DESCRIPTION
Title of Invention: WIRELESS COMMUNICATION APPARATUS AND WIRELESS COMMUNICATION METHOD Technical Field
[0001] The present invention relates to a wireless communication apparatus and also relates to a technique for updating route information in a network composed of a plurality of wireless communication apparatuses. Background Art
[0002] A wireless M2M (Machine-to-Machine) system has been widely applied to cost reduction of wireless modules and expansion of a band not requiring licenses due to frequency reorganization. The wireless M2M system is a system that transmits and receives monitoring information or control data between devices by wireless communication. In the wireless M2M system, since communication is performed between devices arranged in a wide area, extension of communication distance is one of issues.
[0003] As a technique to extend the communication distance, there is a multi-hop communication technology in which a relay node is placed between a transmission source node and a destination node, data transmitted from the transmission source node is received by the relay node, and the relay node transmits the data to the destination node. By applying the multi-hop communication technology, it becomes possible to extend the communication distance between the transmission source node and the destination node without extending communication distance of a wireless link. As one of the multi-hop communication technologies, there is RPL (IPv6 Routing Protocol for Low Power and Lossy Networks) standardized by IETF (see Non-Patent

Literature 1 mentioned below).
[0004] In wireless communication, the situation of radio waves changes from moment to moment, so regular update of a route to communicate is indispensable. In the RPL, a node and a gateway periodically transmit route information for updating a route. Each node constitutes a multi-hop network of a tree structure in which the gateway functions as a root. The node decides an upward route in the direction from the node to the gateway, based on the route information periodically transmitted from the gateway. Also, the node decides a downward route in the direction from the gateway to other nodes, based on the route information periodically transmitted from the other nodes.
[0005] Updating an upward route and a downward route in the RPL will be explained, using Figs. 19 to 21.
Fig. 19 is a diagram illustrating an example of a network configuration. In a network 90, a gateway 91 and nodes 92a to c exist. The node 92a is adjacent to the node 92b. The node 92a is an upper node of the node 92b and the node 92c. The node 92b is adjacent to the node 92c. The node 92b is an upper node of the node 92c. [0006] First, updating an upward route will be explained.
Fig. 20 is a diagram illustrating a sequence for updating the upward route.
The gateway sets upward route information to an upward route control message and periodically transmits the upward route control message by broadcast (S801). Upon receiving the upward route control message from the gateway, the node 92a updates the upward route information toward the gateway (S802). The node 92a sets the updated upward route information to the upward route control message and transmits the upward route control message by broadcast (S803). The node 92b receives the upward route control message from the node 92a and updates

the upward route information toward the gateway (S 804). The node 92b sets the updated upward route information to the upward route control message and transmits the upward route control message by broadcast (S805). The node 92c receives the upward route control message from the node 92b and updates the upward route information toward the gateway (S 806). The node 92c sets the updated upward route information to the upward route control message and transmits the upward route control message by broadcast (S807). [0007] Next, updating a downward route will be explained.
Fig. 21 is a diagram illustrating a sequence for updating the downward route. The nodes 92a to c transmit a downward route control message periodically to adjacent upper nodes by unicast.
The node 92c transmits the downward route control message by unicast to the node 92b which is an adjacent upper node (S901).
Upon receiving the downward route control message, the node 92b updates the downward route information toward the node 92c (S902). In addition, the node 92b transmits the downward route control message in which the updated downward route information is set to the node 92a which is an adjacent upper node (S 903). Upon receiving the downward route control message, the node 92a updates the downward route information toward the node 92c (S904). Further, the node 92a transmits the downward route control message in which the updated downward route information is set to the gateway (S905). Upon receiving the downward route control message, the gateway updates the downward route information toward the node 92c (S906).

Citation List Non-Patent Literature
[0008] Non-Patent Literature 1: IETF RFC6550, "IPv6 Routing Protocol for Low-Power and Lossy Networks" Summary of Invention Technical Problem
[0009] However, there is a problem that in the RPL, a route is dynamically updated
and the route cannot be fixed.
[0010] The present invention is made to solve the problem as described above and
aims to obtain a wireless communication apparatus which fixes a route when using the
RPL.
Solution to Problem
[0011] A wireless communication apparatus according to the present invention,
includes:
a wireless communication control unit to output, upon receiving via another wireless communication apparatus a wireless signal addressed to the wireless communication apparatus including a message related to a route control, the message; and
a network control unit to transmit, when the message input from the wireless communication control unit is a route setting request in which an adjacent wireless communication apparatus which is to be passed through is designated as an upward route toward a gateway, a downward route control message including address information of the wireless communication apparatus thorough an upward route which satisfies a designation of the route setting request. Advantageous Effects of Invention

