Optical wireless communication system, communication device, and communication method

Abstract

To provide an optical wireless communication system capable of enabling jitter suppression while maintaining a communication rate at a shaping rate.SOLUTION: An optical wireless communication system includes a plurality of ONUs 2-i connected to a wireless slave station device wirelessly communicating with a wireless terminal, and an OLT 1 connected to each of the plurality of ONUs 2-i via an optical transmission line and connected to a wireless master station device 3, and limits a communication rate of uplink communication by alternately repeating a period of granting and a period of non-granting bandwidth to each of the plurality of ONUs 2-i in uplink communication. The optical wireless communication system includes a rate calculation unit 13 that calculates a shaping rate, which is a limit value of the communication rate for uplink communication on the basis of allocated resource information, and an uplink communication control unit 10A that determines an amount of bandwidth to be granted in uplink communication and start time of data transmission, to an ONU 2-i, on the basis of the shaping rate and information based on a frame length of data to be transmitted in the uplink communication.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an optical wireless communication system, a communication device, and a communication method for converting an electrical signal into an optical signal and transmitting the optical signal. [Background technology]

[0002] In wireless communication systems such as LTE (Long Term Evolution) and 5G (5th Generation), wireless terminals communicate wirelessly with base stations. Typically, one base station communicates wirelessly with multiple wireless terminals. Therefore, the base station dynamically allocates limited resources to each wireless terminal to prevent signal collisions between the wireless terminals. For example, in LTE uplink communication, when a wireless terminal transmits uplink data to a base station, it first requests a bandwidth from the base station. Upon receiving the bandwidth request, the base station allocates resources to the wireless terminal for transmitting information necessary for scheduling the uplink data, such as buffer capacity and channel conditions, and notifies the wireless terminal of the resources in a response. The wireless terminal then uses the allocated resources to transmit the information necessary for scheduling the uplink data to the base station. The base station then performs scheduling using the received information and allocates resources for transmitting the uplink data to the wireless terminal using a scheduling grant. Only after the above-described exchanges have been completed can the wireless terminal transmit the uplink data to the base station.

[0003] In addition, an optical wireless communication system has been proposed that combines a wireless base station and a PON (Passive Optical Network). In this case, an optical line terminal (OLT), which is an optical terminal on the central station side connected to an optical station, and an optical network unit (ONU), which is an optical terminal on the subscriber side connected to an optical station, are connected using optical fibers and optical splitters. This configuration reduces the number of central station equipment and the number of optical fibers relative to the number of local station equipment, thereby reducing costs.

[0004] In a PON system, one OLT also communicates with multiple ONUs. Therefore, the OLT performs scheduling to dynamically allocate resources to each ONU. When scheduling, the ONU first transmits information about the amount of data stored in its transmission buffer (hereinafter referred to as REPORT information) to the OLT at the timing specified by a transmission permission signal sent from the OLT. The OLT then performs scheduling based on the REPORT information, allocates resources for transmitting upstream data to each ONU, and notifies each ONU of the allocated resources. Only after the above-described exchange can each ONU transmit upstream data to the OLT. However, when a PON system is used as the connection topology between a master station and a slave station, a delay occurs during upstream communication from the slave station to the master station, as each ONU notifies the OLT of the REPORT information stored in each ONU, resources are allocated, and the upstream data is transmitted.

[0005] Patent Document 1 discloses a technology related to a mobile network that uses a PON system as a network between a BBU (Base Band Unit) that manages and controls wireless communications, performs signal processing, etc., and an RRH (Remote Radio Head) that transmits wireless signals to user terminals. The technology disclosed in Patent Document 1 allocates resources over the entire time period of a dynamic bandwidth allocation cycle so that the waiting time for upstream data falls within the allowable delay time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-149738 Summary of the Invention [Problem to be solved by the invention]

[0007] However, wireless communications involve multiple traffic flows transmitted from multiple wireless terminals. Such fluctuations, called jitter, can occur due to network congestion, retransmissions due to frame loss caused by unreliable transmission lines, and queuing, resulting in inconsistent signal intervals. Jitter in wireless signals can degrade the quality of communication services, such as audio and video quality, in voice and real-time video communications. To mitigate jitter, a bandwidth control technique called shaping can be applied, which alternates between periods of bandwidth allocation and periods of no bandwidth allocation. The bandwidth allocated during a given period is determined based on the requested bandwidth and buffer size reported by the transmitting side. In PON systems, determining the amount of bandwidth allocation during shaping typically involves determining the total amount of data transmitted from the transmitting side, but not the frame length of each transmitted frame. This can lead to a problem where the actual communication rate is lower than the shaping rate, which is the limiting value for the communication rate during shaping, depending on the frame length. For example, when a bandwidth of 2000 bytes is allocated, if the frame lengths of the frames to be transmitted are 1300 bytes, 800 bytes, and so on, only the first 1300-byte frame can be transmitted.

[0008] The present disclosure has been made in view of the above, and has an object to provide an optical wireless communication system that is capable of suppressing jitter while maintaining the communication rate at a shaping rate. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the present disclosure provides an optical wireless communication system including a plurality of subscriber-side optical terminals connected to a wireless slave station device that wirelessly communicates with a wireless terminal, and a central office-side optical terminal that is connected to each of the plurality of subscriber-side optical terminals via an optical transmission path and is also connected to a wireless master station device, and that limits the communication rate of the upstream communication by alternately repeating a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted to each of the plurality of subscriber-side optical terminals in upstream communication from each of the plurality of subscriber-side optical terminals to the central office-side optical terminal; The optical terminal device on the central office side is a rate calculation unit that calculates a shaping rate, which is a limit value of the communication rate of upstream communication, for each of a plurality of subscriber-side optical terminals based on allocated resource information indicating resources allocated by the wireless base station device to the wireless terminal; and a bandwidth allocation calculation unit that determines a bandwidth allocation amount and a data transmission start time for upstream communication based on the allocated resource information, and each of the plurality of subscriber-side optical terminals has an output control unit that outputs frames for upstream communication, and a rate control unit that determines a time interval for giving transmission permission to the subscriber-side optical terminal based on a shaping rate, a bandwidth allocation amount, and a data transmission start time notified from the central office-side optical terminal and the frame length of a frame transmitted in the upstream communication, and controls the data transmission start time for upstream communication so that the time interval becomes the determined value. It is characterized by the following. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to obtain an optical wireless communication system that can suppress jitter while maintaining the communication rate at the shaping rate. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a configuration of an optical wireless communication system according to a first embodiment; [Figure 2] FIG. 1 is a diagram showing a functional configuration of an OLT according to a first embodiment; [Figure 3] 1 is a flowchart illustrating an operation of an OLT according to a first embodiment. [Figure 4] FIG. 1 is a diagram illustrating a first example of a hardware configuration of an OLT according to a first embodiment. [Figure 5] FIG. 10 is a diagram illustrating a second example of a hardware configuration of an OLT according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing a functional configuration of an ONU and an OLT in an optical wireless communication system according to a second embodiment. [Figure 7] 10 is a flowchart illustrating the operation of an OLT according to a second embodiment. [Figure 8] 10 is a flowchart illustrating the operation of an ONU according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a first example of a hardware configuration of an ONU according to a second embodiment. [Figure 10] FIG. 10 is a diagram illustrating a second example of a hardware configuration of an ONU according to a second embodiment. [Figure 11] FIG. 10 is a diagram showing a functional configuration of an OLT and a wireless base station device according to a third embodiment. [Figure 12] 10 is a flowchart illustrating an operation of the wireless master station device according to the third embodiment. [Figure 13] 10 is a flowchart illustrating the operation of an OLT according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an optical wireless communication system, a communication device, and a communication method according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0013] Embodiment 1 FIG. 1 is a diagram illustrating a configuration of an optical wireless communication system 100A according to a first embodiment. The optical wireless communication system 100A includes an optical line terminal (OLT) 1 connected to a wireless base station device 3 and optical network units (ONUs) 2-1 to 2-n connected to multiple wireless slave station devices 4-1 to 4-n, respectively. The OLT 1 ​​is connected to each of the multiple ONUs 2-1 to 2-n via an optical fiber OF and a star coupler S. The wireless base station device 3 is connected to an upper network, and each of the wireless slave station devices 4-1 to 4-n can wirelessly connect to a wireless terminal, transmitting upstream data from the wireless terminal to the wireless base station device 3 and downstream data from the wireless base station device 3 to the wireless terminal. The OLT 1 ​​and the ONUs 2-1 to 2-n form a point-to-multipoint PON system, transmitting and receiving data using optical signals.

