JP2016197835A - Transmission device, reception device, and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission device, a reception device, and a radio communication system that can reduce frequency bandwidth used for radio communication while maintaining the anti-eavesdropping performance and confidentiality of secret data.SOLUTION: A transmission device comprises a plurality of transmission systems each including a modem for modulating input data and outputting it as a radio signal at a prescribed carrier wave frequency and an antenna device for emitting the radio signal as a radio wave, and switches a modulation scheme and a carrier wave frequency used per transmission system at prescribed intervals on the basis of a combination pattern generated by a pattern generation unit.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transmission device, a reception device, and a wireless communication system including them.

In general, in a wireless communication system, a modulation / demodulation method, a carrier wave frequency, and the like are defined as standard communication methods used in wireless communication. Some communication systems can be switched between modulation / demodulation systems and carrier frequencies, but these communication systems are usually selected appropriately from predetermined modulation / demodulation systems and carrier frequencies according to the communication quality and the like. .
That is, in a general wireless communication system, a modulation / demodulation method and a carrier wave frequency used for wireless communication are determined, so that a wireless signal transmitted / received between a transmission device and a reception device by a third party may be intercepted. There is. In that case, there is a possibility that the contents of communication may be wiretapped by performing signal processing and analysis on the intercepted radio signal.

For example, Patent Documents 1 and 2 propose a technique for making it difficult to eavesdrop by such a third party and improving the secrecy of data that is not desired to be intercepted during communication (secret data).
Patent Document 1 describes a technique that makes it difficult for a third party to eavesdrop by switching the modulation / demodulation method and the carrier wave frequency at predetermined time intervals or packet units. Patent Document 1 also discloses that the modulation / demodulation method and carrier frequency used by the transmission device and the reception device coincide with each other by encrypting and transmitting information indicating the modulation / demodulation method and carrier frequency to be used next from the transmission device to the reception device. Is described. Further, Patent Document 1 describes that it is difficult for a third party to eavesdrop on confidential data by simultaneously transmitting dummy data together with the confidential data.

  Patent Document 2 describes a technique that makes it difficult for a third party to eavesdrop by switching a communication slot and a carrier frequency used for data transmission in a wireless communication system employing a time division multiple access method. .

JP 2004-336720 A JP 2008-011159 A

According to the techniques described in Patent Documents 1 and 2 described above, information necessary for interception by a third party can be reduced by switching the modulation / demodulation method, carrier frequency, or communication slot. Interceptability can be improved.
In addition, if the dummy data is transmitted simultaneously with the confidential data, even if the confidential data is intercepted by a third party, it is difficult to discriminate it from the dummy data intercepted at the same time. Can be difficult.

  However, the configuration in which secret data and dummy data are transmitted using a plurality of wireless systems has a problem that it is necessary to maintain a wide frequency band for wireless communication.

  The present invention was made to solve the problems of the background art as described above, and a transmission device that can reduce the frequency bandwidth used for wireless communication while maintaining the interception resistance and confidentiality of the confidential data, An object is to provide a receiving apparatus and a wireless communication system.

In order to achieve the above object, a transmission apparatus of the present invention comprises a plurality of transmission systems including a modem that modulates input data and outputs a radio signal having a predetermined carrier frequency, and an antenna apparatus that radiates the radio signal as a radio wave;
A route switching and dummy output unit that outputs the input secret data to at least one of the transmission systems, and outputs dummy data to another transmission system different from the transmission system that outputs the secret data,
A pattern generator for generating a combination pattern of a modulation scheme and a carrier frequency used for transmission of the secret data and the dummy data;
Instructing the transmission system for outputting the secret data and the dummy data to the path switching and dummy output unit according to the combination pattern generated by the pattern generation unit, the modulation scheme performed by the modem and the carrier frequency used for transmission, A control unit for instructing
Have
The modem is
The modulation scheme and the carrier frequency to be implemented are switched in a predetermined period based on the combination pattern generated by the pattern generator.

