WO2010143780A2

WO2010143780A2 - Multi-cell cooperative communication system and terminal device

Info

Publication number: WO2010143780A2
Application number: PCT/KR2009/005201
Authority: WO
Inventors: 고영조; 안재영; 김재흥; 이희수
Original assignee: 한국전자통신연구원
Priority date: 2009-06-10
Filing date: 2009-09-11
Publication date: 2010-12-16
Also published as: WO2010143780A3

Abstract

Disclosed is a data transmission system that transmits data by using relay. The relay may select a transmission terminal from among a plurality of terminals accessing a base station. The base station may transmit base station data to the relay during a first time slot, the transmission terminal may transmit terminal data to the relay. The relay may transmit the terminal data to the base station and may transmit the base station data to the transmission terminal during a second time slot.

Description

Multi-Cell Cooperative Communication System and Terminal Device

The present invention relates to a multi-cell cooperative communication system and a terminal device, and more particularly, to a multi-cell cooperative communication system and a terminal device to enable a plurality of base station devices to cooperate with each other to perform MIMO communication with the terminal device.

In general, a terminal device located at a cell boundary is transmitted not only from a data signal transmitted from a base station device of a serving cell to which it belongs, but also from a neighbor cell base station device that manages a neighboring cell adjacent to a serving cell. Affected by the signal.

In general cellular communication, since the data signal transmitted from the neighbor cell base station apparatus acts as an interference with the data signal transmitted from the serving cell base station apparatus, the data signal transmitted from the neighbor cell base station apparatus The greater the interference, the more limited the data rate.

In this case, if the data signal transmitted from the neighbor cell base station apparatus is a data signal for the terminal apparatus, the data rate can be improved as compared with the case of transmitting the data signal using a general cellular communication method. As described above, a method in which a plurality of base station devices cooperate with each other to perform data communication with a terminal device is called multi-cell cooperative communication.

An object of the present invention is to provide a multi-cell cooperative communication system that enables a plurality of cells to cooperate with each other to perform multi-antenna communication with a terminal device.

A multi-cell cooperative communication system according to an embodiment of the present invention includes at least one first antenna and transmits a data signal to a terminal device having at least one second antenna by using the at least one first antenna. A plurality of base station apparatuses, each of the plurality of base station apparatuses comprising the same codebook, precoding at least one data symbol based on the codebook to generate a data signal, and The data signal is transmitted to the terminal device.

In addition, a multi-cell cooperative communication system according to an embodiment of the present invention includes at least one first antenna, and is transmitted from a terminal device having at least one second antenna using the at least one first antenna. A plurality of base station apparatus for receiving a data signal, the plurality of base station apparatus including a serving cell base station apparatus and at least one neighboring cell base station apparatus, the serving cell base station apparatus receiving a first data signal, The at least one neighbor cell base station apparatus receives a second data signal, and the at least one neighbor cell base station apparatus receives at least one of the second data restored from the second data signal and the information about the second data signal. The serving cell base station apparatus transmits the second data and the second data to the serving cell base station apparatus. Using at least one of the information about the call to recover the first data from the first data signal.

In addition, the terminal device according to an embodiment of the present invention includes a storage unit for storing a codebook including at least one precoding matrix consisting of a plurality of precoding vectors, a receiving unit for receiving a radio signal from the plurality of base station devices, A channel estimator for estimating a state of a plurality of channels formed between the plurality of base station apparatuses and the terminal apparatus based on the radio signal, and any one of the at least one precoding matrix based on the estimated state of the plurality of channels A preselection matrix for selecting a precoding matrix, and selecting at least one precoding vector from among a plurality of precoding vectors constituting any one precoding matrix, and information on the selected at least one precoding vector. At least one of the plurality of base station apparatus to the second feedback signal It comprises transmitting unit for transmitting to the base station apparatus.

According to the present invention, a plurality of cells can cooperate with each other to perform multi-antenna communication with a terminal device.

1 is a diagram illustrating a concept of downlink multi-cell cooperative communication involving two base station apparatuses according to an embodiment of the present invention.

2 is a diagram for describing a method of configuring a supercell based on a location of a terminal device.

3 is a view for explaining a method of configuring a fixed supercell regardless of the position of the terminal device.

4 is a diagram illustrating a concept of uplink multi-cell cooperative communication involving three base station apparatuses according to an embodiment of the present invention.

5 is a block diagram showing a detailed configuration of a terminal device 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. However, the present invention is not limited or limited by the embodiments. Like reference numerals in the drawings denote like elements.

