JP2018182523A - Communication system and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase difficulty of data read in radio communication.SOLUTION: In a communication system having a plurality of transmitters which transmit data by radio, one or more receivers which receive the data, and one or more information processing devices which are connected to the transmitters and the receivers, the information processing device includes a setting unit which sets a transmission timing to transmit a radio wave of transmitting the data for each transmitter, according to each distance between the transmitter and the receiver. The transmitter includes a radio wave transmitter unit which transmits the radio wave to the receiver at the transmission timing, on the basis of an Hadamard code. The receiver includes a radio wave receiver unit which receives the radio wave.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a communication system and a communication method.

  Conventionally, in communication, modulation such as FDMA (Frequency Division Multiple Access System, Frequency-Division Multiple Access), TDMA (Time Division Multiple Access System, Time Division Multiple Access), CDMA (Code Division Multiple Access System, Code Division Multiple Access), etc. The scheme is known.

  Also, there is known a method of transmitting data to a receiving apparatus from three or more base stations in order to transmit confidential data. Specifically, first, the information distribution center station calculates the distribution delay time based on the time when radio waves reach the receiving device from each base station. Next, each base station waits to transmit data until the calculated distribution delay time has elapsed from a reference time as a reference. After waiting, each base station modulates and transmits the encrypted delivery information. Then, the receiving device receives the information at the same time, and receives the distribution information only for a predetermined time. Thus, there is known a method of securing the secrecy of data without increasing resources used by radio waves (see, for example, Patent Document 1 etc.).

JP, 2005-223529, A

  However, in the conventional method, data transmitted by wireless may be deciphered by a third party illegally receiving radio waves. Therefore, in the conventional method, the obfuscation of data may be low for a third party in wireless communication.

  One aspect of the present invention is made in view of such a problem, and it is an object of the present invention to enhance obfuscation of data in wireless communication.

In order to solve the problems described above and achieve the object, in one embodiment of the present invention, a plurality of transmitting devices that transmit data wirelessly, one or more receiving devices that receive the data, the transmitting device and In a communication system having one or more information processing devices connected to the receiving device,
The information processing apparatus is
A setting unit configured to set a transmission timing for transmitting a radio wave for transmitting the data, for each of the transmission devices, based on a distance between each of the transmission devices and the reception devices;
The transmitting device is
A radio wave transmission unit for transmitting the radio wave to the reception apparatus at the transmission timing based on a Hadamard code;
The receiving device is
It has a radio wave receiver that receives the radio wave.

  According to the present invention, obfuscation of data can be enhanced in wireless communication.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows the example of whole structure of the communication system in embodiment of this invention. It is a block diagram showing the example of hardware constitutions of the transmitting set in an embodiment of the present invention, a receiving set, and an information processor. It is a sequence diagram which shows an example of the whole process by the communication system in embodiment of this invention. It is a conceptual diagram which shows the example of transmission of the detection in the communication system in embodiment of this invention. It is a timing chart which shows an example of arrival time in an embodiment of the present invention. It is a timing chart showing an example of setting of transmission timing in an embodiment of the present invention. It is a schematic diagram which shows the example of a change which rearranges the line of the Hadamard matrix which concerns on one Embodiment of this invention. It is a schematic diagram which shows the example of a change which rearranges the column of the Hadamard matrix which concerns on one Embodiment of this invention. It is a schematic diagram (the 1) which shows the usage example of the Hadamard code which concerns on one Embodiment of this invention. It is a schematic diagram (the 2) which shows the usage example of the Hadamard code which concerns on one Embodiment of this invention. It is a functional block diagram showing an example of functional composition of a communication system concerning one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the present specification and the drawings, components having substantially the same functional configuration are given the same reference numerals, and redundant description will be omitted.

<Example of overall configuration>
FIG. 1 is a conceptual diagram showing an example of the overall configuration of a communication system in an embodiment of the present invention. For example, the communication system 1 includes a plurality of transmitting devices 1S1, 1S2, 1S3, 1S4, 1S5, 1S6, 1S7 and 1S8, a receiving device 1R, and a server 1SER as an example of an information processing device. In the illustrated example, eight transmitters are used. Hereinafter, although an example of eight transmission devices will be described, the number of transmission devices is not limited to eight, and may be plural.

  As illustrated, the reception device 1R can receive data wirelessly by receiving radio waves transmitted by the respective transmission devices. Hereinafter, a radio wave transmitted by the transmission device to transmit data is simply referred to as "radio wave". Further, in the communication system 1, the server 1 SER controls each transmitting device and the receiving device 1R.

  For example, the transmitting devices 1S1, 1S2, 1S3, 1S4, 1S5, 1S6, 1S7, 1S8, the receiving device 1R and the server 1SER are devices having the following hardware configuration.