[0012] According to the present invention, it is possible to fix the route using the
RPL.
Brief Description of Drawings
[0013] Fig. 1 is a diagram illustrating an example of a network configuration according to a first embodiment;
Fig. 2 is a block diagram illustrating an example of a functional configuration of a node according to the first embodiment;
Fig. 3 is a block diagram illustrating an example of a hardware configuration of the node according to the first embodiment;
Fig. 4 is a diagram illustrating an example of a format of a route setting request according to the first embodiment;
Fig. 5 is a flowchart illustrating operation of a network control unit according to the first embodiment;
Fig. 6 is a flowchart illustrating operation of the network control unit according to the first embodiment;
Fig. 7 is a schematic diagram illustrating operation that a gateway sets a fixed route to a node according to the first embodiment;
Fig. 8 is a diagram illustrating an example of a fixed route list held by a route storage unit according to the first embodiment;
Fig. 9 is a schematic diagram illustrating operation that a node receives a DIO from another node according to the first embodiment;
Fig. 10 is a schematic diagram illustrating operation that the gateway sets an exclusion route to the node according to the first embodiment;
Fig. 11 is a diagram illustrating an example of an exclusion route list held by the route storage unit according to the first embodiment;

Fig. 12 is a schematic diagram illustrating operation that a node receives a DIO from another node according to the first embodiment;
Fig. 13 is a schematic diagram illustrating operation that a node receives a DIO according to the first embodiment;
Fig. 14 is a flowchart illustrating operation of the network control unit according to the first embodiment;
Fig. 15 is a block diagram illustrating an example of a functional configuration of a node according to a second embodiment;
Fig. 16 is a block diagram illustrating an example of a hardware configuration of the node according to the second embodiment;
Fig. 17 is a flowchart illustrating operation of a network control unit according to the second embodiment;
Fig. 18 is a flowchart illustrating operation of the network control unit according to the second embodiment; and
Fig. 19 is a diagram illustrating an example of a network configuration;
Fig. 20 is a sequence diagram illustrating operation for updating an upward route; and
Fig. 21 is a sequence diagram illustrating operation for updating a downward route.
Description of Embodiments [0014] First Embodiment
First, a network configuration of the present invention will be explained.
Fig. 1 is a diagram illustrating an example of a configuration of a network 10 according to the first embodiment. The network 10 is a network which is composed of a gateway 11 and nodes 12a to d as wireless communication apparatuses. Also, the

network 10 is a network of a tree structure with the gateway 11 functioning as a root. The gateway 11 builds the network and transmits data to and receives data from a node directly or through other nodes. Also, the gateway 11 transmits data to and receives data from apparatuses connected above the gateway 11 or other networks. [0015] The direction from each node to the gateway 11 is upward, and the direction from the gateway 11 to each node is downward. The node 12a and the node 12b are lower nodes of the gateway 11, and routes with the gateway 11 have been established. The node 12c exists at a distance that enables the node 12c to communicate wirelessly with the node 12a and the node 12b, but the routes have not yet been established. The node 12d is a lower node of the node 12c, and a route with the node 12c has been established. Links 13a to e are links between nodes. Each of the solid lines in Fig. 1 indicates that a route has already been established. Each of the dotted lines in Fig. 1 indicates that a route has not yet been established. For example, in a case of the route between the gateway 11 and the node 12a, "the route has been established" is a situation where the gateway 11 holds the downward route information toward the node 12a and the node 12a holds the upward route information toward the gateway 11. [0016] Next, a configuration of the node 12a which is the wireless communication apparatus of the present invention will be explained. The nodes 12b to d have the same configuration as that of the node 12 a.
Fig. 2 is a block diagram illustrating an example of a functional configuration of the node 12a according to the first embodiment. The node 12a includes an application unit 21, a network control unit 22, a route storage unit 23, a wireless communication control unit 24, a network interface control unit 25, and a sensor interface control unit 26. A wireless antenna 30 is connected to the wireless communication control unit 24. The network interface control unit 25 transmits data

