JP2017017670A - Communication device and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aggregate data between gateways in consideration of a transmission time limit when achieving a gateway role between a sensor and a server, so as to reduce the number of simultaneous connections to mobile communication by a gateway.SOLUTION: A communication device 1, which plays the role of the gateway between a sensor 2 and a server 3, includes: a sensor communication unit 11 which receives data from the sensor 2; a gateway communication unit 13 which transmits the data received from the sensor 2 to a neighboring communication device 1, and receives data transmitted from a neighboring communication device 1; a server communication unit 14 which transmits to the server 3 the data received from the sensor 2 and the data received from the neighboring communication device 1; and a control unit 12 which determines to output the data, received from the sensor 2, to which of the gateway communication unit 13 and the server communication unit 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication device that plays the role of a gateway, and in particular, reduces the number of simultaneous mobile communication connections such as LTE by aggregating data received from devices such as sensors by communicating between a plurality of gateways. The present invention relates to a target communication device and communication method.

  M2M (Machine to Machine Communication) and IoT (Internet of Things) exist as systems in which devices communicate with each other and perform desired processing. These systems are used in a wide range of fields, such as vending machine inventory management, farm monitoring, building management, and smart meters.

  In the above system, a gateway having a communication function is used to collect data from devices such as sensors through a network. A device such as a sensor is connected to a gateway by a local radio such as Wi-Fi or Bluetooth (registered trademark) in addition to a wired connection, and transmits data to the gateway. The gateway is connected to the Internet via a fixed line such as FTTH and mobile communication such as 4G (LTE) or 3G, and transmits data received from devices such as sensors to a server or the like. Mobile communication is easy to install because there is no need for line construction, and mobile communication modules for M2M / IoT are provided by each company. In recent years, high-performance gateways capable of advanced control with software have also appeared.

  By the way, in recent years, 920 MHz band radio has been applied to the M2M / IoT field. The 920MHz band is an unlicensed frequency band. As wireless standards for the 920 MHz band, there are IEEE802.15.4 / 4g (Zigbee (registered trademark) 920 / Wi-SUN), IEEE802.11ah, etc., and Wi-SUN is applied to smart meters. Since the communication distance is about several hundred meters, it is also suitable for communication between smart meters installed between homes.

  On the other hand, the use of the 920 MHz band is defined by the ARIB standard “920 MHz band telemeter, radio equipment for telecontrol and data transmission” (ARIB STD-T108). As shown in the table of FIG. 11, the standard specifies that the total transmission time per hour is 360 seconds or less for the transmission time limit of the 920 MHz band.

  Patent Document 1 provides a method for clustering nodes so as to minimize communication collision between nodes for the purpose of improving packet delivery reliability and reducing transmission delay in an M2M network. The ability (CHC) of a node to become a cluster head is determined based on information such as the remaining energy ratio of each node, and the nodes are clustered so that the higher the CHC, the higher the probability of being selected as a cluster head. Distributed control is performed at each node without using global parameters.

  Patent Document 2 provides a wireless device and a control method that reduce energy consumption of a wireless network and improve network robustness, reliability, and real-time performance. The plurality of subnodes aggregates data into aggregation nodes. Energy consumption is reduced by setting a random sleep time for the sub-node. The aggregation node monitors the state of the subnode. When the subnode is active, data is acquired from the subnode, and when the subnode is in the sleep mode, the data of the subnode is estimated according to a predetermined algorithm.

  Non-Patent Document 1 provides a technique for consolidating and compressing data in preparation for a large load on a communication network due to a large amount of small-scale data such as power usage information with the spread of smart grids. Data collected at the gateway is analyzed, and data from a plurality of sensors having metadata with high temporal similarity and spatial similarity are aggregated in a spatio-temporal block, thereby reducing the amount of metadata information.

JP 2014-204436 A JP 2012-1000025 A

Efficient aggregation and transmission technology of spatio-temporal sensing data by many sensors (Osaka University, KDDI)

  In mobile communication such as LTE, there is a limit to the number of simultaneous connections of radio resources, so radio resources are released after a certain period of time has elapsed after completion of data transmission. When a gateway that transmits data using mobile communication transmits data at an interval shorter than the time until radio resources are released, there is a problem that the radio resources are not released and the number of simultaneous connections is reduced.

