Modulation / demodulation method and wireless communication device using the same

Abstract

To provide a modulation / demodulation method that can avoid overshoot that occurs during a signal point transition process on a constellation even when the Y-00 encryption communication method is applied to a modulation method used in wireless communication, and a wireless communication device using the method.SOLUTION: A modulation method using the Y-00 encryption communication method by phase modulation of information for wireless communication, includes determining a reference position in a constellation of a previous signal point indicating previously transmitted data, making a certain range determined by the reference position a prohibited area so that a transition path of the signal point avoids passing near the origin on the constellation, determining a relative position of the current signal point from the reference position based on a current running key and currently transmitted data within a range excluding the prohibited area, determining I / Q coordinates on the constellation from the current signal point to generate modulated data, and performing multi-value phase modulation.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a wireless communication device using Yuen quantum cryptography and a modulation / demodulation method thereof, and more particularly to a method for avoiding overshoot that occurs during the transition of signal points on a constellation specific to Yuen quantum cryptography when performing modulation using a modulation method used in wireless communication. [Background technology]

[0002] Yuen quantum cryptography (Y-00) has been considered for application mainly in the field of optical communications. In optical communications, quantum fluctuations (quantum shot noise) occur in the signal light, causing the level of the signal light to change minutely. In general optical communications, signals represent two values, '0' and '1', and the aforementioned quantum fluctuations are weak compared to the amplitude (or phase) that represents these two values, so they do not have a significant adverse effect on the receiver's ability to distinguish the two values.

[0003] In Yuen quantum cryptography, the signals that represent the aforementioned binary values ​​are treated as one set (called a basis), and multiple M bases are prepared. The basis to be used for sending data is randomly determined by a pseudorandom number according to the encryption key. By designing the intervals between each level of the signals (distance between signals) generated by these M bases to be small enough that they cannot be identified by the aforementioned quantum fluctuations, an eavesdropper cannot identify and restore the data from the received signal. On the other hand, the legitimate receiver shares the aforementioned encryption key with the sender and can use the same basis using the same pseudorandom number algorithm, so all that is required is to identify the binary values ​​represented by the basis. Since quantum fluctuations are weak enough to determine the binary values, the legitimate receiver can ignore the effects of this noise, enabling accurate communication.

[0004] In this way, Yuen quantum cryptography can be considered a type of symmetric key cryptography that enables communication by possessing a common encryption key and pseudorandom number algorithm between the sender and receiver, and the encryption protocol using this modulation method is called the Yuen-2000 cryptographic communication protocol (abbreviated as Y-00 cryptographic communication method).

[0005] This Y-00 cryptographic communication method is also considered for application to wireless communication using radio waves. For example, the Y-00 cryptographic communication method can be realized with phase modulation or quadrature amplitude modulation, which are the mainstream modulation methods in wireless communication. Here, when applying the Y-00 cryptographic communication method, it is considered that noise equivalent to quantum fluctuations of light cannot occur in wireless communication, and as an alternative, a method of intentionally superimposing noise on the transmitting side can be considered. A specific example of noise superimposition is the method described in Patent Document 1.

[0006] Here, let us take QPSK (Quadrature Phase Shift Keying), a common phase modulation method in wireless communication, as an example. QPSK expresses four values, "00", "01", "10", and "11", at four signal points. In general QPSK, during the signal point transition process, an overshoot occurs in which the signal significantly extends outside the signal point position on the constellation. This occurs particularly when the signal point transitions through the origin. In the case of a signal format that generates a large overshoot, the input and output power of the power amplifier that determines the output of the wireless communication device are operated in an excessive range, and the power amplifier has to be used in the low power range. This generally reduces power efficiency, which has the disadvantage of restricting use in mobile wireless communication, where low power consumption is particularly important. Therefore, as a technology in general wireless communication, π / 4 shift QPSK and offset QPSK are adopted to avoid passing near the origin on the constellation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-80720 A Summary of the Invention [Problem to be solved by the invention]

[0008] As a phase modulation method to which the Y-00 encryption communication method is applied, for example, in the case of QPSK to which the Y-00 encryption communication method is applied (hereinafter referred to as Y-00QPSK), the conventional π / 4 shift QPSK and offset QPSK methods cannot avoid passing near the origin on the constellation. That is, in the case of Y-00QPSK, the signal point has any phase angle in the range of -π / 4 to π / 4 depending on the basis. As a result, even if the phase angle is alternately shifted by π / 4 as in π / 4 shift QPSK, a situation may occur in which the signal passes near the origin depending on the value of the basis before and after the transition. Also, even if a method such as offset QPSK is adopted, since the signal point can have multiple phase angles depending on the basis, for example, a transition may occur from a signal point with a positive Q value on the Q axis to a signal point with a negative Q value, passing through the origin cannot be avoided.

