JP7352241B2 - Wireless communication system, wireless communication method, and wireless node - Google Patents

Description

The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless node.

In existing cellular communication systems, a base station that provides wireless access lines for user equipment and a backbone network (sometimes referred to as a core network) are connected by a wired backhaul (BH) network. many.

On the other hand, one form of realizing a new generation of mobile communications is wireless multi-hop connectivity between multiple wireless nodes (e.g., base stations or access points) that provide wireless communication areas with a radius of several tens of meters. A system or network is being considered.

Japanese Patent Application Publication No. 2005-143046 International Publication No. 2011/105371

Multi-stage relay wireless backhaul technology for wireless LAN access points RF World No. 33, pp89-105, February 2016; Hiroshi Furukawa

There is room for consideration regarding rescue control when some wireless links become unusable in a wireless BH network.

A wireless communication system according to one aspect includes a plurality of wireless nodes that configure a backhaul network, and a first node of the plurality of wireless nodes is configured to connect a plurality of wireless links established between the plurality of nodes. a transmitting unit that transmits a control signal including information specifying at least one first wireless link among the wireless nodes, and a second node of the plurality of wireless nodes includes a receiving unit that receives the control signal; configuring a second route as an alternative to the first route for data communication using the first wireless link among the remaining wireless links other than the first wireless link specified by the information of the received control signal; and a control unit that determines a second wireless link based on an index regarding the propagation quality of one or more wireless links through which the control signal passed.

In the wireless communication method according to one aspect, a first node of a plurality of wireless nodes configuring a backhaul network connects at least one first wireless link of a plurality of wireless links established between the plurality of nodes. A second node of the plurality of wireless nodes receives the control signal and transmits a control signal including information specifying a link, and a second node of the plurality of wireless nodes receives the first wireless node specified by the information of the received control signal. Propagation of one or more wireless links through which the control signal passes through a second wireless link that constitutes an alternative route to the data communication route using the first wireless link among the remaining wireless links excluding the link. Make decisions based on quality metrics.

The wireless node according to one aspect is one of a plurality of wireless nodes configuring a backhaul network, and is at least one first wireless link of a plurality of wireless links established between the plurality of nodes. out of the remaining wireless links excluding the first wireless link specified by the information of the received control signal, the first wireless link is used. and a control unit that determines a second wireless link constituting an alternative route to the data communication route based on an index regarding the propagation quality of one or more wireless links through which the control signal passed.

According to a non-limiting aspect of the present disclosure, rescue control can be realized when some wireless links become unusable in a wireless BH network.

1 is a block diagram illustrating a configuration example of a wireless communication system according to an embodiment. FIG. FIG. 3 is a diagram illustrating a protocol stack of a wireless node according to an embodiment. FIG. 2 is a block diagram illustrating an example of a hardware configuration of a wireless node according to an embodiment. FIG. 2 is an image diagram of data transfer in the upstream direction between hop links to which BF transmission is applied according to an embodiment. FIG. 2 is an image diagram of data transfer in the downstream direction between hop links to which BF transmission is applied according to an embodiment. It is a figure showing an example of BF control concerning one embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of a control unit of a wireless node according to an embodiment. 2 is a flowchart illustrating an example of the operation of a core node (CN) according to an embodiment. 3 is a flowchart illustrating an example of the operation of a slave node (SN) according to an embodiment. 3 is a flowchart illustrating an example of the operation of a slave node (SN) according to an embodiment. FIG. 3 is a diagram illustrating an example of a route construction packet according to an embodiment. FIG. 3 is a diagram illustrating an example of a routing table stored in a wireless node according to an embodiment. 12 is a diagram showing an example of alternative relay routes shown in the routing table shown in FIG. 11. FIG.

Embodiments will be described below with appropriate reference to the drawings. The same elements are given the same reference numerals throughout this specification unless otherwise specified. The following description, along with the accompanying drawings, is intended to describe exemplary embodiments and is not intended to represent the only embodiment. For example, when the order of operations is shown in the embodiment, the order of operations may be changed as appropriate within a range that does not cause any inconsistency in the overall operation.

When a plurality of embodiments and/or modifications are illustrated, part of the configuration, function, and/or operation of one embodiment and/or modification may be different from the other embodiments to the extent that no contradiction occurs. and/or may be included in the modified example, or may be replaced with corresponding configurations, functions, and/or operations of other embodiments and/or modified examples.

Further, in the embodiments, more detailed explanation than necessary may be omitted. For example, in order to avoid unnecessary redundancy of explanation and/or obscurity of technical matters or concepts and to facilitate understanding of those skilled in the art, Detailed explanation may be omitted. Further, redundant description of substantially the same configuration, function, and/or operation may be omitted.

The accompanying drawings and the following description are provided to assist in understanding the embodiments, and are not intended to limit the claimed subject matter. Further, the terms used in the following description may be replaced with other terms as appropriate to aid understanding by those skilled in the art.

<Findings that led to this disclosure>
By making the BH network, which is one of the infrastructures of mobile communication, wireless by using wireless multi-hop, it is possible to eliminate the need for laying wired cables and reduce the installation cost required for introducing a mobile communication system. Therefore, for example, when temporarily (or provisionally) introducing a mobile communication system, it is effective to make the BH network wireless by wireless multi-hop.

For example, when a large number of small cell base stations (wireless nodes) are installed in the service area of a mobile communication system to cover the service area, it is effective to make the BH network wireless using wireless multi-hop; It has been widely introduced mainly in wireless LAN (eg, Wi-Fi (registered trademark)) systems.

Furthermore, the 5th generation mobile communication system (5G), which is expected to start commercial services worldwide from around 2019 or 2020, uses radio waves in high frequency bands. The high frequency band is, for example, a centimeter wave band (3 GHz to 30 GHz, sometimes referred to as Super High Frequency (SHF)) or a millimeter wave band (30 GHz to 300 GHz, sometimes referred to as Extreme High Frequency (EHF)). (in some cases). In high frequency bands, the loss of radio wave propagation is large, so the application of beam forming (BF) technology is being considered to compensate for the loss of radio wave propagation.

For example, even when BF technology is applied to a high frequency band access line, the cell radius is 100 meters to several hundred meters, so the cell size becomes small (small cell). Therefore, the number of base stations installed becomes enormous, making it difficult to install wired cables for the BH network. Since wirelessization of the BH network eliminates the need to install wired cables, it is also effective when applying BF technology in high frequency bands.

For example, in the method described in Non-Patent Document 1 (sometimes referred to as "wireless backhaul engine (BE)"), a wireless multi-hop relay route is constructed in advance, and a communication session occurs (data transfer occurs). ), data frames are transferred between wireless nodes along the constructed relay route. This method is a wireless BH technology that separates "route control" for constructing a relay route and "frame transfer (for example, sometimes written as "relay transfer")" of data.

In this embodiment, beam forming (BF) is performed using high frequency bands such as next generation Wi-Fi (IEEE802.11ax and/or IEEE802.11ay) and 5th generation mobile communication system (5G). As an example, apply the wireless BH technology described in Non-Patent Document 1 to the wireless standard to be used.

In order for each node to perform relay transfer (transmission and reception of data along a relay route) using the BF, "route control" for constructing a relay route is performed before transmitting and receiving data. Route control may include establishing a hop link including BF control processing, and constructing a relay route based on the established hop link. By knowing in advance the constructed relay route, each node can improve the efficiency of relay transfer. Here, the BF control processing may include transmission weight control or transmission directivity control of the transmitting antenna at each node, and reception weight control or reception directivity control of the receiving antenna of each node. Further, a hop link may correspond to a mesh link between a certain node and N nodes (N is an integer of 1 or more) around the node.

Although it is possible to perform relay transfer by executing the BF control process when a communication session occurs in a node and relay transfer of data is performed, the time required for relay transfer may increase. Therefore, there is a possibility that the throughput of the BH line will be reduced. Here, the occurrence of a communication session means, for example, that a packet to be relayed and forwarded is on standby at a node, and the node has acquired a wireless channel (radio resource) in Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). You can handle it.

Furthermore, in the method described in Non-Patent Document 1, each node measures the received power of the route control packet (for example, RSSI (Received Signal Strength Indicator) measurement) for the route control packet that is broadcasted. and determine the quality (eg, assigned metric) of each node's hop links. By each node determining the quality of the hop links, route control of relay transfer is efficiently performed.

For example, when BF is applied in data relay transfer, each node transmits and receives unicast routing control packets using BF instead of broadcasting route control packets at the route control stage. The quality of each hop link may be determined by By determining the quality of each hop link based on the transmission and reception of route control packets in unicast to which BF is applied, it is possible to more appropriately select a route for relaying data to which BF is applied.

On the other hand, when BF is applied in data relay transfer, it is possible to communicate using two or more beams with directivity in different directions, so each node can communicate at the same frequency and at the same time. , can communicate with two or more nodes. In other words, when BF is applied in data relay transfer, spatial reuse of frequencies is possible. For example, a root node branching in a relay path can receive data transmitted by multiple neighboring transmitting nodes at the same time and on the same frequency. In this case, each node is desired to process data from a plurality of nodes in parallel at the same time, or to perform time-sharing processing at high speed, for example.

Furthermore, in high frequency bands, because radio waves travel in a straight line, if there is a shield (or obstacle) such as a building, tree, person, or vehicle between the transmitting point and the receiving point, the transmitting point will Loss in radio wave propagation to the receiving point tends to increase. Therefore, the line quality of the wireless link is likely to deteriorate, and in the worst case, the wireless link may be disconnected.

Therefore, the inventors of the present application adapted the method described in Non-Patent Document 1 to apply the BF technology in a high frequency band, and for example, This led to the development of a higher throughput wireless BH network technology that takes advantage of the company's wide bandwidth.

The following is a non-limiting example of wireless BH technology that applies BF to a BH link, which can achieve high throughput by taking advantage of the wide bandwidth of the high frequency band, and can compensate for radio wave propagation loss in the high frequency band. explain.

<System configuration example>
FIG. 1 is a block diagram illustrating a configuration example of a wireless communication system according to an embodiment. The wireless communication system 1 shown in FIG. 1 exemplarily includes a plurality of nodes 3. In FIG. 1, as a non-limiting example, eight nodes 3 are illustrated with node numbers #0 to #7. The number of nodes 3 may be 2 or more and less than 8, or may be 9 or more.

Each node 3 is an example of a wireless device capable of wireless communication. Therefore, each of the nodes 3 may be referred to as a "wireless node 3".

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

Each of the nodes 3 is capable of wirelessly communicating with another node 3 when located in the service area of the other node 3 . The plurality of nodes 3 form, for example, a wireless backhaul (BH) network that wirelessly relays communication between the backbone network 5 and the terminal device 7. A "wireless BH network" may be referred to as a "BH network" by omitting "wireless".

A "BH network" may also 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 backbone network 5 is, for example, a large-scale communication network such as the Internet. The "backbone network" may also be referred to as a "core network", a "global network", or the like.

The routes or sections over which wireless signals are transmitted in the BH network are "wireless BH communication path," "wireless BH transmission path," "wireless BH line," "wireless BH connection," "wireless BH channel," and "wireless link." , or may be interchangeably read as "hop link". In these terms, "wireless" may be omitted, and "BH" may be read as "relay".

On the other hand, for example, a section in which radio signals are transmitted between the terminal device 7 and the BH network may be referred to as a "radio access line" or a "radio access channel." In these terms, "wireless" may be omitted.

Note that in the following description, the term "signal" may be replaced with a term for a unit in which a signal is divided in time, such as a "frame" or a "packet."

Different frequencies (channels) may be assigned to the wireless BH line and the wireless access line.

Some of the nodes 3 among the plurality of nodes 3 may be connected to the backbone network 5 by wire. FIG. 1 exemplifies a mode in which one node #0 is connected to the backbone network 5 by wire. For example, a LAN cable or an optical fiber cable may be applied to the wired connection.

