JP7738535B2 - Optical wireless communication system, communication device, and communication method - Google Patents

Description

This disclosure relates to an optical wireless communication system, communication device, and communication method that converts electrical signals into optical signals and transmits them.

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. To prevent signal collisions between the wireless terminals, the base station dynamically allocates finite resources to each wireless terminal through scheduling. For example, in LTE uplink communications, when a wireless terminal transmits uplink data to a base station, it first requests 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 exchange is completed can the wireless terminal transmit uplink data to the base station.

An optical wireless communication system has also been proposed that combines a wireless base station with a PON (Passive Optical Network). In this case, the OLT (Optical Line Terminal), which is an optical terminal on the central station side connected to the central station, and the ONU (Optical Network Unit), which is an optical terminal on the subscriber side connected to the local station, are connected using optical fiber and an optical splitter. This configuration reduces the number of central station devices and the number of optical fibers relative to the number of local station devices, thereby reducing costs.

In a PON system, one OLT also communicates with multiple ONUs. For this reason, the OLT performs scheduling, dynamically allocating resources to each ONU. When scheduling, an 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 the transmission permission signal sent from the OLT. The OLT then performs scheduling based on the REPORT information, allocates resources to each ONU for transmitting upstream data, and notifies each ONU of the allocated resources. Only after going through the above 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 device and a slave station device, upstream communication from the slave station device to the master station device incurs a delay between each ONU notifying the OLT of the REPORT information stored in each ONU, the allocation of resources, and the transmission of the upstream data.

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

Japanese Patent Application Laid-Open No. 2019-149738

However, wireless communications involve multiple traffic flows transmitted from multiple wireless terminals. Due to factors such as network congestion, retransmissions due to frame loss caused by unreliable transmission lines, and queuing, signal intervals can be irregular, resulting in jitter. 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 bandwidth allocation period is determined based on the requested bandwidth and buffer size reported by the sender. In PON systems, determining the amount of bandwidth allocation during shaping typically involves determining the total amount of data transmitted from the sender, but not the frame length of each transmitted frame. This can lead to a problem where, depending on the frame length, the actual communication rate can be lower than the shaping rate, which is the limiting value for the communication rate during shaping. For example, if a 2000-byte bandwidth is allocated and the frames to be transmitted are 1300 bytes, 800 bytes, and so on, only the first 1300-byte frame can be sent.

The present disclosure has been made in light of the above, and aims to provide an optical wireless communication system that can suppress jitter while maintaining the communication rate at the shaping rate.

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 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 in upstream communication from each of the plurality of subscriber-side optical terminals to the central office optical terminal, the system 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 , based on allocation resource information indicating resources allocated to the wireless terminal by the wireless master station device. Each of the optical terminal devices has a rate calculation unit that calculates a shaping rate, which is a limiting value for the communication rate of upstream communication , and a bandwidth allocation calculation unit that determines the bandwidth allocation amount and data transmission start time for the upstream communication based on the allocated resource information, and each of the multiple optical terminal devices on the subscriber side has an output control unit that outputs frames for the upstream communication, and a rate control unit that determines the time interval for giving transmission permission to the optical terminal device on the subscriber side based on the shaping rate, bandwidth allocation amount and 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 for the upstream communication so that the time interval becomes the determined value .

This disclosure has the advantage of providing an optical wireless communication system that can suppress jitter while maintaining the communication rate at the shaping rate.

FIG. 1 is a diagram showing a configuration of an optical wireless communication system according to a first embodiment; FIG. 1 is a diagram showing a functional configuration of an OLT according to a first embodiment; 1 is a flowchart for explaining an operation of an OLT according to a first embodiment. FIG. 1 is a diagram illustrating a first example of a hardware configuration of an OLT according to a first embodiment. FIG. 1 is a diagram illustrating a second example of a hardware configuration of an OLT according to a first embodiment. FIG. 10 is a diagram showing a functional configuration of an ONU and an OLT included in an optical wireless communication system according to a second embodiment. 10 is a flowchart for explaining the operation of the OLT according to the second embodiment. 10 is a flowchart for explaining the operation of an ONU according to a second embodiment. FIG. 10 is a diagram illustrating a first example of a hardware configuration of an ONU according to a second embodiment. FIG. 10 is a diagram illustrating a second example of a hardware configuration of an ONU according to a second embodiment. FIG. 10 is a diagram showing a functional configuration of an OLT and a wireless base station device according to a third embodiment. 10 is a flowchart for explaining the operation of the wireless master station device according to the third embodiment. 10 is a flowchart for explaining the operation of the OLT according to the third embodiment.

