An Optical Antenna Combination Selection Method for a Fully Generalized Spatial Modulation System

Abstract

The present invention provides an optical antenna combination selection method for a fully generalized spatial modulation system, including: obtaining a channel attenuation coefficient based on an atmospheric turbulence channel to construct a channel model; constructing a probability distribution of a channel state according to an atmospheric turbulence scintillation effect and a pointing error probability distribution function; obtaining the norm data of a channel column vector corresponding to any optical antenna combination, adding the optical antenna combination with a larger norm to a candidate set according to the norm data of the channel column vector, and adding the optical antenna combination with a smaller norm to a to-be-selected set according to the norm data of the channel column vector; selecting the optical antenna combination with a lower degree of correlation with the optical antenna combination in the candidate set from the to-be-selected set and adding it to the candidate set one by one to complete the selection of the optical antenna combination. The present invention only needs to perform vector operations, greatly reducing the computational complexity and effectively improving the bit error performance of the FGSM-FSO system.

Description

Technical Field

[0001] The present invention belongs to the technical field, and specifically relates to an antenna combination selection for a fully generalized space modulation system, which activates different numbers of optical antennas to transmit information by means of norms and similarity methods. Background Art

[0002] In recent years, free space optical communication (FSO) has received extensive attention due to its many advantages such as high security, high transmission bandwidth, strong anti-interference ability, and low cost. However, its development is severely affected by atmospheric turbulence and pointing errors. To counter the effects of atmospheric turbulence and pointing errors on the FSO communication link, multiple input multiple output (MIMO) technology has been widely applied in FSO systems. As a new type of optical multiple input multiple output (OMIMO) technology, spatial modulation (SM) improves the transmission rate of the system by jointly carrying information with traditional digital modulation signals and optical antennas. Since only one optical antenna is activated within its symbol period, the influence of co-frequency interference between channels can be avoided. Therefore, it is crucial to use efficient optical multiple input multiple output technology to resist atmospheric turbulence and pointing errors and improve the performance of the FSO communication system.

[0003] Since spatial modulation can only activate one transmitting antenna at the same time, the improvement of the system transmission rate is limited. Generalized Spatial Modulation (GSM) can activate multiple antennas, but its transmission rate is not ideal when sending the same information at the same time. Based on the GSM technology, Fully Generalized Spatial Modulation (FGSM) transmits signals by activating multiple or even all optical antennas, effectively improving the utilization rate of spatial resources and enhancing the transmission performance of the system. However, in the FGSM-FSO system, when multiple optical antennas send the same signal simultaneously, the receiving end will generate spatial correlation due to inter-channel interference, which will then affect the bit error performance of the system. To solve this problem, a suitable optical antenna selection strategy needs to be adopted. Wang Huiqin et al. proposed a method of selecting the best transmitting antenna by using the channel norm maximization method in the FGSM system. This method does not require traversing all possible antenna combinations and has a low computational complexity. However, it does not consider the correlation between antennas. Due to the non-orthogonality of the transmitting antennas, it may lead to a reduction in the system capacity. Rajasheka R et al. proposed an antenna selection algorithm based on Euclidean distance in the GSM system. By traversing the Euclidean distances between all antennas and selecting antennas with lower correlation, the bit error performance was improved, but its extremely high computational complexity limits the application of this algorithm. Zhaojie Sun et al. proposed an antenna selection algorithm based on cross entropy, which selects the optimal antenna from a finite set of solutions without traversing, effectively reducing the algorithm complexity. However, this algorithm is only suitable for spatial modulation systems.

[0004] Although the above research on antenna selection algorithms has its own characteristics, they all have the defects of poor bit error performance or high complexity. Moreover, the current research on FSO optical space modulation systems is in its infancy. The existing technologies mainly focus on Gamma-Gamma channels or log-normal channels, and fail to comprehensively reflect the system performance problems under other atmospheric effects. In an actual FSO optical space modulation system, in addition to atmospheric turbulence, pointing errors caused by misalignment between the transmitter and the receiver, and atmospheric attenuation caused by atmospheric absorption and scattering will all reduce the transmission performance of the system. In addition, different antenna selection strategies will also lead to obvious differences in the bit error performance of the system. Therefore, the present invention proposes an optical antenna selection algorithm based on channel norm and Sorenson similarity coefficient to improve the channel capacity and anti-fading ability of the system, which can effectively counteract the adverse effects of atmospheric turbulence, pointing errors, and atmospheric attenuation. Summary of the Invention

[0005] The present application aims at the deficiencies of the prior art and proposes an optical antenna combination selection method for a fully generalized spatial modulation system.

