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

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

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CN102104404B
CN102104404B CN200910261902.XA CN200910261902A CN102104404B CN 102104404 B CN102104404 B CN 102104404B CN 200910261902 A CN200910261902 A CN 200910261902A CN 102104404 B CN102104404 B CN 102104404B
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matrix
channel
descending
base station
obtains
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CN200910261902.XA
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CN102104404A (en
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侯晓林
张战
加山英俊
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株式会社Ntt都科摩
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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

The transmission method of multiuser MIMO, base station and user terminal in wireless communication system

Technical field

The present invention relates to wireless communication field, the base station and the user terminal that relate in particular to the transmission method of multi-user's multiple-input and multiple-output (MU-MIMO) in wireless communication system (such as LTE-A system), transmit for MU-MIMO.

Background technology

Multiple-input and multiple-output (MIMO) technology, because can effectively improve the spectrum efficiency of wireless link, has become one of key technology of the system of broadband wireless communication including 3GPP Long Term Evolution (LTE).Can according to support multiple users on identical running time-frequency resource simultaneously, MIMO technology can be divided into again Single User MIMO (SU-MIMO) and multiuser MIMO (MU-MIMO).Wherein, MU-MIMO has more advantages, as support user antenna configuration more flexibly, stronger to the adaptive capacity of channel condition, there is multi-user diversity gain etc.MU-MIMO is suitable for for the uplink downlink of cellular system, but descending MU-MIMO has higher requirement to the channel condition information (CSIT) of transmitting pusher side, require base station (eNB) must obtain each user's (UE) descending channel information.Point 2 kinds of situations conventionally of obtaining of CSIT:

For time division duplex (TDD) system, because uplink downlink takies identical frequency resource, therefore between up-downgoing wireless channel, there is reciprocity, can know down channel by inference according to up channel easily, vice versa.

For Frequency Division Duplexing (FDD) (FDD) system, because uplink downlink takies different frequency resources, between up-downgoing wireless channel, scarcely there is reciprocity, in other words the more difficult acquisition of reciprocity in FDD system, therefore obtaining mostly by feedback channel of CSIT.Certainly, in order to reduce feedback quantity, can be by code book design or quantification technique.

In the time of specific implementation, SU-MIMO and MU-MIMO need to carry out according to CSIT preliminary treatment conventionally to transmitting, to reach respectively the object of match channels and elimination multi-user interference (MUI, multi-userinterference), aforesaid operations is called precoding or beam forming.Because different technology scene description customs is different, in the application, may be used alternatingly this two kinds of titles, but the implication of the two is identical.

At present, the up design of 3GPP LTE Rel-8 only can be supported virtual MU-MIMO, can support multiple single antenna UE to send data simultaneously; Descending design is to be mainly optimized for SU-MIMO, very limited to the support of MU-MIMO, cannot support the transmission of many UE and every UE multiple data stream.In addition,, in order to simplify system, LTE Rel-8 has adopted almost identical design to FDD and TDD, all adopts the beam forming based on code book, the reciprocity of not utilizing wireless channel to exist.

Along with the standard formulation work of LTE Rel-8 is drawn to a close, 3GPP has started the research work of LTE-A in year in 2008.LTE-A is the follow-up evolution of LTE, systematic function is had higher requirement, such as requiring LTE-A system can support the MU-MIMO transmission of many UE and every UE multiple data stream.So, how in LTE-A system, effectively to support that up-downgoing MU-MIMO becomes a study hotspot.Have, in the technical discussion for LTE-A, the reciprocity that how to make full use of wireless channel supports the beam forming of non-code book just receiving increasing concern, especially for TDD system again.

For the problems referred to above, in prior art, modal way is that the uplink downlink of cellular system is adopted to independently MU-MIMO transmission, wherein the simplest implementation (scheme one) is that descending MU-MIMO sends based on Block Diagonalization (BD), and up MU-MIMO does not process and only adopts Multiuser Detection (MUD) to receive at transmitting terminal.Although it is simple that scheme one realizes, owing to only considering how to eliminate the phase mutual interference between multi-user, further do not utilize the characteristic of wireless channel, thereby sacrificed to a certain extent spectrum efficiency.

On the basis of scheme one, prior art has also proposed a kind of associating MU-MIMO scheme (scheme two) for TDD system uplink downlink.That is:, after descending MU-MIMO eliminates multi-user interference by BD criterion, the equivalent channel of each UE is carried out to SVD decomposition, thereby to each UE realization character transmission respectively; Use same wireless channel to carry out under the prerequisite of transfer of data in up-downgoing, up MU-MIMO also can realize the feature transmission of each UE.Can find out, scheme two realizes the orthogonal transmission of the multiple data flow of the multiple users of up-downgoing simultaneously, and spectrum efficiency is improved.But the complexity that SVD decomposes is very high, and numerical stability is poor, makes the realization of scheme two have certain obstacle.Meanwhile, scheme two requires up-downgoing must use identical wireless channel to carry out transfer of data, and this sometimes can not meet in actual cellular system, has also limited the realizability of up MU-MIMO in scheme two.

Summary of the invention

In view of this, main purpose of the present invention is to provide a kind of MU-MIMO transmission method, base station and user terminal.

For achieving the above object, technical scheme of the present invention is specifically achieved in that

A transmission method of multi-user's multiple-input and multiple-output MU-MIMO in wireless communication system, comprising:

Base station receives the detecting pilot frequency SRS sending from N user terminal UE and carries out channel estimating, and generates descending channel information matrix according to the channel reciprocity of channel estimation results and described system, and wherein said N is greater than 1;

QR decomposition is carried out to the descending channel information matrix of described generation in described base station, obtains the multi-user beam moulding MU-BF matrix P of i UE from decompose the Q matrix obtaining (i), and further obtain the descending alone family beam forming SU-BF matrix V of i UE (i), wherein i=1 ..., N;

Described base station is according to described MU-BF matrix P (i)with described descending SU-BF matrix V (i), the transmitting data of i UE is carried out to beam forming processing.

