Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/70—Photonic quantum communication
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
  • H04L25/03006—Arrangements for removing intersymbol interference
  • H04L25/03178—Arrangements involving sequence estimation techniques
  • H04L25/03248—Arrangements for operating in conjunction with other apparatus
  • H04L25/03254—Operation with other circuitry for removing intersymbol interference
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
  • H04L25/03828—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/26—Systems using multi-frequency codes
  • H04L27/2601—Multicarrier modulation systems
  • H04L27/2626—Arrangements specific to the transmitter only
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
  • H04L25/03006—Arrangements for removing intersymbol interference
  • H04L25/03178—Arrangements involving sequence estimation techniques
  • H04L25/03248—Arrangements for operating in conjunction with other apparatus
  • H04L25/0328—Arrangements for operating in conjunction with other apparatus with interference cancellation circuitry

Definitions

• the field of the invention is that of digital communications, in transmission or in broadcasting.
• the invention relates to electromagnetic wave (EM) transmission from at least one transmitter to at least one receiver.
• EM electromagnetic wave
• 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.
• the long-distance transfer of information is routinely performed through antennas radiating electromagnetic (EM) plane waves.
• EM electromagnetic
• An electromagnetic wave is defined by its amplitude, its wave vector, its frequency and its angular momentum.
• 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.
• SAM spin angular momentum
• OAM orbital angular momentum
• 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 non-zero orbital angular momentum, is characterized by an azimuthal dependence of its phase noted e ⁇ ] l (p with the order of the angular momentum orbital (also called “topological load”) corresponding to the number of rotations of the phase per wavelength, and ⁇ the azimuth angle.
• the orbital angular momentum has the effect of producing a wavefront that is no longer equiphase but helical with a value of the phase of the field E which depends on the azimuthal angle and on 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 reception device 13.
• B. Thicht (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.
• 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
• 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.
• the invention proposes a novel solution, in the form of 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
• such a method comprises, for at least one data symbol to be transmitted:
• the invention is based on a new and inventive approach to the transmission of a signal.
• the invention diverts the conventional use of the order of orbital angular momentum usually dedicated to the multiplexing of the information.
• 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.
• the same transport channel identified by its order of orbital angular momentum is used to transport a plurality of symbols of distinct values.
• 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.
• an order of orbital angular momentum is a bijective representation of 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.
• 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.
• 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.
• 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 significant complexity (for example implementing an exponential function) can in particular make it possible to secure the transmission of the symbol.
• 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.
• 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.
• the order of orbital angular momentum is selected when it is equal to the value of the data symbol to be transmitted.
• the transmission method according to the invention further comprises the following steps implemented prior to said selection step:
• a step of forming said sequence of data symbols from said bit stream said forming step taking into account said maximum absolute value of orbital angular momentum order.
• 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.
• 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 orbital angular momentum order equal to -2
• the step of forming symbols from the received bit stream 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 orders of orbital angular momentum.
• 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.
• the training step corresponds to a pulse amplitude modulation (AMP) of N "Pise", N-state PAM.
• AMP pulse amplitude modulation
• N-state PAM N-state PAM
• 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"
• QPSK quadrature phase shift keying
• 16QAM sixteen-state quadrature amplitude modulation 16QAM for "16 state Quadrature Amplitude Modulation
• the transmission method 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.
• the transmission device is a circular array of antennas comprising eight antennas
• 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.
• the invention in another embodiment, 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,
• such a device comprises, for at least one data symbol to be transmitted:
• 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.
• Another aspect of the invention relates to a signal transmitted in the form of an electromagnetic wave carrying an orbital angular momentum.
• 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.
• this signal may carry information on the type of bijective selection implemented on transmission when the reception device does not "know” beforehand this type of bijective selection.
• the invention in another embodiment, 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 a bijectively selected orbital momentum moment when transmitting said signal so as to represent by bijection the value of said data symbol,
• Such a reception method 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.
• 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.
• 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.
• said detection step implements a Fourier transform of said signal.
• 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.
• FFT Fast Fourier Transform
• Such detection is therefore based on the detection of a maximum of energy.
• 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, ⁇ ) maximizing the probability density of the signal received.
• said maximum likelihood detection step is iterative and uses a Fisher information matrix.
• said detection step implements a determination of a phase gradient comprising:
• n (L-1) L being an integer corresponding to a maximum absolute value of order of orbital angular momentum capable of being received multiplied by two.
• the method further comprises a preliminary step of equalizing said baseband signal.