to and receives data from other networks connected to the node 12a. The data may be control information. Also, a sensor 27 is connected to the sensor interface control unit 26.
[0017] Fig. 3 is a block diagram illustrating an example of a hardware configuration of the node 12a according to the first embodiment. The node 12a includes a memory 31, a processor 32, a sensor interface 33, a network interface 34, and a wireless interface 35. The processor 32 is connected to the memory 31, and temporarily stores data necessary for calculation and saves data. Also, the processor 32 is connected to the sensor interface 33, the network interface 34 and the wireless interface 35, and controls each interface according to an instruction from the processor 32. Further, the wireless interface 35 is connected to the wireless antenna 30 and transmits a wireless signal and receives a wireless signal.
[0018] The memory 31 stores programs and data for realizing the functions of the application unit 21, the network control unit 22, the wireless communication control unit 24, the network interface control unit 25, and the sensor interface control unit 26. In addition, the memory 31 stores data for realizing the function of the route storage unit 23. The memory is composed of, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), and an SSD (Solid State Drive).
[0019] The processor 32 reads out the program and the data stored in the memory 31 and implements the functions of the application unit 21, the network control unit 22 and the wireless communication control unit 24. The processor 32 is realized by a processing circuit such as a CPU which executes the program stored in the memory 31, and a system LSI (Large Scale Integration).
It is to be noted that a plurality of processing circuits may be configured to

cooperate to execute the functions of the application unit 21, the network control unit 22 and the wireless communication control unit 24.
[0020] The sensor interface 33 realizes the function of the sensor interface control unit 26.
The network interface 34 realizes the function of the network interface control unit 25.
[0021] Next, transmission and reception of a wireless signal with another node will be explained.
First, a case where the wireless signal is received from another node will be explained.
The wireless antenna 30 receives a wireless signal transmitted by another node and outputs the received wireless signal to the wireless communication control unit 24. The wireless communication control unit 24 converts the wireless signal input from the wireless antenna 30 into a frame and checks a destination of the frame. Two of a MAC address and a network address are set in the destination. The MAC address is an address indicating the next node on a route. The network address is an address of the destination of the frame.
[0022] When the destination of the frame is the same as a MAC address of its own node, the wireless communication control unit 24 outputs the frame to the network control unit 22. When the destination of the frame is different from its own MAC address, the wireless communication control unit 24 discards the frame. The network control unit 22 checks the network address in the destination of the frame input from the wireless communication control unit 24. When the network address in the destination is different from the network address of its own node, the network control unit 22 refers to a route list of the route storage unit 23 and reads out a MAC address

of the next node to be transferred from the route information of a node having the network address in the destination. The network control unit 22 outputs the read-out MAC address and the frame to the wireless communication control unit 24. [0023] When the network address is the same as the network address of its own node and application data is included in a data portion of the frame, the network control unit 22 outputs the data portion of the frame input from the wireless communication control unit 24 to the application unit 21. The application unit 21 outputs data to the network interface control unit 25 or the sensor interface control unit 26 according to the contents of the data. When the data includes control information of the network connected to the network interface control unit 25, the application unit 21 outputs the control information to the network interface control unit 25. Further, when the data includes control information of the sensor 27, the application unit 21 outputs the control information to the sensor interface control unit 26. [0024] When the network address of the frame input from the wireless communication control unit 24 is the same as the network address of its own node and a route control message is included in the data portion of the frame, the network control unit 22 updates the route list held by the route storage unit 23 according to the contents of the route control message.
[0025] Next, a case where the wireless signal is transmitted to another node will be explained.
When data is input from the network interface control unit 25, the application unit 21 outputs the data to the network control unit 22. When a measured value is input from the sensor 27, the sensor interface control unit 26 converts it into data of a prespecified format and outputs the data to the application unit 21. The application unit 21 outputs the data input from the network interface control unit 25 or the sensor

