CN102932043A - Transmission method and device for downlink multi-user multiple input multiple output (MIMO) signal - Google Patents

Abstract

The invention discloses a method for transmitting a downlink multi-user multiple input multiple output (MIMO) signal and a base station. The method comprises the following steps of: dividing remote radio frequency unit (RRU) ports into P/M antenna groups, and storing corresponding relationships between the antenna groups and the ports; judging channels with users, and finding antenna groups corresponding to the channels; receiving pre-coding matrixes fed back from the users, selecting users in different antenna groups, and performing downlink multi-user MIMO transmission; informing the users of the antenna groups and the pre-coding matrixes for downlink data transmission, wherein the pre-coding matrixes are selected from a codebook set with a port number M by the users; and weighting data according to the pre-coding matrixes, outputting the weighted data to the users at antenna ports of the users, and not transmitting the data of the users by using the other ports. Useful signal transmission power is improved, interference is reduced, and indoor cell throughput is improved.

Description

Descending multi-user MIMO signal transmitting method and device

Technical field

The invention belongs to the wireless mobile communications field, relate in particular to the descending multi-user MIMO signal transmitting method and the device that are applicable to the FDD-LTE indoor distributed system.

Background technology

MIMO (multiple-input and multiple-output) technology is by disposing many antennas at transmitting terminal and receiving terminal, utilize the parallel transmission of the independence realization multiple signals of multipath fading between the antenna, in the situation that does not increase system bandwidth and transmitting power, can improve channel capacity, also can be used for improving the reliability of channel, reduce the error rate.Thereby LTE with MIMO as one of essential technology.

LTE overwhelming majority high-speed data service all occurs in indoor, therefore, the indoor covering of how to do well, performance MIMO advantage promotes cell throughout, is the key issue that operator need to solve when carrying out the LTE networking.

After the indoor employing distributed system, consider that the penetration loss between the floor and between the body of wall is larger, generally about 20-30dB, indoor user will mainly receive the signal of its place floor passage, and because the indoor user many places are in inactive state, channel variation is little, therefore compares with outdoor, utilizes indoor environment to carry out multiuser MIMO and has inherent advantage.

At present the descending multi-user MIMO code book in the 3GPP standard is identical with the Single User MIMO code book, all is permanent mould, i.e. each antenna port precoding is only carried out the phase place adjustment and do not had the variation of amplitude.The characteristics of the unbalanced power when indoor user receives many antenna ports of base station are not considered in this precoding codebook design, have both wasted power, increase again and disturb.

Summary of the invention

In view of more than, the present invention proposes descending multi-user MIMO signal transmitting method and device.

Descending multi-user MIMO signal transmitting method may further comprise the steps:

The RRU port is divided into P/M antenna grouping, preserves the corresponding relation of antenna grouping and port, wherein, P is the RRU port number, and M is every floor passage number, and P is greater than M;

Judge user place passage, find antenna grouping corresponding to passage;

Receive the pre-coding matrix of user feedback, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission;

Notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, to be the user select from port number is the codebook set of M described pre-coding matrix, and pre-coding matrix is M * v matrix, and v is the subscriber channel rank of matrix;

According to pre-coding matrix data are weighted, data are exported to the user after user place antenna port is with weighting, and all the other ports do not send this user's data.

Descending multi-user MIMO sender unit comprises:

Mapping block is divided into P/M antenna grouping with the RRU port, preserves the corresponding relation of antenna grouping and port, and wherein, P is the RRU port number, and M is every floor passage number, and P is greater than M;

Grouping module is coupled in mapping block, judges user place passage, finds antenna grouping corresponding to passage;

Select module, be coupled in grouping module, receive the pre-coding matrix of user feedback, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission;

Notification module, be coupled in the selection module, notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, to be the user select from port number is the codebook set of M described pre-coding matrix, pre-coding matrix is M * v matrix, and v is the subscriber channel rank of matrix;

Output module is weighted data according to pre-coding matrix, and data are exported to the user after user place antenna port is with weighting, and all the other ports do not send this user's data.

