CN111698183B - Multi-mode vortex wave orthogonalization self-adaptive transmission method and device - Google Patents
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Abstract
The invention provides a multimode vortex wave orthogonalization self-adaptive transmission method, which comprises the following steps: establishing a bidirectional orbital angular momentum multiplexing communication link; acquiring a channel matrix and a communication requirement on a transmitting device; acquiring a pre-equalization matrix according to the channel matrix; analyzing an optimization target, and constructing an equivalent cyclic matrix meeting the optimization target; constructing an orthogonalized matrix according to the pre-equalization matrix and the equivalent cyclic matrix; and weighting the orbital angular momentum multiplexing data by using the orthogonalization matrix so as to realize the pretreatment of the orbital angular momentum signal. The invention also provides a multimode vortex wave orthogonalization self-adaptive transmission device. The multimode vortex wave orthogonalization self-adaptive transmission method obtains the channel matrix and the communication requirement of a link on the transmitting device, adaptively constructs the orthogonalization matrix meeting the optimization target according to the channel matrix and the communication requirement, improves the OAM modal orthogonality, and can meet different communication requirements in real time.
Description
Technical Field
The invention belongs to the field of wireless communication, and particularly relates to a multimode vortex wave orthogonalization self-adaptive transmission method and device, which are suitable for an orbital angular momentum multiplexing communication system on microwave and millimeter wave frequency bands.
Background
According to quantum mechanics and Maxwell theory, electromagnetic waves radiated by the antenna have wave particle duality and can carry linear momentum and angular momentum like moving particles. The electromagnetic wave Angular Momentum includes two parts of Spin Angular Momentum (SAM) and Orbital Angular Momentum (OAM). Wherein SAM is related to photon rotation, and represents the left-hand or right-hand circular polarization of electromagnetic wave, only
Two orthogonal states; OAM is related to the photon wave function spatial distribution, is the fundamental property of all "vortex electromagnetic waves" in that the beam has a helical isophase surface and propagates along a helix, as shown in fig. 1. Each of the vortex electromagnetic wavesPhoton carrying>
The value of the topological charge l is any integer, and the OAM modes of different topological charges are orthogonal to each other. Therefore, the vortex electromagnetic wave with infinite orthogonal modes can theoretically bear infinite multipath information and multiplex transmission with the same frequency, so that a new information multiplexing degree of freedom independent of time, frequency and polarization is provided, and the network capacity, the frequency spectrum efficiency, the anti-interference and anti-interception capabilities of a wireless communication system are expected to be improved in multiples.
Allen et al since 1992 [1][2] The first test proves that the composition has
Laguerre-Gaussian (LG) vortex beams of phase factors can carry orbital angular momentum, and research on OAM has been carried deep into radio astronomy, atom manipulation, correlated imaging, quantum communication, optics, photonics and the like [3-5] The method comprises the following fields. In recent years, studies have been made [6][7] An infinite number of OAM orthomodes of the vortex electromagnetic wave are found to be independent degrees of freedom for information multiplexing, as are photon energy, frequency and polarization properties. Deep excavation of the dimension of the electromagnetic wave parameter which is not fully utilized, namely OAM, can greatly improve the frequency spectrum efficiency of wireless communication and meet the capacity increase requirement of 2-3 orders of magnitude in the future [8] 。
The secure communication technology is one of the key technologies in various military communication application scenarios. The traditional secret communication method is to design corresponding encryption and decryption algorithms at the transmitting and receiving ends, that is, to realize the secret function through the software algorithm of the application layer. In addition, there is also research on security of wireless communication physical layer, i.e. communication security is guaranteed from physical electromagnetic radiation layer, and the directionality of electromagnetic wave main lobe and suppression of side lobe are especially important for physical layer security [9][10] The addition of artificial noise is a common method for improving the security of the physical layer of wireless communication [11] . The OAM communication has the confidentiality function naturally due to the orthogonality of various modes, and is very suitable for a wireless communication physical layerAnd the communication safety is improved. If the transmitting end uses plane wave to transmit interference information and uses OAM modes to transmit secret information, the secret information is hidden under the interference information, the target receiver can demodulate the secret information by the known OAM mode, and the eavesdropping party can not know the OAM mode and can not break the secret information [12] . OAM has one more degree of freedom compared with the traditional wireless communication technology, namely the OAM mode, and on the basis, OAM mode hopping transmission can be carried out.
The ultrahigh frequency spectrum efficiency of the orbital angular momentum multiplexing communication theory becomes one of the most potential key technologies for solving the contradiction between the scarce frequency spectrum resources of the future communication network and the thousand-time capacity increase demand; meanwhile, the orthogonality among orbital angular momentum modes allows communication signals and interference noise to be randomly transmitted among different OAM intrinsic modes, and is very beneficial to enhancing the anti-interference and anti-interception capability of military communication and improving the electromagnetic power. At present, the technology is successfully applied to various leading-edge fields such as free space optical communication, optical fiber communication, visible light communication, millimeter wave and terahertz communication and the like.
However, in the most commonly used microwave rf band of the wireless communication system, the subject is still in the theoretical exploration and concept verification stage, and one of the major technical bottlenecks is: the modal orthogonality in a complex transmission environment deteriorates. Specifically, the method comprises the following steps: the transmission environment of microwave communication is relatively complex, and the quality of a wireless channel is unstable; the transmission of the vortex electromagnetic wave is not only affected by the transmission medium (such as atmospheric turbulence), but also interfered by small-scale fading such as wave diffraction, shielding and multipath. Due to different application scenes, an Orbital Angular Momentum (OAM) vortex electromagnetic wave communication system can possibly work in an environment interfered by non-ideal factors such as electric wave scattering and reflection, and the like, so that the helical phase of a wavefront is easy to distort due to the non-ideal interference factors, the OAM modal orthogonality is reduced, the transmission performance is reduced, and the frequency spectrum efficiency is difficult to greatly improve; meanwhile, the crosstalk formed among the modes seriously affects the communication interference integrated transmission in a military scene, so that the information hiding and anti-interception capability is greatly reduced.
