JP2015039101A - Radio transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance of an entire network in a radio transmission system in which a radio terminal, such as a mobile phone, and an information terminal use a common base station.SOLUTION: Both a plurality of communication nodes and a concentrator are connected with a first radio transmission path serving as a backhaul. Each of the communication nodes is able to communicate with a radio terminal such as a mobile phone via a second radio transmission path and an information terminal via a third radio transmission path. Each of the communication nodes collects information on a radio terminal connected with the communication node, notifies an upstream communication node of information obtained by integrating the collected information on the radio terminal connected with the communication node and information on a radio terminal connected each downstream communication node collected by each of the downstream communication nodes, and sets transmission bands used by the radio terminals on the basis of the collected information on the terminals. The first radio transmission path is connected in line-type network topology.

Description

  Embodiments described herein relate generally to a wireless transmission system.

  In recent years, the amount of data communication for mobile access has increased rapidly due to the spread of smartphones and the like. In order to cope with this rapidly increasing mobile traffic, each telecommunications carrier is promoting the introduction of an LTE (Long Term Evolution) system that is faster than the conventional 3G system. In addition, a traffic offload technology that accommodates indoor terminal traffic that has been accessed to an outdoor base station in a base station called a femtocell installed indoors or the like is effective.

  When a base station is installed indoors in a femtocell, the range in which the base station can communicate with a wireless terminal via a wireless line is a radius of several tens of meters from the base station. It is necessary to install. In the current installation method, a concentrator is installed on each floor, and each base station (femtocell) is connected to this concentrator by wire. Such an installation method requires a lot of man-hours for laying wired wiring from the concentrator to the base station. In addition, in the case of a new building, laying of wired wiring for information terminals such as PCs and IP telephones also occurs. In this case, the number of wired wiring steps is further increased.

  As a method for avoiding the laying of wired wiring to base stations, wireless connection between base stations can be considered. Wireless communication between base stations is, for example, preparing a plurality of wireless interfaces in a base station assuming a wireless LAN access point, constructing a backbone network and an access link network, and performing communication between base stations in the backbone network A method has been proposed.

Japanese Patent No. 4860381

  However, in the prior art, when a lot of traffic between base stations is transferred, it can be handled by increasing the number of radio interfaces allocated for the backbone, but when a specific radio communication terminal needs a lot of traffic, There is a problem in that there is a restriction on the terminal of the terminal, resulting in a delay. When a mobile phone is assumed as the wireless communication terminal, it is essential that the mobile phone can reliably perform a voice call without delay, and thus the delay amount must be kept within a certain range.

  A problem to be solved by the present invention is that a base station in which a wireless terminal that provides a service in which a delay time during transmission such as a voice call such as a mobile phone is a problem and an information terminal that performs data communication by wireless communication are common In a wireless transmission system that uses (communication nodes), it is possible to suppress a specific base station and a specific wireless transmission path from becoming a bottleneck for communication and improve the performance of the entire network (transmission capacity performance and delay time). It is to provide a wireless transmission system capable of

  The wireless transmission system according to the embodiment includes a plurality of communication nodes and a concentrator having an interface connected to another network, together with a first wireless communication unit connected to a first wireless transmission path serving as a backhaul. It is a transmission system. Each communication node includes a second wireless communication unit that communicates with a wireless terminal that provides a transmission service with a small delay via the second wireless transmission path. In addition, a third wireless communication unit that communicates with the information terminal via the third wireless transmission path is provided. Further, the destination of the transmission frame is determined from the destination information included in the transmission frame transmitted through the first to third wireless transmission paths, and the transfer destination is determined and transferred when the transmission frame needs to be transferred. A transfer unit that performs processing is provided. In addition, the information of the wireless terminal connected to the communication node is collected, the information of the collected wireless terminal connected to the communication node and the information of the wireless terminal connected to each downstream communication node collected by each downstream communication node are collected. A management unit is provided that aggregates and notifies an upstream communication node, and sets a transmission band used by the wireless terminal based on the collected wireless terminal information. The first wireless transmission path is connected by a line type network topology.

