JP2014120883A - Slave station device, master station device, optical communication system, and band control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a slave station device for implementing effective use of a band and further power saving.SOLUTION: A slave station device 1 of an optical communication system in which a plurality of slave station devices 1 (ONU1, 1) and a master station device 3 (OLT3) are connected with optical transmission paths, and the master station device 3 determines a band to be allocated to each slave station device 1 on the basis of a data amount of data that each slave station device 1 desires to transmit operates while switching a normal mode for transmitting/receiving data to/from the master station device 3 and a power saving mode for performing minimum required communication for maintaining a link with the master station device 3 on the basis of a predetermined condition; and notifies the master station device 3 of 0 as a data amount of data desired to be transmitted during operation in the power saving mode.

Description

  The present invention relates to a communication system and a communication method in which a plurality of terminals are connected by a common line, for example, an OLT (Optical Line Terminal) and a plurality of ONUs (Optical Network Unit). PON (Passive Optical Network) system and the like.

  The PON system can accommodate one or more subscriber-side terminators (hereinafter referred to as ONUs) with a single station-side terminator (hereinafter referred to as OLT), compared to an optical access system in which ONUs and OLTs are connected one-to-one. Since communication services can be provided to subscribers at a low price, they are becoming popular in Japan and overseas. In recent years, there has been a demand for power saving of communication devices, and in an optical access network system, power saving is demanded especially for ONUs that occupy most of the power consumption due to the large number of units.

  Here, in the ONU, data communication is not always performed. For example, data communication may not be performed at all at night. As a power saving technique for the Ethernet (registered trademark) PON ONU, a technique for stopping the optical transmission / reception of the ONU during a time when data communication is not performed and shifting the power to the power saving state has been studied (for example, Non-Patent Document 1).

IEEE P1904.1 Draft 3.0

  In the upstream communication of a PON system that is communicating by time division multiple access (TDMA), the time when data cannot be packed in one upstream communication of one ONU, that is, the ONU turns the optical transmitter on and off. There is an overhead time and an overhead time until the OLT stably receives data. Therefore, the bandwidth can be used more effectively by assigning long transmission times little by little than by assigning short transmission times to each ONU many times. Also, the power consumption of the ONU can be reduced by the overhead. However, the technique described in Non-Patent Document 1 has a problem in that no consideration is given to reducing the overhead time ratio.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a slave station device, a master station device, an optical communication system, and a bandwidth control method that realize effective use of bandwidth and further power saving. .

  In order to solve the above-described problems and achieve the object, the present invention is configured such that a plurality of slave station devices and a master station device are connected by an optical transmission line, and each master station device desires transmission by each slave station device. A slave station device of an optical communication system that determines a bandwidth to be allocated to each slave station device based on a data amount of data that is transmitted between the normal mode for transmitting and receiving data to and from the master station device and the master station device It operates while switching the power saving mode for performing the minimum communication necessary for maintaining the link based on a predetermined condition. During the operation in the power saving mode, the data amount of data desired to be transmitted is 0. Is notified to the master station device.

  According to the present invention, there is an effect that it is possible to effectively use the bandwidth of the entire system.

FIG. 1 is a diagram showing a configuration example of an optical communication system according to the present invention. FIG. 2 is a diagram illustrating an example of a bandwidth allocation sequence. FIG. 3 is a diagram illustrating a conventional power saving sequence. FIG. 4 is a diagram showing a conventional band allocation sequence. FIG. 5 is a state transition diagram of a device to which power saving control is applied. FIG. 6 is a configuration diagram of a frame used in bandwidth allocation control.

  Hereinafter, embodiments of a slave station device, a master station device, an optical communication system, and a bandwidth control method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In the following embodiments, an optical communication system according to the present invention will be described by taking a PON (Passive Optical Network) system as an example.

  Here, power saving control and band allocation control in the conventional PON system will be described with reference to FIGS. FIG. 3 is a diagram illustrating a conventional power saving sequence. FIG. 4 is a diagram showing a conventional band allocation sequence. FIG. 5 is a state transition diagram of a device to which power saving control is applied. FIG. 6 is a diagram illustrating a configuration of a frame used in band allocation control.