The method further comprises:

Described base station, according to the MU-BF matrix of i UE and descending SU-BF matrix, carries out, after launching beam forming processes, sending to described UE to the special pilot frequency for user of this UE.

The method further comprises:

I UE receives the descending pilot frequency that described base station sends and carries out channel estimating, obtains the descending channel information matrix for this UE;

This UE carries out QR decomposition to described descending channel information matrix, obtains the uplink single user beam forming SU-BF matrix U of self from decompose the Q matrix obtaining (i);

According to this up SU-BF matrix, transmitting data is carried out to beam forming processing.

Described UE carries out QR to descending channel information matrix and decomposes and obtain up SU-BF matrix and comprise:

The special pilot frequency for user of i UE reception base station transmission carries out channel estimating, obtains descending equivalent channel matrix;

This UE carries out QR decomposition to described descending equivalent channel matrix, and the Q matrix that decomposition is obtained is as the first up SU-BF matrix of described UE.

Described UE carries out QR to descending channel information matrix and decomposes and obtain up SU-BF matrix and comprise:

The cell-specific pilot tone of i UE reception base station transmission is carried out channel estimating, obtains down physical channel matrix, and obtains uplink physical channel matrix according to channel reciprocity;

This UE carries out QR decomposition to described uplink physical channel matrix, obtains the second up SU-BF matrix of described UE from decomposing the Q matrix obtaining.

The method further comprises:

This UE carries out conjugate transpose to up SU-BF matrix;

According to the conjugate transpose of described up SU-BF matrix, the reception data of this UE are carried out after beam forming processing, carry out MIMO and detect.

The method further comprises: this UE, according to described up SU-BF matrix, carries out, after launching beam forming processes, sending to described base station to uplink demodulation pilot tone DMRS.

The method further comprises:

MU-BF matrix and the descending SU-BF matrix of described base station to i UE carries out conjugate transpose;

According to the conjugate transpose of the MU-BF matrix of described UE, the reception data of this base station are carried out to multi-user interference and eliminate MUI, obtain the reception data of i UE, after the conjugate transpose that recycles descending SU-BF matrix is processed the reception data of this UE, carry out MIMO and detect.

Described base station obtains the descending alone family beam forming SU-BF matrix V of i UE (i)comprise:

Described base station is according to the down physical channel matrix H of i UE (i)and MU-BF matrix P (i)obtain H (i)p (i), and to H (i)p (i)carry out QR decomposition, obtain the descending SU-BF matrix V of described UE (i).

Described UE obtains the uplink single user beam forming SU-BF matrix U of self (i)comprise:

UE is by uplink physical channel matrix H uL (i)conjugate transpose H with this uplink physical channel matrix uL (i) Hmultiply each other and obtain H uL (i) Hh uL (i), then by H uL (i) Hh uL (i)and U t-1 (i)after multiplying each other, decompose and obtain up SU-BF matrix U through QR t (i).

For a base station for multi-user's multiple-input and multiple-output MU-MIMO transmission, comprising:

Channel estimating unit, obtains the uplink channel information of more than one user terminal UE, and obtains descending channel information matrix according to channel reciprocity for carrying out channel estimating;

QR resolving cell for described descending channel information matrix is carried out to QR decomposition, obtains the multi-user beam moulding MU-BF matrix of each UE, and further obtains the descending alone family beam forming SU-BF matrix of each UE from decompose the Q matrix obtaining;

Launching beam forming unit, for according to the MU-BF matrix of each UE and descending SU-BF matrix, carries out beam forming processing to the transmitting data of corresponding UE, and the antenna of delivering to this base station transmits.

The R matrix that described QR resolving cell is further used for decomposition to obtain offers MIMO detecting unit;

Described MIMO detecting unit, for the reception data of antenna being carried out to MIMO detection according to described R matrix, recovers the transmission data of each UE.

MU-BF matrix and descending SU-BF matrix that described QR resolving cell is further used for each UE carry out conjugate transpose, offer received beam forming unit;

Described received beam forming unit, eliminate MUI for the reception data of described antenna being carried out to multi-user interference according to the conjugate transpose of the MU-BF matrix of each UE, obtain the reception data of each UE, the conjugate transpose that recycles descending SU-BF matrix sends to described MIMO detecting unit after the reception data of corresponding UE are processed.

The R matrix that described QR resolving cell is further used for obtaining according to decomposition, carries out Adaptive Modulation and Coding AMC control to the data streams of described more than one UE.

Described QR resolving cell is used for according to the down physical channel matrix H of each UE (i)and MU-BF matrix P (i)obtain H (i)p (i), and to H (i)p (i)carry out QR decomposition, obtain the descending SU-BF matrix V of each UE (i), described i is from 1 arbitrary integer to number of users N.

Described channel estimating unit is carried out channel estimating for the detecting pilot frequency SRS sending according to each UE, or obtains uplink channel information according to the uplink demodulation pilot tone DMRS of each UE transmission, and obtains descending channel information matrix according to channel reciprocity.

Described launching beam forming unit is further used for, according to the MU-BF matrix of each UE and descending SU-BF matrix, the special pilot frequency for user of issuing each UE being carried out to beam forming processing.

For a wireless communication system for multi-user's multiple-input and multiple-output MU-MIMO transmission, comprising: user terminal UE and base station;

Described UE comprises: channel estimating unit, QR resolving cell, and launching beam forming unit;

Described channel estimating unit, for carrying out channel estimating, obtains the descending channel information matrix of this UE;

Described QR resolving cell for described descending channel information matrix is carried out to QR decomposition, obtains the uplink single user beam forming SU-BF matrix of this UE from decompose the Q matrix obtaining;

Described launching beam forming unit, carries out beam forming processing for the up SU-BF matrix according to this UE to transmitting data, and sends from the antenna of this UE;

Described base station comprises: second channel estimation unit, the 2nd QR resolving cell, and the second launching beam forming unit;

Described second channel estimation unit, obtains the uplink channel information of more than one UE, and obtains descending channel information matrix according to channel reciprocity for carrying out channel estimating;

Described the 2nd QR resolving cell, for described descending channel information matrix is carried out to QR decomposition, from decompose the Q matrix obtaining, obtain the multi-user beam moulding MU-BF matrix of each UE, and further obtain the descending alone family beam forming SU-BF matrix of each UE;

Described the second launching beam forming unit, for according to the MU-BF matrix of each UE and descending SU-BF matrix, carries out beam forming processing to the transmitting data of corresponding UE, and the antenna of delivering to this base station transmits.

