JP7307909B2 - Wireless node, wireless communication system, and wireless communication method - Google Patents

Description

The present disclosure relates to wireless nodes, wireless communication systems, and wireless communication methods.

In existing cellular communication systems, a base station that provides radio 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, as one form of realizing a new generation of mobile communication, multiple wireless nodes (e.g., base stations or access points) that provide a wireless communication area with a radius of several tens of meters are connected by wireless multi-hop. A system or network that

JP 2005-143046 A WO2011/105371

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

There is room for discussion regarding building a suitable BH network using radio in the high frequency band.

A wireless node according to one aspect includes a control unit that performs training on beamforming with each of a plurality of peripheral nodes that configure a backhaul network, and a plurality of wireless beam links established with each of the peripheral nodes by the training, and a communication unit that performs the data communication using a radio beam link corresponding to a peripheral node selected as a data communication path.

A wireless communication system according to an aspect includes a plurality of wireless nodes that configure a backhaul network, at least one of the wireless nodes performing beamforming training with each of a plurality of peripheral nodes; and a communication unit that performs the data communication using a radio beam link corresponding to a peripheral node selected as a data communication path from among a plurality of radio beam links established with each of the peripheral nodes.

In a wireless communication method according to one aspect, at least one of a plurality of wireless nodes constituting a backhaul network performs beamforming training with each of a plurality of peripheral nodes, and establishes each of the peripheral nodes through the training. The data communication is performed using a radio beam link corresponding to a peripheral node selected for the data communication path among the plurality of radio beam links.

According to a non-limiting aspect of the present disclosure, a suitable BH network using high-frequency radio can be constructed.

1 is a block diagram showing a configuration example of a radio communication system according to an embodiment; FIG. FIG. 3 illustrates protocol stacks of a wireless node according to one embodiment; 3 is a block diagram showing a hardware configuration example of a wireless node according to one embodiment; FIG. FIG. 4 is an image diagram of upstream data transfer between hop links to which BF transmission is applied according to an embodiment; FIG. 4 is an image diagram of downstream data transfer between hop links to which BF transmission is applied according to an embodiment; It is a figure which shows an example of BF control which concerns on one Embodiment. 3 is a block diagram showing a functional configuration example of a control unit of a wireless node according to one embodiment; FIG. 4 is a flow chart showing an operation example of a core node (CN) according to one embodiment; 4 is a flow chart showing an operation example of a slave node (SN) according to one embodiment;

Hereinafter, embodiments will be described with appropriate reference to the drawings. The same reference numerals are used throughout the specification to refer to the same elements unless otherwise specified. The matter described below in conjunction with the accompanying drawings is intended to describe exemplary embodiments, and not to present the only embodiments. For example, when the order of operations is shown in the embodiments, the order of operations may be changed as appropriate within a range that does not cause contradiction in the overall operation.

When multiple embodiments and/or modifications are illustrated, some configurations, functions, and/or operations in one embodiment and/or modification may be the same as those in other embodiments to the extent that there is no contradiction. and/or may be included in variations and replaced with corresponding configurations, functions and/or operations in other embodiments and/or variations.

Moreover, in the embodiments, more detailed description than necessary may be omitted. For example, to avoid unnecessarily redundant description and/or vague technical matters or concepts and to facilitate understanding by those skilled in the art, technical matters that are known or well-known may be omitted. Also, duplicate descriptions of substantially the same configurations, functions and/or operations may be omitted.

The accompanying drawings and the following description are provided to aid in understanding the embodiments and are not intended to limit the claimed subject matter thereby. Also, the terms used in the following description may be appropriately replaced with other terms to help those skilled in the art understand.

<Knowledge leading to this disclosure>
By making the BH network, which is one of the mobile communication infrastructures, wireless by wireless multi-hop, the laying of wired cables can be made unnecessary, and the laying cost required for introducing a mobile communication system can be reduced. Therefore, for example, when a mobile communication system is temporarily (or tentatively) introduced, it is effective to wirelessize the BH network by wireless multi-hop.

For example, when laying a large number of small cell base stations (radio nodes) in the service area of a mobile communication system to cover the service area, it is effective to make the BH network wireless by wireless multi-hop. Most of the installations are in wireless LAN (eg, Wi-Fi®) systems.

Also, from around 2019 or 2020, high-frequency radio waves will be used in the 5th generation mobile communication system (5G), which is about to start commercial services worldwide. 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, Extreme High Frequency (EHF)). in some cases). Since radio wave propagation loss is large in high frequency bands, the application of beamforming (BF) technology is being considered in order to compensate for radio wave propagation loss.

For example, even when BF technology is applied to high-frequency band access lines, the cell size is reduced (becomes a small cell) because the cell radius is 100 meters to several hundred meters. As a result, the number of base stations to be installed becomes enormous, and it is difficult to lay a wired cable for the BH network. A wireless BH network eliminates the need to install wired cables, and is therefore 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 ), the data frame is transferred between the wireless nodes along the constructed relay route. This method is a wireless BH technology that separates "route control" for constructing a relay path from "frame transfer (for example, sometimes referred to as "relay transfer")" for data.

In the present embodiment, next-generation Wi-Fi (IEEE802.11ax and/or IEEE802.11ay) and beamforming (BF) using a high frequency band such as the 5th generation mobile communication system (5G) An example is to 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 (data transmission/reception along the relay route) using BF, "route control" for constructing a relay route is executed before data transmission/reception. Route control may include establishment of hop links including BF control processing, and construction of relay routes based on the established hop links. Each node can improve the efficiency of relay transfer by grasping the constructed relay route in advance. Here, the BF control processing may include transmission weight control or transmission directivity control of transmission antennas at each node, and reception weight control or reception directivity control of reception antennas at each node. A hop link may correspond to a mesh link with N (N is an integer equal to or greater than 1) nodes around a certain node.

Although it is possible to execute BF control processing at the time 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 lowered. Here, the occurrence of a communication session means, for example, a state in which a packet to be relayed is on standby at a node, and the node has acquired a wireless channel (wireless resource) in Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). You can deal with it.

In addition, in the method described in Non-Patent Document 1, each node measures the received power of a routing control packet (for example, RSSI (Received Signal Strength Indicator) measurement) for a routing control packet transmitted (broadcast). and determine the hop-link quality (eg, assigned metric) of each node. Relay routing is efficiently performed by each node determining the quality of the hop links.