  As shown in FIG. 3, in the conventional power saving sequence, the ONU (Optical Network Unit) receives the control frame from the OLT (Optical Line Terminal), and the ONU changes from the normal mode to the power saving cycle. Move to (Power saving cycle). A control frame for shifting to the power saving cycle is a SLEEP_ALLOW (TRx) frame, and a response frame from the ONU is a SLEEP_ACK (TRx) frame. The ONU alternately repeats the active time indicated by T1 and the sleep time indicated by T2 in the power saving cycle. The ONU saves power by stopping the optical transceiver during the sleep time. During this time, not only data frames but also control frames cannot be transmitted / received. In the active time, the ONU operates the optical transceiver normally and can transmit and receive frames. This active time is provided in order to maintain connectivity between the OLT and the ONU by performing connectivity check by transmission / reception of the GATE frame and the REPORT frame periodically performed by the OLT and the ONU. Further, the ONU shifts from the power saving cycle to the normal mode by autonomous determination. At this time, the optical transceiver is operated even in the middle of T2, and the transition to the normal mode is notified to the OLT by the response frame SLEEP_ACK (wakeup). In FIG. 3, the description of the REPORT frame transmitted by the ONU is omitted in order to make it easy to understand the difference between the operation in the normal mode and the operation in the power saving cycle.

  On the other hand, the OLT performs allocation according to the bandwidth requested by the REPORT frame (see FIG. 6) received from the ONU by notifying the bandwidth given by the transmission start time and the transmission time by the GATE frame (see FIG. 6). . The configurations of the GATE frame and REPORT frame shown in FIG. 6 are defined in the document IEEE 802.3-2008. A description of the details of each field is omitted. The OLT allocates an ONU transmission start time in the Grant # x start time field of the GATE frame, and an ONU transmission time in the Grant # x Length field. The ONU requests a bandwidth in the Queue # x Report field of the REPORT frame. When the total requested bandwidth of a plurality of ONUs exceeds the link speed, the OLT assigns a bandwidth to each ONU so as not to exceed the link speed by imparting weights such as fairness or contract. The link speed here is the maximum transmission speed between the OLT and the ONU.

  Next, the bandwidth allocation sequence will be described with reference to FIG. FIG. 4 shows a sequence in which ONUi performs upstream data communication to the OLT while transitioning from the normal mode to the power saving cycle and from the power saving cycle to the normal mode. Here, it is assumed that the uplink data indicated by the rightmost arrow in FIG. 4 has the same size, and one piece of data corresponds to one frame. In FIG. 4, the four states shown in FIG. 5 (S1: normal mode, S2: active state, S3: sleep state, S4: activation preparation state) are shown in time series. “Normal”, “Active”, “Sleep”, and “wakeup” in FIG. 4 are “S1: normal mode”, “S2: active state”, “S3: sleep state”, and “S4: start-up”, respectively. It corresponds to "Ready state".

  Here, the state transition operation of ONUi shown in FIG. 5 will be briefly described. When the sleep condition (Tr1) is satisfied in the normal mode S1, the ONUi shifts to the power saving cycle and enters the active state S2. The sleep condition (Tr1) is, for example, the case where the recently received SLEEP_ALLOW frame does not indicate “wakeup” and the uplink frame accumulation amount is equal to or less than the threshold value. In the active state S2, when the wake-up condition (Tr2) is satisfied, the state transits to the normal mode S1, and when the Active timer expires without satisfying the wake-up condition (Tr2), the state transits to the sleep state S3. The wakeup condition (Tr2) is, for example, a case where a SLEEP_ALLOW frame indicating “wakeup” is received or the amount of accumulated upstream frames exceeds a threshold value. The Active timer is a timer that counts the elapsed time since the transition to the active state S2. In the sleep state S3, when the SLEEP timer that counts the elapsed time since the transition to the sleep state S3 expires or the wake-up condition (Tr2) is satisfied, the state transitions to the activation preparation state S4. In the start preparation state S4, when the start timer that counts the elapsed time since the transition to the start preparation state S4 expires, the transition to the normal mode S1 is performed if the wake-up condition (Tr2) is satisfied, and must be satisfied. Transition to the active state S2.

