appropriate when the buffer amount indicated by the latest buffer status is not less than (Tp−Ts) × R2.

  (Step S109) The sleep determination unit 33 controls the ONU 2 that has transmitted the sleep application to transmit a sleep permission that permits the transition to the sleep mode. Note that the sleep permission may not include the sleep time, or may include the sleep time included in the sleep application. Then, the process returns to step S101.

  (Step S110) The sleep determination unit 33 controls the ONU 2 that has transmitted the sleep request to transmit a sleep permission that permits the transition to the sleep mode. It is assumed that the sleep permission includes a sleep time determined using the latest buffer status related to the ONU 2 that transmitted the sleep application. The sleep time is usually shorter than the sleep time included in the sleep application. Then, the process returns to step S101. For example, as described above, the sleep determination unit 33 may determine the sleep time as Tp-B / R2.

  (Step S111) The sleep determination unit 33 controls the ONU 2 that has transmitted the sleep application to transmit a sleep non-permission that does not permit the transition to the sleep mode. Then, the process returns to step S101.

  In the flowchart of FIG. 4, when sleep is not permitted, sleep non-permission may not be transmitted. Further, the order of processing in the flowchart of FIG. 4 is an example, and the order of each step may be changed as long as the same result can be obtained. In the flowchart of FIG. 4, the process is terminated by power-off or a process termination interrupt.

  Next, the operation of the ONU 2 will be described using the flowchart of FIG. The flowchart of FIG. 5 shows the processing of the ONU 2 related to sleep control. The processing related to optical communication between the OLT 1 and the ONU 2 and the processing of sleep control according to the set sleep time are shown in this flowchart. It is assumed that it is performed separately from the process indicated by.

  (Step S201) The buffer status acquisition unit 25 determines whether it is time to acquire the buffer status. If it is time to acquire the buffer status, the process proceeds to step S202. If not, the process proceeds to step S216. Note that the buffer status acquisition unit 25 may periodically determine, for example, that it is time to acquire the buffer status.

  (Step S202) The buffer status acquisition unit 25 acquires the buffer status.

  (Step S203) The sleep control unit 45 determines whether the sleep condition is satisfied using the buffer status acquired in step S202. If the sleep condition is satisfied, the process proceeds to step S204. If the sleep condition is not satisfied, the process proceeds to step S214.

  (Step S204) The sleep control unit 45 determines whether or not the second communication is in the connected state by using the latest determination result by the second determination unit 44. And when it is in a connected state, it progresses to step S205, and when that is not right, it progresses to step S211.

  (Step S205) The sleep control unit 45 determines the sleep time as the second sleep time.

  (Step S206) The sleep control unit 45 determines whether or not to transmit a sleep application. And when transmitting a sleep application, it progresses to step S207, and when that is not right, it returns to step S201. Note that, for example, when the ONU 2 is not currently in the sleep mode, the sleep control unit 45 may determine to transmit a sleep application. The sleep control unit 45 determines that the sleep application is to be transmitted when the ONU 2 is currently in the sleep mode and the sleep time determined in step S205 or the like is different from the sleep time in the current sleep mode, for example. Also good. When the determined sleep time is the same as the current sleep time, it may be determined that the sleep request is not transmitted.

  (Step S207) The sleep control unit 45 controls the sleep application including the sleep time determined in step S205 or the like to be transmitted to the OLT 1. The sleep application is transmitted at a timing at which the ONU 2 can transmit to the OLT 1.

  (Step S208) The sleep controller 45 determines whether or not the sleep permission transmitted from the OLT 1 is received by the optical receiver 42. If sleep permission is received, the process proceeds to step S209, and if not, the process proceeds to step S210.

  (Step S209) When the sleep time is not included in the sleep permission, or when the sleep time included in the sleep application is included in the sleep permission, the sleep control unit 45 determines the sleep time determined by the ONU 2 Set to sleep mode. On the other hand, when the sleep permission different from the sleep time included in the sleep application is included in the sleep permission, the sleep control unit 45 is set to the sleep mode of the sleep time included in the sleep permission. Set. Thereafter, periodic sleep using the set sleep time is performed. Then, the process returns to step S201.