For example, when BF is applied in relay transfer of data, even in the stage of routing, each node transmits and receives unicast route control packets to which BF is applied, instead of broadcasting route control packets. may determine the quality of each hop link. By judging the quality of each hop link based on the transmission and reception of routing control packets in unicast with BF applied, it is possible to more appropriately select a route for relay transfer of data to which BF is applied.

On the other hand, when BF is applied in data relay transfer, communication using two or more beams having directivities in mutually different directions is possible, so each node uses the same frequency and at the same time , can communicate with more than one node. In other words, when BF is applied in relaying data, spatial reuse of frequencies is possible. For example, a root node that branches off in a relay path can receive data transmitted by multiple neighboring transmitting nodes at the same time and same frequency. In this case, each node, for example, is desired to process data from a plurality of nodes in parallel at the same time, or to perform time-division processing at high speed.

Furthermore, in a high-frequency band, since radio waves travel in a straight line, if there is a shield (or obstacle) such as a building, a tree, a person, or a vehicle between a transmission point and a reception point, The loss of radio wave propagation to the receiving point tends to increase. Therefore, the line quality of the radio link is likely to deteriorate, and in the worst case, the radio link may be disconnected.

Therefore, the inventors of the present application adapted the method described in Non-Patent Document 1 to the case of applying BF technology in a high frequency band, and for example, compared to the bandwidth of existing systems such as LTE, the high frequency band This has led to the development of wireless BH network technology with higher throughput that takes advantage of the wide bandwidth that it possesses.

The following are non-limiting examples of wireless BH technology applying BF to BH links, which can achieve high throughput by making use of the wide bandwidth of high frequency bands and can compensate for radio wave propagation loss in high frequency bands. explain.

<System configuration example>
FIG. 1 is a block diagram showing a configuration example of a radio communication system according to one embodiment. A wireless communication system 1 shown in FIG. 1 illustratively comprises a plurality of nodes 3 . As a non-limiting example, FIG. 1 illustrates eight nodes 3 denoted by node numbers #0 to #7. The number of nodes 3 may be 2 or more and less than 8, or 9 or more.

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

Each node 3 forms an area in which wireless communication is possible. The 'area where wireless communication is possible' may also be referred to as 'wireless communication area', 'wireless area', 'communication area', 'service area', 'coverage area', or 'coverage area'. A wireless communication area formed by nodes 3 conforming to or based on a wireless LAN-related standard may be considered to correspond to a "cell", which is a term used in cellular communication. For example, a wireless communication area formed by each node 3 may be regarded as equivalent to a "femtocell" classified as a "small cell".

Each of the nodes 3 can wirelessly communicate with the other 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." An individual node 3 that is an entity of the BH network may be referred to as a "relay node".

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

Routes or sections through which wireless signals are transmitted in a 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 read interchangeably as "hop link". In these terms, "radio" 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 called a "radio access line" or a "radio access channel". In these terms, "wireless" may be omitted.

In the following description, the term "signal" may be read as a unit in which the signal is separated in time, such as "frame" or "packet."

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

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

Node #0 wired to backbone network 5 may be referred to as a “core node (CN)”. Of the plurality of nodes 3 forming the BH network, individual nodes 3 other than CN#0 may be referred to as "slave nodes (SN)". For example, in FIG. 1, nodes #1 to #7 are all SNs. The number of CNs may be 2 or more, and the number of SNs may be less than 7 or 8 or more.

In FIG. 1, #0 to #7 attached to each node 3 are examples 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, such as node numbers, device identifiers, or address information. A non-limiting example of address information is a MAC (Media Access Control) address.

A 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 a tree topology, SN3 with no child nodes may be referred to as a "leaf node" and SN3 with child nodes may be referred to as an "internal node." For example, in FIG. 1, SNs #2, #6, and #7 all correspond to "leaf nodes." SNs #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 also be referred to as "downlink (DL)" and "uplink (UL)", respectively, following their nomenclature in cellular communications.

A signal flow in the “downlink” (downlink signal) may be referred to as “downstream”, and a signal flow in the “uplink” (uplink signal) may be referred to as “upstream”. The "downlink signal" and "uplink signal" may each include a control signal and a data signal. A “control signal” may include a signal that does not correspond to a “data signal”.

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

Further, when focusing on the "downlink", the "core node" may be referred to as the "starting node" or "starting node", and the "leaf node" may be referred to as the "end node" or "edge node". may "Internal nodes" may also be referred to as "intermediate nodes" or "relay nodes."

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

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

One or a combination of two or more selected from the above index candidates may be used as the propagation quality index. In addition, in this embodiment, an index related to the distance of the route 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 transmission node 3 and the reception node 3 of the control signal, the radio wave propagation loss of the wireless section is calculated at the reception node 3. can ask.

Then, each of the receiving nodes 3 transmits the obtained radio wave propagation loss information included in the control signal, so that the cumulative radio wave propagation loss information (in other words, cumulative value) can be passed between nodes 3.

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

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

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

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

When the terminal device 7 is located in the service area of one of the SNs 3, the terminal device 7 communicates with the backbone network 5 via the BH network by connecting to one of the plurality of SNs 3 forming the BH network via a radio access line. The terminal device 7 may be connected to one of the SNs 3 (SN#3 as an example in FIG. 1) 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 smart phone, or a tablet terminal.

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

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

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

In the following, the term "transmission" of signals is interchangeably read as other terms such as "relay", "transfer", "propagation", "transmission", "routing", or "forwarding" of signals. may "Relay" of a signal may be read as "bridge" of a signal.

Also, the term "transmission" of a signal may include meanings such as "flooding", "broadcast", "multicast" or "unicast" of the signal. The term "connection" of a line may be taken to mean that 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" and "chip".

The node 3 and/or the terminal device 7 may be IoT (Internet of Things) equipment. With IoT, various "things" can be equipped with wireless communication functions. Various "things" equipped with wireless communication functions can communicate with the backbone network 5 via wireless access lines and/or wireless BH lines.

For example, IoT devices may include sensor devices, meters (measuring instruments), and the like that have wireless communication functions. The node 3 and/or the terminal device 7 may correspond to 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 meter. A BH network may thus correspond to, for example, a sensor network and/or a monitoring network. 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 protocol stack and an example hardware configuration of the node 3 that configures 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 one embodiment; As shown in FIG. 2, layer 2.5 is positioned between layer 2 and layer 3 and is responsible for wireless multi-hop transmission on BH lines.

Layer 1 may be referred to as the PHY layer. At layer 1, wireless transmission with BF functionality is illustratively performed. For example, Layer 1 complies with IEEE 802.11ay and/or 5G (NR) wireless standards.

