Wireless communication device, wireless communication system, and wireless communication method

Abstract

To provide a wireless communication device, a wireless communication system, and a wireless communication method capable of selecting a relay route for each application having different requirements in a wireless communication network.SOLUTION: A wireless communication device 10 includes a packet generating unit 12 that generates a packet having information indicating a sender and a transmission destination stored in a header and having route information indicating a route of the packet according to application requirements stored in a predefined position in a payload, and a packet transmitting unit 13 that transmits the packet generated by the packet generating unit 12 to the destination by wireless communication.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a wireless communication device, a wireless communication system, and a wireless communication method. [Background technology]

[0002] In recent years, digital transformation (DX) has been actively promoted in various industries. The first step in DX is digitalization, and IoT (Internet of Things) technology has been developed with the aim of acquiring and collecting the status of facilities and other equipment as digital data. In IoT, wireless communication technology is often used because communication terminals can be easily installed, and many systems have been developed as wireless communication technology (LPWA: Low Power Wide Area) that is slow but capable of long-distance transmission.

[0003] LPWA may have relay and routing functions to improve connectivity for communication terminals installed behind objects and to improve scalability to cover a wide area. Normally, relay in LPWA is performed by specifying a route in advance, and routing is performed by determining a route according to a single metric. The following Patent Documents 1 and 2 disclose an example of a wireless communication system that transfers data by segment routing. Segment routing is a routing technology that represents a network as segments and enables route setting according to the policy by assigning a policy to the segment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-058267 [Patent Document 2] JP 2019-180009 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the future, as the need to utilize IoT increases, it is expected that individual LPWA networks will be built for each application. However, from the viewpoint of sharing communication equipment and efficient operation, it is also expected that multiple applications will be accommodated in a single LPWA network. In this case, if the requirements for communication by different applications are similar, there is no problem, but if the requirements are different, it is considered that while a conventional LPWA network can accommodate one requirement, it will be difficult to satisfy the other requirement. For example, there are cases such as sensing, where some loss is acceptable but it is desirable to have a small number of relays in order to complete communication quickly, and cases such as device control, where it is desirable to select a highly stable route while satisfying the required transmission time in order to minimize loss.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a wireless communication device, a wireless communication system, and a wireless communication method that are capable of selecting a relay route for each application with different requirements in a wireless communication network. [Means for solving the problem]

[0007] In order to solve the above problem, a wireless communication device according to a first aspect of the present invention is a wireless communication device (10) that transmits a packet having a header (HD) and a payload (PL) from a source to a destination via wireless communication based on information indicating the source and the destination stored in the header, and includes a packet generation unit (12) that generates a packet in which the information indicating the source and the destination is stored in the header and route information indicating a route of the packet in accordance with application requirements is stored in a predefined position, and a packet transmission unit (13) that transmits the packet generated by the packet generation unit to the destination via wireless communication.

[0008] A wireless communication device according to a second aspect of the present invention is a wireless communication device according to the first aspect of the present invention, comprising a packet receiving unit (14) that receives an incoming packet, and a packet processing unit (15) that changes information indicating the source and destination stored in the header of the packet based on the route information stored in the packet received by the packet receiving unit, and causes the packet transmitting unit to transmit the changed packet.

[0009] A wireless communication device according to a third aspect of the present invention is a wireless communication device according to the second aspect of the present invention, in which when the packet processing unit changes the information indicating the source and destination stored in the header of a packet received by the packet receiving unit, the packet processing unit also changes the route information in accordance with the changes made.

[0010] A wireless communication device according to a fourth aspect of the present invention is a wireless communication device according to the second or third aspect of the present invention, wherein the packet processing unit performs a process of extracting the payload when the route information stored in a packet received by the packet receiving unit indicates the wireless communication device that generated the packet.

[0011] A wireless communication device according to a fifth aspect of the present invention is a wireless communication device according to the second or third aspect of the present invention, in which, when a packet received by the packet receiving unit is a non-specific packet that does not specify the destination, the packet processing unit performs processing to transmit the non-specific packet to the packet transmitting unit when the received power (RSS) of the wireless signal at the packet receiving unit is below a predetermined threshold (RSSth).

[0012] A wireless communication device according to a sixth aspect of the present invention is a wireless communication device according to the fifth aspect of the present invention, in which, when the packet received by the packet receiving unit is the non-specific packet, the packet processing unit performs processing to transmit the non-specific packet to the packet transmitting unit if the number of times the non-specific packet has been received after a predetermined time has elapsed is still one.