[0009] As described above, in phase modulation using the Y-00 encryption method, there are a huge number of candidates for the arrangement of signal points depending on the basis, and conventional modulation methods have the problem that it is not possible to restrict the path so as not to pass through the vicinity of the origin. The same problem occurs when the Y-00 encryption method is applied to quadrature amplitude modulation (QAM) used in wireless communication.

[0010] Therefore, an object of the present invention is to provide a modulation / demodulation method and a wireless communication device using the same that can avoid overshoot that occurs during signal point transition on a constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication. [Means for solving the problem]

[0011] As an example, the present invention provides a modulation method using the Y-00 encryption communication method by phase modulation of information for wireless communication, which determines a reference position in a constellation of a previous signal point indicating previously transmitted data, sets a certain range determined by the reference position as a prohibited area so that the transition path of the signal point does not pass near the origin on the constellation, determines the relative position of the current signal point from the reference position based on the current running key and the currently transmitted data within the range excluding the prohibited area, determines the I / Q coordinates on the constellation from the current signal point to generate modulated data, and performs multi-level phase modulation. Effect of the Invention

[0012] According to the present invention, it is possible to provide a modulation / demodulation method and a wireless communication device using the same that can avoid overshoot that occurs during signal point transition on a constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing the overall configuration of a typical wireless communication device; [Diagram 2] FIG. 1 is a diagram illustrating conventional QPSK and Y-00QPSK. [Diagram 3] FIG. 1 is a flow diagram of conventional Y-00QPSK modulation processing. [Figure 4] FIG. 1 is a constellation diagram in which conventional Y-00QPSK modulation is applied. [Diagram 5] FIG. 1 is a flow diagram of a conventional Y-00QPSK demodulation process. [Figure 6] FIG. 1 is a diagram illustrating conventional π / 4 shift QPSK. [Figure 7] FIG. 1 is a diagram illustrating a conventional offset QPSK. [Figure 8] FIG. 1 is a diagram for explaining offset QPSK when the conventional Y-00 encryption communication method is applied. [Figure 9] FIG. 1 is a diagram illustrating conventional 16QAM. [Figure 10]FIG. 1 is a diagram for explaining 16QAM to which the conventional Y-00 encryption communication method is applied. [Figure 11] FIG. 1 is a flow diagram of a modulation process of Y-00QPSK in the first embodiment. [Figure 12] FIG. 2 is a diagram for explaining the operation of Y-00QPSK in the first embodiment. [Figure 13] FIG. 11 is a flow diagram of a modulation process of Y-00QPSK in the second embodiment. [Figure 14] FIG. 11 is a diagram for explaining the operation of Y-00QPSK in the second embodiment. [Figure 15] FIG. 11 is a diagram for explaining the operation of 16QAM to which the Y-00 encryption communication method is applied in the second embodiment. [Figure 16] FIG. 11 is a flow diagram of a modulation process of Y-00QPSK in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0015] First, the basic configuration of a general wireless communication device will be described. Fig. 1 is a block diagram of the overall configuration of a general wireless communication device. In Fig. 1, the wireless communication device has, as its hardware configuration, a baseband processing unit 100 as a digital signal processing unit, an RF (Radio Frequency) unit 200 as an analog processing unit, and an antenna 300. Furthermore, each of the baseband processing unit 100 and the RF unit 200 is composed of processing blocks as shown in Fig. 1. Below, the configuration and processing contents of a general wireless communication device will be described with reference to Fig. 1.

[0016] As shown in Fig. 1, the baseband processing unit 100 on the transmitting side accommodates signals used for wireless communication, such as Ethernet frames, at a user interface (101) and converts them into a format for wireless communication at a wireless framer (102). In general, this signal is given an error correction code (103) and then modulated by a modulation unit (104). After modulation, the signal is waveform-shaped at a digital filter (105) and converted to an analog signal at a DA converter (106). Through the above processing, a baseband signal is generated before being superimposed on a carrier wave.

[0017] 1, the RF unit 200 amplifies the converted analog signal in a variable gain amplifier (107) to an appropriate level that can be processed by a quadrature modulator (109), removes unnecessary bands in a low-pass filter (108), combines the signal with a carrier wave generated by a local oscillator (110) in the quadrature modulator (109), and amplifies the signal to an appropriate transmission level in a power amplifier (111) to generate a signal for wireless communication. The signal for wireless communication is selected by a switch (112) for switching between transmission and reception, and then propagates into space via an antenna (300).

