JP2011223419A - Multihop wireless ad hoc network, communication system, information collection and setting device, information terminal, and route search method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multihop wireless ad hoc network that can reduce power consumption.SOLUTION: The multihop wireless ad hoc network constitutes a tree-structured wireless network by having a gateway 12 as a master station. Terminals 1-11 in the network are synchronized with adjacent terminals on a route to the gateway 12 so that all the terminals in the network are synchronized with the gateway 12. An activation cycle, an activation phase, and an activation period are aligned across all the terminals and the gateway 12 in order to perform a changeover operation between activation and sleep. During the activation period, data transfer is executed in an activation section within a synchronization error range. During the sleep period, minimal sections are activated, and resynchronization is performed from the gateway 12 according to the tree structure in order to maintain the synchronization operation.

Description

  The present invention relates to a multi-hop wireless ad hoc network, a communication system, an information collection / setting device, an information terminal, and a route search method.

  Multi-hop wireless ad hoc networks are attracting attention for information collection and control device operation. In multi-hop communication, when direct communication is not possible, such as when the distance to the transmission destination is long or there is no line of sight, it is possible to cover a wide area by relaying communication with other nodes existing in the middle. . In order to realize a multi-hop communication node, a route control technique for realizing a relay function is required in addition to elemental techniques such as a wireless communication technique and an address assignment technique.

  Many routing protocols are being devised and formulated by the Internet Engineering Task Force (IETF) MANET (Mobile Adhoc Network) working group. The MANET route control protocol is roughly classified into a proactive type and a reactive type from the viewpoint of generation timing of route information. The proactive type is a method in which each node always holds route information by periodically exchanging control messages. In the reactive type, route information is acquired only when a communication request occurs, so that the overhead is relatively small.

  As a typical reactive type route search protocol of the reactive type, for example, there is an on-demand type routing protocol (see Non-Patent Document 1).

  In order to reduce the power consumption of the terminal, the sleep mode can be applied. For example, in a wireless network that is not multi-hop, since the terminal needs to consider only the signal addressed to / from itself, the sleep mode can be introduced relatively freely. On the other hand, in a multi-hop wireless ad hoc network, a terminal that has become a relay node needs to relay a signal other than a signal addressed to / from the terminal, and therefore, it is necessary to shift to a sleep mode in consideration of network operation.

IETF RFC3561 “Ad Hoc On-Demand Distance Vector (AODV) Routing” “A survey of geocast routing protocols”, Communications Surveys & Tutorials, IEEE, vol.6, no.2, pp.32-42, Second Quarter 2004 “Efficient forwarding of symbolically addressed geocast messages” Computer Communications and Networks, 2005. ICCCN 2005. Proceedings. 14th International Conference on, vol., No., Pp. 77-83, 17-19 Oct. 2005 IETF (0 Internet Engineering Task Force) RFC3561 “Ad hoc On-Demand Distance Vector (AODV) Routing” Search RFC3561 from http://www.ietf.org/, or http://datatracker.ietf.org/doc/ rfc3561 /

  In a conventional multi-hop wireless ad hoc network, a terminal that has become a relay node needs to relay a signal other than the signal addressed to / from itself, but the transition process to the sleep mode in consideration of the network operation cannot be realized. There was a problem.

  In addition, it is necessary to lengthen the sleep time in order to reduce power consumption, but in conventional multi-hop wireless ad hoc networks, there are many network control signals such as route maintenance and construction, etc. There was a problem.

  In addition, in a wireless network to which CSMA is applied, when the number of terminals increases, the collision of wireless signals increases, and the number of retransmissions of signals that did not reach due to the collision increases, so that the sleep time cannot be extended. It was.

  On the other hand, in sleep mode, communication is not possible during the sleep time, and in order to reduce system throughput and reduce power consumption, lower power consumption is required when high-speed communication such as large file transfer is required. There was a problem that it could not be realized.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a multi-hop wireless ad hoc network capable of realizing low power consumption by realizing an efficient sleep mode.

  In order to solve the above-described problems and achieve the object, the present invention provides a route for all terminals in a network to a gateway in a multi-hop wireless ad hoc network that forms a tree-structured wireless network with the gateway as a master station. Synchronize with the neighboring terminals of the network, and the entire network is synchronized with the gateway, and all terminals and gateways switch between startup and sleep in accordance with the startup cycle, startup phase, and startup period, and the synchronization error range during the startup period The data transfer is performed during the startup period, the minimum part is operated during the sleep period, and the resynchronization is performed from the gateway according to the tree structure in order to maintain the synchronization operation.

  According to the present invention, it is possible to obtain a multi-hop wireless ad hoc network that can realize low power consumption by realizing an efficient sleep mode.

