KR20140083691A - Wireless communication system and method for allocating precoding matrix in the same - Google Patents

Abstract

Disclosed are a wireless communications system and a method for allocating a precoding matrix in the same. The wireless communications system comprises: a digital signal processing device which is connected to a core system and processes a wireless digital signal; and multiple wireless signal processing devices which are physically separated from the digital signal processing device, converts and amplifies the digital signal received from the digital signal processing device, transmits the amplified signal to a terminal based on multi-antenna technology using two antennas, receives the signal transmitted from the terminal based on the multi-antenna technology using two antennas, and transmits the received signal to the digital signal processing device. When two wireless signal processing devices of the wireless signal processing devices are paired to perform quad antenna transmission, the digital signal processing device allocates, to the two wireless signal processing devices, a precoding matrix for transmitting only data transmitted from the wireless signal processing device adjacent to the terminal, to the terminal positioned in a place which is not a boundary region between the two wireless signal processing device within the coverage of the two wireless signal processing devices.

Description

[0001] WIRELESS COMMUNICATION SYSTEM AND METHOD FOR ALLOCATING PRECORDING MATRIX IN THE SYSTEM [0002]

The present invention relates to a wireless communication system and a precoding matrix allocation method in the system.

2. Description of the Related Art Generally, a base station in a wireless communication system includes a digital signal processor (Digital) (hereinafter referred to as "DU") that performs a baseband function and a radio signal processor (hereinafter referred to as "RU Quot;). ≪ / RTI >

A typical base station is implemented with both DU and RU in the center of cell coverage, but recently, DU and RU have been separated and optical cable has been connected between the two. In this case, the RU is located at the center of the cell coverage, the DU can be installed at a remote location, the DUs forming a plurality of cells can be collected and installed in the same place, and an X2 interface can be secured to enable communication between DUs. Furthermore, by setting a plurality of DUs to be managed by one virtualization server, inter-cell interference control in the cell boundary region and cooperative transmission between the base stations become possible.

The base station implemented by virtualization allocates the same physical cell identifier (hereinafter, referred to as "PCI") to a plurality of RUs. A plurality of cell coverage formed by a plurality of RUs using the same PCI form a single large cell coverage.

In addition, using virtualization technology, two RUs with the same PCI can be paired. Assuming that each RU has two transmit antennas, it is possible to use four transmit antennas if two paired RUs act as if they were one RU. Such RU virtualization technology is called Quad Antenna Transmission.

On the other hand, two RUs paired for quad antenna transmission constitute one cell coverage. In other words, since the two RUs operate as one base station, the cell capacity is reduced compared to the case where the two RUs operate as different base stations and reuse the same frequency resources. In order to increase the cell capacity thus reduced, a multi-user multiple input multiple output (MU-MIMO) technique is used.

When MU-MIMO transmission is performed on two UEs with relatively low correlation and relatively far apart within the cell coverage of two RUs paired for the quad antenna transmission, It is difficult to separate the downlink signals transmitted to the respective terminals in the MIMO decoding and it is difficult to relieve the result even if the downlink signals are separated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless communication system capable of applying variable precoding according to a location of a terminal while using a conventional codebook set, and a precoding matrix allocation method in the system.

A wireless communication system according to an aspect of the present invention includes:

A digital signal processing device connected to the core system for processing a wireless digital signal; And converting the digital signal received from the digital signal processor into a digital signal and transmitting the amplified signal to the terminal based on a multi-antenna technique using two antennas, A plurality of radio signal processing apparatuses for receiving a signal transmitted from a terminal and transmitting the signal to the digital signal processing apparatus based on a multi-antenna technique using a plurality of antennas, The digital signal processing apparatus may transmit the quad-antenna transmission to the wireless signal processing apparatuses adjacent to the terminal in the coverage of the two wireless signal processing apparatuses, Lt; RTI ID = 0.0 > A precoding matrix such that characterized in that allocated to the two wireless signal processor.

Here, the precoding matrix includes a sub-matrix composed of some of the matrix elements of one precoding matrix (W) among a plurality of precoding matrices set in the codebook for transmission of the quad antenna, A sub-matrix is a unitary sub-matrix.

(여기서, W^H는 상기 프리코딩 매트릭스(W)의 허미션 매트릭스(Hermitian matrix)이고, M은 데이터 스트림의 개수임)을 따르는 것을 특징으로 한다.Further, the unitary submatrix (W ') satisfies the following relation

(Where W ^H is a Hermitian matrix of the precoding matrix W and M is a number of data streams).

