JP2015207797A - Communication system and redundancy method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system and a redundancy method that are capable of generating at low cost a path (redundant path) to have communication between a master station device and a slave station device detour in a PON.SOLUTION: The present invention comprises: n master station devices S1-Sn for performing optical communication; m slave station devices N1-Nm for performing optical communication with the master station devices; radio communication devices W1-Wm connected with the respective slave station devices; and a controller. When the controller detects a trigger about the slave station device Ni, the controller selects a communication path between the slave station device Uj and the master station device Sl as a redundant path for communication between a user Ui connected with the slave station device Ni and the master station device Sk, and gives an instruction to perform communication between Ui and Sl via the radio communication device Wi, and the radio communication device Wj, and Uj.

Description

  The present invention relates to a communication system and a redundancy method for generating a path for bypassing communication between a master station device and a slave station device in a PON (Passive Optical Network).

  PON is commonly used in access networks. The PON is composed of a master station device, a power splitter (PS), and a slave station device. The master station device and PS and the PS and slave station devices are connected by optical fibers. Through the PS, a plurality of slave station devices can be connected to one master station device.

  By using the techniques described in Non-Patent Documents 1 and 2 when recovering communication between the master station device and the slave station device, such as when a transmission path failure occurs in the optical fiber between the PS and the slave station device. The slave station device can use a redundant path via another slave station device.

  The technique described in Non-Patent Document 1 creates a redundant path by connecting slave station apparatuses with an optical fiber to form a ring topology. The technology described in Non-Patent Document 2 connects redundant slave station devices with an optical fiber to create a redundant path.

C. H. Yeh, C.I. W. Chow, and Y.C. L. Liu, “Self-protected ring-star-architecture TDM passive optical network with triple-play management”, Optics Communications 284 (2011) 3248-3250. Taiming Feng, and Lu Ruan, “Design of a Survivable Hybrid Wireless-Optical Broadband-Access Network,” J. OPT. COMMUN. NETW. , VOL. 3, NO. 5, MAY 2011.

  The technique described in Non-Patent Document 1 has a problem of increasing the installation cost because it is necessary to configure a ring topology between slave station devices. The technique described in Non-Patent Document 2 can calculate a configuration that minimizes the connection cost of backup slave station devices for forming a redundant path. There is a problem that it is necessary to connect, and that laying cost is required.

  Accordingly, in order to solve the above-described problems, the present invention provides a communication system and a redundancy method that can generate a route (redundant route) that bypasses communication between a master station device and a slave station device in a PON at low cost. With the goal.

  In order to achieve the above-described object, the present invention performs a wireless communication between wireless devices connected to each PON slave station device, and uses a wireless section of the wireless communication to make a redundant route via another slave station device. It was decided to form.

Specifically, the communication system according to the present invention is:
PON (Passive Optical Network) in which a master station device and a plurality of slave station devices are connected by an optical communication path;
A wireless communication device connected to each of the slave station devices, wirelessly transmitting a signal from the slave station device to a wireless terminal, and transmitting a signal wirelessly transmitted from the wireless terminal to the slave station device;
With respect to an active communication path from the master station device to one radio communication device connected to one slave station device, the other radio communication device connected to another slave station device to the first radio communication device A controller that forms a redundant communication path via the other slave station device using a wireless path up to,
Is provided.

Further, the redundancy method according to the present invention includes:
A PON in which a master station device and a plurality of slave station devices are connected by an optical communication path;
A wireless communication device connected to each of the slave station devices, wirelessly transmitting a signal from the slave station device to a wireless terminal, and transmitting a signal wirelessly transmitted from the wireless terminal to the slave station device;
A communication system redundancy method comprising:
With respect to an active communication path from the master station device to one radio communication device connected to one slave station device, the other radio communication device connected to another slave station device to the first radio communication device A redundant communication path that passes through the other slave station device is formed using the wireless path up to.

  According to the present invention, a redundant route is formed by using wireless communication between wireless devices, so that a ring topology configuration and an optical fiber are not required, and the cost of forming a redundant route can be reduced. Therefore, the present invention can provide a communication system and a redundancy method capable of inexpensively generating a path (redundant path) that bypasses communication between the master station apparatus and the slave station apparatus in the PON.

