Wireless communication device and wireless communication method

Abstract

A wireless communication device capable of reducing packet loss is provided. [Solution] According to an embodiment, a wireless communication device can configure a wireless mesh network with one or more other wireless communication devices. The wireless communication device includes a wireless communication unit and a route control unit. The wireless communication unit receives a wireless frame including a first information message related to a route from one or more other wireless communication devices. The route control unit determines which other wireless communication device should be a parent node from among the one or more other wireless communication devices based on the route information included in the first information message. When the route control unit determines to change the parent node to a second wireless communication device while the first wireless communication device is the parent node, the wireless communication unit wirelessly connects to the second wireless communication device and then transmits a second information message including information about the second wireless communication device.

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a wireless communication device and a wireless communication method. [Background technology]

[0002] Mesh network technology is known, in which multiple wireless communication devices dynamically construct communication paths and connect wirelessly along the constructed paths. Some wireless communication devices that make up such mesh networks comply with RPL (IPv6 Routing Protocol for Low power and Lossy networks), a routing control protocol for constructing communication paths, and use wireless LAN (Local Area Network) as the wireless communication method.

[0003] However, in conventional mesh network construction methods, although a wireless communication device can newly join an existing mesh network, the procedure for switching from another wireless communication device to which a wireless communication device is currently connected to another wireless communication device is not taken into account.

[0004] This resulted in a problem in that new route information was shared among the wireless communication devices that make up the mesh network before the wireless communication device in question could wirelessly connect to the new destination wireless communication device, resulting in packet loss. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-88574 [Non-patent literature]

[0006] [Non-Patent Document 1] P. Thubert et al., “RPL:IPv6 Routing Protocol for Low-Power and Lossy Networks,” IETF,RFC6550,2012 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a wireless communication device and a wireless communication method that can reduce packet loss. [Means for solving the problem]

[0008] According to an embodiment, a wireless communication device can configure a wireless mesh network with one or more other wireless communication devices. The wireless communication device includes a wireless communication unit and a route control unit. The wireless communication unit receives a wireless frame including a first information message related to a route from one or more other wireless communication devices. The route control unit determines a wireless communication device to be a parent node from the one or more other wireless communication devices based on the route information included in the first information message. When the route control unit determines to change the parent node to a second wireless communication device among the one or more other wireless communication devices while a first wireless communication device among the one or more other wireless communication devices is currently the parent node, the wireless communication unit wirelessly connects to the second wireless communication device and then transmits a second information message including information about the second wireless communication device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a wireless communication device according to a first embodiment. [Figure 2] FIG. 1 shows the configuration of a MAC frame in a wireless LAN system conforming to the IEEE 802.11 standard. [Figure 3] 1 is a diagram showing an example of a connection in which wireless communication devices according to a first embodiment configure a mesh network. [Figure 4] 5 is a flowchart showing a procedure for the wireless communication device of the first embodiment to change a wireless connection. [Figure 5]FIG. 4 is a frame sequence diagram showing a procedure in which the wireless communication device of the first embodiment changes a wireless connection. [Figure 6] A diagram showing the Public Action frame format defined in the IEEE 802.11 standard. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings.

[0011] (First embodiment) First, the first embodiment will be described.

[0012] (Configuration example of wireless communication device) FIG. 1 is a diagram showing an example of the configuration of a wireless communication device 300 according to the first embodiment.

[0013] The wireless communication device 300 includes an antenna 311 , a wireless communication unit 310 , and a control unit 320 .

[0014] Antenna 311 receives analog radio signals transmitted in the 2.4 GHz band, 5 GHz band, 6 GHz band, etc. The received signals received by antenna 311 are input to radio communication unit 310.

[0015] The wireless communication unit 310 includes a PHY (Physical) layer unit 312 and a MAC (Medium Access Control) layer unit 313.

[0016] The PHY layer 312 mainly includes an antenna switch, a wireless receiving unit, a wireless transmitting unit, an oscillator, a demodulator, and a modulator (not shown). When a received signal is input from the antenna 311 to the wireless communication unit 310, the PHY layer 312 frequency-converts (down-converts) the received signal to a signal of an appropriate frequency band (for example, a baseband signal) using a signal of the same frequency as the carrier signal generated by the oscillator. This signal is then converted to a digital signal by an ADC (Analog to Digital Converter) and input to the demodulator. The demodulation unit performs reception processing including predetermined demodulation and decoding processing in accordance with, for example, the IEEE 802.11 standard (IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, IEEE 802.11ac, IEEE 802.11ax, IEEE 802.11be, etc., including 802.11 standards to be defined in the future), converts the input signal into a MAC frame defined in the IEEE 802.11 standard, and transfers it to the MAC layer unit 313.

[0017] (MAC frame format explanation) Here, the format of the MAC frame will be explained.

[0018] FIG. 2 is a diagram showing the configuration of a MAC frame in a wireless LAN system conforming to the IEEE802.11 standard.

[0019] The MAC frame includes a MAC Header portion, a Frame Body portion, and an FCS (Frame Check Sequence) portion.

[0020] The MAC Header section contains information necessary for reception processing in the MAC layer. The Frame Body section contains information according to the type of frame (such as data from a higher layer). The FCS section contains an error detection code CRC (Cyclic Redundancy Code) used to determine whether the MAC Header section and Frame Body section have been received correctly.

[0021] The MAC Header section includes a Frame Control field, a Duration / ID field, an Address field, and a Sequence Control field.

