KR101290918B1 - Communication system for using interference alignment scheme in multicell environment - Google Patents

Communication system for using interference alignment scheme in multicell environment Download PDF

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KR101290918B1
KR101290918B1 KR1020120071020A KR20120071020A KR101290918B1 KR 101290918 B1 KR101290918 B1 KR 101290918B1 KR 1020120071020 A KR1020120071020 A KR 1020120071020A KR 20120071020 A KR20120071020 A KR 20120071020A KR 101290918 B1 KR101290918 B1 KR 101290918B1
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South Korea
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interference
base station
data
terminal
information
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KR1020120071020A
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Korean (ko)
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정방철
신원용
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경상대학교산학협력단
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Priority to KR1020120071020A priority Critical patent/KR101290918B1/en
Priority to PCT/KR2012/009029 priority patent/WO2014003256A1/en
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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
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
    • 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
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0626—Channel coefficients, e.g. channel state information [CSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals

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

Abstract

PURPOSE: A communication system which uses an interference sorting technique in a multiple cellular environment is provided to allow a plurality of portable terminals to transmit data through the interference sorting technique. CONSTITUTION: An interference space matrix generating unit (620) generates an interference space matrix based on information about a channel state. A transmitting unit (630) transmits a null space matrix of the interference space matrix. An interference quantity information receiving unit (640) receives information about interference quantity which the terminal transmits to other cells adjacent to a base station. A controlling unit (650) selects a data transmission terminal based on the information about the interference quantity. A data receiving unit (660) receives data from the selected data transmission terminal. [Reference numerals] (610) Chanel state information receiving unit; (620) Interference space matrix generating unit; (630) Transmitting unit; (640) Interference quantity information receiving unit; (650) Controlling unit; (660) Data receiving unit; (670) Decoding unit

Description

COMMUNICATION SYSTEM FOR USING INTERFERENCE ALIGNMENT SCHEME IN MULTICELL ENVIRONMENT}

The present invention relates to a technique for transmitting data by minimizing the effects of intercell interference in a multicell environment consisting of a plurality of cells.

The amount of signals transmitted using a wireless communication network is gradually increasing over time. In the near future, it is expected that signals of up to several times the capacity of the signals currently transmitted will be transmitted using wireless networks.

The wireless communication network may include a plurality of base stations and terminals. The terminal may receive an interference signal from an adjacent base station in addition to the base station transmitting a desired signal. Such an interference signal is one of the causes of reducing the transmission efficiency of the wireless communication network, and there is a need for a technology capable of reducing or minimizing it.

An object of the following embodiments is to select a terminal to transmit data using an interference alignment technique among a plurality of terminals.

An object of the following embodiments is to select a terminal to transmit data among the terminals having a plurality of antennas.

The purpose of the following embodiments is to minimize intercell interference.

According to an exemplary embodiment, receiving information about a channel state between a base station and the terminals from a plurality of terminals, generating an interference space matrix based on the information on the channel state, Transmitting a null space matrix to the terminals, receiving information about the amount of interference transmitted by the terminal to another cell adjacent to the base station, generated based on the null space matrix, from the terminals; There is provided a data receiving method of a base station comprising selecting a data transmission terminal among the terminals based on the information and receiving data from the selected data transmission terminal.

The method may further include transmitting a pilot signal to the terminals, and the channel state may be generated based on the pilot signal.

The receiving of the data may further include receiving beamformed data from the terminal using a transmission beamforming vector, and decoding the received data using the transmission beamforming vector.

The generating of the interference spatial matrix may be performed by selecting column vectors located to the left or the right of a singular matrix to generate the interference spatial matrix, and the null spatial matrix may interfere with the arbitrary singular matrix. It can be generated from the column vectors remaining without being selected as the spatial matrix.

In the receiving, the data may be received using the null spatial matrix as a reception beamforming vector.

The transmission beam vector may be determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal.

According to yet another exemplary embodiment, the step of transmitting information on the channel state between the base station and the terminal to the base station, receiving a null space matrix generated based on the information on the channel state from the base station, the null Generating information on an amount of interference transmitted from the terminal to another cell adjacent to the base station based on a spatial matrix, transmitting information on the amount of interference to the base station, and transmitting data to the base station based on the amount of interference A data transmission method of a terminal is provided.

The method may further include receiving a pilot signal from the base station, and the channel state may be generated based on the pilot signal.

In the transmitting of the data, the data may be transmitted using only one antenna among a plurality of data transmission antennas.

In addition, the transmitting of the data may transmit beamformed data using a transmission beam vector.

Here, the transmission beam vector may be determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal.

The transmission beam vector may be determined by singular value decomposition (SVD) of a product between a Hermitian matrix of the null space matrix and a matrix including channel states between other cells adjacent to the base station from the terminal. Can be.

Further, the transmission beam vector may be selected from among a plurality of column vectors of a pre-determined codebook matrix.

According to another exemplary embodiment, a channel state information receiver for receiving information on a channel state between a base station and the terminals from a plurality of terminals, an interference space for generating an interference space matrix based on the information on the channel state A matrix generator, a transmitter for transmitting a null space matrix of the interference spatial matrix to the terminals, the receiver is generated based on the null space matrix from the terminals, the terminal transmits to another cell adjacent to the base station There is provided a base station including an interference amount information receiving unit for receiving information on an interference amount, a control unit for selecting a data transmission terminal among the terminals based on the information on the interference amount, and a data receiving unit for receiving data from the selected data transmission terminal. .

Here, the transmitter may transmit a pilot signal to the terminals, and the channel state may be generated based on the pilot signal.

The data receiver may further include a decoder configured to receive beamformed data from the terminal using a transmission beamforming vector and to decode the received data using the transmission beamforming vector.

The data receiver may receive the data using the null spatial matrix as a reception beamforming vector.

