CN117675455A - Communication method, system and storage medium - Google Patents
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Abstract
The disclosure relates to a communication method, a system and a storage medium, belongs to the technical field of communication, and can effectively inhibit crosstalk in an OAM communication system. A method of communication, comprising: receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam has a user signal loaded thereon; demultiplexing and demodulating the multiplexed OAM beam to obtain user receiving signals with each path of distortion; and simultaneously carrying out channel equalization on the multipath distorted user received signals by adopting a channel equalization mode combining blind equalization and blind source separation to obtain each path of corrected user received signals.
Description
Technical Field
The present disclosure relates to the field of communications technologies, and in particular, to a communication method, system, and storage medium.
Background
In an orbital angular momentum (Orbital Angular Momentum, OAM) multiplexed communication system, orthogonality between OAM modes can be cross-talk when the actual communication channel is disrupted by atmospheric turbulence, thereby affecting the quality of the communication. In the related art, multiple-Input multiple-Output (MIMO) equalization is generally used to reduce the multiplexing crosstalk. However, the equalization model adopted in the related art is a multi-stage blind equalization model, that is, only one path of source signal can be equalized in each blind equalization operation. Under the condition that channel estimation is inaccurate or the equalization effect of a pre-stage information source is poor, the performance of the equalizer is deteriorated due to multi-stage blind equalization, and the equalization effect of MIMO is further affected.
Disclosure of Invention
The purpose of the present disclosure is to provide a communication method, a system, and a storage medium, which can effectively suppress crosstalk in an OAM communication system.
According to a first aspect of the present disclosure, there is provided a communication method comprising: receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam has a user signal loaded thereon; demultiplexing and demodulating the multiplexed OAM beam to obtain user receiving signals with each path of distortion; and simultaneously carrying out channel equalization on the multipath distorted user received signals by adopting a channel equalization mode combining blind equalization and blind source separation to obtain each path of corrected user received signals.
Optionally, the channel equalization method that combines blind equalization and blind source separation is used to perform channel equalization on multiple paths of distorted user received signals simultaneously to obtain each path of corrected user received signals, and the method includes: expanding each distorted user receiving signal into an expansion matrix matched with the length of a channel matrix; determining a current user receiving signal corrected by each path based on each path of the expansion matrix and a current crosstalk compensation value corresponding to each path of the expansion matrix; determining a current error per path based on the current corrected statistical modulus of the imaginary part and the real part of the user received signal and the user input signal at the transmitting end, wherein the current error per path comprises the blind equalization error and the blind source separation error; updating the current crosstalk compensation value based on the current error of each path; determining an orthogonalized crosstalk compensation value based on the updated crosstalk compensation value; and taking the orthogonalized crosstalk compensation value as a new current crosstalk compensation value, and returning to the step of determining the current corrected user receiving signal of each path for iteration until the current error of each path reaches a preset error value.
Optionally, the expanding the distorted user received signals of each path into an expansion matrix matched with the length of the channel matrix includes:
expanding the distorted user received signals of each path into an expansion matrix matched with the length of the channel matrix based on the following constraint conditions:
wherein L represents the length of each sub-equalizer of the equalizer for performing channel equalization, and the user received signal of each distortion is L-dimensionally spread; t represents the sum total of the sub-channels of the equalizer,wherein T is j Representing the length of the sub-channel; />Representing performing an upward rounding operation; m represents the input signal path number of the equalizer; n represents the number of output signal paths of the equalizer.
Optionally, the proportion of the blind equalization error and the blind source separation error in the current error is determined according to the requirement that the source separation can be ensured and the current error can reach the preset error value.
Optionally, the updating the current crosstalk compensation value based on the current per-path error includes:
updating the current crosstalk compensation value by using an iterative mode based on the current error of each path, wherein a step factor mu of the iterative mode meets the following conditions:
wherein lambda is max Is the maximum eigenvalue of the autocorrelation matrix of the distorted user received signal of each path.
Optionally, the iterative manner is implemented by the following formula:
wherein j represents the j-th channel equalization in the channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; w (W) j (t-1) represents a crosstalk compensation value obtained by performing t-1 iteration on the jth channel equalization; μ represents an iteration step of the crosstalk compensation value; e (t) represents an error obtained by performing the t-th iteration on the j-th channel equalization;representing a transpose of the expansion matrix of the corrected user received signal.
Optionally, the determining the orthogonalized crosstalk compensation value based on the updated crosstalk compensation value is implemented by the following formula:
wherein,representing an orthogonalized crosstalk compensation value obtained by carrying out the t-th iteration on the jth channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; />Representing the transpose of the first-pass channel equalization matrix.