  In the band allocation sequence illustrated in FIG. 4, initially, ONUi is in the normal mode S1 (Normal). The OLT periodically transmits a GATE frame and allocates a band to the ONUi. When the OLT performs ONU power saving transition permission processing and detects a predetermined sleep condition, the OLT transmits SLEEP_ALLOW (TRx) to ONUi to prompt a power saving cycle transition. Here, (TRx) is to stop the optical transceiver (both optical signal transmission operation and reception operation). In Non-Patent Document 1 described above, a parameter for stopping only the reception operation of the optical transceiver (Rx) is also defined, but the detailed description is omitted.

  Further, the OLT transmits SLEEP_ALLOW (TRx), then transmits a GATE frame, and allocates a band for transmitting a REPORT frame and a band for transmitting an ACK for SLEEP_ALLOW (TRx) to the ONUi. In FIG. 4, the bandwidth allocated to ONUi is shown in parentheses added to “GATE”. For example, GATE (RPT + ACK) indicates that a band for transmitting a REPORT frame and ACK (ACK for SLEEP_ALLOW) is allocated. The numerical value in parentheses added to “REPORT” indicates the amount of data held by ONUi, that is, the number of frames scheduled to be transmitted. For example, REPORT (1) indicates that ONUi holds data for one frame (requesting a band for transmitting data for one frame).

  When the ONUi that has received SLEEP_ALLOW (TRx) detects that the predetermined sleep condition Tr1 is satisfied, the ONUi shifts to the active state S2 (Active), responds with SLEEP_ACK (TRx), and resets the active timer. At this time, one piece of upstream data is generated and stored in the buffer, so that a bandwidth for one frame is requested by the REPORT frame. Receiving this, the OLT allocates the bandwidth for the REPORT frame + 1 frame with the GATE frame while considering the bandwidth request of other ONUs. However, in the sequence example of FIG. 4, ONUi transmits an upstream data frame because it requests a bandwidth with a REPORT frame and then shifts to a sleep state S3 (Sleep) before a GATE frame is transmitted. do not do. Note that ONUi shifts to the sleep state S3 when the active timer reset when it shifts to the active state S2 (Active) expires. When the ONUi shifts to the sleep state S3, it resets the sleep timer and stops the operation of the optical transceiver.

  Thereafter, ONUi accumulates a total of three uplink data, and the sleep timer expires and transitions to the activation preparation state S4 (wake), resets the activation timer, and resumes the operation of the optical transceiver. When the activation timer expires, ONUi does not satisfy the wake-up condition Tr2, and therefore transitions to the active state S2, requests a bandwidth for 3 frames in the REPORT frame, and resets the active timer. Receiving this, the OLT allocates a bandwidth corresponding to the REPORT frame + 3 frames. At this point, the ONUi does not transmit an upstream data frame because the active timer has expired and the state transits to the sleep state S3. In the active state S2, when receiving a GATE frame to which a band corresponding to REPORT frame + 3 frames is received, ONUi does not need to transmit uplink data because ONUi is in a power saving cycle as shown in the lower part of FIG. At this time, an IDLE signal indicating no signal other than the REPORT frame may be transmitted for a given time.

  After that, ONUi detects the wake-up condition Tr2 by collecting five upstream data before the sleep timer expires, and shifts to the normal mode S1 after the activation timer expires via the activation preparation state S4. After shifting to the normal mode S1, first, the SLEEP_ACK frame + 5 frames is requested. Receiving this, the OLT allocates a bandwidth corresponding to REPORT frame + SLEEP_ACK frame + 5 frames by the GATE frame. Upon receiving this GATE frame, the ONUi in the normal mode transmits a REPORT frame + SLEEP_ACK frame + 5 upstream data frames.

  The above is the conventional power saving control and bandwidth allocation control. However, since the power saving control and the bandwidth allocation control are not linked, the operation is inefficient. That is, since the ONU requests the amount of data accumulated in the active state S2 by the REPORT frame, the OLT allocates a longer transmission time accordingly, and the band cannot be used effectively, and the light emission time is long. As a result, the power consumption of the ONU also increases.

  The optical communication system according to the present invention solves the problems in the conventional PON system by adopting the following configuration and operation.