[0013] A wireless communication device according to a seventh aspect of the present invention is a wireless communication device according to the sixth aspect of the present invention, in which the packet processing unit autonomously generates a received power table indicating the received power of wireless signals transmitted from other wireless communication devices based on the received power of wireless signals at the packet receiving unit.

[0014] A wireless communication device according to an eighth aspect of the present invention is the wireless communication device according to the seventh aspect of the present invention, wherein the packet processing unit generates the route information based on the received power table that is generated autonomously.

[0015] A wireless communication system (1) of the present invention includes a plurality of wireless communication devices according to any one of the first to eighth aspects of the present invention, which are connected in a mesh pattern.

[0016] The wireless communication method of the present invention is a wireless communication method for transmitting a packet having a header (HD) and a payload (PL) from a source to a destination via wireless communication based on information indicating the source and destination stored in the header, wherein a packet is generated in which the information indicating the source and destination is stored in the header and route information indicating the route of the packet in accordance with the requirements of an application is stored in a predefined position, and the generated packet is transmitted to the destination via wireless communication. Effect of the Invention

[0017] According to the present invention, it is possible to select a relay route for each application having different requirements in a wireless communication network. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing a schematic configuration of a wireless communication system according to an embodiment of the present invention; [Diagram 2] 1 is a diagram showing the configuration of a packet handled in a wireless communication system according to an embodiment of the present invention. [Diagram 3] 1 is a block diagram showing a configuration of a main part of a wireless communication device according to an embodiment of the present invention; [Figure 4] 1 is a diagram illustrating a wireless communication method according to an embodiment of the present invention. [Diagram 5] 5 is a flowchart illustrating a method for retransmitting a broadcast packet in a wireless communication device according to an embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing how the broadcast packet is gradually received by wireless communication devices located further away as a result of the processing shown in FIG. 5 being performed. [Figure 7] FIG. 2 is a diagram showing how an RSS table is constructed in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wireless communication device, a wireless communication system, and a wireless communication method according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Wireless Communication System FIG. 1 is a diagram showing a schematic configuration of a wireless communication system according to an embodiment of the present invention. As shown in FIG. 1, the wireless communication system 1 of this embodiment includes a plurality of wireless communication devices 10 connected in a mesh pattern. FIG. 1 illustrates a wireless communication system 1 including seven wireless communication devices 10 (wireless communication devices 10a to 10g). In the following description, when there is no need to distinguish between the seven wireless communication devices, they will be referred to as "wireless communication device 10," and when they are to be distinguished, they will be referred to as "wireless communication devices 10a to 10g." In addition, in FIG. 1, for ease of understanding, wireless communication paths established between the wireless communication devices 10 are shown by dashed lines.

[0021] The wireless communication system 1 shown in Fig. 1 constitutes an LPWA network. LPWA is a general term for wireless communication technology that is slow but capable of long-distance transmission, and in Japan, it often refers to systems that mainly use the 920 MHz band. LPWA standards include, for example, LoRa (registered trademark), Wi-SUN FAN (registered trademark), Wi-Fi HaLow (registered trademark), ZETA (registered trademark), SigFox (registered trademark), and ELTRES (registered trademark).

[0022] Also, LPWA can be broadly divided into private network type and public network type. In the former, the wireless communication device 10 is connected to a gateway installed by the user, and the gateway transfers data from the wireless communication device 10 to a private server or a cloud server. The user needs to prepare the communication network between the gateway and the server by himself, but the LPWA network can be constructed wherever necessary. In the latter, the wireless communication device 10 installed within the connection area of ​​the base station constructed by each service provider is connected to the base station, and data from the wireless communication device 10 is stored in a cloud server provided by the service provider via the base station. While data can be collected just by installing the wireless communication device 10, services cannot be received in places without base station facilities.

[0023] The wireless communication system 1 in this embodiment is a privately-operated LPWA network that allows flexibility in network construction and is intended for LoRa (registered trademark), which has a relatively simple configuration.

[0024] In the wireless communication system 1, a part of the function of segment routing is utilized as a method for setting a route corresponding to applications with different requirements. In this embodiment, the routing utilizing the part of the function of segment routing is referred to as "simplified segment routing."