Vortex electromagnetic waveVarious spatial phase distortions occurring in the actual transmission process are main factors causing the orthogonality deterioration of the OAM mode and the reduction of the spectrum efficiency. Although there is some prior art in the aspects of modal orthogonality enhancement and wavefront phase correction, the current prior art and research results of "modal orthogonality enhancement and wavefront phase correction" are mainly focused on the field of free-space optical communication. For example, 2009 Glenn A Tyler et al published literature [13] It is clarified from both theory and experiment that the OAM light beam is influenced by turbulence in the atmosphere and the wavefront phase distortion occurs. Published literature by r.frehlich et al 2000 [14] A series of random phase screens in the direction of beam propagation simulates the inter-modal interference introduced by atmospheric turbulence. Published literature by o.edfors et al, 2012 [15] A random variable is set in an OAM wireless channel model to describe various small-scale fading, and the random variable can be used for analyzing a generation mechanism of a modal orthogonality deterioration problem. Ren et al published 2012 [16] The LDPC code is used for an OAM multiplexing communication system, and the crosstalk between modes is obviously reduced. Zhao et al published 2012 in the literature [17] The phenomena of energy transfer and mode coupling caused by phase distortion of a plurality of modes in OAM multiplex communication are indicated, and a phase aberration correction algorithm based on a wavefront sensor is provided.
In conclusion, in the field of free space optical communication, the method combining adaptive optics and error correction coding can effectively inhibit the interference between OAM modes caused by atmospheric turbulence; however, it is often necessary to add an extra device (e.g., shack-H wavefront sensor) of larger size at the receiving end to achieve phase correction. The method combining the adaptive optics and the error correction coding depends on specific devices, is only suitable for optical communication scenes, and is not suitable for radio communication in a microwave frequency band.
In order to combat the more severe and complex radio wave transmission environment in the microwave frequency band, it is necessary to apply array signal processing and MIMO channel capacity theory to research and design a "digitized" wave front phase optimization and modal orthogonality enhancement algorithm.
See the patent document CN201610505796.5 for a vortex electromagnetic wave generatorApparatus and method for producing " [18] And patent document CN201610504946.0 entitled "multimodal orbital angular momentum multiplexing communication system and method" [19] It discloses: the multi-mode multiplexing communication of vortex electromagnetic waves (namely, radio frequency vortex) on a microwave frequency band can be realized by a circular array antenna at the two ends of signal processing and receiving and transmitting on a digital domain. The method overcomes the defect that the current OAM communication depends heavily on special hardware (such as multimode integrated antenna and quasi-optical device), and solves a series of OAM technical problems in a digital signal processing and matrix analysis mode, namely becoming the mainstream scheme of microwave frequency band OAM communication. However, the above two prior arts only propose digital domain OAM communication architecture, and do not propose corresponding distortion optimization scheme for channel distortion.
According to the publication published by O.Edfors et al 2012 [15] The wireless channel between a pair of circular array antennas that transceive "rf vortices," as shown in fig. 2, can be modeled as follows (as is well known in the art): without loss of generality, the number of array elements (namely, antenna units) on the transmitting circular array antenna and the receiving circular array antenna is assumed to be N; the sequence number of the array element of the transmitting antenna is represented by i, and the radius of the circular ring is R TX (ii) a The number of the array element of the receiving antenna is represented by j, and the radius of the circular ring is R RX； The transmitting array antenna and the receiving array antenna are coaxially arranged, the array surfaces are parallel, and the distance between the circle centers is D. Channel transfer function h between an element i of a transmit array antenna and an element j of a receive array antenna ij Can be expressed as:
wherein dij is the distance between an array element i of the transmitting array antenna and an array element j of the receiving array antenna; λ is the wavelength of the vortex electromagnetic wave; beta is a ij The small-scale fading factor between the array element i of the transmitting array antenna and the array element j of the receiving array antenna is closely related to factors such as transmission environment, antenna characteristics, multipath reflection and the like, and is a key factor for destroying the orthogonality of the OAM mode; h is a total of PL (d ij ) Is a large-size fading factor that is only related to the transmission distance.
Based on this, the wireless channel between the transmitting and receiving circular array antennas can be modeled as a complex matrix with N rows and N columns, which is recorded as a channel matrix H OAM ：
Wherein: symbol
Hadamard products representing matrices; h PL The large-scale fading channel matrix is a cyclic matrix, the cyclic characteristic of the cyclic matrix is a source of orthogonality among the modes of the OAM, and beta is a small-scale fading matrix.
When the Uniform Circular Array (UCA) is used for generating OAM vortex electromagnetic waves for communication, the UCA antenna array elements of the transmitting and receiving parties are the same, so the channel matrix H is considered OAM Is a square matrix. When a multimode vortex wave communication system works in an environment with interference of non-ideal factors such as electric wave reflection and scattering, a receiving and transmitting channel is distorted, and a distorted channel matrix is assumed to be H OAM As is clear from the analysis in the literature published by o.edfors et al, mentioned above
Under UCA antenna array transmission scene, large-scale fading channel matrix H PL Is a cyclic matrix and is full rank, and the correlation of the cyclic matrix and a random small-scale fading matrix beta is further reduced after the Hadamard product is carried out on the cyclic matrix and the random small-scale fading matrix beta, so that a channel matrix H is finally obtained OAM Generally considered to be of full rank, i.e. H OAM It is reversible. The general method of the traditional MIMO zero-forcing equalization is pseudo-inverse (H) H H) -1 H H The method aims to uniformly process the channel matrix into a square matrix and a non-square matrix, and is convenient to perform uniform processing expression in form, but increases the computational complexity. Based on the above analysis, in the OAM communication scenario of this patent, the communication channel matrix is a square matrixAnd reversible, therefore the channel pre-equalization used in this patent is a direct inversion: h -1 The complexity is greatly reduced.
Referring to the literature, the overall effect of OAM phase rotation and data multiplexing can be expressed in terms of Discrete Fourier Transform (DFT) [20] Therefore, OAM multiplex communication can be expressed by the following OAM multiplex communication formula:
y＝F H H OAM Fx
wherein N is T Is the number of transmit antennas, N R Is the number of receive antennas, let N be T ＝N R = N; x is N T *1, a transmit data vector; y is N R *1, a received data vector; f is N R *N T Is a DFT matrix, and superscript H represents the conjugate transpose; h OAM Is N R *N T A channel matrix of (a); h OAM Is a distorted channel matrix, a small-scale fading matrix beta and a large-scale fading matrix H PL Hadamard product of (a).
Further, the distorted channel matrix is H, as is known in the art OAM Singular Value Decomposition (SVD) may be performed:
H OAM ＝U∑ OAM V H ，
wherein, U and V H Is decomposed left and right unitary matrix, sigma OAM Is a diagonal matrix of singular values.