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

In "mesh link establishment", each node scans for peripheral nodes, links up mesh links in the backhaul network, and stores information (node information) about the linked up peripheral nodes. Here, a peripheral node of a certain node 3 may correspond to, for example, a node existing in a position capable of receiving a signal (for example, a beacon signal) transmitted by the certain node 3 .

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

Layer 2.5 makes it possible to grasp in advance to which node the data should be transferred at the stage when the transmitting node executes the data frame transfer, and to execute the data transfer with the delay time kept to a minimum.

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

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

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

When data is transmitted and received using BF between nodes, evaluation of propagation quality is performed in transmission and reception of routing control packets in unicast using BF even in routing control processing that determines multi-hop routes. A more accurate multi-hop route can be constructed by sending and receiving broadcast routing packets.

However, in the process of routing, the evaluation of propagation quality between nodes may be performed by broadcasted routing packets. When the evaluation of propagation quality between nodes is performed by means of broadcast routing packets, the number of transmissions of routing control packets can be suppressed, so the execution time of routing control can be shortened. Moreover, even when evaluating the propagation quality between nodes using broadcast routing packets, it is possible to obtain a certain degree of correct evaluation.

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

In high-frequency bands, such as millimeter-wave bands, radio waves tend to propagate in a straight line. The loss of radio wave propagation becomes extremely large. Therefore, when the line quality of the wireless link between the wireless node that is the transmission point and the wireless node that is the reception point is significantly degraded, relay transmission is performed on 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 a hardware configuration example 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 buses 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 plural.

A plurality of processors 31 may be provided in the node 3 . Also, the processing in the node 3 may be executed by one processor 31 or may be executed by a plurality of processors 31 . Multiple processes may be executed concurrently, in parallel, serially, or in some other manner on one or more processors 31 . 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 illustratively realized by causing hardware such as the processor 31 and memory 32 to read predetermined software. Note that "software" may be read interchangeably 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 data stored in one or both of the memory 32 and storage 33 . Note that the program may be provided to the node 3 by communication via an electric communication line by 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 node 3 . One or more functions of the node 3 are implemented in response to execution of program code contained in the program. All or part of the program code may be stored in memory 32 or storage 33, or may be written as part of an operating system (OS).

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

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

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

Memory 32 may also be 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 optical discs such as CD-ROMs (Compact Disc ROMs), hard disk drives (HDDs), flexible discs, magneto-optical discs (e.g., compact discs, digital versatile discs, Blu-ray disc), smart card, flash memory (eg, card, stick, key drive), floppy disk, magnetic strip, and/or the like. The storage 33 may also be called an auxiliary storage device. The recording medium described above may be, for example, a database, server, or other suitable medium including one or both of memory 32 and storage 33 .

The input/output (I/O) device 34 is an example of an input device that receives a signal input from the outside of the node 3 and an example of 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, switches, buttons, and sensors. Output devices may illustratively include one or more of displays, speakers, and light emitting devices such as LEDs (Light Emitting Diodes).

Buttons may include, for example, a power button and/or a reset button. The power button is operated for starting up and shutting down the node 3, for example. A reset (or reroute) button is operated, for example, to indicate a deliberate reset and/or reconstruction (or reroute) of the tree path.

It should be noted that the input/output (I/O) device 34 may have separate configurations for inputs and outputs. Also, the input/output (I/O) device 34 may have an integrated structure for input and output, such as a touch panel display.

The wireless IF 35 illustratively transmits and receives wireless signals on an access line to and from the terminal device 7 . The wireless IF 35 may include, for example, one or more antennas 350, baseband (BB) signal processing circuitry, MAC processing circuitry, upconverters, downconverters, and amplifiers (not shown).

The BB signal processing circuit of the radio IF 35 illustratively includes an encoding circuit and a modulation circuit for encoding and modulating the transmission signal, and a demodulation circuit and a decoding circuit for demodulating and decoding the reception signal. you can

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

The wireless IF 36 illustratively performs transmission and reception of wireless signals on the BH line between other SNs 3 . An internal configuration example of the wireless IF 36 will be described later.

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

The wired IF 37 illustratively transmits and receives wired signals to and from the backbone network 5 and/or the upstream node 3 . Also, the wired IF 39 illustratively transmits and receives signals to and from the terminal device 7 and/or the downstream node 3 by wire. For the wired IFs 37 and 39, for example, a network interface conforming to the Ethernet (registered trademark) standard may be used. The wired IFs 37 and 39 need only be provided at least in CN3, and may not be provided in SN3 (in other words, they may be optional for 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 including hardware such as a microprocessor, DSP, ASIC, PLD, FPGA. For example, processor 31 may be implemented including at least one of these pieces of hardware. A part or all of each functional block described later with reference to FIG. 5 may be realized by the hardware.

"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 described.

Illustratively, input data from an input/output (I/O) device 34 is input to the wireless IF 36 after being divided into n series of transmission data #1 to transmission data #n (where n is an integer of 1 or more). be done. Here, n represents the maximum number of directional 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 greater than or equal to 2, node 3 simultaneously transmits data in multiple directions (eg, multiple destination nodes).

The transmission digital BF control unit 361, for example, performs encoding and modulation processing on each of the n-sequence transmission data to generate an n-sequence data signal. The transmission digital BF control unit 361 performs, for example, signal weighting (transmission weight multiplication) for forming beams in respective transmission directivity directions of the n sequences.

A digital-to-analog converter (DAC) 362 and an RF transmission unit 363 are provided, for example, corresponding to each of n data signal sequences.

The DAC 362 receives, for example, each of the weighted n-sequence data signals. The DAC 362 , for example, converts the input data signal from a digital signal to an analog signal and outputs the analog signal to the RF transmission section 363 .

The RF transmission unit 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 transmission unit 363 is converted into an analog signal supplied to each antenna element of an antenna (subarray) 360 composed of antenna elements (antenna elements) that transmit radio waves, for example, in a transmission analog BF control unit 364. be. Note that the transmission analog BF control section 364 may include, for example, a power divider, a phase shifter, and an amplifier. Also, 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 sub-arrays and each sub-array has 256 antenna elements, the transmit analog BF controller 364 may output n×256 analog signals.

Duplexer 365, for example, separates transmit and receive signals. For example, an analog signal output from analog BF control section 364 is supplied to antenna 360 through duplexer 365 .

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

For example, when n is 4, the signal supplied through the duplexer 365 is sent out from 4 sub-arrays in 4 directions with each directivity.

