Communication systems, communication methods, and communication programs

Abstract

To communicate while concealing information that one does not want intercepted. [Solution] A radio transmission station transmits a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted at a frequency within that predetermined frequency band. A radio receiving station receives a composite radio wave containing the dummy signal radio wave and the communication signal radio wave, and extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave. In addition, the radio transmission station transmits the communication signal radio wave during a specific time frame within the period in which it is transmitting the dummy signal radio wave.

Description

Technical Field

[0001] The present invention relates to a communication system, a communication method, and a communication program. In particular, it relates to a communication system, a communication method, and a communication program that communicate while concealing information of content that is not desired to be intercepted.

Background Art

[0002] For example, as disclosed in Patent Document 1, there is a technique for wireless communication while concealing information of content that is not desired to be intercepted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The following analysis is made from the perspective of the present invention. The disclosure of the above prior art documents is incorporated herein by reference.

[0005] In the conventional technology including Patent Document 1, the focus is on modifying the communication information itself, such as encrypting information of content that is not desired to be intercepted. However, there is a problem that encryption becomes useless when cryptanalysis technology is developed.

[0006] Therefore, an object of the present invention is to provide a secure communication technology that does not rely on encryption.

Means for Solving the Problems

[0007] According to a first aspect of the present invention, A radio transmission station that transmits a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that it does not want to be intercepted at a frequency included in the predetermined frequency band, A radio receiving station that receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave, A communication system including this is provided.

[0008] According to a second aspect of the present invention, The steps include transmitting a dummy signal radio wave in a predetermined frequency band from a radio radio transmission station, while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted at a frequency included in the predetermined frequency band, The steps include: receiving a composite radio wave at a radio wave receiving station, including the dummy signal radio wave and the communication signal radio wave, and removing the dummy signal radio wave from the composite radio wave to extract the communication signal radio wave; A communication method including this is provided.

[0009] According to a third aspect of the present invention, The computer, acting as a radio wave transmitting station, is instructed to transmit a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted, at a frequency included in the predetermined frequency band. The computer, acting as a radio wave receiving station, receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and performs a process to remove the dummy signal radio wave from the composite radio wave and extract the communication signal radio wave. A communication program is provided. [Effects of the Invention]

[0010] According to each aspect of the present invention, a communication system, a communication method, and a communication program are provided that contribute to communicating information while concealing information that one does not want to be intercepted. [Brief explanation of the drawing]

[0011] [Figure 1]This is a diagram illustrating one outline of the present invention. [Figure 2] This is a diagram showing the communication system 10 of Embodiment 1. [Figure 3] This is a block diagram showing the configuration of a communications satellite (radio wave transmitting station 100). [Figure 4] This is a block diagram showing the configuration of a mobile ship station (radio wave receiving station 200). [Figure 5] This is a flowchart illustrating the processing flow in the communication system 10. [Figure 6] This figure shows an example of a computer acting as a radio wave transmitting station 100. [Figure 7] This figure shows an example of a computer acting as a radio wave receiving station 200. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described in detail with reference to the drawings. The reference numerals in the drawings provided below are for illustrative purposes only and are not intended to limit the present invention to the illustrated embodiments. Furthermore, the connecting lines between blocks in each figure include both bidirectional and unidirectional lines. Unidirectional arrows schematically represent the flow of the main signal (data) and do not exclude bidirectional flow. In addition, although not explicitly shown, input and output ports exist at the input and output ends of each connecting line in the circuit diagrams, block diagrams, internal configuration diagrams, and connection diagrams disclosed herein. The same applies to input / output interfaces.

[0013] First, a general overview of the present invention will be described. As shown in FIG. 1, the communication system 10 of the present invention includes a radio wave transmitting station 100 and a radio wave receiving station 200. The radio wave transmitting station 100 transmits a dummy signal radio wave in a predetermined frequency band while transmitting a communication signal radio wave containing information of content not to be intercepted at a frequency included in the predetermined frequency band. The radio wave receiving station 200 receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave. Here, the radio wave transmitting station 100 may transmit the communication signal radio wave in some time frames within the time period when the dummy signal radio wave is being transmitted.