A plurality of base station apparatuses constituting a multi-cell cooperative communication system may include a relay node as well as a base station apparatus that manages a conventional cell such as a macro cell, a micro cell, and the like. Therefore, the multi-cell cooperative communication system according to an embodiment of the present invention can be applied to various types of cooperative communication such as cooperative communication by conventional cells, cooperative communication of relay nodes, and cooperative communication of conventional cells and relay nodes. .

In general, one physical base station apparatus may manage more than one cell. In the present invention, the term base station device will be used as a concept corresponding to one cell. Therefore, even when one base station device physically manages a plurality of cells, it is assumed that as many logical base station devices exist as the number of cells, and that there is one logical base station device that manages each cell. Hereinafter, the term base station apparatus referred to in the present invention means the above logical base station apparatus, so that one cell is managed.

In FIG. 1, two base station devices involved in downlink communication are limited (that is, a multi-cell cooperative communication system includes two base station devices), but according to an embodiment of the present invention, a multi-cell cooperative communication system is provided. It will be apparent to those skilled in the art that these three or more base station devices may be included.

In the multi-cell cooperative communication system according to an embodiment of the present invention, both the serving cell base station apparatus 120 and the neighbor cell base station apparatus 130 transmit data signals required by the terminal apparatus 110 to the terminal apparatus 110. , Improve the data rate.

In this case, each of the serving cell base station apparatus 120 and the neighbor cell base station apparatus 130 includes at least one first antenna (ie, a transmit antenna), and the terminal device 110 includes at least one second antenna (ie, (Receiving antenna) (in FIG. 1, the serving cell base station apparatus 120 and the neighbor cell base station apparatus 130 are illustrated as having four first antennas, respectively). Accordingly, each of the serving cell base station apparatus 120 and the neighbor cell base station 130 transmits a data signal to the terminal apparatus 110 using at least one first antenna, and the terminal apparatus 110 includes at least one second. Receive a data signal using an antenna. That is, the terminal device 110, the serving cell base station device 120, and the neighbor cell base station device 130 perform multi-in multi-out (MIMO) communication through multi-cell cooperation using a plurality of antennas.

Hereinafter, downlink MIMO communication in which a plurality of base station devices having at least one first antenna cooperate with each other and transmits a data signal to a terminal device having at least one second antenna will be described in detail.

In order to perform multi-cell cooperative MIMO communication in downlink, a plurality of base station apparatuses generate a data signal by precoding a data symbol to be transmitted using the same codebook and generate the same radio signal. The data signal generated using the resource is transmitted to the terminal device 110. In this case, a method of precoding a data symbol using a codebook may be classified into two methods as described below.

1. Joint codebook method

The joint codebook method regards a plurality of cells controlled by a plurality of base station devices involved in cooperative communication as one virtual cell, and includes at least one first antenna provided in the plurality of base station devices and at least one first device provided in the terminal device. Means a method of performing MIMO communication using two antennas.

Since a plurality of cells are regarded as one virtual cell, a terminal device having at least one second antenna performs MIMO communication with one virtual cell base station device having a plurality of first antennas, which manages a virtual cell. Can be considered.

Therefore, the size of at least one precoding matrix included in the codebook is determined according to the sum of the number of first antennas included in each of the plurality of base station apparatuses.

That is, when the sum of the number of the first antennas included in each of the plurality of base station devices involved in the cooperative communication is N (N is a predetermined integer equal to or greater than 1), the precoding matrix included in the codebook has a size of N × N. Have In addition, the precoding matrix is composed of a plurality of precoding vectors. The precoding vector means each column vector of the precoding matrix. In this case, the precoding matrix may be expressed as Equation 1 below.

[Equation 1]

here,

Is the precoding matrix,

To

Is the element of the precoding matrix,

To

Denotes a precoding vector, respectively. The codebook includes one or more such precoding matrices.

Hereinafter, an operation of generating a data signal by precoding at least one data symbol by a plurality of base station apparatuses based on a joint codebook scheme, and transmitting the same to the terminal apparatus 110 will be described in detail.

First, the plurality of base station apparatus selects one precoding matrix to be used for transmitting a data signal from among a plurality of precoding matrices included in the codebook. In this case, each of the plurality of base station devices selects the same precoding matrix. Hereinafter, the precoding matrix represented by Equation 1

Assume that is selected.

Next, the plurality of base station apparatuses selects the selected precoding matrix.