For existing LTE descending multi-user MIMO signal radiation pattern, the present invention is according to the unbalanced characteristics of indoor user link, the user who is in different passages is carried out descending multi-user MIMO pairing, when descending multi-user MIMO signal is launched, user's precoding codebook is selected in the code book of user place floor passage number at port, launch at user place passage to make things convenient for centralized base-station power, to the user not passage do not launch, thereby saving transmitting power, minimizing effectively promotes the indoor cell throughput to pairing user's interference.

Description of drawings

Fig. 1 is mapping relations schematic diagram between FDD-LTE indoor distributed system RRU port of the present invention and the antenna grouping.

Fig. 2 is FDD-LTE indoor distributed system descending multi-user MIMO signal transmitting method flow chart of the present invention.

Fig. 3 is the structural representation of descending multi-user MIMO sender unit of the present invention.

Embodiment

The defective that exists in order to solve prior art, the present invention proposes to be applicable to descending multi-user MIMO signal transmitting method and the device of FDD-LTE indoor distributed system.For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with drawings and Examples the present invention is described in further detail.

Fig. 1 is mapping relations schematic diagram between FDD-LTE indoor distributed system RRU of the present invention (Remote RF Unit, remote radio unit (RRU)) port and the antenna grouping.Consider that RRU port number P counts M greater than every floor passage, P counts N more than or equal to user's reception antenna, in order to take full advantage of the gain of MIMO spatial reuse, the RRU port is divided into P/M antenna grouping.Floor corresponding to each antenna grouping, different floor corresponding to antenna grouping.Antenna between the grouping adopts the identical time frequency unit of multiuser MIMO pattern space division multiplexing at down channel.

Fig. 2 is FDD-LTE indoor distributed system descending multi-user MIMO signal transmitting method flow chart of the present invention.It is as follows that the method comprising the steps of:

In step 201, the RRU port is divided into the grouping of P/M antenna, preserve the corresponding relation of antenna grouping and port.

P/M is resulting to be integer.Consider present network indoor distributed system deployment scenario, most probable two kinds are configured to P=4, M=2; P=2, M=1.

At step 202, judgement user place passage, find antenna grouping corresponding to passage.

The base station can judge that the strongest port of received power is user i place passage according to user i different port up channel received power, finds antenna grouping A corresponding to this passage ⁽ⁱ⁾Grouping for this user i place.

Be the received power of user i at port p, i=0,1 ..., Kp=0,1 ....After determining grouping, the user can also be added the antenna group list ε at place _a=1,2 ... P/M.

Receive the pre-coding matrix of user feedback in step 203, base station, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission.Wherein, the user is selected through the pairing algorithm of prior art in the base station.

In step 204, to notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, described pre-coding matrix be the user selects from port number is the codebook set of M, pre-coding matrix is M * v matrix, v is the subscriber channel rank of matrix.

After receiving user i pre-coding matrix feedback such as, base station, notify the user i will be at the antenna A that divides into groups by downlink signaling ⁽ⁱ⁾Carry out downlink data transmission, pre-coding matrix is

User j will be at the antenna A that divides into groups ^(j)Carry out downlink data transmission, pre-coding matrix is A wherein ⁽ⁱ⁾Be not equal to A ^(j)

In step 205, according to pre-coding matrix data are weighted, base station data after user place antenna port is with weighting are exported to the user, and all the other ports do not send this user's data.Such as, the base station is at the pre-coding matrix of user i place antenna port according to user i feedback

Data are weighted, export to user i, all the other ports do not send the data of user i.User j place port is according to the pre-coding matrix of user j feedback Data are weighted, export to user j, all the other ports do not send the data of user j.

Till this step, finished the base station to the signal emission process of user terminal, when user terminal received signal, user i and user j can also carry out respectively channel estimating, parse the reception signal.