[0014] In such a communication system 10, since the communication signal radio wave is mixed into the dummy signal radio wave, it becomes impossible to know at what frequency the communication signal radio wave is and when the communication signal radio wave is transmitted. As a result, according to the communication system 10, it becomes possible to communicate while concealing information of content not to be intercepted.

[0015] [Embodiment 1] In Embodiment 1, a specific example of the communication system 10 outlined above will be described. As shown in FIG. 2, the communication system 10 of Embodiment 1 includes a communication satellite as the radio wave transmitting station 100, a ship mobile station as the radio wave receiving station 200, a control station, and a ground station.

[0016] The control station transmits a control signal for controlling the orbit and attitude of the communication satellite and a dummy signal that is the source of the dummy signal radio wave to the communication satellite. The ground station transmits a communication signal that is the source of the communication signal radio wave to the communication satellite. Since the control station and the ground station are exemplified by a satellite management station, a communication station, etc., detailed description will be omitted. Note that it is assumed that the dummy signal transmitted from the control station and the communication signal transmitted from the ground station cannot be intercepted.

[0017] As shown in FIG. 3, the communication satellite (radio wave transmitter 100) includes a dummy signal radio wave transmitter 110, a communication signal radio wave transmitter 120, and a transmission control unit 130. The communication satellite may further include an antenna for receiving signals from a control station and a ground station, an amplifier for amplifying the received signals, a converter for converting the received signals into radio waves, a storage medium, etc. However, since their configurations are the same as those of artificial satellites for television broadcasting, detailed descriptions thereof are omitted.

[0018] The dummy signal radio wave transmitter 110 is an antenna that transmits dummy signal radio waves in a predetermined frequency band, and the communication signal radio wave transmitter 120 is an antenna that transmits communication signal radio waves. The transmission control unit 130 creates dummy signal radio waves and communication signal radio waves from the signals received from the control station and the ground station, and transmits them via the dummy signal radio wave transmitter 110 and the communication signal radio wave transmitter 120. Specifically, the transmission control unit 130 transmits communication signal radio waves at frequencies included in the frequency band of the dummy signal radio waves in some time frames within the time period when the dummy signal radio waves are being transmitted. In particular, the transmission control unit 130 transmits the dummy signal radio waves while changing the content of the dummy signal radio waves and / or the frequency of the dummy signal radio waves in accordance with the secrecy rules.

[0019] As shown in FIG. 4, the ship mobile station (radio wave receiver 200) includes a radio receiver 210 and a signal extraction unit 220. The ship mobile station may further include a wave separator, an amplifier, a frequency mixer, a modulator, a noise canceller, a demodulator, an output device, a storage medium, etc. However, since their configurations are the same as those of general radio wave receivers, detailed descriptions thereof are omitted. Note that the ship mobile station is not limited to ships and may be a mobile station such as a vehicle, or a fixed station that does not move.

[0020] The wireless receiver 210 is an antenna that receives a composite radio wave including a dummy signal radio wave and a communication signal radio wave. The signal extraction unit 220 extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave. In particular, the wireless receiver 210 extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave based on a pre-known confidentiality rule. The communication signal radio wave may be extracted by adding an inverse phase wave of the dummy signal radio wave to the composite radio wave, or by digitizing the composite radio wave and then extracting it using successive interference cancellation (SIC) technology.

[0021] The following provides a conceptual explanation of dummy signal radio waves, communication signal radio waves, and composite radio waves.

[0022] Dummy signal radio waves are radio waves intended to be intercepted by a third party. Communication signal radio waves are radio waves containing information that you do not want to be intercepted by a third party. Composite radio waves are radio waves that include individually transmitted dummy signal radio waves and communication signal radio waves. Here, the essence of the present invention lies in concealing a single tree (a single leaf) of communication signal radio waves within a forest of dummy signal radio waves.