At least one precoding vector is selected from among a plurality of precoding vectors constituting. In the following, it is assumed that the number of selected precoding vectors is M (M is a predetermined integer of 1 or more and N or less).

Since one precoding vector is used to precode one data symbol, the number of selected precoding vectors is equal to the number of data symbols to be transmitted from the plurality of base station apparatuses to the terminal apparatus.

A data signal transmitted by an i th antenna is transmitted among N first antennas provided in a plurality of base station devices (that is, provided in a virtual cell base station

, The selected M precoding vectors

, The data symbol you want to send

In this case, data signals transmitted from the N first antennas may be expressed by Equation 2 below.

[Equation 2]

Finally, the plurality of base station apparatuses contains N precoded data signals.

To

Simultaneously transmits to the terminal device using the same radio resource. That is, the N precoded data signals are transmitted to the terminal device using one OFDM subcarrier.

In addition, in order to estimate a channel in a terminal device, according to an embodiment of the present invention, each of a plurality of base station devices uses a plurality of precoding vectors identical to the plurality of precoding vectors used to precode a data signal. reference) signal may be precoded, and the precoded reference signal may be transmitted to the terminal device. In this case, since the data signal and the reference signal are precoded using the same plurality of precoding vectors, the terminal apparatus can easily estimate a channel formed between the terminal apparatus and the base station apparatus. The precoded reference signal is located and transmitted only in a resource block allocated to the terminal device 110.

2. Codebook Method by Cell

The cell-specific codebook method refers to a method of generating a data signal by precoding the same data symbol with the same precoding vector in each of a plurality of base station devices involved in cooperative communication, and transmitting the generated data signal to the terminal device. In this case, each of the plurality of base station devices transmits a data signal to a terminal device having a plurality of second antennas (ie, receiving antennas) using at least one first antenna (ie, a transmitting antenna) to perform MIMO communication. do.

Accordingly, the size of at least one precoding matrix included in the codebook is determined according to the number of at least one first antenna provided in each of the plurality of base station apparatuses. That is, when the number of first antennas included in each of the plurality of base stations involved in the cooperative communication is N, the precoding matrix included in the codebook has a size of N × N. In this case, the precoding matrix may be expressed as in Equation 1 as in the joint codebook method mentioned above.

Hereinafter, an operation of generating a data signal by precoding at least one data symbol based on a cell codebook scheme in each of a plurality of base station apparatuses and transmitting the same to a terminal apparatus will be described in detail.

First, each base station apparatus selects one precoding matrix to be used for data signal transmission from among a plurality of precoding matrices included in the codebook. Each of the plurality of base station devices may select a different precoding matrix. However, when the base station takes the precoding information from the feedback of the terminal device, a limit may be set such that each of the plurality of base station devices selects the same precoding matrix to reduce the amount of feedback.

Hereinafter, the precoding matrix shown in Equation 1

Assume that is selected. Next, each of the plurality of base station apparatuses selects the selected precoding matrix.

At least one precoding vector is selected from among a plurality of precoding vectors included in. Each of the plurality of base station devices may generally select different precoding vectors. However, when precoding information is taken from the feedback of the terminal device, in order to reduce the amount of feedback, a plurality of base station devices may be limited to select the same precoding vector.

In addition, data symbols transmitted from each of the plurality of base station apparatuses are the same data symbol. That is, each of the plurality of base station devices generates a data signal by precoding the same data symbol using the selected precoding vector, and transmits the generated data signal to the terminal device. Hereinafter, it is assumed that the number of selected precoding vectors and the number of data symbols to be transmitted are M.

The data signal transmitted by the i th antenna is transmitted among the N first antennas provided in each of the base station apparatuses.

, The selected M precoding vectors

, The data symbol you want to send

In each of the plurality of base station apparatuses, N data signals transmitted through the N first antennas may be expressed by Equation 2 above.

Finally, each of the plurality of base station apparatuses has N precoded data signals.

To

Simultaneously transmits to the terminal device using the same radio resource. That is, each of the base station apparatuses transmits N precoded data signals simultaneously using one carrier.

In addition, even in the case of the cell-specific codebook scheme, in order to easily estimate the channel formed between the terminal apparatus and the plurality of base station apparatuses, each of the plurality of base station apparatuses has been used to precode data signals. A reference signal may be precoded using a plurality of precoding vectors identical to the vector, and the precoded reference signal may be transmitted to the terminal device. The precoded reference signal is located in a resource block allocated to the terminal device and transmitted.

