JP2017152920A - Communication terminal, multi-hop communication system, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication terminal, a multi-hop communication system, and a program that are capable of suppressing disconnection of a communication link due to an increase in communication traffic.SOLUTION: A slave unit 2 includes a communication unit 2a, a routing unit 2c, and a communication controller 2d. The communication unit 2a exchanges signals with a master unit 1 and an adjacent terminal as the slave unit 2 which can directly communicate with each other. In response to the communication unit 2a receiving a hello packet for determining a communication route from adjacent terminals, the routing unit 2c establishes a communication route passing through this connection terminal by using one of the adjacent terminals as a connection terminal. When the communication unit 2a does not receive the routing packet from the connection terminal during a predetermined standby time T1, the communication controller 2d lowers a transmission rate at which the communication unit 2a transmits a signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication terminal, a multi-hop communication system, and a program.

  Conventionally, when communicating between communication terminals, when communication cannot be performed directly between communication terminals that attempt to transmit information, multi-hop communication that enables communication by using another communication terminal for communication relay It has been known. As a routing protocol for controlling the communication route of multi-hop communication, there is a proactive protocol that periodically exchanges routing packets with other communication terminals and maintains the latest communication route.

  If the communication terminal does not receive the routing packet within a predetermined time, the communication terminal disconnects the communication link established with the adjacent terminal and starts construction of a new communication route (for example, Patent Document 1, 2).

  As described above, in a conventional multi-hop communication system, each communication terminal establishes a communication link with any one of adjacent terminals by exchanging routing packets between the communication terminals.

JP2012-253686A JP 2012-169729 A

  However, when communication traffic in the system increases and packet collision increases, there may be a communication terminal that cannot receive a routing packet even though data packet communication is normally performed. That is, there is a communication terminal that cannot receive a routing packet from an adjacent terminal that establishes a communication link with its own terminal even though data packet communication is normally performed. In this case, a communication terminal that cannot receive a routing packet from an adjacent terminal disconnects the communication link established with the adjacent terminal in spite of normal data packet communication, and performs a new communication. Start building the route. That is, the communication link is disconnected due to an increase in communication traffic, and the communication route is reconstructed.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a communication terminal, a multi-hop communication system, and a program capable of suppressing disconnection of a communication link due to an increase in communication traffic. There is.

  A communication terminal according to one aspect of the present invention constructs a communication route including one or more communication links between a plurality of slave units and the master unit, and the master unit and the plurality of slave units Is a communication terminal used as the slave unit of a multi-hop communication system that performs multi-hop communication with each other, and communicates signals with an adjacent terminal that is a master unit or a slave unit capable of direct communication And a routing unit that constructs a communication route that passes through this connection terminal by using any one of the adjacent terminals as a connection terminal when the communication unit receives a routing packet for determining the communication route from the adjacent terminal. If the communication unit does not receive a routing packet from the connection terminal during a predetermined standby time, the communication unit reduces the transmission rate at which the communication unit transmits a signal. And a department.

  In the multi-hop communication system according to one aspect of the present invention, each of a plurality of slave units establishes a communication route including one or more communication links with the master unit, and the master unit and the plurality of slave units Each of the slave units is a multi-hop communication system that performs multi-hop communication with each of the slave units, and each of the plurality of slave units exchanges signals with an adjacent terminal that is a master unit or a slave unit capable of direct communication. The communication unit receives the routing packet for determining the communication route and the communication unit from the adjacent terminal, and establishes a communication route passing through the connection terminal using any one of the adjacent terminals as the connection terminal. When the communication unit does not receive a routing packet from the routing unit and the connection terminal during a predetermined waiting time, the transmission rate at which the communication unit transmits a signal is reduced. A communication control unit and that.

  The program according to one aspect of the present invention is such that each of a plurality of child devices constructs a communication route including one or more communication links between the parent device and the parent device and the plurality of child devices. An adjacent terminal that is a program executed by a computer included in the slave unit of the multi-hop communication system that performs multi-hop communication with each other, and is a master unit or slave unit that can directly communicate to determine the communication route When the communication unit receives the routing packet transmitted from the network, the function of the routing unit that establishes a communication route passing through this connection terminal with any one of the adjacent terminals as the connection terminal, and the routing packet from the connection terminal Of the communication control unit that reduces the transmission rate at which the communication unit transmits a signal. To achieve the ability to the computer.

  As described above, according to the present invention, there is an effect that it is possible to suppress disconnection of a communication link due to an increase in communication traffic.

It is a block diagram which shows the structure of the multihop communication system which concerns on embodiment of this invention. It is a communication sequence which shows the outline of the routing process using a hello packet in a multihop communication system same as the above. It is a communication sequence which shows an example of the routing process in a multihop communication system same as the above. It is explanatory drawing which shows the construction example of the communication route in a multihop communication system same as the above. It is a flowchart which shows operation | movement of the subunit | mobile_unit in a multihop communication system same as the above. It is a flowchart which shows operation | movement of the subunit | mobile_unit of the modification 1 in a multihop communication system same as the above. It is a block diagram which shows the structure of the subunit | mobile_unit of the modification 2 in a multihop communication system same as the above.

  The present invention relates to a communication terminal, a multi-hop communication system, and a program. More specifically, the present invention relates to a communication terminal that performs proactive multi-hop communication, a multi-hop communication system, and a program used for the communication terminal.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
As shown in FIG. 1, the multi-hop communication system 10 according to the present embodiment includes a single parent device 1 and a plurality of child devices 2. FIG. 1 illustrates a dwelling unit of an apartment house as a consumer facility. However, the customer facility may be a detached house, an office, a store, a tenant of a building, etc., and the form is not limited.

  Each of the master unit 1 and the slave unit 2 is a communication terminal that performs power line carrier communication or wireless communication. In addition, when individually identifying the slave units 2, the slave units 21, 22,. . . , 2N.

