Receiver, transmitter, communication system, and communication method

Abstract

A receiver (20) receives packets respectively transmitted from a plurality of transmitters via wireless communication. The receiver (20) comprises: a communication unit (43) that receives, from any of a plurality of transmitters, a radio wave transmitting first partial data constituting a packet at a time interval from other radio waves transmitting other partial data constituting said packet by being consecutive to the aforementioned partial data; a storage unit (45) that stores a correspondence relationship between each transmitter and a frequency representation of the radio wave received from that transmitter; and an identification unit (44) that identifies the transmitter that transmitted the radio wave from the frequency representation of the radio wave received by the communication unit (43) and on the basis of the correspondence relationship. The receiver (20) contributes to monitoring by wireless communication.

Description

Receiver, transmitter, communication system, and communication method

[0001] The present disclosure relates to a receiver, a transmitter, a communication system, and a communication method.

[0002] In factory automation (FA) sites, multiple sensors are installed to monitor ongoing processes, operating equipment, the environment, and other conditions. If the sensor's sensing results are transmitted wirelessly, the sensing results can be collected without the need for wiring. Furthermore, because such wireless communication typically requires power, transmitters equipped with sensors are often connected to a power line or are battery-powered. In contrast, if transmitters are powered by power generated by energy harvesting, which has been gaining attention in recent years, this can eliminate the need for wiring power lines and the cumbersome task of managing and replacing batteries that deteriorate over time.

[0003] When wireless communication is performed using energy harvesting, it is necessary to reduce the size of transmitted packets. Here, if a technology for identifying a slave station by its unique frequency is used to identify radio waves transmitted from a transmitter, it becomes unnecessary to insert a sender ID (identifier) ​​into the packet, and it becomes possible to reduce the packet size (see, for example, Patent Document 1).

[0004] Japanese Patent Application Publication No. 7-327000

[0005] However, when wireless communication is performed using energy harvesting, it takes a certain amount of time for the capacitor to store the power required to transmit a packet. For example, in Bluetooth (registered trademark), a representative standard for low-power wireless communication, the minimum packet size is 8 bits, and transmission and reception are performed in packets. Therefore, the transmitter must store enough power to transmit at least 8 bits of data before starting transmission. Furthermore, the time required to transmit a packet increases, especially when the packet size is large.

[0006] If it takes time for a packet to start transmitting, the operating status of the transmitter is unknown to the receiver until the packet is received, which may delay the process of correcting the transmitter's communication failure. While the receiver may be able to perform processing using only a portion of the information to be transmitted by the packet, such processing must wait until all information is received before it can be performed. Therefore, there is room for improving the convenience of wireless communication using energy harvesting.

[0007] The present disclosure has been made in light of the above-mentioned circumstances, and aims to improve the convenience of wireless communication using energy harvesting.

[0008] In order to achieve the above object, the receiver of the present disclosure is a receiver that receives packets transmitted by wireless communication from multiple transmitters, and is equipped with a receiving means that receives partial radio waves that transmit partial data that constitute a packet from one of the multiple transmitters, with a time interval between the partial data and other partial radio waves that transmit other partial data that constitute the packet by being consecutive to the partial data, a storage means that stores the correspondence between each transmitter and the frequency representation of the radio waves received from the transmitter, and an identification means that identifies the transmitter that transmitted the partial radio waves based on the correspondence from the frequency representation of the partial radio waves received by the receiving means.

[0009] According to the present disclosure, it is possible to improve the convenience of wireless communication through energy harvesting.

[0010] FIG. 1 is a diagram showing the configuration of a communication system according to the first embodiment. FIG. 2 is a diagram for explaining the transmission of radio waves according to the first embodiment. FIG. 3 is a diagram showing the functional configuration of a receiver according to the first embodiment. FIG. 4 is a diagram for explaining the registration phase according to the first embodiment. FIG. 5 is a diagram for explaining the operation phase according to the first embodiment. FIG. 6 is a diagram for explaining time assignment according to the first embodiment.

[0011] Hereinafter, a communication system according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0012] Embodiment 1. A communication system 1000 according to this embodiment is a system that transmits sensing results from a plurality of sensors via wireless communication using power obtained by energy harvesting in a facility such as a factory or a plant, and collects the sensing results. Packets indicating the sensing results are not transmitted on a packet-by-packet basis, but are divided into partial data that constitute the packets and then transmitted. Specifically, each time power for transmitting partial data of 1 bit size is accumulated, the partial data is transmitted.

[0013] As shown in FIG. 1, the communication system 1000 includes a plurality of transmitters 10 that transmit radio waves, a receiver 20 that receives radio waves from the plurality of transmitters 10, and a display 30 that displays information received by the receiver 20.