[0022] The Frame Control field is set to a value according to the type of frame. The Duration / ID field indicates the period (NAV: Network Allocation Vector) for the wireless communication device to wait for transmission or the identification number assigned to the STA (Station) connected to the AP (Access Point). The Duration / ID field is 16 bits long. When the MSB (most significant bit) is 0, the lower 15 bits indicate the Duration (NAV). When the MSB is 1, part of the lower 15 bits indicates the ID (identification number). There are multiple Address fields. The Address 1 field is set to the MAC address of the direct receiving station. It is used to determine whether the MAC frame is addressed to the device itself. The Address 2 field is set to the MAC address of the direct transmitting station. The Address 3 field is set to the MAC address of the final destination device in the uplink, and to the MAC address of the source device in the downlink. The Address 4 field is present only when a wireless base station transmits to another wireless base station, and is set to the MAC address of the source device. The Sequence Control field is set to the sequence number of the data to be transmitted and the fragment number if the data is fragmented.

[0023] The Frame Control field includes a Type field indicating the type of frame, a Subtype field, a "To DS" field, a "From DS" field, a more fragment field, a retry field, a protected frame field, a +HTC / order field, etc.

[0024] The bit string set in the Type field identifies which frame type the frame belongs to: control frame, management frame, or data frame. Furthermore, the bit string in the Subtype field indicates the type of MAC frame within each frame type. The "To DS" field contains information indicating whether the receiving station is a wireless base station or a wireless terminal, and the "From DS" field contains information indicating whether the transmitting station is a wireless base station or a wireless terminal. The More Fragment field holds information indicating whether subsequent fragment frames exist when data is fragmented. The Retry field is set to indicate that the frame is to be retransmitted. The Protected Frame field contains information indicating whether the frame is protected. The +HTC / Order field indicates that the order of frames must not be changed when relaying frames when non-QoS Data frames are transmitted, and indicates that an HT Control field (not shown) is included in the MAC header when a QoS Data frame is transmitted in an 802.11n / ac / ax physical frame. When the HT Control field is included, it is included between the QoS Control field and the Frame Body and is used to notify some of the functions specified in IEEE802.11n / ac / ax.

[0025] A QoS Control field is added to a QoS Data frame, which is one type of data frame (on the other hand, no QoS Control field is added to non-QoS Data). When a frame's Type field identifies it as a data frame, it is possible to determine whether it is QoS Data or non-QoS Data by checking the bit string set in the Subtype field. This QoS Control field includes a TID (Traffic ID) field (16 types, from 0 to 15), in which an identifier corresponding to the data traffic is set, and an Ack policy field in which a delivery confirmation method is set. By checking the TID field, it is possible to identify the data traffic type, and by checking the Ack policy field, it is possible to determine whether the QoS Data was transmitted using the Normal Ack policy, Block Ack policy, or No Ack policy. For example, a Normal Ack policy indicates that the wireless communication device that received the QoS Data must immediately return a response frame.

[0026] Note that the fields included in the MAC header are not limited to those mentioned above. For example, new IEEE 802.11 standards may add new fields to the MAC frame, such as the QoS Control field added in the IEEE 802.11e standard.

[0027] Returning to FIG. 1, the configuration of wireless communication device 300 will be described.

[0028] In the transmission process, the MAC layer unit 313 generates MAC frames (for example, Data frames, control frames such as Ack (Acknowledge) and BA (BlockAck), and management frames such as Action frames). The MAC layer unit 313 uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) method, which determines whether to transmit a MAC frame after checking the usage status of the wireless channel (for example, whether other wireless devices are transmitting wireless signals). If the wireless channel is unused for a period specified by the IEEE 802.11 standard, it determines that other wireless devices are not transmitting wireless signals, and transfers the MAC frame to the PHY layer unit 312 to start transmission. On the other hand, if the wireless channel is busy, it postpones transmission until the wireless channel becomes unused (idle).

[0029] When a predetermined time has elapsed while the wireless channel is unused (idle), the MAC layer 313 transfers a MAC frame to the PHY layer 312. In the PHY layer 312, a modulation unit performs transmission processing, including predetermined modulation and coding processing conforming to, for example, IEEE 802.11. The digital signal is then converted into an analog baseband signal by a DAC (Digital to Analog Converter), and the analog baseband signal is input to the wireless transmission unit of the PHY layer 312. The wireless transmission unit upconverts the input baseband signal to a predetermined frequency band (for example, frequencies in the 2.4 GHz, 5 GHz, or 6 GHz band) using a carrier signal generated by an oscillator, and transmits the signal as a wireless signal from the antenna 311 via an antenna switch.

[0030] The demodulation section of the PHY layer 312 performs processes such as OFDM (Orthogonal Frequency Division Multiplexing) symbol timing synchronization, FFT (Fast Fourier Transform), deinterleaving, and error correction decoding on the signal converted into a digital signal by the ADC. The PHY header in the demodulated PHY frame (PPDU (PHY Protocol Data Unit)) contains information indicating the frame length, transmission rate, bandwidth information, and the like, and the demodulation section extracts this information. The demodulation section uses this information in the demodulation process and transfers it to the MAC layer 313.

[0031] In the reception process, the MAC layer unit 313 performs a CRC check, MAC header analysis, etc. In the CRC check process, it verifies that the CRC added to the received MAC frame is correct. If the CRC is incorrect, the MAC frame is discarded. In the MAC header analysis process, it verifies whether the address in the Address1 field in the MAC header matches the MAC address of its own device (for example, the MAC address set in the wireless communication unit 310). Basically, if the MAC addresses match and it is determined that the CRC is correct, it forwards the MAC frame to the control unit 320. If the MAC address does not match the MAC address of its own device and the address in the Address1 field is a multicast address, it forwards the MAC frame to the control unit 320 if it is determined that the CRC is correct. Note that the received frame forwarded from the MAC layer unit 313 to the control unit 320 may be the MAC frame itself, or a portion of the MAC frame (for example, information included in the Frame Body, the Frame Body, part of the MAC header, etc.) may be forwarded.

