CN101944979B - Feedback method and device for multi-user multi-input multi-output - Google Patents

Abstract

The embodiment of the invention provides multi-user multi-input multi-output feedback method and equipment, which relates to the field of communication and can be suitable for a bilayer communication mode and further improve the multi-user multi-input multi-output transmission performance. The method comprises the following steps of: acquiring a precoding matrix index PMI of a maximum rank 1 of channel quality information CQI in a precoding matrix of all ranks 1, wherein the PMI is the precoding matrix index of the first precoding matrix; acquiring a second precoding matrix according to the PMI; acquiring CQI2 transmitted by the second precoding matrix according to the PMI; feeding the PMI and the CQI2 back to network equipment. The embodiment of the invention is used for multi-user multi-input multi-output transmission.

Description

Feedback method and device for multi-user multi-input multi-output

technical field

The invention relates to the communication field, in particular to a feedback method and device for multi-user multi-input multi-output.

Background technique

Multiple Input Multiple Output (MIMO) uses multiple antennas to suppress channel fading. Multi-User MIMO (Multi User MIMO, MU-MIMO) improves system capacity by multiplexing multiple users on the same time-frequency resource. In the prior art, the design of MIMO is mainly to optimize the performance of Single User MIMO (Single User MIMO, SU-MIMO), and no more consideration is given to the optimization of multi-user MIMO. Therefore, in the prior art, only a simple MU-MIMO mechanism is used, and its main characteristics are as follows:

1. Use precoding based on single-user codebook;

2. Each MU-MIMO user only uses rank 1 (rank1) transmission;

3. The calculation of CQI (Channel Quality Information, channel quality information) is based on the assumption of single-user MIMO.

In the existing MU-MIMO, each user feeds back the PMI (Precoding Matrix Index, precoding vector index) and CQI of rank 1 to the base station. The base station performs scheduling according to the PMI and CQI fed back by the users, and selects the paired users. Finally, the base station performs MU-MIMO transmission on the selected paired users.

In the process of realizing the above-mentioned MU-MIMO, the inventors found that at least the following problems exist in the prior art:

Currently, the MU-MIMO feedback mode in the prior art is based on SU-MIMO, and each MU-MIMO user can only support single-layer transmission, and the CQI feedback is also fed back in the SU-MIMO manner. Therefore, the performance of MU-MIMO is very low.

Contents of the invention

Embodiments of the present invention provide a feedback method and device for multi-user MIMO, which can adapt to the two-layer transmission mode, and further improve the transmission performance of multi-user MIMO.

In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

A feedback method in multi-user MIMO, when using a rank 2 precoding matrix for transmission, comprising:

In all the precoding matrices of rank 1, obtain the precoding matrix index PMI of rank 1 with the largest channel quality information CQI, and the PMI is the precoding matrix index of the first precoding matrix;

Obtain a second precoding matrix according to the PMI;

Obtain the CQI2 transmitted by the second precoding matrix according to the PMI;

Feedback the PMI and CQI2 to the network device.

A feedback receiving method comprising:

receiving PMI, CQI1 and CQI2 from the user equipment;

If CQI1>CQI2, determine that the PMI corresponds to a rank-1 precoding matrix of CQI1; if CQI2>CQI1, determine that the PMI corresponds to a rank-1 precoding matrix of CQI2.

A user equipment, when transmitting using a rank 2 precoding matrix, includes:

The PMI acquisition unit is configured to obtain a PMI of rank 1 with the largest CQI among all precoding matrices of rank 1, where the PMI is a precoding matrix index of the first precoding matrix;

a second precoding matrix obtaining unit, configured to obtain a second precoding matrix according to the PMI;

A CQI2 obtaining unit, configured to obtain the CQI2 transmitted by the second precoding matrix according to the PMI;

A feedback unit, configured to feed back the PMI and CQI2 to the network device.