[0006] The technical solution adopted by this application to solve the above technical problems is as follows:

[0007] An optical antenna combination selection method for a fully generalized spatial modulation system, which uses the channel norm and the Sørensen similarity coefficient for optical antenna combination selection, includes:

[0008] Based on the atmospheric turbulence channel, a channel model is constructed by using the combined influence of pointing error and atmospheric attenuation to obtain the channel attenuation coefficient; at the same time, based on the atmospheric turbulence channel, the probability distribution of the channel state is constructed according to the atmospheric turbulence scintillation effect and the probability distribution function of the pointing error;

[0009] According to the probability distribution of the channel state, a channel coefficient matrix is obtained, and the channel column vector norm data corresponding to any optical antenna combination is obtained. According to the channel column vector norm data, the optical antenna combinations with larger norms are added to the candidate set, and the optical antenna combinations with smaller norms are added to the set of candidates to be selected;

[0010] According to the channel column vector norm data corresponding to the optical antenna combination, the optical antenna combinations with a lower degree of correlation with the optical antenna combinations in the candidate set are selected from the set of candidates to be selected one by one and added to the candidate set to complete the optical antenna combination selection.

[0011] The obtaining of the channel coefficient matrix according to the probability distribution of the channel state and the obtaining of the channel column vector norm data corresponding to any optical antenna combination include:

[0012] The channel norm Hi corresponding to any optical antenna combination is as follows: η i = ||H i || F , where ‖Hi‖ F is the F norm, i ∈ {1, 2, ···, K}, and H i is the superposition of the channel column vectors corresponding to the i-th optical antenna combination, which is expressed as: where K is the number of all possible optical antenna combinations, and h iNa is the Na-th column of the channel matrix of the transmitting optical antenna combination.

[0013] Define an empty candidate set P, find the optical antenna combination with the largest channel norm in the set of candidates to be selected K, and denote the optical antenna combination with the largest norm as H k-max , and add this antenna combination to P.

[0014] The selecting of the optical antenna combinations with a lower degree of correlation with the optical antenna combinations in the candidate set P from the set of candidates to be selected K one by one and adding them to the candidate set includes:

[0015] Let the Sørensen similarity coefficient between two optical antenna combinations be: And the weight formula is: W i = ||H i || 2 *(1 - β i,j );

[0016] Obtain the Sørensen similarity coefficients of each remaining optical antenna combination in the candidate set K and the optical antenna combinations in the candidate set P. The similarity coefficient is calculated as follows:

[0017] Select the corresponding candidate optical antenna combination in the candidate set K according to the similarity coefficient, multiply the norms of the sum of the channel column vectors corresponding to the candidate optical antenna combination, and calculate the weight: W i = ‖H i ‖ 2 *(1 - β i,k-max ); β i,k-max is the similarity coefficient between the i-th antenna combination in K and the antenna combination in P. Then, select the optical antenna combination with the largest weight according to the weight formula, remove it from the candidate set K, and add it to the candidate set P.

[0018] Continue to calculate the Sørensen similarity coefficients of the remaining K - 2 optical antenna combinations and all optical antenna combinations in the candidate set P. Take the maximum value after calculating each remaining optical antenna combination and the antenna combinations in P as the similarity degree of the optical antenna combination with the set P, then calculate the weight of the optical antenna combination, and add the optical antenna combination with the largest calculated weight to the candidate set P until the number of optical antenna combinations in the candidate set P reaches the set value G, and then stop the selection.

[0019] The obtaining step for the number of optical antenna combinations in the candidate set P to reach the set value G includes:

[0020] Using the FGSM - FSO system model to obtain the number of optical antenna combinations reaching the set value G includes:

[0021] Suppose there are N t optical antennas, N r photoelectric detectors, and the transmitting end activates N a optical antennas each time, N a = 1, ···, N t ;

[0022] Adopting L - order PSK, then the number of all possible optical antenna combinations is

[0023] Since the number of optical antenna combinations used must be a power of 2, only G types need to be selected from K, where G is:

[0024] Construct a channel model using the channel attenuation coefficient; meanwhile, based on the atmospheric turbulence channel, construct the probability distribution of the channel state according to the atmospheric turbulence scintillation effect and the probability distribution function of the pointing error, including:

[0025] The combined channel attenuation coefficient is modeled as: h = h a h p h l ; where h a is the channel fading caused by atmospheric turbulence; h l is the atmospheric attenuation; h p is the pointing error; when the transmission distance is fixed, h l can be considered a fixed constant, which follows the Beer-Lambert law and can be described as h l = exp(-σL), where L is the transmission distance and σ is the attenuation coefficient; h p is the pointing error, and its probability density function can be expressed as: where ξ = w zeq / 2σ s represents the ratio between the equivalent beam radius at the receiving end and the standard deviation of the pointing error offset, A0 = [erf(v)] 2 is the pointing loss, a is the detector radius, w z is the equivalent beam width;

[0026] According to the atmospheric turbulence scintillation effect and the probability distribution function of the pointing error, obtain the probability distribution of the channel state under the combined effect, expressed as: where is the conditional probability density function in the presence of atmospheric turbulence attenuation h a ; is the probability density distribution function of atmospheric turbulence h a .

[0027] The beneficial effects brought by this application are:

[0028] The method described in this application calculates and sorts the channel column vector norms of all optical antenna combinations according to the channel state information of the FGSM-FSO system, and then adds the optical antenna combination with the largest norm to the candidate set. Next, for each unselected optical antenna combination, calculate the similarity coefficient between its channel column vector and the channel column vectors of the selected optical antenna combinations, and multiply the obtained similarity coefficient by the norm of the corresponding unselected optical antenna combination as its weight. Finally, add the unselected optical antenna combination with the largest weight to the candidate set, and repeat the above steps until the number of optical antenna combinations in the candidate set meets the requirements to obtain the final set of transmitting optical antenna combinations. The method described in this application is an incremental algorithm. After calculating the channel norm, the Sorensen similarity coefficient is calculated iteratively. The larger the similarity coefficient, the greater the probability of misjudging the optical antenna combination at the receiving end. In addition, the method described in this application only needs to perform vector operations, greatly reducing the computational complexity and effectively improving the bit error performance of the FGSM-FSO system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flowchart of the method described in this application.

[0030] Figure 2 is a block diagram of the FGSM-FSO system structure described in this application.

[0031] Figure 3 is a schematic diagram of the FGSM-FSO system simulation process.

[0032] Figure 4 is a flowchart of the operation of the optical antenna selection method described in this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solution described in this application will be further described below with reference to the accompanying drawings. Specific Embodiment 1:

[0035] This application provides an embodiment:

[0036] As Figure 1 , a method for selecting optical antenna combinations of a fully generalized spatial modulation system, which uses channel norm and Sorensen similarity coefficient for optical antenna combination selection, includes:

[0037] Based on the atmospheric turbulence channel, a channel model is constructed by using the combined influence of pointing error and atmospheric attenuation to obtain the channel attenuation coefficient; at the same time, based on the atmospheric turbulence channel, the probability distribution of the channel state is constructed according to the atmospheric turbulence scintillation effect and the probability distribution function of the pointing error; the channel coefficient matrix is obtained according to the probability distribution of the channel state, and the norm data of the channel column vector corresponding to any optical antenna combination is obtained. According to the norm data of the channel column vector, the optical antenna combination with a larger norm is added to the candidate set, and the optical antenna combination with a smaller norm is added to the candidate set; according to the norm data of the channel column vector corresponding to the optical antenna combination, the optical antenna combination with a lower correlation degree with the optical antenna combination in the candidate set is selected from the candidate set and added to the candidate set one by one to complete the selection of the optical antenna combination.

[0038] Using the FGSM-FSO system model to obtain the number of optical antenna combinations reaching the set value G, including:

[0039] Suppose there are N t optical antennas, N r photodetectors, and the transmitter activates N a optical antennas each time, N a = 1, ···, N t ;

[0040] If L-order PSK is adopted, the number of all possible optical antenna combinations is

[0041] Since the number of optical antenna combinations used must be an integer power of 2, only G of them need to be selected from K, where G is:

[0042] In the FGSM-FSO system used in this embodiment, such as Figure 2 When performing optical antenna combination selection at the transmitter, two core problems need to be solved: one is to select optical antennas with higher channel gain as much as possible to improve the received signal-to-noise ratio; the other is to select optical antenna combinations with lower correlation degrees to enhance the distinguishability between optical antennas.