Reference documents
[1]L.Allen,et al.,“Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes,”Physical Review A,vol.45,no.11,pp.8185–8189,Jun.1992.
[2]S.Barnett and L.Allen,“Orbital angular momentum and nonparaxial light beams,”Optics Communications,vol.110,no.5,pp.670-678,Sept.1994.
[3]N.B.Simpson,K.Dholakia,L.Allen,et al.,“Mechanical equivalence of spin and orbital angular momentum of light:an optical spanner,”Optics Letters,vol.22,no.1,1997.
[4]B.Jack,J.Leach,J.Romero,et al.,“Holographic ghost imaging and the violation of a Bell inequality,”Physical Review Letters,vol.103,no.9,2009.
[5]J.T.Barreiro,N.K.Langford,N.A.Peters,et al.,“Generation of hyperentangled photon pairs,”Physical Review Letters,vol.95,no.26,2005.
[6]F.Tamburini,E.Mari,A.Sponselli,et al.,“Encoding manychannels on the same frequency through radio vorticity:first experimental test,”New Journal of Physics,vol.14,no.3,2012.
[7]H.Hao,X.Guodong,et al.,“100Tbit/s free-space data link enabled by three-dimensional multiplexing of orbital angular momentum,polarization,and wavelength,”Optics Letters,vol.39,no.2,pp.197-200,Jan.2014.
[8] IMT-2020 (5G) advances the group 5G Wireless technologies architecture white paper (2015-05-29).
[9]M.Yamanaka,N.Morinaga,S.Miyamoto and S.Sampei,“A study on a transmit antenna directivity control of adaptive array for secure wireless transmission based on the multi-path routing,”2012IEEE 75th Veh.Tech.Conf.(VTC Spring),Yokohama,pp.1-5,2012.
[10]Amr Akl,Ahmed Elnakib,Sherif Kishk,“Antenna array thinning for interference mitigation in multi-directional antenna subset modulation,”Physical Communication,vol.26,pp.31-39,2018.
[11]S.Goel and R.Negi,“Guaranteeing secrecy using artificial noise,”IEEE Trans.Wireless Commun.,vol.7,no.6,pp.2180-2189,June 2008.
[12]X.Jiang and C.Zhang,"Secure Transmission Aided by Orbital Angular Momentum Jamming with Imperfect CSI,"ICC 2019-2019IEEE International Conference on Communications(ICC),Shanghai,China,2019,pp.1-6.
[13]G.Tyler and R.Boyd,“Influence of atmospheric turbulence on the propagation of quantum states of light carrying orbital angular momentum,”Optics Letters,vol.34,no.2,2009.
[14]R.Frehlich,“Simulation of laser propagation in a turbulent atmosphere,”Applied Optics,vol.39,no.39,pp.393-397,2000.
[15]O.Edfors,et al.,“Is orbital angular momentum(OAM)based radio communication an un-exploited area？”IEEE Trans.Antennas and Propagation,vol.60,no.2,pp.1126–1131,2012.
[16]Y.Ren,et al.,“Experimental demonstration of LDPC coded free-space,space-division-multiplexed systems using orbital angular momentum modes,”in Proc.IEEE ECOC,2012.
[17]S.Zhao,et al.,“Aberration corrections for free-space optical communications in atmosphere turbulence using orbital angular momentum states,”Optics Express,vol.20,no.1,2012.
[18] Bin, shukai, baoyong, a vortex electromagnetic wave generating apparatus and method, 2016.6.30, china, 201610505796.5
[19] Bin, shukai, brave, a multi-modal orbital angular momentum multiplexing communication system and method, 2016.6.30, china, 201610504946.0
[20]W.Cheng,H.Jing,W.Zhang,Z.Li and H.Zhang,"Achieving Practical OAM Based Wireless Communications with Misaligned Transceiver,"ICC 2019-2019IEEE International Conference on Communications(ICC),Shanghai,China,2019,pp.1-6.
Disclosure of Invention
The invention aims to provide a multimode vortex wave orthogonalization self-adaptive transmission method and device suitable for a non-ideal environment, so as to solve the problem of reduced OAM modal orthogonality.
In order to achieve the above object, the present invention provides a multimode vortex wave orthogonalization adaptive transmission method, including:
s0: establishing a bidirectional orbital angular momentum multiplexing communication link between a transmitting device and a receiving device of the multi-modal orbital angular momentum multiplexing communication system;
s1: obtaining a channel matrix H at a transmitting device OAM And a communication demand R;
s2: for the channel matrix H OAM Inverting to obtain a pre-equalization matrix
S3: analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR ；
S4: according to a pre-equalization matrix
And equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC ；
S5: using an orthogonalizing matrix H PC And weighting the orbital angular momentum multiplexing data s to realize the preprocessing of the orbital angular momentum signals.
In step S1, the transmitting device obtains a channel matrix H from the reverse communication link OAM And a communication demand R.
In the step S3, the optimization target R includes one of increasing the number of data multiplexing paths, approaching channel capacity, and improving information security.
If the optimization target R represents increasing the number of data multiplexing paths, the equivalent circulant matrix H CIR Directly constructed as an original distortion-free large-scale fading matrix H PL ；
If the optimization target R represents the approximate channel capacity, the equivalent cyclic matrix H CIR The construction method of (2) comprises:
s31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix;
s32: diagonal matrix sigma using singular values OAM And formula H C ＝FΣ OAM F H Constructing a circulant matrix H C Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H C F is a DFT matrix, and superscript H represents the conjugate transpose;
if R represents the safety of the promotion information, the equivalent circulant matrix H CIR The construction method of (1) comprises:
s31': for the channelMatrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM Is a diagonal matrix of singular values, and acquires the channel matrix H OAM Matrix sigma of singular values OAM All diagonal elements v of 1 …v m ；
S32': according to the formula
Solving the coefficient p of the equal gain channel, making m diagonal elements corresponding to m sub-channels as p, and constructing a diagonal matrix sigma S ；
S33': using the formula H S ＝FΣ S F H Constructing a circulant matrix H S Then the equivalent circulant matrix H CIR For constructed circulant matrix H S F is the DFT matrix and the superscript H represents the conjugate transpose.
