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    • 专利摘要:
    The invention relates to a transmission method and a transmitter FBMC for transmitting at least a first and a second block of symbols (X0, X1), each block of symbols comprising a temporal sequence of L vectors of predetermined size N. It implements a first and a second FBMC modulation channel, each FBMC modulation channel being associated with an antenna. During a first use of the channel, the vectors of the first block and the vectors of the second block are respectively provided to the first and the second modulation channel FBMC, in the order of said time sequence. During a second use of the channel, the vectors of the first and second blocks are respectively multiplied by a factor jL-1 and - (jL-1 and respectively provided to the second channel and the first modulation channel FBMC, in the order inverse of said time sequence.
    公开号:FR3050344A1
    申请号:FR1653276
    申请日:2016-04-13
    公开日:2017-10-20
    发明作者:Jean-Baptiste Dore
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    TRANSMITTER FOR FBMC SYSTEM WITH SPATIO-TEMPORAL CODING OF ALAMOUTI TYPE
    BY BLOCKS
    DESCRIPTION
    TECHNICAL AREA
    The present invention generally relates to the field of telecommunications systems using a multi-carrier filterbank modulation, also called Filter Bank Multi-Carrier (FBMC) systems. It also concerns the Multiple Input Single Output (MISO) or Multiple Input Multiple Output (MISO) telecommunication systems using spatio-temporal coding.
    STATE OF THE PRIOR ART
    Telecommunication systems using a multi-carrier modulation are well known in the state of the art. The principle of such a modulation consists in dividing the transmission band into a plurality of sub-channels associated with sub-carriers and modulating each of these sub-carriers by the data to be transmitted.
    The most widespread multi-carrier modulation is undoubtedly Orthogonal Frequency Division Multiplexing (OFDM) modulation. However, since the spectral occupation of an OFDM signal is substantially greater than the band of subcarriers that it uses due to the spread of the side lobes, the OFDM modulation is not an optimal solution for applications requiring high out-of-band rejection rates.
    Filter Bank Multi Carrier (FBMC) is a multi-carrier modulation that provides better spectral localization in the subcarrier band. It is also one of the possible solutions for fifth-generation telecommunications systems.
    The principle of the FBMC modulation is based on a filterbank synthesis on transmission and a filter bank analysis on reception, the product of the transfer function of a filter on transmission by the transfer function. the filter corresponding to the reception being equal to the transfer function of the Nyquist filter.
    FBMC systems are typically implemented in the time domain. The structure of an FBMC implemented in the time domain has been described in detail in the article by B. Hirsaky entitled "An orthogonally multiplexed QAM System using the discrete Fourier transform" published in EEE etrans on Comm., Vol. 29 No. 7, pp. 982-989, July 1981, as well as in the article by P. Siohan et al. entitled "Analysis and Design of OFDM / OQAM Systems based on filterbank theory" published in IEEE Trans., Signal Processing, Vol 50, No 5, pp. 1170-1183, May 2002. FBMC systems implemented in the time domain employ to polyphase filter networks hence their denomination PPN-FBMC (Polyphase Network FBMC).
    More recently, it has been proposed to implement a FBMC system in the frequency domain as described in the document by M. Bellangereto. entitled "FBMC physical layer: a primer" available at www.ict-phvdvas.org. FBMC systems implemented in the frequency domain use spectral spreading, hence their denomination FS-FBMC (Frequency Spread FBMC).
    The structure of an FS-FBMC system is shown in FIG. 1.
    At the transmitter, the QAM modulation symbols to be transmitted with a rate Nf with / = / T are grouped in blocks of size N, x0 ["], ...,% _! ["] Where n is the temporal index of the block. Each block of N symbols is provided in parallel with N input channels of a preprocessing module, 110, called preprocessing OQAM (QAM Offset). This pretreatment module has the function of demultiplexing the real part and the imaginary part of the input symbols with a frequency 2 / so that two samples transmitted at the same time on two successive subchannels or two samples transmitted in two successive instants on the same subchannel are one real and the other imaginary. Each of the N output channels of the pretreatment module 110 corresponds to a subchannel.
    Each subchannel is then spread over an interval of adjacent 2K-1 subcarriers, centered on a central subcarrier of the subchannel. Specifically, each OQAM data is spread over 2K-1 adjacent subcarriers and weighted by the (real) value taken by the transfer function of the synthesis filter at the corresponding frequency.
    The frequency spreading and filtering module has been designated by 120 by the prototype filter. Each OQAM data i /, [n] at the input of the module 120 is spread over adjacent 2K-1 subcarriers to give:
    (1)
    Data of the same parity i and i + 2 are spectrally separated and those of opposite parities i and / + 1 overlap as shown in FIG. 2A. This overlap, however, does not cause interference since two contrary parity data are necessarily located respectively on the real axis and the imaginary axis and separated by 772. For example, in FIG. 2A, the data dt [n and dl + 2 [n are real values (represented in solid lines) whereas the data <7i + 1 ["] is an imaginary value (represented by dashed lines). The imaginary values are presented at the input of the IFFT module with an offset of T12 compared to the actual values. The orthogonality in the complex plane is conserved by filtering by the prototype filter since the coefficients Gk are real.
