CN102104404B - Multi-user MIMO transmission method in wireless communication system, base station and user terminal - Google Patents

Abstract

The invention discloses a multi-user multiple input multiple output (MU-MIMO) transmission method in a wireless communication system, a base station and a user terminal. The method comprises the following steps that: the base station receives detection pilot frequency SRS of N users to perform channel estimation and acquires downlink channel information according to the channel estimation result and channel reciprocity of the system, wherein N is more than 1; the base station performs quick response (QR) decomposition on the downlink channel information, acquires a multi-user beamforming (MU-BF) matrix P (i) of the ith user from a Q matrix acquired through decomposition, and acquires a downlink single-user beamforming (SU-BF) matrix V (i) of the ith user further, wherein i=1, ...,N; and the base station performs beamforming processing on transmitting data of the ith user according to the MU-BF matrix P (i) and the SU-BF matrix V (i). The method and equipment acquire beamforming matrixes for uplink and downlink MU-MIMO transmission by means of the channel reciprocity of the system and the QR decomposition, and the MU-MIMO transmission performance can be improved.

Description

Multi-user MIMO transmission method, base station and user terminal in wireless communication system

Technical Field

The present invention relates to the field of wireless communication, and in particular, to a transmission method for multi-user multiple input multiple output (MU-MIMO) in a wireless communication system (e.g., LTE-a system), a base station and a user terminal for MU-MIMO transmission.

Background

Multiple Input Multiple Output (MIMO) technology has become one of the key technologies of broadband wireless communication systems including 3GPP Long Term Evolution (LTE) because of its ability to effectively improve the spectral efficiency of wireless links. MIMO technology can be divided into single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) according to whether multiple users can be supported simultaneously on the same time-frequency resource. Among them, MU-MIMO has more advantages such as supporting more flexible user antenna configuration, stronger adaptability to channel conditions, existence of multi-user diversity gain, etc. MU-MIMO is applicable to both uplink and downlink of cellular systems, but downlink MU-MIMO puts higher requirements on the Channel State Information (CSIT) at the transmitter side, i.e. requires that the base station (eNB) must obtain downlink channel information for each User (UE). Acquisition of CSIT is generally divided into 2 cases:

for a Time Division Duplex (TDD) system, since uplink and downlink occupy the same frequency resources, there is reciprocity between uplink and downlink wireless channels, and the downlink channel can be conveniently inferred according to the uplink channel, and vice versa.

For a Frequency Division Duplex (FDD) system, the uplink and downlink radio channels mostly have no reciprocity because the uplink and downlink occupy different frequency resources, or the reciprocity in the FDD system is more difficult to obtain, so the CSIT acquisition mostly depends on a feedback channel. Of course, to reduce the amount of feedback, codebook design or quantization techniques may be employed.

In particular implementations, SU-MIMO and MU-MIMO generally require preprocessing of the transmitted signal according to CSIT for the purpose of channel matching and multi-user interference (MUI) cancellation, respectively, which is referred to as precoding or beamforming. Due to different technical scenario description conventions, the two names may be used interchangeably in this application, but the meanings of the two are the same.

At present, the uplink design of 3GPP LTE Rel-8 can only support virtual MU-MIMO, namely can support a plurality of single-antenna UEs to simultaneously transmit data; the downlink design is mainly optimized for SU-MIMO, and the support for MU-MIMO is very limited, and multiple UEs and transmission of multiple data streams per UE cannot be supported. Moreover, to simplify system design, LTE Rel-8 adopts almost the same design for FDD and TDD, i.e., both use codebook-based beamforming and do not take advantage of the reciprocity that may exist for wireless channels.

With the gradual end of the work of standard formulation of LTE Rel-8, the 3GPP initiated the work of LTE-a in 2008. LTE-a is a subsequent evolution of LTE, placing higher demands on system performance, such as requiring that LTE-a systems be able to support multiple-UE and multiple-data-stream per UE MU-MIMO transmission. Therefore, how to effectively support uplink and downlink MU-MIMO in the LTE-A system becomes a research hotspot. Furthermore, in the technical discussion for LTE-a, how to fully exploit the reciprocity of wireless channels to support non-codebook beamforming is receiving more and more attention, especially for TDD systems.

In order to solve the above problems, the most common practice in the prior art is to use independent MU-MIMO transmission for uplink and downlink of a cellular system, where the simplest implementation scheme (scheme one) is that downlink MU-MIMO is transmitted based on Block Diagonalization (BD), and uplink MU-MIMO is received only by multi-user detection (MUD) without processing at the transmitting end. Although the first scheme is simple to implement, the characteristics of a wireless channel are not further utilized because only how to eliminate mutual interference among multiple users is considered, and thus, the spectrum efficiency is sacrificed to a certain extent.

On the basis of the first scheme, the prior art also provides a joint MU-MIMO scheme (scheme two) for uplink and downlink of the TDD system. Namely: after multi-user interference is eliminated by the downlink MU-MIMO by means of a BD (block-based multiple-input multiple-output) rule, SVD (singular value decomposition) is carried out on an equivalent channel of each UE (user equipment), so that characteristic transmission is respectively realized for each UE; on the premise that the uplink and the downlink use the same wireless channel for data transmission, the uplink MU-MIMO can also realize the characteristic transmission of each UE. It can be seen that the second scheme simultaneously realizes the orthogonal transmission of a plurality of data streams of a plurality of uplink and downlink users, so that the frequency spectrum efficiency is improved. However, the complexity of SVD decomposition is high and the numerical stability is poor, so that there is a certain obstacle to implementation of the second scheme. Meanwhile, the scheme two requires that the uplink and the downlink must use the same wireless channel for data transmission, which sometimes cannot be met in an actual cellular system, and also limits the realizability of uplink MU-MIMO in the scheme two.

Disclosure of Invention

In view of the above, the present invention is directed to a MU-MIMO transmission method, a base station and a user terminal.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a transmission method of multi-user multiple-input multiple-output (MU-MIMO) in a wireless communication system comprises the following steps:

a base station receives sounding pilot frequency SRS sent by N user terminals UE for channel estimation, and generates a downlink channel information matrix according to a channel estimation result and the channel reciprocity of the system, wherein N is more than 1;

the base station carries out QR decomposition on the generated downlink channel information matrix, and obtains a multi-user beam forming MU-BF matrix P of the ith UE from a Q matrix obtained by decomposition⁽ⁱ⁾And further obtaining a downlink single-user beam forming SU-BF matrix V of the ith UE⁽ⁱ⁾Wherein i 1.., N;

the base station according to the MU-BF matrix P⁽ⁱ⁾And said downstream SU-BF matrix V⁽ⁱ⁾And performing beam forming processing on the transmission data of the ith UE.

The method further comprises the following steps:

and the base station performs transmission beam forming processing on the user-specific pilot frequency of the UE according to the MU-BF matrix and the downlink SU-BF matrix of the ith UE and then sends the processed user-specific pilot frequency to the UE.