The step S0 further includes: sequentially adopting M bit level processing modules, M constellation mapping modules, M orbital angular momentum modulation modules and a digital domain orbital angular momentum multi-mode multiplexing module of the transmitting device to process M paths of information bit streams x and output N paths of parallel orbital angular momentum multiplexing data s; and further comprising step S6: sequentially adopting 2N DAC modules, N up-conversion modules and a ring array transmitting antenna of the transmitting device to process and transmit the preprocessed orbital angular momentum multiplexing data, and then adopting the receiving device to receive the preprocessed orbital angular momentum multiplexing data; m is the multiplexing number of orbital angular momentum modes, N is the array element number of the circular ring array transmitting antenna, and M and N are positive integers.
In another aspect, the invention provides a multi-mode vortex wave orthogonalization self-adaptive transmission device, which comprises a multi-mode orbital angular momentum multiplexing communication system comprising a transmitting device and a receiving device, and a self-adaptive vortex enhancement device embedded between a digital domain orbital angular momentum multi-mode multiplexing module and a DAC module of the transmitting device, wherein the self-adaptive vortex enhancement device comprises an orthogonalization matrix calculation module and an orbital angular momentum signal preprocessing module; transmitting apparatus and receiving apparatusThe method comprises the steps of setting up a bidirectional orbital angular momentum multiplexing communication link; the orthogonalization matrix calculation module is arranged to obtain a channel matrix H OAM And an optimization target R, according to the channel matrix H OAM To obtain a pre-equalization matrix
Analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR And based on the pre-equalization matrix->
And equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC (ii) a The orbital angular momentum signal preprocessing module is a matrix vector multiplier arranged to orthogonalize a matrix H PC And multiplying the orbital angular momentum multiplexing data s vector output by the digital domain orbital angular momentum multi-mode multiplexing module, and outputting the product to the DAC module to realize the pretreatment of the orbital angular momentum signal.
The transmitting device obtains a channel matrix H from a reverse communication link OAM And a communication demand R.
In the step S3, the optimization target R includes one of increasing the number of data multiplexing paths, approaching channel capacity, and improving information security.
If the optimization target R represents increasing the number of data multiplexing paths, the equivalent circulant matrix H CIR Directly constructed as an original distortion-free large-scale fading matrix H PL ；
If the optimization target R represents the approximate channel capacity, the equivalent cyclic matrix H CIR The construction method of (1) comprises:
s31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix is obtained;
s32: diagonal matrix sigma using singular values OAM And formula H C ＝FΣ OAM F H Constructing a circulant matrix H C Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H C F is a DFT matrix, and superscript H represents the conjugate transpose;
if R represents the improvement of information security, the equivalent circulant matrix H CIR The construction method of (1) comprises:
s31': for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM Is a diagonal matrix of singular values, and acquires the channel matrix H OAM Singular value matrix sigma OAM All diagonal elements v of 1 …v m ；
And S32': according to the formula
Solving the coefficient p of the equal gain channel, making m diagonal elements corresponding to m sub-channels as p, and constructing a diagonal matrix sigma S ；
S33': using the formula H S ＝FΣ S F H Constructing a circulant matrix H S Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H S F is the DFT matrix and the superscript H denotes the conjugate transpose.
The transmitting device comprises M bit level processing modules, M constellation mapping modules, M first symbol level processing modules, M orbital angular momentum modulation modules, M second symbol level processing modules and a digital domain orbital angular momentum multi-mode multiplexing module which are sequentially connected, and 2N DAC modules, N up-conversion modules, N radio frequency processing modules and a ring array transmitting antenna which are sequentially connected; m is the multiplexing number of orbital angular momentum modes, N is the array element number of the circular ring array transmitting antenna, and M and N are positive integers.
The multimode vortex wave orthogonalization self-adaptive transmission method acquires the channel matrix and the communication requirement of a link on the transmitting device, adaptively constructs the orthogonalization matrix meeting the optimization target according to the channel matrix and the communication requirement, can meet three different communication requirements in real time while improving the OAM modal orthogonality, realizes the distortion optimization of channel distortion, and can be applied to a multimode OAM multiplexing wireless communication system in a microwave frequency band or a millimeter wave frequency band. The channel matrix and the communication requirement are obtained according to feedback information of a reverse link, so that channel distortion of different multi-mode orbital angular momentum multiplexing communication systems can be better dealt with. In addition, the multimode vortex wave orthogonalization self-adaptive transmission device is embedded between a digital domain orbital angular momentum multi-mode multiplexing module and a DAC module of the transmitting device, wave front phase optimization of radio frequency vortex electromagnetic waves can be realized through signal processing of a digital domain, orthogonality among all modes of OAM can be remarkably improved, extra communication requirements of a system are met, the problem that mode orthogonality of current microwave and millimeter wave frequency band orbital angular momentum multiplexing communication in a complex transmission environment is deteriorated is solved, the problem that a traditional wave front optimization method is seriously dependent on a special antenna and a quasi-optical device is solved, and OAM mode multiplexing number and communication spectrum efficiency can be greatly improved.
Drawings
Fig. 1 is a schematic diagram illustrating the principle of multiplexing the conventional vortex electromagnetic wave with orbital angular momentum.
Fig. 2 is a channel modeling diagram between conventional circular array antennas.
FIG. 3 is a flow chart of the multimode vortex wave orthogonalization adaptive transmission method of the invention.
Fig. 4 is a schematic structural diagram of a transmitting part of the multimode vortex wave orthogonalization adaptive transmission device.
Fig. 5 is a schematic diagram of OAM hopping mode communication.
Fig. 6 is a schematic diagram of an orthogonalization matrix computation module.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The multimode vortex wave orthogonalization self-adaptive transmission method is based on the following principle:
assuming that the communication requirement is R, the constructed orthogonalization matrix is H PC . In accordance with the above formula of the background section, the object of the invention is to orthogonalize the matrix H PC Will probablyDistorted channel matrix H OAM And reconstructing an equivalent cyclic matrix to ensure orthogonality among modes of Orbital Angular Momentum (OAM).
The following description is an orthogonalization matrix H for three different communication requirements R PC The theoretical basis of the construction method of (1).
1) If the communication demand R indicates: increasing the number of data multiplexing paths;
then the constructed orthogonalization matrix is
Namely, the circular channel matrix is constructed into an original distortion-free large-scale fading matrix H PL (since OAM transceiver antenna positions are generally fixed, H is assumed here PL Known).
After the construction method of the orthogonalized matrix is adopted, the orthogonalized matrix H is adopted PC Substituting the OAM multiplexing communication formula in the background technology part can obtain:
as can be seen from the formula, the OAM communication channel equivalently reconstructs the original undistorted large-scale fading matrix H PL . Due to undistorted large-scale fading matrix H PL The OAM multiplexing communication channel represents an original circulating channel which is not distorted at an OAM transceiving end, and ideal OAM multiplexing communication is established on the channel, so that the ideal circulating channel is most favorable for multiplexing communication. Therefore, the construction mode of the orthogonalization matrix can increase the number of data multiplexing paths.