interface control unit 26 and a network address of a destination, to the network control unit 22. The network control unit 22 sets the data input from the application unit 21 in a data portion of a frame and the network address of the destination in a header of the frame. In addition, the network control unit 22 inquires the route storage unit 23 of a MAC address of the next node to be transferred. The network control unit 22 outputs the MAC address obtained from the route storage unit 23 and the frame, to the wireless communication control unit 24. The wireless communication control unit 24 sets the MAC address input from the network control unit 22 in the header of the frame. Also, the wireless communication control unit 24 converts the frame into a wireless signal and outputs the wireless signal to the wireless antenna 30. [0026] In addition, the network control unit 22 generates a route control message from the route information held by the route storage unit 23, and sets the route control message in the data portion of the frame. Further, the network control unit 22 inquires the route storage unit 23 of a MAC address of the next node to be transferred, and outputs the obtained MAC address and the frame to the wireless communication control unit 24. The network control unit 22 outputs the frame to the wireless communication control unit 24, and the wireless communication control unit 24 transmits the frame to another node via the wireless antenna 30. [0027] In the RPL, DIO ((DODAG (Direction-Oriented Directed Acyclic Graph) Information Object)) is used for control of the upward route. DAO (Destination Advertisement Object) is used for control of the downward route. [0028] Each node can grasp a route to the gateway 11 and a route to another node by the DIO and the DAO. The route list of the route storage unit 23 of each node holds route information toward the gateway 11 and toward another node. As the route information of the gateway 11 and another node, an address of a destination apparatus,

an address of the next node, rank information and a lifetime are saved. The address of the next node is an address of an adjacent node on a route to the destination apparatus. The rank information is a value calculated from values such as the number of hops to the gateway 11 and radio wave reception intensity. The lower the rank information is, the more suitable a route is, in terms of the number of hops and radio wave situation. The node selects a node with low rank information and determines a route. The lifetime is a lifetime of the route information. The route information whose lifetime has expired is discarded. The route list holds upward route information toward the gateway 11 and downward route information toward a lower level node.
The network control unit 22 holds an address of its own node, the rank information and the lifetime. The lifetime is a lifetime of the route information and is a value designated as a parameter beforehand.
[0029] Next, operation in a case where the upward route is designated by the route setting request will be explained.
First, a format of the route setting request will be explained.
Fig. 4 is a diagram illustrating an example of the format of the route setting request according to the first embodiment. The route setting request is composed of a message type field, a route setting field, a number-of-route field and a route field. In the message type, an identifier indicating the route setting request is set. In the route setting field, a fixed route enable, an exclusion route enable or disable is set. The fixed route enable indicates that a route indicated in the route field is set to a fixed route. The exclusion route enable indicates that the route indicated in the route field is set to an exclusion route. The disable indicates disabling a fixed route and an exclusion route already set. In the number-of-route field, the number of routes set in

the route field is set. In the route field, a network address of a node is set as a route to be set. If N is set in the number-of-route field, N routes are set in the route field. [0030] Next, a case where the node 12c receives the route setting request will be explained as an example.
Fig. 5 is a flowchart illustrating processing of the network control unit 22 according to the first embodiment. The network control unit 22 of the node 12c starts the processing upon receiving the route setting request from the gateway 11 via the node 12a. The network control unit 22 determines the value of the route setting of the route setting request (step S301). When the route setting is set as the fixed route enable, the network control unit 22 performs a process of enabling the fixed route of the node 12c (step S302). The network control unit 22 registers in the fixed route list the route indicated in the route field, as the process of enabling the fixed route, and ends the processing. The fixed route list is held by the route storage unit 23 (step S303).
[0031] In step S301, when the route setting is set as the exclusion route enable, the network control unit 22 performs a process of enabling the exclusion route of the node 12c (step S304). The network control unit 22 registers in the exclusion route list the route indicated in the route field, as the process of enabling the exclusion route, and ends the processing. The exclusion route list is held by the route storage unit 23 (step S305). In step S301, when the route setting is set as the disable, the network control unit 22 performs a process of disabling the fixed route list and the exclusion route list held by the route storage unit 23 (step S306). The network control unit 22 initializes the fixed route list and the exclusion route list held by the route storage unit 23, as the process of disabling the fixed route list and the exclusion route list (step S307), and ends the processing.