The method further comprises the following steps:

the ith UE receives the downlink pilot frequency sent by the base station to carry out channel estimation, and a downlink channel information matrix aiming at the UE is obtained;

the UE carries out QR decomposition on the downlink channel information matrix, and obtains an uplink single-user beam forming SU-BF matrix U of the UE from a Q matrix obtained by decomposition⁽ⁱ⁾；

And performing beam forming processing on the transmitted data according to the uplink SU-BF matrix.

The UE carries out QR decomposition on the downlink channel information matrix to obtain the uplink SU-BF matrix, and the method comprises the following steps:

the ith UE receives the user special pilot frequency sent by the base station to carry out channel estimation to obtain a downlink equivalent channel matrix;

and the UE carries out QR decomposition on the downlink equivalent channel matrix, and takes a Q matrix obtained by decomposition as a first uplink SU-BF matrix of the UE.

The UE carries out QR decomposition on the downlink channel information matrix to obtain the uplink SU-BF matrix, and the method comprises the following steps:

the ith UE receives the cell dedicated pilot frequency sent by the base station to carry out channel estimation to obtain a downlink physical channel matrix, and obtains an uplink physical channel matrix according to channel reciprocity;

and the UE carries out QR decomposition on the uplink physical channel matrix, and obtains a second uplink SU-BF matrix of the UE from the Q matrix obtained by decomposition.

The method further comprises the following steps:

the UE performs conjugate transposition on the uplink SU-BF matrix;

and performing MIMO detection after the beam forming processing is performed on the received data of the UE according to the conjugate transpose of the uplink SU-BF matrix.

The method further comprises the following steps: and the UE carries out transmitting beam forming processing on the uplink demodulation pilot frequency DMRS according to the uplink SU-BF matrix and then sends the processed uplink demodulation pilot frequency DMRS to the base station.

The method further comprises the following steps:

the base station performs conjugate transposition on an MU-BF matrix and a downlink SU-BF matrix of the ith UE;

and performing multi-user interference cancellation (MUI) on the received data of the base station according to the conjugate transpose of the MU-BF matrix of the UE to obtain the received data of the ith UE, and performing MIMO detection after processing the received data of the UE by using the conjugate transpose of the downlink SU-BF matrix.

The base station obtains a downlink single-user beam forming SU-BF matrix V of the ith UE⁽ⁱ⁾The method comprises the following steps:

the base station is according to the downlink physical channel matrix H of the ith UE⁽ⁱ⁾And MU-BF matrix P⁽ⁱ⁾To obtain H⁽ⁱ⁾P⁽ⁱ⁾And to H⁽ⁱ⁾P⁽ⁱ⁾Carrying out QR decomposition to obtain a downlink SU-BF matrix V of the UE⁽ⁱ⁾。

The UE acquires an uplink single-user beam forming SU-BF matrix U of the UE⁽ⁱ⁾The method comprises the following steps:

UE sends uplink physical channel matrix H_UL ⁽ⁱ⁾And the conjugate transpose H of the uplink physical channel matrix_UL ^(i)HMultiplication to obtain H_UL ^(i)HH_UL ⁽ⁱ⁾Then, H is introduced_UL ^(i)HH_UL ⁽ⁱ⁾And U_t-1 ⁽ⁱ⁾Obtaining an uplink SU-BF matrix U through QR decomposition after multiplication_t ⁽ⁱ⁾。

A base station for multi-user multiple-input multiple-output (MU-MIMO) transmission, comprising:

the channel estimation unit is used for carrying out channel estimation to obtain uplink channel information of more than one user terminal UE and obtaining a downlink channel information matrix according to channel reciprocity;

the QR decomposition unit is used for carrying out QR decomposition on the downlink channel information matrix, acquiring a multi-user beam forming MU-BF matrix of each UE from a Q matrix obtained by decomposition, and further acquiring a downlink single-user beam forming SU-BF matrix of each UE;

and the transmitting beam forming unit is used for carrying out beam forming processing on the transmitting data of the corresponding UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE and transmitting the transmitting data to the antenna of the base station for transmission.

The QR decomposition unit is further used for providing the R matrix obtained by decomposition to the MIMO detection unit;

and the MIMO detection unit is used for carrying out MIMO detection on the received data of the antennas according to the R matrix and recovering the transmitted data of each UE.

The QR decomposition unit is further used for performing conjugate transposition on the MU-BF matrix and the downlink SU-BF matrix of each UE and providing the conjugate transposition for the receiving beam forming unit;

and the receiving beam forming unit is used for executing multi-user interference elimination (MUI) on the received data of the antenna according to the conjugate transpose of the MU-BF matrix of each UE to obtain the received data of each UE, processing the received data of the corresponding UE by using the conjugate transpose of the downlink SU-BF matrix, and then sending the processed received data to the MIMO detection unit.

The QR decomposition unit is further used for carrying out adaptive modulation coding AMC control on the transmitting data flow of more than one UE according to the R matrix obtained by decomposition.

The QR decomposition unit is used for decomposing the downlink physical channel matrix H according to each UE⁽ⁱ⁾And MU-BF matrix P⁽ⁱ⁾To obtain H⁽ⁱ⁾P⁽ⁱ⁾And to H⁽ⁱ⁾P⁽ⁱ⁾QR decomposition is carried out to obtain a downlink SU-BF matrix V of each UE⁽ⁱ⁾And i is an arbitrary integer from 1 to the number N of users.

The channel estimation unit is used for performing channel estimation according to the sounding pilot frequency SRS sent by each UE, or obtaining uplink channel information according to the uplink demodulation pilot frequency DMRS sent by each UE, and obtaining a downlink channel information matrix according to channel reciprocity.

And the transmitting beam forming unit is further used for carrying out beam forming processing on the user-specific pilot frequency sent to each UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE.

A wireless communication system for multi-user multiple-input multiple-output (MU-MIMO) transmission, comprising: a user terminal UE and a base station;

the UE includes: the device comprises a channel estimation unit, a QR decomposition unit and a transmitting beam forming unit;

the channel estimation unit is used for performing channel estimation to obtain a downlink channel information matrix of the UE;

the QR decomposition unit is used for carrying out QR decomposition on the downlink channel information matrix and acquiring an uplink single-user beam forming SU-BF matrix of the UE from a Q matrix obtained by decomposition;

the transmitting beam forming unit is used for carrying out beam forming processing on transmitting data according to the uplink SU-BF matrix of the UE and transmitting the data from the antenna of the UE;

the base station includes: the second channel estimation unit, the second QR decomposition unit and the second transmitting beam forming unit;

the second channel estimation unit is used for performing channel estimation to obtain uplink channel information of more than one UE and obtaining a downlink channel information matrix according to channel reciprocity;

the second QR decomposition unit is configured to perform QR decomposition on the downlink channel information matrix, obtain a multi-user beamforming MU-BF matrix of each UE from the Q matrix obtained by the decomposition, and further obtain a downlink single-user beamforming SU-BF matrix of each UE;

and the second transmitting beam forming unit is used for performing beam forming processing on transmitting data of corresponding UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE, and transmitting the transmitting data to the antenna of the base station for transmission.

