JP2014090481A - Multi-hop communication system, hybrid slave unit and selection method of communication channel in multi-hop communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-hop communication system capable of properly sorting between a power-line carrier communication channel and a radio communication channel for performing multi-hop communication depending on a route formed between a master unit and a slave unit.SOLUTION: A master unit 20 and plural slave units 10 are set as nodes. The master unit 20 and the plural slave units 10 perform a multi-hop communication. The slave unit 10 includes a hybrid slave unit 11 capable of selecting two different communication methods; i.e., radio communication and power-line carrier communication. The hybrid slave unit 11 performs a preprocessing to determine which of the radio communication and the power-line carrier communication should be used among the other neighboring nodes capable of a single hop. The hybrid slave unit 11 has a route establishing section 1101 that, after the preprocessing, performs a main processing to determine a route by calculating the route cost between the master unit 20 and the same.

Description

  The present invention relates to a multi-hop communication system, a hybrid slave used in the multi-hop communication system, and a communication path selection method in the multi-hop communication system.

  2. Description of the Related Art Conventionally, in a communication network including a plurality of nodes, multi-hop communication that allows relaying of communication by other nodes when information is transmitted between the nodes is known. In multi-hop communication, there is also known a communication network in which other nodes communicate with each other as a slave unit with respect to a node as a master unit instead of a node having an equal relationship. For example, Patent Document 1 includes a slave unit (slave station) that acquires a meter reading result for each consumer and a master unit (master station) that collects a meter reading result from the slave unit in order to perform remote meter reading. Communication network is shown. In addition, in the technique described in Patent Document 1, when transmitting information of the meter reading result from any slave unit to the master unit, relaying by another slave unit is permitted, and a communication network that performs multi-hop communication is constructed. Has been.

JP2011-250301A

  Patent Document 1 describes a slave unit that can use both wireless communication and power line carrier communication. If the slave unit fails in power line carrier communication, it forms a communication path with the master unit using wireless communication. There is a statement to do so. That is, the wireless communication channel is used as a spare communication channel for power line carrier communication. That is, the communication path for wireless communication is used as a spare communication path for power line carrier communication, and it is considered that the communication line for power line carrier communication and the communication path for wireless communication are allocated to the right place for use. Absent.

  In the present invention, when performing multi-hop communication between a master unit and a plurality of slave units, a power line carrier communication channel and a wireless communication channel are formed between the master unit and the slave unit. It is an object to provide a multi-hop communication system with high communication reliability while appropriately distributing according to routes and reducing signal interference and packet collision. Furthermore, an object of the present invention is to provide a hybrid slave unit used in the multi-hop communication system and a communication path selection method in the multi-hop communication system.

  In order to achieve the above object, the multi-hop communication system according to the present invention includes a master unit and a plurality of slave units as nodes, and transmits information between the master unit and the slave units. A multi-hop communication system that allows relay of communication by other slave units, wherein the slave unit includes two types of radio communication using a radio wave as a transmission medium and power line carrier communication using a distribution line as a transmission medium. A hybrid slave unit that can select a communication method is included, and the hybrid slave unit determines whether to use the wireless communication or the power line carrier communication with another adjacent node having a hop number of one. A route construction unit is provided that performs preprocessing for determination and then performs main processing for determining a route by determining a route cost with the parent device.

  In this multi-hop communication system, the hybrid slave unit has, for another adjacent node having a hop number of 1, the identification information of the node and an upper route cost that is a route cost between the node and the master unit And a storage unit that manages information including the link cost with the node.

  In this multi-hop communication system, the storage unit includes a first node table that manages information related to nodes connected by the link performing wireless communication among other adjacent nodes having a hop number of 1, and the number of hops. It is preferable that a second node table that manages information related to nodes connected by a link that performs the power line carrier communication among other adjacent nodes that are equal to 1 is provided.

  In this multi-hop communication system, the route construction unit uses the first node table and the second node table as the pre-processing, so that it can communicate with other adjacent nodes having a hop count of 1. It is preferable to perform a process of determining which of the wireless communication and the power line carrier communication is used as the communication method used for the communication path.

  In this multi-hop communication system, the hybrid handset has a minimum route cost out of route costs that are the sum of the upper route cost and the link cost managed in the first node table, and the second route cost. Are compared with the minimum upper route cost among the upper route costs managed in the node table, and the minimum route cost in the first node table is the minimum upper route cost in the second node table. In the case where it is smaller, it is preferable to select the wireless communication as a communication method to be used in the communication path on the upper side which is the base unit side.

  The hybrid handset according to the present invention is used in any of the multihop communication systems described above.