[0014] The transmitter 10 is, for example, a flat tag measuring 1 cm on each side and 1 mm thick. The transmitter 10 includes a power generation unit 11 that generates power by energy harvesting and stores the generated power, a sensor 12 that measures the environmental state of the transmitter 10, a sensor data storage unit 13 that stores the results of measurements by the sensor 12, a control unit 14 that controls the components of the transmitter 10, a memory 15 that temporarily stores data to be transmitted to the receiver 20, and a communication unit 16 that transmits radio waves for transmitting the data to an antenna 17.

[0015] The power generation unit 11 includes a power generation element that generates power from light, heat, vibrations, or electromagnetic waves in the environment of the transmitter 10, and a capacitor that stores the power generated by the power generation element. The power generation element may generate power from sunlight or lighting. Alternatively, the transmitter 10 may be attached to a heat-generating device, and the power generation element may generate power from the heat generated by the device. Alternatively, the transmitter 10 may be attached to a vibrating machine, and the power generation element may generate power from the vibrations of the machine. The power generation element may generate power from vibrations caused by sound waves propagating in the installation environment of the transmitter 10. Alternatively, the power generation element may generate power from electromagnetic waves propagating in the installation environment of the transmitter 10. The power generation efficiency of the power generation element is, for example, 100 microwatts, 1 milliwatt, or 10 milliwatts. The power generated by the power generation unit 11 is provided to each component of the transmitter 10. Specifically, the power generated and stored by the power generation unit 11 is consumed to transmit partial data each time a predetermined threshold is exceeded, as shown in the graph at the top of FIG. 2 . The power generation unit 11 corresponds to an example of a power generation means that generates power from light, heat, vibration, or electromagnetic waves in the environment.

[0016] The sensor 12 measures the physical state of the environment of the transmitter 10. For example, the sensor 12 may measure pressure, flow velocity, temperature, illuminance, humidity, acceleration, current, voltage, magnetism, or the concentration of a specific component in a fluid, or may measure other conditions. The sensor 12 outputs the measurement results to the control unit 14. Note that although FIG. 1 shows that the sensor 12 receives power from the power generation unit 11, the sensor 12 may operate without consuming power.

[0017] The sensor data storage unit 13 includes, for example, a Ferroelectric Random Access Memory (FeRAM). The sensor data storage unit 13 acquires and stores the results of measurements taken by the sensor 12 from the control unit 14, and provides the stored measurement results to the control unit 14 in response to a request from the control unit 14. The sensor data storage unit 13 may accumulate multiple measurement results, or may store only the most recent measurement result.

[0018] The control unit 14 includes a processor as a processing circuit. The control unit 14 stores the measurement results obtained from the sensor 12 in the sensor data storage unit 13. The control unit 14 also generates a packet including the measurement results to be transmitted to the receiver 20 and stores the generated packet in the memory 15. When the amount of power stored in the power generation unit 11 exceeds a threshold value required to transmit partial data constituting a packet, the control unit 14 causes the communication unit 16 to transmit the partial data. As shown at the top of FIG. 2 , a packet is a series of bit values, and partial data is 1-bit data.

[0019] The memory 15 includes, for example, an FeRAM. The memory 15 may be the same storage element as the sensor data storage unit 13, or may be a different storage element. The memory 15 is a first-input, first-output (FIFO) memory. The control unit 14 stores the bit values ​​constituting the packet in order from the beginning in the memory 15, and the communication unit 16 reads out the values ​​one bit at a time.

[0020] The communication unit 16 is a processing circuit integrated with a flat antenna 17. The communication unit 16 reads one bit of partial data from the memory 15 at a timing instructed by the control unit 14, modulates a carrier wave with the partial data, and transmits radio waves transmitting the partial data from the antenna 17. The frequency band of the radio waves is, for example, the 900 MHz band or the 2.4 GHz band. Because the power generation efficiency of the power generation unit 11 is lower than the power consumed to continuously and steadily emit radio waves, the communication unit 16 transmits radio waves intermittently. Specifically, a time interval occurs between the transmission of radio waves by the communication unit 16 for transmitting one piece of partial data and the transmission of radio waves corresponding to the previous and next pieces of partial data, as shown in FIG. 2 .

[0021] The length of this time interval is determined by the power generation efficiency of the power generation unit 11, the designed radio wave strength, and the calculation processing by the control unit 14. However, the length of the time interval is at least longer than the transmission time of radio waves that transmit one bit of data. Therefore, when a device receiving the radio waves performs reception processing assuming that a series of bit values ​​corresponding to one packet has been transmitted by continuous radio waves, the data will be treated as if one or more bits are missing.