Here, the interference space generation unit selects column vectors located at the left or right side of a singular matrix to generate the interference space, and the null space is left unselected as the interference space in the arbitrary singular matrix. Can be generated as column vectors.

The transmission beam vector may be determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal.

According to another exemplary embodiment, a channel state information transmitter for transmitting information on a channel state between a base station and a terminal to the base station, receiving a null space matrix generated based on the information on the channel state from the base station A null space matrix receiver, An interference amount information generator for generating information on the amount of interference transmitted from the terminal to another cell adjacent to the base station based on the null space matrix, Interference amount information transmitter for transmitting the information about the interference amount to the base station And a data transmitter for transmitting data to the base station based on the interference amount.

The apparatus may further include a pilot receiver configured to receive a pilot signal from the base station, and the channel state may be generated based on the pilot signal.

The data transmitter may transmit the data using only one antenna among a plurality of data transmission antennas.

The data transmitter may transmit beamformed data using a transmission beam vector.

Here, the transmission beam vector may be determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal.

The transmission beam vector may be determined by singular value decomposition (SVD) of a product between a Hermitian matrix of the null space matrix and a matrix including channel states between other cells adjacent to the base station from the terminal. Can be.

Further, the transmission beam vector may be selected from among a plurality of column vectors of a pre-determined codebook matrix.

According to the following embodiments, it is possible to select a terminal to transmit data using an interference alignment technique among a plurality of terminals.

According to the following embodiments, it is possible to select a terminal to transmit data among the terminals having a plurality of antennas.

According to the following embodiments, inter-cell interference can be minimized.

1 is a diagram conceptually illustrating an example of an interference alignment technique.
2 illustrates a concept of a communication system for transmitting data using an interference alignment technique.
3 is a flowchart illustrating step by step operations of a communication system according to an exemplary embodiment.
Fig. 4 is a flowchart illustrating a step-by-step method of receiving data according to an exemplary embodiment.
Fig. 5 is a flowchart illustrating a step-by-step method of transmitting data according to an exemplary embodiment.
Fig. 6 is a block diagram showing the structure of a base station according to an exemplary embodiment.
Fig. 7 is a block diagram showing the structure of a terminal according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram conceptually illustrating an example of an interference alignment technique.

1 shows a communication network or communication system including a plurality of base stations 110, 120, 130 and a plurality of terminals 160, 170, 180. The base station 110 forms a pair for transmitting signals to the terminal 160, and likewise, the base station 120 and the base station 130 form a pair for transmitting signals to the terminal 170 and the terminal 180, respectively.

The signal transmitted from each base station may be transmitted to other terminals in addition to the target terminal, and FIG. 1 shows an example of such a situation. Taking the base station 110 as an example, the transmitted signal may be received not only by the designed terminal 160 but also by the undesignated terminals 170 and 180. From the standpoint of the terminal 160, along with the desired signal transmitted from the base station 110, it receives an undesired signal transmitted from the base station 120 and the base station 130. As such, a desired signal may be referred to as a data signal among signals received by each terminal, and an unwanted signal may be referred to as an interference signal. In addition, a base station transmitting a data signal for each of the terminals 160, 170, and 180 may be referred to as a transmitting base station and a base station transmitting an interference signal as an interfering base station. Taking the terminal 160 of FIG. 1 as an example, the base station 110 is a transmitting base station, and the base stations 120 and 130 are interfering base stations.

Each base station may control the signal to be transmitted to reduce the influence of the interference signal in each terminal. A signal to be transmitted may be controlled based on a state of a channel between each base station and each terminal.

According to the embodiment shown in Figure 1, the signal transmitted by the base station 110

Figure 112012052286617-pat00001
The phase of 111 is changed via the channel 131 between the base station 110 and the terminal 160. Terminal 160 is a signal
Figure 112012052286617-pat00002
Is the phase-shifted main signal across channel 131
Figure 112012052286617-pat00003
Figure 112012052286617-pat00004
Receive 161. In addition, the terminal 160 is a signal transmitted by the base station 120
Figure 112012052286617-pat00005
Interferes with the phase shifted channel 141
Figure 112012052286617-pat00006
Figure 112012052286617-pat00007
162 and the signal transmitted by the base station 130
Figure 112012052286617-pat00008
Interference signal phase shifted by channel 151
Figure 112012052286617-pat00009
Figure 112012052286617-pat00010
Receive 163. In this case, the interference signal
Figure 112012052286617-pat00011
Figure 112012052286617-pat00012
162 and interference signal
Figure 112012052286617-pat00013
Figure 112012052286617-pat00014
Main signal at terminal 160 due to 163
Figure 112012052286617-pat00015
Figure 112012052286617-pat00016
161 The reception efficiency may be degraded. Similarly, the terminal 170, the interference signal
Figure 112012052286617-pat00017
Figure 112012052286617-pat00018
171 and interference signal
Figure 112012052286617-pat00019
Figure 112012052286617-pat00020
(173) due to main signal
Figure 112012052286617-pat00021
Figure 112012052286617-pat00022
The reception of 172 may be degraded, and the interference signal is received by the terminal 180.
Figure 112012052286617-pat00023
Figure 112012052286617-pat00024
181 and
Figure 112012052286617-pat00025
Figure 112012052286617-pat00026
182 due to the main signal
Figure 112012052286617-pat00027
Figure 112012052286617-pat00028
Reception of 183 may be degraded. In order to reduce or eliminate such reception efficiency degradation, each base station may control a signal to be transmitted.

