CN107276726B - Massive MIMO FBMC beam space-time coding downlink transmission method - Google Patents

Massive MIMO FBMC beam space-time coding downlink transmission method Download PDF

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CN107276726B
CN107276726B CN201710345148.2A CN201710345148A CN107276726B CN 107276726 B CN107276726 B CN 107276726B CN 201710345148 A CN201710345148 A CN 201710345148A CN 107276726 B CN107276726 B CN 107276726B
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CN107276726A (en
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王慧明
郑修鹏
史珂
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Xian Jiaotong University
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    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H—ELECTRICITY
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    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/0848—Joint weighting
    • H04B7/0854—Joint weighting using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0612—Space-time modulation
    • H—ELECTRICITY
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    • 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
    • H04L25/03305—Joint sequence estimation and interference removal
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    • 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
    • H04L25/03821—Inter-carrier interference cancellation [ICI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04L27/2601—Multicarrier modulation systems
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    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/345—Modifications of the signal space to allow the transmission of additional information
    • H04L27/3461—Modifications of the signal space to allow the transmission of additional information in order to transmit a subchannel
    • H04L27/3483—Modifications of the signal space to allow the transmission of additional information in order to transmit a subchannel using a modulation of the constellation points
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a Massive MIMO FBMC beam space-time coding downlink transmission method, which comprises the steps of carrying out OQAM modulation, Alamouti block coding and FBMC modulation on bit stream information sent to a user in sequence to obtain a signal to be sent, then carrying out linear weighting, enabling a sending channel to reach different users at different moments after undergoing different fading, carrying out FBMC demodulation on the received signal by the user, calculating an equivalent channel, carrying out MMSE channel equalization, and finally carrying out OQAM demodulation to recover the bit stream information sent to the user by a base station.

Description

Massive MIMO FBMC beam space-time coding downlink transmission method
Technical Field
The invention belongs to the technical field of wireless transmission, and particularly relates to a Massive MIMO FBMC beam space-time coding downlink transmission method.
Background
As a key technology in a fifth generation mobile communication system, Massive MIMO employs a large-scale antenna array at a base station, and when antennas tend to be numerous (infinite), channels corresponding to different users are approximately orthogonal in space, so that the base station can serve multiple users in the same time-frequency resource. Much of the performance of the system in Massive MIMO is related to large scale fading, not to small scale. The filter bank multi-carrier (FBMC) technique is listed as one of the candidates for 5G, and by using a prototype filter with good time-frequency focusing characteristics, out-of-band leakage in a multi-carrier modulation system can be effectively reduced while maintaining high-speed data transmission and effectively opposing frequency selective fading. In addition, the FBMC technology introduces operations such as a polyphase filter, fast Fourier transform and the like, and greatly reduces the complexity and the operation amount of the FBMC technology. Obviously, the Massive MIMO and FBMC high-quality technologies are combined together, so that the capacity, the energy efficiency and the spectrum efficiency of the system can be greatly improved, and the application prospect is wide.
Renfors M et al in the literature "A block-Alamouti scheme for filter bank base tubular carrier transmission[C]The scheme of block-shaped Alamouti coding in an FBMC system is provided in a Wireless Conference (EW),2010European. IEEE,2010: 1031-. However, the proposed scheme is only under a flat fading channel, and under a frequency selective fading channel, no corresponding channel equalization scheme is proposed. G.
Figure BDA0001296276320000011
The document "combining beamforming and orthogonal space-time block coding," Information Theory, ieee transactions on, vol.48, No.3, pp.2599-2613,2002 proposes a signal transmission scheme combining beamforming and orthogonal space-time block coding. And designing a beam former coefficient by using the obtained partial channel information and combining a given space-time block code, and minimizing the system error rate. However, the article considers point-to-point communication systems and does not consider the problem of multiple users.
