Space-time shift keying constellation generation and bit mapping method in secure communication scene

Abstract

The invention discloses a space-time shift keying constellation generation and bit mapping method in a secure communication scene. The method comprises the following steps: S1, a base station acquires statistical channel information of related links of legal users and eavesdropping users; s2, the base station designs a space-time shift keying dispersion matrix set, a power distribution scheme, an amplitude phase shift keying constellation set and a bit mapping scheme according to the channel information; s3, according to the input bit stream, the base station modulates the modulated amplitude phase shift keying symbol to amplitude phase shift keying, the modulated amplitude phase shift keying symbol is sent by the base station, and the space-time shift keying symbol is modulated to the intelligent reflecting surface and is transmitted in a space-time shift keying mode; and S4, after the modulated amplitude phase shift keying symbol and the space-time shift keying symbol are propagated through a wireless channel, a legal user and an eavesdropping user receive joint information, and then the space-time shift keying symbol and the amplitude phase shift keying symbol are jointly detected and demodulated through a maximum likelihood detection mode. According to the invention, the network spectrum utilization rate can be improved and the bit error rate performance of legal users is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario. Background Art

[0002] With the increasing scarcity of existing spectrum resources, the industry is currently committed to developing data communications in higher frequency bands, such as millimeter waves, terahertz waves, visible light, etc. This makes the devices for processing information more complex and brings an increase in power consumption. The index modulation technology can transmit information without consuming additional radio frequency chains, and can significantly reduce the system power consumption while improving the spectrum efficiency. It is particularly suitable for scenarios such as large-scale Internet of Things and ultra-dense networks with strict requirements for energy efficiency and spectral efficiency in the 5G / 6G era.

[0003] Due to the limitation of orthogonal coding in traditional space-time block codes, the matrix dimension and coding rate are limited. In 2010, S Sugiura et al. first proposed the space-time shift keying technology in "IEEE Transactions on Communications". The space-time shift keying extends the index dimension to the time dimension on the basis of space modulation, and transmits index information by activating different dispersion matrices, having the ability to flexibly balance the rate and diversity. Compared with the space-time block code scheme, the space-time shift keying has no limitation of orthogonal coding, and completely relies on the differences of different space-time matrices to distinguish bit information. In high-dimensional coding scenarios, this index modulation scheme has better error code performance.

[0004] Since index modulation can carry additional information in a low-power and low-cost manner, it has good applications in Internet of Things devices. However, because the power consumption that Internet of Things devices can bear is often small, it is difficult to use traditional encryption technologies to ensure information security. Therefore, introducing intelligent reflecting surfaces and physical layer security methods is an effective means to improve the security of index information. In addition, from the recent schemes combining intelligent reflecting surfaces and index technologies, the academic community's exploration of new index modulation schemes mainly focuses on higher symbol transmission rates and more novel transmission schemes, while ignoring their security.

[0005] On the one hand, although the introduction of intelligent reflecting surfaces can improve the transmission performance of index modulation, in the previous combined applications of intelligent reflecting surfaces and index modulation, the intelligent reflecting surfaces either only play the beamforming function or only play the function of carrying index bits, and there is also a lack of relevant research on the combination of intelligent reflecting surfaces and space-time shift keying. Early research on space-time shift keying mostly used precoding modulation at the transmitter to implement space-time shift keying. This method not only needs to consider the constraint of transmission power but also is limited by the number of antennas. Although in 2024, X Jin et al. first attempted the combination of intelligent reflecting surfaces and space-time shift keying in "IEEE Transactions on Vehicular Technology", due to the pursuit of high-rate transmission of index information and excessive focus on the ability of intelligent reflecting surfaces to carry index bits, the beamforming ability of intelligent reflecting surfaces was not maximized.