In the embodiment of FIG. 1, each terminal 160, 170, 180 may estimate a channel state with each base station 110, 120, 130, and report the estimated channel state to the base station. That is, the terminal 160 estimates the channel state 131 with the base station 110, the channel state 141 with the base station 120, and the channel state 151 with the base station 130, and estimates the estimated channel. The states 131, 141, and 151 may be reported to the base stations 110, 120, and 130. In a similar manner, the terminal 170 estimates the channel states 132, 142, and 152 and reports them to the base stations 110, 120, and 130, and the terminal 180 reports the channel states 133, 143, and 153. It can be estimated and reported to each base station (110, 120, 130). Therefore, each base station (110, 120, 130) can control the signal to be transmitted in consideration of the information of all channel states (131, 141, 151, 132, 142, 152, 133, 143, 153). As an example of the transmission signal control, the transmission signal may be precoded so that the signal received by the terminal through the channel has a specific phase.

All embodiments of the present specification are frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiplexing (FDD). Signal can be transmitted and received using Frequency Division Duplex (TDD) and Time Division Duplex (TDD).

In the case of time division multiplexing, it may be assumed that the state of the uplink channel and the state of the downlink channel between the base stations 110, 120, 130 and the terminal 160, 170, 180 are the same. Accordingly, the base stations 110, 120, and 130 may receive pilot signals from the terminals 160, 170, and 180, and estimate a state of an uplink channel based on the pilot signals. Since the state of the uplink channel is the same as that of the downlink channel, the state information of the uplink channel can be used as the downlink channel state information.

An embodiment in which the frequency division multiplexing scheme is used will be described in detail with reference to FIG. 1. In the frequency division multiplexing scheme, the state of the uplink channel and the state of the downlink channel between the base stations 110, 120, 130 and the terminals 160, 170, 180 are not the same. Accordingly, each terminal 160, 170, 180 may estimate the state of the downlink channel, and transmit the estimated state of the downlink channel to each base station (110, 120, 130). Each base station (110, 120, 130) may control the transmission signal based on the state (131, 141, 151, 132, 142, 152, 133, 143, 153) of the downlink channel as described above.

FIG. 1 shows an embodiment of an interference alignment scheme in which a transmission signal is controlled such that phases of interference signals received by each terminal are the same. Terminal 160 is the main signal

Figure 112012052286617-pat00029
Figure 112012052286617-pat00030
161 other interference signal
Figure 112012052286617-pat00031
Figure 112012052286617-pat00032
162 and
Figure 112012052286617-pat00033
Figure 112012052286617-pat00034
Receive 163. Signal transmitted by base station 120
Figure 112012052286617-pat00035
Phase is changed in the process of being received by the terminal 160 via the channel 141. In other words, the interference signal
Figure 112012052286617-pat00036
Figure 112012052286617-pat00037
The phase of 162 is
Figure 112012052286617-pat00038
The phase is changed differently. Similarly interference signal
Figure 112012052286617-pat00039
Figure 112012052286617-pat00040
The phase of 163 is
Figure 112012052286617-pat00041
The phase is changed differently.

Base station 120 and base station 130 is an interference signal received by the terminal 160

Figure 112012052286617-pat00042
Figure 112012052286617-pat00043
162 and
Figure 112012052286617-pat00044
Figure 112012052286617-pat00045
Transmission signal so that the phase of 163 is the same
Figure 112012052286617-pat00046
121 and
Figure 112012052286617-pat00047
The phase of 131 can be controlled respectively. Similarly, the base station 110 and the base station 130, the interference signal received by the terminal 170
Figure 112012052286617-pat00048
Figure 112012052286617-pat00049
(171) and
Figure 112012052286617-pat00050
Figure 112012052286617-pat00051
Transmission signal so that the phase of 173 is the same
Figure 112012052286617-pat00052
(111) and
Figure 112012052286617-pat00053
It is possible to control the phase of 131, the base station 110 and the base station 120 is the interference signal received by the terminal 180
Figure 112012052286617-pat00054
Figure 112012052286617-pat00055
181 and
Figure 112012052286617-pat00056
Figure 112012052286617-pat00057
Transmission signal so that the phase of 182 is the same
Figure 112012052286617-pat00058
(111) and
Figure 112012052286617-pat00059
The phase of 121 can be controlled. As described above, phase control of the transmission signal may be performed by applying precoding to the transmission signal.

As such, when the plurality of interference signals received by each terminal have the same phase, the terminal may be regarded as receiving one interference signal transmitted with relatively large power. In addition, even if the number of interference signals increases, the terminal may consider that only one interference signal is received if the phase of the received interference signal is the same. For example, each terminal illustrated in FIG. 1 may remove two interference signals having the same phase as one interference signal.

The interference neutralization method refers to a method in which a plurality of interfering base stations control and transmit a phase of a transmission signal so that the phases of the plurality of interference signals received by the terminal are reversed. Like the interference alignment method, when the terminal receives interference signals to which the interference neutralization method is applied, the terminal may regard them as one interference signal. For example, when the phases of two interference signals are 180 degrees apart, the sums may be regarded as one interference signal having a relatively small magnitude.

2 illustrates a concept of a communication system for transmitting data using an interference alignment technique.

Although only two cells are shown in FIG. 2, the communication system described herein is a cellular mobile communication system having K cells.

In FIG. 2, the first cell includes a first base station 210 and a plurality of terminals 231, 232, 233, and 234. The first base station 210 includes three data receiving antennas 221, 222, and 223, and each of the terminals 231, 232, 233, and 234 has two data transmitting antennas.

The second cell includes a second base station 250 and a plurality of terminals 261, 262, 263, and 264. The second base station 250 includes three data receiving antennas 251, 252, and 253, and each of the terminals 261, 262, 263, and 264 has two data transmitting antennas.

According to one side, the first base station 210 selects some of the terminals 233, 234 from among the plurality of terminals 231, 232, 233, 234 as the data transmission terminal 240. In this case, the number of data transmitting terminals 240 may be smaller than the number of data receiving antennas of the first base station 210.

In addition, the second base station 250 selects some terminals 263 and 264 from among the plurality of terminals 261, 262, 263 and 264 as the data transmission terminal 270. In this case, the number of data transmitting terminals 270 may be smaller than the number of data receiving antennas of the second base station 250.