(여기서, A는 안테나 선택을 위한 매트릭스이고, 연산자 o는 두 매트릭스간 하다마드 프로덕트(Hadamard product)를 의미하며, α는 선택적인 안테나 사용으로 전체 송신파워가 감소하는 것을 보상해주거나 송신파워를 조절하기 위한 상수 값임)을 따르는 것을 특징으로 한다.Further, the unitary submatrix (W ') satisfies the following relation

(Where A is the matrix for antenna selection, o is the inter-matrix Hadamard product, α is the selective antenna used to compensate for the reduction of the overall transmit power, And a constant value for the following.

중에서 상기 단말의 위치에 의해 결정되는 것을 특징으로 한다.The matrix (A)

Which is determined by the location of the terminal.

인 경우, 상기 유니터리 서브매트릭스(W')는,

중에서 상기 안테나 선택을 위한 매트릭스(A)에 의해 결정되는 것을 특징으로 한다.Also, if the precoding matrix W is

, The unitary sub-matrix W '

(A) for the antenna selection.

In addition, when the terminal is located within the coverage of any one of the wireless signal processing apparatuses other than the boundary region between the two wireless signal processing apparatuses, the digital signal processing apparatus may include a CRS AP mapped to the two wireless signal processing apparatuses depending on the information and the sub-unitary matrix W ', and W _{11' 12} or W ', and W _{21' 22} characterized in that allocated to the two wireless signal processing apparatus as a pre-coding matrix.

When the terminal is located in a boundary area between the two radio signal processing apparatuses, the digital signal processing apparatus may transmit the unitary submatrices W _'31 and W' ₃₁ according to the CRS AP information mapped to the two radio signal processing apparatuses. W _'32 or W' ₄₁ and W _'42 as a precoding matrix to the two radio signal processing apparatuses.

The digital signal processing apparatus may further include: a resource allocation unit allocating resources to the two radio signal processing apparatuses, wherein the resources include CRS AP information mapped to the two radio signal processing apparatuses; A position determiner for determining a position of the terminal; A mapping analyzer for analyzing CRS AP information mapped to the two radio signal processing devices by the resource allocator; A submatrix storage unit for storing the unitary submatrix information; And selecting a unitary submatrix among the unitary submatrices stored in the submatrix storage unit based on the position of the terminal determined by the position determination unit and the CRS AP information analyzed by the mapping analysis unit And a matrix allocating unit for allocating the signals to the two radio signal processing apparatuses.

If it is determined by the location determination unit that the terminal is located in a coverage area adjacent to one wireless signal processing apparatus rather than in a boundary area between the two wireless signal processing apparatuses, And a unitary sub-matrix for transmitting data only in the antenna corresponding to the CRS AP mapped to the processing apparatus is selected.

According to another aspect of the present invention, there is provided a method of allocating precoding matrices,

A method for allocating a precoding matrix to a plurality of wireless signal processing apparatuses installed in a service area for processing wireless signals, the method comprising the steps of: Mapping each CRS AP to two radio signal processing apparatuses performing antenna transmission; Determining a location of the terminal; When it is determined that the mobile station is located in a coverage area of the two radio signal processing apparatuses, the two radio signal processing apparatuses transmit data using only the CRS APs mapped to the two radio signal processing apparatuses And assigning a precoding matrix to the two radio signal processing apparatuses.

In the allocating step, it is determined whether the terminal is located in the boundary area. Determining a CRS AP mapped to an adjacent radio signal processor if the terminal is determined not to be located in the border area; And a unitary submatrix for transmitting data only to the APs 0 and 1 when the UE is mapped to the CRS APs 0 and 1 to the adjacent radio signal processor, Which is a unitary matrix among sub-matrices consisting of some of the matrix elements of one precoding matrix (W) among a plurality of precoding matrices set in the codebook for the wireless signal processing apparatus And allocating a unitary sub-matrix to other radio signal processing apparatuses such that only CRS 2 and 3 transmit data.

In the step of determining the mapped CRS AP, when the UE is mapped to the CRS APs 0 and 2 to the adjacent radio signal processor, only the APs 0 and 2 transmit the data, Allocating a matrix to a wireless signal processing apparatus adjacent to the terminal and allocating a unit submatrix to another wireless signal processing apparatus so that only CRS 1 and 3 transmit data.

Determining a matrix for selecting a corresponding antenna according to a CRS AP mapped to the two wireless signal processing apparatuses; Determining the unitary submatrix using a matrix for selecting the determined antenna; And assigning the determined unit sub-matrices to the two radio signal processing apparatuses, respectively.

In addition, an index is assigned to a matrix for selecting the antenna, and the index is transmitted to the terminal in addition to the control information.

Determining a mapped CRS AP for the two wireless signal processing devices when it is determined that the terminal is located in the border area; And a unit submatrix for allowing the two wireless signal processing apparatuses to transmit different data streams through a CRS AP mapped to the two wireless signal processing apparatuses when the two wireless signal processing apparatuses transmit the two data streams, To the signal processing apparatuses.

