CN110958104B - Communication method based on 16QAM partial position embedded signal watermark - Google Patents
Communication method based on 16QAM partial position embedded signal watermark Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
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- H—ELECTRICITY
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- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/3405—Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power
- H04L27/3416—Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power in which the information is carried by both the individual signal points and the subset to which the individual points belong, e.g. using coset coding, lattice coding, or related schemes
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Abstract
The invention provides a communication method based on embedding signal watermarks in 16QAM (Quadrature amplitude modulation) partial positions, which is characterized in that information to be sent is distinguished, public information is used as carrier information, and secret information is used as watermark information; on one hand, carrier information generates modulated carrier information in a 16QAM modulation mode; in another aspect, the watermark information is spread into a signal watermark that is embedded at low power in 4 locations of + -3 j of the 16QAM constellation of the modulated carrier information. The signal watermark is embedded in the specified part, and the influence of the signal watermark on the carrier information is greatly reduced on the premise of ensuring low-power embedding. Compared with the existing scheme of embedding the signal watermark into all positions, the method ensures the transmission of the watermark information, and reduces the error rate of the carrier information to a great extent, so that the concealment of the whole communication process is improved.
Description
Technical Field
The invention belongs to the communication physical layer security technology, and relates to a 16QAM (quadrature Amplitude modulation) modulation technology and a signal watermarking technology.
Background
In recent years, physical layer signal watermarks are widely applied to physical layer identity authentication, and a receiving end can realize high watermark authentication rate under low signal-to-noise ratio through a certain watermark embedding and extracting algorithm.
Signal watermarking is proposed as a new type of physical layer technology for the purpose of improving physical layer security. Physical layer signal watermarking is a mechanism for transmitting a secret secure authentication code or tag simultaneously with a signal. At the receiving end, the identity of the communication user can be identified by extracting the special authentication watermark. Therefore, the research on the physical layer signal watermark is of great significance for improving the physical layer security. However, the conventional physical layer signal watermark is usually superimposed on the whole carrier information, and reduces the concealment of the carrier information.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for improving communication safety by reducing the influence of signal level on the concealment of carrier information.
The technical scheme adopted by the invention for solving the technical problems is that a communication method for embedding signal watermarks based on 16QAM partial positions comprises the following steps:
A. the transmitting terminal carries out the following steps:
A1) and carrier information position classification step:
distinguishing information to be sent, using public information as carrier information and using secret information as watermark information; classifying the carrier information according to the 16QAM constellation mapping positions, dividing 4 constellation positions of +/-3 j into an A class needing embedding the signal watermark, and dividing the rest 12 constellation mapping positions into a B class needing no embedding of the signal watermark;
A2) watermark information spreading step:
negotiating with a receiving end to generate two constant envelope zero auto-correlation (CAZAC) sequences PN1 and PN0 with cross-correlation coefficient of 0 and the same length, spreading the watermark information with value 1 by using a sequence PN1, and spreading the watermark information with value 0 by using a sequence PN0 to obtain a signal watermark;
A3) signal watermark embedding step:
superposing the signal watermark on the A-type modulated carrier information modulated by 16QAM according to the set low embedding strength, directly modulating the B-type carrier information by 16QAM to obtain modulated carrier information, and finally obtaining modulated carrier information X embedded with the signal watermark; the low embedding strength is the lowest strength under the condition of not influencing the extraction of the signal watermark by the receiving end;
A4) a sending step:
transmitting modulated carrier information embedded with the signal watermark;
B. the receiving end carries out the following steps:
B1) receiving and demodulating:
receiving modulated carrier information which is transmitted through a channel and embedded with a signal watermark; directly carrying out 16QAM demodulation on the received modulated carrier information embedded with the signal watermark to recover the carrier information;
B2) and (3) extracting a signal watermark:
obtaining a signal watermark to be extracted by a non-blind extraction method; segmenting the signal watermark according to the known CAZAC sequence length cr;
3) and a correlation coefficient calculation step:
calculating the correlation coefficients cor0 and cor1 of each segment in the signal watermark;
B4) watermark information extraction:
and extracting watermark information corresponding to each segment according to the correlation coefficients cor1 and cor0 of each segment in the calculated signal watermark.
The invention distinguishes the information to be sent, uses the public information as carrier information and uses the secret information as watermark information; on one hand, carrier information generates modulated carrier information in a 16QAM modulation mode; in another aspect, the watermark information is spread into a signal watermark that is embedded at low power in 4 locations of + -3 j of the 16QAM constellation of the modulated carrier information. Because 4 positions of +/-3 j are 4 points with the farthest European distance in a 16QAM constellation diagram, the embedding mode of the signal watermark can greatly reduce the influence of the embedding of the signal watermark on carrier information.