<Hardware configuration example>
FIG. 2 is a block diagram showing an example of the hardware configuration of the transmission device, the reception device, and the information processing device in the embodiment of the present invention. For example, the transmission device, the reception device, and the information processing device have the same hardware configuration as illustrated. The respective devices do not have to have the same hardware configuration. That is, each device is not limited to the illustrated hardware configuration. For example, each transmission device and reception device may be a portable terminal or a smartphone. Furthermore, the information processing apparatus may be, for example, a PC (Personal Computer).

  In the following, each device has a hardware configuration as illustrated, and an example of the same hardware configuration will be described. Therefore, the following description will be made on the hardware configuration of only the transmission device 1S1 and redundant description will be omitted.

  The transmitting device 1S1 has a hardware configuration including, for example, a central processing unit (CPU) HW1, a storage device HW2, an input device HW3, an output device HW4, a transceiver HW5, an antenna HW6, and a network interface HW7. is there.

  The CPU HW 1 is an arithmetic device that performs arithmetic operations to realize each process. The CPU HW 1 is a control device that controls each piece of hardware.

  The storage device HW2 is a main storage device such as a so-called memory. The storage device HW2 may have an auxiliary storage device.

  The input device HW3 is an interface or the like that receives an operation or data from an external device. For example, the input device HW3 is a connector or the like. The input device HW3 may be connected to a device such as a keyboard.

  The output device HW4 is an interface or the like that outputs data or the like to an external device. For example, the output device HW4 is a connector or the like. The output device HW4 may be connected to a device such as a display.

  The transmitter / receiver HW5 wirelessly transmits / receives data to / from an external device by the antenna HW6. For example, the transceiver HW5 is an IC (Integrated Circuit) or the like.

  The network interface HW 7 is an interface that transmits and receives data to and from an external device via a network. For example, the network interface HW7 is a connector, an IC, or the like.

  The hardware configuration is not limited to the illustrated configuration, and may be, for example, a configuration further including an arithmetic device, a control device, a storage device, and the like. Further, the information processing apparatus may have, for example, a configuration without the transceiver HW5, the antenna HW6, and the like.

  In addition, each device may not be one device. That is, each device may be configured by, for example, a plurality of information processing devices.

<Example of overall processing>
FIG. 3 is a sequence diagram showing an example of the entire processing by the communication system in the embodiment of the present invention. For example, the communication system 1 performs the following overall processing.

<Transmission example of detection> (step S01)
In step S01, the reception device 1R transmits a radio wave (hereinafter referred to as "detection") for measuring the distance to each transmission device. For example, step S01 is a process performed as follows.

  FIG. 4 is a conceptual diagram showing an example of transmission of detection in the communication system in the embodiment of the present invention. In the example illustrated in FIG. 1, as illustrated, the reception device R1 transmits the detection RW1 to each transmission device. It is assumed that the server 1SER can grasp the timing at which the reception device R1 transmits the detection RW1, that is, the transmission time.

  And each transmitting apparatus assumes that each position differs. Hereinafter, it is assumed that the distances between the respective transmitters and the receiver R1 are all different. As in this example, even if the receiving device R1 simultaneously transmits the detection RW1 to the respective transmission devices, the distance at which the detection RW1 is transmitted is different, so the timing at which the detection RW1 arrives at each transmission device is It is different timing. That is, based on the transmission time, the time it takes for the detection RW 1 to arrive at each transmission device (hereinafter referred to as “arrival time”) takes different values according to the distance.

  In the following description, in order to simplify the description, the arrival time can be calculated based on only the distance traveled by the radio wave, that is, it can be calculated by "arrival time = distance / speed of radio wave". On the other hand, the arrival time may include the time at which the IC performs processing in transmission and reception.

  Then, each transmission device transmits the reception time at which the detection RW1 is received to the server 1SER. Thus, when each reception time is grasped, the server 1 SER can calculate the arrival time by calculating the difference between the transmission time and the reception time.

<Calculation Example of Arrival Time> (Step S02)
In step S02, the server 1 SER calculates each arrival time for each transmission device. For example, the arrival time is calculated as follows.

  FIG. 5 is a timing chart showing an example of the arrival time in the embodiment of the present invention. In the illustrated example, the timing at which the reception device R1 transmits the detection RW1 is referred to as “transmission time TMS”. Then, the detection RW1 transmitted to the transmission time TMS is received by each transmission device. Hereinafter, the reception time at which the detection RW1 is received by the transmission device 1S1 is referred to as “reception time TMR1”. Similarly, the reception time at which the detection RW1 is received by the transmitter 1S2 is referred to as "reception time TMR2". Hereinafter, the other transmitters are similarly received, but in the following example, the transmitters 1S1 and 1S2 are taken as an example, and the description will be omitted.

