JP2012209652A - Radio communication system, communication device, information apparatus, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system for performing radio communication in a frame of an information apparatus.SOLUTION: A first communication device 3 has: a first transmission part transmitting a communication signal through an antenna; and a first control part 6 making the first transmission part transmit the communication signal. A second communication device 4 has: a second reception part receiving the communication signal through an antenna; a second measurement part measuring a reception level of the communication signal received by the second reception part; and a second control part 7 which utilizes the communication signal received by the second reception part in the case that the reception level measured by the second measurement part is within a predetermined window, and does not utilize the communication signal received by the second reception part in the case that the reception level measured by the second measurement part is not within a predetermined window.

Description

  The present invention relates to a wireless communication system that performs wireless communication in a housing of an information device.

  Wireless communication has generally been used as a technique for transmitting information between remote points. The reason for this is that, as a matter of course, wiring work is necessary in the case of wired communication, and the longer the desired communication section, the more labor and cost for preparing equipment for that purpose. In addition, in the case of wire, since a wire material is used for the wire, manufacturing of the wire itself requires cost and energy, and the maintenance cost also increases. Therefore, unnecessary wireless communication such as cost has been used.

  In recent years, not only long-distance communication but also very short-distance communication, wireless communication using a frequency band that does not require a radio license, such as a wireless LAN or Bluetooth (registered trademark), is often used. (For example, refer nonpatent literature 1). This is a result of the daily advancement and improvement of the conventional drawbacks such as the low communication speed of wireless communication and low reliability compared to wired communication due to research on new communication methods.

  In these wireless communications, technology development assuming use cases has been performed. This is no exception even in short-range wireless communication systems. Short-range wireless communication is generally provided as a common (standardized) communication method, assuming propagation paths in free space, standard indoor space, etc., taking into account communication failures that occur there. Yes.

On the other hand, for example, information equipment such as bank ATM (Automated Teller Machine) machines, copiers, vending machines, etc. are covered with a metal case, and send and receive paper and metal inside, and identify them. The mechanical parts that perform physical recognition and the like are packed in a complicated manner. In such an information device, wireless information transmission is not common, and wired wiring is common. The reason for this is that the device itself is about 1 m ³ in size, and it has been thought that communication related to control may be wired, or it is surrounded by a metal enclosure and a number of metal components inside it. There are some cases where wireless communication has been considered difficult.

  In addition, there is communication using a metal waveguide, but the metal waveguide is an information / power transmission means using the characteristics of radio waves (mode propagation characteristics), and you want to handle the output power with a lower loss than a cable. For example, it is a material for information transmission similar to that of a normal cable, which is used when a high power output is desired. Therefore, transmission within an information device using a metal waveguide is in a category different from wireless communication within the information device.

“Bluetooth”, [online], March 23, 2011, [March 25, 2011 search], Wikipedia, Internet <URL: http: // ja. wikipedia. org / wiki / Bluetooth>

  Even if wireless communication that has been performed in free space or in a house is applied as it is to an information device (for example, an ATM machine) covered with a metal frame, it cannot be communicated properly. There's a problem. The reason for this is that since the inside of the device has a complicated structure, multipath increases, code interference occurs, and space propagation loss increases compared to free space. Therefore, communication with weak radio waves is performed inside the information device, and it is easy to receive radio wave interference from the outside. Information equipment is covered with a metal housing, but in reality, external radio waves leak into the inside, for example, from the touch panel or resin part, so that the inside and outside of the equipment can be isolated for communication. May not have been. As an actual measurement result, although depending on the position of the wireless transmission / reception device in the device, the shielding amount by the housing is, for example, about 20 to 30 dB in the ISM 2.4 GHz band. Therefore, when communication is performed with weak radio waves inside the device as described above, the communication quality is deteriorated due to external interference radio waves. And when communication quality deteriorates, there exists a problem that an information apparatus does not operate | move appropriately, or malfunctions.

  SUMMARY An advantage of some aspects of the invention is to provide a wireless communication system and the like that can perform appropriate wireless communication in a housing of an information device.

In order to achieve the above object, a wireless communication system according to the present invention includes one or more first communication devices and one or more second communication devices provided in a housing of an information device. A wireless communication system that performs wireless communication with a second communication device, the first communication device transmitting a communication signal via an antenna and a first transmission of the communication signal A second control unit that transmits the communication signal via the antenna, and a reception level of the communication signal received by the second reception unit. And a second measurement unit that uses the communication signal received by the second reception unit when the reception level measured by the second measurement unit is within a predetermined window. The reception level measured by the If not within the window, and a second control unit which does not use a communication signal by the second reception unit receives, with a, but.
With such a configuration, since the communication signal is used only when the reception level is within a predetermined window, it is possible to prevent malfunction due to interference radio waves from the outside of the housing. Appropriate wireless communication can be realized.

The wireless communication system according to the present invention includes a plurality of first communication devices and / or a plurality of second communication devices, and each first communication device and each second communication device includes: You may communicate using a different communication channel among several communication channels.
With such a configuration, communication can be performed without interference between each first communication device and each second communication device.

Further, in the wireless communication system according to the present invention, the first control unit sends a dummy communication signal that is a dummy communication signal to a communication channel that does not perform communication of an actual communication signal that is a communication signal used for transmitting and receiving information. The first transmission unit may be controlled to transmit.
With this configuration, when communication of an actual communication signal is performed, even if a radio wave is intercepted outside the housing, it is disturbed so that it does not understand what the actual communication signal means Can be.

In the wireless communication system according to the present invention, the first communication device receives a first reception unit that receives a communication signal via an antenna and a reception level of the communication signal received by the first reception unit. The first control unit further includes a communication signal received by the first reception unit when the reception level measured by the first measurement unit is within a predetermined window. When the reception level measured by the first measurement unit is not within a predetermined window, the communication signal received by the first reception unit is not used, and the second communication device is an antenna. A second transmission unit that transmits a communication signal via the second transmission unit may be further provided, and the second control unit may cause the second transmission unit to transmit the communication signal.
With such a configuration, bidirectional communication can be performed between the first communication device and the second communication device.

The wireless communication system according to the present invention includes a plurality of first communication devices and / or a plurality of second communication devices, and each first communication device and each second communication device includes: A first communication channel that performs communication using different communication channels among a plurality of communication channels and controls transmission of communication signals for communication channels that do not perform communication of an actual communication signal that is a communication signal used for transmission / reception of information. The control unit or the second control unit may perform control so that a dummy communication signal that is a dummy communication signal is transmitted in the communication channel.
With this configuration, when communication of an actual communication signal is performed, even if a radio wave is intercepted outside the housing, it is disturbed so that it does not understand what the actual communication signal means Can be.

In the wireless communication system according to the present invention, the first control unit causes the first transmission unit to transmit a communication signal for acquiring propagation characteristics, and the second control unit performs communication for acquiring propagation characteristics. The first transmission device is configured to transmit a signal to the second transmission unit, and the first communication device acquires the first propagation characteristic using the communication signal for acquiring the propagation characteristic received by the first reception unit. A communication signal using the encryption key acquired by the first encryption key acquiring unit and the first encryption key acquiring unit that acquires the encryption key using the propagation characteristics acquired by the first propagation characteristic acquiring unit An encryption unit that encrypts the communication signal, wherein the first transmission unit transmits the communication signal encrypted by the encryption unit, and the second reception unit transmits the encrypted communication signal. The second communication device receives the propagation characteristics received by the second receiver. A second propagation characteristic acquisition unit that acquires a propagation characteristic using a communication signal for use, a second encryption key acquisition unit that acquires an encryption key using the propagation characteristic acquired by the second propagation characteristic acquisition unit, You may further provide the decoding part which decodes the encrypted communication signal which the 2nd receiving part received using the encryption key which the 2nd encryption key acquisition part acquired.
With such a configuration, propagation characteristics between the first and second communication devices, that is, highly secure communication by acquiring an encryption key using information that only both devices can know and performing encrypted communication. Will be able to do.