In the above, a joint codebook method and a cell codebook method for generating data signals by precoding data symbols and transmitting the generated data signals have been described. Hereinafter, a control operation of a plurality of base station apparatuses which are applied to the joint codebook method and the cell codebook method in the same manner will be described.

According to an embodiment of the present invention, a plurality of base station apparatuses may exchange information about radio resources and precoding information for selecting a precoding matrix and a precoding vector. This is for allowing the same precoding matrix, the same precoding vector, and the same radio resource to be selected in each of the plurality of base station apparatuses.

In this case, each of the plurality of base station devices precodes at least one data symbol further based on the interchanged precoding information, and uses the radio resource used for transmission of the data signal based on the information on the interchanged radio resources. You can decide.

Communication between a plurality of base station devices may be performed using a backbone network connected to a network, a dedicated line directly connecting the base station devices to each other, and wireless communication. When a plurality of base station apparatuses exchange information through wireless communication, the plurality of base station apparatuses may use part of a frequency band used for communication between the base station apparatus and the terminal apparatus, or a frequency used for communication between the base station apparatus and the terminal apparatus. Other frequency bands may be used that are separate from the band.

In addition, the precoding information may be obtained from the terminal device. In this case, the terminal device can transmit precoding information to the serving cell base station device.

The serving cell base station apparatus having received the precoding information from the terminal apparatus may select a precoding matrix and a precoding vector based on the received precoding information.

In addition, the serving cell base station apparatus transmits scheduling information including at least one of received precoding information, information on radio resources allocated to the terminal apparatus, and Modulation and Coding Scheme (MCS) information to the neighbor cell base station apparatus. Can transmit

In this case, the neighbor cell base station apparatus may further generate a data signal based on the scheduling information and transmit the generated data signal to the terminal apparatus. That is, the neighbor cell base station apparatus may transmit a data signal to the terminal apparatus based on the scheduling information transmitted from the serving cell base station. At this time, it is preferable that the serving cell base station and the neighbor cell base station apparatus are synchronized.

In addition, in order for a plurality of base station apparatuses to cooperate with each other to perform MIMO communication, a subject that collectively directs cooperative communication performed between the base station apparatuses may be required. Accordingly, according to an embodiment of the present invention, the plurality of base station apparatuses may include a first base station apparatus for controlling cooperative communication and at least one second base station apparatus controlled by the first base station apparatus. Hereinafter, the first base station apparatus is referred to as a supernode, and the set of at least one cell managed by the at least one second base station apparatus is referred to as a supercell.

The supernode determines scheduling for at least one terminal that participates in cooperative communication, and transmits scheduling information about the determined at least one terminal to at least one second base station apparatus that manages the supercell, thereby transmitting the second base station apparatus. May control the second base station apparatus to transmit the data signal according to the scheduling information.

Hereinafter, a method of configuring a supercell will be described in detail with reference to FIGS. 2 and 3.

First, FIG. 2 is a diagram for describing a method of configuring a supercell based on positions of

terminal devices

210 and 220.

According to one embodiment of the invention, the terminal device (210, 220) receives a radio signal from a plurality of base station devices located in its vicinity, and measures the intensity (intensity) of the received plurality of radio signals, the measurement Information on the sizes of the plurality of wireless signals may be transmitted to the supernode. As one example, the wireless signal may be a reference signal.

In this case, the supernode may select at least one second base station apparatus that manages the supercell among the plurality of base station apparatuses based on the information on the sizes of the plurality of received radio signals.

As an example, the supernode may select, as the second base station apparatus, a base station apparatus that has transmitted a radio signal having a strength greater than a preset intensity among a plurality of wireless signals. Accordingly, the

terminal devices

210 and 220 may be guaranteed a good wireless channel environment regardless of their location.

In general, since the strength of the radio signal is inversely proportional to the distance, the closer the position between the

terminal apparatuses

210 and 220 and the cell is, the greater the intensity of the radio signal transmitted from the base station apparatus that manages the cell. Therefore, according to an embodiment of the present invention, the supernode may select at least one base station apparatus close to the

terminal apparatuses

210 and 220 as the second base station apparatus.

For example, as shown in FIG. 2, since the terminal device 210 is located in close proximity to the cell A 230, the cell B 240, and the cell D 260, the super node is the cell A 230. , Cell B 240, and cell D 260 may be selected as supercells for the terminal device 210.

