![]() METHOD FOR TRANSMITTING A SEQUENCE OF DATA SYMBOLS, TRANSMISSION DEVICE, SIGNAL, RECEPTION METHOD, R
专利摘要:
The invention relates to a method for transmitting a sequence of data symbols comprising at least two distinct value data symbols, delivering an electromagnetic wave carrying an orbital angular momentum. According to the invention, such a method comprises, for at least a data symbol to be transmitted: a bijective selection step (34) of an order of orbital angular momentum, associating with each distinct value of a data symbol a distinct order of orbital angular momentum, and delivering an order of orbital angular momentum selected representative, by bijection, of the value of said at least one data symbol to be transmitted, - a step of transmission (35) of said electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order corresponds to said order of angular momentum selected orbital. 公开号:FR3014271A1 申请号:FR1361884 申请日:2013-11-29 公开日:2015-06-05 发明作者:Philippe Mary;Abdullah Haskou;Christian Brousseau 申请人:INST NAT SCIENCES APPLIQ;Centre National de la Recherche Scientifique CNRS;Universite de Rennes 1;Institut National des Sciences Appliquees de Rennes; IPC主号:
专利说明:
[0001] A method of transmitting a sequence of data symbols, transmission device, signal, reception method, receiving device and corresponding computer program. FIELD OF THE INVENTION The field of the invention is that of digital communications, in transmission or in broadcasting. More precisely, the invention relates to electromagnetic wave (EM) transmission from at least one transmitter to at least one receiver. In particular, the invention relates to the transmission of information by electromagnetic wave carrying an orbital angular momentum. This type of wave is used in particular in the field of optical digital communications and digital radio communications. 2. Prior art 2.1 Definition of orbital angular momentum The transfer over long distances of information is commonly carried out by means of antennas radiating electromagnetic (EM) plane waves. An electromagnetic wave (EM) is defined by its amplitude, its wave vector, its frequency and its angular momentum. In the 1930s, it was demonstrated in theoretical physics that the angular momentum is decomposed into two parts, namely the intrinsic angular momentum, called the spin angular momentum (SAM), associated with the polarization of the wave, and the extrinsic angular momentum, called orbital angular momentum (OAM) associated with the spatial distribution of the electric field. [0002] With regard to the angular momentum of spin which can take only two orthogonal values, the orbital angular momentum can advantageously take an infinity of discrete orthogonal values. An electromagnetic wave carrying an orbital angular momentum, in other words characterized by a nonzero orbital angular momentum, is characterized by an azimuthal dependence of its phase denoted e-119 with the order of the angular momentum orbital (also called topological ") corresponding to the number of rotations of the phase per wavelength, and cp the angle of azimuth. In other words, the orbital angular momentum has the effect of producing a wavefront which is no longer equiphase but helical with a value of the phase of the field E 'which depends on the azimuthal angle and the order 1 of the orbital angular momentum as represented in FIG. 1 representing the wave carrying an order I 121 angular orbital moment transmitted in a channel 12 between a transmission device T 11 and a receiving device R 13. At the beginning of the years 1990, the first practical uses of the orbital angular momentum of an electromagnetic wave in the optical domain have emerged, and the use of orbital angular momentum as an additional degree of freedom in the field of optical links has recently been described by I. Djordevic ("LDPC-Coded OAM Modulation and Multiplexing for Deep-Space and Near-Earth Optical Communications", International Conference on Space Optical Systems and Communications). [0003] In parallel, B. Thidé ("Utilization of photon orbital orbital angular momentum in the low frequency radio domain", Physical Review Letters, vol 99, n ° 8, August 2007) also demonstrated the possibility of generating electromagnetic waves carrying a orbital angular momentum from network antennas, such as a circular antenna array illustrated in FIG. 2 representing a transmission device T 21 corresponding to a circular network of antennae of radius a of which only three antennas are represented and a device of FIG. reception R 22, remote from the transmission device by a distance D and corresponding to a circular array of antennas with a radius greater than a of which only four antennas are represented, or alternatively reflector antenna. This work has also been supplemented by studies to measure the orbital angular momentum of an electromagnetic wave such as that implemented by SM Mohammadi ("Orbital Angular Momentum in Radio - A system Study", IEEE Transaction on antennas and Propagation , vol 58, n ° 2, February 2010). Currently, the properties of the orbital angular momentum are little exploited or essentially used for the generation of orthogonal channels available for information multiplexing. 2.2 Techniques for transmitting digital information according to the prior art Numerous techniques for transmitting digital information have been developed. These techniques include optical transmission techniques and radio frequency transmission techniques illustrated respectively by the documents cited above. These techniques use distinct transmission schemes because of intrinsic differences in optical signals and digital signals, respectively. There is therefore a need to provide a transmission technique which is as applicable in the optical field as in the radiofrequency domain, while presenting a complexity and a cost of implementation and transposition of the optical domain to the limited radiofrequency domain. 3. DISCLOSURE OF THE INVENTION The invention proposes a novel solution, in the form of a method for transmitting a sequence of data symbols comprising at least two symbols of data of distinct values, delivering an electromagnetic wave carrying a moment According to the invention, such a method comprises, for at least one data symbol to be transmitted: a step of bijective selection of an orbital angular momentum order, associating with each distinct value of a data symbol an order of angular momentum distinct orbital, and delivering a selected order of orbital angular momentum representative, by bijection, of the value of said at least one data symbol to be transmitted, a step of transmission of said electromagnetic wave carrying an orbital angular momentum whose order of angular momentum orbital corresponds to the selected order of orbital angular momentum. Thus, the invention is based on a new and inventive approach to the transmission of a signal. Indeed, the invention diverts the conventional use of the order of orbital angular momentum usually dedicated to the multiplexing of the information. [0004] According to this conventional use, the order of orbital angular momentum is used to identify an information transport channel, wherein a plurality of orthogonal transport channels identified by their orbital angular momentum order are used for the multiplexed transmission of a plurality of data symbols. distinct values. In other words, according to this conventional use, the same transport channel identified by its order of orbital angular momentum is used to transport a plurality of symbols of distinct