Described channel estimating unit is carried out channel estimating for the special pilot frequency for user sending according to base station, obtains descending equivalent channel matrix;

Described QR resolving cell is for carrying out QR decomposition to described descending equivalent channel matrix, and the Q matrix that decomposition is obtained is as the first up SU-BF matrix of this UE.

Described channel estimating unit is carried out channel estimating for the cell-specific pilot tone sending according to base station, obtains down physical channel matrix, and obtains uplink physical channel matrix according to channel reciprocity;

Described QR resolving cell, for described uplink physical channel matrix is carried out to QR decomposition, obtains the second up SU-BF matrix of this UE from decomposing the Q matrix obtaining.

The R matrix that described QR resolving cell is further used for decomposition to obtain offers MIMO detecting unit;

Described MIMO detecting unit, for carrying out MIMO detection according to described R matrix to the reception data of this UE.

brief description of the drawings

Described QR resolving cell is further used for the up SU-BF matrix of this UE to carry out conjugate transpose, offers received beam forming unit;

Described received beam forming unit, after the reception data of this UE being processed according to the conjugate transpose of described up SU-BF matrix, sends to described MIMO detecting unit.

The R matrix that described QR resolving cell is further used for obtaining according to decomposition, carries out Adaptive Modulation and Coding AMC control to more than one of described UE data streams.

Described launching beam forming unit is further used for the up SU-BF matrix according to this UE, and to uplink demodulation pilot tone, DMRS carries out beam forming processing.

As seen from the above technical solution, this MU-MIMO transmission method of the present invention is lower by complexity, the good QRD of numerical stability calculates the beam forming matrix (comprising MU-BF matrix and SU-BF matrix) for up-downgoing MU-MIMO transmission, and on this basis transceiver architecture (base station and user terminal) is simplified and optimized, be beneficial to Project Realization.Can find out, the present invention makes full use of the reciprocity of wireless channel in communication system, for the uplink downlink of LTE-A system designs the MU-MIMO transmission plan of non-code book, be used for supporting the transmission of multi-user's multiple data stream, the beam forming of this non-code book can be realized wireless channel is mated to promote transmission performance more accurately, simultaneously without feeding back precoding matrix index value (PMI), thereby can reduce feedback overhead to improve spectrum efficiency.

Fig. 1 is the system model of MU-MIMO in one embodiment of the invention;

Fig. 2 is the flow chart that in one embodiment of the invention, up-downgoing resource is distributed MU-MIMO up-downgoing transmission when identical;

Fig. 3 is the schematic diagram of eNB side QRD iteration;

Fig. 4 is the flow chart of MU-MIMO downlink transfer when up-downgoing resource is distributed difference in one embodiment of the invention;

Fig. 5 is the flow chart of MU-MIMO uplink when up-downgoing resource is distributed difference in one embodiment of the invention;

Fig. 6 is the schematic diagram of UE side QRD iteration;

Fig. 7 is the structural representation for the base station of MU-MIMO transmission in one embodiment of the invention;

Fig. 8 is the structural representation for the user terminal of MU-MIMO transmission in one embodiment of the invention;

Fig. 9 is prior art and the comparison schematic diagram of the embodiment of the present invention on descending throughput performance;

Figure 10 is prior art and the comparison schematic diagram of the embodiment of the present invention on up throughput performance.

Embodiment

For making object of the present invention, technical scheme and advantage clearer, referring to the accompanying drawing embodiment that develops simultaneously, the present invention is described in more detail.

In one embodiment of the invention, as shown in Figure 1, this model is considered 1 base station (eNB) 2 users' (UE) situation to the system model of MU-MIMO transmission, and these 2 UE are isolated users of selecting by multi-subscriber dispatching.This eNB has 4 antennas, and each UE has 2 antennas.It should be noted that, owing to may having a lot of users in cellular system, before carrying out MU-MIMO transmission, should pick out the separate user of several space channels by multi-subscriber dispatching algorithm, participate in MU-MIMO transmission.In the following description, after only considering that multi-subscriber dispatching completes, between isolated user, how to carry out MU-MIMO transmission.

For the system model shown in Fig. 1, the signal model of descending MU-MIMO transmission is expressed as:

y DL ( i ) = H ( i ) Σ k = 1 2 P ( k ) V ( k ) d DL ( k ) + n DL ( i ) , i = 1,2 - - - ( 1 )

Wherein:

Y dL (i)it is the reception signal phasor (2*1) of i UE;

H (i)for the down channel matrix (2*4) from eNB to i UE;

P (k)it is multi-user beam moulding (MU-BF) matrix (4*2) of k UE;

V (k)it is descending alone family beam forming (SU-BF) matrix (2*2) of k UE;

D dL (k)it is the downlink data flow vector (2*1) of i UE;

N dL (i)it is additive white Gaussian noise (AWGN, the Additive White GaussianNoise) noise vector (2*1) of i UE.

The allocation of radio resources of supposing uplink downlink is identical, and the signal model of up MU-MIMO transmission can be expressed as:

y UL = Σ i = 1 2 [ H ( i ) ] H U ( i ) d UL ( i ) + n UL - - - ( 2 )

Wherein:

Y uLfor the reception signal phasor (4*1) of eNB;

[H (i)] hfor the up channel matrix (4*2) from i UE to eNB;

U (i)it is uplink single user beam forming (SU-BF) matrix (2*2) of i UE;

D uL (i)it is the upstream data flow vector (2*1) of i UE;

N uLfor the AWGN noise vector (4*1) of eNB.