Node #0 wired to the backbone network 5 may be referred to as a "core node (CN)." Among the plurality of nodes 3 forming the BH network, each node 3 other than CN #0 may be referred to as a "slave node (SN)." For example, in FIG. 1, nodes #1 to #7 are all SNs. Note that the number of CNs may be two or more, and the number of SNs may be less than seven or eight or more.

Note that in FIG. 1, #0 to #7 assigned to each node 3 is an example of information used to identify each node 3 (hereinafter sometimes abbreviated as "node identification information"). The node identification information may be any information that can uniquely identify each node 3 in the same BH network, and may be, for example, a node number, a device identifier, or address information. A non-limiting example of address information is a MAC (Media Access Control) address.

The BH network may have one or more tree structures (which may be referred to as "tree topology") with one CN3 (#0) as the root node. Note that the structure of the BH network is not limited to the tree structure.

In the tree topology, SN3s without child nodes may be referred to as "leaf nodes" and SN3s with child nodes may be referred to as "internal nodes." For example, in FIG. 1, SN #2, #6, and #7 all correspond to "leaf nodes." Further, SN #1, #3, #4, and #5 all correspond to "internal nodes."

The wireless BH line may include a "downlink" in the direction from the core node 3 to the leaf node 3 and an "uplink" in the direction from the leaf node 3 to the core node 3. "Downlink" and "uplink" may be called "downlink (DL)" and "uplink (UL)," respectively, following the names used in cellular communications.

The flow of signals (downlink signals) in the "downlink" may be referred to as "downstream", and the flow of signals (uplink signals) in the "uplink" may be referred to as "upstream". Each of the "downlink signal" and "uplink signal" may include a control signal and a data signal. The "control signal" may include signals that do not fall under the "data signal."

Note that a "child node" may be considered to correspond to a node (downstream node) connected downstream of a certain node via a wireless link when focusing on a "downlink". When focusing on the downlink, a node connected upstream of a certain node via a wireless link may be referred to as a "parent node" or "upstream node." When focusing on the "uplink", the relationship between the "child node" (downstream node) and the "parent node" (upstream node) is reversed.

Furthermore, when focusing on the "downlink", the "core node" may be referred to as the "start node" or "origin node", and the "leaf node" may be referred to as the "end node" or "edge node". It's okay. An "internal node" may also be referred to as an "intermediate node" or a "relay node."

A tree-structured route (tree topology) in the BH network may be constructed, for example, based on the metric of the route from the CN 3 to the specific SN 3 (hereinafter sometimes abbreviated as "route metric"). An index (hereinafter referred to as "propagation quality index") indicating the quality or performance of radio wave propagation in the wireless section from CN 3 to specific SN 3 may be used as the route metric.

Non-limiting examples of propagation quality indicators include radio signal received power or strength (eg, RSSI; Received Signal Strength Indicator), radio wave propagation loss, propagation delay, and the like. "Radio wave propagation loss" may be read as "path loss."

As the propagation quality index, one or a combination of two or more selected from the above index candidates may be used. Note that in this embodiment, an index related to route distance such as the number of hops may not be used as the propagation quality index.

For example, by transmitting a signal (for example, a control signal) starting from CN3, for each wireless section between the control signal transmitting node 3 and receiving node 3, the radio wave propagation loss of the corresponding wireless section is calculated at the receiving node 3. You can ask for it.

Then, each of the receiving nodes 3 transmits information on the calculated radio wave propagation loss by including it in the control signal, so that information on the cumulative radio wave propagation loss (in other words, cumulative value) can be communicated between nodes 3.

For example, each node 3 calculates a route metric based on the cumulative radio propagation loss for each upstream node candidate that is the transmission source of the control signal, and calculates, for example, the route metric that indicates the minimum among the upstream node candidates. Select one node 3. As a result, a tree-structured route with minimum radio wave propagation loss is constructed.

The tree-structured route (hereinafter sometimes referred to as "tree route") can be updated dynamically or adaptively by periodically or irregularly transmitting a control signal starting from the CN3.

Hereinafter, processing or control related to the construction and updating of such tree routes may be referred to as "route control" for convenience.

Note that at least one of the downlink and uplink of the BH line may include a wired line. When at least one of the downlink and uplink of the BH line includes a wired line, the route metric for the wired section is calculated using a predetermined value (for example, the minimum value) that is smaller than the expected propagation loss in the wireless section. good.

When the terminal device 7 is located in the service area of any SN 3, it communicates with the backbone network 5 via the BH line by connecting to any of the plurality of SNs 3 forming the BH network via a wireless access line. Note that the terminal device 7 may be connected to any one of the SNs 3 (in FIG. 1, SN#3 as an example) via a wired line (wired IF). As a non-limiting example, the terminal device 7 may be a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal.

Examples of wireless access lines include CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), and SC-FDMA (Single Access). Carrier Frequency Division Multiple Access), etc. may be applied. OFDMA may be implemented by, for example, wireless technologies such as IEEE802.11, IEEE802.16, LTE (Long Term Evolution), and LTE-Advanced.

MIMO (Multiple Input Multiple Output) technology using an antenna array having a plurality of antenna elements may be applied to all or part of the downlink and/or uplink in the wireless BH line and/or the radio access line.

For example, even if beamforming using an antenna array is performed in the downlink and/or uplink in any one or more of the sections between CN3 and SN3, between SN3 and SN3, and between SN3 and terminal device 7, good. Note that beamforming using an antenna array will be described later.

In addition, in the following, the term "transmission" of a signal may be interchanged with other terms such as "relay", "transfer", "propagation", "transmission", "routing", or "forwarding" of a signal. It's okay. A "relay" of a signal may be read as a "bridge" of a signal.

Further, the term "transmission" of a signal may include meanings such as "flooding", "broadcast", "multicast", or "unicast" of a signal. The term "connection" of a line may be taken to mean a state in which a wired and/or wireless communication link is "established" or "linked up."

The term "apparatus" may be interchanged with terms such as "circuit," "device," "unit," or "module." The term "interface (IF)" may be interchanged with terms such as "adapter," "board," "card," or "module," or "chip."

The node 3 and/or the terminal device 7 may be an IoT (Internet of Things) device. IoT allows various "things" to be equipped with wireless communication functions. Various "things" equipped with a wireless communication function can communicate by connecting to the backbone network 5 via a wireless access line and/or a wireless BH line.

For example, the IoT device may include a sensor device, a meter (measuring device), and the like that have a wireless communication function. The node 3 and/or the terminal device 7 may be a device having a sensing function and/or a monitoring function, such as a surveillance camera and/or a fire alarm equipped with a sensor device and/or a meter. A BH network may therefore correspond to a sensor network and/or a monitoring network, for example. Note that wireless communication by IoT devices is sometimes referred to as MTC (Machine Type Communications). Therefore, IoT devices are sometimes referred to as "MTC devices."

An example of the protocol stack and an example of the hardware configuration of the node 3 that constitutes the wireless communication system 1 will be described below.

<Example of protocol stack of node 3>
FIG. 2 is a diagram illustrating a protocol stack of a wireless node according to an embodiment. As shown in FIG. 2, layer 2.5 is located between layer 2 and layer 3, and is responsible for wireless multi-hop transmission of the BH line.

Layer 1 may be referred to as the PHY layer. In layer 1, wireless transmission having a BF function is performed, for example. For example, layer 1 complies with IEEE802.11ay and/or 5G (NR) wireless standards.

At layer 2.5, "mesh link establishment" and "route control" are separated and independent.

In "mesh link establishment", each node scans surrounding nodes, links up mesh links in the backhaul network, and stores information (node information) regarding the linked up surrounding nodes. Here, a peripheral node of a certain node 3 may correspond to, for example, a node that exists in a position where it can receive a signal (for example, a beacon signal) transmitted by a certain node 3.

In "route control", multi-hop routes between each slave node and the core node are dynamically constructed. In the two-layer hierarchy of layer 2.5, "mesh link establishment" is positioned at the lower layer of layer 2.5, and "route control" is positioned at the upper layer of layer 2.5.

Due to the layer 2.5 hierarchization, when a transmitting node performs frame transfer of data, it is possible to know in advance to which node the data should be transferred, and data transfer can be performed with the delay time minimized.

When applying high frequency band BF transmission to wireless multi-hop transmission on a BH line, the following three processes are executed in the protocol stack of the wireless node 3 including layer 2.5, for example.

(1) In the mesh link establishment process, each node stores information (node information) regarding neighboring nodes, and BF control process for BF transmission between nodes is executed. Note that the BF control will be described later.

(2) In route control processing, the route control packet, which is the subject of RSSI measurement for evaluating the propagation quality between nodes, is unicast using the BF between nodes instead of being broadcast. Each node receives unicast routing control packets and performs RSSI measurements.

When data is sent and received using BF between nodes, evaluation of the propagation quality in sending and receiving unicast routing control packets using BF is also performed in the routing control process that determines multi-hop routes. By doing so, a more accurate multi-hop route can be constructed than by transmitting and receiving broadcast route control packets.

However, in the route control process, evaluation of the propagation quality between nodes may be performed using broadcast route control packets. When evaluation of the propagation quality between nodes is performed using route control packets that are broadcast, the number of times the route control packets are transmitted can be suppressed, so the execution time of route control can be shortened. Further, even when evaluating the propagation quality between nodes using broadcast route control packets, accurate evaluation is possible to some extent.

(3) In route control processing, a relay route is determined in advance when some of the wireless links between nodes included in the mesh link are excluded (in other words, not used). A relay route determined in route control with some wireless links excluded may be referred to as an "alternative relay route." Then, when the line quality of the wireless link between nodes deteriorates, a relay route that is switched to an alternative relay route that does not include the deteriorated wireless link is determined.

In high frequency bands, for example, the millimeter wave band, radio waves travel in a straight line, and if there are obstacles such as buildings, trees, people, vehicles, etc. between the transmitting point and the receiving point, The loss of radio wave propagation becomes extremely large. Therefore, if the line quality of the wireless link between a wireless node that is a transmission point and a wireless node that is a reception point deteriorates significantly, relay transmission is performed using a multi-hop route that does not include the degraded wireless link due to route control processing. A route is selected and relay transmission is performed on that route.

<Example of hardware configuration of node 3>
FIG. 3 is a block diagram showing an example of the hardware configuration of the wireless node 3 according to one embodiment. The configuration example illustrated in FIG. 3 may be common to CN3 and SN3. As shown in FIG. 3, the node 3 includes, 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. good.

Note that in the hardware configuration example illustrated in FIG. 3, the hardware may be increased or decreased as appropriate. For example, addition or deletion of arbitrary hardware blocks, division, integration in arbitrary combinations, addition or deletion of the bus 38, etc. may be performed as appropriate.

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

The node 3 may include a plurality of processors 31. Furthermore, the processing in the node 3 may be executed by one processor 31 or by a plurality of processors 31. In one or more processors 31, a plurality of processes may be executed simultaneously, in parallel, or sequentially, or may be executed by other techniques. Note that the processor 31 may be a single-core processor or a multi-core processor. Processor 31 may be implemented using one or more chips.

One or more functions of the node 3 are exemplarily realized by loading predetermined software into hardware such as the processor 31 and the memory 32. Note that "software" may be interchanged with other terms such as "program," "application," "engine," or "software module."

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

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

The processor 31 is an example of a processing unit, and controls the entire computer by operating an OS, for example. 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, registers, and the like.

Further, the processor 31 reads out one or both of a program and data from the storage 33 to the memory 32 and executes various processes, for example.

The memory 32 is an example of a computer-readable recording medium, and may be configured using at least one of ROM, EPROM, EEPROM, RAM, SSD, etc., for example. 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 be referred to as registers, cache, main memory, work memory, or main storage.