values. According to the present technique the order of orbital angular momentum directly represents the value of the data symbol to be transmitted. Thus, an orbital angular momentum order value corresponds to only a single value of data symbols. This approach based on a new use of orbital angular momentum to represent a symbol of data to be transmitted has the additional advantage of being applicable to both the radiofrequency and optical communications domains. Thus, according to the present technique the role played by the orbital angular momentum passes from transport to direct representation of the information. In other words, unlike the conventional use of the order of orbital angular momentum where the same order of orbital angular momentum conveys indifferently several data symbols of distinct values, an order of orbital angular momentum represents in a bijective way a single data symbol value. The present technique therefore makes it possible to dedicate an orbital angular momentum order to represent a single data symbol value. [0005] The transmission of a sequence of data symbols therefore requires, according to the present technique, the transmission of a series of electromagnetic waves each carrying an orbital angular momentum whose order represents the value of a data symbol. Thus, a sequence of data formed from five successive symbols of distinct values will be transmitted by means of five temporally successive electromagnetic waves, the order of the orbital angular momentum carried by each of these waves being distinct from one electromagnetic wave to another, each separate order respectively representing each value of the five successive data symbols. For example, the bijective selection of the orbital angular momentum order representing a data symbol value is a one-to-one correspondence relationship between an orbital angular momentum order and a data symbol value to be transmitted. This bijective correspondence relation corresponds for example to a bijective mathematical function whose input parameter is the value of the symbol to be transmitted. The choice of a non-trivial bijematic mathematical function of low complexity (for example a linear combination,) or of high complexity (for example implementing an exponential function) can in particular make it possible to secure the transmission of the symbol. According to another example, this relation is defined by a table establishing for example directly the correspondence between a set of binary values defining the value of the symbol to be transmitted and the value of the corresponding orbital angular momentum order. Like the non-trivial mathematical function mentioned above, a correspondence table also makes it possible to secure the transmission, since a third party can not identify the information transmitted without knowing the bijective relation used by the transmission method according to the invention. According to a particular aspect of the invention, the order of orbital angular momentum is selected when it is equal to the value of the data symbol to be transmitted. [0006] Such equality between the order of orbital angular momentum and the value of the symbol to be transmitted allows a simple and fast selection of the transmission mode of the electromagnetic wave carrying an orbital angular momentum. Thus, this bijective relationship of identity between order of orbital angular momentum and data symbol value makes it possible in particular to accelerate the transmission of a value sequence with regard to the aforementioned correspondence relations. [0007] According to an exemplary implementation, the transmission method according to the invention further comprises the following steps implemented prior to said selection step: a step of receiving a bit stream of data, a step of determining the maximum absolute value of order of angular momentum orbital capable of being transmitted by a transmission device implementing said transmission method, a step of forming said sequence of data symbols from said bit stream, said training step taking into account of said maximum absolute value of order of orbital angular momentum. This exemplary implementation takes into account the ability of the transmission device to produce a plurality of separate transmission orbital angular momentum orders and transforms a bit stream according to the maximum number of orbital angular momentum orders that can be produced. [0008] For example, the transmission device, optical or radiofrequency is able to transmit a maximum absolute value of order of angular momentum orbital equal to 4, orders of angular momentum orbital belong to the set {-4, -3, - 2, -1, 0, +1, +2, +3, +4}. The step of forming symbols from the received bitstream converts a group of bits into a value belonging to the set {-4, -3, -2, -1, 0, +1, +2, +3 , +4}, when the bijective relation between the data symbol value and the order of the orbital angular momentum is an identity relation. The value -2 of the symbol obtained after the formation step will then correspond directly according to the bijective identity relation to an order of orbital angular momentum equal to -2 When the bijective relation is more complex than the relation of identity illustrated above. above, the step of forming symbols from the received bitstream, transforms a group of bits into a value belonging to an intermediate set whose values are the antecedents, in mathematical terms, of the set of angular momentum orders orbital. According to a particular implementation example, the training step corresponds to an N-state modulation, where N is an integer equal to twice said maximum absolute value of orbital angular momentum plus one. For example, for a radiofrequency transmission device or an optical transmission device, the training step corresponds to a pulse amplitude modulation (PAM) with N states, called N-ary PAM. [0009] For an optical transmission device, a single or double polarization modulation, for example a quadrature phase shift keying (QPSK) or a sixteen-state quadrature amplitude modulation 16QAM for "16 state Quadrature Amplitude Modulation"), also allows to associate a representation value of the symbol in the constellation (also called state value) to a group of several bits. According to a particular embodiment, when the transmission method is implemented by a radiofrequency transmission device comprising a plurality of transmission elements, the transmission method further comprises a serial-parallel replication step of the order of selected orbital angular momentum delivering the order of orbital angular momentum at the input of each of said plurality of transmit elements. For example, when the transmission device is a circular array of antennas comprising eight antennas, if the order of orbital angular momentum equal to -4 is selected for a value equal to -4 of a data symbol, each of the eight antennas receives the value -4 in order to form an electromagnetic wave having a number of phase rotations equal to -4 per wavelength. In another embodiment, the invention relates to a device for transmitting a sequence of data symbols comprising at least two distinct value data symbols, delivering an electromagnetic wave carrying an orbital angular momentum, according to the invention. such device comprises, for at least one data symbol to be transmitted: a bijective selection module of an order of orbital angular momentum, associating with each distinct value of a data symbol a distinct orbital angular momentum order, and delivering an order of orbital angular momentum