A signal received at an antenna 360 having n subarrays is input to a reception analog BF controller 366 through a duplexer 365, for example. The number of analog signals corresponding to 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 sub-arrays and each sub-array has 256 antenna elements, the receive analog BF controller 366 may receive n×256 analog signals.

The reception analog BF controller 366 has, 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 received signal according to the formed reception directivity. The reception analog BF control section 366 divides the processed reception signal into n signal sequences according to the received sub-array, and outputs the sequence to the RF reception section 367 .

An RF receiver 367 and an Analog to Digital Converter (ADC) 368 are provided, for example, corresponding to each of n signal sequences.

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

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

The reception digital BF control unit 369, for example, weights (multiplies reception weights) the signals associated with the directions of the reception directivities of the n digital signal sequences, and converts the n digital signal sequences to Separate and process. The reception digital BF control unit 369, for example, performs demodulation processing and decoding processing on each of the n-sequence signals, generates n-sequence reception data, and inputs/outputs (I/O) the n-sequence reception data. output to device 34;

In the BF control (determination of BF directivity) described later with reference to FIG. Directivity direction) and reception directivity direction (receiving directivity direction of the wireless node on the receiving side) are determined. In this determination process, for example, a unique data pattern for power measurement is used for transmission data.

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

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

FIG. 4 is an image diagram of upstream data transfer between hop links to which BF transmission is applied 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. Also, FIG. 4 shows an example of the transmission directivity of SN#1 to SN#5 when signals are transmitted in the upstream direction (the direction from the leaf node to CN#0).

In the present disclosure, for wireless standards that use BF in high frequency bands, applying wireless BH technology that separates "path control" for constructing a relay path and "frame transfer" for data is applied. Take one example. In FIG. 4, as a result of route control, each wireless node knows the wireless node that is the data transmission destination. More specifically, in the storage 33 installed in each node, information indicating to which node data should be transmitted in upstream data transfer (for example, transmission destination (destination, transfer destination, or transmission (which may be referred to as the previous), and parameter information that can be BF-transmitted to that node may be stored. For example, the parameter information includes information for realizing drive currents to be supplied to each antenna element forming the antenna array. Each node achieves BF transmission by calling information stored in the storage 33 when receiving data to be transferred upstream.

Each transmitting node that has data to transmit checks whether or not there is a free channel prior to transmission in order to acquire a radio channel (radio resource) for transmission. For example, confirmation of idle channels is performed by means such as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). A transmitting node that acquires an empty channel performs data transmission using BF on a wireless link established in advance with a receiving node in layer 2.5. "Layer 2.5" or "hierarchy belonging to layer 2.5" may be referred to as "mesh layer" for convenience. The processing of the MAC layer, which is the processing of acquiring a radio channel, may follow CSMA/CA and the like as they are in this embodiment as well.

In FIG. 4, the radio link from SN#4 to SN#3, the radio link from SN#3 to SN#1, the radio link from SN#2 to CN#0, the radio link from SN#1 to CN, Also, it indicates that BF transmission is performed on the radio link from SN#5 to SN#1. A radio link to which BF is applied may be referred to as a radio beam link. In a wireless beam link, a wireless node on the transmitting side forms a transmission beam and a wireless node on the receiving side forms a reception beam to perform data communication (data transmission/reception). In the radio beam link, at least one radio node on the transmitting side and the receiving side may form a beam to 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 only an image diagram of data transfer. For example, the transmission beams (transmission directivity) shown in FIG. 4 may not be formed at the same time. For example, downstream data transfer is being performed between SN#3 and SN#4 at the same time as upstream data transfer is being performed between SN#5 and SN#1. Circumstances are also assumed.

When BF transmission is applied, the transmission distance of the radio 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). Also, the energy of the radio waves sent out in a direction different from the desired direction is suppressed. Also, at the receiving destination node, the application of BF reception suppresses the energy of the received radio wave arriving from a direction different from the desired direction. A received radio wave arriving from a direction different from the desired direction may be regarded as an interference wave at the destination node.

Therefore, in data transfer to which BF transmission is applied, the probability that the same frequency can be used for data transmission in the vicinity at the same time (at the same time or the time width including the same timing) is higher than in the case where 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 on the same frequency at the same time. In this case, CN#0 can receive data transmitted from SN#2 and receive data transmitted from SN#1 at the same frequency and at the same time. Also, data transmission from SN#3 to SN#1 and data transmission from SN#5 to SN#1 can be executed 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 radio nodes (for example, CN#0 and SN#1) may receive data of multiple different sequences (at least two sequences in the example of FIG. 4) at the same time. For example, the hardware configuration example of the wireless node described with reference to FIG. 3 can receive data of multiple different sequences (n sequences).

Being able to use the same frequency in the vicinity at the same time will lead to a significant increase in the frequency utilization efficiency of the wireless BH circuit, thereby increasing the system capacity of the wireless communication system.

In addition, when determining an available channel by CSMA/CA, the wireless node applies Request to Send/Clear to Send (RTS/CTS) to determine one transmission node to acquire the transmission right. good. In this case, even if the wireless node has a configuration that does not receive data of different sequences at the same time, it is possible to minimize the probability of multiple data transfers colliding in the receiving node. For example, in the present embodiment, each node transfers data using BF, so each node not involved in the transfer 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 path can reduce interference while the data transfer along which the node is a path is not being performed. Training can be done at the same time.

FIG. 5 is an image diagram of downstream data transfer between hop links to which BF transmission is applied 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. Also, FIG. 5 shows an example of transmission directivity of CN#0 and SN#1 to SN#5 when signals are 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 the wireless node that is the data transmission destination. The difference from the upstream data transfer in FIG. 4 is that unlike the upstream data transfer in which data is transferred to CN#0, the downstream data transfer differs in the leaf node that is the transfer destination. be. Although the same route is illustrated in FIGS. 4 and 5, the present disclosure is not limited to this. The path for downstream data transfer and the path for upstream data transfer may be different from each other. For example, in radio wave conditions that change from moment to moment, the data transfer route may also change from moment to moment.

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

In FIG. 5, a radio link from CN#0 to SN#2, a radio link from CN#0 to SN#1, a radio link from SN#1 to SN#3, and a radio link from SN#1 to SN#5 are shown. BF transmission is performed on the link and the radio 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 radio 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.

As in FIG. 4, by applying BF transmission, radio waves transmitted from the source node have sharp directivity in the direction of the destination node (desired direction). Also, the energy of the radio wave that is being sent out in a direction different from the desired direction is suppressed. Also, at the receiving destination node, the application of BF reception suppresses the energy of the received radio wave arriving from a direction different from the desired direction. A received radio wave arriving from a direction different from the desired direction may be regarded as an interference wave at the destination node.