According to a second aspect of the present disclosure, there is provided a communication system comprising: a receiver for receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam has a user signal loaded thereon; a demultiplexer for demultiplexing the multiplexed OAM beam; the demodulator is used for demodulating the demultiplexed signals to obtain user receiving signals with each path of distortion; and the equalizer is used for carrying out channel equalization on the multipath distorted user received signals simultaneously by adopting a channel equalization mode combining blind equalization and blind source separation to obtain each path of corrected user received signals.
According to a third aspect of the present disclosure there is provided a non-transitory computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of the method of any of the first aspects of the present disclosure.
According to a fourth aspect of the present disclosure, there is provided a communication system comprising: a memory having a computer program stored thereon; a processor for executing the computer program in the memory to implement the steps of the method of any of the first aspects of the present disclosure.
By adopting the technical scheme, the blind equalization and the blind source separation are combined in the channel equalization mode, so that the purpose of simultaneously separating the blind equalization and the blind source can be achieved by simultaneously restraining the cost function of the blind equalization and the cost function of the blind source separation, all the transmission signals transmitted by the transmitting end can be simultaneously recovered, crosstalk in the OAM multiplexing communication system is effectively restrained, and the performance and the communication quality of the OAM multiplexing communication system are improved. Moreover, compared with the related art, the situation that the equalizer effect is deteriorated due to multi-stage blind equalization is avoided, and the error rate of the equalized output signal is reduced more than that of the related art.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
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The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:
fig. 1 is a flow chart of a communication method according to one embodiment of the present disclosure.
Fig. 2 is a schematic block diagram of a communication method according to one embodiment of the present disclosure.
Fig. 3 is a schematic diagram of a blind equalization algorithm incorporating blind source separation according to an embodiment of the present disclosure.
Fig. 4 is a schematic block diagram of a communication system according to one embodiment of the present disclosure.
Fig. 5 is a block diagram of a first communication system, shown according to an exemplary embodiment.
Fig. 6 is a block diagram of a second communication system, shown according to an exemplary embodiment.
Detailed Description
Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
It should be noted that, all actions for acquiring signals, information or data in the present disclosure are performed under the condition of conforming to the corresponding data protection rule policy of the country of the location and obtaining the authorization given by the owner of the corresponding device.
The OAM multiplexing technology exploits the space dimension to communicate, and provides a new way for increasing the communication capacity. The vortex beam has OAM, which means that the topological charge number l can be infinite, and the modes are orthogonal to each other. These two properties make OAM multiplexing technology a new communication multiplexing mode, which can not only communicate in a new space dimension and increase channel capacity, but also use the orthogonality to make this dimension and the previous dimension not mutually influence, and is well compatible.
Fig. 1 is a flow chart of a communication method according to one embodiment of the present disclosure. As shown in fig. 1, the communication method may include the following steps S11 to S13.
In step S11, a multiplexed OAM beam transmitted by an atmospheric turbulence channel is received, wherein the multiplexed OAM beam is loaded with a user signal.
After the user signal input by the transmitting end is processed by the optical modulator and the mode converter, the user obtains multiplexed OAM beams, and the multiplexed OAM beams are received by the receiving end through the transmission of the atmospheric turbulence channel.
In step S12, the multiplexed OAM beam is demultiplexed and demodulated to obtain a distorted user received signal for each path.
The received multiplexed OAM beam is demultiplexed and demodulated at the receiving end. Each of the user received signals demultiplexed and demodulated is distorted due to various noise and crosstalk present in the atmospheric turbulence channel.
In step S13, a channel equalization method combining blind equalization and blind source separation is adopted to perform channel equalization on multiple paths of distorted user received signals at the same time, so as to obtain corrected user received signals of each path.
For example, assuming that there are N distorted received signals, the N distorted received signals are simultaneously channel equalized, where the channel equalization is a channel equalization method that combines blind equalization and blind source separation.
The blind equalization may be any blind equalization algorithm that is capable of correcting the phase of the constellation of the distorted user received signal, e.g., a multimode blind equalization algorithm (Modified Constant Modulus Algorithm, MCMA).
Blind source separation may be any blind source separation algorithm capable of source separation, such as the multiuser peak (Multiuser Kurtosis, MUK) algorithm.
By adopting the technical scheme, the channel equalization mode is a channel equalization mode combining blind equalization and blind source separation, so that the purpose of simultaneously separating blind equalization from blind sources can be achieved by simultaneously restraining the cost function of blind equalization from the cost function of blind source separation, all the transmission signals transmitted by the transmitting end can be simultaneously recovered, crosstalk in an OAM multiplexing communication system is effectively restrained, and the performance and communication quality of the OAM multiplexing communication system are improved. Moreover, compared with the related art, the situation that the equalizer effect is deteriorated due to multi-stage blind equalization is avoided, and the error rate of the equalized output signal is reduced more than that of the related art.
