WIRELESS COMMUNICATION SYSTEM AND WIRELESS COMMUNICATION METHOD

Abstract

A first regular device (300) transmits two first dummy radio waves at different times. A second regular device (300) transmits a second dummy radio wave at the same time as the transmission of one of the first dummy radio waves and at a different time than the transmission of the other of the first dummy radio waves. A partner device (200) receives a receiving radio wave that is the sum of the first dummy radio wave, the second dummy radio wave, and the jamming radio wave; receives a receiving radio wave that is the sum of the first dummy radio wave and the jamming radio wave; receives a receiving radio wave that is the sum of the second dummy radio wave and the jamming radio wave; and, based on the three received receiving radio waves, generates a first filter for communication with the first regular device and a second filter for communication with the second regular device.

Description

Wireless communication system and wireless communication method

[0001] TECHNICAL FIELD This disclosure relates to wireless communications under jamming.

[0002] With wireless communication, as long as radio waves reach the communication line, an unspecified number of devices can access the communication from a distance. Therefore, wireless communication is more susceptible to jamming than wired communication, and the impact of jamming is greater. Therefore, measures to prevent jamming are more important for wireless communication. In particular, in use cases where communication availability is required, technology is needed that not only detects jamming but also maintains communication as much as possible even under jamming.

[0003] Non-Patent Document 1 discloses a method for maintaining communication under communication jamming in a MIMO communication system using multiple antennas. Specifically, the method is as follows: First, using the MMSE method, the components due to communication radio waves from authorized terminals and the components due to jamming radio waves from unauthorized terminals are estimated from the channel information of the received radio wave signal. The MMSE method is one of the estimation methods in MIMO systems. The received radio wave signal is the sum of the communication radio waves from authorized terminals, the jamming radio waves from unauthorized terminals, and other noise. The channel information is a matrix with complex number components, and represents how the amplitude and phase of radio waves propagated through a certain path change. Then, using the two estimated channel information, a digital filter is created that separates the communication radio wave signals from authorized terminals from the received radio wave signals. By applying this digital filter, only signals from authorized terminals can be received even under communication jamming. Note that Non-Patent Document 1 assumes that communication by authorized terminals is randomly stopped for signal separation. In other words, it is assumed that only jamming radio waves from unauthorized terminals can be received. MIMO is an abbreviation for Multiple-Input and Multiple-Output, and MMSE is an abbreviation for Minimum Mean Square Error.

[0004] Regarding jamming of communications by radio waves, one commonly used method is to continuously emit jamming signals indiscriminately. Another method is reactive, which monitors communications from legitimate devices and emits jamming signals only when it detects communication signals.

[0005] T. T. Do et al. , “Jamming-Resistant Receivers for the Massive MIMO Uplink”, IEEE Transactions on Information Forensics and Security (Volume: 13, Issue: 1, Jan. 2018)

[0006] The method of Non-Patent Document 1 requires that only jamming radio waves be received in order to separate the signals, and therefore cannot deal with communication jamming using reactive methods that can stop communication following random stops of legitimate terminals.

[0007] The present disclosure aims to enable wireless communication even when communication is disrupted by reactive methods.

[0008] A wireless communication system according to the present disclosure performs wireless communication using a digital filter. The digital filter is a filter for extracting legitimate radio waves from received radio waves that include legitimate radio waves transmitted from a legitimate device and jamming radio waves transmitted from an unauthorized device. The wireless communication system includes: a first legitimate device that transmits two first dummy radio waves at different timings; a second legitimate device that transmits a second dummy radio wave at the same timing as the transmission of one of the first dummy radio waves and at a different timing from the transmission of the other first dummy radio wave; and a counterpart device that receives received radio waves that are the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves, receives received radio waves that are the sum of the first dummy radio waves and the jamming radio waves, and receives received radio waves that are the sum of the second dummy radio waves and the jamming radio waves, and creates a first digital filter for communication with the first legitimate device and a second digital filter for communication with the second legitimate device based on the three received radio waves.

[0009] According to the present disclosure, wireless communication is possible even when communication is disrupted by reactive methods.

[0010] 1 is a configuration diagram of a wireless communication system 100 according to a first embodiment. A configuration diagram of a counterpart device 200 according to the first embodiment. A functional configuration diagram of the counterpart device 200 according to the first embodiment. A configuration diagram of a legitimate device 300 according to the first embodiment. A functional configuration diagram of the legitimate device 300 according to the first embodiment. A flowchart of a wireless communication method according to the first embodiment. A flowchart of step S110 according to the first embodiment. A sequence diagram of step S110 according to the first embodiment. A flowchart of step S120 according to the first embodiment. A sequence diagram of step S120 according to the first embodiment. A configuration diagram of a wireless communication system 100 according to a first example. A configuration diagram of a counterpart device 200 according to a second example. A flowchart of a wireless communication method according to the second example. A flowchart of a wireless communication method according to a third example. A configuration diagram of a wireless communication system 100 according to a fourth example. A flowchart of step S110 according to the fourth example. A flowchart of step S110 according to a fifth example. A configuration diagram of a wireless communication system 100 according to a second embodiment. A configuration diagram of a counterpart device 200 according to the second embodiment. A configuration diagram of a legitimate device 300 according to the second embodiment. A flowchart of a wireless communication method according to the second embodiment. A flowchart of step S210 in embodiment 2. A relationship diagram of the counterpart device 200 and the authorized device 300 in embodiment 2. A hardware configuration diagram of the counterpart device 200 in the embodiment. A hardware configuration diagram of the authorized device 300 in the embodiment.