The channel estimation unit is used for carrying out channel estimation according to the user special pilot frequency sent by the base station to obtain a downlink equivalent channel matrix;

and the QR decomposition unit is used for carrying out QR decomposition on the downlink equivalent channel matrix and taking a Q matrix obtained by decomposition as a first uplink SU-BF matrix of the UE.

The channel estimation unit is used for carrying out channel estimation according to the special pilot frequency of the cell sent by the base station to obtain a downlink physical channel matrix and obtaining an uplink physical channel matrix according to channel reciprocity;

and the QR decomposition unit is used for carrying out QR decomposition on the uplink physical channel matrix and obtaining a second uplink SU-BF matrix of the UE from the Q matrix obtained by decomposition.

The QR decomposition unit is further used for providing the R matrix obtained by decomposition to the MIMO detection unit;

and the MIMO detection unit is used for carrying out MIMO detection on the received data of the UE according to the R matrix.

Drawings

The QR decomposition unit is further used for performing conjugate transposition on an uplink SU-BF matrix of the UE and providing the uplink SU-BF matrix for the receiving beam forming unit;

and the receiving beam forming unit is used for processing the receiving data of the UE according to the conjugate transpose of the uplink SU-BF matrix and then sending the processed receiving data to the MIMO detection unit.

The QR decomposition unit is further used for carrying out adaptive modulation coding AMC control on more than one transmitting data stream of the UE according to the R matrix obtained by decomposition.

And the transmitting beam forming unit is further used for carrying out beam forming processing on the uplink demodulation pilot frequency DMRS according to the uplink SU-BF matrix of the UE.

According to the technical scheme, the method for MU-MIMO transmission calculates the beam forming matrix (comprising the MU-BF matrix and the SU-BF matrix) for uplink and downlink MU-MIMO transmission by means of QRD with low complexity and good numerical stability, and simplifies and optimizes the transceiver structure (the base station and the user terminal) on the basis, so as to be beneficial to engineering realization. It can be seen that the invention makes full use of reciprocity of wireless channels in a communication system, designs a non-codebook MU-MIMO transmission scheme for uplink and downlink links of an LTE-A system, and is used for supporting multi-user multi-data stream transmission.

FIG. 1 is a system model for MU-MIMO according to an embodiment of the present invention;

fig. 2 is a flowchart of MU-MIMO uplink and downlink transmission with the same uplink and downlink resource allocation in an embodiment of the present invention;

fig. 3 is a schematic diagram of eNB side QRD iteration;

fig. 4 is a flowchart of MU-MIMO downlink transmission when uplink and downlink resource allocations are different in one embodiment of the present invention;

fig. 5 is a flowchart of MU-MIMO uplink transmission when uplink and downlink resource allocations are different in one embodiment of the present invention;

fig. 6 is a diagram of UE side QRD iteration;

FIG. 7 is a block diagram of a base station for MU-MIMO transmission according to an embodiment of the present invention;

FIG. 8 is a diagram illustrating a structure of a user terminal for MU-MIMO transmission according to an embodiment of the present invention;

FIG. 9 is a graph illustrating a comparison of prior art and embodiments of the present invention in terms of downlink throughput performance;

fig. 10 is a diagram illustrating a comparison between the prior art and the embodiment of the present invention in terms of uplink throughput performance.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and examples.

In one embodiment of the present invention, a system model for MU-MIMO transmission is shown in fig. 1, which considers the case of 1 base station (eNB) and 2 Users (UEs), where the 2 UEs are independent users selected by multiuser scheduling. The eNB has 4 antennas and 2 antennas per UE. It should be noted that, since there may be many users in the cellular system, before performing MU-MIMO transmission, a plurality of users with mutually independent spatial channels should be selected by means of a multi-user scheduling algorithm to participate in MU-MIMO transmission. In the following description, only how MU-MIMO transmission is performed between independent users after completion of multi-user scheduling is considered.

For the system model shown in fig. 1, the signal model for the downlink MU-MIMO transmission is represented as:

<math><mrow> <msubsup> <mi>y</mi> <mi>DL</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msup> <mi>H</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msup> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mn>2</mn> </munderover> <msup> <mi>P</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msup> <msup> <mi>V</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msup> <msubsup> <mi>d</mi> <mi>DL</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <msubsup> <mi>n</mi> <mi>DL</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mo>,</mo> <mi>i</mi> <mo>=</mo> <mn>1,2</mn> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow></math>

wherein:

y_DL ⁽ⁱ⁾a received signal vector (2 x 1) for the ith UE;

H⁽ⁱ⁾a downlink channel matrix (2 x 4) from the eNB to the i-th UE;

P^(k)a multi-user beamforming (MU-BF) matrix (4 x 2) for a kth UE;

V^(k)forming (SU-BF) matrix (2 x 2) for the downlink single user of the kth UE;

d_DL ^(k)a downlink data stream vector (2 x 1) for the ith UE;

n_DL ⁽ⁱ⁾additive White Gaussian Noise (AWGN) noise vector (2 × 1) for the ith UE.

Assuming that the radio resource allocation of the uplink and downlink is the same, the signal model of uplink MU-MIMO transmission can be expressed as:

<math><mrow> <msub> <mi>y</mi> <mi>UL</mi> </msub> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mn>2</mn> </munderover> <msup> <mrow> <mo>[</mo> <msup> <mi>H</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msup> <mo>]</mo> </mrow> <mi>H</mi> </msup> <msup> <mi>U</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msup> <msubsup> <mi>d</mi> <mi>UL</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <msub> <mi>n</mi> <mi>UL</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow></math>

wherein:

y_ULa received signal vector (4 x 1) for eNB;

[H⁽ⁱ⁾]^Han uplink channel matrix (4 x 2) from the ith UE to the eNB;

U⁽ⁱ⁾forming (SU-BF) matrix (2 x 2) for uplink single user beam of ith UE;

d_UL ⁽ⁱ⁾an uplink data flow vector (2 x 1) for the ith UE;

n_ULAWGN noise vector for eNB (4 × 1).

It should be noted that in TDD system, when uplink and downlink occupy the same radio channel, there is reciprocity between the radio channels of uplink and downlink, i.e. if the downlink channel matrix from eNB to ith UE is denoted as H⁽ⁱ⁾Then the uplink channel matrix from the ith UE to the eNB can be represented as [ H ]⁽ⁱ⁾]^TI.e. the uplink and downlink channel matrices satisfy the transpose relationship. In the embodiment of the present invention, in order to simplify the calculation of the uplink and downlink SU-BF matrices, it is necessary to make the uplink and downlink channel matrices satisfy the conjugate transpose relationship, that is, if the downlink channel matrix from the eNB to the ith UE is denoted as H⁽ⁱ⁾Then the uplink channel matrix from the ith UE to the eNB is denoted as [ H ]⁽ⁱ⁾]^T. In order to satisfy the conjugate transpose relationship, only one conjugate operation needs to be performed before the uplink signal is transmitted and before the uplink received signal is processed.