It is pointed out that in TDD system, in the time that uplink downlink takies identical wireless channel, between the wireless channel of up-downgoing, have reciprocity, if the down channel matrix notation from eNB to i UE is H (i), the up channel matrix from i UE to eNB just can be expressed as [H so (i)] t, that is up-downgoing channel matrix meets transposition relation.In an embodiment of the present invention, in order to simplify the calculating of up-downgoing SU-BF matrix, need to make to meet conjugate transpose relation between up-downgoing channel matrix, if the down channel matrix notation from eNB to i UE is H (i), the up channel matrix from i UE to eNB is expressed as [H so (i)] t.In order to meet this conjugate transpose relation, only need before upward signal transmitting and before the processing of uplink receiving signal, respectively carry out conjugate operation one time.

Based on the model of Fig. 1, under the identical prerequisite of uplink downlink allocation of radio resources, the flow process of up-downgoing associating MU-MIMO transmission as shown in Figure 2, comprises the following steps:

Step 201: multiple UE (suppose that number of users is N, N is greater than 1) send detecting pilot frequency (SRS) to eNB, and wherein i UE is UE i, i=1 ..., N.In the present embodiment, N=2.

Step 202:eNB carries out channel estimating according to SRS, knows the uplink physical channel of multiple UE, then knows down physical channel by inference according to channel reciprocity H DL = Δ H ( 1 ) H ( 2 ) .

Step 203:eNB carries out 4*4QR and decomposes (QRD, QR decomposition), for each UE calculates MU-BF matrix P separately (i), i=1,2.Wherein, QR decomposes also referred to as orthogonal matrix trigonometric ratio, is decomposed into an orthogonal matrix Q and a upper triangular matrix R by certain matrix A.

With P (2)for example, to H dLconjugate transpose H hcarry out QRD, obtain H h=QR.Wherein, Q is the unitary matrix of 4*4, and R is the upper triangular matrix of 4*4, and front 2 row of Q and rear 2 row are written as to 2 submatrixs, i.e. Q=[Q (1)q (2)].So, P (2)=Q (2)the MU-BF matrix that is UE2, meets H (1)p (2)=0 2 × 2

Step 204:eNB is according to UE idown physical channel H (i)with MU-BF matrix P (i)calculate H (i)p (i), i=1,2, for H (i)p (i), i=1,2 carry out the QRD iteration of 2*2, obtain UE idescending SU-BF matrix V (i).

Concrete iterative process is shown in Fig. 3.Along with the increase of iterations, UE imultiple data flow between interference reduction, but calculation delay also can correspondingly increase, common 1 iteration can reach better performance.

Step 205:eNB uses the BF matrix P of cascade (i)v (i)transmitting data is carried out to beam forming (Tx-BF).

Step 206:eNB also carries out same beam forming to special pilot frequency for user (UE-specific RS).

Step 207:eNB sends the Downlink Control Information (DCI, Downlink Control Information) for transfer of data to each UE.It may be noted that this step is optional.

Step 208:eNB sends special pilot frequency for user and the data through beam forming to each UE.

Step 209:UE carries out channel estimating according to the special pilot frequency for user receiving, and obtains descending equivalent channel H ~ DL ( i ) = H ( i ) P ( i ) V ( i ) .

Step 210:UE carries out 2*2QRD to descending equivalent channel, and the Q battle array obtaining is the first up SU-BF matrix U of this UE 1 (i).That is to say the first up SU-BF matrix U 1 (i)according to descending equivalent channel obtain.

Step 211: by the first up SU-BF matrix U of UE 1 (i)conjugate transpose [U 1 (i)] has the received beam moulding (Rx-BF) of this UE, obtain the reception data after beam forming it may be noted that this step is optional.

d ~ DL ( i ) = [ U ( i ) ] H y DL ( i ) = R DL ( i ) d DL ( i ) + n ~ DL ( i )

Wherein, R DL ( i ) = r DL , 11 ( i ) r DL , 12 ( i ) 0 r DL , 22 ( i ) , This R dL (i)it is descending equivalent channel carry out the upper triangular matrix obtaining after 2*2QRD; d dL (i)it is the downlink data flow vector (2*1) of i UE; n ~ DL ( i ) = [ U ( i ) ] H n DL ( i ) .

Step 212:UE carries out MIMO detection to receiving data.

If execution step 211, after passing through received beam moulding, UE couple carry out MIMO detection.Consider that the down link of LTE-A system is based on OFDM (OFDMA), R dL (i)this upper three-legged structure can support multiple different MIMO detection algorithm, comprise QR-SIC, QRM-MLD, SD etc.It is pointed out that the operation of received beam moulding is optional, therefore also can be directly to y in the MU-MIMO transmission shown in Fig. 2 dL (i)carrying out ZF/MMSE detection or ML detects.

Step 213:UE uses the first up SU-BF matrix U 1 (i)send data, and uplink demodulation pilot tone (DMRS) is carried out to same beam forming.

Step 214:UE will send to eNB through DMRS and the data of beam forming processing.

Step 215:eNB uses the conjugate transpose [P of MU-BF matrix (i)] hcarry out multi-user interference (MUI) elimination, thereby isolate the upstream of different UEs.It may be noted that this step is optional.

Step 216:eNB carries out channel estimating according to DMRS.