[0014] Here, ONUs 2-1 to 2-n may be collectively referred to as ONU 2-i, and wireless slave station devices 4-1 to 4-n may be collectively referred to as wireless slave station device 4-i, where i is a positive integer.

[0015] The optical wireless communication system 100A can transmit data between the wireless master station device 3 and the wireless terminals connected to the wireless slave station devices 4-i. The following mainly describes functions of the optical wireless communication system 100A related to upstream scheduling, which is a scheduling function for reducing the delay time of upstream communication from the wireless terminals connected to the wireless slave station devices 4-i to the wireless master station device 3. In upstream communication, data transmitted from the wireless terminals is transmitted to the wireless master station device 3 via the wireless slave station devices 4-i, ONU2-i, and OLT1. At this time, the wireless master station device 3 performs upstream scheduling to allocate resources to each wireless terminal connected to the wireless slave station device 4-i. This upstream scheduling performed by the wireless master station device 3 is referred to as "wireless upstream scheduling." Furthermore, in upstream communication between the OLT1 and the ONU2-i, shaping is performed within the PON system, alternating between a grant period in which bandwidth is granted and a non-grant period in which bandwidth is not granted, in order to suppress jitter. The upstream scheduling in which the OLT 1 ​​allocates resources to each ONU 2-i for shaping is called "optical upstream scheduling."

[0016] The wireless base station device 3 outputs downlink data including wireless uplink scheduling information to the OLT 1. The wireless uplink scheduling information includes allocation resource information that instructs each wireless terminal connected to the wireless slave station device 4-i about the resources allocated by the wireless base station device 3 to each wireless terminal. The allocation resource information instructs each wireless terminal about the amount of data to transmit and during what time period. When transmitting uplink data to the wireless base station device 3, each wireless terminal transmits the uplink data using the resources instructed by the allocation resource information.

[0017] 2 is a diagram showing the functional configuration of the OLT 1 ​​according to the first embodiment. The OLT 1 ​​includes a cooperative information receiving unit 11, an information analyzing unit 12, a rate calculating unit 13, a bandwidth allocation calculating unit 14, a bandwidth correcting unit 15, a GATE generating unit 16, a data multiplexing unit 17, an optical transmitting / receiving unit 18, and a traffic monitoring unit 19. The bandwidth allocation calculating unit 14, the bandwidth correcting unit 15, and the traffic monitoring unit 19 are collectively referred to as an upstream communication control unit 10A. Note that FIG. 2 shows only the parts necessary to explain the features of the first embodiment, and the OLT 1 ​​may have a configuration other than that shown in FIG. 2.

[0018] The cooperation information receiving unit 11 receives cooperation information transmitted from the wireless base station device 3, and transfers the received cooperation information to the information analyzing unit 12. The cooperation information includes wireless uplink scheduling information and the like.

[0019] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11 and extracts wireless uplink scheduling information from the cooperation information. The information analysis unit 12 transmits the extracted wireless uplink scheduling information to the rate calculation unit 13. The wireless uplink scheduling information includes the amount of allocated resources, the data arrival time, and the wireless terminal buffer amount.

[0020] The rate calculation unit 13 determines a shaping rate, which is a limiting value of the communication rate of upstream communication between the OLT 1 ​​and the ONU 2-i, based on the wireless upstream scheduling information received from the information analysis unit 12. The rate calculation unit 13 also determines a shaping bandwidth grant amount and an IDLE length based on the determined shaping rate. The shaping bandwidth grant amount is the amount of data that the OLT 1 ​​grants transmission permission to the ONU 2-i when shaping is performed. The IDLE length is the length of the period from when the OLT 1 ​​grants transmission permission to the ONU 2-i to when it grants the next transmission permission, and is the time interval between granting transmission permission to the ONU 2-i. Therefore, the rate calculation unit 13 determines the shaping bandwidth grant amount and the IDLE length so that the ratio of the shaping bandwidth grant amount to the IDLE length is the shaping rate. The rate calculation unit 13 transmits the shaping rate to the bandwidth correction unit 15 and transmits rate information including the shaping rate, the shaping bandwidth grant amount, and the IDLE length to the bandwidth allocation calculation unit 14.

[0021] Based on the rate information received from the rate calculation unit 13, the bandwidth allocation calculation unit 14 calculates a grant start time (GST) indicating the start time of upstream data transmission and a grant bandwidth for each ONU 2-i, and transmits the calculated GST and grant bandwidth to the bandwidth correction unit 15. Specifically, the bandwidth allocation calculation unit 14 calculates the grant bandwidth by adding overhead required in the PON system to the shaping grant bandwidth included in the rate information. Here, the overhead refers to the amount of data required in addition to the pure data amount, taking into account, for example, periods such as the light emission start period Ton, the light emission end period Toff, and the synchronization period Synctime, as well as 64B / 66B encoding and FEC (Forward Error Correction). The bandwidth allocation calculation unit 14 also determines the timing of granting transmission permission to each ONU 2-i so that the GSTs of the multiple ONUs 2-i do not overlap and so that the interval from the timing of the previous transmission permission is equal to the IDLE length. Specifically, the bandwidth allocation calculation unit 14 calculates the GST by adding the idle length to the most recent GST for the target ONU 2-i.

[0022] The bandwidth correction unit 15 corrects at least one of the GST and the bandwidth allocation amount received from the bandwidth allocation calculation unit 14 based on a notification from the traffic monitoring unit 19. If there is no notification from the traffic monitoring unit 19, the bandwidth correction unit 15 transmits the received GST and bandwidth allocation amount to the GATE generation unit 16 without making any corrections. If there is a notification from the traffic monitoring unit 19, the bandwidth correction unit 15 receives the source ONU information, reception time, and received data amount notified from the traffic monitoring unit 19, compares the bandwidth allocated to ONU2-i with the amount of data actually transmitted from ONU2-i, and corrects at least one of the GST and the bandwidth allocation amount. The bandwidth correction unit 15 transmits the corrected GST and bandwidth allocation amount to the GATE generation unit 16.

[0023] The GATE generation unit 16 stores the GST and the bandwidth allocation amount received from the bandwidth correction unit 15 in a GATE frame, and transmits the GATE frame to the data multiplexing unit 17 .

[0024] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 and the GATE frame received from the GATE generation unit 16, and transmits the multiplexed data to the optical transceiver unit 18.