    The frequency-spread and filtered data are then subjected to an IFFT of size KN at 130.
    The time sample block at the IFFT output is combined by means of the combination module 140 as shown in FIG. 3. The set of IFFT output samples represents a FBMC symbol in the time domain, two successive FBMC symbols being shifted by T12 (ie NI2 samples) and FBMC symbols each having a KT duration (ie a size of KN samples). A symbol FBMC is combined in the module 140 with the K -1 symbols FBMC previous and K -1 symbols FBMC following. For this reason, K is still called an overlapping factor or interleaving factor. Note that a sample output from the combination module 140 is the sum of 2K- consecutive FBMC symbol samples.
    The signal thus obtained is then translated on a carrier frequency.
    After transmission on the channel 150, the received signal, demodulated in baseband, is sampled by the receiver at the rate Nf and then converted into blocks of size KN by the series-parallel converter 160.
    A sliding FFT (the sliding FFT window of NU samples between two FFT calculations) of size KN is performed in the FFT module 170 on blocks of KN consecutive samples at the output of the serial-parallel converter 160.
    The outputs of the FFT are then subjected to filtering and spectral despreading in the module 180. The despreading operation takes place in the frequency domain as shown in FIG. 2B. More precisely, the samples d [rk [n , k = -K + 1, ..., 0, .. K-1 corresponding to the 2K-1 frequencies
    are multiplied by the values of the transfer function of the analysis filter (translated in frequency from that of the prototype filter) to the frequencies in question and the results obtained are summed, namely:
    (2)
    It will be noted that, as in FIG. 2A, obtaining data having ranks of the same parity, for example d- ["] and dri + 2 [n , uses disjoint sample blocks whereas those of two consecutive ranks, of inverse parities, overlap. Thus, obtaining the data drM n uses the samples
    as well as to the sample:
    The despreading of real data is represented by continuous lines whereas that of the imaginary data is represented by dashed lines.
    The data d. [n] thus obtained are then provided to an aftertreatment module 190, performing the inverse processing of that of the module 110, in other words an OQAM demodulation. The QAM symbols are restored.
    FBMC technology is one of the fifth-generation candidate technologies for wireless telecommunication systems. In particular, this should make it possible to meet the needs of spectral fragmentation and transmission asynchrony of machine-type communications (MTC). The application of FBMC technology to à (Multiple Input Multiple Output) type space diversity telecommunication systems is, however, much more complicated than in OFDM because FBMC inherently uses orthogonality in the complex plane to eliminate interference between FBMC symbols.
    Spatial time-blocking or Alamouti-type Spatial Time Block Coding (STBC) has recently been proposed for a FBMC system in the article by M. Renfors et al. entitled "A block-based Alamouti scheme for filtering-based multicarrier transmission" published in Proceedings of European Wireless Conference EW 2010, April 12-15, 2010, Lucca, Italy. 2010. pp. 1031-1037.
    It is recalled first of all that an Alamouti encoding is a Space Time Block Coding (STBC) coding for a configuration with two transmitting antennas and a receiving antenna. Its coding matrix is given by:
    (3) in which x0 and xt are two complex symbols (belonging to a modulation alphabet) to be transmitted. During a first use of the channel (that is to say a first transmission interval), the transmission antennas transmit xQ and x1 respectively and, during a second use of the channel, these antennas transmit -x * and x * Q.
    The signals received respectively during the first and the second use of the channel, y0, y {can then be expressed as: (4-1)
    (4-2) where / 10, / ij are respectively the complex coefficient of the first elementary channel between the first transmitting antenna and the receiving antenna, and the complex coefficient of the second elementary channel between the second transmitting antenna and the receiving antenna, and where n0, i are noise samples that are assumed to be additive, independent and from the same white centered Gaussian process.
    Assuming the known channel, the receiver estimates the transmitted symbols from a combination of the received signals:
    (5-1) (5-2) The aforementioned Renfors article uses a suitable filtering technique, already used for Alamouti coding in the presence of intersymbol interference, presented in the article by E. Lindskog and al. entitled "A transmit scheme for channels with intersymbol interference" published in Proc. IEEE of Int'l Conf. on Communications, ICC 2000, pp.307-311, June 2000.
    The Alamouti encoding is performed by blocks of input data vectors, a block consisting of a sequence of L vectors-columns and can therefore be represented by an X matrix of size NxL where N is the number of subsets. carriers. Each column-vector of the matrix X, ie X "1, m = 0, ..., L1, represents here a vector of complex symbols at the output of the modulator OQAM, it is recalled that due to the OQAM modulation, two elements Any adjacent ones (according to the rows or columns) of the X matrix are one real and the other imaginary.