On the other hand, the receiving device of the present invention is an antenna device that receives a radio signal transmitted from a transmitting device, down-converts the radio signal received by the antenna device into a baseband signal of a predetermined frequency band, and indicates the indicated demodulation A plurality of receiving systems including modems that demodulate and reproduce received data
A signal determination unit that extracts and outputs the confidential data from the reception data reproduced by the plurality of reception systems;
A pattern generator for generating a combination pattern of a demodulation method and a conversion frequency corresponding to a modulation method and a carrier frequency used in the transmission device;
A control unit for instructing the modem to receive the secret data according to the combination pattern generated by the pattern generation unit to the signal determination unit, and for instructing the modem a demodulation method and a conversion frequency to be applied to the radio signal; ,
Have
The controller is
In this configuration, the demodulation method and the conversion frequency used for each reception system are switched in a predetermined period based on the combination pattern generated by the pattern generation unit.

  The wireless communication system of the present invention includes the above-described transmission device and the above-described reception device.

  ADVANTAGE OF THE INVENTION According to this invention, the frequency bandwidth utilized for radio | wireless communication can be reduced, maintaining the interception resistance and secrecy of secret data.

It is a schematic diagram which shows a mode that the carrier wave frequency used for transmission of secret data and dummy data is switched. It is a schematic diagram which shows a mode that the modulation system used for transmission of secret data and dummy data is switched. It is a schematic diagram which shows a mode that the other modulation system used for transmission of secret data and dummy data is switched. It is a block diagram which shows the example of 1 structure of the transmitter of this invention. It is a block diagram which shows the example of 1 structure of the receiver of this invention. It is a schematic diagram which shows the example of a switching of the modulation system used for transmission of secret data and dummy data, a carrier frequency, and the number of transmission systems.

Next, the present invention will be described with reference to the drawings.
In the present invention, the dummy data is transmitted simultaneously with the confidential data. Here, as a communication method used for transmission / reception of confidential data and dummy data, a communication method using a plurality of carrier frequencies, such as a frequency-division multiple access (FDMA) method, and a code division multiple It can be roughly classified into communication systems that use the same carrier frequency, such as a connection (Code Division Multiple Access: CDMA) system.
Therefore, in the case of a communication scheme that uses (or can use) a plurality of carrier frequencies, such as the FDMA scheme, a predetermined period in which carrier frequencies used for transmission of secret data and dummy data are set in advance as shown in FIG. Switch at every unit time or every communication. Further, as shown in FIG. 2, the modulation / demodulation method used for transmission of the secret data and the dummy data is switched in a predetermined period (every unit time or every communication).
On the other hand, in the case of a communication method using the same carrier frequency as in the CDMA method, the spreading code used for modulation of secret data and dummy data is switched in a predetermined period (every unit time or every communication). In this case, the apparent radio wave shape is changed by overlapping the transmission radio wave of the secret data and the transmission radio wave of the dummy data as shown in FIG.

FIG. 4 is a block diagram showing a configuration example of the transmission apparatus of the present invention, and FIG. 5 is a block diagram showing a configuration example of the reception apparatus of the present invention.
As shown in FIG. 4, the transmission device of the present invention includes a terminal device 11, a path switching and dummy output unit 12, a plurality of modems 13, a plurality of power amplifiers 14, a plurality of antenna devices 15, a control unit 16, and a pattern generation unit. 17.

  As shown in FIG. 4, the transmission device of the present invention includes a plurality of transmission systems 10 including a modem 13, a power amplifier 14, and an antenna device 15. Each transmission system 10 may be composed of a modem 13, a power amplifier 14 and an antenna device 15 having the same characteristics, or may be composed of a modem 13, an antenna apparatus 14 and a power amplifier 15 having different characteristics. The power amplifier 14 and the antenna device 15 may be configured to transmit radio signals in a plurality of carrier frequency bands, or may be configured to operate optimally in a specific carrier frequency band. The modem 13 is configured to be able to modulate input data using a designated modulation method among a plurality of modulation methods. The modem 13 is configured to convert input data into a radio signal having a designated carrier frequency among a plurality of carrier frequencies. FIG. 4 shows a configuration example in which the transmission apparatus includes three transmission systems 10 including the modem 13, the power amplifier 14, and the antenna apparatus 15. However, the number of transmission systems 10 may be any number as long as it is two or more.