The storage 33 is an example of a computer-readable recording medium, and includes an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive (HDD), a flexible disk, a magneto-optical disk (for example, a compact disk, a digital versatile disk, Blu-ray discs), smart cards, flash memory (eg, cards, sticks, key drives), flexible discs, magnetic strips, and the like. Storage 33 may also be called an auxiliary storage device. The above-mentioned recording medium may be, for example, a database including one or both of memory 32 and storage 33, a server, or other suitable medium.

The input/output (I/O) device 34 is an example of an input device that receives a signal from outside the node 3 and an output device that outputs a signal from the node 3 to the outside. Input devices may illustratively include one or more of a keyboard, mouse, microphone, switch, button, and sensor. Output devices may illustratively include one or more of a display, a speaker, and a light emitting device such as a light emitting diode (LED).

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

Note that the input/output (I/O) device 34 may have separate configurations for input and output. Further, the input/output (I/O) device 34 may have an integrated input and output structure, such as a touch panel display, for example.

The wireless IF 35 exemplarily transmits and receives wireless signals to and from the terminal device 7 over an access line. The wireless IF 35 may include, for example, one or more antennas 350, a baseband (BB) signal processing circuit, a MAC processing circuit, an upconverter, a downconverter, and an amplifier (not shown).

The BB signal processing circuit of the wireless IF 35 includes, for example, an encoding circuit and a modulation circuit for encoding and modulating a transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding a reception signal. It's fine.

The antenna 350 may be, for example, an m-multiplex MIMO antenna that multiplexes m signals. For example, m may be 8, or m may be a positive integer different from 8.

The wireless IF 36 exemplarily transmits and receives wireless signals to and from other SNs 3 on the BH line. Note that an example of the internal configuration of the wireless IF 36 will be described later.

The wireless IF 35 and the wireless IF 36 may be referred to as a wireless communication unit 35 and a wireless communication unit 36, respectively.

The wired IF 37 exemplarily transmits and receives signals to and from the backbone network 5 and/or the upstream node 3 by wire. Further, the wired IF 39 exemplarily transmits and receives signals to and from the terminal device 7 and/or the downstream node 3 by wire. For example, a network interface compliant with the Ethernet (registered trademark) standard may be used for the wired IFs 37 and 39. Note that the wired IFs 37 and 39 only need to be provided at least in the CN3, and do not need to be provided in the SN3 (in other words, they may be optional for the SN3). However, when part of the BH line is wired, 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, DSP, ASIC, PLD, and FPGA. For example, processor 31 may be implemented including at least one of these pieces of hardware. Part or all of the functional blocks described later in FIG. 5 may be realized by the hardware.

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."

The wireless IF 36 (wireless communication unit 36) will be explained.

For example, input data from the input/output (I/O) device 34 is divided into n series of transmission data #1 to transmission data #n (n is an integer of 1 or more) and input to the wireless IF 36. be done. Here, n represents the maximum number of directivity directions that node 3 can transmit simultaneously. For example, if n is 1, node 3 transmits data in one direction (eg, one destination node). If n is 2 or more, the node 3 simultaneously transmits data in multiple directions (eg, multiple destination nodes).

The transmission digital BF control unit 361 performs encoding and modulation processing on each of the n series of transmission data, for example, to generate n series of data signals. The transmission digital BF control unit 361 weights signals (multiplies transmission weights) to form beams in the directions of the transmission directivity of each of the n sequences, for example.

A Digital to Analog Converter (DAC) 362 and an RF transmitter 363 are provided, for example, corresponding to each of the n data signal sequences.

For example, each of n weighted data signals is input to the DAC 362 . The DAC 362 converts the input data signal from a digital signal to an analog signal, for example, and outputs it to the RF transmitter 363.

The RF transmitter 363 converts, for example, a baseband analog signal input from the DAC 362 into a carrier frequency band analog signal.

The output of the RF transmitting section 363 is converted into an analog signal supplied to each antenna element of an antenna (sub-array) 360 composed of antenna elements (antenna elements) that transmit radio waves, for example, in a transmitting analog BF control section 364. Ru. Note that the transmission analog BF control section 364 may include, for example, a power divider, a phase shifter, and an amplifier. Furthermore, the transmission analog BF control section 364 may output the number of analog signals according to the configuration of the antenna 360, which will be described later. For example, if the antenna 360 has n subarrays and each subarray has 256 antenna elements, the transmission analog BF control unit 364 may output n×256 analog signals.

For example, the duplexer 365 separates a transmitted signal and a received signal. For example, an analog signal output from the analog BF control section 364 is supplied to the antenna 360 through a duplexer 365.

Antenna 360 has, for example, n subarrays. Each subarray has, for example, 256 antenna elements. For example, n may be 4 or a positive integer different from 4. Further, the number of antenna elements in each subarray may be 256 elements or may be different from 256 elements. Further, the number of antenna elements may differ for each subarray. The greater the number of antenna elements per subarray, the narrower and sharper the directivity of the subarray.

For example, when n is 4, the signals supplied through the duplexer 365 are sent out from the four subarrays with directivity in each of the four directions.

A signal received at an antenna 360 having n subarrays is input to a reception analog BF control unit 366 through a duplexer 365, for example. A number of analog signals depending on the configuration of the antenna 360 may be input to the reception analog BF control section 366. For example, if the antenna 360 has n subarrays and each subarray has 256 antenna elements, n×256 analog signals may be input to the reception analog BF control unit 366.

The reception analog BF control section 366 includes, for example, a low noise amplifier (LNA) and a phase shifter. The reception analog BF control unit 366 performs control (adjustment) to match the phase of the reception signal according to the reception directivity to be formed. The reception analog BF control section 366 divides the processed reception signal into n signal sequences according to the received subarray, and outputs them to the RF reception section 367.

The RF receiving section 367 and the analog to digital converter (ADC) 368 are provided, for example, corresponding to each of the n signal sequences.

The RF receiving section 367 converts, for example, a carrier frequency band analog signal input from the reception analog BF control section 366 into a baseband analog signal.

The ADC 368 converts, for example, a baseband analog signal input from the RF receiving section 367 into a digital signal.

For example, the reception digital BF control unit 369 weights the signals associated with the direction of reception directivity of each of the series of n digital signals (multiplying the reception weight). Separate and process. For example, the reception digital BF control unit 369 performs demodulation processing and decoding processing on each of the n-series signals, generates n-series reception data, and inputs/outputs (I/O) the n-series reception data. Output to device 34.

In addition, in BF control (determination of BF directivity), which will be described later in FIG. A process of determining the receiving directivity direction (the receiving directivity direction of the wireless node on the receiving side) is performed. In this determination process, for example, a unique data pattern for power measurement is used as the transmission data.

A configuration including the processor 31, memory 32, storage 33, etc. of the wireless node 3 may be referred to as a control unit 40. The control unit 40 controls, for example, data transmission and reception operations including layer 2.5 processing of the wireless communication unit 36, data transmission and reception operations of the wireless communication unit 35, and data transmission and reception operations via the wired IFs 37 and 38. The configuration of the control section 40 will be described later.

Next, an example in which the wireless node 3 performs data transfer using BF in the wireless communication system 1 shown in FIG. 1 will be described with reference to FIGS. 4 and 5.

FIG. 4 is an image diagram of data transfer in the upstream direction between hop links using BF transmission according to an embodiment. FIG. 4 shows the backbone network 5, CN#0, and SN#1 to SN#5 in the wireless communication system 1 shown in FIG. 1. Further, FIG. 4 shows an example of the transmission directivity of SN#1 to SN#5 when a signal is transmitted in the upstream direction (direction from the leaf node toward CN#0).

This disclosure describes the application of a wireless BH technology that separates "route control" for constructing a relay route and "frame transfer" of data to a wireless standard that uses BF in a high frequency band. Let's take one example. In FIG. 4, as a result of route control, each wireless node knows which wireless node is the data transmission destination. Further, in this embodiment, as a result of route control, each wireless node knows the wireless node to which data is transmitted on the alternative relay route. More specifically, the storage 33 installed in each node contains information indicating to which node data should be sent in upstream data transfer (for example, transmission destination (destination, transfer destination, or BF transmission information) and parameter information that can be transmitted by BF to that node may be stored. For example, the parameter information includes information for realizing a drive current to be supplied to each antenna element making up the antenna array. When each node receives data to be transferred in the upstream direction, it realizes BF transmission by calling up information stored in the storage 33.

In order to acquire a radio channel (radio resource) for transmission, each transmitting node that has data to transmit checks whether or not there is an empty channel prior to transmission. For example, confirmation of free channels is performed by means such as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). The transmitting node that has acquired a free channel performs data transmission using the BF over a wireless link established in advance at layer 2.5 with the receiving node. Note that "layer 2.5" or "layer belonging to layer 2.5" may be referred to as a "mesh layer" for convenience. The MAC layer processing, which is the processing for acquiring a wireless channel, may be similar to CSMA/CA etc. in this embodiment as well.

In FIG. 4, a radio link from SN#4 to SN#3, a radio link from SN#3 to SN#1, a radio link from SN#2 to CN#0, a radio link from SN#1 to CN, This also indicates that BF transmission is performed on the wireless link from SN#5 to SN#1. Note that a wireless link to which BF is applied may be referred to as a wireless beam link. In a wireless beam link, a wireless node on the transmitting side forms a transmitting beam, and a wireless node on the receiving side forms a receiving beam to perform data communication (transmission and reception of data). Note that in the wireless beam link, at least one of the wireless nodes on the transmitting side and the receiving side may form a beam and perform data communication. These BF transmissions may be performed at different times. Alternatively, some or all of these BF transmissions may be performed at the same time as each other. Alternatively, some or all of these BF transmissions may be performed at partially overlapping times on the time axis. In other words, FIG. 4 is just an image diagram of data transfer. For example, the transmission beams (transmission directivity) shown in FIG. 4 do not need to be formed at the same time. For example, at the same time that data is being transferred in the upstream direction between SN#5 and SN#1, data is being transferred in the downstream direction between SN#3 and SN#4. The situation is also assumed.

When BF transmission is applied, the transmission distance of the wireless link can be extended compared to when BF transmission is not applied. For example, BF transmission from SN#2 to CN#0 in FIG. 3 can be realized by extending the transmission distance.

By applying BF transmission, radio waves transmitted from a source wireless node (source node) have sharp directivity in the direction (desired direction) of a destination wireless node (destination node). Furthermore, the energy of radio waves transmitted in a direction different from the desired direction is suppressed. Further, at the receiving destination node, by applying BF reception, the energy of the received radio waves arriving from a direction different from the desired direction is suppressed. Received radio waves arriving from a direction different from the desired direction may be considered as interference waves at the destination node.

Therefore, in data transfer using BF transmission, the probability that the same frequency can be used for data transmission in the vicinity at the same time (same time or time width that includes the same timing) is greater than when BF transmission is not applied. . For example, in FIG. 4, data transmission from SN#2 to CN#0 and data transmission from SN#1 to CN#0 can be performed at the same frequency and at the same time. In this case, CN#0 can receive data transmitted from SN#2 and data transmitted from SN#1 at the same frequency and at the same time. Furthermore, data transmission from SN#3 to SN#1 and data transmission from SN#5 to SN#1 can be performed at the same frequency and at the same time. In this case, SN#1 can receive data from SN#3 to SN#1 and receive data from SN#5 to SN#1 at the same frequency and at the same time.

In this case, the wireless nodes (for example, CN#0 and SN#1) may receive data from multiple different streams (at least two streams in the example of FIG. 4) at the same time. For example, the example hardware configuration of the wireless node described in FIG. 3 is capable of receiving data of a plurality of different sequences (n sequences).

The fact that the same frequency can be used in the vicinity at the same time leads to a significant increase in the frequency utilization efficiency of the wireless BH line, and it is possible to increase the system capacity of the wireless communication system.