Based on the model in fig. 1, on the premise that the uplink and downlink radio resource allocations are the same, the flow of uplink and downlink joint MU-MIMO transmission is shown in fig. 2, and includes the following steps:

step 201: a plurality of UEs (assuming that the number of users is N, N is greater than 1) send sounding pilot (SRS) to the eNB, wherein the ith UE is the UE_i1., N. In this embodiment, N is 2.

Step 202: the eNB carries out channel estimation according to the SRS, acquires uplink physical channels of a plurality of UEs, and then deduces downlink physical channels according to channel reciprocity <math><mrow> <msub> <mi>H</mi> <mi>DL</mi> </msub> <mover> <mrow> <mi></mi> <mo>=</mo> </mrow> <mi>&Delta;</mi> </mover> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msup> <mi>H</mi> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> </mtd> </mtr> <mtr> <mtd> <msup> <mi>H</mi> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </msup> </mtd> </mtr> </mtable> </mfenced> <mo>.</mo> </mrow></math>

Step 203: the eNB performs a 4 × 4QR decomposition (QRD, QR decomposition) to compute a respective MU-BF matrix P for each UE⁽ⁱ⁾And i is 1 and 2. QR decomposition is also referred to as orthogonal matrix triangulation, i.e., decomposition of a matrix a into an orthogonal matrix Q and an upper triangular matrix R.

With P⁽²⁾For example, for H_DLConjugate transpose of (H)^HQRD is performed to obtain H^HQR. Where Q is a unitary 4 × 4 matrix, R is an upper triangular 4 × 4 matrix, and the first 2 columns and the last 2 columns of Q are written as 2 sub-matrices, i.e., Q ═ Q⁽¹⁾Q⁽²⁾]. Then, P⁽²⁾＝Q⁽²⁾Namely an MU-BF matrix of the UE2, satisfying H⁽¹⁾P⁽²⁾＝0_2×2

Step 204: eNB according to UE_iDownlink physical channel ofH⁽ⁱ⁾And MU-BF matrix P⁽ⁱ⁾Calculating to obtain H⁽ⁱ⁾P⁽ⁱ⁾I 1, 2 for H⁽ⁱ⁾P⁽ⁱ⁾And performing QRD iteration of 2 x 2 on i-1 and 2 to obtain UE_iDownstream SU-BF matrix V⁽ⁱ⁾。

The specific iterative process is shown in fig. 3. As the number of iterations increases, the UE_iThe interference between the multiple data streams is reduced, but the calculation delay is also increased correspondingly, and generally 1 iteration can achieve better performance.

Step 205: eNB Using cascaded BF matrices P⁽ⁱ⁾V⁽ⁱ⁾Beamforming (Tx-BF) is performed on the transmit data.

Step 206: the eNB also performs similar beamforming on a user-specific pilot (UE-specific RS).

Step 207: the eNB transmits Downlink Control Information (DCI) for data transmission to each UE. Note that this step is optional.

Step 208: the eNB sends beamformed user-specific pilots and data to each UE.

Step 209: UE carries out channel estimation according to received user special pilot frequency to obtain downlink equivalent channel ${\tilde{H}}_{\mathrm{DL}}^{\left(i\right)}=H^{\left(i\right)}{P}^{\left(i\right)}{V}^{\left(i\right)}.$

Step 210: UE carries out 2X 2QRD to the downlink equivalent channel, and the obtained Q matrix is the first uplink SU-BF matrix U of the UE₁ ⁽ⁱ⁾. That is, the first upstream SU-BF matrix U₁ ⁽ⁱ⁾Is based on the downlink equivalent channelAnd (4) obtaining the product.

Step 211: a first uplink SU-BF matrix U of the UE is processed₁ ⁽ⁱ⁾Conjugate transpose of [ U ]₁ ⁽ⁱ⁾]^HAs reception beamforming (Rx-BF) of the UE, reception data after beamforming is obtainedNote that this step is optional.

${\tilde{d}}_{\mathrm{DL}}^{\left(i\right)}={\left[U^{\left(i\right)}\right]}^H{y}_{\mathrm{DL}}^{\left(i\right)}=R_{\mathrm{DL}}^{\left(i\right)}{d}_{\mathrm{DL}}^{\left(i\right)}+{\tilde{n}}_{\mathrm{DL}}^{\left(i\right)}$

Wherein, $R_{\mathrm{DL}}^{\left(i\right)}=\left[\begin{array}{cc}{r}_{\mathrm{DL},11}^{\left(i\right)}& r_{\mathrm{DL},12}^{\left(i\right)}\\ 0& r_{\mathrm{DL},22}^{\left(i\right)}\end{array}\right],$ the R is_DL ⁽ⁱ⁾Is a downlink equivalent channelPerforming 2 × 2QRD to obtain an upper triangular array; d_DL ⁽ⁱ⁾A downlink data stream vector (2 x 1) for the ith UE; ${\tilde{n}}_{\mathrm{DL}}^{\left(i\right)}={\left[U^{\left(i\right)}\right]}^H{n}_{\mathrm{DL}}^{\left(i\right)}.$

step 212: and the UE performs MIMO detection on the received data.

If step 211 is performed, the UE pair after the reception beamformingAnd carrying out MIMO detection. Considering that the downlink of the LTE-A system is based on Orthogonal Frequency Division Multiple Access (OFDMA), R_DL ⁽ⁱ⁾The upper triangular structure of (a) may support a variety of different MIMO detection algorithms, including QR-SIC, QRM-MLD, SD, etc. It is noted that in the MU-MIMO transmission shown in fig. 2, the operation of receive beamforming is optional, and thus may also be applied directly to y_DL ⁽ⁱ⁾ZF/MMSE detection or ML detection is performed.

Step 213: UE uses the first uplink SU-BF matrix U₁ ⁽ⁱ⁾Data is transmitted and the same beamforming is performed on the uplink demodulation pilot (DMRS).

Step 214: and the UE transmits the DMRS and the data subjected to the beam forming processing to the eNB.

Step 215: eNB uses conjugate transpose of MU-BF matrix P⁽ⁱ⁾]^HAnd carrying out multi-user interference (MUI) elimination, thereby separating uplink data streams of different UEs. Note that this step is optional.

Step 216: and the eNB carries out channel estimation according to the DMRS.

Step 217-218: eNB obtains downlink SU-BF matrix V of UE through QRD⁽ⁱ⁾And using its conjugate transpose [ V ]⁽ⁱ⁾]^HPerforming receiving beam forming to obtain the received data after beam formingIt is noted that these two steps are also optional.