  Furthermore, in the communication system according to the present invention, the PON is plural, and the controller forms the redundant communication path in another PON different from the one PON in the working communication path. . The present invention can form a redundant path between a plurality of PONs.

  The controller of the communication system according to the present invention is characterized in that when there are a plurality of redundant communication paths to be formed, the other slave station devices are selected so that the redundant communication paths are distributed. To do. The present invention can realize efficient traffic transfer by using inexpensive wireless communication and distributing redundant paths.

  Redundant routes are distributed as follows.

  The controller of the communication system according to the present invention uses a condition that the number Kj of wireless terminals that use the other slave station device as the redundant communication path is a predetermined value or less, and uses the other PON as the redundant communication path. The other slave station device is selected so as to satisfy at least one of the conditions in which the number of wireless terminals Kl to be equal to or less than a predetermined value.

  The controller of the communication system according to the present invention is configured so that the wireless communication strength or communication quality between the wireless communication devices is a certain value or more, or the distance between the wireless communication devices is within a certain value. A slave station device is selected.

  The controller of the communication system according to the present invention selects the other slave station device so as to minimize the maximum value of the number Kj or the number Kl.

  The controller of the communication system according to the present invention selects the other slave station device in consideration of a weight for each wireless terminal.

  The present invention can provide a communication system and a redundancy method capable of inexpensively generating a route (redundant route) that bypasses communication between a master station device and a slave station device in a PON.

It is a figure explaining the structure of the radio | wireless communications system which concerns on this invention. It is a figure explaining the table regarding the state yi of the subunit | mobile_unit apparatus of the radio | wireless communications system which concerns on this invention. It is a figure explaining the table regarding the state xij of the redundant path | route of the sub_station | mobile_unit apparatus of the radio | wireless communications system which concerns on this invention. It is a figure explaining the table regarding the electromagnetic wave intensity dij between the slave station apparatuses of the radio | wireless communications system which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a sequence diagram showing the process sequence of each apparatus in the redundancy method which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a figure explaining the objective function and constraint conditions for determining a redundant path | route in the redundancy method which concerns on this invention. It is a figure explaining the user network structure in the radio | wireless communications system which concerns on this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are embodiments of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

<First Embodiment>
1st Embodiment of this invention is described using FIGS. FIG. 1 is a diagram illustrating a configuration of a communication system 301 according to the present embodiment. The communication system 301 includes a PON in which a master station device (OSU) and a plurality of slave station devices (ONU) are connected via an optical communication path,
A wireless communication device (W) connected to each of the slave station devices, wirelessly transmitting a signal from the slave station device to a wireless terminal, and transmitting a signal wirelessly transmitted from the wireless terminal to the slave station device;
With respect to an active communication path from the master station device to one radio communication device connected to one slave station device, the other radio communication device connected to another slave station device to the first radio communication device A controller (Ctrl) that forms a redundant communication path via the other slave station device using a wireless path up to
Is provided.

  Further, the PON is plural, and the controller can form the redundant communication path in another PON different from the one PON in the working communication path.

  In FIG. 1, 11 is a master station apparatus. This is S1. S1 is connected to the splitter 12 by an optical fiber, and the splitter 12 is connected to the slave station devices (13, 14, 15). These are N1, N2, and N3. N1, N2, and N3 are connected to the wireless communication devices (16, 17, and 18), respectively. These are W1, W2, and W3. Similarly, 21 is a master station device, which is S2. S2 is connected to the splitter 22 by an optical fiber, and the splitter 22 is connected to the slave station devices (23, 24, 25), which are N4, N5, and N6. N4, N5, and N6 are connected to the wireless communication devices (26, 27, and 28), respectively, and are designated as W4, W5, and W6.

  S1 and S2 may be physically different devices, or may be different interfaces connected to the same chassis sharing a power source or the like. S 1 and S 2 are connected to the controller 31. The connection between S1 and S2 and the controller 31 may be wired or wireless, and other network devices may be connected therebetween. Further, a wireless terminal is connected to each slave station device via a wireless communication device, and user identifiers of wireless terminals under each slave station device are U1 to U6. The method of assigning the identifier of each device is not limited as long as each device can be identified.