Embodiment.
FIG. 1 is a diagram showing a configuration example of an optical communication system according to the present invention, and also shows a configuration example of each device constituting the system. As shown in the figure, the PON system as an optical communication system has a plurality of subscriber-side terminal devices (also referred to as “Optical Network Units”, hereinafter referred to as “ONUs”) 1 ₁ to 1 _n operating as slave station devices. A station-side terminal device (also referred to as “Optical Line Terminal”, hereinafter referred to as “OLT”) 3 operating as a master station device. The plurality of ONUs _{1 1} to 1 _n and the OLT 3 are n-to-1 connected via the optical distributor 2. The device configurations of the ONUs _{1 1} to 1 _n are the same and perform similar operations. In the present embodiment, when the matters common to the ONUs _{1 1} to 1 _n are described, the ONUs _{1 1} to 1 _n are collectively expressed as ONU ₁ .

  As shown in FIG. 1, the ONU 1 includes a multipoint media access control (MPMC) unit 11, a line interface (IF) unit 12, an upstream buffer unit 13 as a data holding unit, a sleep control unit 14, a PON physical unit. A layer (PHY) unit 15 and an optical transmission / reception unit 16 are provided. The MPMC unit 11 includes a REPORT generation unit 21, a multiplexing unit 22, a separation unit 23, and a transmission control unit 24 as a data amount notification unit. The OLT 3 includes a multipoint media access control (MPMC) unit 31, an optical transmission / reception unit 32, a PON physical layer (PHY) unit 33, a bandwidth control unit 34, and an ONU sleep (Sleep) control unit 35 as a sleep permission device determination unit. And a line IF unit 36. The MPMC unit 31 includes a separation unit 41 and a multiplexing unit 42.

  Next, the operation of each part of the ONU 1 will be described. In the ONU 1, the line IF unit 12 performs line physical layer processing on an uplink data signal received from a user terminal (not shown) and sends the uplink data signal as an uplink frame to the uplink buffer unit 13 of the MPMC unit 11. The upstream buffer unit 13 stores upstream frames and notifies the REPORT generation unit 21 and the sleep control unit 14 of the stored data amount.

  The sleep control unit 14 generates a control frame related to the sleep control of the self ONU 1 and issues an operation instruction to the REPORT generation unit 21 and the optical transmission / reception unit 16 according to each state including the sleep state. When the SLEEP_ALLOW frame described in the power saving control in the conventional PON system is received, the sleep control unit 14 performs the state transition shown in FIG. 5 (instructs each unit to perform an operation corresponding to each state).

  The REPORT generation unit 21 generates a REPORT frame based on the accumulated data amount from the upstream buffer unit 13 and outputs the REPORT frame to the multiplexing unit 22. Based on the transmission permission timing control from the transmission control unit 24, the multiplexing unit 22 reads the uplink data from the uplink buffer unit 13 and transmits it together with a control frame such as a REPORT frame generated by the REPORT generation unit 21. In addition, when the sleep control unit 14 generates a SLEEP_ACK frame, the frame is also transmitted.

  When receiving a transmission frame, the PON physical layer unit 15 performs PON physical layer processing and transmits it with an electrical signal. Further, when a downstream electrical signal is received, PON physical layer processing is performed and transmitted as a downstream frame to the separation unit 23 of the MPMC unit 11.

  The optical transmission / reception unit 16 converts the electrical signal received from the PON physical layer unit 15 into an optical signal based on the transmission permission timing control from the transmission control unit 24 when the operation stop control from the sleep control unit 14 is OFF. To send. Further, the downstream optical signal from the OLT 3 is converted into an electrical signal and transmitted to the PON physical layer unit 15 regardless of the transmission permission timing.

  When receiving the downstream frame from the PON physical layer unit 15, the separation unit 23 receives a power saving control frame such as a SLEEP_ALLOW frame, an ONU control frame such as a GATE frame, other downstream frames addressed to the own ONU, and a frame addressed to another ONU. Classify into: Then, the frame addressed to the other ONU is discarded, the power saving control frame is transmitted to the sleep control unit 14, the ONU control frame is transmitted to the transmission control unit 24, and the other frames are transmitted to the line IF unit 12.

  The transmission control unit 24 controls the REPORT generation 21, the multiplexing unit 22, and the optical transmission / reception unit 16 so as to receive the GATE frame and transmit the uplink frame according to the transmission start time and the transmission time specified by the GATE frame. The transmission time designated by the GATE frame is information indicating the length of the period from the start of transmission at the transmission start time to the end of transmission. Description of other ONU control frame processing is omitted.