  As shown in FIG. 4, when the distance L1 between the reception device R1 and the transmission device 1S1 is different from the distance L2 between the reception device R1 and the transmission device 1S2, the reception time is different as shown in FIG. Specifically, as shown in FIG. 4, when the position of the transmitter 1S2 is closer to the receiver R1 than the position of the transmitter 1S1 as in the example shown in FIG. TMR2 is earlier than reception time TMR1.

  Further, in this example, each arrival time is a difference between the transmission time TMS and each reception time, as shown in FIG. Hereinafter, the arrival time from the reception device R1 to the transmission device 1S1 is referred to as “arrival time T1”. Similarly, the arrival time from the reception device R1 to the transmission device 1S2 is referred to as "arrival time T2." Hereinafter, the difference between the arrival time T1 and the arrival time T2 is referred to as “delay amount DY”. Further, as in the illustrated example, when L2 is shorter than the distance L1, the arrival time T2 is shorter than the arrival time T1.

  As described above, the server 1 SER calculates each arrival time for each transmitter. In this example, "T1 = L1 ÷ speed of radio wave" and "T2 = L2 ÷ speed of radio wave". Then, the server 1 SER calculates “DY = T1−T2”.

<Setting Example of Timing for Transmitting Radio Wave> (Step S03) (FIG. 3)
In step S03, the server 1 SER sets the timing for transmitting the radio wave to each of the transmission devices. For example, in the example illustrated in FIG. 5, the server 1 SER sets the transmission device 1S1 and the transmission device 1S2 based on the arrival time T1 and the arrival time T2 calculated in step S02. Specifically, the server 1SER sets the transmission device 1S1 and the transmission device 1S2 to transmit radio waves at the following timings.

  FIG. 6 is a timing chart showing an example of transmission timing setting in the embodiment of the present invention. For example, in the case of using the calculation result shown in FIG. 5, the server 1SER sets the transmitting device 1S1 to transmit radio waves at the transmission timing TMS1 as illustrated, and the transmitting device 1S2 transmits Set to transmit radio waves on TMS2. Specifically, the transmission timing TMS2 is a timing delayed by the delay amount DY from the transmission timing TMS1.

  At such transmission timing, as shown in the figure, radio waves transmitted from the respective transmission devices are received by the reception device R1 at substantially the same timing. Specifically, at the transmission timing TMS1, the radio wave transmitted from the transmitter 1S1 reaches the receiver R1 after the arrival time T1. On the other hand, at the transmission timing TMS2, the radio wave transmitted from the transmitter 1S2 reaches the receiver R1 after the arrival time T2. Then, as shown in FIG. 5, there is a difference between the arrival time T1 and the arrival time T2 of the delay amount DY. Therefore, when a delay corresponding to the delay amount DY is set to each transmission timing, the radio wave reaches the reception device R1 at substantially the same timing as illustrated. As described above, the server 1SER sets each transmission device so that each radio wave reaches the reception device R1 at almost the same timing.

<Selection Example of Transmission Device for Transmitting Radio Wave> (Step S04) (FIG. 3)
In the communication system 1, it is desirable that the transmission device that transmits data be changed for each predetermined unit. Hereinafter, an example will be described in which a transmitting apparatus for transmitting a radio wave is selected for each bit unit of data to be transmitted.

  In step S04, the server 1 SER selects a transmission device that transmits a radio wave. Specifically, in the example shown in FIG. 1, the server 1SER selects a plurality of transmitting devices that perform the subsequent step S05 from among the transmitting devices 1S1, 1S2, 1S3, 1S4, 1S5, 1S6, 1S7 and 1S8. Therefore, the transmission device selected in step S04 performs the subsequent step S05. On the other hand, the transmitters not selected transmit, for example, noise data to be noise components.

  For example, for each bit of data to be transmitted, the server 1 SER randomly selects a transmitter. In this case, the transmitter for transmitting radio waves is configured to be changed every time in each bit. Therefore, even if the third party tries to illegally acquire data from the radio wave, it is difficult for the third party to specify the transmission device that transmits the radio wave because the transmission device is different for each bit. Therefore, the communication system 1 can make it difficult for a third party to acquire data. The predetermined unit for changing the transmission apparatus is not limited to the bit unit, and may be another unit.

<Example of radio wave transmission> (step S05)
In step S05, each transmitter transmits a radio wave. Specifically, each transmitter transmits radio waves at each transmission timing set in step S03.

  In addition, each transmission device reduces the radio wave and transmits. As shown in FIG. 6, in each transmission device, the reception device R1 receives each radio wave. Therefore, since the phases of the respective radio waves coincide with each other at the position of the reception device R1, the radio waves can be received by the reception device R1 even if the transmission power of the respective radio waves is small. On the other hand, since radio waves transmitted with small transmission power have small transmission power, it is difficult for a third party to detect radio waves. In this way, the communication system 1 can make it difficult for the third party to receive the transmitted data.

