JP7465462B2 - Wireless communication system and wireless node - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies (1) Website address: https://prtimes.jp/main/html/rd/p/000000025.000035736.html Posted on: September 2, 2019 (2) Website address: https://tech.nikkeibp.co.jp/atcl/nxt/column/18/00001/02933/ Posted on: September 27, 2019 (3) Publication name: BE Construction Equipment, October 2019 Issue Date of publication: September 28, 2019

The present invention relates to a wireless communication system and a wireless node.

In a cellular communication system, base stations that provide wireless access lines for user devices are sometimes connected to a backbone network (sometimes called a core network) by a wired backhaul (BH) network.

JP 2005-143046 A International Publication No. 2011/105371

On the other hand, as one form of realizing a new generation of mobile communications, a system or network that connects multiple wireless devices (e.g., base stations or access points) that provide wireless communication areas with a radius of several tens of meters by wireless (e.g., wireless multi-hop) is being considered. Note that "wireless devices" may also be called "wireless nodes" or "wireless communication devices."

For example, in a construction site or other work site, when it is desired to temporarily (or provisionally) introduce a wireless communication environment on different floors of a building for on-site workers, there is room for improvement in how to make the wireless communication environment easily constructed and removed.

One non-limiting objective of the present invention is to provide wireless communication technology that can easily establish and remove three-dimensional wireless routes, including in the vertical direction.

A wireless communication system according to one embodiment includes a core node located on a first horizontal plane, a wireless repeater located on a second horizontal plane different from the first horizontal plane, and a wireless device located on a third horizontal plane, the core node including a first antenna having directivity toward the wireless repeater, the wireless repeater including a second antenna having directivity toward the core node, a third antenna, and a processing unit that performs at least one of the following: a process of processing a downstream wireless signal received by the second antenna and transmitting the downstream wireless signal from the third antenna to the wireless device, and a process of processing an upstream wireless signal received by the third antenna and transmitting the upstream wireless signal from the second antenna to the core node.

A wireless node according to one embodiment is a wireless node located on a first horizontal plane, and includes a first antenna having directivity toward a core node located on a second horizontal plane different from the first horizontal plane, a second antenna, and a processing unit that performs at least one of the following: a process for processing a downstream wireless signal received by the first antenna and transmitting the signal from the second antenna to the wireless device; and a process for processing an upstream wireless signal received by the second antenna and transmitting the signal from the first antenna to the core node.

According to a non-limiting aspect of the present invention, it is possible to provide a wireless communication technology that can easily construct a three-dimensional wireless route, including in the vertical direction, and can also be easily removed.

FIG. 2 is a diagram illustrating a first state of an introduction example of a wireless communication system according to one embodiment. FIG. 2 is a diagram illustrating a first state of an introduction example of a wireless communication system according to one embodiment. FIG. 11 is a diagram illustrating a second state of an introduction example of a wireless communication system according to one embodiment. FIG. 11 is a diagram illustrating a second state of an introduction example of a wireless communication system according to one embodiment. FIG. 2 is a block diagram showing an example of a hardware configuration of a node according to an embodiment. FIG. 2 is a diagram illustrating an example of the directivity of an antenna of a node according to an embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of a node according to an embodiment. 6 is a block diagram showing an example of a functional configuration of a control unit shown in FIG. 5 . 11 is a flowchart illustrating an example of a link setup procedure between nodes according to an embodiment. FIG. 2 is a diagram showing a first example of a mesh link in the wireless communication system shown in FIGS. 1A and 1B. FIG. 2 is a diagram showing a second example of a mesh link in the wireless communication system shown in FIGS. 1A and 1B. 4 is a flowchart illustrating an example of the operation of a core node (CN) including tree routing on a mesh link according to one embodiment. 1 is a flowchart illustrating an example of the operation of a slave node (SN) including tree routing on a mesh link according to one embodiment. FIG. 9 is a diagram showing an example of a tree path constructed in the first example of the mesh link shown in FIG. 8 . 10 is a diagram showing an example of a tree path constructed in the second example of the mesh link shown in FIG. 9 .

Below, the embodiments will be described with reference to the drawings as appropriate. Unless otherwise specified, the same elements are given the same reference numerals throughout this specification. The matters described below together with the attached drawings are intended to explain exemplary embodiments, and are not intended to represent the only embodiments. For example, when an order of operations is indicated in an embodiment, the order of operations may be changed as appropriate within the scope of no inconsistency in the overall operation.

When multiple embodiments and/or variants are given as examples, some configurations, functions and/or operations in one embodiment and/or variant may be included in other embodiments and/or variants to the extent that no inconsistency arises, or may be replaced with the corresponding configurations, functions and/or operations in other embodiments and/or variants.

In addition, in the embodiments, more detailed explanations than necessary may be omitted. For example, detailed explanations of publicly known or well-known technical matters may be omitted in order to avoid unnecessarily lengthy explanations and/or ambiguity in technical matters or concepts, and to facilitate understanding by those skilled in the art. Furthermore, duplicate explanations of substantially identical configurations, functions, and/or operations may be omitted.

The accompanying drawings and the following description are provided to aid in understanding the embodiments, and are not intended to limit the subject matter described in the claims. Furthermore, the terms used in the following description may be appropriately replaced with other terms to aid in the understanding of those skilled in the art.

<The knowledge that led to this invention>

By making the BH network, which is one of the infrastructures for mobile communications, wireless through wireless multi-hop, it is possible to eliminate the need to lay wired cables, thereby reducing the installation costs required for introducing a mobile communications system. Therefore, for example, when introducing a mobile communications system temporarily (or provisionally), it is effective to make the BH network wireless through wireless multi-hop.

Here, for example, at a construction site or other work site, when a wireless communication environment is temporarily (or provisionally) introduced on different floors of a building for on-site workers, the wireless communication environment may change from moment to moment depending on the progress of the work.

For example, in a situation where the foundation and framework of a building have been completed but the exterior wall construction has not yet been carried out, the wireless nodes installed outside the building and the wireless nodes installed inside the building are in a line of sight (LOS) environment or an environment close to an LOS environment. Therefore, it is easy to ensure the expected wireless communication quality between the wireless nodes.

However, for example, as construction of an exterior wall progresses, the wireless nodes approach a non-line-of-sight (NLOS) environment, and the quality of wireless communication may deteriorate depending on the progress of the construction.

For example, at a building construction site, construction of the building framework and construction of the exterior walls may be carried out in that order for each floor of the building. Radio waves from a wireless node installed outside the building can reach wireless nodes installed on floors inside the building where exterior wall construction has not yet been completed. On the other hand, the wireless waves from a wireless node installed outside the building are more likely to be blocked as exterior wall construction progresses, and may not reach wireless nodes installed on floors where exterior wall construction has been completed.

The inventors of the present application have therefore developed wireless communication technology that, for example, applies wireless BH network technology to easily create three-dimensional wireless routes, including in the vertical direction, according to the progress of construction work, and that can also be easily removed.

This wireless communication technology can be useful, for example, for establishing a temporary wireless environment at a construction site. Non-limiting examples are described below.

In the present invention, even if the radio wave propagation environment between wireless nodes changes before and after exterior wall construction, as in the example described above, it is possible to suppress deterioration of wireless communication quality due to the change.

<System configuration example>
1A and 1B are diagrams showing a first state of an example of introduction of a wireless communication system according to an embodiment. FIG. 1A and 1B show an example in which a wireless communication system 1 is introduced at a construction site of a building. FIG. 1A and 1B respectively show an X-axis, a Y-axis, and a Z-axis representing a three-dimensional space. The XY plane indicates a horizontal plane defined along the ground surface. The Z-axis defines the height direction (up and down direction). FIG. 1A is a diagram viewed from the negative direction of the Y-axis, and FIG. 1B is a diagram viewed from the positive direction of the Z-axis.

Figures 1A and 1B show a building under construction having four floors, from the first to the fourth floor. The fourth floor of the building is a floor where exterior wall construction has not yet been completed, and the first to third floors of the building are floors where exterior wall construction has been completed. Figures 1A and 1B also show a tower crane that transports construction materials transported by a construction vehicle to a high position, a work area on the ground where the construction materials are brought in (accumulated), and a power supply box installed in a position that avoids the work area.