The following describes in detail an optical wireless communication system, communication device, and communication method according to embodiments of the present disclosure, with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

Embodiment 1.
FIG. 1 illustrates 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 ONUs 2-1 to 2-n connected to multiple wireless slave stations 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 a higher-level network, and each of the wireless slave stations 4-1 to 4-n can wirelessly connect to a wireless terminal. The wireless base station device 3 transmits 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.

Here, ONUs 2-1 to 2-n may be collectively referred to as ONU 2-i. Wireless slave station devices 4-1 to 4-n may be collectively referred to as wireless slave station device 4-i. Note that i is a positive integer.

The optical wireless communication system 100A can transmit data between the wireless master station 3 and the wireless terminals connected to the wireless slave station 4-i. The following describes the functions of the optical wireless communication system 100A, focusing mainly on upstream scheduling, which is a scheduling method for reducing the latency of upstream communications from the wireless terminals connected to the wireless slave station 4-i to the wireless master station 3. In upstream communications, data transmitted by the wireless terminals is transmitted to the wireless master station 3 via the wireless slave station 4-i, ONU 2-i, and OLT 1. At this time, the wireless master station 3 performs upstream scheduling, allocating resources to each wireless terminal connected to the wireless slave station 4-i. This upstream scheduling performed by the wireless master station 3 is referred to as "wireless upstream scheduling." Furthermore, in upstream communications between the OLT 1 and ONU 2-i, shaping is performed within the PON system, alternating between periods of bandwidth allocation and periods of bandwidth non-allocation to suppress jitter. The upstream scheduling in which OLT1 allocates resources to each ONU2-i to perform shaping is called "optical upstream scheduling."

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.

Figure 2 shows the functional configuration of the OLT 1 according to the first embodiment. The OLT 1 includes a cooperation information receiver 11, an information analyzer 12, a rate calculator 13, a bandwidth allocation calculator 14, a bandwidth corrector 15, a GATE generator 16, a data multiplexer 17, an optical transmitter/receiver 18, and a traffic monitor 19. The bandwidth allocation calculator 14, the bandwidth corrector 15, and the traffic monitor 19 are collectively referred to as the upstream communication controller 10A. Note that Figure 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 Figure 2.

The cooperation information receiver 11 receives cooperation information transmitted from the wireless base station device 3 and transfers the received cooperation information to the information analyzer 12. The cooperation information includes wireless uplink scheduling information, etc.

The information analysis unit 12 analyzes the coordination information transferred from the coordination information reception unit 11 and extracts wireless uplink scheduling information from the coordination 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 capacity.

The rate calculation unit 13 determines the shaping rate, which is the limit value for the communication rate of upstream communication between OLT1 and ONU2-i, based on the wireless upstream scheduling information received from the information analysis unit 12. The rate calculation unit 13 also determines the shaping bandwidth allocation and IDLE length based on the determined shaping rate. The shaping bandwidth allocation is the amount of data that OLT1 grants transmission permission to ONU2-i when shaping. The IDLE length is the length of the period from when OLT1 grants transmission permission to ONU2-i until the next transmission permission is granted, and is the time interval between granting transmission permission to ONU2-i. Therefore, the rate calculation unit 13 determines the shaping bandwidth allocation and IDLE length so that the ratio of the shaping bandwidth allocation to the IDLE length is the shaping rate. The rate calculation unit 13 sends the shaping rate to the bandwidth correction unit 15, and sends rate information including the shaping rate, shaping bandwidth allocation amount, and IDLE length to the bandwidth allocation calculation unit 14.