Step 217-218:eNB obtains the descending SU-BF matrix V of UE by QRD (i), and use its conjugate transpose [V (i)] hcarry out received beam moulding, obtain the reception data after beam forming it may be noted that these two steps are also optional.

d ~ DL ( i ) = [ V ( i ) ] H [ P ( i ) ] H y UL = R UL ( i ) d UL ( i ) + n ~ UL ( i )

Wherein, R UL ( i ) = r UL , 11 ( i ) r UL , 12 ( i ) 0 r UL , 22 ( i ) , This R uL (i)it is up equivalent channel now H ~ UL ( i ) = [ V ( i ) ] H [ P ( i ) ] H [ H ( i ) ] H U ( i ) Carry out the upper triangular matrix obtaining after 2*2QRD; d uL (i)it is the upstream data flow vector (2*1) of i UE; n ~ UL ( i ) = [ V ( i ) ] H [ P ( i ) ] H n UL . Consider that the up link of LTE-A system is based on single-carrier frequency division multiple access (SC-FDMA), R uL (i)this upper three-legged structure can support the MIMO detection algorithm based on QR-SIC.

Step 219:eNB utilizes R uL (i)carry out MIMO detection.

It should be noted that, in the flow process shown in Fig. 2, after step 214, have two kinds of situations:

(1) if eNB carries out up joint-detection, just without the operation of carrying out received beam moulding.So, eNB carries out channel estimating according to DMRS and obtains up equivalent channel H ~ UL ( i ) = [ H ( i ) ] H U ( i ) , Then directly to y uLcarrying out ZF/MMSE detects.

(2), if eNB carries out up independent detection, use the conjugate transpose [P of MU-BF matrix (i)] hisolate the upstream of different UEs, re-use descending SU-BF matrix V (i)conjugate transpose [V (i)] hcarry out received beam moulding, then right carry out MIMO detection.

So far, once the transmitting procedure of the complete up MU-MIMO of descending MU-MIMO+ completes.Wherein, eNB uses MU-BF matrix P (i)with descending SU-BF matrix V (i)carry out Tx-BF, the each UE that participates in MU-MIMO transmission uses the first up SU-BF matrix U 1 (i)carry out Tx-BF.Alternatively, each UE can also use the conjugate transpose of the first up SU-BF matrix to carry out Rx-BF, and eNB also can use the conjugate transpose of MU-BF matrix and descending SU-BF matrix to carry out Rx-BF.

Under the prerequisite not changing at channel condition, the P that the MU-MIMO of up-downgoing transmission can be based on having obtained (i), V (i)and U (i), and (seeing step 209) and (seeing step 216) proceeded down.In the time that channel condition changes, need to restart to take turns the flow process shown in Fig. 2.

In said process, the concrete iteration of step 204 as shown in Figure 3, comprising: matrix H (i)p (i)one tunnel obtains P through Hermitian deferring device 301 (i) Hh (i) H, another road is through matrix multiplier 302 Hes V t - 1 ( i ) ( V 0 ( i ) = I 2 × 2 ) Multiply each other and obtain H (i)p (i)v t-1 (i).H (i)p (i)v t-1 (i)after QR decomposer 303, obtain U t-1 (i), U t-1 (i)through matrix multiplier 304 and P (i) Hh (i) Hmultiply each other and obtain P (i) Hh (i) Hu t-1 (i).P (i) Hh (i) Hu t-1 (i)obtain respectively V through QR decomposer 305 t (i)and R t (i).According to the iterations setting in advance, V t (i)can also conduct V t - 1 ( i ) ( V 0 ( i ) = I 2 × 2 ) Feed back to matrix multiplier 302.

Up-downgoing MU-MIMO transmitting procedure shown in Fig. 2 requires the allocation of radio resources of uplink downlink identical.In the time that the allocation of radio resources of uplink downlink is different, the transmitting procedure of descending MU-MIMO and up MU-MIMO should independently be carried out, and respectively as shown in Figure 4 and Figure 5, but still can utilize the reciprocity of up-downgoing wireless channel.

As seen from Figure 4, resource distributes difference not bring impact to descending MU-MIMO transmitting procedure, and the step 201-212 in this process and Fig. 2 is similar, repeats no more herein.Wherein, optional step (such as step 407,410,411) is shown in broken lines.

Fig. 5 is the transmitting procedure of up MU-MIMO when up-downgoing resource is distributed difference in one embodiment of the invention, and this process and Fig. 2 are different, specifically comprise:

Step 501-504 is referring to the corresponding step in Fig. 2.Particularly, step 501 and step 201 are similar, and step 502 and step 202 are similar, and step 503 and step 207 are similar, and step 504 and step 208 are similar, difference be in Fig. 5 eNB send be cell-specific pilot tone (Cell-specific RS).

The cell-specific pilot tone that step 505:UE sends according to eNB is carried out channel estimating, knows the down physical channel H of 2*4 (i), then know the uplink physical channel H of 4*2 by inference according to channel reciprocity uL (i)for [H (i)] t.

Step 506: according to this uplink physical channel matrix H uL (i), UE carries out 2*2QRD iteration and obtains the second up SU-BF matrix U 2 (i)(can be expressed as again U phy (i)), this iteration can be controlled by different iterationses is set.It should be noted that the second up SU-BF matrix U now 2 (i)calculate according to uplink physical channel, be different from Fig. 2 and calculate the first up SU-BF matrix U according to descending equivalent channel 1 (i).

Step 507:UE uses the second up SU-BF matrix U 2 (i)carry out data transmission, and DMRS also needs to carry out same launching beam moulding.

DMRS after step 508:UE transmission beam forming and data are to eNB.

Step 509-510:eNB carries out channel estimating according to DMRS and obtains equivalent channel, and combines ZF/MMSE and detect.

In addition, the concrete iteration of step 506 as shown in Figure 6, comprising: by uplink physical channel matrix H uL (i)one road is delivered to Hermitian deferring device 601 and is obtained H uL (i) H, matrix multiplier 602 and H are delivered in another road uL (i) Hmultiply each other and obtain H uL (i) Hh uL (i); By H uL (i) Hh uL (i)deliver to matrix multiplier 603 and U t-1(U 0=I) multiply each other after, obtain U through QR decomposer 604 t; By U tas U t-1(U 0=I) feed back to matrix multiplier 602.