  The line IF unit 12 performs line physical layer processing on the downlink frame received from the demultiplexing unit 23 and outputs the downlink frame to the user terminal as downlink data.

  Next, the operation of each part of the OLT 3 will be described. In the OLT 3, when receiving an upstream optical signal from each ONU 1 via the optical fiber and the optical distributor 2, the optical transmission / reception unit 32 converts it into an electrical signal and outputs it to the PON physical layer unit 33. Further, when a downstream electrical signal is received from the PON physical layer unit 33, it is converted into an optical signal and transmitted to each ONU 1 through the optical fiber and the optical distribution unit 2.

  The PON physical layer unit 33 performs PON physical layer processing on the signal received from the optical transmission / reception unit 32 and sends the signal to the separation unit 41 as an uplink frame. Further, the PON physical layer process is performed on the downstream frame received from the multiplexing unit 42 and transmitted to the optical transmission / reception unit 32 as a downstream electrical signal.

  When the separation unit 41 receives the upstream frame from the PON physical layer unit 33, the separation unit 41 classifies it into a power saving control frame such as a SLEEP_ACK frame, an OLT control frame such as a REPORT frame, and other upstream frames. The power saving control frame is transmitted to the ONU sleep control unit 35, the ONU control frame is transmitted to the bandwidth control unit 34, and the other frames are transmitted to the line IF unit 36.

  The ONU sleep control unit 35 receives the SLEEP_ACK frame, grasps the power saving state of each ONU 1, performs power saving transition permission processing for each ONU 1, and generates a SLEEP_ALLOW frame when a predetermined sleep condition is detected. The generated SLEEP_ALLOW frame is output to the multiplexing unit 42.

  Note that the power saving transition permission process is not defined here. The ONU sleep control unit 35 receives, for example, the result of the MPMC unit 31 monitoring the number of downlink frames for each ONU 1 at a fixed period, determines that the ONU 1 for which no downlink frame is transmitted is permitted to save power cycle, and SLEEP_ALLOW addressed to the ONU 1 Generate a frame. Also, the MPMC unit 31 receives the result of collecting the number of transmission / reception frames of each ONU 1 at regular intervals using an OAM frame, etc., determines that the ONU 1 having no uplink / downlink transmission / reception frame is permitted to save power cycle, and A SLEEP_ALLOW frame may be generated.

  The bandwidth control unit 34 receives the REPORT frame, totals the requested bandwidth for each ONU 1, performs bandwidth allocation processing so as not to exceed the link speed by applying a fairness or a weight by contract, and the GATE frame corresponding to the allocation Is generated. The generated GATE frame is output to the multiplexing unit 42.

  The line IF unit 36 performs line physical layer processing on the uplink frame received from the separation unit 41 and transmits the uplink frame as an uplink data signal. Also, the downlink physical signal received from the line is subjected to line physical layer processing and transmitted to the multiplexing unit 42 as a downlink frame.

  The multiplexing unit 42 multiplexes the SLEEP_ALLOW frame received from the ONU sleep control unit 35, the GATE frame received from the bandwidth control unit 34, the downlink frame received from the line IF unit 36, and outputs the multiplexed frame to the PON physical layer unit 33.

  The ONU power saving transition permission process performed by the OLT 3 is not defined here. For example, the OLT 3 may monitor the number of downlink frames for each ONU at regular intervals, and may determine that an ONU in which no downlink frame is transmitted is permitted to save power cycle, and the number of ONU transmission / reception frames may be determined using an OAM frame or the like. May be collected at regular intervals, and ONUs having no uplink / downlink transmission / reception frame may be determined as power saving cycle transition permission.