[0023] For example, suppose a communications satellite transmits dummy signals on multiple frequencies while simultaneously transmitting a communications signal on a specific frequency. Ideally, the communications satellite would transmit dummy signals on multiple frequencies to cover the entire frequency band used for satellite-based communications. In this case, the dummy signals and communications signals would interfere with each other, potentially resulting in the communications signal being encrypted within the composite signal. Even if a third party intercepts the composite signal, they would need to know what the dummy signals are in order to extract the communications signal from it. Here, the dummy signals are subjected to interference from the communications signal, and further interference occurs between the dummy signals themselves, potentially leading to the encryption of the dummy signals as well. Therefore, it becomes extremely difficult to revert to the individual dummy signals, that is, to know what the dummy signals are, making the interception of communications signals difficult. Furthermore, since third parties cannot determine which frequencies of radio waves are communication signals, it is possible to have a communication satellite simultaneously transmit dummy signals at the same frequency as the communication signals, thereby misleading third parties into believing that only dummy signals are being transmitted.

[0024] Alternatively, the communications satellite may transmit dummy signals while changing frequencies. In this case, interference between radio waves will occur at times and not at other times, making the encryption of both the communications signal and the dummy signal even more complex.

[0025] For example, suppose a communications satellite transmits a dummy signal containing content for 24 hours while simultaneously transmitting a communications signal for only a brief moment. In this case, the communications signal would appear as noise within the dummy signal. Furthermore, if noise is deliberately added to the content contained in the dummy signal, it becomes impossible to distinguish which noise is the communications signal. Of course, the dummy signal does not need to contain content, and in fact, it is preferable that it does not. For a third party, they would receive a composite signal containing the communications signal for only a brief moment while continuously receiving the dummy signal for almost 24 hours. Here, since the communications signal appears as noise, using a typical noise canceller would remove the communications signal as noise. Therefore, a third party would have to analyze what the dummy signal is without noise cancellation, making it difficult to intercept the communications signal.

[0026] A communications satellite may transmit dummy signals while changing the content and / or frequency of the dummy signals in accordance with confidentiality rules. In this case, it becomes difficult to analyze what the dummy signals are, and as a result, it becomes difficult to intercept communications signals.

[0027] It should be noted that the "encryption" referred to here is not encryption achieved through intentional alteration of communication signals, but rather encryption resulting from interference between radio waves. Therefore, even the party transmitting the communication signal radio waves cannot predict how the signal radio waves will be encrypted, making logical cryptographic analysis impossible. Nevertheless, encrypting the communication signal itself is also within the scope of this invention.

[0028] On the other hand, the mobile ship station (radio wave receiving station 200) is aware of the dummy signal waves and secrecy rules in advance, so it can remove the dummy signal waves from the composite radio waves and extract the communication signal waves. Even if the dummy signal waves interfere with each other, there is no problem as long as the mobile ship station is aware of the dummy signal waves after interference in advance. The noise canceller installed in the mobile ship station is used to remove noise from the extracted communication signal waves.

[0029] Next, an example of the processing flow by the communication system 10 will be explained. As shown in Figure 5, the communication satellite receives a dummy signal from the control station, generates a dummy signal radio wave, and transmits it (step S01). At this point, the ship mobile station does not need to perform any processing even if it receives the dummy signal radio wave. The transmission of the dummy signal radio wave continues from step S01 onward.

[0030] Next, the communications satellite receives a communications signal from the ground station, generates a communications signal radio wave, and transmits it. Because the dummy signals are being transmitted continuously, the communications satellite transmits both the dummy signals and the communications signals simultaneously (step S02). The dummy signals and communications signals transmitted from the communications satellite mix together along the way to form a composite radio wave. The transmission of dummy signals continues even after step S02.

[0031] The ship-based mobile station receives the composite radio waves, removes the dummy signal radio waves, and extracts the communication signal radio waves (step S03).

[0032] As described above, the communication system 10 of the present invention makes it possible to communicate while concealing information that one does not want to be intercepted.

[0033] [Variant form] The following describes various forms of modification. For example, if the radio wave transmitting station 100 is a communications satellite that emits radio waves onto the Earth, it is acceptable to emit dummy signal radio waves to only a portion of the area within the area where the communications signal radio waves are emitted. In other words, the communications satellite only needs to emit dummy signal radio waves to areas where there are third parties attempting to intercept the communications signal radio waves. By narrowing the area to which dummy signal radio waves are emitted, the power consumed by the communications satellite can be reduced. Furthermore, since communications signal radio waves can be received directly in areas where dummy signal radio waves are not emitted, there is no need to extract communications signal radio waves from composite radio waves.