[0025] In simple segment routing, similar to segment routing, a route is selected according to an assigned policy, and a different label is assigned to each selected route. For example, when "minimum delay time" is assigned as a policy, a route with a small number of hops is selected, and a certain label (e.g., label A) is assigned to the selected route. In contrast, when "maximum reliability" is assigned as a policy, a route with a large link margin is selected, and a different label (e.g., label B) is assigned to the selected route.

[0026] However, the wireless communication device 10 constituting the wireless communication system 1 for LoRa has limited computing resources. Also, it is difficult to increase the packet size in the wireless communication system 1 for LoRa. For this reason, in simple segment routing, a label is stored in the payload of the packet as route information, and the wireless communication device 10 refers to this label to identify the next destination (next hop).

[0027] Fig. 2 is a diagram showing the configuration of a packet handled in a wireless communication system according to an embodiment of the present invention. As shown in Fig. 2, a packet has a header HD and a payload PL. The header HD stores a source ID (Source ID) indicating the wireless communication device 10 as the source, an ID (PAN ID) indicating the PAN (Personal Area Network), and a destination ID (Dest. ID) indicating the wireless communication device 10 as the destination. The above-mentioned label is stored at the beginning of the payload PL. The rest of the payload PL except for the part where the label is stored is used as the original payload for storing data. Specific examples of labels will be described later.

[0028] Wireless Communication Device Fig. 3 is a block diagram showing the main configuration of a wireless communication device according to an embodiment of the present invention. As shown in Fig. 3, a wireless communication device 10 of this embodiment includes a label storage unit 11, a packet generation unit 12, a packet transmission unit 13, a packet reception unit 14, and a packet processing unit 15. Such a wireless communication device 10 transmits a packet having a header HD and a payload PL shown in Fig. 2 from a source to a destination by wireless communication based on a source ID and a destination ID (information indicating a source and a destination) stored in the header HD.

[0029] The label storage unit 11 stores the labels used in the above-mentioned simple segment routing. These labels can also be considered as route information indicating the route of a packet according to the requirements of an application. The label storage unit 11 stores labels for the policies assigned to the segments. Details of the labels will be described later.

[0030] The packet generator 12 generates a packet as shown in Fig. 2. Specifically, the packet generator 12 generates a packet in which a source ID, an ID indicating a PAN, and a destination ID are stored in the header HD, and a label according to an assigned policy is stored in the leading portion of the payload PL. The remaining portion of the payload PL of the generated packet stores, for example, data to be transmitted. The packet generator 12 outputs the generated packet to the packet transmitter 13.

[0031] The packet transmitting unit 13 transmits, via wireless communication, to a destination, a packet output from the packet generating unit 12 or a packet output from the packet processing unit 15. Specifically, the packet transmitting unit 13 transmits a packet output from the packet generating unit 12 or a packet output from the packet processing unit 15 to the wireless communication device 10 identified by a destination ID stored in the header HD of the packet.

[0032] The packet receiving unit 14 receives packets transmitted from other wireless communication devices 10. The packet receiving unit 14 outputs the received packets to the packet processing unit 15. The packet receiving unit 14 is also capable of detecting received signal strength (RSS) of wireless signals transmitted from other wireless communication devices 10. The received signal strength of the wireless signals detected by the packet receiving unit 14 is output to the packet processing unit 15.

[0033] The packet processing unit 15 performs a predetermined process on the packet received by the packet receiving unit 14. For example, the packet processing unit 15 performs a relay process on the packet received by the packet receiving unit 14. Specifically, the packet processing unit 15 changes the source ID and destination ID stored in the header HD of the packet received by the packet receiving unit 14 based on the label stored in the payload PL of the packet, and causes the packet transmitting unit 13 to transmit the changed packet. Here, when the packet processing unit 15 changes the source ID and destination ID stored in the header HD of the packet received by the packet receiving unit 14, it also changes the label stored in the payload PL according to the changed content.

[0034] Furthermore, the packet processing unit 15 performs processing to extract data stored in the packet received by the packet receiving unit 14. Specifically, when a label stored in the payload PL of the packet received by the packet receiving unit 14 indicates the wireless communication device 10 that generated the packet, the packet processing unit 15 performs processing to extract the payload (a portion of the payload PL shown in FIG. 3 excluding the portion where the label is stored).