Fig. 2 is a schematic block diagram of a communication method according to one embodiment of the present disclosure.
As shown in fig. 2, at the transmitting end, a user input signal is input to the optical modulator, wherein the user input signal is denoted as a j (t),j∈[1,N]N represents how many user inputs in totalAnd (5) entering. User input signal a j (t) may be an input signal modulated by a modulation method such as 16QAM or QPSK, and by using these modulation methods, the information transmission rate can be effectively increased.
The light modulator then outputs the user input signal a j (t) onto a beam containing orbital angular momentum, such as a Gaussian beam, a Laguerre-Gaussian (LG) beam, or the like. In the following description, the user input signal a is used j (t),j∈[1,N]Is described as being modulated onto an LG beam. The LG beam can be expressed as:
wherein r and θ represent the radiation radius and azimuth angle, respectively; l represents the topological charge number, and the larger the numerical value of l is, the larger the carrier aperture radius is; p is a radial index; omega 0 Representing the beam waist radius;representing Laguerre polynomials; exp (ilθ) is the helical optical phase of the gaussian optical addition.
The light beam modulated by the optical modulator is converted into an OAM light beam by an OAM mode converter, and then the N-path OAM light beam is multiplexed and transmitted coaxially by an OAM multiplexer. Then, the OAM multiplexed beam modulated with information can be expressed as:
wherein U is MUX (r, θ, t) represents an OAM multiplexed beam; r and θ represent the radius of radiation and azimuth angle, respectively, and t represents time; n represents how many user inputs in total; l (L) j Representing the topological charge number of the jth path OAM beam; a is that lj (r) represents the intensity amplitude of the OAM beam; e, e -iljθ Represents the helical phase of the OAM beam, thus the OAM beam LG lj (r, θ) available A lj (r)e -iljθ And (3) representing. User input signal a j (t),j∈[1,N]Loading onto LG beam amplitude is similar to the process of amplitude modulation.
The multiplexed OAM beam loaded with information about the user input signal is then transmitted via the atmospheric turbulence channel to the receiving end. Namely, the OAM multiplexing beam of formula (2) is transmitted through free space, and under the influence of an atmospheric turbulence channel, the OAM multiplexing transmission beam obtained by the receiving end can be expressed as:
wherein,representing an OAM multiplexed transmission beam received at a receiving end; />A random phase screen for simulating atmospheric turbulence; v (t) represents additive white gaussian noise in an atmospheric turbulence channel; />Reflects the nature of the atmospheric turbulence channel and is therefore +.>It can be shown that the light beam loaded with the user input signal is subject to atmospheric turbulence on its phase. Will->Expanded into a form of fourier series, as follows:
wherein l q A topological load number value of the q-th expansion term is represented, and q represents the number of Fourier series expansion;coefficients, which are fourier series, can be expressed as:
to more clearly demonstrate this expansion process, j=1 in equation (2) is taken as the first user input signalFor example, a first path of user input signal a 1 (t) being subjected to atmospheric turbulence transmission +.>The impact, reaching the receiving end, can be expressed as:
wherein,is the topological charge number is l 1 Intensity amplitude at the time; />A phase factor representing an atmospheric turbulence channel; l (L) 1n Representing that due to l 1 The topology charge number affected by the power diffusion; the value of n has infinity. By taking the equation (4) into the equation (6), the Fourier series coefficient U can be obtained 1n (r, t) can be expressed as:
then, the formula (4) and the formula (6) are brought into the formula (7), and the following can be obtained:
wherein Δ=l 1n -l 1 ；g Δ (r) is a turbulence influencing factor; l (L) q A topology charge number value representing a q-th expansion term; l (L) 1 Representing the number of topology charges of the 1 st path; l (L) 1n Represented by l 1 The topology charge number affected by the power spread. As can be seen from the analysis of the formula (8), when the topological charge number is l 1 If the OAM beam does not have the phenomenon of power dispersion, namely, the condition of no atmospheric turbulence with the delta value of zero; conversely, if the OAM beam has the phenomenon of power dispersion, the adjacent topological charge number l is influenced 1n I.e. atmospheric turbulence where delta is not zero.
