CN108512584B - Joint receiving method in direction modulation - Google Patents

Joint receiving method in direction modulation Download PDF

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CN108512584B
CN108512584B CN201810291070.5A CN201810291070A CN108512584B CN 108512584 B CN108512584 B CN 108512584B CN 201810291070 A CN201810291070 A CN 201810291070A CN 108512584 B CN108512584 B CN 108512584B
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receiving end
signal
eavesdropper
legal
receiving
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CN108512584A (en
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肖燕平
张红燕
肖悦
王金福
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
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Abstract

The invention has the beneficial effect that the invention provides a combined receiving method in direction modulation. By introducing a distortion factor in the transmit beamforming vector, an eavesdropper at any location will receive the distorted signal. And the introduced distortion factor may be randomly changed, thereby further distorting the eavesdropper received signal. Meanwhile, the scheme can enable a legal receiver to recover the transmission symbols by using a simple detection method. And therefore ultimately the bit error rate of an eavesdropper will be significantly higher than that of a legitimate receiver, no matter where the eavesdropper is located.

Description

Joint receiving method in direction modulation
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a joint receiving method in direction modulation. The present invention relates to a Phased antenna Array (PA) technique and a Directional Modulation (DM) technique.
Background
Physical layer security technology is concerned by more and more researchers today when information security is particularly important, and compared with the traditional encryption technology, the physical layer security technology has the advantage that the communication security is ensured by fully utilizing the characteristics of a channel without depending on the complexity of an encryption algorithm. The directional modulation technology is one of the hot spots of research in the field of physical layer secure communication in recent years, the technology realizes the directional modulation function of digital communication information by using different radio frequency structures at a radio frequency end, so that a received signal of a transmitted wireless communication signal in an expected direction and a baseband digital modulation signal have the same modulation signal space, and a traditional digital receiver can normally demodulate the communication information; and the relative position relation between the received signal constellation points in the unexpected direction generates distortion, so that the demodulation performance of the eavesdropping receiver is influenced, and even if the power of the signal received by the eavesdropping end is the same as or even higher than that of the signal received in the expected direction, the information cannot be accurately recovered.
The conventional modulation technology is to convert various baseband signals into digital modulation signals suitable for channel transmission, and the method is to use the baseband signals to control the change of certain parameters of carrier signals, and load communication information on the parameters to form modulated signals for transmission. And directional modulation is used as a radio frequency modulation technology, and is different from the traditional modulation technology in that: in the traditional communication system, signals are directly up-converted to radio frequency after being digitally modulated and transmitted through an antenna array, the modulated signals received by receivers in any direction are the same, only the difference of gain and signal-to-noise ratio exists, and the directional modulation can lead the signals to be consistent with a received signal constellation diagram and a transmitted signal only in the expected direction, and the amplitude and the phase distortion occur in the unexpected direction.
Although most of the previous researches on directional modulation are based on phased antenna arrays, in these researches, it is usually assumed that the direction of an eavesdropper is different from the direction of a legal receiver, however, in practical application scenarios, the eavesdropper is often in a silent state, that is, the eavesdropper cannot emit energy outwards, so that the position of the eavesdropper is often unknown, that is, the eavesdropper may be in the same direction as the legal receiver, in this case, the eavesdropper can decode a correct transmission signal, and the transmission of information becomes no longer secure.
Disclosure of Invention
The invention aims to provide a joint receiving method in direction modulation, which leads an eavesdropper to receive distorted signals at any position by introducing a distortion factor into a transmitting beam forming vector of a DM system. And the introduced distortion factor may be randomly changed, thereby further distorting the eavesdropper received signal. Meanwhile, the scheme can enable a legal receiver to recover the transmission symbols by using a simple detection method. And therefore ultimately the bit error rate of an eavesdropper will be significantly higher than that of a legitimate receiver, no matter where the eavesdropper is located.
The specific process of randomly selecting the direction modulation of the receiving end is characterized by comprising the following steps:
a transmitting end:
a. angle measurement: the transmitter makes angle measurements for each receiving end of a legitimate user.
b. Channel acquisition: the transmitter antenna array adopts a uniform linear array, the geometric center of the array is a phase center reference point, and then the guide vector of the transmitter array is expressed as:
Figure BDA0001617536000000021
where θ is the angle of directivity of the receiving end, NtIs the number of transmitter antennas, λ is the signal wavelength, and d is the array element spacing. The angle of the ith receiving end of the legal user is thetai,i＝1,2,...,NbIn which N isbFor the number of the receiving ends of the legal users, each receiving end only has one antenna, and each receiving end can perform cooperative communication. The channel of the legitimate user can be represented as
Figure BDA0001617536000000022