In addition, in the case of the terminal device 220, since the cell A 230, the cell C 250, and the cell D 260 are located close to each other, the supernode is the cell A 230, the cell C 250, and The cell D 260 may be selected as a supercell for the terminal device 220.

Next, FIG. 3 is a diagram for describing a method of configuring a fixed supercell regardless of the positions of the

terminal devices

310 and 320.

In FIG. 3, the cell A 330, the cell B 340, and the cell C 350 constitute one supercell (hereinafter referred to as a first supercell) regardless of the positions of the

terminal devices

310 and 320. The cell D 360, the cell E 370, and the cell F 380 constitute another supercell (hereinafter referred to as a second supercell). Accordingly, the terminal device 310 may receive a radio signal from the first supercell, and the terminal device 320 may receive a radio signal from the second supercell.

In this case, since the terminal device located at the boundary between the supercells such as the terminal device 310 may receive interference by radio signals transmitted from neighboring supercells, inter-supercell interference control may be performed to mitigate the interference between the supercells. Can be performed. For example, a fractional frequency reuse (FFR) method may be used for interference control between supercells.

According to an embodiment of the present invention, the supernode may restrict only some cells from the cells belonging to the supercell controlled by the supernode to participate in the cooperative communication.

That is, according to an embodiment of the present invention, the supernode (ie, the first base station apparatus) selects at least one third base station apparatus from at least one second base station apparatus that manages at least one cell belonging to the supercell. In addition, only the selected third base station apparatus may control to transmit the data signal to the terminal apparatus. In this case, the third base station apparatuses are subjects for transmitting the actual data signal. Hereinafter, a cell controlled by at least one third base station apparatus will be referred to as an active cell.

When only the active cell transmits the data signal to the terminal device, the terminal device measures only the active cell without performing channel state measurement and reporting of the measured channel state and precoding information for all cells belonging to the supercell. And since the report is performed, it is possible to reduce the amount of computation and feedback overhead of the terminal device.

In this case, the terminal device can measure the intensity of a radio signal (for example, a reference signal) transmitted from the serving cell and the neighboring cell of the serving cell and feed it back to the supernode. The supernode may select a cell that can be substantially helpful to the terminal device based on the information fed back from the terminal device as an active cell, and transmit information on the selected active cell to the terminal device.

For example, assuming that the supercell is configured as shown in FIG. 3, cell A 330 and cell C 350 may be selected as active cells for the terminal device 310. In this case, cell B 340 does not actually participate in the transmission of the data signal. In addition, since the terminal device 320 is located at the center of the supercell, all of the cells D 360, E 370, and F 380 may be selected as active cells for the terminal device 320. .

When the channel environment around the terminal device is changed, the supernode may change the active cell based on the measurement result of the radio signal strength fed back from the terminal device. In this case, the supernode retransmits the information about the changed active cell to the terminal device.

In FIG. 4, the base station apparatus involved in uplink communication is limited to three (that is, the multi-cell cooperative communication system includes three base station apparatuses). However, the multi-cell cooperative communication system according to an embodiment of the present invention. It will be apparent to those skilled in the art that these two or more base station devices may be included.

The terminal device 410 transmits a data signal not only to the base station apparatus 420 of the serving cell but also to the neighbor cell base station apparatus 430 and the neighbor cell base station apparatus 440 that manage neighboring cells adjacent to the serving cell. Hereinafter, the data signal received by the serving cell base station apparatus 420 will be referred to as a first data signal, and the data signals received by the neighbor cell base station apparatus 430 and the neighbor cell base station apparatus 440 will be referred to as a second data signal. .

The neighbor cell base station apparatus 430 and the neighbor cell base station apparatus 440 that have received the second data signal may process the second data signal and transmit the processed second data signal to the serving cell base station apparatus 420. In this case, the serving cell base station apparatus 410 may demodulate the first data from the first data signal using the processed second data signal. The processed second data signal may include at least one of second data included in the second data signal and information on the second data signal.

Hereinafter, a method of transmitting the processed second data signal from the plurality of neighboring cell base station apparatuses to the serving cell base station apparatus will be described in detail.

A. Method of transmitting the second data signal to the serving cell base station

According to an embodiment of the present invention, the neighbor cell base station apparatus may transmit the received second data signal itself to the serving cell base station apparatus. In addition, according to another embodiment of the present invention, the neighboring cell base station apparatus may quantize the received second data signal and transmit it to the serving cell base station apparatus.

In this case, the neighbor cell base station apparatus transmits information on the second data signal to the serving cell base station apparatus, and the information on the second data signal is the second data signal itself or the quantized second data signal.