In summary, the transmission of N OAM multiplexed beams loaded with information about the user input signal through atmospheric turbulence eventually reaches the receiving end, can be expressed as follows according to equation (6):
wherein U is MUXn (r, t) is the fourier coefficient of the N-way signal;represented as the spiral phase of the OAM beam. According to formula (8) can be expressed as:
wherein Δ' =l n -l j The method is used for representing the difference value between the nth path topology charge number and the jth path topology charge number. It is worth noting that the larger the numerical difference of the topological charges l between adjacent channels, the smaller the crosstalk between them. Will eta nj (r) is defined as a channel crosstalk factor, which can be expressed as:
thus, taking equations (10), (11), and (9) into equation (3), an OAM multiplexed beam that is transmitted through atmospheric turbulence (i.e., an OAM multiplexed beam received at an OAM demultiplexer) can be expressed as:
after the distorted OAM multiplexed beam transmission reaches the receiving end, the OAM demultiplexes, the OAM mode inverse converter performs inverse conversion processing and demodulates the OAM multiplexed beam through the optical demodulator, wherein the inverse conversion processing refers to that each path of received signal is multiplied by a spiral phase factor opposite to the topological charge number of the input end at the receiving end so as to remove the spiral phase factor. That is, the signal arriving at the OAM demultiplexer is converted into a user received signal b with distortion per channel by inverse transformation k (t),k∈[1,N]This process can be expressed as:
wherein,indicating that there is->OAM beams of opposite topological charge numbers; l (L) j 、l k 、l n The method comprises the steps of respectively representing the jth path topological charge number, the kth path topological charge number and the nth path topological charge number, wherein j represents a variable of the signal path number and n represents a variable of the signal path number; />Indicating that there is->Reverse topologyAmplitude of the load number OAM beam;indicating that there is->The spiral phase factor of an OAM beam of opposite topology charges. For multiplexed signals->Multiplying byThe demultiplexing purpose can be achieved.
For a user communication system with N inputs and N outputs, the expression of N receiving end user signals can be written according to the formula (13) as follows:
formula (14) is written in the form of a matrix, which can be expressed as:
B＝H·A+V (15)
wherein the channel influencing factor h kj And v k (t) are respectively expressed as:
to solve the crosstalk problem, MIMO equalization is introduced to correct crosstalk between signals. The signal output through the MIMO equalizer is denoted as c j (t),j∈[1,N]The specific process is as follows:
wherein C= [ C ] 1 (t)c 2 (t)...c N (t)]，A＝[a 1 (t)a 2 (t)...a N (t)]The method comprises the steps of carrying out a first treatment on the surface of the W is a MIMO equalization system function, and may be selected according to the equalization method, and may be basically expressed as a matrix of weighting coefficients ω:
wherein omega ij ,i,j∈[1,N]Defined as the complex weighting coefficients of the equalizer.
As can be seen from equation (18), equalizer output signal c j (t),j∈[1,N]The vector matrix C is subjected to equalizer input signal b j (t),j∈[1,N]Vector matrix B and equalizer coefficient ω ij ,i,j∈[1,N]Is provided, the influence of the vector matrix W of (a). Equalizer input signal b j (t),j∈[1,N]And is the input signal a of the user at the transmitting end j (t),j∈[1,N]Distorted signal obtained after transmission through atmospheric turbulence channel, i.e. equalizer input signal b j (t) is determined by the variation of the characteristics of the atmospheric turbulence channel, i.e. by the atmospheric turbulence channel influence factor h kj And v k The effect of (t); equalizer coefficient vector omega ij ,i,j∈[1,N]The setting of (2) should be changed according to the characteristics of the atmospheric turbulence channel, so that the error rate of the output result of the equalizer is reduced. The W matrix is the channel compensation of the H matrix, also called crosstalk compensation value, the better the compensation effect, the equalizer output signal c j (t),j∈[1,N]The closer to the sender user input signal a j (t),j∈[1,N]。
Thus, the key to the equalizer performing channel equalization is to determine the W matrix in an iterative manner. How channel equalization is performed is described in detail below.
Firstly, expanding each distorted user receiving signal into an expansion matrix matched with the length of a channel matrix, and determining the current user receiving signal corrected by each channel based on each expansion matrix and the current crosstalk compensation value corresponding to each expansion matrix. That is, according to equation (18), the equalizer output signal may be expressed as:
wherein,is equalizer received signal b j (t),j∈[1,N]For example, a Toeplitz matrix) for the purpose of enabling each distorted user to receive signal b j (t) is expanded into a matrix that matches the matrix length of the atmospheric turbulence channel. The expansion matrix can be expressed as:
wherein,the matrix obtained by L-dimensionally expanding the jth received signal is shown. L is the length of each sub-equalizer, the condition should be satisfied:
wherein,T j representing the length of the sub-channel; />Performing upward rounding operation; m represents the input signal path number of the equalizer; n represents the number of output signal paths of the equalizer; t represents the sum total of equalizer subchannels.