For example, when no power supply construction work is being carried out to create an environment for supplying power to electrical equipment, the power supply box is installed in a corner of the construction site to supply power to the electrical equipment used at the construction site. For example, the power supply box is installed in a position near the construction work area where it can be connected to a system power supply and in a position that does not impede the passage of construction vehicles (or construction machinery). Therefore, for example, the power supply box is installed a predetermined distance away from the construction area.

In order to tow materials using a tower crane, the materials are piled up on the ground directly below the tower crane, within the crane's working range. The tower crane then tows the piled up materials to a higher position in turn, ensuring the tower crane's working range. Therefore, the power supply box is installed at the construction site, for example, to avoid the tower crane's working range. The working range may also be referred to as the "access range" where construction vehicles enter.

At a construction site, at least one of the multiple wireless nodes that make up the temporary BH network may be connected, for example, by wire to a power box and receive power from the power box.

In addition, in FIG. 1A, which is a side view of the X-Z plane viewed from the side (negative direction of the Y axis), configurations at different positions in the Y axis direction are shown on the same surface. Also, in FIG. 1B, which is an overhead view of the X-Y plane viewed from above (positive direction of the Z axis), configurations at different positions in the Z axis direction are shown on the same surface.

The state shown in Figures 1A and 1B, in which the exterior wall construction of the building on the first to third floors has been completed but the exterior wall construction on the fourth floor is incomplete, may be referred to below as the "first state."

The wireless communication system 1 shown in Figures 1A and 1B illustratively includes a plurality of wireless nodes (hereinafter sometimes abbreviated as "nodes") 3. As a non-limiting example, Figures 1A and 1B illustrate seven nodes 3, indicated by node numbers #0 to #6. The number of nodes 3 may be 2 or more and less than 7, or may be 8 or more.

Some of the nodes 3 among the multiple nodes 3 may be wired to the backbone network 5. FIGS. 1A and 1B illustrate an example in which node #0 is wired to the backbone network 5. For example, a LAN cable or an optical fiber cable may be used for the wired connection.

Node #0, which is connected by wire to the backbone network 5, may be referred to as a "core node (CN)." Of the multiple nodes 3 forming the BH network, each node 3, except for CN #0, may be referred to as a "slave node (SN)."

In the wireless communication system 1 shown in Figures 1A and 1B, CN#0 and SN#1 are provided at specific locations.

For example, CN#0 is provided near a power supply box on the ground surface (for example, within a range that can be connected by a power cable) and is supplied with power from the power supply box. The XY plane on which CN#0 is provided may be referred to as the "first horizontal plane." Note that the location at which CN#0 is provided is not limited to being near the power supply box. CN#0 may be provided in a position that provides a wired connection to the backbone network 5.

SN#1 is located on a floor of a building under construction where exterior wall construction has not yet been completed, near the side of the building facing CN#0, which is located in a power supply box. SN#1 is provided, for example, at the swivel base of a tower crane. The swivel base may correspond to the part that does not rotate when the tower crane tows materials and rotates to transport the materials inside the building. The XY plane on which SN#1 is provided is sometimes referred to as the "second horizontal plane."

Tower cranes are used to pull materials to raise the framework of a building under construction, and are typically positioned above the top level of the completed framework. As the framework of an upper level is completed, the tower crane is then repositioned above the top level of the next building to pull materials for the framework of the next top level.

As described below, since SN#1 directly receives radio waves from CN#0, it is desirable that there be no obstructions between CN#0 and SN#1. From this perspective, the rotating base of a tower crane is located on the top floor of a building under construction, regardless of the progress of the construction work (e.g., the height of the building). Therefore, the rotating base of a tower crane is suitable for mounting SN#1. Furthermore, tower cranes have a rotating structure that rotates the operating part, but if SN#1 is placed on the rotating part, the receiving strength of the radio waves may fluctuate depending on the operation of the crane, making communication unstable. Therefore, it is more suitable to install SN#1 in a position facing CN#0 on the rotating base rather than installing it on the rotating part.

As an example, CN#0 and SN#1 are provided on the same X-Z plane (see dotted line L1 in FIG. 1B). In other words, in this embodiment, as an example, the X-axis and Y-axis are defined so that CN#0 and SN#1 are provided on the same X-Z plane. Note that the positions of the X-axis and Y-axis with respect to the positions of CN#0 and SN#1 are relative, so the positional relationship of these nodes is not limited to the positional relationship shown in the figure.

SN#2 and SN#3 are located on the fourth floor of the building. SN#4 to SN#6 are located on the third to first floors of the building, respectively. Here, the XY plane on which SN#2 is located may be considered an example of the "third horizontal plane." The third horizontal plane may be the same as the second horizontal plane described above. Also, for example, SN#2 may be located on a different XZ plane from CN#0 and SN#1 (see dotted line L2 in Figure 1B).

Each node 3 is an example of a wireless device capable of wireless communication. Therefore, each node 3 may be referred to as a "wireless node 3." A communication protocol that complies with (or is based on) a wireless LAN (Local Area Network) related standard such as IEEE802.11b/g/a/n/ac/ad/ay may be applied to the wireless communication.

Each node 3 forms an area in which wireless communication is possible. The "area in which wireless communication is possible" may be called a "wireless communication area," "wireless area," "communication area," "service area," "coverage area," or "cover area," etc. A wireless communication area formed by nodes 3 that conform to or are based on wireless LAN-related standards may be considered to correspond to a "cell," a term used in cellular communication. For example, a wireless communication area formed by individual nodes 3 may be considered to correspond to a "femtocell," which is classified as a "small cell."

When each node 3 is located in the service area of another node 3, it is capable of wireless communication with the other node 3. A plurality of nodes 3 form, for example, a wireless backhaul (BH) network that wirelessly relays communication between a backbone network and a terminal device 7. A "wireless BH network" may be referred to as a "BH network" by omitting "wireless."

The "BH network" may be referred to as a "relay network." Individual nodes 3 that are entities of the BH network may be referred to as "relay nodes."

The path or section through which a wireless signal is transmitted in a BH network may be interchangeably referred to as a "wireless BH communication path," a "wireless BH transmission path," a "wireless BH line," a "wireless BH connection," or a "wireless BH channel." In these terms, "wireless" may be omitted, and "BH" may be interchangeably referred to as "relay."

The wireless BH line may include at least one of a "downlink" in the direction from the core node 3 to the slave node 3 and an "uplink" in the direction from the slave node 3 to the core node 3. The "downlink" and "uplink" may be referred to as "downlink (DL)" and "uplink (UL)", respectively, following the names used in cellular communications.

For example, when information is broadcast (notified) from the backbone network 5 to one or more slave nodes 3 via the core node 3, the wireless BH line may include a downlink line and may not include an uplink line. Also, when information is broadcast (notified) from one or more slave nodes 3 to the backbone network 5 via the core node 3 and the information is aggregated in the backbone network 5, the wireless BH line may include an uplink line and may not include a downlink line. Even in the case of one-way information transmission via the uplink line and the downlink line, the configuration of this embodiment encompasses both.

The flow of signals (downlink signals) on the "downlink" may be referred to as "downstream," and the flow of signals (uplink signals) on the "uplink" may be referred to as "upstream." The "downlink signals" and "uplink signals" may each include control signals and data signals. "Control signals" may include signals that do not fall under the category of "data signals." In addition, the "downlink signals" and "uplink signals," which are wireless signals, may be referred to as "downlink wireless signals" and "uplink wireless signals," respectively.

Note that a "child node" may be considered to correspond to a node (downstream node) connected downstream of a certain node by a wireless link when focusing on the "downstream line." A node connected upstream of a certain node by a wireless link when focusing on the downstream line may be called a "parent node" or "upstream node." When focusing on the "upstream line," the relationship between the "child node" (downstream node) and the "parent node" (upstream node) is reversed.

In contrast, for example, the section where wireless signals are transmitted between the terminal device 7 and the BH network may be called a "wireless access line" or a "wireless access channel." In these terms, "wireless" may be omitted.

The wireless access line may include at least one of a "downlink" in the direction from node 3 included in the BH network to terminal device 7, and an "uplink" in the direction from terminal device 7 to node 3 included in the BH network. Here, node 3 may be a node with which a wireless connection with terminal device 7 has been established.

