Communication system, concentrator and communication method

Abstract

To suppress generation of interference power and influences of a propagation loss.SOLUTION: A communication system (1) comprises a plurality of terminals (3) each transmitting a data signal through radio communication, and a concentrator (2) by which the data signals are received and aggregated. The concentrator includes an array antenna (240), a beam control section (221) and a communication section (222). The array antenna transmits / receives signals in a beam direction which is set by beamforming. The beam control section controls a beam direction (80). The communication section transmits number request signals requesting terminal numbers to the plurality of terminals through broadcast communication in a first beam direction, extracts a terminal which successes transmission / reception in the first beam direction as an extraction terminal from among the plurality of terminals and establishes a link with the extraction terminal. Each of the plurality of terminals transmits the data signal after the link is established.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication system, a concentrator included in the communication system, and a communication method performed by the communication system, which can be suitably used, for example, for the concentrator to aggregate data signals from a plurality of terminals. [Background technology]

[0002] There is a demand for technology that aggregates data collected by multiple terminals distributed in a desired range by wireless communication. As an example, a method of aggregating data from sensor terminals using LPWANs (Low Power Wide Area Networks) operated in the 920 MHz band in Japan often involves installing an aggregation station called a gateway or concentrator in each of multiple types of systems, collecting data at the aggregation station, and then registering it in a server. This requires that an aggregation station be installed for each system, which increases the installation costs required for data aggregation. One solution to this problem is to install a general-purpose concentrator that can aggregate information from multiple systems in one place. This method makes it possible to share the installation costs of general-purpose concentrators among multiple systems, contributing to cost reduction.

[0003] In relation to the above, Non-Patent Document 1 (D. Kominami, M. Sugano, M. Murata, T. Hatauchi, and J. Machida, “Energy saving in intermittent receiver-driven multi-hop wireless sensor networks,” 2010 IEEE Int. Conf. on Sensor Netw., Ubiquitous, and Trustworthy Comput., Newport Beach, CA, USA, pp.296-303, published in June 2010) discloses an IRDT (Intermittent Receiver-Driven Data Transmission) protocol. The IRDT protocol adds an intermittent operation to a transmitting terminal that operates asynchronously with respect to a receiving terminal, thereby reducing the power consumption of the transmitting terminal. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] D. Kominami, M. Sugano, M. Murata, T. Hatauchi, and J. Machida, “Energy saving in intermittent receiver-driven multi-hop wireless sensor networks,” 2010 IEEE Int. Conf. on Sensor Netw., Ubiquitous, and Trustworthy Comput., Newport Beach, CA, USA, pp.296-303, June 2010. Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, to realize a general-purpose concentrator, it is necessary to be able to receive various signals used by multiple systems with different reception performance and communication quality. Also, in order to reduce the number of concentrators to be installed, it is better to have a wide range in which communication with terminals is possible. However, in order to meet this requirement, there are problems such as the increase in interference power as the total number of signals transmitted simultaneously increases, and the problem that signals transmitted from far away are attenuated by propagation loss and become buried in noise or other signals.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a communication system, a concentrator, and a communication method that suppress the generation of interference power and the influence of propagation loss. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] The means for solving the problems will be described below using the numbers and symbols used in the description of the embodiment of the invention. These numbers and symbols are added in parentheses for reference purposes to show an example of the correspondence between the description of the claims and the description of the embodiment of the invention. Therefore, the description in parentheses should not be interpreted as limiting the scope of the claims.

[0008] According to one embodiment, a communication system (1) includes a plurality of terminals (3) each transmitting a data signal by wireless communication, and a concentrator (2) receiving and consolidating the data signals. The concentrator (2) includes an array antenna (240), a beam control unit (221), and a communication unit (222). The array antenna (240) transmits and receives signals in a beam direction set by beamforming. The beam control unit (221) controls the beam direction (80). The communication unit (222) transmits a number request signal requesting each terminal number to the plurality of terminals (3) by broadcast communication in a first beam direction (80), extracts a terminal (3) among the plurality of terminals (3) that has succeeded in transmitting and receiving in the first beam direction (80) as an extracted terminal, and establishes a link with the extracted terminal. Each of the plurality of terminals (3) transmits a data signal after the link is established.

[0009] According to one embodiment, the concentrator (2) includes an array antenna (240), a beam control unit (221), and a communication unit (222). The array antenna (240) transmits and receives signals in a beam direction (80) set by beamforming. The beam control unit (221) controls the beam direction (80). The communication unit (222) transmits a number request signal requesting each terminal number to a plurality of terminals (3) by broadcast communication in a first beam direction (80), extracts a terminal (3) among the plurality of terminals (3) that has succeeded in transmitting and receiving in the first beam direction (80) as an extracted terminal, establishes a link with the extracted terminal, and receives and consolidates data signals transmitted from the plurality of terminals (3) after the link is established.