• the equalization is a maximum likelihood equalization, a zero forcing equalization (ZF), a decision feedback equalization ), or even an equalization based on a minimum mean square error (of the "Minimum Mean Square Error"
• the third example of implementation is particularly effective when the transmission channel is any, in other words, when the channel takes into account the loss of free space but also a fading, which requires prior implementation of an equalization.
• the invention in another embodiment, 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.
• 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 the implementation of 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.
• FIG. 1 already described in relation with the prior art, illustrates the wavefront helical helical wave of an electromagnetic wave carrying an orbital angular moment
• FIG. 2 already described in relation with the prior art, illustrates a radiofrequency system for 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 radiofrequency transmission device according to an example of the invention.
• FIGS. 5A and 5B issued from the prior art respectively represent the general principle of an optical transmission module of an electromagnetic wave having an angular orbital angular moment of predetermined order and the corresponding waveguide architecture
• FIG. 6 is a representation of the spatial location of a reception element of a radiofrequency 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 reception method according to the invention
• Figures 11 and 12 respectively illustrate the simplified structure of a transmission device implementing a transmission technique, and a receiving device implementing a reception technique according to a particular embodiment of the invention.
• 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.
• the present invention proposes to dedicate a order of orbital angular momentum to the representation of a single data symbol value.
• the technique according to the invention makes it possible to increase the spatial diversity and can in particular be applied for short-range transmissions for example to transfer identification data.
• the reconstruction of the emitted data symbol is sim ple and efficient because it can be deduced by a sim ple inversion of the bijective relation used on transmission to select the order of orbital angular momentum to be used. to generate the electromagnetic wave.
• the transm ission method receives (31) as input M binary data to be transmitted [d] 1: M , M being an integer and a binary value equal to 1 or 0.
• the method implements a step of determining (32) the maximum absolute value of order 1 max of orbital angular momentum capable of being transmitted by the transm ission device used.
• 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 radiofrequency transmission and an optical transm ission.
• the radio frequency transmission module (44) of Figure 4 has eight transmitting elements (T 0, T, T 2, T 3j T 4, T 5, T 6, T 7) and is adapted to generate electromagnetic waves carrying an orbital angular momentum whose order 1 E ⁇ -4, -3, -2, -1, 0, 1, 2, 3 ⁇ .
• 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 Exhibition (OFC / NFOEC), 2012 and the National Fiber Optic Engineers Conference, pages 1 to 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 able to generate electromagnetic waves carrying an orbital angular momentum whose order of E ⁇ -2, -1, 0, 1, 2], while FIG. 5B represents a transmission module optical device capable of generating electromagnetic waves carrying an orbital angular momentum whose order l E ⁇ - 4, - 3, - 2, - 1, 0, 1, 2, 3, 4 ⁇ .
• (32) of the maximum absolute value of order 1 max of orbital angular momentum capable of being transmitted by the transmission device used are independent and can be implemented successively, in an indifferent order, or in parallel as shown in FIG. figure 3.
• the method according to the embodiment FIG. 3 implements a step of forming (33) a sequence of data symbols from the bit stream, taking into account the maximum absolute value of order 1 max of orbital angular momentum.
• the digital symbol train [d] 1: M where M is an integer and a binary value equal to 1 or 0 is "encoded" in an alphabet of data symbols defined by the commands (or states) of the orbital angular momentum, these commands being delimited by the maximum absolute value of order 1 max of orbital angular momentum capable of being transmitted by the transmission device previously determined.
• 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.
• the training step corresponds to a pulse amplitude modulation (PAM) of N states, called PAM N-ary.
• PAM pulse amplitude modulation
• 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.
• 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.
• the method according to the invention implements a step of selection (34) of a bijective 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.
• a spatial modulation is created.
• FIG. 4 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 (T 0 , Ti, T 2 , T 3j T 4 , T 5 , T 6 , T 7 ).
• the bijective selection (34) according to the invention of an order of orbital angular momentum is implemented by a selection module (45).
• the order of orbital angular momentum is selected when it is equal to the value of the data symbol to be transmitted.
• 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.
• the bijective selection is based on a bijective relation associating with each distinct pair of coordinates a distinct order of orbital angular momentum.
• the method according to The invention implements a step of transmission (35) of said electromagnetic wave carrying an orbital angular momentum whose orbital angular momentum order corresponds to said selected orbital angular momentum order.
• the transmitted signal (35) by the eight radio-frequency antennae (T 0, T, T 2, T 3j T 4, T 5, T 6, T 7) forming the circular antenna array corresponding to the transmission module (44) is therefore transmitted in the following form: where l represents the N-ary information symbol to be transmitted.