For example, when information is broadcast (notified) from the backbone network 5 to the terminal device 7 via one or more nodes 3, the wireless BH line and wireless access line may include a downlink line and may not include an uplink line. Also, when information is broadcast (notified) from the terminal device 7 to the backbone network 5 via one or more nodes 3 and the information is aggregated in the backbone network 5, the wireless BH line and wireless access line may include an uplink line and may not include a downlink line. Even in the case of one-way information transmission via the uplink line and the downlink line, the configuration of this embodiment encompasses these cases.

The BH network may have one or more tree structures (which may be referred to as "tree topologies") with one CN3 (#0) as the root node.

For example, a tree-structured route (tree topology) in a BH network may be constructed based on the metric of the route from CN3 to a specific SN3 (hereinafter sometimes abbreviated as "route metric"). The route metric may be an index indicating the quality or performance of radio wave propagation in the wireless section from CN3 to a specific SN3 (hereinafter referred to as "propagation quality index").

Non-limiting examples of propagation quality indicators include the received power or strength of a wireless signal (e.g., Received Signal Strength Indicator (RSSI)), radio wave propagation loss, and propagation delay.

For example, by transmitting a signal (e.g., a control signal) starting from CN3, the radio wave propagation loss of each wireless section between the transmitting node 3 and the receiving node 3 of the control signal can be calculated at the receiving node 3.

Then, each receiving node 3 transmits the obtained radio wave propagation loss information together with the control signal, so that information on the cumulative radio wave propagation loss (in other words, the cumulative value) of the wireless section through which the control signal has propagated can be transmitted between nodes 3.

Each node 3 calculates a route metric based on the cumulative radio wave propagation loss for each upstream node candidate that is the source of the control signal, and selects one node 3 from among the upstream node candidates that has, for example, the smallest route metric. This allows a tree-structured route with the smallest radio wave propagation loss to be constructed.

In the example of Figures 1A and 1B, SN#2 and CN#0 are in a line-of-sight environment (LOS environment), and therefore have a positional relationship that allows for the construction of a wireless BH line. In this way, when SN#2 and CN#0 are in the positional relationship shown in Figures 1A and 1B, SN#2 and CN#0 can communicate directly, or can communicate via SN#1. In this embodiment, depending on the radio wave conditions at the time of communication, direct communication between SN#2 and CN#0 and communication via SN#1 are compared, and the route with the better radio wave conditions is selected. The selection of the route will be described later.

For example, when exterior wall construction is completed on the fourth floor where SN#2 is located, SN#2 and CN#0 will be in a non-line-of-sight (NLOS) environment.

Note that the state in which the exterior wall construction on the fourth floor of the building has been completed, as shown in Figures 2A and 2B, may be referred to as the "second state" below.

2A and 2B are diagrams showing a second state of an example of the introduction of a wireless communication system according to an embodiment. Similar to FIGS. 1A and 1B, FIGS. 2A and 2B show an example of the introduction of a wireless communication system 1 at a building construction site. In FIGS. 2A and 2B, the exterior wall construction on the fourth floor, which was incomplete in FIGS. 1A and 1B, is completed, and a floor (fifth floor) where the exterior wall construction is incomplete is built one floor above the fourth floor. In FIGS. 2A and 2B, SN#7 is built on the fifth floor. In FIGS. 2A and 2B, the tower crane is shown to be further extended in the height direction (Z-axis direction) than in FIGS. 1A and 1B.

As shown in Figures 2A and 2B, when the exterior wall construction is completed on the fourth floor where SN#2 is installed, SN#2 and CN#0 will be in a non-line-of-sight environment (NLOS environment), and will no longer be in a positional relationship that allows a wireless BH line to be directly established. As a result, the established wireless BH line will be easily disconnected.

In this embodiment, in order to avoid disconnection of the established wireless BH line, a system design is performed in which the wireless BH line is established preferentially between SN#1 and CN#0.

For example, the wireless BH line is configured to maintain the radio wave propagation loss between SN#1 and CN#0 lower than the radio wave propagation loss between SNs other than SN#1 (e.g., SN#2 and SN#7) and CN#0.

For example, the antenna of CN#0 has directivity toward SN#1, and the antenna of SN#1 has directivity toward CN#0.

The directional antenna may be a single planar antenna, or an antenna that controls its directionality using a multiple antenna array. The directivity of the antenna may be adjusted manually or automatically. For example, the antenna's directionality may be adjusted by mechanically adjusting the orientation of the antenna, or the directivity may be adjusted by signal processing of the signal transmitted and received by the antenna.

1A, the antenna of CN#0 has directivity in the XZ plane in the direction where SN#1 is provided (e.g., in the direction of _θ1 with respect to the positive direction of the X-axis). Also, among the antennas of SN#1, the antenna that performs wireless communication with the upstream node (CN#0) has directivity in the XZ plane in the direction where CN#0 is provided (e.g., in the direction of _θ1 with respect to the negative direction of the X-axis).

The angle defined on the X-Z plane may be called the "elevation angle" or "depression angle." The angle defined on the X-Y plane may be called the "azimuth angle."

Antennas generally used to construct a BH network are designed to radiate radio waves in a horizontal plane in order to connect nodes 3 together in a mesh pattern. In contrast, in this embodiment, when radiating radio waves in the height direction (Z-axis direction in the figure) to wirelessly connect CN#0 installed on the ground surface with SN#1 on the top layer, strong directivity is given to the radiated radio waves by an antenna array with directivity control. For example, by orienting the directivity in the direction of _θ1 , the wireless communication environment between CN#0 and SN#1 can be optimized.

Also, in the example of FIG. 1A, among the antennas of SN #1, the antenna that performs wireless communication with the downstream node (SN #2) has directivity oriented in the direction in which SN #2 is located on the XY plane (for example, in the direction of _θ2 with respect to the positive direction of the X-axis).

An antenna with no directivity (for example, an omnidirectional antenna) can emit radio waves with a practical strength, although weaker than that of the horizontal plane, if the elevation angle (or depression angle) from the horizontal plane is in the range of about 20 degrees to 30 degrees. Therefore, as long as the angle (elevation angle) between SN#1 and SN#2 is 30 degrees or less, good communication may be ensured. However, as described above, SN#1 installed on the tower crane is relocated (moved) to the top floor as the construction progresses, so that the elevation angle between SN#1 and SN#2 may exceed 30 degrees. In such a case, wireless communication between SN#1 and SN#2 using an antenna with no directivity is difficult. Therefore, it is preferable to give directionality to the radio waves between SN#1 and SN#2. For example, it is preferable to give the antenna of SN#1 directivity in the elevation angle direction.

In addition, instead of giving the antenna of SN#1 directivity in the elevation angle direction, the antenna of SN#2 may be given directivity in the elevation angle direction. Alternatively, both the antennas of SN#1 and SN#2 may have directivity in the elevation angle direction.

The SN3 antenna installed on each floor of a building may or may not have directionality. For example, if multiple SN3s are installed on each floor of a building, a wireless mesh may be constructed for each floor. In this case, a specific SN3 on each floor may be set as the node that serves as the starting point of the wireless mesh for that floor.

In the example of FIG. 1A and FIG. 1B, SN#3, which is placed in the same layer as SN#2, may communicate with SN#1 via SN#2. That is, the route from SN#3 to CN#0 may be a route that connects SN#3 to SN#2 and SN#1 and reaches CN#0. A directional antenna is weaker in radiating radio waves to a range other than the range to which the directivity is directed than a normal antenna. Therefore, for example, if SN#2 is set as the node that is the starting point of the wireless mesh on the 4th floor, it is preferable to use a normal antenna that does not have directivity for SN#3 (and other SN3s on the 4th floor, not shown) in constructing the wireless mesh on this layer. That is, in each layer under construction, a specific SN3 having directivity for sending and receiving in the directivity direction of SN#1 may be placed in the directivity range of SN#1 and set as the node that is the starting point of the wireless mesh on each layer. Then, in areas not covered by a specific SN3 on each level, an SN3 having an antenna that radiates radio waves widely in the horizontal plane may be placed.