  Also, each transmitting apparatus calculates a spreading code for communication based on the Hadamard code, and transmits data using the calculated spreading code. That is, the Hadamard code determines the secret key in encryption and decryption. Each transmitting apparatus may use different Hadamard codes each time. On the other hand, the receiver decodes the data using the despreading code of the spreading code used for transmission. As described above, the communication system 1 transmits data in a so-called CDMA system using different codes. First, the Hadamard code will be described below.

<About the Hadamard code>
The Hadamard code is, for example, a Hadamard matrix [H] shown in the following equation (1).

上記（１）式で示すように、アダマール行列［Ｈ］は、Ｎ個の行と、Ｎ個の列とから構成され、Ｎ×Ｎの各構成要素が、「１」又は「−１」のいずれかとなる行列である。すなわち、アダマール行列［Ｈ］は、上記（１）式で示すように、２次元の行列等である。なお、アダマール符号は、２次元より高次元となる他の次元であってもよい。また、上記（１）式で示すように、アダマール行列［Ｈ］は、転置行列［Ｈ］^Ｔが乗じられると、単位行列のＮ倍となる行列である。

As shown by the above equation (1), the Hadamard matrix [H] is composed of N rows and N columns, and each component of N × N is “1” or “−1”. It is a matrix that will be either. That is, the Hadamard matrix [H] is a two-dimensional matrix or the like as shown in the above equation (1). Note that the Hadamard code may be another dimension that is higher than two dimensions. Further, as shown in the above equation (1), the Hadamard matrix [H] is a matrix that is N times the unit matrix when multiplied by the transposed matrix [H] ^T.

  Further, the Hadamard matrix [H] can be represented as the following equation (2), for example, in the Sylvester type. The Hadamard matrix [H] may be an M-sequence type or the like.

また、上記（１）式に示すアダマール行列［Ｈ］の行及び列を以下のように並べ替えると、変更行列［Ｈ］'が生成できる。

Further, when the rows and columns of the Hadamard matrix [H] shown in the above equation (1) are rearranged as follows, a modified matrix [H] ′ can be generated.

FIG. 7 is a schematic view showing a modification of rearranging rows of Hadamard matrix according to an embodiment of the present invention. As illustrated, the rearrangement of the rows is a modification example in which the rows of the x _{i th} row of the Hadamard matrix [H] and the rows of the i th row are rearranged.

FIG. 8 is a schematic view showing a modification of rearranging the columns of the Hadamard matrix according to the embodiment of the present invention. As shown in the figure, the rearrangement of columns is a modification example of rearranging the y _{j th} column and the j th column of the Hadamard matrix [H].

  The relationship between the matrix before the change and the matrix after the change shown in FIG. 7 and FIG. 8, that is, the relationship between the Hadamard matrix [H] and the change matrix [H] ′ is the following (3) It can be shown as a formula.

また、アダマール符号に、対角行列等の対角符号を乗算する処理が行われる場合がある。すなわち、変更符号は、アダマール行列に乗じられる対角行列等でもよい。以下、対角符号が対角行列であり、かつ、生成される変更符号の例である変更行列を第２変更行列［Ｈ］''とする。この例では、変更前の行列と、変更前の行列に対して対角行列を乗算する変更を行った変更後の行列との関係、すなわち、アダマール行列［Ｈ］と、第２変更行列［Ｈ］''との関係は、下記（４）式のように示せる。

In addition, processing may be performed in which the Hadamard code is multiplied by a diagonal code such as a diagonal matrix. That is, the change code may be a diagonal matrix or the like by which the Hadamard matrix is multiplied. Hereinafter, a diagonal matrix is a diagonal matrix, and a modification matrix which is an example of a generated modification code is referred to as a second modification matrix [H] ′ ′. In this example, the relationship between the matrix before the change and the matrix after the change obtained by multiplying the matrix before the change by the diagonal matrix, that is, the Hadamard matrix [H], and the second change matrix [H The relationship with]] can be shown as the following equation (4).

また、図７又は図８のように、アダマール符号の行又はアダマール符号の列を並べ替えた変更行列と、アダマール符号に乗じる対角行列とを組み合わせた変更符号が生成されてもよい。すなわち、後段の処理では、並べ替えた変更行列と、対角行列による乗算とを組み合わせた変換が行われてもよい。

Also, as shown in FIG. 7 or FIG. 8, a modified code may be generated by combining a modified matrix in which the row of Hadamard codes or the column of Hadamard codes is rearranged and the diagonal matrix by which Hadamard codes are multiplied. That is, in the process of the latter stage, conversion may be performed by combining the rearranged change matrix and multiplication by the diagonal matrix.