  A method for selecting a communication path in a multi-hop communication system according to the present invention includes a master unit and a plurality of slave units as nodes, and other information is transmitted when information is transmitted between the master unit and the slave units. A method of selecting a communication path in a multi-hop communication system that allows relay of communication by a slave unit, wherein the slave unit includes radio communication using radio waves as a transmission medium, and power line carrier communication using distribution lines as transmission media The hybrid slave unit is capable of selecting either the wireless communication or the power line carrier communication with another adjacent node having a hop number of one. A pre-processing for determining whether to use the device is performed, and then a main processing for determining a route by obtaining a route cost with the parent device is performed.

  According to the configuration of the present invention, when performing multi-hop communication between a master unit and a plurality of slave units, a communication path for power line carrier communication and a communication path for wireless communication are set between the master unit and the slave unit. There is an advantage that it can be appropriately distributed according to the route formed.

It is a figure which shows an example of the communication network in embodiment. It is a figure which shows the specific example same as the above. It is a block diagram which shows the subunit | mobile_unit used for the same as the above. It is a figure which shows an example of the node table used for the same as the above. It is a figure which shows the example of the format of the Hello packet used for the same as the above. It is a figure which shows the other example of a communication network same as the above. It is a figure which shows the other example of the node table used for the same as the above. It is a figure which shows the further another example of the communication network same as the above. It is a figure which shows the further another example of the node table used for the same as the above. It is a figure which shows another example of the communication network in the same as the above. It is a figure which shows another example of the node table used for the same as the above.

  In the embodiment described below, a slave unit is attached to a power meter in a power consumer, and a single master unit is used to collect meter reading data acquired from each power meter by a plurality of slave units. And a case where a plurality of slave units communicate with each other. However, the function of the slave unit is not limited to the collection of meter reading data.If the electrical device used by the consumer has a predetermined communication function, the slave unit has a function to manage power energy by communicating with the electrical device. It is also possible to grant.

  The parent device is assumed to be a management server operated by an electric power company or a service provider entrusted by the electric power company. The management server does not mean a single computer, but may be realized by a plurality of computers. Further, the base unit may construct a communication network that is hierarchized into a plurality of hierarchies. For example, a higher-level communication network may be constructed by the management server and a plurality of relay devices, and a lower-level communication network that communicates with the slave unit may be constructed for each relay device.

  The embodiment described below is not limited to the use of power management. In other words, a communication network that performs communication between a parent device and a plurality of child devices, in which a child device that transmits information to and from the parent device allows relaying of information by other child devices. It is applicable if In the embodiment described below, a specific usage example will not be described in detail, and a function for constructing a communication network between a parent device and a child device will be mainly described.

  As above-mentioned, a subunit | mobile_unit acquires meter-reading data from a consumer's electric power meter, and transmits meter-reading data from a subunit | mobile_unit to a main | base station. An example of a communication network is shown in FIG. The communication network shown in FIG. 2 is constructed by one master unit 20 and a plurality of slave units 10. Moreover, the subunit | mobile_unit 10 can manage the operation | movement (management or setting) of an apparatus by communicating between apparatuses which have a communication function among the apparatuses which a consumer uses.

  On the other hand, the slave unit 10 that allows relaying by another slave unit 10 with the master unit 20 has a function of performing wireless communication using a radio wave as a transmission medium and a function of performing power line carrier communication using a distribution line as a transmission medium. And at least one of them.

  That is, the subunit | mobile_unit 10 is classified into three types, the structure which performs both wireless communication and power line carrier communication, the structure which performs only wireless communication, and the structure which performs only power line carrier communication. Hereinafter, the slave unit 10 that performs both wireless communication and power line carrier communication is referred to as “hybrid slave unit 11”, the slave unit 10 that performs only wireless communication is “wireless slave unit 12”, and the slave unit that performs only power line carrier communication. The machine 10 is referred to as a “wired slave 13”. In FIG. 2, the communication line La for power line carrier communication is indicated by a solid line, and the communication path Lb for wireless communication is indicated by a broken line.

  The hybrid handset 11 can select a communication method with different physical layers, such as wireless communication and power line carrier communication, as well as frequency bands with different information reachable range and signal interference range even with the same wireless communication. Or the modulation method may be selectable as the communication method. In any case, the information transmission range and the signal interference range may be different by selecting different communication methods.

  In the configuration example shown in FIG. 2, a case is assumed in which a plurality of customers sharing one building such as an apartment house or a tenant building and a consumer occupying one building such as a detached house are mixed. Yes. That is, the plurality of slave units 10 connected to the distribution line L1 in the right part of the figure correspond to the former, and the independent slave units 10 in the left part of the figure correspond to the latter.

  The distribution line L1 is connected to the secondary side of the step-down transformer T1, to which the hybrid slave unit 11 or the wired slave unit 13 is connected, and among the slave units 10 connected to the distribution line L1, the basic Specifically, power line carrier communication is performed using the distribution line L1 as a transmission medium. However, wireless communication is allowed between the plurality of slave units 10 connected to the distribution line L1 when the communication quality deteriorates. In the drawing, the wired slave unit 13 is described for the sake of explanation, but all the slave units 10 connected to the distribution line L1 may be the hybrid slave units 11.

