KR20150111026A - Method and apparatus for transmitting feedback in multi user multiple input multiple output - Google Patents

Method and apparatus for transmitting feedback in multi user multiple input multiple output Download PDF

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KR20150111026A
KR20150111026A KR1020140034281A KR20140034281A KR20150111026A KR 20150111026 A KR20150111026 A KR 20150111026A KR 1020140034281 A KR1020140034281 A KR 1020140034281A KR 20140034281 A KR20140034281 A KR 20140034281A KR 20150111026 A KR20150111026 A KR 20150111026A
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South Korea
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precoding matrix
matrix indicator
terminal
alignment list
mimo
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KR1020140034281A
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Korean (ko)
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조대순
김일규
방승찬
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한국전자통신연구원
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radio Transmission System (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

A feedback transmission method of the UE in the MU-MIMO is provided. The UE generates a PMI sort list including the PMIs sorted in descending order of performance, and provides the PMI sort list to the other UEs. The UE selects an optimal PMI from its PMI alignment list considering the PMI alignment list of other UEs, and transmits feedback including the optimal PMI to the BS.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a feedback transmission method and apparatus for multi-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback transmission method and apparatus in multiuser multi-antenna transmission / reception.

A multiple input multiple output (MIMO) system using multiple antennas at a transmitter and a receiver has received attention in wireless / mobile communication systems. The MIMO scheme can be classified into a single user MIMO (SU-MIMO) scheme and a multi-user MIMO scheme (MU-MIMO scheme) depending on how many users simultaneously use the same radio resource.

At this time, in order to operate the MU-MIMO, the terminal, i.e., the user transmits feedback information to the base station, and the base station determines whether the MU-MIMO operation is possible based on the feedback information. When operating the MU-MIMO, the base station searches for an optimal precoding matrix combination in real time in order to pair the users and increase the performance of the paired multi-users.

Meanwhile, the UE assumes the SU-MIMO state without considering whether it is the SU-MIMO state or the MU-MIMO state, and calculates the feedback information, so that the base station can not accurately reflect the state information for the MU-MIMO operation. For this, it is necessary to transmit feedback information by knowing that the paired users are in the MU-MIMO state. However, in the existing MU-MIMO scheme, it is difficult to perform accurate MU-MIMO operation because information sharing among the paired users is impossible.

A problem to be solved by the present invention is to provide a feedback transmission method and apparatus in an MU-MIMO that can share information among users.

According to an embodiment of the present invention, a feedback transmission method of a terminal in an MU-MIMO is provided. The feedback transmission method includes: generating a precoding matrix indicator alignment list including a precoding matrix indicator aligned in order of performance; providing the precoding matrix indicator alignment list to another terminal; Selecting an optimal precoding matrix indicator from the precoding matrix indicator alignment list of the other terminal in consideration of the precoding matrix indicator alignment list of the other terminal; And transmitting feedback including the optimal precoding matrix indicator to a base station.

The terminal may be connected to the other terminal through a sidehaul.

At this time, the terminal may form a moving personal cell (mPC).

The step of generating the precoding matrix indicator alignment list may include generating a precoding matrix indicator alignment list from a codebook shared by the terminal and the base station.

The precoding matrix indicator alignment list may further include a channel quality indicator indicating a channel quality corresponding to the precoding matrix indicator.

Wherein the step of selecting the optimal precoding matrix indicator further comprises the step of selecting a precoding matrix indicator that is included in the precoding matrix indicator of the other terminal among the precoding matrix indicators indicated in the precoding matrix indicator alignment list of its own, And selecting the precoding matrix indicator satisfying the -MIMO application condition as the optimal precoding matrix indicator.

According to another embodiment of the present invention, a method of receiving feedback of a base station in MU-MIMO is provided. The feedback receiving method includes receiving a precoding matrix indicator from each of a plurality of terminals, and generating an MU-MIMO precoding matrix using a precoding matrix indicated by the precoding matrix indicator of the plurality of terminals . At this time, the plurality of terminals share information on the precoding matrix indicator.

The plurality of terminals may be connected to each other through a side hole.

At this time, each terminal can form a mobile personal cell (mPC).

The information on the precoding matrix indicator may include a precoding matrix indicator alignment list of each MS. The precoding matrix indicator alignment list may include a precoding matrix indicator aligned in order of performance.

The precoding matrix indicator of each terminal received by the base station may be an optimal precoding matrix indicator determined based on the precoding matrix indicator alignment list.