In addition, the neighbor cell base station apparatus may quantize all signals received from the terminal apparatus as well as the second data signal and transmit them to the serving cell base station apparatus. For example, the neighbor cell base station apparatus may quantize and transmit a signal carried on a subcarrier through which a reference signal is transmitted.

B. A method of transmitting a soft decision value and an effective noise variance value for each of a plurality of second data symbols included in a second data signal to a serving cell base station

According to an embodiment of the present invention, the neighbor cell base station apparatus derives a soft decision value for each of the plurality of second data symbols included in the second data signal and an effective noise variance value for each of the plurality of second data symbols. The flexible determination value and the effective noise variance value for each of the derived plurality of second data symbols may be transmitted to the serving cell base station apparatus.

That is, the neighbor cell base station apparatus may transmit information on the second data signal to the serving cell base station apparatus, and the information on the second data signal may be a soft decision value and an effective noise variance value for each of the plurality of second data symbols. .

Here, each of the plurality of base station apparatuses includes a symbol detector and a channel decoder, wherein the soft decision value and the effective variance value are the values of the output of the symbol detector and the input of the channel decoder.

The serving cell base station apparatus determines the softness determination value and the effective noise variance value for each of the plurality of first data symbols included in the first data signal based on the softness determination value and the effective noise variance value for each of the plurality of second data symbols. Can be derived.

In the plurality of base station apparatuses, an example of deriving a soft decision value and an effective variance value will be described in detail below. The example below assumes OFDM transmission.

The number of second antennas (ie, transmit antennas) included in the terminal device

,The number of data symbols transmitted per one carrier in the terminal device

, The number of first antennas (ie, receiving antennas) included in the base station apparatus

vector data symbols transmitted from the terminal device using the j th carrier

Vector data signal received from the base station apparatus

If you mark with,

Wow

The relationship between the following equations is established between the livers.

[Equation 3]

here,

Is a sum of Additive White Gaussian Noise (AWGN) noise and interference noise for each receiving antenna of the jth carrier,

Is indicated by

Is applied to the jth carrier

×

Means a precoding matrix having a size of

Is

×

It means the channel matrix of the j-th carrier having a size of.

Here, it is assumed that the average transmission power for each transmitting antenna is normalized as shown in Equation 4 below.

[Equation 4]

Where E {} is the effective power, superscript H is Hermitian Transpose,

Is

Each means a matrix having a size of.

According to an embodiment of the present invention, the base station apparatus may detect a transmission signal of each antenna using a zero-forcing (ZF) detection scheme. In this case, the softness determination value of the data symbol may be derived according to Equation 5 below.

[Equation 5]

here,

Denotes a softness determination value of the j th data symbol according to the ZF detection scheme, and a superscript eff denotes an effective value, respectively.

Also, the effective noise variance of the jth carrier

(here,

Is the i th data symbol transmitted on the j th carrier

Is the effective noise variance for.

[Equation 6]

According to another embodiment of the present invention, the base station apparatus may detect a transmission signal of each antenna by using a minimum mean square error (MMSE) detection scheme. In this case, the softness determination value of the data symbol may be derived according to Equation 7 below.

[Equation 7]

here,

Denotes a softness determination value of the j th data symbol according to the MMSE detection scheme.

In addition, the effective noise variance of the j th carrier may be derived from Equation 6 above.

C. A method of transmitting a soft decision value and an average effective noise variance value for each of a plurality of second data symbols included in a second data signal to a serving cell base station

According to an embodiment of the present invention, the neighbor cell base station apparatus derives a soft decision value and an effective noise variance value for each of the plurality of second data symbols included in the second data signal, and uses the derived effective noise variance value. Deriving an average effective noise variance value for all resource blocks allocated to the terminal device or resource blocks of a predetermined size, and serving the soft decision value and the average effective noise variance value for each of the plurality of derived second data symbols It can transmit to the cell base station apparatus.

That is, the neighbor cell base station apparatus transmits information on the second data signal to the serving cell base station apparatus, and the information on the second data signal may be a soft decision value and an average effective noise variance value for each of the plurality of second data symbols. have.

In this case, the average effective noise variance value derived for each section, rather than the individual effective noise variance value, is transmitted to the serving cell base station apparatus, thereby reducing the amount of transmitted data.

An example of deriving an average effective noise variance value in a neighbor cell base station apparatus will be described in detail.