c. Information modulation: the information bits are conveyed by amplitude-phase modulation (APM). Selecting the constellation point symbol to be transmitted as bmM1, 2, M, where M is a modulation order, a set of symbols
Figure BDA0001617536000000023
d. Designing a beam forming vector: distortion factor corresponding to ith receiving end of legal user is alphai,i＝1,2,...,NbIn which N isbFor the number of the receivers of the legal users, both the sender and the legal receivers know the distortion factor and the corresponding relationship between the distortion factor and each legal receiver. The sender randomly selects the ith receiving end to make the wave beam aim at the receiving end, introduces the distortion factor corresponding to the receiving end into the wave beam forming vector, and designs the wave beam forming vector as
wi＝αih(θi)/Nt
The beamforming vector can be realized by the combination of radio frequency end components and can also be realized by baseband signal processing.
e. Signal transmission: the antenna transmit signal may be denoted as xi m＝wibm。
Receiving end:
f. signal receiving: the signal received by the legitimate person can be expressed as:
Figure BDA0001617536000000031
where n is a complex Gaussian white noise signal vector, each element of the vector is an independent identically distributed mean of 0 and a variance of σ2Complex gaussian variable of (a). The eavesdropper receiving the signal can be expressed as:
Figure BDA0001617536000000032
wherein n isEIs that the mean value is 0 and the variance is sigmaE 2Complex Gaussian variable of thetaEAngle of direction, h, of an eavesdropperH(θE) Is an eavesdropper channel.
g. Signal detection: using the Maximum Likelihood (ML) test, the legitimate person can recover the signal:
Figure BDA0001617536000000033
the signal recovered by the eavesdropper is:
Figure BDA0001617536000000034
the invention has the beneficial effects that: the invention provides a joint receiving method in direction modulation, which leads an eavesdropper to receive distorted signals at any position by introducing distortion factors into a sending beam forming vector of a DM system; and the introduced distortion factor can be changed randomly, thus further distorting the signal received by the eavesdropper; meanwhile, the scheme can ensure that a legal receiver can recover the transmission symbol by using a simple detection method; and therefore ultimately the bit error rate of an eavesdropper will be significantly higher than that of a legitimate receiver, no matter where the eavesdropper is located.
Drawings
Fig. 1 is a flowchart of an algorithm of a joint receiving method in directional modulation according to the present invention;
fig. 2 is a system model diagram of a joint receiving method in directional modulation according to the present invention;
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description so that those skilled in the art can better understand the invention. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.
Examples
In this example, QPSK modulation is used, and the number of transmitter antennas NaNumber of legitimate users receiving end N32b2, the two receiving end angles are each θ1＝15°，θ2At 95 °, the distortion factors corresponding to the two receiving ends are
Figure BDA0001617536000000035
a. Angle measurement: the transmitter makes angle measurements for each receiving end of a legitimate user.
b. Channel acquisition: the transmitter antenna array adopts a uniform linear array, the geometric center of the array is a phase center reference point, and then the guide vector of the transmitter array is expressed as:
Figure BDA0001617536000000041
where θ is the angle of directivity of the receiving end, NtIs the number of transmitter antennas, λ is the signal wavelength, and d is the array element spacing. The angle of the ith receiving end of the legal user is thetai,i＝1,2,...,NbIn which N isbFor the number of the receiving ends of the legal users, each receiving end only has one antenna, and each receiving end can perform cooperative communication. The channel of the legitimate user can be represented as
Figure BDA0001617536000000042
c. Information modulation: the information bits are conveyed by amplitude phase modulation. Selecting the constellation point symbol to be transmitted as bmM1, 2, M, where M is a modulation order, a set of symbols
Figure BDA0001617536000000045
d. Designing a beam forming vector: distortion factor corresponding to ith receiving end of legal user is alphai,i＝1,2,...,NbIn which N isbFor the number of the receivers of the legal users, both the sender and the legal receivers know the distortion factor and the corresponding relationship between the distortion factor and each legal receiver. The sender randomly selects the ith receiving end to make the wave beam aim at the receiving end, introduces the distortion factor corresponding to the receiving end into the wave beam forming vector, and designs the wave beam forming vector as
wi＝αih(θi)/Nt
The beamforming vector can be realized by the combination of radio frequency end components and can also be realized by baseband signal processing.
e. Signal transmission: the antenna transmit signal may be denoted as xi m＝wibm。
Receiving end:
f. signal receiving: the signal received by the legitimate person can be expressed as:
Figure BDA0001617536000000043
where n is a complex Gaussian white noise signal vector, each element of the vector is an independent identically distributed mean of 0 and a variance of σ2Complex gaussian variable of (a). The eavesdropper receiving the signal can be expressed as:
Figure BDA0001617536000000044
wherein n isEIs that the mean value is 0 and the variance is sigmaE 2Complex Gaussian variable of thetaEAngle of direction, h, of an eavesdropperH(θE) Is an eavesdropper channel.
g. Signal detection: using ML detection, the legitimate person can recover the signal:
Figure BDA0001617536000000051
the signal recovered by the eavesdropper is:
Figure BDA0001617536000000052
the invention provides a joint receiving method in direction modulation. By introducing a distortion factor into the transmit beamforming vector of the DM system, an eavesdropper will receive the distorted signal anywhere. And the introduced distortion factor may be randomly changed, thereby further distorting the eavesdropper received signal. Meanwhile, the scheme can enable a legal receiver to recover the transmission symbols by using a simple detection method. And therefore ultimately the bit error rate of an eavesdropper will be significantly higher than that of a legitimate receiver, no matter where the eavesdropper is located.