  Each cordless handset 2 is provided in one corresponding customer facility. Each slave unit 2 has a function of transmitting predetermined data related to a customer facility provided with the slave unit 2 to one master unit 1. The master unit 1 acquires predetermined data regarding each of the customer facilities from the plurality of slave units 2, and uses the acquired predetermined data to a higher-level management device using an optical fiber line or a wide-area communication network such as the Internet. It has a function to transmit. For example, the remote meter reading system can be configured by the master device 1 acquiring meter reading data such as power usage, gas usage, and water usage at each customer facility from the slave device 2. In addition, each of the remote monitoring system and the customer facility in which the parent device 1 monitors the state of each device in the customer facility by transmitting and receiving predetermined information set in advance to and from the child device 2 It is also possible to configure a remote control system or the like that controls the state of the device.

  In the multi-hop communication system 10, the master unit 1 and the slave unit 2 transmit and receive signals to each other by proactive multi-hop communication. That is, in the multi-hop communication system 10, communication is performed directly or indirectly between the parent device 1 and the child device 2, and the child device 2 that cannot directly communicate with the parent device 1 is connected to another child at a communicable distance. The machine 2 can communicate with the parent machine 1 by sequentially relaying the communication packets. In addition, the subunit | mobile_unit 2 which relays the communication packet which the other communication terminal (parent | base_unit 1, the subunit | mobile_unit 2) transmitted is called a relay terminal.

  Base unit 1 includes communication unit 1a, storage unit 1b, routing unit 1c, and communication control unit 1d.

  The communication unit 1a functions as a communication interface that exchanges signals with other communication terminals (slave devices 2). The communication method used by the communication unit 1a is power line carrier communication or wireless communication, and the communication method is not limited to a specific method.

  The storage unit 1b is preferably composed of a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read-Only Memory) or a flash memory. And the memory | storage part 1b has memorize | stored the communication route information showing the communication route constructed | assembled between the subunit | mobile_units 2. Further, the storage unit 1b stores programs such as a control program for operating the parent device 1, information necessary for executing each program, terminal information of the parent device 1, and the like. The terminal information is, for example, address information of communication terminals, information on communication quality, and the like.

  The routing unit 1c has a function of performing a routing process defined by a communication protocol for proactive multi-hop communication by communicating with the slave unit 2 via the communication unit 1a.

  The communication control unit 1d controls multi-hop communication using the communication route constructed by the routing unit 1c.

  The subunit | mobile_unit 2 is provided with the communication part 2a, the memory | storage part 2b, the routing part 2c, the communication control part 2d, and the packet monitoring part 2e.

  The communication unit 2a functions as a communication interface that exchanges signals with other communication terminals (base unit 1 and other handset 2). The communication method used by the communication unit 2a is power line carrier communication or wireless communication, and the communication method is not limited to a specific method.

  Storage unit 2b is preferably composed of a rewritable nonvolatile memory such as an EEPROM or a flash memory. The storage unit 2b stores communication route information representing a communication route established with the base unit 1. Further, the storage unit 2b stores programs such as a control program for operating the slave unit 2, information necessary for executing each program, terminal information of the slave unit 2, and the like.

  The routing unit 2c has a function of performing a routing process defined by a communication protocol for proactive multi-hop communication by communicating with the parent device 1 or another child device 2 via the communication unit 2a. Prepare.

  The communication control unit 2d controls multihop communication using the communication route constructed by the routing unit 2c.

  The packet monitoring unit 2e monitors the reception status of a later-described hello packet (Hello Packet) transmitted from the connection terminal. In the present embodiment, the parent device 1 and the other child device 2 that can directly communicate with each other (can be communicated in one hop) are adjacent terminals, and among the adjacent terminals, the child device 2 establishes a communication link. The adjacent terminal is the connection terminal. That is, the connection terminal is a communication terminal of the first hop in the communication route from the child device 2 to the parent device 1. Specifically, as shown in FIG. 2, the packet monitoring unit 2e of the slave unit 2 receives the hello packet 100 from the connection terminal until a predetermined waiting time T1 elapses after receiving the hello packet 100 from the connection terminal. Whether the communication unit 2a receives 100 again is monitored. Further, the transmission cycle T2 of the hello packet 100 is determined in advance, and the standby time T1 is set to, for example, three times the time length of the transmission cycle T2. The standby time T1 only needs to be longer than the transmission cycle T2, and the specific time length is not limited.

  And the routing part 1c of the main | base station 1 broadcasts the hello packet 100 regularly. The hello packet 100 is a packet for notifying the existence of the own device, and has a function as a routing packet used for establishing and maintaining a communication route between communication terminals. The hello packet 100 transmitted by the parent device 1 is added with terminal information (for example, address information, information on communication quality, etc.) of the parent device 1 that is the transmission source. In addition, the hello packet 100 transmitted by the parent device 1 may be further added with terminal information of the child device 2 with which the parent device 1 as the transmission source can directly communicate.

  And the routing part 2c of the subunit | mobile_unit 2 also broadcasts the hello packet 100 regularly. The hello packet 100 transmitted by the child device 2 is added with terminal information (for example, address information, information on communication quality, etc.) of adjacent terminals (the child device 2, the parent device 1) with which the own device can directly communicate. . Further, the hello packet 100 transmitted from the child device 2 that has established a communication route with the parent device 1 represents the communication route information indicating the communication route to the parent device 1 and the communication quality of this communication route. Route quality information is further added. Moreover, only the terminal information of the connection terminal (master device 1 or slave device 2) of the slave device 2 that is the transmission source may be added to the hello packet 100 transmitted by the slave device 2.

  In FIG. 3, the routing unit 2 c of the child device 21 can construct a one-hop communication route with the parent device 1 by receiving the hello packet 100 broadcast by the parent device 1.