    If X0 and Xx are two consecutive blocks, the block Alamouti encoding matrix, as proposed in the Renfors article, can be expressed as:
    (6)
    The block columns of the block matrix here represent the antennas and the block lines represent the uses of the channel. In each of the blocks, the lines represent the sub-carriers and the columns represent the time. T is an anti-diagonal matrix of size LxL whose anti-diagonal elements are equal to 1, and thus reflects a time reversal. Thus, if X is a vector sequence X °, X1, ..., Xi'_1, the block XT consists of the sequence Xi-1, XL-2, ..., X0.
    Fig. 4 schematically represents a sequence of symbol blocks transmitted by a FBMC transmitter with a block Alamouti encoding.
    A first block sequence, 401, is formed by a first guard block 411, a first block of L symbol vectors, X0,421, a second guard block, 431, a first transformed block, -X * T, 441 , consisting of L symbol vectors, followed by a third guard block 451.
    A second block sequence, 402, is formed by a first guard block, 421, a second block consisting of L symbol vectors, X ,, 422, a second guard block, 432, a second transformed block X ^ T, 442, consisting of L symbol vectors, followed by a third guard block, 452.
    The guard blocks consist of nuisance symbols and are intended to isolate the successive blocks of the interference generated by the adjacent blocks.
    The first block sequence is transmitted by the first antenna 491 after FBMC modulation. The signal obtained at the output of the FBMC modulator can be considered as a temporally overlapping sequence of FBMC symbols, as explained with reference to FIG. 3. The signal thus obtained is transmitted on the first antenna after having been translated into an RF band.
    Similarly, the second block sequence is transmitted by the second antenna 492 after being modulated by a second FBMC modulator of identical structure to the first.
    Fig. 5 schematically shows the architecture of a receiver FBMC for receiving the symbol block sequences transmitted by the transmitter of FIG. 4. It is important to note that this FBMC receiver has a classical architecture (time implementation) and not an FS-FBMC architecture (frequency implementation).
    The receiver comprises a sampling module 510 for sampling the received baseband signal at the rate Nf where N is the number of subcarriers and / is the frequency of the FBMC symbols. The samples are grouped into blocks of size N by a series-parallel converter 520.
    Each block is filtered by a transmultiplexer constituted by a battery of N polyphase filters (PPN), 530, then subjected to a FFT of size N, in the FFT module 540, operating on the N outputs of these filters.
    The receiver is supposed to be synchronized to the FBMC symbols, ie the beginning of an FFT window coincides with the first sample of an FBMC symbol (emitted by one or the other of the transmitting antennas). In addition, the receiver is supposed to be synchronized on the times of use of the channel so that it knows the times of reception of the first and second blocks
    A demultiplexer 550 provides the output vectors of the FFT on a first output 551 during the first use of the channel and on a second output 552 during the second use of the channel. The L vectors (of size N) generated sequentially on the first output are stored in a first buffer 561 configured as a FIFO (First In First Out) buffer. The vectors L generated sequentially on the second output are also stored in a second buffer 562, configured as a LIFO (Lost In First Out) buffer. The conjugation module 570 thus reads the L vectors in the inverse order of their storage order, so as to effect a time reversal, and performs a complex conjugation of each of these vectors.
    Each element of a vector generated on the first output is multiplied at 581 by the complex conjugate of the coefficient of the first elementary channel between the first transmitting antenna and the receiving antenna, at the frequency of the subcarrier bearing the element in question (the operation is here symbolized by a multiplication of the vector at the output of the buffer memory by the matrix H * defined below) and at 583 by the complex conjugate of the coefficient of the second elementary channel between the second antenna of transmission and the receiving antenna, at the same subcarrier frequency (the operation is symbolized here by a multiplication of the sample vector at the output of FFT by the matrix Hj). It is understood that the matrices H0 and Hj are here of size NxN and here represent the coefficients of the elementary channels for the N subcarriers. The matrices H0 and Hj are diagonal. The matrices H0 and Hj are assumed constant over the duration of the sequence (deflatfading hypothesis in time).
    Similarly, each element of a vector generated on the second output is multiplied by the coefficient 582 of the channel between the first transmitting antenna and the receiving antenna at the frequency of the subcarrier carrying the element. question (operation symbolized by a multiplication of the vector at the output of the FFT by the matrix Ho) and at 584 by the channel coefficient between the second transmitting antenna and the receiving antenna at the frequency of the same subcarrier ( operation symbolized by a multiplication of the vector at the output of the FFT by the matrix H,).
    The vectors at the output of the multiplier 581 are summed element by element with those at the output of the multiplier 584 in the summator 591. The successive vectors at the output of the summator 591 are then supplied to a first OQAM demodulator (not shown).
    Similarly, the vectors at the output of the multiplier 583 are subtracted, element by element, from those at the output of the multiplier 582, in the summator 592. The successive vectors at the output of the summator 592 are then supplied to a second OQAM demodulator (not shown ).
    In other words, if we write Y0 and Yl the matrices of size NxL representing the sequence of L vectors-column at the output of the FFT, respectively during the first and the second use of the channel, the estimations of the vectors of symbols X0 and Xl are obtained by:
    (7-1) (7-2)
    The reception method described above works for a FBMC receiver implemented using a polyphase filter bank. It is not applicable to an FS-FBMC receiver as described in connection with the right-hand part of FIG. 1, since the filtering is then downstream of the FFT.