FIG. 1 is a diagram illustrating a configuration of a multi-hop wireless ad hoc network according to the first embodiment. FIG. 2 is a diagram for explaining the entry operation of a new terminal. FIG. 3 is a diagram for explaining the synchronization operation. FIG. 4 is a diagram for explaining another synchronization operation. FIG. 5 is a diagram for explaining the sleep operation. FIG. 6 is a diagram for explaining the operation of the periodic resynchronization sequence. FIG. 7 is a diagram for explaining the switching operation between the continuous mode and the low power consumption mode. FIG. 8 is a diagram showing a system configuration of a conventional communication system. FIG. 9 is a diagram for explaining a problem of a conventional communication system. FIG. 10 is a diagram illustrating a configuration of a communication system according to the fourth embodiment. FIG. 11 is a diagram illustrating an example of correction. FIG. 12 is a diagram illustrating an example of correction. FIG. 13 is a diagram illustrating a system configuration example when the number of information terminals covered by one relay terminal is three or less and a communication path is established based on the initial state of FIG. FIG. 14 is a functional block diagram of the information collection / setting apparatus according to the fourth embodiment. FIG. 15 is a diagram illustrating functional blocks of the information terminal according to the fourth embodiment. FIG. 16 is a diagram illustrating a configuration of an initial state of the communication system according to the fifth embodiment. FIG. 17 is a diagram illustrating a configuration of a communication system according to the fifth embodiment. FIG. 18 is a diagram illustrating functional blocks of the information terminal according to the sixth embodiment. FIG. 19 is a diagram for explaining a conventional local path repair operation. FIG. 20 is a diagram for explaining the operation in the case where the local path repair fails. FIG. 21 is a diagram for explaining an operation of local path repair according to the eighth embodiment. FIG. 22 is a flowchart showing processing corresponding to FIG. FIG. 23 is a diagram for explaining an operation of local route repair according to the ninth embodiment. FIG. 24 is a flowchart showing processing corresponding to FIG. FIG. 25 is a diagram for explaining the local path repair operation according to the tenth embodiment. FIG. 26 is a flowchart showing processing corresponding to FIG.

  Hereinafter, embodiments of a multi-hop wireless ad hoc network, a communication system, an information collection / setting device, an information terminal, and a route search method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration of a multi-hop wireless ad hoc network according to the first embodiment. The terminals 1 to 11 are arranged in a distributed manner, each connected by a wireless link, and connected to a gateway (hereinafter referred to as GW) 12. A terminal that cannot be directly wirelessly connected to the GW 12 is connected to the GW 12 by relaying with another terminal. Communication with other networks is performed via the GW 12.

  In order to achieve low power consumption of the terminal, for example, a sleep mode is introduced into the terminal, the start mode is set only during the time when the terminal transmits / receives data, the other time is set as the sleep mode, and the sleep mode is operating. Can be considered to stop the operation of the radio unit. However, in a multi-hop wireless ad hoc network, a terminal that has become a relay route needs to operate as a start-up mode in addition to the data transmission / reception time of the local station and the time for relaying data of other terminals. In the present embodiment, all the terminals under the GW are synchronized with the GW time, and the GW and all the terminals transmit and receive data within the activation time together with the activation time.

  In FIG. 1, when a multi-hop wireless ad hoc network starts up, each terminal searches for nearby terminals and the GW 12, and selects and connects an optimal neighboring terminal based on the number of wireless links to the GW 12, the wireless signal strength, and the like. By operating in this way, a link that connects autonomously from a terminal near the GW 12 to the GW 12 is formed, and the network gradually expands outward.

  FIG. 2 is a diagram for explaining the entry operation of a new terminal. In the peripheral terminal search for a new terminal, when the peripheral terminal (participated terminal) is operating at low power (operating in the low power consumption mode), communication is impossible at the timing during the sleep period. Therefore, the new terminal repeatedly executes transmission of a search signal for searching for a peripheral terminal (peripheral terminal search) in a short cycle. When the peripheral terminal is in the sleep state (Sleep), the search signal is ignored, the response signal (peripheral terminal information) is not returned, and when the peripheral terminal is in the active state (Active), a response signal to the search signal is returned. Since the peripheral terminals are simultaneously in the start-up mode within the synchronization error range, the search for the peripheral terminals is completed by confirming the received signal for a predetermined time from the time when the response signal is returned from a certain terminal. The new terminal performs synchronization processing on the connection terminal (or GW) that is the optimal GW path based on the peripheral terminal information (number of hops to the GW, wireless signal strength, etc.) from the peripheral terminal.

  FIG. 3 is a diagram for explaining the synchronization operation. The synchronization process is executed using a synchronization sequence used in NTP (Network Time Protocol) or the like. For example, before the synchronization process, the time master (for example, GW12) and the slave (for example, terminal 1) are operated by independent clocks. In this state, the slave sends a time synchronization request signal in which the slave transmission time (T1) is set. The time master that has received the time synchronization request signal returns a time synchronization response signal in which the reception time (T2) of the time synchronization request signal and the transmission time (T3) of the time synchronization response are set. The slave that has received the time synchronization response signal sets the reception time (T4) of the time synchronization response signal. Assuming that the uplink / downlink transmission times are equal, the transmission time d is “d = ((T4−T1) − (T3−T2)) / 2”, and the time difference Toffset between the time master and the slave is “Toffset”. = T4-T3-d ", the slave corrects its own clock by Toffset and synchronizes with the clock of the time master. Since the time synchronization request signal and the time synchronization response signal are used for delay time measurement, an error increases when retransmission at the wireless MAC layer occurs. For this reason, these signals are transmitted using multicast packets for which retransmission control does not occur. Also, the peripheral terminal search process and the synchronous process may be executed simultaneously by placing time synchronization information on the peripheral terminal search and peripheral terminal information shown in FIG.