[0022] 2, radio waves transmitted from transmitter 10 are received at time intervals by receiver 20. However, due to environmental factors including diffraction of radio waves in the environment in which communication system 1000 is constructed, movement of at least one of transmitter 10 and receiver 20, and reflection by other moving objects, the radio waves received by receiver 20 vary from the radio waves transmitted by transmitter 10. Based on such variations in frequency characteristics, receiver 20 identifies transmitter 10 that transmitted the radio waves, as will be described later.

[0023] 1 , the receiver 20 may be a device dedicated to communication, an industrial PC (Personal Computer), or other device. While the transmitter 10 operates on power obtained by energy harvesting, the receiver 20 may operate on power supplied from an external source or on battery power. The receiver 20 corresponds to an example of a receiver that receives packets transmitted by wireless communication from each of the multiple transmitters 10.

[0024] The receiver 20 has a communication unit 22 that receives radio waves from the transmitter 10 via an antenna 21, a control unit 23 that controls the components of the receiver 20, a memory unit 24 that stores information, and an I / F (Interface) unit 25 for communicating with an external display 30.

[0025] The communication unit 22 is a processing circuit that is configured integrally with the antenna 21. The communication unit 22 outputs the waveform of the radio wave received by the antenna 21 to the control unit 23.

[0026] The control unit 23 includes a processor as a processing circuit. The control unit 23 performs arithmetic processing on the waveform of the radio wave received by the communication unit 22 and stores the arithmetic results in the storage unit 24. The control unit 23 also performs arithmetic processing on the data stored in the storage unit 24 and outputs information indicating the arithmetic results to the I / F unit 25.

[0027] The storage unit 24 includes at least one of a volatile memory such as a RAM and a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). The storage unit 24 stores information provided by the control unit 23 and provides the stored information to the control unit 23 in response to a request from the control unit 23.

[0028] The I / F unit 25 includes a network interface circuit for communicating via the network NW, and transmits information output from the control unit 23 to the display device 30 via the network NW.

[0029] The display 30 is a user interface terminal such as an industrial PC. The display 30 receives information from the receiver 20 via the network NW and presents the received information to the user of the display 30.

[0030] Fig. 3 shows the functional configuration of the receiver 20. As shown in Fig. 3, the receiver 20 has, as its functions, a registration unit 41 that registers the frequency representation of radio waves received when each bit value is transmitted from each transmitter 10, an instruction unit 42 that instructs the transmitter 10 to change the frequency to be used, a communication unit 43 that receives radio waves from the transmitter 10, an identification unit 44 that identifies the transmitter 10 that transmitted the radio waves and the bit value transmitted by the radio waves, a storage unit 45 that stores various information, a restoration unit 46 that restores a packet from the identified bit value, and a time assignment unit 47.

[0031] The registration unit 41 is mainly realized by the control unit 23. The registration unit 41 registers, in the correspondence table 451 of the storage unit 45, frequency representations of radio waves transmitted from each transmitter 10 via different transmission characteristics due to the environment of the communication system 1000 at the time of reception. Specifically, as shown in FIG. 4 , in the registration phase, the first transmitter and the second transmitter, which are examples of the transmitter 10, sequentially transmit radio waves carrying a registration packet, and the communication unit 43 receives the radio waves. The registration packet includes a sender ID for identifying the transmitter 10 and predetermined initialization data having at least one bit value that is zero and one bit value that is one. This initialization data is common to the transmitter 10 and the receiver 20 and is known to the registration unit 41. The registration unit 41 extracts waveforms corresponding to each bit value constituting the initialization data from the waveform of the received radio waves and obtains frequency representations for each bit by fast Fourier transform. The registration unit 41 then registers, for each transmitter 10, the frequency representation at the time of receiving radio waves that transmit each bit value in the correspondence relationship table 451. When a radio wave corresponding to one bit is received in the operation phase, the correspondence relationship table 451 is used to identify the transmitter 10 that is the source of the radio wave and the bit value transmitted by the radio wave.

[0032] The frequency representations registered in the correspondence table 451 are the frequencies and intensities of multiple frequency components that constitute radio waves. If each transmitter 10 transmits radio waves with a different peak frequency and each transmitter 10 can still be identified based on the transmission characteristics up to the receiver 20, the transmitter 10 may be identified by determining the peak frequency. However, as the number of transmitters 10 increases, the task of assigning different peak frequencies to each transmitter 10 and setting them to transmit radio waves of the assigned frequencies becomes complicated. For this reason, even if the frequencies of radio waves transmitted from two or more transmitters 10 are the same, it is preferable to identify the transmitter 10 using characteristics other than the peak frequency among the information indicated by the frequency spectra at the time of reception that have become different due to transmission characteristics.