[0025] The optical transceiver 18 is connected to the ONU2-i, receives upstream data from the ONU2-i, and transmits the upstream data to the traffic monitor 19. The optical transceiver 18 also transmits the downstream data and GATE frames multiplexed by the data multiplexer 17 to the ONU2-i.

[0026] The traffic monitoring unit 19 monitors the upstream data received from the optical transceiver 18, and notifies the bandwidth correction unit 15 of the source ONU information, the reception time, and the amount of received data. The traffic monitoring unit 19 also transfers the upstream data to the wireless base station device 3.

[0027] ONU2-i transmits upstream data to OLT1 based on the GST and bandwidth allocation amount stored in the GATE frame transmitted from OLT1. To prevent upstream data collisions in the PON section, the amount of upstream data transmitted by ONU2-i is limited to a range that does not exceed the waiting time allocated by OLT1.

[0028] Next, the operation of the OLT 1 ​​will be described.

[0029] 3 is a flowchart for explaining the operation of the OLT 1 ​​according to the first embodiment. The cooperation information receiving unit 11 of the OLT 1 ​​receives cooperation information transmitted from the wireless base station device 3, and transfers the received cooperation information to the information analyzing unit 12 (step S101).

[0030] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11, extracts wireless uplink scheduling information from the cooperation information, and transmits the extracted wireless uplink scheduling information to the rate calculation unit 13 (step S102). The wireless uplink scheduling information includes the amount of allocated resources, the data arrival time, and the wireless terminal buffer amount.

[0031] Based on the wireless uplink scheduling information received from the information analysis unit 12, the rate calculation unit 13 determines the shaping rate, shaping bandwidth allocation amount, and IDLE length of the shaping to be performed between OLT1 and ONU2-i, transmits rate information including the shaping rate, shaping bandwidth allocation amount, and IDLE length to the bandwidth allocation calculation unit 14, and transmits the shaping rate to the bandwidth correction unit 15 (step S103).

[0032] Based on the rate information received from the rate calculation unit 13, the bandwidth allocation calculation unit 14 calculates, for each ONU2-i, a GST indicating the data transmission start time and a bandwidth allocation amount, and transmits the calculated GST and bandwidth allocation amount to the bandwidth correction unit 15 (step S104).

[0033] The bandwidth correction unit 15 determines whether or not there is a notification from the traffic monitoring unit 19 (step S105).

[0034] If no notification is received from the traffic monitoring unit 19 (step S105: No), the bandwidth correction unit 15 does not perform any correction and transmits the GST and bandwidth allocation amount received from the bandwidth allocation calculation unit 14 to the GATE generation unit 16 as is (step S106).

[0035] If a notification is received from the traffic monitoring unit 19 (step S105: Yes), the bandwidth correction unit 15 adds up the amount of data received within the period to which bandwidth is allocated for each ONU2-i based on the notified source ONU information, reception time, and received data amount, and calculates the amount of data actually transmitted during that period for each ONU2-i (step S107).

[0036] The bandwidth correction unit 15 corrects at least one of the GST and the bandwidth allocation amount received from the bandwidth allocation calculation unit 14 based on the amount of data actually transmitted, and transmits the corrected GST and bandwidth allocation amount to the GATE generation unit 16 (step S108).

[0037] Here, two examples of the correction method implemented by the bandwidth correction unit 15 will be described. The ONU 2-i transmits data to the OLT 1 ​​according to the GST and the allocated bandwidth allocated by the OLT 1. However, although the OLT 1 ​​can grasp the amount of data that the ONU 2-i plans to transmit, it does not grasp the frame length of each frame. Therefore, even if the OLT 1 ​​determines the GST and the allocated bandwidth based on the shaping rate, the actual communication rate may fall below the shaping rate, making it impossible to maintain the shaping rate. For example, when the OLT 1 ​​allocates a 2000-byte bandwidth to the ONU 2-i, if the upstream frame lengths are 1300 bytes, 800 bytes, and so on, the ONU 2-i transmits data so that the data is below the allocated bandwidth, and therefore can only transmit the first 1300-byte frame. In this case, the OLT 1 ​​determines the allocated bandwidth so that the communication rate is equal to the shaping rate when 2000 bytes of data are transmitted to the GST. Therefore, the actual communication rate falls far below the shaping rate. Therefore, the bandwidth correction unit 15 corrects at least one of the GST and the bandwidth allocation amount based on the amount of data actually transmitted by ONU2-i to OLT1, thereby enabling the communication rate to maintain the shaping rate.

[0038] First, the first correction method is a method of maintaining a desired shaping rate by correcting the allocated bandwidth. In the first correction method, the bandwidth correction unit 15 compares the previous allocated bandwidth Da for each ONU 2-i with the amount of data Db actually transmitted for each ONU 2-i calculated in step S107, and calculates a difference Dc by subtracting the actual amount of data Db from the allocated bandwidth Da. The bandwidth correction unit 15 corrects the allocated bandwidth by adding the difference to the allocated bandwidth at the time of the next bandwidth allocation.

[0039] Next, the second correction method is a method of maintaining a desired shaping rate by correcting the IDLE length and GST while keeping the bandwidth allocation constant. In the second correction method, the bandwidth correction unit 15 corrects the IDLE length Ta based on the amount of data Db actually transmitted for each ONU2-i calculated in step S107 and the shaping rate R determined in step S103, and calculates the GST based on the corrected IDLE length Ta. The corrected IDLE length Ta can be calculated by dividing the amount of data actually transmitted Db by the shaping rate R, as shown in the following equation (1).

[0040] Ta=Db / R (1)

[0041] Although the first correction method is a method of correcting the bandwidth allocation amount and the second correction method is a method of correcting the GST, these may be combined to correct both the bandwidth allocation amount and the GST. For example, the bandwidth correction unit 15 may correct both the bandwidth allocation amount and the GST at one correction timing, or may select a correction method to be used from the first method of correcting the bandwidth allocation amount and the second method of correcting the GST at each correction timing.

[0042] Returning to the explanation of Fig. 3, the GATE generation unit 16 stores the GST and the allocated bandwidth received from the bandwidth correction unit 15 in a GATE frame, and transmits the GATE frame to the data multiplexing unit 17 (step S109).

[0043] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 and the GATE frame received from the GATE generation unit 16, and transmits the multiplexed data to the optical transceiver unit 18 (step S110).

[0044] The optical transceiver 18 receives upstream data from the ONU 2-i and transmits it to the traffic monitor 19. The optical transceiver 18 also transmits the downstream data and the GATE frame multiplexed by the data multiplexer 17 to the ONU 2-i (step S111).

[0045] The traffic monitoring unit 19 monitors the upstream data received from the optical transceiver 18, and notifies the bandwidth correction unit 15 of the source ONU information, the reception time, and the amount of received data (step S112). The traffic monitoring unit 19 also transfers the upstream data to the wireless base station device 3.