[0010] According to one embodiment, the communication method includes the concentrator (2) transmitting a number request signal requesting each terminal number to a plurality of terminals (3) by broadcast communication in a first beam direction (80) set by beamforming (S21). The communication method further includes the concentrator (2) extracting a terminal (3) that has succeeded in the transmission and reception in the first beam direction (80) from among the plurality of terminals (3) as an extracted terminal (S25). The communication method further includes the concentrator (2) establishing a link with the extracted terminal (S25). The communication method further includes each of the plurality of terminals (3) transmitting a data signal by wireless communication after the link is established (S31). The communication method further includes the concentrator (2) receiving and aggregating the data signals (S32, S35). Effect of the Invention

[0011] According to one embodiment, it is possible to suppress the generation of interference power and the influence of propagation loss. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Diagram 2] FIG. 2 is a block circuit diagram showing an example of a configuration of a concentrator according to an embodiment. [Diagram 3] FIG. 3 is a block circuit diagram showing a configuration example of a terminal according to an embodiment. [Figure 4] FIG. 4 is a flowchart illustrating an example of a process of a communication method according to an embodiment. [Figure 5A] FIG. 5A is a diagram for explaining the beam direction in a radiation pattern representing the directivity of an array antenna according to one embodiment. [Figure 5B] FIG. 5B is a diagram for explaining the beam direction in a radiation pattern representing the directivity of an array antenna according to one embodiment. [Figure 6]FIG. 6 is a sequence diagram showing an example of a part of the process of a communication method according to an embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the positional relationship between the concentrator 2, the terminal 3, and the radiation pattern according to an embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the positional relationship between the concentrator 2, the terminal 3, and the radiation pattern according to an embodiment. [Figure 9] FIG. 9 is a diagram showing an example of the positional relationship between the concentrator 2, the terminal 3, and the radiation pattern according to an embodiment. [Figure 10] FIG. 10 is a sequence diagram showing an example of a part of the process of a communication method according to an embodiment. [Figure 11] FIG. 11 is a table showing an example of specifications for a computer simulation of a communication system and a communication method according to an embodiment. [Figure 12] FIG. 12 is a table illustrating an example of the results of a computer simulation of a communication system and method according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE DRAWINGS With reference to the accompanying drawings, embodiments for implementing a communication system, a concentrator, and a communication method according to the present disclosure will be described below.

[0014] (First embodiment) As shown in Fig. 1, a communication system 1 according to an embodiment includes a concentrator 2 and a plurality of terminals 3. The communication system may further include an external server (not shown). The plurality of terminals 3 are arranged so as to be distributed in an area 9 surrounding the concentrator 2. Each of the plurality of terminals 3 transmits a signal representing data observed using a sensor to the concentrator 2. The concentrator 2 receives and aggregates the signals transmitted from each of the plurality of terminals 3, and transmits the aggregated information to the external server.

[0015] 2, the concentrator 2 according to an embodiment may be configured as a so-called computer. The concentrator 2 includes a bus 21, a computing device 22, a storage device 23, a communication device 24, and an input / output device 25. The bus 21 is configured to connect the computing device 22, the storage device 23, the communication device 24, and the input / output device 25 so that they can communicate with each other.

[0016] The arithmetic device 22 includes a beam control unit 221 and a communication unit 222. The storage device 23 includes a program storage unit 231 that stores an aggregated program, and a data storage unit 232 that stores various data. The arithmetic device 22 executes the aggregated program to realize the processing of the beam control unit 221 and the communication unit 222. The beam control unit 221 and the communication unit 222 are virtual function blocks that are realized by the arithmetic device 22 and the storage device 23 working together. The beam control unit 221 controls the beam direction of the array antenna 240 by setting various parameters for beamforming. The communication unit 222 controls the communication device 24 to transmit and receive signals to and from the terminal 3. Details of the processing realized by the beam control unit 221 and the communication unit 222 will be described later.

[0017] The aggregation program may be read from the recording medium 230 and stored in the program storage unit 231. The recording medium 230 may be a non-transitory and tangible medium.

[0018] The communication device 24 transmits and receives signals to and from the terminal 3 by wireless communication via the array antenna 240. The communication device 24 may also transmit and receive signals to and from an external server by wired communication and / or wireless communication. Furthermore, the communication device 24 may communicate with other external terminals. The aggregation program may be acquired from the outside via the communication device 24 and stored in the program storage unit 231.

[0019] The input / output device 25 outputs information to a user and accepts operations input by the user. As an example, the input / output device 25 includes a display device that outputs images, a keyboard that accepts key input operations, a touch panel that accepts touch operations and outputs images, and the like.

[0020] 3, the terminal 3 according to an embodiment may be configured as a so-called computer. The terminal 3 includes a bus 31, a computing device 32, a storage device 33, a communication device 34, and a sensor device 35. The bus 31 is configured to connect the computing device 32, the storage device 33, the communication device 34, and the sensor device 35 so that they can communicate with each other.

[0021] The arithmetic device 32 includes a measurement unit 321 and a communication unit 322. The storage device 33 includes a program storage unit 331 that stores a terminal program, and a data storage unit 332 that stores various data. The arithmetic device 32 executes the terminal program to realize the processing of the measurement unit 321 and the communication unit 322. The measurement unit 321 and the communication unit 322 are virtual function blocks that are realized by the arithmetic device 32 and the storage device 33 working together. The measurement unit 321 controls the sensor device 35 to generate measurement data that represents the results of the measurement. The communication unit 322 controls the communication device 34 to transmit and receive signals to and from the concentrator 2. Details of the processing realized by the measurement unit 321 and the communication unit 322 will be described later.

[0022] The terminal program may be read from the recording medium 330 and stored in the program storage unit 331. The recording medium 330 may be a non-transitory and tangible medium.

[0023] The communication device 34 transmits and receives signals to and from the concentrator 2 via an antenna 340 by wireless communication.