  In the optical communication system configured as described above, power saving control is performed in the same procedure as in the conventional PON system. That is, the OLT 3 and each ONU 1 according to the present embodiment switch between a normal mode and a power saving cycle according to the control procedure shown in FIG. More specifically, after receiving the SLEEP_ALLOW frame from the OLT, the ONU 1 transmits SLEEP_ACK (TRx) when detecting that a predetermined sleep condition is satisfied, and shifts to a power saving cycle. When the power saving cycle ends and the normal mode is restored, SLEEP_ACK (wakeup) is transmitted. As already described, in the power saving cycle, the active state S2, the sleep state S3, and the startup preparation state S4 are periodically repeated until a predetermined wakeup is satisfied (see FIG. 5). In the active state S2, the ONU 1 can transmit and receive optical signals, that is, can communicate with the OLT 3. In the sleep state S3 and the start preparation state S4, the optical transmission / reception unit 16 is stopped or started, and transmission / reception of optical signals is impossible (or operation is unstable).

  Next, the bandwidth allocation control operation in the optical communication system according to the present embodiment will be described. FIG. 2 is a diagram illustrating an example of a bandwidth allocation sequence. Similar to FIG. 4 showing the conventional bandwidth allocation sequence, FIG. 2 shows a sequence in which the ONU performs uplink data communication to the OLT while transitioning from the normal mode to the power saving cycle and from the power saving cycle to the normal mode. . Further, the four states shown in FIG. 5 are shown in time series. The uplink data indicated by the rightmost arrow in the figure has the same size, and one piece of data corresponds to one frame.

  The ONU 1 receives a GATE frame from the OLT 3 in the normal mode (Normal) (step S11). As a result, a bandwidth capable of transmitting the REPORT frame and the x data frame is assigned to the ONU 1, and the ONU 1 transmits the data for the REPORT frame and the x frame (steps S12 and S13). The OLT 3 that has received the REPORT frame in step S12 determines that the ONU 1 does not request a bandwidth for transmitting uplink data, and transmits a GATE frame that allocates only the bandwidth for transmitting the REPORT frame (step S14). The ONU 1 transmits a REPORT frame in which the requested bandwidth for uplink data transmission is set to 0 (0 frame) (step S15). Thereafter, the OLT 3 detects that the ONU 1 satisfies the TRx sleep condition (the condition for shifting to the power saving cycle), and transmits a SLEEP_ALLOW frame indicating that the ONU 1 can shift to the power saving cycle (step S16). The OLT 3 also transmits a GATE frame (step S17). The SLEEP_ALLOW frame transmitted in step S16 instructs to stop the optical signal transmission operation and reception operation in the sleep state S3 in the power saving cycle. In step S17, considering the contents of the REPORT frame received in step S15 and the transmission of the SLEEP_ALLOW frame in step S16, a GATE frame having contents for allocating a band for transmitting the REPORT frame and the ACK for the SLEEP_ALLOW frame is obtained. Send.

  When the ONU 1 receives the SLEEP_ALLOW frame, the ONU 1 shifts to an active state (Active) of the power saving cycle and transmits a REPORT frame and a SLEEP_ACK frame (a frame for notifying that the power saving cycle has been entered) (steps S18 and S19). Thereafter, when a predetermined time (T1) has passed since the active state was entered, the state transits to the sleep state (Sleep). Here, the ONU 1 has accumulated uplink data for one frame at the time of execution of step S18, but transmits a REPORT frame in which the requested bandwidth for uplink data transmission is set to 0 (0 frame). The ONU 1 transitions to the activation preparation state (wakeup) at a predetermined timing before the fixed time T2 elapses after the transition to the sleep state, and transitions to the active state when the fixed time T2 elapses.

  The OLT 3 transmits a GATE frame that allocates only the REPORT frame transmission band based on the content of the REPORT frame received from the ONU 1 in step S17 (step S20).

  Since ONU1 is in a sleep state at the time of execution of step S20, it cannot receive a GATE frame and does not transmit a REPORT frame.

  Thereafter, the OLT 3 transmits a GATE frame for allocating a band for REPORT frame transmission to the ONU 1 (step S21).

  Since ONU1 is in an active state at the time of execution of step S21, it receives a GATE frame, and transmits a REPORT frame based on the amount of uplink data accumulated at this time (step S22). Here, uplink data for three frames is stored in the ONU 1, but it is determined that the storage amount has not reached a certain value (threshold value), and the requested bandwidth for uplink data transmission is set to 0 (0 frame). The REPORT frame set to is transmitted.

  Thereafter, the OLT 3 periodically transmits a GATE frame to which a band for REPORT frame transmission is allocated (steps S23 and S24).

