CN114826358B - Direction modulation method and system with high anti-decoding performance - Google Patents
Direction modulation method and system with high anti-decoding performance Download PDFInfo
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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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
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Abstract
The invention provides a direction modulation method with high anti-decoding performance. The technical scheme comprises the following five steps: (1) Performing baseband modulation on input bit stream data to obtain a modulation signal s; (2) Performing M weighted transformation operations on the modulation signal s to obtain M weighted transformed signals x; (3) The signal x after M weighted transformation is transmitted by an antenna after precoding; (4) The legal receiver receives a signal Y B through an antenna, and carries out K weighted inverse transformation operations on the received signal Y B, so as to obtain a modulated signal Y after K weighted inverse transformation; (5) And demodulating the modulated signal Y obtained after K weighted inverse transformation to obtain received bit stream data. The method has stronger anti-decoding capability.
Description
Technical Field
The present invention relates to the field of digital communications technologies, and in particular, to a method and a system for processing signals with anti-hacking performance.
Background
DM (directional modulation ) is a directional PLS (PHYSICAL LAYER security, physical layer security) transmission technology implemented by multiple antenna technology in the space domain, and can be used for phased arrays and frequency control arrays. For convenience of description, taking phased array as an example, the DM method based on phased array is: assuming a uniform linear phased array comprising N antennas, there is one transmitter Alice in free space, one legitimate receiver Bob and one eavesdropper Eve, the desired direction and eavesdropping direction are θ B and θ E,θB≠θE, respectively, with respect to the first antenna element of transmitter Alice. At the transmitting end, baseband modulation is carried out on input bit stream data to obtain a modulation signal, then the modulation signal is transmitted by utilizing a phased array after being subjected to precoding to designate a transmitting direction, and a digital modulation signal with direction characteristics can be synthesized at a legal receiving end (namely, designate the transmitting direction), so that the safety problem of information transmission is solved. However, the above-mentioned existing DM technology is to be improved in that: the bit error rate beam of the received signal at the legal receiving end is wider, and the safety rate is low.
In order to solve the problem of wider error bit rate beam in the prior DM technology, a DM method of adding artificial noise is adopted at a transmitting end, and the main idea of the DM method of adding artificial noise (recorded as AN-DM) in the following two documents ：[1]Xie T,Zhu J,Li Y.Artificial-Noise-Aided Zero-Forcing Synthesis Approach for Secure Multi-Beam Directional Modulation[J].IEEE Communications Letters,2017,22(2):276-279.[2]Cheng Q,Fusco V,Zhu J,et al.SVD-Aided Multi-Beam Directional Modulation Scheme Based on Frequency Diverse Array[J].IEEE Wireless Communication Letters,2019,9(3):420-423. is that the transmitting end carries out baseband modulation on input bit stream data to obtain a modulation signal, then adds the artificial noise in the modulation signal, and then transmits the modulation signal through AN antenna after precoding, wherein the artificial noise only causes disturbance on the signal in AN unexpected direction, so the cracking difficulty of AN eavesdropper is increased, the error bit rate beam is narrower, but the power utilization rate of a system is greatly reduced due to the addition of the artificial noise.
In order to solve the problem of low power utilization rate of the existing DM technology, a DM (WPE-DM) method assisted by four weighted fractional Fourier transforms is adopted at a transmitting end to replace artificial noise, and the four weighted fractional Fourier transforms are referred to as WPE-DM in literature ：[3]Cheng Q,Fusco V,Zhu J,et al.WFRFT-aided Power-efficient Multi-beam Directional Modulation Schemes Based on Frequency Diverse Array[J].IEEE Transactions on Wireless Communications,2019,18(11):5211-5226.4-WFRFT(four weighted fractional Fourier transform,, which belongs to a DM method of signal transformation and can well improve the power efficiency of a system. For the WPE-DM method, the main idea is that at a transmitting end, baseband modulation is carried out on input bit stream data to obtain a modulation signal, then four weighted fractional Fourier transform (4-WFRFT) is carried out on the modulation signal, and then the modulation signal is transmitted through an antenna after being precoded; at the receiving end, the receiving bit stream data can be obtained by adopting the inverse process of the transmitting end. However, this method has a great disadvantage: in the process of sending information, the conversion order of the receiving end is sent along with the secret information, and as the receiving end and the transmitting end have the same communication architecture, namely all adopt four weighted fractional Fourier transforms and are open to all communication parties, once the conversion order is intercepted by an eavesdropper Eve in the process of sending the information, the information can be easily decoded by the eavesdropper Eve.
Disclosure of Invention
In order to solve the above problems, the present invention provides a direction modulation method with high anti-cracking performance, which can achieve stronger anti-cracking capability.