  The routing unit 2c of the child device 22 receives the hello packet 100 broadcasted by the child device 21 after the child device 21 establishes the communication route, and thereby receives two hops with the parent device 1 via the child device 21. Communication routes can be established.

  The routing unit 2c of the child device 23 receives the hello packet 100 broadcasted by the child device 22 after the child device 22 has established the communication route, so that it can communicate with the parent device 1 via the child devices 22 and 21. A 3-hop communication route can be constructed.

  And after each routing part 2c of the subunit | mobile_unit 21,22,23 establishes a communication route between the main | base stations 1, each communication control part 2d of the subunit | mobile_unit 21,22,23 is the above-mentioned communication route. Multi-hop communication using can be performed with the base unit 1 (see FIG. 4). In addition, since the construction | assembly process of the communication route in the subunit | mobile_unit 2 after receiving the hello packet 100 is known, detailed description is abbreviate | omitted.

  Further, in FIG. 4, the slave unit 24 constructs a one-hop communication route with the master unit 1. In addition, the slave unit 25 constructs a two-hop communication route with the master unit 1 via the slave unit 24. In addition, the slave unit 26 constructs a two-hop communication route with the master unit 1 via the slave units 25 and 24. Furthermore, the slave unit 27 constructs a one-hop communication route with the master unit 1. Further, the slave unit 28 constructs a two-hop communication route with the master unit 1 via the slave unit 27.

  In FIG. 4, two communication terminals connected by a solid line or a broken line are adjacent to each other. Further, the solid line between the communication terminals indicates a communication link constituting the current communication route. Also, the numbers in parentheses attached to the communication links between the communication terminals in FIG. 4 indicate the communication quality in the communication link between the communication terminals. The smaller the number, the higher (good) the communication quality.

  As described above, the slave unit 2 can construct a communication route with the best communication quality based on the communication route information and route quality information added to the received hello packet 100. And the routing part 2c of the subunit | mobile_unit 2 broadcasts the hello packet 100 regularly, even after building a communication route. The routing unit 2c of the handset 2 that has already established the communication route can maintain the communication link with the connection terminal by receiving the hello packet 100 transmitted from the connection terminal. That is, the routing unit 2c of the handset 2 that has already established a communication route can maintain the current communication route by receiving the hello packet 100 transmitted from the connection terminal.

  However, congestion may occur due to an increase in communication traffic, and a state in which the slave unit 2 cannot receive the hello packet 100 broadcast from the connection terminal may occur due to a collision between packets. The reception failure state of the hello packet 100 is caused by an increase in communication traffic. If the communication traffic decreases, the reception probability of the hello packet 100 is improved. Therefore, the slave unit 2 executes the process shown in the flowchart of FIG.

  First, the packet monitoring unit 2e of the slave unit 2 is in a waiting state for receiving the hello packet 100 (S1).

  The packet monitoring unit 2e of the slave unit 2 has a timekeeping function, and the communication unit 2a is connected from the connection terminal until the waiting time T1 elapses after the communication unit 2a receives the hello packet 100 from the connection terminal. It is monitored whether or not the hello packet 100 is received (S2).

  If the communication unit 2a receives the hello packet 100 within the waiting time T1, the packet monitoring unit 2e resets the timekeeping value and again enters a reception waiting state (S3). At this time, the routing unit 2c maintains a communication link with the current connection terminal.

  When the communication unit 2a does not receive the hello packet 100 within the waiting time T1, the communication control unit 2d increments a counter that measures the number of times the hello packet 100 cannot be received (S4). Then, the communication control unit 2d compares the number of reception failures with a predetermined M times (S5).

  If the number of unreceivable times is less than the predetermined M times, the communication control unit 2d reduces the transmission rate at which the communication unit 2a transmits packets (S6). After the transmission rate decreases, the packet monitoring unit 2e enters a state of waiting for the hello packet 100 (S1).

  If the number of reception failures is M or more, the communication control unit 2d resets the number of reception failures (S7). Next, the communication control unit 2d further reduces the transmission rate (S8). Then, the communication control unit 2d disconnects the communication link with the current connection terminal and reconstructs the communication route (S9). Thereafter, the packet monitoring unit 2e enters a state of waiting for receiving the hello packet 100 (S1). Note that in step S8 described above, the communication control unit 2d may initialize the transmission rate by increasing the transmission rate to the initial value (maximum value).

  Thereafter, the slave unit 2 repeats the above-described operation.

  As an example, the operation of the slave unit 22 will be described with reference to FIG.

  When the base unit 1 transmits a data packet with the slave unit 23 as a destination, the slave units 21 and 22 serve as relay terminals to relay and transmit the data packet. At this time, the master unit 1 and the slave units 21 and 22 are transmitting data packets at a transmission rate of 10 Mbps. Accordingly, communication traffic around the child device 22 increases, and the child device 22 may not be able to receive the hello packet 100 from neighboring neighboring terminals (child devices 21, 23, 25, 26).

  Then, it is assumed that the slave unit 22 cannot receive the hello packet 100 from the slave unit 21 that is the connection terminal within the waiting time T1 (unreceivable count = 1). In this case, the amount of decrease in the transmission rate is set to a constant value, for example, 2 Mbps, and the slave unit 22 reduces the transmission rate from 10 Mbps to 8 Mbps. That is, since the slave unit 22 relays and transmits the data packet at a transmission rate of 8 Mbps even when the master unit 1 transmits a data packet to the slave unit 23, communication traffic around the slave unit 22 can be reduced. Therefore, the probability that the slave unit 22 can receive the hello packet 100 from the slave unit 21 that is the connection terminal is improved due to the decrease in communication traffic.