    The object of the present invention is to propose a method of transmitting an encoded FBMC symbol block sequence by means of an Alamouti block coding, which allows a very simple reception by an FS-FBMC receiver.
    STATEMENT OF THE INVENTION
    The present invention is defined by a FBMC transmission method of at least a first and a second symbol block (X0, X,), each block of symbols comprising a time sequence of L vectors of predetermined size N, said method having a first and second FBMC modulation channels, each FBMC modulation channel being associated with an antenna and, - during a first use of the transmission channel, the vectors of the first block and the vectors of the second block are respectively supplied to the first FBMC modulation channel and the second FBMC modulation channel, in the order of said time sequence; the first block is transformed by multiplying the vectors of this block by a factor jL-1 where L is an even number and inverting the temporal order of the sequence of vectors thus obtained, and the second block is transformed by multiplying the vectors of this block by a factor - (jL ~ l) and by reversing the temporal order of the sequence of vectors thus obtained; during a second use of the transmission channel, the vectors of the first and second blocks thus transformed are respectively supplied to the second modulation channel and to the first modulation channel FBMC, in the inverse order of said time sequence.
    According to a first variant, each FBMC modulation channel advantageously comprises an OQAM preprocessing step providing alternately real and imaginary data, each data thus obtained being spread over a 2K-1 plurality of adjacent sub-carriers and filtered in the spectral domain by a prototype filter for providing a vector of KN components, the vector of KN components being subjected to an IFFT of size KN to generate a symbol FBMC of KN samples, the consecutive symbols FBMC being shifted by N / 2 samples, each symbol FBMC being combined with the preceding K-1 FBMC symbols and the following K-1 FBMC symbols for providing, after RF band translation, an antenna signal transmitted by an antenna associated with said channel.
    According to a second variant, each FBMC modulation channel comprises an OQAM preprocessing step providing a vector of N alternately real and imaginary components, the vector of N components being subjected to an IFFT of size N to generate a plurality of sub-channels, each sub-channel. -channel being filtered by a polyphase filter, the polyphase filters being translated versions in frequency of 2k IT of a prototype filter whose impulse response is of duration KT where T is the sampling period, the outputs of the polyphase filters being on -sampled by a factor N12 and delayed by 0 to N -1 sampling periods before being summed to provide, after translating in an RF band, an antenna signal transmitted by an antenna associated with said channel.
    According to a first advantageous exemplary embodiment, during the first use of the channel, a guard block consisting of a predetermined number of vectors which is harmful to the first and second modulation channels is provided before supplying them respectively with the vectors of the first block and the vectors. the second block, and during the second use of the channel, provides a guard block constituted by said predetermined number of vectors harmful to the first and second modulation channels before supplying respectively the vectors of the second transformed block and the vectors of the first transformed block.
    Preferably, the predetermined number of nuisance vectors is chosen equal to K + E where E is the time spread of the transmission channel expressed in number of samples.
    According to a second advantageous example of embodiment, during the first use of the channel, first and second preambles, constituted by a predetermined number of vectors known to the receiver, are provided to the first and second modulation channels before supplying them respectively with the vectors of the first block and the vectors of the second block, and during the second use of the channel, there is provided a guard block constituted by said predetermined number of vectors harmful to the first and second modulation channels before supplying them respectively the vectors of the second transformed block and the vectors of the first transformed block.
    Preferably, said predetermined number is equal to K + E where E is the time spread of the transmission channel expressed in number of samples.
    The number L can typically be a power of 2. The invention also relates to a transmitter FBMC adapted to transmit at least a first and a second symbol block (X0, X,), each block of symbols comprising a temporal sequence of L vectors of predetermined size N, first and second modulation means FBMC, respectively associated with a first and a second transmission antenna, in which: during a first use of the transmission channel, the vectors of the first block and the vectors of the second block are respectively provided to the first FBMC modulation channel and the second FBMC modulation channel, in the order of said time sequence, and said transmitter comprises: first transformation means adapted to transform the first block by multiplying the vectors of this block by a factor jL ~ x, where L is an even number, and inverting the temporal order of the sequence of vectors thus obtained, and transforming means conds adapted to transform the second block by multiplying the vectors of this block by a factor ~ (jL ~ 1) and by reversing the temporal order of the sequence of vectors thus obtained; the transmitter FBMC being configured so that, during a second use of the transmission channel, the first and second transformation means provide the vectors of the first and second blocks thus transformed to the second modulation channel and to the first FBMC modulation channel, in the inverse order of said time sequence.
    BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will appear on reading preferred embodiments of the invention with reference to the appended figures among which:
    Fig. 1 schematically shows a telecommunication system FS-FBMC known from the state of the art;
    Fig. 2A illustrates the spectral spread made upstream of the IFFT module of FIG. 1;
    Fig. 2B illustrates the spectral despreading performed downstream of the FFT module in FIG. 1;
    Fig. 3 illustrates the combination of the FBMC symbols in FIG. 1;
    Fig. 4 schematically shows the transmission of two symbol block sequences by a transmitter FBMC using a block Alamouti coding known from the state of the art;
    Fig. 5 schematically shows the architecture of a receiver FBMC for receiving the symbol block sequences transmitted by the transmitter of FIG. 4;
    Fig. 6 schematically shows the architecture of an FS-FBMC receiver, for receiving symbol block sequences encoded by block Alamouti encoding;
    Fig. 7A schematically shows the transmission of two symbol block sequences by a transmitter FBMC using a first block Alamouti encoding, according to a first embodiment of the invention;
    Fig. 7B schematically shows the transmission of two symbol block sequences by a transmitter FBMC using a second block Alamouti encoding, according to a second embodiment of the invention;
    Fig. 8 schematically shows the architecture of an FS-FBMC transmitter, for issuing blocks of symbol sequences according to FIGS. 7A and 7B.
    DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
    To facilitate the understanding of the notations, we will first consider an FS-FBMC transmitter, as described in connection with FIG. 1. Unlike the preceding notations, the column vectors Xm, m = 0, ..., L-1, of size N, will represent in the following input data vectors, in other words data at the input of the OQAM modulator. The elements of these vectors are therefore real values.
    The signal emitted by the transmitter at time m may be represented by a column vector Zm of size KN whose elements are samples at frequency Nf. The vector Zm can be expressed according to the vectors Xm "^" 1 *, ..., Xm, ..., Xm + ^ "1 * of input data, ie:
    (8) where G is the product of Hadamard, F is the discrete Fourier transform matrix of size KNxKN, G is a matrix of size KNxN representing the spectral spread and the transfer function of the prototype filter in the frequency domain, ie :
    (9)
    Mm is a vector-column of size N which translates the OQAM modulation, namely a vector whose elements are given by:
    (10) and is an offset matrix of ί samples, of size KNxKN defined by:
    (11) where KN_l is the size identity matrix (KN- £) x (KN- £)
    It will be understood that the terms under the sum sign in Expression (8) represent the 2K-FBMC symbols which are combined in FIG. 3.
    The signal received by the receiver FBMC at time m may similarly be expressed in the form of a data vector output from the OQAM demodulator, noted here Ym, of size KN. The vector Ym can be expressed as a function of the vector Zm representing the transmitted signal, or by abstracting the noise term:
    (12) again, considering that GiiFFHG = 1 ^ and that (Xm OM ") gM" * - Xm:
    (13) with:
    (14)
    It will be noted that GH - G 7 since the coefficients of the transfer matrix of the filter are real.
    It is now assumed that Alamouti is coded in blocks, with a coding matrix defined by:
    (15)
    As described below, a receiver implemented in the frequency domain (FS-FBMC receiver) and combining the two output blocks of the FFT module (module 170 of Fig. 1) can be used respectively in the first and second the second use of the channel.
    X ™ is the same input data vector of the first block X0 and X ™ is the same input data vector of the second block Xj. Note also W "the m th sample vector at the output of the FFT module, before despreading and filtering, during the first use of the channel. Similarly, we denote W "the m th sample vector at the output of the FFT module, before despreading and filtering, during the second use of the channel.
    When using the channel for the first time, the vector W "can be expressed as follows:
    (16)
    (17)
    Similarly, during the second use of the channel, the vector W "can be expressed as follows:
    (18) expression in which the input data vectors were taken advantage of being real values.
    It will be noted that the transfer matrices of the elementary channels, H0 and Hj, are here of size KNxKN because of the spectral spreading.
    If one transforms the block of vectors W ", m = 0, ..., Ll, by time reversal and complex conjugation of the block, the m th vector of the thus transformed block can be written, starting from (18) :
    (19)
    Considering that:
    where it was assumed that the block size L was an even number, and that:
    the vector of the returned block can finally be written:
    (20)
    The transmitted data vectors X ", XJ" can then be estimated by combining W0m and W / '-' "- 1 * vectors:
    (21-1) (21-2)
    then spectral filtering and despreading and finally OQAM demodulation:
    (22-1) (22-2)
    Fig. 6 schematically shows the architecture of an FS-FBMC receiver, for receiving blocks of symbols sequences coded by Alamouti blocks.
    The receiver comprises a sampling module 610 for sampling the received baseband signal at the rate Nf where N is the number of subcarriers and / is the frequency of the FBMC symbols. The samples are grouped as blocks of size KN by a series-parallel converter 620.
    The receiver is supposed to be synchronized to the FBMC symbols, ie the beginning of an FFT window coincides with the first sample of an FBMC symbol (emitted by one or the other of the transmitting antennas). In addition, the receiver is supposed to be synchronized on the times of use of the channel so that it knows the times of reception of the first and second blocks.
    The sample blocks are subjected to a FFT of size KN in the FFT 630 module.