FIG. 1 is a diagram illustrating a configuration example of the entire wireless transmission system according to the first embodiment. FIG. 2 is a diagram illustrating band characteristics of the wireless transmission path according to the first embodiment. FIG. 3 is a diagram showing a data flow (route) of the mobile phone and the information terminal. FIG. 4 is a diagram showing a state in which the transmission band of communication between information terminals presses the band necessary for the mobile phone. FIG. 5 is a diagram for explaining a control method for solving the problem that the transmission band of communication between information terminals presses the band necessary for the mobile phone. FIG. 6 is a diagram illustrating a configuration of a communication node according to the first embodiment. FIG. 7 is a diagram for explaining the operation during data transfer in the first embodiment. FIG. 8 is a diagram for explaining the operation at the time of data transfer in the first embodiment. FIG. 9 is a diagram illustrating a configuration of the concentrator according to the first embodiment. FIG. 10 is a diagram illustrating a configuration example of the entire wireless transmission system according to the second embodiment. FIG. 11 is a diagram illustrating an example of band characteristics of the wireless transmission path in the second embodiment. FIG. 12 is a diagram illustrating a configuration example of the entire wireless transmission system according to the third embodiment. FIG. 13 is a diagram illustrating the configuration of the communication node B ′ in the third embodiment. FIG. 14 is a diagram illustrating the configuration of the communication node B ″ in the third embodiment. FIG. 15 is a diagram showing a conventional system configuration example.

(First embodiment)
An example of the configuration of the entire wireless transmission system of the first embodiment is shown in FIG. In FIG. 1, the wireless unit M and the communication units (A, B,..., N) provided in the concentrator described below include the concentrator and each communication node ( In order to correspond to A, B,..., N), −0, −1, −2,..., −n, etc. are added to the reference numerals (the same applies to FIGS. 3, 10, and 12 described later). .

  The wireless transmission system in the present embodiment is representative of an interface connected to another network via a wired transmission path, a concentrator having a wireless unit M communicating with a wireless transmission path serving as a backhaul, and a mobile phone (hereinafter abbreviated as a mobile phone). A wireless unit L (for example, femtocell) and information having a base station function for communicating with a wireless transmission path serving as an access link, respectively connected to a wireless terminal and an information terminal represented by an information processing apparatus such as a PC A concentrator is composed of a wireless unit W (communication standard is arbitrary) that is wirelessly connected to a terminal and a plurality of communication nodes (abbreviated as nodes in the drawing) having a wireless unit M that communicates with a wireless transmission path serving as a backhaul. And multiple communication nodes connected in a line-type network topology via a backhaul wireless transmission path To have. This wireless transmission path is capable of bidirectional wireless transmission. Note that in this specification, a mobile phone will be described as an example of a wireless terminal that provides a service in which a delay time during transmission such as a voice call is a problem.

  A plurality of communication nodes are connected by a wireless transmission path serving as a backhaul as described above. The wireless transmission path serving as a backhaul may adopt a general wireless LAN standard, or a millimeter wave Alternatively, a communication means or standard using microwaves, terahertz waves, or the like may be adopted, and the communication means or standard is not limited.

  FIG. 2 shows the band characteristics of the wireless transmission path in the present embodiment. The mobile phone has a communication form in which each mobile phone is directly connected to a server prepared by a communication carrier. For this reason, in the network topology having the configuration shown in the overall system configuration diagram of the present embodiment, the terminal connected to the communication node n from the downstream communication node B is connected to the wireless transmission path section where the concentrator and the communication node A are connected. Since all the traffic is concentrated, it is necessary to satisfy this as the transmission band of the wireless transmission path serving as the backhaul. On the other hand, the bandwidth required for the terminal communication node can be small. On the other hand, the information terminals may be connected to a server on another network (not shown) different from the mobile phone network, but there are also forms in which the information terminals are connected to each other.

  FIG. 3 shows a data flow (route) of the mobile phone and the information terminal. Communication between a mobile phone server and a mobile phone on another network and communication between information terminals can be performed via a wireless transmission path serving as a backhaul. Since mobile phones also make voice calls, a significant delay occurs, making it difficult to talk due to the time difference between the two-way voice communications, and the voice is interrupted due to data loss due to packet loss. Need to prevent.

  FIG. 4 shows a state in which the transmission band for communication between information terminals presses the transmission band necessary for the mobile phone. In this case, a transmission band necessary for the mobile phone cannot be secured, and a delay occurs.