  Even when the transmission rate is reduced to 8 Mbps, the slave unit 22 cannot receive the hello packet 100 from the slave unit 21 as the connection terminal within the waiting time T1 (the number of times reception is impossible = 2), and the transmission rate is set to 8 Mbps. To 6 Mbps. Therefore, since the communication traffic further decreases, the probability that the handset 22 can receive the hello packet 100 from the handset 21 that is the connection terminal is further improved.

  Here, if M = 3 times, the slave unit 22 does not receive the hello packet 100 from the slave unit 21 as the connection terminal within the waiting time T1 even when the transmission rate is reduced to 6 Mbps (the number of times reception is impossible). = 3 times), reset the number of reception impossible to 0 times. Then, the slave unit 22 reconstructs the communication route by reducing the transmission rate from 6 Mbps to 4 Mbps. Thereafter, the slave unit 22 can reduce the transmission rate stepwise by repeating the above-described operation.

  Therefore, the subunit | mobile_unit 22 becomes easy to maintain the communication link between the subunit | mobile_units 21 which are the present connection terminals, and can suppress the cutting | disconnection of the communication link by the increase in communication traffic. Moreover, the subunit | mobile_unit 22 can suppress the fall of the communication efficiency by reducing a transmission rate too much by reducing a transmission rate in steps.

  In step S2, if the communication unit 2a continues to receive the hello packet 100 from the connected terminal until the waiting time T1 elapses, if this reception state continues for a certain period, the communication control unit 2d Increase the transmission rate to the initial value. Alternatively, the communication control unit 2d may return the transmission rate to the initial value by gradually increasing the transmission rate as the duration of the reception state becomes longer.

  Next, Modification 1 of the present embodiment will be described.

  The subunit | mobile_unit 2 has stored the terminal information (for example, address information, information regarding communication quality, etc.) of an adjacent terminal in the memory | storage part 2b. The communication control unit 2d can specify the number of adjacent terminals with reference to the storage unit 2b. Further, the communication control unit 2d can specify the communication terminal (master unit 1, slave unit 2) that is the transmission source of the hello packet 100 from the hello packet 100 received by the communication unit 2a. And the communication control part 2d determines whether the hello packet 100 was received from each of an adjacent terminal for every unit period (for example, every minute). That is, the communication control unit 2d determines that an adjacent terminal that is a transmission source of the hello packet 100 that cannot be received by the communication unit 2a in a unit period (a period from the previous determination process to the current determination process) is an unreceived terminal in this unit period. Can be recognized as.

  Then, the communication control unit 2d obtains the ratio of the number of unreceived terminals to the total number of adjacent terminals [number of unreceived terminals / total number of adjacent terminals] for each unit period. Further, the communication control unit 2d obtains a moving average of [number of unreceived terminals / total number of adjacent terminals] as a ratio of unreceived terminals.

  Table 1 shows unit periods Ta1, Ta2, Ta3,. . . [Number of unreceived terminals / total number of adjacent terminals] (percentage of unreceived terminals per unit period) for each of Y1, Y2, Y3,. . . Is shown. In Table 1, “O” indicates that the communication unit 2a can receive the hello packet 100 in the unit period, and “X” indicates that the communication unit 2a cannot receive the hello packet 100 in the unit period. Then, the communication control unit 2d obtains the average (moving average) of the latest N [number of unreceived terminals / total number of adjacent terminals] as the ratio of unreceived terminals. For example, when N = 3, the ratio of unreceived terminals in the unit period Ta5 is [(Y5 + Y4 + Y3) / 3].

  And it is preferable that the communication control part 2d reduces a transmission rate only when the ratio of unreceived terminals is more than a threshold value. That is, as shown in the flowchart of FIG. 6, the communication control unit 2d determines whether or not the ratio of unreceived terminals is equal to or greater than the threshold before reducing the transmission rate (the first stage of step S6) (S11). The communication control unit 2d proceeds to step S6 and reduces the transmission rate only when the unreceived terminal ratio is equal to or greater than the threshold value. When the unreceived terminal ratio is less than the threshold value, the communication control unit 2d proceeds to steps S7 to S8 to reconstruct the communication route without reducing the transmission rate. In Modification 1 (see FIG. 6), the transmission rate lowering process in step S9 (see FIG. 5) is deleted, and the transmission rate is not lowered when the ratio of unreceived terminals is less than the threshold.

  Here, if the ratio of unreceived terminals is high, it is considered that the handset 2 is difficult to receive the hello packet 100 because the communication traffic is high. Further, if the ratio of unreceived terminals is low, it is considered that the handset 2 can easily receive the hello packet 100 because the communication traffic is low.

  Therefore, when the unreceived terminal ratio is equal to or greater than the threshold value, it is considered difficult to receive the hello packet 100 of the connected terminal because the communication traffic is high, so the handset 2 reduces the communication rate by reducing the transmission rate. Reduce. As a result, the handset 2 has a higher probability of receiving the hello packet 100 transmitted by the connecting terminal within the waiting time T1.

  In addition, when the ratio of unreceived terminals is less than the threshold value, communication with the connected terminal may be impossible due to background noise increase due to removal of the connected terminal, operation stop of the connected terminal, installation of electrical equipment, etc. Conceivable. Therefore, the slave unit 2 quickly disconnects the communication link without unnecessarily prolonging the incommunicable period when communication with the connection terminal becomes impossible by not executing the transmission rate reduction process. Can be done.

  Moreover, in the above-described modification 1, the communication control unit 2d determines that the communication quality of the received hello packet 100 is less than or equal to a predetermined level among the adjacent terminals that are the transmission source of the hello packet 100 received by the communication unit 2a in the unit period. Preferably, adjacent terminals are not included in the total number of adjacent terminals. That is, the communication control unit 2d uses only the adjacent terminals in which the communication quality of the received hello packet 100 exceeds a predetermined level in the formula [number of unreceived terminals / total number of adjacent terminals] used when calculating the ratio of unreceived terminals. Count as the total number of adjacent terminals. As the communication quality, for example, a received signal strength (RSSI), an S / N ratio, or the like is used.