Then, based on the current each corrected statistical model of the user received signal and the imaginary and real parts of the transmitting end user input signal, determining the current each error, wherein the current each error comprises a blind equalization error and a blind source separation error. This will be described in detail in connection with the blind equalization algorithm shown in fig. 3.
Fig. 3 is a schematic diagram of a blind equalization algorithm incorporating blind source separation according to an embodiment of the present disclosure. As shown in fig. 3, if the MIMO equalizer is M input N output, N equalizer vectors and N common iterations are required, as follows:
wherein M sub-equalizers form a large equalizer W j (t), and coefficients (e.g., ω) of the sub-equalizer 1j (t)、ω 2j (t)…ω Mj (t)) is L.
The jth path cost function of the blind equalization algorithm combined with blind source separation is as follows:
J(W j )＝J blind equalization (W j )+J Blind source separation (W j ) (24)
Wherein J is Blind equalization (W j ) Cost function, J, representing blind equalization algorithm Blind source separation (W j ) Representing the cost function of a blind source separation algorithm, the former compensating for channel distortion due to multipath effects in order to ensure equalization capability, and the latter ensuring source separation. To recover the common equalization of the N source signals, the equalization scheme of fig. 3, the combined cost function of equation (26), may be used to perform the iterative operation of the equalizer. It will be appreciated by those skilled in the art that equation (26) is a cost function that combines the MUK algorithm and the MCMA algorithm, and that if other blind source separation algorithms other than the MUK algorithm and other blind equalization algorithms other than the MCMA algorithm are employed, equation (26) will change accordingly as the algorithm changes.
Taking a MUK algorithm as an example, the blind source separation algorithm adopts the following cost functions:
taking the MCMA algorithm as an example, the blind equalization algorithm adopts the following cost function:
wherein:
R r ＝E[|Re(a)| 4 ]/E[|Re(a)| 2 ]
R i ＝E[|Im(a)| 4 ]/E[|Im(a)| 2 ]
substituting equation (25) and equation (26) into equation (24) can obtain the cost function of the MUK-MCMA algorithm (i.e. the MCMA blind equalization algorithm combined with the MUK blind source separation algorithm, which is a blind equalization algorithm based on high order statistics) as follows:
from equation (27), it can be seen that the cost function of the MUK-MCMA algorithm is subject to equalizer output signal c j (t),j∈[1,N]Input of user signal a j (t),j∈[1,N]The statistics of the ideal constellation point a and the influence of the equalizer W. η is a weight factor of the MUK algorithm, and also reflects the proportion of blind equalization term and blind source separation term selection, and the weight factor needs to be selected most advantageously, so that not only can the implementation of source separation be ensured, but also steady-state errors can be reduced, for example, the errors in the formula (28) reach a preset error value. The preset error value may be a preset value, for example, may be 10 -7 Or other numerical values.
For (27) W j Deriving, and obtaining an error function as follows:
from equation (28), it can be seen that the error function of the MUK-MCMA algorithm is subject to equalizer output signal c j (t),j∈[1,N]And input user signal a j (t),j∈[1,N]The effect of the statistics of the ideal constellation point a.
Then, the current crosstalk compensation value is updated based on the current per-path error. That is, after the error function is obtained, the iterative formula of the j-th equalizer is:
wherein j represents the j-th channel equalization in the channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; w (W) j (t-1) represents a crosstalk compensation value obtained by performing t-1 iteration on the jth channel equalization; μ represents an iteration step of the crosstalk compensation value; e (t) represents an error obtained by performing the t-th iteration on the j-th channel equalization;representing a transpose of the expansion matrix of the corrected user received signal. Mu is a positive constant step factor, the value of which satisfies the following condition:
wherein lambda is max Is the maximum eigenvalue of the b (t) autocorrelation matrix.
Then, an orthogonalized crosstalk compensation value is determined based on the updated crosstalk compensation value. That is, after the iterative formula of W is obtained, W in formula (29) can be determined based on the constraint in formula (27) j (t) orthogonalization, expressed as follows:
wherein,representing orthogonalized crosstalk obtained by performing t-th iteration on jth channel equalizationA compensation value; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; />Representing the transpose of the first-pass channel equalization matrix.
To ensure that the N equalizer vectors are orthogonal to each other, then the N equalizer vectors of the common iteration need to be orthogonalized. Also because of the cross-correlation term of the equalized signal, i.e., the decorrelation term of the output signal, equation (29) can be expressed as:
in the above, κ is 0 Is a correlation factor, which is a positive constant that should be chosen to ensure the convergence of the algorithm; k (k) 1 And k 2 Is an integer selected according to the channel delay spread; (. Cndot.) H represents the transpose.