${\tilde{d}}_{\mathrm{DL}}^{\left(i\right)}={\left[V^{\left(i\right)}\right]}^H{\left[P^{\left(i\right)}\right]}^H{y}_{\mathrm{UL}}=R_{\mathrm{UL}}^{\left(i\right)}{d}_{\mathrm{UL}}^{\left(i\right)}+{\tilde{n}}_{\mathrm{UL}}^{\left(i\right)}$

Wherein, $R_{\mathrm{UL}}^{\left(i\right)}=\left[\begin{array}{cc}{r}_{\mathrm{UL},11}^{\left(i\right)}& r_{\mathrm{UL},12}^{\left(i\right)}\\ 0& r_{\mathrm{UL},22}^{\left(i\right)}\end{array}\right],$ the R is_UL ⁽ⁱ⁾Is the uplink equivalent channel at this time ${\tilde{H}}_{\mathrm{UL}}^{\left(i\right)}={\left[V^{\left(i\right)}\right]}^H{\left[P^{\left(i\right)}\right]}^H{\left[H^{\left(i\right)}\right]}^H{U}^{\left(i\right)}$ Performing 2 × 2QRD to obtain an upper triangular array; d_UL ⁽ⁱ⁾An uplink data flow vector (2 x 1) for the ith UE; ${\tilde{n}}_{\mathrm{UL}}^{\left(i\right)}={\left[V^{\left(i\right)}\right]}^H{\left[P^{\left(i\right)}\right]}^H{n}_{\mathrm{UL}}.$ considering that the uplink of the LTE-A system is based on Single Carrier frequency division multiple Access (SC-FDMA), R_UL ⁽ⁱ⁾The upper triangular structure of (a) can support a QR-SIC based MIMO detection algorithm.

Step 219: eNB utilizing R_UL ⁽ⁱ⁾And carrying out MIMO detection.

It should be noted that in the flow shown in fig. 2, there are two cases after step 214:

(1) if the eNB performs uplink joint detection, the operation of receiving beam forming is not needed. Then, the eNB carries out channel estimation according to the DMRS to obtain an uplink equivalent channel ${\tilde{H}}_{\mathrm{UL}}^{\left(i\right)}={\left[H^{\left(i\right)}\right]}^H{U}^{\left(i\right)},$ Then directly to y_ULAnd performing ZF/MMSE detection.

(2) If the eNB performs uplink independent detection, the conjugate transpose [ P ] of the MU-BF matrix is used⁽ⁱ⁾]^HSeparating the uplink data streams of different UEs and then using the downlink SU-BF matrix V⁽ⁱ⁾Conjugate transpose of [ V ]⁽ⁱ⁾]^HPerforming receive beamforming, and then performingAnd carrying out MIMO detection.

And finishing the complete transmission process of the downlink MU-MIMO and the uplink MU-MIMO. Wherein the eNB uses the MU-BF matrix P⁽ⁱ⁾And downlink SU-BF matrix V⁽ⁱ⁾Tx-BF, each UE participating in MU-MIMO transmission using a first uplink SU-BF matrix U₁ ⁽ⁱ⁾Tx-BF was performed. Optionally, each UE may also use the conjugate transpose of the first uplink SU-BF matrix for Rx-BF, and the eNB may also use the conjugate transpose of the MU-BF matrix and the downlink SU-BF matrix for Rx-BF.

In the absence of channel conditionsWith the change, uplink and downlink MU-MIMO transmission can be based on the obtained P⁽ⁱ⁾、V⁽ⁱ⁾And U⁽ⁱ⁾And an(see step 209) and(see step 216) continues. When the channel conditions change, a round of the flow shown in fig. 2 needs to be restarted.

In the above process, a specific iteration of step 204 is shown in fig. 3, and includes: matrix H⁽ⁱ⁾P⁽ⁱ⁾One path is processed by a Hermitian transposer 301 to obtain P^(i)HH^(i)HThe other path passes through matrix multiplier 302 and <math><mrow> <msubsup> <mi>V</mi> <mrow> <mi>t</mi> <mo>-</mo> <mn>1</mn> </mrow> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <msubsup> <mi>V</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>I</mi> <mrow> <mn>2</mn> <mo>&times;</mo> <mn>2</mn> </mrow> </msub> <mo>)</mo> </mrow> </mrow></math> multiplication to obtain H⁽ⁱ⁾P⁽ⁱ⁾V_t-1 ⁽ⁱ⁾。H⁽ⁱ⁾P⁽ⁱ⁾V_t-1 ⁽ⁱ⁾Obtaining U after passing through a QR decomposer 303_t-1 ⁽ⁱ⁾，U_t-1 ⁽ⁱ⁾Through matrix multiplier 304 and P^(i)HH^(i)HMultiplication to obtain P^(i)HH^(i)HU_t-1 ⁽ⁱ⁾。P^(i)HH^(i)HU_t-1 ⁽ⁱ⁾V is obtained by QR decomposer 305_t ⁽ⁱ⁾And R_t ⁽ⁱ⁾. According to a preset number of iterations, V_t ⁽ⁱ⁾Can also be used as <math><mrow> <msubsup> <mi>V</mi> <mrow> <mi>t</mi> <mo>-</mo> <mn>1</mn> </mrow> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <msubsup> <mi>V</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>I</mi> <mrow> <mn>2</mn> <mo>&times;</mo> <mn>2</mn> </mrow> </msub> <mo>)</mo> </mrow> </mrow></math> Fed back to the matrix multiplier 302.

The uplink and downlink MU-MIMO transmission process shown in fig. 2 requires the same allocation of radio resources for uplink and downlink. When the uplink and downlink radio resource allocations are different, the transmission process of the downlink MU-MIMO and the uplink MU-MIMO should be performed independently as shown in fig. 4 and fig. 5, respectively, but still can utilize the reciprocity of the uplink and downlink radio channels.

As can be seen from fig. 4, the difference in resource allocation does not affect the downlink MU-MIMO transmission process, which is similar to step 201 and step 212 in fig. 2 and will not be described herein again. Wherein optional steps (such as steps 407, 410, 411) are shown with dashed lines.

Fig. 5 is a transmission process of uplink MU-MIMO in an embodiment of the present invention when uplink and downlink resource allocation is different, which is different from fig. 2, and specifically includes:

step 501-504 is referred to as the corresponding step in fig. 2. Specifically, step 501 is similar to step 201, step 502 is similar to step 202, step 503 is similar to step 207, and step 504 is similar to step 208, except that the eNB in fig. 5 sends a Cell-specific pilot (Cell-specific RS).