For existing LTE descending multi-user MIMO signal radiation pattern, the present invention is according to the unbalanced characteristics of indoor user link, the user who is in different passages is carried out descending multi-user MIMO pairing, when descending multi-user MIMO signal is launched, user's precoding codebook is selected in the code book of user place floor passage number at the antenna port number, launch at user place passage to make things convenient for centralized base-station power, to the user not passage do not launch, thereby saving transmitting power, minimizing effectively promotes the indoor cell throughput to pairing user's interference.

Below by specific embodiment, the technical solution of the present invention is further elaborated.But principle involved in the present invention and method are not limited to lower port and antenna number configuration.

Consider the actual conditions of base station, user terminal, indoor distributed system, the embodiment of the invention will be received 1 terminal, indoor 2 passages as example take 4 port RRU, 2.Indoor each floor adopts 2 passage compartment systems, and each floor has 2 independent radio-frequency channels, namely on each spaced antenna position 2 transmit antennas is arranged.Floor 1 and floor 2 are the grouping of the first antenna, and corresponding RRU port one and RRU port 2, floor 3 and floor 4 are the grouping of the second antenna, corresponding RRU port 3 and RRU port 4.

RRU port number 4 is greater than every layer of antenna number 2, also greater than user's reception antenna several 2 in the present embodiment.When adopting the Single User MIMO pattern, down channel maximum order in alone family is 2; When adopting the multiuser MIMO pattern, can support two users to carry out simultaneously the maximum order of down channel is 2 transmission, and power system capacity will be multiplied.

User i belongs to the grouping of the first antenna at floor 1, corresponding RRU port one and RRU port 2, and the down channel order is 2.User j belongs to the grouping of the second antenna at floor 3, corresponding RRU port 3 and RRU port 4, and the down channel order is 2.According to the MU-MIMO of 3GPP standard, user i and user j will be to select pre-coding matrixes, the pre-coding matrix of selecting according to channel sequence 2 in 4 the code book at port

With

Be 4 * 2 matrixes.Because the code book of present 3GPP standard has constant modulus property, each antenna port amplitude equates that just phase weighting is different, loads identical to guarantee the power amplifier that is connected to each antenna.Although therefore the main reception of user i comes from the signal of 2 passage antennas of floor 1, receiving the 2 passage antenna powers that come from floor 3 can be very little, and the base station still can send user i data S at port one-port 4 with the power that equates ₁With S ₂In like manner can send user j data S at port one-port 4 with the power that equates for user j base station ₃With S ₄

Suppose the descending RI=2 of user i, PMI=0, wherein, RI (Rank Indicator), channel sequence indication, PMI (Precoding Matrix Indicator), pre-coding matrix indication.The user can pass through different algorithms after carrying out channel estimating, SINR/ minimizes error sign ratio etc. such as maximization, selects pre-coding matrix, and then pre-coding matrix is:

$W_4^{\left(i\right)}=\left(\begin{array}{cc}0.3536& 0.3536\\ 0.3536& -0.3536\\ 0.3536& -0.3536\\ 0.3536& 0.3536\end{array}\right)$

The descending RI=2 of user j, PMI=1, then pre-coding matrix:

$W_4^{\left(j\right)}=\left(\begin{array}{cc}0.3536& -0.3536i\\ 0.3536i& 0.3536\\ -0.3536& -0.3536i\\ -0.3536i& 0.3536\end{array}\right)$

When carrying out MU-MIMO, the signal of base station emission

$S=W_4^{\left(i\right)}\left(\begin{array}{c}{S}_1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\end{array}\right)+W_4^{\left(j\right)}\left(\begin{array}{c}{S}_3\\ {\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\end{array}\right)=\left(\begin{array}{cc}0.3536& 0.3536\\ 0.3536& -0.3536\\ 0.3536& -0.3536\\ 0.3536& 0.3536\end{array}\right)\left(\begin{array}{c}{S}_1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\end{array}\right)+\left(\begin{array}{cc}0.3536& -0.3536i\\ 0.3536i& 0.3536\\ -0.3536& -0.3536i\\ -0.3536i& 0.3536\end{array}\right)\left(\begin{array}{c}{S}_3\\ {\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\end{array}\right)$