[0018] Meanwhile, on the receiving side, when radio waves are received via the antenna (300), in the RF section 200, they are amplified via the switch (112) in the low noise amplifier (114) to an appropriate level that can be processed by the quadrature demodulator (115). The quadrature demodulator (115) combines the signal with a sine wave from the local oscillator (110) to extract the received baseband signal. Unnecessary bands are then removed by the low pass filter (116), and the signal is corrected to an appropriate level by the variable gain amplifier (117).

[0019] Then, in the baseband processing unit 100, the signal from the RF unit 200 is converted to a digital signal by AD conversion (118), then waveform shaping is performed by a digital filter (119), and the received data is restored by demodulation processing (120) in a demodulation unit. Then, after error correction (121) is performed based on the added error correction code, the wireless frame is terminated by a wireless deframer (122), and the received signal conforming to the user interface (101) is restored and sent out.

[0020] Next, the modulation process (104) of QPSK used in general wireless communication devices will be described. Generally, signals transmitted by wireless communication consist of signals transmitted and received in a specific format such as Ethernet frames, and are divided and accommodated in frames for wireless communication. Therefore, the actual state of the communicated signal is a continuous bit stream expressed in binary '0' and '1'.

[0021] When modulating this signal with QPSK, each 2-bit value is separated into two components, I and Q, according to the rules shown in the top part of Figure 2. That is, four signal points, "00", "01", "10", and "11", are defined in the I and Q coordinates; for example, if the value of the first 2 bits of the bit stream is (11), it is converted to values ​​of I=1, Q=1. If the next 2 bits are (01), it is converted to values ​​of I=-1, Q=1. The I and Q values ​​separated in this way are superimposed on a wireless carrier wave using a quadrature modulator or the like, and transmitted as radio waves.

[0022] Meanwhile, on the receiving side, the I and Q components are extracted from the received radio waves using a quadrature demodulator, etc. The extracted components are also distributed to one of the four points on the constellation as shown in the upper part of Figure 2, so they are restored to 2-bit signals according to the I and Q distribution there.

[0023] Here, in the case of Y-00QPSK, the concept of bases is added to the above-mentioned general QPSK where 2-bit values ​​are replaced by I and Q values ​​according to a simple conversion rule. In other words, the set of four values ​​of the four signal points of general QPSK, "00", "01", "10", and "11", is considered as one base. This base is increased to M, and the signal points are arranged on the same circumference by shifting the phase angle for each base. In addition, the signal points expressing the four values ​​are rotated sequentially for each base to prevent adjacent signal points from showing the same value. In Y-00QPSK, the case where the number of bases is 2 is shown in the middle of Figure 2, and the case where the number of bases is 8 is shown in the bottom of Figure 2. In practice, the number of bases is set to several thousand or more, and the design is made so that the spread in the phase direction of the superimposed noise exceeds the distance between the signals.

[0024] FIG. 3 shows a flow diagram of the modulation process in the case of normal Y-00QPSK. In FIG. 3, first, in step S101, a common key shared with the receiving device is prepared. Then, in step S102, a long string of numbers is generated using a pseudorandom number generator having a predetermined algorithm such as an LFSR (linear feedback shift register) using this as a seed value. In step S103, the running key generating unit divides this string of numbers into bit strings of a certain length, for example, a 12-bit string, to generate a running key. Next, in step S104, a basis selection process is performed to convert the generated running key into basis information according to a predetermined rule. In this example, for simplicity, the rule that running key = basis is adopted as the predetermined rule is explained. Then, since the basis is a number expressed by 12 bits, it can take a value from 0 to 4095. Then, a process of combining the basis information with the transmission binary data (S105) to determine a signal point is performed. Then, in step S106, the basis value is treated as a rotation angle on the constellation, and Y-00QPSK modulation is performed to convert the binary data (S105) to I / Q components according to the basis value. In the case of QPSK, the constellation showing the four points in the upper part of Fig. 2, which serves as the reference, is rotated (counterclockwise) by (basis value) / 4096 × π / 2, with the maximum rotation angle being π / 2.

[0025] In addition, the 2-bit data to be transmitted may be directly mapped to 4 points on the phase-rotated constellation, but if an exclusive OR is taken with the 2 LSB bits of the base, it is possible to rotate the signal points sequentially for each base as described above, thereby preventing adjacent signal points from showing the same value.

[0026] In this way, Y-00QPSK determines the I / Q coordinates on the constellation by combining two bits of transmission data with the basis to generate modulation data, and outputs the transmission I / Q data (S107) expressed in binary I and Q. Here, I and Q become signals that can take multiple positions on the same circumference by combining the basis, and multi-level phase modulation can be performed. A simulation of this operation is shown in Figure 4.