FIG. 4 is a diagram for explaining another synchronization operation. Here, an example of a synchronization operation that can further improve the synchronization accuracy is shown. FIG. 3 shows an operation example using only signals in the ad hoc network layer, but FIG. 4 shows a synchronization operation using a MAC layer signal in order to reduce synchronization errors. In FIG. 4, the time synchronization request signal and the time synchronization response signal of the ad hoc network layer are transmitted as a unicast signal of the wireless MAC layer, and the Ack signal of the wireless MAC layer is received as the response, and the uplink and downlink delay time is approximately Assuming that they are equal, the communication delay time d1 is obtained by “d1 = (T _c −T _a ) / 2”. The communication delay time d1 + d2 is “d1 + d2 = (T _e −T _a ) − (T _d −T _b )”, and the communication delay time d2 can be obtained. Therefore, the time difference Toffset between the time master and the slave is obtained by “Toffset = T _e − (T _d + d2) = (T _a −2T _b + T _c ) / 2”. (In FIG. 4, it is clear from the fact that the time difference between the midpoint of the slave time T _a -T _c and the time T _b of the time master is the offset amount.)

  Here, the slave corrects its own clock by Toffset and synchronizes with the clock of the time master. When retransmission at the MAC layer occurs, d1 and d2 are calculated using the wireless MAC transmission signal time and the Ack reception time when communication is completed.

  FIG. 5 is a diagram for explaining the sleep operation. The new terminal that has completed synchronization with the clock of the GW has a preset start cycle (start / sleep is repeated every 3 seconds, etc.), start phase (from which timing start / sleep cycle operation starts), start Start / sleep operation of the terminal is started according to the period (start: sleep = 1: 5, etc.). A plurality of terminals perform the same operation, but each terminal has a synchronization error. The terminal has a time other than the protection time (hatched portion: assumed time error in the figure) against the synchronization error set in advance at the beginning and end of the activation time (active slot) (white portion in the middle of the activation time in the figure: (Sendable time). The receiving side operates so as to be able to receive during the entire activation time, and enables communication between terminals in consideration of a difference in activation time between terminals.

  FIG. 6 is a diagram for explaining the operation of the periodic resynchronization sequence. Since each terminal operates by an independent clock source signal, the synchronization is shifted as time passes. Therefore, periodic resynchronization processing is necessary to maintain synchronization between terminals. In the resynchronization process, for example, the GW 12 determines the control order of terminals to be synchronized based on the route information of all terminals. Since the synchronization control of the terminal includes a synchronization error, it is performed from the order close to the GW 12 for each path of each tree structure so that the influence of the synchronization error is minimized. In this example, first, the route including the terminal 1 is synchronized in the order of 1 → 7 → 11 → 10 (whichever is the same for 10 and 11), and then proceeds to the route of the terminal 2, Repeat the operation. The terminal that has received the synchronization instruction from the GW 12 performs a synchronization process with the terminal one higher in the route to the GW 12 or the GW 12 (the terminal 1 is synchronized with the GW 12 and the terminal 7 is synchronized with the terminal 1), and synchronizes itself. .

  In the present embodiment, the control order of the terminals to be synchronized by the GW 12 has been described. However, the control order of the terminals to be synchronized with the GW 12 by another network such as a network management apparatus connected to the GW 12 can also be implemented. . In this case, the route information of all the terminals held by the GW 12 is notified to the network management device, the network management device determines the control order of the terminals to be synchronized, and notifies the GW 12 of the synchronization instruction transmission request. Then, the GW 12 that has received the synchronization instruction transmission request transmits a synchronization instruction to the terminal in the same manner as the above operation. Instead of the synchronization instruction, the resynchronization execution time information may be passed from the GW 12 to the terminal in advance, and the higher station may be resynchronized by the operation from the terminal at the set time.

  As described above, in this embodiment, it is possible to obtain a multi-hop wireless ad hoc network that can realize low power consumption by realizing an efficient sleep mode.

Embodiment 2. FIG.
In the low power consumption mode (mode for realizing low power consumption), the power consumption of the terminal can be further reduced by shortening the startup time and the sleep time. In order to shorten the startup time, it is necessary to reduce the number of signals transmitted and received by the terminal. Conventional on-demand ad hoc protocols such as AODV are said to have few signals to be transmitted and received, but in this embodiment, further signal reduction is attempted with respect to AODV.

  In the conventional AODV, a route search is performed every time communication occurs. For example, in the case of file transfer, a path search is performed before the start of file transfer to establish a path, and then file transfer (multiple signals) is performed. Also, when the next file transfer is performed to the same destination after a certain period, it is performed again from the route search. On the other hand, in the present embodiment, utilizing the characteristics of the tree structure with GW 12 as the root, if the destination is the same (for example, GW 12), communication is attempted using the previous route. The route search is executed again only when the previous route cannot be used due to a change in the wireless state or the like.