Based on the rate information received from the rate calculation unit 13, the bandwidth allocation calculation unit 14 calculates the grant start time (GST), indicating the start time of upstream data transmission, and the bandwidth allocation amount for each ONU 2-i, and transmits the calculated GST and bandwidth allocation amount to the bandwidth correction unit 15. Specifically, the bandwidth allocation calculation unit 14 calculates the bandwidth allocation amount by adding the overhead required in the PON system to the shaping bandwidth allocation amount included in the rate information. Here, the overhead amount 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, light emission end period Toff, and 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 multiple ONUs 2-i do not overlap and so that the interval from the timing of the previous transmission permission is 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.

Based on notification from the traffic monitoring unit 19, the bandwidth correction unit 15 corrects at least one of the GST and bandwidth allocation amount received from the bandwidth allocation calculation unit 14. 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 by the traffic monitoring unit 19, compares the bandwidth allocated to ONU 2-i with the amount of data actually transmitted from ONU 2-i, and corrects at least one of the GST and bandwidth allocation amount. The bandwidth correction unit 15 transmits the corrected GST and bandwidth allocation amount to the GATE generation unit 16.

The GATE generation unit 16 stores the GST and 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.

The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless base 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.

The optical transceiver 18 is connected to ONU 2-i, receives upstream data from ONU 2-i, and transmits it to the traffic monitor 19. The optical transceiver 18 also transmits downstream data and GATE frames multiplexed by the data multiplexer 17 to ONU 2-i.

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.

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

Next, we will explain the operation of OLT1.

Figure 3 is a flowchart illustrating 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).

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 capacity.

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 for shaping between OLT1 and ONU2-i, and 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).

Based on the rate information received from the rate calculation unit 13, the bandwidth allocation calculation unit 14 calculates the GST indicating the data transmission start time and the bandwidth allocation amount for each ONU 2-i, and transmits the calculated GST and bandwidth allocation amount to the bandwidth correction unit 15 (step S104).

The bandwidth correction unit 15 determines whether or not there has been a notification from the traffic monitoring unit 19 (step S105).

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 directly to the GATE generation unit 16 (step S106).

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 of bandwidth allocation for each ONU 2-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 ONU 2-i (step S107).

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).

Here, we will explain two examples of the correction method implemented by the bandwidth correction unit 15. ONU2-i transmits data to OLT1 according to the GST and bandwidth allocation allocated by OLT1. However, while OLT1 can determine the amount of data ONU2-i plans to transmit, it does not know the frame length of each frame. Therefore, even if OLT1 determines the GST and bandwidth allocation 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, if OLT1 allocates a bandwidth of 2000 bytes to ONU2-i and the upstream frame lengths are 1300 bytes, 800 bytes, and so on, ONU2-i will transmit data below the allocated bandwidth, and will only be able to transmit the first 1300-byte frame. In this case, when 2000 bytes of data are sent to the GST, OLT1 determines the bandwidth allocation amount so that the communication rate will be the shaping rate, so the actual communication rate will be significantly lower than 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 sent by ONU2-i to OLT1, allowing the communication rate to maintain the shaping rate.

First, the first correction method is a method of maintaining the desired shaping rate by correcting the bandwidth allocation. In the first correction method, the bandwidth correction unit 15 compares the previous bandwidth allocation 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 data amount Db from the bandwidth allocation Da. The bandwidth correction unit 15 corrects the bandwidth allocation by adding the difference to the bandwidth allocation at the time of the next bandwidth allocation.

The second correction method maintains the 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 ONU 2-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):

Ta=Db/R...(1)

Note that the first correction method shows a method of correcting the bandwidth allocation amount, and the second correction method shows a method of correcting the GST, but 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 the correction method to use from the first method of correcting the bandwidth allocation amount and the second method of correcting the GST for each correction timing.

Returning to the explanation of Figure 3, the GATE generation unit 16 stores the GST and 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 (step S109).

The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless base 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 (step S110).

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

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.

Figure 4 is a diagram illustrating a first example of the 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, an MPCP (Multi-Point Control Protocol) 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 Figure 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.