According to the present invention, it is possible to apply variable precoding according to the position of the terminal while using a conventional set of codebooks.

Therefore, scheduling a plurality of UEs to the same frequency resource by applying a variable precoding scheme can have the same effect as MU-MIMO.

In addition, each RU that is paired in the quad antenna transmission method exists in its own coverage, and independent downlink data transmission is possible by reusing the same frequency resources to terminals physically far apart.

Therefore, the performance of the radio communication is improved because there is no correlation between terminals physically distant from each other.

1 is a diagram schematically illustrating a general quad antenna transmission method through a paired RU.
2 is a diagram illustrating an example of an LTE MIMO codebook set.
3 is a diagram illustrating an embodiment in which a unitary submatrix is used according to an embodiment of the present invention.
4 is a schematic configuration diagram of a network according to an embodiment of the present invention.
5 is a specific configuration block diagram of DU shown in FIG.
6 is a flowchart of a pre-coding matrix allocation method 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, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise. Also, the terms " part, "" module," and " module ", etc. in the specification mean a unit for processing at least one function or operation and may be implemented by hardware or software or a combination of hardware and software have.

In this specification, a terminal includes a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user equipment , An access terminal (UE), an access terminal (AT), and the like, and may include all or some functions of a terminal, a mobile terminal, a subscriber station, a mobile subscriber station, a user equipment,

In this specification, a base station (BS) includes an access point (AP), a radio access station (RAS), a node B, an evolved NodeB (eNodeB) A base station (BTS), a mobile multihop relay (MMR) -BS, or the like, and may perform all or a part of functions of an access point, a radio access station, a Node B, an eNodeB, a base transceiver station, .

First, a general quad antenna transmission method through a paired RU will be described with reference to FIG.

1 is a diagram schematically illustrating a general quad antenna transmission method through a paired RU.

Referring to FIG. 1, RUs 21 and 23 are located at the center of two cells 11 and 13, respectively. These RUs 21 and 23 are paired with each other and located in two cells 11 and 13 And provides a quad antenna transmission service to the terminals 31, 33, and 35.

In this quad antenna transmission method, each of the RUs 21 and 23 has two physical antennas, and each physical antenna must be mapped to a common reference signal (CRS) AP (Antenna Port). For example, AP 0 is mapped to the first antenna 41 of the RU 1 21, AP 1 is mapped to the second antenna 42, AP 2 is mapped to the first antenna 43 of the RU 2 23, AP 3 may be mapped to the second antenna 44.

Therefore, the terminals 31, 33, and 35 within the cell coverage formed by the RU1 21 and the RU2 23 receive the four transmit antennas 41, 42, 43, and 44 from the RU1 21 and the RU2 23, respectively. The downlink signal is received.

However, since the terminal 33 is located in the border area between the RUs 21 and 23, all the AP signal strengths are similarly received. However, in the case of the terminal 31, the terminal 33 is adjacent to the RU 21, , AP 0 and 1 signals are received relatively strongly and AP 2 and 3 signals are received relatively weakly.

On the contrary, in the case of the terminal 35, AP 2 and AP 3 signals are relatively strongly received and AP 0 and AP 1 signals are relatively strong because AP 3 is adjacent to RU 2 23 but relatively far away from RU 1 21 .

In the case of terminals 31 and 35 as described above, even when transmission with orthogonality between data streams is possible, since the difference in receiving power between signals transmitted by the respective APs is large, it is difficult to separate the data streams in MIMO decoding. There arises a problem that it is not sufficiently obtained.

Hereinafter, embodiments of the present invention for solving the above problems will be described.

(4 Tx, Rank 2) codebook set among the Long Term Evolution (LTE) MIMO codebook sets is used because the number of receiving antennas of the UE is two and four transmitting antennas are used for the quad antenna transmission. An example of such a codebook set is shown in FIG. The codebook set shown in FIG. 2 is a set of codebooks when the number of transmit antennas is 4, and the MIMO rank is 1, 2, 3, and 4. For each MIMO rank, the codebook set is composed of 16 precoding matrices, and each precoding matrix has a codebook index (n) from 0 to 15 times. In order to use the precoding matrix having the codebook index n, first, a matrix W _n is calculated from u _n by using the following equation (1).

[Equation 1]

Since the W _n matrix is composed of a 4- _ary vector, the precoding matrix W selects and uses a column vector of the MIMO rank in the W _n matrix. As shown in FIG. 2, a column vector corresponding to a predetermined column vector index is selected from W _n and used as a column vector of the precoding matrix W. For example, if n = 0 and the MIMO rank is 2, first calculate W ₀ from u ₀ . Next, the first and fourth column vectors of W ₀ are selected and the column vectors of the precoding matrix W are used in the selected order.

On the other hand, the precoding matrices included in the codebook set shown in FIG. 2 are all unitary matrices.