[0032] Furthermore, if the received MAC frame is a frame that requests a response, the MAC layer unit 313 generates a response frame (for example, an Ack frame or a BlockAck frame). The response frames generated by the MAC layer unit 313 are mainly frames that require an immediate response, and are returned SIFS (Short Interframe Spacing: for example, 16 usec) after the end of the MAC frame that requests the response frame (for example, a QoS Data or Action frame).

[0033] In the transmission process, the MAC layer unit 313 generates a MAC frame and performs a CRC calculation. The MAC layer unit 313 generates a frame by including data transferred from the control unit 320 (for example, a User Datagram Protocol (UDP) or Transmission Control Protocol (TCP) packet, etc.) in the Frame Body and adding a MAC header containing necessary information such as the destination MAC address and the MAC address of its own device. The MAC layer unit 313 then performs a CRC calculation on the frame and adds the CRC calculation result to the FCS field to generate a MAC frame. The MAC frame is then transferred to the PHY layer unit 312. Note that the data transferred from the control unit 320 may be a packet such as a TCP packet, or may be a frame for which the control unit 320 has generated a MAC header and Frame Body. In the latter case, the MAC layer unit 313 performs a CRC calculation on the frame and generates a MAC frame. The MAC layer unit 313 may also generate a response frame, such as an Ack frame or BlockAck frame, that does not include data from the control unit 320 and transfer it to the PHY layer unit 312.

[0034] The control unit 320 includes a wireless link control unit 321 and a route control unit 322, and performs control for wireless communication and constructs routes for the mesh network. It also generates packets of data to be transmitted (for example, generating UDP packets, TCP packets, etc.).

[0035] The wireless link control unit 321 performs control for wirelessly connecting the wireless communication unit 310 to another wireless communication device as a connection destination. For example, the wireless link control unit 321 performs a scan process for searching for other wireless communication devices around the wireless communication unit 310, an association process for wirelessly connecting to the wireless communication device determined by the route control unit 322 as a connection destination, and a deauthentication process for disconnecting the connection with the currently connected wireless communication device.

[0036] The route control unit 322 performs a parent node search operation to search for an appropriate connection destination based on route information received from surrounding wireless communication devices to construct a mesh network, and a parent node notification operation to notify the root node of the determined parent node information after determining an appropriate connection destination. The route information sent and received by the route control unit 322 is basically transmitted via IP (Internet Protocol) packets.

[0037] The radio link control unit 321 and the route control unit 322 exchange information with each other. For example, when the route control unit 322 determines an appropriate connection destination, it notifies the radio link control unit 321 of information about the connection destination (for example, an IP address). When the radio link control unit 321 wirelessly connects to the notified wireless communication device of the connection destination, the radio link control unit 321 notifies the route control unit 322 that the connection has been completed.

[0038] Each processing unit in the device configuration of wireless communication device 300 may be realized as an analog or digital circuit, or may be realized by software executed by a CPU (Central Processing Unit), etc. Wireless communication device 300 may be implemented in a single LSI (Large Scale Integration), or control unit 320 and wireless communication unit 310 may be implemented in different LSIs.

[0039] (Wireless network configuration explanation) Next, the configuration of the wireless network will be described. Figure 3 is a diagram showing an example of connections in which four wireless communication devices [1] 300 to [4] 300 (represented as STA1 to STA4) configure a mesh network.

[0040] The wireless communication device [1] 300 is called the root node, and is the wireless communication device 300 located at the highest level among the wireless communication devices 300 that make up the mesh network. The child nodes wirelessly connected to the wireless communication device [1] 300 as the parent node are the wireless communication device [2] 300 and the wireless communication device [3] 300. Finally, the child node wirelessly connected to the wireless communication device [2] 300 as the parent node is the wireless communication device [4] 300. The wireless communication devices [1] 300 to [4] 300 are shown as an example of wireless communication using the wireless LAN system.

[0041] The wireless communication device [1] 300 may be configured to be connectable to the Internet via Ethernet (registered trademark). For example, in this case, the wireless communication device [4] 300 can access the Internet via the wireless communication device [2] 300 and the wireless communication device [1] 300.

[0042] The wireless communication device [1] 300 has at least the function of accommodating other wireless communication devices 300.

[0043] The wireless communication device [2] 300 and the wireless communication device [3] 300 have at least a function to be accommodated by another wireless communication device 300 and a function to accommodate another wireless communication device 300.

[0044] The wireless communication device [4] 300 has at least the function of being accommodated by another wireless communication device 300.

[0045] (Explanation of the function to accommodate other wireless communication devices) The function of accommodating other wireless communication devices 300 includes wirelessly connecting to one or more other wireless communication devices 300, transferring information from the one or more other wireless communication devices 300 to a wireless communication device 300 subordinate to the wireless communication device 300, and receiving information from the subordinate wireless communication device 300. The function also includes spontaneously transmitting a management frame (e.g., a beacon frame) including the wireless functions and the like of the wireless communication device 300, returning a response frame (e.g., a probe response frame) in response to a management frame (e.g., a probe request frame) received by the other wireless communication device 300 to search for a connection partner, and executing negotiation processing (e.g., association and authentication) for wireless connection with the other wireless communication device 300 (for example, this may be an access point (AP) function in a wireless LAN, or may have part of the AP function). Of the wireless communication devices 300 that form a wireless mesh network, the wireless communication device 300 that serves as a parent node has this function.