The functions of the cooperation information receiver 11, information analyzer 12, rate calculator 13, bandwidth allocation calculator 14, bandwidth correction unit 15, GATE generator 16, data multiplexer 17, optical transmitter/receiver 18, and traffic monitor 19 of the OLT 1 shown in FIG. 2 are realized by processing circuits. For example, the functions of the information analyzer 12, rate calculator 13, bandwidth allocation calculator 14, bandwidth correction unit 15, and traffic monitor 19 are realized by the optical-wireless cooperation scheduling circuit 55 or the 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 the multiplexer circuit 57, and the function of the optical transmitter/receiver 18 is realized by the optical transmitter/receiver circuit 58.

The optical transceiver circuit 58 is connected to ONU 2-i, and upon receiving an optical signal from 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 ONU 2-i. The MPCP circuit 56 has an MPCP function within the PON system. The MPCP function allows the OLT1 to recognize multiple ONUs 2-i connected to the PON, and includes functions such as measuring the round trip time (RTT) required for communication between each ONU 2-i and the OLT1, assigning logical link identifiers (LLIDs), and synchronizing the time between the ONUs 2-i and the OLT1.

The optical-wireless cooperation scheduling circuit 55 receives upstream data from the demultiplexing circuit 59 and 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 obtains the time used in the PON system, called LocalTime, from the MPCP circuit 56 and determines the 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 allocated to the MPCP circuit 56. Note that 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.

Figure 5 is a diagram showing 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 shown in Figure 5, the processing circuit is a CPU (Central Processing Unit), and the functions of each part of the OLT 1 shown in Figure 5 are realized by software, firmware, or a combination of these. The software and firmware are written as programs and stored in memory. The CPU constituting the processing circuit realizes the functions of each of the above parts by reading and executing programs stored in memory.

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

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

As described above, according to the first embodiment, the optical wireless communication system 100A comprises a plurality of ONUs 2-i, which are subscriber-side optical terminals connected to wireless slave station devices 4-i that communicate wirelessly with wireless terminals, and an optical line terminal (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 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 alternating between grant periods in which bandwidth is granted and non-grant periods in which 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 for the upstream communication rate, for each of the multiple ONUs 2-i based on allocated resource information indicating the resources allocated to the wireless terminal by the wireless base station 3, and an upstream communication control unit 10A that determines the upstream communication bandwidth allocation and the data transmission start time (GST) for each of the multiple ONUs 2-i based on the shaping rate and information based on the data volume per frame of data actually transmitted in the upstream communication. This configuration allows the optical wireless communication system 100A to determine the upstream communication bandwidth allocation and GST based on information based on the frame length of the data actually transmitted, thereby enabling jitter suppression while maintaining the communication rate at the shaping rate.

In embodiment 1, the rate calculation unit 13 and 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 upstream communication rate satisfies the shaping rate; a traffic monitoring unit 19 that outputs the data volume and reception time of upstream communication from each of multiple ONUs 2-i as monitoring information; and a bandwidth correction unit 15 that corrects at least one of the GST and bandwidth allocation amount based on the monitoring information so that the communication rate approaches the shaping rate. In embodiment 1, the amount of data actually transmitted by ONU 2-i is monitored. When ONU 2-i actually transmits upstream data, the upstream data is transmitted in frame units, so 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 ONU 2-i is an example of information based on frame length.

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 during a predetermined period of time and the allocated bandwidth amount to the allocated bandwidth amount for each of the multiple ONUs 2-i. This allows the bandwidth correction unit 15 to bring the actual communication rate of upstream communication closer to the shaping rate.

Alternatively, the bandwidth correction unit 15 may correct the time interval at which transmission permission is granted to each of multiple ONUs 2-i based on the amount of data actually transmitted and the amount of bandwidth allocated during 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.