The terminal device 11 is a device used by a user who uses the transmission device shown in FIG. 4 and outputs confidential data such as user data to be communicated. The terminal device 11 can be realized by an information processing device (computer) including a CPU (Central Processing Unit) that executes processing according to a program, a memory, an input device, an output device, and the like.
The terminal device 11 does not need to be included in the transmission device, and may be configured independently from the transmission device.

  The path switching and dummy output unit 12 outputs the secret data from the terminal device 11 to any one of the transmission systems 10 (modems 13) according to the instruction of the control unit 16. Further, the path switching and dummy output unit 12 generates dummy data, and outputs the dummy data to a transmission system (modem 13) 10 different from the transmission system 10 that has output the confidential data. There is no need for one transmission system for outputting the secret data or dummy data, and there may be a plurality of transmission systems.

  The modem 13 modulates the input confidential data or dummy data according to the instruction of the control unit 16 according to the designated modulation method, and up-converts it to a radio signal having the designated carrier frequency and outputs it. The modem 13 includes a known frequency synthesizer and up-converter, for example, and has a configuration capable of up-converting secret data and dummy data into radio signals having different carrier frequencies by changing the oscillation frequency of the frequency synthesizer. As a modulation method by the modem 13, analog modulation such as amplitude modulation (AM), phase modulation (PM), frequency modulation (FM), amplitude shift keying (ASK), phase shift keying (PSK), frequency shift keying (FSK). Various schemes such as digital modulation such as quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) are conceivable. These modulation schemes can use a plurality of carrier frequencies as in the FDMA scheme. Further, as a modulation method by the modem 13, there is also spread spectrum used in the CDMA method. The modem 13 includes, for example, a plurality of modulation ICs (Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field-Programmable Gate Arrays), and the like that realize different modulation schemes. The modulation method may be switched by switching the FPGA or the like.

  The power amplifier 14 amplifies the radio signal output from the modem 13 to the power necessary for transmission. The radio signal amplified by the power amplifier 14 is radiated as a radio wave from the antenna device 15. When a radio signal is output from the modem 13 with power required for transmission, the power amplifier 14 may not be provided.

  The control unit 16 controls the path switching and the switching operation of the secret data and dummy data output destination by the dummy output unit 12 and the switching method of the modulation method and the carrier frequency by the modem 13.

  The pattern generator 17 generates a combination pattern of a modulation scheme and a carrier frequency for each transmission system 10 used for transmission of secret data and dummy data. The control unit 16 instructs the path switching and dummy output unit 12 on the transmission system 10 that outputs secret data and dummy data according to the combination pattern generated by the pattern generation unit 17. Further, the control unit 16 instructs each modem 13 according to the combination pattern generated by the pattern generation unit 17 and the modulation method applied to the secret data or dummy data and the carrier frequency used for transmission of the secret data and dummy data. The control unit 16, the pattern generation unit 17, and the path switching / dummy output unit 12 are, for example, an information processing device (computer) that includes a CPU, a DSP, a memory, or the like that executes processing according to a program, or an information processing IC. realizable.

  As shown in FIG. 5, the receiving device of the present invention includes a terminal device 21, a signal determination unit 22, a plurality of modems 23, a plurality of radio signal reception units 24 and a plurality of antenna devices 25, a control unit 26, and a pattern generation unit 27. It is the structure which has. The receiving apparatus of the present invention receives a radio signal transmitted from the transmitting apparatus shown in FIG. 4, and performs demodulation processing and down-conversion processing corresponding to the modulation scheme and carrier frequency used by the wireless apparatus for transmission. The secret data and dummy data are reproduced.