  In the wireless communication system according to the present invention, the casing of the information device may be a metal casing.

  An information device according to the present invention includes the wireless communication system, and transmits and receives signals in the device through wireless communication between the first communication device and the second communication device.

  The wireless communication method according to the present invention uses one or more first communication devices and one or more second communication devices provided in a housing of an information device, and uses the first communication device and the second communication device. The first communication device transmits a communication signal via an antenna, and the second communication device receives the communication signal via an antenna. The second communication device measures the reception level of the received communication signal, the second communication device determines whether the measured reception level is within a predetermined window, and the second The communication device uses the received communication signal when the reception level is within a predetermined window, and receives the communication signal when the reception level is not within the predetermined window. A step that does not use, those having a.

  According to the wireless communication system and the like according to the present invention, appropriate wireless communication can be performed in the casing of the information device.

1 is a block diagram showing a configuration of a wireless communication system according to Embodiment 1 of the present invention. The block diagram which shows the structure of the 1st communication apparatus by the embodiment The block diagram which shows the structure of the 2nd communication apparatus by the embodiment The flowchart which shows operation | movement of the 1st communication apparatus by the embodiment The flowchart which shows operation | movement of the 1st communication apparatus by the embodiment The flowchart which shows operation | movement of the 2nd communication apparatus by the embodiment The flowchart which shows operation | movement of the 2nd communication apparatus by the embodiment The figure which shows an example of the internal structure of the information equipment by the embodiment The figure for demonstrating the setting of the window in the embodiment The figure for demonstrating the reception using the window in the embodiment

  Hereinafter, the radio | wireless communications system by this invention is demonstrated using embodiment. In the following embodiments, components and steps denoted by the same reference numerals are the same or equivalent, and repetitive description may be omitted.

(Embodiment 1)
A radio communication system according to Embodiment 1 of the present invention will be described with reference to the drawings. The wireless communication system according to the present embodiment performs wireless communication within a housing of an information device.

  FIG. 1 is a block diagram showing a configuration of a wireless communication system 1 according to the present embodiment. The wireless communication system 1 according to the present embodiment includes a first communication device 3 and a second communication device 4 provided in a housing 5 of the information device 2. The first communication device 3 and the second communication device 4 perform wireless communication in the housing 5. Although FIG. 1 shows a case where the wireless communication system 1 includes one first communication device 3 and one second communication device 4 for convenience of explanation, the present embodiment Now, a case where the wireless communication system 1 includes one first communication device 3 and two or more second communication devices 4 will be described. Generally speaking, the wireless communication system 1 only needs to include one or more first communication devices 3 and one or more second communication devices 4.

  The information device 2 may be any device as long as it performs some information processing. The information device 2 may be an ICT (Information and Communication Technology) device. The information device 2 may be, for example, a bank ATM machine, a copy machine, a printer, a vending machine such as a beverage, a transportation ticket vending machine, or other equipment. The housing 5 of the information device 2 may be, for example, a metal housing, at least a part of a metal housing, or a non-metal housing. Moreover, in the housing | casing 5 of the information equipment 2, the 1st communication apparatus 3 and the 2nd communication apparatus 4 perform radio | wireless communication in order to transfer the signal in an apparatus. In other words, signal transmission and reception that is conventionally performed by wire is performed by wireless communication using the first communication device 3 and the second communication device 4. Therefore, although depending on the size of the information device 2, the distance between the two devices is, for example, about 10 cm to 1 m, and is usually separated by about 3 cm or more. It should be noted that the distance between the two devices may be longer or shorter. In the present embodiment, the first communication device 3 receives a communication signal from the control unit 6 of the information device 2 and transmits it to the second communication device 4, and receives the communication signal received from the second communication device 4. It is assumed to be passed to the control unit 6. In addition, the second communication device 4 passes the communication signal received from the first communication device 3 to the controlled unit 7 included in the information device 2, and the communication signal received from the controlled unit 7 is transmitted to the first communication device. 3 is transmitted. The control unit 6 controls the controlled unit 7, and the controlled unit 7 may be, for example, a sensor or a drive unit (for example, a motor) controlled by the control unit 6. Moreover, although this Embodiment demonstrates the case where communication between the control part 6 and the to-be-controlled part 7 is performed by the radio | wireless communications system 1, it does not need to be so. It goes without saying that communication between other components in the information device 2 may be performed by the wireless communication system 1. For example, wireless communication for data exchange not related to control may be performed by the wireless communication system 1.

  FIG. 2 is a block diagram showing a configuration of the first communication device 3 according to the present embodiment. In FIG. 2, the first communication device 3 according to the present embodiment includes a first transmission unit 32, a first reception unit 33, a first measurement unit 34, and a first propagation characteristic acquisition unit 35. The first encryption key acquisition unit 36, the encryption unit 37, and the first control unit 38 are provided.

  The first transmission unit 32 transmits a communication signal via the first antenna 31. Note that, when the communication signal to be transmitted is encrypted by the encryption unit 37, the first transmission unit 32 may transmit the encrypted communication signal. The first transmission unit 32 appropriately performs transmission processing such as modulation on the communication signal to be transmitted received from the first control unit 38, and transmits the transmission signal via the first antenna 31. In the present embodiment, both the signal before modulation and the signal transmitted via the first antenna 31 after modulation are referred to as communication signals. The same applies to the second communication device 4 described later. Moreover, the 1st transmission part 32 may transmit a communication signal via any communication channel among several communication channels (frequency channel). The communication channel may be determined for each communication destination device, for example.

  The first receiving unit 33 receives a communication signal via the first antenna 31. The first receiving unit 33 appropriately performs reception processing such as demodulation on the communication signal received by the first antenna 31. In this embodiment, both the signal before demodulation and the signal after demodulation are called communication signals. The same applies to the second communication device 4 described later. Further, the first receiving unit 33 may receive a communication signal of any one of a plurality of communication channels. The communication channel may be determined for each communication destination device, for example. Moreover, the 1st receiving part 33 shall also receive the communication signal for propagation characteristic acquisition. It is assumed that the communication signal includes a transmission level at the time of transmission of the communication signal.

  Although FIG. 2 shows a case where the first transmission unit 32 and the first reception unit 33 transmit and receive communication signals via the same first antenna 31, this need not be the case. The antenna that transmits the communication signal and the antenna that receives the communication signal may be different. Even in that case, as will be described later, the propagation characteristics acquired by the communication signal transmitted from the first communication device 3 to the second communication device 4, and the first communication device 4 to the first When the propagation characteristics acquired by the communication signal transmitted to the communication device 3 need to be the same, the transmitting antenna and the receiving antenna have the same characteristics and are close to each other. It is preferred that they are arranged. The same applies to the second communication device 4.

  The first measuring unit 34 measures the reception level of the communication signal received by the first receiving unit 33. The reception level may be, for example, a received signal strength (RSSI: Received Signal Strength Indication / Indicator) or other reception levels. The first measurement unit 34 may measure the reception level using, for example, the signal after demodulation by the first reception unit 33, or may receive using the signal before demodulation by the first reception unit 33. The level may be measured. In the former case, for example, the reception level of the communication channel received by the first receiving unit 33 may be measured. In the latter case, for example, only a signal corresponding to the communication channel received by the first receiving unit 33 may be extracted using a bandpass filter or the like, and the reception level of the signal may be measured. Note that a method for measuring the reception level is already known, and a detailed description thereof will be omitted. The measured reception level may be stored in a recording medium (not shown).