  Next, a control method for solving this problem will be described. FIG. 5 is a diagram for explaining a control method for solving this problem. Each communication node obtains information (here, the model of the mobile phone) of the mobile phone connected to the radio unit L via a radio line from the radio unit L having a base station function connected to the communication node. It is possible. The mobile phone information handled by the own communication node and the information collected by the downstream communication node are aggregated and the information is notified to the higher-level communication node (the mobile phone information is also received from the upstream so that all communication nodes can share the information) May be notified). Each communication node stores transmission band information in which the mobile phone model and the transmission band necessary for the model are associated with each other in the memory unit 15, and the backhaul between the communication nodes by sharing the information. Since the transmission band required by the mobile phone is known as a breakdown of the transmission band of the wireless transmission path, the transmission band used by the mobile phone is reserved and set in advance. That is, by controlling the transmission band of the wireless transmission path, a transmission band necessary for transmission that does not allow delay is secured. Regarding the transmission band to be controlled, when the transmission band used by the mobile phone is different from the transmission band used by the information terminal, the transmission band may be determined in order from the upstream side, or may be determined by arbitration between all nodes. May be.

  Further, when distinguishing and managing the transmission band used by the mobile phone and the transmission band used by the information terminal, for example, a virtual network based on a concept such as a tag VLAN (Virtual Local Area Network) which is a general network configuration method And make the configuration logically separated separately. Thereby, it is possible to easily manage the transmission band used by each of the mobile phone and the information terminal.

  FIG. 6 shows the configuration of each communication node of this embodiment. Each communication node of the wireless transmission system according to the present embodiment is connected via the interface unit 17 and the wireless transmission / reception units 11 and 12 for communicating with the wireless transmission path serving as the backhaul, the wireless unit M including an antenna, and the interface unit 17. A wireless unit L having a base station function for communicating with a mobile phone, a wireless unit W for communicating with an information terminal, and each wireless unit (M, L, W) for mutual transfer of frames The transfer processing unit 16 is connected to each wireless unit (M, L, W), collects necessary information (such as MAC address and frame information), gives instructions (via the wireless unit M), and adjacent communication nodes And a management unit 13 for exchanging information about a transmission band required for the mobile phone, information collected from each wireless unit (M, L, W) by the management unit 13 and an adjacent communication node (via the wireless unit M) The information collected from And a determination unit 14 that determines a transfer path between the wireless units (M, L, W) from the information collected by the management unit 13 and gives the result to the transfer processing unit 16. . With this configuration, each communication node recognizes a received frame received via a wireless transmission path serving as a backhaul and transfers it to an appropriate wireless transmission path, and each wireless unit (M, L, W) and (wireless Exchanging information with neighboring communication nodes (via part M), and sharing and storing information (part or all) and comparing the collected information and transmitted frames to determine the appropriate transfer destination Function.

  Subsequently, the operation at the time of data transfer will be described with reference to FIGS.

  A reception frame received via a wireless transmission path includes a destination address that is a transmission destination. For example, a frame structure such as an L2 frame that is a general communication standard includes a MAC address of a transmission destination. The management unit 13 includes the MAC address of the wireless unit L having a base station function for communicating with a mobile phone connected in advance, and the information terminal connected to the wireless terminal W via the access link network. The MAC address is collected and learned, and stored in the memory unit 15. This learning may be performed at the time of activation, may be performed at regular intervals, or may be performed as a trigger when a terminal (mobile phone or information terminal) is connected to the wireless unit (L or W).

  The determination unit 14 analyzes the destination MAC address of the received frame, compares it with the information stored in the memory unit 15, and the destination MAC address is the wireless unit L of this communication node (if a mobile phone is connected, It is determined whether the wireless unit L is the MAC address of the transmission destination), the information terminal connected to this communication node, or the other, and the transfer processing unit 16 In contrast, the frame flow is switched. When the destination MAC address of the received frame is not the wireless unit L of its own communication node or the information terminal connected to this communication node (FIG. 8), the received frame is transmitted to the wireless transmission path connected in the line type network topology. Send out.

FIG. 9 shows the configuration of the concentrator of this embodiment.
Each communication node in the present embodiment has a common interface unit 17 to which the radio units L and W are connected. For this reason, the concentrator can be configured by connecting the wired unit 18 instead of the wireless unit W. In the figure, the functions of the components common to the configuration of the communication node are the same.