As described above, even with a normal antenna, communication can be ensured if it is about 30 degrees from the horizontal plane. Therefore, the present invention is preferably implemented when the angle (θ1 direction) between the core node CN#0 placed on the ground surface and the wireless repeater SN#2 that is assumed to directly communicate wirelessly with CN# ₀ is 30 degrees or more, as in this embodiment.

In this embodiment, the communication between the slave nodes is configured to select the optimal route depending on the radio wave conditions. Therefore, if there is no obstruction between SN#1 and SN#3 and the elevation angle (or depression angle) is not large, the radio wave conditions of the route from SN#1 through SN#2 and SN#3 (first route) and the route from SN#1 to SN#3 (second route) are compared, and if the second route has better radio wave conditions than the first route, the second route may be selected. If the second route is selected, it is possible to reduce the load on SN#2.

In this embodiment, the method of installing (mounting) SN#1 on the tower crane is not limited. For example, SN#1 does not have to be completely fixed when installed on the tower crane. For example, a method may be adopted in which a fixing member (not shown) is fixed to the tower crane base and SN#1 is detachably mounted on the fixing member. For example, the fixing member is threaded and fixed by a bolt penetrating the exterior of SN#1. Since the tower crane is exposed to wind and rain during the construction period, it is desirable that SN#1 be firmly mounted to prevent SN#1 from coming off or changing its orientation. On the other hand, if SN#1 is completely fixed, when the tower crane is relocated, the movement work of the huge crane will be performed with SN#1 attached. In this case, there is a risk that a large load will be unintentionally applied to SN#2 during the movement work, and SN#2, which is a precision instrument, may be damaged. In addition, if the antenna of SN#2 has an array configuration, the mutual positional relationship of the antenna array may deviate from the desired mutual positional relationship. Therefore, it is preferable to attach SN#1 to the tower crane in a manner that allows it to be easily attached and detached. Also, to prevent adverse effects on radio waves, it is best to avoid using strong magnets such as neodymium magnets.

When transitioning from the first state shown in Figures 1A and 1B to the second state shown in Figures 2A and 2B, the directivity of the antenna and the placement position of the node that is the starting point of each layer may be adjusted.

2A, the antenna of CN#0 has directivity in the XZ plane in the direction in which SN#1 is provided (e.g., in the direction of _θ3 with respect to the positive direction of the X-axis as the reference). Also, among the antennas of SN#1, the antenna that performs wireless communication with the upstream node (CN#0) has directivity in the XZ plane in the direction in which CN#0 is provided (e.g., in the direction of _θ3 with respect to the negative direction of the X-axis as the reference).

Also, in the example of FIG. 2A, among the antennas of SN #1, the antenna that performs wireless communication with the downstream node (SN #7) has directivity oriented in the direction in which SN #7 is located on the X-Z plane (for example, in the direction of _θ4 with respect to the positive direction of the X-axis).

In addition, the antenna of node 3 is not limited to having directivity in the X-Z plane, and may have directivity in the X-Y plane. In other words, the antenna of node 3 may have directivity in both the X-Y plane and the X-Z plane, that is, three-dimensional directivity.

For example, in the example of FIG. 1B, among the antennas of SN#1, the antenna that performs wireless communication with the downstream node (SN#2) has directivity oriented in the direction in which SN#2 is provided on the X-Z plane (for example, the direction of _φ1 based on the positive direction of the X-axis). Then, when transitioning from the first state to the second state, among the antennas of SN#1, the antenna that performs wireless communication with the downstream node (SN#7) has directivity oriented in the direction in which SN#7 is provided on the X-Z plane (for example, the direction of _φ2 based on the positive direction of the X-axis).

In this way, by having a directional antenna, the wireless backhaul link between SN#1 and CN#0 is preferentially established to avoid disconnection of the established wireless backhaul link.

<Example of node 3 configuration>
(Hardware configuration example of node 3)
Next, a hardware configuration example of the node 3 will be described with reference to Fig. 3. The configuration example illustrated in Fig. 3 may be common to the CN 3 and the SN 3. As shown in Fig. 3, the node 3 may include, for example, a processor 31, a memory 32, a storage 33, an input/output (I/O) device 34, wireless IFs 35 and 36, a wired IF 37, a wired IF 39, and a bus 38.

In addition, in the example hardware configuration shown in FIG. 3, the amount of hardware may be increased or decreased as appropriate. For example, any hardware block may be added, removed, divided, or integrated in any combination, and bus 38 may be added or removed as appropriate.

The processor 31, memory 32, storage 33, input/output device 34, wireless IFs 35 and 36, and wired IFs 37 and 39 can be connected to, for example, a bus 38 to communicate with each other. The number of buses 38 may be one or more.

A plurality of processors 31 may be provided in the node 3. Furthermore, the processing in the node 3 may be executed by one processor 31 or by multiple processors 31. In one or multiple processors 31, multiple processes may be executed simultaneously, in parallel, or sequentially, or may be executed by other methods. The processor 31 may be a single-core processor or a multi-core processor. The processor 31 may be implemented using one or more chips.

One or more functions possessed by node 3 are realized, for example, by loading specific software into hardware such as processor 31 and memory 32. Note that "software" may be interchangeably interpreted as other terms such as "program," "application," "engine," or "software module."

For example, the processor 31 reads and executes a program by controlling the reading and/or writing of data stored in the memory 32 and/or the storage 33. The program may be provided to the node 3 by communication via a telecommunication line using at least one of the wireless IF 35, the wireless IF 36, and the wired IF 37.

The program may be a program that causes a computer to execute all or part of the processing in node 3. One or more functions of node 3 are realized in response to execution of program code contained in the program. All or part of the program code may be stored in memory 32 or storage 33, or may be written as part of the operating system (OS).

For example, the program may include program code that embodies the functional blocks described below with reference to Figures 5 and 6. For convenience, a program that includes such program code may be referred to as a "wireless route control program."

The processor 31 is an example of a processing unit, and for example, operates an OS to control the entire computer. The processor 31 may be configured using a central processing unit (CPU) that includes an interface with peripheral devices, a control device, an arithmetic unit, a register, etc.

The processor 31 also reads, for example, one or both of programs and data from the storage 33 to the memory 32 and executes various processes.

The memory 32 is an example of a computer-readable recording medium, and may be configured using at least one of, for example, a ROM, an EPROM, an EEPROM, a RAM, and an SSD. Note that "ROM" is an abbreviation for "Read Only Memory", and "EPROM" is an abbreviation for "Erasable Programmable ROM". "EEPROM" is an abbreviation for "Electrically Erasable Programmable ROM", "RAM" is an abbreviation for "Random Access Memory", and "SSD" is an abbreviation for "Solid State Drive".

Memory 32 may also be called a register, cache, main memory, work memory, or primary storage device.

Storage 33 is an example of a computer-readable recording medium, and may be configured using at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive (HDD), a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a flexible disk, a magnetic strip, etc. Storage 33 may also be referred to as an auxiliary storage device. The above-mentioned recording medium may be, for example, a database, a server, or other suitable medium that includes one or both of memory 32 and storage 33.

The input/output (I/O) device 34 is an example of an input device that accepts signal input from outside the node 3, and an output device that outputs signals from the node 3 to the outside. The input device may include, for example, one or more of a keyboard, a mouse, a microphone, a switch, a button, and a sensor. The output device may include, for example, one or more of a display, a speaker, and a light-emitting device such as an LED (Light Emitting Diode).

As described above, in this embodiment, the node 3 has the function of a simple PC having a processor 31, a memory 32, etc. With this configuration, a so-called edge computing environment is realized, and by storing some information in one of the nodes 3, it is also possible to perform typical work without reading data from SN#1 via CN#0 → via the external Internet (e.g., backbone network 5). In this embodiment, CN#0 and SN#1, which is a wireless repeater, are the communication routes for almost all slave nodes 3 other than SN#1, so it is also preferable to store data that is used all the time, such as labor management sheets and/or work process manuals, in one of the nodes 3. For example, in the node 3 that is the starting point of each layer arranged in each layer, data used in that layer is stored, making it possible to complete data communication within the corresponding layer. From this perspective, the storage 33 mounted on SN#1 may be made larger in capacity than the storage 33 of the node (SN#2 in FIG. 1A) that is the starting point of each layer. Furthermore, the storage 33 of the node 3 that is the starting point of each hierarchy may have a larger capacity than the storage 33 of the slave node 3 (SN#3 in FIG. 1A) that is connected to the starting node 3.