[0032] Next, operation of setting the upward route by the node 12c will be explained.
Fig. 6 is a flow chart illustrating processing of the network control unit 22 according to the first embodiment. The network control unit 22 of the node 12c starts the processing upon receiving the DIO from the node 12a. The network control unit 22 determines the current route setting (step S401). When the fixed route and the exclusion route are set disable, the network control unit 22 selects the upward route based on the route information notified by the received DIO. The network control unit 22 decides the upward route according to a standard protocol of the RPL. For example, there are a method of selecting by the smallest number of times of relaying and a method of selecting by the strength of reception electric field intensity. The network control unit 22 sets an adjacent upper node decided as the upward route to the next node address of the upward route information (step S402). Subsequently, the network control unit 22 transmits the DAO which is the downward route control message to the upper node decided as the upward route. When the node 12a is selected as the upward route, the network control unit 22 transmits the DAO to the node 12a. As described above, the upper node sets the downward route information toward the node 12c, by receiving the DAO (step S403). [0033] On the other hand, when the fixed route enable is set in step S 401, the network control unit 22 determines whether or not a transmission source network address (node 12 a) of the received DIO is registered in the fixed route list (step S404). When the transmission source network address (node 12a) of the DIO is registered in the fixed route list, the network control unit 22 sets the node 12a to the next node address of the upward route information toward the gateway 11 (step S402) and transmits the DAO to the node 12a (step S403). When the transmission source network address (node 12a) of the DIO is not registered in the fixed route list, the

network control unit 22 discards the received DIO, as it is not the DIO notified from the fixed route. Here, the network control unit 22 does not set the upward route and does not transmit the DAO (step S405).
[0034] When the exclusion route enable is set in step S 401, the network control unit 22 determines whether or not the transmission source network address (node 12 a) of the received DIO is registered in the exclusion route list (step S406). When the transmission source network address (node 12a) of the received DIO is registered in the exclusion route list, the network control unit 22 discards the received DIO, as it is the DIO notified from the exclusion route. The network control unit 22 does not set the upward route and does not transmit the DAO (step S405). When the transmission source network address (node 12a) of the received DIO is not registered in the exclusion route list, the network control unit 22 sets the node 12a to the next node address of the upward route information toward the gateway 11 (step S402) and transmits the DAO to the node 12a (step S403).
[0035] Next, operation of setting the fixed route will be explained using a specific example.
Fig. 7 is a schematic diagram illustrating operation of setting the fixed route to the node 12c by the gateway 11 according to the first embodiment.
When the gateway 11 transmits the route setting request for setting the link 13c to be the fixed route to the node 12c, the fixed route enable is set in the route setting field, 1 is set in the number-of-route field, and the network address of the node 12a is set in the route field.
[0036] Fig. 8 is a diagram illustrating an example of the fixed route list held by the route storage unit 23 according to the first embodiment. When the link 13c is set as the fixed route, the network address of the node 12a is set in the fixed route list of the

node 12c as illustrated in Fig. 8.
Fig. 9 is a schematic diagram illustrating operation of receiving the DIO from the nodes 12a and 12b by the node 12c according to the first embodiment. When the node 12a is registered in the fixed route list of the node 12c, upon receiving the DIO from the node 12a which is registered in the fixed route list, the node 12c selects the node 12a as an upward route and transmits the DAO to the node 12a. Also, upon receiving the DIO from the node 12b which is not registered in the fixed route list, the node 12c discards the received DIO. Therefore, the node 12c sets the upward route via the node 12a which is set as the fixed route.
[0037] Next, operation of setting the exclusion route will be explained using a specific example.
Fig. 10 is a schematic diagram illustrating operation of setting the exclusion route to the node 12c by the gateway 11 according to the first embodiment.
When the gateway 11 transmits the route setting request for setting the link 13d as the exclusion route to the node 12c, the exclusion route enable is set in the route setting field, 1 is set in the number-of-route field, and the network address of the node 12b is set in the route field.
[0038] Fig. 11 is a diagram illustrating an example of the exclusion route list held by the route storage unit 23 according to the first embodiment. When the link 13d is set as the exclusion route, the network address of the node 12b is set in the exclusion route list of the node 12c as illustrated in Fig. 11.
Fig. 12 is a schematic diagram illustrating operation of receiving the DIO from the nodes 12a and 12b by the node 12c according to the first embodiment. When the node 12b is registered in the exclusion route list of the node 12c, upon receiving the DIO from the node 12a which is not registered in the exclusion route list,