[0011] In the embodiments and drawings, the same or corresponding elements are denoted by the same reference numerals. The description of elements denoted by the same reference numerals as those already described will be omitted or simplified as appropriate. Arrows in the drawings primarily indicate the flow of data or the flow of processing.

[0012] First Embodiment A wireless communication system 100 will be described with reference to FIGS.

[0013] ***Description of Configuration*** The configuration of a wireless communication system 100 will be described with reference to Fig. 1. The wireless communication system 100 is a system that performs wireless communication using a digital filter.

[0014] The wireless communication system 100 includes a counterpart device 200 and two legitimate devices 300. The counterpart device 200 is a wireless device on the receiving side. However, the counterpart device 200 may have a transmitting function. A specific example of the counterpart device 200 is a base station. The position of the base station is fixed. The legitimate device 300 is a wireless device on the transmitting side. However, the legitimate device 300 may have a receiving function. A specific example of the legitimate device 300 is a mobile terminal. The radio waves transmitted from the legitimate device 300 are referred to as communication radio waves 101. The wireless devices are devices that communicate wirelessly.

[0015] The unauthorized device 110 is a wireless device that interferes with wireless communication in the wireless communication system 100. Radio waves transmitted from the unauthorized device 110 are referred to as jamming radio waves 111.

[0016] The configuration of the counterpart device 200 will be described with reference to Fig. 2. The counterpart device 200 is a computer that includes hardware such as a processor 201, a memory 202, a storage 203, and a wireless communication interface 204. These pieces of hardware are connected to each other via signal lines.

[0017] The processor 201 is an IC that performs arithmetic processing and controls other hardware. For example, the processor 201 is a CPU. IC is an abbreviation for Integrated Circuit. CPU is an abbreviation for Central Processing Unit.

[0018] The memory 202 is a volatile or non-volatile storage device. The memory 202 is also called a primary storage device or a main memory. For example, the memory 202 is a RAM. Data stored in the memory 202 is saved in the storage 203 as needed. RAM is an abbreviation for Random Access Memory.

[0019] The storage 203 is a non-volatile storage device. For example, the storage 203 is a ROM, a HDD, a flash memory, or a combination of these. Data stored in the storage 203 is loaded into the memory 202 as needed. ROM is an abbreviation for Read Only Memory. HDD is an abbreviation for Hard Disk Drive.

[0020] The wireless communication interface 204 has multiple antennas 205. The wireless communication interface 204 is a receiver and a transmitter. For example, the wireless communication interface 204 is a communication chip or a NIC. Communication with the counterpart device 200 is performed using the wireless communication interface 204. NIC is an abbreviation for Network Interface Card.

[0021] The counterpart device 200 includes elements such as a receiving unit 210, a creating unit 220, and an applying unit 230. These elements are realized by software.

[0022] The storage 203 stores a wireless communication program for causing the computer to function as the receiving unit 210, the creating unit 220, and the applying unit 230. The wireless communication program is loaded into the memory 202 and executed by the processor 201. The storage 203 also stores an OS. At least a portion of the OS is loaded into the memory 202 and executed by the processor 201. The processor 201 executes the wireless communication program while executing the OS. OS is an abbreviation for Operating System.

[0023] Input and output data of the wireless communication program is stored in the storage unit 290. The storage 203 functions as the storage unit 290. However, a storage device such as the memory 202, a register in the processor 201, or a cache memory in the processor 201 may function as the storage unit 290 instead of or together with the storage 203.

[0024] The counterpart device 200 may include a plurality of processors that replace the processor 201 .

[0025] The wireless communication program can be recorded (stored) in a computer-readable manner on a non-volatile recording medium such as an optical disk or a flash memory.

[0026] The functional configuration of the counterpart device 200 will be described with reference to Fig. 3. The receiver 210 includes a radio wave receiver 211, a digital converter 212, and a Fourier transformer 213. The generator 220 includes a channel estimator 221 and a filter generator 222. The applicator 230 includes a filtering unit 231 and a frame processor 232. Data such as a filter 291 and radio wave information 292 are stored in the storage unit 290. These data will be described later.

[0027] The configuration of the authorized device 300 will be described with reference to Fig. 4. The authorized device 300 is a computer that includes hardware such as a transmission unit 310 and a control unit 320. These pieces of hardware are connected to each other via signal lines.