  In this case, the communication control unit 2d can obtain the total number of adjacent terminals according to the actual communication quality by counting only the adjacent terminals with good communication quality.

  Next, a second modification of the present embodiment will be described.

  The subunit | mobile_unit 2 of the modification 2 is further provided with the traffic calculation part 2f, as shown in FIG. The traffic calculation unit 2f has a function of obtaining communication traffic around the own device based on the signal amount transmitted and received by the communication unit 2a. Specifically, the traffic calculation unit 2f periodically obtains the occupation rate of the transmission path per unit time by the packet received by the communication unit 2a and the packet transmitted by the communication unit 2a as communication traffic. The unit time is set to an arbitrary time length such as 1 minute or 1 hour.

  Alternatively, the traffic calculation unit 2f uses the reception intensity in the communication unit 2a to calculate the occupation rate of the transmission path per unit time instead of obtaining the occupation rate of the transmission path per unit time by the packet received by the communication unit 2a. You may ask for it. In this case, the traffic calculation unit 2f can obtain the occupation rate of the transmission path in consideration of the packet and noise of other communication systems by using the reception intensity.

  Furthermore, the traffic calculation unit 2f may obtain the occupation rate of the transmission path per unit time by using all of the packet received by the communication unit 2a, the reception intensity at the communication unit 2a, and the packet transmitted by the communication unit 2a.

  Here, the higher the communication traffic, the higher the probability that the hello packet 100 cannot be received within the waiting time T1. On the other hand, if the communication traffic is low, the reason why the hello packet 100 cannot be received within the waiting time T1 is that the connection terminal is disconnected, the operation of the connection terminal is stopped, or the background noise increases due to the installation of electrical equipment. There is a high possibility that communication is impossible.

  Therefore, it is preferable that the communication control unit 2d determines the amount of decrease in the transmission rate based on the communication traffic (traffic calculation value) obtained by the traffic calculation unit 2f. Specifically, the communication control unit 2d determines the amount of decrease in the transmission rate based on the difference (traffic difference amount) between the allowable traffic and the communication traffic obtained by the traffic calculation unit 2f. The allowable traffic is an upper limit value determined in advance for communication traffic, and is represented by an upper limit value (for example, 40%) of the packet occupation rate of the transmission path.

  When the traffic calculation value exceeds the allowable traffic, the communication control unit 2d determines the amount of decrease in the transmission rate so that the traffic calculation value matches the allowable traffic in step S6 of FIGS. At this time, the communication control unit 2d can estimate the amount of decrease in the transmission rate at which the traffic calculation value matches the allowable traffic based on the traffic difference amount.

  Therefore, the subunit | mobile_unit 2 can control in a short time to the transmission rate which can fully suppress communication traffic.

  Further, when the traffic calculation value is lower than the allowable traffic, the communication control unit 2d sets the amount of decrease in the transmission rate to a predetermined constant value (for example, 2 Mbps) in step S6 in FIGS. It should be noted that this fixed amount of decrease only needs to be set to an arbitrary value according to the specifications of the parent device 1 and the child device 2, and specific numerical values are not limited.

  The traffic calculation unit 2f may use the total number of packets, which is the total number of packets received by the communication unit 2a and the number of packets transmitted by the communication unit 2a, as communication traffic. In this case, the allowable traffic is represented by the upper limit value of the total number of packets.

  The traffic calculation unit 2f preferably uses all packets received by the communication unit 2a for calculation of communication traffic, including not only packets addressed to itself but also packets not addressed to itself. In this case, the traffic calculation unit 2f can accurately estimate the current communication traffic. Therefore, the communication control unit 2d can set the amount of decrease in the transmission rate to an appropriate value based on the current communication traffic.

  In addition, the traffic calculation unit 2f determines communication traffic by packets relayed to other communication terminals (master unit 1, slave unit 2) among the packets received by the communication unit 2a according to the number of hops of the communication route after relaying. Preferably obtained. Specifically, when it takes 5 hops to reach the base unit 1 after relaying a packet, relay processing by other five relay terminals is required. Therefore, when it takes 5 hops to reach the base unit 1 after relaying the packet, the traffic calculation unit 2f calculates the communication traffic by multiplying the packet occupation rate or the number of packets of the transmission path by this packet by 5 times. That is, the traffic calculation unit 2f increases the calculated value of communication traffic by this packet in proportion to the number of relay terminals on the communication route where the packet transmitted by the communication unit 2a reaches the base unit 1. As a result, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Therefore, the traffic calculation unit 2 f can estimate communication traffic over a wider range in the multi-hop communication system 10. Therefore, the communication control unit 2d can set the amount of decrease in the transmission rate to a value based on communication traffic over a wider range.

  Moreover, it is preferable that the traffic calculation part 2f increases the calculated value of communication traffic, so that there are many adjacent terminals of an own machine. Specifically, when the number of adjacent terminals is four (one of which is a connection terminal), the communication traffic is obtained by multiplying the packet occupation rate or the number of packets of the transmission path by the packet transmitted by the communication unit 2a by four times. . That is, the traffic calculation unit 2f increases the calculated value of communication traffic by this packet in proportion to the number of adjacent terminals. As a result, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Therefore, the traffic calculation unit 2 f can estimate communication traffic over a wider range in the multi-hop communication system 10. As a result, the communication control unit 2d can set the amount of decrease in the transmission rate to a value based on communication traffic over a wider range.