[0046] 4 is a diagram illustrating a first example of a hardware configuration of the OLT 1 ​​according to the first embodiment. The OLT 1 ​​includes a receiving circuit 51, a transmitting circuit 52, a processor 53, a memory 54, an optical-wireless cooperation scheduling circuit 55, a Multi-Point Control Protocol (MPCP) circuit 56, a multiplexing circuit 57, an optical transceiver circuit 58, and a demultiplexing circuit 59. The receiving circuit 51, the transmitting circuit 52, the processor 53, the optical-wireless cooperation scheduling circuit 55, the MPCP circuit 56, the multiplexing circuit 57, the optical transceiver circuit 58, and the demultiplexing circuit 59 are processing circuits. In FIG. 4, the receiving circuit 51, the transmitting circuit 52, the processor 53, the optical-wireless cooperation scheduling circuit 55, the MPCP circuit 56, the multiplexing circuit 57, the optical transceiver circuit 58, and the demultiplexing circuit 59 are dedicated hardware. When the processing circuitry is dedicated hardware, the processing circuitry may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0047] 2, the functions of the cooperation information receiver 11, information analyzer 12, rate calculator 13, bandwidth allocation calculator 14, bandwidth corrector 15, GATE generator 16, data multiplexer 17, optical transmitter / receiver 18, and traffic monitor 19 of the OLT 1 ​​are realized by processing circuits. For example, the functions of the information analyzer 12, rate calculator 13, bandwidth allocation calculator 14, bandwidth corrector 15, and traffic monitor 19 are realized by an optical-wireless cooperation scheduling circuit 55 or an MPCP circuit 56. Furthermore, the function of the GATE generator 16 is realized by the MPCP circuit 56, the function of the data multiplexer 17 is realized by a multiplexer circuit 57, and the function of the optical transmitter / receiver 18 is realized by the optical transmitter / receiver circuit 58.

[0048] The optical transceiver circuit 58 is connected to the ONU 2-i, and upon receiving an optical signal from the ONU 2-i, outputs the received optical signal to the demultiplexer circuit 59. If the received optical signal contains REPORT information, the demultiplexer circuit 59 extracts the REPORT information from the optical signal and outputs it to the MPCP circuit 56. Furthermore, upon receiving an optical signal containing upstream data, the demultiplexer circuit 59 outputs the upstream data to the optical-wireless cooperation scheduling circuit 55 and the wireless base station device 3. Furthermore, the multiplexer circuit 57 multiplexes the upstream data received from the wireless base station device 3 with the GATE frame output by the MPCP circuit 56, and outputs the multiplexed data to the optical transceiver circuit 58. The optical transceiver circuit 58 transmits the GATE frame and upstream data output by the multiplexer circuit 57 to the ONU 2-i. The MPCP circuit 56 has an MPCP function within the PON system. The MPCP function allows the OLT1 to recognize multiple ONU2-i connected to the PON, and includes functions such as measuring the RTT (Round Trip Time) required for communication between each ONU2-i and the OLT1, assigning LLIDs (Logical Link IDentifiers), and time synchronization between the ONU2-i and the OLT1.

[0049] The optical-wireless cooperation scheduling circuit 55 receives upstream data from the demultiplexing circuit 59 and receives cooperation information from the wireless base station device 3. The optical-wireless cooperation scheduling circuit 55 performs optical upstream scheduling. At this time, the optical-wireless cooperation scheduling circuit 55 acquires a time used in the PON system, called LocalTime, from the MPCP circuit 56 and determines a GST based on the LocalTime. As a result of performing optical upstream scheduling, the optical-wireless cooperation scheduling circuit 55 outputs the determined GST and a Grant indicating the amount of bandwidth allocation to the MPCP circuit 56. In the example shown in FIG. 4, the receiving circuit 51 is connected to a management system (not shown in FIGS. 1 and 2), and the processor 53 controls the OLT 1 ​​based on information received from the management system. The transmitting circuit 52 transmits information received by the receiving circuit 51, information generated by the processor 53, and the like to the optical-wireless cooperation scheduling circuit 55.

[0050] FIG. 5 is a diagram illustrating a second example of the hardware configuration of the OLT 1 ​​according to the first embodiment. The OLT 1 ​​includes a receiving circuit 61, a transmitting circuit 62, a processor 63, a memory 64, a GATE generating circuit 65, a multiplexing circuit 66, an optical transmitting / receiving circuit 67, a demultiplexing circuit 68, a REPORT receiving circuit 69, and a traffic monitoring circuit 70. In the example illustrated in FIG. 5, the processing circuit is a CPU (Central Processing Unit), and the functions of each unit of the OLT 1 ​​illustrated in FIG. 5 are realized by software, firmware, or a combination thereof. The software and firmware are written as programs and stored in memory. The CPU constituting the processing circuit realizes the functions of each unit described above by reading and executing programs recorded in memory.

[0051] 5, the cooperation information receiving unit 11 is realized by a receiving circuit 61. Furthermore, the functions of the information analyzing unit 12, the rate calculating unit 13, the bandwidth allocation calculating unit 14, and the bandwidth correcting unit 15 are realized by a processor 63. Furthermore, the function of the GATE generating unit 16 is realized by a GATE generating circuit 65. The function of the data multiplexing unit 17 is realized by a multiplexing circuit 66. The function of the optical transmitting and receiving unit 18 is realized by an optical transmitting and receiving circuit 67. The function of the traffic monitoring unit 19 is realized by a traffic monitoring circuit 70.

[0052] Note that the hardware configurations shown in Figures 4 and 5 are examples. The OLT 1 ​​can be realized using various hardware configurations other than the examples shown here. For example, some of the functions of each unit may be realized by dedicated hardware, and some may be realized by software or firmware. The OLT 1 ​​can also be realized by combining the configuration shown in Figure 4 and the configuration shown in Figure 5. In this way, the processing circuit can realize each of the above functions by hardware, software, firmware, or a combination of these.

[0053] As described above, according to the first embodiment, the optical wireless communication system 100A includes a plurality of ONUs 2-i, which are subscriber-side optical terminals connected to wireless slave station devices 4-i that wirelessly communicate with wireless terminals, and an OLT 1, which is a central office-side optical terminal connected to each of the plurality of ONUs 2-i via an optical transmission path and connected to the wireless master station device 3. Furthermore, the optical wireless communication system 100A performs shaping to limit the communication rate of upstream communication from each of the plurality of ONUs 2-i to the OLT 1 ​​by alternately repeating a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted to each of the plurality of ONUs 2-i. The optical wireless communication system 100A also includes a rate calculation unit 13 that calculates a shaping rate, which is a limiting value of the communication rate of upstream communication, for each of the plurality of ONUs 2-i based on allocated resource information indicating resources allocated to the wireless terminal by the wireless base station 3, and an upstream communication control unit 10A that determines an upstream communication allocation bandwidth and a data transmission start time GST for each of the plurality of ONUs 2-i based on the shaping rate and information based on the data amount per frame of data actually transmitted in the upstream communication.With this configuration, the optical wireless communication system 100A determines the upstream communication allocation bandwidth and GST based on information based on the frame length of the data actually transmitted, making it possible to suppress jitter while maintaining the communication rate at the shaping rate.

[0054] In the first embodiment, the rate calculation unit 13 and the upstream communication control unit 10A are provided in the OLT 1. The upstream communication control unit 10A includes a bandwidth allocation calculation unit 14 that determines the bandwidth allocation amount and GST so that the communication rate of the upstream communication satisfies the shaping rate; a traffic monitoring unit 19 that outputs the data volume and reception time of the upstream communication from each of the multiple ONUs 2-i as monitoring information; and a bandwidth correction unit 15 that corrects at least one of the GST and the bandwidth allocation amount based on the monitoring information so that the communication rate approaches the shaping rate. In the first embodiment, the amount of data actually transmitted by the ONU 2-i is monitored. When the ONU 2-i actually transmits upstream data, the upstream data is transmitted in frame units. Therefore, the amount of data actually transmitted is the frame length of one frame or the sum of the frame lengths of multiple frames. Therefore, the amount of data actually transmitted by the ONU 2-i is an example of information based on the frame length.