Disclosure of Invention
The invention aims to overcome the problems in the prior art, and provides a Massive MIMO FBMC beam space-time coding downlink transmission method, so that the capacity, the energy efficiency and the spectral efficiency of a system are improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the user nodes comprise a base station, the number of antennas is M, U single antennas are not overlapped with each other when the angle is considered; the number of subcarriers in the FBMC system is MscThe prototype filter is a PHYDYAS prototype filter, the overlapping factor is K, and the length is L; the transmission method comprises the following steps:
1) the base station carries out QPSK constellation point modulation on the bit stream information sent to each user to obtain constellation point complex data symbols, and the real part and the imaginary part of the constellation point complex data symbols are separated, so that the complex data symbols are converted into real data symbols;
2) performing serial-to-parallel conversion on real data symbols, and dividing a serial-to-parallel converted data symbol block into two data blocks x in a time dimensionm,n'And ym,n'Performing Alamouti coding;
3) carrying out FBMC modulation on the data symbols after Alamouti coding to obtain a transmitting end space-time block code FBMC signal matrix Z;
4) the base station adopts a transmitting terminal linear weighting coefficient matrix W to carry out linear weighting on a transmitting terminal space-time block code FBMC signal matrix Z;
5) the transmission channel experiences different fading to reach different users at different time, and the user receives the signal yu；
6) At the receiving end, the user pairs the received signal yuPerforming FBMC demodulation and calculating equivalent channel
Figure BDA0001296276320000021
And MMSE channel equalization is performed;
7) and performing OQAM demodulation on the equalized data to recover bit stream information sent to a user by the base station.
Further, the data symbol obtained by Alamouti encoding in step 2) is:
Figure BDA0001296276320000031
wherein a and b respectively represent real number data symbols which are coded by Alamouti on two antennas, u represents the u-th user, m represents a subcarrier, N' represents time, NaIndicating the number of real data symbols, including the data guard column, transmitted in total.
Further, step 3) adds an initial phase, IFFT and polyphase filtering to the Alamouti encoded data symbol to obtain an FBMC modulated signal, and the modulated signals on the two antennas are used separately
Figure BDA0001296276320000032
And
Figure BDA0001296276320000033
represents:
Figure BDA0001296276320000034
Figure BDA0001296276320000035
here, k ∈ (— ∞, ∞) represents a discrete variable after sampling, and g (k) represents a discrete form of the prototype filter; initial phase needs to satisfy conditions
Figure BDA0001296276320000036
The signal matrix of the transmitting terminal space-time block code FBMC is expressed as
Figure BDA0001296276320000037
Wherein
Figure BDA00012962763200000313
And
Figure BDA00012962763200000310
are column vectors consisting of FBMC modulated signals.
Further, in step 4), designing a originating linear weighting coefficient matrix W as follows:
W＝[W1,W2,…,WU]＝[V1M1,V2M2,…,VUMU]
wherein, according to the azimuth angle V of the useruIs formed by column approximation of a specific range in a DFT transformation matrix D, wherein the element of the ith row and the jth column in the DFT transformation matrix D is
Figure BDA00012962763200000311
Further, the selection steps of the columns required in D are specifically as follows:
suppose user u has a central azimuth angle thetauAngle expansion delta thetauThen the angle of arrival range of user u is [ theta ]u-Δθu,θu+Δθu](ii) a Sine and corresponding transformation are carried out on the range of the arrival angle of the user u, and the transformed result is rounded, so that the selected range of the column D is obtained
Figure BDA00012962763200000312
Wherein round (·) represents a rounding operation;
Figure BDA0001296276320000041
the energy is normalized according to the number of users.