    A demultiplexer 640 provides the output vectors of the FFT on a first output 641 on the first use of the channel and on a second output 642 on the second use of the channel. The L vectors (of size KN) generated sequentially on the first output are stored in a first buffer 651 configured as a FIFO. The vectors L generated sequentially on the second output are also stored in a second buffer 652 configured as LIFO. The module 660 thus reads the L vectors in the inverse order of the storage order (LIFO), so as to perform a time reversal, and also carries out a complex conjugation of each of these vectors. A multiplier 670 multiplies the elements of the vectors at the output of the module 660 by (j) L ', in other words by j if L is an even number.
    In particular, we can choose L equal to a power of 2: L-21 with i integer strictly greater than 1.
    Each element of a vector generated on the first output is multiplied in 681 by the complex conjugate of the coefficient of the first elementary channel between the first transmitting antenna and the receiving antenna, at the frequency of the subcarrier bearing the element in question (the operation is symbolized here by a multiplication of the vector at the output of the buffer memory by the matrix H *) and at 683 by the complex conjugate of the coefficient of the second elementary channel between the second transmission antenna and the receiving antenna, at the same subcarrier frequency (the operation is here symbolized by a multiplication of the sample vector at the output of FFT by the matrix H *). It is understood that the matrices H0 and Hj here are of size KNxKN and here represent the coefficients of the elementary channels for the spectrally spread subcarrier KNs. We can choose an identical channel coefficient for K frequencies from the same subcarrier. The matrices H0 and Hj are assumed constant over the duration of the sequence (deflatfading hypothesis in time).
    Similarly, each element of a vector generated on the second output is multiplied by 682 by the coefficient of the channel between the first transmitting antenna and the receiving antenna at the frequency of the subcarrier carrying the element. question (operation symbolized by a multiplication of the vector at the output of the FFT by the matrix Ho) and at 684 by the coefficient of the channel between the second transmitting antenna and the receiving antenna at the frequency of the same subcarrier ( operation symbolized by a multiplication of the vector at the output of the FFT by the matrix HJ.
    The vectors at the output of the multiplier 681 are summed, element by element, with those at the output of the multiplier 684, in the summator 691. The successive vectors, of size N, at the output of the summator 691 are then supplied to a first spectral despreading module and filtering 695.
    Likewise, the vectors at the output of the multiplier 682 are subtracted, element by element, with those at the output of the multiplier 683 in the summator 692. The successive vectors, of size N, at the output of the summator 692 are then supplied to a second module of spectral despreading and filtering 696.
    The vectors obtained by the first and second modules 695 and 696 are then subject to an OQAM demodulation (not shown) to obtain the estimated data vectors X ™ and X ™, m = 0,..., L-1. .
    The present invention is based on the observation that the structure of the receiver of FIG. 6 can be simplified when the FBMC transmitter uses, in place of the coding given by (15), the Alamouti block coding defined by:
    (23)
    In this case, the multiplication by the factor (j 1) can be suppressed on reception and therefore the multiplier 670 can be omitted.
    Fig. 7A schematically shows the transmission of two symbol block sequences by a transmitter FBMC using a first block Alamouti encoding, according to a first embodiment of the invention.
    The blocks of data to be transmitted are considered here upstream of the OQAM modulation.
    A first block sequence, 701, is formed by a first guard block 711, a first block of L input data vectors, X0, 721, a second guard block, 731, followed by a first transformed block, (j '') XjT, 741, obtained by time reversal and multiplication by the factor - (jL ~ 1) of the first block of input data.
    A second block sequence, 702, is formed by a first guard block, 712, a second block of L input data vectors, X1r 722, a second guard block, 732, followed by a second transformed block X0T, 742, obtained by time reversal and multiplication by the factor (jL ~ 1) of the second block of input data.
    The size L of the data blocks is assumed to be even, ie (y £ 1) = j or
    The guard blocks consist of nuisance vectors to prevent interference between the data blocks and the transformed blocks. The number of harmful vectors in the guard blocks is advantageously equal to K + E where K is the length of the prototype filter and E is the time delay of the channel expressed in number of samples at the sampling frequency (Nf).
    The first and second sequences are respectively transmitted by the first and second antennas, 791 and 792, after FBMC modulation.
    Fig. 7B schematically shows the transmission of two symbol block sequences by a transmitter FBMC using a second block Alamouti encoding, according to a second embodiment of the invention.
    The second example is identical to the first with the difference that the first guard block is replaced in the first sequence by a first preamble 711 'and in the second sequence by a second preamble, 712'. The other blocks remain unchanged and are therefore not described again.
    The first and second preambles generate an interference affecting the first symbols of the blocks X0 and Xp interference which does not symmetrically affect the blocks -XjT and X0T. This asymmetry does not eliminate the interference for X ™, X ™ input data vectors at the beginning of the block. However, the symbols of the preamble being known to the receiver, it is possible to eliminate this interference when an estimate of the transmission channel is available.
    Fig. 8 schematically shows the architecture of an FS-FBMC transmitter, according to a first embodiment of the invention. This transmitter makes it possible to emit symbol block sequences encoded by an Alamouti coding according to FIGS. 7A and 7B. The blocks of symbols to be transmitted are noted as previously X0 and Xj.