  In the conventional AODV route search, a route search signal from the route search source is notified (flooded) to the entire network, and the route is established by the Ack. On the other hand, in the present embodiment, the characteristics of the tree structure with GW 12 as a root are utilized, flooding is not performed, a search signal is transmitted only to the adjacent terminal of the route search source, and the hop to GW 12 by the Ack signal from the adjacent terminal The optimum neighboring terminal of the route to the GW 12 is selected from the number and the information of the radio signal strength.

  Also, in a multi-hop wireless ad hoc network that forms a tree-structured wireless network with GW 12 as a master station, downlink (GW 12 → terminal) signals are scheduled in GW 12, and uplink (terminal → GW 12) signals are GW 12 By controlling the uplink signal transmission time of the terminal based on the timing signal notification from the mobile station, radio signal collisions in the multi-hop wireless ad hoc network are reduced, and an increase in unnecessary traffic is suppressed. The timing signal notification from the GW 12 may be a polling operation for each data transmission or an operation in which a transmission start time is designated in advance from the GW 12 to the terminal and the terminal transmits uplink data at each time.

  In this embodiment, these operations are performed to minimize the traffic and extend the sleep time.

Embodiment 3 FIG.
In the low power consumption mode in which activation / sleep is switched periodically as described above, since the sleep time cannot be communicated, the system throughput decreases according to the activation / sleep ratio. On the other hand, in parallel with the requirement for reducing the power consumption of the system, there is also a requirement to use the maximum performance of the physical medium when necessary. In order to satisfy these requirements, the present embodiment realizes a switching operation between the continuous mode and the low power consumption mode.

  FIG. 7 is a diagram for explaining the switching operation between the continuous mode and the low power consumption mode. A terminal that wants to shift to the continuous operation mode for execution of large-volume file transfer, etc., during the startup time of the low power consumption mode, a signal in which continuous mode transition information for shifting to the continuous mode is added to the header, Send to communication partner and switch to continuous operation mode. Further, the relay terminal that transfers this signal checks the header at the time of relaying, and switches the local station to the continuous operation mode when the continuous mode transition information is set. Thereafter, the same operation is performed in the station that finally arrives (GW 12 in this example), and switching to the continuous mode is performed.

  By the operation of the present embodiment, the terminal and the GW on the path to which the signal in which the continuous mode transition information is set is transferred shifts to the continuous operation mode, and data communication at the maximum speed of the wireless medium becomes possible. In subsequent communication, communication in the continuous mode is maintained by continuously setting the continuous mode information in the data header. Thereafter, when the mass file transfer is completed and the continuous mode transition information is not received for a certain period or longer, each terminal ends the continuous mode and returns to the low power consumption mode.

Embodiment 4 FIG.
First, a conventional communication system will be described before describing the configuration and operation of the communication system according to the present embodiment.

  Conventionally, a method of networking a plurality of communication terminals and managing the network in association with the actual location information of the terminals as well as logical connections has been studied. Thereafter, with the spread of GPS (Global Positioning System), it becomes easy for information terminals to acquire position information, and research on route search when the position of the information terminal is not fixed and the information terminal moves is also underway.

  The method of searching for a route is roughly divided into the following two methods. The first is a method represented by LBM (Location Based Multicast) that performs flooding that is inquiry information only in the direction of the location of the target information terminal, and a communication path and map information that are logically formed based on this method. There is a method to make the shortest distance by connecting. As a method of connecting the communication route and the map information so as to be the shortest distance, a method using a Voronoi map, a method for constructing a mesh, a method called GeoGRID (see Non-Patent Document 2) in which the terrain is converted into a GRID. There is.

  The second is a method for constructing a route based on position information of the target information terminal without requiring flooding. Examples include a method called URAD (Unicast Routing with Area Delivery) and a method called GeoNode.

  With each of the above conventional methods, each terminal can establish a communication path by associating position information with an information terminal that cannot perform direct communication, and can transmit information using this path. .

  Moreover, in order to improve information efficiency, it is necessary not to frequently search for communication paths. In order to realize this, the information terminals belonging to the network need to store the network route (topology) inside. However, when the number of information terminals accommodated in the network increases, the number of information terminals to be managed by the information terminals increases, and the cost of memory, CPU, etc. increases. Therefore, conventionally, it has been proposed to hierarchize the network, such as providing a representative of the area (see Non-Patent Document 3).

  FIG. 8 is a diagram showing a system configuration of a conventional communication system. This communication system includes an information terminal (41, 42, etc.) for collecting information from a plurality of sensors, external devices, etc., and a relay terminal (31-35, etc.) representing an area among these information terminals. The information collecting / setting device (21) using wireless communication is used to easily set numerical values in the terminal. The information terminal and the relay terminal may be the same, or the relay terminal may have higher performance.

  Here, the position information is divided into two-dimensional areas, the X-axis is set to X1 to X5, the Y-axis is set to Y1 to Y4, and the information is collected and set by the conventional GeoGRID type. A case where information is exchanged with the information terminal 41 will be described. The route is indicated by an arrow.