Returning the orthogonalized equalizer coefficients to the equation (20), repeating the iterations (20), (28), (29) and (31) until the optimal equalizer tap coefficients are found, and the error function reaches an optimal solution, for example, the error reaches a preset error value, so that the equalization is completed. The preset error value may be a preset value, for example, may be 10 -7 Or other numerical values.
That is, the general flow of the channel equalization method in combination with blind source separation according to the embodiments of the present disclosure is: first to R r 、R i Initializing with the W matrix, then calculating the equalizer output signal according to equation (20), then calculating the error according to equation (28), then updating the W matrix according to equation (29), then calculating the orthogonalized W according to equation (31) j (t), i.e. calculateThen orthogonalize W j And (t) returning to the formula (20), and continuously iterating the formulas (20), (28) (29) and (31) until the error reaches a preset error value, and completing the equalization. Wherein the preset error value may be presetThe value of the setting may be, for example, 10 -7 Or other numerical values.
By adopting the technical scheme, the channel equalization mode is a channel equalization mode combining blind equalization and blind source separation, so that the purpose of simultaneously separating blind equalization from blind sources can be achieved by simultaneously restraining the cost function of blind equalization from the cost function of blind source separation, all the transmission signals transmitted by the transmitting end can be simultaneously recovered, crosstalk in an OAM multiplexing communication system is effectively restrained, and the performance and communication quality of the OAM multiplexing communication system are improved. Moreover, compared with the related art, the situation that the equalizer effect is deteriorated due to multi-stage blind equalization is avoided, and the error rate of the equalized output signal is reduced more than that of the related art. In addition, the communication method according to the embodiment of the disclosure can also correct the constellation rotation phenomenon of the output signal by increasing the correction factor of the phase with respect to the phase rotation phenomenon.
Fig. 4 is a schematic block diagram of a communication system according to one embodiment of the present disclosure. As shown in fig. 4, the communication system includes: a receiver 41 for receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam is loaded with a user signal; a demultiplexer 42 for demultiplexing the multiplexed OAM beam; a demodulator 43 for demodulating the demultiplexed signals to obtain user received signals with each distortion; and the equalizer 44 is configured to perform channel equalization on multiple paths of distorted user received signals simultaneously by using a channel equalization mode combining blind equalization and blind source separation, so as to obtain each path of corrected user received signal.
By adopting the technical scheme, the channel equalization mode is a channel equalization mode combining blind equalization and blind source separation, so that the purpose of simultaneously separating blind equalization from blind sources can be achieved by simultaneously restraining the cost function of blind equalization from the cost function of blind source separation, all the transmission signals transmitted by the transmitting end can be simultaneously recovered, crosstalk in an OAM multiplexing communication system is effectively restrained, and the performance and communication quality of the OAM multiplexing communication system are improved. Moreover, compared with the related art, the situation that the equalizer effect is deteriorated due to multi-stage blind equalization is avoided, and the error rate of the equalized output signal is reduced more than that of the related art.
Optionally, the equalizer 44 is further configured to: expanding each distorted user receiving signal into an expansion matrix matched with the length of a channel matrix; determining a current user receiving signal corrected by each path based on each path of the expansion matrix and a current crosstalk compensation value corresponding to each path of the expansion matrix; determining a current error per path based on the current corrected statistical modulus of the imaginary part and the real part of the user received signal and the user input signal at the transmitting end, wherein the current error per path comprises the blind equalization error and the blind source separation error; updating the current crosstalk compensation value based on the current error of each path; determining an orthogonalized crosstalk compensation value based on the updated crosstalk compensation value; and taking the orthogonalized crosstalk compensation value as a new current crosstalk compensation value, and returning to the step of determining the current corrected user receiving signal of each path for iteration until the current error of each path reaches a preset error value.
Optionally, the equalizer 44 is further configured to spread the distorted user received signal of each channel into a spreading matrix matching the length of the channel matrix based on the following constraints:
wherein L represents the length of each sub-equalizer for performing channel equalization, and the distorted user received signal of each path is L-dimensionally spread; t represents the sum total of the sub-channels of the equalizer,wherein T is j Representing the length of the sub-channel; />Representing performing an upward rounding operation; m represents the input signal path number of the equalizer; n representsThe number of output signal paths of the equalizer.
Optionally, the proportion of the blind equalization error and the blind source separation error in the current error is determined according to the requirement that the source separation can be ensured and the current error can reach a preset error value.
Optionally, the equalizer 44 is further configured to update the current crosstalk compensation value in an iterative manner based on the current per-path error, where a step factor μ of the iterative manner satisfies the following condition:
wherein lambda is max Is the maximum eigenvalue of the autocorrelation matrix of the distorted user received signal of each path.