[0033] Note that, although the following description focuses on an example in which the frequencies and intensities of multiple frequency components are treated as frequency representations to be registered in the correspondence table 451, the frequency representation is not limited to this. For example, a frequency representation including a phase may be registered in the correspondence table 451, or an envelope of the intensity distribution may be registered.

[0034] 4 may be realized by an operator operating each transmitter 10 to transmit a registration packet, or may be started by receiving a start instruction via wireless communication from the receiver 20. When the operation of the transmitter 10 is started by a start instruction, each transmitter 10 may transmit a registration packet at a timing based on a unique serial number that is stored in advance in the transmitter 10 itself. The registration unit 41 corresponds to an example of a registration means that registers the frequency representation of the received radio waves in a storage means when each transmitter 10 sequentially transmits radio waves.

[0035] 3 , the instruction unit 42 is mainly realized by the control unit 23. When the frequency representations to be registered in the correspondence table 451 by the registration unit 41 are equivalent for two transmitters 10, the instruction unit 42 instructs at least one of these two transmitters 10 via wireless communication to change the frequency of the radio waves to be transmitted. Here, the fact that the frequency representations are equivalent means that it is not possible to determine which transmitter 10 is the source of the transmission, or that the probability of erroneous determination is higher than a predetermined threshold, or that the similarity indicating the degree to which the frequency representations are similar is higher than a predetermined threshold.

[0036] The instruction unit 42 may simply instruct to change the frequency, or may specify a new frequency. The new frequency is preferably a frequency at which a new frequency representation different from the frequency representations already registered in the correspondence table 451 is expected to be received. For example, the instruction unit 42 may specify a frequency that is not included in any of the frequency representations already registered in the correspondence table 451, or a frequency that is different from a peak in any of the frequency representations, as the new frequency. The instruction unit 42 corresponds to an example of an instruction means that instructs the first transmitter to change the frequency of the radio waves to be transmitted when the frequency representation of the radio waves received from a first transmitter among the multiple transmitters is equal to the frequency representation of the radio waves received from a second transmitter. Furthermore, the registration unit 41 corresponds to an example of a registration means that registers the frequency representation of the radio waves received from the first transmitter in a storage means after the instruction means instructs to change the frequency.

[0037] The communication unit 43 is mainly realized by the antenna 21 and the communication unit 22. In the registration phase, the communication unit 43 outputs the waveform of the received radio waves to the registration unit 41, and transmits the frequency change instruction from the instruction unit 42 to each transmitter 10. In the operation phase, the communication unit 43 intermittently receives radio waves corresponding to 1-bit partial data, and outputs the waveform of the received radio waves to the identification unit 44. The communication unit 43 corresponds to an example of a receiving means that receives, from one of the multiple transmitters, a partial radio wave transmitting partial data that constitutes a packet, at a time interval from other partial radio waves that are consecutive to the partial data and thereby transmit other partial data that constitute packets together with the partial data.

[0038] The identification unit 44 is mainly realized by the control unit 23. As shown in FIG. 5 , the identification unit 44 converts the waveform of the radio wave corresponding to one bit from each transmitter 10 into a frequency representation. The identification unit 44 also identifies the transmitter 10 that transmitted the radio wave and the bit value transmitted by the radio wave by comparing the frequency representation obtained by the conversion with the frequency representation registered in the correspondence table 451. The identification unit 44 then writes information indicating the identified transmitter 10 and bit value into the storage unit 45. The identification unit 44 corresponds to an example of an identification means that identifies the transmitter that transmitted the partial radio wave based on the correspondence from the frequency representation of the partial radio wave received by the receiving means.

[0039] The storage unit 45 is mainly realized by the storage unit 24. The storage unit 45 corresponds to an example of a storage means that stores the correspondence between each transmitter 10 and the frequency representation of the radio waves received from that transmitter.

[0040] The restoration unit 46 is mainly realized by the control unit 23. The restoration unit 46 refers to the source transmitter 10 and bit values ​​identified by the identification unit 44 and stored in the storage unit 45, and restores a packet, which is a series of bit values, from the bit values ​​transmitted consecutively at time intervals from the same transmitter 10, as shown at the bottom of FIG. 5. The restoration unit 46 then outputs the measurement results of the sensor 12 indicated by the restored packet to the time assignment unit 47. The restoration unit 46 corresponds to an example of a restoration means that restores a packet from partial data transmitted by partial radio waves that are received multiple times by the receiving means and that are consecutively identified by the identification means as having been transmitted from the same transmitter.