[0046] (Description of functions contained in other wireless communication devices) The function accommodated in the other wireless communication device 300 is a function of wirelessly connecting to a wireless communication device 300 that has a function of accommodating other wireless communication devices 300. The function transmits information to the wireless communication device 300 to which the wireless communication device 300 belongs, and receives information from the wireless communication device 300. The function also transmits management frames (e.g., probe request frames) for searching for wireless communication devices 300 that have a function of accommodating other wireless communication devices 300, receives response frames (e.g., probe response frames) in response thereto, and executes negotiation processes (e.g., association and authentication) for wirelessly connecting to a wireless communication device 300 that is determined as a connecting device from among the searched wireless communication devices 300 (for example, this may be a station (STA) function in a wireless LAN, or may have part of the STA function). Of the wireless communication devices 300 that form a wireless mesh network, the wireless communication device 300 that becomes a child node connected to a parent node has this function.

[0047] (RPL Overview) Wireless communication device [1] 300 to wireless communication device [4] 300 are compliant with RPL, a routing control protocol, in order to autonomously build a mesh network. RPL builds a mesh network by exchanging various control messages. There are four main control messages:

[0048] ·DIS(DODAG[Destination-Oriented Directed Acyclic Graph] Information Solicitation) ·DIO(DODAG Information Object) ·DAO(Destination Advertisement Object) ·DAO-ACK(Destination Advertisement Object Acknowledgment) The wireless communication device 300 acting as a parent node transmits a DIO message including a metric (for example, a rank value) and routing information.

[0049] A child node that is already connected to an existing mesh network, or a new node attempting to connect, refers to the metrics and routing information contained in the DIO messages received from one or more surrounding parent nodes, and selects a parent node to which it will connect from among those parent nodes.

[0050] The new node or child node transmits a DAO message to the selected parent node, addressed to wireless communication device 300 (STA1 in FIG. 1) operating as the root node. The parent node (STA2 in FIG. 1) that is not the root node receives the DAO message and forwards it to a node above it.

[0051] The root node that receives the DAO message sends a DAO-ACK message to the child node that sent the DAO message.

[0052] The root node also creates and maintains a routing table based on the information in the DAO messages sent by each child node. This routing table allows the root node to determine which route to take when it receives information addressed to a specific child node.

[0053] A new node or a child node may send a DIS message to request a DIO message.

[0054] (Explanation of the procedure for STA4 to change the connection from STA2 to STA3) Next, the procedure by which STA4 changes its wireless connection from STA2 to STA3 will be described with reference to the flowchart of FIG.

[0055] The route control unit 322 of STA4 receives the DIO message (S1). STA1 to STA3 periodically transmit a WLAN frame (for example, a Public Action frame) including a DIO message. When a WLAN frame (for example, a Public Action frame) including a DIO message transmitted by STA2 to STA3 is received, the control unit 320 of STA4 extracts an IP packet from the Public Action frame and extracts the DIO message from the IP packet. The control unit 320 then transfers the DIO message to the route control unit 322. Note that in this embodiment, STA4 does not transmit a DIO message, but STA4 may also have a function to transmit a WLAN frame including a DIO message. Also, in this embodiment, STA4 is not capable of receiving a DIO message from STA1 (it receives DIO messages from STA2 and STA3).

[0056] The route control unit 322 of STA4 extracts the rank value from the DIO message (S2). The DIO message includes the rank value of the wireless communication device 300 that generated it. The rank value is a value calculated using a metric such as the number of hops to the root node. For example, if the rank value is determined by the number of hops to the root node, the rank value of the root node is 0. The rank values ​​of nodes (STA2 and STA3) that are directly connected to the root node (STA1) are 1. Furthermore, the rank value of STA4 that is connected to STA2 is 2.

[0057] The route control unit 322 of STA4 determines a parent node (STA3 is the new parent node in this embodiment) based on the rank value (S3). The route control unit 322 of STA4 determines the parent node to be the node with the lowest rank value among the parent node candidates detected by receiving the DIO message that is lower than the rank value of the own device. The calculation of the rank value may include not only the number of hops but also other information. For example, the rank value may be calculated based on the received power value of a WLAN frame (e.g., a Beacon frame, a Probe Response frame, a Public Action frame, etc.) received from each node. In this embodiment, the rule is that if the received power of a Beacon frame received by a node from a parent node is -X [dBm], +X is added to the rank value (this is an example, and other calculation methods are also possible). If the received power of a Beacon frame received by STA2 from STA1 is -60 [dBm], the rank value of STA2 is increased by 1, which is the number of hops to the root node, to become 61. On the other hand, if the received power of the Beacon frame received by STA3 from STA1 is −70 [dBm], the rank value of STA3 is 71. As a result, in this embodiment, when STA4 newly joins the mesh network, STA2, whose rank value is smaller than STA4 and whose rank value is the smallest among the detected DIO messages, is determined to be the parent node (here, the rank value of STA4 before STA4 joins the mesh network is the maximum value (65535). Also, STA4 is assumed to be in a position where the WLAN frame containing the DIO message from STA1 cannot reach it). In this embodiment, if the received power of the Beacon frame received by STA3 from STA1 changes to −50 [dBm] (the reason for this increase in received power may be, for example, when STA3 is closer to STA1 or when an obstacle that existed in the communication path between STA3 and STA1 is removed), the rank value of STA3 is updated to 51. In this case, since STA3 has a lower rank value than STA2, the route control unit 322 of STA4 determines STA3 as the new parent node.