Certainly, the described method of the embodiment of the present invention can directly be generalized to the situation of any number of users and antenna number, as long as meet restriction relation (3).

n eNB ≥ Σ i n UEi - - - ( 3 )

Wherein, n eNBfor the antenna number of eNB, n uEibe the antenna number of i UE, i>=1.

Can find out, up-downgoing MU-MIMO transmission method based on QRD provided by the invention, use the reciprocity of (such as TDD or FDD system) up-downgoing interchannel in system, thereby on the uplink downlink of LTE-A system, can effectively support the orthogonal or accurate orthogonal transmission of multi-user's multiple data stream.

Further, embodiments of the invention provide a kind of base station for MU-MIMO transmission, comprising: many antennas, switch element 701, channel estimating unit 702, QR resolving cell 703, launching beam forming unit 704, the MIMO detecting unit, received beam forming unit 706, the MUI Processing for removing unit 707 that arrange for each UE.In the present embodiment, setting eNB has 4 antennas, and the number of users N that participates in MU-MIMO transmission is 2, and each user is provided with 2 antennas, and MIMO detecting unit comprises: the MIMO detecting unit 7051 of UE1 and the MIMO detecting unit 7052 of UE2.

When real work, channel estimation results is offered QR resolving cell 703 by channel estimating unit 702, by QR resolving cell 703, channel matrix decomposed, and obtains each user's MU-BF matrix and descending SU-BF matrix, is P in the present embodiment (1), P (2), V (1), V (2), offer launching beam forming unit 704.Further, QR resolving cell 703 provides V (1) Hand V (2) Hgive received beam forming unit 706, P is provided (1) Hand P (2) Hgive MUI Processing for removing unit 707.Further, the R matrix generating in decomposing is offered MIMO detecting unit by QR resolving cell 703, to carry out MIMO detection.Further, QR resolving cell 703 also will generate AMC control signal (such as utilizing the R matrix generating in decomposition), data streams be controlled, to adapt to different channel conditions.

When data transmission, launching beam forming unit 704 uses V (1)data streams 1 to UE1 and data streams 2 are carried out SU-BF matrix disposal, then use P (1)carry out MU-BF matrix disposal, obtain 4 circuit-switched data stream a1-d1.Similarly, launching beam forming unit 704 uses V (2)data streams 1 to UE2 and data streams 2 are carried out SU-BF matrix disposal, then use P (2)carry out MU-BF matrix disposal, also obtain 4 circuit-switched data stream a2-d2.After the data flow superposition that UE1 and UE2 are obtained after launching beam moulding, output to antenna, send such as delivering to certain root antenna after the data flow a2 superposition of the data flow a1 of UE1 and UE2.

When data receiver, receive 4 circuit-switched data stream a3-d3 from 4 antennas, every circuit-switched data stream is delivered to respectively to multiple users' MUI Processing for removing unit 707, then deliver to received beam forming unit 706.Such as, the MUI Processing for removing unit that data flow a3 is delivered to UE1 and UE2, uses respectively P (1) Hand P (2) Heliminate MUI, then use respectively the conjugate transpose V of SU-BF (1) Hand V (2) Hcarry out received beam moulding.It may be noted that MUI Processing for removing unit 707 and received beam forming unit 706 are the upper optional unit of eNB.Afterwards, through the processing of MIMO detecting unit, recover the data streams of UE.

Further, embodiments of the invention provide a kind of user terminal for MU-MIMO transmission, comprising: many antennas, switch element 801, channel estimating unit 802, QR resolving cell 803, launching beam forming unit 804, MIMO detecting unit 805, received beam forming unit 806.Wherein, launching beam forming unit 804 comprises SU-BF processing unit 8041, and received beam forming unit 806 comprises SU received beam forming unit 8061.It may be noted that received beam forming unit 806 is optional on user terminal.

The channel estimation results that QR resolving cell 803 provides according to channel estimating unit, decomposes channel matrix, obtains up SU-BF matrix U (i)(can be the first up SU-BF matrix U 1 (i), can be also the second up SU-BF matrix U 2 (i)), and further obtain the conjugate transpose [U of up SU-BF matrix (i)] h, offer respectively SU-BF processing unit 8041 and SU received beam forming unit 8061.Further, the R matrix that QR resolving cell 803 obtains decomposition offers MIMO detecting unit 805, or controls for AMC.

Can find out, method of the present invention, base station and user terminal are in the time carrying out MU-MIMO transmission, without the SVD by high complexity, even in the time not adopting MMSE to detect, also matrix inversion that can high complexity, but realize beam forming by the lower QRD of complexity.On the one hand, the unitary matrix that QRD produces can be used for MU-BF and SU-BF, and can be simultaneously for transmitting and receiving beam forming; On the other hand, the upper triangular matrix that QRD produces can be used for MIMO and detects and Adaptive Modulation and Coding (AMC).For example, can obtain the channel gain of each (standard) orthogonal channel according to the diagonal entry of upper triangular matrix, can calculate signal to noise ratio (SNR) in conjunction with noise power, select suitable modulation coding mode (MCS) for each (standard) orthogonal channel accordingly, when being included in channel condition and being not enough to support other MCS of lowermost level, select to close this data flow, thereby realize the adaptively changing of transmission exponent number (Rank).

Utilize the simulation parameter shown in table one, the method that the embodiment of the present invention is provided is carried out link level simulation.In this emulation, suppose the current multi-subscriber dispatching that completed, it is independent that the wireless channel of 2 UE remains, each UE supports 2 data flow.If considered SU-BF in MU-BF, 2 data streams adopt respectively 64QAM and 4QAM modulation so; If do not consider SU-BF in MU-BF, 2 data flow adopt identical modulation system so, are 16QAM.In addition, in this emulation, suppose ideal communication channel estimation, but beam forming is the average channel (instead of instantaneous channel of each subcarrier) based in Resource Block to carry out, although this can cause hydraulic performance decline to a certain degree, the requirement of more realistic system.