A network device comprising:

a receiving unit, configured to receive PMI, CQI1 and CQI2 from the user equipment;

The judging unit, if CQI1>CQI2, determines that the PMI corresponds to a rank-1 precoding matrix of CQI1; if CQI2>CQI1, determines that the PMI corresponds to a rank-1 precoding matrix of CQI2.

In the multi-user multiple-input multiple-output feedback method and device provided by the embodiments of the present invention, when a rank-2 precoding matrix is used for transmission, among all rank-1 precoding matrices, the channel quality information CQI of the largest rank-1 is obtained. The precoding matrix indexes the PMI, and then obtains the second precoding matrix according to the PMI, and obtains the CQI2 transmitted by the second precoding matrix; then feeds back the PMI and the CQI2 to the network device. Change the existing technology that only supports one-layer transmission mode, and can support two-layer transmission. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides more information for MU-MIMO scheduling. Good flexibility, improves the performance of MU-MIMO.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a flowchart of a feedback method in MU-MIMO provided in Embodiment 1 of the present invention;

FIG. 2 is a flowchart of a feedback method in MU-MIMO provided by Embodiment 2 of the present invention;

FIG. 3 is a schematic diagram of a rank-2 precoding matrix in the feedback method in MU-MIMO provided by Embodiment 2 of the present invention;

FIG. 4 is a schematic diagram of using one codeword to map to two layers in the feedback method in MU-MIMO provided by Embodiment 2 of the present invention;

FIG. 5 is a schematic diagram of mapping two codewords to two layers in the feedback method in MU-MIMO provided by Embodiment 2 of the present invention;

FIG. 6 is a flowchart of a feedback method in MU-MIMO provided by Embodiment 3 of the present invention;

7 is a schematic diagram of a rank 2 precoding matrix in the feedback method in MU-MIMO provided by Embodiment 3 of the present invention;

FIG. 8 is a schematic diagram of using one codeword to map to two layers in the feedback method in MU-MIMO provided by Embodiment 3 of the present invention;

FIG. 9 is a schematic diagram of mapping two codewords to two layers in the feedback method in MU-MIMO provided by Embodiment 3 of the present invention;

FIG. 10 is a structural block diagram of a user equipment provided in Embodiment 4 of the present invention;

FIG. 11 is a flowchart of a feedback receiving method provided in Embodiment 5 of the present invention;

FIG. 12 is a structural block diagram of a network device provided by Embodiment 6 of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1:

The feedback method in the multi-user multi-input multi-out provided by the embodiment of the present invention is illustrated by taking LTE-A (LTE Advanced Evolution) as an example, the base station can have up to 8 transmit antennas, and can be configured in a dual-polarized manner . That is, 4 transmit antennas form a group and are configured in one polarization mode; the other 4 antennas form another group and are configured in another polarization mode. In LTE-A, the dual-polarization configuration mode of 8 transmitting antennas of the base station provides the possibility of supporting two-layer transmission for each user, that is, each polarization mode supports one layer.

When the rank 2 precoding matrix is used for transmission, as shown in Figure 1, the method steps include:

S101. Among all the precoding matrices of rank 1, obtain the precoding matrix index PMI of rank 1 with the largest channel quality information CQI, where the PMI is the precoding matrix index of the first precoding matrix;

S102. Obtain a second precoding matrix according to the PMI;

S103. Obtain the CQI2 transmitted by the second precoding matrix according to the PMI;

S104. Feed back the PMI and CQI2 to the network device.

Specifically, in step S101, the method for obtaining the maximum CQI may be as follows:

Assuming that the base station has M transmitting antennas, the UE has N receiving antennas, and sends K data streams, the receiving model is (flat fading channel):

$\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; HVs</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In (1), y is the receiving vector of N×1, H is the channel matrix of N×M, V is the precoding matrix of the transmitting end, which is a vector of M×1, s is the symbol vector transmitted, and n is N×1 noise vector, when the noise is zero mean, n is a Gaussian white noise vector with variance σ ² . In (1), $\tilde{h}=\mathrm{HV}$ for the equivalent channel.