Also, in embodiment 1, OLT 1 is an example of a communications device that determines the upstream communication bandwidth allocation and data transmission start time for each of multiple ONUs 2-i. OLT 1 includes a rate calculation unit 13, which is a shaping rate acquisition unit that acquires a shaping rate, which is a limiting value for the upstream communication rate, calculated for each of multiple ONUs 2-i based on allocated resource information indicating the resources allocated to the wireless terminal by the wireless base station device 3, and an upstream communication control unit 10A that determines the upstream communication bandwidth allocation and data transmission start time for each of multiple 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.

Embodiment 2.
FIG. 6 is a diagram illustrating the functional configuration of an ONU 2B-i and an OLT 1B included in an optical wireless communication system 100B according to the second embodiment. Note that FIG. 6 illustrates only the portions necessary for explaining the features of the second embodiment, and each of the ONU 2B-i and the OLT 1B may have a configuration other than that shown in FIG. 6. The optical wireless communication system 100B includes an ONU 2B-i and an OLT 1B. Note that, although omitted from FIG. 6, the optical wireless communication system 100B includes a plurality of ONUs 2B-1 to 2B-n. As in the first embodiment, ONU 2B-i collectively refers to a plurality of ONUs 2B-1 to 2B-n. In the optical wireless communication system 100B, the connection between the ONU 2B-i and the OLT 1B is the same as the connection between the ONU 2-i and the OLT 1 in the optical wireless communication system 100A shown in FIG. 1. The OLT 1B is connected to each of the plurality of ONUs 2B-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. The wireless master station device 3 is connected to the OLT 1B.

In embodiment 1, OLT 1 monitored the amount of upstream data transmitted by ONU 2-i, and adjusted the communication rate by correcting at least one of the next allocated bandwidth and IDLE length based on the amount of received data. In embodiment 2, an example is described in which ONU 2-i monitors the amount of upstream data it transmits and adjusts the communication rate by correcting the IDLE length based on the amount of transmitted data.

OLT 1B has a cooperation information receiver 11, an information analyzer 12, a rate calculator 13B, a bandwidth allocation calculator 14B, a GATE generator 16B, a data multiplexer 17, and an optical transmitter/receiver 18. ONU 2B-i has an optical transmitter/receiver 21, a GATE extractor 22, a rate controller 23, and an output controller 24. The rate controller 23 and output controller 24 are collectively referred to as the upstream communication controller 10B.

The cooperation information receiver 11 receives cooperation information transmitted from the wireless base station device 3 and transfers the received cooperation information to the information analyzer 12. The cooperation information includes wireless uplink scheduling information, etc.

The information analysis unit 12 analyzes the coordination information transferred from the coordination information reception unit 11 and extracts wireless uplink scheduling information from the coordination information. The information analysis unit 12 transmits the extracted wireless uplink scheduling information to 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 capacity.

The rate calculation unit 13B determines the shaping rate between OLT 1B and 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.

The bandwidth allocation calculation unit 14B calculates the GST, which indicates the data transmission start time for upstream communication, and the bandwidth allocation amount for each ONU 2-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.

The GATE generation unit 16B stores the GST and 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. The location where the shaping rate is stored in the GATE frame is not specified in the GATE MPCPDU defined in IEEE 802.3, so it can be stored, for example, in the Pad/Reserved field of the GATE MPCPDU. The location where the shaping rate is stored in the GATE frame is not particularly limited as long as it can notify the shaping rate to ONU 2B-i.

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

The optical transceiver 18 is connected to ONU 2B-i, receives upstream data from ONU 2B-i, and transmits it to the wireless base station device 3. The optical transceiver 18 also transmits downstream data and GATE frames multiplexed by the data multiplexer 17 to ONU 2B-i.

The optical transceiver 21 of ONU2B-i receives downstream data from OLT1B and transmits it to the GATE extraction unit 22. The optical transceiver 21 also transmits upstream data transmitted from the output control unit 24 to OLT1B.

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, bandwidth allocation, and shaping rate from the GATE frame received from the optical transceiver 21. The GATE extraction unit 22 transmits the GST and bandwidth allocation to the output control unit 24, and transmits the shaping rate to the rate control unit 23.

The rate control unit 23 determines the 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. By determining the IDLE length, the rate control unit 23 controls the communication rate of upstream communication from ONU 2B-i to OLT 1B. 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.