  The information collection / setting device 21 stores the position information of all terminals. Each relay terminal stores information terminals in the area covered by the terminal itself, but does not store information terminals in other areas. Each relay terminal stores connection information between relay terminals. Thereby, the information addressed to the information terminal 41 from the information collection / setting device 21 is transmitted to the relay terminal 34 while passing through the relay terminals 31, 32, 33, 34. The received information is transmitted to the information terminal 41. Through such operations, each relay terminal reduces the number of information terminals to be stored.

  Further, for example, when a failure occurs in the relay terminal 32, it is not necessary to perform a route search for the information terminal 41, and a route connecting the relay terminal 31 and the relay terminal 33 (31 （35⇔33 in the figure) is used. Just establish it. Thereby, the time required for communication path restoration can be reduced.

However, the conventional communication system has the following problems. This will be described with reference to FIG. As an example, the communication system of FIG. 9 includes a plurality of information terminals, relay terminals 31 to 39, and an information collection / setting device 21.
(1) For example, when the network form is one-dimensional, when the relay terminal 32 breaks down, it is necessary to search for an alternative route, such as making another information terminal a relay terminal.
(2) In wireless communication, there is a case where the geographical distance and the wireless quality do not match due to radio wave shielding (O1 in the figure) by a high-rise building or the like, and interference (I1) by another system using the same frequency.
(3) There are cases where the number of wireless terminals accommodated by one relay terminal becomes excessive and exceeds the processing capacity and storage capacity of the relay terminal (in the figure, the relay terminal 36 exceeds the management of a maximum of eight units and the ninth unit enters is doing).

  It continues and demonstrates the communication system of this Embodiment. FIG. 10 is a diagram illustrating a configuration of a communication system according to the fourth embodiment. It is assumed that the information collection / setting device 21 grasps all the information terminals (51 to 63) belonging to the information and holds the position information of each information terminal. Here, the accuracy of the position information is not necessary, and is used as an initial state. FIG. 10 shows an example of an initial state held by the information collection / setting device 21.

  From the initial state, the information collection / setting device 21 reduces the connection relationship between the information terminals, which is impossible in terms of distance, and temporarily creates a logical connection. At this time, when the transmission output, reception performance, and transmission speed are different in each information terminal, the logical connection may be disconnected for each condition. In the initial state, there is no distinction between a relay terminal and an information terminal.

  In this embodiment, the distance between the information terminals is L, for example, the distance between the information collection / setting device 21 and the information terminal 60 is represented as L (21-60), and the information collection / setting device 21 The distance between the information terminals 51 is represented as L (21-51), and the distance between the information terminals 51 and 52 is represented as L (51-52). If the distance is clearly impossible to communicate, it is excluded from the connection.

  Further, as shown in FIGS. 11 and 12, when there is an object that shields radio waves based on two-dimensional map information, correction for adding a distance or correction for connection relation may be performed. 11 and 12 are diagrams illustrating an example of correction.

Then, the information collection / setting apparatus 21 extracts relay terminals from the following viewpoints from the remaining connection relationship.
(1) The communication quality between relay terminals is expected to exceed a desired value.
(2) The number of relay terminals can be set small.
(3) The number of information terminals covered by the relay terminal does not exceed a certain number.
(4) An alternative route can be established when a relay terminal fails.
In addition, when extracting a relay terminal, it is not necessary to satisfy | fill all said (1)-(4), and the case where some are satisfy | filled may be sufficient.

  FIG. 13 is a diagram illustrating a system configuration example when the number of information terminals covered by one relay terminal is three or less and a communication path is established based on the initial state of FIG. A solid line represents a logical connection, and a dotted line is an alternative route at the time of failure. In FIG. 13, as an example, 55, 56, 58, and 59 are extracted as relay terminals.

  Next, the configuration of each device included in the communication system according to the present embodiment will be specifically described. FIG. 14 is a diagram illustrating functional blocks of the information collection / setting apparatus 21 according to the present embodiment. The information collection / setting device 21 includes a display I / F unit 71 that performs processing for inputting information from an administrator, and processing for outputting communication management information to the administrator and information for information collection, and an information terminal It comprises a control unit 72 for managing communication paths, instructing and setting information collection to the information terminal, and a wireless communication unit 73 for performing wireless communication with the information terminal.

  The control unit 72 includes a communication path control unit 81 that calculates a communication path of the information terminal, and an information collection / setting unit 82 that collects and sets information from the information terminal. In addition, the communication path control unit 81 includes a terminal position information management unit 91 that manages position information of accommodated information terminals, a map information / terrain information management unit 92 that manages map information / terrain information, and a position of the information terminal. The communication path calculation unit 93 calculates the logical connection relationship between the information terminals from the information and the map, and the communication path holding unit 94 holds the calculated communication path.

  The administrator can add an information terminal, add map information / terrain information, and update an algorithm for obtaining a communication path to the communication path control unit 81 via the display I / F unit 71. It is also possible to display the calculated communication path.

  The information collection / setting unit 82 can refer to the route from the communication route control unit 81 to the information terminal during communication. In addition, the information collection / setting unit 82 performs predetermined exchanges with the wireless communication unit 73 that performs modulation / demodulation to a wireless signal and communication control. The wireless communication unit 73 exchanges wireless signals with an external wireless terminal.