representative, by bijection, of the value of said at least one data symbol to be transmitted, a transmission module of said electromagnetic wave carrying an orbital angular momentum whose order of orbital angular momentum corresponds to said order of orbital angular momentum selected. [0010] Such a transmission device is radiofrequency or optical, and is particularly suitable for implementing the transmission method described above. This transmission device may of course include the various characteristics relating to the transmission method described above, which can be combined or taken separately. Thus, the characteristics and advantages of this transmission device are the same as those of the transmission method. Therefore, they are not detailed further. [0011] Another aspect of the invention relates to a signal transmitted in the form of an electromagnetic wave carrying an orbital angular momentum. According to the invention, said electromagnetic wave carrying an orbital angular momentum has an orbital angular momentum momentarily selected during the transmission of said signal so as to represent by bijection the value of a data symbol to be transmitted. This signal may of course include the various characteristics relating to the transmission method of the invention. In particular, this signal may carry information on the type of bijective selection implemented on transmission when the receiving device does not "know" beforehand this type of bijective selection. In another embodiment, the invention relates to a method of receiving a transmitted signal in the form of an electromagnetic wave carrying an angular momentum, delivering an estimate of a data symbol of a sequence of data symbols. comprising at least two distinct value data symbols, said electromagnetic wave carrying an orbital angular momentum having an orbital angular momentum momentarily selected upon transmission of said signal so as to represent by bijection the value of said data symbol, Such a method receiver comprises a step of estimating the value of said data symbol, implementing a step of detecting said order of orbital angular momentum. Such a reception method is particularly suitable for receiving and estimating a sequence of data symbols transmitted according to the transmission method of the invention. Thus, if the transmission method is applied to all the symbols of the data sequence, the reception method will be implemented as many times as there are symbols in the data sequence. Indeed, a sequence of data symbols transmitted according to the transmission method of the invention requires the successive transmission of as many electromagnetic waves as there are data symbols in the sequence to be transmitted according to this method. In reception, as many detections of order of orbital angular momentum as of data symbols to be estimated will therefore be implemented. For example, a sequence of twelve data symbols transmitted and distinct from one another will result in twelve detections of distinct orbital angular momentum orders. According to another example, four symbols of identical values have been successively transmitted by means of four identical electromagnetic waves of order of angular moment, the same order of orbital angular momentum will therefore be detected four times in succession. According to a first example of implementation, said detection step implements a Fourier transform of said signal. [0012] Assuming, for example, that the propagation channel does not fade, such detection takes advantage of the properties of the Fourier transform, for example a Fast Fourier Transform (FFT), according to which after application to the received signal, the only non-zero input of the signal identifies the identified orbital angular momentum order. [0013] Such detection is therefore based on the detection of a maximum of energy. According to a second exemplary implementation, said detection step is a maximum likelihood detection. Such a detection is then based on the value of the torque formed by the order of the angular momentum and the pointing angle, in particular the value of the torque (1, 0) that maximizes the probability density of the signal received. In particular, according to a variant of this second implementation example, said maximum likelihood detection step is iterative and uses a Fisher information matrix. According to a third example of implementation, said detection step implements a determination of a phase gradient comprising: a step of shaping said signal in vector form, a step of unfolding a phase of each term of said vector form and determining a product phase of the terms of said vector form, a step of obtaining said estimated orbital angular momentum order implementing a division of said product phase of the terms of said vector form by the term ira - 1), where L is an integer corresponding to a maximum absolute value of order of orbital angular momentum capable of being received multiplied by two. According to a variant of the previous implementation examples, the method further comprises a preliminary step of equalizing said baseband signal. [0014] For example, the equalization is a maximum likelihood equalization, a Zero forcing (ZF) equalization, a Decision Feedback Equalization ("Decision Feedback Equalization") ), or equalization based on a minimum mean square error (MMSE). [0015] In particular, the third implementation example is particularly effective when the transmission channel is arbitrary, in other words, when the channel takes into account the loss of free space but also of a fading, which requires in advance the implementation of an equalization. In another embodiment, the invention relates to a device for receiving a signal transmitted in the form of an electromagnetic wave carrying an angular momentum, delivering an estimate of a data symbol of a sequence of data symbols. comprising at least two distinct value data symbols, said electromagnetic wave carrying an orbital angular momentum having an orbital angular momentum momentarily selected upon transmission of said signal so as to represent by bijection the value of said data symbol. According to the invention, such a device comprises an estimator of the value of said data symbol, implementing a detector of said order of orbital angular momentum. Such a reception device is radiofrequency or optical, and is particularly adapted to implement the reception method described above. This transmission device may of course include the various characteristics relating to the transmission method described above, which can be combined or taken separately. Thus, the characteristics and advantages of this receiving device are the same as those of the reception method. Therefore, they are not detailed further. The invention also relates to a computer program comprising instructions for implementing a transmission or reception method described above when this program is executed by a processor. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape. The methods according to the invention can therefore be implemented in various ways, in particular in hard-wired form and / or in software form. The invention also relates to one or more computer-readable information carriers, and including instructions of one or more computer programs as mentioned above. 4. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a particular embodiment, given as a simple illustrative and non-limiting example, and the accompanying drawings, among which: FIG. 1, already described in relation with the prior art, illustrates the helical wavefront of an electromagnetic wave carrying an orbital angular momentum, FIG. 2, already described in relation with the prior art, illustrates a system radiofrequency transmission-reception of an electromagnetic wave carrying an orbital angular momentum. FIG. 3 presents the main steps of the transmission method according to one embodiment of the invention, FIG. 4 is a schematic representation of a radio frequency transmission device according to an example of the invention, FIGS. 5A and 5B the prior art respectively represent the general principle of an optical transmission module of an electromagnetic wave having an angular angular orbital moment of predetermined order and the corresponding waveguide architecture, FIG. 6 is a representation of the Spatial localization of a reception element of a radio frequency reception device according to the invention, FIG. 7 presents the main steps of the reception method according to the invention, FIGS. 8 to 10 illustrate various examples of implementation of the radio reception method. according to the invention, FIGS. 11 and 12 respectively illustrate the simplified structure of a device for transmission implementing a transmission technique, and a receiving device implementing a reception technique according to a particular embodiment of the invention. 5. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 5.1 GENERAL PRINCIPLE The general principle of the invention is based on a new technique for the transmission of information by electromagnetic wave based on the use of the orbital angular momentum. The order of angular orbital momentum of the electromagnetic wave to be emitted is in fact directly representative of the data symbol value to be transmitted, a bijective relation being established according to the invention between the angular orbital moment order and the value of symbol of data to be transmitted. Thus, in view of the techniques of the prior art where the properties of the orbital angular momentum are essentially used for the generation of orthogonal channels available for the transport of information associated with an information multiplexing, the present invention proposes to dedicate a order of orbital angular momentum to the representation of a single data symbol value. [0016] The technique according to the invention makes it possible to increase spatial diversity and can in particular be applied for short-range transmissions, for example to transfer identification data. At the reception, the reconstruction of the transmitted data symbol is simple and efficient because it can be deduced by a simple inversion of the bijective relation used on transmission to select the order of orbital angular momentum to be used to generate the 'electromagnetic wave. In the following, with reference to FIG. 3, the main steps implemented by a transmission method according to one embodiment of the invention are presented. 5.2 Description of Implementation Examples of the Transmission Method According to a particular implementation example, the transmission method according to the invention receives (31) at the input M binary data to be transmitted (d 1, m, M being an integer and a binary value equal to 1 or 0. In addition, the method implements a step of determining (32) the maximum absolute value of order 1 n, of angular momentum orbital capable of being transmitted by the device. For example, when the transmission device has N = 5 transmission elements, the maximum absolute value of order 1, also called mode, of orbital angular momentum, which can be coded separately is then such that that abs (1) <N / 2, let m '= 2, so that 1 E (-2, -1, 0, 1, 2). In another example, the transmission device has N = 8 elements d emission, the possible values of the order /, also called modes, of orbital angular momentum, e can be distinctly encoded such that -N / 2 1 <N / 2 so that / E (-4, -3, -2, -1, 0, 1, 2, 3}. [0017] Transmitting modules for transmitting an electromagnetic wave carrying an orbital angular momentum with a predetermined order are for example represented by FIGS. 4 and 5A, 5B respectively relating to a radio frequency transmission and an optical transmission. In particular, the radiofrequency transmission module (44) of FIG. 4 has 8 emission elements (T0, T1, T2, T3, T4, T5, T6, T7) and is therefore able to generate electromagnetic waves carrying a moment orbital angle whose order / E (-4, -3, -2, -1, 0,1, 2, 31 It should also be noted that other transmission modules capable of exciting an orbital angular momentum have been set at the point such a conventional parabolic reflector but deformed ("twisted") to induce an azimuthal phase distribution as described by F. [0018] Tamburini et al. ("Encoding many channels on the same frequency through radio vorticity: first exeprimental test", New Journal of Physics, Vol 14, 2012, 033001), or a phase plate as described by R. Niemiec ("Angular momentum excitation"). orbital (OAM) of a wave in millimetric band, from a phase blade ', 18' National Microwave Day, 15-17 May 2013). According to another example, illustrated by FIGS. 5A and 5B, an optical transmission module (5000 and 5001) corresponding to a silicon photonic integrated circuit may also be used to generate an electromagnetic wave carrying an orbital angular momentum with a predetermined order l as described by NK Fontaine et al. ("Efficient multiplexing and demultiplexing of free-space orbital angular momentum using photonic integrated circuits", Optical Fiber Communication Conference and Exposition (OFC / NFOEC), 2012 and the National Fiber Optic Engineers Conference, pages 1-3, 4-8 March 2012 ). Such an optical transmission module comprises in particular a circular array coupler (54) and a star coupler (51). The circular array coupler is based in particular on the use of monomode openings (54) emitting or collecting light, which is then guided to the star coupler (51) by means of optical waveguides (53). ), the length of which is adapted as a function of the location of the opening in the wavefront considered in order to convert an azimuthal phase (50), representative of the order of the orbital angular momentum corresponding to the number of rotations of the phase per wavelength, and an amplitude variation in linear phase variations (52). FIG. 5A represents an optical transmission module capable of generating electromagnetic waves carrying an orbital angular momentum whose order of 1 E (-2, -1, 0, 1, 2), whereas FIG. 5B represents a transmission module optical device capable of generating electromagnetic waves carrying an orbital angular momentum whose order I E (-4, -3, -2, -1, 0, 1, 2, 3, 41 These existing transmission modules, conventionally used for the transport of information associated with a multiplexing of the information does not, as such, make it possible to implement the invention, since no relation is established between the value of the data symbol to be transmitted and the order of angular momentum orbital. [0019] The steps of reception (31) of M binary data to be transmitted and determination (32) of the maximum absolute value of order 1 m ', of orbital angular momentum able to be transmitted by the transmission device used are independent and can be implemented successively, in an indifferent order, or in parallel as shown in FIG. [0020] Once these two steps have been performed, the method according to the embodiment shown in FIG. 3 implements a step of forming (33) a sequence of data symbols from the bit stream, taking into account the absolute value. maximum order | m '' of orbital angular momentum. In