[0043] To solve the above problems, the optical antenna combination selection method for the fully generalized space modulation system proposed in this embodiment is as follows:

[0044] Step 1: Establish a channel model. Based on the Gamma-Gamma atmospheric turbulence channel, considering the combined influence of pointing error and atmospheric attenuation at the same time, the combined channel attenuation coefficient is modeled as: h = h a h p h l ; where h ais the channel fading caused by atmospheric turbulence; h l is the atmospheric attenuation; h p is the pointing error; when the transmission distance is fixed, h l can be considered as a fixed constant, which follows the Beer-Lambert law and can be described as h l = exp(-σL), where L is the transmission distance and σ is the attenuation coefficient; h p is the pointing error, and its probability density function can be expressed as: where ξ = w zeq / 2σ s represents the ratio between the equivalent beam radius at the receiving end and the standard deviation of the pointing error offset, A0 = [erf(v)] 2 is the pointing loss, a is the detector radius, w z is the equivalent beam width;

[0045] According to the atmospheric turbulence scintillation effect and the pointing error probability distribution function, the probability distribution of the channel state under the joint effect is obtained and expressed as: where is the conditional probability density function in the presence of atmospheric turbulence attenuation h a ; is the probability density distribution function of atmospheric turbulence h a ;

[0046] Step 2: The FGSM-FSO system model is as Figure 2 shown; using the FGSM-FSO system model to obtain the number of optical antenna combinations reaching the set value G, including:

[0047] Suppose there are N t optical antennas and N r photodetectors. Each time at the transmitter, N a optical antennas are activated, N a = 1, ···, N t ;

[0048] If PSK of order L is adopted, then all possible numbers of optical antenna combinations are

[0049] Since the number of optical antenna combinations used must be an integer power of 2, then only G types need to be selected from K, where G is:

[0050] Step 3: Assume that both the transmitter and the receiver know the current channel state information. Then, the transmitter can select a suitable optical antenna combination according to the current channel state information and complete the mapping of the corresponding information according to the mapping relationship, so as to transmit the signal;

[0051] Step 4: Optical antenna selection algorithm. Obtain the channel coefficient matrix H according to the probability distribution function under the combined effect in Step 1, calculate and sort the norms of the channel column vectors corresponding to each optical antenna combination, then select the optical antenna combination with the largest norm and add it to the candidate set P. Finally, select the optical antenna combinations with a relatively low degree of correlation with the optical antenna combinations in the candidate set from the set K to be selected and add them to the candidate set P one by one.

[0052] Step 5: As Figure 3 , after the signal X at the transmitting end is modulated, the modulated signal is received by a photodetector after passing through the atmospheric channel. Let the output signal of the photodetector be Y = ηHx + N, where: N is additive white Gaussian noise with a mean of zero and a variance of σ n 2 ; η is the photoelectric conversion efficiency, and H is an N r ×N t -dimensional channel fading matrix.

[0053] Step 6: The received signal at the receiving end is demodulated using the maximum likelihood detection algorithm, and its expression is: where and represent the index of the detected active optical antenna and the transmitted modulation symbol respectively. Finally, the detected active optical antenna index and modulation symbol are inverse mapped according to the mapping relationship to recover the original signal.

[0054] Specifically, the specific steps of Step 4 are as follows:

[0055] Step 401: In the FGSM-FSO system, considering there are N t optical antennas and N r photodetectors, and the transmitting end activates N a (N a = 1, ···, N t ) optical antennas each time. At this time, the alternative set of all optical antenna combinations in the FGSM-FSO system is types, but the available optical antenna combinations are types. Therefore, there are a total of selectable schemes.

[0056] Step 402: Initialize where represents the empty set, and then add one combination to P in each step until the selection of optical antenna combinations is completed.

[0057] Preferably, as Figure 4, calculate the channel column vectors and norms corresponding to each possible active optical antenna combination and sort them. Select the optical antenna combination with the largest norm and add it to the candidate set P. The idea is to select the sub-channel with the largest norm to transmit information, and essentially, it is the maximum received signal-to-noise ratio. In the next step where n > 1, calculate the Sørensen similarity coefficient between the channel column vectors corresponding to each unselected optical antenna combination and the channel column vectors corresponding to the selected optical antenna combinations respectively. Multiply the calculated similarity coefficient by the norm of the sum of the channel column vectors corresponding to the corresponding unselected optical antenna combination. Select the optical antenna combination with the largest product and remove it from the candidate set K, and add it to the candidate set P until the selection of G optical antenna combinations is completed.