  FIG. 15 is a diagram illustrating functional blocks of the information terminal according to the present embodiment. The information terminals (51 to 63) include an external I / F unit 101 that outputs input information collected from the outside and setting information to the outside, management of the communication route of the information terminal and information collection instructions to the information terminal, It comprises a control unit 102 that performs settings, and a wireless communication unit 103 that performs wireless communication with other information terminals and the information collection / setting device 21.

  The control unit 102 also includes a communication path control unit 111 including a terminal information management unit 121 that manages information terminals existing in the periphery and the route, and a communication path holding unit 122 that stores the communication route, and information from the information terminal. It comprises an information collection / setting unit 112 that performs collection and setting.

  The wireless communication unit 103 exchanges wireless signals with an external wireless terminal. Information related to the communication path is exchanged with the communication path control unit 111, and information collected from the information terminal and information related to the setting are exchanged with the information collection / setting unit 112. The information collection / setting unit 112 collects and sets information via the external I / F unit 101.

  The distance calculation method in the present embodiment is not limited to the above, and may be combined with an algorithm for obtaining a minimum sum of distances such as a Voronoi diagram and a Delaunay diagram.

  As described above, in the present embodiment, a communication topology considering the form of the wireless communication network to be applied and geographical factors is created, and a representative relay terminal is selected. As a result, the information terminals can reduce the number of terminals to be grasped, so that cost reduction can be realized, and furthermore, the network form can be grasped simply, so that an early recovery from a failure is possible. Can be realized.

Embodiment 5 FIG.
In the present embodiment, differences from the above-described fourth embodiment will be described. In the present embodiment, the information collection / setting device 21 is not the input from the administrator but the adjacent information detected by the information terminals through communication when grasping the connection relationship of all information terminals belonging to the information terminal. Connection with the information terminal to be used.

  FIG. 16 is a diagram illustrating a configuration of an initial state of the communication system according to the present embodiment. Here, the initial state of the connection relation collected by each information terminal (51-67) is shown. In this state, for example, the information terminal 55 needs to grasp all the information terminals 58, 59, 62, 63, 66, and 67 connected to the information terminal 55. At this time, the information terminal 55 needs to store information in the internal management table that, for example, wireless signals addressed to the information terminals 62, 63, 66, and 67 are relayed to the terminal 59. In the state of FIG. 16, there is a possibility that a new information terminal cannot be connected due to an increase in the management table. In addition, problems remain in the route search method of the information terminal at the time of failure.

  Therefore, in the present embodiment, the information collection / setting device 21 uses the communication path (initial state) shown in FIG. 16 as a relay device, for example, as shown in FIG. Change to the set communication path. As a result, the information terminal 55 needs to grasp only the information terminal 58 and the relay terminal 59. And the relay terminal 59 will grasp | ascertain four information terminals (62, 63, 66, 67) which exist in an own area.

  When a new information terminal is detected, the neighboring information terminal or relay terminal that has detected the new information terminal notifies the information collection / setting device 21 that the network has been expanded. Then, the information collection / setting device 21 performs processing for newly setting a relay terminal as necessary.

  As described above, according to the present embodiment, the number of terminals that each information terminal should grasp can be reduced without requiring an administrator input when operating the network. Can be realized. In addition, since it is possible to simply grasp the form of the network, it is possible to realize early recovery in the event of a failure.

Embodiment 6 FIG.
In the present embodiment, differences from the above-described fourth embodiment will be described. In the present embodiment, a mechanism for verifying whether the route set by the information collection / setting device 21 is an optimal route is added.

  The information collection / setting device 21 notifies each information terminal of the communication path, and after establishing the initial communication path, collects the measurement results of the communication quality of the peripheral information terminals from a specific information terminal or all information terminals. Communication quality includes SNR, RSSI, SINR, and the like.

  FIG. 18 is a diagram illustrating functional blocks of the information terminal according to the present embodiment. Compared with the communication path control unit 111 described above, the communication path control unit 111a of the control unit 102a of the present embodiment has a communication performance measurement unit 123a that measures the communication quality with each information terminal and a communication that holds the measurement result. A performance holding unit 124 a is added, and the communication performance measuring unit 123 a measures communication performance with other information terminals according to instructions from the information collecting / setting device 21, and the measurement result is sent to the information collecting / setting device 21. Has the ability to report.

  As described above, in the present embodiment, the communication quality measured at each information terminal can be reflected in the network, so that a communication path that matches the actual environment can be constructed.

Embodiment 7 FIG.
In the present embodiment, differences from the above-described fourth embodiment will be described. In the present embodiment, it is assumed that the type of wireless communication to be used shares a frequency to be used with another wireless system, such as an ISM band or a specific low power radio. Here, as another wireless system sharing the frequency, for example, in wireless communication in an office environment, a wireless system in which a daytime usage rate is high and a nighttime usage rate is low can be considered.

  In this way, when it is possible to grasp that the communication environment varies depending on the time zone, season, day of the week, etc., from the measurement by the administrator or from the communication quality information obtained from the information terminal, the information is transmitted to the communication path. You may reflect in the calculating part 93. FIG. In addition, the information collection / setting device 21 and the communication route holding unit in each information terminal may hold a plurality of communication routes and switch the communication route according to the time zone, season, day of the week, or the like.