[0035] In addition, the packet processing unit 15 autonomously generates a received power table indicating the received power of wireless signals transmitted from other wireless communication devices 10, based on the received power of the wireless signals detected by the packet receiving unit 14. The packet processing unit 15 generates a label based on the autonomously generated received power table, and stores the generated label in the label storage unit 11.

[0036] In order to generate the above-mentioned received power table, the packet processing unit 15 causes the packet transmitting unit 13 to transmit a packet with no specified destination. Here, a packet with no specified destination is a packet (non-specific packet) with a destination ID of 0xFFFF in the header HD. Since the destination of this packet is not specified, it can be said to be a broadcast packet that is transmitted simultaneously to all wireless communication devices 10.

[0037] Specifically, when the packet received by the packet receiving unit 14 is a broadcast packet, the packet processing unit 15 performs a process of retransmitting the broadcast packet. Specifically, the packet processing unit 15 judges whether or not the reception power (RSS) of the radio signal detected by the packet receiving unit 14 when the broadcast packet is received by the packet receiving unit 14 is greater than a predefined threshold (RSSth). When the packet processing unit 15 judges that the reception power of the radio signal detected by the packet receiving unit 14 is equal to or less than the predefined threshold (RSSth), the packet processing unit 15 performs a process of causing the packet transmitting unit 13 to transmit the broadcast packet received by the packet receiving unit 14.

[0038] On the other hand, when the packet processing unit 15 determines that the reception power of the wireless signal detected by the packet receiving unit 14 is greater than a predetermined threshold (RSSth), the packet processing unit 15 determines whether the number of times the broadcast packet has been received remains one until a predetermined time has elapsed. In other words, the packet processing unit 15 determines whether a broadcast packet has been received again since the broadcast packet was received. When the packet processing unit 15 determines that the number of times the broadcast packet has been received remains one, the packet processing unit 15 performs a process of causing the packet transmitting unit 13 to transmit the broadcast packet received by the packet receiving unit 14.

[0039] Wireless Communication Method Fig. 4 is a diagram for explaining a wireless communication method according to an embodiment of the present invention. Fig. 4(a) is a diagram showing an example of a route along which a packet is transmitted, and Figs. 4(b) and (c) are diagrams showing an example of the contents of the transmitted packet. In Fig. 4(a), the wireless communication devices 10a to 10g shown in Fig. 1 are illustrated as nodes N1 to N7. Also, the node numbers of the nodes N1 to N7 are "1" to "7" as illustrated. Also, in Fig. 4(a), the numerical values ​​attached to the lines connecting each node (numerical values ​​between nodes) are the received power (RSS) [dBm] of the wireless signal.

[0040] 4 shows an example of a route with label A and a route with label B. The route with label A is, for example, a route with a small number of hops and with a policy of "minimum delay time." The route with label B is, for example, a route with a large link margin and with a policy of "maximum reliability."

[0041] Here, the label given to the route is obtained by arranging the node numbers of the remaining nodes excluding the first node among the multiple nodes existing on the route in route order, with the node number of the first node at the end, followed by a delimiter indicating the boundary with the payload (Payload in Fig. 3). For example, label A is obtained by arranging the node numbers "4" and "7" of the remaining nodes N4 and N7, excluding the first node N1, among the multiple nodes N1, N4, and N7 existing on the route in route order, with the node number "1" of the first node N1 at the end, followed by the delimiter "_" (471_). In addition, label B is the node numbers "2", "4", "5", and "7" of the remaining nodes N2, N4, N5, and N7 on the route, excluding the first node N1, arranged in route order, with the node number "1" of the first node N1 listed last, followed by the delimiter "_" (24571_).

[0042] Here, an example will be described in which a packet is transmitted along a route to which a label A is attached. For ease of explanation, it is assumed that the label A is stored in the label storage unit 11 of the wireless communication device 10a (node ​​N1). First, the packet generation unit 12 of the wireless communication device 10a (node ​​N1) reads the label A stored in the label storage unit 11, and generates a packet to be transmitted along the route to which the label A is attached, based on the read label A.

[0043] Specifically, as shown in Fig. 4(b), the read label A (471_) is stored at the beginning of the payload PL, and a packet is generated in which a source ID and destination ID based on label A and an ID indicating the PAN are stored in the header HD. The source ID based on label A is "0001" indicating the node number of node N1, and the destination ID is "0004" indicating the node number of node N4. The ID indicating the PAN in the example shown in Fig. 4(b) is "1111".