2) If the communication demand R indicates: approaching the channel capacity;
then the constructed orthogonalization matrix is
Wherein H c ＝F H Σ OAM F, F is DFT matrix, sigma OAM Being singular values, i.e. H C Is original H OAM A circulant matrix constructed from the singular values of (a). When given distortionThe channel capacity is determined after the channel and the snr, and therefore a channel coding method is needed to approximate the channel capacity.
After the construction method of the orthogonalized matrix is adopted, the orthogonalized matrix is substituted into an OAM multiplexing communication formula, and the following can be obtained:
from the formula, it can be seen that the OAM communication channel is equivalently reconstructed as the original H OAM The singular values of (a) constitute a circulant matrix. Due to H C Is the original distorted singular value ∑ OAM The structure can ensure that the signal-to-noise ratio of the decomposed parallel sub-channels does not change, and the structure mode can be known to approach the channel capacity of the physical distortion channel to the maximum extent according to the water filling principle.
3) If the communication demand R indicates: and the information safety is improved.
Then the constructed orthogonalization matrix is
Wherein H S ＝F∑ S F H ，∑ S Is prepared by reacting H OAM Singular value matrix sigma OAM The designed diagonal matrix is averaged by the diagonal elements of (a).
The traditional communication system only has two degrees of freedom of time and frequency, and the OAM communication adds a third degree of freedom of OAM mode on the basis of the two degrees of freedom. The OAM modes are mutually orthogonal, so that the OAM is very suitable for secret communication. The traditional wireless communication security method is generally to design a related high-complexity encryption algorithm at the high level of a protocol stack to encrypt data information, so as to prevent an eavesdropper from cracking the data information. The physical layer secure communication method is to shield a potential eavesdropper from a physical signal, so that the eavesdropper cannot physically receive a valid secure data signal.
Therefore, as shown in fig. 5, an OAM mode-hopping transmission method is designed based on orthogonality of each mode of OAM, and the OAM mode-hopping transmission method is an efficient mode-hopping transmission methodThe physical layer secret communication method of (1). The communication parties pre-define the 'OAM mode hopping pattern' used in the secret data transmission, so that the target receiver can demodulate the received signal of the data according to the 'OAM mode hopping pattern'. Because the various modes of OAM are orthogonal to one another, a potential eavesdropper cannot learn the "OAM mode pattern," and thus cannot physically demodulate an effectively secure data signal. For such an OAM secure communication strategy, on the basis of designing an "OAM hopping pattern" to ensure that an eavesdropper cannot receive an effective secure signal, it is necessary to further ensure the communication QoS between the transmitting end and the target receiver. The effective solution is to make the gains of the sub-channels of each mode the same as much as possible, so that when data is transmitted in a 'hopping mode', because the gains of the sub-channels of each mode are the same, signals can not be changed violently, and the method is favorable for signal transmission of a transmitting terminal and a target receiving terminal. Based on the above OAM secure communication scheme analysis and the foregoing OAM channel decomposition, it can be seen that only Σ is required S The singular values of the OAM sub-channels are the same, so that the channel gains of the constructed parallel OAM sub-channels are the same, and the QoS of a transmitting end and a target receiver is guaranteed. In order that the constructed equivalent cyclic channel does not further affect the transmission power, it may be preferable to adopt a scheme of constructing the equivalent cyclic channel such that the OAM parallel subchannel gains are averaged as follows.
Suppose H OAM Matrix sigma of singular values OAM Are respectively v 1 …v n Let Σ S The diagonal elements of (a) are all p, satisfy
Solving p to construct a cyclic matrix H s ＝F∑ S F H After the construction method of the orthogonalization matrix is adopted, the orthogonalization matrix is substituted into an OAM multiplexing communication formula to obtain:
namely, the OAM is channelized into equal-gain sub-channels, each sub-channel corresponds to one mode of the OAM, a transmitting party and a target receiving party can carry out stable communication according to a preset 'OAM mode hopping pattern', and an eavesdropper cannot demodulate an effective signal because the 'OAM mode hopping pattern' cannot be known.
As shown in fig. 3, according to the above principle, the multimode vortex wave orthogonalization adaptive transmission method of the present invention is suitable for non-ideal environments, and mainly includes:
step S0: as shown in fig. 4, a bidirectional Orbital Angular Momentum (OAM) multiplexing communication link is established between a transmitting device and a receiving device of the multi-modal orbital angular momentum multiplexing communication system;
as shown in fig. 4, the multi-modal orbital angular momentum multiplexing communication system is a multi-modal orbital angular momentum multiplexing communication system disclosed in patent document with application publication No. CN106130655A, and includes a transmitting device 100 and a receiving device (not shown).
The step S0 further includes: m bit level processing modules 101, M constellation mapping modules 102, M first symbol level processing modules 103, M OAM modulation modules 104, M second symbol level processing modules 105, and a digital domain orbital angular momentum multi-modal multiplexing module 106 of the transmitting device are sequentially adopted to process M channels of information bit streams x, and N channels of parallel OAM multiplexing data S (i.e., input data of the OAM signal preprocessing module 2) are output;
furthermore, in other embodiments, the first symbol-level processing module 103 and/or the second symbol-level processing module 105 and their processing of signals may be omitted.
Step S1: obtaining a channel matrix H at a transmitting device OAM And a communication demand R;
wherein a data frame in a communication link in the reverse direction from the receiving device to the transmitting device would carry a channel matrix H OAM And a communication requirement R, the transmitting device obtains a channel matrix H from a reverse communication link OAM And a communication demand R. The channel matrix H OAM And the communication requirement R is used as the input of an orthogonalization matrix calculation module in the subsequent step.
Channel matrix H OAM The method of acquiring (1) is the prior art, and different acquiring methods exist for different communication systems. For example, in a time division multiplexing communication system, a channel estimation matrix can be obtained according to the reciprocity of channels
As a channel matrix H OAM . In the multi-mode orbital angular momentum multiplexing communication system, the channel estimation matrix obtained by a reverse transmission channel is adopted to be used for->
And as the channel matrix H OAM (the present invention assumes that the channel estimates are completely accurate, and the following uses the channel matrix H OAM Replacement of a channel estimation matrix->
)。
Step S2: for the channel matrix H OAM Inverting to obtain a pre-equalization matrix
Wherein a channel matrix H is obtained OAM On the basis of the channel matrix H, in order to resist channel distortion, directly matching the channel matrix H OAM Inverting to obtain a pre-equalization matrix
The pre-equalization matrix functions to pre-equalize the channel distortion.