  In addition, the traffic calculation unit 2f increases as the number of the parent device 1 and the child device 2 (that is, the neighboring terminal of the neighboring terminal and called the one-hop neighboring terminal) that the neighboring terminal of the own device can directly communicate with increases. It is preferable to increase the calculated value of communication traffic. When viewed from the handset 2, the 1-hop neighboring terminal may become a hidden terminal. A communication terminal having a relationship in which signals transmitted to each other cannot be directly received is referred to as a hidden terminal. If each of the communication terminals in the hidden terminal relationship transmits a packet, packet collision is likely to occur, and there are adverse effects such as frequent retransmissions and an increase in transmission delay.

  Therefore, the traffic calculation unit 2f increases the calculated value of communication traffic in proportion to the number of 1-hop neighboring terminals that may become hidden terminals. As a result, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Moreover, it is preferable that the communication control part 2d transmits the information (decrease amount judgment information) for making the other subunit | mobile_unit 2 determine the fall amount of a transmission rate from the communication part 2a.

  Specifically, when transmitting the hello packet 100, the communication control unit 2d of the child device 2 adds the communication traffic data obtained by the traffic calculation unit 2f of the own device to the hello packet 100. And the communication control part 2d of the subunit | mobile_unit 2 can recognize the communication traffic of an adjacent terminal by receiving the hello packet 100 of the other subunit | mobile_unit 2. FIG. And the communication control part 2d selects the highest communication traffic among the communication traffic of an own machine and the communication traffic of an adjacent terminal. The communication control unit 2d determines the amount of decrease in the transmission rate based on the traffic difference amount that is the difference between the selected highest communication traffic and allowable traffic.

  Therefore, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Alternatively, the communication control unit 2 d of the slave unit 2 adds data of a decrease in the transmission rate of the own unit to the hello packet 100 when transmitting the hello packet 100. And the communication control part 2d of the subunit | mobile_unit 2 can recognize the fall amount of the transmission rate in an adjacent terminal by receiving the hello packet 100 of the other subunit | mobile_unit 2. FIG. Then, the communication control unit 2d selects the lower transmission rate decrease amount among the current transmission rate decrease amount of the own device and the adjacent terminal transmission rate decrease amount. The communication control unit 2d controls the transmission rate so that the selected transmission rate is reduced.

  Accordingly, the communication control unit 2d can control the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Moreover, it is preferable that the communication control part 2d transmits the signal (instruction signal) which instruct | indicates whether the transmission rate is reduced with respect to the other subunit | mobile_unit 2 from the communication part 2a.

  Specifically, it is assumed that the communication control unit 2d of the handset 2 has the communication traffic obtained by the traffic calculation unit 2f exceeding the allowable traffic after the transmission rate is lowered in the above-described step S6. In this case, the communication control unit 2d transmits a decrease instruction signal that instructs the other slave units 2 to decrease the transmission rate (broadcast or unicast). In the handset 2 that has received the decrease instruction signal, the communication control unit 2d decreases the transmission rate of the communication unit 2a by a certain value. Alternatively, the communication control unit 2d may reduce the transmission rate of the communication unit 2a to a value instructed by the received decrease instruction signal.

  Therefore, the subunit | mobile_unit 2 can suppress the communication traffic of the other subunit | mobile_unit 2 (adjacent terminal), when the communication traffic calculated | required by the traffic calculation part 2f is high. As a result, the subunit | mobile_unit 2 can suppress the communication traffic by the adjacent terminal which self-unit does not participate in transmission and relay.

  The above-described slave unit 2 constructs a communication route including one or more communication links between the plurality of slave units 2 and the master unit 1, and each of the master unit 1 and the plurality of slave units 2 Are communication terminals used as slave units of a multi-hop communication system that performs multi-hop communication with each other. The subunit | mobile_unit 2 is provided with the communication part 2a, the routing part 2c, and the communication control part 2d. The communication unit 2a sends and receives signals to and from an adjacent terminal that is a parent device 1 or a child device 2 capable of direct communication. The routing unit 2c receives a routing packet (hello packet 100) for determining a communication route from the adjacent terminal by the communication unit 2a, so that any one of the adjacent terminals is used as a connection terminal and the communication route passes through this connection terminal. Build up. When the communication unit 2a does not receive the routing packet from the connection terminal during the predetermined waiting time T1, the communication control unit 2d reduces the transmission rate at which the communication unit 2a transmits a signal.

  Therefore, the subunit | mobile_unit 2 becomes easy to maintain the communication link between the present connection terminals, and can suppress the cutting | disconnection of the communication link by the increase in communication traffic.

  Further, among the adjacent terminals, an adjacent terminal in which the communication unit 2a cannot receive a routing packet is set as an unreceived terminal, and the communication control unit 2d transmits a transmission if the ratio of the number of unreceived terminals to the total number of adjacent terminals is equal to or greater than a threshold. It is preferable to reduce the rate.

  In this case, when the ratio of unreceived terminals is equal to or greater than the threshold value, it is considered difficult to receive the hello packet 100 of the connected terminal due to high communication traffic. Then, the subunit | mobile_unit 2 reduces communication traffic by reducing a transmission rate. As a result, the handset 2 has a higher probability of receiving the hello packet 100 transmitted by the connecting terminal within the waiting time T1.

  If the percentage of unreceived terminals is less than the threshold, it may be impossible to communicate with the connected terminal due to removal of the connected terminal, suspension of the connected terminal operation, increased background noise due to installation of electrical equipment, etc. . Therefore, the slave unit 2 quickly disconnects the communication link without unnecessarily prolonging the incommunicable period when communication with the connection terminal becomes impossible by not executing the transmission rate reduction process. Can be done.

  Moreover, it is preferable that the communication control unit 2d counts only adjacent terminals that are transmission sources of routing packets whose communication quality at the time of reception by the communication unit 2a exceeds a predetermined level as the total number of adjacent terminals.

  In this case, the communication control unit 2d can obtain the total number of adjacent terminals according to the actual communication quality by counting only the adjacent terminals with good communication quality.