the node 12c selects the node 12a as the upward route and transmits the DAO to the
node 12a. Also, upon receiving the DIO from the node 12b which is registered in the
exclusion route list, the node 12c discards the received DIO. Therefore, the node 12c
sets an upward route via other node than the node 12b which is set as the exclusion
route.
[0039] Next, operation of changing the fixed route will be explained.
Fig. 13 is a schematic diagram illustrating operation of changing the fixed route by the node 12c according to the first embodiment.
Fig. 14 is a flowchart illustrating processing of the network control unit 22 according to the first embodiment. It is to be noted that in the node 12c the node 12a which is designated as the fixed route is set as the next node address of the upward route information toward gateway 11. At this time, the network control unit 22 of the node 12c starts the processing upon receiving the route setting request for setting the node 12b as the fixed route. The network control unit 22 of the node 12c refers to the fixed route list and determines whether or not there is a node registered in the fixed route list (step S501). If there is the node registered in the fixed route list, the network control unit 22 of the node 12c deletes the registered node 12a from the fixed route list (step S502). Also, the network control unit 22 of the node 12c registers the node 12b notified by the route setting request in the fixed route list (step S503). [0040] The network control unit 22 of the node 12c determines whether or not the registered node 12a has been set as the upward route (step S504). If the node 12a has been set as the next node address of the upward route information toward the gateway 11, the network control unit 22 of the node 12c transmits the DAO in which Lifetime = 0 is set to the node 12a. Upon receiving the DAO in which the Lifetime = 0 is set, the node 12a deletes the downward route information of the node 12c (step S505) if the

node 12a holds the downward route information of the node 12c. The network control unit 22 of the node 12c transmits the DAO to the node 12b notified by the route setting request (step S506). Also, the network control unit 22 of the node 12c sets the node 12b notified by the route setting request as the next node address of the upward route information toward the gateway 11 (step S507) and ends the processing. [0041] In step S501, if there is no node registered in the fixed route list, the processing proceeds to step S506. In step S504, if the node 12a is not set as the upward route, the processing proceeds to step S506.
[0042] In the present embodiment, it has been described that the route list holds the upward route information toward the gateway 11, however, the route list may hold route information via other upper node than a node set as the next node address of the upward route information toward the gateway 11. Further, the route list may hold the upward route information toward the upper node.
[0043] As described above, in the present embodiment, the wireless communication control unit 24 and the network control unit 22 are included. Upon receiving via another node a message related to a route control and addressed to its own node, the wireless communication control unit 24 outputs the message. When the message input from the wireless communication control unit is a route setting request in which a first adjacent node which is to be passed through is designated as an upward route toward a gateway, the network control unit 22 transmits a downward route control message including address information of its own node thorough an upward route which satisfies a designation of the route setting request. Therefore, it is possible to fix a route using the RPL. [0044] Further, when an upward route via a first adjacent node is designated by the

route setting request and an upward route control message received from the first adjacent node is input, the network control unit 22 outputs a downward route control message addressed to the first adjacent node. Therefore, it is possible to establish a route with the first adjacent node which is designated as the fixed route.
Moreover, when an upward route via the first adjacent node is designated by the route setting request and an upward route control message received from a second adjacent wireless communication apparatus is input, the network control unit 22 does not output a downward route control message addressed to the second adjacent node. Therefore, it is possible to avoid establishing a route with a second adjacent node which is not a fixed route.
[0045] Further, when an upward route via the second adjacent node is designated by a new route setting request after the upward route via the first adjacent node is designated by the route setting request, the network control unit 22 outputs a downward route control message addressed to the first adjacent node, indicating disablement of a downward route toward its own node. The wireless communication control unit 24 transmits the downward route control message input from the network control unit to the first adjacent node. Therefore, it is possible to change the fixed route.
[0046] Further, when an upward route excluding the third adjacent node is designated by the route setting request and an upward route control message received from the fourth adjacent node is input, the network control unit 22 outputs the downward route control message addressed to the fourth adjacent node. Therefore, it is possible to establish a route with a fourth adjacent node which is not an exclusion route.
Furthermore, wherein when the upward route excluding the third adjacent node is designated by the route setting request and an upward route control message

received from the third adjacent node is input, the network control unit 22 does not
output the downward route control message addressed to the third adjacent node.
Therefore, it is possible to avoid establishing a route with a third adjacent node which
is designated as an exclusion route.
[0047] Further, when disablement of a route excluding the third adjacent node is
designated by a new route setting request after the upward route excluding the third
adjacent node is designated by the route setting request, the network control unit 22
deletes the upward route information including the address information of the third
node from the exclusion route list. Therefore, it is possible to change the exclusion
route.
[0048] Second Embodiment
In the first embodiment described above, a route is fixed based on the route setting request. The present embodiment describes an embodiment in a case where a communication failure has occurred on a fixed route.
In the present embodiment, matters different from those in the first embodiment will be explained.
[0049] Fig. 15 is a block diagram illustrating an example of a functional configuration of a node 12a according to the second embodiment. The difference from the functional configuration of the node 12a of the first embodiment is that a route maintenance timer 28 is added.
Fig. 16 is a block diagram illustrating an example of a hardware configuration of the node 12a according to the second embodiment. The difference from the hardware configuration of the node 12a of the first embodiment is that a timer 36 is added. The timer 36 realizes the function of the route maintenance timer 28. [0050] First, a communication failure detection method will be explained.