  As shown in FIG. 5, the receiving device of the present invention includes a plurality of receiving systems 20 including a modem 23, a radio signal receiving unit 24, and an antenna device 24. Each receiving system 20 may be configured by a modem 23, a radio signal receiving unit 24, and an antenna device 25 having the same characteristics, or may be configured by a modem 23, a radio signal receiving unit 24, and an antenna apparatus 25 having different characteristics. Good. The radio signal receiving unit 24 and the antenna device 25 may be configured to receive radio signals in a plurality of carrier frequency bands, or may be configured to operate optimally in a specific carrier frequency band. The modem 23 is configured to be able to demodulate a radio signal input by a designated demodulation method among a plurality of demodulation methods. The modem is configured to convert a radio signal having a plurality of carrier frequencies into a baseband signal having a predetermined frequency band. FIG. 5 shows a configuration example in which the receiving device includes three receiving systems 20 including the modem 23, the radio signal receiving unit 24, and the antenna device 25. However, the number of receiving systems 20 is any number as long as the number is 2 or more. Good.

The terminal device 21 is a device used by a user who uses the receiving device shown in FIG. 5, and receives confidential data such as user data to be communicated. The terminal device 21 can be realized by, for example, an information processing device (computer) that includes a CPU, a memory, an input device, an output device, and the like that execute processing according to a program.
The terminal device 21 does not need to be included in the receiving device, and may be configured independently from the receiving device.

  The antenna device 25 receives a radio signal transmitted from the transmission device. The radio signal received by the antenna device 25 is amplified and output by the radio signal receiving unit 24. The radio signal receiving unit 24 includes a filter that extracts a radio signal in a predetermined carrier frequency band from the received radio signal, a low noise amplifier that amplifies the radio signal, and the like. When a radio signal with sufficient power is obtained from the antenna device 25, the radio signal receiving unit 24 may not be provided.

  The modem 23 down-converts the radio signal output from the radio signal receiving unit 24 into a baseband signal in a predetermined frequency band in accordance with an instruction from the control unit 26. The modem 23 is configured to be able to demodulate a radio signal by a demodulation method designated by the control unit 26 among a plurality of demodulation methods. The modem 23 includes, for example, a well-known frequency synthesizer and down converter, and can convert radio signals of different carrier frequencies into baseband signals of predetermined frequency bands by changing the oscillation frequency of the frequency synthesizer. The demodulation method by the modem 23 is a demodulation method corresponding to the modulation method implemented by the transmission apparatus shown in FIG. The modem 23 includes, for example, a plurality of demodulation ICs, DSPs, FPGAs, and the like that realize different demodulation methods, and the demodulation methods may be switched by switching the ICs, DSPs, FPGAs, and the like used for radio signal demodulation.

  The signal determination unit 22 extracts confidential data from the confidential data and dummy data output from the plurality of modems 23 according to an instruction from the control unit 26 and outputs the confidential data to the terminal device 21.

The control unit 26 controls the secret data extraction operation by the signal determination unit 22 and the demodulation method and conversion frequency switching operation by the modem 23.
The pattern generation unit 27 generates a combination pattern of a demodulation method and a carrier frequency (conversion frequency) for each reception system 20 used for demodulating secret data and dummy data. The control unit 26 instructs each modem 23 on the demodulation method and conversion frequency to be applied to the radio signal according to the combination pattern generated by the pattern generation unit 27. Further, the control unit 26 instructs the signal determination unit 22 to output the confidential data according to the combination pattern generated by the pattern generation unit 27, and outputs the confidential data reproduced by the modem 23 to the terminal device 21. Let

  The control unit 26, the pattern generation unit 27, and the signal determination unit 22 can be realized by, for example, an information processing apparatus (computer) that includes a CPU, a DSP, a memory, or the like that executes processing according to a program, or an information processing IC.

  4 shows a configuration example of the transmission device and FIG. 5 shows a configuration example of the reception device. By combining the configurations shown in FIG. 4 and FIG. 5, functions of both the transmission device and the reception device are shown. You may implement | achieve the communication apparatus provided with. In that case, the power amplifier 14 and the radio signal receiver 24 shown in FIGS. 4 and 5 may be provided, and the functions of the path switching and dummy output unit 12 and the signal determination unit 22 may be realized by a common circuit. The wireless communication system of the present invention only needs to be configured to include the transmission device shown in FIG. 4 and the reception device shown in FIG. 5 and transmit and receive confidential data and dummy data between the transmission device and the reception device. That is, the wireless communication system of the present invention includes a configuration for transmitting and receiving secret data and dummy data between the communication devices.