  (Step S210) The sleep control unit 45 determines whether or not the sleep non-permission transmitted from the OLT 1 is received by the optical receiving unit 42. And when sleep non-permission is received, it returns to step S201, and when that is not right, it returns to step S208.

  (Step S211) The sleep control unit 45 determines whether or not the first communication is in the connected state using the latest determination result by the first determination unit 43. And when it is in a connection state, it progresses to step S212, and when that is not right, it progresses to step S213.

  (Step S212) The sleep control unit 45 determines the sleep time to be equal to or less than the first sleep time according to the latest buffer status.

  (Step S213) The sleep control unit 45 determines the sleep time as the third sleep time.

  (Step S214) The sleep control unit 45 determines whether the ONU 2 is in the sleep mode. If it is in the sleep mode, the process proceeds to step S215. If not, the process returns to step S201.

  (Step S215) The sleep control unit 45 cancels the sleep mode. It should be noted that the OLT 1 is notified that the sleep mode has been canceled.

  (Step S216) The sleep control unit 45 determines whether it is time to make a determination by the first and second determination units 43 and 44. If it is the determination timing, the process proceeds to step S217, and if not, the process proceeds to step S218. Note that the sleep control unit 45 may periodically determine, for example, that the determination timing is reached.

  (Step S217) The first determination unit 43 determines whether or not the first communication is in a connected state. The second determination unit 44 determines whether the second communication is in a connected state. When there are a plurality of second communications, the second determination unit 44 may make a determination for each communication. Then, the process returns to step S201.

  (Step S218) The sleep control unit 45 determines whether or not the sleep release instruction transmitted from the OLT 1 is received by the optical receiving unit 42. If a sleep release instruction is received, the process proceeds to step S219. If not, the process returns to step S201.

  (Step S219) The sleep control unit 45 cancels the sleep mode. Then, the process returns to step S201.

  Note that when the OLT 1 determines that the sleep condition of the ONU 2 is not satisfied while the ONU 2 is sleeping, a sleep release instruction is transmitted from the OLT 1 to the ONU 2. Therefore, in the flowchart of FIG. 5, the ONU 2 is in the sleep state. Although it is considered that the sleep non-permission is not received, if such a sleep non-permission is received, the sleep mode may be canceled after determining YES in step S210. Further, during the period determined in advance after the sleep non-permission is received in step S210, it may not be determined in step S203 that the sleep condition is satisfied. When the sleep condition is not satisfied for the downlink transmission data in the OLT 1 and the sleep condition is satisfied for the uplink transmission data in the ONU 2, the transmission of the sleep application and the reception of the sleep non-permission are repeated in a short time This is to avoid the problem. Further, the order of processing in the flowchart of FIG. 5 is an example, and the order of each step may be changed as long as the same result can be obtained. Further, in the flowchart of FIG. 5, the process is ended by powering off or interruption for aborting the process.

  Further, processes other than determining the sleep time, for example, a process in which the OLT 1 knows the sleep timing of the ONU 2 and a process in which the OLT 1 changes the sleep timing of the ONU 2 are already known (for example, Patent Document 1 above). The detailed description is omitted.

Next, the operation of the passive optical network system according to this embodiment will be described using a specific example. In this specific example, it is assumed that the first communication is a TCP communication and the second communication is a call using SIP. In this specific example, the first to third sleep times Ts1 to Ts3 and the active time Ta are set as follows. The period Tp takes a different value depending on the sleep time, and is Ts + Ta. Note that, by setting the active time Ta to a short constant time in this way, when the sleep time is long, the ratio of the active time is shortened, and as a result, the power consumption can be further reduced. On the other hand, when the sleep time is short, the proportion of the active time increases accordingly, so that much more data can be communicated. Therefore, the degree of power saving and the amount of data that can be communicated can be controlled simply by controlling the sleep time.
First sleep time Ts1: 200 (ms)
Second sleep time Ts2: 50 (ms)
Third sleep time Ts3: 900 (ms)
Active time Ta: 20 (ms)