  On the other hand, the two slave units 10 in the left part of FIG. 2 are wireless slave units 12 and do not perform power line carrier communication. However, even if the customer occupies one building such as a detached house, when communicating with the relay device described above using a distribution line connected to the secondary side of the step-down transformer, these slave units 10 are It is possible to replace the hybrid slave unit 11 or the wired slave unit 13 with each other.

  A configuration example of the hybrid slave unit 11 is shown in FIG. The hybrid handset 11 basically includes a control unit 110, a storage unit 111, and a communication unit 112.

  The control unit 110 includes a device that operates according to a program, such as a microcomputer, as a main hardware element. The control unit 110 selects a route construction unit 1101 that performs processing for constructing a communication route, a communication processing unit 1102 that performs communication using the constructed communication route, and power line carrier communication or wireless communication. And a selection processing unit 1103 for performing.

  The storage unit 111 stores a program for operating the control unit 110 and includes at least a first node table 1111 and a second node table 1112. The storage unit 111 preferably uses a device different from the control unit 110, but may be integrated.

  The communication unit 112 includes a wireless communication interface unit 1121 that transmits and receives radio waves to perform wireless communication, and a power line carrier communication interface unit 1122 connected to the distribution line L1 (see FIG. 2) to perform power line carrier communication. Prepare. Hereinafter, “wireless communication interface unit” is abbreviated as “wireless I / F”, and “power line carrier communication interface unit” is abbreviated as “power line I / F”. In the hybrid handset 11, which of the wireless I / F 1121 and the power line I / F 1122 is used is determined by the selection processing unit 1103 in the control unit 110 based on the route construction result by the route construction unit 1101.

  The wireless slave unit 12 has a configuration in which the selection processing unit 1103 and the power line I / F 1122 in the hybrid slave unit 11 are omitted, and the wired slave unit 13 includes the selection processing unit 1103 and the wireless I / F in the hybrid slave unit 11. The configuration is such that F1121 is omitted. Actually, the configuration of the storage unit 111 is different between the hybrid slave unit 11, the wireless slave unit 12, and the wired slave unit 13, but the hardware configuration is almost the same.

  By the way, the communication network constructed by the child device 10 and the parent device 20 performs multi-hop communication in which the child device 10 that transmits information to and from the parent device 20 allows other child devices 10 to relay information. Therefore, it is necessary to select which handset 10 is used for relay. Therefore, handset 10 searches for and stores a route (route) with good communication quality in advance, and performs communication with base unit 20 using a route with good communication quality searched in advance. In addition, when the information transmission with the parent device 20 fails, the child device 10 performs retransmission using the same route, or selects the route having the next highest communication quality and performs retransmission. Since these techniques are well-known techniques, description thereof is omitted.

  Hereinafter, a procedure for performing the above-described route search by the route construction unit 1101 will be described. That is, a procedure for searching for a route for communicating with the parent device 20 for each child device 10 will be described. Here, when other nodes are not included in the route between nodes that transmit information (the generic term of the slave unit 10 and the master unit 20), a communication path formed between the nodes is referred to as a “link”. Also, the evaluation value of the communication quality of the link is called “link cost”, and the link cost of the entire route between nodes that transmit information is called “route cost”. That is, the route cost is the sum of the link costs in all links included in the route. The link cost is an integer value obtained using the SNR and signal strength for each link, and is calculated so as to be smaller as the communication quality is higher. Further, the number of links constituting the route is referred to as “hop number”. Therefore, the number of hops when communication is performed directly without passing through the other handset 10 is 1. When the number of hops between two nodes is 1, the other node is called “adjacent node” with respect to one node.

  Here, when wireless communication is performed between two nodes, a difference in link cost may occur depending on the direction of transmission / reception if the reception sensitivity and radio wave interference state differ between nodes. Therefore, in order to accurately determine the link cost, it is necessary to perform bidirectional communication between the two nodes. However, in a communication network including a large number of nodes, if wireless communication is performed bidirectionally with respect to all adjacent nodes, it takes a long time to acquire a link cost.

  Therefore, in the present embodiment, the provisional link cost is calculated using only the reception quality of the radio signal, and the provisional route cost is obtained from the provisional link cost. If it is a provisional link cost using only the reception quality, it can be calculated only by receiving a Hello packet, which will be described later, and a provisional route cost can also be calculated only by receiving the Hello packet. That is, the time required to acquire the link cost and route cost is shortened, and the increase in traffic is suppressed.

  Here, each child device 10 will be described assuming that the link cost and the route cost have been calculated after searching for an adjacent node. Since the hybrid handset 11 can select a communication path for wireless communication and a communication path for power line carrier communication, the route construction unit 1101 is connected to the wireless I / F 1121 when transmitting information between adjacent nodes. It is necessary to select which of the power line I / F 1122 is used. Selection between the wireless I / F 1121 and the power line I / F 1122 is performed using data in the first node table 1111 shown in FIG. 4A and the second node table 1112 shown in FIG.