  Moreover, although the radio | wireless communications system with which the radio | wireless communication apparatus (W1-6) and the radio | wireless terminal (U1-6) were connected by radio | wireless was demonstrated in FIG. 1, the form of a user network like FIG. 12 is connected. It may be a wireless communication system. In the user network U7, a home gateway (HGW) is connected to the slave station device N7 and the wireless communication device W7, and the HGW and each user terminal are connected by wire or wirelessly. The user terminal is a personal computer, a telephone, a TV, a tablet terminal, a smart phone, or the like. Further, the HGW and the wireless communication device may be integrated. As such a user identifier of the user network U7, a VLAN ID or the like is used.

  The identifiers representing the slave station devices are i and j. The one slave station device is Ni, and the other slave station device is Nj. In this example, 1 ≦ i ≦ 6 and 1 ≦ j ≦ 6. The identifiers representing the master station devices are k and l. The master station device of the one PON is Sk, and the master station device of the other PON is Sl. In this example, 1 ≦ k ≦ 2, and 1 ≦ l ≦ 2.

  As shown in FIG. 2, the controller 31 has a table for storing the state yi of each slave station device i. Usually, yi = 1 is set. When a trigger for Ni is detected, yi = 0 is updated. As an example of the trigger, it is conceivable that a survival check is performed between the controller and the ONU or the wireless communication device, and when the survival check is interrupted, it is determined that the communication is disconnected and the trigger is detected.

  Next, as shown in FIG. 3, the controller 31 has a table for storing the state xij of the Ni redundant path. If Nj is used as the Ni redundant path, xij = 1, otherwise xij = 0.

  Further, as shown in FIG. 4, the controller 31 has a table for storing wireless connectivity dij between Wi and Wj. Here, it is assumed that dij can have only two values of 1 or 0. The controller 31 communicates with W1 to W6 and updates dij. For this procedure, LLDP (Link Layer Discovery Protocol) or the like is used. If the wireless communication strength between Wi and Wj is greater than or equal to a certain value and wireless connection is possible, then dij = 1, otherwise dij = 0 and dii = 1. When the user a is updated from ya = 1 to ya = 0, it is updated to dia = 0 including dii.

  When the controller 31 detects the trigger and yi is updated, the table of the redundant route state xij of Ui is updated as follows. In particular, when a trigger for a plurality of Nis is detected due to a failure of the master station device Sk, a transmission path failure, or the like, redundant paths are set for all of Nis where yi = 0.

  When there are a plurality of redundant communication paths to be formed, the controller 31 selects the other slave station device so that the redundant communication paths are distributed. In particular, the controller 31 selects the other slave station device so as to satisfy a condition that the number Kj of wireless terminals that use the other slave station device as the redundant communication path is a predetermined value or less. Specifically, the controller 31 determines xij so that Nj used as a redundant path is distributed. As a constraint condition at this time, it is used that the number Kj of Ui using Nj as a redundant path is equal to or less than a certain value K, that yj = 1 and dij = 1 for Nj. That is, the controller 31 determines xij so as to minimize the maximum value of Kj while satisfying the above constraint conditions using the equation shown in FIG. Further, for Ui, instead of performing communication using Ni, communication is started using Nj where xij = 1 as a redundant path. Assuming that the master station device connected to Nj is Sl, Ui communicates with master station device S1 via Wi, Wj, and Nj. When there is no Nj available for the redundant path because there is no other user near Ui, max dij = 0 and no redundant path is set.

  The update of xij will be described using an example. For N1, N2, and N3, it is assumed that a transmission path failure has occurred and a trigger has been detected at the same time. In this case, y1 = 0, y2 = 0, and y3 = 0 (as shown in FIG. 2). It is assumed that d14, d15, d16, d24, d25, d26, d34, d35, and d36 are all 1. At this time, combinations of xij that minimize the maximum value of Kj include x14 = 1, x25 = 1, x36 = 1, x44 = 1, x55 = 1, and x66 = 1. Therefore, the controller 31 updates the table as shown in FIG.

