The present invention relates to a communication system in a sensor network consisting of a slave station and a master station.
Various services using sensor networks have been provided with the development of information communication technologies. For example, there are services for acquiring various kinds of physical data through attachment to users' bodies and for managing safety operations through attachment to plant equipment (for example, see Patent Literature 1).
A configuration example of a sensor network in the related art is illustrated in
A typical configuration example of the slave station in the sensor network in the related art is illustrated in
The radio wave emitting unit has a function of transmitting the received transmission signal with the radio wave to the master station. The power supply unit has a function of supplying power to the sensor, the control unit, and the radio wave emitting unit. The radio wave emitting unit in the configuration example is formed of an electronic circuit with an oscillation circuit and an amplification circuit integrated thereon. In the slave station in the sensor network in the related art, an electronic circuit is typically used to realize communication using radio waves.
In a sensor network in the related art, it has been difficult to form a slave station in the sensor network with a transistor using an organic semiconductor or the like and having a low operation frequency. This is because the transistor of an electronic circuit is required to operate at a high frequency in communication using radio waves.
An object of embodiments of the present invention is to provide a communication system that operates with an electronic circuit with a low operation frequency.
An embodiment of the present invention provides a communication system using a sound wave signal for slave-to-master transmission, the communication system including one or a plurality of slave stations and a master station, in which each of the one or plurality of the slave stations includes a sensor configured to detect a sensor signal, a control unit configured to generate a first electrical signal at a predetermined frequency using the sensor signal, and a sound wave emitting unit configured to convert the first electrical signal into a sound wave signal and emit the sound wave signal, and the master station includes a sound wave receiving unit configured to receive the sound wave signal and convert the sound wave signal into a second electrical signal and a control unit configured to detect that the sensor in the slave station has detected the sensor signal based on the second electrical signal.
An embodiment of the present invention provides a communication method performed in a communication system using a sound wave signal for transmission of a signal from one or a plurality of slave stations to a master station, the method including: by each of the slave stations, detecting a sensor signal; generating a first electrical signal at a predetermined frequency using the sensor signal; and converting the first electrical signal into a sound wave signal and emitting the sound wave signal; and by the master station, receiving the sound wave signal; converting the sound wave signal into a second electrical signal; and detecting that the slave station has detected the sensor signal based on the second electrical signal.
According to embodiments of the present invention, it is possible to provide a communication system that operates with an electronic circuit with a low operation frequency.
Hereinafter, embodiments of the present invention will be described based on the drawings. The present invention is not limited to the following embodiments.
The configuration example is different from the related art in that a component corresponding to a radio wave emitting unit 103 is formed of the sound wave emitting unit 13. In the configuration example, the power supply unit 14 can be formed of a general button battery or the like. The sensor 11 can be formed of a general photodiode configured to generate a current when the photodiode detects light.
A configuration example of the control unit 12 is illustrated in
A configuration example of the sound wave emitting unit 13 is illustrated in
First, communication operations in the present embodiment will be described. In the slave station 10, when the sensor 11 does not detect light, the sensor signal output from the sensor 11 is not valid, and the switch of the control unit 12 is in an OFF state in a state in which the sensor 11 has not detected light. Thus, no power is supplied to the oscillation circuit 15, no electrical signal is generated, and no sound waves are transmitted to the master station. Because the master station has not received any sound waves from the slave station, it is possible to determine that the slave station has not detected light.
On the other hand, in a state in which the sensor 11 in the slave station 10 has detected light, the sensor signal is valid, and the switch of the control unit 12 is brought into an ON state. In this manner, the power is supplied to the oscillation circuit 15, the RC oscillation circuit 15 performs oscillation, and an electrical signal is generated at a predetermined frequency determined by the R and C values. The electrical signal is converted into a sound wave signal by the piezoelectric speaker and is then transmitted as the sound wave signal to the master station. The master station can detect that the slave station has detected light based on the reception of the sound wave from the slave station.
A configuration example of the master station according to the present embodiment is illustrated in
As illustrated in
As described above, according to the present embodiment, it is possible to enable communication at a low frequency using sound waves caused by oscillation of air and to provide a communication system that operates with an electronic circuit at a low operation frequency.
In the present embodiment, the slave station can be formed of a transistor having a low operation frequency. However, effects obtained by the present embodiment are not limited thereto. For example, it is possible to obtain effects such as an improvement in ease of design due to the low operation frequency, an improvement in noise tolerance (communication quality), and reduction of power consumption. Further, it is possible to use the transistor having a low operation frequency such as an organic semiconductor and thereby to expect effects such as production by a printing process and cost reduction.
In the present embodiment, the example in which the power supply unit is formed of a battery has been described. However, the power supply unit is not limited to the battery and may be any device as long as the device can supply power. For example, an energy harvesting device using light, electromagnetic induction, or oscillation may be used.