The buttons may include, for example, a power button and/or a reset button. The power button is operated, for example, to start up and shut down the node 3. The reset (or reroute) button is operated, for example, to indicate an intentional reset and/or reconstruction (or reroute) of the tree path.

The input/output device 34 may be configured with separate input and output. Alternatively, the input/output device 34 may be configured with an integrated input and output, such as a touch panel display.

The wireless IF 35, for example, transmits and receives wireless signals over an access line between the terminal device 7. The wireless IF 35 may include, for example, one or more antennas 350, a baseband (BB) signal processing circuit, a MAC processing circuit, an up-converter, a down-converter, and an amplifier (not shown).

The BB signal processing circuit of the wireless IF 35 may, for example, include an encoding circuit and a modulation circuit for encoding and modulating the transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding the received signal.

The wireless IF 36, for example, transmits and receives wireless signals over a BH line with other SNs 3. Like the wireless IF 35, the wireless IF 36 may include one or more antennas 360, a BB signal processing circuit, a MAC processing circuit, an up-converter, a down-converter, and an amplifier (not shown).

The BB signal processing circuit of the wireless IF 36 may, for example, include an encoding circuit and a modulation circuit for encoding and modulating the transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding the received signal.

In addition, in CN#0 and SN#1 illustrated in Figures 1A to 2B, the antenna 360 of the wireless IF 36 has directionality. For example, the antenna 360 of the wireless IF 36 may be an antenna array whose directivity is controllable. Beamforming may be performed by an antenna array having multiple directional antennas.

The wired IF 37, for example, transmits and receives signals via a wired connection between the backbone network 5 and/or the upstream node 3. The wired IF 39, for example, transmits and receives signals via a wired connection between the terminal device 7 and/or the downstream node 3. For the wired IFs 37 and 39, for example, a network interface conforming to the Ethernet (registered trademark) standard may be used. Note that the wired IFs 37 and 39 only need to be provided in at least the CN 3, and do not have to be provided in the SN 3 (in other words, they may be optional for the SN 3). However, if part of the BH line is connected via a wired connection, the wired IFs 37 and 39 may be used for the wired connection.

The node 3 may be configured to include hardware such as a microprocessor, a DSP, an ASIC, a PLD, and an FPGA. For example, the processor 31 may be implemented to include at least one of these pieces of hardware. The hardware may realize some or all of the functional blocks described below in FIG. 5 and FIG. 6.

Note that "DSP" is an abbreviation for "Digital Signal Processor," and "ASIC" is an abbreviation for "Application Specific Integrated Circuit." "PLD" is an abbreviation for "Programmable Logic Device," and "FPGA" is an abbreviation for "Field Programmable Gate Array."

(Example of antenna directivity of node 3)
Next, an example of the directivity of the antenna 360 of the wireless IF 36 of each node 3 between CN#0 and SN#1 shown in FIGS. 1A and 1B will be shown.

Figure 4 is a diagram showing an example of the directivity of an antenna of a node according to one embodiment. Figure 4 shows an example of the directivity of an antenna of CN#0, SN#1, and SN#2 and each node in the wireless communication system 1 shown in Figures 1A and 1B.

The antenna 360 of CN#0 has directivity toward SN#1, which is the downstream node 3. And the antenna 360-1 of SN#1 has directivity toward CN#0, which is the upstream node 3. With this configuration, the line conditions of the wireless link between CN#0 and SN#1 can be made better than the line conditions of the wireless link between CN#0 and an SN other than SN#1.

Furthermore, the antenna 360-2 of SN#1 may have directivity toward SN#2, which is the downstream node 3. With this configuration, the line conditions of the wireless link between SN#1 and SN#2 can be made better than the line conditions of the wireless link between SN#1 and an SN different from SN#2.

(Example of functional configuration of node 3)
Next, a functional configuration example of the node 3 will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a block diagram showing a functional configuration example of the node 3 according to an embodiment, and Fig. 6 is a block diagram showing a functional configuration example of the control unit exemplified in Fig. 5.

As shown in FIG. 5, in terms of the functional configuration, node 3 may include a wireless communication unit 301 for a wireless access line, a wireless communication unit 302 for a wireless BH line, a wired communication unit 303, a control unit 304, and a memory unit 305.

The wireless communication unit 301 for the wireless access line is a functional block including the wireless IF 35 and the access line antenna 350 illustrated in FIG. 3. The wireless communication unit 302 for the wireless BH line is a functional block including the wireless IF 36 and the BH line antenna 360 illustrated in FIG. 3.

The wired communication unit 303 is a functional block including the wired IFs 37 and 39 illustrated in FIG. 3. The memory unit 305 is a functional block including one or both of the memory 32 and the storage 33 illustrated in FIG. 3.

The wireless communication unit 301 may include, for example, at least one of a transmission processing unit that transmits a control signal and/or a data signal addressed to the terminal device 7, and a reception processing unit that receives a control signal and/or a data signal transmitted by the terminal device 7.

In other words, the wireless communication unit 301, which is an example of a processing unit, may perform at least one of processing a downstream wireless signal transmitted from the antenna 350 to the terminal device 7 and processing an upstream wireless signal received by the antenna 350.

The wireless communication unit 302 may include, for example, at least one of a transmission processing unit that transmits control signals and/or data signals to a BH line that is linked up with another node 3, and a reception processing unit that receives control signals and/or data signals from the linked up wireless link.

In other words, the wireless communication unit 302, which is an example of a processing unit, may perform at least one of the following processes: a process of processing a downstream wireless signal received by the antenna 360 and transmitting the signal from the antenna 360 to the downstream node 3; and a process of processing an upstream wireless signal received by the antenna 360 and transmitting the signal from the antenna 360 to the upstream node 3. Note that the antenna 360 that receives the downstream wireless signal and the antenna 360 that transmits the upstream wireless signal may be the same or different from each other.

The processing of the wireless communication unit 301 and/or the wireless communication unit 302 may differ for each node 3. For example, the processing of CN3 and SN3 may differ from each other. Furthermore, the processing of the wireless communication unit 301 and/or the wireless communication unit 302 may be changed depending on the direction and/or purpose of information transmission in the wireless network.

The wireless communication unit 301 and/or the wireless communication unit 302 may have a MIMO function. For example, when the wireless communication unit 302 has a MIMO function, the wireless communication unit 302 may simultaneously perform a part of the operation of transmitting and receiving signals with an upstream node in the BH line and/or a part of the operation of transmitting and receiving signals with a downstream node in the BH line.

For example, in the above-mentioned SN#1, the wireless communication unit 302 may be provided for each of antenna 360-1 (see FIG. 4) having directivity toward CN#0 and antenna 360-2 (see FIG. 4) having directivity toward SN#2. SN#1 may include two systems of transmission/reception circuits for signals transmitted and received by antenna 360-1 and signals transmitted and received by antenna 360-2. For example, by having the wireless communication unit 302 of the above-mentioned SN#1 have a MIMO function, it can be realized with one system of transmission/reception circuit (e.g., wireless communication unit 302).

The wired communication unit 303 may include, for example, a transmitting unit that transmits control signals and/or data signals to the backbone network 5, and a receiving unit that receives control signals and/or data signals from the backbone network 5.

The control unit 304 performs overall control of the operation of the node 3. For example, the control unit 304 controls communication via one or more of the wireless access line, the wireless BH line, and the wired line by providing a control signal to one or more of the wireless communication unit 301, the wireless communication unit 302, and the wired communication unit 303.

The control unit 304 is realized, for example, by the processor 31 shown in FIG. 3 reading a program stored in the memory unit 305 and executing the read program.

The storage unit 305 stores, for example, the node identification information described above and the route metric described below. As described below, if the transmission power value of the source node 3 is not included in the route construction packet, the transmission power value of the source node 3 may be stored in the storage unit 305.

(Example of configuration of control unit 304)
As shown in FIG. 6, the control unit 304 may illustratively include a scan processing unit 341, a node management unit 342, a tree path control unit 343, and an IPT control unit 344.