In the prior art (Patent Literature 1, Patent Literature 2, Non-Patent Literature 1), the data of a plurality of nodes (gateways) is aggregated and transmitted to one node, thereby reducing the number of simultaneous connections. At this time, it is conceivable to use 920 MHz band radio to collect data.
However, the prior art does not consider the limitation on the total transmission time per hour in the 920 MHz radio described above, and there is a problem in that data may not be aggregated between gateways due to this transmission time limitation.

  The present invention has been proposed in view of the above circumstances, and communication that enables data to be aggregated between gateways in consideration of transmission time limitations when realizing the role of a gateway between a sensor and a server. The object is to provide a device.

In order to achieve the above object, a first aspect of the present invention is a communication device that serves as a gateway between a single or a plurality of sensors and a server, and includes the following configuration.
A sensor communication unit that receives data from the sensor.
A gateway communication unit that transmits data received from the sensor to a nearby communication device and receives data transmitted from the nearby communication device.
A server communication unit that transmits data received from the sensor and data received from the neighboring communication device to the server.
A control unit that determines whether data received from the sensor is output to the gateway communication unit or the server communication unit.

Claim 2 is the communication apparatus of claim 1,
The control unit transmits an aggregation request packet to a neighboring communication device, and the neighboring communication device performs the determination based on an aggregation approval packet obtained by analyzing the aggregation request packet.

Claim 3 is the communication apparatus of claim 2,
The gateway communication unit uses 920 MHz band radio, and the control unit performs the determination in consideration of a transmission time limit of 920 MHz band radio.

Claim 4 is the communication apparatus of claim 3,
The gateway communication unit transmits the aggregation request packet to the neighboring communication device when the total transmission time in the 920 MHz band radio does not exceed the transmission time limit of the 920 MHz band.

Claim 5 is the communication apparatus of claim 4,
The gateway communication unit transmits the aggregation request packet to the neighboring communication device when the total transmission time in the 920 MHz band wireless does not exceed the transmission time limit of the 920 MHz band and when a predetermined time has elapsed. It is characterized by that.

Claim 6 is the communication apparatus according to claim 4 or 5,
The aggregation request packet includes an aggregation request packet transmission source address and a data rate received from the sensor.

Claim 7 is the communication apparatus according to claim 4 or claim 5,
When the aggregation request packet is received, the aggregation approval packet is received when the sum of the data rate received from the sensor and the data rate received from the neighboring communication device is equal to or lower than the data rate that can be transmitted by the server communication unit. It is characterized by replying.

Claim 8 is the communication apparatus of claim 2,
The aggregation request packet includes the number of hops on a communication path, and the determination takes the number of hops into consideration.

Claim 9 is the communication apparatus of claim 7,
The aggregation approval packet includes an aggregation approval packet transmission source address and the number of gateways that have already aggregated data.

Claim 10 is the communication apparatus of claim 1,
When receiving data from the neighboring communication device, it waits for a predetermined time and aggregates a plurality of data received within the predetermined time.

Claim 11 is the communication apparatus of claim 10,
When a plurality of data is aggregated, the data is compressed to reduce the data size.

Claim 12 is a communication method performed between a plurality of communication devices that receive data from a single sensor or a plurality of sensors and upload the data to a server,
Each communication device serves as a gateway between the sensor and the server,
One communication device that has received data from the sensor sends an aggregation request packet for aggregating the data to another communication device when the sum of the transmission times in the 920 MHz band radio does not exceed the transmission time limit of the 920 MHz band. Send
The other communication device is directed to the one communication device when the sum of the data rate received from the sensor and the data rate received from the neighboring communication device is equal to or less than a data rate that can be transmitted between the communication devices. Send back the aggregate approval packet,
The one communication device determines a communication device that aggregates data in consideration of the number of already aggregated gateways included in the aggregation approval packet, outputs the data to the communication device by the 920 MHz band radio, and A communication device that aggregates data is characterized by uploading.