In order to achieve the above object, the technical scheme of the present invention is as follows: the direction modulation method with high anti-decoding performance is characterized by comprising the following five steps:
(1) Performing baseband modulation on input bit stream data to obtain a modulation signal s;
(2) Performing M weighted transformation operations on the modulation signal s to obtain M weighted transformed signals x;
(3) The signal x after M weighted transformation is transmitted by an antenna after precoding;
(4) The legal receiver receives a signal Y B through an antenna, and carries out K weighted inverse transformation operations on the received signal Y B, so as to obtain a modulated signal Y after K weighted inverse transformation;
(5) And demodulating the modulated signal Y obtained after K weighted inverse transformation to obtain received bit stream data.
A direction modulation system with high decoding resistance is characterized in that the method is adopted for direction modulation.
Compared with the prior art, the invention has the beneficial effects that:
In the method of the present invention, since the transmitting end and the receiving end adopt different communication architectures, that is, adopt weighted transformations of different terms, for the eavesdropper Eve, even if the eavesdropper Eve can obtain the number of transformation terms adopted by the transmitting end by analyzing the physical characteristics of the received signal and intercept the inverse transformation order accompanied by the transmission of the secret information by a certain means, the eavesdropper Eve has difficulty in decrypting the secret information because the eavesdropper Eve does not know which weighted transformation is adopted by the legal receiver. Therefore, the method has stronger anti-cracking capability. In addition, in the method of the invention, the transmitting end and the receiving end use different conversion item numbers and conversion orders, namely, different communication architectures are used, so that the communication function of the system is not affected, more freedom of communication flexibility and communication safety design is provided, and the method has wider application prospect.
Drawings
FIG. 1 is a schematic flow chart of the steps of the technical method of the invention;
FIG. 2 is a graph of experimental results for verifying the bit error rate performance curve of the technical method of the present invention;
Fig. 3 is a graph of experimental results (expressed as "bit error rate performance") for verifying the anti-deciphering performance of the technical method of the present invention.
Detailed Description
The present invention will be described in detail below. Referring to fig. 1 (a) a transmitting end and (b) a receiving end, the method comprises the following five steps:
(1) Performing baseband modulation on input bit stream data to obtain a modulation signal s;
(2) Performing M weighted transformation operations on the modulation signal s to obtain M weighted transformed signals x;
When M weighted transform operations are performed on the modulated signal s, M refers to the number of transform terms for performing the weighted transform operations, M is a positive integer greater than or equal to 4, the corresponding transform order is α M and α M e [ a, b ], and a and b are real numbers. It should be noted that α M is randomly valued within a set range, and only b-a=4 is required. The M term weighted transformation calculation expression is shown in the formula (1):
Wherein the method comprises the steps of Representing M weighted transforms of the modulated signal s,Representing 4 weighted transforms of the modulated signal s.
(3) The signal x after M weighted transformation is transmitted by an antenna after precoding;
(4) The legal receiver receives a signal Y B through an antenna, and carries out K weighted inverse transformation operations on the received signal Y B, so as to obtain a modulated signal Y after K weighted inverse transformation;
When the received signal Y B is subjected to K weighted inverse transform operations, K refers to the number of transform terms to which the weighted inverse transform operations are performed, and the corresponding inverse transform order is β K. The K term weighted inverse transformation calculation expression is shown as the formula (2)
Wherein the method comprises the steps ofRepresenting the K-term weighted inverse transform of the received signal Y B. It is specifically stated that the inverse transform order at the receiving end and the transform order at the transmitting end satisfy the following relationship: mβ K＝-KαM.
(5) And demodulating the modulated signal Y obtained after K weighted inverse transformation to obtain received bit stream data.
Fig. 2 and 3 are results of simulation experiments performed by the inventive method.
Simulation experiment conditions: based on MATLAB platform, antenna array element number n=9, baseband modulation mode adopts Quadrature Phase Shift Keying (QPSK), and center frequency f 0 =9 GHz.
Fig. 2 is a graph comparing BER performance curves of the method of the present invention with WPE-DM method and DM method with artificial noise added, with the change of propagation direction angle, under the condition that the signal-to-noise ratio is 10dB and the expected direction θ B =50°. In fig. 2, the abscissa represents a direction angle, and the ordinate represents an error rate; the solid legend plus right triangle represents the error rate performance curve of the WPE-DM method, the solid legend plus open circle represents the error rate performance curve of the DM method with artificial noise added, the dashed legend plus "+" represents the error rate performance curve of the method of the present invention when the transmitting end adopts 4-term weighted transform, the transform order is 0.5, and the legal receiving end adopts 4-term weighted inverse transform, the inverse transform order is-0.5, i.e., m=4, α M＝0.5,K＝4,βK = -0.5. The dashed-line plus-multiplication-sign of the legend represents the error rate performance curve of the method of the present invention when the transmitting end adopts 4-term weighted transformation, the transformation order is 0.5, and the legal receiving end adopts 8-term weighted inverse transformation, the inverse transformation order is-1, i.e., m=4, α M＝0.5,K＝8,βK = -1. The dashed line plus square in the legend represents the error rate performance curve of the method of the present invention when the transmitting end adopts 4-term weighted transform, the transform order is 0.5, and the legal receiving end adopts 16-term weighted inverse transform, the inverse transform order is-1.5, i.e., m=4, α M＝0.5,K＝16,βK = -2. From fig. 2, it can be seen that the WPE-DM method and the inventive method have better bit error rate performance than the DM method with artificial noise added when the legal receivers Bobs of the three methods are all at 50 ° in the desired direction.