The invention has the advantages that the signal watermark is embedded in the specified part of the position, and the influence of the signal watermark on the carrier information is greatly reduced on the premise of ensuring low-power embedding. Compared with the existing scheme of embedding the signal watermark into all positions, the method ensures the transmission of the watermark information, and reduces the error rate of the carrier information to a great extent, so that the concealment of the whole communication process is improved.
Drawings
Fig. 1 is a comparison of BER of carrier information of a 16QAM modulation scheme, in which no watermark is present, a watermark is completely embedded, and a watermark is partially embedded.
Fig. 2 shows a comparison of the BER of the watermark in the 16QAM modulation scheme between the fully embedded watermark and the partially embedded signal.
Fig. 3 shows the correlation coefficient of the watermark of the signal in the full embedding watermark and the partial embedding mode in the 16QAM modulation mode.
Fig. 4 shows the channel capacity of the watermark for the full watermark embedding and the partial position embedding in the 16QAM modulation scheme.
Detailed Description
The terms used in the present invention are explained first:
16 QAM: the qam scheme includes 16 symbols and is a digital modulation scheme. The 16 symbols respectively correspond to 16 points of (3,3), (1,1), (3,1), (1,3), (-3, -3), (-1, -1), (-3, -1), (-1, -3), (-3,3), (-1,1), (-3,1), (-1,3), (3, -3), (1, -1), (3, -1), (1, -3) in the constellation diagram, wherein 4 positions of +/-3 j are 4 points with the longest European distance in the 16QAM constellation diagram.
Spread spectrum watermarking: the spread spectrum system has strong anti-interference capability, low interception probability characteristic and high confidentiality. The original watermark information can be spread spectrum modulated by a broadband pseudo-random noise sequence generator, and can be embedded into carrier information as a watermark signal to be embedded after modulation. For the present invention, the signal watermark length is the spread spectrum signal length, and it is required to ensure that the information length of the class a carrier is not less than the length of the spread spectrum signal watermark.
The implementation steps are as follows:
A. the transmitting terminal carries out the following steps:
A1) and carrier information position classification step:
distinguishing information to be sent, using public information as carrier information and using secret information as watermark information; classifying the carrier information according to the 16QAM constellation mapping positions, dividing 4 constellation positions of +/-3 j into an A class needing embedding the signal watermark, and dividing the rest 12 constellation mapping positions into a B class needing no embedding of the signal watermark;
A2) watermark information spreading step:
negotiating with the receiving end to generate two CAZAC sequences PN1 and PN0 with cross-correlation coefficient of 0 and length of 64, spreading the watermark information with value of 1 with sequence PN1, and spreading the watermark information with value of 0 with sequence PN0Frequency, obtaining a signal watermark
Wherein,
an ith sequence of segments representing a watermark of the signal, ω (k) representing a kth bit of watermark information;
A3) signal watermark embedding step:
superposing the signal watermark on the A-type modulated carrier information modulated by 16QAM according to the set low embedding strength, directly modulating the B-type carrier information by 16QAM to obtain modulated carrier information, and finally obtaining modulated carrier information X embedded with the signal watermark; the low embedding strength is the lowest strength under the condition of not influencing the extraction of the signal watermark by the receiving end;
A4) a sending step:
transmitting modulated carrier information embedded with the signal watermark;
B. the receiving end carries out the following steps:
B1) receiving and demodulating:
receiving modulated carrier information Y which is transmitted through a channel and embedded with a signal watermark;
w is represented as additive white noise on the channel that follows a complex gaussian distribution;
directly carrying out 16QAM demodulation on the received modulated carrier information embedded with the signal watermark to recover the carrier information;
B2) and (3) extracting a signal watermark:
obtaining a signal watermark to be extracted by a non-blind extraction method
Wherein, YAFor reception of noise-containing class A modulated carrier information, S'AThe recovered A-type carrier information is obtained;
and segmenting the signal watermark according to the known CAZAC sequence length cr:
in the formula, segment serial number i is 1,2 …, where a: B represents all integer elements from a to B, and the ith segment in wchip is the signal watermark
The (i-1) × cr +1 th bit to the (i × cr) th bit;
B3) and a correlation coefficient calculation step:
calculating the correlation coefficient of each segment in the signal watermark:
wherein x is respectively taken as a CAZAC sequence PN1 and PN0, and y represents each segment in wchip; when x is PN1, the cor is calculated to be cor 1; when x is PN0, the cor is calculated to be cor 0;
B4) watermark information extraction:
extracting watermark information corresponding to each segment according to the correlation coefficients cor1 and cor0 of each segment in the calculated signal watermark as follows:
wr (k) denotes the kth bit in the watermark information.