Claim 13 is the communication method of claim 12,
Each of the communication devices includes an access point connected to a fixed line.

Claim 14 is the communication method of claim 13,
When the communication apparatus is an access point, the aggregation approval packet is returned as a value obtained by adding a predetermined value to the actual aggregation number.

  According to the communication device of claim 1 and the communication method of claim 12, the control unit determines whether the data received from the sensor is output to the gateway communication unit or the server communication unit, thereby determining the data transmission destination. By switching from the server to the gateway and transmitting the data from the gateway to the server (collecting data between the gateways), the number of simultaneous connections to mobile communication by the gateway can be reduced.

  According to claim 2, the determination of whether to output to the gateway communication unit or the server communication unit in the control unit refers to the aggregation request packet and the aggregation approval packet, so that the situation of the destination gateway is taken into consideration Switching can be done.

  According to the third to fifth aspects, the determination can be performed in consideration of the feature of the 920 MHz band radio that transmission cannot exceed 360 seconds per hour.

  According to the sixth and seventh aspects, the control unit can make the determination in consideration of the aggregation request packet transmission source address and the data rate received from the sensor.

  According to the eighth aspect, it is possible to perform the determination in the control unit in consideration of the number of hops on the communication path.

  According to the ninth aspect, it is possible to make the determination in the control unit in consideration of the number of gateways that have already aggregated data in the aggregation approval packet.

  According to the tenth aspect, it is possible to improve the efficiency of aggregation by aggregating a plurality of data received within a predetermined time.

  According to the eleventh aspect, it is possible to improve the efficiency of aggregation by compressing data and reducing the data size.

  According to the thirteenth aspect, the access point can be selected as the aggregation destination gateway.

  According to the fourteenth aspect, the access point can be easily selected as the aggregation destination gateway.

It is a block diagram which shows the structure of the communication apparatus of this invention. It is a flowchart which shows the process sequence in the control part of a communication apparatus. In a communication system in which a plurality of communication devices are used and each communication device receives data from a sensor and uploads the data to a server, the communication device that has received the data indicates a state in which an aggregation request has been transmitted to another communication device (gateway) It is a model figure. It is a model figure which shows the state which another communication apparatus (gateway) transmitted aggregation approval in the communication system which each communication apparatus receives and uploads to the server the data from a sensor using a several communication apparatus. It is a model figure which shows the state which changed the data transmission destination using the 920MHz band in the communication system which each communication apparatus receives and uploads to the server the data from a sensor using a several communication apparatus. FIG. 3 is a model diagram illustrating a state in which transmission in a 920 MHz band is stopped and switched to LTE in a communication system in which a plurality of communication devices are used and each communication device receives data from a sensor and uploads the data to a server. It is a model figure in the case of collecting data with the communication system which set the upper limit of the number of hops to "3", and was applied with the communication apparatus of this invention. In the communication system using the communication apparatus of this invention, it is a model figure in the case of collecting waveform data from a power sensor. It is a model figure in the case of collecting data with the communication system which does not apply the communication apparatus of this invention. It is a model figure in the case of collecting data with the communication system to which the communication apparatus of this invention is applied. It is a table | surface which shows the ARIB standard in the radio equipment for 920MHz band radio telemeters, telecontrol, and data transmission.

  A plurality of communication devices according to the present invention are installed assuming the spread of M2M / IoT, and each communication device is assumed to be used in an environment where the communication device serves as a gateway between the sensor and the server. In the M2M / IoT field, 920MHz band wireless that does not require a license is applied, so by communicating between the communication devices (gateways) with 920MHz band wireless, the data received from the sensor connected to the communication device is optimally communicated The purpose is to reduce the number of simultaneous connections in the mobile communication between the server and the communication device by collecting the data in the device and transmitting data from the communication device to the server.

  Examples of gateways include devices developed for gateways such as home gateways, network devices such as routers and switches, general-purpose development boards such as Arduino and RaspberryPi, and information terminals such as smartphones and PCs.