Assuming that the precoding vector of rank 1 is taken from a codebook {C ₁ , C ₂ , ..., C _B } whose number of sets is B, when the precoding matrix is C _i , the receiving model is:

y=HC _i s+n (2)

Then the UE calculates the weighted matrix G _i (1×N) at the receiving end through H, C _i , and σ ² , and obtains:

z=G _i y=G _i HC _i s+G _i n=T _i s+G _i n (3)

In (3), T _i =G _i HC _i . At the receiving end, when C _i is used for rank-1 precoding, the calculation formula of the signal-to-noise ratio SNR _i is:

${\mathrm{<span\; class="notranslate">\; SNR</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In (4), E(x) represents the mean value of x, and P=E(|s ² |) is the signal power.

Afterwards, according to the SNR _i , the CQI _i is obtained by looking up a table.

Finally, among the B CQIs, the largest CQI is selected, and a corresponding rank-1 precoding matrix C is obtained.

In the multi-user MIMO feedback method provided by the embodiment of the present invention, when a rank 2 precoding matrix is used for transmission, in all rank 1 precoding matrices, the rank 1 precoding with the largest channel quality information CQI is obtained Matrix index PMI, then obtain the second precoding matrix according to the PMI, and obtain the CQI2 transmitted by the second precoding matrix; then feed back the PMI and CQI2 to the network device. It changes the mode that only supports one layer of transmission in the prior art. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides better flexibility for MU-MIMO scheduling. Improved MU-MIMO performance.

Example 2:

The feedback method in the multi-user multiple-input multiple-output provided by the embodiment of the present invention assumes that one user supports the codeword mapping mode of two-layer transmission and the corresponding CQI reporting mode. When one codeword or two codewords are used to map to two layer, and when using a rank 2 precoding matrix for transmission, as shown in Figure 2, the method steps include:

S201. Obtain a rank-1 precoding matrix index PMI with the largest CQI among all rank-1 precoding matrices, where the PMI is a precoding matrix index of a first precoding matrix. Here, for the method of obtaining the maximum CQI, reference may be made to the obtaining method in Embodiment 1.

S202. Obtain the corresponding CQI1 of the first precoding matrix transmission of rank 1 according to the PMI.

S203. Obtain the CQI2 of the second precoding matrix transmission of rank 2 according to the PMI. Wherein, the second precoding matrix of rank 2 nests the first precoding matrix of rank 1 above. That is, the precoding codebook matrix is nested, and a low-rank precoding matrix can be obtained from a high-rank precoding matrix. For example, what is shown in FIG. 3 is a precoding matrix of rank 2, which includes two column vectors. In this embodiment, it is assumed that the first column is the first precoding matrix with rank 1.

S204. Obtain the CQI2 of the second precoding matrix transmission of rank 2 according to the PMI, as shown in FIG. 3 .

S205. Feedback the PMI, CQI1, and CQI2 to the network device.

Specifically, when it is assumed that one codeword is used to map to two layers, as shown in FIG. 4 , CQI1 represents the CQI for data transmission using one layer; CQI2 represents the CQI for data transmission using two layers. At this time, only PMI and CQI2 may be reported.

When it is assumed that two codewords are used to map to two layers, as shown in Figure 5, CQI1 represents the CQI of codeword 1 that uses one layer for data transmission; CQI2 represents the code when two layers are used for data transmission CQI of word 2.

In the multi-user MIMO feedback method provided by the embodiment of the present invention, when a rank 2 precoding matrix is used for transmission, in all rank 1 precoding matrices, the rank 1 precoding with the largest channel quality information CQI is obtained The matrix index PMI, according to which the CQI1 of the first precoding matrix transmission corresponding to rank 1 is obtained, and then the second precoding matrix of rank 2 is obtained according to the PMI, and the CQI2 of the second precoding matrix transmission of rank 2 is obtained; then Feedback the PMI, CQI1, and CQI2 to the network device. It changed the mode of only supporting one-layer transmission in the prior art, and can support two-layer transmission. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides MU-MIMO scheduling Better flexibility, improved MU-MIMO performance.