Simulation result
Fig. 1 shows that the length of a spreading sequence is 64, the length of information is 1000000, 16QAM modulation is adopted, and when no watermark is present and the watermark is completely embedded, the BER performance of the watermark embedding algorithm of the partial position embedding signal provided by the present invention is compared when the watermark embedding strength is 0.05. As can be seen from FIG. 1, there is a performance difference of 1dB between the information error code of partial position embedded watermark and the information error code of complete embedded watermark, and the difference of the information error code rate between the partial position embedded watermark and the information error code of no watermark is very small, thus greatly enhancing the concealment of information.
Fig. 2, fig. 3 and fig. 4 show graphs comparing watermark error code, watermark correlation coefficient and watermark channel capacity under the 16QAM full watermark embedding scheme and the partial position watermark embedding scheme, respectively. In the low signal-to-noise ratio area, the watermark error code, the watermark correlation coefficient and the watermark channel capacity of the partial embedding watermark scheme are obviously superior to those of the complete embedding watermark scheme. The invention not only ensures the concealment of information transmission, but also can realize high watermark authentication under low signal-to-noise ratio on the premise of meeting the low-power embedding.
Claims (3)
1. A communication method for embedding a signal watermark based on a 16QAM partial position, comprising the steps of:
A. the transmitting terminal carries out the following steps:
A1) and carrier information position classification step:
distinguishing information to be sent, using public information as carrier information and using secret information as watermark information; classifying the carrier information according to the 16QAM constellation mapping positions, dividing 4 constellation positions of +/-3 j into an A class needing embedding the signal watermark, and dividing the rest 12 constellation mapping positions into a B class needing no embedding of the signal watermark;
A2) watermark information spreading step:
negotiating with a receiving end to generate two constant envelope zero auto-correlation (CAZAC) sequences PN1 and PN0 with cross-correlation coefficient of 0 and the same length, spreading the watermark information with value of 1 by using the sequence PN1, and spreading the watermark information with value of 0 by using the sequence PN0 to obtain the signal watermark
Wherein,
an ith sequence of segments representing a signal watermark, ω (k) representing a k-th bit of watermark information;
A3) signal watermark embedding step:
superposing the signal watermark on the A-type modulated carrier information modulated by 16QAM according to the set low embedding strength, directly modulating the B-type carrier information by 16QAM to obtain modulated carrier information, and finally obtaining modulated carrier information X embedded with the signal watermark; the low embedding strength is the lowest strength under the condition that the signal watermark extraction of a receiving end is not influenced;
A4) a sending step:
transmitting modulated carrier information embedded with the signal watermark;
B. the receiving end carries out the following steps:
B1) receiving and demodulating:
receiving modulated carrier information Y which is transmitted through a channel and embedded with a signal watermark; directly carrying out 16QAM demodulation on the received modulated carrier information embedded with the signal watermark to recover the carrier information;
B2) and (3) extracting a signal watermark:
obtaining a signal watermark to be extracted by a non-blind extraction method
Wherein, YAIs received type A modulated carrier information, S'AThe recovered A-type carrier information is obtained;
and segmenting the signal watermark according to the known CAZAC sequence length cr:
in the formula, the segment sequence number i is 1,2 …; b represents all integer elements from A to B, and the ith segment in wchip is the signal watermark
The (i-1) × cr +1 th bit to the (i × cr) th bit;
B3) and a correlation coefficient calculation step:
calculating the correlation coefficient of each segment in the signal watermark:
wherein x is respectively taken as a CAZAC sequence PN1 and PN0, and y represents each segment in wchip; when x is PN1, the cor is calculated to be cor 1; when x is PN0, the cor is calculated to be cor 0;
B4) watermark information extraction:
extracting watermark information corresponding to each segment according to the correlation coefficients cor1 and cor0 of each segment in the calculated signal watermark as follows:
wr (k) denotes watermark information of the k-th bit.
2. The method of claim 1, wherein the CAZAC sequence length is set to 64.
3. The method of claim 1, wherein the signal watermark embedding strength α is set to 0.05.
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| US7577272B2 (en) * | 2005-11-30 | 2009-08-18 | Microsoft Corporation | Digital fingerprinting using synchronization marks and watermarks |
| CN101699508B (en) * | 2009-09-03 | 2012-01-11 | 中兴通讯股份有限公司 | Image digital watermark embedding and extracting method and system |
| CN108882236B (en) * | 2017-05-17 | 2021-04-13 | 中国电子科技集团公司第三十研究所 | Physical layer signal watermark embedding method based on S transformation |
| CN110290126B (en) * | 2019-06-19 | 2020-11-17 | 华中科技大学 | Radio frequency watermark transmission method based on FSK signal modulation |
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| CN103455972A (en) * | 2013-09-10 | 2013-12-18 | 山东省计算中心 | Multiple-bit spread spectrum watermark method with robustness enhanced by utilization of carrier |
| CN106209297A (en) * | 2016-07-05 | 2016-12-07 | 华中科技大学 | Radio frequency watermark embedding based on the modulation of QPSK signal and extracting method and system |
Non-Patent Citations (2)
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