The output control unit 24 transmits upstream data to the optical transceiver unit 21 based on the GST and 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.

Figure 7 is a flowchart illustrating the operation of the OLT 1B according to the second embodiment. The cooperation information receiving unit 11 of the OLT 1B receives cooperation information transmitted from the wireless base station device 3 and transfers the received cooperation information to the information analyzing unit 12 (step S201).

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 capacity.

The rate calculation unit 13B determines the shaping rate between OLT 1B and 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).

The bandwidth allocation calculation unit 14B calculates the GST indicating the data transmission start time and the bandwidth allocation amount for each ONU 2B-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).

The GATE generation unit 16B stores the GST and 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).

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

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

Figure 8 is a flowchart for explaining the operation of ONU2B-i according to the second embodiment. The optical transceiver 21 of ONU2B-i receives downstream data from OLT1B and transmits the received downstream data to the GATE extraction unit 22 (step S208).

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, bandwidth allocation, and shaping rate from the GATE frame received from the optical transceiver 21, transmits the extracted GST and bandwidth allocation to the output control unit 24, and transmits the extracted shaping rate to the rate control unit 23 (step S209).

The rate control unit 23 determines the IDLE length so as to satisfy the shaping rate 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 (step S210).

If the shaping rate is R (bits/sec) and the transmission frame length indicated by the transmission frame length information is Dd (bits), the IDLE length Tb (sec) is expressed by the following formula (2):

Tb=Dd/R...(2)

The rate control unit 23 determines whether ONU2B-i has sent upstream data to OLT1B since its startup (step S211).

If ONU2B-i has never transmitted upstream data to OLT1B (step S211: No), the rate control unit 23 transmits a transmission possible flag to the output control unit 24 (step S212).

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

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. In addition, 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), ONU2B-i repeats the process from step S213.

Figure 9 is a diagram showing a first example of the hardware configuration of ONU2B-i according to the second embodiment. In the first example shown in Figure 9, 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.

The functions of each unit shown in Figure 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.

Figure 10 is a diagram showing a second example of the hardware configuration of ONU2B-i according to the second embodiment. In the second example shown in Figure 10, 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 shown in Figure 10 are realized by software, firmware, or a combination of these. 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.

Note that 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 Figure 9 and the second example shown in Figure 10. The processing circuit can realize each function by hardware, software, firmware, or a combination of these.

As described above, according to embodiment 2, the optical wireless communication system 100B comprises a plurality of ONUs 2B-i connected to a wireless slave station device 4-i that wirelessly communicates with a wireless terminal, 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 a 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 for the upstream communication rate, for each of the multiple 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 the upstream communication bandwidth allocation and GST, which indicates the data transmission start time, for each of the multiple ONUs 2B-i based on the shaping rate and frame length information, which is information based on the frame length of the data transmitted in the upstream communication. With this configuration, the optical wireless communication system 100B determines the upstream communication bandwidth allocation and GST based on information based on the frame length of the data actually transmitted, specifically, frame length information indicating the frame length of the frame actually transmitted, making it possible to suppress jitter while maintaining the communication rate at the shaping rate.

OLT1B has a rate calculation unit 13B and a bandwidth allocation calculation unit 14B that determines the bandwidth allocation amount and 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 also 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 the IDLE length, which is the time interval for granting transmission permission to ONU 2B-i, based on the shaping rate, bandwidth allocation, and GST notified from OLT1B, and controls the data transmission start time for upstream communication so that the time interval becomes the determined value.

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 shaping rate. The output control unit 24 also transmits a transmission start signal to the rate control unit 23 at the timing when it starts transmitting an upstream communication frame, 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 receiving the transmission start signal.

Also, in embodiment 2, ONU2B-i is an example of a communications device that determines the upstream communication bandwidth allocation amount and data transmission start time for each of multiple ONU2B-i. ONU2B-i has a GATE extraction unit 22, which is a shaping rate acquisition unit that acquires the shaping rate calculated by the rate calculation unit 13B of OLT1B for each of multiple ONU2B-i based on allocation resource information indicating the resources allocated to the wireless terminal by the wireless base station device 3. ONU2B-i also has an upstream communication control unit 10B that determines the bandwidth allocation amount and data transmission start time for ONU2B-i based on the acquired shaping rate and frame length information, which is information based on the frame length transmitted in upstream communications.