The precoding matrix W of a set of (4 Tx, Rank 2) codebooks in the codebook set shown in FIG. 2 can be generalized and expressed as Equation (2).

&Quot; (2) "

Since the precoding matrix W is a unitary matrix, it satisfies W ^H W = I. By precoding the plurality of data streams using the precoding matrix W, the data streams are separated by spatial multiplexing or MIMO decoding.

In the embodiment of the present invention, among submatrices of the precoding matrix W, a submatrix W 'that satisfies the following formula (3) is defined as a unitary submatrix.

&Quot; (3) "

Here, W ^H is a Hermitian matrix of the precoding matrix W, and M is the number of data streams.

The RUs 21 and 23 perform precoding using the properties of the unitary submatrix, and the UE can perform MIMO decoding using a precoding matrix W as in the prior art.

In configuring the unitary submatrix, if a row vector of W is selected and configured, the RUs 21 and 23 have the same effect as selecting an antenna to be used for downlink transmission.

Two examples of the unitary submatrices are shown in Equation (4).

&Quot; (4) "

Here, α is a constant value for adjusting the transmission power while compensating for the decrease of the total transmission power due to the use of the selective antenna.

The RU1 (21) and RU2 (23) in Figure 1, when the unitary sub-matrix W 'using ₁₁ pre-coding is to transmit data signals using only 1 and AP 0 time only as a result, RU1 (21) And participate in data transmission.

On the contrary, if precoding is performed using the unitary submatrix W _'12 , the data signals are transmitted using only the APs 2 and 3, and as a result, only the RU2 23 participates in the data transmission.

At this time, the terminals 31 and 35 can perform MIMO decoding using the precoding matrix W as in the conventional art using the properties of the unitary submatrix.

Meanwhile, the following equation (5) shows a method of constructing the sub-matrix W 'in the precoding matrix W. [

&Quot; (5) "

Where A is a matrix for antenna selection and operator 'o' represents a matrix product between two matrices. A Hadamard product means an inter-element multiplication of two matrices at the same position.

An example of the sub-matrix W ' _xy = αWoA _xy constructed using various antenna selection patterns is shown in the following Equation (6).

&Quot; (6) "

In the above, for all data streams, A ₁₁ selects AP 0 and 1, and A ₁₂ selects AP 2 and 3.

For all data streams, A ₂₁ selects APs 0 and 2, and A ₂₂ selects APs 1 and 3.

A ₃₁ selects AP 0 and 1 for the first data stream and AP 2 and 3 for the second data stream.

A ₃₂ selects AP 2 and 3 for the first data stream and AP 0 and 1 for the second data stream.

A ₄₁ selects AP 0 and 2 for the first data stream and AP 1 and 3 for the second data stream.

A ₄₂ selects AP 1 and 3 for the first data stream and AP 0 and 2 for the second data stream.

On the other hand, in the codebook set shown in Fig. 2, the precoding matrix that can be composed of the unitary submatrix is limited. The following Table 1 shows a codebook index that can be composed of a unitary submatrix according to the antenna selection pattern.

Submatrix Codebook index W _'11 , W' ₁₂ , W _'31 , W' ₃₂ 0, 4, 5, 6, 7, 9, 10, 11, 13, 14 W _'21 , W' ₂₂ , W _'41 , W' ₄₂ 0, 1, 2, 3, 4, 5, 8, 9, 12, 15

Here, the codebook index is a codebook index for the codebook set shown in FIG. 2, and is applied only to the MIMO Rank 2 codebook set.

Hereinafter, a method of using a unitary submatrix will be described. Here, the unitary sub-matrix that is used is _{W '11, W' 12,} W '21, W' is _22.

Among the unitary sub-matrix as described above, _{W '11, W' 12,} W '21, W' 22 is optional, use is possible in accordance with the AP mapping method of pairing a RU1 (21) and RU2 (23) .

If the APs 0 and 1 are allocated to the RU1 21 and the APs 2 and 3 are allocated to the RU2 23, data may be precoded by unitary submatrix W 'downlink data is pre-coded by _11, and transmits to the mobile station 35 existing within the coverage of RU2 (23) is a unitary sub-matrix W' _12.

By assigning the unitary submatrices to the RU1 21 and the RU2 23 as described above, the terminal 31 receives the downlink data from the RU1 21 adjacent to itself and the downlink data from the remote RU2 23 Lt; / RTI > In addition, as shown in Equation (3), since the transmission power is increased by using the alpha value, the reception strength for the downlink data transmitted by the adjacent RU1 21 is further increased.

Likewise, the terminal 35 also receives the downlink data from the RU2 23 adjacent thereto and does not receive the downlink data from the remote RU1 21. Also, as shown in Equation (3), since the transmission power is increased by using the alpha value, the reception strength for the downlink data transmitted by the adjacent RU2 23 is further increased.