[0028] The processor 301 is an IC that performs arithmetic processing and controls other hardware. For example, the processor 301 is a CPU. The memory 302 is a volatile or non-volatile storage device. The memory 302 is also called a primary storage device or main memory. For example, the memory 302 is a RAM. Data stored in the memory 302 is saved in the storage 303 as needed. The storage 303 is a non-volatile storage device. For example, the storage 303 is a ROM, a HDD, a flash memory, or a combination thereof. Data stored in the storage 303 is loaded into the memory 302 as needed. The wireless communication interface 304 has an antenna 305. The wireless communication interface 304 is a receiver and a transmitter. For example, the wireless communication interface 304 is a communication chip or a NIC. Communication with the authorized device 300 is performed using the wireless communication interface 304.

[0029] The authorized device 300 includes elements such as a transmission unit 310 and a control unit 320. These elements are realized by software.

[0030] The storage 303 stores a wireless communication program for causing the computer to function as the transmitter 310 and the controller 320. The wireless communication program is loaded into the memory 302 and executed by the processor 301. The storage 303 also stores an OS. At least a portion of the OS is loaded into the memory 302 and executed by the processor 301. The processor 301 executes the wireless communication program while executing the OS.

[0031] Input and output data of the wireless communication program is stored in the memory unit 390. The storage 303 functions as the memory unit 390. However, a storage device such as the memory 302, a register in the processor 301, or a cache memory in the processor 301 may function as the memory unit 390 instead of or together with the storage 303.

[0032] The authorized device 300 may include multiple processors that replace the processor 301 .

[0033] The wireless communication program can be recorded (stored) in a computer-readable manner on a non-volatile recording medium such as an optical disk or a flash memory.

[0034] The functional configuration of the legitimate device 300 will be described with reference to Fig. 5. The transmitter 310 includes a radio wave transmitter 311, an analog converter 312, and an inverse Fourier transformer 313. The controller 320 includes a communication controller 321 and a frame processor 322. Data such as time slot information 391 and allocation information 392 are stored in the memory 390. These data will be described later. The time slot information 391 and allocation information 392 are also stored in the memory 290 of the counterpart device 200.

[0035] ***Explanation of Operation*** The operational procedure of the wireless communication system 100 corresponds to a wireless communication method. The counterpart device 200 is capable of MIMO communication. The counterpart device 200 and the two legitimate devices 300 are time-synchronized. The unauthorized device 110 jams communication using a reactive method. In the reactive method, communication of the communication radio waves 101 is monitored, and jamming radio waves 111 are transmitted when the communication radio waves 101 are detected.

[0036] The wireless communication method will be described with reference to Fig. 6. One of the regular devices 300 will be referred to as the first regular device 300, and the other regular device 300 will be referred to as the second regular device 300.

[0037] In step S110, the counterpart device 200 creates a first filter 291 and a second filter 291. The first filter 291 is a filter 291 for communication with the first legitimate device 300. The second filter 291 is a filter 291 for communication with the second legitimate device 300. The filter 291 is a digital filter for extracting regular radio waves from received radio waves that include regular radio waves and jamming radio waves 111. The regular radio waves are communication radio waves 101 that include regular frames. The regular frames are communication frames that are the target of communication.

[0038] The procedure of step S110 will be described with reference to Figures 7 and 8. In step S111, two legitimate devices 300 simultaneously transmit dummy radio waves. Specifically, the first legitimate device 300 transmits a first dummy radio wave, and the second legitimate device 300 transmits a second dummy radio wave at the same timing as the transmission of the first dummy radio wave. The dummy radio waves are communication radio waves 101 that include a dummy frame. The dummy frame is a dummy communication frame.

[0039] The dummy radio waves are transmitted as follows: First, the frame processing unit 322 generates a dummy frame. Next, the inverse Fourier transform unit 313 processes the dummy signal using the dummy frame as a dummy signal with an inverse fast Fourier transform. Next, the analog conversion unit 312 converts the processed dummy signal from a digital signal to an analog signal. Then, the radio wave transmission unit 311 emits the converted dummy signal from the antenna 305 as a dummy radio wave.

[0040] The unauthorized device 110 detects the first dummy radio wave and the second dummy radio wave and transmits a jamming radio wave 111 .

[0041] The counterpart device 200 receives the received radio wave which is the sum of the first dummy radio wave, the second dummy radio wave and the jamming radio wave 111.

[0042] The received radio waves are processed as follows. First, the radio wave receiving unit 211 receives the received radio waves. Next, the digital converting unit 212 converts the received signal from an analog signal to a digital signal, using the received radio waves as a received signal. Next, the Fourier transforming unit 213 processes the received signal using a fast Fourier transform. The Fourier transforming unit 213 then converts the processed received signal into radio wave information 292 and stores the radio wave information 292 in the storage unit 290.

[0043] In S112, each regular device 300 transmits a new dummy radio wave in its own time slot. The own time slot refers to the assigned time slot. Specifically, the first regular device 300 transmits a new first dummy radio wave in the first time slot, and the second regular device 300 transmits a new second dummy radio wave in the second time slot. The first time slot is the time slot assigned to the first regular device 300. The second time slot is the time slot assigned to the second regular device 300, and has a different timing from the first time slot.

[0044] The communication control unit 321 determines its own time slot. The communication control unit 321 determines its own time slot based on time slot information 391 and allocation information 392. The time slot information 391 indicates the timing of each time slot. The allocation information 392 indicates the time slot number assigned to each legitimate device 300.