According to one side, the first base station 210 and the second base station 250 may receive data from the data transmission terminal (240, 270) using an interference alignment technique. In this case, the number of terminals 233, 234, 263, and 264 selected as data transmission terminals 240 and 270 in each cell is determined by the data receiving antennas 221, 222, 223, of the base stations 210 and 250. 251, 252, and 253 may be smaller than the number.

When data is transmitted using a plurality of cells as shown in FIG. 2, the data transmission terminals 240 included in the first cell may transmit an interference signal to the base station 250 included in the second cell. In addition, the data transmission terminals 270 included in the second cell may transmit an interference signal to the base station 210 included in the first cell. Therefore, eliminating such inter-cell interference is an important task for improving the performance of the data transmission system shown in FIG.

3 is a flowchart illustrating step by step operations of a communication system according to an exemplary embodiment.

The communication system described in FIG. 3 is a multi-cell communication system composed of K cells, and each cell may include one base station 310 and a plurality of terminals. In FIG. 3, only one terminal 320 is shown for convenience of description.

In step 331, the base station 310 transmits a pilot signal to the terminal 320. According to one side, the base station 310 may transmit a pilot signal using a plurality of data reception antennas, the terminal 320 may receive a pilot signal using a plurality of data transmission antennas.

In step 332, the terminal 320 generates information on the channel state between the terminal 320 from the base station 310 by using the received pilot signal. According to one side, the information about the channel state may be in the form of a matrix whose size is determined according to the number of data receiving antennas and the number of data transmitting antennas. In this case, the information about the channel state may be referred to as a channel state matrix.

In step 333, the terminal 320 transmits information about the channel state to the base station 310.

In step 341, the base station generates an interference spatial matrix based on the information about the channel state. Also, in step 342, a null space matrix of the interference spatial matrix of the base station is generated. According to one side, the interference spatial matrix of the k-th cell using the interference alignment technique can be expressed by Equation 1 below.

[Equation 1]

Figure 112012052286617-pat00060

here,

Figure 112012052286617-pat00061
Denotes the interference spatial matrix of the k-th cell using the interference alignment technique,
Figure 112012052286617-pat00062
Column vectors
Figure 112012052286617-pat00063
Are orthonormal vectors having an isotropic distribution and generated independently of each other. In addition, M is the number of data receiving antennas provided in the base station, S is the number of terminals selected as the data transmission terminal is less than or equal to M.

In this case, the null space matrix may be represented as in Equation 2 below.

&Quot; (2) "

Figure 112012052286617-pat00064

Where a null space matrix

Figure 112012052286617-pat00065
Are the column vectors of
Figure 112012052286617-pat00066
The
Figure 112012052286617-pat00067
It has the property of and is orthonormal vectors.

According to one side, in step 341, the base station 310 may set an arbitrary singular matrix of M × M size. The base station 310 may generate the interference spatial matrix by selecting the M-S column vectors on the left in an arbitrary singular matrix or by selecting the M-S column vectors on the right.

In this case, at step 342, base station 310 may generate a null spatial matrix with the remaining S column vectors that are not selected as the interference spatial matrix in any singular matrix.

In step 343, the base station 310 transmits information about the null space matrix to all terminals located within the coverage of the base station 310.

In step 350, the terminal 320 determines the transmission beamforming vector used to transmit data to the base station 310. According to one side, the terminal 320 selects and transmits any one of 1) an antenna selection scheme, 2) an SVD scheme, and 3) a vector quantization scheme. The beam vector can be determined.

In step 351, the terminal 320 generates information on the amount of interference based on the null space matrix. Here, the information on the amount of interference generated by the terminal 320 is information on the amount of interference transmitted by the terminal 320 to another base station.

According to one side, the terminal 320 may generate information on the amount of interference according to Equation 3 below.

&Quot; (3) "

Figure 112012052286617-pat00068

Figure 112012052286617-pat00069

here,

Figure 112012052286617-pat00070
Means information on the amount of interference generated by the j-th terminal included in the i-th cell,
Figure 112012052286617-pat00071
Denotes an orthogonal projection for basis A. Also,
Figure 112012052286617-pat00072
Is a cross-link channel matrix indicating a channel state from the j th terminal included in the i th cell to the base station of the k th cell. Also,
Figure 112012052286617-pat00073
Is a transmission beam vector used by the j-th terminal included in the i-th cell to transmit data.

In step 352, the terminal 320 transmits the information on the generated interference amount to the base station 310.

Hereinafter, the configuration of the terminal 320 to determine the transmission beam vector in step 350 and the configuration of generating information on the amount of interference in step 351 will be described briefly.

1) Antenna Selection Technique

The terminal 320 may be provided with a plurality of data transmission antennas. According to the antenna selection scheme, the terminal 320 may select any one of the antennas and transmit data using only the selected antennas.

In this case, the terminal 320 may be regarded as determining the transmission beamforming vector such that the weight of the selected antenna is '1' and the weight of the other antenna is '0'.

Thus, in the case where the terminal 320 is equipped with L data transmission antennas, in step 350, the terminal 320 transmits a beam vector of any column vector in an identity matrix of size L × L. Can be determined by a vector.

In the antenna selection scheme, the optimal transmission beamforming vector may be regarded as a vector in which interference amount information in Equation 3 is minimized.

Therefore, optimal transmission beamforming vector according to antenna selection technique

Figure 112012052286617-pat00074
If is determined as one column vector in the identity matrix, the index of the column vector can be determined according to Equation 4 below.

&Quot; (4) "

Figure 112012052286617-pat00075

here,

Figure 112012052286617-pat00076
Is the index of the column vector whose size is determined as the transmission beamforming vector among the identity matrixes of size L × L,
Figure 112012052286617-pat00077
Cross-link channel matrix
Figure 112012052286617-pat00078
Is the l-th column vector of.