  Based on the updated xij, the controller 31 instructs N4 to relay the communication of U1, relays N4, W4, and W1 to U1, and instructs N4 to be a redundant path. U1 starts communication with the master station device S2 via W1, W4, and N4. Similarly, an instruction to relay the communication of U2 is issued to N5, and an instruction to relay N5, W5, and W2 to U2 and make N5 a redundant route is issued. U2 starts communication with the master station device S2 via W2, W5, and N5. Further, an instruction to relay the communication of U3 is issued to N6, an instruction to relay N6, W6, and W3 to U3 and to use N6 as a redundant route is issued. U3 starts communication with the master station device S2 via W3, W6, and N6. As one of communication path instruction methods, there is a method using OpenFlow. For example, the controller 31 functions as an OpenFlow controller, each wireless communication device functions as an OpenFlow switch, and a communication path can be specified by the OpenFlow protocol to start communication.

  The above procedure will be described with reference to the sequence diagram of FIG. An OSU (1, 2), which is a master station device, is connected to the controller. When the controller detects the trigger for the ONU 2 that is the slave station device and the wireless communication device connected to the ONU 2 (Step 01), the controller performs a detour path calculation (Step 02), and as a result, selects the ONU 1 that is the slave station device. . An instruction to relay ONU2 communication is issued to ONU1 (Step 03), and a wireless communication terminal is relayed to ONU2 to issue an instruction to use ONU1 as a redundant path (Step04). The ONU 2 communicates with the ONU 1 via the wireless communication terminal, and starts communication with the OSU 1 (Step 05). Further, the controller detects that the wireless terminal under the ONU 2 has recovered communication through the redundant path (Step 06).

  This method is low-cost because it does not require optical fiber laying, and has the feature that a redundant path can be set flexibly according to the detection range of the trigger. For example, it is possible to bypass the user communication when the station apparatus is down due to a failure or a disaster, and to restore it quickly.

  In the present embodiment, a case has been described in which a plurality of PONs are set and a redundant path is formed across different PONs. However, a redundant path can also be formed in the same PON. For example, the communication system 301 can set the redundant paths for the paths S1, N1, and W1 that are the working paths as the paths S1, N2, W2, and W1 for the path U1 that communicates with S1.

<Second Embodiment>
The second embodiment of the present invention is based on the premise that there are three or more master station devices, and differs from the first embodiment in the following points. The controller selects the other slave station device so as to satisfy a condition that the number Kl of wireless terminals using the other PON as the redundant communication path is a predetermined value or less. In other words, instead of the number Kj of Ui using Nj as a redundant path described in the first embodiment being a certain value or less, the number Kl of Ui using S1 as a redundant path is less than a certain value. Is used. For example, the controller has an OSU-ONU correspondence table, and uses this correspondence table to count the number Kl of Ui that uses Sl as a redundant path. As shown in FIG. 7, a redundant route is calculated using a constraint condition that Kl is equal to or less than a certain value L. By this method, it is possible to distribute the master station devices used as redundant paths and suppress traffic congestion on the redundant paths.

<Third Embodiment>
The third embodiment of the present invention is premised on that there are three or more master station devices, and differs from the first embodiment in the following points. The controller has a condition that the number Kj of wireless terminals using the other slave station device as the redundant communication path is equal to or less than a predetermined value, and a number Kl of wireless terminals using the other PON as the redundant communication path are predetermined. The other slave station device is selected so as to satisfy a condition that is less than or equal to the value. That is, in addition to the number Kj of Ui using Nj as a redundant path described in the first embodiment being a certain value or less, the number K1 of Ui using S1 as a redundant path is less than a certain value. Is used. For example, the controller has an OSU-ONU correspondence table, and uses this correspondence table to count the number Kl of Ui that uses Sl as a redundant path. As shown in FIG. 8, a redundant route is calculated using a constraint condition that Kl is equal to or less than a certain value L. By this method, it is possible to disperse the slave station devices and the master station devices that are used as redundant paths, and to suppress traffic congestion on the redundant paths.

<Fourth Embodiment>
The fourth embodiment of the present invention differs from the first to third embodiments in the following points. The controller selects the other slave station device so that the distance between the wireless communication devices is within a certain value. That is, instead of setting dij = 1 when the wireless communication strength between Wi and Wj is greater than or equal to a certain value and wireless connection is possible, the distance Dij between Wi and Wj is used, and when this is less than a certain value, dij = Set to 1. The distance Dij is acquired by using a method such as directly inputting from the outside as a parameter or acquiring from the position management system. With this method, it is possible to calculate a redundant route based on the geographical arrangement of the slave station devices. Further, the condition regarding the wireless communication intensity and the distance condition may be used together.