[0045] In the first time slot, the unauthorized device 110 detects a new first dummy radio wave and transmits a jamming radio wave 111. In the second time slot, the unauthorized device 110 detects a new second dummy radio wave and transmits a jamming radio wave 111.

[0046] In the first time slot, the counterpart device 200 receives a received radio wave which is the sum of the new first dummy radio wave and the jamming radio wave 111. In the second time slot, the counterpart device 200 receives a received radio wave which is the sum of the new second dummy radio wave and the jamming radio wave 111. Each received radio wave is processed in the same way as in step S111.

[0047] Steps S111 and S112 may be executed in reverse order.

[0048] In step S113, based on the three received radio waves in steps S111 and S112, the counterpart device 200 creates filters 291 for communication with each legitimate device 300. Specifically, a first filter 291 and a second filter 291 are created.

[0049] The filter 291 is created using the following procedure. First, the channel estimation unit 221 estimates channel information for each of the first and second legitimate devices 300 and 300 based on three pieces of radio wave information 292 stored in the storage unit 290. The channel information is a matrix whose components are complex numbers, and represents how the amplitude and phase of the communicated radio waves have changed. A specific example of an estimation method is the MMSE method. The MMSE method is one of the estimation methods for MIMO systems, and is disclosed in Non-Patent Document 1. In Non-Patent Document 1, the channel information for each of the legitimate terminal and the unauthorized device is estimated based on the sum of the radio waves transmitted from the legitimate terminal and the radio waves transmitted from the unauthorized device, and the radio waves transmitted from the unauthorized device. Meanwhile, the channel estimation unit 221 estimates the channel information for each of the first and second legitimate devices 300 and 300 as follows.

[0050] The channel estimation unit 221 estimates channel information of the first legitimate device 300 and channel information of the pair of the second legitimate device 300 and the unauthorized device 110 based on the 0th radio wave information 292 and the second radio wave information 292. The channel estimation unit 221 estimates channel information of the second legitimate device 300 and channel information of the pair of the first legitimate device 300 and the unauthorized device 110 based on the 0th radio wave information 292 and the first radio wave information 292. The 0th radio wave information 292 is radio wave information 292 of received radio waves which is the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves 111. The first radio wave information 292 is radio wave information 292 of received radio waves which is the sum of the first dummy radio waves and the jamming radio waves 111. The second radio wave information 292 is radio wave information 292 of received radio waves which is the sum of the second dummy radio waves and the jamming radio waves 111.

[0051] Next, the filter creation unit 222 creates a first filter 291 based on the channel information of the first legitimate device 300. The filter creation unit 222 also creates a second filter 291 based on the channel information of the second legitimate device 300. A specific example of the creation method is the method disclosed in Non-Patent Document 1. In this method, an RZF filter is used. RZF is an abbreviation for Regularized Zero-Forcing.

[0052] Then, the filter creation unit 222 stores the first filter 291 and the second filter 291 in the storage unit 290 .

[0053] 6, the description will continue from step S 120. In step S 120, the counterpart device 200 performs wireless communication using the first filter 291 and the second filter 291.

[0054] The procedure of step S120 will be described with reference to Figures 9 and 10. In step S121, the two authorized devices 300 simultaneously transmit communication radio waves 101.

[0055] In the first time slot, the first regular device 300 transmits the first regular radio wave, and the second regular device 300 transmits the second dummy radio wave. In the second time slot, the first regular device 300 transmits the first communication radio wave 101 in the second time slot, and the second regular device 300 transmits the second dummy radio wave.

[0056] Regular radio waves are transmitted as follows: First, the upper layer generates regular data and transmits it to the frame processing unit 322. Next, the frame processing unit 322 receives the regular data and generates a regular frame containing the regular data. Next, the inverse Fourier transform unit 313 processes the regular frame as a regular signal using an inverse fast Fourier transform. Next, the analog conversion unit 312 converts the processed regular signal from a digital signal to an analog signal. Then, the radio wave transmission unit 311 emits the converted regular signal from the antenna 305 as a regular radio wave.

[0057] In the first time slot, the unauthorized device 110 detects the first regular radio wave and the second dummy radio wave and transmits a jamming radio wave 111. In the second time slot, the unauthorized device 110 detects the first dummy radio wave and the second regular radio wave and transmits a jamming radio wave 111.

[0058] In the first time slot, the counterpart device 200 receives a received radio wave that is the sum of the first regular radio wave, the second dummy radio wave, and the jamming radio wave 111. In the second time slot, the counterpart device 200 receives a received radio wave that is the sum of the first dummy radio wave, the second regular radio wave, and the jamming radio wave 111. Each received radio wave is processed in the same way as in step S111.

[0059] In step S122, the counterpart device 200 uses the filter 291 to extract the regular radio waves from the received radio waves.

[0060] In the first time slot, the counterpart device 200 extracts a first regular radio wave from the received radio wave using the first filter 291. Specifically, the filtering unit 231 extracts a first regular signal from the radio wave information 292 of the received radio wave using the first filter 291. The first regular signal is a signal of the first regular radio wave. In the second time slot, the counterpart device 200 extracts a second regular radio wave from the received radio wave using the second filter 291. Specifically, the filtering unit 231 extracts a second regular signal from the radio wave information 292 of the received radio wave using the second filter 291. The second regular signal is a signal of the second regular radio wave.

[0061] In step S123, the counterpart device 200 processes the communication frame. Specifically, the frame processing unit 232 decodes the communication frame using regular radio waves as the communication frame and transmits the decoded communication frame to the upper layer. The upper layer then receives the decoded communication frame and processes the received communication frame.

[0062] Furthermore, if the counterpart device 200 has a transmitter like the legitimate device 300, the counterpart device 200 operates as follows. The upper layer generates communication data according to the processing result and transmits the communication data to the frame processing unit 232. The frame processing unit 232 receives the communication data and creates a communication frame including the communication data. The transmission unit emits communication radio waves including the communication frame from the antenna 205.

[0063] Returning to FIG. 6 , step S130 will be described. In step S130, the counterpart device 200 and each legitimate device 300 determine whether an update period has arrived. Specifically, the creation unit 220 determines whether a certain amount of time has elapsed since the previous update period. Furthermore, the control unit 320 determines whether a certain amount of time has elapsed since the previous update period. The certain amount of time is a predetermined length of time. For example, the certain amount of time is one second.

[0064] If the update period has arrived, the process proceeds to step S110, which periodically updates the filter 291. If the update period has not arrived, the process proceeds to step S120.

[0065] ***Effects of First Embodiment*** The wireless communication system 100 extends the technique of Non-Patent Document 1 by intentionally regarding the communication radio waves 101 of one of the authorized devices 300 as jamming radio waves. The wireless communication system 100 then estimates channel information for the signal of the desired radio wave (first authorized radio wave) using the signal of the entire received radio waves (the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves 111) and the signal of the jamming radio waves (the sum of the second dummy radio waves and the jamming radio waves 111). This makes it possible to create a digital filter. Then, by applying the digital filter, it is possible to obtain only the radio wave signal from the authorized device 300 even when there is reactive communication jamming by the unauthorized device 110.

[0066] ***Description of the First Embodiment*** A first embodiment will be described with reference to Fig. 11. The wireless communication system 100 includes a wireless device 120. The wireless device 120 includes two authorized devices 300.

[0067] A second embodiment will be described. The configuration of the counterpart device 200 will be described with reference to FIG. 12. The counterpart device 200 further includes an element called a control unit 240. The wireless communication program of the counterpart device 200 further causes a computer to function as the control unit 240. A wireless communication method will be described with reference to FIG. 13. In step S101, the counterpart device 200 performs normal wireless communication while detecting communication jamming. Normal wireless communication is wireless communication performed without using the filter 291. The detection of communication jamming is performed by the control unit 240. For example, the control unit 240 inspects the communication frame and detects communication jamming when a number of consecutive reception errors in the communication frame exceeds a threshold number of times. A specific example of the inspection is error detection using CRC. The threshold number of times is, for example, 10 times. CRC is an abbreviation for Cyclic Redundancy Code. Alternatively, the control unit 240 measures the strength of the received radio wave and detects communication jamming when the increase in the strength of the received radio wave exceeds the threshold number of times. The increase threshold is, for example, 10 dBm. Alternatively, the control unit 240 measures the direction of arrival of the radio waves and detects communication jamming when the change in the direction of arrival is equal to or greater than the change threshold. The change threshold is, for example, 30 degrees. If communication jamming is detected, the control unit 240 notifies the two legitimate devices 300 of the timing to switch communication methods. For example, the control unit 240 transmits a pulse sequence corresponding to a pre-shared code sequence to the two legitimate devices 300. This notification method temporarily changes the modulation method to intensity modulation. This notification method significantly reduces the communication bit rate compared to widely used modulation methods such as OFDM. Therefore, this notification method is used only when the communication method is to be switched. OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. After the notification, the process proceeds to step S110.

[0068] A third embodiment will be described. The third embodiment is a modification of the second embodiment. The configuration of the counterpart device 200 is the same as that in the second embodiment. A wireless communication method will be described with reference to FIG. 14. After step S110, the process proceeds to step S140. In step S140, the counterpart device 200 performs normal wireless communication while detecting communication jamming. The detection of communication jamming is the same as that in the second embodiment. If communication jamming is detected, the process proceeds to step S120. In the third embodiment, the counterpart device 200 determines whether or not to apply the filter 291 depending on the communication quality. Therefore, there is no need to notify each legitimate device 300 of the timing to switch the communication method.