  On the other hand, the ONU 1 detects that the amount of uplink data accumulated has reached 5 frames from the execution of step S23 to the execution of step S24, and determines that the wake-up condition has been satisfied. Then, it returns to the normal mode from the sleep state through the startup preparation state. Note that the threshold value set as the wake-up condition is determined to a value that does not cause an overflow in consideration of, for example, the capacity of the upstream buffer unit 13.

  Since the ONU 1 is in the normal mode when step S24 is executed, the ONU 1 receives the GATE frame and transmits a REPORT frame having contents based on the amount of uplink data accumulated at this point (step S25). Since the REPORT frame to be transmitted here is transmitted for the first time after returning to the normal mode, a band for transmitting the power saving control frame is also requested. Specifically, a REPORT frame having a content for requesting a band for transmitting the SLLEP_ACK frame for notifying the return to the normal mode and 5 frames of uplink data is transmitted.

  The OLT 3 that has received the REPORT frame in step S25 transmits a GATE frame indicating a band allocation result based on the content of the received REPORT frame (step S26), and the ONU 1 uses the allocated band to generate a REPORT frame and a SLEEP_ACK frame. And a data frame is transmitted (steps S27, S28, S29). The SLEEP_ACK frame transmitted in step S28 is a frame indicating that the power saving cycle is completed and the normal mode is restored. “W” of SLEEP_ACK (w) shown in FIG. 2 indicates “wakeup”.

  As described above, the ONU 1 of the present embodiment periodically repeats the first state in which the optical signal transmission / reception operation is stopped and the second state in which the optical signal transmission / reception operation is performed for a short period of time. When operating in a power-saving mode (power-saving cycle) that suppresses power consumption while maintaining a link to the data, a bandwidth for data transmission is not requested (in the second state, the REPORT with the data accumulation amount set to 0) Frame). For example, in steps S18 and S22 shown in FIG. 2, a band for data transmission is not requested even though uplink data is held. As a result, the OLT 3 allocates more bandwidth to other ONUs 1 (ONUs that are not power saving cycles), and the assigned bandwidth and the sleep state overlap (the assigned bandwidth is not used). Therefore, effective use of the bandwidth of the entire system can be realized. In addition, since the duration of the power saving cycle is longer than before, further power saving can be realized. Also, even when a GATE frame is received in an active state during a power saving cycle, unlike the conventional case, since a given band is only for a REPORT frame, there is no wasted time for transmitting an IDLE signal, and ONU1 Can save more power.

  In the above description, the optical signal transmission / reception operation is stopped in the sleep state. However, only one of the transmission operation and the reception operation may be stopped.

  In the above description, the ONU 1 does not request a data transmission band when the amount of uplink data stored is less than a predetermined threshold (for example, 5 frames) (in the case of a power saving cycle). Requests the bandwidth for data transmission as before even in the power saving cycle, and the OLT 3 has a request amount (data accumulation amount notified in the REPORT frame) when the ONU 1 is highly likely to be in the power saving cycle. If it is less than the threshold value, a band for data transmission may not be allocated. Whether the ONU 1 is highly likely to be in the power saving cycle can be determined from the contents of the SLEEP_ACK frame transmitted from the ONU 1. That is, it is determined that there is a high possibility that the ONU 1 is in the power saving cycle after receiving the SLEEP_ACK frame indicating that the power saving cycle has been entered and before receiving the SLLEP_ACK frame indicating that the normal mode has been restored. .

  In the above description, after the OLT 3 monitors the state of each ONU 1 and permits the transition to the power saving cycle (after transmitting the SLEEP_ALLOW frame), the permitted ONU 1 detects the transition condition to the power saving cycle. Then, although it decided to transfer to a power saving cycle, you may make it judge whether each ONU1 transfers to a power saving cycle independently, without making determination in OLT3.

  As described above, in the slave station device according to the present invention, the master station device and a plurality of slave station devices are connected in one-to-many manner, and the uplink communication from each slave station device to the master station device is performed by TDMA. Useful for.