When AP # 0 and # 2 are allocated to the RU1 21 and AP # 1 and AP # 3 are allocated to the RU2 23, the terminal 31 existing in the coverage of the RU1 21 downlink data to be transferred is W 'downlink data is pre-coded by _21, and transmits to the mobile station 35 existing within the coverage of RU2 (23) is W' may be precoded to _22.

By doing so, the terminals 31 and 35 which are far from each other receive the downlink data from the RUs 21 and 23 adjacent to the terminals 31 and 35, do not receive the downlink data from the remote RUs 21 and 23, the value of? is used to increase the transmission power, the reception strength for the downlink data transmitted by the adjacent RUs 21 and 23 is further increased.

Therefore, the two terminals 31 and 35, which are located within the cell coverage of the two RUs 21 and 23 but are relatively far away from each other, receive the downlink data only from the adjacent RUs 21 and 23 , There is no need to separate the downlink data, and the reliability of the received downlink data can be improved.

On the other hand, if there is little correlation between the two terminals 31 and 35 located in the coverage of each of the RU1 21 and the RU2 23, the downlink data to be transmitted to the two terminals 31 and 35 are transmitted using the same frequency resource .

At this time, in order to allow the different RUs 21 and 23 to transmit the downlink data to the two terminals 31 and 35 as described above, if W _x1 is used for precoding in order to transmit data of the terminal 31 , W _x2 must be used for precoding in order to transmit data of the terminal 35. [ The opposite is also the case.

Using the above method, each of the RUs 21 and 23 paired in the quad antenna transmission method reuses the same frequency resources to the terminals 31 and 35 existing in its coverage, thereby performing independent downlink data transmission .

3 is a diagram illustrating an embodiment in which a unitary submatrix is used according to an embodiment of the present invention.

3, the terminal 31, that is, UE2 is performed to W 'pre-coded using _11, and the terminal 35, that is UE3, the W' in the precoding using ₁₂ transmits a downlink data signal for example, Respectively.

At this time, the transmission vector x that the RUs 21 and 23 transmit to the terminals 31 and 35 can be expressed by the following equation (7).

&Quot; (7) "

Here, s is a data vector, s _UE2 is a data vector of the terminal UE2 and is composed of data streams of s _{UE2 , 1} and s _UE2,2 , s _UE3 is a data vector of the terminal _{UE3 ,} and s _{UE3, 2} < / RTI > In addition,? 1 is a constant value corresponding to RU1 (21), and? 2 is a constant value corresponding to RU2 (23).

As described above, the RUs 21 and 23 can transmit downlink signals to the two terminals 31 and 35 at the same time using the same frequency resources as in the conventional MU-MIMO transmission.

Further, when compared with the prior art, each of the terminals 31 and 35 receives the downlink data signal only from the neighboring RUs 31 and 35 thereof. Therefore, it is not necessary to separate the data signals transmitted by the terminals 31 and 35 even in the MIMO decoding, and performance can be improved because each of the terminals 31 and 35 receives a relatively strong data signal.

Also, rank 2 MIMO transmission is possible for each of the terminals 31 and 35.

Next, a method of using a unitary sub-matrix different from the above will be described. Here, the unitary submatrices used are W _'31 , W' ₃₂ , W _'41 and W' ₄₂ .

Two RU (21, 23) for the terminals (33) located in the coverage boundary between the unitary sub-matrix _{W '31, W' 32,} W '41, W' 42 is pairing with RU1 (21) and RU2 ( 23) according to the AP mapping method. This is a method of making the two RUs 21 and 23 transmit different data streams to one terminal 33 because the correlation between the physical antennas of the RU1 21 and the RU2 23 is small .

If the APs 0 and 1 are allocated to the RU1 21 and the APs 2 and 3 are allocated to the RU2 23, the coverage boundary between the two RUs 21 and 23, that is, The downlink data signal transmitted from the two RUs 21 and 23 to the terminal 33 can be precoded using W _'31 or W' ₃₂ .

On the contrary, if the APs 0 and 2 are assigned to the RU1 21 and the APs 1 and 3 are assigned to the RU2 23, the terminal located at the coverage edge between the two RUs 21 and 23 33, the downlink data signals transmitted by the two RUs 21, 23 can be precoded using W _'41 or W' ₄₂ .

On the other hand, the unitary sub-matrix _{W '11, W' 12,} W '21, W' using a ₂₂ and a unitary sub-matrix _{W '31, W' 32,} W '41, W' 42 as described above, There is an advantage that the same control information is used as in the conventional method, so that it can be used without changing the operation of the terminal.