According to another embodiment of the present invention, a feedback transmission apparatus in MU-MIMO is provided. The feedback transmission apparatus includes a processor, a first transceiver, and a second transceiver. Wherein the processor generates a precoding matrix indicator alignment list including precoding matrix indicators aligned in order of performance and selects a best precoding matrix indicator alignment list from its precoding matrix indicator alignment list in consideration of a precoding matrix indicator alignment list of other terminals Lt; / RTI > precoding matrix indicator. The first transceiver provides its own precoding matrix indicator alignment list to the other terminal and receives the precoding matrix indicator alignment list of the other terminal from the other terminal. The second transceiver transmits feedback including the optimal precoding matrix indicator to the base station.

The first transceiver may be connected to the other terminal through a side hole.

The terminal may form a mobile personal cell (mPC).

The processor may generate a precoding matrix indicator alignment list from a codebook shared by the terminal and the base station.

According to an embodiment of the present invention, each terminal can select an optimum PMI for applying MU-MIMO by sharing PMI information between the terminals through the side holes.

1 is a diagram illustrating an SU-MIMO system.
2 is a diagram showing an MU-MIMO system.
3 is a diagram illustrating an MU-MIMO system according to an embodiment of the present invention.
4 is a flowchart of a feedback transmission method for MU-MIMO according to an embodiment of the present invention.
5 is a schematic block diagram of a feedback transmission apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal may be referred to as a user equipment (UE), a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS) a high reliability mobile station (HR-MS), a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT) MS, AMS, HR-MS, SS, PSS, AT, and the like.

Also, a base station (BS) includes a node B, an evolved node B, an advanced base station (ABS), a high reliability base station (HR- (BS), an access point (AP), a radio access station (RAS), a base transceiver station (BTS) BS AP, RAS, BTS, and the like.

Now, a method and apparatus for transmitting precoding matrix information according to an embodiment of the present invention will be described in detail with reference to the drawings.

First, a single user multiple input multiple output (SU-MIMO) system and a multiuser multiple input multiple output (MU-MIMO) system will be described with reference to FIG. 1 and FIG. do.

1 is a diagram illustrating an SU-MIMO system, and FIG. 2 is a diagram illustrating an MU-MIMO system.

Referring to FIGS. 1 and 2, a base station 100 has at least one antenna port 110, 120, and 130, and communicates with a plurality of terminals 210, 220, and 230. Each terminal 210, 220, 230 also has at least one antenna port 211, 212, 221, 222, 231, 232.

1, in the SU-MIMO system, when the base station 100 transmits a plurality of layers through a plurality of antenna ports 110, 120, and 130, all layers are transmitted to one terminal. In the SU-MIMO system, one base station 100 and one terminal 210 may form a MIMO channel, and a plurality of antenna ports 210, 220, and 230 of the base station 100 of one terminal 210 may be used. Can receive all of the signals from the base station.

2, when a base station 100 transmits a plurality of layers through a plurality of antenna ports 110, 120, and 130, a plurality of layers 210, 220, and 230 Lt; / RTI > In the MU-MIMO system, one base station 100 and a plurality of terminals 210, 220, and 230 may form a MIMO channel. Accordingly, data for a plurality of terminals in the same time / frequency domain can be scheduled.

A condition for selecting the MU-MIMO in the MIMO transmission scheme at the next base station will be described. For convenience of explanation, it is assumed that MU-MIMO is applied to two terminals.

The UE 1 selects an optimal precoding matrix from the precoding matrices already defined and feeds back a precoding matrix indicator (PMI) indicating the selected precoding matrix to the base station. The terminal 2 also selects an optimal precoding matrix from among the precoding matrices already defined and feeds back the PMI indicating the selected precoding matrix to the base station. At this time, it is assumed that the terminals 1 and 2 and the base station share a codebook, and a precoding matrix is predefined in the codebook. The matrix indicated by the PMI fed back by the UE 1 is W 1 and the matrix indicated by the PMI fed back by the UE 2 is W 2 .

The base station then the guy (norm) of the pseudo-inverse matrix (pseudo inverse) (W 1 H ) and the terminal 2 is feedback a precoding matrix (W 2) of the precoding matrix (W 1) by the terminal 1 feedback, as Equation (1) If it is less than or equal to the threshold value (?), It can be determined to apply MU-MIMO.

Figure pat00001

At this time, the threshold value [Delta] is a non-negative real number, and an optimal value can be determined through a simulation or the like. For a stable operation of the MU-MIMO system, the threshold value? Can be determined to be zero. When the threshold value? Is 0, it means that the precoding matrix W 1 fed back by the UE 1 and the precoding matrix W 2 fed back by the UE 2 are orthogonal. Therefore, when a base station performs scheduling based on a terminal 1, if there is a terminal that feeds back a precoding matrix orthogonal to the precoding matrix W 1 fed back by the terminal 1, MU-MIMO is applied to the terminal 1 and the corresponding terminal And MU-MIMO is not applied if there is no UE that fed back the orthogonal precoding matrix.