Step 505: UE carries out channel estimation according to the special pilot frequency of the cell sent by eNB, and acquires 2 x 4 downlink physical channelH⁽ⁱ⁾Then, the 4 x 2 uplink physical channel H is deduced according to the channel reciprocity_UL ⁽ⁱ⁾Is [ H ]⁽ⁱ⁾]^T。

Step 506: according to the uplink physical channel matrix H_UL ⁽ⁱ⁾The UE executes 2X 2QRD iteration to obtain a second uplink SU-BF matrix U₂ ⁽ⁱ⁾(also can be represented as U)_phy ⁽ⁱ⁾) The iteration can be controlled by setting different iteration times. It should be noted that the second upstream SU-BF matrix U is now used₂ ⁽ⁱ⁾Is calculated according to the uplink physical channel, which is different from the calculation of the downlink equivalent channel to obtain the first uplink SU-BF matrix U in FIG. 2₁ ⁽ⁱ⁾。

Step 507: UE uses the second uplink SU-BF matrix U₂ ⁽ⁱ⁾Data transmission is performed, and DMRS also needs to be similarly transmit beamformed.

Step 508: and the UE sends the DMRS and the data after the beam forming to the eNB.

Step 509-510: and the eNB carries out channel estimation according to the DMRS to obtain an equivalent channel and carries out combined ZF/MMSE detection.

In addition, the specific iteration of step 506 is shown in fig. 6, and includes: will go up the physical channel matrix H_UL ⁽ⁱ⁾One path is sent to a Hermitian transposer 601 to obtain H_UL ^(i)HAnd the other is sent to matrix multiplier 602 and H_UL ^(i)HMultiplication to obtain H_UL ^(i)HH_UL ⁽ⁱ⁾(ii) a H is to be_UL ^(i)HH_UL ⁽ⁱ⁾To matrix multiplier 603 and U_t-1(U₀I) are multiplied and passed through QR decomposer 604 to obtain U_t(ii) a Will U_tAs U_t-1(U₀I) is fed back to the matrix multiplier 602.

Of course, the method described in the embodiment of the present invention can be directly generalized to the case of any number of users and any number of antennas, as long as the constraint relationship (3) is satisfied.

<math><mrow> <msub> <mi>n</mi> <mi>eNB</mi> </msub> <mo>&GreaterEqual;</mo> <munder> <mi>&Sigma;</mi> <mi>i</mi> </munder> <msub> <mi>n</mi> <mi>UEi</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow></math>

Wherein n is_eNBNumber of antennas of eNB, n_UEiThe number of antennas of the ith UE is, i is more than or equal to 1.

It can be seen that, the uplink and downlink MU-MIMO transmission method based on QRD provided by the present invention utilizes reciprocity between uplink and downlink channels in a system (such as TDD or FDD system), thereby effectively supporting orthogonal or quasi-orthogonal transmission of multiple data streams of multiple users on uplink and downlink of LTE-a system.

Further, an embodiment of the present invention provides a base station for MU-MIMO transmission, including: a plurality of antennas, a switch unit 701, a channel estimation unit 702, a QR decomposition unit 703, a transmission beam forming unit 704, a MIMO detection unit provided for each UE, a reception beam forming unit 706, and an MUI removal processing unit 707. In this embodiment, it is assumed that the eNB has 4 antennas, the number N of users participating in MU-MIMO transmission is 2, and each user is provided with 2 antennas, and then the MIMO detection unit includes: MIMO detection unit 7051 of UE1 and MIMO detection unit 7052 of UE 2.

In actual operation, the channel estimation unit 702 provides the channel estimation result to the QR decomposition unit 703, and the QR decomposition unit 703 decomposes the channel matrix to obtain the MU-BF matrix and the downlink SU-BF matrix of each user, which is P in this embodiment⁽¹⁾、P⁽²⁾、V⁽¹⁾、V⁽²⁾And provided to a transmit beamforming unit 704. Further, the QR decomposition unit 703 supplies V^(1)HAnd V^(2)HProviding P to the receive beamforming unit 706^(1)HAnd P^(2)HFor MUIA removal processing unit 707. Further, the QR decomposition unit 703 supplies the R matrix generated in the decomposition to the MIMO detection unit for MIMO detection. Further, the QR decomposition unit 703 may also generate AMC control signals (e.g., using the R matrix generated in the decomposition) to control the transmitted data stream to adapt to different channel conditions.

In data transmission, the transmit beamforming unit 704 uses V⁽¹⁾SU-BF matrix processing is performed on transmit data stream 1 and transmit data stream 2 of UE1, and P is used⁽¹⁾And performing MU-BF matrix processing to obtain 4 paths of data streams a1-d 1. Similarly, transmit beamforming unit 704 uses V⁽²⁾SU-BF matrix processing is performed on transmit data stream 1 and transmit data stream 2 of UE2, and P is used⁽²⁾And performing MU-BF matrix processing to obtain 4 paths of data streams a2-d 2. Data streams obtained by performing transmit beamforming on the UE1 and the UE2 are superimposed and output to an antenna, for example, a data stream a1 of the UE1 and a data stream a2 of the UE2 are superimposed and sent to a certain antenna.

In data reception, 4 data streams a3-d3 are received from 4 antennas, and each data stream is sent to MUI removal processing section 707 of a plurality of users and then to reception beam forming section 706. For example, the MUI cancellation processing unit for data stream a3 to UE1 and UE2, respectively, using P^(1)HAnd P^(2)HEliminating MUI, and respectively using conjugate transpose V of SU-BF^(1)HAnd V^(2)HAnd performing receiving beam forming. Note that the MUI removal processing unit 707 and the receive beamforming unit 706 are optional units on the eNB. And then, recovering the transmission data stream of the UE through the processing of the MIMO detection unit.

Further, an embodiment of the present invention provides a user terminal for MU-MIMO transmission, including: multiple antennas, switch section 801, channel estimation section 802, QR decomposition section 803, transmission beam forming section 804, MIMO detection section 805, and reception beam forming section 806. The transmit beamforming unit 804 includes an SU-BF processing unit 8041, and the receive beamforming unit 806 includes an SU receive beamforming unit 8061. Note that the receive beamforming unit 806 is optional at the user terminal.

QR decomposition unit 803 decomposes the channel matrix according to the channel estimation result provided by the channel estimation unit to obtain an uplink SU-BF matrix U⁽ⁱ⁾(may be the first upstream SU-BF matrix U₁ ⁽ⁱ⁾Or may be a second uplink SU-BF matrix U₂ ⁽ⁱ⁾) And further obtaining the conjugate transpose [ U ] of the uplink SU-BF matrix⁽ⁱ⁾]^HAnd are supplied to the SU-BF processing unit 8041 and the SU reception beamforming unit 8061, respectively. Further, QR decomposition unit 803 supplies the decomposed R matrix to MIMO detection unit 805 or for AMC control.