[0024] The sensor device 35 measures a desired physical quantity under the control of the measurement unit 321, generates data representing the result of the measurement, and stores the generated data in the data storage unit 332 of the storage device 33. As an example, if the parameter to be measured is the air temperature near the terminal 3, the sensor device 35 may include a temperature sensor that measures the temperature and an analog-digital conversion circuit that generates a digital signal representing the measured value of the temperature. As another example, if the parameter to be measured is the amount of gas consumed in the home, the sensor device 35 may include a gas meter that measures the amount of gas consumed and an analog-digital conversion circuit that generates a digital signal representing the measured value of the gas consumption. The sensor device 35 may perform measurement and generate and store data as a measurement process separate from the communication process with the concentrator 2 of the terminal 3. The sensor device 35 may perform the measurement process periodically, or may perform the measurement process each time a predetermined condition is satisfied, such as when the desired physical quantity exceeds a threshold value.

[0025] An example of the process of the communication method according to an embodiment will be described with reference to the flowchart of Fig. 4. The process of the flowchart of Fig. 4 may start when the concentrator 2 is started. When the process of the flowchart of Fig. 4 starts, step S1 is executed.

[0026] In step S1, the beam control unit 221 of the concentrator 2 shown in Fig. 2 determines the beam direction. Here, the beam direction represents the direction of the main lobe with the highest transmission and reception performance among the radiation patterns of the array antenna 240 provided in the concentrator 2. The beam direction determined here is hereinafter referred to as the reference beam direction.

[0027] After step S1 in Fig. 4, step S2 is executed. In step S2, the communication unit 222 of the concentrator 2 shown in Fig. 2 transmits a signal in the reference beam direction determined in step S1 in Fig. 4 to establish links with some of the terminals 3. Details of step S2 will be described later.

[0028] After step S2 in Fig. 4, step S3 is executed. In step S3, the communication unit 222 of the concentrator 2 shown in Fig. 2 receives data from the terminal 3 with which the link was established in step S2 in Fig. 4. Details of step S3 will be described later.

[0029] After step S3 in Fig. 4, the process returns to step S1. In step S1 executed this time, the beam control unit 221 of the concentrator 2 shown in Fig. 2 determines a reference beam direction different from the reference beam direction determined in step S1 executed previously. As an example, the reference beam direction may be rotated horizontally by a predetermined angle clockwise or counterclockwise each time step S1 is repeated.

[0030] 5A and 5B are diagrams for explaining the beam direction 80 in the radiation pattern 8 representing the directivity of the array antenna 240 shown in FIG. 2. The radiation pattern 8 includes one or more main lobes 81 and one or more side lobes 82. Here, in a plane coordinate system centered on the array antenna 240, the direction of the main lobe 81 relative to the direction of 0° parallel to one coordinate axis is referred to as the beam direction 80. FIG. 5A shows an example of the radiation pattern 8 when the beam direction 80 of the main lobe 81 is 36°. FIG. 5B shows an example of the radiation pattern 8 when the beam direction 80 of the main lobe 81 is 72°. In the examples of FIG. 5A and FIG. 5B, each time step S1 of FIG. 4 is repeatedly executed, the beam direction 80 of the reference beam direction rotates counterclockwise while increasing by 36°. However, this is merely an example and does not limit the present embodiment.

[0031] The beam control unit 221 of the concentrator 2 shown in FIG. 2 performs beamforming to direct the directivity of the array antenna 240 to a desired beam direction 80 by setting a combination of amplitude and phase of signals input to each of the multiple antenna elements included in the array antenna 240. Here, each of the multiple antenna elements may be an omnidirectional antenna element. By performing this beamforming when transmitting a signal from the concentrator 2, it is possible to limit the range in which the transmitted signal reaches to the beam direction 80 and its surroundings. In addition, by performing this beamforming when the concentrator 2 receives a signal, it is possible to improve the reception performance for the beam direction 80 and its surroundings. Furthermore, the signals received by each antenna element are individually stored, and a virtual received signal when the signal received by the concentrator 2 is received from an arbitrary beam direction 80 can be calculated based on the signal stored for each antenna element and the combination of amplitude and phase for each antenna element corresponding to an arbitrary beam direction 80.

[0032] The combination of the amplitude and phase of the signal corresponding to each antenna element can be expressed as a complex weight. When the beam control unit 221 in FIG. 2 sets the combination of the amplitude and phase of the signal to each antenna element, the beam control unit 221 multiplies the signal input to the antenna element by a complex weight representing the amplitude and phase of the set combination. Furthermore, the combination of the amplitude and phase corresponding to the multiple antenna elements included in the array antenna 240 can be expressed as a matrix including multiple complex weights. By calculating the complex weight matrix corresponding to each beam direction 80 of the array antenna 240, it is possible to easily calculate a virtual received signal when the signal received by the concentrator 2 is received from any beam direction 80.

[0033] The process of step S2 in Fig. 4 will be described in more detail with reference to the sequence diagram of Fig. 6. When step S2 starts, the terminal 3 executes step S21 in Fig. 6, and the concentrator 2 executes step S22.

[0034] In step S21, the communication unit 322 of each terminal 3 shown in FIG. 3 judges whether there is data to be transmitted to the concentrator 2. More specifically, the communication unit 322 judges whether there is data that has not yet been transmitted to the concentrator 2 by referring to the data storage unit 332 of the storage device 33. If there is no data to be transmitted (NO) as a result of the judgment, the processing of the terminal 3 returns to step S21 in FIG. 6. If there is data to be transmitted (YES), the processing of the terminal 3 proceeds to step S23 in FIG. 6. In the example shown in FIG. 7, among the multiple terminals 3, terminals 3A, 3B, 3C, 3D, etc. that have data to be transmitted are indicated by diagonal lines, and terminals 3E, etc. that do not have data to be transmitted are indicated by white lines. Note that the terminals 3 that do not have data to be transmitted to the concentrator 2 may be in an intermittent state to save power consumption.