[0027] Next, the demodulation process will be described. The received signal, which has passed through a quadrature demodulator and has been extracted again into I and Q components on the receiving side, is processed according to the demodulation process flow shown in Fig. 5. The method of generating the basis from common key acquisition to basis selection process in steps S501 to S504 shown in Fig. 5 is the same as S101 to S104 in Fig. 3. Therefore, the value of the basis, which changes every cycle, matches in transmission and reception, and the transmitted data can be accurately restored in units of two bits.

[0028] Specifically, in step S506, the signal points on the constellation received as the received I / Q data (S505) are rotated clockwise by (base value) / 4096×π / 2 (i.e., rotated in the opposite direction from the processing on the transmitting side), and Y-00QPSK demodulation is performed to convert the I / Q components into received binary data. Furthermore, by taking an exclusive OR with the LSB 2 bits of the base again, the signal points can be restored to the original general QPSK modulation signal point positions.

[0029] In this way, in Y-00QPSK modulation, the transmitted data is converted into a signal that can take multiple positions using a basis, but because the signal conversion rules are shared between the transmitter and receiver, Y-00QPSK demodulation can accurately demodulate the received binary data (S507).

[0030] Generally, during the signal point transition process, an overshoot occurs in which the signal extends significantly outside the signal point position on the constellation. This occurs particularly when the signal point transitions through the origin. The occurrence of overshoot leads to a decrease in power efficiency. For this reason, π / 4 shift QPSK and offset QPSK are adopted as techniques in general wireless communication to avoid passing near the origin on the constellation.

[0031] π / 4 shift QPSK is a method of alternately switching the reference position of a signal point so as not to pass through the vicinity of the origin on the constellation. FIG. 6 is a diagram for explaining conventional π / 4 shift QPSK. If a signal is located at one of the four signal points in the upper part of FIG. 6, it will transition to one of the four signal points shown in the middle part of FIG. 6 in the next cycle. In the next cycle, it will return to the signal point shown in the upper part of FIG. 6. By alternately shifting the signal point positions by π / 4 in this way, the transition path of the signal point will become as shown in the lower part of FIG. 6, and there will be no path that passes through the vicinity of the origin.

[0032] Moreover, offset QPSK is a method of modulation in which the transition timings of I and Q of a signal point are shifted by 1 / 2 cycle. FIG. 7 is a diagram for explaining conventional offset QPSK. In FIG. 7, assuming that a signal is initially present at signal point 701, when transitioning from there to signal point 703, first, only the Q coordinate is transitioned after 1 / 2 cycle. Here, the I coordinate is unchanged, and if only the Q coordinate transitions from 1 to -1, the signal point transitions once to the position of signal point 702. If only the I coordinate transitions after another 1 / 2 cycle, this time the Q coordinate is unchanged, and the I coordinate transitions from 1 to -1, and the signal point transitions to signal point 703. As a result, when transitioning from signal point 701 to signal point 703, the operation is such that the signal does not pass through the vicinity of the origin, but passes once through the position of signal point 702.

[0033] Here, in the case of a phase modulation method to which the Y-00 encryption communication method is applied, for example, Y-00QPSK, there is a problem that the conventional π / 4 shift QPSK or offset QPSK method cannot avoid passing through the vicinity of the origin on the constellation. This is because, in the case of Y-00QPSK, as described above, the signal point has an arbitrary phase angle in the range of -π / 4 to π / 4 depending on the basis. This means that even if the phase angle is alternately shifted by π / 4 like π / 4 shift QPSK, a situation may occur in which the signal passes through the vicinity of the origin depending on the value of the basis before and after the transition. Also, even if a method such as offset QPSK is adopted, for example, as shown in FIG. 8, when the signal point 800 is I=1, Q=1, a transition may occur from signal point 801 with I=0, Q=1.41 (root 2) to signal point 802 with I=0, Q=-1.41, so even if only Q is transitioned first and then I is transitioned, it is not possible to avoid passing through the origin once.

[0034] As described above, in phase modulation using the Y-00 encryption communication method, there are a huge number of candidates for the arrangement of signal points depending on the basis, and conventional modulation methods have the problem that it is not possible to restrict the route so as not to pass near the origin.