Example 3:

The feedback method in the multi-user multiple-input multiple-output provided by the embodiment of the present invention assumes that one user supports the codeword mapping mode of two-layer transmission and the corresponding CQI reporting mode. When one codeword or two codewords are used to map to two layer, and when using a rank 2 precoding matrix for transmission, as shown in Figure 6, the method steps include:

S601. Obtain a rank-1 precoding matrix index PMI with the largest CQI among all rank-1 precoding matrices, where the PMI is a precoding matrix index of a first precoding matrix. Specifically, as shown in FIG. 7 , it is a precoding matrix of rank 2, including two column vectors. It is assumed that the number of precoding codewords included in the precoding codebook matrix is K, and the number of transmitting antennas is Nt. That is, for a rank-2 precoding matrix, there are K precoding matrices in total, and each precoding matrix is an Nt×2-dimensional matrix. Each column of each matrix is an Nt by 1 vector. In this way, there are 2K Nt×1 vectors in total. Among the 2K Nt×1 vectors, the PMI of rank 1 is selected according to the criterion of maximizing the CQI of rank 1. In this embodiment, it is assumed that the PMI is the precoding matrix index of the first column of the rank 2 precoding matrix, That is, the first precoding matrix of rank 1 is the first column of the rank 2 precoding matrix. Here, for the method of obtaining the maximum CQI, reference may be made to the obtaining method in Embodiment 1.

S602. Obtain the corresponding CQI1 of the first precoding matrix transmission of rank 1 according to the PMI.

S603. Obtain the second precoding matrix of rank 1 according to the PMI, where the second precoding matrix of rank 1 and the first precoding matrix of rank 1 are two columns of the precoding matrix of rank 2 respectively. As shown in Figure 7, since the first precoding moment of rank 1 is assumed to be the first column of the precoding matrix of rank 2 in step S601, the second precoding matrix of rank 1 in step S603 is the precoding moment of rank 2. Encodes the second column of the matrix. It should be noted that the first precoding matrix of rank 1 referred to here is the first column of the precoding matrix of rank 2 for illustration only, and is not limited thereto in practice.

S604. Obtain the CQI2 transmitted by the second precoding matrix of rank 1 according to the PMI. As shown in FIG. 7 , in this embodiment, it is assumed that the second precoding matrix of rank 1 is the second column of the precoding matrix of rank 2.

S605. Feed back the PMI, CQI1, and CQI2 to the network device.

Further, after the user feeds back the above-mentioned PMI, CQI1, and CQI2 to the network device, if the network device (base station in this implementation) determines that the user is using rank 1 transmission, then the size of the CQI1 and CQI2 can be compared to determine the user Desired rank-1 precoding matrix. That is, if CQI1>CQI2, it is determined that the PMI corresponds to a precoding matrix of rank 1, that is, the first column of the rank 2 matrix; if CQI2>CQI1, then it is determined that the PMI corresponds to another precoding matrix of rank 1, that is, the first column of the rank 2 matrix two columns.

Specifically, assuming that one codeword is used to map to two layers, as shown in Figure 8, CQI1 represents the CQI that only uses layer 1 for data transmission; CQI2 represents the CQI when only layer 2 is used for data transmission .

Assuming that two codewords are used to map to two layers, as shown in Figure 9, CQI1 represents the CQI of codeword 1 that only uses layer 1 for data transmission; CQI2 represents that when only layer 2 is used for data transmission The CQI of codeword 2 of .