Hereinafter, an exemplary embodiment of a communication apparatus (gateway) according to the present invention will be described with reference to the drawings.
As shown in the block diagram of FIG. 1, the communication device 1 receives the sensor communication unit 11 that acquires data from the sensor 2, the control unit 12 that determines the destination of the data received from the sensor 2, and the control unit 12. A gateway communication unit 13 that transmits data to a neighboring gateway (communication device 1) and a server communication unit 14 that transmits data received from the control unit 12 to the server 3 are configured.

  The sensor communication unit 11 receives data by communicating with the sensor 2 and outputs the data to the control unit 12. For connection between the sensor communication unit 11 and the sensor 2, local wireless communication such as Wi-Fi or Bluetooth (registered trademark) is used in addition to a wired connection such as a serial cable or a USB cable. The sensor 2 connected to the sensor communication unit 11 and transmitting various data may be one or plural.

  The sensor 2 may operate as a device different from the communication device 1 or may be incorporated as a part of the communication device 1. Examples of the sensor 2 include a temperature sensor, a power sensor, and a camera.

  The type and size of the sensed data vary depending on the type of sensor 2. For example, if S sensors are connected to the gateway g and the data rate of the sensor s is represented by d (s) (bps), the total data rate a (g) that the gateway g receives via the sensor communication unit 11 ) (Bps) is expressed by Equation 1.

  For example, it is assumed that S = 3 (pieces) sensors 2 are connected to the communication device (gateway) 1 and each sensor 2 transmits 100-bit data to the gateway g once every 10 seconds. At this time, the data rate of each sensor 2 is 100/10 = 10 (bps), and the total data date a (g) of the gateway g is calculated by Equation 2.

The control unit 12 determines whether the data received from the sensor 2 is output to the gateway communication unit 13 or the server communication unit 14.
The determination is performed based on the aggregation approval packet transmitted by transmitting the aggregation request packet to the neighboring communication device 1 and analyzing the aggregation request packet by the neighboring communication device 1. At that time, the determination is performed in consideration of the transmission time limit of the 920 MHz band radio (the transmission cannot exceed 360 seconds per hour), the total data rate on the neighboring communication device 1 side does not exceed the threshold, and the like. It is. The detailed procedure of the determination process will be described later with reference to the flowchart of FIG.

  The gateway communication unit 13 transmits the data received from the control unit 12 to the neighboring gateway (communication device 1) using 920 MHz band radio. In addition, it receives data transmitted from the neighboring gateway (communication device 1).

  The server communication unit 14 transmits data received from the control unit 12 (including data received from neighboring gateways) to the server 3 using mobile communication such as LTE.

  Therefore, according to the communication device 1 described above, the control unit 12 determines whether the data received from the sensor 2 is output to the gateway communication unit 13 or the server communication unit 14, so that the data transmission destination is sent from the server 2. By switching to the neighboring communication device 1 (gateway) and transmitting the data from the gateway to the server 2 collectively, that is, collecting and transmitting data between the gateways, the number of simultaneous connections to mobile communication by the communication device (gateway) 1 is reduced. can do.

Next, the detailed process in the control part 12 is demonstrated with reference to the flowchart of FIG. 2, and the model figure of FIGS.
The communication system is configured to use a plurality of communication devices 1 so that each communication device 1 receives data from the sensor 2 and uploads it to the server 3. In the communication system, communication between communication devices 1 uses 920 MHz band wireless (for example, Wi-SUN), communication between the communication device 1 and sensor 2 uses local wireless communication (for example, Wi-Fi), and communication device. For communication between 1 and the server 32, mobile communication (for example, LTE) is used.

In addition to the communication device (gateway) 1, an access point (router) connected to a fixed line such as optical communication may also be used as an aggregation destination. In this case, the access point (router) is set to be communicable with the communication device (gateway) 1 by wireless in the 920 MHz band.
By using an access point, it is possible to send data to an access point connected to a fixed line and send data to the server 3 via the fixed line, reducing the number of simultaneous mobile communications such as LTE. it can.

  A processing procedure in the control unit 12 of the communication device (gateway) 1A (address 192.168.10.12) that acquires data from the sensor 2 will be described.

[S1] Activation The communication device (gateway) 1A is connected to the power source and activated.