[0006] On the other hand, the design of the space-time shift keying dispersion matrix set is relatively difficult: The current design criteria for the space-time shift keying dispersion matrix include two types, namely the discrete input continuous output memoryless channel capacity and the Chernoff upper bound, which respectively correspond to the reliability and effectiveness of the space-time shift keying system. Since the discrete input continuous output memoryless channel capacity contains multiple integrals of the channel, it is difficult to obtain a closed-form expression. After approximation by the Monte Carlo averaging method, the computational complexity of generating the space-time shift keying dispersion matrix is greatly increased. In addition, traditional random generation and heuristic search schemes also have the problem of unstable search, resulting in difficulties in designing the space-time shift keying dispersion matrix set. Although the Chernoff upper bound simplifies the search space, the Chernoff upper bound only has a simple expression under the Rayleigh channel, and its application scenarios are limited. Summary of the Invention

[0007] In order to overcome the above deficiencies of the prior art, the purpose of the present invention is to provide a method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario, which organically combines an intelligent reflecting surface and space-time shift keying. By optimizing the dispersion matrix, that is, different phase shift patterns of the intelligent reflecting surface, it can simultaneously achieve intelligent reflecting surface beamforming to ensure physical layer security and carry index bits. While improving the network spectrum utilization rate, it ensures information secure communication in a low-power manner, and at the same time utilizes the diversity and coding gain advantages brought by space-time shift keying to improve the bit error performance of legitimate users.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A method for generating space-time shift keying constellations and bit mapping in a secure communication scenario. In the scenario of the integration of space-time shift keying and intelligent reflecting surface, it includes a base station, an intelligent reflecting surface, a single-antenna legitimate user, and a single-antenna eavesdropping user. The intelligent reflecting surface is controlled by the base station for its phase shift matrix to transmit space-time shift keying symbols. Each transmission occupies T symbol intervals. The method includes the following steps:

[0010] S1, the base station obtains the statistical channel information of the relevant links between the legitimate user and the eavesdropping user;

[0011] S2, the base station designs a set of space-time shift keying dispersion matrices {Φ1,…,Φ m ,…,Φ M}, a power allocation scheme w, an amplitude phase shift keying constellation set {s1,…,s l ,…,s L}, and a bit mapping scheme Γ according to the channel information; where Φ m represents the m-th dispersion matrix, and s l represents the l-th amplitude phase shift keying symbol;

[0012] S3, according to the input bit stream, the base station modulates the modulated amplitude phase shift keying symbols onto the amplitude phase shift keying and sends them. The space-time shift keying symbols are modulated onto the intelligent reflecting surface and transmitted in the way of space-time shift keying;

[0013] S4, after the modulated amplitude phase shift keying symbols and space-time shift keying symbols propagate through the wireless channel, the legitimate user and the eavesdropping user receive the combined information, which are y b and y e respectively, and then jointly detect and demodulate the space-time shift keying symbols and amplitude phase shift keying symbols through maximum likelihood detection.

[0014] Further, in S1, the base station obtains the statistical channel information between the legitimate user and the base station and between the eavesdropping user and the base station by the legitimate user sending training pilot signals to the base station and the pilot signal leakage of the eavesdropping user. The base station receives these pilot information and measures the statistical channel information between itself and the legitimate user and the eavesdropping user according to the pilot sequence.

[0015] In S1, the channel information includes noise power, Rice fading coefficient, distance, departure angle, and arrival angle information.

[0016] Further, the specific method of step S2 is as follows:

[0017] S21, the base station uses Gray code mapping. The combined symbol s l Φ m corresponding to the b-th Gray code satisfies {b→(m,l)|b=(m - 1)L + 1};

[0018] The index of the combined symbol is b → (m, l);

[0019] S22. The base station optimizes the space-time shift keying dispersion matrix set {Φ1, …, Φ , …, Φ m , …, Φ M}, the power allocation scheme w, the amplitude-phase shift keying constellation set {s1, …, s l , …, s L} and the bit mapping scheme Γ according to the minimum Hamming-Euclidean distance between the received symbol constellations of legitimate users. Since the Hamming distance is introduced as a scaling factor of the Euclidean distance in the criterion, the optimization process will force the constellation points to be automatically arranged;

[0020] The Hamming-Euclidean distance is expressed as:

[0021]

[0022] where H 1,b = diag(h rb,LoS )·h ar,LoS w, H2 = h ar,LoS w, h rb,LoS is the line-of-sight component of the intelligent reflecting surface-legitimate user channel, and h ar,LoS is the line-of-sight component of the base station-intelligent reflecting surface channel; P w is the base station transmission power, k is the Rice factor of the Rice channel, and α ar , α rb , α ab are the loss coefficients of the base station-intelligent reflecting surface, intelligent reflecting surface-legitimate user, and base station-legitimate user channels respectively. S23. The base station jointly optimizes the space-time shift keying dispersion matrix set and the amplitude-phase shift keying constellation set through the penalty function-assisted gradient descent algorithm, and the problem is transformed into the following formula:

[0023]

[0024] where is the Euclidean distance between the received symbols at the eavesdropping user, γ th is its maximum threshold, t is the slack variable, and λ and μ are the penalty factors;

[0025] S24. The base station obtains the optimal power allocation matrix w through the semidefinite relaxation technique;

[0026] S25. The base station alternately optimizes by repeatedly executing S23 and S24, and finally obtains the optimal space-time shift keying symbol set, amplitude-phase shift keying symbol constellation set, and optimal power allocation matrix that maximize the minimum Hamming-Euclidean distance.

[0027] In S25, the design criterion of the base station is to maximize the minimum Hamming-Euclidean distance between the received symbol constellations of legitimate users:

[0028]

[0029] is the Hamming distance for symbol pairs between, B is the symbol set, D ED is the corresponding Euclidean distance, is the expectation for the channel. Further, the specific steps of step S3 are as follows:

[0030] S31. Take the optimal space-time shift keying symbol set and amplitude shift keying symbol constellation set optimized in the previous step as the modulation symbol set, map the symbols to binary Gray codes, and the base station selects the space-time shift keying symbols and amplitude shift keying symbols to be sent according to the bit stream to be transmitted;

[0031] S32. Select the mapped transmission symbols Φ m ,…,Φ M} and amplitude shift keying symbol set {s1,…,s l ,…,s L} from the space-time shift keying symbol set according to the binary bit stream to be transmitted, where the space-time shift keying symbol Φ m and s l . Among them, the space-time shift keying symbol Φ m is M-order modulation, so it carries log2M bits of information. The base station controls the intelligent reflecting surface through the controller to regulate the corresponding dispersion matrix for transmitting additional log2M bits of index information and realizing beamforming;

[0032] The amplitude shift keying symbol s l is L-order modulation, so it carries log2L bits of information. The base station itself selects the corresponding amplitude shift keying symbol from the signal constellation set to send, and the two parts of information are used to jointly carry the bit information that the transmitting end needs to send.

[0033] Further, step S4 is specifically to receive, detect, and demodulate the space-time shift keying symbols and amplitude shift keying symbols transmitted in S3. The specific steps are as follows:

[0034] S41. Legitimate users and eavesdropping users will receive the signals transmitted in S3. After the signals are transmitted through the wireless channel, the received signal y b of the legitimate user is expressed as:

[0035]

[0036] The received signal y e of the eavesdropping user is expressed as:

[0037]

[0038] where h rb 、h ar 、h re 、 are the instantaneous channels between the intelligent reflecting surface - legitimate user, base station - intelligent reflecting surface, intelligent reflecting surface - eavesdropping user, base station - legitimate user, and base station - eavesdropping user respectively, and n B and n E are the additive Gaussian noises at the receiving ends of the legitimate user and the eavesdropping user;

[0039] S42. The legitimate user and the eavesdropping user respectively perform maximum likelihood detection on the signals received in S41 through the instantaneous channel information, and jointly demodulate the space - time shift keying symbols and the amplitude - phase shift keying symbols:

[0040]

[0041] where is the estimated symbol at the receiving end, is the corresponding signal;

[0042] S43. The legitimate user and the eavesdropping user remap the symbols demodulated in S42 back to the binary Gray code to obtain the actually received bit - stream information, and the upper bound of the average bit - error rate can be expressed as:

[0043]

[0044] where Q(·) is the right - tail function of the standard normal distribution. Since the symbol distances of the signals received by the eavesdropping user are smaller, the bit - error rate will be higher than that of the legitimate user.

[0045] Advantages of the present invention:

[0046] (1) Since the information transmitted by the base station is divided into two parts, the present invention considers a joint coding scheme. On this basis, a maximized minimum Hamming - Euclidean distance criterion is constructed. This design criterion introduces the Hamming distance as a weight factor for the symbol Euclidean distance, which can guarantee the best bit - error performance. And since in the Rayleigh channel, the expected channels of the legitimate user and the eavesdropping user have no difference, the present invention uses the Rice channel model and gives the theoretical value of the Hamming - Euclidean distance of the expected channel on the Rice channel.