  Moreover, if the ratio of the number of unreceived terminals to the total number of adjacent terminals is equal to or greater than the threshold, the communication control unit 2d preferably reduces the transmission rate by a certain amount.

  In this case, the subunit | mobile_unit 2 can suppress the fall of the communication efficiency by reducing a transmission rate too much by reducing a transmission rate in steps.

  Moreover, it is preferable that the subunit | mobile_unit 2 is further provided with the traffic calculation part 2f which calculates | requires communication traffic based on the signal amount which the communication part 2a transmitted and received. If the ratio of the number of unreceived terminals to the total number of adjacent terminals is equal to or greater than the threshold, the communication control unit 2d transmits based on the difference between the communication traffic obtained by the traffic calculation unit 2f and the upper limit value of the communication traffic. Determine the rate drop.

  In this case, the subunit | mobile_unit 2 can control in a short time to the transmission rate which can fully suppress communication traffic.

  Moreover, it is preferable that the signal amount received by the communication unit 2a includes a signal amount transmitted through a communication route that does not pass through the terminal itself.

  In this case, the traffic calculation unit 2f can accurately estimate the current communication traffic. Therefore, the communication control unit 2d can set the amount of decrease in the transmission rate to an appropriate value based on the current communication traffic.

  Moreover, it is preferable that the traffic calculation unit 2f increases the calculated value of the communication traffic as the number of relay terminals that are the slave units 2 on the communication route where the signal transmitted by the communication unit 2a reaches the master unit 1 increases.

  In this case, the traffic calculation unit 2 f can estimate communication traffic over a wider range in the multi-hop communication system 10. Therefore, the communication control unit 2d can set the amount of decrease in the transmission rate to a value based on communication traffic over a wider range.

  Moreover, it is preferable that the traffic calculation part 2f increases the calculated value of communication traffic, so that there are many adjacent terminals.

  In this case, the traffic calculation unit 2 f can estimate communication traffic over a wider range in the multi-hop communication system 10. As a result, the communication control unit 2d can set the amount of decrease in the transmission rate to a value based on communication traffic over a wider range.

  Moreover, it is preferable that the traffic calculation unit 2f increases the calculated value of communication traffic as the number of the parent device 1 and the child device 2 with which the adjacent terminal can directly communicate is larger.

  In this case, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Moreover, it is preferable that the communication control part 2d transmits the information for making the other subunit | mobile_unit 2 determine the fall amount of a transmission rate from the communication part 2a.

  In this case, the communication control unit 2d can determine the amount of decrease in the transmission rate in consideration of a wider range of communication traffic in the multi-hop communication system 10.

  Moreover, it is preferable that the communication control part 2d transmits the signal which instruct | indicates whether the transmission rate is reduced with respect to the other subunit | mobile_unit 2 from the communication part 2a.

  In this case, when the communication traffic obtained by the traffic calculation unit 2f is high, the slave unit 2 can suppress communication traffic of other slave units 2 (adjacent terminals). As a result, the subunit | mobile_unit 2 can suppress the communication traffic by the adjacent terminal which self-unit does not participate in transmission and relay.

  In the above-described multi-hop communication system 10, each of the plurality of slave units 2 establishes a communication route including one or more communication links with the master unit 1, and the master unit 1 and the plurality of slave units 2. Of each other perform multi-hop communication with each other. Each of the plurality of slave units 2 includes a communication unit 2a, a routing unit 2c, and a communication control unit 2d. The communication unit 2a sends and receives signals to and from an adjacent terminal that is a parent device 1 or a child device 2 capable of direct communication. The routing unit 2c receives a routing packet (hello packet 100) for determining a communication route from the adjacent terminal by the communication unit 2a, so that any one of the adjacent terminals is used as a connection terminal and the communication route passes through this connection terminal. Build up. When the communication unit 2a does not receive the routing packet from the connection terminal during the predetermined waiting time T1, the communication control unit 2d reduces the transmission rate at which the communication unit 2a transmits a signal.

  Therefore, the multi-hop communication system 10 makes it easy to maintain a communication link between the child device 2 and the current connection terminal for each of the plurality of child devices 2, and suppresses disconnection of the communication link due to an increase in communication traffic. be able to.

  Moreover, the main | base station 1 is provided with the computer and each function of the above-mentioned main | base station 1 is implement | achieved when this computer runs a program. A computer mainly includes a device having a processor for executing a program, an interface device for transmitting / receiving data to / from other apparatuses, and a storage device for storing data. Prepare. A device provided with a processor may be a CPU (Central Processing Unit) or MPU (Micro Processing Unit) which is a separate body from the semiconductor memory, or a microcomputer integrally including a semiconductor memory. As a storage device, a storage device having a short access time such as a semiconductor memory and a large-capacity storage device such as a hard disk device are used in combination.

  Moreover, the subunit | mobile_unit 2 is provided with the computer, and each function of the above-mentioned subunit | mobile_unit 2 is implement | achieved when this computer runs a program. A computer mainly includes a device having a processor for executing a program, an interface device for transmitting / receiving data to / from other apparatuses, and a storage device for storing data. Prepare. The device provided with the processor may be any one of a microcomputer integrally provided with a semiconductor memory in addition to a CPU or MPU which is a separate body from the semiconductor memory. As a storage device, a storage device having a short access time such as a semiconductor memory and a large-capacity storage device such as a hard disk device are used in combination.

  As a form of providing a program for the master unit 1 and the slave unit 2, a computer-readable ROM (Read Only Memory), a form stored in advance in a recording medium such as an optical disk, and the like via a wide-area communication network including the Internet There are forms supplied to the recording medium.