[0058] The route control unit 322 of STA4 extracts the IP address of STA3 from the DIO message received from the new parent node (STA3 in this embodiment) (S4). The route control unit 322 of STA4 extracts the IP address of STA3 from the source IP address field of the IP packet containing the DIO message received from STA3. The payload of the DIO message also contains the IP address of the root node. By checking this IP address, it is possible to recognize that the node belongs to the mesh network group to which the device itself should connect.

[0059] The route control unit 322 of STA4 stops forwarding the DAO message containing the new parent node information (S5). The route control unit 322 of STA4 has a function for sending a DAO message containing the IP address of the node that STA4 recognizes as the parent node. Here, if STA4 recognizes STA2 as the parent node, the final destination of the IP packet containing the DAO message containing the IP address of STA2 is the root node. The direct recipient of the WLAN frame (e.g., a Data type frame) containing that IP packet is the currently wirelessly connected parent node (STA2 in this case). When STA2 receives that IP packet from STA4, STA2 forwards it to STA1, so that the DAO message is ultimately delivered to the root node.

[0060] Incidentally, when the route control unit 322 of STA4 selects STA3 as the parent node, the wireless communication unit 310 of STA4 may still be wirelessly connected to STA2. In this state, STA4 is not yet wirelessly connected to STA3. If a new DAO message including the IP address of STA3 is sent to the root node in this state, the route table held by the root node will record a different state from the current connection (STA4 is connected to STA2) if STA4 is connected to STA3 as its parent node. If this incorrect recognition occurs, when transmitting information from the root node to STA4, the root node will transmit the information via STA3, and as a result, the information will not be delivered to STA4 (the information will be lost (packet loss)).

[0061] To prevent such packet loss from occurring, in this embodiment, STA4 controls itself so as not to send a DAO message containing the IP address of STA3 until it wirelessly connects to a new parent node (STA3 in this embodiment).

[0062] More specifically, STA4 is prevented from sending the DAO message itself. For example, route control unit 322 of STA4 may not generate a DAO message including the IP address of STA3, route control unit 322 may not forward the DAO message to control unit 320 or wireless communication unit 310, or even if route control unit 322 generates a DAO message including the IP address of STA3, wireless communication unit 310 of STA4 may not transmit a WLAN frame including the DAO message.

[0063] The route control unit 322 of STA4 notifies the wireless link control unit 321 of the IP address of the new parent node (S6). When the route control unit 322 of STA4 selects STA3 as the new parent node, it notifies the wireless link control unit 321 of the IP address (IP_Addr3) of STA3.

[0064] The radio link control unit 321 of STA4 extracts the source MAC address (MAC_Addr3) of the WLAN MAC frame containing the DIO message transmitted by STA3 (S7). STA4 temporarily stores in memory a list of at least those source MAC addresses during the process of receiving and processing WLAN MAC frames containing DIO messages from multiple nodes, and presents the list upon request from the radio link control unit 321. For example, the MAC layer unit 313 or control unit 320 of STA4 extracts an IP packet from the WLAN MAC frame (e.g., a Public Action frame) containing the DIO message received from STA3, and extracts the source IP address (i.e., the IP address of STA3). It also extracts the source MAC address (i.e., the MAC address of STA3) from the MAC header in the Public Action frame. The source MAC address can be extracted from the Address2 field of the MAC header. The MAC layer unit 313 or the control unit 320 stores the extracted IP address (IP_Addr3) and MAC address (MAC_Addr3) as a pair in the address list. The wireless link control unit 321 searches the address list for a pair that matches the IP address (IP_Addr3) notified by the route control unit 322, and extracts the MAC address (MAC_Addr3) that is paired with the matched IP address.

[0065] The wireless link control unit 321 of STA4 instructs the wireless communication unit 310, which holds the extracted MAC address, to execute a wireless connection (association) (S8). STA4 executes a disconnection process with STA2 and a connection procedure with STA3. First, STA4 disconnects the wireless connection with STA2. Specifically, STA4 transmits a Deauthentication frame, which is a WLAN frame, to STA2 and executes a disconnection sequence. After completing the disconnection with STA2, STA4 transmits a Probe Request frame (the destination address of this frame may be multicast or unicast to STA3). After receiving a Probe Response frame from STA3, STA4 executes authentication and association processes with STA3 (exchanging authentication frames and association frames). When STA4 transmits an Association Request frame addressed to STA3 and receives an Association Response frame from STA3 containing information indicating success, the connection process is successful.

[0066] If STA4 has successfully established a wireless connection to STA3 (S9: Yes), the wireless link control unit 321 of STA4 notifies the route control unit 322 that the wireless connection has been successful (S10). The wireless link control unit 321 of STA4 checks the status of the MAC layer unit 313, and if the wireless connection with STA3 has been successful, notifies the route control unit 322 to that effect.

[0067] Only after receiving this notification does route control unit 322 of STA4 transfer a DAO message including new parent node information (S11). After receiving notification from radio link control unit 321 that connection to STA3 has been successful, route control unit 322 of STA4 generates a DAO message including the IP address of STA3 and transfers it to control unit 320. Control unit 320 generates an IP packet including the DAO message from route control unit 322 and transfers it to MAC layer unit 313. In this case, the destination IP address of the IP packet is the root node, and the source IP address is the IP address of STA4.

[0068] The wireless communication unit 310 of STA4 transmits a wireless LAN MAC frame containing the DAO message as a wireless signal (S12). When the MAC layer unit 313 of STA4 receives the IP packet containing the DAO message, it generates a wireless LAN MAC frame (for example, a Data frame or a QoS Data frame) containing the IP packet and transfers it to the PHY layer unit 312. In this case, the receiver MAC address (Address1 field) of the MAC frame is the MAC address of STA3, and the source MAC address (Address2 field) is the MAC address of STA4.