In this case, in step 351, the terminal 320 may calculate the interference amount information as shown in Equation 5 below.

&Quot; (5) "

Figure 112012052286617-pat00079

2) Singular Value Decomposition

According to the singular value decomposition technique, the terminal 320 may determine the transmission beamforming vector such that the amount of interference transmitted by the terminal 320 to another cell is minimized.

In the case of using the singular value decomposition technique, the amount of interference transmitted by the terminal 320 to another cell may be expressed as in Equation 6 below.

&Quot; (6) "

Figure 112012052286617-pat00080

here,

Figure 112012052286617-pat00081
Is the amount of interference transmitted by the terminal 320 to another cell when using the singular value decomposition technique,
Figure 112012052286617-pat00082
Can be approximated as Equation 7 below.

&Quot; (7) "

Figure 112012052286617-pat00083

here,

Figure 112012052286617-pat00084
May be singular value decomposition (SVD) as shown in Equation 8.

&Quot; (8) "

Figure 112012052286617-pat00085

here,

Figure 112012052286617-pat00086
The
Figure 112012052286617-pat00087
As left singular vectors of,
Figure 112012052286617-pat00088
Has the property of Also,
Figure 112012052286617-pat00089
The
Figure 112012052286617-pat00090
As right singular vectors
Figure 112012052286617-pat00091
Has the property of

Figure 112012052286617-pat00092
The
Figure 112012052286617-pat00093
Figure 112012052286617-pat00094
Has phosphorus properties,
Figure 112012052286617-pat00095
Heard
Figure 112012052286617-pat00096
Eigen values of,
Figure 112012052286617-pat00097
to be.

In this case, in step 350, the terminal 320 determines the optimal transmission beamforming vector in the case of using the singular value decomposition technique.

Figure 112012052286617-pat00098
It can be determined as shown in Equation 9.

&Quot; (9) "

Figure 112012052286617-pat00099

here,

Figure 112012052286617-pat00100
The
Figure 112012052286617-pat00101
Idiosyncratic vector
Figure 112012052286617-pat00102
L-th column vector.

In this case, in step 351, the terminal 320 may determine the information on the amount of interference as shown in Equation 10 below.

[Equation 10]

Figure 112012052286617-pat00103

here,

Figure 112012052286617-pat00104
Is information on the amount of interference when singular value decomposition is used.
Figure 112012052286617-pat00105
The
Figure 112012052286617-pat00106
Is the smallest of the eigenvalues

3) Vector Quantization Technique

According to the vector quantization technique, in step 350, the terminal 320 may determine any one column vector among the plurality of column vectors included in the predetermined codebook matrix as the transmission beam vector.

The codebook matrix may be determined as in Equation 11 below.

[Equation 11]

Figure 112012052286617-pat00107

here,

Figure 112012052286617-pat00108
Is the number of column vectors in the codebook matrix,
Figure 112012052286617-pat00109
to be.
Figure 112012052286617-pat00110
To classify the transmission beam vector determined from among the column vectors,
Figure 112012052286617-pat00111
Bits are required.

&Quot; (12) "

Figure 112012052286617-pat00112

Here, according to the vector quantization technique, in step 350, the terminal 320 may determine the transmission beamforming vector such that the amount of interference transmitted by the terminal 320 to another cell is minimized as shown in Equation 13 below.

&Quot; (13) "

Figure 112012052286617-pat00113

here,

Figure 112012052286617-pat00114
Is the optimal transmission beamforming vector when vector quantization is applied.

If the codebook is big enough,

Figure 112012052286617-pat00115
Of equation (9)
Figure 112012052286617-pat00116
Close to In this case, Equation 13 may be expressed as Equation 14 below.

&Quot; (14) "

Figure 112012052286617-pat00117

In this case, in step 351, the terminal 320 may generate information about the amount of interference as shown in Equation 15 below.

&Quot; (15) "

Figure 112012052286617-pat00118

In step 360, the base station 310 selects a data transmission terminal among the terminals based on the information on the amount of interference received from each terminal. According to one side, the base station can select only the terminals having a small amount of interference transmitted by each terminal to the base station belonging to the other cell as the data transmission terminal. Hereinafter, it is assumed that the terminal 320 is selected as the data transmission terminal.

In step 361, the base station 310 informs the terminals selected as the data transmission terminal that the data transmission terminal has been selected.

In step 370, the data transmission terminal transmits data to the base station 310. According to one side, the data transmission terminal may perform transmission beamforming on data using the transmission beamforming vector, and transmit the transmission beamformed data to the base station 310.

In step 380, the base station 310 receives the transmit beamformed data using the plurality of data receive antennas. The signal received by the base station 310 may be represented by Equation 16 below.

&Quot; (16) "

Figure 112012052286617-pat00119

here,

Figure 112012052286617-pat00120
Denotes a signal received by the i-th base station.

Also,

Figure 112012052286617-pat00121
Is a signal transmitted by the data transmission terminals included in the i-th cell, and is a signal desired by the base station. But,
Figure 112012052286617-pat00122
Is a signal transmitted by data transmission terminals included in another cell, and is inter-cell interference. And,
Figure 112012052286617-pat00123
Is a complex Gaussian noise whose mean is zero and whose variance is determined by SNR.

According to one side, the base station 310 is a received signal

Figure 112012052286617-pat00124
To eliminate intercell interference in
Figure 112012052286617-pat00125
Receive beamforming may be performed using, and decoding may be performed using a zero forcing (ZF) equalizer. Receive beamforming is performed, and the received signal to which the ZF equalizer is applied can be represented by Equation 17 below.

[Equation 17]

Figure 112012052286617-pat00126

here,

Figure 112012052286617-pat00127
Is the received signal with equalizer applied,
Figure 112012052286617-pat00128
Is a matrix having tap coefficients of a ZF equalizer as an element, and can be expressed by Equation 18 below.