[0044] The packet generated by the packet generation unit 12 of the wireless communication device 10a (node ​​N1) is output to the packet transmission unit 13. Then, the packet is transmitted by the packet transmission unit 13 of the wireless communication device 10a (node ​​N1) to the destination (node ​​N4) indicated by the destination ID stored in the header HD.

[0045] When the packet receiver 14 of the wireless communication device 10d (node ​​N4) receives a packet transmitted from the wireless communication device 10a (node ​​N1), it outputs the received packet to the packet processor 15. The packet processor 15 relays the packet output from the packet receiver 14. Specifically, the packet processor 15 changes the source ID and destination ID stored in the header HD of the packet based on the label (471_) stored in the payload PL of the packet received by the packet receiver 14. Specifically, as shown in FIG. 4(c), it changes the source ID in the header HD to "0004" indicating the node number of node N4, and changes the destination ID to "0007" indicating the node number of node N7.

[0046] When the packet processing unit 15 of the wireless communication device 10d (node ​​N4) changes the source ID and destination ID stored in the packet header HD, it also changes the label stored in the payload PL according to the changes. Specifically, it deletes the beginning of the label (471_) stored in the payload PL. That is, as shown in FIG. 4(c), it changes the label to (71_) with the node number (4) of the wireless communication device 10d (node ​​N4) deleted.

[0047] The packet that has been subjected to the above processing is output from the packet processing unit 15 of the wireless communication device 10d (node ​​N4) to the packet transmitting unit 13. Then, the packet is transmitted by the packet transmitting unit 13 of the wireless communication device 10d (node ​​N4) to the destination (node ​​N7) indicated by the destination ID stored in the header HD.

[0048] Upon receiving a packet transmitted from wireless communication device 10d (node ​​N4), packet receiver 14 of wireless communication device 10g (node ​​N7) outputs the received packet to packet processor 15. Like packet processor 15 of wireless communication device 10d (node ​​N4), packet processor 15 attempts to relay the packet output from packet receiver 14. However, when packet processor 15 deletes the beginning of the label (71_) stored in the payload PL of the packet output from packet receiver 14, the new label becomes (1_).

[0049] The packet processing unit 15 determines that there is no need to forward the packet because the new label has one character before the delimiter. The packet processing unit 15 also recognizes that the packet was generated by the wireless communication device 10a (node ​​N1) indicated by the character (1) before the delimiter, and that the final destination of the packet is its own device (wireless communication device 10g (node ​​N7)). The packet processing unit 15 then performs a process of extracting the payload (a portion of the payload PL shown in FIG. 3 excluding the portion where the label is stored).

[0050] By carrying out the above process, the packet is transmitted along a route to which label A is assigned (e.g., a route with a small number of hops). Note that, when a packet is transmitted along a route to which label B is assigned (e.g., a route with high and stable received power), the same operation as described above is carried out.

[0051] <Method of collecting information for establishing relay routes> In the wireless communication system 1 using simple segment routing, it is necessary to grasp the structure and state of the network when selecting a relay route. Since the transmission speed of LPWA is slow, if data transmission for grasping the state is not performed efficiently, it may affect the transmission of application data. For this reason, in the wireless communication system 1 of this embodiment, only broadcast packets (broadcast messages) are exchanged between the wireless communication devices 10, so that all the wireless communication devices 10 obtain the same network topology information.

[0052] Fig. 5 is a flowchart showing a method for retransmitting a broadcast packet in a wireless communication device in one embodiment of the present invention. It is possible that the broadcast packet will not reach a wireless communication device 10 located far away from the wireless communication device 10 to which the broadcast packet was transmitted. For this reason, the wireless communication device 10 that received the broadcast packet transmits (retransmits) the broadcast packet according to the process of the flowchart shown in Fig. 5, so that the wireless communication device 10 located far away can also receive the broadcast packet. The process of the flowchart shown in Fig. 5 is started when each of the wireless communication devices 10 constituting the wireless communication system 1 receives a broadcast packet.

[0053] 5 starts, first, the packet processing unit 15 of the wireless communication device 10 judges whether or not the received power (RSS) of the wireless signal detected by the packet receiving unit 14 is greater than a predefined threshold (RSSth) (step S11). If the packet processing unit 15 judges that the received power (RSS) of the wireless signal is equal to or less than the threshold (RSSth) (if the judgment result in step S11 is "NO"), it performs a process of causing the packet transmitting unit 13 to transmit the broadcast packet received by the packet receiving unit 14 (step S12).