Table one simulation parameter

Fig. 8 is prior art and the comparison schematic diagram of the embodiment of the present invention on downlink throughput capacity.Wherein, the descending unified MMSE detection algorithm that adopts, emulation obtains totally 5 performance curves for 3 kinds of descending MU-MIMO methods, is respectively that BD, BD+SVD and the method that the present invention is based on QRD (are curve B D-QRD eq 0, BD-QRD eq 1, BD-QRD eq 2), wherein the iterations of SU-BF is set to respectively 0,1,2.In the time that iterations is 0, mean and do not carry out SU-BF to only have MU-BF.

As can be seen from Figure 8: 1. for MU-BF, the performance of Performance Ratio traditional B D based on QRD is better, reason is that MU-BF matrix based on QRD, on the basis of Block Diagonalization, further realized the trigonometric ratio of hypermatrix, can reduce the interference between data flow; 2. for SU-BF, the iterative convergence speed based on QRD is very fast, only needs 1-2 iteration can reach the performance of SVD.

Fig. 9 is prior art and the comparison schematic diagram of the embodiment of the present invention in uplink throughput, the up unified associating MMSE detection algorithm that adopts, and emulation obtains totally 7 performance curves for 4 kinds of up MU-MIMO methods.These 4 kinds up MU-MIMO methods are respectively: make a start do not carry out beam forming (NoBF), SVD, the present invention is directed to equivalent channel, to carry out QRD (be curve QRD eq 0, QRD eq 1, QRD eq 2), the present invention is directed to physical channel, to carry out QRD (be curve QRD phy 1, QRD phy 2).Wherein, while carrying out QRD for equivalent channel, uply only carry out QRD 1 time, and the iterations of descending QRD is set to respectively 0,1,2; While carrying out QRD for physical channel, up iterations is set to respectively 1 and 2.

As can be seen from Figure 9: 1. distribute when identical when up-downgoing resource, the QRD based on equivalent channel can reach the performance identical with SVD, and ascending performance is less to the dependence of descending QRD iterations; 2. in the time that up-downgoing resource is distributed difference, can carry out QRD iteration based on physical channel, although performance declines to some extent compared with QRD or SVD based on equivalent channel, still have obvious performance gain compared with not carrying out beam forming.

The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any amendment of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (24)