In the multi-user MIMO feedback method provided by the embodiment of the present invention, when a rank 2 precoding matrix is used for transmission, in all rank 1 precoding matrices, the rank 1 precoding with the largest channel quality information CQI is obtained The matrix index PMI, according to which the CQI1 of the first precoding matrix transmission corresponding to rank 1 is obtained, and then the second precoding matrix of rank 1 is obtained according to the PMI, and the CQI2 of the second precoding matrix transmission of rank 1 is obtained; then Feedback the PMI, CQI1, and CQI2 to the network device. It changed the mode of only supporting one-layer transmission in the prior art, and can support two-layer transmission. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides MU-MIMO scheduling Better flexibility, improved MU-MIMO performance.

In addition, because this implementation is equivalent to doubling the number of precoding vectors using rank 1, the performance of rank 1 transmission is also improved.

Example 4:

The user equipment provided by the embodiment of the present invention assumes that a user supports the codeword mapping method of two-layer transmission and the corresponding CQI reporting method. When one codeword or two codewords are used to map to two layers, and rank 2 is used The precoding matrix, in this embodiment, the precoding matrix of rank 2 includes two column vectors, when transmitting, as shown in Figure 10, the device includes:

The PMI obtaining unit 1001 is configured to obtain the PMI of rank 1 with the largest CQI among all the precoding matrices of rank 1, where the PMI is the precoding matrix index of the first precoding matrix;

For obtaining the maximum CQI, the PMI obtaining unit 1001 may further include a signal-to-noise ratio calculation module, a CQI _i obtaining module and a selection module.

Specifically, the signal-to-noise ratio calculation module is used to calculate the received signal-to-noise ratio SNR _i , and its specific steps are the same as the method for calculating the signal-to-noise ratio SNR _i in the above-mentioned embodiment 1, which will not be repeated here.

The CQI _i obtaining module is configured to obtain the CQI _i by looking up a table according to the signal-to-noise ratio SNR _i .

The selection module selects the largest CQI from the obtained CQI _i .

A second precoding matrix obtaining unit 1002, configured to obtain a second precoding matrix according to the PMI;

The CQI2 obtaining unit 1003 is configured to obtain the CQI2 transmitted by the second precoding matrix according to the PMI;

The feedback unit 1004 is configured to feed back the PMI and CQI2 to the network device.

Further, the user equipment also includes:

The CQI1 obtaining unit 1005 is configured to obtain the corresponding CQI1 of the first precoding matrix transmission of rank 1 according to the PMI.

Correspondingly, the feedback unit 1004 feeds back the PMI, CQI1, and CQI2 to the network device.

When one codeword or two codewords are used to map to two layers, the second precoding matrix obtaining unit 1002 obtains the second precoding matrix of rank 2 according to the PMI, wherein the second precoding matrix of rank 2 A first precoding matrix of matrix nesting rank 1.

Correspondingly, the CQI2 obtaining unit 1003 obtains the CQI2 transmitted by the second precoding matrix of rank 2 according to the PMI.

In this way, when the rank 2 precoding matrix is used for transmission, among all the precoding matrices of rank 1, the PMI acquisition unit obtains the precoding matrix index PMI of rank 1 with the largest channel quality information CQI, and the CQI1 acquisition unit obtains the corresponding The CQI1 of the first precoding matrix transmission of rank 1, and then the second precoding matrix acquisition unit obtains the second precoding matrix of rank 2 according to the PMI, and the CQI2 acquisition unit obtains the CQI2 of the second precoding matrix transmission of rank 2; then The feedback unit feeds back the PMI, CQI1, and CQI2 to the network device. It changed the mode of only supporting one-layer transmission in the prior art, and can support two-layer transmission. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides MU-MIMO scheduling Better flexibility, improved MU-MIMO performance.

When one codeword or two codewords are used to map to two layers, the second precoding matrix obtaining unit 1002 obtains the second precoding matrix of rank 1 according to the PMI, wherein the second precoding matrix of rank 1 The matrix and the first precoding matrix of rank 1 are two columns of the precoding matrix of rank 2 respectively.