  The first propagation characteristic acquisition unit 35 acquires the propagation characteristic using the propagation characteristic acquisition communication signal received by the first reception unit 33. The propagation characteristic may be, for example, a propagation loss or a delay characteristic profile. As described above, the housing 5 of the information device 2 has a very complicated configuration as compared to the free space, and an ideal delay characteristic profile cannot often be acquired. Therefore, it is considered that it is more preferable to acquire the propagation loss that is the propagation characteristic than to acquire the delay characteristic profile that is the propagation characteristic. Therefore, in the present embodiment, the case where the propagation characteristic is a propagation loss will be mainly described. That is, the first propagation characteristic acquisition unit 35 receives the reception level of the propagation characteristic acquisition communication signal and the transmission level included in the propagation characteristic acquisition communication signal measured by the first measurement unit 34. It is assumed that a propagation characteristic that is a propagation loss is acquired using. For example, when the reception level and transmission level are logarithmic, the logarithmic propagation characteristic can be obtained by subtracting the reception level from the transmission level. For example, when the reception level or the like is not in logarithmic notation, the propagation characteristic that is not logarithmic can be acquired by dividing the reception level by the transmission level. The acquired propagation characteristics may be stored in a recording medium (not shown).

  The first encryption key acquisition unit 36 acquires the encryption key using the propagation characteristic acquired by the first propagation characteristic acquisition unit 35. For example, the first encryption key acquisition unit 36 may acquire the encryption key using a function having the propagation characteristic as an argument. Also, for example, the first encryption key acquisition unit 36 acquires an encryption key corresponding to the propagation characteristic acquired by the first propagation characteristic acquisition unit 35 using information that associates the propagation characteristic with the encryption key. Also good. Note that the encryption key acquired by the first communication device 3 and the encryption key acquired by the second communication device 4 need to be the same. On the other hand, the propagation characteristics acquired by both apparatuses are likely to be the same, but it is considered that the propagation characteristics do not match exactly. In particular, when the propagation characteristic is a propagation loss, it is considered that there is almost no possibility of exact matching. Therefore, it is preferable to perform rounding processing (fraction processing) to the extent that the propagation characteristics are the same for the propagation characteristics acquired by both apparatuses, and to acquire the encryption key using the propagation characteristics after the processing. It is. The rounding process itself may be considered to be included in the encryption key acquisition process. The encryption key acquired by the first encryption key acquisition unit 36 may be stored on a recording medium (not shown).

  The encryption unit 37 encrypts the communication signal using the encryption key acquired by the first encryption key acquisition unit 36. The encryption by the encryption unit 37 may be encryption by a common key encryption method, for example. The encryption unit 37 may or may not encrypt all the communication signals to be transmitted. In the present embodiment, the latter case will be described. That is, for example, the encryption unit 37 encrypts a communication signal transmitted to a transmission destination that is determined to perform encrypted communication, and does not perform encryption on a communication signal transmitted to a non-transmission destination. Alternatively, communication signals with a large amount of data, such as communication signals including ASCII characters, are encrypted, and communication signals with a small amount of data of about 1 to several bits are not encrypted. Also good.

The first control unit 38 uses the communication signal received by the first reception unit 33 when the reception level measured by the first measurement unit 34 is within a predetermined window, and performs the first measurement. When the reception level measured by the unit 34 is not within the predetermined window, the communication signal received by the first receiving unit 33 is not used. The window has an upper threshold and a lower threshold. Therefore, the first control unit 38 only when the reception level of the communication signal received by the first receiving unit 33 is between a predetermined lower threshold value and an upper threshold value. If the communication signal is used, otherwise, the communication signal is not used. As a result, for example, even if an interference radio wave enters from the outside of the information device 2 or each mechanism inside the information device 2 generates a noise radio wave, there is a possibility that the noise radio wave is received by mistake. Can be reduced. Conventionally, a communication signal has been detected using a lower threshold value for carrier sense in free space, but here, the target communication signal is also detected using an upper threshold value. It is a feature. By doing in this way, for example, even when performing wireless communication using a signal detection level, on-off modulation (On Off Keying), or the like that does not use an advanced modulation / demodulation method in the information device 2, A wireless communication signal inside the housing 5 and a wireless communication signal outside the housing 5 can be distinguished. Note that the window information is stored in a recording medium (not shown), and the first control unit 38 may read and use the information. The information on the window may be set at the stage of operating the information device 2, for example. This is because the position of the window may change depending on the installation location of the information device 2 or the like. Also, using the communication signal may mean passing the communication signal to a subsequent component, for example, the control unit 6 or may be processing for using other communication signals. Also, not using a communication signal may mean discarding the communication signal, not passing the communication signal to a subsequent component, or not using another communication signal. It may be a process.
The first control unit 38 also performs processing for causing the first transmission unit 32 to transmit a communication signal. At this time, as described above, the first control unit 38 determines whether or not encryption is necessary, and when encryption is necessary, the encryption unit 37 performs encryption, and encryption is not necessary. In this case, the encryption unit 37 may be controlled not to perform encryption.

In addition, the first control unit 38 transmits the dummy communication signal, which is a dummy communication signal, to a communication channel that does not perform communication of the actual communication signal, which is a communication signal used for transmission / reception of information. The transmission unit 32 may be controlled. For example, the first transmission unit 32 is configured to transmit an actual communication signal using a plurality of communication channels, and transmits the actual communication signal using one or more of the communication channels. If not, the first control unit 38 may control the first transmission unit 32 to transmit the dummy communication signal in a communication channel that does not transmit the actual communication signal. The dummy communication signal may be a randomly generated communication signal or a predetermined communication signal. This dummy communication signal is transmitted for the purpose of disturbance so that the meaning of the actual communication signal cannot be understood even when a radio wave is intercepted outside the information device 2. For example, by observing the movement of the information device 2 and the radio wave leaking outside from the outside of the housing 5, it may be possible to analyze what movement is being performed by a certain radio wave. On the other hand, since the dummy communication signal is also transmitted, it is possible to prevent the movement of the information device 2 from being easily associated with the radio wave leaked to the outside, and the safety can be improved. Therefore, it is preferable that the signal is similar to the actual communication signal. For example, the dummy communication signal may be a signal having the same number of bits as the actual communication signal. Further, since the dummy communication signal is transmitted for the above purpose, it is preferable that the dummy communication signal is transmitted at the same timing as the actual communication signal. For example, in the case where the first transmission unit 32 performs transmission using a plurality of communication channels and transmits an actual communication signal only on one of the communication channels, the first control unit 38 performs other communication. In the channel, the first transmission unit 32 may be controlled so that the dummy communication signal is transmitted at the same timing as the actual communication signal. In addition, for example, when the actual communication signal is transmitted periodically (for example, every 10 seconds) on another communication channel, the first control unit 38 synchronizes with the transmission timing of the actual communication signal. And you may control the 1st transmission part 32 so that a dummy communication signal may be transmitted. Since the dummy communication signal is preferably transmitted so as not to interfere with the actual communication signal, it is preferable that the dummy communication signal is not transmitted in the communication channel in which the actual communication signal is communicated. The dummy communication signal may be transmitted so that the communication signal can be recognized as a dummy communication signal on the receiving side, or may not be. In the former case, for example, information indicating that the dummy communication signal is a dummy may be included, or the dummy communication signal may be transmitted at a transmission level different from that of the actual communication signal. However, even in such a case, it is necessary that a person who intercepts leaked radio waves outside the housing 5 does not know whether the communication signal is a dummy communication signal.
The first control unit 38 causes the first transmission unit 32 to transmit a communication signal for acquiring propagation characteristics. A communication signal for acquiring propagation characteristics is a communication signal including a transmission level as described above. Note that the communication signal for acquiring propagation characteristics is preferably sent before transmission of the encrypted actual communication signal. This is because the encryption key is acquired before the transmission of the encrypted actual communication signal.

  FIG. 3 is a block diagram showing a configuration of the second communication device 4 according to the present embodiment. 3, the second communication device 4 according to the present embodiment includes a second transmission unit 42, a second reception unit 43, a second measurement unit 44, and a second propagation characteristic acquisition unit 45. , A second encryption key acquisition unit 46, a decryption unit 47, and a second control unit 48.

  The second transmission unit 42 transmits a communication signal via the second antenna 41. The second transmission unit 42 is the same as the first transmission unit 32, and a description thereof will be omitted. In the present embodiment, it is assumed that second transmission unit 42 does not transmit an encrypted communication signal.