1. a transmission method of multi-user's multiple-input and multiple-output MU-MIMO in wireless communication system, is characterized in that, comprising:
Base station receives the detecting pilot frequency SRS sending from N user terminal UE and carries out channel estimating, and generates descending channel information matrix according to the channel reciprocity of channel estimation results and described system, and wherein said N is greater than 1;
QR decomposition is carried out to the descending channel information matrix of described generation in described base station, obtains the multi-user beam moulding MU-BF matrix P of i UE from decompose the Q matrix obtaining (i), and further obtain the descending alone family beam forming SU-BF matrix V of i UE (i), wherein i=1 ..., N;
Described base station is according to described MU-BF matrix P (i)with described descending SU-BF matrix V (i), the transmitting data of i UE is carried out to beam forming processing.
2. method according to claim 1, is characterized in that, further comprises:
Described base station, according to the MU-BF matrix of i UE and descending SU-BF matrix, carries out, after launching beam forming processes, sending to described UE to the special pilot frequency for user of this UE.
3. method according to claim 1, is characterized in that, further comprises:
I UE receives the descending pilot frequency that described base station sends and carries out channel estimating, obtains the descending channel information matrix for this UE;
This UE carries out QR decomposition to described descending channel information matrix, obtains the uplink single user beam forming SU-BF matrix U of self from decompose the Q matrix obtaining (i);
According to this up SU-BF matrix, transmitting data is carried out to beam forming processing.
4. method according to claim 3, is characterized in that, described UE carries out QR to descending channel information matrix and decomposes and obtain up SU-BF matrix and comprise:
The special pilot frequency for user of i UE reception base station transmission carries out channel estimating, obtains descending equivalent channel matrix;
This UE carries out QR decomposition to described descending equivalent channel matrix, and the Q matrix that decomposition is obtained is as the first up SU-BF matrix of described UE.
5. method according to claim 3, is characterized in that, described UE carries out QR to descending channel information matrix and decomposes and obtain up SU-BF matrix and comprise:
The cell-specific pilot tone of i UE reception base station transmission is carried out channel estimating, obtains down physical channel matrix, and obtains uplink physical channel matrix according to channel reciprocity;
This UE carries out QR decomposition to described uplink physical channel matrix, obtains the second up SU-BF matrix of described UE from decomposing the Q matrix obtaining.
6. method according to claim 3, is characterized in that, further comprises:
This UE carries out conjugate transpose to up SU-BF matrix;
According to the conjugate transpose of described up SU-BF matrix, the reception data of this UE are carried out after beam forming processing, carry out MIMO and detect.
7. according to the method described in claim 3-6 any one, it is characterized in that, further comprise: this UE, according to described up SU-BF matrix, carries out, after launching beam forming processes, sending to described base station to uplink demodulation pilot tone DMRS.
8. method according to claim 1, is characterized in that, further comprises:
MU-BF matrix and the descending SU-BF matrix of described base station to i UE carries out conjugate transpose;
According to the conjugate transpose of the MU-BF matrix of described UE, the reception data of this base station are carried out to multi-user interference and eliminate MUI, obtain the reception data of i UE, after the conjugate transpose that recycles descending SU-BF matrix is processed the reception data of this UE, carry out MIMO and detect.
9. method according to claim 1, is characterized in that, described base station obtains the descending alone family beam forming SU-BF matrix V of i UE (i)comprise:
Described base station is according to the down physical channel matrix H of i UE (i)and MU-BF matrix P (i)obtain H (i)p (i), and to H (i)p (i)carry out QR decomposition, obtain the descending SU-BF matrix V of described UE (i).
10. method according to claim 3, is characterized in that, described UE obtains the uplink single user beam forming SU-BF matrix U of self (i)comprise:
UE is by uplink physical channel matrix conjugate transpose with this uplink physical channel matrix multiply each other and obtain again will with after multiplying each other, decompose and obtain up SU-BF matrix through QR
11. 1 kinds of base stations for multi-user's multiple-input and multiple-output MU-MIMO transmission, is characterized in that, comprising:
Channel estimating unit, obtains the uplink channel information of more than one user terminal UE, and obtains descending channel information matrix according to channel reciprocity for carrying out channel estimating;
QR resolving cell for described descending channel information matrix is carried out to QR decomposition, obtains the multi-user beam moulding MU-BF matrix of each UE, and further obtains the descending alone family beam forming SU-BF matrix of each UE from decompose the Q matrix obtaining;
Launching beam forming unit, for according to the MU-BF matrix of each UE and descending SU-BF matrix, carries out beam forming processing to the transmitting data of corresponding UE, and the antenna of delivering to this base station transmits.
12. base stations according to claim 11, is characterized in that, the R matrix that described QR resolving cell is further used for decomposition to obtain offers MIMO detecting unit;
Described MIMO detecting unit, for the reception data of antenna being carried out to MIMO detection according to described R matrix, recovers the transmission data of each UE.
13. base stations according to claim 12, is characterized in that, MU-BF matrix and descending SU-BF matrix that described QR resolving cell is further used for each UE carry out conjugate transpose, offer received beam forming unit;
Described received beam forming unit, eliminate MUI for the reception data of described antenna being carried out to multi-user interference according to the conjugate transpose of the MU-BF matrix of each UE, obtain the reception data of each UE, the conjugate transpose that recycles descending SU-BF matrix sends to described MIMO detecting unit after the reception data of corresponding UE are processed.
14. according to the base station described in claim 11-13 any one, it is characterized in that the R matrix that described QR resolving cell is further used for obtaining according to decomposition carries out Adaptive Modulation and Coding AMC control to the data streams of described more than one UE.
15. according to the base station described in claim 11-13 any one, it is characterized in that, described QR resolving cell is used for according to the down physical channel matrix H of each UE (i)and MU-BF matrix P (i)obtain H (i)p (i), and to H (i)p (i)carry out QR decomposition, obtain the descending SU-BF matrix V of each UE (i), described i is from 1 arbitrary integer to number of users N.
16. according to the base station described in claim 11-13 any one, it is characterized in that, described channel estimating unit is carried out channel estimating for the detecting pilot frequency SRS sending according to each UE, or the uplink demodulation pilot tone DMRS sending according to each UE obtains uplink channel information, and obtains descending channel information matrix according to channel reciprocity.
17. according to the base station described in claim 11-13 any one, it is characterized in that, described launching beam forming unit is further used for, according to the MU-BF matrix of each UE and descending SU-BF matrix, the special pilot frequency for user of issuing each UE being carried out to beam forming processing.
18. 1 kinds of wireless communication systems for multi-user's multiple-input and multiple-output MU-MIMO transmission, is characterized in that, comprising: user terminal UE and base station;
Described UE comprises: channel estimating unit, QR resolving cell, and launching beam forming unit;
Described channel estimating unit, for carrying out channel estimating, obtains the descending channel information matrix of this UE;
Described QR resolving cell for described descending channel information matrix is carried out to QR decomposition, obtains the uplink single user beam forming SU-BF matrix of this UE from decompose the Q matrix obtaining;
Described launching beam forming unit, carries out beam forming processing for the up SU-BF matrix according to this UE to transmitting data, and sends from the antenna of this UE;
Described base station comprises: second channel estimation unit, the 2nd QR resolving cell, and the second launching beam forming unit;
Described second channel estimation unit, obtains the uplink channel information of more than one UE, and obtains descending channel information matrix according to channel reciprocity for carrying out channel estimating;
Described the 2nd QR resolving cell, for described descending channel information matrix is carried out to QR decomposition, from decompose the Q matrix obtaining, obtain the multi-user beam moulding MU-BF matrix of each UE, and further obtain the descending alone family beam forming SU-BF matrix of each UE;
Described the second launching beam forming unit, for according to the MU-BF matrix of each UE and descending SU-BF matrix, carries out beam forming processing to the transmitting data of corresponding UE, and the antenna of delivering to this base station transmits.
19. systems according to claim 18, is characterized in that, described channel estimating unit is carried out channel estimating for the special pilot frequency for user sending according to base station, obtains descending equivalent channel matrix;
Described QR resolving cell is for carrying out QR decomposition to described descending equivalent channel matrix, and the Q matrix that decomposition is obtained is as the first up SU-BF matrix of this UE.
20. systems according to claim 18, is characterized in that, described channel estimating unit is carried out channel estimating for the cell-specific pilot tone sending according to base station, obtains down physical channel matrix, and obtains uplink physical channel matrix according to channel reciprocity;
Described QR resolving cell, for described uplink physical channel matrix is carried out to QR decomposition, obtains the second up SU-BF matrix of this UE from decomposing the Q matrix obtaining.
21. according to the system described in claim 18-20 any one, it is characterized in that, the R matrix that described QR resolving cell is further used for decomposition to obtain offers MIMO detecting unit;
Described MIMO detecting unit, for carrying out MIMO detection according to described R matrix to the reception data of this UE.
22. systems according to claim 21, is characterized in that, described QR resolving cell is further used for the up SU-BF matrix of this UE to carry out conjugate transpose, offers received beam forming unit;
Described received beam forming unit, after the reception data of this UE being processed according to the conjugate transpose of described up SU-BF matrix, sends to described MIMO detecting unit.
23. according to the system described in claim 18-20 any one, it is characterized in that the R matrix that described QR resolving cell is further used for obtaining according to decomposition carries out Adaptive Modulation and Coding AMC control to more than one of described UE data streams.
24. according to the system described in claim 18-20 any one, it is characterized in that, described launching beam forming unit is further used for the up SU-BF matrix according to this UE, and to uplink demodulation pilot tone, DMRS carries out beam forming processing.
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