<Fifth Embodiment>
The fifth embodiment of the present invention differs from the first to third embodiments in the following points. The controller selects the other slave station device so that the wireless communication strength or communication quality between the wireless communication devices is a certain value or more. That is, the communication quality Qij between Wi and Wj is used instead of dij = 1 when the wireless communication strength between Wi and Wj is equal to or higher than a certain level and wireless connection is possible. As Qij, throughput, delay, or the like is used, and dij = 1 is set when the throughput is equal to or higher than a certain value or the delay is within a certain value. By this method, it is possible to use a redundant route while maintaining the communication quality of user traffic. Moreover, you may use together with the conditions regarding wireless communication intensity or distance.

<Sixth Embodiment>
The sixth embodiment of the present invention is premised on that there are three or more master station devices, and differs from the first to fifth embodiments in the following points. That is, instead of determining xij so as to minimize the maximum value of Kj described in the first embodiment, xij is determined so as to minimize the maximum value of the number K1 of Ui using Sl as a redundant path. To do. For example, the controller has an OSU-ONU correspondence table, and uses this correspondence table to count the number Kl of Ui that uses Sl as a redundant path. Then, as shown in FIG. 9, redundant path calculation is performed for the purpose of minimizing the maximum value of Kl. This example includes a constraint that the number Kj of Ui that uses Nj as a redundant route is equal to or less than a certain value and a constraint that the number Kl of Ui that uses Sl as a redundant route is equal to or less than a certain value. However, there are methods that do not include either or both. By this method, it is possible to distribute the master station devices used as redundant paths and suppress traffic congestion on the redundant paths.

<Seventh Embodiment>
The seventh embodiment of the present invention differs from the first to fifth embodiments in the following points. That is, instead of simply determining xij so as to minimize the maximum value of the number of Ui Kj that uses Nj as a redundant path, a weight wi is set for each user Ui, and a weight is assigned to Ui that uses Nj as a redundant path. xij is determined so as to minimize the maximum value of the values K′j multiplied by wi. As shown in FIG. 10, the redundant path calculation is performed for the purpose of minimizing the maximum value of K′j. This example includes a constraint that the number Kj of Ui that uses Nj as a redundant route is equal to or less than a certain value and a constraint that the number Kl of Ui that uses Sl as a redundant route is equal to or less than a certain value. However, there are methods that do not include either or both. With this method, it is possible to set a redundant route in consideration of a difference in traffic amount caused by a difference in contract bandwidth for each user.

<Eighth Embodiment>
The eighth embodiment of the present invention is premised on that there are three or more master station devices, and differs from the first to sixth embodiments in the following points. That is, instead of simply determining xij so as to minimize the maximum number Kl of Ui that uses Sl as a redundant path, a weight wi is set for each user Ui, and Ui that uses Sl as a redundant path is weighted xij is determined so as to minimize the maximum value of the values K′l multiplied by wi. For example, the controller has an OSU-ONU correspondence table and a table of weights wi for each user, and by using these tables, a number K′l obtained by multiplying Ui that uses Sl as a redundant path by multiplying each by weight wi. Ask for. After that, as shown in FIG. 11, redundant path calculation is performed for the purpose of minimizing the maximum value of K′l. This example includes a constraint that the number Kj of Ui that uses Nj as a redundant route is equal to or less than a certain value and a constraint that the number Kl of Ui that uses Sl as a redundant route is equal to or less than a certain value. However, there are methods that do not include either or both. With this method, it is possible to set a redundant route in consideration of a difference in traffic amount caused by a difference in contract bandwidth for each user.

[Appendix]
The following describes the communication system of the present embodiment.
<Issues>
To realize an inexpensive detour path for communication between the master station device and the slave station device.
<Solution>
In the present invention, n master station devices S1 to Sn that perform optical communication, m slave station devices N1 to Nm that perform optical communication with the master station device, and wireless communication connected to each of the slave station devices Devices W1 to Wm and a controller, and the controller communicates between the user Ui connected to the slave station device Ni and the master station device Sk when detecting a trigger for the slave station device Ni. As a redundant path, a communication path between the slave station device Uj and the master station device S1 is selected, and Ui and S1 are connected via the wireless communication device Wi and the wireless communication devices Wj and Uj. To communicate between the two.