Alternatively, in addition to the conventional control information, the unitary sub-matrix information used for antenna selection as described above may be included. To this end, an antenna selection matrix Axy is defined by attaching an index to be used as control information, such as [v 2].

index Axy 0 A ₁₁ One A ₁₂ 2 A ₂₁ 3 A ₂₂ 4 A ₃₁ 5 A ₃₂ 6 A ₄₁ 7 A ₄₂

Therefore, the precoding matrix W is informed to the respective terminals 31, 33, and 35 using the same PMI information as the conventional control channel, and the control information on the antenna selection matrix used for forming the unitary sub- Can be informed by the index defined in.

Hereinafter, a network structure to which an embodiment of the present invention is applied will be described with reference to FIG.

4 is a schematic configuration diagram of a network according to an embodiment of the present invention.

Referring to FIG. 4, a network according to an embodiment of the present invention includes an RU 100, a DU 200, and a core system 300.

The RU 100 converts a digital signal received from the DU 200 as a radio signal processing unit into a radio frequency (RF) signal according to a frequency band and amplifies the digital signal. Then, the signal is transmitted to the terminal through the antenna, and the signal is received from the terminal through the antenna, processed and transmitted to the DU 100.

A plurality of RUs 100, 110, 120, and 130 are connected to the DU 200, and each RU 100 is installed in a service area, that is, a cell. The RU 100 and the DU 200 may be connected by an optical cable.

The DU 200 performs processing such as encryption and decryption of a wireless digital signal and is connected to the core system 300. Unlike the RU 100, the DU 200 is not installed in a service area, but is a server that is mainly installed in a central office of a communication company and is a virtualized base station. The DU 200 transmits and receives signals to and from a plurality of RUs 100.

The existing communication base station includes a processing unit corresponding to each of the RU 100 and the DU 200 in one physical system, and one physical system is installed in the service target area. On the contrary, the system according to the embodiment of the present invention physically separates the RU 100 and the DU 200, and only the RU 100 is installed in the service area.

The core system 300 handles the connection between the DU 200 and the external network, and includes an exchange (not shown) and the like.

The RU 110 may correspond to the RU1 23 shown in FIG. 1 and the RU 120 may correspond to the RU2 23.

5 is a specific configuration block diagram of DU shown in FIG.

5, a DU 200 according to an exemplary embodiment of the present invention includes a transceiver 210, a resource allocator 220, an AP mapping analyzer 230, a submatrix storage 240, A determination unit 250, and a precoding matrix assignment unit 260. [

The transceiver unit 210 receives a resource allocation request from the RUs 110 and 120 and transmits resource information allocated to the RUs 110 and 120 to the RUs 110 and 120. The resource information includes AP mapping information and precoding matrix allocation information for each RU 110 and 120.

The resource allocation unit 220 allocates resources for the RUs 110 and 120 that request resource allocation through the transceiver unit 210. [ Among the allocated resources, AP mapping information for each RU 110 and 120 is included.

The AP mapping analysis unit 230 analyzes AP mapping information for each RU 110 and 120 allocated by the resource allocation unit 220 and determines which APs are mapped by the RUs 110 and 120. For example, it can be confirmed that AP 0 and 1 are mapped to RU1 110 and AP 2 and 3 are mapped to RU2 120.

The submatrix storage unit 240 stores submatrix information for each codebook index as shown in [Table 1]. At this time, the information to be stored is the codebook index and the corresponding sub-matrix information, and the sub-matrix information is unitary sub-matrix W ' _xy information as shown in Equation (5).

The location determination unit 250 determines the locations of the terminals 31, 33, and 35 that have requested the resource allocation in order for the RUs 110 and 120 to transmit data. That is, the location determination unit 250 determines whether the location of the terminal is within a coverage boundary area of the RU 110 or 120, or within a coverage boundary area. Such location determination can be determined based on a signal transmitted from the terminal to the RUs 110 and 120, which are well known and will not be described in detail here.

The precoding matrix assigning unit 260 transmits the AP mapping information to the terminal based on the AP mapping information for each RU 110 and 120 and the location of the terminal determined by the position determining unit 250, Matrix from among the submatrices stored in the submatrix storage unit 240 and transmits the selected precoding matrix to the RUs 11 and 120 through the transceiver unit 210. [

The method for the precoding matrix assignment unit 260 to select the submatrices stored in the submatrix storage unit 240 based on the AP mapping information for each RU 110 and 120 and the location of the terminal is as described above. For example, when the AP mapping for the RU1 110 is AP 0 and the AP mapping for the RU 2 120 is 2 and 3 and the location of the terminal is the same as that of the terminal 31, assigning a coverage within the back precoding matrix assignment unit 260 is a sub-matrix storage unit ', W, and assigned to RU1 (110) of _11' (240) W in a unitary sub-matrix that is stored in the ₁₂ to RU2 (120) So that the downlink data is transmitted only from the RU1 110 to the terminal 31 and the downlink data is not transmitted from the RU2 120. [

Meanwhile, the precoding matrix assigning unit 260 transmits the antenna selection matrix Axy information related to the selected unitary sub-matrix to inform the RUs 110 and 120 of the unitary sub-matrix information selected by the sub-matrix storage unit 240 .