$=\left(\begin{array}{c}0.3536{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_1+0.3536{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2+0.3536S_3-0.3536i{\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\\ 0.3536S_1-0.3536{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2+0.3536i{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_3+0.3536{\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\\ 0.3536S_1-0.3536S_2-0.3536S_3-0.3536i{\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\\ 0.3536{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_1+0.3536S_2-0.3536{\mathrm{iS}}_3+0.3536i{\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\end{array}\right)$

Can be found out that by base station transmit signals S expression formula finally each antenna port transmitted signal is user i data S ₁, S ₂With user j data S ₃, S ₄Carry out the constant power stack.For user i, half power dissipation is arranged at port 3 and port 4, and can cause interference to user j like this.In like manner for user j, half power dissipation is arranged at port one and port 2, and can cause interference to user i.

Therefore the present invention proposes, and user i is to carry out descending PMI according to the order v of down channel in the code book of M to select feedback at antenna port.In the concrete present embodiment, user i and user j are according to down channel order 2 feedback precoding codebooks in 2 the code book at the antenna port number

With

The precoding codebook of selecting is 2 * 2 matrixes.

Suppose the descending RI=2 of user i, PMI=1, the then pre-coding matrix of user feedback:

$W_2^{\left(i\right)}=\left(\begin{array}{cc}0.5& 0.5\\ 0.5& -0.5\end{array}\right)$

The descending RI=2 of user j, PMI=2, the then pre-coding matrix of user feedback:

$W_2^{\left(j\right)}=\left(\begin{array}{cc}0.5& 0.5\\ 0.5i& -0.5i\end{array}\right)$

The base station notifies the downlink data of user i to transmit at antenna port 1 and port 2, and the downlink data of user j will be in antenna port 3 and port 4 transmission.

The base station is according to the pre-coding matrix of user i feedback

To downlink data S ₁, S ₂Transmit at antenna port 1 and port 2 after the weighting, according to the pre-coding matrix of user j feedback To downlink data S ₃, S ₄Transmit at antenna port 3 and port 4 after the weighting.

Be user i data S at antenna for base station port one and port 2 transmitted signals finally ₁With S ₂Constant power stack, be user j data S at antenna port 3 and port 4 transmitted signals ₃With S ₄Constant power stack.For user i, do not have power dissipation at port 3 and port 4 like this, and reduce user j is caused interference.In like manner for user j, do not have power dissipation at port one and port 2, and reduce user i is caused interference.

For P=4, M=2, the pre-coding matrix that the base station receives user feedback is 2 * 2, and the emission port of base station is 4, be 4 * 2 to the canonical matrix of downlink data weighting namely, for the pre-coding matrix according to user feedback is weighted, other usefulness 0 of canonical matrix represented, carry out the data transmission thereby only reach at user place passage, other ports do not send the purpose of this user data.

So, finally the pre-coding matrix of base station side is as follows:

P=2, during M=1,

$\left[\begin{array}{c}1\\ 0\end{array}\right]$ $\left[\begin{array}{c}0\\ 1\end{array}\right]$

P=4, during M=2,

$\frac{1}{2}\left[\begin{array}{cc}1& 1\\ 1& -1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}1& 1\\ i& -i\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& 0\\ 0& 1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ 1& -1\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ i& -\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">i</figure-callout>}\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 0\\ 0& 1\end{array}\right]$

Still have constant modulus property because the antenna port number is 2 precoding codebook, therefore when carrying out descending multi-user MIMO, on the whole, each antenna port still has constant modulus property after the transmission end of base station weighting.