[0054] On the other hand, if the packet processing unit 15 determines that the received power (RSS) of the wireless signal is greater than the threshold (RSSth) (if the determination result in step S11 is "YES"), it waits for a certain period of time (step S13). The waiting time can be set arbitrarily taking into consideration the number of wireless communication devices 10 provided in the wireless communication system 1, etc. After waiting for the certain period of time, the packet processing unit 15 determines whether the number of times the broadcast packet has been received is two or more (step S14).

[0055] If the packet processing unit 15 determines that the broadcast packet has not been received twice or more (if the determination result in step S14 is "NO"), it performs processing to have the packet transmitting unit 13 transmit the broadcast packet received by the packet receiving unit 14 (step S12). This is because there is a risk that the broadcast packet has not reached a location farther away than the device itself.

[0056] On the other hand, if the packet processing unit 15 determines that the broadcast packet has been received twice or more (if the determination result in step S14 is "YES"), the packet processing unit 15 ends the series of processes shown in Fig. 5 without causing the packet transmitting unit 13 to transmit the broadcast packet. This is because it is considered that there is another wireless communication device 10 (for example, a wireless communication device 10 located farther away than the own device) that has received the broadcast packet.

[0057] Fig. 6 is a diagram showing how the broadcast packet is gradually received by wireless communication devices located further away by performing the process shown in Fig. 5. Fig. 5(a) is a diagram showing the case where the broadcast packet is transmitted for the first time, Fig. 5(b) is a diagram showing the case where the broadcast packet is transmitted for the second time, and Fig. 5(c) is a diagram showing the case where the broadcast packet is transmitted for the third time. In Fig. 6, it is assumed that eight nodes N10 to N17 (wireless communication devices 10) are arranged as shown in the figure. It is also assumed that the first broadcast packet is transmitted by node N10.

[0058] 6 also shows two concentric circles CR1 and CR2 of different sizes. The inner concentric circle CR1 is a circle showing a portion where the received power (RSS) of the wireless signal is a threshold (RSSth). The outer concentric circle CR2 is a circle showing a portion where the received power (RSS) of the wireless signal is the minimum received power (RSSmin) at which the wireless signal can be received. In other words, nodes located outside the outer concentric circle CR2 cannot receive broadcast packets.

[0059] 6(a), the first broadcast packet transmitted from node N10 is received by nodes N11 to N13 arranged inside the outer concentric circle CR2. Therefore, the number of times the broadcast packet is received by nodes N11 to N13 is one.

[0060] Here, in the nodes N11 and N12 arranged inside the inner concentric circle CR1, the received power (RSS) of the wireless signal becomes greater than the threshold (RSSth). In contrast, in the node N13 located between the inner concentric circle CR1 and the outer concentric circle CR2, the received power (RSS) of the wireless signal becomes equal to or less than the threshold (RSSth). Therefore, by the process of the flowchart shown in FIG. 5, the nodes N11 and N12 enter a standby state, and the second broadcast packet is transmitted from the node N13.

[0061] 6(b), the second broadcast packet transmitted from node N13 is received by nodes N12, N15, and N17 located inside the outer concentric circle CR2. Therefore, the number of times the broadcast packet is received at nodes N15 and N17 is one, and the number of times the broadcast packet is received at node N12 is two. Note that node N10, which transmitted the broadcast packet, is excluded.

[0062] Here, in the nodes N12, N15, and N17 arranged inside the inner concentric circle CR1, the received power (RSS) of the wireless signal becomes greater than the threshold (RSSth). Therefore, the nodes N12, N15, and N17 enter a standby state by the process of the flowchart shown in Fig. 5. When a certain time has elapsed since the node N11 entered the standby state, the node N11 transmits a third broadcast packet by the process of the flowchart shown in Fig. 5.

[0063] As shown in Fig. 6(c), the third broadcast packet transmitted from node N11 is received by nodes N14 and N16 arranged inside the outer concentric circle CR2. Therefore, the number of times the broadcast packet is received at nodes N14 and N16 is one. Note that node N10 that transmitted the broadcast packet is excluded. This operation is repeated, and the broadcast packet is gradually received by wireless communication devices 10 located farther away.