&Quot; (18) "

Figure 112012052286617-pat00129

Referring to Equation 18, in order for the base station 310 to decode the received signal using the ZF equalizer, the transmission beamforming vector used by the j-th data transmission terminal included in the i-th cell

Figure 112012052286617-pat00130
You should know

In this case, base station 310 is a transmit beamforming vector.

Figure 112012052286617-pat00131
May be received from the terminal 310.

Fig. 4 is a flowchart illustrating a step-by-step method of receiving data according to an exemplary embodiment.

In step 410, the base station transmits a pilot signal to a plurality of terminals. According to one side, the pilot signal may be used to estimate the channel state between the base station and the terminals.

In step 420, the base station receives information on the channel state between the base station and the terminals from the plurality of terminals. Here, the base station may include a plurality of data reception antennas, and each terminal may include a plurality of data transmission antennas. In this case, the channel between the base station and each terminal may be represented by a channel state matrix.

In step 430, the base station generates an interference spatial matrix for the channel between the base station and the terminals. The base station also generates a null space matrix for the channel between the base station and the terminals. Here, the column vectors included in the null spatial matrix may be orthogonal to each other with the column vectors included in the interference spatial matrix.

According to one side, the base station may generate an interference space matrix and a null space matrix using any singular matrix. For example, at step 430, the base station may set up a random singular matrix of size M × M. M is the number of data reception antennas provided in the base station. The base station may generate the interference spatial matrix by selecting the left M-S column vectors in an arbitrary singular matrix or by selecting the right M-S column vectors. In addition, the base station may generate a null spatial matrix with the remaining S column vectors not selected as the interference spatial matrix in any singular matrix.

In step 440, the base station transmits a null space matrix to the terminals.

The terminals generate information on the amount of interference based on the null space matrix. Here, the information on the amount of interference is information on the amount of interference that each terminal transmits to another base station. According to one side, each terminal determines the transmission beamforming vector for each terminal to transmit data to the base station, and when the data is transmitted to the base station using the determined transmission beamforming vector, the terminal of the interference to be transmitted to other base stations Information about the amount can be determined as the amount of interference.

According to one side, each terminal can determine the transmission beamforming vector based on the channel state and the null space matrix between different cells from each terminal. Methods of determining the transmission beamforming vector include 1) an antenna selection technique, 2) a specific value decomposition technique, and 3) a vector quantization technique. The above descriptions are described in detail above, and thus a detailed description thereof will be omitted.

In step 450, the base station receives information on the amount of interference from each terminal.

In step 460, the base station selects a data transmission terminal among the terminals. According to one side, the base station may select a terminal with less interference among the terminals as a data transmission terminal.

In step 470, the base station receives data from data transmission terminals. According to one side, the data received by the base station may be data beam-forming by the data transmission terminal using the transmission beamforming vector. According to one side, the base station may perform receive beam forming on the data transmitted by using the plurality of data receiving antennas. According to one side, the base station may receive data using a null spatial matrix as a reception beamforming vector.

In step 480 the base station decodes the received data. According to one side, the base station may perform equalization on the received data. In this case, the base station may perform equalization using the transmission beamforming vector used by the terminal to transmit data.

Fig. 5 is a flowchart illustrating a step-by-step method of transmitting data according to an exemplary embodiment.

In step 510, the terminal receives a pilot signal from the base station. According to one side, the terminal may estimate the channel state between the terminal and the base station using the pilot signal. If the base station has a plurality of data reception antennas and the terminal has a plurality of data transmission antennas, the estimated channel state may be represented by a channel state matrix.

In step 520, the terminal transmits information about the channel state to the base station.

In step 530, the terminal receives a null space matrix from the base station.

In step 540, the terminal generates information on the amount of interference using the null space matrix. Here, the information on the amount of interference is information on the amount of interference that the terminal transmits to another base station adjacent to the base station. According to one side, the terminal may generate information about the amount of interference using the transmission beamforming vector. Methods of determining the transmission beamforming vector include 1) an antenna selection technique, 2) a specific value decomposition technique, and 3) a vector quantization technique. The above descriptions are described in detail above, and thus a detailed description thereof will be omitted.

In step 550, the terminal transmits information on the amount of interference to the base station. The base station may receive information on the amount of interference of each terminal from a plurality of terminals, and may select a data transmission terminal among the plurality of terminals based on the received information on the amount of interference. In this case, the base station can select the terminal with less interference as the data transmission terminal.

According to one side, in step 550, the terminal may compare the information on the amount of interference with a predetermined threshold, and transmit the information on the amount of interference to the base station according to the comparison result. For example, the terminal may transmit information on the amount of interference to the base station only when the information on the amount of interference is greater than a threshold. In this case, since the signaling overhead from the terminal to the base station is reduced, the radio channel between the terminal and the base station can be used more efficiently.

In step 560, the terminal selected as the data transmission terminal may transmit data to the base station. According to one side, the terminal may transmit the data beamforming using the transmission beamforming vector, and transmit the transmission beamformed data to the base station.

The base station may receive the transmission beamformed data and perform equalization on the received data. In this case, the base station may perform equalization using the transmission beamforming vector used by the terminal. In this case, the terminal may transmit a transmission beamforming vector to the base station in step 570.

Fig. 6 is a block diagram showing the structure of a base station according to an exemplary embodiment. The base station 600 according to an exemplary embodiment includes a channel state information receiver 610, an interference spatial matrix generator 620, a transmitter 630, an interference amount information receiver 640, a controller 650, and a data receiver 660. ) And a decoding unit 670.

The base station 600 transmits a pilot signal to the plurality of terminals 681 and 682. According to one side, the pilot signal may be used to estimate the channel state between the base station 600 and the terminals (681, 682).