  Below, the case where the communication network shown in FIG. 1 is constructed | assembled is demonstrated as an example. Squares in the figure represent nodes, and solid lines or broken lines connecting the nodes represent links. Of the links, a solid line represents a link that performs power line carrier communication, and a broken line represents a link that performs wireless communication. The numerical value shown in the square representing the node is identification information of the node, and the numerical value written in the link is the link cost.

  The route construction unit 1101 performs preprocessing for constructing a communication network as shown in FIG. 1 before the main processing for determining the route by obtaining the route cost. That is, the route construction unit 1101 uses the first node table 1111 shown in FIG. 4 (a) and the second node table 1112 shown in FIG. 4 (b) as preprocessing, so that power line carrier communication is performed for each link. And processing for determining whether to use wireless communication.

  The first node table 1111 and the second node table 1112 manage information regarding the route passing through the adjacent node with the parent device 20 for each adjacent node of the target hybrid child device 11. Specifically, the node tables 1111 and 1112 include the identification information of the adjacent node of the hybrid child device 11, the number of hops of the route between the parent device 20 and the adjacent node, and the identification of the child device 10 included in the route. Information and the order of relaying on the route. Further, the node tables 1111 and 1112 indicate, for each adjacent node, the route cost between the parent device 20 (referred to as “upper route cost”), the link cost between the hybrid child device 11, the parent device 20 and the hybrid. And the total route cost with the handset 11. The sum of the upper route cost and the link cost matches the overall route cost.

  Here, information on the route is managed by being distributed to the first node table 1111 and the second node table 1112 in accordance with the type of link between the target hybrid child machine 11 and the adjacent node. That is, adjacent nodes connected by a link performing wireless communication are stored in the first node table 1111, and adjacent nodes connected by a link performing power line carrier communication are stored in the second node table 1112.

  Assuming that the slave unit 10 whose identification information is “13” is the hybrid slave unit 11 to which attention is paid, the adjacent nodes of the hybrid slave unit 11 have the identification information “1” “3” “12” “14” “23”. ”Becomes the handset 10. Here, the slave unit 10 with the identification information “1” “3” is the wireless slave unit 12, the slave unit 10 with the identification information “12” “14” is the hybrid slave unit 11, and the identification information is It is assumed that the child device 10 that is “23” is the wired child device 13. Hereinafter, the slave unit 10 whose identification information is “n” is referred to as a “n” slave unit 10.

  Since the communication network shown in FIG. 1 is assumed, the adjacent nodes registered in the first node table 1111 with respect to the hybrid slave device 11 of “13” are the slave device 10 and the master device 20 of “1” and “3”. It becomes. Of these, focusing on the “3” slave unit 10, the route passing through the “3” slave unit 10 between the “13” hybrid slave unit 11 and the master unit 20 is the “2” slave unit 10. The first hop from the parent device 20 is the “2” child device 10, and the second hop is the “3” child device 10. The child device 10 of “3” which is an adjacent node has 2 hops from the parent device 20 and has an upper route cost of 15 (= 6 + 9). Further, since the link cost between the “13” hybrid handset 11 and the “3” handset 10 is 8, the total route cost is 23 (= 15 + 8). Similarly, data is registered for other adjacent nodes.

  On the other hand, since the adjacent nodes registered in the second node table 1112 in the hybrid slave unit 11 of “13” are adjacent nodes connected by a link that performs power line carrier communication, “12” “14” “23 "Becomes a handset 10. Focusing on the “14” child device 10, the route passing through the “14” child device 10 between the “13” hybrid child device 11 and the parent device 20 includes the “2” child device 10. The first hop from the machine 20 is the "2" child machine 10, and the second hop is the "14" child machine 10. In addition, the child device 10 of “14” which is an adjacent node has 2 hops from the parent device 20 and has an upper route cost of 17 (= 6 + 11). Similarly, data is registered for other adjacent nodes.

  When data is registered in the first node table 1111 and the second node table 1112, the selection processing unit 1103 displays the minimum route cost in the first node table 1111 and the minimum value in the second node table 1112. Compare higher route cost. When the minimum route cost in the first node table 1111 is smaller than the minimum upper route cost in the second node table 1112, the total route cost is the adjacent node selected from the first node table 1111. Is smaller.

  That is, when the above-described relationship is established, the route including the adjacent node selected from the second node table 1112 has a lower route cost than the route passing through the adjacent node that minimizes the route cost in the first node table 1111. There is nothing. Therefore, it can be said that it is preferable to select a wireless communication channel for the route to the parent device 20 in the hybrid child device 11 of interest.

  In order to perform the above-described operation, the selection processing unit 1103 notifies the minimum route cost in the first node table 1111 to the hybrid slave unit 11 and the wired slave unit 13 included in the adjacent nodes through the power line I / F 1122. To do. When notifying the adjacent node of the route cost through the power line I / F 1122, a Hello packet (hereinafter referred to as “H packet”) indicating that the node is operating in multi-hop communication is used. The H packet is broadcast from each node, and notifies other nodes that the node that sent the H packet exists in the communication network.