[0064] How to build an RSS table The packet processing unit 15 of the wireless communication device 10 provided in the wireless communication system 1 can know the received power (RSS) of wireless signals transmitted from other wireless communication devices 10 by transmitting and receiving broadcast packets according to the processing of the flowchart shown in Fig. 5. This allows the packet processing unit 15 provided in each of the wireless communication devices 10 to autonomously build a table (RSS table) relating to the received power of other wireless communication devices 10 located in the vicinity.

[0065] Here, each of the wireless communication devices 10 broadcasts an RSS table related to the device itself (hereinafter, referred to as its own RSS table) at regular intervals (e.g., every hour, etc.) As a result, each of the wireless communication devices 10 transmits a broadcast packet at least once within the regular interval.

[0066] The RSS table stores the received power values ​​of other wireless communication devices 10. However, when the wireless communication device 10 broadcasts its own RSS table, for simplicity, it does not transmit the received power values ​​themselves, but classifies the received power values ​​into categories according to their strength, and transmits the classified categories.

[0067] For example, when the receiving sensitivity is -120 dBm, the received power value is classified into the following four categories: "A", "B", "C", and "N". A:RSS>-80dBm B:-80dBm≧RSS>-100dBm C:-100dBm≧RSS>-120dBm N: Not observable

[0068] Here, in the own RSS table, received power values ​​are listed in order of the numbers (node ​​numbers) of the wireless communication devices 10. For this reason, when the wireless communication device 10 broadcasts its own RSS table, it broadcasts as a payload a list of categories according to the strength of received power values ​​in order of the numbers (node ​​numbers) of the wireless communication devices 10. For example, when there are "10" wireless communication devices 10, the own RSS table broadcast from the wireless communication device 10 with node number 1 will be something like "ZAACBCNNBC". Note that "Z" in the own RSS table indicates the own device.

[0069] The wireless communication device 10 that receives the RSS table broadcast from the wireless communication device 10 with node number 1 understands the connection state with the wireless communication device 10 with node number 1. Also, each wireless communication device 10 broadcasts its own RSS table at an appropriate timing. By repeating such operations, the same RSS table is constructed in all wireless communication devices 10.

[0070] Fig. 7 is a diagram showing how an RSS table is constructed in one embodiment of the present invention. The RSS table shown in Fig. 7 is for six wireless communication devices 10. This RSS table is constructed by, for example, broadcasting its own RSS table in order from the wireless communication device 10 with node number 6 to the wireless communication device 10 with node number 1, and updating the RSS table in each of the wireless communication devices 10.

[0071] The RSS table shown in Fig. 7(a) is an initial state RSS table in a wireless communication device 10 with node number 6. The RSS table shown in Fig. 7(b) is an RSS table in a wireless communication device 10 with node number 5 after the wireless communication device 10 with node number 6 broadcasts its own RSS table. The RSS table shown in Fig. 7(c) is an RSS table in a wireless communication device 10 with node number 4 after the wireless communication device 10 with node number 5 broadcasts its own RSS table. The RSS table shown in Fig. 7(d) is an RSS table in a wireless communication device 10 with node number 6 after the wireless communication device 10 with node number 1 broadcasts its own RSS table.

[0072] As shown in Fig. 7(a), in the initial state, all the entries in the RSS table of the wireless communication device 10 with node number 6 are "N". First, assume that the wireless communication device 10 with node number 6 transmits its own RSS table, which causes the wireless communication devices 10 with node numbers 1 and 3 to retransmit broadcast packets. Then, as shown in Fig. 7(b), the RSS table of the wireless communication device 10 with node number 5 contains the received power of node numbers 1, 3, and 6.

[0073] Next, assume that the wireless communication device 10 with node number 5 transmits its own RSS table, which causes the wireless communication devices 10 with node numbers 1 to 3 and 6 to retransmit broadcast packets. Then, as shown in FIG 7(c), the RSS table of the wireless communication device 10 with node number 4 obtains the received power of the wireless communication devices 10 with node numbers 1 to 3, 5 and 6.

[0074] Suppose that the wireless communication devices 10 with node numbers 4, 3, 2, and 1 successively transmit their own RSS tables. Then, as shown in Fig. 7(d), the RSS table of the wireless communication device 10 with node number 6 contains the connection status with all other wireless communication devices 10. Note that wireless communication devices 10 other than the wireless communication device 10 with node number 6 also construct RSS tables similar to the RSS table shown in Fig. 7(d).