  Furthermore, the code is as shown in the following equation (5).

上記（５）式に示すように、符号「Ｃ」は、Ｎ個の要素がＭ個集まった集合である。さらに、上記（５）式では、右上の添え字は、番号を示し、任意の番号を「ｍ」としている。そして、上記（５）式における符号「Ｃ」のｍ番目の要素である「ｃ^ｍ」は、上記（５）式の下式に示すように、「０」乃至「Ｎ−１」までのＮ個の集まりを示す。

As shown in the above equation (5), the code "C" is a set of M pieces of N elements. Furthermore, in the above equation (5), the subscript in the upper right indicates a number, and an arbitrary number is “m”. Then, “ ^{m m} ”, which is the m-th element of the code “C” in the above equation (5), is N from “0” to “N−1” as shown in the lower equation of the above equation (5) Indicates a collection of pieces.

Also, the combination for rearranging the rows and columns of the Hadamard matrix [H] is “2 × log ₂ N!” Bits. Furthermore, the number of patterns in the diagonal matrix is "N" bits. The combination which rearranges the row | line and column of such Hadamard matrix [H] can be defined like the following (6) Formula, for example.

上記（６）式では、「ｍ」及び「ｎ」が、アダマール行列［Ｈ］の行及び列を示す。そして、上記（６）式では、「ｓ_ｉ」及び「ｒ_ｉ」によって、アダマール行列［Ｈ］における行及び列の並べ替えを表現している。上記の通り、「ｓ_ｉ」及び「ｒ_ｉ」は、互いに重複がなく、かつ、「０」乃至「Ｎ−１」のうちの任意の値となる。さらに、上記（６）式における「ｔ_ｉ」は、対角行列を示す。

In the above equation (6), “m” and “n” indicate the rows and columns of the Hadamard matrix [H]. Then, in the above (6), by "s _i" and "r _i" expresses the sorting of rows and columns in a Hadamard matrix [H]. As described above, “s _i ” and “r _i ” do not overlap with each other, and take any value of “0” to “N−1”. Furthermore, “t _i ” in the above equation (6) indicates a diagonal matrix.

  According to the above definition, in the code “C”, the correlation between the sequences is orthogonal as shown in the following equation (7).

したがって、「Ｎ」の正方行列のアダマール行列［Ｈ］は、下記（８）式に示す特性がある。

Therefore, Hadamard matrix [H] of the square matrix of "N" has the characteristic shown in the following equation (8).

通信において、アダマール行列［Ｈ］の行及び列の並べ替えの組み合わせと、対角行列のパターンとを特定できるデータを通信の暗号化及び復号における秘密鍵とする。したがって、受信装置Ｒ１は、あらかじめ取得する秘密鍵によって、送信装置が使う拡散符号を特定でき、逆拡散符号を生成することができる。

In communication, data that can specify combinations of row and column permutations of Hadamard matrix [H] and patterns of diagonal matrix is used as a secret key in communication encryption and decryption. Therefore, the receiving device R1 can specify the spreading code used by the transmitting device by the secret key acquired in advance, and can generate the despreading code.

<Example of using Hadamard code>
Hereinafter, an example using a 4 × 4 Hadamard matrix [H] will be described.

  FIG. 9 is a schematic diagram (part 1) showing an example of use of Hadamard code according to an embodiment of the present invention. For example, when the second row LN2 and the third row LN3 of the 4 × 4 Hadamard matrix [H] are added and overlapped, an output result OUT1 as shown in the drawing is obtained.

  In this example, the secret key is a parameter (r, s, t) that can specify how to make the Hadamard code. Therefore, the parameters (r, s, t) become data shared in advance between the transmitting side and the receiving side.

  The output result OUT1 shown in FIG. 9 corresponds to a decodable hash value. First, Hadamard codes can generate different Hadamard codes by row permutation, column permutation, or diagonal column multiplication. The illustrated example is an example of spreading and multiplexing bits using the second and third rows of the Hadamard code.

  Also, in the illustrated example, the parameters (r, s, t) are not included because the Hadamard code used is a simple Sylvester type. Using such a Hadamard code, the communication system expresses the "0" and "1" bits as "+1" or "-1" and multiplies the second and third rows by their respective rows. Add up the calculation results.

  Then, if the Hadamard code, that is, the secret key is known, the receiving side can decode the bit from the result of the addition based on the correlation equation shown in the above equation (8).

  In this example, two are added, but the number to be added may be two or more. As the number to be added increases, the value before being added can be difficult to guess. On the other hand, if the parameter (r, s, t), that is, a parameter that can specify what matrix the Hadamard code is, is shared as a secret key, the Hadamard code can be specified and data can be decoded.