[0058] Specific examples are as follows:

[0059] First, calculate the channel column vectors and the norm of H i as follows: η i = ||H i || F , where ‖Hi‖ F is the F-norm, i ∈ {1, 2, ···, K}, and H i is the superposition of the channel column vectors corresponding to the i-th optical antenna combination, expressed as: h iNa is the Na-th column of the channel matrix of the i-th optical antenna combination. Traverse and calculate the F-norms of all combinations in the K set, find the channel vector corresponding to the optical antenna combination with the largest norm, denoted as H K-max , and move this optical antenna combination from the K set to the set P;

[0060] Then, the Sørensen similarity coefficient between two optical antenna combinations is: And the weight formula is: W i = ||H i || 2 *(1 - β i,j ); Obtain the Sørensen similarity coefficients between each remaining optical antenna combination in the candidate set K and the optical antenna combinations in the candidate set P. The similarity coefficient is calculated as follows: Select the corresponding candidate optical antenna combination in the candidate set K according to the similarity coefficient, multiply the norm of the sum of the channel column vectors corresponding to the candidate optical antenna combination, and calculate the weight: W i = ‖H i ‖ 2 *(1 - β i,k-max ); β i,k-max is the similarity coefficient between the i-th antenna combination in K and the antenna combination in P;

[0061] Next, calculate the similarity coefficients between the remaining K - 2 optical antenna combinations and the two active optical antenna combinations in the candidate set P. After calculating for each of the remaining optical antenna combinations and the optical antenna combinations in the candidate set P, two values are obtained, and the larger value is taken as the final similarity coefficient of this optical antenna combination with the candidate set P. Then, calculate the weights of the remaining combinations in the candidate set K according to the weight formula, and add the optical antenna combination with the largest final weight, that is, the one with both a larger channel norm and a lower correlation, to the candidate set P;

[0062] Finally, repeat the above steps to calculate the weights of all optical antenna combinations between the remaining candidate set K and the candidate set P, and then add the optical antenna combination with the largest weight to the candidate set P. When the number of optical antenna combinations in the candidate set P reaches the set value G, stop the loop, and the optical antenna combinations in the candidate set P are the active optical antenna selection scheme.

[0063] When the method described in this application performs optical antenna selection, it fully considers the channel vector norm, calculates the channel norm of each optical antenna combination accordingly, and selects the optical antenna combination with the largest norm and adds it to the candidate set. Selecting the optical antenna combination with the largest norm can, on the one hand, reduce the bit error rate of the FGSM - FSO system, and on the other hand, the computational complexity of this method is extremely low; at the same time, when performing optical antenna selection, by calculating the similarity coefficients between the optical antenna combinations and the combinations in the candidate set, the optical antenna combinations with smaller similarity coefficients are successively selected and added to the candidate set. The optical antenna combinations selected according to this method have higher recognizability at the receiving end and better bit error performance of the FGSM - FSO system; moreover, the computational complexity of the method described in this application is only related to the number of optical antennas and has nothing to do with the modulation order, and it can be applied to application scenarios with different modulation orders; and, in order to accurately evaluate the performance of the FGSM - FSO system under the real turbulent channel, the method described in this application comprehensively considers the combined effects of atmospheric turbulence, pointing error, and atmospheric attenuation; furthermore, by introducing full - generalized spatial modulation in the FSO system and making full use of all possible optical antenna combinations to transmit information, the transmission performance of the FGSM - FSO system is further improved.

[0064] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily make changes or substitutions, which all belong to the protection scope of this application. Therefore, the protection scope of this application is subject to the protection scope of the claims.