other words, the digital symbol train (d) 1, m, M being an integer and a binary value equal to 1 or 0 is "coded" in an alphabet of data symbols defined by the commands (or states) of the orbital angular momentum, these orders being delimited by the maximum absolute value of order 1 ma of orbital angular momentum capable of being transmitted by the transmission device previously determined. According to a particular implementation example, the training step corresponds to an N-state modulation, N being an integer equal to twice said maximum absolute value of orbital angular momentum order plus one. For example, for a radiofrequency transmission device or optical transmission device, the training step corresponds to an amplitude pulse modulation (AMP) of N states, called PAM N-ary. [0021] Such an N-ary PAM modulation (42) is illustrated in particular by FIG. 4, thus a set of bits of the bitstream 1011..01 is represented by data symbols whose value in the constellation is -2.1.0. , -4. The correspondence between the binary sequence 1011..01 and the representation (of the English "mapping") in the constellation is for example established by means of a coding such as the Gray coding or any other means allowing to establish a such "mapping". A quadrature phase shift keying (QPSK) or a sixteen state amplitude modulation (16QAM) can also be used to associate a value of representation of the data symbol in the constellation (also called state value) to a group of several bits. It should be noted that by "value" is meant any information that makes it possible to locate a data symbol in a constellation, such a value can therefore correspond to an integer value associated with a position number in the constellation, but also to a pair of coordinates in the constellation plane. [0022] Once the formation of the data symbols and the definition of their value in the constellation have been carried out, the method according to the invention implements a bijective selection step (34) of an order of orbital angular momentum, associating with each distinct value said data symbol is a distinct order of orbital angular momentum, and delivers a selected orbital angular momentum order representative, by bijection, of the value of said at least one data symbol to be transmitted. [0023] Thus, by having the value of the symbol carried by the order of orbital angular momentum, a spatial modulation is created. This aspect is illustrated in particular by FIG. 4, wherein said transmission method is implemented by a radiofrequency transmission device (40) comprising a plurality of transmission elements (T0, T1, T2, T3, T4, T5, T6, T7). The bijective selection (34) according to the invention of an order of orbital angular momentum is implemented by a selection module (45). According to the example illustrated in FIG. 4, the order of orbital angular momentum is selected when it is equal to the value of the data symbol to be transmitted. Thus, according to this example, the bijective relation between the order of orbital angular momentum and the value representing the data symbol in the constellation is therefore an identity relation, in other words of equality, between the value representing the data symbol in the constellation and order of orbital angular momentum. Such a bijective selection based on an equality between the value representing the data symbol in the constellation and the order of orbital angular momentum is only possible when the mode of forming and representing data symbols in the constellation delivers a value whole. In other words, when the data symbol is represented by the value -4 in the constellation, an order of angular momentum orbital / = -4 is selected. As a result, the order of angular momentum directly represents the value of the information to be transmitted. When the value corresponds for example to a pair of coordinates in the constellation plane, the bijective selection is based on a bijective relation associating with each distinct pair of coordinates a distinct order of orbital angular momentum. [0024] Next, with regard to the embodiment represented by FIG. 4 representing a radiofrequency transmission device (40), the transmission method further comprises a series-parallel replication step (43) of the selected orbital angular momentum order. = -4 so that it is delivered at the input of each transmitting element (T0, T1, T2, T3, T4, T5, T6, T7). [0025] Once the bijective selection of the order of orbital angular momentum to be transmitted has been carried out, the method according to the invention implements a step of transmission (35) of said electromagnetic wave carrying an orbital angular momentum whose order of angular momentum orbital corresponds to said selected orbital angular momentum order. [0026] An example of this transmission is for example illustrated in FIG. 4, where the order of orbital angular momentum = -4 has been selected and transmitted by / V = 8 transmission elements corresponding to eight radio frequency transmission antennas. The transmitted signal (35) by the eight radiofrequency antennas (To, T1, Tz, T3, T4, T5, T6, T7) forming the circular antenna array corresponding to the transmission module (44) is therefore transmitted in the following form : 1/27, r / 1 [127e N = XI where 1 represents the N-ary information symbol to be transmitted. ./17/ 1 (N-1) e N Thus, with regard to the illustration of Figure 4, when = -4, the antenna T6 generates a (-4) .6 1 2rc electromagnetic wave whose expression includes the term N It should be noted that the receiving (31), determining (32), training and replication (43) steps are optional, their implementation being able to be suppressed when the transmission device receives directly the representative values in the constellation each data symbol to be transmitted and / or when the transmission device uses a single transmission element such as an optical waveguide. [0027] In addition, the steps of the reception method according to the invention are repeated as many times in succession as there are data symbols in the previously transmitted data symbol sequence. 5.3 Description of implementation examples of the reception process. 5.3.1 Case of a transmission channel without fading The received signal r, corresponding to the signal transmitted according to the transmission method previously described, has the expression: r = Hx + n, where H is the representative matrix of the channel 12 between the transmission device T and the reception device R as represented by FIG. 1 and represents only the loss in free space of a communication between these two devices, and n such that n (-> CH (0, o-2 / N), a complex Gaussian noise, for example, a complex circular Gaussian noise received by each of the receiving elements, these receiving elements corresponding to radio frequency antennas when the communication system (formed of at least one transmission device and at least one receiving device) is radiofrequency. [0028] It should be noted that for a radiofrequency communication system, it is equally possible to implement a system comprising N transmission elements and N reception elements, than to implement a system comprising NE transmission elements and NR reception elements, NE and NR being distinct. In the case of a radiofrequency communication system NxN, the matrix H e_jkcii2 to representative of the channel is written H = - d21 4r e-ilcdNN one, dNN - with k = -27 the wave number, dmn the distance between the m-th reception element, with: zm2 dm u = a2 + 2zmtanOmcos (07, - On) COS m where a is the radius of the