Note that when determining free channels using CSMA/CA, a wireless node applies Request to Send/Clear to Send (RTS/CTS) to determine one transmitting node to acquire the transmission right. good. In this case, even if the wireless node has a configuration in which it does not receive multiple different series of data at the same time, it is possible to minimize the probability that multiple data transfers will collide at the receiving node. For example, in this embodiment, each node uses BF to transfer data, so each node that is not involved in the transfer either does not receive unnecessary radio waves, or even if it does, the radio waves are very weak. be. Therefore, each node that is not included in the relay route will have less interference while data transfer is not being performed using that node as the route, and for example, it will be able to perform other data transfers or as described below. It becomes possible to perform training at the same time.

Note that in this embodiment, if deterioration in the line quality of the hop link is detected during relay transfer and/or in the process of monitoring the line quality of the hop link, each wireless node changes the frame transfer route. Switch to an alternative relay route. Note that the process of monitoring the line quality of the hop link may be referred to as self-healing process. Information regarding alternative relay routes is also updated at predetermined intervals and stored by each wireless node.

Switching of an alternative relay route during data transfer in the upstream direction will be explained using as an example the case in which deterioration in the line quality of the hop link (uplink) going from SN #3 to SN #1 is detected in FIG. 4. do.

Note that hereinafter, a hop link from node #j to node #k may be written as L(j, k). j and k are identifiers for identifying nodes, and are, for example, integers greater than or equal to 0. For example, in FIG. 4, the hop link from SN#3 to SN#1 is written as L(3,1).

Further, a relay route may be expressed using L(j,k). For example, if the relay route includes a hop link from node #j to node #k, the relay route may be expressed as including L(j,k).

In Figure 4, when SN#3 detects deterioration in the line quality of L(3,1), SN#3 changes the route used for frame transfer before the detection to L(3,1). Switch to the corresponding alternative relay route. Here, the alternative relay route corresponding to L(3,1) is, for example, the optimal route determined under the condition of excluding L(3,1).

For example, in FIG. 4, if the alternative relay route corresponding to L(3,1) includes L(3,5), SN#3 uses the data transfer destination for frame transfer before detection. SN#1, which is the transfer destination on the alternate route corresponding to L(3,1), is switched to SN#5, which is the transfer destination on the alternative relay route corresponding to L(3,1).

For example, a wireless node may determine deterioration in line quality based on an ACK/NACK response from a destination node in response to data transfer to a destination wireless node (destination node). For example, if an ACK is not returned, the wireless node may determine that the line quality of the hop link with the destination node has deteriorated. Further, for example, the wireless node may determine that the line quality of the hop link with the destination node has deteriorated when the number of times that ACK is not returned consecutively becomes a predetermined number (for example, three times) or more. Note that the case where ACK is not returned may include the case where NACK is returned.

The wireless node determines that the line quality of the hop link has deteriorated when the number of times that ACK is not returned consecutively reaches a predetermined number (for example, 3 times) or more, thereby reducing the line quality of the hop link. It is possible to determine whether or not this has continued for a predetermined period of time or longer. This makes it possible to avoid switching to an alternative relay route even though the line quality deterioration of the hop link is instantaneous (for example, less than a predetermined time).

FIG. 5 is an image diagram of data transfer in the downstream direction between hop links using BF transmission according to an embodiment. Similar to FIG. 4, FIG. 5 shows the backbone network 5, CN#0, and SN#1 to SN#5 in the wireless communication system 1 shown in FIG. Further, FIG. 5 shows an example of the transmission directivity of CN#0 and SN#1 to SN#5 when a signal is transmitted in the downstream direction (direction from CN#0 to leaf nodes).

In FIG. 5, as in FIG. 4, as a result of route control, each wireless node knows which wireless node is the data transmission destination. Further, in this embodiment, as a result of route control, each wireless node knows the wireless node to which data is transmitted on the alternative relay route. The difference from the upstream data transfer in Figure 4 is that unlike the upstream data transfer, which only requires data to be transferred toward CN#0, the downstream data transfer has a different destination leaf node. be. Note that although the same route is illustrated in FIGS. 4 and 5, the present disclosure is not limited thereto. The route for data transfer in the downstream direction and the route for data transfer in the upstream direction may be different from each other. For example, when radio wave conditions change from moment to moment, the data transfer route may also change from moment to moment.

In order to acquire a radio channel (radio resource) for transmission, each transmitting node that has data to transmit checks whether or not there is an empty channel prior to transmission. For example, confirmation of free channels is performed by means such as CSMA/CA. A transmitting node that has acquired a free channel performs data transmission using a BF over a wireless link that has been established in advance at layer 2.5 (for example, a mesh layer) with a receiving node. The MAC layer processing, which is the processing for acquiring a wireless channel, may follow a method such as CSMA/CA in this embodiment as well.

In Figure 5, there is a wireless link from CN#0 to SN#2, a wireless link from CN#0 to SN#1, a wireless link from SN#1 to SN#3, and a wireless link from SN#1 to SN#5. This indicates that BF transmission is performed in the link and the wireless link from SN#3 to NS#4. These BF transmissions may be performed at different times. Alternatively, some or all of these BF transmissions may be performed at the same time as each other. Alternatively, some or all of these BF transmissions may be performed at partially overlapping times on the time axis.

When BF transmission is applied, the transmission distance of the wireless link can be extended compared to when BF transmission is not applied. For example, BF transmission from CN#0 to SN#2 in FIG. 5 can be realized by extending the transmission distance.

Similar to FIG. 4, by applying BF transmission, the radio waves transmitted from the source node have sharp directivity in the direction of the destination node (desired direction). Furthermore, the energy of radio waves being sent in a direction different from the desired direction is suppressed. Further, at the receiving destination node, by applying BF reception, the energy of the received radio waves arriving from a direction different from the desired direction is suppressed. Received radio waves arriving from a direction different from the desired direction may be considered as interference waves at the destination node.

Therefore, in data transfer using BF transmission, the probability that the same frequency can be used for data transmission in the vicinity at the same time is greater than when BF transmission is not applied. For example, in FIG. 5, CN#0 can transmit data to SN#2 and transmit data to SN#1 at the same frequency and at the same time. Further, SN #1 can transmit data to SN #3 and transmit data to SN #5 at the same frequency and at the same time.

In this case, the wireless nodes (for example, CN#0 and SN#1) may perform data transmission of multiple different streams (at least two streams in the example of FIG. 5) at the same time. For example, the example hardware configuration of the wireless node described in FIG. 3 can perform data transmission of a plurality of different sequences (n sequences).

Similar to the data transfer in the upstream direction in FIG. 4, in the data transfer in the downstream direction in FIG. 5, the same frequency can be used in the vicinity at the same time, which leads to a significant increase in the frequency utilization efficiency of the wireless BH line. Therefore, the system capacity of the wireless communication system can be increased.

Note that in this embodiment, as described above, if deterioration in the line quality of the hop link is detected during relay transfer and/or self-healing processing, each wireless node switches the frame transfer route to an alternative route. Switch to relay route. Information regarding alternative relay routes is also updated at predetermined intervals and stored by each wireless node.

Regarding switching of the alternative relay route for data transfer in the downstream direction, consider the case in which deterioration in the line quality of the hop link (downlink) (L (1, 3)) going from SN #1 to SN #3 in Fig. 5 is detected. Let me explain using an example.

In Figure 5, when SN#1 detects deterioration in the line quality of L(1,3), SN#1 transfers the route used for frame transfer before the detection to L(1,3). Switch to the corresponding alternative relay route. Here, the alternative relay route corresponding to L(1,3) is, for example, an optimal route determined under the condition of excluding L(1,3).

For example, in FIG. 5, if the alternative relay route corresponding to L(1,3) includes L(1,5) and L(5,3), SN#1 determines the data transfer destination before detection. SN#3, which is the transfer destination on the route used for frame transfer, is switched to SN#5, which is the transfer destination on the alternative relay route corresponding to L(1,3). In other words, SN#1 is set to SN#3 and SN#5 as transfer destinations in the route used for frame transfer before detection, but the alternative relay route corresponding to L(1,3) Then, SN#3 is excluded from the transfer destination.

Additionally, SN#5 corresponding to the leaf node on the route used for frame transfer before detection is set to SN#3 as the data transfer destination on the alternative relay route corresponding to L(1,3). Switch to relay node.

For example, a wireless node may determine deterioration in line quality based on an ACK/NACK response from a destination node in response to data transfer to a destination wireless node (destination node). For example, if an ACK is not returned, the wireless node may determine that the line quality of the hop link with the destination node has deteriorated. Further, for example, the wireless node may determine that the line quality of the hop link with the destination node has deteriorated when the number of times that ACK is not returned consecutively becomes a predetermined number (for example, three times) or more. Note that the case where ACK is not returned may include the case where NACK is returned.

The wireless node determines that the line quality of the hop link has deteriorated when the number of times that ACK is not returned consecutively reaches a predetermined number (for example, 3 times) or more, thereby reducing the line quality of the hop link. It is possible to determine whether or not this has continued for a predetermined period of time or longer. This makes it possible to avoid switching to an alternative relay route even though the line quality deterioration of the hop link is instantaneous (for example, less than a predetermined time).

<Example of BF control>
Next, an example of the above-mentioned BF control will be explained. FIG. 6 is a diagram illustrating an example of BF control according to an embodiment. In BF control, a wireless node determines the directivity of the BF. The BF control shown in FIG. 6 is an example of control for executing training related to BF. Note that the BF control shown in FIG. 6 may be executed under the control of the control unit 40 of the wireless node 3, for example.

For example, in BF control, a wireless node determines a transmission beam suitable for transmitting a signal to a wireless node with which it is communicating, from among a plurality of beams having directivity in different directions. In addition, in BF control, a wireless node determines a receiving beam suitable for receiving a signal transmitted from a wireless node with which it is communicating, from among a plurality of receiving beams having directivities in mutually different directions.

For example, in FIG. 6, transmission and reception are performed between a transmission initiating node (which may be referred to as an Initiator) that starts transmission and a destination node (which may be referred to as a Responder) that is the destination of a signal transmitted by the transmission initiating node. The signal to be used is shown.

For example, in the example of FIG. 6, a transmitting beam (transmitting directivity) having directivity in 64 different directions and a receiving beam (receiving directivity) having directivity in 64 different directions are prepared. Then, the wireless node determines one transmission beam and one reception beam in the optimal direction from each of the 64 directions. In the example of FIG. 6, the determination process is executed in four steps from STEP1 to STEP4. In addition, in FIG. 6, an example will be explained in which the beam in the optimal direction (optimal beam) is the beam that provides the maximum received power on the receiving side among the beams having directivity in 64 different directions.

In STEP 1, the transmission start node switches the directivity in 64 directions prepared in advance in a time-division manner (for example, sequentially) and transmits a signal. This process may be referred to as sector sweep. The signal transmitted by the transmission start node may include, for example, a data pattern sequence whose received power is to be measured. The destination node waits to receive a signal with the maximum beam width, and receives the signal transmitted by the sector sweep of the transmission start node with the maximum beam width. Note that reception with the maximum beam width may be, for example, reception of a beam without directivity or reception of a beam with omnidirectionality. The destination node then measures the received power for 64 different directivities and stores the measurement results. The measurement results to be stored may be all of the received power for the 64 directivity types, or some of them, for example, information regarding the directivity with the highest received power (for example, information about the directivity with the highest received power (for example, 1 of the index number assigned to each beam). (for example, #i)).

In STEP 2, the same processing as in STEP 1 is performed by replacing the signal transmitting side and receiving side in STEP 1. For example, the destination node time-divisionally switches the directivity among 64 directions prepared in advance and transmits the signal. The signal transmitted by the destination node may include, for example, a data pattern sequence whose received power is to be measured. Alternatively, the signal transmitted by the destination node may include the measurement result of the destination node in STEP 1 (for example, the index number #i of the beam having the directivity with the highest received power). The transmission start node waits to receive a signal with the maximum beam width, and receives the transmission signal by the sector sweep from the destination node with the maximum beam width. The transmission start node then measures the received power for 64 different directivities and stores the measurement results. The measurement results to be stored may be all of the received power for the 64 directivity types, or information regarding the directivity with the highest received power (for example, one of the index numbers assigned to each beam (for example, #r ).Furthermore, the transmission start node stores the measurement result of the destination node in STEP 1, which is included in the received signal.