Correspondingly, the CQI2 obtaining unit 1003 obtains the CQI2 transmitted by the second precoding matrix of rank 1 according to the PMI.

In this way, when the rank 2 precoding matrix is used for transmission, among all the precoding matrices of rank 1, the PMI acquisition unit obtains the precoding matrix index PMI of rank 1 with the largest channel quality information CQI, and the CQI1 acquisition unit obtains the corresponding The CQI1 transmitted by the first precoding matrix of rank 1, and then the second precoding matrix acquisition unit obtains the second precoding matrix of rank 1 according to the PMI, and the CQI2 acquisition unit obtains the CQI2 of the second precoding matrix transmission of rank 1; then The feedback unit feeds back the PMI, CQI1, and CQI2 to the network device. It changed the mode of only supporting one-layer transmission in the prior art, and can support two-layer transmission. For MU-MIMO, it provides a flexible rank-adaptive CQI reporting method, and provides MU-MIMO scheduling Better flexibility, improved MU-MIMO performance.

In addition, because this implementation is equivalent to doubling the number of precoding vectors using rank 1, the performance of rank 1 transmission is also improved.

Example 5:

For embodiment 3, the embodiment of the present invention provides a feedback receiving method, as shown in FIG. 11 , the method includes:

S1101. Receive PMI, CQI1 and CQI2 from the user equipment;

S1102. If CQI1>CQI2, determine the precoding matrix of rank 1 corresponding to the PMI of CQI1, that is, the first column of the precoding matrix of rank 2 in embodiment 3;

If CQI2>CQI1, it is determined that the PMI corresponds to the rank 1 precoding matrix of the CQI2, that is, the second column of the rank 2 precoding matrix in Embodiment 3.

In this way, in the rank 2 precoding matrix, the network device can find the rank 1 precoding matrix with the largest CQI, so as to perform rank 1 precoding and improve the quality of single-layer transmission.

Embodiment 6:

For Embodiment 5, the embodiment of the present invention provides a network device, as shown in FIG. 12 , the device includes:

A receiving unit 1201, configured to receive PMI, CQI1 and CQI2 from user equipment;

The judging unit 1202, if CQI1>CQI2, determines that the PMI corresponds to a rank-1 precoding matrix of CQI1; if CQI2>CQI1, determines that the PMI corresponds to a rank-1 precoding matrix of CQI2.

In this way, in the rank 2 precoding matrix, the network device can find the rank 1 precoding matrix with the largest CQI, so as to perform rank 1 precoding and improve the quality of single-layer transmission.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (14)