  In such a configuration, as described above, in the configuration in which the secret data and the dummy data are transmitted at the same time, it is necessary to maintain a wide frequency band used for wireless communication. Therefore, in the present invention, the number and bandwidth of transmission systems 10 used for simultaneous transmission of secret data and dummy data are limited. Furthermore, in the present invention, the modulation scheme and carrier wave frequency used for transmission of secret data and dummy data are switched in a predetermined period (every unit time or every communication).

The number of transmission systems 10 used for transmitting secret data and dummy data is 2 in the smallest case because one is used for transmitting secret data and the other is used for transmitting dummy data. However, if one transmission system 10 is always used for transmission of confidential data and the other transmission system 10 is used for transmission of dummy data, the possibility of confidential data being intercepted by a third party cannot be denied. Therefore, in the present invention, the modulation scheme and carrier frequency for each transmission system 10 used for transmission of secret data and dummy data are switched in a predetermined period (every unit time or every communication). The bandwidth used for transmission of the secret data and the dummy data can be controlled by, for example, a selected modulation method and transmission speed.
In the present invention, a period in which either one of the secret data or the dummy data is transmitted using the two transmission systems 10 may be provided. In that case, it is desirable that the transmission system 10 included in the transmission device and the reception system 20 included in the reception device be 3 or more. The control unit 16 may determine the transmission system 10 used for transmitting the secret data or the dummy data according to the combination pattern generated by the pattern generation unit 17.

  Note that it is not always necessary to transmit both the secret data and the dummy data. A period in which only the secret data is transmitted using one or a plurality of transmission systems 10 or only dummy data is transmitted to one or a plurality of transmission systems 10. You may provide the period which transmits using.

FIG. 6 is a schematic diagram illustrating an example of switching between the modulation scheme, the carrier frequency, and the number of transmission systems used for transmission of secret data and dummy data.
In the example shown in FIG. 6, at time t = t ₀ , dummy data is transmitted in the modulation scheme 1 in the frequency band where the carrier frequency is f ₀ and wider than the dummy data in the frequency band where the carrier frequency is f _1. The secret data is transmitted by the modulation method 2 which is a bandwidth. Further, at time t = t ₁ , the confidential data is transmitted in the modulation scheme 3 in the frequency band with the carrier frequency f _2, and the bandwidth is the same as that of the confidential data in the frequency band with the carrier frequency f _3. Dummy data is transmitted by the modulation method 4. Further, at time t = t ₂ , the confidential data is transmitted by the modulation scheme 5 in the frequency band where the carrier frequency is f _4, and the bandwidth is about the same as the confidential data in the frequency band where the carrier frequency is f _5. sends dummy data modulation scheme 6, and further transmits a carrier frequency in a frequency band to f _6, the dummy data modulation scheme 7 as a narrower bandwidth than confidential data.

The transmission system 10 used for transmission of the secret data and the dummy data, the modulation method, and the carrier frequency may be determined by the transmission device and the reception device, for example, using a common key. If the common key is used in this way, the modulation method and carrier frequency of the transmission system 10 that transmits the secret data and dummy data are associated with the demodulation method and conversion frequency of the reception system 20 that receives the secret data and dummy data. be able to. The common key includes a known one-way function (for example, a hash function such as MD5) and a numerical table in which values calculated by the one-way function are arranged. In that case, the transmission apparatus and the reception apparatus may sequentially generate a modulation / demodulation scheme and a combination pattern of carrier wave frequencies used for transmission and reception based on values (calculated values) obtained using the same numerical table and one-way function.
The numerical table in which the values calculated by the one-way function are arranged does not need to be provided in each of the transmission device and the reception device. You may be notified. In that case, the input information may be notified by being encrypted using a known common key or public key, or may be notified without being encrypted.

  The combination pattern generated by the transmission device includes the modulation scheme and carrier frequency used for each transmission system 10, and information for identifying the transmission system 10 used for transmission of confidential data and dummy data. In addition, the combination pattern generated by the reception device includes a demodulation method and a conversion frequency used for each reception system 20, and information for identifying the reception system 20 that receives the confidential data and the dummy data.