  It is assumed that a user operating a device on the downstream side of the ONU 2-1 has uploaded a plurality of images taken with a digital camera to the cloud. In this case, since there are many ONU2-1 upstream transmission frames, the transition to the sleep mode is not performed (steps S201 to S203, S214). After that, it is assumed that image uploading is finished, and the user starts browsing and starts browsing the website. Then, the first determination unit 43 detects a TCP three-way handshake and determines that the TCP is in a connected state (steps S216 and S217). At this time, it is assumed that the start of the SIP call is not detected. Further, it is assumed that the user has read a document described on a certain website. Thereafter, at the timing when the buffer status of the transmission buffer 21 is acquired by the buffer status acquisition unit 25, since the transmission interval of the upstream transmission frame is large and the buffer amount is small, the sleep control unit 45 determines that the sleep condition is satisfied. (Steps S201 to S203). In addition, since the SIP communication is not performed and the TCP communication is performed, the sleep control unit 45 sets the sleep time Ts to the first sleep time “200 (ms)” according to the buffer status. Determine (steps S204, S211, and S212). Then, the sleep application including the sleep time Ts is transmitted to the OLT 1 (steps S206 and S207).

  The sleep application is received by the optical receiver 32 of the OLT 1 and passed to the sleep determination unit 33 (step S106). When receiving the sleep application, the sleep determination unit 33 uses the sleep time “200 (ms)” to determine whether the sleep condition is satisfied (step S107). In this case, since there are almost no downlink transmission frames, it is assumed that the condition is satisfied without changing the sleep time (step S108). Then, the sleep permission including the sleep time “200 (ms)” is transmitted from the OLT 1 to the ONU 2-1 (step S109).

  The sleep permission is received by the optical receiver 42 of the ONU 2-1 and passed to the sleep controller 45 (step S 208). Upon receipt of the sleep permission, the sleep control unit 45 sets the sleep mode so that periodic sleep using the sleep time “200 (ms)” included in the sleep permission is performed (Step S45). S209). In this way, a periodic sleep that repeats a sleep period of 200 (ms) and an active period of 20 (ms) is performed.

  Thereafter, it is assumed that the user frequently clicks a link destination of a website in order to investigate. However, even in that situation, it is assumed that the sleep condition is satisfied. Then, it is assumed that the sleep control unit 45 determines the sleep time Ts to be 100 (ms) that is equal to or less than the first sleep time Ts1 according to the arrival interval of the uplink transmission frame (steps S201 to S204, S211, and S212). . Then, the sleep application is transmitted again (steps S206 and S207). Also in this case, if the sleep permission including the sleep time “100 (ms)” is transmitted from the OLT 1, the sleep time is shortened to 100 (ms) accordingly (steps S208 and S209). In addition, by shortening the sleep time as described above, the responsiveness to the click of the link destination by the user is improved, and the quality of experience of the user is improved.

  Next, it is assumed that a SIP call is started by another user and the user of the ONU 2-1 responds to it. Then, since the number of downlink transmission frames increases, a sleep cancel instruction is transmitted from the OLT 1 to the ONU 2-1 (steps S101 to S105), and accordingly, the sleep in the ONU 2-1 is canceled (steps S218 and S219). Further, the second determination unit 44 determines that the SIP call has been connected (steps S216 and S217). Thereafter, in the call, there is a period in which both are silent, and during that time, audio data is not transmitted and received, and the sleep condition is satisfied (steps S201 to S203). In this case, since the SIP call is in the connected state, the sleep control unit 45 determines the sleep time Ts to be the second sleep time “50 (ms)”, and sends a sleep application including the sleep time to the OLT 1. Transmit (steps S204 to S207). Also in this case, if the sleep permission including the sleep time “50 (ms)” is transmitted from the OLT 1, the sleep control unit 45 sets the sleep mode so that the periodic sleep using the sleep time is performed. Setting is performed (steps S208 and S209). For this reason, it is possible to reduce power consumption by repeating sleep for a short time, but not to cause a large delay when conversation is resumed. When the conversation is resumed, the sleep condition is not satisfied and sleep is canceled (steps S201 to S203, S214, and S215). The sleep cancellation may be performed by transmitting a sleep cancellation instruction from the OLT 1 to the ONU 2-1.