In STEP 3, the transmission start node forms a transmission beam based on the measurement results reported in STEP 2, and transmits a signal to the destination node. For example, the transmission start node transmits a signal using the beam #i of the index number corresponding to the transmission directivity which is the directivity with the highest received power in STEP1. The signal transmitted by the transmission start node may include the measurement result of the transmission start node in STEP 2 (for example, the index number #r of the beam having the directivity with the highest received power). The destination node receives the signal transmitted by the transmission initiation node with the maximum beam width. The destination node stores the measurement result of the transmission starting node in STEP 2, which is included in the received signal.

In STEP 4, the destination node uses the directivity #r to send a response (Acknowledgment (ACK)) confirming that the BF control process (i.e., the confirmation process of the directivity #i and the directivity #r) has been successfully completed. Send it back to the starting node. The transmission start node receives ACK on beam #i and confirms completion of the BF control process.

Note that in the BF control process shown in FIG. 6, an optimal transmission beam is determined by executing a sector sweep (transmission sector sweep) during signal transmission. Then, the receiving beam having the directivity corresponding to the optimal transmitting beam is determined to be the optimal receiving beam.

This embodiment is not limited to the BF control process shown in FIG. For example, each node may determine the receive beam separately from determining the transmit beam. For example, the optimal receive beam may be determined by performing a sector sweep (receive sector sweep) during signal reception. For example, in a reception sector sweep, the destination node time-divisionally switches the directivity among 64 directions prepared in advance, and receives the signal transmitted by the transmission start node using the maximum beam width. Then, the destination node may determine the beam having the highest directivity with the highest reception power as the optimal reception beam. In the reception sector sweep, the destination node and the transmission start node may exchange signal transmission and reception, and the transmission start node may determine the beam having the directivity with the highest reception power as the optimal reception beam.

The BF control process illustrated in FIG. 6 may be executed between a node and a terminal when applying BF transmission on an access line. In this case, the BF control process may be executed every time data transmission/reception occurs between the node and the terminal (or before data transmission/reception is performed).

On the other hand, in this embodiment, BF transmission is applied in the BH line. In this case, link up of the hop link including BF control processing may be performed at predetermined time intervals (predetermined frequency) independently of data transfer. The BF control process corresponds to a process of determining (or finalizing) information on beam directivity #i and directivity #r between each wireless node. Information on the determined beam directivity #i and directivity #r may be referred to as BF control information. Further, link up refers to a state in which, when data transfer is executed, information used for data transfer (for example, BF control information) is known in each wireless node and preparation for data transfer is completed.

BF control information can be updated by performing link up of hop links including BF control processing at predetermined time intervals (predetermined frequency).

In this way, the process of linking up a hop link and updating information used for data transfer including BF control information may be referred to as mesh link establishment. In this embodiment, by including BF control processing in the mesh establishment, when data transfer between wireless nodes occurs, data transfer using BF transmission can be immediately executed. Establishing a mesh link may be regarded as establishing a radio beam link with neighboring nodes.

Next, a configuration example of the control unit 40 of the wireless node 3 will be described.

FIG. 7 is a block diagram showing an example of a functional configuration of the control unit 40 of the wireless node 3 according to an embodiment. The functions of the control unit 40 include a scan processing unit 401, a node management unit 402, a frame transfer processing unit 403, a route control unit 404, a mesh link establishment unit 405, and an IPT (Interminent Periodic Transmission) control unit 406.

The scan processing unit 401 performs processing to scan neighboring nodes and link up mesh links in the BH network. In this embodiment, in order to apply BF to data transmission and reception between wireless nodes, scan processing section 401 executes a scan including BF control processing in cooperation with mesh link establishment section 405, which will be described later.

The node management unit 402 stores information regarding peripheral nodes that the wireless node 3 has grasped as a result of the processing by the scan processing unit 401.

Further, the node management unit 402 stores a routing table that stores node numbers of transfer destination (destination) nodes when performing relay data transfer. For example, the node management unit 402 updates the routing table when a relay route is updated in route control. The routing table is an upstream routing table that stores forwarding destination nodes on a route heading toward the core node (uplink route), and a forwarding destination node that stores forwarding destination nodes on a route heading in the opposite direction from the core node (downlink route). and a downstream routing table.

The mesh link establishment unit 405 scans the BF control processing function for performing link up of the mesh link by applying the BF control described in FIG. 6 during the peripheral node scanning process executed by the scan processing unit 401. The information is provided to the processing unit 401. In cooperation with the mesh link establishment unit 405 and the scan processing unit 401, link up of the mesh link is executed at a predetermined frequency (period).

The mesh link establishment section 405 includes a BF control processing section 4051 and a BF parameter storage section 4052.

The BF control processing unit 4051 provides the scan processing unit 401 with a BF control processing function for performing link-up of mesh links by applying BF control.

The BF parameter storage unit 4052 stores parameters obtained by performing link-up of mesh links by applying BF control. The parameters may be conveniently referred to as "BF parameters" or "mesh link parameters." The mesh link parameters may include, for example, control information regarding the transmitting BF and control information regarding the receiving BF. Furthermore, the mesh link parameters may include, for example, an optimal transmit beam index and an optimal receive beam index for each of the peripheral nodes.

As the radio wave environment changes from moment to moment, by being able to update the latest mesh link parameters, accurate BF transmission can be performed in frame transfer between wireless nodes. In addition, the route control packets transmitted and received in the route control processing executed by the route control unit 404, which will be described later, can be executed by unicast using BF transmission and reception with neighboring wireless nodes instead of broadcast. . Therefore, more accurate route construction is possible.

The route control unit 404 controls the construction and updating of routes on mesh links by transmitting route control packets on mesh links. To construct and update a route, for example, as described later, information on a wireless link to be registered in the route (or excluded from the route) is selected (or the selection is canceled) from among multiple wireless links forming the mesh link. It may be done by

The route control unit 404 determines a dynamic route in the mesh link based on an index representing route quality called a route metric. Below, an example will be explained in which the smaller the value of the route metric, the better the line quality of the route. For example, the route control unit 404 evaluates the line quality between nodes by performing RSSI measurements of route control packets transmitted by nearby wireless nodes. The route control packet includes cumulative route metrics up to neighboring nodes.

The route control packet generation unit 4041 of the route control unit 404 generates a route control packet. The route control packet is an example of a control signal that is generated in the CN3 and propagated to each node 3 starting from the CN3 in the BH network.

The route metric calculation unit 4042 of the route control unit 404 determines the route metric of the hop link between the neighboring node and the own node obtained by RSSI measurement. The route metric calculation unit 4042 calculates the cumulative route metric up to the own wireless node based on the cumulative route metric included in the route control packet and the route metric between the neighboring nodes and the own node.

The route update unit 4043 of the route control unit 404 compares the route metric calculated by the route metric calculation unit 4042 with the route metric stored in the route update unit 4043, and determines whether to update the route. The route update unit 4043 determines to update the route when the calculated route metric is smaller than the stored route metric. When the calculated route metric is smaller than the stored route metric, the route corresponding to the calculated route metric is composed of multi-hop wireless links whose line quality is better than the route corresponding to the stored route metric. represents something.

This route control procedure can follow, for example, the route control method described in Non-Patent Document 1. However, when the BH line is intended for transmission and reception using BF in a high frequency band, the route control unit 404 may have, for example, the following two functions.

(1) In transmitting and receiving route control packets, BF transmission using BF control information determined by the BF control described in FIG. 6 is applied.

In route control, a more accurate route can be constructed by transmitting and receiving route control packets by unicasting with peripheral nodes using BF instead of broadcasting.

(2) In route control processing, when the line quality of a wireless link between nodes deteriorates, a multi-hop route that does not include the deteriorated wireless link is determined as a relay transmission path.

In high frequency bands, radio waves tend to travel in a straight line, and if there are obstacles such as buildings, trees, people, or vehicles between the transmitting and receiving points, the loss of radio wave propagation from the transmitting point to the receiving point increases. Easy to do. Therefore, in case the line quality of the wireless link between the transmission point and the reception point deteriorates and the wireless link is disconnected, for example, the route update unit 4043 included in the route control unit 404 updates the route. I do. In this embodiment, the millimeter wave band has been mainly described as an example, but the present invention is not limited to this band. For example, in a millimeter wave band or a higher frequency band, a short period of interruption of radio waves at a certain point in a wireless network may cause a situation in which communication in the wireless network is interrupted. According to this embodiment, the optimal tree route is updated periodically or aperiodically, so it is suitable for application in a communication environment of a millimeter wave band or a higher frequency band. For example, when a communication environment is realized, even if communication is normally good, the communication environment may deteriorate due to a vehicle stopped due to a traffic light, or the communication environment may deteriorate while a passerby crosses a route where BF is applied. may deteriorate. In the case of such temporary deterioration of the communication environment, if the environment uses a lower frequency band such as the microwave band, the communication speed will be reduced temporarily, but in the millimeter wave band, the communication speed will be reduced temporarily. This may result in a blockage. Therefore, it is preferable to apply this embodiment in a communication environment of a millimeter wave band or a higher frequency band.

Determination and updating of the relay route and the alternative relay route are executed by the core node transmitting a route control packet at a predetermined period, although details will be described later in FIG. 8 and subsequent figures. Note that the predetermined period may be set arbitrarily. However, as mentioned above, in the millimeter wave band or higher frequency band where radio wave propagation loss is large, when applying BF transmission and reception to compensate for radio wave propagation loss and secure the required transmission distance, the transmitting node and receiving node The deterioration of line quality due to the insertion of a shield between the lines is extremely large, and may even lead to communication interruption. From this point of view, it is desirable to eliminate the effects of this deterioration in line quality as quickly as possible. For example, it is desirable to quickly construct a new optimal relay route under conditions where a wireless link with degraded line quality exists. Therefore, the shorter the route control cycle (for example, the transmission cycle of route control packets in the core node), the better. However, an increase in the number of transmissions and receptions of route control packets may increase the traffic load and cause deterioration in the performance of the wireless communication system. In order to suppress deterioration in the performance of the wireless communication system, it is better to have a longer route control cycle. Therefore, the above-described predetermined period is not limited to being set to a uniform value (for example, a uniform optimal value). For example, in an environment where a wireless node is installed, interference such as the insertion of a shielding The period of route control may be determined for each wireless communication system, taking into consideration the frequency with which the triggering factor occurs and the degree of influence of deterioration in line quality on the QoS of the wireless communication system. According to this embodiment, in which an alternative relay route is determined in advance assuming a wireless link with deteriorated line quality, even if unexpected line quality deterioration occurs, relay transfer can be performed by switching to an alternative relay route. Can continue. Therefore, it is possible to avoid setting the route control cycle short, or reduce the number of route control operations, and prevent unexpected line quality deterioration without having to execute route control processing at an excessively short cycle. can.

For example, when the line quality of the wireless link deteriorates, in order to avoid a decrease in the throughput of the BH network or stop the BH network, and to suppress the delay time related to updating the BH network route, the relay route is It may be possible to switch to an alternative relay route excluding the wireless link whose quality has deteriorated. In addition, in order to avoid a decrease in the throughput of the BH network or stoppage of the BH network when the line quality of the wireless link deteriorates, and to suppress the delay time related to updating the route of the BH network, the core node transmits a route. The transmission cycle of control packets may be controlled. In other words, switching to an alternative relay route and controlling the transmission cycle of route control packets may be used together. For example, when the line quality of the wireless link deteriorates, switching to an alternative relay route may be performed, and the transmission period of the route control packet may be set short.