In this manner, the RUs 110 and 120 that have received the unitary submatrix from the DU 200 perform precoding on the downlink data using the corresponding unitary submatrix, and transmit the downlink data to the UE.

Next, a precoding matrix allocation method according to an embodiment of the present invention will be described with reference to FIG.

6 is a flowchart of a pre-coding matrix allocation method according to an embodiment of the present invention.

6, when the resource allocation unit 220 of the DU 200 receives a resource allocation request from the RU1 110 and the RU2 120 through the transmission / reception unit 210 (S100), the RU1 110 and the RU2 And performs resource allocation for the resource 120 (S110). In this case, resources allocated to the RU1 110 and the RU2 120 by the resource allocation unit 220 include AP mapping information mapped by the RUs 110 and 120.

Thereafter, the AP mapping analysis unit 230 analyzes the AP mapping information for each of the RUs 110 and 120 allocated by the resource allocation unit 220, and determines which APs are mapped by the RUs 110 and 120 At the same time, the RUs 110 and 120 determine the location of the UE requesting resource allocation to transmit data (S120).

The precoding matrix assignment unit 260 determines whether the position of the UE determined in step S120 is a border area of the RU 110 or 120 in step S130, And allocates a unitary submatrix according to the AP mapping information for each RU 110 and 120 if it is a border area. That is, when the APs mapped to the RU1 110 are 0 and 1 (S140), the precoding matrix assignment unit 260 assigns the unitary submatrices W _'31 and W' ₃₂ to the RUs 110 and 120 (S150).

However, not the AP is 1 and 0 maps to RU1 (110) is 2 and 3 (S140), the precoding matrix assignment unit 260 is a unitary sub-matrix W _'41 and W' ₄₂ RU (110, 120) (S160).

In step S130, if the location of the terminal is within the coverage of the RUs 110 and 120 that are not the boundary areas of the RUs 110 and 120, the APs mapped to the RU1 110 are 0 and 1 and determining (S170), if so, the pre-coding matrix assignment unit 260 is a unitary sub-matrix W ', W and RU1 is assigned to (110) _{11' 12} assigns to RU2 (120) (S180).

However, the AP is mapped to RU1 (110) in said step (S170) is 2 and 3 precoding matrix assignment unit 260 is a unitary sub-matrix W 'is assigned a ₂₁ to RU1 (110), and W' ₂₂ to the RU2 120 (S190).

Thereafter, the precoding matrix assigning unit 260 transmits the unitary sub-matrix information allocated to the RUs 110 and 120 to the respective RUs 110 and 120 (S200).

Accordingly, the RUs 110 and 120 can precode the downlink data according to precoding matrix information, i.e., unitary matrix information, transmitted from the DU 200, and transmit the downlink data to the UE.

As described above, in the embodiment of the present invention, by allocating a unit sub-matrix for selecting an antenna for each RU 110 and 120 to a precoding matrix used in precoding for downlink data, Since the downlink data can be transmitted only in the adjacent RUs 110 and 120 for the terminals located in the coverage area other than the border area, the terminal does not need to separate the received data signals even in the MIMO decoding.

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 (16)

A digital signal processing device connected to the core system for processing a wireless digital signal; And
And converting the digital signal received from the digital signal processor into a digital signal and transmitting the amplified signal to the terminal based on a multi-antenna technique using two antennas, And a plurality of radio signal processing apparatuses for receiving a signal transmitted from a terminal based on a multi-antenna technique using an antenna and transmitting the received signal to the digital signal processing apparatus,
When two radio signal processing apparatuses of the plurality of radio signal processing apparatuses are paired to perform a quad antenna transmission, the digital signal processing apparatus may perform a quad antenna transmission in the coverage of the two radio signal processing apparatuses A precoding matrix is allocated to the two wireless signal processing apparatuses so that only data transmitted from a wireless signal processing apparatus adjacent to the terminal is transmitted to the terminal for a terminal located in a boundary region between the two wireless signal processing apparatuses
And the wireless communication system. The method according to claim 1,
The precoding matrix includes a plurality of precoding matrices (W) set in a codebook for transmission of the quad antenna, and a sub-matrix among a plurality of matrix elements of the precoding matrix (W) Wherein the wireless communication system is a sub-matrix. 3. The method of claim 2,
The unitary submatrix (W ') has the following relationship

Where W ^H is a Hermitian matrix of the precoding matrix W,
M is the number of data streams
To the wireless communication system. The method of claim 3,
The unitary submatrix (W ') has the following relationship