The channel state information receiver 610 receives information about a channel state between the base station 600 and the terminals 681 and 682 from the plurality of terminals 681 and 682. Here, the base station 600 may include a plurality of data reception antennas, and each terminal 681 and 682 may include a plurality of data transmission antennas. In this case, the channel between the base station 600 and each of the terminals 681 and 682 may be represented by a channel state matrix.

The interference space matrix generator 620 generates an interference space matrix for a channel between the base station 600 and the terminals 681 and 682. In addition, the interference space matrix generator 620 generates a null space matrix for a channel between the base station 600 and the terminals 681 and 682. Here, the column vectors included in the null spatial matrix may be orthogonal to each other with the column vectors included in the interference spatial matrix.

According to one side, the interference space matrix generator 620 may generate an interference space matrix and a null space matrix using an arbitrary singular matrix. For example, the interference spatial matrix generator 620 may set an arbitrary singular matrix of M × M size. M is the number of data receiving antennas provided in the base station 600. The interference space matrix generator 620 may generate an interference space matrix by selecting M-S column vectors on the left side or M-S column vectors on the right side in an arbitrary singular matrix. In addition, the interference spatial matrix generator 620 may generate a null spatial matrix using the remaining S column vectors that are not selected as the interference spatial matrix in any singular matrix.

The transmitter 630 transmits a null space matrix to the terminals 681 and 682.

The terminals 681 and 682 generate information on the amount of interference based on the null space matrix. Here, the information on the amount of interference is information on the amount of interference that each terminal (681, 682) transmits to the other base station. According to one side, each terminal (681, 682) determines the transmission beam forming vector for each terminal (681, 682) to transmit data to the base station 600, the base station 600 by using the determined transmission beam forming vector In the case of transmitting data using the information, information on the amount of interference to be transmitted to other base stations may be determined as the amount of interference.

According to one side, each terminal (681, 682) can determine the transmission beamforming vector based on the channel state and the null space matrix between the different cells from each terminal (681, 682). Methods of determining the transmission beamforming vector include 1) an antenna selection technique, 2) a specific value decomposition technique, and 3) a vector quantization technique. The above descriptions are described in detail above, and thus a detailed description thereof will be omitted.

The interference amount information receiving unit 640 receives information on the amount of interference from the terminals 681 and 682.

The controller 650 selects a data transmission terminal from the terminals 681 and 682. According to one side, the controller 650 may select the terminal 681 having a low interference amount among the terminals 681 and 682 as a data transmission terminal. Hereinafter, it is assumed that the terminal 681 is selected as the data transmission terminal.

The data receiver 660 receives data from the data transmission terminal 681. According to one side, the data received by the data receiver 660 may be data beam-formed by the data transmission terminal 681 using the transmission beamforming vector. According to one side, the data receiver 660 may perform receive beamforming on the data transmitted using the plurality of data receive antennas. According to one side, the data receiver 660 may receive data using a null spatial matrix as a reception beamforming vector.

The decoding unit 670 decodes the received data. According to one side, the decoding unit 670 may perform equalization on the received data. In this case, the decoding unit 670 may perform equalization using the transmission beamforming vector used by the data transmission terminal 681 to transmit data.

Fig. 7 is a block diagram showing the structure of a terminal according to an exemplary embodiment. The terminal 700 according to an exemplary embodiment includes a pilot receiver 710, a channel state information transmitter 720, a null space matrix receiver 730, an interference amount information generator 740, an interference amount information transmitter 750, and It includes a data transmission unit 760.

The pilot receiver 710 receives a pilot signal from the base station 780. According to one side, the base station 780 is provided with a plurality of data receiving antennas (781, 782, 783, 784), and transmits a pilot signal using the plurality of data receiving antennas (781, 782, 783, 784) Can be. In this case, the terminal 700 may include a plurality of data transmission antennas and receive pilot signals using the plurality of data transmission antennas.

The pilot receiver 710 may estimate the channel state between the terminal and the base station using the pilot signal. If the base station has a plurality of data reception antennas and the terminal has a plurality of data transmission antennas, the estimated channel state may be represented by a channel state matrix.

The channel state information transmitter 720 transmits information about the channel state to the base station 780.

The null space matrix receiver 730 receives a null space matrix from the base station.

The interference amount information generator 740 generates information on the amount of interference using a null spatial matrix. Here, the information on the amount of interference is information on the amount of interference that the terminal 700 transmits to another base station adjacent to the base station 780. According to one side, the terminal 700 may generate information on the amount of interference using the transmission beamforming vector. Methods of determining the transmission beamforming vector include 1) an antenna selection technique, 2) a specific value decomposition technique, and 3) a vector quantization technique. The above descriptions are described in detail above, and thus a detailed description thereof will be omitted.

The interference amount information transmitter 750 transmits information on the amount of interference to the base station. The base station 780 may receive information on the amount of interference of each terminal from the plurality of terminals, and may select a data transmission terminal among the plurality of terminals based on the received information about the amount of interference. In this case, the base station can select the terminal with less interference as the data transmission terminal.

According to one side, the interference amount information transmitter 750 may compare the information on the interference amount with a predetermined threshold, and transmit the information on the interference amount to the base station 780 according to the comparison result. For example, the interference amount information transmitter 750 may transmit the information about the interference amount to the base station 780 only when the information about the interference amount is greater than the threshold. In this case, since the signaling overhead from the terminal 700 to the base station 780 is reduced, it is possible to more efficiently use the radio channel between the terminal 700 and the base station 780.

The data transmitter 760 may transmit data to the base station 780. According to one side, the data transmission unit 760 may transmit the data beam-forming using the transmission beamforming vector, and transmit the transmission beam-formed data to the base station 780.

The base station 780 may receive the transmission beamformed data and perform equalization on the received data. In this case, the base station 780 may perform equalization using the transmission beamforming vector used by the terminal. In this case, the data transmitter 760 may transmit the transmission beamforming vector to the base station 780.