  In the present embodiment, compared to the conventional system configuration shown in FIG. 15, the above configuration performs bandwidth control between communication nodes (base stations) based on the connection status of mobile phones communicating with other networks, and data with high priority. (For example, voice data) is controlled so as not to be delayed, so that it is possible to suppress a specific base station (node) and a specific wireless transmission path from becoming a bottleneck for communication, and the performance of the entire network (transmission capacity) Performance and delay time).

(Second Embodiment)
Next, the wireless transmission system according to the second embodiment will be described. FIG. 10 is a diagram illustrating a configuration example of the entire wireless transmission system according to the second embodiment.

  The wireless transmission system according to the present embodiment includes an interface unit 17 connected to another network via a wired transmission path, a concentrator having a wireless unit M communicating with a wireless transmission path serving as a backhaul, a wireless terminal represented by a mobile phone, and a PC. A wireless unit L (for example, a femto cell) having a base station function for communicating with a wireless transmission path serving as an access link, which is connected to an information terminal represented by an information processing device such as Part W (communication standard is arbitrary) and a plurality of communication nodes having a wireless part M that communicates with a wireless transmission path serving as a backhaul. The concentrator and the plurality of communication nodes serve as a backhaul wireless transmission. They are connected by a ring-type network topology via a road. This wireless transmission path is capable of bidirectional wireless transmission.

  A plurality of communication nodes are connected by a wireless transmission path serving as a backhaul as described above. The wireless transmission path serving as a backhaul may adopt a general wireless LAN standard, or a millimeter wave Alternatively, a communication means or standard using microwaves, terahertz waves, or the like may be adopted, and the communication means or standard is not limited.

  The above is the same as in the first embodiment except that the concentrator and a plurality of communication nodes are connected in a ring network topology via a wireless transmission path serving as a backhaul. In order to employ a ring-type network topology, the concentrator includes two sets of a radio unit M and an antenna that are connected to a radio communication path serving as a backhaul, similar to a communication node.

  As a frame flow, the downstream transmission direction from the other network starts from the concentrator and is transmitted in order from the communication node A to the communication node B and is transmitted to the communication node n. The communication node n recognizes that it is the last communication node in the downlink direction, and does not transfer a frame thereafter. The upstream direction to the other network starts from the communication node A and is transmitted in the same direction as the downstream direction, and the communication node n is transmitted to the other network by being transmitted to the concentrator. In this embodiment, since the frame is transmitted as described above, the wireless transmission path is a one-way transmission path.

  FIG. 11 shows an example of band characteristics of the wireless transmission path in the present embodiment. In the figure, the mobile phone performs two-way voice communication. Looking at the input / output bandwidth of each communication node, the downstream transmission bandwidth from the mobile phone server to the mobile phone is almost the same as the upstream transmission bandwidth from the mobile phone to the mobile phone server. There is almost no band difference. For this reason, the transmission band required for the mobile phone occupying the wireless transmission path between the communication nodes can be made almost constant. Therefore, it is possible to suppress in advance that a specific base station (node) and a specific wireless transmission path become a bottleneck for communication, and it is possible to improve the performance (transmission capacity performance and delay time) of the entire network. . In addition, since the dead time for switching between transmission and reception of the wireless transmission path can be eliminated, transmission efficiency is improved. Further, the two transmission / reception units in the wireless unit M can be made into a single-function transmission unit and reception unit, and the cost can be reduced.

(Third embodiment)
FIG. 12 is a diagram illustrating a configuration example of the entire wireless transmission system according to the third embodiment.

  The wireless transmission system according to the present embodiment includes an interface unit 17 connected to another network and a wired transmission line, a concentrator having a wireless part M communicating with a wireless transmission line serving as a backhaul, a wireless terminal represented by a mobile phone, and a PC. A wireless unit L (for example, a femto cell) having a base station function for communicating with a wireless transmission path serving as an access link, which is connected to an information terminal represented by an information processing device such as Part W (communication standard is arbitrary) and a plurality of communication nodes having a wireless part M that communicates with a wireless transmission path serving as a backhaul. The concentrator and the plurality of communication nodes serve as a backhaul. In addition to being connected via a transmission line in a line or ring network topology (the example in FIG. Emission type), they are connected in a form that includes a tree-type network topology connecting branches from the radio transmission path to be a backhaul. This wireless transmission path is capable of bidirectional wireless transmission.