  The second receiving unit 43 receives a communication signal via the second antenna 41. The second receiving unit 43 is the same as the first receiving unit 33, and a description thereof will be omitted. In the present embodiment, the second receiving unit 43 also receives an encrypted communication signal.

  The second measuring unit 44 measures the reception level of the communication signal received by the second receiving unit 43. The second measurement unit 44 is the same as the first measurement unit 34, and a description thereof will be omitted.

  The second propagation characteristic acquisition unit 45 acquires the propagation characteristic using the communication signal for propagation characteristic acquisition received by the second reception unit 43. The second propagation characteristic acquisition unit 45 is the same as the first propagation characteristic acquisition unit 35, and a description thereof will be omitted. It is assumed that the type of propagation characteristic acquired by the second propagation characteristic acquisition unit 45 is the same as the type of propagation characteristic acquired by the first propagation characteristic acquisition unit 35. For example, both may be a propagation loss or a delay characteristic profile. In addition, it is preferable that the propagation characteristic acquired by the second propagation characteristic acquisition unit 45 matches the propagation characteristic acquired by the first propagation characteristic acquisition unit 35 within an error range. Therefore, for example, using the communication signal for propagation characteristic acquisition communicated at the same time, the propagation characteristic is acquired by the first propagation characteristic acquisition unit 35 and the propagation characteristic is acquired by the second propagation characteristic acquisition unit 45. Acquisition is preferably performed.

  The second encryption key acquisition unit 46 acquires the encryption key using the propagation characteristic acquired by the second propagation characteristic acquisition unit 45. The second encryption key acquisition unit 46 is the same as the first encryption key acquisition unit 36, and the description thereof is omitted. Note that the method in which the second encryption key acquisition unit 46 acquires the encryption key and the method in which the first encryption key acquisition unit 36 acquires the encryption key are the same. For example, when an encryption key is acquired using a function, the same function is used for both. As described above, when the propagation characteristic acquired by the first propagation characteristic acquisition unit 35 and the propagation characteristic acquired by the second propagation characteristic acquisition unit 45 are the same, the first encryption key acquisition unit 36. The encryption key acquired by the second encryption key acquisition unit 46 is the same as that acquired by the second encryption key acquisition unit 46. However, as described above, even if both propagation characteristics differ by an error, both encryption keys are the same. Thus, it is preferable that a rounding process is appropriately performed when the encryption key is acquired.

  The decryption unit 47 decrypts the encrypted communication signal received by the second reception unit 43 using the encryption key acquired by the second encryption key acquisition unit 46. Decryption by the decryption unit 47 may be, for example, decryption by a common key encryption method. The decrypting unit 47 decrypts all communication signals when all communication signals are encrypted, and encrypts them when some communication signals are encrypted. Decoding may be performed only on the communication signal. Whether the communication signal is encrypted may be determined, for example, by information included in the header of the communication signal, the format of the communication signal, or may be determined by other methods.

The second control unit 48 uses the communication signal received by the second reception unit 43 when the reception level measured by the second measurement unit 44 is within a predetermined window, and performs the second measurement. When the reception level measured by the unit 44 is not within the predetermined window, the communication signal received by the second receiving unit 43 is not used. This process is the same as the process by the first control unit 38, and the description thereof is omitted. Note that using a communication signal may mean passing the communication signal to a subsequent component, for example, the controlled unit 7, or processing for using another communication signal.
The second control unit 48 also performs processing for causing the second transmission unit 42 to transmit a communication signal. In the present embodiment, since the second communication device 4 does not perform encryption, the second control unit 48 does not perform processing related to encryption.

In addition, the second control unit 48 transmits the dummy communication signal, which is a dummy communication signal, to the communication channel where the actual communication signal, which is a communication signal used for transmitting and receiving information, is not communicated. The transmission unit 42 may be controlled. This process is the same as the process by the first control unit 38, and the description thereof is omitted. In addition, when communication of an actual communication signal is performed in a certain communication channel and communication of a dummy communication signal is performed in another communication channel, the first communication device 3 and the second communication device 4 are used. Of these, a dummy communication signal may be transmitted from one device. That is, the first control unit 38 or the second control unit 48 that controls the transmission of the communication signal for the communication channel in which the actual communication signal is not communicated is controlled so that the dummy communication signal is transmitted in the communication channel. May be. Then, which device transmits the dummy communication signal may be set in advance. Therefore, the first control unit 38 and the second control unit 48 may not control the dummy communication signal to be transmitted even in a communication channel in which the actual communication signal is not communicated. Even in the above-described case, dummy communication signals may be transmitted from both devices in one communication channel.
Further, the second control unit 48 causes the second transmission unit 42 to transmit a communication signal for acquiring propagation characteristics. A communication signal for acquiring propagation characteristics is a communication signal including a transmission level as described above. Note that the communication signal for acquiring propagation characteristics is preferably sent before transmission of the encrypted actual communication signal. This is because the encryption key is acquired before the transmission of the encrypted actual communication signal.

When the wireless communication system 1 includes a plurality of first communication devices 3 and / or a plurality of second communication devices 4, each first communication device 3 and each second communication You may communicate with the apparatus 4 using a different communication channel among several communication channels. That is, the communication channel may be different for each combination of the first communication device 3 and the second communication device 4. Note that which communication channel is used between which devices may be set in advance, or sensing may be performed at the time of starting communication to assign a communication channel. In this way, a different communication channel is used for each combination of the first communication device 3 and the second communication device 4, so that in a certain combination of the first communication device 3 and the second communication device 4. Even when communication is performed, communication can be performed in a combination of the other first communication device 3 and the second communication device 4.
Note that the window differs for each transmission source device and for each communication channel. Therefore, a window may be set for all combinations of a transmission source device and a communication channel, or a communication channel window used for communication with a device before the communication with the device is started. It may be set. Thus, the timing at which the window used for communication is set does not matter. In addition, control such as changing the channel when the information device 2 is not performing service may be performed at random.

  Further, when the controlled unit 7 in the information device 2 is a sensor, the sensor often transmits a status signal by wired communication. For example, the sensor transmits a status signal that is at a high level for a long time, or transmits a status signal that is at a low level for a long time. When such a state signal is transmitted by digital wireless communication, sampling is performed at an appropriate time interval, and the state signal is quantized. That is, when communicating the status signal by wired communication, the status signal is continuously communicated, but when communicating the status signal by wireless communication, each sampled status signal is communicated. It will be.

  In addition, the frequency band used for wireless communication in the housing 5 of the information device 2 may be, for example, an ISM 2.4 GHz band that can be used without a wireless license in Japan, and other bands. May be. Also, when the information device 2 is a bank ATM machine or the like, and the user of the ATM machine uses the ATM machine or the like while performing Bluetooth (registered trademark) communication with the PDA device or the like. The PDA device or the like can be an external interference device, and the Bluetooth (registered trademark) communication can be an interference wave from the outside of the information device 2. And the interference radio wave from the external interference device reaches the first communication device 3 or the second communication device 4 and may be received by each, but by performing wireless communication using a window The possibility of receiving the interference radio wave in error can be significantly reduced.

Next, the operation of the first communication device 3 will be described using the flowchart of FIG.
(Step S101) Acquisition of propagation characteristics, acquisition of an encryption key, setting of a window, etc. are performed. Details of this processing will be described later with reference to the flowchart of FIG.

  (Step S102) The first receiver 33 determines whether a communication signal has been received. If received, the process proceeds to step S103, and if not, the process proceeds to step S106.

  (Step S103) The first measuring unit 34 measures the reception level.

  (Step S104) The first control unit 38 determines whether or not the reception level measured by the first measurement unit 34 is within the window. If it is within the window, the process proceeds to step S105. If not, the process returns to step S102. In addition, when returning to step S102, you may perform the process which discards the communication signal which the 1st receiving part 33 received.

  (Step S105) The first control unit 38 uses the received communication signal. The use may be, for example, passing a communication signal to the control unit 6. Then, the process returns to step S102.