transmitting antenna, zm the distance between the plane of the antenna d emission and that of reception, Om the pointing angle on the reception antenna m in spherical coordinates, (Pm the azimuth of the sensor of the reception antenna in spherical coordinates and f2 = 71. the angular position of the elements in the plane of the antenna network N, these parameters being illustrated in FIG. 6. In the following, with reference to FIG. 7, the main steps implemented by a reception method according to an embodiment are presented. According to an example of a particular implementation, the reception method according to the invention receives it (71) input an electromagnetic wave 0Em. [0029] According to the invention, the Dow electromagnetic wave carries an orbital angular momentum having an orbital angular momentum momentarily selected during the transmission of the signal so as to represent by bijection the value of a data symbol. Once this reception step has been performed, the method according to the embodiment shown in FIG. 7 implements a step of estimating (72) the value of the transmitted data symbol, comprising a step of detecting (721) the order of orbital angular momentum of the electromagnetic wave 0Em. Once the order of orbital angular momentum de of the electromagnetic wave EEm is detected, the receiving method according to the invention determines (722) the value Vs representing in the constellation the transmitted data symbol. This determination implements, in particular, InvB inversion of the bijective relation which allowed selection of the order of orbital angular momentum. Then, starting from the value Vs, one or more bits are determined D_Bits (723) by correspondence between the value Vs in the constellation (of the English e-jlcd21 diN n-th emission element and the "demapping") and a binary set comprising at least one bit by means for example of a decoding such as the decoding of Gray . A) Detection of the Order of Orbital Angular Moment Based on the Implementation of a Fourier Transform The signal r is received (71) by the reception module 81 of the reception device 80, illustrated in FIG. 8, comprising for example a plurality of receiving elements (optical or radiofrequency as shown in Figure 8) and belonging to an NxN communication system. For example, when the receiving device is a radio frequency or optical receiving device, a baseband conversion is applied. A Fast Fourier Transform (FFT) is then applied (821) to the received vector dm], Vm E (0, ..., N - N being an integer corresponding to the number of receiving elements, so that y the resulting vector is expressed as follows: y = FNr = FNHx + FNn FNUI X) + fi FNh C) FNx + h 0 81n + 11, - with h = FNh the Fourier transform the first line h of the transmission channel between the N transmission elements and the first reception element. By property, the FFT of the vector 1 if / = nx is a 8/7 dirac, such that: ain - = 10 if 1 # n moreover and are respectively the convolution and circular convolution operators of Hadamard (in other words term-term product). [0030] Thus by construction, a single entry of y contains information on the order of orbital angular momentum used. Without noise n, the only non-zero input of y gives the order / of the orbital angular momentum used. For example, if N = 8 and 1 transmitted = -4, then: ## EQU1 ##, and ## EQU1 ## Consequently, the decision on the order / orbital angular momentum used during the transmission is based on the detection of the maximum energy of the elements constituting the vector y-h3 713 11-4 F14 h, 115 h6 n6 h7 , assuming the channel does not fade. After a parallel-series conversion (822) of the elements constituting the vector y to create a block of N elements in line y '= [y [0], y [N-1]], the detection of the order of angular momentum The orbital used during the transmission is therefore implemented by means of an energy detector such that: = maxilyi12, with / e [0, / V - 1]. In other words, the absolute value squared is taken on the elements constituting the vector y, ie lyi12 and the maximum index i gives the value of the order of orbital angular momentum used, with the following rule: N-1 - if the maximal index im 'E IO, j} is such that then i = imoz - if iinax E - 1/2] + 1, -, N - 1) then i = f- [N / 2], - -, - 1). Finally, once the order of orbital angular momentum I of the electromagnetic wave Chm is detected, the reception method according to the invention determines D_Vs (824) the value Vs representing in the constellation the transmitted data symbol by setting inversion of the bijective relation which allowed the selection of the order of orbital angular momentum 1 '. Then, from the value Vs, one or more bits are determined (824) by correspondence between the value Vs of representation in the constellation (of the English "demapping") and a binary set comprising at least one bit by means of example of a decoding such as the decoding of Gray. [0031] B) Maximum Likelihood Detection of the Order of Orbital Angular Momentum Hereinafter, a variant embodiment is presented with regard to the previously described detection based on the implementation of a Fourier transform. The present variant is based on maximum likelihood detection ("scoring"). [0032] According to this variant embodiment, the signal r is received (71) by the reception module 81, and then admitting that the value of the opening angle Om (represented in FIG. 6) is also unknown, it is necessary to estimate the vector a = [1, AND maximizing the density of probability (ddp) Ky; a) the received signal. Assuming that H. = 0, V m E (1, ..., N), the probability density is expressed in the following form: 1 'Al r ose e-ikcozso eir = j-diOnejaksin o cos (0m- On) 12 no.2m e 0_2 7710 Y 0711 1 KY; a) = 47/7 I - The following relation is obtained: max, Ky; <=> maxa In Ky; at). According to an implementation variant, the search for the vector a is implemented by successive iterations from an initial state of a and the information matrix of Fisher 1, in particular the value of a at the moment kf 1, is such that: 1,, a in KY; a) I ak-Ei = ak I la), with 1 (a), the information matrix of Fisher on the yy a = ak a2 ln p (y, a) parameter a, and whose generic term is: (1 (a)) 1,1 = aa. 5.3.2 Case of any transmission channel The received signal r, corresponding to the signal transmitted according to the previously described transmission method, always has the expression: r = - Hx n, where H is the representative matrix of the channel 12 between the transmission device T and the reception device R as represented by FIG. 1, such that ffee'N where each element hm, n consists of the loss portion in free space as well as a complex coefficient Emn - CH (0,1) whose gain is a Rayleigh law. In the far field, the expression of the element hm, n is the following: it.cosern jk z ejaksinem cos (4) m-On) e cosom hm, n E mn 47rz The signal r is received (71) by the reception module 81 of the reception device 90, illustrated by FIG. 9, comprising, for example, a plurality of M reception elements (optical or radiofrequency elements as represented in FIG. 9) belonging to an NxM communication system, with M> N, N and M respectively representing the number of transmission elements and the number of reception elements. According to an exemplary implementation of the reception method according to the invention in any channel, an estimator (91) is implemented for estimating the transmitted data vector x and implements a maximum likelihood equalization (912) ( MV), this equalization being optimal because it has a minimum variance