  Such an output result OUT1 is a spread code in the spread spectrum system or the like. Then, the transmission device encrypts the data to be transmitted using a spread code, and transmits the data by radio waves.

  Also, a 4 × 4 Hadamard matrix [H] may be used, for example, as follows.

  FIG. 10 is a schematic diagram (part 2) showing an example of use of Hadamard codes according to an embodiment of the present invention. For example, three rows of the second row LN2, the third row LN3, and the fourth row LN4 of the 4 × 4 Hadamard matrix [H] may be overlapped.

  Specifically, when the third line LN3 and the fourth line LN4 are added to the second line LN2, an output result OUT2 as shown in the drawing is obtained.

  On the other hand, when the third line LN3 is added to the second line LN2 and the fourth line LN4 is further subtracted, an output result OUT3 as shown in the drawing is obtained.

  As described above, when the Hadamard matrix [H] is used, the transmitter transmits the sum of products of each row of the Hadamard matrix [H] and the data by radio waves. Then, the receiving apparatus receives data indicating the sum of the encoded data by receiving the radio wave. Next, the receiving apparatus calculates an inner product of each element constituting the sum of the encoded data and the despreading code. The Hadamard matrix [H] has orthogonality as shown in the above equation (8). Therefore, the receiving apparatus can decode the transmitted data by calculating the inner product of the Hadamard matrix [H] to be used and the sum of the encoded and multiplexed data.

<About position>
When radio waves are transmitted at the transmission timing determined as shown in FIG. 6 by the detection RW1 (see FIG. 4), the radio waves transmitted by the respective transmitters have the same phase at the position of the reception device R1, ie, the position where the detection RW1 is transmitted. The receiver R1 can demodulate the transmitted radio wave. Moreover, since Hadamard codes do not interfere with each other when they are synchronized, they do not become noise and become harmless signals.

On the other hand, since each radio wave becomes noise at a position other than the reception device R1, it can be difficult to demodulate the radio wave except for the position of the reception device R1. For example, it is assumed that the following conditions are satisfied.

Center frequency of radio wave F: 2.56 G [Hz (hertz)]
Speed of radio wave V: 3.0 × 10 ⁸ [m / s (meters per second)]

Assuming the above conditions, it can be said that the following condition exists.

Distance traveled by radio waves in one cycle of frequency: V ÷ F
= (3.0 × 10 ⁸ ) ÷ (2.56 × 10 ⁹ )
= 0.1171875 [m (meters)]
1 11.72 cm (centimeter)

Therefore, at a frequency of 0.5 cycle, the radio wave travels 11.72 cmcm2 ≒ 6 cm. In simple BPSK modulation, if the frequency is shifted by 0.5 cycles, bit errors are likely to occur, so synchronization acquisition is performed so that phase synchronization falls within 0.5 cycles.

Furthermore, it is assumed that the following conditions are satisfied.

Bit transmission rate BPS: 1 M [bps (bits per second)]
Code length R: 256

Further, since radio waves of 2 [Hz] are used to transmit 1-bit data, the above conditions have the following relationship.

Bandwidth W = 2 [Hz] x BPS x R = 512 M [Hz]

Then, it is assumed that one bit of transmission data used for spreading, that is, the number of cycles per one chip is “10”. And based on said conditions, it can calculate as follows, for example.

F / (BPS × R) = (2.56 × 10 ⁹ ) / (1 × 10 ⁶ × 256) = 10

In CDMA, a plurality of coded data are multiplexed, and when an orthogonal code such as Hadamard code is used, interference occurs between codes if the phase between data deviates by 0.5 chip or more. , Bit errors are more likely to occur. Therefore, it is difficult to demodulate radio waves at positions different by 0.5 chips (5 cycles, 60 cm) or more. That is, in this example, at positions different by 0.5 chip or more, each radio wave becomes a radio wave corresponding to noise.

  In this way, the communication system can make it difficult to demodulate the transmitted radio wave unless it is at a specific position, and can prevent unauthorized acquisition of data by a third party.

  Among the above conditions, the code length, the bit transmission rate, the center frequency of the radio wave, and the like are conditions that can be set. Therefore, for example, by changing the code length from the above condition, it is possible to adjust the allowable range in which the radio wave can be demodulated.

<About the number of transmitters>
The number of transmitters that transmit data is preferably equal to or greater than the number that uniquely determines the position of the receiver. For example, on a plane, it is desirable that there be three or more transmitters. That is, when the transmitting devices and the receiving devices are all located at substantially the same height, the positional relationship between the devices can be considered on a plane. On the plane, the position which can be specified by each distance from three points is one point. Therefore, on the plane, when radio waves are transmitted from three or more transmitters, it is possible to prevent the third party from demodulating the radio waves.