  Thereafter, it is assumed that the user ends the SIP call and the browsing of the website, and goes to bed. Then, the first determination unit 43 determines that the TCP communication is no longer in a connected state, and the second determination unit 44 determines that the SIP call is no longer in a connected state (steps S216 and S217). Then, after the sleep condition is satisfied, the sleep time Ts is determined as the third sleep time “900 (ms)” (steps S201 to S204, S211 and S213). In addition, a sleep application including the sleep time is transmitted to the OLT 1 (steps S206 and S207). Also in this case, if a sleep permission including the sleep time “900 (ms)” is transmitted from the OLT 1, a transition to the sleep mode using the sleep time “900 (ms)” is performed (step S1). S208, S209). Thus, at night when communication is not performed at all, a long sleep can be realized, and the power saving effect is increased. On the other hand, since the line between the OLT 1 and the ONU 2-1 can be kept connected, for example, even when another user makes a SIP call to the ONU 2-1 user. The user terminal can receive the INVITE message. When such a long sleep is performed, the response to the call can be delayed, but even if there is such a delay, the user's quality of experience will not be greatly reduced. Therefore, it is not considered to be a problem.

  Note that, for example, when TCP communication as the first communication is performed, communication by RTP (Real-time Transport Protocol) is performed according to establishment of a session corresponding to a predetermined application, and the RTP communication is performed. When the communication corresponds to the second communication, the second determination unit 44 may determine that the second communication has been started. Further, when the RTP communication is terminated (for example, when a RTCP (Real-time Transport Control Protocol) BYE message is communicated), the second determination unit 44 terminates the second communication. It may be determined that

  As described above, according to the passive optical network system according to the present embodiment, since the sleep time is determined according to whether or not the communication is in the connected state, even if the buffer amount is small, the communication is still connected. If so, a relatively short sleep time is set. As a result, when transmission / reception of data is resumed in communication in a connected state, responsiveness to the resumption can be improved. As a result, it is possible to improve the quality of experience of the user, for example. In addition, the connection state of such communication can be comprehensively grasped by the first communication of the lower layer, and can be grasped individually by the second communication of the upper layer, so that omissions are reduced. It is possible to grasp the connection state of communication. In addition, by grasping the communication state of the lower layer, even if communication based on a new communication standard (protocol) in the upper layer using the first communication of the lower layer is added, the communication standard can be supported. Will be able to. Also, whether or not the sleep application can be shifted to the sleep mode by transmitting the sleep request to the OLT 1 and performing the transition to the sleep mode in the ONU 2 in response to the sleep permission corresponding to the transmission being transmitted from the OLT 1. Judgment can be made more strictly.

  In the present embodiment, the case where the second communication is SIP communication has been mainly described, but it is needless to say that this is not necessary. The second communication may be, for example, communication using a session establishment protocol other than SIP using UDP in the transport layer.

  In the present embodiment, when ONU 2 shifts to the sleep mode, a sleep request is transmitted to OLT 1, and when sleep permission is transmitted according to the transmission, ONU 2 shifts to the sleep mode. It does n’t have to be. When the sleep condition is satisfied in the ONU 2, the ONU 2 may enter the sleep mode regardless of the determination in the OLT 1. Even in this case, in order for the OLT 1 to know the active period of the ONU 2 that has shifted to the sleep mode, it is preferable that the fact that it has shifted to the sleep mode is transmitted from the ONU 2 to the OLT 1. The transition to the sleep mode preferably includes a sleep time.