[0069] On the other hand, if STA4 fails to connect wirelessly to STA3 (S9: No), the wireless link control unit 321 of STA4 notifies the route control unit 322 that the wireless connection has failed (S13). When STA4 transmits an Association Request frame addressed to STA3, if it receives an Association Response frame from STA3 containing connection refusal information, or if no Association Response frame is returned, the connection process is deemed to have failed. In this case, since STA4 was unable to connect wirelessly to STA3, the wireless link control unit 321 notifies the route control unit 322 of the wireless connection failure.

[0070] The route control unit 322 of STA4 discards the determined parent node information (for example, the fact that STA3 has been selected as the new parent node, the IP address of STA3, etc.) (S14). After receiving notification from the wireless link control unit 321 that the connection to STA3 has failed, the route control unit 322 of STA4 discards information such as the IP address of STA3 and the fact that STA3 has been selected as the parent node. After this, STA4 collects DIO messages again and searches for a new parent node.

[0071] Next, the procedure for STA4 to change its wireless connection from STA2 to STA3 will be described using the frame sequence diagram in Fig. 5. Assume that STA4 is wirelessly connected to STA2 as its parent node.

[0072] STA1 transmits a DIO message as a multicast packet (a1). In this embodiment, it is assumed that the DIO message reaches STA2 and STA3 but not STA4.

[0073] STA2 and STA3 each transmit a DIO message as a multicast packet (a2). In this embodiment, STA4 receives these DIO messages. A Public Action frame, for example, is used as a MAC frame when transmitting a DIO message wirelessly. This Public Action frame can be received even by wireless communication devices 300 that are not connected to the device itself. While it is possible to include a DIO message in other MAC frames, such as a Probe Request frame or a Probe Response frame, Probe Request and Probe Response are difficult to use due to transmission timing restrictions. For example, Probe Request is a frame transmitted during a period when searching for a wireless communication device that will become a master device, and Probe Response is a frame transmitted in response to a Probe Request. Therefore, in order to transmit a DIO message using Probe Request or Response at a desired timing, existing wireless LAN functions must be modified, which may increase the implementation load. In contrast, Public Action frames are flexible because they do not have such transmission timing restrictions.

[0074] If the Rank value in the received DIO remains unchanged, STA4 does not update its parent node. STA4 sends a DAO message (indicated as DAO1(IP_Addr2) in FIG. 5) including the IP address of STA2 to the wireless communication unit 310 operating as the parent node of STA2 (a3). The final destination of this DAO message is set to the root node (STA1). Therefore, STA2 sends the DAO message to STA1 from its wireless communication unit operating as a child node (a4).

[0075] When STA1 receives the DAO message from STA4, it returns a DAO-Ack (represented as DAO-Ack1 in Figure 5) (a5). STA1 then sends the DAO-Ack message to STA4 via STA2 (a5'). The DAO message and DAO-ACK message are sent using a Data frame or a QoS Data frame. The exchange of DAO messages and DAO-ACK messages is performed after each node completes its wireless connection, and the DAO message and DAO-ACK message are sent as IP packets. Therefore, using a Data-type WLAN MAC frame reduces the implementation load.

[0076] When STA4 receives DIO messages from STA2 and STA3 (a6), if there is a change in the rank value in the DIO message (if the rank value of STA3 is smaller than that of STA2), STA4 changes the parent node (a7). If it decides to change the parent node from STA2 to STA3, STA4 stops sending DAO messages (a8).

[0077] STA4 disconnects from STA2. Specifically, STA4 transmits a Deauthentication frame to the parent node of STA2 (a9).

[0078] After disconnecting from STA2, STA4 executes a scan process and a connection process. Specifically, STA4 transmits a Probe Request frame (a10) and receives a Probe Response frame from STA3 (a11). In this case, a multicast address (or a broadcast address) may be set in the Address1 field of the MAC header of the Probe Request frame, or the MAC address of the parent node of STA3 may be set. If a Probe Response frame is not received from STA3, the decision to designate STA3 as the parent node is discarded, and the process of searching for a parent node is performed again.

[0079] After receiving the Probe Response frame from STA3, STA4 performs connection processing to STA3. Specifically, STA4 transmits an Authentication frame to STA3 (a12) and receives the Authentication frame from STA3 (a13). Next, STA4 transmits an Association Request frame to STA3 (a14) and receives an Association Response from STA3 (a15). If the Association Response frame contains information indicating a successful connection, STA4 determines that the connection with STA3 has been successful.

[0080] After the connection with STA3 is successfully established, STA4 releases the suspension of DAO message transmission (a16).

[0081] In other words, once STA4 has successfully connected to STA3, it sends a DAO message including the IP address of STA3 (represented as DAO2(IP_Addr3) in FIG. 5) to the wireless communication unit 310 operating as the parent node of STA3 (a17). The final destination of this DAO message is set to the root node (STA1). Therefore, STA3 sends the DAO message to STA1 from the wireless communication unit 310 operating as the child node (a18).

[0082] When STA1 receives the DAO message from STA4, it returns a DAO-Ack (indicated as DAO-Ack2 in Figure 5) (a19). STA1 then sends the DAO-Ack message to STA4 via STA3 (a19'). As before, DAO and DAO-ACK messages are sent using Data frames or QoS Data frames.

[0083] (Explanation of the format of the Public Action frame used to send DIS and DIO messages) Next, the format of the Public Action frame used to transmit the DIS message and the DIO message will be described.

[0084] FIG. 6 is a diagram showing the Public Action frame format defined in the IEEE 802.11 standard.

[0085] The Public Action frame is defined as a MAC frame that can be transmitted and received even if the wireless communication device is not associated.