For example, the transmission cycle of route control packets may be controlled by the core node. Alternatively, the transmission cycle of route control packets may be instructed from the backbone network.

For example, the core node may set a short transmission period for the route control packets it transmits.

Alternatively, instead of uniformly shortening the transmission cycle of route control packets in a wireless BH line using a high frequency band, the transmission cycle of route control packets may be controlled based on a certain condition. For example, the core node counts the number of times per hour that the line quality of the wireless link significantly deteriorates (for example, deteriorates below a predetermined quality), and the larger the number of times, the shorter the transmission period of the route control packet is controlled. You may. In other words, the transmission period of the route control packet may be variably controlled in accordance with fluctuations in the line quality of the wireless link.

Alternatively, the core node may control the transmission cycle of route control packets based on a request from an application provided in the wireless communication system. For example, when the quality of service (QoS), which indicates the level of demand for suppressing temporary line disconnection time and/or delay time associated with line disconnection time requested by an application, is high, the transmission cycle of route control packets is may be set shorter. For example, applications that perform real-time data transmission, such as voice calls and video distribution, require high QoS.

Route update processing is a process performed by transmitting and receiving route control packets over a wireless link, so by variably controlling the transmission cycle of route control packets, the frequency of route update processing can be adaptively suppressed. Decrease in line throughput can be suppressed.

Further, in the route update process, the above-described determination and update of the alternative relay route may be executed. Each wireless node 3 has a function of determining and storing in advance an alternative relay route that does not use a wireless link with degraded line quality. The alternative relay route may be considered to be the optimal relay route under conditions that exclude wireless links with degraded line quality. Thereby, it is possible to avoid setting the transmission cycle of the route control packet to be too short, and it is possible to continue relay transmission on the BH line without any problems.

The process of constructing (determining) the relay route and the alternative relay route may be performed independently of the data transfer process, such as during a time period when no data transfer is occurring. Since the process of constructing (determining) the relay route and the alternative relay route can be executed less frequently, the influence on the decrease in the throughput of the BH line can be suppressed.

Furthermore, as will be described later in FIG. 9, by providing commonality in the processing methods for constructing a normal relay route and constructing an alternative relay route, it is easy to add or remove this function from the layer 2.5 software configuration. Can be done. Here, the normal relay route may correspond to a relay route determined without excluding each linked-up mesh link. In this embodiment, the "relay route" may indicate a normal relay route that is distinguished from the "alternative relay route."

In addition, in order to avoid switching to an alternative relay route when the deterioration of the line quality of the hop link is instantaneous, the wireless node determines whether the line quality will deteriorate if one frame transfer fails. Instead of determining that the line quality of the hop link has deteriorated, it may be determined that the line quality of the hop link has deteriorated when frame transfer has failed a predetermined number of times (for example, three times) in a row. A frame transfer failure may correspond to, for example, no ACK being returned from the receiving node.

For example, the IPT control unit 406 controls packet transmission timing by the wireless communication unit for the BH line according to a transmission cycle according to the frequency reuse interval.

The frame transfer processing unit 403 adds a layer 2.5 control information header to transfer data coming down from an upper layer (layer 3 or above) to layer 2.5, and converts it into a frame to be transferred at a lower layer (layer 2 or below). Execute the adjustment process.

(CN operation example)
Next, an example of the operation of the CN will be explained. FIG. 8 is a flowchart illustrating an example of the operation of the core node (CN) according to one embodiment. The flowchart in FIG. 8 may be considered to be executed in the control unit 40 of the CN, for example.

The control unit 40 sets the transmission cycle of the route control packet (S101).

The transmission cycle when periodically transmitting route control packets may be constant, and since the route constructed in this embodiment is asymptotically stable, the transmission cycle may vary depending on the number of times the flowchart in FIG. 8 is executed. may be changed. The predetermined time may be set to a "specific timing" or may be set by a user of the wireless communication system. Further, the control unit 40 may control the transmission cycle of the route control packet based on a certain condition. For example, the control unit 40 may count the frequency of line quality deterioration (line disconnection, etc.) of hop links, and variably control the transmission period of the route control packet according to the counted frequency. For example, the control unit 40 sets the transmission period of the route control packet to be shorter as the frequency of line quality deterioration increases. For example, the frequency of line quality deterioration of a hop link may be counted in a self-healing process described below.

The count may be performed by a self-healing process (corresponding to S105) in which the core node checks each slave node to see if the slave nodes are operating normally. In addition, if the QoS (Quality of Service), which indicates the level of demand for minimizing temporary line disconnection time and associated delay time of applications provided within the wireless communication system, is high, the route control packet transmission cycle may be changed. Variable control may be applied to make the length shorter.

For example, the control unit 40 monitors whether a specific event has been detected (S102). The "specific event" may include, for example, CN being activated, a reset button being operated, and a specific timing arriving. An example of the "specific timing" is, for example, a transmission timing set for regularly or irregularly transmitting a route control packet.

If a specific event is not detected (NO in S102), the process in S104 is executed.

When a specific event is detected (YES in S102), the control unit of the CN generates a route control packet, and transmits the route control packet to the neighboring SN identified based on the neighboring node information, for example, through the wireless communication unit. Send (S103). The route control packet may be broadcast or unicast using BF transmission.

For example, when the activation of the CN is detected and when the transmission timing of the route construction packet is detected, the route construction packet is transmitted to the neighboring SN. When the operation of the reset button is detected and when the transmission timing of the reset packet is detected, the reset packet is transmitted to the neighboring SN.

Next, the control unit 40 determines whether it is time to execute the self-healing process (S104). Self-healing processing is processing in which a core node checks whether a slave node is operating normally. For example, in a self-healing process, a core node sends a self-healing packet (which may be called a hello packet) to a slave node, and based on the response from the slave node, determines whether the slave node is operating normally. Check whether

If it is not the timing to execute the self-healing process (NO in S104), the process in S107 is executed.

If it is the timing to execute the self-healing process (YES in S104), the control unit 40 executes self-healing (S105). Then, the control unit 40 detects the frequency (number of times) of deterioration of the line quality of the hop link based on the result of self-healing (S106).

Next, the control unit 40 determines whether the self-healing execution period has elapsed (timed out) (S107).

If the self-healing execution period has not elapsed (timed out) (NO in S107), the process in S104 is executed.

If the self-healing execution period has elapsed (timed out) (YES in S107), the control unit 40 determines whether a specific event was detected in S102 (S108). In other words, the control unit 40 determines whether a route control packet has been transmitted.

If the specific event is not detected in S102 (NO in S108), the process in S101 is executed. If a specific event has been detected in S102 (YES in S108), the control unit 40 determines whether the execution period of the route control process has elapsed (timed out) (S109).

If the execution period of the route control process has not elapsed (timed out) (NO in S109), the process in S101 is executed.

If the execution period of the route control process has elapsed (timed out) (YES in S109), the control unit 40 sets a relay route (S110). For example, the control unit 40 sets a normal relay route while not detecting deterioration in the line quality of the current adjacent hop links on the upstream side and the downstream side. Further, for example, when the control unit 40 detects deterioration in the line quality of the current hop links adjacent to each other on the upstream side and the downstream side, the control unit 40 sets an alternative relay route excluding the hop link where the line quality has deteriorated.

Then, the control unit 40 may start data packet processing (data relay transfer) (S111). When the execution period of the route control process has elapsed (timed out), the data relay route between the core node and the slave node is updated to the latest state. Note that as a result of the route control process, the data relay route does not need to change before and after the route control process.

Next, the control unit 40 detects deterioration (for example, the frequency (number of times) of deterioration) of the line quality of the hop link (S112). For example, the control unit 40 may detect the frequency of line quality deterioration based on the response from the slave node in the self-healing process.

If deterioration in the line quality of the hop link is not detected (NO in S112), the flow ends. When deterioration in the line quality of the hop link is detected (YES in S112), the control unit 40 updates the frequency of deterioration in the line quality of the hop link (S113). Then the flow ends.

As described above, the core node transmits a routing control packet to each of the multiple wireless links linked up with the peripheral nodes (for example, unicast using BF transmission), thereby controlling the slave nodes that constitute the BH network. A route control packet is propagated to each.

Note that the process of determining a relay route may also be applied to determining an alternative relay route. An alternative relay route is a relay route that does not use a specific hop link. Note that in this embodiment, an example in which there is one specific hop link will be described as an example, but the present disclosure is not limited to this. A particular hop link may be a combination of two or more hop links. Even if the specific hop link is a combination of two or more hop links, an alternative relay route can be determined by the same process as in the case where there is only one specific hop link.

When it is detected that the line quality of the hop link has deteriorated in the relay transfer process and/or self-healing process by determining and/or updating the alternative relay route in advance, each wireless node The destination of frame transfer is switched based on the alternative relay route. This switching allows the relay transmission of the BH line to continue without interruption.

Similar to normal relay routes, alternative relay routes are route control packets that contain information on route metrics that reflect propagation quality indicators (referred to as link metrics) measured by RSSI measurements for each hop link. It may be determined by transmission and reception. The route control packet is propagated from the core node side toward the downstream wireless node side.

Note that in the case of an alternative relay route, unlike a normal relay route, the link metric for the excluded hop link is set (replaced) to a prescribed value corresponding to extremely low line quality. For example, if the lower the line quality, the larger the value of the link metric, the specified value may be an extremely large value, for example, computationally infinite (∞), or the upper limit of the possible values of the link metric. By setting (replacing) the link metric in this way, the alternative relay route is determined to be a relay route that propagates the route control packet in the same way as a normal relay route and does not include the hop link to be excluded.

In other words, the process of determining an alternative relay route can be executed in the same way as the process of determining a normal relay route, except for setting the link metric (replacing the link metric) described above.

Note that whether to determine an alternative relay route or to determine a normal relay route may be determined, for example, by the core node based on an event that occurs in S102 described above. Information (flag) indicating whether to determine an alternative relay route or to determine a normal relay route may be included in the route control packet transmitted by the core node in S103 described above. For example, determining an alternative relay route corresponds to determining an alternative relay route assuming that a certain wireless link is disconnected, so below, as an example, it will be shown that determining an alternative relay route is performed. The information may be described as "assumed amputation." In other words, the information (flag) indicating whether to determine an alternative relay route or a normal relay route indicates either "disconnection assumption" or "normal".

Furthermore, when the routing control packet includes information indicating that an alternative relay route is to be determined, the routing control packet may include information indicating hop links to be excluded in the alternative relay route. The hop links that are excluded in the alternative relay route may be referred to as "hop links that are assumed to be disconnected." Note that the configuration of the route control packet will be described later.

Non-limiting examples of propagation quality indicators (link metrics) include received power or strength of radio signals (eg, RSSI; Received Signal Strength Indicator), radio wave propagation loss, propagation delay, and the like. Also, for example, if the transmission technology specifications applied to each hop link are different, instead of using the RSSI to calculate the link metric (an index that reflects the line quality of the hop link), the RSSI and the transmission technology specifications are associated. Link throughput may be used to calculate link metrics. Examples of transmission technology specifications that determine link throughput include wireless standards (802.11n, 802.11ac, 802.11ax, 5GNR (5th generation mobile communications specification; 5G New Radio)), number of MIMO streams, adaptive modulation method, etc. . For example, if the RSSI is the same between the two hop links but the wireless standards are different between the two hop links, the link throughput will be different between the two hop links. In such a case, by using the link throughput in calculating the link metric, the reliability of the line quality of the constructed route can be improved. Note that the example in which link throughput is used to calculate the link metric may correspond to an example in which the lower the line quality, the smaller the value of the link metric.

Note that when link throughput is used as the link metric in the process of determining an alternative relay route, the link metric for the excluded hop link may be set (replaced) to a value corresponding to 0 bps. By setting (replacing) the link metric in this manner, the hop link to be excluded can be reliably excluded from the alternative relay route.