  (Step S106) The first control unit 38 determines whether it is time to perform transmission. If it is time to perform transmission, the process proceeds to step S107. If not, the process returns to step S102. Note that the first control unit 38 may determine, for example, that it is a timing to perform transmission periodically, may determine that it is a timing to perform transmission in response to occurrence of a predetermined event, or Alternatively, it may be determined that the transmission is performed at other timing.

  (Step S107) The first control unit 38 determines whether there is an actual communication signal to be transmitted. If there is an actual communication signal, the process proceeds to step S108, and if not, the process proceeds to step S111. For example, the first control unit 38 may determine that an actual communication signal exists when the actual communication signal is stored in a buffer memory in which the actual communication signal to be transmitted is temporarily stored.

  (Step S108) The first control unit 38 determines whether to perform encryption. If the encryption is to be performed, the process proceeds to step S109. If not, the process proceeds to step S110. Note that the first control unit 38 may determine that encryption is performed, for example, when transmitting to a transmission destination that is determined to perform encrypted communication.

  (Step S109) The encryption unit 37 encrypts the actual communication signal to be transmitted.

  (Step S <b> 110) The first transmission unit 32 transmits the actual communication signal via the first antenna 31. If the encryption in step S109 is performed, the encrypted actual communication signal is transmitted. Then, the process returns to step S102.

  (Step S <b> 111) The first transmission unit 32 transmits a dummy communication signal via the first antenna 31. The dummy communication signal may be stored in advance on a recording medium (not shown), or may be generated by the first control unit 38. Then, the process returns to step S102. In addition, when the substantial communication signal transmitted on another communication channel is encrypted in parallel with the transmission of the dummy communication signal, the dummy communication signal may be encrypted accordingly.

  In the flowchart of FIG. 4, the process ends when the power is turned off or the process ends. In the flowchart of FIG. 4, when the first transmission unit 32 performs transmission using a plurality of communication channels, the processing of steps S107 to S111 may be repeated for the number of communication channels.

  FIG. 5 is a flowchart showing details of the setting process (step S101) in the flowchart of FIG. In the present embodiment, a case will be described in which first communication device 3 first transmits a communication signal for acquiring propagation characteristics, and second communication device 4 transmits a communication signal for acquiring propagation characteristics accordingly. .

  (Step S201) The first control unit 38 configures a communication signal for acquiring propagation characteristics including a transmission level, and controls the first transmission unit 32 to transmit the communication signal at the transmission level. As a result, the first transmission unit 32 transmits the communication signal for acquiring the propagation characteristics at the transmission level.

  (Step S202) The first receiving unit 33 determines whether a communication signal for acquiring propagation characteristics transmitted from the second communication device 4 has been received in response to transmission of a communication signal for acquiring propagation characteristics. If received, the process proceeds to step S203. If not, the process of step S202 is repeated until received.

  (Step S203) The first measuring unit 34 measures the reception level of the communication signal for acquiring propagation characteristics received by the first receiving unit 33.

  (Step S204) The first propagation characteristic acquisition unit 35 uses the reception level acquired by the first measurement unit 34 and the transmission level indicated by the communication signal for acquisition of propagation characteristics received by the first reception unit 33. Thus, the propagation characteristic which is the propagation loss is acquired.

  (Step S205) The first encryption key acquisition unit 36 acquires the encryption key using the propagation characteristics acquired by the first propagation characteristic acquisition unit 35.

  (Step S206) The first control unit 38 sets a window using the reception level acquired by the first measurement unit 34. The window includes an upper threshold value that is higher than a reception level measured by the first measurement unit 34 by a predetermined level and a lower threshold value that is lower than the reception level by a predetermined level. You may have. And it returns to the flowchart of FIG.

  In the flowchart of FIG. 5, when the first receiving unit 33 performs reception using a plurality of communication channels, the process of the flowchart of FIG. 5 may be performed for the number of communication channels.

Next, the operation of the second communication device 4 will be described using the flowchart of FIG.
(Step S301) Acquisition of propagation characteristics, acquisition of an encryption key, setting of a window, etc. are performed. Details of this processing will be described later with reference to the flowchart of FIG.

  (Step S302) The second receiving unit 43 determines whether a communication signal has been received. If it is received, the process proceeds to step S303, and if not, the process proceeds to step S308.

  (Step S303) The second measuring unit 44 measures the reception level.

  (Step S304) The second control unit 48 determines whether or not the reception level measured by the second measurement unit 44 is within the window. If it is within the window, the process proceeds to step S305; otherwise, the process returns to step S302. In addition, when returning to step S302, you may perform the process which discards the communication signal which the 2nd receiving part 43 received.

  (Step S305) The second control unit 48 determines whether or not the received communication signal is encrypted. If it is encrypted, the process proceeds to step S306. If not, the process proceeds to step S307. Whether it is encrypted or not may be determined by the format of the communication signal.

  (Step S306) The decryption unit 47 decrypts the encrypted communication signal.

  (Step S307) The first control unit 38 uses the received communication signal. The use may be, for example, passing a communication signal to the controlled unit 7. Then, the process returns to step S302.

  (Step S308) The second control unit 48 determines whether it is time to perform transmission. If it is time to perform transmission, the process proceeds to step S309. If not, the process returns to step S302. Note that the second control unit 48 may determine, for example, that it is time to perform transmission periodically, may determine that it is time to perform transmission in response to occurrence of a predetermined event, or Alternatively, it may be determined that the transmission is performed at other timing.

  (Step S309) The second control unit 48 determines whether there is an actual communication signal to be transmitted. If there is an actual communication signal, the process proceeds to step S310. If not, the process proceeds to step S311. For example, the second control unit 48 may determine that an actual communication signal exists when the actual communication signal is stored in a buffer memory in which the actual communication signal to be transmitted is temporarily stored.

  (Step S <b> 310) The second transmission unit 42 transmits the actual communication signal via the second antenna 41. Then, the process returns to step S302.

  (Step S <b> 311) The second transmission unit 42 transmits a dummy communication signal via the second antenna 41. The dummy communication signal may be stored in advance on a recording medium (not shown), or may be generated by the second control unit 48. Then, the process returns to step S302.

  In the flowchart of FIG. 6, the process ends when the power is turned off or the process ends. In the flowchart of FIG. 6, when the second transmission unit 42 performs transmission using a plurality of communication channels, the processes of steps S309 to S311 may be repeated for the number of communication channels.

FIG. 7 is a flowchart showing details of the setting process (step S301) in the flowchart of FIG.
(Step S401) The second receiving unit 43 determines whether or not a communication signal for acquiring propagation characteristics has been received. If received, the process proceeds to step S402. If not, the process of step S401 is repeated until received.

  (Step S402) The second control unit 48 configures a communication signal for obtaining propagation characteristics including a transmission level, and controls the second transmission unit 42 to transmit the communication signal at the transmission level. As a result, the second transmitter 42 transmits the communication signal for acquiring the propagation characteristics at the transmission level. Thus, even if there is a time change in the interference radio wave from the outside of the housing 5 by transmitting the communication signal for acquiring the propagation characteristics immediately after receiving the communication signal for acquiring the propagation characteristics, the first The difference in propagation characteristics acquired by the communication device 3 and the second communication device 4 can be reduced.

  (Step S403) The second measuring unit 44 measures the reception level of the communication signal for acquiring propagation characteristics received by the second receiving unit 43.

  (Step S404) The second propagation characteristic acquisition unit 45 uses the reception level acquired by the second measurement unit 44 and the transmission level indicated by the communication signal for acquisition of propagation characteristic received by the second reception unit 43. Thus, the propagation characteristic which is the propagation loss is acquired.

  (Step S405) The second encryption key acquisition unit 46 acquires the encryption key using the propagation characteristics acquired by the second propagation characteristic acquisition unit 45.