For example, in response to the startup of a node 3, the scan processing unit 341 scans and discovers the presence of other nodes 3 located in the vicinity (nearby) of the node 3. The scan may be a passive scan or an active scan. In the case of passive scan as an example, a beacon signal is generated in the scan processing unit 341 and transmitted to the surrounding area via the wireless communication unit 302.

Note that nodes 3 that are in a position where they can receive a beacon signal are referred to as "peripheral nodes 3" or "neighboring nodes 3."

The beacon signal may include, for example, information that explicitly or implicitly indicates the SSID (Service Set Identifier) or BSSID (Basic SSID), the transmission period of the beacon signal, and the available channel (frequency). For convenience, this information may be referred to as "BSS (Basic Service Set) related information."

In the case of active scanning, a probe request signal may be generated in the scan processing unit 341 and transmitted to the surrounding area via the wireless communication unit 302. The probe request signal is used, for example, to prompt the surrounding node 3 to transmit a beacon signal. If a beacon signal is not received within a certain period of time in passive scanning, active scanning may be performed.

The node management unit 342 stores, for example, information about the peripheral nodes 3 discovered by a scan performed by the scan processing unit 341 (for example, node identification information and BSS-related information) in the storage unit 305. In each node 3, information about the peripheral nodes 3 (hereinafter sometimes abbreviated as "peripheral node information") is stored in the storage unit 305, and as described below, mesh links are constructed in the BH network, linking the nodes 3 in a mesh shape using multiple wireless links.

"Constructing a mesh link" may be understood to mean that multiple available wireless links are established or linked up between nodes 3 located within an area where wireless communication is possible between the nodes 3. Therefore, the surrounding node information may be understood to indicate information on available wireless links between the nodes 3. For convenience, "wireless link information" may be abbreviated to "link information."

The tree route control unit 343 controls the construction and updating of tree routes on mesh links by transmitting route control packets on the mesh links.

The IPT control unit 344 controls the timing of packet transmission by the wireless communication unit 302 for the BH line, for example, according to a transmission period corresponding to the frequency reuse interval.

(Example of the configuration of the tree route control unit 343)
As illustrated in FIG. 6 , the tree route control unit 343 may include, for example, a route control packet generation unit 3431 , a route metric calculation unit 3432 , and a tree route update unit 3433 .

The route control packet generator 3431 generates a route control packet. A route control packet is an example of a control signal that is generated in CN3 in the BH network and propagated to each node 3 starting from CN3.

For example, CN3 floods a control signal to each of the wireless links that are linked up in CN3. When SN3 receives a control signal from one of the wireless links that are linked up in SN3, it floods the control signal to each of the wireless links that are linked up in SN3. In this way, the control signal transmitted from CN3 propagates or transmits through the mesh links sequentially or in a chain.

Similarly, SN3 waits for the arrival (reception) of a control signal while maintaining the link-up state of the wireless link with CN3 or another SN3. Then, when it receives a control signal from a wireless link in the link-up state, it transmits the control signal to the other wireless links that maintain the link-up state.

SN3 may add information to be transmitted to other SN3s to a control signal to be transmitted to other wireless links that maintain a linked up state. A non-limiting example of information to be added to the control signal is a route metric calculated by the route metric calculation unit 3432. SN3 may also exclude wireless links that have received a control signal from among the wireless links that are linked up in the SN3 from among the candidate destinations for the control signal. This can prevent control signals from being transmitted unnecessarily or redundantly through mesh links.

The route control packets may include, for example, route construction packets and reset packets. The types of these packets may be identified, for example, by the type value in the packet header.

A route construction packet is, for example, a packet that is transmitted when constructing or updating a tree route. A route construction packet may include cumulative route metrics calculated at each of the nodes 3 to which the route construction packet has propagated. For example, a node 3 may transmit a route construction packet that includes the route metric from the core node to the node immediately preceding the node itself.

When SN3 receives the route construction packet, it selects information about the wireless links to be registered in the tree route from among the available wireless links with surrounding node 3 that form a mesh link based on the cumulative route metric.

A reset packet is a packet that is sent, for example, when CN3 requests SN3 to clear the tree route built in the mesh link. When SN3 receives the reset packet, it deselects the information of the wireless link that was selected for the tree route.

The route metric calculation unit 3432, for example, calculates the propagation quality index of the wireless link between the neighboring node 3, which is the source of the received route construction packet, and obtains a new route metric by adding the calculation result to the route metric included in the received route construction packet.

As an example of the propagation quality indicator of the wireless link between nodes 3, RSSI (Received Signal Strength Indicator) may be used.

For example, when the new route metric calculated by the route metric calculation unit 3432 is smaller than the old route metric, the tree route update unit 3433 selects the upstream wireless link corresponding to the new route metric in the surrounding node information as a valid tree route.

For example, in SN3, when a route construction packet is received from each of the different routes, the route metrics of one or more wireless links through which each of the route construction packets propagates are calculated in the route metric calculation unit 3432 separately for each of the different routes.

Based on the route metrics calculated separately for the different routes, the tree route update unit 3433 selects, from among the wireless links linked up at the SN, a wireless link that corresponds to one of the different routes that received a route construction packet as the route to be used for transmitting the data signal.

Since the tree route constructed in the mesh link has a tree structure, there is always one upstream node 3 for each SN 3. Therefore, the tree route update unit 3433 can construct or update a tree route, for example, by selecting or deselecting a wireless link (link information) between the mesh link and the upstream node 3 as a wireless link to be registered in the tree route.

<Example of operation>
An example of the operation of the above-mentioned wireless communication system 1 will now be described.

(Link setup procedure)
FIG. 7 is a flowchart showing an example of a link setup procedure between nodes 3 (in other words, wireless BH lines in a BH network) according to an embodiment.

As shown in FIG. 7, in the BH network, each of the nodes 3, including the CN and SN, scans for surrounding nodes 3 (hereinafter sometimes referred to as "surrounding nodes") in response to startup, for example, in IBSS mode (S11).

"IBSS" is an abbreviation for "Independent Basic Service Set." IBSS mode is sometimes called ad-hoc mode. "Starting up" a node 3 may include turning on the power of the node 3 and restarting the node 3 by resetting it. "Starting up" a node 3 may also include restarting triggered by adding, deleting, or changing the position of a node 3 in the wireless communication system 1.

For example, in the scanning process S11, each of the nodes 3 starts transmitting a beacon signal to the surrounding area in response to startup. The beacon signal is generated, for example, in the scanning processing unit 341 of the control unit 304 and transmitted from the BH line antenna 360 (wireless communication unit 302).

In the scanning process S11 in IBSS mode, in order to avoid collisions between beacon signals, each activated node 3 may transmit a beacon signal in turn (for example, at a timing that is pseudo-randomly managed by node 3).

A node 3 that receives a beacon signal transmitted by another node 3 stores information contained in the received beacon signal, for example, in the storage unit 305 (S12). The transmission and reception of the beacon signal may be performed for each channel on which the node 3 operates (in other words, for each available channel).

The scanning process (S11) may therefore be referred to as a "channel scan." Note that a node 3 that receives a beacon signal may stop transmitting the beacon signal on the channel on which the beacon signal was received.

Each node 3 can store BSS-related information contained in beacon signals received from other nodes 3, thereby managing information on surrounding nodes 3 with which it can communicate via wireless links (hereinafter sometimes referred to as "surrounding node information"). By each node 3 storing and managing the surrounding node information, available wireless links (which may also be read as "channels") are managed by each node 3, as shown in FIG. 7, for example. This completes link setup of the wireless BH line, and the mesh links are linked up in the BH network.

In this manner, a mesh-like wireless link using the IBSS mode is formed (or constructed) between the nodes 3. The mesh-like wireless link constructed using the IBSS mode as described above may be referred to as an IBSS mesh link.

As described above, in the example of Figures 1A and 1B, among the nodes 3, the antenna 360 of CN#0 has directivity toward SN#1, which is the downstream node 3. And the antenna 360-1 of SN#1 has directivity toward CN#0, which is the upstream node 3. Therefore, in the link setup procedure, the beacon signal transmitted by CN#0 is received by SN#1 and does not have to be received by a node 3 other than SN#1. Also, the beacon signal transmitted by SN#1 may be received by CN#0.