[S2] Aggregation Request Transmission Next, the communication device (gateway) 1A transmits an aggregation request to another communication device (gateway) 1 (FIG. 3).
That is, in order to aggregate the data of the sensor 2 to the neighboring gateway 1 using the gateway communication unit (920 MHz band wireless) 13 of the communication device (gateway) 1A, a certain time has elapsed since the activation of the aggregation request packet to the neighboring gateway 1 Broadcast later. In FIG. 3, the communication device 1A (address 192.168.10.12) sends an aggregation request packet to three neighboring gateways 1 (address 192.168.10.10), (address 192.168.10.11), and (address 192.168.10.13). .
In this state, data acquired by the sensor 2 of the communication device (gateway) 1A is transmitted to the server 3 using mobile communication (LTE).

The aggregation request packet includes information on the aggregation request source address and the data rate a (g).
The aggregation request source address is an address that can uniquely identify the gateway that has transmitted the aggregation request packet. In addition to service-specific addresses, MAC addresses and IP addresses can be used as the aggregation request source address.
The data rate a (g) is the total data rate (bps) that the gateway g receives from the sensor.

  The aggregation request packet may include information on the number of hops on the communication path. The number of hops is the number of relays on the communication path from the gateway that transmitted the aggregation request packet to the gateway that received the aggregation request packet. The hop count of the gateway that directly communicates with the gateway that transmitted the aggregation request packet is set to “1”, and increases by “1” every time the aggregation request packet is transferred.

  The operation when the aggregation request packet is received will be described later in [S11] and [S12].

[S3] Aggregation Approval Reception When the neighboring gateway 1 receives the aggregation request and satisfies a predetermined condition, it transmits an aggregation approval packet to the communication device (gateway) 1A and responds (FIG. 4). The transmission of the aggregation approval packet will be described later in [S13]. The aggregation approval packet includes information on the number of aggregation gateways currently aggregated and the aggregation approval transmission source address. When the aggregation request packet includes hop count information, the aggregation approval packet also includes hop count information.
The aggregation gateway number is the number of gateways that have aggregated (received data) when the gateway that has transmitted the aggregation approval packet transmits the transmission approval packet.

  The aggregation approval transmission source address is an address that can uniquely identify the gateway that has transmitted the aggregation approval packet. In addition to service-specific addresses, MAC addresses and IP addresses can be used as the aggregate approval source address.

  Since the aggregation request packet is broadcast, the communication apparatus (gateway) 1A may receive the aggregation approval packet from a plurality of gateways. At this time, the aggregation approval packet is transmitted from a plurality of gateways that have received the aggregation request packet, and there is a possibility that a collision occurs. IEEE802.15.4 / 4e and IEEE802.11ah, which are 920MHz band radios, provide collision avoidance at the MAC layer, which is used to avoid collisions.

  When the communication device (gateway) 1A receives at least one aggregation approval packet, the data is transmitted to the neighboring gateway using the gateway communication unit (920 MHz band wireless). Set to the neighboring gateway (FIG. 5). In the case of FIG. 5, the transmission is switched from transmission to the server 3 using mobile communication (LTE) to transmission by 920 MHz band wireless (Wi-SUN) whose destination is changed to the neighboring gateway 1 (address 192.168.10.10).

  On the other hand, when the communication device (gateway) 1A does not receive any aggregation approval packet, data is transmitted to the server 3 using the server communication unit (mobile communication) 14, so that data transmission is performed in [S5] described later. The destination is set in the server 3.

[S4] Destination Gateway Setting When the communication device (gateway) 1A receives only one aggregation approval packet, the aggregation approval transmission source address included in the aggregation approval packet is set as the destination.
When the communication device (gateway) 1A receives a plurality of aggregation approval packets, the number of aggregation gateways included in the aggregation approval packet is compared, and the gateway having the largest aggregation gateway number (aggregation number) is set as the destination. As described above, in addition to the gateway, an access point (router) connected to a fixed line such as optical communication may be used as an aggregation destination.
As a result, data can be aggregated by adding to the gateway that has already aggregated data of more gateways, and the effect of reducing the number of simultaneous connections in mobile communication is enhanced.
If there are multiple gateways with the largest number of aggregated gateways, select one of the gateways. In this case, in order to prevent an increase in transmission time (details will be described later), a gateway with a small number of hops is selected. If the number of hops is the same, the gateway to be selected may be determined by means such as random, the smallest ID, and the first aggregation approval packet received.