[0047] (2) The scheme proposed by the present invention can effectively guarantee the security of the system, can greatly improve the receiving performance of the legitimate user and restrict the receiving performance of the eavesdropper, realizes the simultaneous guarantee of physical - layer security and the transmission of index information on the intelligent reflecting surface, and achieves secure transmission communication in a low - cost manner.

[0048] (3) Due to the introduction of the symbol distance constraint for eavesdropping users in the present invention, the proposed scheme of the present invention can continuously improve the bit error performance of legitimate users as the number of intelligent reflecting units increases, while the bit error performance of eavesdroppers remains almost unchanged after being suppressed. Therefore, increasing the number of reflecting units can effectively improve the security performance of the system, providing a guarantee for the large-scale application of practical intelligent reflecting surfaces. Description of the Drawings

[0049] Figure 1 It is a model diagram of the intelligent reflecting surface integrated space-time shift keying transmission system used in the present invention.

[0050] Figure 2 It is a schematic diagram of the transmission scheme used in the present invention.

[0051] Figure 3 It is the overall flowchart of the implementation of the present invention.

[0052] Figure 4 It is the received symbol constellation diagram of legitimate users and eavesdropping users in the present invention.

[0053] Figure 5 It is the bit error performance diagram of legitimate users and eavesdropping users in the present invention under different numbers of reflecting units. Detailed Implementation Manner

[0054] The present invention will be further described in detail below with reference to the drawings.

[0055] As Figure 1 shown, in the scenario of integrating space-time shift keying and intelligent reflecting surface, it includes a base station, an intelligent reflecting surface, a single-antenna legitimate user, and a single-antenna eavesdropping user. In addition to directly transmitting information, the base station also adjusts the phase shift of the intelligent reflecting surface through a controller and modulates the space-time shift keying information on the intelligent reflecting surface to transmit space-time shift keying symbols. Each transmission occupies T symbol intervals. After the signal propagates through the wireless channel, the single-antenna legitimate user will receive the direct signal from the base station and the signal modulated by the intelligent reflecting surface. Among them, the single-antenna eavesdropper will try to eavesdrop on the propagated signal and demodulate the useful information.

[0056] As Figure 2 shown, the base station hands over a part of the B-bit binary bit stream information to the intelligent reflecting surface for transmission through space-time shift keying, and the other part is transmitted by the base station itself through amplitude phase shift keying. At the receiving end, the combined signal s l Φ m is detected, and the two parts of information can be demodulated through maximum likelihood detection. In this way, the base station can effectively improve the spectral efficiency.

[0057] As Figure 3 shown, the implementation steps of the present invention are as follows:

[0058] S1. The base station obtains the statistical channel information of the links related to the legitimate user and the eavesdropping user, including information such as noise power, Rice fading coefficient, distance, departure angle, and arrival angle.

[0059] S2. The base station designs a set of space-time shift keying dispersion matrices {Φ1, …, Φ m , …, Φ M}, a power allocation scheme w, an amplitude phase shift keying constellation set {s1, …, s l , …, s L}, and a bit mapping scheme Γ, where Φ m represents the m-th dispersion matrix, s l represents the l-th amplitude phase shift keying symbol, and the index of the combined symbol is b → (m, l). The design criterion of the base station is to maximize the minimum Hamming-Euclidean distance between the received symbol constellations of the legitimate users. is the Hamming distance between symbol pairs , B is the symbol set, D ED is the corresponding Euclidean distance, is the expectation for the channel.

[0060] S3. According to the input bit stream, the base station modulates log2L bits onto the amplitude phase shift keying and transmits them. Additionally, log2M bits of information are modulated onto the intelligent reflecting surface and transmitted in a space-time shift keying manner.

[0061] S4. After the modulated amplitude phase shift keying symbols and space-time shift keying symbols propagate through the wireless channel, the legitimate user and the eavesdropping user receive the combined information, which are y b and y e respectively. Then, the space-time shift keying symbols and amplitude phase shift keying symbols are jointly detected and demodulated through maximum likelihood detection.

[0062] Further, the base station obtains the channel statistical information between the legitimate user and the base station, and between the eavesdropping user and the base station, by the legitimate user sending a training pilot signal to the base station and the pilot signal leakage of the eavesdropping user. The base station receives these pilot information and measures the statistical channel information between itself and the legitimate user and the eavesdropping user according to the pilot sequence.