[0034] Ideally, the dummy signal radio waves should be transmitted from the radio wave transmitting station 100 to cover the entire frequency band used for communication, but it is sufficient if the frequency band covers at least the frequencies of the communication signal radio waves.

[0035] The radio wave transmitting station 100 may transmit a dummy signal radio wave with a high power density while simultaneously transmitting a communication signal radio wave with a low power density. In terms of signal-to-noise ratio (SNR), in this invention, the communication signal radio wave is essentially the signal and the dummy signal radio wave is the noise. However, by making the high power density dummy signal radio wave appear as a signal while the low power density communication signal radio wave appears as noise, it becomes possible to further reduce the possibility of the communication signal radio wave being intercepted.

[0036] When the radio wave receiving station 200 receives only the dummy signal, it may synchronize with the dummy signal. That is, since the communication signal is received as a composite radio wave mixed with the dummy signal, synchronization with the dummy signal is useful when receiving the communication signal included in the composite radio wave.

[0037] Dummy signal radio waves and communication signal radio waves may be transmitted from individual radio wave transmitting stations 100 (communication satellites). In other words, the communication system 10 may include a (first) radio wave transmitting station 100 equipped with a dummy signal radio wave transmitting unit 110 and a (second) radio wave transmitting station 100 equipped with a communication signal radio wave transmitting unit 120. Alternatively, each of the multiple radio wave transmitting stations 100 (communication satellites) may transmit dummy signal radio waves in separate frequency bands.

[0038] Furthermore, the present invention can also be realized as a program that causes a computer to execute processing. That is, the computer acting as a radio wave transmitting station 100 includes memory (ROM: Read Only Memory, RAM: Random Access Memory, cache memory, etc.), a CPU: Central Processing Unit, and an interface, as shown in Figure 6. The interface is connected to a dummy signal radio wave transmitting unit 110 and a communication signal radio wave transmitting unit 120. The CPU reads a program from memory and realizes a processing module corresponding to the transmission control unit 130. Similarly, the computer acting as a radio wave receiving station 200 includes memory, a CPU, and an interface, as shown in Figure 7, and is connected to a radio receiving unit 210 via the interface. The CPU reads a program from memory and realizes a processing module corresponding to the signal extraction unit 220.

[0039] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0040] (Note 1) A radio transmission station that transmits a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that it does not want to be intercepted at a frequency included in the predetermined frequency band, A radio receiving station that receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave, A communication system that includes this.

[0041] (Note 2) The communication system as described in Appendix 1, wherein the radio wave transmitting station transmits the communication signal radio waves during a portion of the time frame within the period in which it transmits the dummy signal radio waves.

[0042] (Note 3) The aforementioned radio wave transmitting station transmits the dummy signal radio wave while changing the content of the dummy signal radio wave and / or the frequency of the dummy signal radio wave in accordance with confidentiality rules. The communication system according to Appendix 1 or 2, wherein the radio wave receiving station extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave based on the confidentiality rules that have been known in advance.

[0043] (Note 4) The communication system according to any one of the appendices 1 to 3, wherein the radio wave transmitting station is a communications satellite that irradiates radio waves onto the Earth, and the dummy signal radio waves are irradiated onto a portion of the irradiation area of ​​the communications signal radio waves.

[0044] (Note 5) The steps include transmitting a dummy signal radio wave in a predetermined frequency band from a radio radio transmission station, while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted at a frequency included in the predetermined frequency band, The steps include: receiving a composite radio wave at a radio wave receiving station, including the dummy signal radio wave and the communication signal radio wave, and removing the dummy signal radio wave from the composite radio wave to extract the communication signal radio wave; A communication method that includes this.

[0045] (Note 6) The computer, acting as a radio wave transmitting station, is instructed to transmit a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted, at a frequency included in the predetermined frequency band. The computer, acting as a radio wave receiving station, receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and performs a process to remove the dummy signal radio wave from the composite radio wave and extract the communication signal radio wave. Communication program.