Optionally, equalizer 44 is also used to implement the iterative approach by:
wherein j represents the j-th channel equalization in the channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; w (W) j (t-1) represents a crosstalk compensation value obtained by performing t-1 iteration on the jth channel equalization; μ represents an iteration step of the crosstalk compensation value; e (t) represents an error obtained by performing the t-th iteration on the j-th channel equalization;representing a transpose of the expansion matrix of the corrected user received signal.
Optionally, the equalizer 44 is further configured to determine an orthogonalized crosstalk compensation value based on the updated crosstalk compensation value by:
wherein,representing an orthogonalized crosstalk compensation value obtained by carrying out the t-th iteration on the jth channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; />Representing the transpose of the first-pass channel equalization matrix.
The specific manner in which the respective modules perform the operations in relation to the communication system in the above-described embodiments has been described in detail in relation to the embodiments of the method, and will not be described in detail herein.
Fig. 5 is a block diagram of a first communication system 700, shown in accordance with an exemplary embodiment. As shown in fig. 5, the first communication system 700 may include: a first processor 701, a first memory 702. The first communication system 700 can also include one or more of a multimedia component 703, a first input/output (I/O) interface 704, and a first communication component 705.
Wherein the first processor 701 is configured to control the overall operation of the first communication system 700 to perform all or part of the steps in the communication method described above. The first memory 702 is used to store various types of data to support operation on the first communication system 700, which may include, for example, instructions for any application or method operating on the first communication system 700, as well as application related data, such as contact data, messages, pictures, audio, video, and the like. The first Memory 702 may be implemented by any type or combination of volatile or non-volatile Memory devices, such as static random access Memory (Static Random Access Memory, SRAM for short), electrically erasable programmable Read-Only Memory (Electrically Erasable Programmable Read-Only Memory, EPROM for short), programmable Read-Only Memory (Programmable Read-Only Memory, PROM for short), read-Only Memory (ROM for short), magnetic Memory, flash Memory, magnetic disk or optical disk. The multimedia component 703 can include a screen and an audio component. Wherein the screen may be, for example, a touch screen, the audio component being for outputting and/or inputting audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signals may be further stored in the first memory 702 or transmitted through the first communication component 705. The audio assembly further comprises at least one speaker for outputting audio signals. The first I/O interface 704 provides an interface between the first processor 701 and other interface modules, which may be a keyboard, mouse, buttons, etc. These buttons may be virtual buttons or physical buttons. The first communication component 705 is configured to perform wired or wireless communication between the first communication system 700 and other devices. Wireless communication, such as Wi-Fi, bluetooth, near field communication (Near Field Communication, NFC for short), 2G, 3G, 4G, NB-IOT, eMTC, or other 5G, etc., or one or a combination of more of them, is not limited herein. The corresponding first communication component 705 may thus comprise: wi-Fi module, bluetooth module, NFC module, etc.
In an exemplary embodiment, the first communication system 700 may be implemented by one or more application specific integrated circuits (Application Specific Integrated Circuit, abbreviated ASIC), digital signal processor (Digital Signal Processor, abbreviated DSP), digital signal processing device (Digital Signal Processing Device, abbreviated DSPD), programmable logic device (Programmable Logic Device, abbreviated PLD), field programmable gate array (Field Programmable Gate Array, abbreviated FPGA), controller, microcontroller, microprocessor, or other electronic components for performing the communication methods described above.
In another exemplary embodiment, a computer readable storage medium comprising program instructions which, when executed by a processor, implement the steps of the communication method described above is also provided. For example, the computer readable storage medium may be the memory 702 including program instructions described above, which are executable by the first processor 701 of the first communication system 700 to perform the communication method described above.
Fig. 6 is a block diagram illustrating a second communication system 1900 according to an example embodiment. For example, the second communication system 1900 may be provided as a server. Referring to fig. 6, the second communication system 1900 includes a second processor 1922, which may be one or more in number, and a second memory 1932 for storing computer programs executable by the second processor 1922. The computer program stored in the second memory 1932 may include one or more modules each corresponding to a set of instructions. Further, the second processor 1922 may be configured to execute the computer program to perform the communication method described above.
In addition, the second communication system 1900 may further include a power component 1926 and a second communication component 1950, the power component 1926 may be configured to perform power management of the second communication system 1900, and the second communication component 1950 may be configured to enable communication of the second communication system 1900, e.g., wired or wireless communication. In addition, the second communication system 1900 may also include a second input/output (I/O) interface 1958. The second communication system 1900 may operate based on an operating system, such as Windows Server, stored in the second memory 1932 TM ，Mac OS X TM ，Unix TM ，Linux TM Etc.