[0063] Further, the specific method of step S2 is as follows:

[0064] S21. The base station adopts Gray code mapping, and the combined symbol s l Φ m corresponding to the b-th Gray code satisfies {b → (m, l)|b = (m - 1)L + 1}, where m and l are the index numbers of the space-time shift keying and amplitude phase shift keying symbols respectively.

[0065] S22, the base station optimizes the space-time shift keying dispersion matrix set {Φ1, …, Φ , …, Φ m , …, Φ M}, the power allocation scheme w, the amplitude phase shift keying constellation set {s1, …, s l , …, s L}, and the bit mapping scheme Γ according to the minimum Hamming-Euclidean distance between the received symbol constellations of legitimate users. Since the Hamming distance is introduced as a scaling factor of the Euclidean distance in the criterion, the optimization process will force the constellation points to be automatically arranged;

[0066] The Hamming-Euclidean distance is expressed as:

[0067]

[0068] where H 1,b = diag(h rb,LoS )·h ar,LoS w, H2 = h ar,LoS w, h rb,LoS is the line-of-sight component of the intelligent reflecting surface-legitimate user channel, and h ar,LoS is the line-of-sight component of the base station-intelligent reflecting surface channel; P w is the base station transmission power, k is the Rice factor of the Rice channel, and α ar , α rb , α ab are the loss coefficients of the base station-intelligent reflecting surface, intelligent reflecting surface-legitimate user, and base station-legitimate user channels respectively;

[0069] S23, the base station jointly optimizes the space-time shift keying dispersion matrix set and the amplitude phase shift keying constellation set through the penalty function-assisted gradient descent algorithm, and the problem is transformed into the following formula:

[0070]

[0071] where is the Euclidean distance between the received symbols at the eavesdropping user, γ th is its maximum threshold, t is the slack variable, and λ and μ are the penalty factors;

[0072] S24, the base station obtains the optimal power allocation matrix w through the semidefinite relaxation technique;

[0073] S25, the base station alternately optimizes by repeatedly executing S23 and S24, and finally obtains the optimal space-time shift keying symbol set, amplitude phase shift keying symbol constellation set, and optimal power allocation matrix that maximize the minimum Hamming-Euclidean distance.

[0074] Furthermore, the specific steps of step S3 are as follows:

[0075] S31. Take the optimal space-time shift keying symbol set and amplitude shift keying symbol constellation set obtained in the previous step as the modulation symbol set, map the symbols to binary Gray codes, which can further improve the bit error performance. The base station selects the space-time shift keying symbols and amplitude shift keying symbols to be transmitted according to the bit stream to be transmitted.

[0076] S32. Select the transmitted symbols Φ m ,…,Φ M} and amplitude shift keying symbol set {s1,…,s l ,…,s L} according to the binary bit stream to be transmitted. Among them, the space-time shift keying symbol Φ m and s l . The space-time shift keying symbol Φ m is M-order modulation, so it carries log2M bits of information. The base station controls the intelligent reflecting surface to regulate the corresponding dispersion matrix through the controller to transmit additional log2M bits of index information and achieve beamforming;

[0077] The amplitude shift keying symbol s l is L-order modulation, so it carries log2L bits of information. The base station itself selects the corresponding amplitude shift keying symbol from the signal constellation set to send for transmitting traditional communication signals.

[0078] Further, step S4 needs to receive, detect and demodulate the space-time shift keying symbols and amplitude shift keying symbols transmitted in S3. The specific steps are as follows:

[0079] S41. The legitimate user and the eavesdropping user will receive the signals transmitted in S3. After the signals are transmitted through the wireless channel, the received signal y b of the legitimate user can be expressed as:

[0080]

[0081] The received signal y e of the eavesdropping user can be expressed as:

[0082]

[0083] Where h rb , h ar , h re , are the instantaneous channels between the intelligent reflecting surface - legitimate user, base station - intelligent reflecting surface, intelligent reflecting surface - eavesdropping user, base station - legitimate user, and base station - eavesdropping user respectively. n B and n E are the additive Gaussian noises at the receiving ends of the legitimate user and the eavesdropping user.

[0084] S42. The legitimate user and the eavesdropping user respectively perform maximum likelihood detection on the signals received in S41 through the instantaneous channel information, and jointly demodulate the space-time shift keying symbols and the amplitude-phase shift keying symbols:

[0085]

[0086] where is the estimated symbol at the receiving end, is the corresponding signal.