[0035] Next, a modulation process of quadrature amplitude modulation (QAM), which is a modulation method used in general wireless communication devices, will be described. FIG. 9 is a diagram for explaining conventional 16QAM. As shown in FIG. 9, 16QAM has 16 signal points, each of which has a 4-bit value of "0000", "0001" to "1110", "1111". For example, when a signal point position of "0000" is transitioned to a position of "1010", the transition passes through the vicinity of the origin, and a large overshoot occurs similarly in the case of QAM. When the Y-00 encryption communication method is applied to this QAM, various methods can be considered for allocating 4-bit values ​​to adjacent signal points. For example, as shown in FIG. 10, the signal point of normal 16QAM is basically distributed as a plurality of signal points. Therefore, there is a problem that an overshoot occurs similarly in QAM to which the Y-00 encryption communication method is applied.

[0036] Therefore, in this embodiment, a modulation / demodulation method that can avoid overshoot that occurs during signal point transition on a constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication will be described below.

[0037] The modulation method in this embodiment is a partial modification of the Y-00 modulation processing flow in FIG. 3 described above, and restricts the transition of the signal point so that it does not pass near the origin on the constellation.

[0038] A flow diagram of the modulation process in the case of Y-00QPSK in this embodiment is shown in Fig. 11. In Fig. 11, obtaining a common key (S201), generating pseudo-random numbers (S202), and generating a running key (S203) are the same as S101 to S103 in Fig. 3.

[0039] Here, when performing the basis selection process in step S204, a one-cycle delay process (step S208) is added to supply basis information from one cycle before. In step S204, the signal point from one cycle before is set as a reference position, and the relative angle from there is determined according to the basis value based on the supplied running key and the transmission binary data (S205), and is set as a new signal point. Then, in step S206, Y-00QPSK modulation is performed to convert to I / Q components corresponding to the new signal point. Then, transmission I / Q data (S207) expressed by the binary values ​​of I and Q is output, and multi-level phase modulation based on the basis value and the transmission binary data can be performed. After modulation, the digital filter (105) and DA conversion (106) in the baseband processing unit 100 are used to convert to analog signals as in the conventional method, and a baseband signal is generated. Then, in the RF section 200, when applying the Y-00 encryption communication method to wireless communication, the intentionally superimposed noise described above is superimposed on a baseband signal and also on a wireless carrier wave, and transmitted as radio waves via an antenna (300).

[0040] A specific example of the modulation process in Fig. 11 is shown in Fig. 12. Here, the circumference is divided into 5 equal parts starting from the reference position (901) to form 5 arcs, and the arcs diagonally opposite the origin are defined as the prohibited area (902). In other words, the prohibited area is a relative angle of π+ / -θ=π+ / -π / 5=π+ / -36° from the reference position (901). Then, one point on the remaining 4 arcs excluding the prohibited area is defined as a signal point representing (11), (01), (00), and (10) of the transmission binary data (S205), and the position where it is rotated by (base value) / 4096×π / 2×4 / 5=(base value) / 4096×2π / 5 becomes the signal point. As with conventional Y-00QPSK modulation, the signal point positions (11), (01), (00), and (10) may be rotated sequentially by taking the exclusive OR of the two least significant bits of the base and the two bits of transmission data. As a result of this process, the circle (904) inscribed in the pentagram (903) connecting the center points of each arc becomes a non-passage area, making it possible to avoid passing near the origin on the constellation.

[0041] The demodulation process in this embodiment takes the phase difference between the previous signal point and the current signal point (delayed detection), and then, as with conventional Y-00QPSK demodulation, performs reverse rotation processing and exclusive OR processing based on the basis information generated by the same calculation process to restore the received data.

[0042] In this embodiment, the circumference is divided into five parts and one diagonal arc is set as the prohibited area. However, it is possible to limit the transition area of ​​the constellation by defining the prohibited area using a similar method or by defining a relative area in which transitions are permitted.

[0043] Furthermore, if the angle range θ of the forbidden area is variable, it is possible to expand or reduce the area through which signal points can be prevented from passing.

[0044] Also, in the above, the current signal point position is determined using the signal point one cycle before as the reference position, but in other words, the next signal point position may be determined using the current signal point as the reference position.

[0045] As described above, according to this embodiment, the value of the current signal point is determined by the relative angle from the previous signal point as a reference, and a part of the relative angle is set as a prohibited area and transition is not permitted, thereby avoiding passing near the origin. This makes it possible to provide a modulation / demodulation method and a wireless communication device using the same that can avoid overshoot that occurs during signal point transition on the constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication. EXAMPLES

[0046] In this embodiment, a method will be described in which a transition is not made linearly between the previous signal point and the current signal point, but rather a waypoint is provided to avoid passing near the origin.