In an environment where an access point can be selected instead of a gateway, the access point is preferentially selected as an aggregation destination. Therefore, the access point that receives the aggregation request packet has a large value (such as 100) The aggregation approval packet may be returned as the aggregation number to include the value obtained by adding the (fixed value) in the aggregation approval packet. This makes it easier to select an access point as a destination (aggregation destination) when selecting an aggregation destination in [S4].
Further, as a method of clearly indicating an access point, a flag indicating whether or not it is an access point may be set in the aggregation approval packet, and the flag may be preferentially selected.

[S5] Destination Server Setting When the communication device (gateway) 1A has not received any aggregation approval packet, the server 3 that collects data is set as the destination. It is assumed that the address of the server 3 is known in advance or can be obtained by DNS or the like.
The data collection destination is a server for convenience, but it may be a PC, a smartphone, an M2M platform, or the like.

[S6] Data reception from sensor Data is received from the sensor 2 through the sensor communication unit 11 of the communication device (gateway) 1A. If received, the data is transmitted to the destination set in [S4] or [S5] ([S15]).

[S7] Data reception from gateway Data is received from neighboring gateways through the gateway communication unit 13 of the communication device (gateway) 1A. The received data is held in a storage area such as a memory, and waiting for reception for a predetermined time w. If data is further received from the neighboring gateway during reception standby, it is added to the storage area.

When data is received from the sensor during reception standby ([S8]), or when reception standby time w has elapsed ([S9]), reception standby is terminated.
The reception waiting time w is an arbitrarily set parameter. By setting the reception waiting time w to 0, the data can be transmitted to the server immediately after receiving the data from the neighboring gateway. Increasing the reception waiting time w increases the chances of data aggregation.

[S10] Receive multiple data
[S7] When a plurality of data is received at [S8], the received data is collected.
When only one data is received, the received data is transmitted ([S15]).

[S11] Data aggregation Aggregate multiple received data. As a method of aggregating a plurality of data, there is a method in which a plurality of transmission source addresses and a plurality of data are collected into one packet. By combining multiple packets into one packet, you can expect a traffic reduction effect by reducing the header size.

A method of compressing a plurality of data is conceivable. By compressing multiple data, data size can be reduced and traffic reduction effect can be expected.
In any case, the server side needs a mechanism for interpreting one received packet as a plurality of data from a plurality of gateways.
If such a mechanism cannot be incorporated on the server side, the received data may be transmitted to the server 3 as it is without being aggregated. In that case, although the traffic reduction effect as described above cannot be obtained, the effect of reducing the number of simultaneous connections, which is the original purpose, can be obtained.

  In general, the data size of M2M / IoT is often smaller than the data size of a smartphone or the like. If a band equivalent to a smartphone or the like is allocated to the M2M / IoT gateway, the excessively allocated band may be wasted. By aggregating data, the effect of reducing this waste of bandwidth is also expected.

[S12] Aggregation request reception The aggregation request packet transmitted by the neighboring gateway is received. If received, it is determined in [S13] whether the aggregation condition is satisfied, as described later.

[S13] When the aggregation condition is satisfied The effect of reducing the number of simultaneous connections increases as data is collected by more gateways. However, mobile communication bands such as LTE are limited, and there is a limit to the amount of data that can be transmitted in a certain time. When data is received and aggregated from neighboring gateways exceeding this limit, all data cannot be transmitted to the server 3.
Therefore, the data rate C that can be transmitted by mobile communication is compared with the data rate received from the sensor 2 or the neighboring gateway, and it is determined whether the data of the gateway that transmitted the aggregation request packet can be received or aggregated.

  Here, the total data rate A (h) (bps) received from G neighboring gateways and transmitted by the gateway h is expressed by the following equation (3).