[0035] In step S22, the communication unit 222 of the concentrator 2 shown in FIG. 2 transmits a number request signal to the multiple terminals 3 shown in FIG. 1. More specifically, the communication unit 222 of the concentrator 2 notifies each of the multiple terminals 3 of the start of the process of aggregating data by broadcast communication in the reference beam direction determined in step S1 of FIG. 4, and transmits a number request signal to each terminal 3 to request a terminal number. The terminal number is information for identifying the terminal 3. As an example, the terminal number is stored in the data storage unit 232 of the storage device 23 of each terminal 3. Here, among the multiple terminals 3 arranged in the area 9 of FIG. 1, the terminals 3 that can receive the number request signal are only the terminals 3 located in the reference beam direction or in a range around it as seen from the concentrator 2. In this way, even if the concentrator 2 does not know the terminal numbers of each terminal 3 or the positions of each terminal 3, it is possible to transmit a number request signal to only some of the multiple terminals 3 arranged in the area 9 by performing broadcast communication by beamforming. As a result, the probability that interference power increases in the concentrator 2 when multiple terminals 3 transmit various signals to the concentrator 2 decreases, and the probability that the concentrator 2 successfully receives various signals transmitted from multiple terminals 3 increases. After step S22, the process of the concentrator 2 proceeds to step S25 in FIG.

[0036] In step S23, it is determined whether the communication unit 322 of each terminal 3 shown in FIG. 3 has received a number request signal transmitted from the concentrator 2. If the result of the determination is that the number request signal has not been received (NO), the process of each terminal 3 returns to step S21 in FIG. 6. If the number request signal has been received (YES), the process of each terminal 3 proceeds to step S24 in FIG. 6. As an example, when terminals 3A, 3B, 3C, 3D, and 3E are arranged as shown in FIG. 7, terminals 3A, 3B, and 3E can receive the main lobe 81 component. Furthermore, terminal 3C can receive the side lobe 82 component even though it cannot receive the main lobe 81 component. Terminal 3D cannot receive either the main lobe 81 or the side lobe 82 component.

[0037] In step S24, the communication unit 322 of each terminal 3 shown in FIG. 3 transmits a transmission request signal to the concentrator 2 in response to the number request signal received from the concentrator 2. More specifically, first, the communication unit 322 generates a transmission request signal for requesting the concentrator 2 to transmit a reply confirmation signal. The transmission request signal includes a terminal number for identifying each terminal 3. Next, the communication unit 322 controls the communication device 34 to transmit the transmission request signal to the concentrator 2 by wireless communication. Here, a case will be described in which this wireless communication is performed as single-hop communication in which the terminal 3 directly transmits a signal to the concentrator 2, but the present embodiment is not limited to this example, and can be applied to, for example, the last hop in which a signal is transmitted from any terminal 3 to the concentrator 2 in multi-hop communication via another terminal 3. After step S24, the processing of the terminal 3 proceeds to step S27 in FIG. 6. In the example shown in Figure 7, among the multiple terminals 3, terminals 3A, 3B, and 3C that receive components of the main lobe 81 or side lobe 82 and have data to transmit transmit a transmission request signal, while other terminals 3D, 3E, etc. do not transmit a transmission request signal.

[0038] In step S25, the communication unit 222 of the concentrator 2 shown in FIG. 2 extracts the terminal 3 that has transmitted the received transmission request signal as an extracted terminal, stores the terminal number included in the received transmission request signal, and establishes a link. More specifically, the communication unit 222 first extracts, as an extracted terminal, a terminal 3 that has successfully received the number request signal transmitted by the concentrator 2 and transmitted the transmission request signal that the concentrator 2 has successfully received, among the multiple terminals 3 arranged in the area 9. Here, the communication unit 222 determines that the number request signal has been successfully received when the attempt to demodulate the number request signal is successful. The communication unit 222 attempts to demodulate the number request signal in each of multiple reception beam directions. The reception beam direction is the direction in which the reception performance of the array antenna 240 is maximized, and represents the direction of the main lobe of the radiation pattern obtained when a signal having an arbitrary combination of amplitude and phase is input to each of the multiple antenna elements provided in the array antenna 240. As an example, the candidate of the reference beam direction determined in step S1 of FIG. 4 may be used as the reception beam direction. As shown in Fig. 5A and Fig. 5B, when the beam direction 80 is rotated by 36 degrees, there are a total of 10 types of candidates for the reference beam direction. The communication unit 222 calculates a virtual signal when a transmission request signal is received from each of the reference beams included in the candidates based on a combination of the amplitude and phase of the signal input to each antenna element corresponding to each of the multiple candidates, and attempts to demodulate each of the calculated virtual signals. However, the above-mentioned receiving beam direction is merely an example and does not limit the present embodiment. As another example of the receiving beam direction, a receiving beam direction may be selected one by one in order from a group of receiving beam directions prepared in advance.