In the present embodiment, the example in which the sensor in the slave station is formed of an optical sensor such as a photodiode has been described. However, the sensor is not limited to the optical sensor, and another sensor may be used. For example, the sensor may be formed of a device sensing, for example, temperature, humidity, water, soil constituents, smoke, oscillation, positions, distortions, or mechanical operations (ON/OFF).
In the present embodiment, the example in which the sound wave emitting unit is configured with a piezoelectric speaker has been described. However, the sound wave emitting unit is not limited to the piezoelectric speaker, and another speaker can also be used as long as the speaker is configured to be able to generate sound waves. For example, the sound wave emitting unit may be configured with an electrostatic-type speaker using a capacitor or a magnetic-type speaker using a magnet.
In the present embodiment, the example in which the piezoelectric speaker is driven with one transistor has been described. However, the configuration of the piezoelectric speaker is not limited to the configuration. For example, a configuration in which the piezoelectric speaker is driven using two transistors as in
In the present embodiment, the configuration example in which the RC oscillation circuit is used as the oscillation circuit of the control unit has been described. However, the oscillation circuit is not limited to the RC oscillation circuit and may be configured with an LC oscillation circuit or a solid oscillator such as quartz.
Although the case in which a sound wave signal is transmitted from the master station and the slave station to the slave station in a one-to-one correspondence has been described in the configuration example in the first embodiment, a case in which sound wave signals are transmitted from a plurality of slave stations to a master station in a multiple-to-one correspondence will be described in a second embodiment. The slave station 10 is configured to emit sound waves of about 10 kHz and notify the master station 20 of the fact that the slave station 10 has detected light when the slave station 10 detects light in the second embodiment similarly to the first embodiment.
A configuration example of a communication system 1 according to the present embodiment is illustrated in
In the configuration example in
If a unique frequency is allocated to each of the slave stations (10-1 to 10-3), and the master station 20 receives a sound wave at a frequency f1, for example, then the master station 20 can detect that the slave station 10-1 has detected light. Also, in a case in which the master station 20 has received sound waves at a plurality of frequencies, for example, the frequency f1 and the frequency f2 at the same time, the master station 20 can detect that the slave station 10-1 and the slave station 10-2 have detected light.
A configuration example of the master station according to the present embodiment is illustrated in
As described above, according to the present embodiment, it is possible to configure the communication system in which the master station and the slave stations perform communication in one-to-multiple correspondence using sound waves. The master station can identify each of the slave stations by allocating mutually different frequencies to the slave stations such that no collision occurs even in a case in which the plurality of slave stations transmit sound waves at the same time.
A third embodiment relates to a case in which sound signals are transmitted from a plurality of slave stations to a master station in a multiple-to-one correspondence similarly to the second embodiment. The third embodiment is different from the second embodiment in terms of the method in which the master station identifies the slave stations. The slave stations 10 are configured to emit sound waves of about 10 kHz and notify the master station 20 of the fact that the slave stations 10 have detected light when the slave stations 10 detect light in the present embodiment similarly to the first embodiment.
A configuration example of a communication system 1 according to the present embodiment is illustrated in
The slave stations (10-1 to 10-3) according to the present embodiment modulate the electrical signal with the identification numbers allocated to the stations themselves. A configuration example of the control unit 12 according to the present embodiment is illustrated in
The storage circuit 16 stores the identification number unique to the slave station. In the configuration example of
When the slave station 10 detects light, a first switch is turned on, and the first oscillation circuit (15-1) and the second oscillation circuit (15-2) perform oscillation to generate electrical signals. Signals 0, 1, and 0 corresponding to the identification number are output from the storage circuit 16 in order in accordance with the electrical signal (third electrical signal) from the second oscillation circuit (15-2). The signals 0, 1, and 0 corresponding to the identification number serve as an ON/OFF signal of the second switch, and the electrical signal output from the first oscillation circuit (15-1) is modulated through an ON/OFF operation of the second switch. With such a configuration, the slave station 10 can transmit the sound wave signal modulated with the signals corresponding to the identification number allocated to the slave station 10 itself to the master station 20. The master station 20 can identify from which slave station the master station 20 has received radio waves with the identification number obtained by demodulating an electrical signal obtained by converting the received sound signal.
The configuration of the master station according to the present embodiment is illustrated in
In the present embodiment, the configuration example in which amplitude modulation is performed on the electrical signal based on the identification number has been described. However, the scheme for modulating the sound wave is not limited to the amplitude modulation, and another modulation scheme may be used as long as it is possible to modulate the sound wave with the identification number and to transmit the modulated sound wave to the master station with the configuration. For example, phase modulation or frequency modulation may be used.
In the configuration of the control units in the slave stations in
As described above, according to the present embodiment, it is possible to enable communication at a low frequency using sound waves caused by oscillation of air and to provide a communication system that operates with an electronic circuit with a low operation frequency.
This application is a national phase entry of PCT Application No. PCT/JP2019/025383, filed on Jun. 26, 2019, which application is hereby incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2019/025383 | 6/26/2019 | WO |