Further, in step 5), the number of paths of the multipath channel is assumed to be P, wherein
Figure BDA0001296276320000042
Is the channel vector for the P-th path to user u, P ═ 1,2, …, P; there is a certain time difference between the different paths for the channel to reach the user, and here, without loss of generality, it is assumed that the signal reaching the user u through the 1 st path can be completely synchronized, the 2 nd path is later than the 1 st path, the 3 rd path is later than the 2 nd path, …, and so on, and then the signal reaching the user u through the p-th path is:
Figure BDA0001296276320000043
the signal finally received by the user u is
Figure BDA0001296276320000044
Wherein eta isuFor additive white Gaussian noise vector, η, received by user uu～CN(0,σ2I)。
Further, in step 6), for the user u, the weighting matrix W of the transmitting side and the actual channel are combined
Figure BDA0001296276320000045
The product of (A) is regarded as the p-th path in the equivalent multipath channel, the equivalent channel
Figure BDA0001296276320000046
The calculation of (a) is specifically as follows:
Figure BDA0001296276320000047
then the received signal is represented as a convolution of the transmitted signal with the equivalent channel;
Figure BDA0001296276320000048
wherein the content of the first and second substances,
Figure BDA0001296276320000049
and
Figure BDA00012962763200000410
are modulated signals, eta, on two antennas respectivelyuAn additive white gaussian noise vector received for user u.
Further, in step 6), the demodulation of the FBMC specifically includes: at the receiving end, after serial-to-parallel conversion, polyphase filtering and FFT, the signals received by the user are removed of the initial phase, the demodulation of the FBMC is completed, and the frequency-time coordinate (m) is obtained0,n0) The demodulated signal is:
Figure BDA0001296276320000051
wherein a and b respectively represent real data symbols which are coded by Alamouti on two antennas, u represents the u-th user, k belongs to (- ∞, infinity) represents discrete variables after sampling, and g (k) represents the discrete form of a prototype filter; l ishRepresents the channel length; τ ═ 0,1,2, …, Lh-1, representing a time delay;
equation (7) is abbreviated as:
Figure BDA0001296276320000052
wherein the content of the first and second substances,
Figure BDA0001296276320000053
next, let
Figure BDA0001296276320000054
Figure BDA0001296276320000055
Figure BDA0001296276320000056
Figure BDA0001296276320000057
The recovered signals are written in matrix form:
Figure BDA0001296276320000058
wherein the content of the first and second substances,
Figure BDA0001296276320000059
is composed of four parts
Figure BDA00012962763200000510
Here, the first and second liquid crystal display panels are,
Figure BDA0001296276320000061
Figure BDA0001296276320000062
Figure BDA0001296276320000063
and
Figure BDA0001296276320000064
forms and
Figure BDA0001296276320000065
and
Figure BDA0001296276320000066
are identical to each other, respectively
Figure BDA0001296276320000067
And
Figure BDA0001296276320000068
and forming a Toeplitz matrix.
Further, in step 6), the MMSE channel equalization specifically includes: order to
Figure BDA0001296276320000069
Figure BDA00012962763200000610
Wherein the content of the first and second substances,
Figure BDA00012962763200000611
the operation of the real part is shown,
Figure BDA00012962763200000612
representing operations taking the imaginary part, 1ΔThe delta column representing the unit array is calculated according to the MMSE criterion:
Figure BDA00012962763200000613
Figure BDA00012962763200000614
thus, a weighting matrix is obtained:
Figure BDA00012962763200000615
finally recovering the transmitted real data symbol
Figure BDA00012962763200000616
Figure BDA00012962763200000617
Compared with the prior art, the method has the beneficial effects that:
1. the invention combines two high-quality technologies of Massive MIMO and FBMC together, provides a mixed beam forming and multi-carrier space-time coding scheme under multi-user communication, and greatly improves the capacity, energy efficiency and spectral efficiency of the system;
2. when the linear weighting matrix is designed, the invention eliminates the interference among users by utilizing the non-overlapping of the angles of all the users, and simultaneously effectively reduces the operation amount compared with the method of utilizing the covariance matrix of the channel to carry out SVD decomposition to obtain the weighting matrix.
3. The Alamouti coding scheme suitable for the FBMC is considered, the self-interference in the FBMC system can be reduced, and meanwhile, a multi-tap MMSE equalizer is adopted at a receiving end, so that the error rate performance of the system is better improved.
Drawings
FIG. 1 is a schematic diagram of a system model in accordance with the method of the present invention.
Fig. 2(a) is a schematic diagram of Alamouti coding on the first antenna in FBMC.
Fig. 2(b) is a schematic diagram of Alamouti coding on the second antenna in FBMC.