In the combination pattern, the time of the transmission device and the reception device is synchronized in advance. For example, the transmission device and the reception device use the respective pattern generation units 17 and 27 at or before the predetermined pattern switching time. Can be generated.
The pattern switching time does not need to be determined in advance, and the switching interval may be changed at random. In this case, for example, the next pattern switching time may be notified in advance from the transmission apparatus to the reception apparatus. The switching time of the pattern notified from the transmitting device to the receiving device is not limited to the next switching time, and a plurality of switching times may be notified at the same time.

  The combination pattern need not be generated at the pattern switching time, but may be generated and stored before that time. For example, the reception device may generate and store the next combination pattern using the pattern generation unit 27 when the next pattern switching time is notified from the transmission device. In that case, the receiving apparatus returns a response message indicating the completion of generation of the combination pattern to the transmitting apparatus, and the transmitting apparatus generates the next combination pattern using the pattern generation unit 17 when the response message is received. It is possible.

  The pattern generation units 17 and 27, for example, sequentially read numerical values from a numerical table at each pattern switching time, calculate with one-way functions, and use combinations that correspond to the calculated values by the one-way function using a conversion table prepared in advance. What is necessary is just to select a pattern. The value input to the one-way function does not need to be obtained from a numerical table, and may be generated using a known random number generator.

According to the present invention, since the number and bandwidth of the transmission systems 10 used for simultaneous transmission of secret data and dummy data are limited, the frequency band to be used can be saved. Furthermore, in the present invention, since the modulation scheme and carrier wave frequency used for transmission are switched in a predetermined period (unit time, communication, or random interval), it is difficult to intercept confidential data by a third party. Can be.
Therefore, the frequency bandwidth used for wireless communication can be reduced while maintaining the interception resistance and confidentiality of the confidential data.

DESCRIPTION OF SYMBOLS 10 Transmission system 11, 21 Terminal device 12 Path switching and dummy output part 13, 23 Modem 14 Power amplifier 15, 25 Antenna apparatus 16, 26 Control part 17, 27 Pattern generation part 20 Reception system 22 Signal determination part 24 Radio signal reception part

Claims (5)

A plurality of transmission systems including a modem that modulates input data and outputs a radio signal having a predetermined carrier frequency and an antenna device that radiates the radio signal as a radio wave;
A route switching and dummy output unit that outputs the input secret data to at least one of the transmission systems, and outputs dummy data to another transmission system different from the transmission system that outputs the secret data,
A pattern generator for generating a combination pattern of a modulation scheme and a carrier frequency used for transmission of the secret data and the dummy data;
Instructing the transmission system for outputting the secret data and the dummy data to the path switching and dummy output unit according to the combination pattern generated by the pattern generation unit, the modulation scheme performed by the modem and the carrier frequency used for transmission, A control unit for instructing
Have
The modem is
A transmission apparatus that switches a modulation scheme and a carrier frequency to be performed in a predetermined period based on a combination pattern generated by the pattern generation unit.   The transmission apparatus according to claim 1, wherein the number of transmission systems is two. The controller is
The transmission apparatus according to claim 1, wherein a period for transmitting either the secret data or the dummy data using two transmission systems is provided. An antenna device that receives a radio signal transmitted from a transmitter, down-converts the radio signal received by the antenna device into a baseband signal of a predetermined frequency band, and demodulates the received data by demodulating it with an instructed demodulation method Equipped with multiple receiving systems including modems
A signal determination unit that extracts and outputs the confidential data from the reception data reproduced by the plurality of reception systems;
A pattern generator for generating a combination pattern of a demodulation method and a conversion frequency corresponding to a modulation method and a carrier frequency used in the transmission device;
A control unit for instructing the modem to receive the secret data according to the combination pattern generated by the pattern generation unit to the signal determination unit, and for instructing the modem a demodulation method and a conversion frequency to be applied to the radio signal; ,
Have
The controller is
A receiving apparatus that switches a demodulation method and a conversion frequency to be used for each reception system in a predetermined period based on a combination pattern generated by the pattern generation unit. The transmission device according to any one of claims 1 to 3,
A receiving device according to claim 4;
A wireless communication system.

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