Furthermore, wired transmission such as a wired LAN cable or Power Line Communications (PLC) may be applied to some hop link transmission techniques in addition to or in place of wireless transmission. In this way, when the transmission technology specifications applied to each hop link are different, link throughput can be used to calculate the link metric or the route metric, which is a comprehensive index of the link metric for multiple hop links included in the relay route. It is possible to calculate a more accurate index of line quality. By using more accurate line quality, for example, it may be possible to construct a route with better line quality than when link throughput is not used.

For example, by transmitting a signal (e.g., a control signal) starting from the CN, it is possible for the receiving node to determine the radio wave propagation loss for each wireless section between the control signal sending node and the receiving node. can.

Then, each of the receiving nodes transmits the obtained radio wave propagation loss information by including it in the control signal, so that information on the cumulative radio wave propagation loss (in other words, the cumulative value) of the wireless section where the control signal propagated is transmitted. ) can be transmitted between nodes.

For example, each node calculates a route metric based on the cumulative radio propagation loss for each upstream node candidate that is a transmission source of a control signal, and selects a node with a minimum route metric from among the upstream node candidates. Choose one. As a result, a tree-structured route with minimum radio wave propagation loss is constructed. Each node may write, in at least one of the memory 32 and the storage 33, either or both of the selected transfer destination node information and the parameter information for BF transmission on the tree-structured relay route. Here, for example, when transfer destination node information or parameter information is stored in a server, a time lag occurs because each node reads the information from the server in order to use a tree-structured relay route. In order to instantly configure a tree-structured relay route without a time lag, it is desirable that the destination node information and/or parameter information be stored using a storage medium possessed by each node. The information stored by each node does not need to be limited to the above-mentioned transfer destination node information and/or parameter information.

(Example of SN operation)
FIG. 9 is a flowchart illustrating an example of the operation of a slave node (SN) according to an embodiment. An example of the operation of the SN will be described with reference to FIG. The flowchart in FIG. 9 may be considered to be executed in the control unit 40 of the SN.

The SN determines whether a self-healing hello packet is received by the wireless communication unit 36 of the BH line, for example (S201).

If the self-healing hello packet is not received (NO in S201), the process in S203 is executed.

When a self-healing hello packet is received (YES in S201), the control unit 40 of the SN reports the self-healing result to the CN (S202).

Next, the control unit 40 determines whether the route control packet is received by the wireless communication unit 36 of the BH line, for example (S203).

If the route control packet is not received (NO in S203), the process in S201 is executed. If a routing control packet is received (YES in S203), the control unit 40 of the SN checks the type of the routing control packet. For example, the control unit 40 checks whether the received route control packet is a reset packet (S204).

If the received route control packet is a reset packet (YES in S204), the control unit 40 performs initialization processing (S205). The initialization process may include, for example, the following process.
・Deselection of the link selected as a valid tree route in the surrounding node information ・Initialization of the stored route metric to the initial value (for example, maximum value)

After the initialization process, the control unit 40 transmits, for example, the received reset packet to the neighboring SNs (S206). Then, the process of S201 is executed. Note that the reset packet may include an identifier (ID). Each of the nodes may store the ID included in the received reset packet. Further, the reset packet may be transmitted by unicast or multicast.

If the ID of the received reset packet matches the stored ID, in other words, if it indicates that the reset packet has been transmitted (transferred) in the past, each node does not transmit the reset packet further. do not have. This can 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 (NO in S204), the control unit 40 checks whether the route control packet is a route construction packet (S207).

If the received route control packet is not a route construction packet (NO at S207), the process at S201 is executed. If the received route control packet is a route construction packet (YES in S207), the control unit 40 refers to peripheral node information (S208).

Then, the control unit 40 checks whether the flag of the received route control packet indicates "disconnection assumption" (S209).

If the flag of the received route control packet does not indicate "assumed disconnection" (NO in S209), the control unit 40 executes the process in S212.

When the flag of the received route control packet indicates "disconnection assumed" (YES at S209), the control unit 40 stores information about the hop link (for example, L(j, k)) that is included in the route control packet and is assumed to be disconnected. , and determines whether the own node is node #k (S210).

Note that in S210, in addition to determining whether the own node is node #k, it may be determined whether the source node of the received route control packet is node #j. In this case, "NO in S210", which will be explained below, may correspond to a case where the own node is not node #k and/or the source node is not node #j. Further, "YES in S210", which will be explained below, may correspond to a case where the own node is node #k and the transmission source node is node #j.

If the own node is not node #k (NO in S210), the control unit 40 executes the process of S212.

If the own node is node #k (YES in S210), the control unit 40 replaces the propagation quality index (link metric) (S211). For example, the propagation quality index may be replaced with a value (eg, infinity) that corresponds to the fact that L(j,k) is disconnected (or the line quality is extremely low). Then, the control unit 40 executes the process of S213.

The control unit 40 calculates a propagation quality index (for example, radio wave propagation loss) of the link that received the route construction packet (S212).

In other words, if the flag of the received route control packet is "assumed to be disconnected" and the own wireless node 3 is on the receiving side of a hop link that is expected to be disconnected, the radio wave quality index indicates that the hop link is disconnected. Replace it with a propagation quality index equivalent to that. The control unit 40 refers to the peripheral node information and instead of calculating the propagation quality index (for example, radio wave propagation loss) of the link that received the route construction packet, performs a process of replacing the propagation quality index.

Then, the control unit 40 calculates the route metric (S213). For example, the control unit 40 calculates the cumulative radio propagation loss by adding the calculated radio propagation loss or the replaced propagation quality index and the propagation quality index included in the received route construction packet. Calculate as new route metric.

Then, the control unit 40 compares the new route metric with the old route metric that was stored before the new route metric was calculated, and determines whether it is necessary to update the route metric (S214).

For example, if the new route metric is smaller than the old route metric, the control unit 40 determines to update the old route metric to the new route metric (YES at S214). Note that if it is determined not to update (NO in S214), the control unit 40 may execute the process in S201.

Then, the control unit 40 checks whether the flag of the received route control packet indicates "disconnection assumption" (S215).

If the flag of the received route control packet does not indicate "assumed disconnection" (NO in S215), the control unit 40 selects the upstream wireless link corresponding to the new route metric in the peripheral node information as a valid route ( Update of selected link) (S217).

Note that the selected link update process is executed when the flag of the route construction packet is "normal", and is not executed when the flag of the route construction packet is "disconnect setting".

If the flag of the received route control packet indicates "assumed disconnection" (YES in S215), the control unit 40 determines the upstream wireless link corresponding to the alternative relay route in the peripheral node information as a valid route, and It is stored in the relay route information (S216).

After updating the selected link or storing the alternative relay route information, the control unit 40 transmits, for example, a route construction packet including the new route metric to the neighboring SNs identified in the neighboring node information (S218). For example, the route construction packet may be transmitted by multicast or by unicast using BF transmission.

After that, the control unit 40 monitors whether a certain period of time has elapsed (timeout) (S219). If a timeout is not detected (NO in S219), the process in S201 is executed.

If a timeout is detected (YES in S219), the control unit 40 sets a relay route (S220). For example, the control unit 40 sets a normal relay route while not detecting deterioration in the line quality of the current adjacent hop links on the upstream side and the downstream side. Further, for example, when the control unit 40 detects deterioration in the line quality of the current hop links adjacent to each other on the upstream side and the downstream side, the control unit 40 sets an alternative relay route excluding the hop link where the line quality has deteriorated.

Then, the control unit 40 may start data packet transmission processing (relay transfer) (S221). The data packet transmission process may be, for example, a data packet transfer process to a destination node. The data packet transmission process is executed according to the relay route in the routing table that stores the node number of the transfer destination (destination) when relay transfer is performed. The routing table may include a downstream routing table and an upstream routing table. Each wireless node 3 stores adjacent hop links of alternative relay routes in the routing table when deterioration in line quality of the current adjacent hop links on the upstream side and downstream side is detected. Then, in the relay transfer process or self-healing process, if it is detected that the line quality of the current adjacent hop link described above has deteriorated, each wireless node 3 updates the frame based on the predetermined alternative relay route. Switch the forwarding destination. As a result, relay transmission on the BH line can be continued without a hitch. During route control, until a new relay route is finalized and the information regarding the new relay route is stored and updated in the memory 32 or storage 33, each node provides information on the forwarding destination node and information on the forwarding destination as an emergency measure. Parameter information for BF transmission with a node may be read from the memory 32 or storage 33 and relay transmission may be performed.

Next, the control unit 40 detects deterioration (for example, the frequency (number of times) of deterioration) of the line quality of the hop link (S222). For example, the control unit 40 may detect the frequency of line quality deterioration based on the response from the slave node in the self-healing process.

If deterioration in the line quality of the hop link is not detected (NO in S222), the flow ends. If deterioration in the line quality of the hop link is detected (YES in S222), the control unit 40 updates the frequency of deterioration in the line quality of the hop link (S223). Then the flow ends.

Note that if the received route control packet is neither a reset packet nor a route construction packet, the control unit 40 may shift the process to a route control packet reception monitoring process.

Furthermore, 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 unnecessary, the control unit 40 may also shift the process to the process of monitoring the reception of route control packets.

As described above, in response to receiving a route construction packet, the SN selects one of the multiple wireless links linked up with neighboring nodes based on the route metric. As a result, a tree route is constructed and updated based on the route metric in the BH network where the mesh link is linked up.

Further, when the flag of the route construction packet indicates "disconnection assumption", the SN selects one of the plurality of wireless links linked up with neighboring nodes based on the route metric. As a result, an alternative relay route is constructed and updated based on the route metric in the BH network where the mesh link has been linked up. The alternative relay route constructed and updated here does not include hop links that are assumed to be disconnected (hop links to be excluded).

In other words, by processing similar to normal relay route construction, the SN connects multiple wireless links that have been linked up in response to receiving a route construction packet whose "normal/disconnection assumption" flag is "disconnection assumption". can be determined based on the route metric under conditions excluding hop links that are assumed to be disconnected. As a result, in a BH network where mesh links are linked up, even if the line quality of some hop links suddenly deteriorates (for example, due to extremely large reductions or disconnections), the alternative relay route can be switched to the tree route. can be executed without delay. This allows for stable operation through rapid relay route switching, even in cases where the radio wave propagation loss from the transmitting point to the receiving point is extremely large and the line quality of the wireless link is significantly degraded in high-frequency bands with high straightness. It is possible to provide sustainable wireless BH network technology.

Next, an example of the configuration of a route control packet (route construction packet) will be described with reference to FIG. 10. FIG. 10 is a diagram illustrating an example of a route construction packet according to an embodiment.

The route construction packet includes a flag indicating "normal or expected to be disconnected", information on the wireless link expected to be disconnected, source node number, destination node number, route metric, and propagation quality measurement target (for example, RSSI measurement target) data. Contains series.

If the flag indicating "normal or disconnection assumption" is "normal", as explained in FIGS. 8 and 9, it is a route construction packet that dynamically constructs and updates a normal relay route. shows.

If the flag indicating "normal or disconnection assumed" is "disconnection assumed", this is a route construction packet for constructing and dynamically updating an alternative relay route, as explained in FIGS. 8 and 9. Show that. For example, an alternative relay route is constructed and updated in case a situation occurs in the future where the line quality of a part of the wireless link deteriorates and should not be included in the relay route.

The information on wireless links that are assumed to be disconnected includes information on hop links that are excluded in alternative relay routes. For example, when a hop link from wireless node #j to wireless node #k is excluded, the information on the wireless link that is assumed to be disconnected includes information representing L(j, k).

The source node number is a number that identifies the source node of the route control packet. For example, in a route control packet transmitted from wireless node #m to wireless node #n, the source node number may be set to #m.

The destination node number is a number that identifies the destination node of the route control packet. For example, in a route control packet sent from wireless node #m to wireless node #n, the destination node number may be set to #n.