[0041] The time assigning unit 47 is realized mainly by cooperation between the control unit 23 and the I / F unit 25. The time assigning unit 47 assigns a time corresponding to the measurement to measurement result data indicating the result of measurement by the sensor 12, which is included in the packet restored by the restoration unit 46, as shown in Fig. 6. The time assigning unit 47 then notifies the display device 30 of the measurement result to which the time has been assigned, thereby transmitting time-series data of the measurement result to the display device 30. The time assigning unit 47 corresponds to an example of time assigning means that assigns a time to information indicated by a packet restored by the restoration means and outputs the information.

[0042] The time assigned by the time assigning unit 47 may be a value included in the packet. For example, if the transmitter 10 inserts a timestamp value indicating the timing of measurement into the packet along with the measurement result, the value may be assigned as the time by the time assigning unit 47. The assigned time may also be the result of performing a predetermined arithmetic operation on the value included in the packet. For example, if the timestamp indicates UNIX® time, the time assigning unit 47 may convert the UNIX® time into a value indicating the date and time and then assign the value to the measurement result. The time assigning unit 47 may also assign to the measurement result the time when the first bit value constituting the packet is received by the communication unit 43. The reception time assigned to the measurement result may be the time when any predetermined bit value among the bit values ​​constituting the packet is received.

[0043] The display 30 displays the progress of the measurement results to the user of the display 30 as shown in the lower part of Fig. 6. In the example of Fig. 6, the progress from the measurement result assigned with time T1 to the measurement result assigned with time T2 is displayed in a graph format.

[0044] 7 and 8, a communication process executed in the communication system 1000 will be described. This communication process corresponds to an example of a communication method executed in the communication system 1000.

[0045] In the communication process, the receiver 20 executes a registration process (step S1). In the registration process, as shown in FIG. 8, the communication unit 43 of the receiver 20 receives radio waves from one of the transmitters 10 (step S11). This radio wave carries a registration packet. Next, the registration unit 41 divides the radio waves received in step S11 into segments with time widths corresponding to 1-bit partial data, and converts the radio waves of each segment into a frequency representation (step S12).

[0046] The registration unit 41 determines whether the frequency representation obtained in step S12 is equal to any of the frequency representations already registered in the correspondence table 451 for a transmitter 10 other than the transmitter 10 that transmitted the radio waves received in step S11 (step S13). If it is determined that the frequency representations are equal (step S13; Yes), the instruction unit 42 instructs the transmitter 10 that transmitted the radio waves received in step S11 to change the frequency, and the communication unit 43 again receives the radio waves with the changed frequency from the transmitter 10 (step S14). Thereafter, the processing from step S12 onwards is repeated. As a result, a frequency representation that enables the transmitter 10 to be distinguished from other transmitters 10 as a transmission source is registered in the correspondence table 451.

[0047] If it is determined in step S13 that the frequencies are not equal (step S13; No), the registration unit 41 associates the frequency representation of the separated radio waves with the transmitter 10 that transmitted the radio waves received in step S11 and the value of the 1-bit partial data corresponding to the radio waves separated in step S12, and registers the frequency representation of the separated radio waves in the correspondence relationship table 451 (step S15). Specifically, the registration unit 41 associates the frequency and intensity of the multiple frequency components of the radio waves corresponding to the bit values ​​constituting the initialization data of the registration packet with the sender ID included in the registration packet, and registers the frequencies and intensities of the multiple frequency components of the radio waves corresponding to the bit values ​​in the correspondence relationship table 451.

[0048] Next, the registration unit 41 determines whether registration has been completed for all transmitters 10 (step S16). The registration unit 41 may make a positive determination in step S16 when frequency representations have been registered for the number of transmitters 10 designated in advance by the user of the receiver 20. Alternatively, the registration unit 41 may make a positive determination in step S16 when the length of time during which radio waves are not received from any transmitter 10 exceeds a predetermined threshold.

[0049] If it is determined that registration has not been completed for all transmitters 10 (step S16; No), the processes from step S11 onwards are repeated. As a result, the frequency representations of radio waves of transmitters 10 whose frequency representations have not yet been registered are registered. On the other hand, if it is determined that registration has been completed for all transmitters 10 (step S16; Yes), the processing by the receiver 20 returns from the registration process in Fig. 8 to the communication process in Fig. 7. This ends the registration phase and starts the operation phase.

[0050] 7 , the communication unit 43 of the receiver 20 receives radio waves corresponding to 1-bit partial data transmitted from one of the transmitters 10 (step S2). Next, the identification unit 44 converts the radio waves received in step S2 into a frequency representation (step S3). The identification unit 44 then compares the frequency representation obtained by the conversion with the frequency representations registered in the correspondence table 451 to identify the transmitter 10 that transmitted the radio waves and the partial data transmitted by the radio waves (step S4). The identified transmitter 10 and the partial data are stored in the storage unit 45 in association with each other.