  Therefore, the H packet basically only needs to include the operation code, the identification information of the node that is the transmission source, the sequence number, and the type of the transmission destination node, as shown in FIG. However, as described above, since the H packet needs to notify the other nodes of the route cost when the wireless I / F 1121 is used, except for the H packet used when the node joins the communication network. , H packets also include route costs.

  Here, the operation code is an identifier indicating the type of packet. In addition to the H packet, a plurality of types of packets such as a response packet returned by the node that has received the H packet as needed, and a packet for notifying the communication quality are used as the packet type. As the identification information of the transmission source node, the MAC address of the node can be used in addition to the identification information uniquely assigned. The sequence number is a number assigned to a packet at the time of communication, and the same sequence number is assigned to a packet used in a series of communication to indicate that it is a related packet. The route cost is the minimum route cost obtained from the first node table 1111.

  When the hybrid handset 11 transmits the H packet including the route cost to the adjacent node through the power line I / F 1122, the adjacent node that has received the H packet compares it with the upper route cost stored in the second node table 1112. . Here, when the received route cost is smaller than the upper route cost, the selection processing unit 1103 of the adjacent node selects the wireless I / F 1121 to form a communication path on the upper side (side closer to the parent device 20). To do. Even when the wireless I / F 1121 is selected, the power line I / F 1122 is selected for the lower side.

  As described above, the selection processing unit 1103 selects which of the wireless I / F 1121 and the power line I / F 1122 is used according to the following procedure. That is, the hybrid handset 11 first transmits an H packet including the minimum route cost of the first node table 1111 using the power line I / F 1122. Next, the selection processing unit 1103 of the hybrid handset 11 that has received the H packet compares the route cost included in the H packet with the minimum upper route cost in the second node table 1112. When the route cost is smaller than the upper route cost, the selection processing unit 1103 selects the wireless I / F 1121 for the upper side and selects the power line I / F 1122 for the lower side. Further, the selection processing unit 1103 selects only the power line I / F 1122 when the route cost is higher than the upper route cost.

  When the selection processing unit 1103 performs the processing described above, only the power line I / F 1122 is used for the hybrid slave units 11 of “12” and “14”, for example, in the communication network shown in FIG. Further, the wireless slave 11 of “13” uses the wireless I / F 1121 on the upper side and the power line I / F 1122 on the lower side. The hybrid slave units 11 of “11” and “15” are the same as the hybrid slave unit 11 of “13”. As a result, it is possible to limit the number of hybrid slave units 11 that are connected to the upper side using the wireless I / F 1121 to a small number with good route quality.

  The selection processing unit 1103 described above uses the route cost as a selection criterion for selecting whether to use the wireless I / F 1121 or the power line I / F 1122 on the upper side, but other selections are used to determine the communication path. A criterion may be used.

  As a communication channel selection criterion, for example, the number of adjacent nodes that perform power line carrier communication can be used. That is, in the hybrid slave unit 11 having a large number of adjacent nodes that perform power line carrier communication, a selection criterion that the wireless I / F 1121 is used for higher-level communication may be set.

  Hereinafter, an example of operation will be described using the communication network shown in FIG. 6 as an example. In the communication network shown in FIG. 6, if the slave unit 10 of “12” is the hybrid slave unit 11 that focuses attention, the adjacent nodes that perform power line carrier communication are the slave units 10 of “11”, “13”, “21”, and “22”. Become.

  When the number of adjacent nodes is used as a selection criterion, the number of links when communication is performed using the power line I / F 1122 is required as an item of the second node table 1112 in the hybrid slave unit 11. Since this link number is an adjacent node that uses power line carrier communication, it includes the hybrid slave unit 11 and the wired slave unit 13.

  Therefore, the content of the second node table 1112 in the hybrid child device 11 of “12” is as shown in FIG. In the illustrated example, the identification information of the child device 10 included in the route between the parent device 20 and the adjacent node and the information related to the relay order on the route are omitted, but this information may be included. The number of hops in the second node table 1112 is the number of hops by wireless communication, and since it is assumed that the child devices 10 of “21” and “22” do not perform wireless communication, “21” in the illustrated example. The “22” handset 10 does not include hop count information.

  According to the second node table 1112 shown in FIG. 7, it can be seen that the number of adjacent nodes (that is, the number of links) performing power line carrier communication is “4”. On the other hand, looking at the item of the number of links, it can be seen that the maximum number of links in the adjacent node is “2”. As described above, the selection processing unit 1103 of the hybrid slave unit 11 can know the number of adjacent nodes (number of links) and the number of links for each adjacent node by using the second node table 1112. In this example, since the number of links of the “12” hybrid slave unit 11 is larger than the number of links in other adjacent nodes that perform power line carrier communication, the wireless slave unit 11 of “12” has the wireless I / F 1121 set. To form a higher-level communication path.