Fig. 3 shows the simulation result of the system error rate.
Detailed Description
A multi-beam space-time coding multi-user downlink channel transmission method in a Massive MIMO FBMC system comprises a base station with a large-scale uniform linear array, wherein the number of antennas is M, and U user nodes with single antennas are not overlapped with each other when the angle is considered; the number of subcarriers in the FBMC system is MscThe prototype filter is a PHYDYAS prototype filter, the overlap factor is K, and the length is L.
A method for transmitting mixed beam forming and space-time coding multi-user downlink signals in a Massive MIMO system is disclosed, a system model of the method is shown in figure 1, a base station carries out Alamouti coding on transmitting data at a transmitting end and adopts FBMC modulation, a plurality of users are served by multi-beams at the same time with the same frequency, and the method specifically comprises the following steps:
1) and the base station carries out OQAM modulation on the data sent to the user to obtain a real data symbol.
The base station carries out QPSK constellation point modulation on the bit stream information sent to each user to obtain constellation point complex data symbols, and the real part and the imaginary part of the constellation point complex data symbols are separated, so that the complex data symbols are converted into real data symbols.
2) And performing Alamouti block coding on the transmitted real data symbols.
Performing serial-to-parallel conversion on real data symbols, and dividing a serial-to-parallel converted data symbol block into two data blocks x in a time dimensionm,n'And ym,n'Finally, Alamouti encoding was performed as shown in FIGS. 2(a) and 2 (b). In Alamouti coding, the data symbol pair (x)m,n'ym,n') The result of the encoding is
Figure BDA0001296276320000081
Wherein a and b respectively represent real number data symbols which are coded by Alamouti on two antennas, superscript u represents the u-th user, subscript m represents subcarrier, N' represents time, NaIndicating the number of real data symbols, including the data guard column, transmitted in total.
3) And carrying out FBMC modulation on the Alamouti coding result to obtain a signal to be transmitted, which is called as a transmitted space-time block code FBMC signal matrix Z.
The data symbols after Alamouti coding are added with initial phase, IFFT, polyphase filtering and the like to obtain FBMC modulation signals, and the modulation signals on the two antennas are respectively used
Figure BDA0001296276320000082
And
Figure BDA0001296276320000083
to represent
Figure BDA0001296276320000084
Figure BDA0001296276320000085
Here, k ∈ (— ∞, infinity) represents a discrete variable after sampling. g (k) represents a discrete form of the prototype filter. Initial phase needs to satisfy conditions
Figure BDA0001296276320000086
Wherein
Figure BDA0001296276320000087
To represent
Figure BDA0001296276320000088
Conjugation of (1). The transmitting terminal space-time block code FBMC signal matrix can be expressed as
Figure BDA0001296276320000089
Wherein
Figure BDA00012962763200000814
And
Figure BDA00012962763200000812
are column vectors consisting of FBMC modulated signals.
4) And the base station carries out linear weighting on the FBMC signal matrix Z for transmitting the space-time block code to obtain WZ. The originating linear weighting coefficient matrix W is designed as:
W＝[W1,W2,…,WU]＝[V1M1,V2M2,…,VUMU]
wherein, VuIt can be composed of a specific range of column approximations in the DFT transform matrix D according to the azimuth at which the user is located, where U is 1,2, …, U. The ith row and jth column elements in the DFT transform matrix D are
Figure BDA00012962763200000813
To obtain the key component V in the weighting matrixuThe method for selecting the columns in D is as follows:
suppose user u has a central azimuth angle thetauAngle expansion delta thetauThen the angle of arrival range of user u is [ theta ]u-Δθu,θu+Δθu]. Sine and corresponding transformation are carried out on the range of the arrival angle of the user u, and the transformed result is rounded, so that the selected range of the column D is obtained
Figure BDA0001296276320000091
Where round (·) represents a rounding operation.
In addition, in order to reduce interference, achieve optimal system performance,
Figure BDA0001296276320000092
the energy is normalized according to the number of users.
5) The transmission channel experiences different fading to reach different users at different times.