Fig. 17 is a flowchart illustrating processing of the network control unit 22 according to the second embodiment. The network control unit 22 of the node 12c starts the processing upon receiving the route setting request message for setting the node 12a as a fixed route. The network control unit 22 of the node 12c activates the route maintenance timer 28 (step S601). The network control unit 22 of the node 12c waits to receive the DIO from the node 12a which is set as the fixed route (step S602). The network control unit 22 of the node 12c determines whether or not the DIO is received from the node 12a which is set as the fixed route (step S603). When the DIO is received from the node 12a, the network control unit 22 resets the route maintenance timer 28 (step S604). If the DIO is not received from the node 12a, the process proceeds to step S603.
[0051] Next, operation of re-setting a route in a case where the route maintenance timer 28 times out will be explained.
Fig. 18 is a flowchart illustrating processing of the network control unit 22 according to the second embodiment. When the route maintenance timer 28 times out, the network control unit 22 of the node 12c starts the processing. When the route maintenance timer 28 times out, the network control unit 22 of the node 12c determines that a communication failure has occurred on the fixed route (node 12a) (step S701). The communication control unit 22 of the node 12c collects route information of other routes than the fixed route when determining that the communication failure has occurred. The route information to be collected is information necessary for route selection, for example, the number of relays and reception electric field intensity of a route (step S702). The network control unit 22 of the node 12c generates a communication failure notice. The communication failure notice includes that a communication failure has occurred and the collected

route information (step S703).
[0052] The network control unit 22 of the node 12c sets a temporary route so as to notify the gateway 11 of the communication failure notice. At this time, the network control unit 22 selects an adjacent upper node which is to be passed through as an upward route, from the collected route information. Here, it is assumed that the node 12b is selected as the upper node (step S704). The network control unit 22 of the node 12c transmits the communication failure notice to the gateway 11 via the node 12b, and ends the processing (step S705).
[0053] The gateway 11 transmits the route setting request to the node 12c based on the communication failure notice received from the node 12c. By receiving the route setting request from the gateway 11, the node 12c re-sets a route. The route setting request transmitted by the gateway 11 may be, for example, one for setting the node 12a as the exclusion route or for setting the node 12b as the fixed route. [0054] In the present embodiment, it has been described that the network control unit 22 sets a temporary upward route from the collected route information. However, if the route list holds upward route information via other node than the route determined to have a communication failure, the held upward route information may be used as a temporary route.
[0055] As described above, in the present embodiment, when an upward route control message is not received from a first adjacent node after a predetermined time has elapsed since reception of a route setting request in which the upward route via a first adjacent node is designated, the network control unit 22 transmits via another adjacent node, a communication failure notice notifying the gateway of a communication failure of the first adjacent node. Therefore, it is possible to monitor whether a communication failure has occurred on the fixed route and which enables

the gateway 11 to grasp that the communication failure has occurred on the fixed route. Upon grasping that the communication failure has occurred on the fixed route, the gateway 11 can set a new fixed route. Reference Signs List [0056] 10 and 90: network
11 and 91: gateway
12a to e and 92a to c: node
13a to e: link
21: application unit
22: network control unit
23: route storage unit
24: wireless communication control unit
25: network interface control unit
26: sensor interface control unit
27: sensor
28: route maintenance timer
30: wireless antenna
31: memory
32: processor
33: sensor interface
34: network interface
35: wireless interface
36: timer.