  Moreover, although this Embodiment demonstrated the case where cyclic sleep which makes the optical transmission part 41 and the optical reception part 42 sleep periodically at the same timing was demonstrated in ONU2, it does not need to be so. For example, as described above, the optical receiver 42 may perform periodic sleep, and the optical transmitter 41 may sleep according to the buffer status. That is, when the buffer status acquired by the buffer status acquisition unit 25 indicates that there is no uplink transmission data, the sleep control unit 45 causes the optical transmission unit 41 to sleep, and when uplink transmission data is generated. The sleep of the optical transmission unit 41 may be canceled and the transmission may be performed. In that case, since it is not necessary to periodically provide an active period for the optical transmitter 41, the sleep period can be maximized, and the effect of reducing power consumption is increased. Even after uplink transmission data is generated, uplink transmission may not be performed immediately. That is, depending on the transmission schedule of each ONU 2 determined by the OLT 1, it may be necessary to wait for uplink transmission a little. In such a case, for example, even after uplink transmission data is generated, sleep of the optical transmission unit 41 may be continued until actual transmission is possible. The optical transmitter 41 may be controlled not to sleep.

  In the present embodiment, when specific communication is performed, it may be determined that the sleep condition is not satisfied. For example, if a game requiring real-time communication is being performed, it may be better not to sleep even if the buffer amount is small. For example, even if the sleep time is about 50 (ms), the game result may differ depending on the delay. Therefore, when a game communication requiring real-time performance is performed, the sleep control unit 45 may determine that the sleep condition is not satisfied. When such a game requiring real-time performance is being played, it is considered that the data transmission frequency is high. Accordingly, by appropriately setting the threshold of the data arrival interval in the sleep condition, when such game communication is being performed, the sleep condition may be set not to be satisfied.

  Further, in the present embodiment, the second communication is communication that performs communication other than the first communication in the first layer, but this need not be the case. As long as the second communication is specific communication in the second layer, the communication method in the first layer is not limited. In that case, for example, the SIP communication by TCP may be considered as the second communication. By doing so, it is only necessary to look at the second layer to determine whether a certain communication is the second communication, and the determination process is simplified. On the other hand, when the second communication is communication that performs communication other than the first communication in the first layer, for example, a protocol that does not require high responsiveness compared to UDP, such as TCP, Since a short sleep time is not set, there can be a merit from the viewpoint of power saving.

  In the present embodiment, the sleep control unit 45 uses the RTT (round trip time) with the communication partner, and the first communication is in the connected state and the second communication is not in the connected state. The sleep time may be determined or the second sleep time may be determined. Specifically, the sleep control unit 45 measures the RTT of the first communication or the second communication. The measurement may be performed using, for example, a packet transmitted / received for establishing a TCP connection, or may be performed using other transmission / reception (for example, an ACK is returned for transmission). . Then, the sleep control unit 45 may perform control so that the sleep time becomes long when the RTT is large, and control so that the sleep time becomes short when the RTT is small. For example, when the RTT is 1200 (ms), even if the sleep time is shortened from 200 (ms) to 50 (ms), it is considered that the user's experience quality does not change. On the other hand, when the RTT is 200 (ms), it is considered that the quality of experience of the user is improved if the sleep time is shortened from 200 (ms) to 50 (ms). Therefore, by controlling the sleep time according to the RTT as described above, the sleep time can be lengthened and the power consumption can be further reduced without impairing the user's quality of experience. It is conceivable that the sleep period may be straddled during the measurement of the RTT. That is, a sleep period may be entered after a packet is transmitted until an ACK corresponding to the packet is returned. In this case, since the accurate RTT cannot be measured, the sleep control unit 45 may perform the above-described control using an RTT that does not extend over the sleep period.

  In the above embodiment, each process or each function may be realized by centralized processing by a single device or a single system, or may be distributedly processed by a plurality of devices or a plurality of systems. It may be realized by doing.

  In the above embodiment, the information exchange between the components is performed by one component when, for example, the two components that exchange the information are physically different from each other. It may be performed by outputting information and receiving information by the other component, or when two components that exchange information are physically the same, one component May be performed by moving from the phase of the process corresponding to to the phase of the process corresponding to the other component.