Embodiment 3.
Fig. 11 is a diagram showing 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 the OLT 1C and the wireless base station device 3 may each 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.

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 the upstream communication control unit 10C.

The frame information generation unit 31 transmits frame information received from the wireless slave station device 4-i, etc., including the wireless terminal buffer capacity, the frame length stored in the buffer, and the number of frames, to the cooperation information transmission unit 32.

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

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

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

The rate calculation unit 13C determines the shaping rate between OLT1C and ONU2-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 from the number of frames and frame length included in the allocated resource amount. The rate calculation unit 13C stores frame lengths by, for example, storing the frame length for each entry in a ring buffer, with one frame as one entry, and invalidating the entry each time 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 shaping rate. The rate calculation unit 13C transmits rate information including the shaping rate, shaping bandwidth allocation amount, and IDLE length to the bandwidth allocation calculation unit 14.

Based on the rate information received from the rate calculation unit 13C, the bandwidth allocation calculation unit 14 calculates the GST indicating the data transmission start time and the bandwidth allocation amount for each ONU 2-i, and transmits the GST and bandwidth allocation amount to the GATE generation unit 16.

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

The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless base 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.

The optical transceiver 18 receives upstream data from 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 frames multiplexed by the data multiplexer 17 to ONU 2-i.

Figure 12 is a flowchart illustrating 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).

The cooperation information transmission unit 32 generates wireless uplink scheduling information based on the frame information received from the frame information generation unit 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, data arrival time, wireless terminal buffer amount, the number of frames included in the allocated resource amount, and the frame length included in the allocated resource amount.

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

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

The rate calculation unit 13C determines the shaping rate between OLT1C and ONU2-i based on the allocated resource amount, data arrival time, and wireless terminal buffer amount contained in the wireless uplink scheduling information received from the information analysis unit 12 (step S305).

The rate calculation unit 13C stores frame length information in a table based on the number of frames and 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 first valid entry stored in the table as the shaping bandwidth allocation amount.

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, shaping rate, and shaping bandwidth allocation amount to the bandwidth allocation calculation unit 14 (step S307).

If 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):

Tc=De/R...(3)

The bandwidth allocation calculation unit 14 calculates the GST and 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 bandwidth allocation amount to the GATE generation unit 16 (step S308).

The GATE generation unit 16 stores the GST and 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).

The data multiplexing unit 17 multiplexes the downstream data transmitted from the wireless base 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 (step S310).

The optical transceiver 18 transmits the downstream data and GATE frame multiplexed by the data multiplexer 17 to ONU2-i (step S311).

Note that the functions of OLTs 1B and 1C according to embodiments 2 and 3 can also be realized using processing circuits, as explained in embodiment 1. The processing circuits may be dedicated hardware, or may use software, firmware, etc.

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 from the wireless base station device 3, the cooperation information including frame information indicating the frame length of the downstream data. 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 GST are determined taking into account the frame length of the frame actually transmitted. This makes it possible to suppress jitter while maintaining the communication rate at the shaping rate.

Frame information includes the number of frames and frame length. Scheduling is performed after determining the number of frames and frame length in advance, making it possible to achieve more accurate, real-time performance, and adjust to the desired communication rate.

Also, in embodiment 3, OLT 1C is an example of a communications device that determines the bandwidth allocation amount and data transmission start time for upstream communications for each of multiple ONUs 2-i. 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 wireless terminals by the wireless base station device 3 for each of multiple ONUs 2-i, and an upstream communications control unit 10C that determines the bandwidth allocation amount and data transmission start time for ONUs 2-i based on the shaping rate and information based on the frame length transmitted in upstream communications.

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. Parts of the configuration may also be omitted or modified without departing from the spirit of the invention.

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 Transmission 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 demultiplexing 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 (5)

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 : 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. 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 . 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: 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: