WO2023037661A1 - Wireless communication system and wireless communication method - Google Patents

Abstract

A wireless communication system in which a first wireless device and a second wireless device anonymize information using a physical key and communicate in order to share the same common key without being affected by uncertainty due to error when using a common key for encrypted communication of unique physical quantities based on propagation characteristics, in which the first wireless device and the second wireless device share chronological change of dynamically changing propagation characteristics and communicate, the first wireless device transmits the least significant bit of a predetermined range of a first discrete value determined by the first wireless device on the basis of the propagation characteristics and a lower bit following the least significant bit in the first discrete value to the second wireless device, the second wireless device estimates a common key in the first wireless device from a second discrete value determined by the second wireless device on the basis of the propagation characteristics and from the least significant bit and the lower bit received from the first wireless device, and the common key becomes the physical key.

Description

Wireless communication system and wireless communication method

The present invention relates to a wireless communication system and a wireless communication method, and more particularly to a wireless communication system and a wireless communication method using rotationally polarized wave communication suitable for cryptographic communication.

In wireless communication, since the free space that is open to the outside is used as a transmission path, in principle, an outsider can easily acquire the energy of the electromagnetic wave containing the communication information. Therefore, confidentiality of information to be transmitted is an important technical issue in wireless communication.

As a technology for confidentiality of information, a technology that encrypts and transmits information is used. In this technique of information transmission by encryption, a new problem arises as to how to conceal the mathematical key shared by the sender and the receiver from outsiders.

In Patent Document 1, in rotary polarized wave communication, a pair of rotary polarized radio devices share time-series changes in polarization rotation, and cryptographic communication is performed using a physical quantity based on a dynamically changing polarization phase as a common key. A method is disclosed.

Japanese Patent Application Laid-Open No. 2021-40258

Due to the reversibility of propagation by the antenna, even if the transmitting side and the receiving side are exchanged, they have the same propagation characteristics, so a pair of wireless stations can share unique physical quantities based on the propagation characteristics. On the other hand, it cannot be shared except between transmitting and receiving stations.

On the other hand, according to the conventional technology described above, by using a unique physical quantity based on the propagation characteristics as a common key for cryptographic communication between a pair of transmitting and receiving stations, the confidentiality of the common key can be enhanced. .

However, in the above-described prior art, there is an error ("uncertainty" because the true value is unknown) associated with conversion (digitizing) of a unique physical quantity based on propagation characteristics, that is, an analog value, into a common key for cryptographic communication, that is, a digital value. (often referred to as ) should be considered further. This is because the same common key cannot be shared between a pair of radio stations, because when digitizing substantially the same physical quantity, that is, an analog value, it may be converted into a different digital value due to errors (uncertainty). It may not be possible, and the encrypted communication may not be established.

Therefore, the present invention aims to share the same common key without being affected by error (uncertainty) when using a unique physical quantity based on propagation characteristics as a common key for cryptographic communication.

In order to achieve the above-described problems, one of the representative wireless communication systems of the present invention is wireless communication in which a first wireless device and a second wireless device perform communication while keeping information confidential using a physical key. A system in which a first radio and a second radio share time-series changes in dynamically changing propagation characteristics to perform communication, and the first radio itself is based on the propagation characteristics transmitting the least significant bit of the predetermined range of the obtained first discrete value and the least significant bit following the least significant bit in the first discrete value to the second radio, and the second radio transmits estimating a common key in the first radio from the second discrete value obtained based on the characteristics and the least significant bit and the least significant bit received from the first radio, and the common key being a physical key is.

According to the present invention, only the bits below the temporary LSB are exchanged, and the high-order bits used for the common key are not exchanged, the common key is kept secret, and the same common key is generated without being affected by errors (uncertainties). can be shared.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the basic embodiment of this invention as Example 1 of this invention. FIG. 10 is a diagram illustrating an example of processing when generating a common key; FIG. 3 is a flowchart showing a processing procedure performed by the master station 10 shown in FIG. 2; 3 is a diagram showing, in a flowchart, a processing procedure performed by a child station 20 shown in FIG. 2; FIG. This is a table in the case of rounding the lower bits of the provisional LSB with 0 or 1. FIG. It is a table in the case of truncating the lower bits of the provisional LSB as rounding. FIG. 2 is a diagram showing the configuration of a radio communication system according to Example 2 of the present invention; FIG. 4 is a diagram illustrating a first example of a common key handover method; FIG. 10 is a diagram illustrating a second example of a common key handover method; FIG. 10 is a diagram illustrating a third example of a common key handover method; FIG. 10 is a diagram showing a fourth example of a common key handover method; FIG. 12 is a diagram illustrating a fifth example of a common key handover method; FIG. 10 is a diagram showing a frequency and polarization angle hopping table as a first pattern of Example 3; FIG. 12 is a diagram showing a frequency-only hopping table for a case where the partner station does not have a rotary polarization communication function, as a second pattern of the third embodiment; FIG. 12 is a diagram showing a hopping table that is changed in response to occurrence of a communication failure as a third pattern of the third embodiment; 1 is a diagram showing an example of a configuration of a wireless communication system that performs confidential information communication using a polarization shift characteristic unique to a wireless device that performs communication as an encryption key; FIG. FIG. 3 is a diagram showing an example of a communication protocol of each radio device of the radio communication system according to the present invention; FIG. 10 is a diagram showing an outline of another example of a wireless communication system that performs confidential information communication using a polarization shift characteristic unique to a wireless device that performs communication as an encryption key; 19 is a diagram showing an example of a communication protocol used by each wireless device shown in FIG. 18; FIG. FIG. 11 is a diagram showing a first configuration example and its operation mode as a representative example of a receiver of a radio communication system according to a fourth embodiment; FIG. 4 is a diagram showing the relationship between a transmission waveform and a reception waveform; FIG. 3 is a diagram showing correlation with a received signal by shifting a strong autocorrelation weak cross-correlation bit string shared by a transmitting station and a receiving station; FIG. 12 is a diagram showing a second configuration example as a receiver used in the wireless communication system according to the fourth embodiment; FIG. 12 is a diagram showing a third configuration example as a receiver of the wireless communication system according to the fourth embodiment; FIG. 14 is a diagram showing a fourth configuration example as a representative example of a transmitter of a radio communication system according to the fourth embodiment; FIG. 12 is a diagram showing a fifth configuration example as a transmitter used in the wireless communication system according to the fourth embodiment; FIG. 12 is a diagram showing a sixth configuration example as a representative example of a wireless device pair (transmitter/receiver) used in the wireless communication system according to the fourth embodiment; FIG. 17 is a diagram showing a seventh configuration example as a wireless device pair (transmitter/receiver) used in the wireless communication system according to the fourth embodiment;

Hereinafter, Embodiments 1 to 4 will be described with reference to the drawings as modes for carrying out the present invention. Here, in the description of the drawings, the same parts are indicated by the same reference numerals.

Before describing the embodiments of the present invention, an outline of a wireless communication system that performs confidential information communication according to the present invention will be described.

FIG. 16 is a diagram showing an example of the configuration of a wireless communication system that performs confidential information communication using a polarization shift characteristic unique to a wireless device that performs communication as an encryption key.
This radio communication system comprises a master station 10-1 and slave stations 20-1, 20- and 2. FIG. A shield 31, a reflector 32, and the like exist around the transmitter/receiver.

Between the transmitter of the master station 10-1 and the receiver of the slave station 20-1, there is no entity that blocks the line-of-sight propagation path. The polarization shift is 0° when performing rotational polarization communication.

On the other hand, between the transmitter of the master station 10-1 and the receiver of the slave station 20-2, there is a shielding object 31 on the line-of-sight propagation path. It becomes a received wave of the receiver of the slave station 20-2 via the reflector 32. FIG. Upon reflection, a unique polarization shift occurs that is determined by the normal vector of the reflector 32 and the incident vector of the transmitted wave, and the polarization shift when performing rotary polarization communication is different from 0°. . Moreover, since the polarization shift depends on the incident vector of the transmission wave, the difference between the polarization angle of the transmission wave and the polarization angle at the time of reception is not constant.

FIG. 1 is a diagram showing a basic embodiment of the present invention as Example 1 of the present invention.
FIG. 1 is a graph showing the relationship between the polarization angle (transmitting side polarization angle) ΦTX of the radio wave sent from the transmitting side and the polarization angle (receiving side polarization angle) ΦRX of the radio wave received at the receiver side.

As described above, since the deviation shift occurs due to the effects of reflection, diffraction, etc. in the middle of the propagation path, ΦRX=ΦTX does not hold. Moreover, since the polarization shift depends on the incident vector of the transmission wave, the difference between the polarization angle of the transmission wave and the polarization angle of the reception wave is not constant. Therefore, the relationship is not necessarily linear. Note that due to the reciprocity of antennas and propagation, the curves are the same even if the transmit and receive sides are interchanged.

Also, if the conditions of the transmitting station and the receiving station are different, the relationship between the transmitting-side polarization angle ΦTX and the receiving-side polarization angle ΦRX will have different curves as shown in conditions 1 and 2 in FIG.

Therefore, the difference between the curve and the straight line ΦRX=ΦTX, that is, the value of ΦRX−ΦTX, or the difference between the curve and the straight line ΦRX=ΦTX+ΔΦ, that is, the value of ΦRX−ΦTX−ΔΦ, is converted into discretized values DA and DB. Based on this, a first method of generating the common key KEYA=KEYB and a second method of generating the common key KEYA=KEYB from the positive/negative of the discretized values DA and DB can be considered.

First, according to the first method, a larger number of bits of information can be obtained per sampling, so an encryption key with a larger number of bits can be generated. On the other hand, however, it is susceptible to errors (uncertainty) associated with digitization, so it is necessary to perform uncertainty elimination processing, which will be described later with reference to FIG. 2 and subsequent figures.

In addition, due to 1/f fluctuations inherent in physical phenomena, there is a tendency for the upper bits to change less and the lower bits to change more. ). However, this is not the case when the originally included encryption algorithm is used as the bit position shuffling operation.

Next, according to the second method, since only 1-bit information of a sign representing positive or negative is obtained per sampling, it is necessary to obtain values of n samples in order to generate an n-bit encryption key. There is

Also, when the sampled value is near 0, it is susceptible to errors (uncertainty) associated with digitization, so it is necessary to perform uncertainty elimination processing, which will be described later using Fig. 2 and later. In this case, if the sign bit is the provisional LSB, the sign bit will be exchanged between the master station and the slave station by communication. can be kept secret.

Here, as a unique physical quantity based on propagation characteristics used as a common key for cryptographic communication, values such as the propagation time or propagation loss between a pair of wireless stations can be considered in addition to the above-described polarization angle.

Here, even if the value of propagation time or propagation loss is used, it is desirable to generate a common key based on the difference between the theoretically estimated value and the actually measured value so that it is not easily estimated as an encryption key. Specifically, a common key is generated based on the difference between the theoretical value of propagation time derived from the distance between wireless stations and the measured value, or the difference between the theoretical value of propagation loss (signal strength) and the measured value. It is desirable to

Also, by performing cryptographic communication using the common key thus obtained, it is possible to keep information confidential. Further, by combining a plurality of multistage encryption methods and encryption keys, for example, by combining a conventional common key with a common key obtained by the present invention, the encryption strength can be increased.

FIG. 2 is a diagram showing an example of processing when generating a common key KEYA=KEYB based on values DA and DB obtained by discretizing the polarization angle values in the propagation characteristics.

The master station 10 performs fraction processing (S106 shown in FIGS. 2 and 3) on the value DA obtained by discretizing the propagation characteristics with the provisional LSB, that is, tLSB as the least significant bit, to obtain the encryption key KEYA.

Similarly, in the slave station 20, the value DB obtained by discretizing the propagation characteristic is treated as a provisional LSB, that is, tLSB as the least significant bit, and the fraction processing (S206 shown in FIGS. 2 and 4) and the uncertainty resolution processing (FIG. 2 and S207) shown in FIG. 4 to obtain the encryption key KEYB.

At this time, the master station 10 transmits tLSB of the value DA and two bits one bit lower than it (S102 shown in FIGS. 2 and 3). On the other hand, the slave station 20 receives these 2 bits (shown in FIGS. 2 and 4, S202), predicts the result of rounding in the master station 10 (shown in FIGS. 2 and 4, S206), This uncertainty elimination process (S207) is performed by matching the result of the uncertainty elimination process (S207 shown in FIGS. 2 and 4) of the value DB with the predicted value.

FIG. 3 is a flowchart showing the processing procedure performed by the master station 10 shown in FIG. Note that since the master station 10 is the subject of processing from step 100 (S100) to step 112 (S112) below, the notation of the subject of processing will be omitted below.

Processing is started as step 100 (S100).
At step 101 (S101), the bit position k of the provisional LSB is set to the initial value k0.

At step 102 (S102), the k-th bit and k−1-th bit of the value DA obtained by discretizing the propagation characteristics are transmitted to the slave station 20.

At step 104 (S104), the contents of transmission from the slave station 20 to the master station 10 are confirmed.
If the content of transmission from the slave station 20 to the master station 10 is NG (corresponding to step 211 (S211) shown in FIG. 4), in step 112 (S112), the bit position k of the provisional LSB is moved one bit higher. Then, the process returns to step 102 (S102), and the process of step 102 (S102) is performed.

If the contents of transmission from the slave station 20 to the master station 10 are OK (corresponding to step 205 (S205) shown in FIG. 4), in step 106 (S106), the value DA is left-shifted by k bits (the value DA is Arithmetic shift for signed integers) and rounding to KEYA. Here, since the least significant bit of KEYA is transmitted from the parent station 10 to the child station 20, it may not be used as the encryption key, and the higher bits may be used as the encryption key.

At step 108 (S108), encrypted communication with the slave station 20 is started using KEYA as a common key.

At step 109 (S109), it is checked whether or not the encrypted communication has succeeded.
If the cryptographic communication is not successful (N), go through step 112 (S112) (move the bit position k of the provisional LSB one bit higher), return to step 102 (S102), and step 102 (S102). process.

If the encrypted communication is successful (Y), at step 110 (S110), the series of processes is terminated, and the encrypted communication with the slave station 20 is continued using the KEYA as the common key.

FIG. 4 is a flowchart showing a processing procedure performed by the child station 20 shown in FIG. It should be noted that since the processing subject of the following steps 200 (S200) to step 212 (S212) is the child station 20, the notation of the processing subject will be omitted below.
Processing is started as step 200 (S200).
At step 201 (S201), the bit position k of the provisional LSB is set to the initial value k0.

At step 202 (S202), the k-th bit and k-1-th bit of the value DA obtained by discretizing the propagation characteristics are received from the master station 10 (corresponding to step 102 (S102) shown in FIG. 3).

At step 203 (S203), the difference ε between the value DA and the value DB is calculated from the k-th and k-1-th bits of the value DA and the k-th and k-1-th bits of the value DB.

At step 204 (S204), it is determined whether or not the value of the difference ε is less than 1 provisional LSB.
If the difference ε is equal to or greater than 1 provisional LSB (N), the slave station 20 transmits "NG" to the master station 10 in step 211 (S211). Subsequently, in step 212 (S212), the bit position k of the provisional LSB is moved one bit higher, and the process of step 202 (S202) is performed.

If the difference ε is less than 1 provisional LSB (Y), the slave station 20 transmits "OK" to the master station 19 in step 205 (S205).

At step 206 (S206), the value DB is left-shifted by k bits (arithmetic shift if DB is a signed integer), rounded, and set to KEYB.

At step 207 (S207), the uncertainty resolution process shown in FIG. 5 or 6 is executed. Here, since the least significant bit of KEYA (=KEYB) is transmitted from the master station 10 to the child station 20, it may not be used as the encryption key, and the higher bits may be used as the encryption key.

At step 208 (S208), encrypted communication with the master station 10 is started using KEYB as a common key.

At step 209 (S209), it is checked whether or not the encrypted communication has succeeded.
If the encrypted communication is not successful (N), go through step 212 (S212) (move the bit position k of the provisional LSB to one bit higher), return to step 202 (S202), and step 202 (S202). process.

If the encrypted communication is successful (Y), at step 210 (S210), the series of processes is terminated, and the encrypted communication with the master station 10 is continued using KEYB as the common key.

Next, the uncertainty elimination process in step 207 (S207) will be explained. 5 and 6 show tables used for uncertainty processing.

FIG. 5 is a table when the lower bits of the provisional LSB (tLSB) are "rounded off by 0", which corresponds to the rounding off of decimal numbers, as the fraction processing (S106, S206).
On the other hand, FIG. 6 is a table for rounding down the lower bits of the temporary LSB (tLSB) as rounding (S106, S206).

Uncertainty elimination processing (S207) is executed based on these tables.
In each table, the horizontal direction is the parent station, the vertical direction is the child station, and the provisional LSB (tLSB), its lower bit value, and the rounding result are shown in parentheses. At the intersection of the parent station and the child station, the result after the uncertainty elimination process (S207) and the corrected value of the rounding result of the child station are shown in parentheses.

Regarding the correction value of the rounding result of the slave station, "±0" indicates that correction is not required, "+1" indicates that 1 should be added, and "-1" indicates that 1 should be subtracted. "X" indicates that the difference between the value DA and the value DB is 1 provisional LSB or more, and the provisional LSB must be moved to a higher position for rounding.

For example, in FIG. 5, the top row indicates that the provisional LSB and the lower bits of the child station are 00, etc., and indicates that they become 0 when "0 is rounded off", and the leftmost column indicates that the parent station The provisional LSB and the lower bits of are 00... and become 0 when "0 is rounded off". "±0" indicates that correction is unnecessary.

Also, in the second column from the left in the same row, the provisional LSB and the lower bits of the master station are 01 . becomes 1, and the correction of the rounding result of the slave station is "+1", indicating that addition of 1 is required.

FIG. 7 is a diagram showing the configuration of a radio communication system according to Embodiment 2 of the present invention.
FIG. 7(a) shows a configuration example in which a plurality of mobile stations, namely m1 station 20-1 and m2 station 20-2, exist for station A 10, which is a parent station.

Encrypted communication is performed between the parent station A station 10 and the moving child stations m1 station 20-1 and m2 station 20-2 using common keys KYAm1 and KEIAm2, respectively. Further, between the m1 station 20-1 and the m2 station 20-2, which are moving child stations, encrypted communication is performed using a common key KEYm1m2.

In (b) of FIG. 7, one moving child station m station 20 exists for a plurality of parent stations A station 10-1, B station 10-2 and C station 10-3. Give an example.

The shared key KEYAB is used between the parent stations A station 10-1 and B station 10-2, and the shared key KEYBC is used between the B station 10-2 and C station 10-3. will be Further, a common key KEYAm is used between the master station A station 10-1 and the moving slave station m station 20, and the master station B station 10-2 and the moving slave station m station 20 are connected. Between , the common key KEYBm is used, and encrypted communication is performed respectively.

Next, referring to FIGS. 8 to 12, the common service areas 11-1, 11-2 and 11-3 of the different master stations A station 10-1, B station 10-2 and C station 10-3 A key handover method will be explained.

FIG. 8 is a diagram showing a first example of a common key handover method.
In the first example, each time cryptographic communication is performed, a common key is generated and established from the polarization angle by the method according to the first embodiment between the master station and the slave station, and cryptographic communication is performed.

When station m 20, which is a moving child station, exists in the service area 11-1 of station A 10-1, which is a parent station, each time encrypted communication is performed, between station A 10-1 and station m 20: A common key KEYAm is generated and established from the polarization angle by the method according to the first embodiment, and cryptographic communication is performed using the common key KEYAm.

Subsequently, when station m 20, which is a moving child station, enters service area 11-2 of station B 10-2, which is a parent station, each time encrypted communication is performed, A common key KEYBm is generated and established from the polarization angle by the method according to the first embodiment, and cryptographic communication is performed using the common key KEYBm.

Thus, according to the first example, since the common key is frequently updated, even if the common key leaks, the damage can be minimized.

FIG. 9 is a diagram showing a second example of a common key handover method.
In the second example, each time a slave station enters the service areas of a plurality of master stations, a common key is generated and established to perform encrypted communication. That is, when a child station enters the service area of a parent station, a common key is generated and established from the polarization angle by the method according to the first embodiment between the parent station and the child station. is in the service area of this master station, encrypted communication is performed using the common key. After that, when the slave station enters the service area of another master station, another common key is generated and established from the polarization angle by the method according to the first embodiment between the other master station and the slave station. , and thereafter, while the slave station is in the service area of another master station, encrypted communication is performed using another common key.

When station m 20, which is a moving child station, enters the service area 11-1 of station A 10-1, which is a parent station, the communication between station A 10-1 and station m 20 according to the first embodiment A common key KEYAm is generated and established from the polarization angle according to the method, and cryptographic communication is performed using the common key KEYAm.

Subsequently, when station m 20, which is a mobile station, enters the service area 11-2 of station B 10-2, which is a parent station, communication between station B 10-2 and station m 20 is performed according to the first embodiment. A common key KEYBm is generated and established from the polarization angle by such a method, and cryptographic communication is performed using the common key KEYBm.

Thus, according to the second example, the overhead for generating and establishing a common key can be reduced, so communication efficiency can be improved.

FIG. 10 is a diagram showing a third example of a common key handover method.
In the third example, when the slave station first enters the service area of the master station, a common key is generated and established from the polarization angle by the method according to the first embodiment between the master station and the slave station, Thereafter, even if the slave station enters the service area of another master station, it will continue to use the common key to perform encrypted communication.

The A station 10-1 and B station 10-2, which are parent stations, are equipped with antennas with high ground clearance and high gain because they are base stations. Therefore, communication over a longer distance than that of the m-station 20, which is a child station, is possible, and communication is also possible over ground communication lines.

Further, when the A station 10-1 and the B station 10-2 perform wireless communication, prior to that, the common key KEYAB is generated and established from the polarization angle by the method according to the first embodiment, and encrypted with the common key KEYAB. Communication is also possible.

When station m 20, which is a moving child station, enters the service area 11-1 of station A 10-1, which is a parent station, the communication between station A 10-1 and station m 20 according to the first embodiment A common key KEYAm is generated and established from the polarization angle according to the method, and cryptographic communication is performed using the common key KEYAm.

Subsequently, when station m 20, which is a moving child station, enters service area 11-2 of station B 10-2, which is a parent station, common key KEYAm is shared from station A 10-1 to station B 10-2. It is sent after being encrypted with the key KEYAB, or sent via a ground communication line. After that, the m-station 20 and the B-station 10-2 perform encrypted communication using the common key KEYAm.

Thus, according to the third example, the overhead for generating and establishing the common key can be reduced, so communication efficiency can be improved. In addition, spoofing of the parent station or the child station can be prevented by using the common key as information for authentication at the time of handover.

FIG. 11 is a diagram showing a fourth example of the common key handover method.
In the fourth example, when the slave station first enters the service area of the master station, a common key is generated and established from the polarization angle by the method according to the first embodiment between the master station and the slave station, Encrypted communication is performed using the common key, and when the slave station enters the service area of another master station, the first master station sends the first common key as authentication information to the other master station.

The A station 10-1 and B station 10-2, which are parent stations, are equipped with antennas with high ground clearance and high gain because they are base stations. Therefore, communication over a longer distance than that of the m-station 20, which is a child station, is possible, and communication is also possible over ground communication lines.

Further, when the A station 10-1 and the B station 10-2 perform wireless communication, prior to that, the common key KEYAB is generated and established from the polarization angle by the method according to the first embodiment, and encrypted with the common key KEYAB. Communication is also possible.

When station m 20, which is a moving child station, enters the service area 11-1 of station A 10-1, which is a parent station, the communication between station A 10-1 and station m 20 according to the first embodiment A common key KEYAm is generated and established from the polarization angle according to the method, and cryptographic communication is performed using the common key KEYAm.

Subsequently, when station m 20, which is a moving child station, enters the service area 11-2 of station B 10-2, which is a parent station, authentication information common to stations A 10-1 to B 10-2 is transmitted. The key KEYAm is encrypted with the common key KEYAB and sent, or sent via a ground communication line.

Station B 10-2 confirms that encrypted communication with station m 20 is established using the common key KEYAm. Thereby, the B station 10-2 confirms that the m station 20 entering the service area 11-2 is valid. After that, the common key KEYBm is generated and established from the polarization angle by the method according to the first embodiment between the B station 10-2 and the m station 20, and after that, the m station 20 and the B station 10-2 performs encrypted communication using a common key KEYBm.

Thus, according to the fourth example, spoofing of the parent station or the child station can be prevented by using the common key as information for authentication during handover.

FIG. 12 is a diagram showing a fifth example of a common key handover method.
In the fifth example, the child station confirms whether or not the previous day's encrypted communication is established for authentication at the start of work within the service area of the first parent station.

First, at the start of work, the parent station A station 10-1 confirms that encrypted communication with the child station m station 20 is established using the common key KEYAm from the previous day. Thereby, the A station 10-1 confirms that the m station 20 existing in the service area 11-1 is legitimate at the start of work.

After that, when the moving child station m station 20 enters the service area 11-1 of the parent station A station 10-1, the first embodiment is established between the A station 10-1 and the m station 20. A common key KEYAm is generated and established from the polarization angle by the method according to the above, and cryptographic communication is performed using the common key KEYAm. The subsequent operation mode is the same as the third example shown in FIG.

Thus, according to the fifth example, by using the common key as information for authentication at the time of handover, it is possible not only to prevent spoofing of the parent station or the child station, but also to use the common key from the previous day at the start of work. By using it as information for authentication, it is possible to prevent spoofing of the parent station or the child station.

A third embodiment of the present invention has an embodiment for hopping at least one of the frequency and the polarization angle used for communication.
FIG. 13 is a diagram showing a hopping table for hopping frequencies and polarization angles as the first pattern of the third embodiment.

In the first pattern, the frequency and polarization angle used for communication are switched regularly in time series for each of steps 1 to n.

Specifically, in step 1, communication is performed at frequency f1 and polarization angle p1, in step 2, communication is performed at frequency f2 and polarization angle p3, and in step 3, communication is performed at frequency f3 and polarization angle p3. , and thereafter, in step n, the frequency and polarization angle used for communication are periodically switched according to the form of communication at frequency fn and polarization angle pn.

It goes without saying that if the frequencies differ, communication will not be established. Furthermore, if the polarization angles differ by θ, the signal strength will decrease to cos θ, and theoretically the signal strength will be 0 when θ=90 degrees. However, in practice the signal strength drops by 10-20 dB.

If the polarization angle is changed at random, the signal strength will fluctuate at random even if the frequency is the same. Therefore, unless you have the hopping table information in advance, normal decoding becomes difficult and normal communication is established. Gone.

Conventionally, a method called frequency hopping, which periodically switches frequencies, has been widely used for the confidentiality of communications. On the other hand, in the third embodiment, by periodically switching not only the frequency but also the polarization angle, the secrecy of communication can be increased.

The table of combinations of frequencies and polarization angles for each step (hopping table) can be kept secret from third parties to improve the secrecy of communication. In particular, if the hopping table is realized using the physical quantity of the polarization angle, the secrecy of the hopping table can be enhanced.

FIG. 14 is a diagram showing a hopping table for hopping only the frequency when the partner station does not have a rotary polarization communication function, as the second pattern of the third embodiment.

If the partner station has a rotary polarization communication function, frequency and polarization angle hopping is performed by using a frequency and polarization angle hopping table prepared in advance. If it does not have a communication function, it performs only frequency hopping as in the second example.

According to the second pattern, it is possible to communicate with a partner station that does not have a rotary polarization communication function, in other words, it is possible to maintain communication compatibility with conventional wireless stations. However, according to the second example, it is not possible to perform cryptographic communication using the propagation characteristics obtained in the first embodiment, especially the physical quantity of the polarization angle, as a common key, so it is necessary to share the common key in some way.

In addition, in order to confirm in advance whether the partner station has the rotary polarized wave communication function, prior to starting communication with the partner station, the rotary polarized wave communication function may be exchanged to indicate whether or not they have

FIG. 15 is a diagram showing a hopping table that is changed in response to the occurrence of a communication failure as the third pattern of the third embodiment.

In the third pattern, if a communication failure occurs due to interference by interfering waves or the like in either frequency or polarization angle hopping, the hopping table is changed to avoid this.

As shown in FIG. 15(a), if a communication failure occurs in step 5 due to interference by interfering waves, etc., in this step 5, the frequency and polarization used in another step (step 6 in the figure) are changed. Communicate with waves.

As shown in FIG. 15(b), if communication failure occurs in steps 5 and 6 due to interference by interfering waves, these steps 5 and 6 are used in another step (step 7 in the figure). communication at the same frequency and polarization angle.

As shown in FIG. 15(c), at all polarization angles in steps 5 to 8 for transmission at frequency f2, if communication failure occurs due to interference due to interfering waves, etc., in these steps 5 to 8, Communication is performed at the frequency and polarization angle of the step using different frequencies (step 9 using frequency f3 in the figure).

As described above, according to the third embodiment, when communication failure occurs due to interference due to interference waves at least one of the frequency and the polarization angle used for hopping, the frequency and polarization angle at which the communication failure occurs from the next time. Since communication is performed while avoiding at least one of them, it is possible to secure a more stable communication state that is resistant to interference caused by interfering waves.

As a fourth embodiment according to the present invention, a configuration example of a confidential information communication system using polarization shift characteristics unique to a pair of wireless devices that communicate as an encryption key will be described with reference to FIGS. 16 to 20. FIG.

If the absolute time can be obtained by separately using GPS or standard radio waves, it is possible to measure the propagation time or obtain the transmission timing of the radio wave at a specific polarization angle by synchronization. .

First, the operation mode of the fourth embodiment according to the present invention will be described using the wireless communication system shown in FIG.
A transmitter of the master station 10-1 assigns a sine wave and a cosine wave of a plurality of polarization rotation frequencies of the same frequency and different phases to each bit of a bit string with strong autocorrelation and weak cross-correlation of a signal, Two summed sine waves and summed cosine waves obtained by superimposing a plurality of sine waves and a plurality of cosine waves, respectively, are up-converted at the carrier frequency, respectively, and radiated into space from spatially orthogonal antennas to obtain a rotationally polarized wave. to form the transmission wave of

Since the received waves of the rotationally polarized waves of the receivers of the child stations 20-1 and 20-2 have different polarization shifts, each bit of the bit string with strong autocorrelation and weak cross-correlation has the same frequency and different phase. are allocated, and two added sine waves and added cosine waves obtained by superimposing the plurality of sine waves and the plurality of cosine waves are applied to the down-converted signal of the received wave through a delay device When multiplied, the result has extreme values at different delay amounts.

Therefore, in the received wave, a plurality of sine waves and cosine waves of the same frequency and different phases are assigned to each bit of a bit string with strong autocorrelation and weak cross-correlation having different polarization shifts. The diffused signal is mixed with the superposition of the wave and multiple cosine waves. In this case, by multiplying the superposition with the signal obtained by downconverting the received wave by the carrier wave with a different amount of delay, the received signal is included in the transmitted signal from the receiver with a different polarization shift. Information can be separated.

FIG. 17 is a diagram showing an example of a communication protocol for each radio in the radio communication system according to the present invention.
With reference to FIG. 17, a communication protocol for one-to-one communication between the wireless devices A and B in a wireless communication system that performs confidential information communication using the polarization shift characteristics unique to the wireless devices that communicate as an encryption key will be described.

First, a processing mode until the wireless device A transmits a synchronization signal (bit) including an ID will be described. Although the subject of the following processing mode is the wireless device A, the description of the subject is omitted.
The wireless device B is selected as the communication destination, and an ID shared by both wireless devices is determined in advance.

A division number (polarization division number) M for dividing one period of the rotationally polarized wave is set.
A plurality of identification code strings represented by bit strings having the number of bits of the number of divisions M are provided, and one of them is selected.

M sine waves and cosine waves having initial phases shifted by the period of the rotationally polarized wave divided by the number of divisions M are weighted with a synchronization signal (bit) including an ID spread by each bit of the identification code string. The set of superimposed sine and cosine waves are upconverted at the carrier frequency.
The up-converted signals are radiated into space by two spatially orthogonal antennas, and transmitted as rotationally polarized transmission waves.

Next, the processing mode of the wireless device B will be described. Although the subject of the following processing mode is the wireless device B, the description of the subject is omitted.
After the received waves are received by two spatially orthogonal antennas, the received signals are down-converted at the carrier frequency.
Demodulate the down-converted received signal.

It selects one of a plurality of identification code strings commonly provided in both radios.
A set of M sine waves and cosine waves whose initial phases are shifted by the period of the rotationally polarized wave divided by the polarization division number M weighted and added by each bit of the selected identification code string is generated as a synchronous replica signal. do.

Using this synchronous replica signal, the signals obtained by down-converting from the two antennas are multiplied by sequentially delaying the synchronous replica signal by M divisions of the rotational polarization cycle.

The multiplication result is compared with a predetermined threshold.
If the comparison result does not exceed the threshold value (no), another identification code string is selected from the plurality of identification code strings and the process is repeated.
If the comparison result exceeds the threshold (yes), the delay amount in that case is determined as the polarization shift.

By delaying the synchronous replica signal by this polarization shift, the signals obtained by down-converting from the two antennas are demodulated to reproduce the information signal.

If the sync bit is detected from the reproduced signal (yes), the ACK signal and the ID of the own station are processed in the same manner as the above-described processing performed by the wireless device A when transmitting. Send.

Next, a processing mode after radio A receives a signal from radio B will be described. Although the subject of the following processing mode is the wireless device A, the description of the subject is omitted.
A received wave from the wireless device B is received by two spatially orthogonal antennas, and the received signal is down-converted by the carrier frequency.

The received signal is demodulated, and one of the identification code strings selected from a plurality of identification code strings shared by both radios is weighted and added with each bit of the identification code string. A set of M sine and cosine waves with an initial phase shift is generated as a synchronous replica signal.

Using this synchronous replica signal, the signals obtained by down-converting from the two antennas are multiplied by sequentially delaying the synchronous replica signal by M divisions of the rotational polarization cycle.

This multiplication result is compared with a predetermined threshold value.
If the comparison result does not exceed the threshold value (no), the processing returns to the process of selecting another identification code string from among the plurality of identification code strings, and the above-described processing procedure is repeated.
If the comparison result exceeds the threshold (yes), the processing from down-conversion of the received signal is repeated to reproduce the bit string transmitted by the wireless device B. FIG.

If the reproduced bit string is information about ACK and ID (yes), M sine waves and cosine waves whose initial phases are shifted by the period of the rotationally polarized wave divided by the division number M are added to the identification code string. A set of weighted and superimposed sine and cosine waves with an information signal (bit) containing the ID spread at each bit is upconverted at the carrier frequency.

These up-converted signals are radiated into space by two spatially orthogonal antennas and transmitted as rotationally polarized transmission waves.

If the reproduced bit string is not information related to ACK and ID (no), the above-described series of processing procedures starting from down-conversion of the received signal are repeated.

FIG. 18 is a diagram showing an overview of another example of a wireless communication system that performs confidential information communication using a polarization shift characteristic unique to a wireless device that performs communication as an encryption key.

It differs from the wireless communication system shown in FIG. 16 in the following points.
- For the master station 10-1, there are slave stations 20-5 and 20-6 having the same polarization shift as the slave station 20-1.
- For the master station 10-1, there are slave stations 20-4 and 20-7 having the same polarization shift as the slave station 20-2.
• With respect to the master station 10-1, there is a slave station 20-3 whose line-of-sight communication path is blocked by a second shield 33 having a different polarization shift from both the slave stations 20-1 and 20-2.

Here, due to the duality of wireless communication, in the operation of receiving a transmission wave from a slave station, the master station generates two summed sine waves and a summed cosine wave formed by superimposing a plurality of sine waves and a plurality of cosine waves, respectively. , the polarization shift detected by each child station can be known from the amount of delay when the received wave is multiplied by the signal down-converted by the carrier frequency.

As a result, the master station 10-1 operates in the same manner as in the wireless communication system shown in FIG. A wave shift is checked in advance and an ID-polarization shift table is created.

Using the ID-polarization table, the master station 10-1 uses different bit strings with strong autocorrelation and weak cross-correlation for a plurality of slave stations having the same polarization shift, as in FIG. communication.

As a result, the combination of different polarization shifts between the parent station and child stations and different bit strings with strong autocorrelation and weak cross-correlation increases the number of child stations that can communicate simultaneously with the parent station.

19 is a diagram showing an example of a communication protocol used by each wireless device shown in FIG. 18. FIG.
With reference to FIG. 19, a processing mode using a communication protocol for one-to-many communication by a wireless communication system that performs confidential information communication using a polarization shift characteristic unique to a wireless device that performs communication as an encryption key will be described.

First, a processing mode until the wireless device 0 transmits a synchronization signal (bit) including an ID will be described. Although the subject of the following processing mode is the wireless device 0, the description of the subject is omitted.
The wireless device n is selected as the communication destination, and an ID shared by both wireless devices is determined in advance.

A division number (polarization division number) M for dividing one period of the rotationally polarized wave is set.
A plurality of identification code strings represented by bit strings having the number of bits of the number of divisions M are provided, and one of them is selected.

M sine waves and cosine waves whose initial phases are shifted by the period of the rotationally polarized wave divided by the number of divisions M are weighted with a synchronization signal (bit) containing an ID spread by each bit of the identification code string and superimposed. The set of combined sine and cosine waves are upconverted at the carrier frequency.

The up-converted signal is radiated into space by two spatially orthogonal antennas and transmitted as a rotationally polarized transmission wave.

Next, the processing mode of the wireless device n will be described. Although the subject of the following processing mode is the wireless device n, the description of the subject is omitted.
After the received waves are received by two spatially orthogonal antennas, the received signals are down-converted at the carrier frequency.
Demodulate the down-converted received signal.

It selects one of a plurality of identification code strings commonly provided in both radios.
A set of M sine waves and cosine waves whose initial phases are shifted by the period of the rotationally polarized wave divided by the polarization division number M weighted and added by each bit of the selected identification code string is generated as a synchronous replica signal. do.

Using this synchronous replica signal, the signals obtained by down-converting from the two antennas are multiplied by sequentially delaying the synchronous replica signal by M divisions of the rotational polarization cycle.

This multiplication result is compared with a predetermined threshold value.
If the comparison result does not exceed the threshold value (no), another identification code string is selected from the plurality of identification code strings and the process is repeated.

If the comparison result exceeds the threshold (yes), the delay amount used at that time is determined as the polarization shift.
The synchronous replica signal is delayed by this polarization shift, and the signals obtained by down-converting from the two antennas are demodulated to reproduce the information signal.

If the regenerated signal detects the synchronization bit (yes), the ACK signal, the ID of the local station, and the value of the polarization shift are processed in the same manner as the radio 0 performed when transmitting. send to

Next, a processing mode after the radio device 0 receives a signal from the radio device n will be described. Although the subject of the following processing mode is the wireless device 0, the description of the subject is omitted.
A reception wave from a wireless device n is received by two spatially orthogonal antennas, and the received signal is down-converted by a carrier frequency.

The received signal is demodulated, and one of the identification code strings selected from a plurality of identification code strings shared by both radios is weighted and added with each bit of the identification code string. A set of M sine and cosine waves with an initial phase shift is generated as a synchronous replica signal.

Using this synchronous replica signal, the signals obtained by down-converting from the two antennas are multiplied by sequentially delaying the synchronous replica signal by M divisions of the rotational polarization cycle.

This multiplication result is compared with a predetermined threshold value.
If the comparison result does not exceed the threshold value (no), the processing returns to the process of selecting another identification code string from among the plurality of identification code strings, and the above-described processing procedure is repeated.

If the comparison result exceeds the threshold (yes), the processing from down-conversion of the received signal is repeated to reproduce the bit string transmitted by the wireless device n.

If the reproduced bit string is information about ACK and ID (yes), the ID and the polarization shift value are extracted from the reproduced bit string and stored.

By referring to the stored content and a plurality of identification code strings, a correspondence relationship between the two that maximizes the amount of information that can be transmitted simultaneously is calculated, and a correspondence map of ID, polarization shift and identification code string is created. .

The above processing procedure is repeated by the wireless device 0 for all other wireless devices that perform one-to-many communication.
After the same processing is completed for all the wireless devices, individual information is simultaneously transmitted to a plurality of wireless devices n using the correspondence map of ID, polarization shift, and identification code string.

Next, referring to FIGS. 20 to 28, as a fourth embodiment of the present invention, a wireless device (receiving A configuration example of a transmitter or transmitter) and a wireless device pair (transmitter/receiver) will be described.

Here, by using the wireless device and the wireless device pair configured as shown in FIG. In addition, CDMA (code division multiple access) in the polarization angle domain using variable strong autocorrelation and weak cross-correlation bit strings becomes possible. This enables communication between one-to-many wireless stations shown in FIG. 7(a).

Furthermore, the components on the left side of high- frequency mixers 105 and 106 can be realized not only by hardware but also by software radio consisting of DSP and software. This method can be implemented in a short development period and at low cost using general-purpose hardware.

In addition, although the current technology is accompanied by a decrease in performance, if a method based on undersampling is used, it is possible to realize a software radio comprising a DSP and software, including the high- frequency mixers 105 and 106, further reducing the cost. enable

FIG. 20 is a diagram showing a first configuration example and its operation mode as a representative example of a receiver of a radio communication system according to the fourth embodiment.
A first antenna 103 and a second antenna 104, which are spatially orthogonal to each other, receive transmission waves transmitted by a transmitter and use them as input signals.

The output of each antenna (103, 104) is down-converted by the output of the carrier frequency generation circuit 101 and the first high frequency mixer 105 and the second high frequency mixer 106.

The output of the first high-frequency mixer 105 is branched into two and input to the receiving mixer 121 and the second analog-to-digital converter (ADC) 123 .

On the other hand, the output of the polarization rotation frequency generation circuit 102 is branched through a first variable delay circuit 115 whose delay amount is controlled by a central processing unit (CPU) 109, and each of the branches is sent to a reception delay device 112-i. Each ±bit 111-i of the strong autocorrelation weak cross-correlation bit string 111 is weighted by the receive multiplier 113-i and superimposed by the receive summation circuit 114.

The result of this superposition and the output of the first high-frequency mixer 105 are multiplied by the receiving mixer 121, and the multiplied result is converted into a digital signal by the first analog-to-digital converter (ADC) 122, and the central processing unit ( CPU) 109.

Here, the strong autocorrelation weak cross-correlation bit string 111 is generally called a "PN (Pseudo random noise) signal", and a typical example is an "M sequence".

FIG. 21 is a diagram showing the relationship between a transmission waveform and a reception waveform.
As shown in FIG. 21, the received waveform is generally delayed from the transmitted waveform by T (the difference in reference time between the transmitting station and the receiving station plus the propagation time). Here, a strong autocorrelation weak cross-correlation bit string (PN code or M sequence) is superimposed on the transmission waveform.

FIG. 22 is a diagram in which the strong autocorrelation weak cross-correlation bit string (PN code or M sequence) shared by the transmitting station and the receiving station is shifted by Δt and correlated with the received signal.

The properties of strong autocorrelation and weak cross-correlation bit strings are that when Δt=T (when the timings match), the correlation value is maximized (strong autocorrelation), and when Δt=T (when the timings do not match). time), the correlation value becomes smaller (weak cross-correlation).

As described above, identifying T (the difference between the reference times of the transmitting station and the receiving station plus the propagation time) is the time at which the signal currently received at the receiving station was transmitted at the transmitting station. It leads to the identification (synchronization) of things.

In particular, in the case of rotating polarized waves that change the polarization of the transmitted radio wave with time, the information about what time it was transmitted at the transmitting station leads to the information about what angle of polarization it was transmitted. Therefore, by continuously changing the polarization angle at the transmitting station, in the present invention, it is possible to obtain the relationship between the polarization angle at the transmitting station and the polarization angle at the receiving station, which is used as a common key. can be done.

Returning to FIG. 20, the other two-branched output of the first harmonic mixer 105 is output by a second analog-to-digital converter (ADC) 123, and the output of the second harmonic mixer 106 is Each is converted into a digital signal by the third analog-to-digital converter 124 .

Each digital signal becomes two inputs of a comparison circuit 127 via a second variable delay circuit 125 and a third variable delay circuit 126 whose delay amount is independently controlled by a central processing unit (CPU) 109 .

The comparison circuit 127 outputs the difference between the input values as ±1 based on the determination threshold stored in the threshold storage circuit 128 and inputs this comparison output to the central processing unit (CPU) 109 .

A central processing unit (CPU) 109 changes the delay amount of the first variable delay circuit 115 by using the properties of the strong autocorrelation weak cross-correlation bit string (PN code or M-sequence) 111 described above. The delay amount that maximizes the output of one analog-to-digital converter 122 is measured, and the polarization shift with the transmitter that is communicating is determined based on this delay amount.

In rotationally polarized wave communication, if the distance between the transmitter and receiver is static, the output signals from two spatially orthogonal antennas will be orthogonal sine waves. The dashed line in the upper graph of FIG. 20 shows this relationship. Also, as shown in the upper graph of FIG. 20, if the phase difference between the transmission rotationally polarized wave and the receiving rotationally polarized wave is constant, the dashed line is shifted by the phase shift T to form a dashed line.

　In the actual communication environment, the phase of the polarization rotation of the rotary polarized wave is not constant, and leads or lags. This phenomenon is illustrated by the solid line in the upper graph of FIG. By associating this "advance" and "delay" with "0" and "1", a bit string that can be used as a physical encryption key generated by the unique propagation characteristics between transceivers performing wireless communication can be obtained. be able to.

As described above, according to the first configuration example, in radio communication using rotationally polarized waves, by using the inherent propagation characteristics between transmitters and receivers that perform radio communication, physical characteristics unique to the same propagation characteristics that cannot be known by other radio devices can be obtained. A bit string that can be used as an encryption key can be automatically obtained without communicating information about this bit string between wireless devices.

Therefore, this bit string can be used as a cryptographic key to conceal the information signal by an appropriate cryptographic algorithm for communication, which has the effect of realizing a highly secure wireless communication system.

FIG. 23 is a diagram showing a second configuration example as a receiver used in the wireless communication system according to the fourth embodiment.

The difference from the first configuration example shown in FIG. 20 is that a variable strong autocorrelation weak cross-correlation bit string 116 is used instead of the strong autocorrelation weak cross-correlation bit string 111.

The variable strong autocorrelation weak cross-correlation bit string 116 can generate mutually different strong autocorrelation weak cross-correlation bit strings by the central processing unit (CPU) 109 .

As described above, according to the second configuration example, since the master station can transmit and receive simultaneously with a plurality of slave stations having the same polarization shift, there is an effect of increasing the communication capacity of the wireless communication system and improving the throughput. .

FIG. 24 is a diagram showing a third configuration example as a receiver of the wireless communication system according to the fourth embodiment.

A first antenna 103 and a second antenna 104 that are spatially orthogonal receive the transmission wave transmitted by the transmitter and use it as an input signal.

The output of each antenna (103, 104) is down-converted by the output of the carrier frequency generation circuit 101 and the first high frequency mixer 105 and the second high frequency mixer 106.

The output of the second high-frequency mixer 106 is branched into two and input to the first reception mixer 121 and the second analog-to-digital converter (ADC) 123 .

On the other hand, one of the outputs of the polarization rotation frequency generating circuit 102 is branched into two via a first variable delay circuit 115 whose delay amount is controlled by a central processing unit (CPU) 109, and each of the branches is Each ±bit 111-i of the strong autocorrelation weak cross-correlation bit string 111 is weighted by the first receive multiplier 113-i through the first receive delay unit 112-i, and the first receive summation circuit 114 Overlap with .

The result of this superimposition and the output of the second high-frequency mixer 106 are multiplied by the first reception mixer 121 , and the multiplication result is input to the reception synthesis circuit 131 .

The output of the first high-frequency mixer 105 is branched into two and input to the second reception mixer 141 and the third analog-to-digital converter (ADC) 124 .

On the other hand, the other branch of the output of the polarization rotation frequency generation circuit 102 is passed through the polarization rotation frequency band 90° phase shifter 136, and the second output whose delay amount is controlled by the central processing unit (CPU) 109 , and each of the branches is subjected to second reception multiplication using each ±bit 111-i of the strong autocorrelation weak cross-correlation bit string 111 via the second reception delay unit 132-i. weighted by the unit 133-i and superimposed by the second reception summation circuit 134;

The result of this superposition and the output of the first high-frequency mixer 105 are multiplied by the second reception mixer 141 , and the multiplication result is input to the reception synthesizing circuit 131 .

After that, the output of this reception synthesizing circuit 131 is converted into a digital signal by a first analog-to-digital converter (ADC) 122 and input to the central processing unit (CPU) 109 .

The bifurcated other of the outputs of the first harmonic mixer 105 and the bifurcated other of the outputs of the second harmonic mixer 106 are coupled to a second analog-to-digital converter (ADC) 123 and a third analog converter (ADC) 123, respectively. It is converted into a digital signal by a digital converter (ADC) 124 .

Each digital signal becomes two inputs of a comparison circuit 127 via a second variable delay circuit 125 and a third variable delay circuit 126 whose delay amount is independently controlled by a central processing unit (CPU) 109 .

The comparison circuit 127 outputs the difference of each input value as ±1 based on the judgment threshold stored in the threshold storage circuit 128 and inputs this comparison output to the central processing unit (CPU) 109 .

As described above, according to the third configuration example, compared to the first configuration example of the receiver shown in FIG. 20, the signal power for determining the polarization shift between the parent station and the child station can be doubled. .

Therefore, the measurement accuracy of the polarization shift is improved, and the stability of the physical encryption key generated by the unique propagation characteristics between the transmitter and receiver used to conceal the information signal is increased, contributing to the further stabilization of the communication of the wireless communication system. do.

FIG. 25 is a diagram showing a fourth configuration example as a representative example of the transmitter of the wireless communication system according to the fourth embodiment.

A central processing unit (CPU) 109 generates and supplies information signals to a digital data generator 158 .

This digital data generator 158 inputs the bit string to a plurality of transmission multiplier circuits 157-i, weights each ± bit 151-i of the strong autocorrelation weak cross-correlation bit string 151, and then divides it into two.

In one of the two branches, the first branch obtained by bifurcating the output of the polarization rotation frequency generation circuit 102 is delayed by the polarization rotation frequency band 90° phase shifter 168, and a plurality of first transmission delay multiplied by a plurality of first transmit multipliers 163-i with different phases via multipliers 162-i.

The outputs of a plurality of first transmission multipliers 163-i are superimposed by a first transmission summation circuit 164, and the output of this first transmission summation circuit 164 is fed to the first high frequency mixer by the output of the carrier wave frequency generation circuit 101. It is up-converted at 105 and radiated into space from the first antenna 103 .

In the other bifurcated branch, a second branch obtained by bifurcating the output of the polarization rotation frequency generation circuit 102 is transmitted through a plurality of second transmission delay devices 152-i to a plurality of second transmission delay devices 152-i. Multiplied by multiplier 153-i.

The outputs of a plurality of second transmission multipliers 153-i are superimposed by a second transmission summation circuit 154, and the output of this second transmission summation circuit 154 is fed to a second high-frequency mixer by the output of the carrier wave frequency generation circuit 101. It is up-converted at 106 and radiated into space from a second antenna 104 that is spatially orthogonal to the first antenna 103 .

As described above, according to the fourth configuration example, an information signal can be formed into a rotationally polarized wave by an aggregate of sine waves and cosine waves of the same polarization rotational frequency with different initial phases and different bit weights, and can be wirelessly communicated. As a result, it is possible to increase the capacity and improve the throughput of the rotary polarization communication system.

FIG. 26 is a diagram showing a fifth configuration example as a transmitter used in the wireless communication system according to the fourth embodiment.

The difference from the fourth configuration example shown in FIG. is converted by the second transmission multiplier circuit 159 and supplied to the digital data generator 158 .

As described above, according to the fifth configuration example, the information signal is encrypted and rotationally polarized wave communication can be performed, so that the wireless communication system can be made highly secure.

FIG. 27 is a diagram showing a sixth configuration example as a representative example of a wireless device pair (transmitter/receiver) used in the wireless communication system according to the fourth embodiment.

A first antenna 103 and a second antenna 104 that are spatially orthogonal receive the transmission wave transmitted by the transmitter and use it as an input signal.

The output of each antenna (103, 104) is down-converted by the output of the carrier frequency generation circuit 101 and the first high frequency mixer 105 and the second high frequency mixer 106.

A first transmission/reception changeover switch 165 and a second transmission/reception changeover switch 166 are coupled to the first high-frequency mixer 105 and the second high-frequency mixer 106, and the output of the second transmission/reception changeover switch 166 is branched into two. is input to the first receive mixer 121 .

Here, one of the two-branched output of the polarization rotation frequency generating circuit 102 is branched via a first variable delay circuit 115 whose delay amount is controlled by a central processing unit (CPU) 109, and each of the branches is Each ±bit 111-i of the strong autocorrelation weak cross-correlation bit string 111 is weighted by the first receive multiplier 113-i through the first receive delay unit 112-i, and the first receive summation circuit 114 superimpose.

The result of this superimposition and the output of the first high-frequency mixer 105 are multiplied by the first reception mixer 121 , and the multiplication result is input to the reception synthesizing circuit 131 .
On the other hand, the output of the first transmission/reception selector switch 165 is branched into two, one of which is input to the second reception mixer 141 .

Here, the other branch of the output of the polarization rotation frequency generation circuit 102 is passed through the polarization rotation frequency band 90° phase shifter 136, and the central processing unit (CPU) 109 controls the amount of delay. each of the branches via a second receive delay circuit 132-i and a second receive multiplier using each ± bit 111-i of the strong autocorrelation weak cross-correlation bit string 111 133-i and superimposed by the second receive summation circuit 134. FIG.

The result of this superposition and the output of the first high-frequency mixer 105 are multiplied by the second reception mixer 141 , and the multiplication result is input to the reception synthesizing circuit 131 .

The output of this reception synthesizing circuit 131 is converted into a digital signal by a first analog-to-digital converter (ADC) 122 and input to the central processing unit (CPU) 109 .

The output of the first harmonic mixer 105 is the other branch of the first transmission/reception selector switch 165, and the output of the second harmonic mixer 106 is the other branch of the second transmission/reception selector switch 166, respectively. are converted into digital signals by a second analog-to-digital converter (ADC) 123 and a third analog-to-digital converter (ADC) 124, and the delay amount is independently controlled by the central processing unit (CPU) 109. It becomes two inputs of a comparison circuit 127 via two variable delay circuits 125 and a third variable delay circuit 126 .

The comparison circuit 127 outputs the difference of each input value as ±1 based on the judgment threshold stored in the threshold storage circuit 128 , and inputs this comparison output to the second transmission multiplication circuit 159 .

A central processing unit (CPU) 109 generates an information signal including an ID unique to the wireless device stored in an ID memory 129, and a second transmission multiplier circuit 159 generates propagation path information unique to the pair of wireless devices communicating. This information signal encrypted with a physical key based on is supplied to the digital data generator 158 .

This digital data generator 158 inputs a bit string to a plurality of transmission multiplier circuits 157-i, weights each ± bit 151-i of the strong autocorrelation weak cross-correlation bit string 151, and then divides it into two.

Regarding one branch, the first branch obtained by bifurcating the output of the polarization rotation frequency generation circuit 102 is delayed by the polarization rotation frequency band 90° phase shifter 168, and the plurality of first transmission delay devices 162-i are multiplied by a plurality of transmission multipliers 163-i with different phases via the transmission multipliers 163-i, the outputs of the plurality of transmission multipliers 163-i are superimposed by a transmission summation circuit 164, and the output of this transmission summation circuit 164 is used as the first transmission/reception switching. Input to the transmission terminal of the switch 165 .

The output of the common terminal of the first transmission/reception selector switch 165 is up-converted by the first high-frequency mixer 105 according to the output of the carrier wave frequency generation circuit 101 and radiated from the first antenna 103 into space.

As for the other branch, the second branch obtained by branching the output of the polarization rotation frequency generation circuit 102 into two is passed through a plurality of second transmission delay devices 152-i to a plurality of second transmission multipliers with different phases. 153-i, the outputs of a plurality of transmission multipliers 153-i are superimposed in a transmission summation circuit 154, and the output of this transmission summation circuit 154 is input to the transmission terminal of the second transmission/reception selector switch 166. FIG.

The output of the common terminal of the second transmission/reception changeover switch 166 is up-converted by the second high-frequency mixer 106 by the output of the carrier wave frequency generation circuit 101, and the second antenna spatially orthogonal to the first antenna 103 is generated. 104 radiates into space.

As described above, according to the sixth configuration example, the information signal is concealed by the propagation path characteristics unique to a specific wireless device pair that performs rotationally polarized wave communication, and a plurality of rotationally polarized waves having different initial phases are used. Since information signals can be transmitted, a highly secure and large-capacity radio communication system can be realized.

FIG. 28 is a diagram showing a seventh configuration example as a wireless device pair (transmitter/receiver) used in the wireless communication system according to the fourth embodiment.

The difference from the sixth configuration example shown in FIG. 27 is that instead of the strong autocorrelation weak cross-correlation bit strings 111 and 151, variable strong autocorrelation weak cross-correlation bit strings 116 and 156 are used.

For example, the variable strong autocorrelation weak cross-correlation bit string 116 can generate mutually different strong autocorrelation weak cross-correlation bit strings by the central processing unit 109 . Since each value 116-i of this variable strong autocorrelation weak cross-correlation bit string 116 can be changed by the central processing unit (CPU) 109, one of the total number M of variable strong autocorrelation weak cross-correlation bit strings 116 is Selectively, the remaining M−1 variable strong autocorrelation weak cross-correlation bitstreams 116 are not signaled. Then, the input power of the receiving multipliers 113-i and 133-i is set to zero, and the polarization rotation period is divided by M for one of the selected variable strong autocorrelation weak cross-correlation bit strings 116. Among the timings, L timings where L<M are selected, and an information signal is sent to only one of the variable strong autocorrelation weak cross-correlation bit strings 116 selected only at the L timings.

This realizes the polarization angle hopping shown in the third embodiment. As described above with respect to the third embodiment, it is desirable that the polarization of the electromagnetic waves emitted from the transmitter be uniformly distributed in the direction of polarization rotation. For example, for M polarization angles, L polarization angles are selected at equal intervals or randomly.

As described above, according to the seventh configuration example, the central processing unit (CPU) 109 selects a plurality of variable strong autocorrelation and weak cross-correlation bit strings 116 and 156 to make it highly resistant to interference caused by interfering waves shown in the third embodiment. In addition to the effect of ensuring a more stable communication state, the master station can transmit and receive simultaneously with a plurality of slave stations having the same polarization shift. Compared to the example, it is possible to increase the communication capacity and improve the throughput of the wireless communication system.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to the above-described respective embodiments, and various modifications are possible without departing from the gist of the present invention.

Reference Signs List 10 Master station 11 Service area 20 Slave station 31, 33 Shield 32 Reflector 101 Carrier frequency generation circuit 102 Polarization rotation frequency generation circuit 103, 104 Antenna 105 , 106... High-frequency mixer 109... CPU 111, 151... Strong autocorrelation weak cross-correlation bit string 112, 132... Receiving delay unit 113, 133... Receiving multiplier 114... Receiving summation circuit 115, 125, 126, 135... variable delay circuit 116, 156... variable strong autocorrelation weak cross-correlation bit string 119... encryption generator circuit 121, 141... receiving mixer 122, 123, 124... analog-to-digital converter 127... comparison circuit 128... Threshold storage circuit 129 ID memory 131 reception synthesizing circuit 136, 168 polarization rotation frequency band 90° phase shifter 152 transmission delayer 153, 163 transmission multiplier 154, 164 transmission total Circuits 157, 159... Transmission multiplier circuit 158... Digital data generator 165, 166... Transmission/reception selector switch

Claims (15)

1. A wireless communication system in which a first wireless device and a second wireless device communicate with confidential information using a physical key,
   The first radio and the second radio communicate by sharing time-series changes in dynamically changing propagation characteristics,
   The first wireless device converts the least significant bit of the predetermined range of the first discrete value obtained by itself based on the propagation characteristics and the least significant bit of the first discrete value to the second to the radio of
   The second radio uses a second discrete value obtained by itself based on the propagation characteristics and the least significant bit and the least significant bit received from the first radio to deduce a common key,
   A wireless communication system, wherein the common key is the physical key.
2. A wireless communication system according to claim 1,
   A wireless communication system, wherein the propagation characteristic is a propagation time between the first and second radios.
3. A wireless communication system according to claim 1,
   A wireless communication system, wherein the propagation characteristic is propagation loss or signal strength between the first and second radios.
4. A wireless communication system according to claim 1,
   The first radio and the second radio communicate using a rotationally polarized wave communication function,
   A wireless communication system, wherein the propagation characteristic is a polarization angle of a rotationally polarized wave.
5. A wireless communication system according to claim 1,
   the first radio and the second radio mutually exchange information as to whether or not they have a rotationally polarized wave communication function;
   A radio communication system according to claim 1, wherein said propagation characteristic is a polarization angle of a rotationally polarized wave when both said first radio device and said second radio device have said rotationally polarized wave communication function.
6. The wireless communication system according to claim 4 or 5,
   A radio communication system characterized in that at least one of the frequency used for the communication and the angle of the polarization angle is changed in time series.
7. A wireless communication system according to claim 6,
   A radio communication system characterized in that, when at least one of the frequency and the polarization angle is subject to interference by an interfering wave, at least one of the frequency and the polarization angle subject to the interference is excluded.
8. A wireless communication system according to claim 4,
   The first radio and the second radio share a strong autocorrelation weak cross-correlation bit string and transmit the strong autocorrelation weak cross-correlation bit string superimposed on the rotationally polarized wave, A radio communication system, wherein a time difference at which correlation between a received signal and said strong autocorrelation and weak cross-correlation bit sequence is maximized is shared as said time series change of said rotationally polarized wave.
9. A wireless communication system according to claim 8,
   A radio communication system characterized by modulating a polarization angle of said rotationally polarized wave with said strong autocorrelation weak cross-correlation bit string in order to superimpose said strong autocorrelation weak cross-correlation bit string on said rotationally polarized wave.
10. The wireless communication system according to claim 8 or 9,
    A wireless communication system, wherein the strong autocorrelation weak cross-correlation bit string is a PN code or an M-sequence signal.
11. A wireless communication system according to any one of claims 1 to 10,
    A wireless communication system, wherein each of the first wireless device and the second wireless device is one of a plurality of wireless devices.
12. A wireless communication method in which a first wireless device and a second wireless device communicate with confidential information using a physical key,
    The first radio and the second radio communicate by sharing time-series changes in dynamically changing propagation characteristics,
    The first radio obtains a first discrete value by itself based on the propagation characteristics, and converts the least significant bit in a predetermined range of the first discrete value and the least significant bit in the first discrete value transmitting the following lower bits to the second radio;
    The second radio device itself obtains a second discrete value based on the propagation characteristic, and from the least significant bit and the least significant bit received from the first radio device and the second discrete value estimating a common key in the first radio;
    A wireless communication method, wherein the common key is the physical key.
13. A wireless communication method according to claim 12,
    A radio communication method, wherein the propagation characteristic is a propagation time between the first and second radios.
14. A wireless communication method according to claim 12,
    A radio communication method, wherein the propagation characteristic is propagation loss or signal strength between the first and second radios.
15. A wireless communication method according to claim 12,
    The first radio and the second radio communicate using a rotationally polarized wave communication function,
    A wireless communication method, wherein the propagation characteristic is a polarization angle of a rotationally polarized wave.

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