  When the above-described operation is adopted, the selection processing unit 1103 selects which of the wireless I / F 1121 and the power line I / F 1122 is used according to the following procedure. That is, the hybrid handset 11 transmits an H packet including the number of links obtained from the information stored in the second node table 1112 using the power line I / F 1122. As shown in FIG. 5B, the H packet includes the number of links in addition to the operation code, transmission source identification information, sequence number, and destination node type. Therefore, the selection processing unit 1103 of the hybrid handset 11 that has received the H packet can store the number of links included in the H packet in the item of the number of links in the second node table 1112.

  When the data is stored in the item of the number of links of all adjacent nodes in the second node table 1112, the selection processing unit 1103 determines the maximum number of links in the second node table 1112 and the number of adjacent nodes. Compare. When the number of adjacent nodes is larger than the maximum number of links, the selection processing unit 1103 selects the wireless I / F 1121 for the upper side and the power line I / F 1122 for the lower side. The selection processing unit 1103 selects only the power line I / F 1122 when the maximum number of links is equal to or less than the number of adjacent nodes. As a result, the number of hybrid slave units 11 that use the wireless I / F 1121 on the upper side can be limited to the minimum necessary.

  Here, in the above-described operation, instead of notifying the number of adjacent nodes in H packets, a list of identification information of adjacent nodes may be notified.

  The communication path selection criterion may be a topology related to an adjacent node of the hybrid slave unit 11. That is, whether or not to form a communication path on the upper side of the hybrid slave unit 11 by using the wireless I / F 1121 depending on whether the upper side link in the adjacent node is one or plural. May be. When there is one upper link in the adjacent node of the hybrid slave unit 11, the adjacent node establishes a route with the master unit 20 only through the hybrid slave unit 11. In the case of such a topology, a communication path on the upper side of the hybrid slave unit 11 is formed by the wireless I / F 1121.

  Hereinafter, an operation example will be described by taking the communication network shown in FIG. 8 as an example. In the communication network shown in FIG. 8, when the slave unit 10 of “11” is the hybrid slave unit 11 of interest, the adjacent nodes that perform power line carrier communication are the slave units 10 of “12”, “21”, and “22”.

  When the topology related to the adjacent node is used as the selection criterion, the identification information of the adjacent node for each adjacent node is required as an item of the second node table 1112 in the hybrid slave unit 11. That is, in the communication network, it is necessary to know the link for the slave unit 10 within the range of 2 hops from the target hybrid slave unit 11. Therefore, the second node table 1112 in the hybrid child device 11 of “11” includes the identification information of the adjacent node viewed from the second hop node as shown in FIG. In the illustrated example, the node identification information included in the route between the parent device 20 and the adjacent node and the information related to the relay order on the route are omitted, but this information may be included.

  According to the second node table 1112 shown in FIG. 9, the identification information of the next adjacent node is included for each adjacent node that performs power line carrier communication. That is, the adjacent nodes of the hybrid child device 11 of “11” are the child devices 10 of “12”, “21”, and “22”, and the adjacent nodes of the child device 10 of “12” are “11”, “13”, “ 22 "handset 10. Further, the adjacent nodes of the “21” child device 10 are only the “11” child device 10, and the adjacent nodes of the “22” child device 10 are the “11” and “12” child devices 10.

  As described above, the selection processing unit 1103 of the hybrid slave unit 11 includes the slave unit 10 in which the upper link is formed only with the hybrid slave unit 11 by using the second node table 1112. You can know whether or not. In this example, since only the “11” hybrid slave unit 11 is an adjacent node in the “21” slave unit 10, the “11” hybrid slave unit 11 uses the wireless I / F 1121 as a host. Side communication path.

  When the above-described operation is adopted, the selection processing unit 1103 selects which of the wireless I / F 1121 and the power line I / F 1122 is used according to the following procedure. That is, the hybrid handset 11 first transmits an H packet including the number of links obtained from the information stored in the second node table 1112 using the power line I / F 1122. As shown in FIG. 5C, the H packet includes identification information of adjacent nodes for each adjacent node in addition to the operation code, transmission source identification information, sequence number, and destination node type. Therefore, the selection processing unit 1103 of the hybrid handset 11 that has received the H packet can store data in the item of identification information of the adjacent node viewed from each of the adjacent nodes.

  The selection processing unit 1103, for all adjacent nodes in the second node table 1112, stores data in the identification information item of the adjacent node viewed from the adjacent node, and the adjacent node having only one adjacent node Determine the presence or absence. When there is an adjacent node having only one adjacent node, the wireless I / F 1121 is selected for the higher-order side of the target hybrid slave unit 11. Further, the power line I / F 1122 is selected for the lower side of the hybrid slave unit 11. In short, for each adjacent node of the target hybrid slave unit 11, the adjacent node viewed from the adjacent node is extracted, and when the condition that there is only one adjacent node is satisfied, The wireless I / F 1121 is selected for the side. As a result, while the number of hybrid slave units 11 using the wireless I / F 1121 on the upper side is suppressed, the slave unit 10 connected to the lower side by power line carrier communication can generate a communication route of good quality. .