[0069] A fourth embodiment will be described. The configuration of the wireless communication system 100 will be described with reference to FIG. 15. The wireless communication system 100 includes a plurality of legitimate devices 300. Specifically, the wireless communication system 100 includes N legitimate devices 300, where "N" is an integer equal to or greater than 3. The configuration of the counterpart device 200 is the same as that in the second embodiment. The procedure of step S110 will be described with reference to FIG. 16. In step S115, the control unit 240 selects a legitimate device pair including an unselected legitimate device 300 from the legitimate device list. The legitimate device pair consists of two legitimate devices 300. The legitimate device list indicates a plurality of legitimate devices 300 and is stored in the storage unit 290. The control unit 240 then notifies each legitimate device 300 in the selected legitimate device pair. After step S115, the process proceeds to step S111. Steps S111 to S113 are executed for the selected legitimate device pair. That is, one of the regular devices 300 is set as the first regular device 300 and the other regular device 300 is set as the second regular device 300, and steps S111 to S113 are executed. After step S113, the process proceeds to step S114. In step S114, the control unit 240 determines whether there is an unselected regular device 300. If there is an unselected regular device 300, the process proceeds to step S114. If there is no unselected regular device 300, the process ends. In this way, N digital filters are created.

[0070] A fifth embodiment will be described. The fifth embodiment is a variation of the fourth embodiment. The configuration of the wireless communication system 100 is the same as that of the fourth embodiment. Priority is assigned to each legitimate device 300. The procedure of step S110 will be described with reference to FIG. 17. In step S116, the control unit 240 selects two or more legitimate devices 300 from the legitimate device list based on the priority. The legitimate device list indicates multiple legitimate devices 300 and the priority of each legitimate device 300. Specifically, the control unit 240 selects K legitimate devices 300 from N legitimate devices 300, where "K" is an integer equal to or greater than 2 and less than N. In step S117, the control unit 240 selects a legitimate device pair from the selected two or more legitimate devices 300. The control unit 240 then notifies each legitimate device 300 in the selected legitimate device pair. After step S117, the process proceeds to step S111. Steps S111 to S114 are the same as those in the fourth embodiment. In the fifth embodiment, digital filters are created for each of the K regular devices 300 with the highest priority. The conditions for creating the digital filters are shared in advance by the counterpart device 200 and the plurality of regular devices 300 together with the time slot information 391.

[0071] Each embodiment may be implemented alone or in combination with other embodiments.

[0072] Second Embodiment A second embodiment in which the counterpart device 200 moves and the position of the authorized device 300 is fixed will be described, focusing mainly on the differences from the first embodiment, with reference to Figs.

[0073] ***Description of Configuration*** The configuration of the wireless communication system 100 will be described with reference to Fig. 18. The wireless communication system 100 includes a legitimate device 300 and one or more counterpart devices 200. The position of the legitimate device 300 is fixed. A specific example of the legitimate device 300 is a base station. The counterpart device 200 performs positioning while moving. A specific example of the counterpart device 200 is a mobile terminal.

[0074] The configuration of the counterpart device 200 will be described with reference to Fig. 19. The counterpart device 200 further includes elements such as a positioning unit 250 and a calculation unit 260. The wireless communication program of the counterpart device 200 causes the computer to further function as the positioning unit 250 and the calculation unit 260.

[0075] The configuration of the authorized device 300 will be described with reference to Fig. 20. The authorized device 300 includes a plurality of antennas 305.

[0076] ***Description of Operation*** In the counterpart device 200, location information of the legitimate device 300 is stored in the storage unit 290. In addition, the positioning unit 250 periodically obtains location information of the counterpart device 200 by positioning. A specific example of a positioning method is a method using GPS. GPS is an abbreviation for Global Positioning System.

[0077] The wireless communication method will be described with reference to Fig. 21. In step S210, the counterpart device 200 creates a filter 291.

[0078] Steps S220 and S230 are the same as steps S120 and S130 in the first embodiment.

[0079] The procedure of step S210 will be described with reference to Fig. 22. In step S211, the authorized device 300 transmits dummy radio waves. The unauthorized device 110 detects the dummy radio waves and transmits jamming radio waves 111. The counterpart device 200 receives radio waves that are the sum of the dummy radio waves and the jamming radio waves 111.

[0080] In step S212, the calculation unit 260 calculates the relative direction of the normal device 300 based on the position information of the counterpart device 200 and the position information of the normal device 300. The relative direction of the normal device 300 is the direction in which the normal device 300 is located, with the counterpart device 200 as the base point.

[0081] In step S213, the creation unit 220 creates a filter 291 for communication with the authorized device 300 based on the relative direction and the received radio wave.

[0082] The filter 291 is created in the following procedure. First, the channel estimation unit 221 estimates channel information of the legitimate device 300 based on the relative direction and radio wave information 292. The estimation method will be described later. Then, the filter creation unit 222 creates the filter 291 based on the channel information of the legitimate device 300.

[0083] A method for estimating channel information of the genuine device 300 will be described with reference to Figure 23. There are no obstacles between the counterpart device 200 and the genuine device 300. The counterpart device 200 has two antennas 205. "Rx1" means the first antenna 205. "Rx2" means the second antenna 205. The genuine device 300 has two antennas 205. "Tx1" means the first antenna 205. "Tx2" means the second antenna 205. "L" means the distance between the antennas. The distance L is known. "θ" means an angle indicating the relative direction of the genuine device 300.

[0084] The distance between the counterpart device 200 and the legitimate device 300 is sufficiently longer than the distance L. Therefore, when the communication radio wave 101 is approximated by a plane wave, the channel information for the angle θ is expressed by equation (1). "j" represents the imaginary unit. "f" represents frequency. "c" represents the speed of light. "α" is a complex number representing the attenuation rate and the phase change due to propagation.

[0085]

[0086] The channel estimation unit 221 calculates the channel information h of the legitimate device 300 by calculating equation (2), where α is 1.

[0087]

[0088] This means that the entire subspace orthogonal to the channel information h in the linear space formed by the channel information of the sum of the dummy signal and the jamming signal 111 is treated as the channel information of the jamming signal 111.

[0089] ***Effects of Embodiment 2*** According to embodiment 2, even if there is reactive communication interference (jamming) by an unauthorized device 110, it is possible to obtain only the radio wave signal from the authorized device 300 without having to prepare multiple authorized devices 300.

[0090] *** Supplementary Information about the Embodiment *** The hardware configuration of the counterpart device 200 will be described with reference to Fig. 24. The counterpart device 200 includes a processing circuit 209. The processing circuit 209 is hardware that realizes a receiving unit 210, a creating unit 220, an applying unit 230, a control unit 240, a positioning unit 250, and a calculating unit 260. The processing circuit 209 may be dedicated hardware, or may be a processor 201 that executes a program stored in a memory 202.

[0091] When the processing circuit 209 is dedicated hardware, the processing circuit 209 may be, for example, a single circuit, a multiple circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0092] The counterpart device 200 may include a plurality of processing circuits that replace the processing circuit 209 .

[0093] In the processing circuit 209, some functions may be realized by dedicated hardware, and the remaining functions may be realized by software or firmware.

[0094] In this way, the functions of the counterpart device 200 can be realized by hardware, software, firmware, or a combination of these.

[0095] The hardware configuration of the legitimate device 300 will be described with reference to Fig. 25. The legitimate device 300 includes a processing circuit 309. The processing circuit 309 is hardware that implements a transmission unit 310 and a control unit 320. The processing circuit 309 may be dedicated hardware, or may be a processor 301 that executes a program stored in a memory 302.

[0096] When processing circuitry 309 is dedicated hardware, processing circuitry 309 may be, for example, a single circuit, multiple circuits, a programmed processor, parallel programmed processors, an ASIC, an FPGA, or a combination thereof.

[0097] The authorized device 300 may include multiple processing circuits that replace the processing circuit 309 .

[0098] In the processing circuit 309, some functions may be realized by dedicated hardware, and the remaining functions may be realized by software or firmware.

[0099] In this way, the functions of the authorized device 300 can be realized by hardware, software, firmware, or a combination of these.

[0100] Each embodiment is an example of a preferred embodiment and is not intended to limit the technical scope of the present disclosure. Each embodiment may be implemented in part or in combination with other embodiments. Procedures described using flowcharts, etc. may be modified as appropriate.

[0101] The "part" of each element of the counterpart device 200 and the authorized device 300 may be read as a "process," a "step," a "circuit," or a "circuitry."

[0102] 100 Wireless communication system, 101 Communication radio waves, 110 Unauthorized device, 111 Jamming radio waves, 120 Wireless device, 200 Counterpart device, 201 Processor, 202 Memory, 203 Storage, 204 Wireless communication interface, 205 Antenna, 209 Processing circuit, 210 Receiving unit, 211 Radio wave receiving unit, 212 Digital conversion unit, 213 Fourier transform unit, 220 Creation unit, 221 Channel estimation unit, 222 Filter creation unit, 230 Application unit, 231 Filtering unit, 232 Frame processing unit, 240 Control unit, 250 Positioning unit, 260 Calculation unit, 290 Storage unit, 291 Filter, 292 Radio wave information, 300 Authorized device, 301 Processor, 302 Memory, 303 Storage, 304 Wireless communication interface, 305 Antenna, 309 Processing circuit, 310 Transmitting unit, 311 radio wave transmitting unit, 312 analog converting unit, 313 inverse Fourier transform unit, 320 control unit, 321 communication control unit, 322 frame processing unit, 390 storage unit, 391 time slot information, 392 allocation information.

Claims

1. A wireless communication system that performs wireless communication using a digital filter, wherein the digital filter is a filter for extracting legitimate radio waves from received radio waves that include legitimate radio waves transmitted from legitimate devices and jamming radio waves transmitted from unauthorized devices, comprising: a first legitimate device that transmits two first dummy radio waves at different timings; a second legitimate device that transmits a second dummy radio wave at the same timing as the transmission of one of the first dummy radio waves, and transmits the second dummy radio wave at a different timing from the transmission of the other first dummy radio wave; and a counterpart device that receives received radio waves that are the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves, receives received radio waves that are the sum of the first dummy radio waves and the jamming radio waves, and receives received radio waves that are the sum of the second dummy radio waves and the jamming radio waves, and creates a first digital filter for communication with the first legitimate device and a second digital filter for communication with the second legitimate device based on the three received radio waves.