When the base station applies MU-MIMO to the terminal 1 and the terminal 2, the precoding matrix P used by the base station is determined as shown in Equation (2).

Figure pat00002

In Equation 2, W is defined as [W 1 W 2] by a precoding matrix by the first feedback terminal (W 1) and the feedback precoding matrix, the terminal 2 (W 2).

If the first and second columns of the precoding matrix P are P 1 and P 2 , respectively, the precoding vectors of the terminal 1 and the terminal 2 are P 1 and P 2 , respectively. If, when the terminal 1 is feedback a precoding matrix (W 1) and the feedback precoding matrix, the terminal 2 (W 2) are orthogonal, and the P 1 = W 1, P 2 = W 2.

Hereinafter, a feedback transmission method in MU-MIMO according to an embodiment of the present invention will be described with reference to FIG. 3 and FIG.

FIG. 3 is a diagram illustrating an MU-MIMO system according to an embodiment of the present invention, and FIG. 4 is a flowchart of a feedback transmission method for MU-MIMO according to an embodiment of the present invention.

Referring to FIG. 3, a plurality of terminals 320, 330, 340, and 350 are located in a cell area of the large base station 310.

Each of the terminals 320, 330, 340, and 350 forms a personal cell that provides mobility, that is, a moving personal cell (mPC). The terminals 320, 330, 340, and 350 are connected to each other through a sidehaul. At this time, the mobile base station 310 may be connected to the mobile personal cell through a backhaul.

Referring to FIG. 4, each UE measures the performance according to a precoding matrix indicated by predetermined PMIs in a private cell (S410). At this time, the PMI may be predefined by the codebook.

The terminals 320, 330, 340, and 350 and the base station 310 may share the codebook illustrated in Table 1 or Table 2. Table 1 shows an example of a codebook that can be used when there are two antenna ports, and Table 2 shows an example of codebooks that can be used when there are four antenna ports. As illustrated in Table 1 and Table 2, the codebook indicates a precoding matrix corresponding to the PMI according to the number of layers.

Figure pat00003

Figure pat00004

In Table 2,

Figure pat00005
And I is a 4-by-4 identity matrix.

Next, each UE generates a PMI sorting list by sequentially listing the PMIs indicating the best performing precoding matrix and the PMIs indicating the worst performing precoding matrix (S420). For example, each terminal can calculate the channel quality when using the precoding matrix indicated by each PMI, and determine that the precoding matrix is good in order of channel quality. As another example, the UE can determine that the precoding matrix has better performance in the order that the channel quality can increase the downlink transmission power.

Meanwhile, each terminal may include a channel quality indicator (CQI) indicating the channel quality corresponding to each PMI in the PMI alignment list.

Each terminal transmits the PMI sort list to other terminals through a side hole (S430). Through this process, the terminals 320, 330, 340, and 350 can share the PMI sort list with other terminals.

After sharing the PMI alignment list, each UE determines the PMI corresponding to the optimal precoding matrix considering the PMI of the other UE (S440), and transmits the feedback including the determined optimal PMI to the base station 310 (S450). At this time, the feedback may further include a CQI corresponding to the optimal PMI.

For example, if the precoding matrix indicated by the PMI included in the PMI sort list provided by the other UE and the precoding matrix indicated by the PMI included in the PMI ordered list of the UE are MU-MIMO applied conditions The condition of Equation (1)) can be determined. In this case, each UE selects a PMI in order of performance from the PMIs included in its PMI sort list, selects a PMI in order of performance from the PMI included in the PMI sort list of other UEs, and selects the MU- Can be searched for. That is, each UE determines whether the combination of the PMI selected by the PMI included in its own PMI alignment list and the PMI selected by the PMI included in the PMI ordered list of the other terminals satisfies the MU-MIMO applying condition, The PMI included in the PMI combination having the PMI having the high performance as a whole can be determined as the optimal PMI. As another example, each mobile station may select a PMI that can minimize the interference on itself based on the PMI included in the PMI sort list of the other mobile stations as an optimal PMI.

After receiving the optimal PMI from each terminal, the base station 310 determines an MU-MIMO precoding matrix from these PMIs and transmits the data to the terminals 320, 330, 340, and 350 using the MU- (S460).

As described above, according to the embodiment of the present invention, each terminal can select an optimum PMI for applying MU-MIMO by sharing PMI information between the terminals through the side holes.