Assume the number of paths of a multipath channel is P, where
Figure BDA0001296276320000093
Is the channel vector for the P-th path to user u, P ═ 1,2, …, P. There is a certain time difference between the different paths for the channel to reach the user, and here, without loss of generality, it is assumed that the signal reaching user u via path 1 can be completely synchronized, 2 is later than 1, 3 is later than 2, …, and so on. Then the signal that reaches user u via the p-th path is:
Figure BDA0001296276320000094
the signal finally received by the user u is
Figure BDA0001296276320000095
Wherein eta isuThe mean received for user u is 0 and the variance is σ2White gaussian noise of additive natureVector ηu～CN(0,σ2I)，σ2Representing the noise power and I the identity matrix.
6) An equivalent channel is calculated. For user u, the weighting matrix W of the transmitting end and the actual channel can be combined
Figure BDA0001296276320000096
The product of (a) is considered the p-th path in the equivalent multipath channel. Equivalent channel
Figure BDA0001296276320000097
The calculation of (a) is specifically as follows:
Figure BDA0001296276320000098
then, the received signal may be represented as a convolution of the transmitted signal and the equivalent channel. Receiving signal yuCan be written as
Figure BDA0001296276320000099
7) At the receiving end, the user performs FBMC demodulation on the received signal and MMSE channel equalization.
After serial-parallel conversion, polyphase filtering and FFT, the signal received by the user is processed to remove the initial phase, namely, the demodulation of FBMC is completed, and the frequency-time coordinate (m) is obtained0,n0) The demodulated signal is
Figure BDA0001296276320000101
Wherein L ishDenotes the channel length, τ -0, 1,2, …, Lh-1 represents the time delay. The above formula can be further abbreviated as
Figure BDA0001296276320000102
Wherein the content of the first and second substances,
Figure BDA0001296276320000103
next, let
Figure BDA0001296276320000104
Figure BDA0001296276320000105
Figure BDA0001296276320000106
Figure BDA0001296276320000107
The recovered signal can be further written in a matrix form
Figure BDA0001296276320000108
Wherein the content of the first and second substances,
Figure BDA0001296276320000109
is composed of four parts
Figure BDA00012962763200001010
Here, the first and second liquid crystal display panels are,
Figure BDA0001296276320000111
Figure BDA0001296276320000112
Figure BDA0001296276320000113
and
Figure BDA0001296276320000114
forms and
Figure BDA0001296276320000115
and
Figure BDA0001296276320000116
are identical to each other, respectively
Figure BDA0001296276320000117
And
Figure BDA0001296276320000118
and forming a Toeplitz matrix.
Order to
Figure BDA0001296276320000119
Wherein the content of the first and second substances,
Figure BDA00012962763200001110
the operation of the real part is shown,
Figure BDA00012962763200001111
the representation takes the imaginary part operation. 1ΔThe delta column of the unit array can be calculated according to the MMSE criterion
Figure BDA00012962763200001112
Figure BDA00012962763200001113
According to
Figure BDA00012962763200001114
The weighting matrix can be obtained as
Figure BDA00012962763200001115
Finally, the transmitted real data symbols can be recovered
Figure BDA00012962763200001116
Figure BDA00012962763200001117
8) And performing OQAM demodulation on the equalized data to obtain transmitted bit stream information.
And recovering the real data symbols into complex data symbols in each path by the recovered multi-path real data symbols, then performing parallel-serial conversion, performing QPSK demodulation, and recovering bit stream information sent to a user by the base station.
The simulation results of the entire system are shown in fig. 3. The simulation conditions are that the number of subcarriers is 64, the number of antennas is 200, the channel has 5 paths, two users are respectively positioned at-30 degrees and 45 degrees, and the angle expansion is 10 degrees. From the simulation results, it can be seen that the bit error rate of two users is significantly better than the performance when Alamouti coding is adopted for two transmitters and one receiver, and the bit error rate performance of-30 ° user is better than that of 45 ° user.