Here, A is a matrix for antenna selection,
The operator o stands for a two-matrix Hadamard product,
α is a constant value to compensate for the reduction of the total transmission power due to the use of an optional antenna or to adjust the transmission power
To the wireless communication system. 5. The method of claim 4,
The matrix A for antenna selection includes:

And the location of the terminal. 6. The method of claim 5,
If the precoding matrix W is

Quot;
The unitary sub-matrix W '

(A) for the antenna selection. The method according to claim 6,
If the terminal is located within the coverage of any one of the RF signal processing apparatuses other than the boundary region between the two RF signal processing apparatuses, the digital signal processing apparatus may include a CRS (Common Reference signal) wireless communication, characterized in that allocated to the two wireless signal processing apparatus for according to the AP (Antennal Port) information unitary submatrix W _'11 and W' ₁₂ or W _'21 and W' ₂₂ as a pre-coding matrix system. The method according to claim 6,
When the terminal is located in a boundary area between the two radio signal processing apparatuses, the digital signal processing apparatus calculates unitary submatrices W _'31 and W''according to the CRS AP information mapped to the two radio signal processing apparatuses, ₃₂ or W _'41 and W' ₄₂ as precoding matrices to the two radio signal processing devices. 3. The method of claim 2,
The digital signal processing apparatus
A resource allocation unit allocating resources to the two radio signal processing apparatuses, wherein the resources include CRS AP information mapped to the two radio signal processing apparatuses;
A position determiner for determining a position of the terminal;
A mapping analyzer for analyzing CRS AP information mapped to the two radio signal processing devices by the resource allocator;
A submatrix storage unit for storing the unitary submatrix information; And
Selects two unitary submatrices among the unitary submatrices stored in the submatrix storage unit based on the position of the terminal determined by the position determination unit and the CRS AP information analyzed by the mapping analysis unit A matrix assigning unit for assigning the matrix to each of the two radio signal processing apparatuses,
≪ / RTI > 10. The method of claim 9,
When the position determination unit determines that the terminal is located in a coverage area adjacent to one wireless signal processing apparatus rather than in a boundary area between the two wireless signal processing apparatuses, And selects a unitary sub-matrix for transmitting data only in the antenna corresponding to the CRS AP mapped to the CRS AP. A method of allocating a precoding matrix to a plurality of wireless signal processing apparatuses installed in a service area for processing wireless signals, the method comprising:
Mapping a CRS (Common Reference Sign) AP (Antenna Port) to two radio signal processing apparatuses that are paired among the plurality of radio signal processing apparatuses and perform Quad Antenna Transmission;
Determining a location of the terminal;
When it is determined that the mobile station is located in a coverage area of the two radio signal processing apparatuses, the two radio signal processing apparatuses transmit data using only the CRS APs mapped to the two radio signal processing apparatuses And assigning a precoding matrix to the two wireless signal processing apparatuses
/ RTI > 12. The method of claim 11,
In the allocating step,
Determining whether the terminal is located in the border area;
Determining a CRS AP mapped to an adjacent radio signal processor if the terminal is determined not to be located in the border area; And
A unitary submatrix for transmitting data only to the APs 0 and 1 when the UE is mapped to the CRS APs 0 and 1 to the adjacent radio signal processor, A unitary matrix among sub-matrices consisting of some of the matrix elements of one precoding matrix (W) among a plurality of precoding matrices set in the codebook for the adjacent radio signal processing apparatus And allocating a unitary sub-matrix to other radio signal processing apparatuses so that only the CRS 2 and 3 transmit data
/ RTI > 13. The method of claim 12,
In the step of determining the mapped CRS AP,
When the UE is mapped to the CRS APs 0 and 2 to the adjacent radio signal processor, the UE allocates a unit sub-matrix for transmitting data only to the APs 0 and 2 to the adjacent radio signal processor And allocating a unitary sub-matrix to another radio signal processor to transmit data only to CRS 1 and 3. The method according to claim 12 or 13,
In the allocating step,
Determining a matrix for selecting a corresponding antenna according to a CRS AP mapped to the two wireless signal processing apparatuses;
Determining the unitary submatrix using a matrix for selecting the determined antenna; And
And assigning a determined unitary sub-matrix to each of the two wireless signal processing apparatuses
/ RTI > 15. The method of claim 14,
Assigning an index to the matrix for selecting the antenna, and adding the index to the control information and transmitting the matrix to the terminal. 13. The method of claim 12,
Determining a CRS AP mapped to the two wireless signal processing devices when it is determined that the terminal is located in the border area; And
When the two radio signal processing apparatuses transmit two data streams, the two radio signal processing apparatuses transmit a different data stream through the CRS AP mapped to the two radio signal processing apparatuses, Respectively,
/ RTI >

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