Therefore, in data transfer to which BF transmission is applied, the probability that the same frequency can be used for data transmission in the vicinity at the same time is higher than in the case where BF transmission is not applied. For example, in FIG. 5, CN#0 can perform data transmission to SN#2 and data transmission to SN#1 on the same frequency at the same time. Also, SN#1 can perform data transmission to SN#3 and data transmission to SN#5 at the same time on the same frequency.

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

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

<Example of BF control>
Next, an example of the BF control described above will be described. FIG. 6 is a diagram illustrating an example of BF control according to one embodiment. In BF control, the radio node determines the directivity of the BF. The BF control shown in FIG. 6 is an example of control for executing BF training. 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 radio node determines a transmission beam suitable for transmitting a signal to a radio node, which is a communication partner, from among a plurality of beams having directivities in mutually different directions. Also, in BF control, the wireless node determines a reception beam suitable for receiving a signal transmitted from the wireless node, which is the communication partner, from among a plurality of reception beams having directivities in mutually different directions.

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

For example, in the example of FIG. 6, a transmission beam (transmitting directivity) having directivity in 64 directions and a receiving beam (receiving directivity) having directivity in 64 directions are prepared. Then, the wireless node determines one transmission beam and one reception beam in the optimum 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. Note that FIG. 6 illustrates an example in which the beam in the optimum direction (optimum beam) is the beam that provides the maximum reception power on the receiving side among the beams having directivity in 64 different directions.

In STEP 1, the transmission start node switches 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. A signal transmitted by the transmission start node may include, for example, a data pattern sequence whose reception power is to be measured. The destination node waits for reception of the 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. Reception of the maximum beam width may be reception of a beam having no directivity or reception of a beam having omni-directivity, for example. Then, the destination node 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 powers for the 64 different directivities, or some of them, for example, information on the directivity with the highest received power (for example, the index number 1 attached to each beam). It may be one (eg, #i)).

In STEP2, the same processing as in STEP1 is executed by switching the signal transmission side and reception side in STEP1. For example, the destination node switches the directivity in 64 directions prepared in advance in a time division manner and transmits a signal. A signal transmitted by a destination node may include, for example, a data pattern sequence for which received power is 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 for signal reception with the maximum beam width, and receives the transmission signal by the sector sweep of the destination node with the maximum beam width. Then, the transmission start node measures the reception power for 64 different directivities and stores the measurement results. The stored measurement results may be all of the received power for 64 different directivities, or information on the directivity with the highest received power (for example, one of the index numbers attached to each beam (for example, #r ), and the transmission start node stores the measurement result of the destination node in STEP 1, which is included in the received signal.

In STEP3, the transmission start node forms a transmission beam based on the measurement result reported in STEP2 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 start node with the maximum beam width. The destination node stores the measurement result of the transmission start node in STEP2 included in the received signal.

In STEP 4, the destination node uses directivity #r to send a response (Acknowlegdement (ACK)) confirming that the BF control process (that is, directivity #i and directivity #r determination process) has been completed normally. Send back to the initiating node. The transmission start node receives ACK on beam #i and confirms the completion of BF control processing.

In the BF control process shown in FIG. 6, an optimum transmission beam is determined by executing a sector sweep (transmission sector sweep) in signal transmission. A receive beam having directivity corresponding to the optimum transmit beam is then determined to be the optimum receive beam.

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

The BF control process illustrated in FIG. 6 may be performed between the node and the terminal when BF transmission is applied on the access line. In this case, the BF control process may be executed before data transmission/reception (or while data transmission/reception is not performed) each time data transmission/reception occurs between the node and the terminal.

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

The BF control information can be updated by executing the link-up of the hop link including the BF control process at predetermined time intervals (predetermined frequency).

Thus, the process of performing linkup of hop links and updating information used for data transfer, including BF control information, may be referred to as mesh link establishment. In this embodiment, BF control processing is included in this mesh establishment, so that when data transfer between wireless nodes occurs, data transfer applying BF transmission can be executed immediately. Establishing a mesh link may be regarded as establishing a radio beam link with a peripheral node.

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

FIG. 7 is a block diagram showing a functional configuration example of the controller 40 of the wireless node 3 according to one 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 for scanning peripheral nodes and linking up mesh links in the BH network. In this embodiment, since BF is applied to data transmission/reception between wireless nodes, the scan processing unit 401 cooperates with the mesh link establishment unit 405 described later to execute scanning including BF control processing.

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

The node management unit 402 also stores a routing table that stores the node numbers of transfer destination (destination) nodes when performing relay data transfer. For example, the node management unit 402 updates the routing table when there is a relay route update in route control. The routing table stores an upstream routing table storing transfer destination nodes on a route toward the core node (uplink route) and a transfer destination node on a route opposite to the core node (downlink route). 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. Provided to the processing unit 401 . Through cooperation between the mesh link establishment unit 405 and the scan processing unit 401, mesh link up is performed at a predetermined frequency (cycle).

The mesh link establishment section 405 has 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 applying BF control to execute linkup of mesh links.

The BF parameter storage unit 4052 stores parameters obtained by applying BF control and performing link-up of mesh links. Such parameters may conveniently be referred to as 'BF parameters' or 'mesh link parameters'. Mesh link parameters may include, for example, control information for the transmit BF and control information for the receive BF. The mesh link parameters may also include, for example, the optimal transmit beam index and the optimal receive beam index for each of the neighboring nodes.

Since the latest mesh link parameters can be updated while the radio wave environment fluctuates from moment to moment, accurate BF transmission can be executed in frame transfer between wireless nodes. Also, the routing control packet transmitted and received in the routing control processing executed by the routing control unit 404, which will be described later, can be executed by unicast to which BF transmission and reception is applied between peripheral wireless nodes instead of broadcasting. . Therefore, more accurate route construction is possible.

The routing controller 404 controls the building and updating of routes on mesh links by transmitting routing packets on the mesh links. For building and updating a route, for example, as will be described later, among a plurality of wireless links forming a mesh link, wireless link information to be registered in the route (or excluded from the route) is selected (or the selection is canceled). It may be done by

The route control unit 404 determines a dynamic route in the mesh link based on a route quality indicator called a route metric. In the following, an example will be described in which the smaller the value of the route metric, the better the line quality of the route. For example, the routing control unit 404 evaluates the channel quality between nodes by measuring the RSSI of routing packets transmitted by neighboring wireless nodes. A route control packet contains a cumulative route metric up to a peripheral node.