Claims

1. A method for selecting an optical antenna combination for a fully generalized spatial modulation system, which uses a channel norm and a Thoresen similarity coefficient to select an optical antenna combination, characterized in that: include: Based on the atmospheric turbulence channel, the channel attenuation coefficient is obtained by using the joint influence of pointing error and atmospheric attenuation to construct the channel model; at the same time, based on the atmospheric turbulence channel, the probability distribution of the channel state is constructed according to the atmospheric turbulence scintillation effect and the pointing error probability distribution function; Obtain a channel coefficient matrix according to the probability distribution of the channel state, and obtain channel column vector norm data corresponding to any optical antenna combination, add the optical antenna combination with the largest norm to the candidate set according to the channel column vector norm data, and add the remaining optical antenna combinations with small channel column vector norm data to the candidate set; According to the channel column vector norm data corresponding to the optical antenna combination, optical antenna combinations with the lowest correlation with the optical antenna combinations in the candidate set are selected from the candidate set and added to the candidate set one by one to complete the optical antenna combination selection, including: Obtaining similarity coefficients between the remaining optical antenna combinations in the candidate set and the optical antenna combination with the largest norm; Selecting a corresponding candidate optical antenna combination in the candidate set according to the similarity coefficient, and multiplying the norms of the channel column vectors and corresponding to the candidate optical antenna combination to obtain a weight; Select the optical antenna combination with the largest weight, remove it from the candidate set, and add it to the candidate set; Respectively obtain similarity coefficients of the remaining K-2 optical antenna combinations in the candidate set and the two optical antenna combinations to be activated in the candidate set, obtain two values, and take the larger value as the final similarity coefficient between the optical antenna combination and the candidate set; According to the weights of the remaining combinations in the candidate set, the optical antenna combination with the maximum channel norm and the lowest correlation is added to the candidate set; Repeat the above steps until the number of optical antenna combinations in the candidate set reaches a set value G, then stop the loop, and the optical antenna combination in the candidate set is the activated optical antenna selection scheme; Assume that the Thoresen similarity coefficient between two optical antenna combinations is: And the weight formula is: W i =||H i || 2 *(1-β i,j ); The Thoresen similarity coefficient of each remaining optical antenna combination in the candidate set and the optical antenna combination in the candidate set is obtained. The similarity coefficient is calculated as follows: According to the similarity coefficient, the corresponding candidate optical antenna combination in the candidate set is selected, and the norms of the channel column vectors and corresponding to the candidate optical antenna combination are multiplied, and the weight is calculated: W i =||H i || 2 *(1-β i，k-max );β i，k-max is the similarity coefficient between the ith antenna combination in the candidate set and the antenna combination in the candidate set; The step of obtaining that the number of optical antenna combinations in the candidate set reaches a set value G comprises: The FGSM-FSO system model is used to obtain the number of optical antenna combinations to reach the set value G, including: Assume that there is N t Optical antennas, N r The transmitter activates N photodetectors each time. a Optical antennas, N a =1,···,N t ; Using L-order PSK, the number of all possible optical antenna combinations is K: Since the number of optical antenna combinations used must be an integer power of 2, it is only necessary to select G types from the candidate set, where G is: H i is the superposition of the channel column vectors corresponding to the i-th optical antenna combination; H j is the superposition of the channel column vectors corresponding to the j-th optical antenna combination; H k-max is the channel vector corresponding to the optical antenna combination with the largest norm.

2. The optical antenna combination selection method for a fully generalized spatial modulation system according to claim 1, characterized in that: The obtaining of a channel coefficient matrix according to the probability distribution of the channel state, and obtaining channel column vector norm data corresponding to any optical antenna combination, includes: The channel column vector and H corresponding to any optical antenna combination i The norm of is as follows: η i =||H i || F , where ||H i || F is the F-norm, i∈{1,2,···,K}, H i It is expressed as: is the Nth channel matrix of the i-th optical antenna combination b List.

3. The optical antenna combination selection method for a fully generalized spatial modulation system according to claim 1, characterized in that: The channel attenuation coefficient constructs a channel model; at the same time, based on the atmospheric turbulence channel, the probability distribution of the channel state is constructed according to the atmospheric turbulence scintillation effect and the pointing error probability distribution function, including: The joint channel attenuation coefficient is modeled as: h = h a h p h l ; Among them, h a Channel fading caused by atmospheric turbulence; Among them, h l is the atmospheric attenuation, and when the transmission distance is constant, h l is considered to be a fixed constant that obeys the Beers-Lambert law, described as h l =exp(-σL), L is the transmission distance, σ is the attenuation coefficient; Among them, h p is the pointing error, and its probability density function can be expressed as: where ξ=w zeq / 2σ s A0 is the ratio of the equivalent beam radius at the receiving end to the standard deviation of the pointing error offset, A0 = [erf(v)] 2 To point to the loss, a is the detector radius, w z is the equivalent beam width; According to the atmospheric turbulence scintillation effect and the pointing error probability distribution function, the probability distribution of the channel state under the joint effect is obtained, which is expressed as: in, is the channel fading caused by atmospheric turbulence h a The conditional probability density function under the existence of; is the channel fading caused by atmospheric turbulence h a The probability density distribution function of .

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