2. The wireless communication system of claim 1, wherein the first regular device transmits a first regular radio wave in a first time slot and transmits the first dummy radio wave in a second time slot; the second regular device transmits the second dummy radio wave in the first time slot and transmits a second regular radio wave in the second time slot; and the other device uses the first filter in the first time slot to extract the first regular radio wave from a received radio wave that is the sum of the first regular radio wave, the second dummy radio wave, and the jamming radio wave; and uses the second filter in the second time slot to extract the second regular radio wave from a received radio wave that is the sum of the first dummy radio wave, the second regular radio wave, and the jamming radio wave.

3. The wireless communication system described in claim 1 or claim 2, wherein the counterpart device estimates channel information of the second authorized device based on the received radio waves which are the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves and the received radio waves which are the sum of the first dummy radio waves and the jamming radio waves, and creates the second filter based on the estimated channel information, and estimates channel information of the first authorized device based on the received radio waves which are the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves and the received radio waves which are the sum of the second dummy radio waves and the jamming radio waves, and creates the first filter based on the estimated channel information.

4. A wireless communication system according to any one of claims 1 to 3, wherein the first authorized device and the second authorized device are mobile wireless devices, and the counterpart device updates the first filter and the second filter at each update period.

5. The wireless communication system according to any one of claims 1 to 4, comprising a wireless device, and the wireless device comprises the first authorized device and the second authorized device.

6. The wireless communication system according to any one of claims 1 to 5, wherein the counterpart device detects communication interference, and when the communication interference is detected, notifies the first authorized device and the second authorized device to create the first filter and the second filter.

7. A wireless communication system according to any one of claims 1 to 5, wherein the counterpart device detects communication interference, and when the communication interference is detected, performs communication using the first filter and the second filter.

8. The wireless communication system according to any one of claims 1 to 7, wherein the wireless communication system comprises a plurality of genuine devices, and the counterpart device sequentially selects a pair of genuine devices consisting of two genuine devices from the plurality of genuine devices, and for each pair of genuine devices, designates one of the genuine devices as the first genuine device and the other genuine device as the second genuine device to create the first filter and the second filter.

9. The wireless communication system according to any one of claims 1 to 7, wherein the wireless communication system comprises a plurality of authorized devices each having a priority level, and the counterpart device selects two or more authorized devices from the plurality of authorized devices based on the priority level of each authorized device, sequentially selects authorized device pairs each consisting of two authorized devices from the two or more authorized devices, and for each authorized device pair, designates one authorized device as the first authorized device and the other authorized device as the second authorized device, thereby creating the first filter and the second filter.

10. A wireless communication method using a digital filter for wireless communication, wherein the digital filter is a filter for extracting legitimate radio waves from received radio waves that include legitimate radio waves transmitted from legitimate devices and jamming radio waves transmitted from unauthorized devices, wherein a first legitimate device transmits two first dummy radio waves at different timings, a second legitimate device transmits a second dummy radio wave at the same timing as the transmission of one of the first dummy radio waves and transmits the second dummy radio wave at a different timing from the transmission of the other first dummy radio wave, the other device receives received radio waves that are the sum of the first dummy radio waves, the second dummy radio waves, and the jamming radio waves, receives received radio waves that are the sum of the first dummy radio waves and the jamming radio waves, and receives received radio waves that are the sum of the second dummy radio waves and the jamming radio waves, and creates a first digital filter for communication with the first legitimate device and a second digital filter for communication with the second legitimate device based on the three received radio waves.

11. A wireless communication system that performs wireless communication using a digital filter, wherein the digital filter is a filter for extracting legitimate radio waves from received radio waves that are the sum of legitimate radio waves transmitted from legitimate devices and jamming radio waves transmitted from unauthorized devices, the wireless communication system comprising: a legitimate device whose location is fixed; and a counterpart device that performs positioning while moving, wherein the legitimate device transmits a dummy signal; the counterpart device receives received radio waves that are the sum of the dummy signal and the jamming radio waves, calculates the relative direction of the legitimate device based on its own location information and the location information of the legitimate device, and creates the digital filter based on the calculated relative direction and the received radio waves.

12. The wireless communication system according to claim 11, wherein the authorized device transmits authorized radio waves, and the counterpart device uses the digital filter to extract the authorized radio waves from received radio waves that are the sum of the authorized radio waves and the jamming radio waves.

13. A wireless communication system as described in claim 11 or claim 12, wherein the counterpart device estimates channel information of the legitimate device based on the received radio waves, which are the sum of the dummy signal and the jamming radio waves, and the relative direction, and creates the digital filter based on the estimated channel information.

14. A wireless communication method for a wireless communication system that performs wireless communication using a digital filter, wherein the digital filter is a filter for extracting legitimate radio waves from received radio waves that are the sum of legitimate radio waves transmitted from legitimate devices and jamming radio waves transmitted from unauthorized devices, and the wireless communication system comprises: a legitimate device whose location is fixed; and a counterpart device that performs positioning while moving, wherein the legitimate device transmits a dummy signal; the counterpart device receives received radio waves that are the sum of the dummy signal and the jamming radio waves; calculates the relative direction of the legitimate device based on its own location information and the location information of the legitimate device; and creates the digital filter based on the calculated relative direction and the received radio waves.

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