(1):
N master station devices S1 to Sn for optical communication;
M slave station devices N1 to Nm that perform optical communication with the master station device;
Wireless communication devices W1 to Wm connected to each of the slave station devices,
A controller,
A communication system comprising:
The controller is
When a trigger is detected for the slave station Ni,
As a redundant path for communication between the user Ui connected to the slave station device Ni and the master station device Sk, a communication path between the slave station device Uj and the master station device Sl is selected, and the wireless communication device Instructing communication between Ui and Sl via Wi and the wireless communication devices Wj and Nj,
A communication system characterized by the above.

(2):
The controller is
With respect to the slave station device Ni, when a trigger for a plurality of i is detected, Nj used as a redundant path is selected to be distributed.
The communication system according to (1) above, wherein

(3):
The controller is
The number Kj of Ui that uses Nj as a redundant path, or the number Kl of Ui that uses S1 as a redundant path is equal to or less than a certain value.
Nj is selected under the condition
The communication system according to (2) above, wherein

(4):
The controller is
The wireless communication strength or communication quality between Wi and Wj is a certain value or more.
Or, the distance between Wi and Wj is within a certain value,
Nj is selected under the condition
The communication system according to (3) above, wherein

(5):
The controller is
Choose Nj to minimize the maximum value of Kj or Kl.
The communication system according to (4) above, wherein

(6):
The controller is
Nj is selected in consideration of the weight for each user Ui.
The communication system according to (5) above, wherein

<Effect>
In the PON, in order to generate a route that bypasses communication between the master station device and the slave station device in the PON, low-cost wireless communication is used, and efficient traffic transfer is realized by distributing redundant routes. can do.

11: Master station device 12: Splitter 13: Slave station device 1-1
14: Slave station device 1-2
15: Slave station device 1-3
16: Wireless communication device 1-1
17: Wireless communication device 1-2
18: Wireless communication device 1-3
21: Master station device 22: Splitter 23: Slave station device 2-1
24: Slave station device 2-2
25: Slave station device 2-3
26: Wireless communication apparatus 2-1
27: Wireless communication device 2-2
28: Wireless communication device 2-3
31: Controller 41: User network

Claims (8)

PON (Passive Optical Network) in which a master station device and a plurality of slave station devices are connected by an optical communication path;
A wireless communication device connected to each of the slave station devices, wirelessly transmitting a signal from the slave station device to a wireless terminal, and transmitting a signal wirelessly transmitted from the wireless terminal to the slave station device;
With respect to an active communication path from the master station device to one radio communication device connected to one slave station device, the other radio communication device connected to another slave station device to the first radio communication device A controller that forms a redundant communication path via the other slave station device using a wireless path up to,
A communication system comprising: The PON is plural,
The communication system according to claim 1, wherein the controller forms the redundant communication path in another PON different from the one PON in the working communication path. The controller is
3. The communication system according to claim 1, wherein when there are a plurality of redundant communication paths to be formed, the other slave station devices are selected so that the redundant communication paths are distributed. . The controller is
The condition that the number Kj of wireless terminals that use the other slave station device as the redundant communication path is equal to or less than a predetermined value, and the number Kl of wireless terminals that use the other PON as the redundant communication path are equal to or less than a predetermined value. 4. The communication system according to claim 3, wherein the other slave station device is selected so as to satisfy at least one of the following conditions. The controller is
The other slave station device is selected such that the wireless communication strength or communication quality between the wireless communication devices is a certain value or more, or the distance between the wireless communication devices is within a certain value. The communication system according to claim 4. The controller is
6. The communication system according to claim 5, wherein the other slave station device is selected so as to minimize the maximum value of the number Kj or the number Kl. The controller is
The communication system according to claim 6, wherein the other slave station device is selected in consideration of a weight for each wireless terminal. A PON in which a master station device and a plurality of slave station devices are connected by an optical communication path;
A wireless communication device connected to each of the slave station devices, wirelessly transmitting a signal from the slave station device to a wireless terminal, and transmitting a signal wirelessly transmitted from the wireless terminal to the slave station device;
A communication system redundancy method comprising:
With respect to an active communication path from the master station device to one radio communication device connected to one slave station device, the other radio communication device connected to another slave station device to the first radio communication device A redundant communication path that passes through the other slave station device using a wireless path up to

Images