[0087] S43. The legitimate user and the eavesdropping user remap the symbols demodulated in S42 back to the binary Gray code to obtain the actually received bit stream information. The upper limit of the average bit error rate can be expressed as:

[0088]

[0089] where Q(·) is the right-tail function of the standard normal distribution. Since the symbol distance of the signals received by the eavesdropping user is smaller, the bit error rate will be higher than that of the legitimate user.

[0090] The performance of the present invention will be further described below in combination with simulation experiments.

[0091] Figure 4 shows the received symbol constellation diagrams of the legitimate user and the eavesdropping user of the present invention. The space-time shift keying and the amplitude-phase shift keying each modulate 1 bit of information, and a total of 2 bits of fourth-order information are transmitted. It can be clearly seen that the constellation diagram of the symbols received by the legitimate user can clearly distinguish four symbols. However, due to the beamforming of the optimized space-time dispersion matrix generating a null around the eavesdropping user, the Euclidean distance between multiple symbols is small, making the constellation of the received symbols Figure 4 disperse the information of multiple symbols together, and the effective information cannot be distinguished. Therefore, it can be shown that the proposed scheme of the present invention has high security performance.

[0092] Figure 5 shows the bit error performance diagrams of the legitimate user and the eavesdropping user under different numbers of reflecting elements. As the number of reflecting elements increases, it can be seen that the average bit error rate of the legitimate user drops rapidly, while the bit error rate of the eavesdropping user shows the same level under different numbers of reflecting elements. This phenomenon is due to the introduction of the constraint on the Euclidean distance between the symbols received by the eavesdropping user in the optimization. This constraint makes the bit error rate of the eavesdropping user not lower than a certain value. Therefore, as the number of reflecting elements increases, the bit error rate of the eavesdropping user will not change much.

[0093] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of the present invention.

Claims

1. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario, characterized in that It includes the following steps: S1. The base station obtains the statistical channel information of the links related to the legitimate user and the eavesdropping user; S2, the base station designs a space-time shift keying dispersion matrix set {Φ1, …, Φ m , …, Φ M}, a power allocation scheme w, an amplitude phase shift keying constellation set {s1, …, s l , …, s L}, and a bit mapping scheme Γ; where Φ m represents the m-th dispersion matrix, and s l represents the l-th amplitude phase shift keying symbol; S3. According to the input bit stream, the base station modulates the modulated amplitude phase shift keying symbols onto the amplitude phase shift keying and transmits them by the base station, and modulates the space-time shift keying symbols onto the intelligent reflecting surface and transmits them in the way of space-time shift keying; S4. After the modulated amplitude shift keying symbols and space-time shift keying symbols propagate through the wireless channel, the legitimate user and the eavesdropping user receive the combined information, which are y b and y e , and then jointly detect and demodulate the space-time shift keying symbols and amplitude shift keying symbols by means of maximum likelihood detection.

2. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 1, characterized in that, In S1, the base station obtains the statistical channel information between the legitimate user and the base station and between the eavesdropping user and the base station by the legitimate user sending a training pilot signal to the base station and the pilot leakage signal of the eavesdropping user respectively. The base station receives these pilot information and measures the statistical channel information between itself and the legitimate user and the eavesdropping user according to the pilot sequence.

3. A space-time shift keying constellation generation and bit mapping method in a secure communication scenario according to claim 1, characterized in that In S1, the channel information includes noise power, Rice fading coefficient, distance, departure angle and arrival angle information.

4. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 1, characterized in that, The specific method of step S2 is as follows: S21, the base station uses Gray code mapping, and the combined symbol s corresponding to the b-th Gray code l Φ m satisfies {b → (m, l)|b = (m - 1)L + 1}; the index of the combined symbol is b → (m, l); S22, the base station optimizes the space-time shift keying dispersion matrix set {Φ1, …, Φ , …, Φ m , …, Φ M}, the power allocation scheme w, the amplitude phase shift keying constellation set {s1, …, s l , …, s L}, and the bit mapping scheme Γ according to the minimum Hamming-Euclidean distance between the received symbol constellations of legitimate users; the optimization process forces the constellation points to be automatically arranged; The Hamming-Euclidean distance is expressed as: where H 1,b = diag(h rb,LoS )·h ar,LoS w, H2 = h ar,LoS w, h rb,LoS is the line-of-sight component of the intelligent reflecting surface-legitimate user channel, and h ar,LoS is the line-of-sight component of the base station-intelligent reflecting surface channel; P w is the transmit power of the base station, k is the Rice factor of the Rice channel, and α ar , α rb , α ab are the loss coefficients of the base station-intelligent reflecting surface, intelligent reflecting surface-legitimate user, and base station-legitimate user channels respectively; S23. The base station jointly optimizes the space-time shift keying dispersion matrix set and the amplitude phase shift keying constellation set through the penalty function-assisted gradient descent algorithm, and the problem is transformed into the following formula: where is the Euclidean distance between received symbols at the eavesdropper, γ th is its maximum threshold, t is a slack variable, and λ and μ are penalty factors; S24. The base station obtains the optimal power allocation matrix w through the semi-definite relaxation technique; S25. The base station alternately optimizes by repeatedly executing S23 and S24, and finally obtains the optimal space-time shift keying symbol set, amplitude phase shift keying symbol constellation set and optimal power allocation matrix that maximize the minimum Hamming-Euclidean distance.

5. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 4, characterized in that, In S25, the design criterion of the base station is to maximize the minimum Hamming-Euclidean distance between the received symbol constellations of the legitimate users; is the Hamming distance between symbol pairs B is the symbol set, D ED is the corresponding Euclidean distance is the expectation for the channel 6. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 4, characterized in that, The specific steps of step S3 are as follows: S31. Take the optimal space-time shift keying symbol set and amplitude phase shift keying symbol constellation set optimized in the previous step as the modulation symbol set, map the symbols to the binary Gray code, and the base station selects the space-time shift keying symbols and amplitude phase shift keying symbols to be sent according to the bit stream to be transmitted; S32, select the transmitted symbols Φ m ,…,Φ M} and the amplitude shift keying symbol set {s1,…,s l ,…,s L} for mapping according to the binary bit stream to be transmitted, where the space-time shift keying symbol Φ m and s l , the space-time shift keying symbol Φ m is M-order modulation, so it carries log2M bits of information. The base station controls the intelligent reflecting surface through the controller to adjust the corresponding dispersion matrix for transmitting additional log2M bits of index information and realizing beamforming; Amplitude Phase Shift Keying symbol s l For L-level modulation, it carries log2L bits of information. The base station itself selects the corresponding Amplitude Phase Shift Keying symbol from the signal constellation set for transmission. The two parts of information are used together to carry the bit information that the transmitting end needs to send.

7. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 6, characterized in that, Step S4 is specifically to receive, detect and demodulate the space-time shift keying symbols and amplitude phase shift keying symbols transmitted in S3. The specific steps are as follows: S41. The legitimate user and the eavesdropping user will receive the signal transmitted in S3. After being transmitted through the wireless channel, the received signal y of the legitimate user b is expressed as: Eavesdrop on the received signal y of the user e It is expressed as: where h rb , h ar , h re , are the instantaneous channels between IRS-legitimate user, BS-IRS, IRS-eavesdropper, BS-legitimate user, and BS-eavesdropper, respectively, and n B and n E are the additive Gaussian noises at the receivers of the legitimate user and the eavesdropper; S42. The legitimate user and the eavesdropping user respectively perform maximum likelihood detection on the signals received in S41 through the instantaneous channel information, and jointly demodulate the space-time shift keying symbols and amplitude phase shift keying symbols; wherein is the estimated symbol at the receiving end, is the corresponding signal; S43. The legitimate user and the eavesdropping user remap the symbols demodulated in S42 back to the binary Gray code to obtain the actually received bit stream information, and the upper limit of the average bit error rate is expressed as: where Q(·) is the right tail function of the standard normal distribution.

8. A method for generating a space-time shift keying constellation and bit mapping in a secure communication scenario according to claim 1, characterized in that, In the scenario of the fusion of space-time shift keying and intelligent reflecting surface, it includes a base station, an intelligent reflecting surface, a single-antenna legitimate user and a single-antenna eavesdropping user. The intelligent reflecting surface is controlled by the base station for its phase shift matrix to transmit space-time shift keying symbols, and each transmission occupies T symbol intervals.

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