First, assuming that there are a total of M carriers in a resource block to be averaged, the effective noise variance value

Mean of

May be derived as in Equation 8 below.

[Equation 8]

Where average

This effective noise variance value

In order to represent well the representative of the carriers located in the average resource block is located adjacent to each other in the frequency space, it is preferable that the same precoding is applied. I.e. for all j

It is desirable that the relationship is established. This is due to the fact that, when different precodings are applied, the effective noise variance value is likely to be large for each carrier.

D. A method of transmitting a soft decision value for each of a plurality of second data bits included in a second data signal to a serving cell base station

According to an embodiment of the present invention, the neighbor cell base station apparatus derives a softness determination value for each of the plurality of second data bits included in the second data signal, and determines the softness determination for each of the derived plurality of second data bits. The value may be transmitted to the serving cell base station apparatus.

That is, the neighbor cell base station apparatus may transmit information on the second data signal to the serving cell base station apparatus, and the information on the second data signal may be a softness determination value for each of the plurality of second data bits.

Here, the softness determination value for each of the plurality of second data bits refers to a Log Likelihood Ratio (LLR) in units of bits obtained after passing through a symbol detector. That is, if the LLR of the second data bit b is denoted as LLR (b), the LLR (b) is the probability that the second data bit b is "1" (p (b = 1)) and the probability "0" (p). (b = 0)) is the natural logarithm of the ratio. This can be expressed as in Equation (9).

[Equation 9]

Here, the LLR for each data bit transmitted to the serving cell base station apparatus may be an input value of the channel decoder or an output value generated as a decoding result.

E. Method of transmitting demodulated second data from the second data signal to the serving cell base station

According to an embodiment of the present invention, the neighbor cell base station apparatus may perform symbol detection, decoding, etc. on the second data signal to demodulate the second data and transmit the demodulated second data to the serving cell base station apparatus.

That is, the neighbor cell base station apparatus may transmit the second data itself to the serving cell base station apparatus.

In this case, the neighbor cell base station apparatus may transmit demodulated second data only when demodulation of the second data is successfully performed.

F. Other

According to an embodiment of the present invention, the neighbor cell base station apparatus is generated according to the method of A to E only when receiving information on the second data signal or a request for transmission of the second data from the serving cell base station apparatus. Information about the two data signals or the second data may be transmitted to the serving cell base station apparatus.

In addition, according to an embodiment of the present invention, when demodulation of the second data is successfully performed, the neighbor cell base station apparatus transmits the demodulated second data to the serving cell base station apparatus and successfully demodulates the second data. If not performed, information on the second data signal generated according to the above methods A to D may be transmitted to the serving cell base station apparatus.

In addition, according to an embodiment of the present invention, the neighbor cell base station apparatus may transmit only information on whether the demodulation succeeds or fails about whether the second data has been successfully demodulated to the serving cell base station apparatus.

In this case, the serving cell base station apparatus may transmit the information on the second data signal or the request for transmitting the second data to the neighbor cell base station apparatus based on the information on whether the demodulation succeeds or fails. If the demodulation of the second data is not successfully performed, the neighbor cell base station apparatus receiving the transmission request transmits information on the second data signal generated according to the method of A to D to the serving cell base station apparatus. When demodulation of the second data is not successfully performed, the second data generated according to the above E scheme may be transmitted to the serving cell base station apparatus.

Hereinafter, a terminal device performing cooperative communication with a plurality of base station devices will be described in detail with reference to FIG. 5.

5 is a block diagram showing a detailed configuration of a terminal device 500 according to an embodiment of the present invention.

The terminal device 500 according to an embodiment of the present invention includes a storage unit 510, a receiver 520, a channel estimator 530, a selector 540, and a transmitter 550. Hereinafter, the function of each component will be described in detail.

The storage unit 510 stores a codebook including at least one precoding matrix composed of a plurality of precoding vectors. The codebook stored in the storage unit 510 is the same codebook stored in the plurality of base station apparatuses.

The receiver 520 receives a radio signal from a plurality of base station apparatuses. In one example, the wireless signal may be either a reference signal or a data signal.

The channel estimator 530 estimates the state of the plurality of channels formed between the plurality of base station apparatuses and the terminal apparatus 500 based on the received radio signal.

The selector 540 selects one precoding matrix from at least one precoding matrix included in the codebook based on the estimated state of the plurality of channels, and selects a plurality of precodings constituting the selected precoding matrix. At least one precoding vector is selected from the vectors.