A routing control packet generation unit 4041 of the routing control unit 404 generates a routing control packet. A route control packet is an example of a control signal generated in CN3 and propagated to each node 3 starting from 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 the 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 peripheral node and the own node.

The route updating unit 4043 of the route control unit 404 compares the route metric calculated by the route metric calculating unit 4042 with the route metric stored in the route updating unit 4043, and determines whether or not to update the route. If the calculated route metric is smaller than the stored route metric, the route updating unit 4043 determines to update the route. A case where the calculated route metric is smaller than the stored route metric means that the route corresponding to the calculated route metric has better line quality than the route corresponding to the stored route metric and is composed of multi-hop wireless links. represents

This route control procedure can follow the route control method described in Non-Patent Document 1, for example. However, in the case of performing transmission/reception using BF in a high frequency band on a BH line, the path control unit 404 may have, for example, the following two functions.

(1) BF transmission using BF control information determined by the BF control described in FIG. 6 is applied in transmission and reception of routing control packets.

In routing control, a more accurate route can be constructed by performing transmission/reception of routing control packets with unicast with BF applied between peripheral nodes 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 route.

In the high-frequency band, radio waves tend to propagate in a straight line, and if there is an obstacle such as a building, tree, person, or vehicle between the transmitting point and the receiving point, the radio wave propagation loss from the transmitting point to the receiving point increases. easy to do Therefore, in preparation for the case where the line quality of the radio link between the transmission point and the reception point is degraded and the radio link is disconnected, for example, the route updating section 4043 included in the route control section 404 updates the route. I do. In the present embodiment, the millimeter wave band has been mainly exemplified and explained, but the present invention is not limited to this band. For example, in the millimeter wave band or even in the high frequency band, a short-time interruption of radio waves at a certain point in the wireless network may cause a situation in which communication of the wireless network is interrupted. According to this embodiment, since the optimal tree route is updated periodically or aperiodically, it is suitable to be applied in a communication environment in the millimeter wave band or higher frequency band. For example, when a communication environment is realized, even if good communication is normally possible, the communication environment deteriorates due to a vehicle stopped by a traffic light, or the communication environment deteriorates while a passerby crosses the route to which BF is applied. may deteriorate. In the case of such a temporary deterioration of the communication environment, if it is an environment that applies a lower frequency band such as a microwave band, it will only be a temporary decrease in communication speed, but in the millimeter wave band, communication may be blocked. Therefore, it is preferable to apply the present embodiment in a communication environment in the millimeter wave band or a higher frequency band.

Although details will be described later with reference to FIGS. 8 and 9, the route is updated by the core node transmitting a route control packet at predetermined intervals. Note that the predetermined cycle may be set arbitrarily. However, as described above, when BF transmission/reception is applied to compensate for radio wave propagation loss and secure a required transmission distance in the millimeter wave band or a higher frequency band where radio wave propagation loss is large, the transmission node and the reception node The insertion of a shielding object between the two will greatly degrade the quality of the line, and may even result in a disconnection of communication. From such a point of view, it is desired to eliminate the influence of the line quality deterioration as soon as possible. For example, it is desired to promptly construct a new optimum relay route under the condition that there is a radio link with deteriorated line quality. Therefore, the cycle of routing control (for example, the transmission cycle of routing packets in core nodes) should be short. However, an increase in the number of transmissions and receptions of routing control packets may increase the traffic load and degrade the performance of the wireless communication system. In order to suppress the deterioration of the performance of the wireless communication system, the longer the cycle of routing control, the better. Therefore, the predetermined period described above is not limited to an example in which it is set to a uniform value (for example, a uniform optimal value). The cycle of route control may be determined for each wireless communication system in consideration of the frequency of occurrence of inducing factors, the degree of impact on the QoS of the wireless communication system due to degradation of line quality, and the like. For example, in a communication environment in which the possibility of line quality deterioration is low, the cycle of route control may be, for example, about 1 to 10 minutes. On the other hand, in a communication environment in which line quality is frequently degraded, the cycle of route control is preferably about 1 to 3 seconds, for example. Moreover, route control is not limited to an example of periodic execution. For example, route control may be executed when an event occurs in which an abnormality of the wireless link is detected as a result of determining whether the wireless link is normal or abnormal in the self-healing process. When there is route control based on the occurrence of an event in self-healing processing and periodic route control, both the cycle of self-healing processing and the cycle of route control depend on the required QoS of each wireless communication system. (system throughput, delay time, etc.) should be considered and optimized.

For example, when the line quality of a wireless link deteriorates, a route transmitted by a core node to avoid a decrease in BH network throughput or stoppage of the BH network and suppress delay time associated with updating the BH network route. A transmission cycle of control packets may be controlled. For example, control of the transmission period of routing packets may be performed by a core node. Alternatively, the transmission period of routing packets may be dictated by the backbone network.

For example, the core node may set a short transmission cycle of routing packets transmitted by the core node.

Alternatively, instead of uniformly shortening the transmission cycle of routing control packets in a wireless BH line using a high frequency band, the transmission cycle of routing 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, deterioration below a predetermined level). You may In other words, the transmission period of the routing control packet may be variably controlled according to the fluctuation of the line quality of the radio link.

Alternatively, the core node may control the transmission cycle of routing packets based on requests from applications provided in the wireless communication system. For example, when the Quality of Service (QoS), which indicates the degree of request to suppress the temporary line disconnection time and/or the delay time associated with the line disconnection time requested by the application, is high, the transmission cycle of the route control packet can be set shorter. For example, QoS is high in applications that perform real-time data transmission such as voice calls and video distribution.

Since the route update process is a process performed by transmitting and receiving a routing control packet over a wireless link, the frequency of the route update process can be adaptively suppressed by variably controlling the transmission cycle of the routing control packet. A decrease in line throughput can be suppressed.

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

The frame transfer processing unit 403 adds a layer 2.5 control information header to the transfer data coming down from the upper layer (layer 3 or higher) to layer 2.5 and converts it into a frame to be transferred in the lower layer (layer 2 or lower). Execute the trimming process.

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

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

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

It may be counted by the self-healing process (corresponding to S105), which is the work of the core node checking whether the slave node is operating normally for each slave node. In addition, when QoS (Quality of Service), which indicates the degree of demand for minimizing temporary line disconnection time and delay time associated with an application provided within a wireless communication system, is high, the route control packet transmission cycle is set. A variable control to make it shorter may be applied.