[0055] The bandwidth correction unit 15 can correct the bandwidth allocation amount calculated by the bandwidth allocation calculation unit 14 by adding the difference between the amount of data actually transmitted in a predetermined period and the bandwidth allocation amount for each of the multiple ONUs 2-i to the bandwidth allocation amount. This allows the bandwidth correction unit 15 to bring the actual communication rate of upstream communication closer to the shaping rate.

[0056] Alternatively, the bandwidth correction unit 15 may correct the time interval at which transmission permission is granted to each of the ONUs 2-i based on the amount of data actually transmitted and the amount of bandwidth allocated in a predetermined period so that the communication rate approaches the shaping rate, and then correct the data transmission start time based on the corrected time interval. This configuration also enables the bandwidth correction unit 15 to bring the actual communication rate of upstream communication closer to the shaping rate.

[0057] In the first embodiment, the OLT 1 ​​is an example of a communication device that determines the allocated bandwidth amount and the data transmission start time for upstream communication for each of the plurality of ONUs 2-i. The OLT 1 ​​includes a rate calculation unit 13 that is a shaping rate acquisition unit that acquires a shaping rate, which is a limit value for the communication rate of upstream communication, calculated based on allocated resource information indicating resources allocated to the wireless terminal by the wireless base station device 3, for each of the plurality of ONUs 2-i, and an upstream communication control unit 10A that determines the allocated bandwidth amount and the data transmission start time for each of the plurality of ONUs 2-i based on the shaping rate and the actual amount of data in the upstream communication, which is information based on the frame length transmitted in the upstream communication.

[0058] Embodiment 2 FIG. 6 is a diagram illustrating functional configurations of ONU2B-i and OLT1B included in an optical wireless communication system 100B according to a second embodiment. Note that FIG. 6 illustrates only parts necessary for explaining the features of the second embodiment, and each of the ONU2B-i and the OLT1B may have a configuration other than that illustrated in FIG. 6. The optical wireless communication system 100B includes an ONU2B-i and an OLT1B. Note that, although not illustrated in FIG. 6, the optical wireless communication system 100B includes a plurality of ONU2B-1 to 2B-n. As in the first embodiment, ONU2B-i collectively refers to the plurality of ONU2B-1 to 2B-n. In the optical wireless communication system 100B, the connection between the ONU2B-i and the OLT1B is the same as the connection between the ONU2-i and the OLT1B in the optical wireless communication system 100A illustrated in FIG. 1. The OLT1B is connected to each of the plurality of ONU2B-i via an optical fiber OF and a star coupler S. Each of the plurality of ONUs 2B-i is connected to a wireless slave station device 4-i. A wireless master station device 3 is connected to the OLT 1B.

[0059] In the first embodiment, the OLT 1 ​​monitors the amount of upstream data transmitted by the ONU 2-i, and adjusts the communication rate by correcting at least one of the next bandwidth allocation amount and the IDLE length based on the amount of received data. In the second embodiment, an example will be described in which the ONU 2-i monitors the amount of upstream data transmitted by itself, and adjusts the communication rate by correcting the IDLE length based on the amount of transmitted data.

[0060] The OLT 1B has a cooperation information receiving unit 11, an information analyzing unit 12, a rate calculating unit 13B, a bandwidth allocation calculating unit 14B, a GATE generating unit 16B, a data multiplexing unit 17, and an optical transmitting / receiving unit 18. The ONU 2B-i has an optical transmitting / receiving unit 21, a GATE extracting unit 22, a rate control unit 23, and an output control unit 24. The rate control unit 23 and the output control unit 24 are collectively referred to as an upstream communication control unit 10B.

[0061] The cooperation information receiving unit 11 receives cooperation information transmitted from the wireless base station device 3, and transfers the received cooperation information to the information analyzing unit 12. The cooperation information includes wireless uplink scheduling information and the like.

[0062] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11 and extracts wireless uplink scheduling information from the cooperation information. The information analysis unit 12 transmits the extracted wireless uplink scheduling information to each of the rate calculation unit 13B and the bandwidth allocation calculation unit 14B. The wireless uplink scheduling information includes the amount of allocated resources, the data arrival time, and the wireless terminal buffer amount.

[0063] The rate calculation unit 13B determines a shaping rate between the OLT 1B and the ONU 2B-i based on the wireless uplink scheduling information received from the information analysis unit 12. The rate calculation unit 13B transmits the determined shaping rate to the GATE generation unit 16B.

[0064] The bandwidth allocation calculation unit 14B calculates the GST indicating the data transmission start time for the upstream communication and the bandwidth allocation amount for each ONU2-i based on the wireless upstream scheduling information received from the information analysis unit 12, and transmits the calculated GST and bandwidth allocation amount to the GATE generation unit 16B.

[0065] The GATE generation unit 16B stores the GST and the bandwidth grant amount received from the bandwidth allocation calculation unit 14B and the shaping rate received from the rate calculation unit 13B in a GATE frame, and transmits the GATE frame to the data multiplexing unit 17. The storage location of the shaping rate in the GATE frame is not specified in the GATE MPCPDU specified in IEEE802.3, so it can be stored in, for example, the Pad / Reserved field of the GATE MPCPDU. The storage location of the shaping rate in the GATE frame is not particularly limited as long as it can notify the ONU 2B-i of the shaping rate.

[0066] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 and the GATE frame received from the GATE generation unit 16B, and transmits the multiplexed data to the optical transceiver unit 18.

[0067] The optical transceiver 18 is connected to the ONU2B-i, receives upstream data from the ONU2B-i, and transmits the upstream data to the wireless base station device 3. The optical transceiver 18 also transmits the downstream data and GATE frame multiplexed by the data multiplexer 17 to the ONU2B-i.

[0068] The optical transceiver 21 of the ONU 2B-i receives downstream data from the OLT 1B and transmits it to the GATE extractor 22. The optical transceiver 21 also transmits upstream data transmitted from the output controller 24 to the OLT 1B.

[0069] The GATE extraction unit 22 transmits the downstream data received from the optical transceiver 21 to the wireless slave station device 4-i, and extracts the GST, the allocated bandwidth, and the shaping rate from the GATE frame received from the optical transceiver 21. The GATE extraction unit 22 transmits the GST and the allocated bandwidth to the output control unit 24, and transmits the shaping rate to the rate control unit 23.

[0070] The rate control unit 23 determines an IDLE length to satisfy the shaping rate based on the shaping rate received from the GATE extraction unit 22 and the transmission frame length information and transmission start signal received from the output control unit 24. The rate control unit 23 controls the communication rate of upstream communication from the ONU 2B-i to the OLT 1B by determining the IDLE length. The rate control unit 23 also transmits a transmission ready flag to the output control unit 24 when the IDLE length has elapsed since the previous transmission start signal was received from the output control unit 24. The rate control unit 23 also transmits a transmission ready flag to the output control unit 24 when the optical wireless communication system 100B is started up.

[0071] The output control unit 24 transmits upstream data to the optical transceiver unit 21 based on the GST and the bandwidth allocation amount received from the GATE extraction unit 22 and the transmission enable flag received from the rate control unit 23. When transmitting upstream data, the output control unit 24 transmits transmission frame length information and a transmission start signal to the rate control unit 23. The transmission frame length information includes at least the frame length of the frame transmitted by the output control unit 24 to the optical transceiver unit 21 at that timing.

[0072] 7 is a flowchart for explaining the operation of the OLT 1B according to the embodiment 2. The cooperation information receiving unit 11 of the OLT 1B receives the cooperation information transmitted from the wireless base station device 3, and transfers the received cooperation information to the information analyzing unit 12 (step S201).