[0086] The Frame Control field is set to 0xd0 (0x means a hexadecimal value), which indicates an Action frame, which is one of the management frames in a MAC frame.

[0087] The Duration field is set to 0. When transmitting a DIS message or a DIO message, the Address1 field is set to 0 in order to set a multicast address.

[0088] The Address1 field is set to a multicast address (or a broadcast address).

[0089] The Address2 field is set with the MAC address of the wireless communication unit that transmits the Public Action frame.

[0090] The Address3 field is set to "ff:ff:ff:ff:ff:ff", which means the wildcard BSSID.

[0091] The Sequence Control field is set to a sequence number.

[0092] The Category field is set to a value that indicates that the frame is a Public Action frame, for example, 0x04.

[0093] The Public Action field is set to 0x09, which means that it is Vendor Specific (meaning that the contents of the Frame Body of the Public Action frame are in a format specified independently by the vendor).

[0094] The OUI field is set to the vendor ID.

[0095] The OUI field is the field for setting values ​​stipulated by the wireless LAN standard. The fields after this are in a format set uniquely by the vendor.

[0096] The OUI Type / Subtype field is an identifier for identifying the purpose for which this frame is used. In this embodiment, for example, in a Mesh network, a value indicating that the frame transmits an RPL message (for example, 0 in the Type field and 0 in the Subtype field) is set. For other purposes, for example, to include information other than an RPL message, the value of the Subtype field can be set to a different value, and if the information is to be transmitted outside the Mesh network, it can be distinguished by setting the value of the Type field to a different value.

[0097] The version field is set to the version that defines this frame.

[0098] The RPL Container field stores an RPL message (DIS message or DIO message). The RPL Length field is set to the octet length of the RPL Message. The RPL Message field is set to the DIS message or DIO message.

[0099] According to this Public Action frame format, wireless communication device 300 can analyze that a DIS message and a DIO message are included. For example, MAC layer unit 313 can determine that the received MAC frame is an Action frame by checking the Frame Control field of the received MAC frame. Next, MAC layer unit 313 can determine that the frame is a Public Action frame by checking the Category field. Furthermore, MAC layer unit 313 can determine that the frame is in a vendor-specific frame format by checking the Public Action field. Then, MAC layer unit 313 can determine that the frame is used by the vendor of its own device by checking the vendor ID in the OUI field.

[0100] By checking the subsequent OUI Type field and Subtype field, the MAC layer unit 313 determines that this frame is a frame that transmits an RPL message used in a Mesh network.

[0101] As a result, it can be seen that the field following the Version field is an RPL Container field, and the first two bytes of that field are an RPL Length field. By checking the RPL Length field, it is possible to know the length of the RPL Message field that follows. By extracting an RPL Message of that length, an IPv6 (Internet Protocol Version 6) packet containing a DIS message or a DIO message is extracted. The Type field included in the ICMPv6 (Internet Control Message Protocol for IPv6) in this IPv6 packet indicates that it is an RPL message, and the value of the Code field makes it possible to distinguish between a DIS message and a DIO message (a Code field value of 0 indicates a DIS message, and a Code field value of 1 indicates a DIO message). Furthermore, by checking the Source Address in the IPv6 packet, it is possible to identify the IPv6 address of wireless communication device 300, the source that sent this RPL message.

[0102] Next, an example of the configuration of wireless communication device 300 when it takes on the role of any one of STA1 to STA4 will be described again.

[0103] (Configuration example of wireless communication device 300 of STA1) In this embodiment, the wireless communication device 300 of STA1 accommodates a wireless communication device 300 operating in STA mode and has a function for wireless communication (AP mode). Therefore, the wireless communication unit 310 of STA1 operates in AP mode. This allows STA1 to accommodate STA2 and STA3.

[0104] (Configuration example of wireless communication device 300 of STA2 and STA3) In this embodiment, the wireless communication devices 300 of STA2 and STA3 have a function (STA mode) of wirelessly connecting to a wireless communication device 300 operating in AP mode and capable of wireless communication, and a function (AP mode) of accommodating a wireless communication device operating in STA mode and capable of wireless communication. Therefore, the wireless communication units of STA2 and STA3 operate in AP mode and STA mode. As a result, STA2 and STA3 can wirelessly connect to STA1 and can accommodate STA4.

[0105] As a configuration for allowing wireless communication device 300 to operate in AP mode and STA mode, there are, for example, a method of operating in a time-division manner and a method of providing two wireless communication units.

[0106] In the time-division operation method, the wireless communication unit 310 separately stores a MAC address set in the device when operating in AP mode and a MAC address when operating in STA mode, and switches between AP mode and STA mode in a time-division manner. The switching timing can be, for example, switching based on a period or switching based on a packet being transmitted or received. Switching based on a period involves, for example, operating in AP mode for the first 50 ms and then repeatedly operating in STA mode for the next 50 ms. Alternatively, switching based on a packet does not have a time period. If a MAC address destined for AP mode is set in the Address1 field of a received MAC frame, the MAC frame is processed in AP mode. If a MAC address destined for STA mode is set, the MAC frame is processed in STA mode. Regarding transmission operations, based on information about the destination of a packet transferred from an upper layer, transmission processing is performed in STA mode if the destination is toward the root node (uplink direction), and transmission processing is performed in AP mode if the destination is opposite to the root node (downlink direction).

[0107] On the other hand, in the method of providing two wireless communication units, wireless communication units having the same functions as wireless communication unit 310 are provided in parallel, and each wireless communication unit is connected to control unit 320. For example, wireless communication unit 310 is operated in AP mode to accommodate STA4, and the other wireless communication unit is operated in STA mode to wirelessly connect to STA1.