  (Step S406) The second control unit 48 sets a window using the reception level measured by the second measurement unit 44. The window includes an upper threshold value that is higher than a reception level measured by the second measuring unit 44 by a predetermined level and a lower threshold value that is lower than the reception level by a predetermined level. You may have. And it returns to the flowchart of FIG.

  In the flowchart of FIG. 7, when the second reception unit 43 performs reception using a plurality of communication channels, the process of the flowchart of FIG. 7 may be performed for the number of communication channels.

  Note that the timing at which the setting processing in steps S101 and S301 is performed does not matter. For example, the setting process may be performed when the information device 2 is turned on, or the setting process may be performed when the wireless communication in the information device 2 is reset. Further, the resetting of the wireless communication may be performed, for example, when a situation in which an interference radio wave from the outside of the housing 5 can change, such as the movement of the information device 2, occurs.

  In the setting process shown in the flowcharts of FIGS. 5 and 7, the case where the first communication apparatus 3 starts the setting process has been described, but this need not be the case. The second communication device 4 may start the setting process. In the setting process, after the window setting is completed, a communication signal notifying the completion of the setting may be transmitted to the communication destination. Further, in the setting process, the case where the window is set using the communication signal for acquiring the propagation characteristics has been described, but this need not be the case. The acquisition of the propagation characteristics and the window setting may be performed using different communication signals. When setting the window, the transmission level may be lowered within a range in which appropriate communication is performed between both apparatuses, and the window may be set according to the transmission level. This is to reduce power consumption during transmission during operation. In this case, the actual communication signal is transmitted according to the transmission level at which the window is set.

  Next, the operation of the wireless communication system 1 according to the present embodiment will be described using a specific example. In this specific example, as shown in FIG. 8, one first communication device 3 and five second communication devices 4 a to 4 e provided in the housing 5 of the information device 2. A case in which wireless communication using communication channels CH1 to CH5 is performed will be described. The second communication devices 4a to 4e are connected to the controlled units 7a to 7e, respectively, pass the received communication signals to the controlled units 7a to 7e, and receive the signals received from the controlled units 7a to 7e. The data is transmitted to the first communication device 3. The configuration and operation of the second communication devices 4a to 4e are the same as those of the second communication device 4 described above.

  First, when the information device 2 is turned on, setting processing is performed between the first communication device 3 and the second communication devices 4a to 4e (steps S101 and S301). Specifically, first, the first control unit 38 configures a communication signal for acquiring propagation characteristics including a transmission level, and transmits the communication signal at the transmission level on the communication channel CH1. 1 transmission unit 32 is controlled. Then, the first transmitter 32 transmits the communication signal for acquiring the propagation characteristics at the set transmission level and on the communication channel CH1 (step S201). The second receiving unit 43 of the second communication device 4a receives the communication signal for propagation characteristic acquisition transmitted from the first communication device 3 through the communication channel CH1, and performs the second control on the received communication signal. To the unit 48 and the second propagation characteristic acquisition unit 45 (step S401). Then, the second control unit 48 configures a communication signal for acquiring propagation characteristics including a transmission level, and transmits the communication signal at the transmission level via the communication channel CH1. To control. Then, the second transmitter 42 transmits the communication signal for acquiring the propagation characteristics at the set transmission level and on the communication channel CH1 (step S402). The second measuring unit 44 measures the reception level of the propagation characteristic acquisition communication signal received by the second receiving unit 43, and the measured reception level is compared with the second control unit 48 and the second control unit 48. It passes to the propagation characteristic acquisition part 45 (step S403). The second propagation characteristic acquisition unit 45 uses the transmission level indicated by the communication signal received from the second reception unit 43 and the reception level received from the second measurement unit 44 to determine the propagation characteristic that is a propagation loss. Obtain it and pass it to the second encryption key obtaining unit 46 (step S404). The second encryption key acquisition unit 46 generates an encryption key using the received propagation characteristics, and passes the generated encryption key to the decryption unit 47 (step S405). The decryption unit 47 stores the received encryption key in a recording medium (not shown). Further, the second control unit 48 sets the window using the reception level received from the second measurement unit 44. That is, the second control unit 48 sets a window having an upper limit threshold obtained by adding a predetermined level to the reception level and a lower limit threshold obtained by subtracting the predetermined level from the reception level to the communication channel CH1. The information is stored in association with a recording medium (not shown) (step S406). For example, it is assumed that the communication signal for acquiring the propagation characteristics of the communication channel CH1 received by the second receiving unit 43 is as shown in FIG. Then, since the reception level is measured by the second measurement unit 44 and passed to the second control unit 48, the second control unit 48 has upper and lower thresholds as shown in FIG. 9A. Sets the window that is the value.

  The first receiving unit 33 of the first communication device 3 receives the communication signal for acquiring propagation characteristics transmitted from the second communication device 4a through the communication channel CH1 (step S202). The first measurement unit 34 measures the reception level of the propagation characteristic acquisition communication signal received by the first reception unit 33, and uses the measured reception level as the first control unit 38 and the first propagation characteristic. The data is transferred to the acquisition unit 35 (step S203). The first propagation characteristic acquisition unit 35 uses the transmission level indicated by the communication signal received from the first reception unit 33 and the reception level received from the first measurement unit 34 to determine the propagation characteristic that is a propagation loss. Obtain and pass to the first encryption key obtaining unit 36 (step S204). The first encryption key acquisition unit 36 generates an encryption key using the received propagation characteristics, and passes the generated encryption key to the encryption unit 37 (step S205). The encryption unit 37 stores the received encryption key in a recording medium (not shown). Further, the first control unit 38 sets a window using the reception level received from the first measurement unit 34 and stores it in a recording medium (not shown) in association with the communication channel CH1 (step S206).

  Note that the same processing is performed between the first communication device 3 and the second communication devices 4b to 4e (steps S201 to S206, S401 to S406). As a result, as shown in FIG. 9C, the first control unit 38 sets windows for the communication channels CH1 to CH5.

  In the subsequent transmission of the communication signal, the first transmission unit 32 and the second transmission unit 42 transmit the actual communication signal at the same transmission level as when the communication signal for propagation characteristic acquisition was transmitted. . On the other hand, in this specific example, when transmitting the dummy communication signal, the first transmission unit 32 and the second transmission unit 42 transmit at a transmission level different from that when the communication signal for propagation characteristic acquisition is transmitted. And In addition, each of the second communication devices 4a to 4e performs communication every T seconds (for example, every 10 seconds) with the time point when the power of the information device 2 is turned on. . On the other hand, transmission from the first communication device 3 is performed irregularly.

  Here, a reception process using a window will be briefly described. For example, assume that the second communication device 4c receives a communication signal of the communication channel CH3 (step S302). Then, when the reception level measured at that time is larger than the lower limit threshold and smaller than the upper limit threshold, that is, when it is within the window as shown in FIG. The communication signal is used (steps S303, S304, S307). When the communication signal is encrypted, the encryption is released and used (steps S305 and S306). On the other hand, when the measured reception level is smaller than the lower threshold, that is, when it is outside the window as shown in FIG. 10B, or the measured reception level is larger than the upper threshold. In this case, that is, when it is outside the window as shown in FIG. 10C, the communication signal is not used (steps S303 and S304). This is because these communication signals are considered to be interference radio waves from the outside of the housing 5 of the information device 2 or noise radio waves generated in the information device 2. Thus, the selection of the communication signal according to the set window is the same when the first communication apparatus 3 performs reception (steps S102 to S105).