• reception (31), determination (32), training and replication (43) steps are optional, their implementation being able to be eliminated when the transmission device directly receives the values representing in the constellation each symbol. of data to be transmitted and / or when the transmission device uses a single transmission element such as an optical waveguide.
• 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.
• 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
• n such that n ⁇ CJf (0, ⁇ 2 / ⁇ )
• a complex Gaussian noise for example, a circular complex Gaussian noise received by each of the reception elements, these reception elements corresponding to radiofrequency antennas when the communication system (consisting of at least one transmission device and at least one receiving device) is radiofrequency.
• N transmission elements and N reception elements it is equally possible to implement a system comprising N transmission elements and N reception elements, than to implement a system comprising N E transmission elements and N R receiving elements, N E and N R being distinct.
• a is the radius of the transmitting antenna
• z m the distance between the plane of the transmitting and receiving antenna
• 9 m the pointing angle on the receiving antenna m in spherical coordinates
• ⁇ ⁇ the azimuth of the receiving antenna sensor in spherical coordinates
• the reception method according to the invention receives (71) as input an electromagnetic wave EM .
• the electromagnetic wave EM carries an orbital angular momentum having a bijectively selected orbital angular momentum during transmission of the signal so as to represent the value of a data symbol by bijection.
• 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 EM electromagnetic wave.
• the reception method determines (722) the value Vs representing in the constellation the transmitted data symbol. This determination notably implements an inversion lnv B of the bijective relation which allowed the selection of the orbital angular momentum order l.
• one or more bits are determined D_Bits (723) by correspondence between the value Vs of representation in the constellation (of English "Demapping") and a bit set comprising at least one bit by means for example of a decoding such as Gray decoding.
• 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 reception elements (optical or radiofrequency elements as shown in FIG. to an NxN communication system.
• 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 r ⁇ m], Vm £ [0, ..., N-1], where N is an integer corresponding to the number of receiving elements, so that the resulting vector is expressed as follows:
• a single entry of y contains the information on the order of orbital angular momentum used.
• the decision on the order of orbital angular momentum used during the transmission is based on the detection of the maximum energy of the elements constituting the vector y, assuming that the channel does not fade.
• the reception method determines D_Vs (824) the value Vs representing in the constellation the data symbol transmitted by setting a reversal of the bijective relation that allowed the selection of the order of orbital angular momentum l.
• 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.
• the present variant is based on maximum likelihood detection ("scoring").
• the signal r is received (71) by the reception module
• H is the matrix representative of the channel 12 between the transmission device T and the reception device R, as shown in Figure 1, such as HEC MxN
• each element h mn consists of the loss portion in free space as well as a complex coefficient e mn ⁇ CJf (0,1) whose gain is a Rayleigh law.
• 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. to an NxM communication system, with M ⁇ N, N and M respectively representing the number of transmission elements and the number of reception elements.
• M ⁇ N, N and M respectively representing the number of transmission elements and the number of reception elements.
• 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.
• the vector x is an estimate of the vector x plus a noise vector so each constituent element is a complex number.
• 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. 8.
• 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:
• L N.
• MV maximum likelihood equalization
• phase of the vector x is determined by phase unfolding, that is to say that when the phase gradient between two measurement points exceeds ⁇ , the measured phase is corrected by adding a multiple of 2 ⁇ .
• Phase unfolding methods making it possible to determine such a multiple are disclosed, in another context, by M. Desvignes ("Phase deposition: application to the correction of geometric distortions in MRI", Signal 2000 Processing, Volume 17, No. 4, pp. 313-324).
• phase measurement at each point is disturbed by a noise term, but this is attenuated by the prior equalization.
• FIGS. 11 and 12 respectively, the simplified structure of a transmission device and the structure of a receiving device according to a particular embodiment of the invention are presented.
• such a transmission device comprises a memory 1110 comprising a buffer memory, a processing unit 1111, equipped for example with a ⁇ microprocessor, and driven by the computer program 1112, implementing the method transmission according to one embodiment of the invention.
• 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 represents by bijection the value of the data symbol to be transmitted.
• 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.
• modules are driven by the microprocessor of the processing unit 1111.
• a receiving device has a memory 1210 comprising a buffer memory, a processing unit 1211, equipped for example with a ⁇ microprocessor, and driven by the computer program 1212. , implementing the reception method according to one embodiment of the invention.
• 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.
• 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.
• modules are driven by the microprocessor of the processing unit 1211.

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