$S=W_2^{\left(i\right)}\left(\begin{array}{c}{S}_1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\end{array}\right)+W_2^{\left(j\right)}\left(\begin{array}{c}{S}_3\\ {\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\end{array}\right)=\left(\begin{array}{cc}0.5& 0.5\\ 0.5& -0.5\\ 0& 0\\ 0& 0\end{array}\right)\left(\begin{array}{c}{S}_1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\end{array}\right)+\left(\begin{array}{cc}0& 0\\ 0& 0\\ 0.5& 0.5\\ 0.5i& -0.5i\end{array}\right)\left(\begin{array}{c}{S}_3\\ {\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\end{array}\right)=\left(\begin{array}{c}0.5{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_1+0.5{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\\ 0.5S_1-{0.5\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\\ 0.5{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_3+{0.5\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">S</figure-callout>}}_4\\ 0.5i{S}_3-{0.5\mathrm{<figure-callout\; id="4"\; label="iS"\; filenames="HDA0000081615610000011.png"\; state="\{\{state\}\}">iS</figure-callout>}}_4\end{array}\right)$

User i receives signal:

$y^{\left(i\right)}=H^{\left(i\right)}S+n=\left(\begin{array}{cccc}{h}_{11}^i& h_{12}^i& h_{13}^i& h_{14}^i\\ h_{21}^i& h_{22}^i& h_{23}^i& h_{24}^i\end{array}\right)\left(\begin{array}{c}{S}_{\left(1\right)}\\ S_{\left(2\right)}\\ S_{\left(3\right)}\\ S_{\left(4\right)}\end{array}\right)+n$

User j receives signal:

$y^{\left(j\right)}=H^{\left(j\right)}S+n=\left(\begin{array}{cccc}{h}_{11}^j& h_{12}^j& h_{13}^j& h_{14}^j\\ h_{21}^j& h_{22}^j& h_{23}^j& h_{24}^j\end{array}\right)\left(\begin{array}{c}{S}_{\left(1\right)}\\ S_{\left(2\right)}\\ S_{\left(3\right)}\\ S_{\left(4\right)}\end{array}\right)+n$

In the prior art, base station RRU has the individual port of P (4), the user should choose pre-coding matrix from port number is the codebook set of P (4), but because every floor only has the individual passage of M (2) in the indoor distributed system, P＞M, and the floor gap isolation is larger, cause the subscriber channel rank of matrix can reduce (most cases is M (2) rather than P (4)), if carry out the Single User MIMO transmission, pass at most the individual stream of M (2), therefore be fit to do multiuser MIMO.

Among the present invention, carry out multi-user MIMO transmissions, can support simultaneously two users to divide the individual stream of supplementary biography M (2), be total to the individual stream of 2M (4), the user chooses pre-coding matrix from port number is the codebook set of M (2), rather than carries out the selection feedback of pre-coding matrix from port number is 4 codebook set.For each subscriber signal, only in the emission of user place antenna packet ports, reduce disturbance when increasing the useful signal transmitting power promotes the indoor cell throughput.

As shown in Figure 3, the present invention also proposes descending multi-user MIMO sender unit, comprises mapping block, grouping module, selection module, notification module and output module, and the described device that comprises above-mentioned module can be arranged on the base station.Wherein:

Mapping block is divided into P/M antenna grouping with the RRU port, preserves the corresponding relation of antenna grouping and port, and wherein, P is the RRU port number, and M is every floor passage number, and P is greater than M.The resulting divisor of P/M is integer.

Grouping module is coupled in mapping block, judges user place passage, finds antenna grouping corresponding to passage.Wherein, grouping module can according to user's different port up channel received power, judge that the strongest passage corresponding to port of received power is user place passage.Further, grouping module can also add the user antenna group list at place, selects module can select to be in according to the pairing algorithm of prior art the user of different antennae group list.

Select module, be coupled in grouping module, receive the pre-coding matrix of user feedback, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission.

Notification module, be coupled in the selection module, notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, to be the user select from port number is the codebook set of M described pre-coding matrix, pre-coding matrix is M * v matrix, and v is the subscriber channel rank of matrix.

Output module is coupled in notification module, according to pre-coding matrix data is weighted, and data are exported to the user after user place antenna port is with weighting, and all the other ports do not send this user's data.

As the conclusion to describing in detail, should notice that those skilled in the art will be apparent to make many variations and modification to preferred embodiment, and not break away from fact principle of the present invention.This variation and modification are included within the described scope of the present invention of appended claims.