[0047] FIG. 13 is a flow diagram of the modulation process in the case of Y-00QPSK in this embodiment. In FIG. 13, common key (S301) acquisition, pseudorandom number generation (S302), running key generation (S303), and one-cycle delay (S308) are the same as S201 to S203 and S208 in FIG. 11. Here, in step S304, the signal point one cycle before and the signal point of the current cycle are referenced, and the phase difference between them and the like are calculated. Then, in step S309, the value of the midpoint (phase difference / 2) is determined as the signal point of the midpoint from the phase difference between them. In addition, in step S310, the signal point of the current cycle is selected, and the signal point of the midpoint and the signal point of the current cycle are alternately output by toggling the selector (S311) at twice the speed of one cycle. Then, in step S306, Y-00QPSK modulation is performed to convert the alternately output intermediate signal point and the current cycle signal point into I / Q components. Then, transmission I / Q data (S307) expressed in binary I and Q is output, and multi-level phase modulation based on the base value and transmission binary data can be performed. In other words, the signal transitions to the signal point that should have been reached originally via a specified intermediate point.

[0048] An example of the transition operation is shown in Fig. 14. As shown in Fig. 14, when transitioning from signal point 1401 to signal point 1402 which should originally be reached, first the signal is transitioned to signal point 1403 after 1 / 2 cycle, and then to signal point 1402 after that 1 / 2 cycle. Similarly, when transitioning from signal point 1402 to signal point 1404 which should originally be reached, first the signal is transitioned to signal point 1405 after 1 / 2 cycle, and then to signal point 1404 after that 1 / 2 cycle. This makes it possible to avoid passing near the origin and to transition between desired signal points.

[0049] Regarding the demodulation process for Y-00QPSK in this embodiment, the position of the signal point for each cycle is the same as that of conventional Y-00QPSK modulation (the path of the midpoint is different), so the demodulation process can be performed using the same method as conventional methods.

[0050] In the above, a method of simply taking a position of phase difference / 2, i.e., a midpoint on the same circumference, has been described, but there are multiple possible ways to take the midpoint. For example, while the angle of phase difference / 2 is still calculated, a method of shortening the detour route by passing through a point on a circle with a smaller radius rather than on the same circumference, or a method of setting predetermined candidate points and selecting the optimal point from among them, and passing through them, are possible. Also, a method of setting n points instead of one midpoint is possible. In this case, the number of midpoints during one transmission cycle is set to n, and the n midpoints in the constellation between the previous signal point position and the current signal point position are sequentially shifted every 1 / n cycle time.

[0051] Furthermore, even in the case of QAM, a method is conceivable in which predetermined candidate points are provided as waypoints, and when the path length before and after the signal point transition is equal to or longer than a certain length, one of the candidate points is selected as the waypoint with the smallest total path length. That is, a plurality of midpoint candidates are provided in advance other than near the origin on the constellation, and the midpoint candidate with the smallest sum of the vector from the previous signal point position to the midpoint candidate and the vector from the midpoint candidate to the current signal point position is determined as the midpoint, and the signal point transition path is prevented from passing near the origin on the constellation by transitioning from the previous signal point position to the current signal point position via the midpoint.

[0052] A specific example is shown in Figure 15. The via points are based on the 16QAM signal points shown in Figure 9, and do not pass through signal points near the origin. Also, when the previous signal point is in the first quadrant, the candidate points are limited to the second and fourth quadrants, and when it is in the second quadrant, the candidate points are limited to the first and third quadrants. That is, in Figure 15, when the previous signal point is located at the signal point (1501) in the first quadrant and the current signal point is about to transition to the signal point (1502) in the third quadrant, the candidate points (1503) to (1506) in the second and fourth quadrants are set as via points. Here, signal points (1507) and (1508) are excluded from the candidate points of the via route because they are signals near the origin. Among these, the route length passing through each of the candidate points (1503) to (1506) is calculated, and the candidate point with the shortest length is selected. When there are multiple candidate points with the same path length, a priority may be set for each candidate point, or a rule may be established such that, for example, if there is a signal point in the first quadrant, then only the candidate points in the second quadrant can be used, and if there is a signal point in the second quadrant, then only the candidate points in the third quadrant can be used.

[0053] By determining the midpoint in this way, it is possible to avoid passing near the origin of the constellation even in QAM, and to suppress the amount of overshoot, thereby enabling multi-level quadrature amplitude modulation based on the base value and transmission binary data to be performed.

[0054] As described above, according to this embodiment, instead of a linear transition between the previous signal point and the current signal point, a waypoint is provided to avoid passing through the vicinity of the origin. This makes it possible to provide a modulation / demodulation method and a wireless communication device using the same that can avoid overshooting that occurs during signal point transition on a constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication. EXAMPLES

[0055] In this embodiment, when calculating a running key that is a key for determining the current signal point, if the running key is within a predetermined range, i.e., a range of values ​​that can pass near the origin, the key is skipped and the next running key is adopted, thereby avoiding passing near the origin.