5 is a schematic block diagram of a feedback transmission apparatus according to an embodiment of the present invention.

5, the feedback transmission apparatus 500 includes a processor 510, a first transceiver 520, a second transceiver 530, and a memory 540. [ The discovery apparatus 500 may be included in the terminal or may be the terminal itself.

The processor 510 generates the PMI sort list by sorting the PMIs included in the codebook in descending order of performance, and selects an optimal PMI from the PMI sort list based on the PMI sort list of the other terminals.

The first transceiver 520 is connected to another terminal through a side hole. The first transceiver 520 provides its own PMI sort list to other terminals, receives PMI sort lists from other terminals, and shares the PMI sort list.

The second transceiver 530 transmits the feedback including the optimal PMI to the base station and receives the data transmitted by applying the MU-MIMO from the base station.

The memory 540 stores instructions for execution in the processor 510 or temporarily stores the instructions loaded from a storage device (not shown), and the processor 510 is stored in the memory 54 Execute the loaded command. The memory 540 or storage device may also store a codebook that is shared with the base station.

The processor 510 and the memory 540 are connected to each other via a bus (not shown), and an input / output interface (not shown) may be connected to the bus. At this time, the transceivers 520 and 530 are connected to the input / output interface, and peripheral devices such as an input device, a display, a speaker, and a storage device may be connected.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (15)

A method for feedback transmission of a terminal in a multi-user multiple input multiple output (MU-MIMO)
Generating a precoding matrix indicator alignment list including a precoding matrix indicator aligned in order of performance;
Providing the precoding matrix indicator alignment list to another terminal,
Receiving a precoding matrix indicator alignment list of the other terminal from the other terminal,
Selecting an optimal precoding matrix indicator from the precoding matrix indicator alignment list of its own considering the precoding matrix indicator alignment list of the other terminal; and
Transmitting feedback including the optimal precoding matrix indicator to a base station
/ RTI > The method of claim 1,
Wherein the terminal is connected to the other terminal through a sidehaul. 3. The method of claim 2,
Wherein the terminal forms a moving personal cell (mPC). The method of claim 1,
Wherein generating the precoding matrix indicator alignment list comprises generating a precoding matrix indicator alignment list from a codebook shared by the terminal and the base station. The method of claim 1,
Wherein the precoding matrix indicator alignment list further comprises a channel quality indicator indicating a channel quality corresponding to the precoding matrix indicator. The method of claim 1,
Wherein the step of selecting the optimal precoding matrix indicator further comprises the step of selecting a precoding matrix indicator that is included in the precoding matrix indicator of the other terminal among the precoding matrix indicators indicated in the precoding matrix indicator alignment list of its own, And selecting a precoding matrix indicator satisfying -MIMO applying conditions as the optimal precoding matrix indicator. A method of receiving feedback from a base station in a multi-user multiple input multiple output (MU-MIMO)
Receiving a precoding matrix indicator from each of a plurality of terminals, and
A step of generating an MU-MIMO precoding matrix using a precoding matrix indicated by a precoding matrix indicator of the plurality of terminals;
/ RTI >
Wherein the plurality of terminals share information on the precoding matrix indicator. 8. The method of claim 7,
Wherein the plurality of terminals are connected to each other through sideholes. 9. The method of claim 8,
Each terminal forming a moving personal cell (mPC). 8. The method of claim 7,
Wherein the information on the precoding matrix indicator comprises a precoding matrix indicator alignment list of each terminal,
Wherein the precoding matrix indicator alignment list includes a precoding matrix indicator aligned in order of performance. 11. The method of claim 10,
Wherein the precoding matrix indicator of each terminal received by the base station is an optimal precoding matrix indicator determined based on the precoding matrix indicator alignment list. A feedback transmission apparatus in a multi-user multiple input multiple output (MU-MIMO)
A precoding matrix indicator alignment list including a precoding matrix indicator aligned in order of performance is generated, and an optimal precoding matrix indicator alignment list is generated from the precoding matrix indicator alignment list of the mobile station in consideration of the precoding matrix indicator alignment list of other terminals A processor for selecting a matrix indicator,
A first transceiver for providing the precoding matrix indicator alignment list of its own to the other terminal and receiving a precoding matrix indicator alignment list of the other terminal from the other terminal,
A second transceiver for transmitting feedback including the optimal precoding matrix indicator to a base station
/ RTI > The method of claim 12,
And the first transceiver is connected to the other terminal through a sidehaul. The method of claim 13,
Wherein the terminal forms a moving personal cell (mPC). The method of claim 12,
Wherein the processor generates a precoding matrix indicator alignment list from a codebook shared by the terminal and the base station.
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