These values are calculated based on the information of a (g) included in the aggregation request packet, and only when A (h) <C, it is determined that the aggregation condition is satisfied, and the aggregation approval packet is transmitted ([S14 ]).
Further, when considering the number of hops, the aggregation request packet is transferred via (hops) a plurality of gateways. Since the relaying gateway relays data using the 920 MHz band radio, as the number of hops increases, the transmission time of the 920 MHz band radio increases in many gateways. Thus, in order to avoid reaching the transmission time limit of the 920 MHz band radio and not being able to perform aggregation, an upper limit is set on the number of hops for relaying the aggregation request packet.
That is, the aggregation request packet is transferred to the neighboring gateway only when the number of hops included in the transmission request packet is less than a predetermined value.
The predetermined value is a parameter that is arbitrarily set. When the predetermined value is “1”, data is aggregated only with an adjacent gateway (a gateway capable of direct communication using 920 MHz band radio).

For example, in FIG. 7, consider an example in which the gateway 1A transmits an aggregation request packet in consideration of the number of hops. When the upper limit of the number of hops is set to “3”, the aggregation request packet transmitted by the gateway A1 is transmitted up to 3 hops ahead of the upper limit of the number of hops. Therefore, in the example of FIG. 7, the gateways 1B, 1C, 1D, 1E, 1F, and 1G receive the aggregation request packet. In FIG. 7, reference numeral 4 denotes a base station to which the communication device (gateway) 1 is connected, and 6 denotes a mobile phone connected to the base station 4 by mobile communication.
The gateways 1B to 1G that have received the aggregation request packet transmit an aggregation approval packet including its own address, the number of aggregations, and the number of hops to the gateway 1A.
The gateway 1A that has received the aggregation approval packet from the gateways 1B to 1G can determine the destination gateway from among the gateways 1B to 1G from the information included in the aggregation approval packet.

[S16] The total transmission time is equal to or greater than a predetermined value As described above, there is a restriction that the 920 MHz band radio cannot transmit more than 360 seconds per hour. Therefore, after sending data in [S15], calculate the total transmission time in the 920MHz band so far, and if it is greater than or equal to the predetermined value, set the destination in the server ([S5]), and wireless the 920MHz band (Wi- Transmission by SUN) is stopped and switching to transmission by mobile communication (LTE) is performed (FIG. 6). The predetermined value is a settable parameter and may be set as 360-α (seconds) (α is a margin).

[S17] Aggregation request transmission conditions are met
There is a restriction that 920MHz band radio cannot transmit more than 360 seconds per hour. Therefore, the aggregate request transmission condition is “the total transmission time in the 920 MHz band is less than or equal to a predetermined value” and “predetermined time t has elapsed since the previous aggregation request transmission”, and the aggregation request is transmitted only when this is satisfied ([S2] ).

As a result, the data is aggregated between the gateways within the limits of the 920 MHz band radio.
The predetermined time t is a parameter that can be set. By setting t to infinity, the gateways to be aggregated can be set not to change. The predetermined value is a settable parameter and may be set as 360-α (seconds) (α is a margin).

Next, a specific example of collecting data using a plurality of communication devices that serve as gateways between the sensor and the server will be described with reference to FIGS.
As the data to be collected, for example, as shown in FIG. 8, an example is considered in which waveform data is acquired once every 10 seconds from a power sensor provided at home and uploaded to the server 3 via a gateway (communication device 1). .
The gateway (communication device 1) includes a Wi-Fi module, an LTE module, and a Wi-SUN module. The power sensor 2 and the gateway 1 are connected by Wi-Fi. Data received from the power sensor 2 is transmitted to the server 3 using LTE. LTE shall release radio resources only when communication is not performed for 30 seconds.

  An example in which data is collected by a communication system to which the communication apparatus of the present invention is not applied is shown in FIG. The hexagonal areas (f1, f2, f3) represent LTE cells. Three gateways shown in FIG. 8 are installed in each cell. When the communication device of the present invention is not applied, each gateway transmits data to the server via LTE. Since data is transmitted once every 10 seconds, no radio resources are released. That is, since “3” connection is always established in each cell, there is a possibility that the number of connected smartphones and mobile routers using LTE may be reduced.