We Claim:
[Claim 1] A wireless communication apparatus comprising:
a wireless communication control unit to output, upon receiving via another wireless communication apparatus a wireless signal addressed to the wireless communication apparatus including a message related to a route control, the message; and
a network control unit to transmit, when the message input from the wireless communication control unit is a route setting request in which an adjacent wireless communication apparatus which is to be passed through is designated as an upward route toward a gateway, a downward route control message including address information of the wireless communication apparatus thorough an upward route which satisfies a designation of the route setting request.
[Claim 2] The wireless communication apparatus according to claim 1,
wherein when an upward route via a first adjacent wireless communication
apparatus is designated by the route setting request and an upward route control
message received from the first adjacent wireless communication apparatus is input,
the network control unit outputs the downward route control message addressed to the
first adjacent wireless communication apparatus, and
the wireless communication control unit transmits the downward route control
message input from the network control unit to the first adjacent wireless
communication apparatus.
[Claim 3] The wireless communication apparatus according to claim 2,

wherein when the upward route via the first adjacent wireless communication apparatus is designated by the route setting request and an upward route control message received from a second adjacent wireless communication apparatus is input, the network control unit does not output the downward route control message addressed to the second adjacent wireless communication apparatus.
[Claim 4] The wireless communication apparatus according to claim 2 or 3,
wherein the wireless communication apparatus comprises a route storage unit which holds route information related to the upward route, and
when the upward route via the first adjacent wireless communication apparatus is designated by the route setting request, the network control unit registers upward route information including address information of the first adjacent wireless communication apparatus in a fixed route list of the route storage unit.
[Claim 5] The wireless communication apparatus according to claim 4,
wherein when disablement of the upward route via the first adjacent wireless communication apparatus is designated by a new route setting request after the upward route via the first adjacent wireless communication apparatus is designated by the route setting request, the network control unit deletes the upward route information including the address information of the first adjacent wireless communication apparatus from the fixed route list.
[Claim 6] The wireless communication apparatus according to any one of claims 2 to 5,
wherein when an upward route via a second adjacent wireless communication

apparatus is designated by a new route setting request after the upward route via the first adjacent wireless communication apparatus is designated by the route setting request, the network control unit outputs a downward route control message addressed to the first adjacent wireless communication apparatus, indicating disablement of a downward route toward the wireless communication apparatus, and
the wireless communication control unit transmits the downward route control message input from the network control unit to the first adjacent wireless communication apparatus.
[Claim 7] The wireless communication apparatus according to any one of claims 2 to 6,
wherein when the upward route control message is not received from the first adjacent wireless communication apparatus after a predetermined time has elapsed since reception of the route setting request in which the upward route via the first adjacent wireless communication apparatus is designated, the network control unit transmits via another adjacent wireless communication apparatus, a communication failure notice notifying the gateway of a communication failure of the first adjacent wireless communication apparatus.
[Claim 8] The wireless communication apparatus according to any one of claims 1 to 7,
wherein when an upward route excluding a third adjacent wireless communication apparatus is designated by the route setting request and an upward route control message received from a fourth adjacent wireless communication apparatus is input, the network control unit outputs the downward route control

message addressed to the fourth adjacent wireless communication apparatus, and
the wireless communication control unit transmits the downward route control message input from the network control unit to the fourth adjacent wireless communication apparatus.
[Claim 9] The wireless communication apparatus according to claim 8,
wherein when the upward route excluding the third adjacent wireless communication apparatus is designated by the route setting request and an upward route control message received from the third adjacent wireless communication apparatus is input, the network control unit does not output the downward route control message addressed to the third adjacent wireless communication apparatus.
[Claim 10] The wireless communication apparatus according to claim 8 or 9,
wherein the wireless communication apparatus comprises a route storage unit which holds route information related to the upward route, and
when the upward route excluding the third adjacent wireless communication apparatus is designated by the route setting request, the network control unit registers upward route information including address information of the third adjacent wireless communication apparatus in an exclusion route list of the route storage unit.
[Claim 11] The wireless communication apparatus according to claim 10,
wherein when disablement of a route excluding the third adjacent wireless communication apparatus is designated by a new route setting request after the upward route excluding the third adjacent wireless communication apparatus is designated by the route setting request, the network control unit deletes the upward route information

including the address information of the third wireless communication apparatus from the exclusion route list.
[Claim 12] A wireless communication method comprising:
a wireless communication control step for outputting, upon receiving via another wireless communication apparatus a wireless signal addressed to the wireless communication apparatus including a message related to a route control, the message; and
a network control step for transmitting, when the message input from the wireless communication control step is a route setting request in which an adjacent wireless communication apparatus which is to be passed through is designated as an upward route toward a gateway, a downward route control message including address information of the wireless communication apparatus thorough an upward route which satisfies a designation of the route setting request.