[0039] Next, the communication unit 222 stores the terminal number included in the transmission request signal received from each extracted terminal in the data storage unit 232 of the storage device 23 shown in FIG. 2 as information for identifying the extracted terminal. Here, the terminal number is stored in the data storage unit 232 in association with the number of the candidate reference beam used when the demodulation of the virtual signal corresponding to the transmission request signal is successful. Note that, for a transmission request signal transmitted from the same terminal 3, if the demodulation of the virtual signal is successful using a plurality of reference beam candidates, the candidate reference beam direction with the maximum RSSI (Received Signal Strength Indicator) may be selected and associated with the terminal number. In the examples shown in FIG. 7, FIG. 8, and FIG. 9, the maximum RSSI is obtained for the transmission request signal transmitted by the terminal 3A in the beam direction of the main lobe 81 shown in FIG. 7. Also, the maximum RSSI is obtained for the transmission request signal transmitted by the terminal 3B in the beam direction of the main lobe 81 shown in FIG. 8. Furthermore, the maximum RSSI is obtained for the transmission request signal transmitted by the terminal 3C in the beam direction of the main lobe 81 shown in FIG. 9. In this case, the communication unit 222 of the concentrator 2 shown in Figure 2 calculates, based on the received signals received for each antenna element of the array antenna 240 and the combination of amplitude and phase of the signals corresponding to the beam directions of the main lobe 81 shown in each of Figures 7, 8, and 9, a virtual signal when the transmission request signals received from the terminals 3A, 3B, and 3C are received from the beam directions of the main lobe 81 shown in each of Figures 7, 8, and 9, as the transmission request signals received from the terminals 3A, 3B, and 3C.

[0040] As a result of successful transmission and reception of the number request signal and the transmission request signal between the concentrator 2 and each of the extracting terminals, a link is established between the concentrator 2 and each of the extracting terminals. After step S25, the process of the concentrator 2 proceeds to step S26 in FIG.

[0041] In step S26, the communication unit 222 of the concentrator 2 shown in Fig. 2 notifies each extracted terminal that it has received the transmission request signal in response to the transmission request signal received from the extracted terminal extracted in step S25, and transmits a reply confirmation signal in the reference beam direction to each extracted terminal to request data transmission. Here, the reply confirmation signal includes a terminal number for identifying each extracted terminal. After step S26, the process of the concentrator 2 proceeds to step S3 in Fig. 4.

[0042] In step S27, the communication unit 322 of each terminal 3 shown in FIG. 3 judges whether or not a reply confirmation signal including the terminal number of each terminal 3 has been received from the concentrator 2 after a predetermined time has elapsed since the transmission of the transmission request signal in step S24 in FIG. 6. If the reply confirmation signal has been received (YES) as a result of the judgment, the processing of the terminal 3 proceeds to step S3 in FIG. 4. If the reply confirmation signal has not been received (NO) as a result of the judgment, the processing of the terminal 3 returns to step S21 in FIG. 6. More specifically, the terminal 3 that has failed to receive the reply confirmation signal returns to a state of waiting for the reception of the next number request signal from the concentrator 2. However, the processing of executing step S24 again after returning to step S23 after step S21 may be limited in order to suppress interference with other terminals 3 that may occur when transmitting a transmission request signal. As an example, the number of times of transmitting the transmission request signal in step S24 from the reception of the number request signal in step S23 in FIG. 6 until the reception of the next number request signal may be limited to a predetermined number of times (for example, six times). Furthermore, even if the result of the determination is that a reply confirmation signal has not been received, the probability of executing step S24 from the second time onwards each time a number request signal is received may be limited to a predetermined value (e.g., 50%). These limitations may be made, for example, in accordance with the IRDT protocol. In either case, if the result of the determination is that a reply confirmation signal has not been received and the process does not return to step S24, the process of terminal 3 may proceed to step S36 in Fig. 10, and terminal 3 may transition to an intermittent state. Details of the intermittent state will be described later.

[0043] The process of step S3 in Fig. 4 will be described in more detail with reference to the sequence diagram of Fig. 10. When step S3 starts, the terminal 3 executes step S31 in Fig. 10, and the concentrator 2 executes step S32.

[0044] In step S31, the communication unit 322 of the terminal 3 shown in Fig. 3 transmits a data signal to the concentrator 2. More specifically, the communication unit 322 of an extracting terminal among the multiple terminals 3 that has established a link with the concentrator 2 generates a data signal including the terminal number of each extracting terminal and data as a result of the measurement process, and transmits the data signal to the concentrator 2 by wireless communication as described above. After step S31, the process of the terminal 3 proceeds to step S34 in Fig. 10.

[0045] In step S32, the communication unit 222 of the concentrator 2 shown in FIG. 2 judges whether or not it has received a data signal from the extracting terminal. More specifically, the communication unit 222 calculates a virtual data signal when it is received from a candidate reference beam direction corresponding to the data signal transmitted by each extracting terminal, based on the received signal received by each antenna element of the array antenna 240 and a combination of amplitude and phase corresponding to the receiving beam direction stored in association with each extracting terminal. When the communication unit 222 succeeds in demodulating the calculated virtual data signal, it judges that it has successfully received a data signal corresponding to the virtual data signal. If the result of the judgment is that a data signal has not been received (NO), the processing of the concentrator 2 returns to step S32 in FIG. 10. If the result of the judgment is that a data signal has been received (YES), the processing of the concentrator 2 proceeds to step S33 in FIG. 10. In other words, the communication unit 222 of the concentrator 2 repeatedly executes step S32 until it receives a data signal transmitted by one or more or all of the extracting terminals, or until a predetermined time has elapsed since the first execution of step S32. If the data signal is not successfully received even after a predetermined time has elapsed, the process of the concentrator 2 may return to step S1 in FIG.