Claims (10)

1. descending multi-user MIMO signal transmitting method may further comprise the steps:

The RRU port is divided into P/M antenna grouping, preserves the corresponding relation of antenna grouping and port, wherein, P is the RRU port number, and M is every floor passage number, and P is greater than M;

Judge user place passage, find antenna grouping corresponding to passage;

Receive the pre-coding matrix of user feedback, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission;

Notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, to be the user select from port number is the codebook set of M described pre-coding matrix, and pre-coding matrix is M * v matrix, and v is the subscriber channel rank of matrix;

According to pre-coding matrix data are weighted, data are exported to the user after user place antenna port is with weighting, and all the other ports do not send this user's data.

2. described descending multi-user MIMO signal transmitting method according to claim 1, in the step that data is weighted according to pre-coding matrix, the pre-coding matrix of base station side is:

P=2, during M=1,

$\left[\begin{array}{c}1\\ 0\end{array}\right]$ $\left[\begin{array}{c}0\\ 1\end{array}\right]$

P=4, during M=2,

$\frac{1}{2}\left[\begin{array}{cc}1& 1\\ 1& -1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}1& 1\\ i& -i\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& 0\\ 0& 1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ 1& -1\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ i& -i\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 0\\ 0& 1\end{array}\right].$

3. described descending multi-user MIMO signal transmitting method is according to claim 1 and 2 judged user place passage, may further comprise the steps:

The base station judges that according to user's different port up channel received power the strongest passage corresponding to port of received power is user place passage.

4. described descending multi-user MIMO signal transmitting method according to claim 3 finds antenna grouping corresponding to passage, and is further comprising the steps of:

The antenna group list that the user is added the place.

5. described descending multi-user MIMO signal transmitting method according to claim 4 adds the antenna group list at place with the user, and is further comprising the steps of:

Select to be in the user of different antennae group list according to the pairing algorithm.

6. descending multi-user MIMO sender unit comprises:

Mapping block is divided into P/M antenna grouping with the RRU port, preserves the corresponding relation of antenna grouping and port, and wherein, P is the RRU port number, and M is every floor passage number, and P is greater than M;

Grouping module is coupled in mapping block, judges user place passage, finds antenna grouping corresponding to passage;

Select module, be coupled in grouping module, receive the pre-coding matrix of user feedback, select to be in the user of different antennae grouping, carry out descending multi-user MIMO transmission;

Notification module, be coupled in the selection module, notify antenna grouping and pre-coding matrix that the user carries out downlink data transmission, to be the user select from port number is the codebook set of M described pre-coding matrix, pre-coding matrix is M * v matrix, and v is the subscriber channel rank of matrix;

Output module is coupled in notification module, according to pre-coding matrix data is weighted, and data are exported to the user after user place antenna port is with weighting, and all the other ports do not send this user's data.

7. described descending multi-user MIMO sender unit according to claim 6, output module to the pre-coding matrix that data are weighted is:

P=2, during M=1,

$\left[\begin{array}{c}1\\ 0\end{array}\right]$ $\left[\begin{array}{c}0\\ 1\end{array}\right]$

P=4, during M=2,

$\frac{1}{2}\left[\begin{array}{cc}1& 1\\ 1& -1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}1& 1\\ i& -i\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& 0\\ 0& 1\\ 0& 0\\ 0& 0\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ 1& -1\end{array}\right]$ $\frac{1}{2}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 1\\ i& -i\end{array}\right]$ $\frac{1}{\sqrt{2}}\left[\begin{array}{cc}0& 0\\ 0& 0\\ 1& 0\\ 0& 1\end{array}\right].$

8. also comprise according to claim 6 or 7 described descending multi-user MIMO sender units:

Grouping module judges that according to user's different port up channel received power the strongest passage corresponding to port of received power is user place passage.

9. described descending multi-user MIMO sender unit according to claim 8 comprises:

Grouping module adds the user antenna group list at place;

Select module to select to be in the user of different antennae group list according to the pairing algorithm.

10. according to claim 6 or 7 described descending multi-user MIMO sender units, be arranged on the base station.

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