Next, an example of an alternative relay route will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram illustrating an example of a routing table stored in a wireless node according to an embodiment. FIG. 12 is a diagram showing an example of alternative relay routes shown in the routing table shown in FIG. 11.

The routing table of FIG. 11 is stored, for example, by SN #3 (node #3) of the BH network shown in FIG. 12. In the routing table of FIG. 11, "excluded hop link", "upstream node of node #3", and "downstream node of node #3" are associated with each other. Note that the "excluded hop link" may correspond to, for example, the "wireless link assumed to be disconnected" shown in FIG. 10.

Here, the case where there is no "excluded hop link" represents a normal relay route. The example in FIG. 11 shows that when there is no "exclusion hop link", the "upstream node of node #3" is node #2, and the "downstream nodes of node #3" are nodes #4 and #5. For example, node #3 performs relay transfer based on this routing table. (a) of FIG. 12 shows a normal relay route corresponding to the case where there is no "excluded hop link".

The case where the "excluded hop link" is "L(1,2)" represents an alternative relay route with L(1,2) excluded. In this case, in the example of FIG. 11, the "upstream node of node #3" is node #1, and the "downstream nodes of node #3" are nodes #2, #4, and #5. For example, (b) in FIG. 12 shows an alternative relay route whose "excluded hop link" corresponds to "L(1,2)".

The case where the "excluded hop link" is "L(3,5)" represents an alternative relay route with L(3,5) excluded. In this case, in the example of FIG. 11, the "upstream node of node #3" is node #2, and the "downstream node of node #3" is node #4. For example, (c) in FIG. 12 shows an alternative relay route whose "excluded hop link" corresponds to "L(3,5)".

As shown in FIG. 11, the wireless node 3 stores an upstream node and a downstream node for each excluded hop link. In other words, the wireless node 3 stores information on a plurality of alternative relay routes each having different excluded hop links.

Note that the wireless node 3 may store information on each alternative relay route in which each wireless link of the linked-up mesh link becomes an excluded hop link. Alternatively, the wireless node 3 may store information on alternative relay routes in which hop links whose disconnection frequency is equal to or higher than a predetermined frequency are excluded hop links.

In the present embodiment described above, one of the plurality of wireless nodes (for example, the core node) configuring the backhaul network excludes at least one of the wireless links established between the plurality of nodes. A control signal (for example, a route construction packet) including information specified for a link (or a link to be disconnected) is transmitted. Then, one of the plurality of wireless nodes (for example, a slave node) selects a wireless link that constitutes an alternative route to a data communication route using the excluded hop link, among the remaining wireless links excluding the excluded hop link. Determine. For example, the determination is made based on an index regarding the propagation quality of one or more wireless links through which the control signal passed.

With this configuration, an alternative route can be constructed in advance assuming that some wireless links become unusable, so rescue control can be implemented in the case that some wireless links become unusable in the wireless BH network.

In addition, the wireless communication system of this embodiment can transfer data between nodes in a high frequency band with sharp beamforming directivity, thereby increasing the spatial reuse efficiency of frequencies. . In addition, even if the radio wave propagation loss from the transmission point to the reception point is large and the line quality of the wireless link is significantly degraded and the wireless link is disconnected, stable operation can be continued by rapid relay route switching.

Note that although this embodiment has shown an example in which each wireless node performs beamforming to transfer data, the present disclosure is not limited thereto. For example, each wireless node may perform data transfer without using beamforming.

In the above explanation, when the number of hop links where deterioration in line quality occurs is 1, the optimal alternative relay route under conditions excluding that hop link is constructed, updated, and stored in advance. was assumed. The present disclosure is not limited thereto, and may be extended to constructing, updating, and storing in advance alternative relay routes when the line quality of multiple (for example, two hop links) deteriorates at the same time.

In the above description, it is assumed that flooding of route control packets in this embodiment is performed by unicast using BF transmission and reception, as an example. This disclosure is not limited thereto. Flooding of route control packets may be performed by broadcast. By performing the process by broadcasting, the time required for processing to construct a relay route and an alternative relay route can be reduced.

In addition, although the alternative relay route is calculated as the relay route with the minimum route metric, the alternative relay route does not necessarily have a high throughput. By constructing an alternative relay route in advance, the probability that some functions of the wireless BH system will deteriorate can be reduced. On the other hand, if the route metric of the alternative relay route is greater than or equal to a predetermined value, there may be a function that sends an alarm to the wireless communication system operator and supports the work of reviewing the number and arrangement positions of wireless nodes.

In addition, in constructing and updating an alternative relay route, we have shown an example that covers each hop link that is assumed to be disconnected (a hop link that is assumed not to be included in the alternative relay route) or a combination of hop links. This disclosure is not limited thereto. For example, in constructing and updating an alternative relay route, it may be limited to some hop links or a combination of hop links. In that case, it may be possible to store which hop links whose line quality frequently deteriorates (including disconnections) and reflect this in the above-mentioned limitation method.

Also, each of the hop links of the wireless backhaul system does not need to apply the same wireless communication standard or the same wireless parameters (eg, transmit power and/or number of MIMO streams). The reason why the RSSI measurement value is used as the link metric indicator is that in a wireless backhaul system where the same wireless communication standard and the same radio parameters are applied between hop links, when the link metric indicator is the RSSI measurement value, Accurate link metrics may be given in constructing relay paths. For example, in a wireless backhaul system where different wireless communication standards and/or wireless parameters coexist in the hop links, the measured RSSI can be used as an example of a link metric indicator based on the wireless communication standards and/or wireless parameters of the hop links. A link metric determined in association with the transmission speed (throughput, bps) may be assigned.

Additionally, a wired link may be included as part of the hop links of the wireless backhaul system. In that case, a node connected to a wired link that cannot perform the wireless flooding reception process for routing control packets will receive the routing control packets via wire and set the link metric to the transmission speed of the wired link. Route construction processing may be performed by replacing it.

In addition, by using (utilizing) the alternative relay route construction method of this embodiment, in constructing a normal relay route, you can specify a hop link that is not included in the normal relay route, and specify the hop link. A relay route that does not include may be constructed. For example, if it is assumed that people or vehicles will come and go between a certain wireless node and another wireless node, hop links between these wireless nodes may not be included in advance. For example, when a moving wireless node avoids forming a hop link with another specific wireless node, the hop link can be set as the wireless link assumed to be disconnected in the route construction packet, and normal relaying can be performed. It may also be used for route construction.

In other words, the present disclosure is capable of constructing a relay route excluding a specific hop link to be set, not only when operating in a high frequency band, but also under various requests and situations, and creating an appropriate wireless BH network. can be constructed.

Also, when including a hop link between a certain wireless node and another wireless node in a relay route or an alternative relay route, the link metric of the hop link is used instead of the link metric calculated from the measured RSSI etc. It may be replaced with a link metric having a sufficiently small value.

For example, two wireless nodes in the same car of a train (eg, one in front of the car and one in the back of the car) move at the same speed, so it is possible to construct a relay route that permanently includes hop links between them. In this way, when a hop link between two wireless nodes in the same train car is included in a relay route, the route construction packet in Figure 10 is expanded to "hop link formation assumption" instead of "disconnection assumption". You may do so. Then, the link metric for the assumed hop link may be replaced with a sufficiently large value in the case of "assuming disconnection", but may be replaced with a sufficiently small value in the case of "assuming hop link formation". By replacing these values, a relay route including specific hop links is constructed.

In other words, the present disclosure is capable of constructing a relay route including specific hop links to be set under various demands and situations, not only when operating in a high frequency band, and can create an appropriate wireless BH network. Can be built.

In addition, in this embodiment, the wireless node includes a control unit that performs beamforming training with each of a plurality of peripheral nodes constituting the backhaul network, and a control unit that performs beamforming training with each of the peripheral nodes that constitute the backhaul network, and a control unit that performs beamforming training with each of the peripheral nodes that constitute the backhaul network. Among them, the communication unit includes a communication unit that performs data communication using a wireless beam link corresponding to a peripheral node selected as a data communication route. With this configuration, it is possible to construct an appropriate BH network using high frequency band radio to which beamforming (BF) technology is applied to compensate for radio wave propagation loss.

Furthermore, according to the present embodiment, even if the radio wave propagation loss from the transmission point to the reception point increases, the throughput in the wireless communication system can be increased by increasing the frequency of route construction (or updating). can suppress the decline in

Furthermore, according to the present embodiment, when linking up a mesh link, BF control processing is executed and a beam suitable for communication between wireless nodes is determined. This can be omitted, and a decrease in BH line throughput can be suppressed.

Furthermore, according to the present embodiment, in route control, the quality of each hop link is determined based on unicast transmission and reception using BF transmission, so a more appropriate route can be selected.

Further, according to the present embodiment, in data transfer, the wireless node has a configuration in which the wireless node transmits data of a plurality of series and/or receives data of a plurality of series at the same time in parallel. good. With this configuration, throughput in the wireless communication system can be improved.

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 40 control unit 350, 360 antenna 401 scan processing unit 402 node management unit 403 frame transfer processing unit 404 route control unit 405 mesh link establishment unit 406 IPT control unit 4041 route control packet generation unit 4042 route metric calculation unit 4043 route update unit 4051 BF control processing unit 4052 BF parameter storage unit

Claims (4)

Equipped with multiple wireless nodes that constitute a backhaul network,
The first node of the plurality of wireless nodes is
a transmitting unit that transmits a control signal including information specifying at least one first wireless link among the plurality of wireless links established between the plurality of nodes;
Equipped with
A second node among the plurality of wireless nodes is
a receiving unit that receives the control signal;
configuring a second route as an alternative to the first route for data communication using the first wireless link among the remaining wireless links other than the first wireless link specified by the information of the received control signal; A control unit that determines a second wireless link based on an index regarding the propagation quality of one or more wireless links through which the control signal passed;
a storage unit that stores information regarding the second wireless link in association with the first wireless link;
Equipped with
When it is detected that the amount of line quality deterioration of the first wireless link is equal to or greater than a threshold, the control unit determines a route to be used for the data communication based on information regarding the second wireless link in the storage unit. switching from the first route to the second route;
Wireless communication system. When the second node corresponds to the receiving side of the first wireless link, the control unit sets an index regarding the propagation quality of the first wireless link to the first wireless link among the values that the index can take. Replace with the value that indicates the most degraded propagation quality ,
The wireless communication system according to claim 1. The first node of the plurality of wireless nodes configuring the backhaul network is
transmitting a control signal including information specifying at least one first wireless link among the plurality of wireless links established between the plurality of nodes;
A second node among the plurality of wireless nodes is
receiving the control signal;
configuring a second route as an alternative to the first route for data communication using the first wireless link among the remaining wireless links other than the first wireless link specified by the information of the received control signal; determining a second wireless link based on an index regarding the propagation quality of one or more wireless links through which the control signal passed;
storing information regarding the second wireless link in association with the first wireless link;
If it is detected that the amount of deterioration in the line quality of the first wireless link is equal to or greater than the threshold, the route used for the data communication is changed from the first route based on the stored information regarding the second wireless link. switching to the second route;
Wireless communication method. One of a plurality of wireless nodes configuring a backhaul network,
a receiving unit that receives a control signal including information specifying at least one first wireless link among the plurality of wireless links established between the plurality of nodes;
configuring a second route as an alternative to the first route for data communication using the first wireless link among the remaining wireless links other than the first wireless link specified by the information of the received control signal; A control unit that determines a second wireless link based on an index regarding the propagation quality of one or more wireless links through which the control signal passed;
a storage unit that stores information regarding the second wireless link in association with the first wireless link;
Equipped with
When it is detected that the amount of line quality deterioration of the first wireless link is equal to or greater than a threshold, the control unit determines a route to be used for the data communication based on information regarding the second wireless link in the storage unit. switching from the first route to the second route;
wireless node.

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