It can be seen that, when performing MU-MIMO transmission, the method, the base station and the user terminal of the present invention do not need to use SVD with high complexity, and even when MMSE detection is not adopted, the method, the base station and the user terminal can realize beam forming by using QRD with lower complexity instead of using matrix inversion with high complexity. On the one hand, QRD generated unitary matrices can be used for MU-BF and SU-BF, and can be used for transmit and receive beamforming simultaneously; on the other hand, the QRD-generated upper triangular matrix can be used for MIMO detection and Adaptive Modulation and Coding (AMC). For example, the channel gain of each (quasi-) orthogonal channel can be obtained according to the diagonal elements of the upper triangular matrix, and the signal-to-noise ratio (SNR) can be calculated by combining the noise power, so as to select a suitable Modulation and Coding Scheme (MCS) for each (quasi-) orthogonal channel, including selecting to turn off the data stream when the channel condition is insufficient to support the MCS of the lowest level, thereby implementing the adaptive change of the transmission order (Rank).

And performing link-level simulation on the method provided by the embodiment of the invention by using the simulation parameters shown in the table I. In this simulation, assuming that multi-user scheduling has been done currently, the radio channels of 2 UEs remain independent all the time, each UE supporting 2 data streams. If SU-BF is considered in MU-BF, then 2 data streams are modulated by 64QAM and 4QAM respectively; if SU-BF is not considered in MU-BF, 2 data streams adopt the same modulation mode, and are all 16 QAM. In addition, the simulation assumes ideal channel estimation, but the beamforming is performed based on an average channel within the resource block (rather than an instantaneous channel per subcarrier), which, although leading to some performance degradation, is more suitable for the requirements of the actual system.

Table-simulation parameters

Fig. 8 is a diagram illustrating a comparison between the prior art and the embodiment of the present invention in terms of downlink throughput. Wherein, MMSE detection algorithm is adopted in downlink unification, 5 performance curves aiming at 3 downlink MU-MIMO methods are obtained through simulation, namely BD, BD + SVD, and QRD-based method (namely curve BD-QRD) of the invention_eq ⁰、BD-QRD_eq ¹、BD-QRD_eq ²) And the iteration times of SU-BF are respectively set to 0, 1 and 2. When the number of iterations is 0, it means that SU-BF is not performed and only MU-BF is performed.

As can be seen from fig. 8: for MU-BF, the QRD-based performance is better than that of the traditional BD, because the QRD-based MU-BF matrix further realizes the triangularization of the block matrix on the basis of block diagonalization, and the interference between data streams can be reduced; and for SU-BF, the QRD-based iteration convergence rate is very high, and the SVD performance can be achieved only by 1-2 iterations.

Fig. 9 is a schematic diagram showing comparison between the prior art and the embodiment of the present invention on uplink throughput, where a joint MMSE detection algorithm is uniformly used in uplink to obtain 7 performance curves in total for 4 uplink MU-MIMO methods through simulation. The 4 uplink MU-MIMO methods are respectively as follows: the QRD (curve QRD) is carried out on the equivalent channel by the invention without carrying out beam forming (NoBF) and SVD at the originating end_eq ⁰、QRD_eq ¹、QRD_eq ²) The invention carries out QRD (curve QRD) aiming at physical channel_phy ¹、QRD_phy ²). Wherein, when QRD is performed for equivalent channel, uplink only proceedsLine 1 QRD, and the iteration times of the downward QRD are respectively set to 0, 1 and 2; when QRD is carried out on a physical channel, the uplink iteration times are respectively set to be 1 and 2.

As can be seen from fig. 9: firstly, when the uplink and downlink resource allocation is the same, the QRD based on the equivalent channel can achieve the same performance as the SVD, and the uplink performance has less dependence on the downlink QRD iteration times; and secondly, when uplink and downlink resources are distributed differently, QRD iteration can be carried out based on the physical channel, although the performance is reduced compared with that of QRD or SVD based on an equivalent channel, the QRD or SVD has obvious performance gain compared with that of no beam forming.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (24)

1. A method for multi-user multiple-input multiple-output (MU-MIMO) transmission in a wireless communication system, comprising:

a base station receives sounding pilot frequency SRS sent by N user terminals UE for channel estimation, and generates a downlink channel information matrix according to a channel estimation result and the channel reciprocity of the system, wherein N is more than 1;

the base station carries out QR decomposition on the generated downlink channel information matrix, and obtains a multi-user beam forming MU-BF matrix P of the ith UE from a Q matrix obtained by decomposition⁽ⁱ⁾And further obtaining a downlink single-user beam forming SU-BF matrix V of the ith UE⁽ⁱ⁾Wherein i is 1, …, N;

the base station according to the MU-BF matrix P⁽ⁱ⁾And said downstream SU-BF matrix V⁽ⁱ⁾And performing beam forming processing on the transmission data of the ith UE.

2. The method of claim 1, further comprising:

and the base station performs transmission beam forming processing on the user-specific pilot frequency of the UE according to the MU-BF matrix and the downlink SU-BF matrix of the ith UE and then sends the processed user-specific pilot frequency to the UE.

3. The method of claim 1, further comprising:

the ith UE receives the downlink pilot frequency sent by the base station to carry out channel estimation, and a downlink channel information matrix aiming at the UE is obtained;

the UE carries out QR decomposition on the downlink channel information matrix, and obtains an uplink single-user beam forming SU-BF matrix U of the UE from a Q matrix obtained by decomposition⁽ⁱ⁾；

And performing beam forming processing on the transmitted data according to the uplink SU-BF matrix.

4. The method of claim 3, wherein the UE performing QR decomposition on the downlink channel information matrix to obtain an uplink SU-BF matrix comprises:

the ith UE receives the user special pilot frequency sent by the base station to carry out channel estimation to obtain a downlink equivalent channel matrix;

and the UE carries out QR decomposition on the downlink equivalent channel matrix, and takes a Q matrix obtained by decomposition as a first uplink SU-BF matrix of the UE.

5. The method of claim 3, wherein the UE performing QR decomposition on the downlink channel information matrix to obtain an uplink SU-BF matrix comprises:

the ith UE receives the cell dedicated pilot frequency sent by the base station to carry out channel estimation to obtain a downlink physical channel matrix, and obtains an uplink physical channel matrix according to channel reciprocity;

and the UE carries out QR decomposition on the uplink physical channel matrix, and obtains a second uplink SU-BF matrix of the UE from the Q matrix obtained by decomposition.

6. The method of claim 3, further comprising:

the UE performs conjugate transposition on the uplink SU-BF matrix;

and performing MIMO detection after the beam forming processing is performed on the received data of the UE according to the conjugate transpose of the uplink SU-BF matrix.

7. The method of any of claims 3-6, further comprising: and the UE carries out transmitting beam forming processing on the uplink demodulation pilot frequency DMRS according to the uplink SU-BF matrix and then sends the processed uplink demodulation pilot frequency DMRS to the base station.

8. The method of claim 1, further comprising:

the base station performs conjugate transposition on an MU-BF matrix and a downlink SU-BF matrix of the ith UE;

and performing multi-user interference cancellation (MUI) on the received data of the base station according to the conjugate transpose of the MU-BF matrix of the UE to obtain the received data of the ith UE, and performing MIMO detection after processing the received data of the UE by using the conjugate transpose of the downlink SU-BF matrix.