  A plurality of communication nodes are connected by a wireless transmission path serving as a backhaul as described above. The wireless transmission path serving as a backhaul may adopt a general wireless LAN standard, or a millimeter wave Alternatively, a communication means or standard using microwaves, terahertz waves, or the like may be adopted, and the communication means or standard is not limited.

  The above is the first embodiment or the second embodiment except that the concentrator and the plurality of communication nodes are connected in a form including a tree-type network topology that is branched and connected from the wireless transmission path serving as the backhaul. In this embodiment, the following communication node B ′ and communication node B ″ are provided in order to include a tree-type network topology including the wireless transmission path B′B ″ shown in FIG.

  FIG. 13 shows the configuration of the communication node B ′ in the present embodiment, and FIG. 14 shows the configuration of the communication node B ″. The communication node B ′ of the radio transmission system in the present embodiment includes the radio unit L and / or The interface unit 17 to which the radio unit W is connected is configured to connect the same radio transmitter / receiver unit (11 or 12) of the radio unit M used for the radio transmission path serving as a backhaul (wireless transmitter / receiver unit 19). Similarly, the communication node B ″ is the same as the wireless transmission / reception unit (11 or 12) of the wireless unit M used for the wireless transmission path serving as the backhaul in the interface unit 17 to which the wireless unit L and / or the wireless unit W is connected. 9 (wireless transmission / reception unit 19) is connected and wired unit 18 (described as the same as the wired unit 18 of the concentrator shown in FIG. 9). Connect a may be), while a configuration omitting the radio unit M having a wireless transceiver 11, 12 for use in the radio transmission path to be a backhaul. With this system configuration, the information terminal can be connected to the wireless transmission system of this embodiment even if it is of a wired connection type that cannot be connected to a wireless transmission path such as a wireless LAN.

  As described above, according to the first to third embodiments, in a wireless transmission system in which a mobile phone and an information terminal performing data communication by wireless communication use a common base station, a specific base station (node ) And a specific wireless transmission path can be prevented from becoming a bottleneck for communication, and the performance of the entire network (transmission capacity performance and delay time) can be improved.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

11, 12, 19 Wireless transmission / reception unit 13 Management unit 14 Determination unit 15 Memory unit 16 Transfer processing unit 17 Interface unit 18 Wired unit (wired communication unit)
M, L, W Wireless part (wireless communication part)

Claims (9)