The invention discloses a multi-beam space-time coding multi-user downlink channel transmission method in a Massive MIMO FBMC system, which combines two high-quality technologies of Massive MIMO and FBMC together, greatly improves the throughput of the system, provides a multi-beam and multi-carrier space-time coding scheme under multi-user communication, and greatly improves the capacity, energy efficiency and spectral efficiency of the system. When the linear weighting matrix is designed, the interference among users is eliminated by utilizing the non-overlapping of the angles of all the users, and meanwhile, compared with the method of computing the weighting matrix by utilizing the covariance matrix of the channel to carry out SVD (singular value decomposition), the calculation amount can be effectively reduced. When Alamouti coding is carried out, a scheme suitable for FBMC is considered, self-interference in an FBMC system can be reduced, and meanwhile, a multi-tap MMSE equalizer is adopted at a receiving end, so that the error rate performance of the system is further improved.

Claims (7)

1. A Massive MIMO FBMC beam space-time coding downlink transmission method is characterized in that: user nodes comprising a base station, the number of antennas being M, U single antennas, are considered to be each otherDo not overlap; the number of subcarriers in the FBMC system is MscThe prototype filter is a PHYDYAS prototype filter, the overlapping factor is K, and the length is L; the transmission method comprises the following steps:
1) the base station carries out QPSK constellation point modulation on the bit stream information sent to each user to obtain constellation point complex data symbols, and the real part and the imaginary part of the constellation point complex data symbols are separated, so that the complex data symbols are converted into real data symbols;
2) performing serial-to-parallel conversion on real data symbols, and dividing a serial-to-parallel converted data symbol block into two data blocks x in a time dimensionm,n'And ym,n'Performing Alamouti coding; m represents a subcarrier, and n' represents time;
3) carrying out FBMC modulation on the data symbols after Alamouti coding to obtain a transmitting end space-time block code FBMC signal matrix Z;
4) the base station adopts a transmitting terminal linear weighting coefficient matrix W to carry out linear weighting on a transmitting terminal space-time block code FBMC signal matrix Z;
5) the transmission channel experiences different fading to reach different users at different time, and the user receives the signal yu；
6) At the receiving end, the user pairs the received signal yuPerforming FBMC demodulation and calculating equivalent channel
Figure FDA0002629775460000011
And MMSE channel equalization is performed; for user u, the linear weighting coefficient matrix W of the transmitting end and the actual channel are combined
Figure FDA0002629775460000012
The product of (A) is regarded as the p-th path in the equivalent multipath channel, the equivalent channel
Figure FDA0002629775460000013
The calculation of (a) is specifically as follows:
Figure FDA0002629775460000014
then the received signal is represented as a convolution of the transmitted signal with the equivalent channel; p represents the number of paths of the multipath channel;
Figure FDA0002629775460000015
wherein the content of the first and second substances,
Figure FDA0002629775460000016
and
Figure FDA0002629775460000017
column vector, η, composed of FBMC modulation signalsuAn additive white Gaussian noise vector received by a user u;
the demodulation of FBMC specifically includes: at the receiving end, after serial-to-parallel conversion, polyphase filtering and FFT, the signals received by the user are removed of the initial phase, the demodulation of the FBMC is completed, and the frequency-time coordinate (m) is obtained0,n0) The demodulated signal is:
Figure FDA0002629775460000021
wherein a and b respectively represent real data symbols which are coded by Alamouti on two antennas, u represents the u-th user, k belongs to (- ∞, infinity) represents discrete variables after sampling, and g (k) represents the discrete form of a prototype filter; l ishRepresents the channel length; τ ═ 0,1,2, …, Lh-1, representing a time delay; phi is am,nInitial phase representing frequency-time coordinate (m, n), m representing subcarrier, n being time coordinate;
Figure FDA0002629775460000022
to represent
Figure FDA0002629775460000023
Conjugation of (A) to (B), NaRepresenting the number of real data symbols including data guard columns transmitted in total;
equation (7) is abbreviated as:
Figure FDA0002629775460000024
wherein the content of the first and second substances,
Figure FDA0002629775460000025
Δ m represents subcarrier number expansion, and Δ n represents time expansion;
next, let
Figure FDA0002629775460000026
Figure FDA0002629775460000027
Figure FDA0002629775460000028
Figure FDA0002629775460000029
x and y respectively represent data symbols which are coded by Alamouti on the two antennas;
the recovered signals are written in matrix form:
Figure FDA0002629775460000031
wherein the content of the first and second substances,
Figure FDA0002629775460000032
is composed of four parts
Figure FDA0002629775460000033
Here, the first and second liquid crystal display panels are,
Figure FDA0002629775460000034
Figure FDA0002629775460000035
Figure FDA0002629775460000036
and
Figure FDA0002629775460000037
forms and
Figure FDA0002629775460000038
and
Figure FDA0002629775460000039
are identical to each other, respectively
Figure FDA00026297754600000310
And
Figure FDA00026297754600000311
forming a topiraz matrix;
7) and performing OQAM demodulation on the equalized data to recover bit stream information sent to a user by the base station.
2. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 1, characterized in that: step 2) the data symbols obtained by Alamouti coding are as follows:
Figure FDA00026297754600000312
wherein, a and b respectively represent real number data symbols coded by Alamouti on two antennas, and n' represents time.
3. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 2, characterized in that: step 3) adding initial phase, IFFT and polyphase filtering to the Alamouti coded data symbols to obtain FBMC modulation signals, wherein the modulation signals on the two antennas are used respectively
Figure FDA00026297754600000313
And
Figure FDA00026297754600000314
represents:
Figure FDA00026297754600000315
Figure FDA00026297754600000316
initial phase needs to satisfy conditions
Figure FDA0002629775460000041
The signal matrix of the transmitting terminal space-time block code FBMC is expressed as
Figure FDA0002629775460000042
Wherein
Figure FDA0002629775460000043
4. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 1, characterized in that: in step 4), designing a originating linear weighting coefficient matrix W as follows:
W＝[W1,W2,…,WU]＝[V1M1,V2M2,…,VUMU]
wherein, according to the azimuth angle V of the userUBy transforming the matrix D with DFTColumn composition of the selected range, the element of the ith row and the jth column in the DFT transformation matrix D is
Figure FDA0002629775460000044
5. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 4, characterized in that: the selection of the columns required in D is as follows:
the azimuth angle of the u center of the user is thetauAngle expansion delta thetauThen the angle of arrival range of user u is [ theta ]u-Δθu,θu+Δθu](ii) a Sine and corresponding transformation are carried out on the range of the arrival angle of the user u, and the transformed result is rounded, so that the selected range of the column D is obtained
Figure FDA0002629775460000045
Wherein round (·) represents a rounding operation;
Figure FDA0002629775460000046
the energy is normalized according to the number of users.
6. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 1, characterized in that: in step 5), P is 1,2, …, P; there is a certain time difference between the different paths when the channel arrives at the user, and it is assumed that the signal arriving at the user u via the 1 st path can be completely synchronized, the 2 nd path is later than the 1 st path, the 3 rd path is later than the 2 nd path, …, and so on, then the signal arriving at the user u via the p-th path is:
Figure FDA0002629775460000047
the signal finally received by the user u is
Figure FDA0002629775460000051
Wherein eta isuFor additive white Gaussian noise vector, η, received by user uu～CN(0,σ2I)。
7. The Massive MIMO FBMC beam space-time coding downlink transmission method according to claim 1, characterized in that: in step 6), MMSE channel equalization specifically includes: order to
Figure FDA0002629775460000052
Figure FDA0002629775460000053
Wherein the content of the first and second substances,
Figure FDA0002629775460000054
the operation of the real part is shown,
Figure FDA0002629775460000055
representing operations taking the imaginary part, 1ΔThe delta column representing the unit array is calculated according to the MMSE criterion:
Figure FDA0002629775460000056
Figure FDA0002629775460000057
thus, a weighting matrix is obtained:
Figure FDA0002629775460000058
finally recovering the transmitted real data symbol
Figure FDA0002629775460000059
Figure FDA00026297754600000510
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