Fig. 3 is a graph of anti-deciphering performance (expressed as "bit error rate performance") of the method of the present invention when the transmitting and receiving ends are transformed differently with the change of signal-to-noise ratio in the case where the desired direction θ B =50°, and the eavesdropping direction θ E =50°. The abscissa represents the signal-to-noise ratio and the ordinate represents the bit error rate; The solid line plus the right triangle in the legend represents the error rate performance curve of the eavesdropper Eve when the WPE-DM method is adopted, the dashed line plus the plus sign in the legend represents the error rate performance curve of the eavesdropper Eve when the transmitting end m=4, α M =0.5, and the legal receiving end k=8, β K = -1 are adopted, and the weighted inverse transformation of the inverse transformation order of-1 is adopted. the dashed-legged plus-sign represents the bit error rate performance curve of the eavesdropper Eve with a weighted inverse transform of k=8 and an inverse transform order of-1 when the transmitting end m=4, α M =0.5, and the legal receiving end k=8, β K = -1 of the method of the present invention. The dashed line plus the square in the legend represents the bit error rate performance curve of the eavesdropper Eve with a weighted inverse transform of k=16 and an inverse transform order of-1 when the transmitting end m=4, α M =0.5, and the legal receiving end k=8, β K = -1 of the method of the present invention. In fact, during the process of sending information from the sending end to the receiving end, the eavesdropper Eve can easily intercept the inverse transformation order sent from the sending end to the legal receiving end, and can obtain the transformation term number by analyzing the physical characteristics of the received signal of the sending end. For the WPE-DM method, the same conversion item number is used by a transmitting end and a receiving end, once the inverse conversion order is intercepted by an eavesdropper Eve, the secret of the system is cracked, and information leakage is caused. As can be seen from fig. 3, for the WPE-DM method, when an eavesdropper Eve intercepts the inverse transform order parameters, it can correctly demodulate the useful information; compared with the method that the legal receiving end correctly transforms the number of terms K=8, when K=4 or K=16 is adopted, the error rate performance of the method is very poor and is about 0.5, and the eavesdropper Eve cannot correctly demodulate the useful information, so that the anti-decoding performance of the system is improved.
Claims (2)
1. The direction modulation method with high anti-decoding performance is characterized by comprising the following five steps:
(1) Performing baseband modulation on input bit stream data to obtain a modulation signal s;
(2) Performing M weighted transformation operations on the modulation signal s to obtain M weighted transformed signals x;
(3) The signal x after M weighted transformation is transmitted by an antenna after precoding;
(4) The legal receiver receives a signal Y B through an antenna, and carries out K weighted inverse transformation operations on the received signal Y B, so as to obtain a modulated signal Y after K weighted inverse transformation;
(5) Demodulating the modulated signal Y obtained after K weighted inverse transformation to obtain received bit stream data;
When M weighted transformation operations are performed on the modulated signal s, M refers to the number of transformation terms for performing the weighted transformation operations, M is a positive integer greater than or equal to 4, the corresponding transformation order is alpha M, alpha M epsilon [ a, b ], and a and b are real numbers, and b-a=4; the M term weighted transformation calculation expression is shown in formula (1):
Wherein the method comprises the steps of Representing M weighted transforms of the modulated signal s,Representing 4 weighted transformations on the modulated signal s;
When the received signal Y B is subjected to K weighted inverse transformation operations, K refers to the number of transformation terms for performing the weighted inverse transformation operations, and the corresponding inverse transformation order is β K; the K term weighted inverse transform calculation expression is shown in formula (2):
Wherein the method comprises the steps of Represents the K-term weighted inverse transform of the received signal Y B, mβ K＝-KαM.
2. A direction modulation system with high anti-deciphering performance, which is characterized in that the direction modulation is performed by the method of claim 1.
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| 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 |
| CN109150368A (en) * | 2018-06-22 | 2019-01-04 | 达新宇 | A kind of anti-parameter scanning communication means of satellite based on ML-WFRFT and AN auxiliary |
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| US11483704B2 (en) * | 2019-12-27 | 2022-10-25 | University Of Electronic Science And Technology Of China | Physical layer secure communication against an eavesdropper with arbitrary number of eavesdropping antennas |
| CN113328969B (en) * | 2021-06-04 | 2022-12-09 | 中国人民解放军空军工程大学 | Multi-beam directional modulation method and system based on MP-WFRFT and artificial noise |
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| 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 |
| CN109150368A (en) * | 2018-06-22 | 2019-01-04 | 达新宇 | A kind of anti-parameter scanning communication means of satellite based on ML-WFRFT and AN auxiliary |
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