In another exemplary embodiment, a computer readable storage medium comprising program instructions which, when executed by a processor, implement the steps of the communication method described above is also provided. For example, the non-transitory computer readable storage medium may be the second memory 1932 described above that includes program instructions executable by the second processor 1922 of the second communication system 1900 to perform the communication methods described above.
In another exemplary embodiment, a computer program product is also provided, comprising a computer program executable by a programmable apparatus, the computer program having code portions for performing the above-mentioned communication method when being executed by the programmable apparatus.
The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (10)
1. A method of communication, comprising:
receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam has a user signal loaded thereon;
demultiplexing and demodulating the multiplexed OAM beam to obtain user receiving signals with each path of distortion;
and simultaneously carrying out channel equalization on the multipath distorted user received signals by adopting a channel equalization mode combining blind equalization and blind source separation to obtain each path of corrected user received signals.
2. The method of claim 1, wherein the channel equalization method that combines blind equalization and blind source separation is used to perform channel equalization on multiple paths of distorted user received signals simultaneously, so as to obtain each path of corrected user received signals, and the method comprises:
expanding each distorted user receiving signal into an expansion matrix matched with the length of a channel matrix;
determining a current user receiving signal corrected by each path based on each path of the expansion matrix and a current crosstalk compensation value corresponding to each path of the expansion matrix;
determining a current error per path based on the current corrected statistical modulus of the imaginary part and the real part of the user received signal and the user input signal at the transmitting end, wherein the current error per path comprises the blind equalization error and the blind source separation error;
updating the current crosstalk compensation value based on the current error of each path;
determining an orthogonalized crosstalk compensation value based on the updated crosstalk compensation value;
and taking the orthogonalized crosstalk compensation value as a new current crosstalk compensation value, and returning to the step of determining the current corrected user receiving signal of each path for iteration until the current error of each path reaches a preset error value.
3. The method of claim 2, wherein expanding the distorted user received signals of each channel into an expanded matrix that matches a length of a channel matrix comprises:
expanding the distorted user received signals of each path into an expansion matrix matched with the length of the channel matrix based on the following constraint conditions:
wherein L represents the length of each sub-equalizer of the equalizer for performing channel equalization, and the user received signal of each distortion is L-dimensionally spread; t represents the sum total of the sub-channels of the equalizer,wherein T is j Representing the length of the sub-channel; />Representing performing an upward rounding operation; m represents the averageThe input signal path number of the weighing apparatus; n represents the number of output signal paths of the equalizer.
4. The method of claim 2, wherein the ratio of the blind equalization error to the blind source separation error in the current per-path error is determined based on requirements that both ensure source separation and enable the current per-path error to reach the preset error value.
5. The method of claim 2, wherein updating the current crosstalk compensation value based on the current per-path error comprises:
updating the current crosstalk compensation value by using an iterative mode based on the current error of each path, wherein a step factor mu of the iterative mode meets the following conditions:
wherein lambda is max Is the maximum eigenvalue of the autocorrelation matrix of the distorted user received signal of each path.
6. The method of claim 5, wherein the iterative manner is implemented by the following formula:
wherein j represents the j-th channel equalization in the channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; w (W) j (t-1) represents a crosstalk compensation value obtained by performing t-1 iteration on the jth channel equalization; μ represents an iteration step of the crosstalk compensation value; e (t) represents an error obtained by performing the t-th iteration on the j-th channel equalization;representing a transpose of the expansion matrix of the corrected user received signal.
7. The method of claim 2, wherein determining an orthogonalized crosstalk compensation value based on the updated crosstalk compensation value is accomplished by:
wherein,representing an orthogonalized crosstalk compensation value obtained by carrying out the t-th iteration on the jth channel equalization; w (W) j (t) represents a crosstalk compensation value obtained by performing the t iteration on the j channel equalization; />Representing the transpose of the first-pass channel equalization matrix.
8. A communication system, comprising:
a receiver for receiving a multiplexed OAM beam transmitted by an atmospheric turbulence channel, wherein the multiplexed OAM beam has a user signal loaded thereon;
a demultiplexer for demultiplexing the multiplexed OAM beam;
the demodulator is used for demodulating the demultiplexed signals to obtain user receiving signals with each path of distortion;
and the equalizer is used for carrying out channel equalization on the multipath distorted user received signals simultaneously by adopting a channel equalization mode combining blind equalization and blind source separation to obtain each path of corrected user received signals.
9. A non-transitory computer readable storage medium having stored thereon a computer program, characterized in that the program when executed by a processor realizes the steps of the method according to any of claims 1-7.
10. A communication system, comprising:
a memory having a computer program stored thereon;
a processor for executing the computer program in the memory to implement the steps of the method of any one of claims 1-7.
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