Claims (1)

1. A joint receiving method in directional modulation, comprising the steps of:
a transmitting end:
a. angle measurement: the transmitter measures the angle of each receiving end of a legal user to obtain the direction angle of the receiving end;
b. channel acquisition: the transmitter antenna array adopts a uniform linear array, the geometric center of the array is a phase center reference point, and then the guide vector of the transmitter array is expressed as:
Figure FDA0001617535990000011
where θ is the angle of directivity of the receiving end, NtIs the number of transmitter antennas, λ is the signal wavelength, d is the array element spacing;
the angle of the ith receiving end of the legal user is thetai,i＝1,2,...,NbIn which N isbFor the number of the receiving ends of the legal users, it is set that each receiving end has only one antenna, and each receiving end can perform cooperative communication, and then the channel of the legal users can be expressed as:
Figure FDA0001617535990000012
c. information modulation: the information bits are conveyed by amplitude phase modulation; selecting the constellation point symbol to be transmitted as bmM1, 2, M, where M is a modulation order, a set of symbols
Figure FDA0001617535990000013
d. Designing a beam forming vector: setting distortion factor corresponding to ith receiving end of legal user as alphai,i＝1,2,...,NbIn which N isbFor the number of the receiving ends of the legal users, the distortion factors are known at the sender and the legal receiving ends, and the corresponding relation between the distortion factors and each legal receiving end is also known; the sender randomly selects the ith receiving end to make the beam align to the receiving end, introduces the distortion factor corresponding to the receiving end into the beam forming vector, and designs the beam forming vector as:
wi＝αih(θi)/Nt
e. signal transmission: the antenna transmits a signal of xi m＝wibm；
Receiving end:
f. signal receiving: the legal person receives the signals as follows:
Figure FDA0001617535990000014
where n is a complex Gaussian white noise signal vector, each element of the vector is an independent identically distributed mean of 0 and a variance of σ2Complex gaussian variable of (a);
the eavesdropper receives the signal as:
Figure FDA0001617535990000021
wherein n isEIs that the mean value is 0 and the variance is sigmaE 2Complex Gaussian variable of thetaEAngle of direction, h, of an eavesdropperH(θE) Is an eavesdropper channel;
g. signal detection: using maximum likelihood detection, the legitimate person can recover a signal:
Figure FDA0001617535990000022
the signal recovered by the eavesdropper is:
Figure FDA0001617535990000023
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104040926A (en) * 2012-11-19 2014-09-10 华为技术有限公司 Modulation mode identification method, sending device, receiving device and system
WO2016061114A1 (en) * 2014-10-13 2016-04-21 Nxgen Partners Ip, Llc Application of orbital angular momentum to fiber, fso and rf
CN106888045A (en) * 2017-04-05 2017-06-23 电子科技大学 A kind of dynamic direction modulator approach based on beam forming
CN107231180A (en) * 2017-06-05 2017-10-03 电子科技大学 A kind of dynamic direction modulator approach based on beam forming
CN107231179A (en) * 2017-06-02 2017-10-03 南京邮电大学 Modulate object function in a kind of radio communication direction

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104040926A (en) * 2012-11-19 2014-09-10 华为技术有限公司 Modulation mode identification method, sending device, receiving device and system
WO2016061114A1 (en) * 2014-10-13 2016-04-21 Nxgen Partners Ip, Llc Application of orbital angular momentum to fiber, fso and rf
CN106888045A (en) * 2017-04-05 2017-06-23 电子科技大学 A kind of dynamic direction modulator approach based on beam forming
CN107231179A (en) * 2017-06-02 2017-10-03 南京邮电大学 Modulate object function in a kind of radio communication direction
CN107231180A (en) * 2017-06-05 2017-10-03 电子科技大学 A kind of dynamic direction modulator approach based on beam forming

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