1 ₁ , 1 _n Subscriber side termination unit (ONU), 2 Optical distributor, 3 Station side termination unit (OLT), 11, 31 Multipoint media access control (MPMC) unit, 12, 36 Line interface (IF) unit , 13 Upstream buffer unit, 14 Sleep control unit, 15, 33 PON physical layer (PHY) unit, 16, 32 Optical transmission / reception unit, 21 REPORT generation unit, 22, 42 Multiplexing unit, 23, 41 Separation unit, 24 Transmission control unit, 34 bandwidth control unit, 35 ONU sleep (Sleep) control unit.

Claims (7)

A plurality of slave station devices and the master station device are connected by an optical transmission line, and the master station device determines a bandwidth to be allocated to each slave station device based on the amount of data that each slave station device desires to transmit. A slave station device for an optical communication system,
Operates while switching between a normal mode for transmitting / receiving data to / from the parent station device and a power saving mode for performing the minimum communication necessary to maintain a link with the parent station device based on a predetermined condition. ,
During operation in the power saving mode, the slave station apparatus notifies the master station apparatus of 0 as the amount of data desired to be transmitted. A plurality of slave station devices and the master station device are connected by an optical transmission line, and the master station device determines a bandwidth to be allocated to each slave station device based on the amount of data that each slave station device desires to transmit. A slave station device for an optical communication system,
A data holding unit for holding data to be transmitted to the master station device;
Based on the data amount of the data held by the data holding unit, the minimum communication necessary for maintaining a link between the normal mode for transmitting / receiving data to / from the parent station device and the parent station device A sleep control unit for switching between power saving modes for performing
When operating in the power saving mode, a data amount notification unit that notifies the master station device of 0 as the data amount of data desired to be transmitted;
A slave station device comprising:   The said sleep control part switches to the said normal mode, when detecting that the data amount of the data which the said data holding part has reached | attained the predetermined threshold value is characterized by the above-mentioned. Slave station device. Multiple slave station devices and a master station device are connected by an optical transmission line, and each slave station device is necessary to maintain a link between the master station device and a normal mode in which data is transmitted to and received from the master station device. A master station device of an optical communication system that operates while switching a power saving mode for performing minimum communication based on a predetermined condition,
Based on the transmission status of downlink data for each slave station device or the data transmission / reception status between each slave station device, it is estimated whether each slave station device is operating in the normal mode or the power saving mode, A base station apparatus, wherein a band for uplink data transmission is not allocated to a slave station apparatus estimated to be operating in a power saving mode. Multiple slave station devices and a master station device are connected by an optical transmission line, and each slave station device is necessary to maintain a link between the master station device and a normal mode in which data is transmitted to and received from the master station device. A master station device of an optical communication system that operates while switching a power saving mode for performing minimum communication based on a predetermined condition,
A sleep permission device determination unit that determines a slave station device that is allowed to shift to the power saving mode based on a transmission status of downlink data to each slave station device or a data transmission / reception status between each slave station device;
A bandwidth control unit for allocating a bandwidth for uplink data transmission to a slave station device other than the slave station device permitted to shift to the power saving mode;
A master station device comprising: An optical communication system in which a plurality of slave station devices and a master station device are connected by an optical transmission line,
The master station device determines a bandwidth to be assigned to each slave station device based on a data amount of data each slave station device desires to transmit,
The slave station device has a predetermined condition of a normal mode for transmitting / receiving data to / from the master station device and a power saving mode for performing a minimum communication necessary for maintaining a link with the master station device. The operation is performed based on switching, and during operation in the power saving mode, the master station apparatus is notified of 0 as the data amount of data desired to be transmitted.
An optical communication system. A band control method in an optical communication system in which a plurality of slave station devices and a master station device are connected by an optical transmission line, and each slave station device transmits uplink data using a band assigned by the master station device. ,
Each of the plurality of slave station devices has a normal mode for transmitting / receiving data to / from the master station device and a power saving mode for performing a minimum communication necessary for maintaining a link with the master station device. A power saving control step for switching based on a predetermined condition;
Each of the plurality of slave station devices notifies the master station device of 0 as the data amount of data desired to be transmitted during the operation in the power saving mode, and stores the desired data during the operation in the normal mode. As a data amount, a data amount notification step of notifying the master station device of a data amount of data held at that time;
A bandwidth allocation step for determining a bandwidth to be allocated to each slave station device based on the data amount notified from each slave station device by the master station device;
A bandwidth control method comprising:

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