  In the present embodiment, at least one of the three types of selection criteria described above can be used to determine a communication path in the hybrid slave unit 11. Here, the hybrid slave unit 11 selects the power line carrier communication with priority over the wireless communication by adopting the selection criteria described above. For example, if a consumer is an apartment house or a tenant building and power line carrier communication is used in the building, the information transmission range is limited to the inside of the building, but in the case of wireless communication, the transmission range is wide. There is a risk of signal interference over a wide range. By the above-described processing, the hybrid slave unit 11 connected to the higher-level side using the wireless I / F 1121 is limited from the plurality of hybrid slave units 11, so that communication traffic on the wireless communication side is reduced and packet collision occurs. Communication errors due to such factors can be suppressed.

  Here, even if the above-described selection criterion is applied and the higher-order communication path of the hybrid slave unit 11 is formed by the wireless I / F 1121, if the link cost of the lower-order communication path of the hybrid slave unit 11 is large, Node communication quality may not be ensured. Therefore, it is preferable to evaluate the link cost with the target hybrid slave unit 11 as well as the upper route cost for the adjacent node of the target hybrid slave unit 11.

  Hereinafter, an example of operation will be described using the communication network shown in FIG. 10 as an example. In the communication network shown in FIG. 10, when the slave unit 10 of “12” is the hybrid slave unit 11 that focuses attention, the adjacent nodes that perform power line carrier communication are the slave units 10 of “11”, “13”, “21”, and “22”. Become. As shown in FIG. 11, the second node table 1112 in this hybrid handset 11 has the same items as in the example shown in FIG. 4B. However, a specific example is described in the link cost by the power line carrier communication with the target hybrid slave unit 11.

  According to the second node table 1112 shown in FIG. 11, the upper route costs related to the hybrid slave units 11 of “11” and “13” which are adjacent nodes are 11 and 12, respectively. On the other hand, the minimum value of the route cost of the target hybrid handset 11 is 15. For this reason, the wireless I / F 1121 is not selected in the hybrid slave unit 11 according to the selection criteria described above. In other words, the route cost of the hybrid child device 11 of “12” is higher than the upper route cost of the hybrid child devices 11 of “11” and “13” that are adjacent nodes. F1122 is selected. On the other hand, here, the wireless I / F 1121 is selected in the hybrid slave device 11 of “12” by considering the link cost between the target hybrid slave device 11 and the adjacent node. It is.

  That is, in the example shown in FIG. 10, the link costs between the “12” hybrid slave units 11 and the adjacent nodes “11” and “13” hybrid slave units 11 are 32 and 41, respectively. Therefore, the route cost of the route passing through the adjacent nodes is 43 and 53, respectively, while the hybrid child device 11 of “12” uses the wireless I / F 1121 for higher-level communication 15. , Has grown significantly. Therefore, when such a condition is established, it is desirable to use the wireless I / F 1121 even in the case of the hybrid slave unit 11 that uses the power line I / F 1122 for higher-order communication, based on the selection criteria described above.

  The selection processing unit 1103 compares the minimum route cost obtained from the first node table 1111 with the route cost that is the sum of the upper route cost and the link cost obtained from the second node table 1112. Then, the selection processing unit 1103 selects the wireless I / F 1121 when the difference between the route costs exceeds a prescribed threshold value. By adding such a restriction, the possibility of forming a route with very poor communication quality is reduced.

  In a communication path that is a link in a communication network formed between the parent device 20 and the child device 10, wireless communication or power line carrier communication is used according to the selection criteria and restrictions described above. By the way, as above-mentioned, the subunit | mobile_unit 10 can communicate between the apparatuses which a consumer uses, and wireless communication or power line carrier communication is used also between apparatuses. Therefore, there is a possibility that communication between the child device 10 and the device interferes with communication between the child device 10 and the parent device 20.

  Therefore, in order to avoid this kind of interference, a transmission medium different from the transmission medium used for communication between the slave unit 10 and the device is preferentially used for communication between the slave unit 10 and the master unit 20. It is preferable. For example, if wireless communication is performed between the child device 10 and the device at the consumer, power line carrier communication is preferentially used for communication between the corresponding child device 10 and the parent device 20. It is preferable to do.

  In order to select the transmission medium of the communication path between the slave unit 10 and the master unit 20 as described above, after selecting the transmission medium of the communication path between the slave unit 10 and the device, the slave unit 10 A transmission medium different from the previously selected transmission medium may be selected within a selectable range. Further, if the selection criteria is weighted so that the selected transmission medium is preferentially used, the communication path between the slave unit 10 and the device and the communication path between the slave unit 10 and the master unit 20 are reduced. Separation becomes easy. If the communication paths are clearly separated in this way, an increase in traffic is suppressed and packet collision is also suppressed. The weighting technique will be described later.