  On the other hand, in consideration of the height of each device and considering in space, it is desirable that there be four or more transmitters. That is, when the transmitting devices and the receiving devices are located at different heights, the positional relationship between the devices can be considered in space. In space, one position can be identified by each distance from four points. Therefore, when radio waves are transmitted from four or more transmitters in space, it is possible to prevent a third party from demodulating the radio waves.

<On the strength of security>
Hereinafter, as shown in FIG. 1, the communication system 1 will be described as an example having eight transmitters. First, in this example, the following conditions are set.

Number of transmitters: 8 [unit]
Code length: 256
Number of sequences used by one transmitter to transmit one bit: 4 [pieces]

Under the conditions as described above, the following number of sequences are used to transmit noise data for preventing unauthorized demodulation of radio waves by a third party.

Number of noise series: (256-8 [unit] x 4 [unit]) / 8 [unit] = 28

The above conditions are conditions under which 1-bit data can be demodulated if the sum of 8 [units] × 4 [pieces] of correlation outputs is taken. That is, if it is not possible to specify 8 [units] × 4 [pieces] = 32 of the 256 sequences, it is a condition that 1-bit data can not be acquired. On the other hand, at certain locations, the above noises are not affected by synchronization.

  As described above, the communication system can set the strength of security by setting the number of transmitters to be used, the code length, or the combination thereof.

Furthermore, under similar conditions, the strength of the security with the secret key can be calculated, for example, as follows.

Number of combinations of sorting in the column direction (or row direction) r: log ₂ (256!) = 1683.99 1 1684 bits

Number of combinations of sequences used s: log ₂ ( ₂₅₆ C ₃₂ ) = 135 bits Number of diagonal sequence combinations t: 256 bits Number of combinations of sequences assigned to each bit u: log 2 (32!) = 117.66 ≒ 118 bits

Security strength = 1684 bits + 118 bits + 135 bits + 256 bits = 2193 bits

When using the Hadamard code, even if the rows and columns are rearranged due to the orthogonality of the Hadamard matrix [H], each inner product can maintain the property of “0”. , The strength of security can be. Similarly, when the Hadamard code is used, the Hadamard matrix [H] has the same characteristic even when the diagonal sequence is multiplied, so the number of patterns of values to be multiplied to the diagonal sequence is the security as described above. The strength of the

<Example of functional configuration>
FIG. 11 is a functional block diagram showing an example of a functional configuration of a communication system according to an embodiment of the present invention. As illustrated, the communication system 1 is a functional configuration including, for example, a setting unit FN1, a radio wave transmission unit FN2, and a radio wave reception unit FN3. Further, as illustrated, the communication system 1 desirably has a functional configuration further including a selection unit FN4. Hereinafter, the illustrated functional configuration will be described as an example.

  The setting unit FN1 performs a setting procedure of setting a transmission timing for transmitting the radio wave RW2 for transmitting data, for each of the transmission devices, based on the distance between each of the transmission devices and the reception device R1. For example, the setting unit FN1 is realized by the network interface HW7 (see FIG. 2) or the like.

  The radio wave transmission unit FN2 performs a radio wave transmission procedure of transmitting the radio wave RW2 to the reception device R1 at the transmission timing set by the setting unit FN1 based on the Hadamard code. For example, the radio wave transmission unit FN2 is realized by the transceiver HW5, the antenna HW6, and the like (see FIG. 2) and the like.

  The radio wave reception unit FN3 performs a radio wave reception procedure for receiving the radio wave RW2 transmitted by the radio wave transmission unit FN2. For example, the radio wave reception unit FN3 is realized by the transceiver HW5, the antenna HW6, and the like (see FIG. 2).

  The selection unit FN4 performs a selection procedure of selecting a transmission device that transmits data among a plurality of transmission devices. For example, the selection unit FN4 is realized by the CPUHW1 and the like (see FIG. 2) and the like.

  First, the server 1 SER can calculate the arrival time by the detection RW1, for example, as shown in FIG. By doing this, the communication system 1 can set the transmission timing to each of the transmission devices by the setting unit FN1, for example, as shown in FIG. When the transmission timing is set in this way, each transmitting device can transmit the radio wave RW2 which can be demodulated at a specific position but is difficult to demodulate at another position.

  Therefore, the radio wave RW2 is received and demodulated by the radio wave receiver FN3 at a specific position. On the other hand, in order to acquire data illegally, the noise component of the radio wave RW2 is strong for a third party who intends to demodulate the radio wave RW2 at another position, and it is difficult to acquire data.