[0073] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11, extracts wireless uplink scheduling information from the cooperation information, and transmits the extracted wireless uplink scheduling information to the rate calculation unit 13B and the bandwidth allocation calculation unit 14B (step S202). The wireless uplink scheduling information includes the amount of allocated resources, the data arrival time, and the wireless terminal buffer amount.

[0074] The rate calculation unit 13B determines a shaping rate between the OLT 1B and the ONU 2B-i based on the wireless uplink scheduling information received from the information analysis unit 12, and transmits the determined shaping rate to the GATE generation unit 16B (step S203).

[0075] The bandwidth allocation calculation unit 14B calculates the GST indicating the data transmission start time and the bandwidth allocation amount for each ONU2B-i based on the wireless uplink scheduling information received from the information analysis unit 12, and transmits the calculated GST and bandwidth allocation amount to the GATE generation unit 16B (step S204).

[0076] The GATE generation unit 16B stores the GST and the bandwidth allocation amount received from the bandwidth allocation calculation unit 14B and the shaping rate received from the rate calculation unit 13B in a GATE frame, and transmits the GATE frame to the data multiplexing unit 17 (step S205).

[0077] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 and the GATE frame received from the GATE generation unit 16B, and transmits the multiplexed data to the optical transceiver unit 18 (step S206).

[0078] The optical transceiver 18 transmits the downstream data and GATE frame multiplexed by the data multiplexer 17 to the ONU 2B-i (step S207).

[0079] 8 is a flowchart for explaining the operation of the ONU 2B-i according to the embodiment 2. The optical transceiver 21 of the ONU 2B-i receives downstream data from the OLT 1B and transmits the received downstream data to the GATE extractor 22 (step S208).

[0080] The GATE extraction unit 22 transmits the downstream data received from the optical transceiver 21 to the wireless slave station device 4-i, extracts the GST, the bandwidth allocation amount, and the shaping rate from the GATE frame received from the optical transceiver 21, transmits the extracted GST and bandwidth allocation amount to the output control unit 24, and transmits the extracted shaping rate to the rate control unit 23 (step S209).

[0081] The rate control unit 23 determines the IDLE length based on the shaping rate received from the GATE extraction unit 22 and the transmission frame length information received from the output control unit 24 so as to satisfy the shaping rate (step S210).

[0082] When the shaping rate is R (bit / sec) and the transmission frame length indicated by the transmission frame length information is Dd (bit), the IDLE length Tb (sec) is expressed by the following equation (2).

[0083] Tb=Dd / R (2)

[0084] The rate control unit 23 determines whether or not the ONU 2B-i has transmitted upstream data to the OLT 1B since the ONU 2B-i was started up until now (step S211).

[0085] If the ONU 2B-i has never transmitted upstream data to the OLT 1B (step S211: No), the rate control unit 23 transmits a transmission possible flag to the output control unit 24 (step S212).

[0086] If ONU2B-i has transmitted upstream data to OLT1B since its startup (step S211: Yes), the rate control unit 23 transmits a transmittable flag to the output control unit 24 after the IDLE length has elapsed since the time when the previous transmission start signal was received (step S213).

[0087] The output control unit 24 determines whether or not a transmission possible flag has been received (step S214). If a transmission possible flag has been received (step S214: Yes), the output control unit 24 transmits upstream data to the optical transceiver unit 21 at the timing of the GST received from the GATE extraction unit 22, within the range of the bandwidth allocation amount. Furthermore, the output control unit 24 transmits a transmission start signal to the rate control unit 23 at the timing of starting transmission of the upstream data, and after completing transmission of the upstream data, transmits transmission frame length information indicating the frame length of the transmitted frame to the rate control unit 23 (step S215). If a transmission possible flag has not been received (step S214: No), the ONU2B-i repeats the process from step S213.

[0088] 9 is a diagram illustrating a first example of a hardware configuration of an ONU2B-i according to the second embodiment. In the first example illustrated in FIG. 9, the ONU2B-i includes a receiving circuit 71, a transmitting circuit 72, a processor 73, a memory 74, a rate control / output control circuit 75, an MPCP circuit 76, a multiplexing circuit 77, an optical transmitting / receiving circuit 78, and a demultiplexing circuit 79.

[0089] The functions of the units shown in Fig. 9 are realized by a processing circuit. When the processing circuit is dedicated hardware, the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0090] FIG. 10 is a diagram illustrating a second example of the hardware configuration of an ONU2B-i according to the second embodiment. In the second example illustrated in FIG. 10, the ONU2B-i includes a receiving circuit 71, a transmitting circuit 72, a processor 73, a memory 74, a rate control / output control circuit 75, a multiplexing circuit 77, an optical transmitting / receiving circuit 78, a demultiplexing circuit 79, a REPORT generating circuit 80, and a GATE receiving circuit 81. When the processing circuit is a CPU, the functions of each unit illustrated in FIG. 10 are realized by software, firmware, or a combination thereof. The software, firmware, etc. are written as programs and stored in a storage device. The processor constituting the processing circuit can realize the functions of each unit by reading and executing the programs stored in the storage device.

[0091] The functions of each part of ONU2B-i may be partially realized by dedicated hardware and partially realized by software, firmware, etc. The configuration of ONU2B-i may also be a combination of the first example shown in Fig. 9 and the second example shown in Fig. 10. The processing circuit can realize each function by hardware, software, firmware, or a combination of these.

[0092] As described above, according to the second embodiment, the optical wireless communication system 100B includes a plurality of ONUs 2B-i connected to wireless slave station devices 4-i that communicate wirelessly with wireless terminals, and an OLT 1B that is connected to each of the plurality of ONUs 2B-i via an optical transmission path and is also connected to the wireless master station device 3, and in upstream communication from each of the plurality of ONUs 2B-i to the OLT 1B, the communication rate of the upstream communication is limited by alternating between a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted to each of the plurality of ONUs 2B-i. The optical wireless communication system 100B includes a rate calculation unit 13B that calculates a shaping rate, which is a limiting value of the communication rate of upstream communication, for each of the plurality of ONUs 2B-i based on allocated resource information indicating resources allocated to the wireless terminal by the wireless base station 3, and an upstream communication control unit 10B that determines, for each of the plurality of ONUs 2B-i, a bandwidth allocation for upstream communication and a GST indicating a data transmission start time, based on the shaping rate and frame length information, which is information based on the frame length of data transmitted in the upstream communication. With this configuration, the optical wireless communication system 100B determines the bandwidth allocation for upstream communication and the GST based on information based on the frame length of data actually transmitted, specifically, frame length information indicating the frame length of the actually transmitted frame, making it possible to suppress jitter while maintaining the communication rate at the shaping rate.

[0093] The OLT 1B has a rate calculation unit 13B and a bandwidth allocation calculation unit 14B that determines the amount of bandwidth granted and the data transmission start time based on the allocated resource information notified from the wireless base station device 3. Each of the multiple ONUs 2B-i has an upstream communication control unit 10B. The upstream communication control unit 10B has an output control unit 24 that outputs upstream communication frames, and a rate control unit 23 that determines an IDLE length, which is the time interval for granting transmission permission to the ONUs 2B-i, based on the shaping rate, bandwidth grant amount, and GST notified from the OLT 1B, and controls the data transmission start time for the upstream communication so that the time interval becomes the determined value.

[0094] After transmitting an upstream communication frame, the output control unit 24 notifies the rate control unit 23 of the frame length of the transmitted frame, and the rate control unit 23 determines the IDLE length based on the notified frame length and the shaping rate. Furthermore, the output control unit 24 transmits a transmission start signal to the rate control unit 23 at the timing when the transmission of the upstream communication frame starts, and the rate control unit 23 controls the data transmission start time by transmitting a transmission ready flag to the output control unit 24 after the determined IDLE length has elapsed since the timing when the transmission start signal was received.