  As described above, in the present embodiment, when another system using the same frequency exists in the network, the operation status of the other system input from the outside or the result obtained by measurement is obtained as a communication path. It was decided to reflect on. Thereby, it is possible to construct a more stable communication path as compared with the fourth embodiment described above.

Embodiment 8 FIG.
First, before explaining the operation of local route repair according to the present embodiment, the operation of conventional local route repair will be described.

  In an application for collecting sensor values, a path from each node to the gateway is configured on a tree. In a tree topology, all nodes maintain a route to the gateway. Therefore, if a relay node fails to transfer a packet to the gateway, a route called a local repair is used to efficiently route the packet. It is possible to search again. In local route restoration, by sending a RREQ (Route Request) message with a limited number of transfer hops (for example, the number of transfer hops = 1), the route is inquired to an adjacent node, and the route is searched again (Non-Patent Document 4). reference).

  FIG. 19 is a diagram for explaining a conventional local path repair operation. In FIG. 19, reference numerals 201 to 206 denote nodes, 301 denotes a gateway (Gate Way), a solid line indicates a transfer route registered in the route table, and a dotted line indicates that the wireless transmission is possible but the route table Indicates a route that is not registered. For example, when a link error occurs in the node 204 (steps S1, S2, and S3), the node 204 broadcasts an RREQ message with a limited number of transfer hops (for example, the number of transfer hops = 1), thereby adjacent nodes. Ask for route. The node 206 that knows the route to the destination returns a RREP message (step S4). The node 204 that has received the RREP message transfers the data to the node 206 (step S5), and the data reaches the gateway 301 via the node 206 (step S6).

  FIG. 20 is a diagram for explaining the operation in the case where the local path repair fails. In FIG. 20, when the node 203 detects a link error (steps S11, S12, and S13), the node 203 performs a local route search by an adjacency inquiry, but there is no adjacent node having a route to the gateway 301, and the local route Repair fails (step S14). In this case, the node 203 transmits a RERR message (step S15), and deletes the route from the route table to the gateway 301. Then, the node 202 that has received the RERR message deletes the route to the gateway 301 from the route table, and further transmits the RERR message to the node 201 (step S16).

  At this time, a node adjacent to the node 201 does not have a route to the gateway 301, and a route cannot be found with an RREQ message in which the number of transfer hops is limited. In order to find a route, a wide-range route search is required by an RREQ message that does not limit the number of transfer hops, and the amount of control traffic increases.

  Next, the operation of local path repair according to the present embodiment will be described. FIG. 21 is a diagram for explaining the operation of local path restoration according to the present embodiment. FIG. 22 is a flowchart showing processing corresponding to FIG.

  In FIG. 21 and FIG. 22, when the node 203 detects a link error (steps S21, S22, S23), the node 203 searches for a local route by an adjacent inquiry, but there is no response, and the local route repair fails (step S24). In this case, the node 203 transmits a RERR (route error) message with a local route repair flag (LR: Local Repair) (step S25).

  When the node 202 receives the RERR message with the local route repair flag, the node 202 searches for a route to the gateway 301 by performing a local route search by an adjacent inquiry (step S26). Also, a RERR message is transmitted to inform the originating node that the data transfer has failed (step S27). However, at this time, a route non-delete flag (N = 1: No delete) is attached to the RERR message.

  Then, the node 201 that has received the RERR message with the route non-deletion flag does not delete the route to the gateway 301. When retransmitting the data, the node 201 holds the route to the gateway 301 and therefore transmits the data to the node 202. Since the node 202 has a route to the gateway 301 by local path repair, data can be transferred to the node 204.

Embodiment 9 FIG.
FIG. 23 is a diagram for explaining the operation of local path restoration according to the present embodiment. FIG. 24 is a flowchart showing processing corresponding to FIG.

  In FIG. 23 and FIG. 24, when the node 203 detects a link error (steps S21, S22, S23), the node 203 searches for a local route by an adjacent inquiry, but there is no response, and the local route repair fails (step S24). In this case, the node 203 transmits a RERR message with a local route repair flag (step S25).

  When the node 202 receives the RERR with the local route repair flag, the node 202 searches for a route to the gateway 301 by performing a local route search based on an adjacent query (step S26). Further, a RERR message (N = 0) is transmitted to notify the originating node that the data transfer has failed (step S28).

  The node 201 that has received the RERR message can retransmit the data. At this time, since the node 201 does not have a route to the gateway 301, the node 201 transmits an RREQ message with a limited number of transfer hops to perform route search. When the node 202 receives the RREQ message, since it has a route to the gateway 301, it can respond to the RREP message, and the node 201 can find the route to the gateway 301.

Embodiment 10 FIG.
FIG. 25 is a diagram for explaining the operation of local path repair according to the present embodiment. FIG. 26 is a flowchart showing processing corresponding to FIG.

  In FIG. 25 and FIG. 26, when the node 203 detects a link error (steps S21, S22, S23), it performs a local route search by an adjacent inquiry, but there is no response, and the local route repair fails (step S24). ). The node 203 transmits a RERR message with a local route repair flag (LR: Local Repair) (step S29). At this time, transfer data is added to the RERR message.