  Thereafter, it is assumed that the control unit 6 passes a request for a measurement value to the controlled unit 7c to the first communication device 3 in order to acquire a value measured by the controlled unit 7c, which is a sensor. The control unit 6 holds information for associating the controlled units 7a to 7e with the communication channels CH1 to CH5 in a recording medium (not shown), and uses the information to correspond to the controlled unit 7c. A communication channel CH3 is specified. And the request | requirement of the measured value to the to-be-controlled part 7c is accumulate | stored in the buffer memory of the actual communication signal corresponding to communication channel CH3. Then, the 1st control part 38 of the 1st communication apparatus 3 judges that it is a timing which performs transmission (step S106), and judges that the actual communication signal which is a request | requirement of a measured value exists about communication channel CH3. (Step S107). It is assumed that encryption communication is not performed in communication over the communication channel CH3. Then, in this case, encryption is not necessary (step S108), and the first transmission unit 32 transmits the actual communication signal through the communication channel CH3 (step S110). Simultaneously with the transmission of the actual communication signal, a dummy communication signal may be transmitted for the other channels CH1, 2, 4, and 5 (step S111). As described above, since the dummy communication signal is transmitted at a transmission level different from the communication signal for acquiring the propagation characteristics, it is not used even if it is received by the second communication devices 4a, 4b, 4d, and 4e ( Steps S302 to S304). On the other hand, the actual communication signal transmitted through the communication channel CH3 is received by the second receiving unit 43 of the second communication device 4c (step S302), the reception level is measured (step S303), and the reception level is within the window. Is determined (step S304) and passed to the controlled unit 7c (steps S305 and S307). When the controlled unit 7 c receives the actual communication signal, the controlled unit 7 c acquires the measured value and passes the actual communication signal that is the measured value to the second control unit 48. Then, when the next transmission timing comes (step S308), the second control unit 48 of the second communication device 4c determines that there is an actual communication signal (step S309), and sends the actual communication signal. The second transmitter 42 is caused to transmit on the communication channel CH3 (step S310). The second control unit 48 of the second communication device 4a, 4b, 4d, 4e other than the second communication device 4c determines that there is no actual communication signal at the transmission timing (step S309), and performs dummy communication. It is assumed that the signal is transmitted to the second transmission unit 42 through each communication channel CH1, 2, 4, 5 (step S311). As a result, the actual communication signal of the communication channel CH3 is transmitted together with the dummy communication signals of the other communication channels, and even if the radio wave is intercepted outside the information device 2, which radio wave is received. Whether it is significant or not will be disturbed, and analysis of the operation algorithm in the device may be hindered. Note that, in the first communication device 3, only the actual communication signal transmitted through the communication channel CH3 is passed to the control unit 6 (steps S102 to S105).

  As described above, according to the wireless communication system 1 according to the present embodiment, wireless communication can be performed in the information device 2 instead of wired communication. Therefore, the wire used inside the information equipment 2 can be reduced. For example, the length of a wire used for one ATM device is several kilometers, and more than 2 million ATM devices are currently used in the world. By making the wires of these information devices 2 wireless, a huge amount of wires can be reduced. Further, in the case of wired communication, since the wiring is complicatedly related to the mechanism configuration inside the information device 2, complicated work is required both during the design work and during the assembly work. Furthermore, the large number of wires is a factor that causes a decrease in maintainability such as wire biting at the time of opening and closing the housing even during operation. On the other hand, wireless design can reduce the design work and assembly work related to wiring, and can also improve the maintainability. Therefore, human costs can be reduced in terms of design, manufacturing, and operation.

  Further, since the wireless communication between the first communication device 3 and the second communication device 4 is not mobile communication but fixed communication, the reception level of the communication signal transmitted by the communication destination is constant. Therefore, by setting a window according to the reception level and using only the communication signal at the reception level in the window, only the intended communication signal can be used, and radio waves from outside the housing can be used. Interference or interference due to the above can be eliminated, and malfunction can be prevented.

  In addition, in wireless communication within the casing 5 of the information device 2, if a high transmission rate can be used, the communication signal can be made redundant, and high quality using a high-level modulation / interference suppression function can be obtained. Wireless communication can be realized. However, the inside of the housing 5 is an environment in which many multipaths occur, and intersymbol interference occurs. Therefore, it is difficult to perform wireless communication at a high transmission rate. In addition, having an advanced interference suppression function at a low transmission rate causes a decrease in data throughput and is not appropriate. Furthermore, a large amount of power is required to operate an advanced signal processing function. For example, in the wireless communication between the sensors in the information device 2 and the control unit that collects the information, in order to reduce the wiring to the limit, only the signal wiring between the sensors and the control unit is deleted. In addition, it is necessary to delete the power supply wiring. In order to delete the power line, it is necessary to drive sensors that fit in a narrow space in the information device 2 with a battery. In order to continue to use the battery without exchange during a certain operation period, it is not appropriate to supply a large amount of power for encoding / decoding, modulation / demodulation of a communication signal. Therefore, it is preferable to perform wireless communication using the set window as described above, rather than realizing high-quality wireless communication using an advanced modulation / interference suppression function.

  Further, when communication is performed using an actual communication signal, a weak radio wave in the information device 2 is weakened by transmitting a dummy communication signal on a communication channel other than the communication channel used for communication of the actual communication signal. It is possible to make it difficult to acquire a serious leak outside the housing 5 or to make an analysis of the acquired radio wave difficult. As a result, it is possible to protect against the side channel method, which is an analysis method for inferring an operation algorithm in the device by collecting radio waves leaking from the information device 2. In particular, in the case of a communication signal with a small amount of data, for example, in the case of a 1-bit communication signal, the information itself is binary (1 or 0) even if 16-bit encryption is performed. If the communication signal is found to be binary even if it is encrypted to the state of (street), there is a problem that the content of the communication signal is read with a probability of 1/2. On the other hand, by transmitting the dummy communication signal, it is difficult to grasp the relationship between the operation of the information device 2 and the internal wireless communication, and the safety is improved.

  Also, secure wireless communication can be realized by acquiring an encryption key using propagation characteristics that only the first communication device 3 and the second communication device 4 can know. This wireless communication may be applied to communication such as serial data inside the information device 2, for example. The propagation characteristics inside the information device 2 are determined by its internal structure, the position / angle of the first communication device 3, the position / angle of the second communication device 4, the reflection coefficient of the internal device, and the like. However, the inside of the information device 2 is usually very complicated, and it is difficult to theoretically calculate the propagation characteristics in the inside. Therefore, when the encryption key is acquired using the propagation characteristics that only the first communication device 3 and the second communication device 4 can know, even if the encryption key acquisition algorithm is known, the Since the propagation characteristics cannot be known, it is difficult to predict what kind of encryption key is used, and the security of encrypted wireless communication is improved.

  In order to conceal wireless communication inside the information device 2, wireless communication using a low-probability characteristic of radio waves by a frequency spreading method is also conceivable. However, the inside of the information device 2 is an environment with many multipaths as described above, and there are many dips in the frequency characteristics. For this reason, wireless communication using the frequency spreading method inside the information device 2 is not appropriate for the occupation of the frequency band because the communication quality deteriorates.

  In the present embodiment, the case of acquiring the propagation characteristic that is the propagation loss has been mainly described. However, as described above, the propagation characteristic may be a delay characteristic profile. In this case, for example, the first propagation characteristic acquisition unit 35 and the second propagation characteristic acquisition unit 45 may acquire a propagation characteristic that is a delay time between paths, and a threshold (predetermined Value, or a value obtained by multiplying the reception level of the first path by a predetermined value less than 1). You may acquire the propagation characteristic which is a value regarding a delay characteristic profile. In addition, the first propagation characteristic acquisition unit 35 and the second propagation characteristic acquisition unit 45 may acquire other propagation characteristics. For example, propagation characteristics such as the dip frequency and the number of dip in a certain frequency band may be acquired.

  Moreover, although the case where encryption was performed by the first communication device 3 and decryption was performed by the second communication device 4 has been described in the present embodiment, this need not be the case. Encryption may be performed in the second communication device 4 and decryption may be performed in the first communication device 3, or encryption may be performed in both the first communication device 3 and the second communication device 4. Both decoding may be performed.

  In the present embodiment, the case where encryption is performed using an encryption key acquired using propagation characteristics has been described, but this need not be the case. Encryption using another encryption key may be performed, or encryption may not be performed. When encryption using the encryption key acquired using the propagation characteristics is not performed, the first communication device 3 includes the first propagation characteristic acquisition unit 35, the first encryption key acquisition unit 36, The encryption unit 37 may not be included, and the second communication device 4 may not include the second propagation characteristic acquisition unit 45, the second encryption key acquisition unit 46, and the decryption unit 47.