The methods according to embodiments of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

600: base station
610: channel state information receiving unit
620: interference spatial matrix generator
630: transmission unit
640: interference amount information receiving unit
650: control unit
660: a data receiving unit
670: decoding unit
681, 682: terminal

Claims (29)

Receiving information on a channel state between the base station and the terminals from a plurality of terminals;
Generating an interference spatial matrix based on the information about the channel state;
Transmitting a null spatial matrix of the interference spatial matrix to the terminals;
Receiving information about the amount of interference transmitted from the terminals to another cell adjacent to the base station, generated based on the null space matrix;
Selecting a data transmission terminal among the terminals based on the information on the interference amount;
Receiving data from the selected data transmission terminal
Data reception method of the base station comprising a. The method of claim 1,
Transmitting a pilot signal to the terminals
Further comprising:
And the channel state is generated based on the pilot signal. The method of claim 1,
The receiving of the data may include receiving beamformed data using a transmission beamforming vector from the terminal,
Decoding the received data using the transmit beamforming vector
Data receiving method of the base station further comprising. The method of claim 1,
The generating of the interference spatial matrix may be performed by selecting column vectors located on the left or right side of a singular matrix to generate the interference spatial matrix.
The null space matrix is a data receiving method of the base station is generated with the remaining column vectors not selected as an interference spatial matrix in the arbitrary singular matrix. The method of claim 3,
And the receiving step comprises receiving the data using the null spatial matrix as a reception beamforming vector. The method of claim 1,
And the transmission beam vector is determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal. Transmitting information about a channel state between a base station and a terminal to the base station;
Receiving a null space matrix generated from the base station based on the channel state information;
Generating information on an amount of interference transmitted from the terminal to another cell adjacent to the base station based on the null space matrix;
Transmitting information on the amount of interference to the base station;
Transmitting data to the base station based on the amount of interference
Data transmission method of the terminal comprising a. The method of claim 7, wherein
Receiving a pilot signal from the base station
Further comprising:
The channel state is generated based on the pilot signal. The method of claim 7, wherein
The transmitting of the information on the amount of interference may include comparing the amount of interference with a predetermined threshold, and transmitting the information on the amount of interference to the base station when the information on the amount of interference is greater than the predetermined threshold. Transmission method. The method of claim 7, wherein
The transmitting of the data may include transmitting the data using only one of a plurality of data transmission antennas. The method of claim 7, wherein
The transmitting of the data may include transmitting data beam-formed using a transmission beam vector. 12. The method of claim 11,
The transmission beam vector is determined according to the channel state between the null space matrix and another cell adjacent to the base station from the terminal. The method of claim 12,
The transmission beam vector is determined by singular value decomposition (SVD) of a product between a Hermitian matrix of the null space matrix and a matrix including a channel state between another cell adjacent to the base station from the terminal. Data transfer method. 12. The method of claim 11,
The transmission beam vector is selected from among a plurality of column vectors of a pre-determined codebook matrix. A channel state information receiver configured to receive information on a channel state between the base station and the terminals from a plurality of terminals;
An interference space matrix generator for generating an interference space matrix based on the information on the channel state;
A transmitter for transmitting a null spatial matrix of the interference spatial matrix to the terminals;
The receiver comprises an interference amount information receiver for receiving information on the amount of interference transmitted by the terminal to another cell adjacent to the base station, generated based on the null space matrix from the terminals;
A controller for selecting a data transmission terminal among the terminals based on the information on the interference amount; And
Data receiving unit for receiving data from the selected data transmission terminal
/ RTI > 16. The method of claim 15,
The transmitter transmits a pilot signal to the terminals,
The channel state is generated based on the pilot signal. 16. The method of claim 15,
The data receiver receives the beamformed data from the terminal using a transmission beamforming vector,
A decoding unit for decoding the received data using the transmission beamforming vector
And a base station. 18. The method of claim 17,
And the data receiving unit receives the data using the null spatial matrix as a reception beamforming vector. 16. The method of claim 15,
The interference space generator generates the interference space matrix by selecting column vectors located on the left or right side of an arbitrary singular matrix,
And the null space matrix is generated with remaining column vectors not selected as interference spaces in the arbitrary singular matrix. 16. The method of claim 15,
The transmit beam vector is determined according to the channel state between the null space matrix and another cell adjacent to the base station from the terminal. A channel state information transmitter for transmitting information about a channel state between a base station and a terminal to the base station;
A null space matrix receiver for receiving a null space matrix generated based on the channel state information from the base station;
An interference amount information generation unit generating information on the amount of interference transmitted from the terminal to another cell adjacent to the base station based on the null space matrix;
An interference amount information transmitter for transmitting the information on the interference amount to the base station; And
A data transmitter for transmitting data to the base station based on the interference amount
Lt; / RTI > The method of claim 21,
Pilot receiver for receiving a pilot signal from the base station
Further comprising:
The channel state is generated based on the pilot signal. The method of claim 21,
The interference amount information transmitting unit compares the information on the amount of interference with a predetermined threshold, and transmits the information on the amount of interference to the base station when the information on the amount of interference is greater than the predetermined threshold. The method of claim 21,
The data transmitter is a terminal for transmitting the data by only one of a plurality of data transmission antennas. The method of claim 21,
The data transmitter is a terminal for transmitting beamformed data using a transmission beam vector. 26. The method of claim 25,
The transmit beam vector is determined according to a channel state between the null space matrix and another cell adjacent to the base station from the terminal. The method of claim 26,
The transmission beam vector is determined by singular value decomposition (SVD) of a product between a Hermitian matrix of the null space matrix and a matrix including a channel state between another cell adjacent to the base station from the terminal. 26. The method of claim 25,
The transmission beam vector is selected from among a plurality of column vectors of a pre-determined codebook matrix. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 14.
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