[0095] In the second embodiment, the ONU2B-i is an example of a communication device that determines the amount of bandwidth granted for upstream communication and the data transmission start time for each of the multiple ONU2B-i. The ONU2B-i includes a GATE extraction unit 22 that is a shaping rate acquisition unit that acquires a shaping rate calculated by a rate calculation unit 13B of the OLT 1B based on allocation resource information indicating resources allocated to wireless terminals by the wireless base station device 3 for each of the multiple ONU2B-i. The ONU2B-i also includes an upstream communication control unit 10B that determines the amount of bandwidth granted and the data transmission start time for the ONU2B-i based on the acquired shaping rate and frame length information that is information based on the frame length transmitted in the upstream communication.

[0096] Embodiment 3 Fig. 11 is a diagram illustrating the functional configuration of an OLT 1C and a wireless base station device 3 according to the third embodiment. Note that Fig. 11 shows only parts necessary for explaining the features of the third embodiment, and each of the OLT 1C and the wireless base station device 3 may have a functional configuration other than that shown in Fig. 11. An optical wireless communication system 100C according to the third embodiment has a plurality of ONUs 2-i and an OLT 1C.

[0097] The wireless base station device 3 has a frame information generation unit 31 and a cooperation information transmission unit 32. The OLT 1C has a cooperation information reception unit 11, an information analysis unit 12, a rate calculation unit 13C, a bandwidth allocation calculation unit 14, a GATE generation unit 16, a data multiplexing unit 17, and an optical transmission / reception unit 18. The bandwidth allocation calculation unit 14 is referred to as an upstream communication control unit 10C.

[0098] The frame information generating unit 31 transmits to the cooperation information transmitting unit 32 frame information including the wireless terminal buffer amount received from the wireless slave station device 4-i and the like, the frame length stored in the buffer, and the number of frames.

[0099] The cooperation information transmitter 32 generates radio uplink scheduling information based on the frame information received from the frame information generator 31, and transmits the cooperation information including the radio uplink scheduling information to the OLT 1C. The radio uplink scheduling information includes the allocated resource amount, the data arrival time, the wireless terminal buffer amount, and the number and length of frames included in the allocated resource amount.

[0100] The cooperation information receiving unit 11 receives cooperation information from the wireless master station device 3 and transfers the received cooperation information to the information analyzing unit 12 .

[0101] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11, extracts the wireless uplink scheduling information from the cooperation information, and transmits the extracted wireless uplink scheduling information to the rate calculation unit 13C.

[0102] The rate calculation unit 13C determines the shaping rate between the OLT 1C and the ONU 2-i based on the wireless uplink scheduling information received from the information analysis unit 12. The rate calculation unit 13C also determines the shaping bandwidth allocation amount based on the number of frames and frame length included in the allocated resource amount. The rate calculation unit 13C stores the frame length for each entry, for example, by storing the frame length in a ring buffer, and invalidates the entry each time a bandwidth is allocated. When the rate calculation unit 13C receives the next information, it adds the next entry to the end of the valid entries, for example. The rate calculation unit 13C determines the idle length based on the shaping bandwidth allocation amount and the shaping rate. The rate calculation unit 13C transmits rate information including the shaping rate, the shaping bandwidth allocation amount, and the idle length to the bandwidth allocation calculation unit 14.

[0103] The bandwidth allocation calculation unit 14 calculates a GST indicating the data transmission start time and a bandwidth allocation amount for each ONU2-i based on the rate information received from the rate calculation unit 13C, and transmits the GST and the bandwidth allocation amount to the GATE generation unit 16.

[0104] The GATE generation unit 16 stores the GST and the bandwidth allocation amount received from the bandwidth allocation calculation unit 14 in a GATE frame and transmits it to the data multiplexing unit 17 .

[0105] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 with the GATE frame received from the GATE generation unit 16 and transmits the multiplexed data to the optical transceiver unit 18 .

[0106] The optical transceiver 18 receives upstream data from the ONU 2-i and transmits the received upstream data to the wireless base station device 3. The optical transceiver 18 also transmits the downstream data and GATE frame multiplexed by the data multiplexer 17 to the ONU 2-i.

[0107] 12 is a flowchart for explaining the operation of the wireless base station device 3 according to the third embodiment. The frame information generation unit 31 of the wireless base station device 3 transmits the wireless terminal buffer capacity, the frame length of the frames stored in the buffer, and the number of frames stored in the buffer as frame information to the cooperation information transmission unit 32 (step S301).

[0108] The cooperation information transmitter 32 generates wireless uplink scheduling information based on the frame information received from the frame information generator 31, and transmits cooperation information including the generated wireless uplink scheduling information to the OLT 1C (step S302). The wireless uplink scheduling information includes the allocated resource amount, the data arrival time, the wireless terminal buffer amount, the number of frames included in the allocated resource amount, and the frame length included in the allocated resource amount.

[0109] 13 is a flowchart for explaining the operation of the OLT 1C according to the third embodiment. The cooperation information receiving unit 11 of the OLT 1C receives the cooperation information transmitted from the wireless base station device 3, and transfers the received cooperation information to the information analyzing unit 12 (step S303).

[0110] The information analysis unit 12 analyzes the cooperation information transferred from the cooperation information reception unit 11, extracts the wireless uplink scheduling information from the cooperation information, and transmits the extracted wireless uplink scheduling information to the rate calculation unit 13C (step S304).

[0111] The rate calculation unit 13C determines the shaping rate between the OLT 1C and the ONU 2-i based on the allocated resource amount, data arrival time, and wireless terminal buffer amount included in the wireless uplink scheduling information received from the information analysis unit 12 (step S305).

[0112] The rate calculation unit 13C stores frame length information in a table based on the number of frames and the frame length included in the allocated resource amount, and determines the shaping bandwidth allocation amount (step S306). Specifically, the rate calculation unit 13C determines the frame length of the entry stored at the top of the valid entries stored in the table as the shaping bandwidth allocation amount.

[0113] The rate calculation unit 13C determines the IDLE length based on the shaping bandwidth allocation amount and the shaping rate, and transmits rate information including the determined IDLE length, the shaping rate, and the shaping bandwidth allocation amount to the bandwidth allocation calculation unit 14 (step S307).

[0114] When the shaping rate is R (bit / sec) and the shaping bandwidth allocation amount is De (bit), the IDLE length Tc (sec) can be calculated using the following formula (3).

[0115] Tc=De / R (3)

[0116] The bandwidth allocation calculation unit 14 calculates the GST and the bandwidth allocation amount for each ONU 2-i based on the rate information received from the rate calculation unit 13, and transmits the calculated GST and the bandwidth allocation amount to the GATE generation unit 16 (step S308).

[0117] The GATE generation unit 16 stores the GST and the bandwidth allocation amount received from the bandwidth allocation calculation unit 14 in a GATE frame, and transmits the GATE frame to the data multiplexing unit 17 (step S309).

[0118] The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless master station device 3 and the GATE frame received from the GATE generation unit 16, and transmits the multiplexed data to the optical transceiver unit 18 (step S310).

[0119] The optical transceiver 18 transmits the downstream data and GATE frame multiplexed by the data multiplexer 17 to the ONU 2-i (step S311).