  Further, the radio wave transmission unit FN2 transmits data using a Hadamard code. Since each transmitting device and receiving device R1 share the secret key KY, the Hadamard code to be used can be specified based on the secret key KY. Thus, the receiver R1 can decrypt the encrypted data using a Hadamard code. On the other hand, it is difficult for a third party to identify the Hadamard code because the third party does not know the secret key KY. Therefore, by using the Hadamard code, the communication system 1 can make the third party obfuscate the data with the security strength shown in the above <For security strength>. Thus, the communication system 1 can increase the obfuscation of data in wireless communication.

  As described above, by transmitting data from a plurality of transmitting devices, the communication system can obfuscate the data to be transmitted.

  Also, by using Hadamard code, the communication system can obfuscate the data to be transmitted by encrypting the data. Knowing the secret key makes it possible to identify the Hadamard code to be used, so that encrypted data can be decrypted.

In addition, the communication system can obfuscate data to be transmitted by changing the Hadamard code for each transmission with the same transmission device. That is, when the transmission device does not change, it may be possible to specify the code and data bits by observing the transmission device. On the other hand, when data is transmitted while changing a plurality of transmission devices for each predetermined unit, it is necessary to observe a plurality of transmission devices and combine a plurality of observation results, which makes observation difficult. Therefore, the communication system can obfuscate the data to be transmitted.
Furthermore, the communication system can obfuscate the data to be transmitted by changing the combination of transmitting devices to transmit for each transmission. Furthermore, by transmitting data to be transmitted bit by bit, the communication system can obfuscate the data to be transmitted.

  By encoding and multiplexing multiple bits, the communication system makes it difficult to identify what code is used in the data to be transmitted and what bits are included, and obfuscates the data. be able to.

<< Other Embodiments >>
Further, each process may be realized by a program for causing a computer such as an information processing apparatus or an information processing system having one or more information processing apparatuses to execute a communication method. Also, the program can be distributed via a computer readable recording medium or a network. The recording medium is, for example, an optical disc, a flash memory, an auxiliary storage device, or the like.

  Furthermore, the processes described above may not be performed in the order shown. That is, each process may be performed at timings other than the illustrated timing. Also, each process may be performed by a plurality of devices in redundant, distributed, parallel, virtualized, or a combination thereof.

  Each device may be two or more devices connected by a network or the like.

  Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and various changes or modifications may be made within the scope of the present invention as set forth in the claims. It is possible.

1 communication system 1S1, 1S2, 1S3, 1S4, 1S5, 1S6, 1S7, 1S8 transmitter 1R receiver 1SER server RW1 detection RW2 radio wave FN1 setting unit FN2 radio wave transmission unit FN3 radio wave reception unit FN4 selection unit KY secret key [H] adamarar matrix

Claims (7)

A communication system comprising: a plurality of transmitting devices for wirelessly transmitting data; one or more receiving devices for receiving the data; and one or more information processing devices connected to the transmitting device and the receiving devices. ,
The information processing apparatus is
A setting unit configured to set a transmission timing for transmitting a radio wave for transmitting the data, for each of the transmission devices, based on a distance between each of the transmission devices and the reception devices;
The transmitting device is
A radio wave transmission unit for transmitting the radio wave to the reception apparatus at the transmission timing based on a Hadamard code;
The receiving device is
A communication system having a radio wave receiver for receiving the radio wave. The receiving device transmits detection to the plurality of transmitting devices,
The information processing apparatus is
The communication system according to claim 1, wherein the transmission timing is calculated based on the time when the detection arrives at each of the transmission devices. It further comprises a selection unit for selecting a transmission device to which the data is to be transmitted among the plurality of transmission devices.
The communication system according to claim 1, wherein the selection unit selects a transmission device that transmits the data for each predetermined unit.   The communication system according to claim 3, wherein the selection unit selects a transmission device that transmits four or more pieces of the data. The transmitting device and the receiving device share a secret key,
The transmitting device encrypts the data based on the Hadamard code based on the secret key,
The communication system according to any one of claims 1 to 4, wherein the receiving apparatus decrypts the data based on the secret key.   The allowable range in which the receiving apparatus can receive the radio wave is adjusted by at least one of the code length of the Hadamard code, the bit transmission rate of the radio wave, and the center frequency of the radio wave. The communication system according to any one of 5. A communication system comprising a plurality of transmitting devices for transmitting data wirelessly, one or more receiving devices for receiving the data, and one or more information processing devices connected to the transmitting device and the receiving device A communication method,
A setting procedure for setting a transmission timing at which the information processing apparatus transmits a radio wave for transmitting the data for each of the transmission devices based on the distance between each of the transmission devices and the reception devices;
A radio wave transmission procedure in which the transmission device transmits the radio wave to the reception device at the transmission timing based on a Hadamard code;
A communication method including: a radio wave reception procedure for receiving the radio wave;

Images