[0046] In step S33, the communication unit 222 of the concentrator 2 shown in Fig. 2 transmits a data confirmation signal to notify the extracting terminal that it has received the data signal transmitted from the extracting terminal. More specifically, the communication unit 222 transmits a data confirmation signal including the terminal number of the extracting terminal that transmitted the received data signal in the reference beam direction. After step S33, the process of the concentrator 2 proceeds to step S35 in Fig. 10.

[0047] In step S34, the communication unit 322 of the terminal 3 shown in FIG. 3 judges whether or not it has received a data confirmation signal. More specifically, the communication unit 322 of each extracting terminal judges whether or not it has received a data confirmation signal including the terminal number of each extracting terminal. If the result of the judgment is that the data confirmation signal has been received (YES), the processing of the terminal 3 proceeds to step S36 of FIG. 10. If the result of the judgment is that the data confirmation signal has not been received (NO), the processing of the terminal 3 returns to step S31 of FIG. 10. However, the processing of returning to step S31 may be limited in order to suppress interference with other terminals 3 that may occur when transmitting a data signal. As an example, the number of times that the data signal is transmitted in step S31 of FIG. 10 may be limited to a predetermined number of times from the reception of a number request signal in step S22 of FIG. 6 until the reception of the next number request signal. This limitation may be performed, for example, in accordance with the IRDT protocol. In either case, if the determination result shows that the data confirmation signal has not been received and the process does not return to step S31, the process of the terminal 3 may proceed to step S36 in Fig. 10, and the terminal 3 may transition to an intermittent state. The intermittent state will be described in detail later.

[0048] In step S35, the communication unit 222 of the concentrator 2 shown in FIG. 2 outputs the aggregated data signal to the outside. More specifically, the communication unit 222 stores the data represented by the data signal received from the terminal 3 in the data storage unit 232 of the storage device 23 shown in FIG. 2, and transmits the stored data to an external server or the like at a predetermined timing. After step S35, the processing of the concentrator 2 returns to step S1 in FIG. 4. As an example, the communication unit 222 may transmit aggregated data to the outside in a period from when the communication unit 222 transmits a number request signal to a certain beam direction 80 in step S21 in FIG. 6 until when the communication unit 222 transmits a number request signal to another beam direction 80 in step S21 in FIG. 6 that is executed next. As another example, the communication unit 222 may transmit aggregated data to the outside in a period from when the communication unit 222 transmits a number request signal to a certain beam direction ... a different beam direction 80 by repeatedly executing step S21 in FIG. 6 for different beam directions 80, and transmits aggregated data to the outside in a period from when the communication unit 222 transmits a number request signal to a certain beam direction in step S21 in FIG. 6 until when the beam direction 80 makes a full circle and the communication unit 222 transmits a number request signal to the first beam direction 80 again.

[0049] In step S36, the communication unit 322 of the terminal 3 shown in Fig. 3 transitions the terminal 3 to an intermittent state. More specifically, regardless of whether the transmission of the data signal has been successful or not, the terminal 3 deletes the data stored in the data storage unit 232, and transitions to an intermittent state in which the power consumption of the terminal 3 is suppressed until the next time a number request signal is received or the next time a measurement process is executed. After step S36, the process of the terminal 3 returns to step S1 in Fig. 4.

[0050] Thereafter, by repeating each process of steps S1 to S3 in FIG. 4 and sequentially selecting the multiple candidate beam directions 80 illustrated in FIG. 5A and FIG. 5B as the reference beam direction, data signals can be concentrated in the concentrator 2 from each of the multiple terminals 3 located in the area 9.

[0051] As described above, according to this embodiment, the concentrator 2 utilizes beamforming to limit the terminals 3 with which a link is established at one time, thereby making it possible to suppress the generation of interference power and the effects of propagation loss.

[0052] Second embodiment The communication system 1, concentrator 2, and terminal 3 according to this embodiment are configured in the same manner as in the first embodiment shown in Figures 1, 2, and 3. The communication method according to this embodiment is obtained by making the following changes to the communication method according to the first embodiment. Hereinafter, detailed explanations of parts of this embodiment that are common to the first embodiment may be omitted.

[0053] In the first embodiment, a configuration was described in which, in step S26 of FIG. 6, the communication unit 222 of the concentrator 2 shown in FIG. 2 transmits a reply confirmation signal to the extracted terminal in the reference beam direction determined in step S1 of FIG. 4. In this embodiment, as a modification of this configuration, beamforming is performed by setting a combination obtained by synthesizing the combination of amplitude and phase of signals corresponding to the beam direction 80 stored in association with the terminal number of each extracted terminal when a transmission request signal is received in step S25 of FIG. 6 for a plurality of extracted terminals. This synthesis is easily performed by calculating the sum of complex weighting matrices representing the combination of amplitude and phase, and normalizing the signal strength of this sum. As a result, a radiation pattern 8 having a plurality of main lobes 81 corresponding to each of the synthesized combinations is obtained. The communication unit 222 transmits a reply confirmation signal to a plurality of beam directions 80 included in the radiation pattern 8 obtained in this way. In this embodiment, by doing so, it is expected that the success rate of each extracted terminal receiving a reply confirmation signal can be increased.