[0051] Next, the restoration unit 46 determines whether the packet can be restored using the partial data received and stored from the same transmitter 10 (step S5). For example, if the packet has a fixed length, it determines whether partial data corresponding to the fixed-length packet has been stored by repeatedly executing step S4. Alternatively, if the packet has a variable length, it may determine whether the packet can be restored by combining the stored partial data and attempting to restore the packet.

[0052] If it is determined that the packet cannot be restored (step S5; No), the processes from step S2 onward are repeated, whereby the partial data intermittently transmitted from each transmitter 10 continues to be received.

[0053] If it is determined that the packet can be restored (Step S5; Yes), the restoration unit 46 restores the packet (Step S6), and the time stamping unit 47 time-stamps the measurement results indicated by the restored packets and outputs them to the display 30 (Step S7). The display 30 then displays a graph of the time-series data of the measurement results as shown in FIG. 6 (Step S8). Thereafter, the processes from Step S2 onward are repeated. This makes it easy to collect and utilize sensing results through wireless communication using energy harvesting.

[0054] As described above, the communication unit 43 receives radio waves transmitting partial data from one of the transmitters 10 at a time interval from other radio waves transmitting other partial data that are successive to the partial data to form a packet, and the identification unit 44 identifies the transmitter 10 that transmitted the radio waves based on the frequency expression of the radio waves and the correspondence table 451. This makes it possible to receive partial data transmitted from the transmitter 10 without waiting for the transmitter 10 to accumulate enough power to transmit the entire packet all at once. This improves the convenience of wireless communication using energy harvesting.

[0055] Furthermore, the identification unit 44 identifies the transmitter 10 that transmitted the radio waves transmitting the partial data based on the frequencies and intensities of multiple frequency components contained in the radio waves, based on the correspondence table 451. The frequencies and intensities of these frequency components vary depending on the transmission characteristics of the radio waves from the transmitter 10 to the receiver 20. Therefore, compared to identifying a transmitting device by setting a unique peak frequency for each transmitting device, the task of setting the peak frequency can be simplified. Furthermore, identifying the transmitter 10 based on multiple frequency components is expected to be more robust against external disturbances than identification based on peak frequency.

[0056] Furthermore, when the frequency representations of the radio waves received from the two transmitters 10 are the same, the instruction unit 42 instructs at least one of the transmitters 10 to change the frequency at which it transmits. If a transmitter changes its frequency, the frequency representations of the radio waves received from these two transmitters 10 will be different. Therefore, it is possible to reliably identify the transmitter 10 that is the source of the radio waves.

[0057] Furthermore, the restoration unit 46 restores packets from partial data received consecutively from the same transmitter 10. This eliminates the need to design a dedicated process for handling partial data.

[0058] The timestamp unit 47 also assigns a time stamp to the measurement results indicated by the packets. This allows appropriate time stamps to be assigned to measurement results transmitted using multiple pieces of partial data obtained over time. Even in cases where it is often difficult for the transmitter 10, which operates by energy harvesting, to acquire time stamps, appropriate time stamps can be assigned to the measurement results. This allows for efficient monitoring of sensing results.

[0059] Second Embodiment Next, a second embodiment will be described, focusing on the differences from the first embodiment described above. Note that the same reference numerals are used for configurations that are the same as or equivalent to those in the first embodiment described above. In the first embodiment described above, it was assumed that radio waves having a frequency representation equivalent to the frequency representation registered in the correspondence table 451 in the registration phase would also be received in the operation phase. However, if the environment of the communication system 1000 changes from the registration phase, the frequency representation of the radio waves received in the operation phase may also change. This makes it difficult to identify the transmitter 10 based on the frequency representation. Below, an example will be described in which information other than the frequency representation is further used to identify the transmitter 10 that transmitted the radio waves.

[0060] 9 shows an example in which radio waves transmitting 1-bit partial data are received six times. Here, the radio waves received the first, third, and fifth times are identified as having a sender that is the first transmitter indicated by "ID:01," and the radio waves received the second and fourth times are identified as having a sender that is the second transmitter indicated by "ID:02."

[0061] However, for the radio wave received the sixth time, the transmitter 10 cannot be identified from its frequency representation, indicating that the source is unknown. In detail, if the frequency representation of the radio wave received the sixth time is not equal to any of the frequency representations registered in the correspondence relationship table 451, or if it is equal to two or more frequency representations registered in the correspondence relationship table 451, the source transmitter 10 is unknown.