    The X ™ input data vectors are stored in a FIFO buffer, 810 and a LIFO buffer, 811. They are supplied in their order of arrival to the multiplexer 841 and in reverse order to the multiplexer 842, after having been delayed by the delay 821 and have been multiplied in 831 by the factor (jL ~ l). Similarly, the input data vectors XJ "are stored in a FIFO buffer, 812 and a LIFO buffer, 813. They are supplied in their order of arrival to the multiplexer 842 and in their order of arrival and in their reverse order to the multiplexer 841, after having been delayed by the delay 822 and multiplied by the factor - (jL at 832. During the first use of the channel, the multiplexers 841 and 842 switch the FIFO, 810 and 811 buffer outputs. on the OQAM preprocessing modules 851 and 852 respectively, during the second use of the channel, the multiplexers 841 and 842 switch the outputs of the buffers LIFO, 812 and 813, after delay and multiplication by the aforementioned factors, on the pretreatment modules 852. and 851 respectively, those skilled in the art will appreciate that other implementations may be equivalently contemplated, and in particular the arrangement of 810, 811, 821 may be replaced by a simple memory read in the forward direction during the first use of the channel and in the opposite direction during the second use of the channel, the vectors read during the second use of the channel being previously multiplied by the factor (jL ~ l) before to be supplied to the pre-treatment module OQAM 852. Similarly, the arrangement constituted by 812, 813, 822, can be replaced by a simple memory read in the forward direction during the first use of the channel and in the direction inverse during the second use of the channel, the vectors read during the second use of the channel being previously multiplied by the factor - (./ 1-1) before being supplied to the preprocessing module OQAM 851.
    The modules 861-862,871-872,881-882 are respectively identical to the modules 820, 830 and 840 and their description will therefore not be repeated here. The signals at the output of the combination modules 881 and 882 are translated in an RF band before being transmitted respectively by the antennas 891 and 892.
    Fig. 9 schematically shows the architecture of a transmitter FBMC, according to a second embodiment of the invention. This emitter differs from that of FIG. 8 to the extent that it is conventionally implemented in the time domain using a polyphase network, as described in the Hirosaki article cited above.
    The elements referenced 910 to 952 are respectively identical to the elements 810 to 852.
    More precisely, the transmitter comprises two FBMC modulation channels. For each of these channels, unlike the first embodiment, the output data vector of the OQAM module is provided to a synthesis filter bank consisting of an IFFT module of size N (961, 962), a plurality N of polyphase filters (971, 972) and a plurality N of oversamplers (981, 982) of factor N / 2, at the output of the different polyphase filters and finally a plurality of delays arranged in parallel and ranging from 0 to N- 1 sampling periods. The polyphase filters are translated versions in frequency of 2k IT of the prototype filter whose impulse response is of duration KT.
    The subchannels at the output of the IFFT are each filtered by a polyphase filter. The outputs of N polyphase filters, oversampled and delayed, are summed by an adder (981, 982). The output signal of the adder is translated in RF band to provide an antenna signal which is then transmitted by the antenna associated with the channel (991, 992).
    权利要求:
    Claims (9)
    [1" id="c-fr-0001]
    FBMC transmission method of at least a first and a second symbol block (X0, X,), each block of symbols comprising a temporal sequence of L vectors of predetermined size N, characterized in that it presents a first and a second FBMC modulation channel, each FBMC modulation channel being associated with an antenna and that, during a first use of the transmission channel, the vectors of the first block and the vectors of the second block are respectively supplied to the first FBMC modulation channel and the second FBMC modulation channel, in the order of said time sequence; the first block is transformed by multiplying the vectors of this block by a factor jL-1 where L is an even number and inverting the temporal order of the sequence of vectors thus obtained, and the second block is transformed by multiplying the vectors of this block by a factor) and by reversing the temporal order of the sequence of vectors thus obtained; during a second use of the transmission channel, the vectors of the first and second blocks thus transformed are respectively supplied to the second modulation channel and to the first modulation channel FBMC, in the inverse order of said time sequence.
    [2" id="c-fr-0002]
    2. FBMC transmission method according to claim 1, characterized in that each FBMC modulation channel comprises an OQAM preprocessing step providing alternately real and imaginary data, each data thus obtained being spread over a 2K-1 plurality of subcarriers adjacent and filtered in the spectral domain by a prototype filter to provide a vector of KN components, the vector of KN components being subjected to an IFFT of size KN to generate a symbol FBMC of KN samples, the consecutive symbols FBMC being shifted by N / 2 samples, each FBMC symbol being combined with the previous K-1 FBMC symbols and the following K - 1 FBMC symbols to provide, after RF band translation, an antenna signal transmitted by an antenna associated with said channel.