[0075] The packet processor 15 provided in the wireless communication device 10 generates a label based on the RSS table generated autonomously by the above process. For example, when the policy "minimum delay time" is assigned, the packet processor 15 searches for a route with the smallest possible number of hops while referring to the RSS table, and generates a label based on the node number of the wireless communication device 10 located on the searched route.

[0076] As described above, in this embodiment, a packet is generated in which a source ID and a destination ID are stored in the header HD, and a label indicating a packet route according to the requirements of an application is stored in a predefined position in the payload PL, and the generated packet is transmitted by wireless communication to a destination specified by the destination ID. This makes it possible to select a relay route for each application with different requirements in a wireless communication network.

[0077] Although the wireless communication device, the wireless communication system, and the wireless communication method according to one embodiment of the present invention have been described above, the present invention is not limited to the above-mentioned embodiment, and can be freely modified within the scope of the present invention. For example, in the above embodiment, for the sake of simplicity, an example has been described in which the wireless communication system 1 is configured with 10 or less wireless communication devices 10, but the number of wireless communication devices 10 constituting the wireless communication system 1 is arbitrary.

[0078] In addition, in the above embodiment, for the sake of simplicity, an example has been given in which the policies "minimum delay time" and "maximum reliability" are assigned, but the present invention is not limited to the assignment of these two policies and can accommodate any policy.

[0079] In the above embodiment, an example has been described in which the label is stored at the beginning of the payload PL, but the position at which the label is stored is not limited to the beginning of the payload PL. The label may be stored at a predetermined position in the header, or at a predetermined position other than the beginning of the payload PL. In other words, it is sufficient that the label is stored at a predetermined position in the packet. [Explanation of symbols]

[0080] 1. Wireless communication systems 10 Wireless communication devices 12 Packet Generation Unit 13 Packet transmitter 14 Packet receiver 15 Packet Processing Unit HD Header PL Payload RSS reception power RSSth threshold

Claims

1. 1. A wireless communication device that wirelessly transmits a packet having a header and a payload from a source to a destination based on information indicating a source and a destination stored in the header, the wireless communication device comprising: a packet generator that generates a packet in which information indicating the source and the destination is stored in the header and route information indicating a route of the packet according to a requirement of an application is stored in a predefined position; a packet transmission unit that transmits the packet generated by the packet generation unit to the destination by wireless communication; A wireless communication device comprising:

2. a packet receiving unit that receives transmitted packets; a packet processing unit that changes information indicating the source and the destination stored in the header of the packet based on the route information stored in the packet received by the packet receiving unit, and causes the packet transmitting unit to transmit the changed packet; The wireless communication device of claim 1 .

3. 3. The wireless communication device of claim 2, wherein when the packet processing unit changes the information indicating the source and destination stored in the header of the packet received by the packet receiving unit, the packet processing unit also changes the route information in accordance with the changes.

4. The wireless communication device according to claim 2, wherein the packet processing unit performs a process of extracting the payload when the route information stored in the packet received by the packet receiving unit indicates the wireless communication device that generated the packet.

5. 3. The wireless communication device of claim 2, wherein the packet processing unit, when the packet received by the packet receiving unit is a non-specific packet that does not specify the destination, performs processing to transmit the non-specific packet to the packet transmitting unit when the received power of the wireless signal at the packet receiving unit is below a predetermined threshold.

6. The wireless communication device of claim 5, wherein when the packet received by the packet receiving unit is the non-specific packet, and the received power of the wireless signal at the packet receiving unit is greater than a predetermined threshold, if the number of times the non-specific packet has been received after a predetermined time has elapsed remains one, the packet processing unit performs processing to transmit the non-specific packet to the packet transmitting unit.

7. The wireless communication device according to claim 6 , wherein the packet processing unit autonomously generates a received power table indicating received power of wireless signals transmitted from other wireless communication devices, based on received power of the wireless signals at the packet receiving unit.

8. The wireless communication device according to claim 7 , wherein the packet processing unit generates the route information based on the received power table that is generated autonomously.

9. A wireless communication system comprising a plurality of wireless communication devices according to claim 1 , connected in a mesh pattern.

10. 1. A wireless communication method for wirelessly transmitting a packet having a header and a payload from a source to a destination based on information indicating a source and a destination stored in the header, the method comprising: generating a packet in which information indicating the source and destination is stored in the header and route information indicating a route of the packet in accordance with a requirement of an application is stored in a predefined location; Transmitting the generated packet to the destination via wireless communication; A wireless communication method.

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