And step S3: analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR ；
Wherein the optimization target R is analyzed by an orthogonalization matrix calculation module 1 of the transmitting device. The optimization target R includes one of increasing the number of data multiplexing paths, approaching channel capacity, and improving information security.
Wherein if the optimization target R represents increasing the number of data multiplexing paths, the equivalent cyclic momentMatrix H CIR Directly constructed into an original distortion-free large-scale fading matrix H PL 。
The OAM general communication scene is that the transceiver position is fixed, so the original undistorted large-scale fading matrix H is known by the transceiver end PL 。H PL The OAM multiplexing communication is established on an original undistorted large-scale fading matrix (namely, an original circulating channel matrix which is not distorted at an OAM transceiving end), and the ideal circulating channel is most favorable for multiplexing communication. Therefore, when the type of the optimization target R is to increase the number of data multiplexing paths, the equivalent circulant matrix H CIR Directly constructed as an original distortion-free large-scale fading matrix H PL 。
For distorted channel H OAM Given the snr, the channel capacity is determined, and no matter what method is used to construct the orthogonalization matrix, the channel capacity cannot be changed, so an equivalent circulant matrix needs to be constructed to approximate the channel capacity. Starting from the SVD channel capacity analysis, the channel matrix H can be used OAM Singular value diagonal matrix sigma OAM And combining the DFT matrix to construct a cyclic matrix, so that the obtained equivalent cyclic channel can approach the channel capacity without changing the signal-to-noise ratio of each parallel sub-channel.
Accordingly, if the optimization target R represents an approximation of the channel capacity, the equivalent circulant matrix H CIR The construction method of (1) comprises:
step S31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix;
step S32: diagonal matrix sigma using singular values OAM And formula H C ＝FΣ OAM F H Constructing a circulant matrix H C Then the equivalent circulant matrix H CIR For constructed circulant matrix H C F is the DFT matrix and the superscript H denotes the conjugate transpose.
Referring to fig. 5 again, according to the above theoretical analysis of the information security improvement part, when the "hopping OAM mode" is used as a physical layer scheme for improving the security of wireless communication, it is necessary to ensure the QoS of the transmitter and the target receiver as much as possible. The method provided by the invention ensures that the sub-channels decomposed from the channels of the transmitter and the target receiver have the same capacity, and each sub-channel corresponds to one path of OAM mode data transmission, thereby ensuring the stability of the channels when the transmitter and the receiver are in the 'OAM hopping mode' and ensuring the communication QoS. The equal gain characteristic of the OAM sub-channel can be ensured by designing the singular value of the equivalent cyclic channel matrix, the singular values are equal, namely, the diagonal matrix is constructed by the same diagonal elements, and then the cyclic matrix is constructed by the diagonal matrix.
Therefore, in order to make the constructed equivalent cyclic channel not further affect the transmission power, it is preferable that the equivalent cyclic matrix H is set to R representing the enhanced information security CIR The construction method of (2) comprises:
step S31': for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM Obtaining the channel matrix H for the diagonal matrix of singular values OAM Singular value matrix sigma OAM All diagonal elements v of 1 …v m Diagonal element v 1 …v m Respectively corresponding to Orbital Angular Momentum (OAM) modes 0 \8230, wherein m and m +1 are orbital angular momentum mode multiplexing numbers;
from the foregoing analysis, v can be found 1 …v m Corresponding to the channel coefficients of the parallel sub-channels decomposed by the SVD.
Step S32': according to the formula
Solving the coefficient p of the equal gain channel, making m diagonal elements corresponding to m sub-channels as p, and constructing a diagonal matrix sigma S (ii) a Thereby, channel gains are averaged.
Step S33': using the formula H S ＝FΣ S F H Constructing a circulant matrix H S Then the equivalent circulant matrix H CIR For constructed circulant matrix H S F is a DFT matrix, and the superscript H denotesThe yoke is transposed.
And step S4: according to a pre-equalization matrix
And an equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC ；
Wherein the orthogonalization matrix is
Orthogonalizing matrix H PC The method is constructed by an orthogonalization matrix calculation module at the transmitting end, namely, the steps S2 to S4 are carried out by adopting the orthogonalization matrix calculation module.
Step S5: using an orthogonalizing matrix H PC Weighting OAM multiplex data S (i.e. orthogonalizing a matrix H) PC And the OAM multiplexing data s vector output by the digital domain orbital angular momentum multi-modal multiplexing module 106) to realize OAM signal preprocessing.
Step S5 is performed by using an OAM signal preprocessing module.
Further, step S6 may be further included: the 2N DAC modules 107, the N up-conversion modules 108, the N radio frequency processing modules 109 and the annular array transmitting antenna 110 of the transmitting device of the multi-mode orbital angular momentum multiplexing system are sequentially adopted to process and transmit the preprocessed OAM multiplexing data, and then the receiving device of the multi-mode orbital angular momentum multiplexing system is adopted to receive the OAM multiplexing data so as to realize multi-mode vortex wave orthogonalization self-adaptive transmission.
Furthermore, in other embodiments, the N rf processing modules 109 and their processing of signals may be omitted.
Thus, the overall OAM transceiving equation can be expressed as:
finally, the channel matrix is reconstructed into a new equivalent cyclic channel matrix, and the channel matrix can adaptively meet three different communication requirements on the basis of ensuring the orthogonality of each mode of the UCA of the receiving device.
Fig. 4 shows a transmitting portion of the multimode vortex wave orthogonalizing adaptive transmission device according to one embodiment of the invention. The multimode vortex wave orthogonalization self-adaptive transmission device comprises a multimode orbital angular momentum multiplexing communication system, wherein the multimode orbital angular momentum multiplexing communication system is disclosed in a patent document with application publication No. CN106130655A and comprises a transmitting device 100 and a receiving device (not shown). The transmitting device 100 and the receiving device are arranged to establish a bi-directional orbital angular momentum multiplex communication link. The transmitting device 100 includes M bit level processing modules 101, M constellation mapping modules 102, M first symbol level processing modules 103, M OAM modulation modules 104, M second symbol level processing modules 105, and a digital domain orbital angular momentum multi-modal multiplexing module 106, which are connected in sequence, and 2N DAC modules 107, N up-conversion modules 108, N radio frequency processing modules 109, and a circular ring array transmitting antenna 110, which are connected in sequence. M is the OAM mode multiplexing number, N is the array element number of ring array transmitting antenna, and M, N are positive integers. In other embodiments, at least one of the first symbol-level processing module 103, the second symbol-level processing module 105, and the radio frequency processing module 109 may be omitted.