  Moreover, although this Embodiment demonstrated the case where a dummy communication signal was transmitted in order to improve safety | security, it may not be so. For example, if there is no problem even if the internal radio wave leaks, or even if it is a signal of about several bits, it is encrypted with a large amount of data by adding a randomly generated signal, etc. The dummy communication signal may not be transmitted.

  Moreover, although this Embodiment demonstrated the case where bidirectional | two-way communication was performed between the 1st communication apparatus 3 and the 2nd communication apparatus 4, it does not need to be so. Transmission may be performed only in the direction from the first communication device 3 to the second communication device 4. In that case, the first communication device 3 may not include the first reception unit 33 and the first measurement unit 34, and the second communication device 4 includes the second transmission unit 42. It does not have to be provided.

  Further, although a case has been described with the present embodiment where communication is performed using a plurality of communication channels, this need not be the case. Communication may be performed using a single communication channel. As described above, communication is performed using a single communication channel, and the wireless communication system 1 includes a plurality of first communication devices 3 and / or a plurality of second communication devices 4. In this case, each first communication device 3 and each second communication device 4 may perform communication while shifting the transmission timing of the communication signal using a single communication channel.

  In the above embodiment, each process or each function may be realized by centralized processing by a single device or a single system, or may be distributedly processed by a plurality of devices or a plurality of systems. It may be realized by doing.

  In the above embodiment, the information exchange between the components is performed by one component when, for example, the two components that exchange the information are physically different from each other. It may be performed by outputting information and receiving information by the other component, or when two components that exchange information are physically the same, one component May be performed by moving from the phase of the process corresponding to to the phase of the process corresponding to the other component.

  In the above embodiment, information related to processing executed by each component, for example, information received, acquired, selected, generated, transmitted, or received by each component In addition, information such as threshold values, mathematical formulas, addresses, etc. used by each component in processing is retained temporarily or over a long period of time on a recording medium (not shown) even when not explicitly stated in the above description. It may be. Further, the storage of information in the recording medium (not shown) may be performed by each component or a storage unit (not shown). Further, reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

  In the above embodiment, when information used by each component, for example, information such as a threshold value, an address, and various setting values used by each component may be changed by the user Even if it is not specified in the above description, the user may be able to change the information as appropriate, or it may not be. If the information can be changed by the user, the change is realized by, for example, a not-shown receiving unit that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. May be. The change instruction received by the receiving unit (not shown) may be received from an input device, information received via a communication line, or information read from a predetermined recording medium, for example. .

  In the above embodiment, when two or more components included in the first communication device 3 or the second communication device 4 include a communication device, an input device, or the like, the two or more components are physically You may have a single device or you may have separate devices.

  Further, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  As described above, according to the wireless communication system and the like according to the present invention, an effect that wireless communication can be realized in the casing of the information device is obtained. Useful as.

DESCRIPTION OF SYMBOLS 1 Wireless communication system 2 Information equipment 3 1st communication apparatus 4, 4a-4e 2nd communication apparatus 5 Case 6 Control part 7, 7a-7e Controlled part 31 1st antenna 32 1st transmission part 33 1st 1 receiver 34 first measurement unit 35 first propagation characteristic acquisition unit 36 first encryption key acquisition unit 37 encryption unit 38 first control unit 41 second antenna 42 second transmission unit 43 second Receiver unit 44 second measurement unit 45 second propagation characteristic acquisition unit 46 second encryption key acquisition unit 47 decryption unit 48 second control unit

Claims (10)

One or more first communication devices and one or more second communication devices provided in a housing of an information device are provided, and wireless communication is performed between the first communication device and the second communication device. A wireless communication system,
The first communication device is:
A first transmitter that transmits a communication signal via an antenna;
A first control unit that causes the first transmission unit to transmit a communication signal,
The second communication device is:
A second receiving unit for receiving a communication signal via an antenna;
A second measuring unit for measuring a reception level of a communication signal received by the second receiving unit;
When the reception level measured by the second measurement unit is within a predetermined window, the reception level measured by the second measurement unit is determined using the communication signal received by the second reception unit. A wireless communication system, comprising: a second control unit that does not use a communication signal received by the second receiving unit when it is not within a predetermined window. A plurality of the first communication devices, and / or a plurality of the second communication devices,
2. The wireless communication system according to claim 1, wherein each of the first communication devices and each of the second communication devices perform communication using different communication channels among a plurality of communication channels. The first control unit transmits the dummy communication signal, which is a dummy communication signal, to a communication channel that does not perform communication of an actual communication signal, which is a communication signal used for exchange of information. The wireless communication system according to claim 2, wherein the wireless communication system is controlled. The first communication device is:
A first receiving unit for receiving a communication signal via an antenna;
A first measuring unit that measures a reception level of a communication signal received by the first receiving unit;
The first control unit uses a communication signal received by the first reception unit when the reception level measured by the first measurement unit is within a predetermined window. When the reception level measured by the measurement unit is not within a predetermined window, the communication signal received by the first reception unit is not used.
The second communication device is:
A second transmitter for transmitting a communication signal via the antenna;
The wireless communication system according to claim 1, wherein the second control unit causes a communication signal to be transmitted by the second transmission unit. A plurality of the first communication devices, and / or a plurality of the second communication devices,
Each of the first communication devices and each of the second communication devices communicate using different communication channels among a plurality of communication channels,
The first control unit or the second control unit that controls transmission of a communication signal for a communication channel in which an actual communication signal that is a communication signal used for transmission / reception of information is not performed is a dummy in the communication channel. The wireless communication system according to claim 4, wherein control is performed such that a dummy communication signal, which is a communication signal of The first control unit causes the first transmission unit to transmit a communication signal for obtaining propagation characteristics,
The second control unit is for causing the second transmission unit to transmit a communication signal for obtaining propagation characteristics,
The first communication device is:
A first propagation characteristic acquisition unit that acquires a propagation characteristic using a communication signal for propagation characteristic acquisition received by the first reception unit;
A first encryption key acquisition unit that acquires an encryption key using the propagation characteristic acquired by the first propagation characteristic acquisition unit;
An encryption unit that encrypts a communication signal using the encryption key acquired by the first encryption key acquisition unit;
The first transmission unit transmits the communication signal encrypted by the encryption unit,
The second receiving unit receives the encrypted communication signal,
The second communication device is:
A second propagation characteristic acquisition unit that acquires a propagation characteristic using the communication signal for propagation characteristic acquisition received by the second reception unit;
A second encryption key acquisition unit that acquires an encryption key using the propagation characteristic acquired by the second propagation characteristic acquisition unit;
The radio | wireless of Claim 4 further provided with the decoding part which decodes the encrypted communication signal which the said 2nd receiving part received using the encryption key which the said 2nd encryption key acquisition part acquired. Communications system. The wireless communication system according to claim 1, wherein the casing of the information device is a metal casing. A wireless communication system according to any one of claims 1 to 7,
An information device that exchanges signals in the device by wireless communication between the first communication device and the second communication device. A receiving unit for receiving a communication signal via an antenna;
A measurement unit for measuring a reception level of a communication signal received by the reception unit;
When the reception level measured by the measurement unit is within a predetermined window, the communication level received by the reception unit is used, and the reception level measured by the measurement unit is not within the predetermined window And a control unit that does not use a communication signal received by the receiving unit. Wireless communication performed between the first communication device and the second communication device using one or more first communication devices and one or more second communication devices provided in a casing of the information device A method,
The first communication device transmits a communication signal via an antenna;
The second communication device receives a communication signal via an antenna;
The second communication device measuring a reception level of the received communication signal;
The second communication device determining whether the measured reception level is within a predetermined window;
The second communication device uses the received communication signal when the reception level is within a predetermined window, and the received communication signal when the reception level is not within the predetermined window. And a step of not using the wireless communication method.

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