  On the other hand, FIG. 10 shows an example of collecting data in a communication system to which the communication apparatus of the present invention is applied. The LTE cell size is approximately 1-3 km. Since the communication distance of Wi-SUN is about several hundred meters, it can be said that communication can be sufficiently performed between gateways in a cell. Data of three gateways installed in the same cell is aggregated. This reduces the number of simultaneous connections in each LTE cell. At this time, each gateway operates in accordance with the above-described sequence, so that data can be aggregated within a range of transmission time restrictions of 920 MHz band radio.

  DESCRIPTION OF SYMBOLS 1 ... Communication apparatus (gateway), 2 ... Sensor, 3 ... Server, 4 ... Base station, 6 ... Mobile phone, 11 ... Sensor communication part, 12 ... Control part, 13 ... Gateway communication part, 14 ... Server communication part.

Claims (14)

A communication device serving as a gateway between a single sensor or a plurality of sensors and a server,
A sensor communication unit for receiving data from the sensor;
A gateway communication unit that transmits data received from the sensor to a neighboring communication device and receives data transmitted from the neighboring communication device;
A server communication unit for transmitting data received from the sensor and data received from the neighboring communication device to the server;
A control unit for determining whether to output the data received from the sensor to the gateway communication unit or the server communication unit;
A communication apparatus comprising:   The communication device according to claim 1, wherein the control unit transmits an aggregation request packet to a neighboring communication device, and the neighboring communication device performs the determination based on an aggregation approval packet obtained by analyzing the aggregation request packet.   The communication apparatus according to claim 2, wherein the gateway communication unit uses 920 MHz band radio, and the control unit performs the determination in consideration of a transmission time limit of 920 MHz band radio.   The communication device according to claim 3, wherein the gateway communication unit transmits an aggregation request packet to the neighboring communication device when a total of transmission times in the 920 MHz band radio does not exceed a transmission time limit of the 920 MHz band.   The gateway communication unit transmits the aggregation request packet to the neighboring communication device when the total transmission time in the 920 MHz band wireless does not exceed the transmission time limit of the 920 MHz band and when a predetermined time has elapsed. The communication apparatus according to claim 4.   The communication device according to claim 4, wherein the aggregation request packet includes an aggregation request packet transmission source address and a data rate received from the sensor.   When the aggregation request packet is received, the aggregation approval packet is received when the sum of the data rate received from the sensor and the data rate received from the neighboring communication device is equal to or lower than the data rate that can be transmitted by the server communication unit. The communication device according to claim 4 or 5, wherein:   The communication apparatus according to claim 2, wherein the aggregation request packet includes the number of hops on a communication path, and the determination considers the number of hops.   The communication apparatus according to claim 7, wherein the aggregation approval packet includes an aggregation approval packet transmission source address and the number of gateways that have already aggregated data.   The communication apparatus according to claim 1, wherein when receiving data from the neighboring communication apparatus, the communication apparatus waits for a predetermined time and aggregates a plurality of data received within the predetermined time.   The communication device according to claim 10, wherein the data size is reduced by compressing the data when a plurality of data is aggregated. A communication method performed between a plurality of communication devices that receive data from a single sensor or a plurality of sensors and upload the data to a server,
Each communication device serves as a gateway between the sensor and the server,
One communication device that has received data from the sensor sends an aggregation request packet for aggregating the data to another communication device when the sum of the transmission times in the 920 MHz band radio does not exceed the transmission time limit of the 920 MHz band. Send
The other communication device is directed to the one communication device when the sum of the data rate received from the sensor and the data rate received from the neighboring communication device is equal to or less than a data rate that can be transmitted between the communication devices. Send back the aggregate approval packet,
The one communication device determines a communication device that aggregates data in consideration of the number of already aggregated gateways included in the aggregation approval packet, outputs the data to the communication device by the 920 MHz band radio, and A communication method, wherein a communication device that aggregates data uploads.   The communication method according to claim 12, wherein each communication device includes an access point connected to a fixed line.   14. The communication method according to claim 13, wherein, when the communication device is an access point, the aggregation approval packet is returned with the value obtained by adding a predetermined value to the actual aggregation number as the aggregation number.