[0056] Fig. 16 is a flow diagram of the modulation process in the case of Y-00QPSK in this embodiment. In Fig. 16, common key (S401) acquisition, pseudorandom number generation (S402), running key generation (S403), and one cycle delay (S408) are the same as S201 to S203 and S208 in Fig. 11. Here, in step S404, a signal point is determined from the running key and the transmission binary data (S405), and compared with the signal point one cycle ago, and the path length between them is calculated. Then, in step S409, it is determined whether the path length is a predetermined length or more, and if the path length is the predetermined length or more, that is, if the path length passes through the vicinity of the origin on the constellation and becomes longer, the current running key is discarded, and the process returns to the running key generation in step S403, and the next running key is used, so that it is possible to restrict the passage of a path of a certain length or more. That is, if the path length is not equal to or longer than a predetermined length, in step S406, Y-00QPSK modulation is performed to convert to I / Q components corresponding to a signal point determined according to a basis value based on a running key and the transmission binary data (S405). Then, transmission I / Q data expressed in binary I and Q values ​​(S407) is output.

[0057] In the present embodiment, the demodulation process for Y-00QPSK is performed by providing an algorithm identical to that in the flow chart of the modulation process for Y-00QPSK in FIG. 11, so that the running key used in S410 matches, and the demodulation process can be performed in the same manner as in the conventional method.

[0058] In the above, we have shown a method of avoiding passing near the origin on the constellation by discarding (skipping) the running key using the path length of the signal points in the previous and current cycles as an index. However, it is also possible to use a method of changing the reference position of a signal point by using a predetermined rule, such as shifting the signal point position by π / 4 or increasing or decreasing the transition angle by a predetermined angle, if the path length is equal to or longer than a predetermined length.

[0059] As described above, according to this embodiment, when calculating a running key that is a key for determining a current signal point, if the running key is within a predetermined range, that is, a range of values ​​that can pass near the origin, the key is skipped and the next running key is adopted to avoid passing near the origin. This makes it possible to provide a modulation / demodulation method and a wireless communication device using the same that can avoid overshooting that occurs during signal point transition on a constellation even when the Y-00 encryption communication method is applied to the modulation method used in wireless communication.

[0060] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are included. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0061] 100: baseband processing unit, 200: RF unit, 300: antenna, 104: modulation processing, 120: demodulation processing

Claims

1. A modulation method using a Y-00 encryption communication method by phase modulation of wireless communication information, determining a reference position in the constellation of a previous signal point indicative of previously transmitted data; A certain range determined by the reference position is set as a prohibited area so that the transition path of the signal point does not pass near the origin on the constellation, and a relative position of the current signal point from the reference position is determined based on the current running key and the current transmission data within the range excluding the prohibited area; A modulation method comprising determining an I / Q coordinate on a constellation from the current signal point to generate modulation data and perform multi-level phase modulation.

2. 2. The modulation method according to claim 1, A modulation method characterized in that the value of the angle θ that defines the forbidden area is variable, thereby limiting the area in which the signal points transition.

3. A modulation method using a Y-00 encryption communication method by phase modulation or quadrature amplitude modulation of wireless communication information, A current signal point position in a constellation of a current signal point indicating current transmission data is determined, and a previous signal point position determined based on a previous running key and a previous transmission data is referenced to calculate a midpoint in the constellation between the current signal point position and the previous signal point position; A modulation method, comprising the steps of performing multi-level phase modulation or multi-level quadrature amplitude modulation via the intermediate point during a transition from a previous signal point position to a current signal point position.

4. 4. The modulation method according to claim 3, A modulation method characterized in that the number of said intermediate points during one transmission cycle is n, and the n intermediate points in a constellation between a previous signal point position and a current signal point position are sequentially transitioned every 1 / n cycle time.

5. 5. The modulation method according to claim 3, a signal point transition path that does not pass near the origin on the constellation by calculating the midpoint from the phase difference between the phase of the current signal point position and the phase of the previous signal point position and determining that the midpoint is located on the same circumference on the constellation.

6. 5. The modulation method according to claim 3, A plurality of candidates for the midpoint are set in advance on the constellation other than near the origin, define the midpoint candidate that minimizes the sum of a vector from the previous signal point position to the midpoint candidate and a vector from the midpoint candidate to the current signal point position as the midpoint; A modulation method, characterized in that the transition path of the signal point avoids passing near the origin on the constellation by transitioning from the previous signal point position to the current signal point position via the intermediate point.