[0120] The functions of the OLTs 1B and 1C according to the second and third embodiments can also be realized using a processing circuit, as explained in the first embodiment. The processing circuit may be dedicated hardware, or may use software, firmware, or the like.

[0121] As described above, in the optical wireless communication system 100C according to the third embodiment, the OLT 1C includes a rate calculation unit 13C, an upstream communication control unit 10C, and a cooperation information receiving unit 11 that acquires cooperation information including frame information indicating the frame length of downstream data from the wireless master station device 3. Here, the frame information included in the cooperation information is an example of information based on frame length. The upstream communication control unit 10C determines the bandwidth allocation amount and the GST, which is the data transmission start time, based on the frame information. Therefore, the bandwidth allocation amount and the GST are determined taking into consideration the frame length of the frame to be actually transmitted. This makes it possible to suppress jitter while maintaining the communication rate at the shaping rate.

[0122] The frame information includes the number of frames and the frame length. Scheduling is performed based on the number of frames and the frame length, which allows for more accurate, real-time scheduling and adjustment to the desired communication rate.

[0123] In the third embodiment, the OLT 1C is an example of a communication device that determines the amount of bandwidth granted for upstream communication and the data transmission start time for each of the plurality of ONUs 2-i. The OLT 1C includes a rate calculation unit 13C, which is a shaping rate acquisition unit that acquires a shaping rate calculated based on allocated resource information indicating resources allocated to the wireless terminal by the wireless base station device 3, for each of the plurality of ONUs 2-i, and an upstream communication control unit 10C that determines the amount of bandwidth granted and the data transmission start time for each ONU 2-i based on the shaping rate and information based on the frame length transmitted in the upstream communication.

[0124] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention. [Explanation of symbols]

[0125] 1, 1B, 1C OLT, 2-1 to 2-n, 2-i, 2B-i ONU, 3 Wireless master station device, 4-1 to 4-n, 4-i Wireless slave station device, 10A, 10B, 10C Upstream communication control unit, 11 Coordination information receiving unit, 12 Information analysis unit, 13, 13B, 13C Rate calculation unit, 14, 14B Bandwidth allocation calculation unit, 15 Bandwidth correction unit, 16, 16B GATE generation unit, 17 Data multiplexing unit, 18, 21 Optical transmission / reception unit, 19 Traffic monitoring unit, 22 GATE extraction unit, 23 Rate control unit, 24 Output control unit, 31 Frame information generation unit, 32 Coordination information transmission unit, 51, 61, 71 Receiving circuit, 52, 62, 72 Transmitting circuit, 53, 63, 73 Processor, 54, 64, 74 Memory, 55 Optical wireless cooperative scheduling circuit, 56,76 MPCP circuit, 57,66,77 Multiplexing circuit, 58,67,78 Optical transceiver circuit, 59,68,79 Separation circuit, 65 GATE generation circuit, 69 REPORT reception circuit, 70 Traffic monitoring circuit, 75 Rate control / output control circuit, 80 REPORT generation circuit, 81 GATE reception circuit, 100A,100B,100C Optical wireless communication system, OF Optical fiber, S Star coupler.

Claims

1. an optical wireless communication system comprising a plurality of subscriber-side optical terminals connected to a wireless slave station device that wirelessly communicates with a wireless terminal, and a central office optical terminal connected to each of the plurality of subscriber-side optical terminals via an optical transmission path and connected to a wireless master station device, wherein in upstream communication from each of the plurality of subscriber-side optical terminals to the central office optical terminal, a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted are alternately repeated for each of the plurality of subscriber-side optical terminals, thereby limiting the communication rate of the upstream communication; The optical terminal device on the central office side a rate calculation unit that calculates a shaping rate, which is a limit value of the communication rate of the upstream communication, for each of the plurality of subscriber-side optical terminal devices based on allocated resource information indicating resources allocated by the wireless base station device to the wireless terminal; a bandwidth allocation calculation unit that determines a bandwidth allocation amount and a data transmission start time for the upstream communication based on the allocated resource information; and Each of the plurality of subscriber side optical terminal devices comprises: an output control unit that outputs the upstream communication frame; a rate control unit that determines a time interval for giving transmission permission to the subscriber-side optical terminal device based on the shaping rate, the allocated bandwidth, and the data transmission start time notified from the optical terminal device on the central office side, and the frame length of the frame transmitted in the upstream communication, and controls the data transmission start time of the upstream communication so that the time interval becomes the determined value; An optical wireless communication system comprising:

2. the output control unit, after transmitting the upstream communication frame, notifies the rate control unit of a frame length of the transmitted frame; 2. The optical wireless communication system according to claim 1, wherein the rate control unit determines a time interval for giving transmission permission to the subscriber-side optical terminal device based on the notified frame length and shaping rate.

3. the output control unit transmits a transmission start signal to the rate control unit at a timing when transmission of the upstream communication frame starts; The optical wireless communication system described in claim 1 or 2, characterized in that the rate control unit controls the data transmission start time by sending a transmission ready flag to the output control unit after a determined length of the non-granting period has elapsed from the time when the transmission start signal was received.

4. A communication device that functions as the subscriber-side optical terminal device constituting an optical wireless communication system comprising: a plurality of subscriber-side optical terminal devices connected to a wireless slave station device that wirelessly communicates with a wireless terminal; and a central office-side optical terminal device that is connected to each of the plurality of subscriber-side optical terminal devices via an optical transmission path and is also connected to a wireless master station device, and that limits the communication rate of the upstream communication by alternately repeating a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted to each of the plurality of subscriber-side optical terminal devices in upstream communication from each of the plurality of subscriber-side optical terminal devices to the central office-side optical terminal device, the optical terminal device on the optical line side calculates a shaping rate, which is a limit value of the communication rate of the upstream communication, a given bandwidth amount for the upstream communication, and a data transmission start time, based on allocated resource information indicating resources allocated to the wireless terminal by the wireless base station device; an output control unit that outputs the upstream communication frame; a rate control unit that determines a time interval for giving transmission permission to the subscriber-side optical terminal device based on the calculated shaping rate, the allocated bandwidth, and the data transmission start time notified from the optical terminal device on the central office side, and the frame length of the frame transmitted in the upstream communication, and controls the data transmission start time of the upstream communication so that the time interval becomes the determined value; A communication device comprising:

5. A communication method for an optical wireless communication system comprising a plurality of subscriber-side optical terminals connected to a wireless slave station that wirelessly communicates with a wireless terminal, and a central office optical terminal that is connected to each of the plurality of subscriber-side optical terminals via an optical transmission path and is also connected to a wireless master station, wherein in upstream communication from each of the plurality of subscriber-side optical terminals to the central office optical terminal, a grant period in which a bandwidth is granted and a non-grant period in which a bandwidth is not granted are alternately repeated for each of the plurality of subscriber-side optical terminals, thereby limiting the communication rate of the upstream communication, The optical terminal device on the optical line side calculating a shaping rate, which is a limit value of the communication rate of the upstream communication, for each of the plurality of subscriber-side optical terminals based on allocated resource information indicating resources allocated by the wireless base station device to the wireless terminal; determining a bandwidth allocation amount and a data transmission start time for the upstream communication based on the allocated resource information; Each of the plurality of subscriber side optical terminal devices outputting the upstream communication frame; determining a time interval for granting transmission permission to said subscriber-side optical terminal device based on the shaping rate, the allocated bandwidth, and the data transmission start time notified from said central office-side optical terminal device, and the frame length of the frame transmitted in the upstream communication; controlling the data transmission start time of the upstream communication so that the time interval is a determined value; A communication method comprising:

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