for the estimation of the transmitted data vector x. Such an equalization (912) is carried out after estimation (911) of the transmission channel H and autocorrelation of the noise so that: 2 = (H where 1-111 is the conjugated transposed matrix of H. In addition, C is the noise covariance matrix such that C = Inne] E Cmxm The signal received after treatment is then expressed by the following equation: x (HI c-111) -1 HI -1 c-1n. an estimate of the vector x plus a noise vector, therefore each constituent element is a complex number Once this estimation of the received signal has been carried out, the detection (82) of the order 1 of orbital angular momentum used during the transmission is based on the implementation of a Fourier transform as described above with regard to FIG. [0033] According to another alternative, after estimation and equalization (101) as described previously or by using any other type of equalizer such as a zero forcing equalizer (of the English "Zero forcing" (ZF)), an equalizer the Decision Feedback Equalizer, or an equalizer based on a minimum mean square error (MMSE), the detection (82) of the Order 1 of orbital angular momentum used during transmission can also be implemented by means of a determination of a phase gradient as illustrated by FIG. 10. Such a determination of a phase gradient comprises: a step of shaping said signal in a vector form, a step of unwinding the phase of each term of said vector form and determining (102) of the phase of the product of the terms of said vector form, a step of obtaining (103) said order of estimated orbital angular momentum implementing a division of the product phase of the terms of said vector form by the term ira - 1), L being an integer corresponding to said maximum absolute value of order of angular momentum orbital capable of to be received multiplied by two. For example, in the case of a radiofrequency transmission module with N emission elements, L = N. In other words, the phase of the product of the terms of the vector 2 is estimated then La-T4-12 [1, ri.-O12TELti + oi divided by 7 (L - 1) such that Î = ° =, with (Pi a random phase term rcg-1) n (1, -1) due to filtered Gaussian noise by means of a Maximum likelihood equalization (MV). Without noise, (Pi = 0 Vi E (0,, L - More precisely, the phase of the vector 2 is determined by phase unfolding, that is to say that when the phase gradient between two measurement points exceeds 7 the measured phase is corrected by an addition of a multiple of 27. Phase unfolding methods for determining such a multiple are disclosed, in another context, by M. Desvignes ("Phase sequence: application to the geometric distortion correction in MRI ", Processing of Signal 2000, Volume 17, No. 4, pages 313 to 324) Of course, the phase measurement at each point is disturbed by a noise term, but this is attenuated by prior equalization. [0034] In the absence of noise, such a detector allows a perfect detection of the order 1 of orbital angular momentum used during the transmission because using the development 12m / = 71 (L - 1). mathematical sum of L - 1 integers, it is obtained: In noisy channel, it can be noted that more L is large plus the noise term n (c-1) for the estimation of 1 will be low. 5.4 Structure of the transmission and reception devices Finally, with reference to FIGS. 11 and 12 respectively, the simplified structure of a transmission device and the structure of a reception device according to a particular embodiment of the invention are presented. invention. As illustrated in FIG. 11, such a transmission device comprises a memory 1110 comprising a buffer memory, a processing unit 1111, equipped for example with a microprocessor itP, and driven by the computer program 1112, implementing the method transmission according to one embodiment of the invention. [0035] At initialization, the code instructions of the computer program 1112 are for example loaded into a RAM before being executed by the processor of the processing unit 1111. The processing unit 1111 receives as input at least a bit stream of data. The microprocessor of the processing unit 1111 implements the steps of the transmission method described above, according to the instructions of the computer program 1112, for generating an electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order represents by bijection the value of the data symbol to be transmitted. For this, the transmission device comprises, in addition to the buffer memory 1110, a bijective selection module of an order of orbital angular momentum, associating with each distinct value of a data symbol a distinct orbital angular momentum order, and delivering an order of selected orbital angular momentum representative, by bijection, of the value of said at least one data symbol to be transmitted, and a transmission module of said electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order corresponds to said moment order angular orbital selected. [0036] These modules are driven by the microprocessor of the processing unit 1111. As illustrated in FIG. 12, a receiving device according to the invention has a memory 1210 comprising a buffer memory, a processing unit 1211, equipped for example with a microprocessor itP, and driven by the computer program 1212, implementing the reception method according to one embodiment of the invention. [0037] At initialization, the code instructions of the computer program 1212 are for example loaded into a RAM memory before being executed by the processor of the processing unit 1211. The processing unit 1211 receives a wave input as input electromagnetic bearing an orbital angular momentum. The microprocessor of the processing unit 1211 implements the steps of the reception method described above, according to the instructions of the computer program 1212, to estimate the transmitted data symbols. For this, the receiving device comprises, in addition to the buffer memory 1210, an estimator of the value of the data symbol, implementing a detector of said order of orbital angular momentum. These modules are controlled by the microprocessor of the 1211.5 processing unit
权利要求:
Claims (15) [0001] REVENDICATIONS1. A method of transmitting a sequence of data symbols comprising at least two distinct value data symbols, delivering an electromagnetic wave carrying an orbital angular momentum, characterized in that it comprises, for at least one data symbol to be transmitted: a bijective selection step (34) of an order of orbital angular momentum, associating with each distinct value of a data symbol a distinct order of orbital angular momentum, and delivering a representative selected orbital angular momentum order, by bijection, of the value of said at least one data symbol to be transmitted, - a transmission step (35) of said electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order corresponds to said selected orbital angular momentum order. [0002] 2. Transmission method according to claim 1, characterized in that said order of orbital angular momentum is selected when it is equal to the value of said data symbol to be transmitted. [0003] 3. Transmission method according to one of the preceding claims, characterized in that it further comprises the following steps implemented prior to said step of selecting: a step of receiving (31) a bit stream of data a step of determining (32) the maximum absolute value of orbital angular momentum order adapted to be transmitted by a transmission device implementing said transmission method, a step of forming (33) said sequence of data from said bit