Note that the link setup procedure shown in FIG. 7 is an example of constructing a mesh link by transmitting and receiving beacon signals between nodes 3, but the present invention is not limited to this. For example, other signals may be used to construct the mesh link. Alternatively, the mesh link may be manually set depending on the installation positions of the nodes 3.

Figure 8 shows a first example of a mesh link in the wireless communication system shown in Figures 1A and 1B.

As shown in FIG. 8, the wireless link available to CN#0 may be identified as the wireless link between CN#0 and SN#1. Furthermore, the wireless links available to each of SN#1 to SN#6 may be determined by the reach of the beacon signal transmitted by each node 3.

Note that even if the antenna 360 of CN#0 has directivity toward SN#1, a beacon signal transmitted by CN#0 may be received by a node 3 other than SN#1. Also, a beacon signal transmitted by a node 3 other than SN#1 may be received by CN#0. In such a case, the wireless links available to CN#0 may include a wireless link between CN#0 and a node 3 other than SN#1.

Figure 9 shows a second example of a mesh link in the wireless communication system shown in Figures 1A and 1B.

Unlike FIG. 8, in FIG. 9, the wireless links available to CN#0 may include the wireless link between CN#0 and SN#2.

(Tree Routing over IBSS Mesh Links)
Next, tree routing on an IBSS mesh link is described.

(Example of CN operation)
10 is a flowchart showing an example of the operation of CN3 including tree routing control on an IBSS mesh link according to one embodiment. The flowchart in FIG. 10 may be considered to be executed in the control unit 304 (e.g., tree routing control unit 343) of CN3.

As shown in FIG. 10, the control unit 304 of CN3 monitors, for example, whether a specific event has been detected (S31; NO). A "specific event" may include, for example, the startup of CN3, the operation of a reset button, and the arrival of a specific timing. An example of a "specific timing" is, for example, a transmission timing set to transmit a route control packet on a regular or irregular basis.

When the route control packets are periodically transmitted, the transmission period may be constant, or since the tree route constructed in this embodiment is asymptotically stable, it may be changed according to the number of times the flowchart in FIG. 10 is executed. Also, for example, as shown in FIGS. 1A and 1B and 2A and 2B, a specified time may be set to a "specific timing" or may be set by the user of the wireless communication system 1 so that the tree route is updated when the exterior wall construction of a certain floor is completed and construction of the next floor is started, when the height of the tower crane is changed, or when the number of nodes 3 increases (or decreases) according to the progress of the construction work.

If a specific event is detected (S31; YES), the control unit 304 of CN3 generates a route control packet and transmits (broadcasts) the route control packet to a neighboring SN3 identified based on the neighboring node information, for example, via the wireless communication unit 302 (S32).

For example, when the start of CN3 is detected and when the timing to send a route construction packet is detected, a route construction packet is sent to the surrounding SN3. When the operation of the reset button is detected and when the timing to send a reset packet is detected, a reset packet is sent to the surrounding SN3.

After transmitting the route control packet, the control unit 304 monitors, for example, whether a certain period of time has elapsed (timeout) (S33). If no timeout is detected (S33; NO), the control unit 304 may transition the process to S31.

On the other hand, if the passage of a certain period of time is detected (S33; YES), the control unit 304 may start transmitting data packets (S34).

As described above, CN3 transmits (broadcasts) a route control packet to each of the multiple wireless links that are linked up with surrounding nodes 3, thereby propagating the route control packet to each of the SN3s that make up the BH network.

As shown in FIG. 8, when the wireless link available to CN#0 is identified as the wireless link between CN#0 and SN#1, the neighboring node information of CN#0 includes SN#1 and does not include an SN different from SN#1. In this case, the route control packet sent by CN#0 may be received by SN#1.

Also, as shown in FIG. 9, if the wireless links available to CN#0 include the wireless link between CN#0 and SN#1 and the wireless link between CN#0 and SN#2, the peripheral node information of CN#0 may include SN#1 and SN#2. In this case, the route control packet transmitted by CN#0 may be received by SN#1 and SN#2. In this embodiment, the antenna 360 of CN#0 has directivity toward SN#1, which is the downstream node 3, and the antenna 360-1 of SN#1 has directivity toward CN#0, which is the upstream node 3. Therefore, the reception quality of the route control packet received by SN#1 is higher than the reception quality of the route control packet received by SN#2. For example, the radio wave propagation loss of the route control packet received by SN#1 is smaller than the radio wave propagation loss of the route control packet received by SN#2.

(SN operation example)
Next, an example of the operation of SN3 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of the operation of SN3 including tree route control on an IBSS mesh link according to one embodiment. The flowchart in Fig. 11 may be considered to be executed in the control unit 304 (e.g., tree route control unit 343) of SN3.

SN3 monitors, for example, whether a route control packet is received in the wireless communication unit 302 (S51; NO).

If reception of a route control packet is detected (S51; YES), the control unit 304 of SN3 checks the type of the route control packet. For example, the control unit 304 checks whether the received route control packet is a reset packet or a route construction packet (S52 and S54).

If the received route control packet is a reset packet (S52; YES), the control unit 304 performs an initialization process (S53). The initialization process may include, for example, the following processes.
Deselecting links that are selected as valid tree routes in the neighboring node information Initializing the stored route metric to an initial value (e.g., the maximum value)

After the initialization process, the control unit 304, for example, transmits (floods) the received reset packet to neighboring SN3 (S53a). The reset packet may include an identifier (ID). Each node 3 may store the ID included in the received reset packet.

If the ID of the received reset packet matches the stored ID, in other words, if it indicates that the reset packet was previously sent (transferred), each node 3 will not further transmit the reset packet. This makes it possible to prevent the reset packet from looping in the BH network.

On the other hand, if the received route control packet is not a reset packet (S52; NO), the control unit 304 checks whether the route control packet is a route construction packet (S54).

If the received route control packet is a route construction packet (S54; YES), the control unit 304 refers to the surrounding node information (S55) and calculates the propagation quality index (e.g., radio wave propagation loss) of the link that received the route construction packet (S56).

Based on the calculated radio wave propagation loss, the control unit 304 calculates the route metric (S57). For example, the control unit 304 calculates the cumulative radio wave propagation loss as the new route metric by adding the calculated radio wave propagation loss and the propagation quality index included in the received route construction packet.

Then, the control unit 304 compares the new route metric with the old route metric that was stored before the new route metric was calculated, and determines whether the route metric needs to be updated (S58).

For example, if the new route metric is smaller than the old route metric, the control unit 304 determines to update the old route metric to the new route metric (S58; YES). In response to this determination, the control unit 304 selects the upstream wireless link that corresponds to the new route metric in the surrounding node information as a valid tree route (update of selected link; S59).

In response to updating the selected link, the control unit 304, for example, transmits (broadcasts) a route construction packet including the new route metric to the neighboring SN3 identified in the neighboring node information (S60).

Then, the control unit 304 monitors whether a certain period of time has elapsed (timeout) (S61). If a timeout is not detected (S61; NO), the control unit 304 may proceed to the process of monitoring the reception of a route control packet (S51). If a timeout is detected (S61; YES), the control unit 304 may start the process of transmitting a data packet (S62).

If the received route control packet is neither a reset packet nor a route construction packet (S52 and S54; NO), the control unit 304 may transition to the process of monitoring the reception of a route control packet (S51).

Also, if the calculated new route metric is greater than or equal to the old route metric and it is determined that updating the selected link is not necessary (S58; NO), the control unit 304 may transition to the process of monitoring the reception of a route control packet (S51).

As described above, in response to receiving a route construction packet, SN3 selects one of the multiple wireless links that are linked up with surrounding node 3 based on the route metric. This allows a tree route based on the route metric to be constructed and updated in the BH network where the mesh links are linked up.

The tree route control shown in FIG. 10 and FIG. 11 is an example, and the present invention is not limited thereto. For example, the construction and update of the tree route may be manually controlled. For example, after the nodes 3 are installed, the administrator of the wireless communication system 1 may set the tree route in advance according to the positions of the nodes 3 and/or the radio wave conditions of the nodes 3. In this case, the link setup procedure shown in FIG. 7 and the tree route control shown in FIG. 10 and FIG. 11 may not be executed.