  When the node 202 receives the RERR message with the local route repair flag, the node 202 searches for a route to the gateway 301 by performing a local route search by an adjacent inquiry (step S26). Further, the node 202 transfers data to the node 204 using the found route (step S30).

  The node 204 transfers the data to the node 205, and can thereby transfer the data to the gateway 301 via the node 205 (step S31).

  As described above, the multi-hop wireless ad hoc network according to the present invention is useful for realizing an efficient sleep mode.

1-11 Terminal 12 Gateway (GW)

Claims (21)

In a multi-hop wireless ad hoc network that configures a tree-structured wireless network with a gateway as a master station,
Synchronize all the terminals in the network with the adjacent terminals in the route to the gateway, and configure a network that is entirely synchronized with the gateway,
All terminals and the gateway perform the switching operation of the start and sleep in accordance with the start cycle, start phase and start period,
During the startup period, data transfer is performed in the startup section within the synchronization error range,
During the sleep period, operate the minimum part,
Resynchronization is performed according to a tree structure from the gateway in order to maintain the synchronization operation.
A multi-hop wireless ad hoc network characterized by that. When a new terminal enters, superimpose a signal necessary for the synchronization process in the peripheral terminal search signal, and simultaneously execute the peripheral terminal search and the synchronization process.
The multi-hop wireless ad hoc network according to claim 1. Use multicast signals for synchronization,
The multi-hop wireless ad hoc network according to claim 1 or 2. Perform time synchronization processing using wireless MAC layer signals,
The multi-hop wireless ad hoc network according to claim 1, 2, or 3. In resynchronization processing,
According to the tree structure with the gateway as the root, the terminal at the next stage of the route to the gateway is synchronized as a timing master, and the entire network is synchronized.
The multi-hop wireless ad hoc network according to any one of claims 1 to 4. When using an on-demand ad hoc network method,
When the terminal starts up, the route construction operation is performed, the route is maintained if communication is possible, and the route construction operation is performed when communication is impossible.
Based on the route information to the gateway of the adjacent terminal and the received power information at the time of route search, the optimum adjacent node to the gateway is determined without performing flooding,
Downlink signals are scheduled at the gateway that operates as the master station,
By controlling the uplink signal transmission time of the terminal based on the timing signal notification from the gateway, the uplink signal reduces radio signal collisions in the ad hoc network, suppresses unnecessary traffic increase,
Extend sleep time by reducing ad hoc network control signals,
The multi-hop wireless ad hoc network according to claim 1. It has a low power consumption mode that sleeps intermittently and a continuous mode that doesn't sleep,
During operation in the intermittent mode, the transmission signal is transmitted with the continuous mode setting information, and the relay station and the destination station that detected the signal shift to the continuous mode.
The multi-hop wireless ad hoc network according to claim 1. A communication system comprising an information collection / setting device and two or more information terminals,
The information collecting / setting device includes:
A communication path calculation unit for determining communication connection relations of information terminals,
With
The information terminal relays communication according to a route determined by the communication route calculation unit.
A communication system characterized by the above. The communication path calculation unit determines a relay node for aggregating path information held by the information terminal based on communication quality.
The communication system according to claim 8. The communication path calculation unit uses information terminal position information for the initial communication connection relationship.
The communication system according to claim 8 or 9, wherein The communication path calculation unit uses the connection information collected from the information terminal for the initial communication connection relationship.
The communication system according to claim 8. The communication path calculation unit reflects the communication quality obtained from the information terminal,
The communication system according to claim 8. The communication path calculation unit reflects the communication quality between information terminals according to the date and time,
The communication system according to claim 8. A communication system comprising an information collection / setting device and two or more information terminals,
Before performing information communication between the information collection / setting device and each information terminal, the information collection / setting device determines a relay terminal from each information terminal and establishes a connection path;
A communication system characterized by the above. Configure a communication system with two or more information terminals,
A communication path calculation unit for determining a communication connection relationship of the information terminal;
An information collecting / setting device comprising: The information terminal in a communication system comprising an information collection / setting device and two or more information terminals,
Relay communication according to the route determined by the information collection / setting device;
An information terminal characterized by that. A route search method in a multi-hop wireless ad hoc network constituting a tree-structured network with a gateway as a root,
Provide a flag to instruct local route repair in the route error message that indicates that a failure has occurred in the data transfer process.
A route search method characterized by that. When a failure occurs in data transfer, it is determined that the data transfer direction is the gateway direction, and if the transfer is in the gateway direction, local route repair is performed.
The route search method according to claim 17, wherein: If local route repair is not successful, send a route error message with a flag indicating local route repair.
19. The route search method according to claim 18, wherein when a route error message to which a flag for instructing local route repair is added is received, local route repair is performed. When local route repair is not successful, a route error message with a flag for instructing local route repair and forwarding data is sent.
The route search method according to claim 18, wherein: If local route repair is successful, send a route error message with a flag indicating non-deletion of route,
The route search method according to claim 17 or 18, characterized in that:

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