9. The method of claim 1, wherein the base station obtains a downlink single-user beamforming (SU-BF) matrix V of an ith UE⁽ⁱ⁾The method comprises the following steps:

the base station is according to the downlink physical channel matrix H of the ith UE⁽ⁱ⁾And MU-BF matrix P⁽ⁱ⁾To obtain H⁽ⁱ⁾P⁽ⁱ⁾And to H⁽ⁱ⁾P⁽ⁱ⁾Carrying out QR decomposition to obtain a downlink SU-BF matrix V of the UE⁽ⁱ⁾。

10. The method of claim 3, wherein the UE obtains its own uplink single-user beamforming SU-BF matrix U⁽ⁱ⁾The method comprises the following steps:

UE will uplink physical channel matrixAnd the conjugate transpose of the uplink physical channel matrixMultiplication to obtainThen will beAndobtaining an uplink SU-BF matrix through QR decomposition after multiplication

11. A base station for multi-user multiple-input multiple-output (MU-MIMO) transmission, comprising:

the channel estimation unit is used for carrying out channel estimation to obtain uplink channel information of more than one user terminal UE and obtaining a downlink channel information matrix according to channel reciprocity;

the QR decomposition unit is used for carrying out QR decomposition on the downlink channel information matrix, acquiring a multi-user beam forming MU-BF matrix of each UE from a Q matrix obtained by decomposition, and further acquiring a downlink single-user beam forming SU-BF matrix of each UE;

and the transmitting beam forming unit is used for carrying out beam forming processing on the transmitting data of the corresponding UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE and transmitting the transmitting data to the antenna of the base station for transmission.

12. The base station of claim 11, wherein the QR decomposition unit is further configured to provide the decomposed R matrix to the MIMO detection unit;

and the MIMO detection unit is used for carrying out MIMO detection on the received data of the antennas according to the R matrix and recovering the transmitted data of each UE.

13. The base station of claim 12, wherein the QR decomposition unit is further configured to perform conjugate transpose on an MU-BF matrix and a downlink SU-BF matrix of each UE, and provide the transpose to the receive beamforming unit;

and the receiving beam forming unit is used for executing multi-user interference elimination (MUI) on the received data of the antenna according to the conjugate transpose of the MU-BF matrix of each UE to obtain the received data of each UE, processing the received data of the corresponding UE by using the conjugate transpose of the downlink SU-BF matrix, and then sending the processed received data to the MIMO detection unit.

14. The base station according to any of claims 11-13, wherein the QR decomposition unit is further configured to perform adaptive modulation coding, AMC, control on the transmitted data streams of the one or more UEs according to the decomposed R matrix.

15. The base station according to any of claims 11-13, wherein the QR decomposition unit is configured to decompose the QR according to the downlink physical channel matrix H of each UE⁽ⁱ⁾And MU-BF matrix P⁽ⁱ⁾To obtain H⁽ⁱ⁾P⁽ⁱ⁾And to H⁽ⁱ⁾P⁽ⁱ⁾QR decomposition is carried out to obtain a downlink SU-BF matrix V of each UE⁽ⁱ⁾And i is an arbitrary integer from 1 to the number N of users.

16. The base station according to any of claims 11-13, wherein the channel estimation unit is configured to perform channel estimation according to the sounding pilot SRS transmitted by each UE, or obtain uplink channel information according to the uplink demodulation pilot DMRS transmitted by each UE, and obtain the downlink channel information matrix according to channel reciprocity.

17. The base station of any of claims 11-13, wherein the transmit beamforming unit is further configured to perform beamforming on the user-specific pilot sent to each UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE.

18. A wireless communication system for multi-user multiple-input multiple-output (MU-MIMO) transmission, comprising: a user terminal UE and a base station;

the UE includes: the device comprises a channel estimation unit, a QR decomposition unit and a transmitting beam forming unit;

the channel estimation unit is used for performing channel estimation to obtain a downlink channel information matrix of the UE;

the QR decomposition unit is used for carrying out QR decomposition on the downlink channel information matrix and acquiring an uplink single-user beam forming SU-BF matrix of the UE from a Q matrix obtained by decomposition;

the transmitting beam forming unit is used for carrying out beam forming processing on transmitting data according to the uplink SU-BF matrix of the UE and transmitting the data from the antenna of the UE;

the base station includes: the second channel estimation unit, the second QR decomposition unit and the second transmitting beam forming unit;

the second channel estimation unit is used for performing channel estimation to obtain uplink channel information of more than one UE and obtaining a downlink channel information matrix according to channel reciprocity;

the second QR decomposition unit is configured to perform QR decomposition on the downlink channel information matrix, obtain a multi-user beamforming MU-BF matrix of each UE from the Q matrix obtained by the decomposition, and further obtain a downlink single-user beamforming SU-BF matrix of each UE;

and the second transmitting beam forming unit is used for performing beam forming processing on transmitting data of corresponding UE according to the MU-BF matrix and the downlink SU-BF matrix of each UE, and transmitting the transmitting data to the antenna of the base station for transmission.

19. The system according to claim 18, wherein said channel estimation unit is configured to perform channel estimation according to a user-specific pilot sent by a base station, so as to obtain a downlink equivalent channel matrix;

and the QR decomposition unit is used for carrying out QR decomposition on the downlink equivalent channel matrix and taking a Q matrix obtained by decomposition as a first uplink SU-BF matrix of the UE.

20. The system according to claim 18, wherein said channel estimation unit is configured to perform channel estimation according to a cell-specific pilot sent by a base station to obtain a downlink physical channel matrix, and obtain an uplink physical channel matrix according to channel reciprocity;

and the QR decomposition unit is used for carrying out QR decomposition on the uplink physical channel matrix and obtaining a second uplink SU-BF matrix of the UE from the Q matrix obtained by decomposition.

21. The system according to any of claims 18-20, wherein the QR decomposition unit is further configured to provide the decomposed R matrix to the MIMO detection unit;

and the MIMO detection unit is used for carrying out MIMO detection on the received data of the UE according to the R matrix.

22. The system according to claim 21, wherein the QR decomposition unit is further configured to perform conjugate transpose on an uplink SU-BF matrix of the UE, and provide the conjugate transpose to the receive beamforming unit;

and the receiving beam forming unit is used for processing the receiving data of the UE according to the conjugate transpose of the uplink SU-BF matrix and then sending the processed receiving data to the MIMO detection unit.

23. The system according to any of claims 18-20, wherein said QR decomposition unit is further configured to perform adaptive modulation coding, AMC, control on more than one transmitted data stream of said UE according to the decomposed R matrix.

24. The system according to any of claims 18-20, wherein said transmit beamforming unit is further configured to perform beamforming on the uplink demodulation pilot DMRS according to the uplink SU-BF matrix of the UE.