stream, said forming step taking into account said maximum absolute value of order of orbital angular momentum. [0004] 4. Transmission method according to one of the preceding claims, characterized in that said forming step corresponds to a modulation (42) N states, N being an integer equal to twice said maximum absolute value of order of angular momentum orbital plus one. [0005] 5. Transmission method according to one of the preceding claims, characterized in that when said transmission method is implemented by a radiofrequency transmission device (40) comprising a plurality of transmission elements (T0, T1, T2 , T3, T4, T5, T6, T7), said transmission method further comprises a series-parallel replication step (43) of said selected orbital angular momentum command outputting said orbital angular momentum command at the input of each element of transmitting said plurality of transmitting elements (T0, T1, T2, T3, T4, T5, T6, T7). [0006] Device for transmitting a sequence of data symbols comprising at least two distinct value data symbols, delivering an electromagnetic wave carrying an orbital angular momentum, characterized in that it comprises, for at least one data symbol to transmitting: a bijective selection module (45) of an order of orbital angular momentum, associating with each distinct value of a data symbol a distinct order of orbital angular momentum, and delivering a representative selected orbital angular momentum order, by bijection , the value of said at least one data symbol to be transmitted, - a transmission module (44) of said electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order corresponds to said selected orbital angular momentum order. [0007] 7. Signal transmitted in the form of an electromagnetic wave carrying an orbital angular momentum, characterized in that said electromagnetic wave carrying an orbital angular momentum has an orbital angular momentum momentarily selected during the transmission of said signal so as to represent by bijection the value of a data symbol to be transmitted. [0008] A method of receiving a transmitted signal in the form of an angular momentum-bearing electromagnetic wave, providing an estimate of a data symbol of a data symbol sequence comprising at least two distinct value data symbols. said electromagnetic wave carrying an orbital angular momentum having an orbital angular momentum momentarily selected upon transmission of said signal so as to represent by bijection the value of said data symbol, characterized in that said receiving method comprises a step of estimating (72) the value of said data symbol, implementing a detection step (721) of said order of orbital angular momentum. [0009] 9. Reception method according to claim 8, characterized in that said detecting step (721) implements a Fourier transform (821) of said signal. [0010] Receiving method according to claim 8, characterized in that said detecting step (721) is a maximum likelihood detection. [0011] 11. The reception method as claimed in claim 10, characterized in that said maximum likelihood detection step (721) is iterative and uses a Fisher.35 information matrix. [0012] 12. The reception method as claimed in claim 8, characterized in that said detecting step implements a determination of a phase gradient comprising: a step of shaping said signal in a vector form, a step of unwinding of said signal; a phase of each term of said vector form and determination (102) of a phase of the product of the terms of said vector form, a step of obtaining (103) said estimated orbital angular momentum order implementing a division of said phase of the product of the terms of said vector form by the term ira - 1), where L is an integer corresponding to a maximum absolute value of order of orbital angular momentum capable of being received multiplied by two. [0013] 13. Reception method according to claim 12, characterized in that it further comprises a prior step of equalization (91, 101) of said baseband signal. [0014] A device (80, 90, 100) for receiving a signal transmitted in the form of an angular momentum-providing electromagnetic wave, providing an estimate of a data symbol of a sequence of data symbols comprising at least two distinct value data symbols, said electromagnetic wave carrying an orbital angular momentum having an orbital angular momentum momentarily selected during transmission of said signal so as to represent by bijection the value of said data symbol, characterized in that said device receiver comprises an estimator of the value of said data symbol, implementing a detector of said order of orbital angular momentum. [0015] 15. A computer program comprising instructions for carrying out a method according to claim 1 or claim 8 when the program is executed by a processor.
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同族专利:
公开号 | 公开日 US20160301479A1|2016-10-13| EP3075084A1|2016-10-05| US10084548B2|2018-09-25| FR3014271B1|2015-12-04| WO2015079020A1|2015-06-04|
引用文献:
公开号 | 申请日 | 公开日 | 申请人 | 专利标题 US20060056807A1|2004-09-10|2006-03-16|New York University|Topologically multiplexed optical data communication| US20130235744A1|2012-03-11|2013-09-12|Broadcom Corporation|Communication system using orbital angular momentum|FR3047859A1|2016-02-17|2017-08-18|Centre Nat D'etudes Spatiales |ELECTROMAGNETIC WAVE EMISSION NETWORK ANTENNA CARRIER OF AN ORBITAL ANGULAR MOMENT AND TRANSMISSION METHOD THEREOF|EP1969793A2|2005-12-29|2008-09-17|Nokia Corporation|Apparatus, method and computer program product providing joint synchronization using semi-analytic root-likelihood polynomials for ofdm systems|JP2017515337A|2014-04-17|2017-06-08|ライ ラディオテレヴィズィオーネ イタリアーナ エッセ.ピー.アー.|System for transmitting and / or receiving signals having electromagnetic mode with orbital angular momentum, and device and method thereof| US11245486B2|2014-10-13|2022-02-08|Nxgen Partners Ip, Llc|Application of orbital angular momentum to Fiber, FSO and RF| CN106788777A|2016-12-07|2017-05-31|中山大学|One kind is voted anonymously method and system based on the coding realization of photon angular momentum|
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2015-11-24| PLFP| Fee payment|Year of fee payment: 3 | 2016-11-25| PLFP| Fee payment|Year of fee payment: 4 | 2017-11-28| PLFP| Fee payment|Year of fee payment: 5 | 2019-11-29| PLFP| Fee payment|Year of fee payment: 7 | 2021-08-06| ST| Notification of lapse|Effective date: 20210705 |
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申请号 | 申请日 | 专利标题 FR1361884A|FR3014271B1|2013-11-29|2013-11-29|METHOD FOR TRANSMITTING A SEQUENCE OF DATA SYMBOLS, TRANSMISSION DEVICE, SIGNAL, RECEPTION METHOD, RECEIVING DEVICE, AND CORRESPONDING COMPUTER PROGRAM|FR1361884A| FR3014271B1|2013-11-29|2013-11-29|METHOD FOR TRANSMITTING A SEQUENCE OF DATA SYMBOLS, TRANSMISSION DEVICE, SIGNAL, RECEPTION METHOD, RECEIVING DEVICE, AND CORRESPONDING COMPUTER PROGRAM| EP14803163.6A| EP3075084A1|2013-11-29|2014-11-28|Method for transmitting a sequence of data symbols, transmission device, signal, receiving method, corresponding receiving device and corresponding computer program| PCT/EP2014/075936| WO2015079020A1|2013-11-29|2014-11-28|Method for transmitting a sequence of data symbols, transmission device, signal, receiving method, corresponding receiving device and corresponding computer program| US15/100,542| US10084548B2|2013-11-29|2014-11-28|Method for transmitting a sequence of data symbols, corresponding device for transmission, signal, method for receiving, device for receiving and computer program| 相关专利
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