  By the way, the link cost of the link included in the communication network is dynamically changed by transmission / reception of the H packet. In the case of power line communication, the SNR changes due to changes in impedance and noise that occur with the operating state of electrical equipment such as home appliances and electrical equipment, and on / off of switches. In the case of wireless communication, even if the parent device 20 or the child device 10 itself does not move, the received signal strength changes due to changes in the surrounding environment such as the movement of a car or a person. However, if the route is changed by a very slight change, it is not preferable in terms of operation management, for example, the route diverges without converging in the entire system. Therefore, after the link according to the characteristics of the power line carrier communication and the wireless communication is once formed, it is preferable to use the link without changing if the link cost does not change significantly.

  Therefore, after determining that the wireless communication device 11 uses the wireless communication for the higher-order communication path, the H-packet in which the flag indicating that the wireless communication is used for the higher-order communication path is set. Is preferably sent out. The hybrid handset 11 of the adjacent node that has received the H packet weights the communication path selection criteria so that the wireless handset 11 with the flag set is preferentially used for wireless communication. That is, in the case where the wireless communication device 11 has already adopted wireless communication as the communication channel, the hybrid slave device 11 weights the communication channel selection criterion so that the wireless communication is easily selected as it is.

  For this weighting, for example, when a selection criterion for comparing the route cost with the higher-order route cost is used, the route cost in the hybrid handset 11 with the flag set may be reduced by a predetermined value. Further, when the number of adjacent nodes is used as the selection criterion, a predetermined number of the numbers included in the H packet transmitted from the hybrid slave unit 11 for which wireless communication is selected may be added.

  As described above, in hybrid handset 11, once it is selected that wireless communication is used for the upper communication path, the state is maintained as much as possible. Therefore, the hybrid handset that uses wireless communication is used. 11 can be prevented from changing frequently.

  Note that the hybrid handset 11 has a probability that different communication methods are selected in selecting the communication method used in the upper communication channel and the communication method used in the lower communication channel. It is preferable to set the selection criterion so that it is higher than that.

10 slave unit 11 hybrid slave unit 12 wireless slave unit 13 wired slave unit 20 master unit 1101 route building unit

Claims (7)

A multi-hop communication system that includes a master unit and a plurality of slave units as nodes, and allows relaying of communications by other slave units when transmitting information between the master unit and the slave units. And
The cordless handset includes a hybrid cordless handset capable of selecting two types of communication methods, wireless communication using radio waves as a transmission medium and power line carrier communication using a distribution line as a transmission medium,
The hybrid handset is
A pre-processing for determining whether to use the wireless communication or the power line carrier communication with another adjacent node having a hop number of 1 is performed, and then a route cost to the parent device A multi-hop communication system, comprising: a route construction unit that performs the main processing for determining a route. The hybrid handset is
For other adjacent nodes with a hop count of 1, the identification information of the node, the upper route cost that is the route cost between the node and the parent device, and the link cost between the node The multi-hop communication system according to claim 1, further comprising a storage unit that manages information. The storage unit
A first node table that manages information related to nodes connected by the link performing wireless communication among other adjacent nodes having a hop number of 1;
The multi-hop according to claim 2, further comprising: a second node table that manages information related to a node connected by a link performing the power line carrier communication among other adjacent nodes having a hop number of 1. Communications system. The route building unit
As the preprocessing, by using the first node table and the second node table, a communication method used for a communication path with another adjacent node having a hop number of 1 is used as the wireless communication and the The multi-hop communication system according to claim 3, wherein processing for determining which one to use for power line carrier communication is performed. The hybrid handset is
Of the route cost that is the sum of the upper route cost and the link cost managed in the first node table, the minimum route cost and the upper route cost managed in the second node table Compare with the lowest top route cost,
When the minimum route cost in the first node table is smaller than the minimum upper route cost in the second node table, the wireless communication system is used as a communication method used in a higher-order communication path that is the parent device side. The multi-hop communication system according to claim 3, wherein communication is selected.   A hybrid handset used in the multi-hop communication system according to any one of claims 1 to 5. Communication in a multi-hop communication system comprising a master unit and a plurality of slave units as nodes, and allowing relaying of communications by other slave units when transmitting information between the master unit and the slave units A method of selecting a road,
The cordless handset includes a hybrid cordless handset capable of selecting two types of communication methods, wireless communication using radio waves as a transmission medium and power line carrier communication using a distribution line as a transmission medium,
The hybrid handset is
A pre-processing for determining whether to use the wireless communication or the power line carrier communication with another adjacent node having a hop number of 1 is performed, and then a route cost to the parent device A method for selecting a communication path in a multi-hop communication system, characterized by performing a main process for determining a route.

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