[0054] In the first embodiment, a configuration was described in which, in step S33 in Fig. 10, the communication unit 222 of the concentrator 2 shown in Fig. 2 transmits a data confirmation signal to the extracting terminal in the reference beam direction determined in step S1 in Fig. 4. In this embodiment, as a modification of this configuration, similar to the case of transmitting a return confirmation signal, the communication unit 222 transmits the data confirmation signal in multiple beam directions 80 included in the radiation pattern 8 having multiple main lobes 81 respectively corresponding to the multiple combined combinations. In this embodiment, by doing so, it is expected to have the effect of increasing the success rate of each extracting terminal receiving the data confirmation signal.

[0055] As described above, according to this embodiment, by transmitting a reply confirmation signal and a data confirmation signal in multiple beam directions 80 corresponding to multiple extracted terminals, respectively, it is expected that the success rate of the extracted terminal receiving these signals can be increased.

[0056] (Third embodiment) The communication system 1, concentrator 2, and terminal 3 according to this embodiment are configured in the same manner as in the first embodiment shown in Figures 1, 2, and 3. The communication method according to this embodiment is obtained by making the following changes to the communication method according to the first embodiment. Hereinafter, detailed explanations of parts of this embodiment that are common to the first embodiment may be omitted.

[0057] In the first embodiment, a configuration has been described in which the communication unit 222 of the concentrator 2 shown in FIG. 2 transmits a reply confirmation signal to be transmitted to the extracting terminal in the reference beam direction in step S26 of FIG. 6 each time it determines a reference beam direction in step S1 of FIG. 4, calculates a received data signal in step S32 of FIG. 10 as a virtual data signal when received from the beam direction 80 corresponding to each extracting terminal, and transmits a reply confirmation signal to be transmitted to the extracting terminal in the reference beam direction in step S33 of FIG. 10.

[0058] In this embodiment, as a modification of this configuration, the communication unit 222 transmits a reply confirmation signal in the beam direction 80 corresponding to each extracted terminal in step S26 of Fig. 6 for each extracted terminal, calculates the received data signal as a virtual data signal when received from the beam direction 80 corresponding to each extracted terminal in step S32 of Fig. 10, and transmits a reply confirmation signal in the reference beam direction in the beam direction 80 corresponding to each extracted terminal in step S33 of Fig. 10. In other words, in this embodiment, the communication unit 222 of the concentrator 2 shown in Fig. 2 repeatedly executes the processes from step S26 of Fig. 6 to step S33 of Fig. 10 once for each extracted terminal.

[0059] In this embodiment, by doing so, it is expected that the success rate of each extracting terminal receiving the reply confirmation signal and the data confirmation signal can be increased. Furthermore, in this embodiment, since each extracting terminal transmits a data signal after receiving a reply confirmation signal including its own terminal number, one extracting terminal transmits a data signal at a time, which is expected to increase the success rate of the concentrator 2 receiving a data signal from each extracting terminal.

[0060] (Simulation results) The inventors performed a computer simulation under the same conditions to compare the average PDR (Packet Delivery Ratio) of the communication system 1 in each of the above-mentioned first, second and third embodiments. Here, the PDR is a ratio obtained by dividing the total number of packets aggregated by the concentrator 2 by the total number of packets generated by the terminal 3. As a further comparison object, a computer simulation under the same conditions was also performed for a communication system including a concentrator in which the beamforming array antenna 240 is replaced with an omnidirectional antenna.

[0061] In this computer simulation, SINR (Signal-to-Interference-plus-Noise Power Ratio) is used instead of RSSI as a criterion for determining the optimal candidate beam direction 80 for transmitting and receiving signals for each extracted terminal. SINR is calculated as the ratio of received signal power divided by the sum of interference power and noise power. More specifically, for each extracted terminal, a candidate beam direction 80 is selected that has a maximum SINR that is equal to or greater than a threshold (e.g., 6 dB).

[0062] The specifications of this computer simulation are as shown in the table in FIG. 11. In particular, a total of 21 omnidirectional antenna elements of the array antenna 240 were installed at equal intervals around a circle with a radius of 0.5 m. For beamforming by the array antenna 240, a Dolph-Chebyshev array was used in which the levels of all side lobes 82 were equal and the level difference between the main lobe 81 and each side lobe 82 was 40 dB. The shape of the radiation pattern 8 was made the same for transmission and reception as seen from the concentrator 2, and normalization was performed so that the transmission power was constant. The Mersenne Twister method was used to randomly arrange multiple terminals 3 in the area 9. After the start of the packet aggregation process, the beam direction 80 was rotated counterclockwise from the 0° direction by 36° as viewed from above each time step S1 in FIG. 4 was executed. During the preparation period of 30 minutes from the start of the process, the packets aggregated by the concentrator 2 were discarded.

[0063] The results of a computer simulation performed under the above conditions are shown in the table in Fig. 12. It was confirmed that the communication systems 1 according to the first, second and third embodiments achieved a better PDR than the non-directional communication system 1 to be compared.