[0062] As shown in FIG. 2 , the amount of power generated by energy harvesting is usually constant. Therefore, as shown in FIG. 9 , the timing at which radio waves are transmitted from each transmitter 10 is periodic. Specifically, the transmission period of radio waves from the first transmitter is period PR1, and the transmission period of radio waves from the second transmitter is period PR2. Therefore, by comparing the length of time elapsed from the last reception of radio waves from each transmitter 10 to the reception of the sixth radio wave with the transmission period of the radio waves from each transmitter 10, it is possible to identify the source of the sixth radio wave.

[0063] 9, the sixth reception timing is the timing when a time equal to the period PR2 has elapsed since the fourth reception of the radio wave from the second transmitter, and therefore the source of the transmission is identified as the second transmitter. Once the second transmitter has been identified, the 1-bit partial data transmitted by this radio wave can be estimated from the frequency representation associated with the second transmitter in the correspondence table 451.

[0064] 10 shows the flow of communication processing according to this embodiment. As shown in FIG. 10, in this communication processing, steps S1 to S4 similar to those in the first embodiment are executed. Next, the identification unit 44 determines whether or not the transmitter 10 and bit value were identified in step S4 (step S21). If they were identified (step S21; Yes), the processing from step S5 onward is executed.

[0065] On the other hand, if the transmitter cannot be identified (step S21; No), the identification unit 44 identifies the transmitter based on the timing of receiving the radio waves and identifies the value of the partial data by referring to the correspondence table 451 (step S22). Specifically, the identification unit 44 predicts the next reception timing for each transmitter 10 from the periodic timing of past reception of radio waves from each transmitter 10, and identifies the transmitter 10 with the predicted reception timing closest to the reception timing of the radio waves whose transmission source could not be identified as the transmission source. Thereafter, the processing from step S5 onwards is executed.

[0066] As described above, the identification unit 44 identifies the transmitter 10 that transmitted the radio waves based on the correspondence relationship table 451 and the timing at which the radio waves were received. In particular, if the frequency expression of the received radio waves is different from any of the frequency expressions registered in the correspondence relationship table 451 or corresponds to two or more registered frequency expressions, the identification unit 44 identifies the transmitter that transmitted the radio waves based on the period in which radio waves were previously received from each transmitter 10. This makes it possible to identify the transmitter even in cases where the transmitter cannot be identified based solely on the frequency expression of the radio wave waveform.

[0067] Although the example of identifying the sender based on the reception timing of the radio wave has been described only when the sender cannot be identified by comparing the frequency representations alone, the present invention is not limited to this example and the identification unit 44 may initially identify the sender based on both the frequency representation and the reception timing.

[0068] Furthermore, although an example has been described in which the timing of transmitting radio waves by the transmitter 10 is periodic, this is not limiting. For example, as indicated by the triangular marks in FIG. 11 , radio waves may be transmitted at timings that are not periodic but have a regularity. In the example of FIG. 11 , groups containing three timings appear periodically, making it possible to predict future reception timings. In this way, if the reception timings are regular, it is possible to identify the sender based on the timing.

[0069] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments.

[0070] For example, an example has been described in which measurement results from the sensor 12 are collected and displayed in a time series format. However, the information transmitted by the packets is not limited to the measurement results from the sensor 12 and may be other information. Furthermore, the processing performed on the information transmitted by the packets after the receiver 20 receives this information is not limited to graph display and may be other processing.

[0071] Although the example in which the receiver 20 includes the storage unit 45, the restoration unit 46, and the time setting unit 47 has been described, the present invention is not limited to this. The identification unit 44 may store the results of identifying the source of the radio waves and the values ​​of the partial data transmitted by the radio waves in an external storage device of the receiver 20 instead of the storage unit 45, and further the external device may perform functions equivalent to those of the restoration unit 46 and the time setting unit 47.

[0072] Although the example in which the size of the partial data is 1 bit has been described, the size of the partial data may be 2 bits or more. However, even when the size of the partial data is 2 bits or more, the partial data does not need to include a source ID because the sender can be identified from the frequency expression of the radio waves. Similarly, a packet consisting of multiple partial data does not need to include a source ID.

[0073] Furthermore, it is not necessary for all transmitters 10 to transmit radio waves with unique frequency characteristics. Even if two or more transmitters 10 transmit radio waves with equivalent frequency characteristics, the frequency representation of the radio waves when received will be different from each other due to the characteristics of the transmission path, and therefore it is possible to identify each of these two or more transmitters 10 as the transmission source.

[0074] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. In other words, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of equivalent disclosures are considered to be within the scope of the present disclosure.

[0075] The present disclosure is suitable for low-power wireless communication.