  In the above embodiment, information related to processing executed by each component, for example, information received, acquired, selected, generated, transmitted, or received by each component In addition, information such as threshold values, mathematical formulas, addresses, and the like used by each constituent element in processing may be temporarily or for a long time held in a recording medium (not shown), even if not specified in the above description. Further, the storage of information on the recording medium (not shown) may be performed by each component or a storage unit (not shown). Further, reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

  In the above embodiment, when information used by each component, for example, information such as a threshold value, an address, and various setting values used by each component may be changed by the user, Even if it is not specified in the description, the user may be able to change the information as appropriate, or may not be so. If the information can be changed by the user, the change is realized by, for example, a not-shown receiving unit that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. May be. The change instruction received by the receiving unit (not shown) may be received from an input device, information received via a communication line, or information read from a predetermined recording medium, for example. .

  In the above-described embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. At the time of execution, the program execution unit may execute the program while accessing the storage unit or the recording medium. The program may be executed by being downloaded from a server or the like, or may be executed by reading a program recorded on a predetermined recording medium (for example, an optical disk, a magnetic disk, a semiconductor memory, or the like). Good. Further, this program may be used as a program constituting a program product. Further, the computer that executes the program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

  Further, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  As described above, according to the slave station device of the present invention, it is possible to control the periodic sleep so that both the power saving and the real-time property can be achieved, and as an ONU in the PON system, Useful.

2 ONU (slave station equipment)
DESCRIPTION OF SYMBOLS 21 Transmission buffer 22 Reception buffer 23 Optical transmission / reception part 25 Buffer status acquisition part 26 Control part 41 Optical transmission part 42 Optical reception part 43 1st judgment part 44 2nd judgment part 45 Sleep control part

Claims (5)

A slave station device in a passive optical network system in which a master station device and a plurality of slave station devices are connected by an optical communication path having a splitter,
A transmission buffer in which data transmitted to the master station device is buffered;
An optical transmitter that transmits data buffered in the transmission buffer to the master station device;
An optical receiver for receiving data transmitted from the master station device;
A buffer status acquisition unit for acquiring a buffer status related to a buffering status of data in the transmission buffer;
A first determination unit configured to determine a connection state related to first communication in a first layer according to at least one of data transmitted by the optical transmission unit and data received by the optical reception unit;
A connection state related to second communication in the second layer, which is a layer higher than the first layer, according to at least one of data transmitted by the optical transmission unit and data received by the optical reception unit A second determination unit for determining
A sleep control unit that periodically sleeps the optical reception unit according to the buffer status acquired by the buffer status acquisition unit,
The sleep control unit
The length of the sleep period in periodic sleep is determined by the first determination unit that the first communication is in a connected state, and the second communication unit is connected by the second determination unit. Is determined to be less than or equal to the first sleep time according to the buffer status acquired by the buffer status acquisition unit, and the second communication is in the connected state by the second determination unit. Is determined to be a second sleep time smaller than the first sleep time, the first determination unit determines that the first communication is not in a connected state, and the second When the second communication unit determines that the second communication is not in the connected state, the slave station device determines a third sleep time that is longer than the first sleep time. The sleep control unit transmits a sleep request to the master station device by the optical transmitter when the optical receiver is put to sleep, and the sleep permission transmitted from the master station device in response to the transmission of the sleep request. The slave station apparatus according to claim 1, wherein when the optical receiving unit is received by the optical receiving unit, the optical receiving unit is caused to sleep periodically. The slave station apparatus according to claim 1 or 2, wherein the sleep control unit also causes the optical transmission unit to sleep according to the buffer status acquired by the buffer status acquisition unit. The slave station apparatus according to claim 3, wherein the sleep control unit causes the optical transmission unit to sleep when there is no data to be transmitted according to the buffer status. The slave station apparatus according to any one of claims 1 to 4, wherein the buffer status is at least one of a data arrival interval and a buffer amount.

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