A wireless transmission system having a first wireless communication unit connected to a first wireless transmission path serving as a backhaul together with a plurality of communication nodes and a concentrator having an interface connected to another network,
Each said communication node
A second wireless communication unit that communicates with a wireless terminal that provides a transmission service with less delay via the second wireless transmission path;
A third wireless communication unit communicating with the information terminal via the third wireless transmission path;
The destination of the transmission frame is determined from destination information included in the transmission frame transmitted through the first to third wireless transmission paths, and the transfer destination is determined when the transmission frame needs to be transferred. A transfer unit that performs
Information on the wireless terminal connected to the communication node is collected, information on the wireless terminal connected to the collected communication node and information on the wireless terminal connected to each downstream communication node collected by each downstream communication node And a management unit that sets a transmission band to be used by the wireless terminal based on the collected information on the wireless terminal;
With
The wireless transmission system, wherein the first wireless transmission paths are connected by a line-type network topology. The wireless terminal information includes information for identifying a model,
The communication node includes a storage unit that stores transmission band information in which the model is associated with a transmission band necessary for the model,
The wireless transmission system according to claim 1, wherein the management unit sets a transmission band used by the wireless terminal from the collected information of the wireless terminal and the transmission band information.   The said management part determines the transmission band to set in order from an upstream side, or mediates between all the communication nodes, when setting the transmission band of the said radio | wireless terminal, or characterized by the above-mentioned. The wireless transmission system according to claim 2.   The management unit collects information on the wireless terminals connected to all communication nodes, and determines a transmission band to be set by arbitrating between all communication nodes when setting the transmission band for the wireless terminal. The wireless transmission system according to claim 1, wherein the wireless transmission system is a wireless transmission system. A network constructed by the wireless transmission system is configured as a tag VLAN (Virtual Local Area Network), and transmission of the transmission frame for the wireless terminal and transmission of the transmission frame for the information terminal are logically separated. The wireless transmission system according to any one of claims 1 to 4, wherein:   The communication node according to any one of claims 1 to 5, wherein an interface unit to which the second wireless communication unit and the third wireless communication unit are connected is shared in the communication node. Wireless transmission system. A wireless transmission system having a first wireless communication unit connected to a first wireless transmission path serving as a backhaul together with a plurality of communication nodes and a concentrator having an interface connected to another network,
Each said communication node
A second wireless communication unit for communicating with a wireless terminal that provides a transmission service with less delay via the second wireless transmission path;
A third wireless communication unit for communicating with the information terminal via the third wireless transmission path;
The destination of the transmission frame is determined from destination information included in the transmission frame transmitted through the first to third wireless transmission paths, and the transfer destination is determined when the transmission frame needs to be transferred. A transfer unit that performs
Information on the wireless terminal connected to the communication node is collected, information on the wireless terminal connected to the collected communication node and information on the wireless terminal connected to each downstream communication node collected by each downstream communication node And a management unit that sets a transmission band to be used by the wireless terminal based on the collected information on the wireless terminal;
With
The first wireless transmission paths are connected in a ring network topology;
Each transfer unit of the communication node transfers the downlink and uplink transmission frames flowing in the first wireless transmission path in the same direction, and the transfer unit of the most downstream communication node transmits in the downlink direction. A wireless transmission system for prohibiting transfer of a frame to another network. A wireless transmission system having a first wireless communication unit connected to a first wireless transmission path serving as a backhaul together with a plurality of communication nodes and a concentrator having an interface connected to another network,
At least one of the communication nodes is
A second wireless communication unit for communicating with a wireless terminal that provides a transmission service with less delay via the second wireless transmission path;
A third wireless communication unit for communicating with the information terminal via the third wireless transmission path;
Information on the wireless terminal connected to the communication node is collected, information on the wireless terminal connected to the collected communication node and information on the wireless terminal connected to each downstream communication node collected by each downstream communication node And a management unit that sets a transmission band to be used by the wireless terminal based on the collected information on the wireless terminal;
With
The at least one set of communication nodes is:
A fourth wireless communication unit connected to a fourth wireless transmission path serving as a backhaul different from the backhaul;
One communication node forming the set does not include the first wireless communication unit, but includes a wired communication unit connected to the information terminal via a wired transmission path,
All communication nodes determine the destination of the transmission frame from the destination information included in the transmission frame transmitted through the first to fourth wireless transmission paths and the wired transmission path, and transfer of the transmission frame is performed. If necessary, a transfer unit that determines the transfer destination and performs transfer processing,
With
The first wireless transmission path serving as the backhaul is connected with a line-type network topology, and the first wireless transmission path and the fourth wireless transmission path serving as the other backhaul are connected with a tree-type network topology. A wireless transmission system characterized by being connected. A wireless transmission system having a first wireless communication unit connected to a first wireless transmission path serving as a backhaul together with a plurality of communication nodes and a concentrator having an interface connected to another network,
At least one of the communication nodes is
A second wireless communication unit for communicating with a wireless terminal that provides a service in which a delay time during transmission is a problem via the second wireless transmission path;
A third wireless communication unit for communicating with the information terminal via the third wireless transmission path;
With
At least one set of the communication nodes includes a fourth wireless communication unit connected to a fourth wireless transmission path serving as a backhaul different from the backhaul,
One communication node forming the set does not include the first wireless communication unit, but includes a wired communication unit connected to the information terminal via a wired transmission path,
All communication nodes determine the destination of the transmission frame from the destination information included in the transmission frame transmitted through the first to fourth wireless transmission paths and the wired transmission path, and need to transfer the transmission frame In this case, a transfer unit that determines the transfer destination and performs transfer processing is provided.
The first wireless transmission path serving as the backhaul is connected in a ring-type network topology, and the first wireless transmission path and the fourth wireless transmission path serving as the other backhaul are connected to each other in a tree type. Connected in a network topology
Each transfer unit of the communication node forming the first wireless transmission path connected in the ring-type network topology transmits the downstream and upstream transmission frames flowing in the first wireless transmission path in the same direction. And the transfer unit of the communication node at the most downstream side prohibits transfer of a transmission frame flowing in the downstream direction to another network.

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