As shown in FIG. 8, when the wireless link available to CN#0 is identified as the wireless link between CN#0 and SN#1, SN#1 receives the route construction packet sent by CN#0. In this case, SN#1 selects the wireless link between CN#0 and SN#1 as a valid tree route, and therefore SN#1 is selected as the downstream node (next hop destination) of CN#0.

Figure 12 is a diagram showing an example of a tree route constructed in the first example of the mesh link shown in Figure 8. When SN#1 selects the wireless link between CN#0 and SN#1 as a valid tree route, a tree route is constructed starting from CN#0 and with SN#1 selected as the downstream node (next hop destination) of CN#0, as shown in Figure 12.

Also, as shown in FIG. 9, if the wireless links available to CN#0 include the wireless link between CN#0 and SN#1 and the wireless link between CN#0 and SN#2, both SN#1 and SN#2 may receive the route construction packet transmitted by CN#0. In this embodiment, the antenna 360 of CN#0 has directivity toward SN#1, which is the downstream node 3, and the antenna 360-1 of SN#1 has directivity toward CN#0, which is the upstream node 3. Therefore, the reception quality of the route construction packet received by SN#1 from CN#0 is higher than the reception quality of the route construction packet received by SN#2 from CN#0. For example, the radio wave propagation loss of the route construction packet received by SN#1 from CN#0 is smaller than the radio wave propagation loss of the route construction packet received by SN#2 from CN#0.

In such a case, the route metric of the direct route between CN#0 and SN#2 is greater than the route metric of the route between CN#0 and SN#2 that includes the wireless link between CN#0 and SN#1 and goes through SN#1. Therefore, SN#2 does not select the wireless link between CN#0 and SN#2 as a valid tree route, but instead selects the wireless route between CN#0 and SN#2 that goes through SN#1 as a valid tree route.

Figure 13 is a diagram showing an example of a tree route constructed in the second example of the mesh link shown in Figure 9. SN#2 selects the wireless route between CN#0 and SN#2 via SN#1 as a valid tree route, and a tree route is constructed starting from CN#0 and with SN#1 selected as the downstream node (next hop destination) of CN#0, as shown in Figure 12.

As described above, the wireless communication system 1 of this embodiment has multiple nodes 3 including CN#0, SN#1, and SN#2. The horizontal plane in which CN#0 is located is different from the horizontal plane in which SN#1 is located. CN#0 is equipped with an antenna 360 having directivity toward SN#1. SN#1 has antennas 360-1 and 360-2. Antenna 360-1 has directivity toward CN#0. The control unit 304 of SN#1 performs at least one of the following processes: processing a downstream wireless signal received by antenna 360-1 and transmitting it from antenna 360-2 to SN#2; and processing an upstream wireless signal received by antenna 360-2 and transmitting it from 360-1 to CN#0. With this configuration, CN#0 establishes a wireless link with SN#1, and CN#0 can communicate wirelessly with SN#2, which has difficulty connecting directly with CN#0, via SN#1, making it easy to build a three-dimensional wireless route that includes the vertical direction.

In the above-described embodiment, an example was described in which SN#1 was provided on a tower crane. The tower crane autonomously changes its height depending on the progress of construction work. Therefore, by providing SN#1 on a tower crane, even if construction progresses to an upper floor, for example, it is not necessary to set up a new installation position for SN#1, and a three-dimensional wireless route can be easily constructed.

In addition, in the above-described embodiment, the antennas with directional characteristics of CN#0 and SN#1 have a degree of freedom in the direction of their directivity, so even if the positional relationship between CN#0 and SN#1 changes as construction work progresses, the wireless route can be maintained by fine-tuning the direction of the directivity.

In addition, in the above-described embodiment, a wireless communication environment can be constructed without connecting nodes with wires, so that, for example, when a temporary (or provisional) wireless communication environment has completed its role, it can be easily removed.

The tower crane shown in the above embodiment is an example of a so-called mast climbing type in which the base of the tower crane is provided outside the area of the building, but the present disclosure is not limited to this. For example, the tower crane may be a so-called floor climbing type in which the base of the tower crane is located inside the area of the building. In the case of a floor climbing type tower crane, as with the mast climbing type, the rotation base of the tower crane is located above the top floor of the building, so SN3 may be provided at the rotation base as in the above embodiment.

In the above embodiment, an example in which one tower crane is provided has been shown, but multiple tower cranes may be provided. In this case, SN3 may be provided on each of the multiple tower cranes, or on some of the multiple tower cranes, or one SN3 may be provided on the tower crane closest to CN3. For example, in this case, the directivity of the antenna of CN3 may be directed to the SN3 of the tower crane closest to CN3, or to the SN3 of the tower crane with the best wireless communication environment with CN3. For example, if the antenna of CN3 has a configuration in which it can be directed to multiple directions or the directivity can be switched over time, it may be directed to each of the SN3s of the tower cranes. In addition, when SN3 is provided on multiple tower cranes, the wireless link between the SN3 of one tower crane and the SN3 of another tower crane may be included in the tree route.

In the above-mentioned embodiment, a building construction site has been used as an example, but the present invention is not limited to this. The present invention may be applied to an environment in which a three-dimensional wireless route, including the vertical direction, is constructed. For example, the present invention may be applied to civil engineering sites such as underground tunnel excavation. Even when civil engineering progresses underground, the present invention can be applied to construct a three-dimensional wireless route, for example, between a CN installed above ground and an SN installed underground.

REFERENCE SIGNS LIST 1 Wireless communication system 3 Wireless node 5 Backbone network 7 Terminal device 31 Processor 32 Memory 33 Storage 34 Input/output (I/O) device 35, 36 Wireless interface (IF)
37, 39 Wired Interface (IF)
38 Bus 301, 302 Wireless communication unit 303 Wired communication unit 304 Control unit 305 Memory unit 341 Scan processing unit 342 Node management unit 343 Tree route control unit 344 IPT control unit 350, 360 Antenna 3431 Route control packet generation unit 3432 Route metric calculation unit 3433 Tree route update unit

Claims (8)

A core node is disposed on the exterior of a building in which at least a portion of the exterior wall construction is incomplete, and is located on a first horizontal plane;
a wireless repeater that is located on a second horizontal plane that is higher than the first horizontal plane and corresponds to a position equal to or higher than the top floor of the area where the exterior wall construction of the building has been completed, and that communicates with the core node;
a wireless device located inside the building and communicating with the wireless repeater;
The core node includes:
a first antenna having directivity toward the wireless repeater;
The wireless repeater includes:
a second antenna having directivity toward the core node;
A third antenna; and
a processing unit that performs at least one of a process of processing a downlink radio signal received by the second antenna and transmitting the signal from the third antenna to the radio device, and a process of processing an uplink radio signal received by the third antenna and transmitting the signal from the second antenna to the core node;
A wireless communication system comprising: The third antenna has directivity toward the radio.
2. The wireless communication system according to claim 1. The processing unit has a multi-input multi-output (MIMO) transmission/reception circuit.
3. A wireless communication system according to claim 1 or 2. The processing unit includes:
selecting a wireless link between the wireless repeater and the core node as a relay target by processing based on information on a propagation loss of each wireless link between the wireless repeater and the core node and between the wireless repeater and at least one of the wireless devices;
A wireless communication system according to any one of claims 1 to 3. The wireless repeater is provided at a position above the building in a construction machine installed on or around the building,
2. The wireless communication system according to claim 1. The construction machine is a crane.
6. The wireless communication system according to claim 5. The wireless device is located within a range of the height of a floor where the exterior wall construction of the building has been completed.
2. The wireless communication system according to claim 1. A wireless node located on a first horizontal plane corresponding to a position on or above the top floor of an area where exterior wall construction of a building has been completed,
A first antenna is disposed outside the building where at least a part of the exterior wall construction is incomplete, and has directivity toward a core node located on a second horizontal plane lower than the first horizontal plane;
A second antenna;
a processing unit that performs at least one of a process of processing a downlink radio signal received by the first antenna and transmitting the signal from the second antenna to a radio device, and a process of processing an uplink radio signal received by the second antenna and transmitting the signal from the first antenna to the core node;
A wireless node comprising:

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