[0046] Furthermore, each disclosure of the above-mentioned patent documents cited is incorporated into this document by reference and may be used as the basis or part of the present invention as necessary. Within the framework of the full disclosure of the present invention (including the claims), further modifications and adjustments to the embodiments or examples are possible based on the basic technical concept. Also, within the framework of the full disclosure of the present invention, various combinations or selections (including partial deletions) of various disclosure elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) are possible. In other words, the present invention naturally includes the full disclosure, including the claims, and various modifications and alterations that a person skilled in the art could make in accordance with the technical concept. In particular, with respect to the numerical ranges described in this document, any numerical value or sub-range included within that range should be interpreted as being specifically described, even if not otherwise stated. Furthermore, each disclosure of the above-mentioned cited documents may, as necessary, be used in part or in whole as part of the disclosure of the present invention, in accordance with the spirit of the present invention, and this is also considered to be included in the disclosure of this application. [Explanation of Symbols]

[0047] 10: Communication Systems 100: Radio wave transmitting station 110: Dummy signal radio wave transmitter 120: Communication signal radio wave transmitting unit 130: Transmission Control Unit 200: Radio wave receiving station 210: Wireless receiver 220: Signal extraction unit

Claims

1. A control station transmits a dummy signal, which is the source of a dummy signal radio wave, to a radio wave transmitting station, A radio transmission station that transmits a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that it does not want to be intercepted at a frequency included in the predetermined frequency band, A radio receiving station that receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave, Includes, The dummy signal radio waves cover at least the frequencies of the communication signal radio waves, and the power density of the dummy signal radio waves is higher than the power density of the communication signal radio waves. Communication system.

2. The communication system according to claim 1, wherein the radio wave transmitting station transmits the communication signal radio waves during a portion of the time frame within the period in which it transmits the dummy signal radio waves.

3. The aforementioned radio wave transmitting station transmits the dummy signal radio wave while changing the content and / or frequency of the dummy signal radio wave in accordance with confidentiality rules. The communication system according to claim 1 or 2, wherein the radio wave receiving station extracts the communication signal radio wave by removing the dummy signal radio wave from the composite radio wave based on the confidentiality rules that have been known in advance.

4. The communication system according to any one of claims 1 to 3, wherein the radio wave transmitting station is a communications satellite that irradiates radio waves onto the Earth, and the dummy signal radio waves are irradiated onto a portion of the irradiation area of ​​the communications signal radio waves.

5. The steps include: transmitting a dummy signal, which will serve as the basis for the dummy signal radio waves, from the control station to the radio wave transmitting station; The steps include transmitting a dummy signal radio wave in a predetermined frequency band from a radio radio transmission station, while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted at a frequency included in the predetermined frequency band, The steps include: receiving a composite radio wave at a radio wave receiving station, including the dummy signal radio wave and the communication signal radio wave, and removing the dummy signal radio wave from the composite radio wave to extract the communication signal radio wave; Includes, The dummy signal radio waves cover at least the frequencies of the communication signal radio waves, and the power density of the dummy signal radio waves is higher than the power density of the communication signal radio waves. Communication method.

6. The communication method according to claim 5, wherein the communication signal radio waves are transmitted during a portion of the time frame within the period in which the dummy signal radio waves are transmitted.

7. Transmit the dummy signal radio waves while changing the content and / or frequency of the dummy signal radio waves in accordance with confidentiality rules. The communication method according to claim 5 or 6, wherein, based on the confidentiality rules known in advance, the dummy signal radio waves are removed from the composite radio waves to extract the communication signal radio waves.

8. A communication method according to any one of claims 5 to 7, wherein a communications satellite that emits radio waves onto the Earth emits the dummy signal radio waves to a portion of the area within the area of ​​the emission of the communications signal radio waves.

9. The computer acting as the control station is instructed to perform the process of transmitting a dummy signal, which will serve as the basis for the dummy signal radio waves, to the radio wave transmitting station. The computer, acting as a radio wave transmitting station, is instructed to transmit a dummy signal radio wave in a predetermined frequency band while simultaneously transmitting a communication signal radio wave containing information that should not be intercepted, at a frequency included in the predetermined frequency band. The computer, acting as a radio wave receiving station, receives a composite radio wave including the dummy signal radio wave and the communication signal radio wave, and performs a process to remove the dummy signal radio wave from the composite radio wave and extract the communication signal radio wave. The dummy signal radio waves cover at least the frequencies of the communication signal radio waves, and the power density of the dummy signal radio waves is higher than the power density of the communication signal radio waves. Communication program.

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