The control unit 40, for example, monitors whether a specific event has been detected (S102). The "specific event" may include, for example, activation of the CN, operation of the reset button, and arrival of a specific timing. An example of "specific timing" is, for example, transmission timing set to transmit a routing packet regularly or irregularly.

If no specific event is detected (NO in S102), the process of S104 is executed.

When a specific event is detected (YES in S102), the control unit of the CN generates a routing control packet and sends the routing control packet to the peripheral SN identified based on the peripheral node information, for example, through the wireless communication unit. Send (S103). Routing packets 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 building packet is detected, the route building packet is transmitted to the neighboring SNs. 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 peripheral SNs.

Next, the control unit 40 determines whether or not it is time to execute the self-healing process (S104). Self-healing processing is processing in which a core node confirms whether a slave node is operating normally. For example, in self-healing processing, the core node transmits a self-healing packet (which may be called a hello packet) to the slave node, and determines whether the slave node is operating normally based on the response from the slave node. Check whether

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

When it is time 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 (the number of times) of deterioration of the line quality of the hop link based on the self-healing result (S106).

Next, the control unit 40 determines whether or not the self-healing execution period has elapsed (timeout) (S107).

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

When the self-healing execution period has elapsed (timeout) (YES in S107), the control unit 40 determines whether or not a specific event has been detected in S102 (S108). In other words, the control unit 40 determines whether or not the route control packet has been transmitted.

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

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

When the execution period of the route control process has elapsed (timeout) (YES in S109), the control unit 40 may start processing the data packet (S110). When the execution period of the route control process elapses (timeout), the data relay route between the core node and the slave node is updated to the latest state. As a result of route control processing, the data relay route may not change before and after route control processing.

Next, the control unit 40 detects deterioration of the line quality of the hop link (for example, frequency of deterioration (number of times)) (S111). For example, the control unit 40 may detect the frequency of line quality deterioration based on responses from slave nodes in the self-healing process.

If no deterioration of the line quality of the hop link is detected (NO in S111), the flow ends. When deterioration of the line quality of the hop link is detected (YES in S111), the control unit 40 updates the frequency of deterioration of the hop link line quality (S112). Then the flow ends.

As described above, the core node transmits a routing control packet (for example, unicast by BF transmission) to each of the plurality of wireless links linked up with the peripheral nodes, thereby making the slave nodes constituting the BH network Propagate routing packets to each.

Non-limiting examples of propagation quality indicators include received power or strength of radio signals (for example, RSSI; Received Signal Strength Indicator), radio wave propagation loss, and propagation delay. Further, for example, when different transmission technical specifications are applied to each hop link, the RSSI is associated with the transmission technical specifications instead of being used to calculate the link metric (an index reflecting the line quality of the hop link). Link throughput may be used to calculate the link metric. Examples of transmission technology specifications that determine link throughput include radio standards (802.11n, 802.11ac, 802.11ax, 5GNR (5th generation mobile communication specifications; 5G New Radio)), the number of MIMO streams, and adaptive modulation schemes. . For example, if the RSSI is the same between two hop-links but the radio standard is 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 to calculate the link metric, it is possible to improve the reliability of the line quality of the constructed route.

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

For example, by transmitting a signal (for example, a control signal) with the CN as a starting point, the radio wave propagation loss in the wireless section can be obtained at the receiving node for each wireless section between the transmission node and the reception node of the control signal. can.

Then, each of the receiving nodes transmits the obtained radio wave propagation loss information in the control signal, thereby obtaining cumulative radio wave propagation loss information (in other words, cumulative value ) can be propagated between nodes.

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

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

The SN determines whether or not a self-healing hello packet is received, for example, in the wireless communication unit 36 of the BH line (S201).

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

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

Next, the control unit 40 determines whether or not the routing control packet is received by the wireless communication unit 36 of the BH line, for example (S203).

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

If the received routing control packet is a reset packet (YES at S204), the control unit 40 performs initialization processing (S205). The initialization process may include, for example, the following processes.
- Deselection of links selected as effective tree routes in peripheral node information - Initialization of stored route metrics to initial values (for example, maximum values)

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

When the ID of the received reset packet matches the stored ID, in other words, when it indicates that the reset packet has been transmitted (transferred) in the past, each node does not further transmit the reset packet. do not have. This prevents reset packets from looping in the BH network.

On the other hand, if the received routing control packet is not a reset packet (NO in S204), the control unit 40 confirms whether or not the routing control packet is a routing packet (S207).

If the received route control packet is not a route construction packet (NO in S207), the process of S201 is executed. If the received route control packet is a route building packet (YES in S207), the control unit 40 refers to the peripheral node information (S208), and calculates the propagation quality index (for example, radio wave propagation loss ) is calculated (S209).

Based on the calculated radio wave propagation loss, the control unit 40 calculates a route metric (S210). For example, the control unit 40 adds the calculated radio wave propagation loss and the propagation quality index included in the received route construction packet to calculate the cumulative radio wave propagation loss as the new route metric.

The control unit 40 then compares the new route metric with the old route metric stored before the new route metric was calculated, and determines whether or not the route metric needs to be updated (S211).

For example, when 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. If it is determined to update the old route metric to the new route metric (YES in S211), the control unit converts the upstream wireless link corresponding to the new route metric in the peripheral node information into a valid tree route. Select (update selected link) (S212). Note that when it is determined not to update the old route metric to the new route metric (NO in S211), the process of S201 may be executed.

In response to the update of the selected link, the control unit 40, for example, transmits a route construction packet including a new route metric to the neighboring SNs identified in the neighboring node information (S213). For example, the route building packet may be transmitted by multicast or may be transmitted by unicast in BF transmission.

After that, the control unit 40 monitors whether or not a certain period of time has elapsed (timeout) (S214). If timeout is not detected (NO in S214), the process of S201 is executed.

If a timeout is detected (YES at S214), control unit 40 may start data packet transmission processing (relay transfer) (S215). The data packet transmission process may be, for example, the data packet forwarding process to the destination node. The data packet transmission process is executed according to the relay route of the routing table that stores the node number of the transfer destination (destination) when relay transfer is performed. The routing tables may include a downstream routing table and an upstream routing table. If data packet transfer is not performed normally, for example, if ACK is not returned from the destination node in three consecutive packet transfers, the data transfer destination is switched to another candidate destination node stored in the routing table. good too. This can be a stopgap measure until a new relay route is determined. In route control, until a new relay route is determined and information about the new relay route is stored and updated in the memory 32 or storage 33, each node, as an emergency measure, stores the node information of the transfer destination and the transfer destination. Parameter information for BF transmission with a node may be read out from the memory 32 or storage 33 and relayed.