[0076] 10 Transmitter, 11 Power generation unit, 12 Sensor, 13 Sensor data storage unit, 14, 23 Control unit, 15 Memory, 16, 22, 43 Communication unit, 17, 21 Antenna, 20 Receiver, 24, 45 Storage unit, 25 I / F unit, 30 Display, 41 Registration unit, 42 Instruction unit, 44 Identification unit, 46 Restoration unit, 47 Time assignment unit, 451 Correspondence relationship table, 1000 Communication system, PR1, PR2 Period, NW Network.

Claims

1. A receiver that receives packets transmitted by wireless communication from a plurality of transmitters, comprising: receiving means for receiving, from one of the plurality of transmitters, a partial radio wave that transmits partial data that constitutes the packet, with a time interval between the partial data and other partial radio waves that transmit other partial data that constitute the packet by being consecutive to the partial data; storage means for storing a correspondence between each of the transmitters and the frequency representation of the radio waves received from the transmitter; and identification means for identifying the transmitter that transmitted the partial radio wave based on the correspondence from the frequency representation of the partial radio wave received by the receiving means.

2. A receiver as described in claim 1, wherein the storage means stores a correspondence relationship between each transmitter and the frequencies and intensities of multiple frequency components contained in the radio waves transmitted from that transmitter, and the identification means identifies the transmitter that transmitted the partial radio waves based on the correspondence relationship from the frequencies and intensities of the multiple frequency components contained in the partial radio waves.

3. A receiver as described in claim 1 or 2, further comprising: a registration means for registering the frequency representation of the received radio waves in said storage means when each of the transmitters sequentially transmits radio waves; and an instruction means for instructing the first transmitter to change the frequency of the radio waves to be transmitted when the frequency representation of the radio waves received from a first transmitter of the plurality of transmitters is equal to the frequency representation of the radio waves received from a second transmitter, wherein the registration means registers the frequency representation of the radio waves received from the first transmitter in said storage means after the instruction to change the frequency has been given by the instruction means.

4. A receiver as claimed in any one of claims 1 to 3, further comprising a restoration means for restoring the packet from the partial data transmitted by the partial radio waves that have been received multiple times by the receiving means and that have been consecutively identified by the identifying means as having been transmitted from the same transmitter.

5. A receiver as described in claim 4, further comprising a time assignment means for assigning a time to information indicated by the packet restored by the restoration means and outputting the information, wherein the packet indicates the result of measurement by a sensor as the information, and the time assignment means assigns the value indicated by the packet, the result of a predetermined operation performed on the value, or the reception time of any of the partial data constituting the packet as the time to the result of the measurement.

6. A receiver according to any one of claims 1 to 5, wherein the identification means identifies the transmitter that transmitted the partial radio wave based on the correspondence relationship and the timing at which the partial radio wave was received.

7. A receiver as described in claim 6, wherein said identification means identifies the transmitter that transmitted the partial radio wave based on the period during which the partial radio wave was previously received from each transmitter when the frequency representation of the partial radio wave received by said receiving means is different from any of the frequency representations stored in said storage means or corresponds to two or more frequency representations stored in said storage means.

8. A receiver according to any one of claims 1 to 7, wherein the time interval is longer than the time length required to transmit one bit of data that constitutes the packet.

9. A receiver according to any one of claims 1 to 8, wherein the size of the partial data is 1 bit.

10. A transmitter that transmits packets by wireless communication, wherein a partial radio wave that transmits partial data constituting the packet is transmitted at a time interval from other partial radio waves that transmit other partial data constituting the packet by being consecutive to the partial data.

11. The transmitter according to claim 10, wherein, when an instruction to change the transmission frequency is given, the partial radio wave is transmitted with the frequency changed in accordance with the instruction.

12. A transmitter according to claim 10 or 11, comprising power generation means for generating power from light, heat, vibrations or electromagnetic waves in the environment, and transmitting the partial radio waves using the power generated by the power generation means.

13. A communication system comprising a receiver according to any one of claims 1, 2, 4 to 9, and a plurality of transmitters according to claim 10 or 12.

14. The communication system according to claim 13, wherein the frequency components contained in the radio waves transmitted by the plurality of transmitters are equal to each other.

15. A communication system comprising: a receiver according to claim 3; and a plurality of transmitters according to claim 11.

16. A communication method for transmitting packets by wireless communication, comprising: a plurality of transmitters each transmitting a partial radio wave transmitting partial data constituting the packet, with a time interval between the partial data and other partial radio waves transmitting other partial data constituting the packet by being consecutive to the partial data; a receiver receiving the partial radio waves; and the receiver identifying the transmitter that transmitted the partial radio waves from the frequency representation of the received partial radio waves based on a correspondence relationship between each of the transmitters and the frequency representation of the radio waves received from the transmitter.

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