[0108] (Configuration example of wireless communication device 300 of STA4) In this embodiment, the wireless communication device 300 of STA4 has a function (STA mode) that enables wireless connection and wireless communication with another wireless communication device 300 operating in AP mode. Therefore, the wireless communication unit 310 of STA4 operates in STA mode. This allows STA4 to wirelessly connect to STA2 or STA3.

[0109] In this embodiment, the wireless communication device 300 of STA4 is described as operating only in STA mode, but the operation of this embodiment can also be applied when operating in AP mode and STA mode, as with STA2 and STA3.

[0110] As described above, the wireless communication device 300 of the first embodiment can prevent a mismatch between the routing table held by the root node and the actual node connection state by stopping the transmission of DAO messages when the parent node is changed. This allows the wireless communication device 300 of the first embodiment to prevent packet loss caused by information from the root node being transmitted via an incorrect route or unnecessary packets being transmitted wirelessly.

[0111] (Second embodiment) Next, a second embodiment will be described. The wireless communication device of the second embodiment has the same configuration as the wireless communication device of the first embodiment. The same components as those in the wireless communication device of the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0112] In the wireless communication device 300 of the first embodiment, when STA4 determines STA3 as the parent node, the method of stopping transmission of the DAO message including the IP address of STA3 is such that STA4 does not transmit the DAO message itself.

[0113] In contrast, wireless communication device 300 of the second embodiment prevents STA4 from sending a new DAO message that includes the IP address of STA3 (that is, it is OK to send a DAO message that includes information about STA2).

[0114] For example, after selecting STA3 as the parent node, the route control unit 322 of STA4 may transmit a DAO message including the IP address of STA2 while STA4 is wirelessly connected to STA2. In this case, information that STA3 is the parent node may be stored in memory, and after STA4 wirelessly connects (associates) with STA3, the route control unit 322 may transmit a DAO message including the IP address of STA3.

[0115] In the wireless communication device 300 of the second embodiment, when the parent node is changed, the transmission of DAO messages including the IP address of the changed parent node is stopped (not the transmission of DAO messages is stopped), thereby eliminating the phenomenon in which the routing table held by the root node does not match the actual node connection state. As a result, like the wireless communication device 300 of the first embodiment, the wireless communication device 300 of the second embodiment can prevent packet loss caused by information from the root node being transmitted via an incorrect route or unnecessary packets being transmitted wirelessly.

[0116] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0117] 300...wireless communication device, 310...wireless communication unit, 311...antenna, 312...PHY layer unit, 313...MAC layer unit, 320...control unit, 321...wireless link control unit, 322...route control unit.

Claims

1. A wireless communication device capable of configuring a wireless mesh network with one or more other wireless communication devices, a wireless communication unit that receives a wireless frame including a first information message related to a route from the one or more other wireless communication devices; a route control unit that determines a wireless communication device to be a parent node from among the one or more other wireless communication devices based on route information included in the first information message; Equipped with When the route control unit determines that a parent node is to be changed to a second wireless communication device among the one or more other wireless communication devices under a situation in which a first wireless communication device among the one or more other wireless communication devices is a parent node, the wireless communication unit wirelessly connects to the second wireless communication device and then transmits a second information message including information about the second wireless communication device. Wireless communication device.

2. The wireless communication device according to claim 1, wherein the wireless communication unit stops transmitting the second information message including information about the second wireless communication device when wirelessly connected to the first wireless communication device after it has been decided to change the parent node from the first wireless communication device to the second wireless communication device.

3. The wireless communication device according to claim 1, wherein the wireless communication unit transmits the second information message including information about the first wireless communication device when wirelessly connected to the first wireless communication device after it has been decided to change the parent node from the first wireless communication device to the second wireless communication device.

4. The wireless communication device according to claim 1, wherein, when the wireless communication unit fails to establish a wireless connection to the second wireless communication device, the route control unit again determines a wireless communication device to be a parent node from among the one or more other wireless communication devices based on the route information contained in the first information message.

5. The wireless communication device according to claim 1 , wherein the wireless communication unit receives an Action frame from a wireless communication device that is not wirelessly connected among the one or more other wireless communication devices.

6. The wireless communication device according to claim 5 , wherein the wireless communication unit receives the first information message by the Action frame.

7. The wireless communication device according to claim 1 , wherein the wireless communication unit transmits the second information message including information about the second wireless communication device using a data type frame defined in a wireless LAN standard.

8. The wireless communication device of claim 7, wherein the data type frame is a non-QoS Data frame or a QoS Data frame.

9. the route information includes a rank value; the route control unit determines, from among the one or more other wireless communication devices, the wireless communication device with the smallest rank value as the wireless communication device to be set as a parent node; The wireless communication device of claim 1 .

10. The first information message is a DIO (DODAG [Destination-Oriented Directed Acyclic Graph] Information Object) message defined in RPL (IPv6 Routing Protocol for Low-power and Lossy networks), a routing protocol; The second information message is a DAO (Destination Advertisement Object) message defined in the RPL. The wireless communication device of claim 1 .

11. A wireless communication method for a wireless communication device capable of configuring a wireless mesh network with one or more other wireless communication devices, comprising: receiving a radio frame including a first information message regarding a route from the one or more other wireless communication devices; determining a wireless communication device to be a parent node from among the one or more other wireless communication devices based on route information included in the first information message; when it is determined that a first wireless communication device among the one or more other wireless communication devices is a parent node and that the parent node is to be changed to a second wireless communication device among the one or more other wireless communication devices, after wirelessly connecting to the second wireless communication device, transmitting a second information message including information about the second wireless communication device; Wireless communication method.

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