The program executed by the computer included in the handset 2 of the multihop communication system 10 described above causes the computer to realize the following functions. The multi-hop communication system 10 constructs a communication route including one or more communication links between each of the plurality of slave units 2 and the master unit 1, and each of the master unit 1 and the plurality of slave units 2 Perform multi-hop communication with each other.
The communication unit 2a receives a routing packet (hello packet 100) transmitted from an adjacent terminal that is a parent device or a child device capable of direct communication in order to determine a communication route. A function of the routing unit 2c that constructs a communication route passing through this connection terminal as a connection terminal.
A function of the communication control unit 2d that reduces the transmission rate at which the communication unit 2a transmits a signal when the communication unit 2a does not receive the routing packet from the connection terminal during the predetermined waiting time T1.

  Therefore, the subunit | mobile_unit 2 becomes easy to maintain the communication link between the present connection terminals, and can suppress the cutting | disconnection of the communication link by the increase in communication traffic.

The multihop communication method described above includes the following steps. The multi-hop communication system 10 constructs a communication route including one or more communication links between each of the plurality of slave units 2 and the master unit 1, and each of the master unit 1 and the plurality of slave units 2 Perform multi-hop communication with each other.
The communication unit 2a receives a routing packet (hello packet 100) transmitted from an adjacent terminal that is a parent device or a child device capable of direct communication in order to determine a communication route. Constructing a communication route passing through the connection terminal as the connection terminal;
A step of reducing the transmission rate at which the communication unit 2a transmits a signal when the communication unit 2a does not receive the routing packet from the connection terminal during the predetermined waiting time T1.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

1 parent device 1a communication unit 1b storage unit 1c routing unit 1d communication control unit 2 (21, 22,...) Slave unit 2a communication unit 2b storage unit 2c routing unit 2d communication control unit 2e packet monitoring unit 2f traffic calculation unit 10 Multi-hop communication system

Claims (13)

A multi-route communication in which each of the plurality of slave units establishes a communication route including one or more communication links with the master unit, and the master unit and each of the plurality of slave units perform multi-hop communication with each other. A communication terminal used as the slave unit of a hop communication system,
A communication unit that sends and receives signals to and from adjacent terminals that are direct parent devices or child devices,
A routing unit that establishes a communication route that passes through this connection terminal with any one of the adjacent terminals as a connection terminal by receiving the routing packet for determining the communication route from the adjacent terminal;
A communication terminal comprising: a communication control unit that reduces a transmission rate at which the communication unit transmits a signal when the communication unit does not receive a routing packet from the connection terminal during a predetermined waiting time. Among the adjacent terminals, the adjacent terminal in which the communication unit cannot receive a routing packet as an unreceived terminal,
The communication terminal according to claim 1, wherein the communication control unit reduces the transmission rate if a ratio of the number of unreceived terminals to the total number of adjacent terminals is equal to or greater than a threshold.   The communication terminal according to claim 2, wherein the communication control unit counts only the adjacent terminals that are transmission sources of routing packets whose communication quality at the time of reception of the communication unit exceeds a predetermined level, as the total number of the adjacent terminals.   4. The communication terminal according to claim 2, wherein the communication control unit reduces the transmission rate by a certain amount if the ratio of the number of unreceived terminals to the total number of adjacent terminals is equal to or greater than a threshold value. A traffic calculation unit for obtaining communication traffic based on the signal amount transmitted and received by the communication unit;
If the ratio of the number of unreceived terminals with respect to the total number of adjacent terminals is equal to or greater than a threshold, the communication control unit, based on the difference between the communication traffic obtained by the traffic calculation unit and the upper limit value of the communication traffic, The communication terminal according to claim 2 or 3, wherein an amount of decrease in transmission rate is determined.   The communication terminal according to claim 5, wherein the signal amount received by the communication unit includes a signal amount transmitted through a communication route that does not pass through the terminal.   The traffic calculation unit increases the calculation value of communication traffic as the number of relay terminals that are the slave units on the communication route to which the signal transmitted by the communication unit reaches the master unit increases. Communication terminal.   The communication terminal according to any one of claims 5 to 7, wherein the traffic calculation unit increases a calculated value of communication traffic as the number of adjacent terminals increases.   The communication terminal according to any one of claims 5 to 8, wherein the traffic calculation unit increases a calculated value of communication traffic as the number of parent devices and child devices with which the adjacent terminal can directly communicate is larger.   The communication terminal according to any one of claims 1 to 9, wherein the communication control unit causes the communication unit to transmit information for causing another slave unit to determine a decrease amount of a transmission rate.   The communication terminal according to any one of claims 1 to 9, wherein the communication control unit causes the communication unit to transmit a signal instructing whether or not to reduce the transmission rate to another child device. A multi-route communication in which each of the plurality of slave units establishes a communication route including one or more communication links with the master unit, and the master unit and each of the plurality of slave units perform multi-hop communication with each other. A hop communication system,
Each of the plurality of slave units is
A communication unit that sends and receives signals to and from adjacent terminals that are direct parent devices or child devices,
A routing unit that establishes a communication route that passes through this connection terminal with any one of the adjacent terminals as a connection terminal by receiving the routing packet for determining the communication route from the adjacent terminal;
A multi-hop communication system comprising: a communication control unit that reduces a transmission rate at which the communication unit transmits a signal when the communication unit does not receive a routing packet from the connection terminal during a predetermined waiting time. A multi-route communication in which each of the plurality of slave units establishes a communication route including one or more communication links with the master unit, and the master unit and each of the plurality of slave units perform multi-hop communication with each other. A program executed by a computer included in the slave unit of the hop communication system,
When the communication unit receives a routing packet transmitted from an adjacent terminal that is a parent device or a child device capable of direct communication in order to determine the communication route, any one of the adjacent terminals is used as a connection terminal. The function of the routing unit that builds a communication route through the terminal,
When the communication unit does not receive a routing packet from the connection terminal during a predetermined standby time, the computer realizes a function of a communication control unit that reduces a transmission rate at which the communication unit transmits a signal. program.

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