7. A modulation method using a Y-00 encryption communication method by phase modulation of wireless communication information, A current signal point position in a constellation of a current signal point indicating current transmission data is determined, and a signal point distance between the current signal point position and the previous signal point position is determined from the previous signal point position determined based on the previous running key and the previous transmission data; a modulation method characterized in that, when the distance between the signal points exceeds a predetermined length, the current running key is discarded, and multi-level phase modulation is performed using subsequent running keys that bring the distance between the signal points within the predetermined length, thereby preventing the transition path of the signal points from passing near the origin on the constellation.

8. 8. The modulation method according to claim 7, A modulation method, characterized in that, when the distance between said signal points exceeds said predetermined length, a current signal point position is converted using a predetermined rule to perform multi-level phase modulation.

9. A wireless communication device having a baseband processing unit which has a modulation unit that performs modulation processing using a Y-00 encryption communication method by phase modulation of wireless communication information and generates a baseband signal, an RF unit which intentionally superimposes noise on the baseband signal and also superimposes it on a carrier wave to generate a signal for wireless communication, and an antenna which transmits the signal for wireless communication as a radio wave, The modulation unit is determining a reference position in the constellation of a previous signal point indicative of previously transmitted data; A certain range determined by the reference position is set as a prohibited area so that the transition path of the signal point does not pass near the origin on the constellation, and a relative position of the current signal point from the reference position is determined based on the current running key and the current transmission data within the range excluding the prohibited area; A wireless communication device which determines I / Q coordinates on a constellation from the current signal point to generate modulation data and executes multi-level phase modulation.

10. 10. The wireless communication device according to claim 9, A wireless communication device, characterized in that the value of the angle θ that defines the forbidden area is variable, thereby limiting the area in which the signal points transition.

11. A wireless communication device having a baseband processing unit which has a modulation unit that performs modulation processing using a Y-00 encryption communication method by phase modulation or quadrature amplitude modulation of wireless communication information and generates a baseband signal, an RF unit which intentionally superimposes noise on the baseband signal and also superimposes it on a carrier wave to generate a signal for wireless communication, and an antenna which transmits the signal for wireless communication as a radio wave, The modulation unit is A current signal point position in a constellation of a current signal point indicating current transmission data is determined, and a previous signal point position determined based on a previous running key and a previous transmission data is referenced to calculate a midpoint in the constellation between the current signal point position and the previous signal point position; A wireless communication device, comprising: a signal point shifting section that shifts from a previous signal point position to a current signal point position and performs multi-level phase modulation or multi-level quadrature amplitude modulation via the intermediate point.

12. 12. The wireless communication device according to claim 11, A wireless communication device, characterized in that the number of said intermediate points during one transmission cycle is n, and the n intermediate points in a constellation between a previous signal point position and a current signal point position are sequentially transitioned every 1 / n cycle time.

13. 13. The wireless communication device according to claim 11, a signal point transition path that does not pass near the origin on the constellation by calculating the midpoint from a phase difference between the phase of the current signal point position and the phase of the previous signal point position and determining that the midpoint is located on the same circumference on the constellation.

14. 13. The wireless communication device according to claim 11, A plurality of candidates for the midpoint are set in advance on the constellation other than near the origin, define the midpoint candidate that minimizes the sum of a vector from the previous signal point position to the midpoint candidate and a vector from the midpoint candidate to the current signal point position as the midpoint; A wireless communication device, characterized in that the transition path of the signal point avoids passing near the origin on the constellation by transitioning from the previous signal point position to the current signal point position via the intermediate point.

15. A wireless communication device having a baseband processing unit which has a modulation unit that performs modulation processing using a Y-00 encryption communication method by phase modulation of wireless communication information and generates a baseband signal, an RF unit which intentionally superimposes noise on the baseband signal and also superimposes it on a carrier wave to generate a signal for wireless communication, and an antenna which transmits the signal for wireless communication as a radio wave, The modulation unit is A current signal point position in a constellation of a current signal point indicating current transmission data is determined, and a signal point distance between the current signal point position and the previous signal point position is determined from the previous signal point position determined based on the previous running key and the previous transmission data; When the distance between the signal points exceeds a predetermined length, the current running key is discarded, and multi-level phase modulation is performed using subsequent running keys that bring the distance between the signal points within the predetermined length, thereby preventing the transition path of the signal points from passing near the origin on the constellation.

16. 16. The wireless communication device according to claim 15, A wireless communication device, characterized in that, when the distance between said signal points exceeds said predetermined length, a current signal point position is converted using a predetermined rule to perform multi-level phase modulation.

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