[0064] Although the invention made by the inventor has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and it goes without saying that various modifications can be made without departing from the gist of the invention. Furthermore, the respective features described in the embodiment can be freely combined within the scope of technical compatibility. [Explanation of symbols]

[0065] 1. Communication Systems 2 Concentrator 21 Bus 22 Arithmetic unit 221 Beam Control Unit 222 Communications Department 23 Storage device 230 Recording media 231 Program Memory Unit 232 Data storage unit 24 Communication Equipment 240 Array Antenna 25 Input / Output Devices 3, 3A, 3B, 3C, 3D, 3E terminal 31 Bus 32 Arithmetic unit 321 Measuring part 322 Communications Department 33 Storage device 330 Recording media 331 Program Memory Unit 332 Data Storage Unit 34 Communication Equipment 340 Antenna 35 Sensor device 8 Radiation Pattern 80 Beam Direction 81 Main Lobe 82 Side Lobe 9 areas

Claims

1. A plurality of terminals each transmitting a data signal by wireless communication; a concentrator for receiving and consolidating the data signals; Equipped with The concentrator comprises: An array antenna that transmits and receives signals in a beam direction set by beamforming; A beam control unit that controls the beam direction; a communication unit that transmits a number request signal requesting each terminal number to the plurality of terminals by broadcast communication in a first beam direction, extracts a terminal that has succeeded in the transmission and reception in the first beam direction from among the plurality of terminals as an extracted terminal, and establishes a link with the extracted terminal; Equipped with Each of the plurality of terminals Transmitting the data signal after the link is established Communication systems.

2. 2. The communication system according to claim 1, The array antenna comprises: Multiple Antenna Elements Equipped with the beam control unit performs the beamforming in the beam direction by setting a combination of amplitudes and phases of signals input to the plurality of antenna elements; The communication unit is Based on the combination and received signals of the data signals transmitted by the plurality of terminals and received by the plurality of antenna elements, a virtual data signal when the data signals are received from the beam direction corresponding to the combination is aggregated as the data signal. Communication systems.

3. 3. The communication system according to claim 2, The communication unit is extracting, as the extracted terminal, a terminal that transmitted a transmission request signal that was successfully received in any one of the beam directions from among the plurality of terminals that transmitted a transmission request signal in response to the number request signal; storing, for each of the extracted terminals, the combination corresponding to the beam direction in which the transmission request signal is successfully received; Transmitting a reply confirmation signal in the first beam direction to the extracting terminal requesting the data signal; For each of the extracting terminals, the virtual data signal when the data signal is received in the beam direction corresponding to the stored combination is aggregated as the data signal of each of the extracting terminals. Communication systems.

4. 4. The communication system according to claim 3, When the communication unit has succeeded in receiving the transmission request signal transmitted from the same extracted terminal in a plurality of the beam directions, the communication unit aggregates, as the data signal, the virtual data signal when the data signal is received in a beam direction in which the received signal strength of the transmission request signal is maximum among the plurality of beam directions. Communication systems.

5. 4. The communication system according to claim 3, The communication unit transmits, in the first beam direction, a data confirmation signal notifying the extracting terminal that the data signal has been successfully received. Communication systems.

6. 3. The communication system according to claim 2, The communication unit is extracting, as the extracted terminal, a terminal that transmitted a transmission request signal that was successfully received in any one of the beam directions from among the plurality of terminals that transmitted a transmission request signal in response to the number request signal; storing, for each of the extracted terminals, the combination corresponding to the beam direction in which the transmission request signal is successfully received; Transmitting a reply confirmation signal requesting the data signal to the extracting terminal in a composite beam direction formed by setting a composite combination obtained by combining combinations of the transmission request signals that have been successfully received; For each of the extracting terminals, the virtual data signal when the data signal is received in the beam direction corresponding to the stored combination is aggregated as the data signal of each of the extracting terminals. Communication systems.

7. 7. The communication system according to claim 6, When the communication unit has succeeded in receiving the transmission request signal transmitted from the same extracted terminal in a plurality of the beam directions, the communication unit selectively combines a beam direction in which the received signal strength of the transmission request signal is maximum among the plurality of beam directions to set the combined combination. Communication systems.

8. 7. The communication system according to claim 6, The communication unit transmits a data confirmation signal in the composite beam direction to notify the extracting terminal that the data signal has been successfully received. Communication systems.

9. 3. The communication system according to claim 2, The communication unit is extracting, as the extracted terminal, a terminal that transmitted a transmission request signal that was successfully received in any one of the beam directions from among the plurality of terminals that transmitted a transmission request signal in response to the number request signal; storing, for each of the extracted terminals, the combination corresponding to the beam direction in which the transmission request signal is successfully received; For each of the stored combinations, in a beam direction corresponding to the combination, a reply confirmation signal is transmitted to the extracting terminal requesting the data signal, the data signal transmitted by the extracting terminal is received and collected, and a data confirmation signal is transmitted to the extracting terminal notifying the extracting terminal that the data signal has been successfully received. Communication systems.

10. An array antenna that transmits and receives signals in a beam direction set by beamforming; A beam control unit that controls the beam direction; a communication unit that transmits a number request signal requesting each terminal number to a plurality of terminals by broadcast communication in a first beam direction, extracts a terminal that has succeeded in the transmission and reception in the first beam direction from among the plurality of terminals as an extracted terminal, establishes a link with the extracted terminal, and receives and aggregates data signals transmitted from the plurality of terminals after the link is established; Equipped Concentrator.

11. a concentrator transmitting number request signals requesting terminal numbers of the respective terminals to a plurality of terminals by broadcast communication in a first beam direction set by beamforming; The concentrator extracts, from among the plurality of terminals, a terminal that has succeeded in transmitting and receiving in the first beam direction as an extracted terminal; said concentrator establishing a link with said extraction terminal; each of the plurality of terminals transmitting a data signal by wireless communication after the link is established; the concentrator receiving and concentrating the data signals; Includes Communication methods.

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