The receiving device comprises a circular array receiving antenna, N second radio frequency processing modules, N down-conversion modules, 2N ADC modules, a digital domain orbital angular momentum demodulation and demultiplexing module, a third symbol level processing module and M detection decoding modules which are sequentially connected. The second rf processing module and/or the third symbol-level processing module may be omitted.
The multimode vortex wave orthogonalization self-adaptive transmission device further comprises a self-adaptive vortex enhancement device 200 which is embedded between a digital domain orbital angular momentum multimode multiplexing module 106 and a DAC module 107 of the transmitting device 100 of the multimode orbital angular momentum multiplexing communication system, wherein the self-adaptive vortex enhancement device 200 comprises an orthogonalization matrix calculation module 1 and an OAM signal preprocessing module 2.
As shown in fig. 6, the orthogonalization matrix calculation module 1 is arranged to obtain the channel matrix H OAM And an optimization target R according to the channel matrix H OAM To obtain a pre-equalization matrix
Analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR And based on the pre-equalization matrix>
And equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC 。
Wherein the optimization target R comprises one of increasing the number of data multiplexing paths, approaching channel capacity, and improving information security.
If the optimization target R represents increasing the number of data multiplexing paths, the equivalent cyclic matrix H CIR Directly constructed as an original distortion-free large-scale fading matrix H PL 。
If the optimization target R represents the approximate channel capacity, the equivalent cyclic matrix H CIR The construction method of (1) comprises:
step S31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein, U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix;
step S32: diagonal matrix sigma using singular values OAM And formula H C ＝FΣ OAM F H Constructing a circulant matrix H C Then the equivalent circulant matrix H CIR For constructed circulant matrix H C F is the DFT matrix and the superscript H represents the conjugate transpose.
If R represents the improvement of information security, the equivalent circulant matrix H CIR The construction method of (2) comprises:
step S31': for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM For singular value diagonal matrix, obtaining the channel matrix H OAM Matrix sigma of singular values OAM All diagonal elements v of 1 …v m Diagonal element v 1 …v m Respectively corresponding to Orbital Angular Momentum (OAM) mode 0 \8230, m +1 are Orbital Angular Momentum (OAM) mode multiplexing numbers;
step S32': according to the formula
Solving the coefficient p of the equal gain channel, making m diagonal elements corresponding to m sub-channels as p, and constructing a diagonal matrix sigma S ；
Step S33': using the formula H S ＝F∑ S F H Constructing a circulant matrix H S Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H S F is the DFT matrix and the superscript H represents the conjugate transpose.
Wherein the orthogonalization matrix is
The OAM signal pre-processing block 2 is a matrix vector multiplier arranged to orthogonalize the matrix H PC And multiplying the OAM multiplexing data s vector output by the digital domain orbital angular momentum multi-mode multiplexing module, and outputting the product to the DAC module 107 to realize OAM signal preprocessing.
Results of the implementation
The transmitting part of the multimode vortex wave orthogonalization adaptive transmission device is specifically described below by taking widely used Orthogonal Frequency Division Multiplexing (OFDM) communication transmitters and receivers as an example.
In this embodiment, in the transmitting part, the bit level processing module 101 is a channel coding module, the first symbol level processing module 103 is an OFDM modulation module, the second symbol level processing module 105 is a pulse shaping module, the up-conversion module 108 is an IQ quadrature modulation module, the rf processing module 109 is a filtering and power amplifying module, the phase synchronization module 111 performs synchronization by using a same local oscillator signal shared by a plurality of rf channels, the OAM modal multiplexing number M =8, and the ring isThe number of array elements of the array transmitting antenna N =8, and the OAM mode l output by the mode definition module 1 …l 8 Corresponding to OAM modes 0 \82307and 7, respectively (modes greater than 3 and OAM negative modes are equivalent). The input data of the OAM signal preprocessing module 2 may be represented as s = FGx, F is a DFT matrix of 8 × 8, G is a correction unit matrix of 8 × 8, and x is an information bit stream (i.e., an input data vector of 8 × 1), where the positions corresponding to 8 modes are 8 channels of data, and the resulting s is 8 channels of OAM multiplexing data and is a vector of 8 × 1. The channel matrix adopted by the orthogonalization matrix calculation module 1 is H OAM Constructing an equivalent circulant matrix H according to the optimization objective CIR . The output of the orthogonalization matrix calculation module is as follows:
on this basis, the output result of the OAM signal preprocessing module 2 is: />
The equivalent circulant matrix H is given below CIR The table is a specific parameter.