1. a feedback method in multi-user MIMO, is characterized in that, when using rank 2 precoding matrix to transmit, comprising: In all the precoding matrices of rank 1, obtain the precoding matrix index PMI of rank 1 with the largest channel quality information CQI, and the PMI is the precoding matrix index of the first precoding matrix; Obtain a second precoding matrix according to the PMI; Obtain the CQI2 transmitted by the second precoding matrix according to the PMI; Feedback the PMI and CQI2 to the network device. 2. The method according to claim 1, characterized in that the method further comprises: Obtain the CQI1 of the first precoding matrix transmission of the corresponding rank 1 according to the PMI; The CQI1 is also fed back to the network device. 3. The method according to claim 1, wherein when a codeword or two codewords are used to map to two layers, said obtaining a second precoding matrix according to said PMI comprises: Obtain a second precoding matrix of rank 2 according to the PMI, where the second precoding matrix of rank 2 nests the first precoding matrix of rank 1. 4. The method according to claim 3, wherein said obtaining the CQI 2 of the second precoding matrix transmission according to the PMI includes: Obtain the CQI2 of the second precoding matrix transmission of rank 2 according to the PMI. 5. The method according to claim 1, wherein when a codeword or two codewords are used to map to two layers, said obtaining a second precoding matrix according to said PMI comprises: Obtaining the second precoding matrix of rank 1 according to the PMI, wherein the second precoding matrix of rank 1 and the first precoding matrix of rank 1 are respectively two columns of the precoding matrix of rank 2 . 6. The method according to claim 5, wherein said obtaining the CQI2 of the second precoding matrix transmission according to the PMI comprises: Obtain the CQI2 of the second precoding matrix transmission of rank 1 according to the PMI. 7. A feedback receiving method, characterized in that, comprising: Receive the precoding matrix index PMI, channel quality information CQI1 and channel quality information CQI2 from the user equipment; If CQI1>CQI2, determine the precoding matrix of rank 1 corresponding to the PMI of CQI1; If CQI2>CQI1, determine that the PMI corresponds to a rank-1 precoding matrix of the CQI2; Wherein, the PMI, CQI1, and CQI2 are the rank-1 PMI with the largest CQI obtained among all rank-1 precoding matrices when the user equipment uses a rank-2 precoding matrix for transmission, and the PMI is the first precoding matrix The precoding matrix index of the coding matrix; the second precoding matrix is obtained according to the PMI; the CQI2 of the second precoding matrix transmission is obtained according to the PMI; the corresponding first precoding matrix transmission of rank 1 is obtained according to the PMI CQI1. 8. A user equipment, characterized in that, when using a rank 2 precoding matrix for transmission, comprising: The PMI acquisition unit is configured to obtain a precoding matrix index PMI of rank 1 with the largest channel quality information CQI among all precoding matrices of rank 1, and the PMI is a precoding matrix index of the first precoding matrix; a second precoding matrix obtaining unit, configured to obtain a second precoding matrix according to the PMI; A CQI2 obtaining unit, configured to obtain the CQI2 transmitted by the second precoding matrix according to the PMI; A feedback unit, configured to feed back the PMI and CQI2 to the network device. 9. The user equipment according to claim 8, wherein the user equipment further comprises: A CQI1 obtaining unit, configured to obtain the corresponding CQI1 of the first precoding matrix transmission of rank 1 according to the PMI; The feedback unit is further configured to feed back the CQI1 to the network device. 10. The user equipment according to claim 8, wherein when one codeword or two codewords are used to map to two layers, The second precoding matrix obtaining unit is specifically configured to obtain a second precoding matrix of rank 2 according to the PMI, wherein the second precoding matrix of rank 2 nests the first precoding matrix of rank 1 matrix. 11. The user equipment according to claim 10, characterized in that, The CQI2 obtaining unit is specifically configured to obtain the CQI2 of the rank 2 second precoding matrix transmission according to the PMI. 12. The user equipment according to claim 8, wherein when one codeword or two codewords are used to map to two layers, The second precoding matrix obtaining unit is specifically configured to obtain the second precoding matrix of rank 1 according to the PMI, wherein the second precoding matrix of rank 1 is the same as the first precoding matrix of rank 1 The encoding matrices are two columns of the rank-2 precoding matrix respectively. 13. The user equipment according to claim 12, characterized in that, The CQI2 obtaining unit is specifically configured to obtain the CQI2 of the second precoding matrix transmission of rank 1 according to the PMI. 14. A network device, comprising: A receiving unit, configured to receive the precoding matrix index PMI, channel quality information CQI1 and channel quality information CQI2 from the user equipment; The judging unit, if CQI1>CQI2, determines the precoding matrix of rank 1 corresponding to the PMI of CQI1; if CQI2>CQI1, determines the precoding matrix of rank 1 corresponding to the PMI of CQI2; Wherein, the PMI, CQI1, and CQI2 are the rank-1 PMI with the largest CQI obtained among all rank-1 precoding matrices when the user equipment uses a rank-2 precoding matrix for transmission, and the PMI is the first precoding matrix The precoding matrix index of the coding matrix; the second precoding matrix is obtained according to the PMI; the CQI2 of the second precoding matrix transmission is obtained according to the PMI; the corresponding first precoding matrix transmission of rank 1 is obtained according to the PMI CQI1.

Images