Next, the control unit 40 detects the deterioration of the line quality of the hop link (for example, the frequency of deterioration (number of times)) (S216). For example, the control unit 40 may detect the frequency of line quality deterioration based on responses from slave nodes in the self-healing process.

If no deterioration of the line quality of the hop link is detected (NO at S216), the flow ends. If deterioration of the line quality of the hop link is detected (YES in S216), the control unit 40 updates the frequency of deterioration of the hop link line quality (S217). Then the flow ends.

If the received routing control packet is neither a reset packet nor a routing packet, the control unit 40 may shift the process to a routing control packet reception monitoring process.

Also, if the calculated new route metric is greater than or equal to the old route metric and it is determined that the selected link need not be updated, the control unit 40 may shift the process to the routing control packet reception monitoring process.

As described above, the SN selects one of the plurality of wireless links linked up with the peripheral node based on the route metric in response to receiving the route construction packet. Thereby, a tree route based on the route metric is constructed and updated in the BH network to which the mesh link is linked up.

In the present embodiment described above, the wireless node includes a control unit that performs training on beamforming with each of a plurality of peripheral nodes that make up the backhaul network, and a plurality of wireless beam links that are established with each of the peripheral nodes by training. and a communication unit that performs data communication using a radio beam link corresponding to a peripheral node selected as a data communication path. With this configuration, an appropriate BH network can be constructed using high-frequency radio to which beamforming (BF) technology is applied to compensate for radio wave propagation loss.

Further, according to the present embodiment, even if the radio wave propagation loss from the transmission point to the reception point increases, by increasing the frequency of route construction (or update), the throughput in the wireless communication system can suppress the decrease in

Further, according to the present embodiment, BF control processing is executed in link-up of a mesh link, and a beam suitable for communication between wireless nodes is determined. It is possible to omit it and suppress the decrease in the throughput of the BH line.

Further, according to the present embodiment, in route control, the quality determination of each hop link is performed based on unicast transmission/reception to which BF transmission is applied, so a more appropriate route can be selected.

Further, according to the present embodiment, in data transfer, a wireless node has a configuration in which a plurality of sequences of data are transmitted and/or a plurality of sequences of data are received in parallel at the same time. good. This configuration can improve the throughput in the wireless communication system.

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 (8)

Training is performed on each of the multiple peripheral nodes that make up the backhaul network and beamforming.determining a beam corresponding to each of the peripheral nodes, and establishing a wireless beam link for communicating with each of the peripheral nodes using the determined beam;a control unit;
BeforeMultiple nodes established with each of the peripheral nodesSaida communication unit that performs the data communication using a radio beam link corresponding to a peripheral node selected as a data communication path among the radio beam links;
equipped with,
The communication unit periodically or aperiodically transmits a control signal for quality measurement of the established radio beam link to the established radio beam link using the beam corresponding to the radio beam link. ,
wireless node. The control unit controls the transmission cycle of the control signal based on at least one index related to the quality of the wireless beam link selected for the route and the service quality of data communication using the wireless beam link selected for the route. to control the
A wireless node according to claim 1 . The control unit shortens the transmission cycle of the control signal when the index indicates quality deterioration equal to or greater than a predetermined value.
A wireless node according to claim 2 . Perform beamforming training with each of a plurality of peripheral nodes that constitute a backhaul network, determine beams corresponding to each of the peripheral nodes, and communicate with each of the peripheral nodes using the determined beams. a control unit that establishes a radio beam link to perform
a communication unit that performs the data communication using a wireless beam link corresponding to a peripheral node selected as a data communication path from among the plurality of wireless beam links established with each of the peripheral nodes;
with
The communication unit is connected to a plurality of peripheral nodes selected for the data communication path.Among them, the first peripheral nodecorrespond to1st beam using 1st beamCommunication by radio beam link and, communication by a second wireless beam link using a second beam corresponding to a second peripheral node different from the first peripheral node;parallel processingUnderstandRu
Nothingline node. Equipped with multiple wireless nodes that make up a backhaul network,
at least one of the wireless nodes,
Training is performed on each of the multiple peripheral nodes and beamforming.determining a beam corresponding to each of the peripheral nodes, and establishing a wireless beam link for communicating with each of the peripheral nodes using the determined beam;a control unit;
Before Multiple nodes established with each of the peripheral nodesSaida communication unit that performs the data communication using a radio beam link corresponding to a peripheral node selected as a data communication path among the radio beam links;
equipped with,
The communication unit periodically or aperiodically transmits a control signal for quality measurement of the established radio beam link to the established radio beam link using the beam corresponding to the radio beam link. ,
wireless communication system. Equipped with multiple wireless nodes that make up a backhaul network,
at least one of the wireless nodes,
Perform beamforming training with each of a plurality of peripheral nodes, determine beams corresponding to each of the peripheral nodes, and establish wireless beam links for communication using the determined beams with each of the peripheral nodes. a control unit that
a communication unit that performs the data communication using a wireless beam link corresponding to a peripheral node selected as a data communication path from among the plurality of wireless beam links established with each of the peripheral nodes;
with
The communication unit performs communication by a first wireless beam link using a first beam corresponding to a first peripheral node among the plurality of peripheral nodes selected for the data communication path; parallel processing communication by a second wireless beam link using a second beam corresponding to a second peripheral node different from the peripheral node;
wireless communication system. At least one of the plurality of wireless nodes that make up the backhaul network,
performing training on beamforming with each of a plurality of peripheral nodes, determining a beam corresponding to each of the peripheral nodes;
establishing a wireless beam link for communicating with each of the peripheral nodes using the determined beam;
performing the data communication using a wireless beam link corresponding to a peripheral node selected as a data communication path from among the plurality of wireless beam links established with each of the peripheral nodes;
transmitting a control signal for quality measurement of the established radio beam link to the established radio beam link periodically or aperiodically using the beam corresponding to the radio beam link;
wireless communication method. At least one of the plurality of wireless nodes that make up the backhaul network,
performing training on beamforming with each of a plurality of peripheral nodes, determining a beam corresponding to each of the peripheral nodes;
establishing a wireless beam link for communicating with each of the peripheral nodes using the determined beam;
performing the data communication using a wireless beam link corresponding to a peripheral node selected as a data communication path from among the plurality of wireless beam links established with each of the peripheral nodes;
communication by a first wireless beam link using a first beam corresponding to the first peripheral node among the plurality of peripheral nodes selected for the data communication path; parallel processing communication over a second wireless beam link using a second beam corresponding to two peripheral nodes;
wireless communication method.

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