    [3" id="c-fr-0003]
    3. FBMC transmission method according to claim 1, characterized in that each FBMC modulation channel comprises an OQAM preprocessing step providing a vector of N alternately real and imaginary components, the vector of N components being subjected to a N-size IFFT. for generating a plurality of subchannels, each sub-channel being filtered by a polyphase filter, the polyphase filters being frequency translation versions of 2k IT of a prototype filter whose impulse response is of duration KT where T is the period sampling, the outputs of polyphase filters being oversampled by a factor NI2 and delayed from 0 to N- sampling periods before being summed to provide, after translation in RF band, an antenna signal emitted by an antenna associated with said path.
    [4" id="c-fr-0004]
    4. FBMC transmission method according to one of the preceding claims, characterized in that during the first use of the channel, there is provided a guard block consisting of a predetermined number of vectors harmful to the first and second modulation channels before their supplying respectively the vectors of the first block and the vectors of the second block, and that during the second use of the channel, providing a guard block constituted by said predetermined number of vectors harmful to the first and second modulation channels before respectively providing them the vectors of the second transformed block and the vectors of the first transformed block.
    [5" id="c-fr-0005]
    5. FBMC transmission method according to claim 4, characterized in that the predetermined number of nuisance vectors is equal to K + E where E is the temporal spread of the transmission channel expressed in number of samples.
    [6" id="c-fr-0006]
    6. FBMC transmission method according to one of claims 1 to 3, characterized in that during the first use of the channel is provided first and second preambles, consisting of a predetermined number of vectors known to the receiver, the first and second modulation channels before supplying respectively the vectors of the first block and the vectors of the second block, and that during the second use of the channel, there is provided a guard block consisting of said predetermined number of vectors harmful to the first and second channels before supplying them respectively the vectors of the second transformed block and the vectors of the first transformed block.
    [7" id="c-fr-0007]
    7. FBMC transmission method according to claim 6, characterized in that said predetermined number is equal to K + E where E is the time spread of the transmission channel expressed in number of samples.
    [8" id="c-fr-0008]
    8. FBMC transmission method according to one of the preceding claims, characterized in that L is a power of 2.
    [9" id="c-fr-0009]
    9. Transmitter FBMC for transmitting at least a first and a second symbol block (X0, Xj), each block of symbols comprising a temporal sequence of L vectors of predetermined size N, characterized in that it comprises first and second FBMC modulation means, respectively associated with a first and a second transmission antenna, characterized in that: during a first use of the transmission channel, the vectors of the first block and the vectors of the second block are respectively supplied to the first FBMC modulation channel and the second FBMC modulation channel, in the order of said time sequence, and said transmitter comprises: first transformation means adapted to transform the first block by multiplying the vectors of this block by a factor jL ~ l, where L is an even number, and inverting the temporal order of the sequence of vectors thus obtained, and second transformation means adapted to tran to form the second block by multiplying the vectors of this block by a factor) and by reversing the temporal order of the sequence of vectors thus obtained; and that, during a second use of the transmission channel, the first and second transformation means supply the vectors of the first and second blocks thus transformed to the second modulation channel and the first modulation channel FBMC, in the order inverse of said time sequence.
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    同族专利:
    公开号 | 公开日
    EP3232626A1|2017-10-18|
    US20170302408A1|2017-10-19|
    FR3050344B1|2019-05-03|
    EP3232626B1|2021-03-03|
    US9967060B2|2018-05-08|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20140348252A1|2011-12-23|2014-11-27|Orange|Method for transmitting at least one multi-carrier signal consisting of ofdm-oqam symbols|
    EP3206353B1|2016-02-09|2020-02-05|Technische Universität München|Filter banks and methods for operating filter banks|
    US10708105B2|2016-04-19|2020-07-07|Telefonaktiebolaget Lm Ericsson |Faster-than-Nyquist signaling for FBMC burst transmissions|
    CN108540271A|2018-03-27|2018-09-14|西安电子科技大学|A kind of Alamouti transmission methods, wireless communication system suitable for FBMC/OQAM|
    CN109547181B|2018-10-08|2020-02-14|华中科技大学|Short filter, single carrier system and multi-carrier system|
    法律状态:
    2017-04-28| PLFP| Fee payment|Year of fee payment: 2 |
    2017-10-20| PLSC| Publication of the preliminary search report|Effective date: 20171020 |
    2018-04-26| PLFP| Fee payment|Year of fee payment: 3 |
    2019-04-29| PLFP| Fee payment|Year of fee payment: 4 |
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    2021-04-29| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1653276A|FR3050344B1|2016-04-13|2016-04-13|TRANSMITTER FOR FBMC SYSTEM WITH SPATIO-TEMPORAL CODING OF BLOCKED ALAMOUTI TYPE|
    FR1653276|2016-04-13|FR1653276A| FR3050344B1|2016-04-13|2016-04-13|TRANSMITTER FOR FBMC SYSTEM WITH SPATIO-TEMPORAL CODING OF BLOCKED ALAMOUTI TYPE|
    EP17166062.4A| EP3232626B1|2016-04-13|2017-04-11|Transmitter for fbmc system with alamouti space-time block coding|
    US15/485,700| US9967060B2|2016-04-13|2017-04-12|Transmitter for FBMC system with block-alamouti type space-time coding|
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