TABLE 1 equivalent circulant matrix H CIR Is calculated as a parameter
| Wavelength lambda | 0.03m |
| Transmit-receive UCA radius R TX R RX | 0.3m |
| Transmitting and receiving UCA circle center distance D | 6m |
From the above parameters according to the following formula:
the original large-scale fading matrix (also the circulant matrix for increasing the number of multiplexing paths) can be calculated as follows:
the distorted channel after passing through the non-ideal environment is (here the distortion is modeled with uniformly distributed amplitude and phase weights)
To H OAM Performing SVD to obtain singular value vector of
V＝[3.65 3.51 2.27 2.20 2.10 2.0 2.0 1.9]。
Then with H OAM The approximate channel capacity cyclic matrix constructed by combining the singular value diagonal matrix and the FFT matrix is as follows:
by the process of the invention to H OAM I.e. m =8, the elements of the above singular value vector V being V i Substitution formula
Available p =2.5. The lifting information security cyclic matrix constructed by taking p as a diagonal matrix element and combining the FFT matrix is as follows:
the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications may be made to the above-described embodiment of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (6)
1. A multimode vortex wave orthogonalization self-adaptive transmission method is characterized by comprising the following steps:
step S0: establishing a bidirectional orbital angular momentum multiplexing communication link between a transmitting device and a receiving device of the multi-modal orbital angular momentum multiplexing communication system;
step S1: obtaining a channel matrix H at a transmitting device OAM And a communication demand T;
step S2: for the channel matrix H OAM Inverting to obtain a pre-equalization matrix
And step S3: analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR ；
In step S3, the optimization target R includes one of increasing the number of data multiplexing paths, approaching channel capacity, and improving information security;
if the optimization target R represents increasing the number of data multiplexing paths, the equivalent circulant matrix H CIR Directly constructed as an original distortion-free large-scale fading matrix H PL ；
If the optimization target R represents the approximate channel capacity, the equivalent cyclic matrix H CIR The construction method of (2) comprises:
step S31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein, U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix is obtained;
step S32: diagonal matrix sigma using singular values OAM And formula H C ＝F∑ OAM F H Constructing a circulant matrix H C Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H C F is a DFT matrix, and superscript H represents the conjugate transpose;
if R represents the improvement of information security, the equivalent circulant matrix H CIR The construction method of (2) comprises:
step S31': for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM Is a diagonal matrix of singular values, and acquires the channel matrix H OAM Matrix sigma of singular values OAM All diagonal elements v of 1 ...v m ；
Step S32': according to the formula
Solving the coefficient p of equal gain channel, making m diagonal elements corresponding to m sub-channels all be p, and constructing diagonal matrix sigma S ；
Step S33': using the formula H S ＝F∑ S F H Constructing a circulant matrix H S Then the equivalent circulant matrix H CIR For constructed circulant matrix H S And F is the DFT matrix,superscript H denotes conjugate transpose;
and step S4: according to a pre-equalization matrix
And equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC ；
Step S5: using an orthogonalizing matrix H PC And weighting the orbital angular momentum multiplexing data s to realize the preprocessing of the orbital angular momentum signals.
2. The method for multi-mode vortex wave orthogonalization and adaptive transmission according to claim 1, wherein in the step S1, the transmitting device obtains a channel matrix H from a reverse communication link OAM And a communication demand T.
3. The multi-mode vortex wave orthogonalizing adaptive transmission method according to claim 1, wherein the step S0 further comprises: sequentially adopting M bit level processing modules (101), M constellation mapping modules (102), M orbital angular momentum modulation modules (104) and a digital domain orbital angular momentum multi-mode multiplexing module (106) of the transmitting device to process M paths of information bit streams x and output N paths of parallel orbital angular momentum multiplexing data s;
and further comprising step S6: sequentially adopting 2N DAC modules (107), N up-conversion modules (108) and a circular array transmitting antenna (110) of the transmitting device to process and transmit the preprocessed orbital angular momentum multiplexing data, and then adopting the receiving device to receive the data;
m is the multiplexing number of orbital angular momentum modes, N is the array element number of the circular ring array transmitting antenna, and M and N are positive integers.
4. A multimode vortex wave orthogonalization self-adaptive transmission device is characterized by comprising a multimode orbital angular momentum multiplexing communication system and an adaptive vortex enhancement device (200), wherein the multimode orbital angular momentum multiplexing communication system comprises a transmitting device (100) and a receiving device, the adaptive vortex enhancement device (200) is embedded between a digital domain orbital angular momentum multimode multiplexing module (106) and a DAC module (107) of the transmitting device (100), and the adaptive vortex enhancement device (200) comprises an orthogonalization matrix calculation module (1) and an orbital angular momentum signal preprocessing module (2);
the transmitting device (100) and the receiving device are arranged to establish a bidirectional orbital angular momentum multiplex communication link;
the orthogonalization matrix calculation module (1) is arranged to obtain a channel matrix H OAM And an optimization target R, according to the channel matrix H OAM To obtain a pre-equalization matrix
Analyzing the optimization target R and constructing an equivalent cyclic matrix H meeting the optimization target R CIR And based on the pre-equalization matrix->
And equivalent circulant matrix H CIR Constructing an orthogonalized matrix H PC ；
The orbital angular momentum signal preprocessing module (2) is a matrix vector multiplier arranged to orthogonalize a matrix H PC Multiplying the multiplied data by an orbital angular momentum multiplexing data s vector output by the digital domain orbital angular momentum multi-mode multiplexing module, and outputting the product to a DAC module (107) to realize the pretreatment of the orbital angular momentum signal;
the optimization target R comprises one of increasing the number of data multiplexing paths, approaching the channel capacity and improving the information security;
if the optimization target R represents increasing the number of data multiplexing paths, the equivalent circulant matrix H CIR Directly constructed into an original distortion-free large-scale fading matrix H PL ；
If the optimization target R represents the approximate channel capacity, the equivalent cyclic matrix H CIR The construction method of (1) comprises:
step S31: for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H Wherein U and V H Is decomposed left and right unitary matrix, sigma OAM A singular value diagonal matrix;
step S32: diagonal matrix sigma using singular values OAM And formula H C ＝F∑ OAM F H Constructing a circulant matrix H C Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H C F is a DFT matrix, and superscript H represents the conjugate transpose;
if R represents the improvement of information security, the equivalent circulant matrix H CIR The construction method of (1) comprises:
step S31': for the channel matrix H OAM Decomposing into H by SVD OAM ＝U∑ OAM V H U and V H Is decomposed left and right unitary matrix, sigma OAM Is a diagonal matrix of singular values, and acquires the channel matrix H OAM Singular value matrix sigma OAM All diagonal elements v of 1 ...v m ；
Step S32': according to the formula
Solving the coefficient p of the equal gain channel, making m diagonal elements corresponding to m sub-channels as p, and constructing a diagonal matrix sigma S ；
Step S33': using the formula H S ＝F∑ S F H Constructing a circulant matrix H S Then the cyclic matrix H is equivalent CIR For constructed circulant matrix H S F is the DFT matrix and the superscript H denotes the conjugate transpose.
5. The apparatus according to claim 4, wherein the transmitter obtains the channel matrix H from the reverse communication link OAM And a communication demand R.
6. The multi-mode vortex wave orthogonalization adaptive transmission device according to claim 4, wherein the transmitting device (100) comprises M bit-level processing modules (101), M constellation mapping modules (102), M first symbol-level processing modules (103), M orbital angular momentum modulation modules (104), M second symbol-level processing modules (105) and a digital domain orbital angular momentum multi-mode multiplexing module (106) which are connected in sequence, and 2N DAC modules (107), N up-conversion modules (108), N radio frequency processing modules (109) and a circular array transmitting antenna (110) which are connected in sequence; m is an orbital angular momentum modal multiplexing number, N is the array element number of the circular array transmitting antenna, and M and N are positive integers.
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