The transmitter 550 may transmit a second feedback signal including information on the selected at least one precoding vector to at least one base station apparatus among the plurality of base station apparatuses.

According to an embodiment of the present invention, the selector 540 precodes any one of at least one precoding matrix based on predetermined resource blocks or based on resource blocks preferred by the terminal device 500. The matrix may be selected and a preferred at least one precoding vector may be selected from among a plurality of precoding vectors included in any one selected precoding matrix.

The size of the resource block targeted by the selected precoding matrix and the precoding vector may be predetermined in various sizes.

According to an embodiment of the present invention, in order to reduce the amount of information of the second feedback signal transmitted through the transmitter 550, the selector 540 may be preferred for predetermined specific resource blocks or by the terminal device 500. Assuming that the same precoding matrix and precoding vector are applied to the resource blocks, the preferred precoding matrix and the precoding vector may be selected.

According to another embodiment of the present invention, the selector 540 may select a preferred precoding matrix and precoding vector for each individual resource block.

In addition, according to an embodiment of the present invention, the terminal device 500 may include an intensity measuring unit (not shown) for measuring the intensity of a plurality of wireless signals. In this case, the transmitter 550 may transmit a first feedback signal including the measured strengths of the plurality of wireless signals.

As mentioned above, the first feedback signal may be used to select at least one second base station apparatus that governs the supercell.

In the supernode (ie, the first base station apparatus), the at least one second base station apparatus that manages the supercell is selected based on the first feedback signal, and only at least one second base station apparatus transmits the data signal to the terminal apparatus 500. In the case of controlling to transmit the signal, the receiving unit 510 receives information on at least one second base station apparatus from a supernode, and receives only a radio signal transmitted from the at least one second base station apparatus based on the received information. can do.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

Claims

In a multi-cell cooperative communication system,

A plurality of base station apparatuses having at least one first antenna and transmitting data signals to a terminal apparatus having at least one second antenna using the at least one first antenna.

Including,

Each of the plurality of base station devices

Contains the same codebook,

Generate a data signal by precoding at least one data symbol based on the codebook,

A multi-cell cooperative communication system for transmitting the data signal to the terminal device using the same radio resource.
The method of claim 1,

Each of the plurality of base station devices

Exchange at least one of precoding information for precoding the at least one data symbol and information on the radio resource,

Precode the at least one data symbol further based on the interchanged precoding information,

And determining a radio resource used for transmission of the data signal based on the information on the radio resource.
The method of claim 1,

The codebook includes at least one precoding matrix, each of the at least one precoding matrix consists of a plurality of precoding vectors,

Each of the plurality of base station devices

Select any one of the at least one precoding matrix,

Selecting at least one precoding vector from among a plurality of precoding vectors constituting the one precoding matrix,

And precode the at least one data symbol using the at least one precoding vector.
The method of claim 3,

Each of the plurality of base station devices

Precoding a reference signal using the at least one precoding vector,

And transmitting the data signal and the precoded reference signal to the terminal device.
The method of claim 3,

The base station apparatus includes a serving cell base station apparatus and at least one neighbor cell base station apparatus.

The serving cell base station apparatus

Receiving precoding information from the terminal device, and selecting the one precoding matrix and the at least one precoding vector based on the received precoding information.
The method of claim 5,

The serving cell base station apparatus transmits scheduling information including at least one of the precoding information, information on radio resources allocated to the terminal apparatus, and Modulation and Coding Scheme (MCS) information to the at least one neighboring cell base station apparatus. Send,

The at least one neighbor cell base station apparatus further generates the data signal based on the scheduling information and transmits the data signal to the terminal apparatus.
The method of claim 1,

The codebook includes at least one precoding matrix,

The size of the at least one precoding matrix is determined according to the sum of the number of the at least one first antenna provided in each of the plurality of base station apparatus.
The method of claim 1,

The codebook includes at least one precoding matrix,

The size of the at least one precoding matrix is determined according to the number of the at least one first antenna provided in each of the plurality of base station apparatus.
The method of claim 1,

The plurality of base station apparatus

A first base station apparatus and at least one second base station apparatus,

And the first base station apparatus controls the transmission of the data signal of the at least one second base station apparatus.
The method of claim 9,

And the first base station apparatus selects the at least one second base station apparatus from among the plurality of base station apparatuses based on the strength of radio signals transmitted by the plurality of base station apparatuses to the terminal apparatus.
The method of claim 9,

The first base station apparatus

Selecting at least one third base station apparatus from the at least one second base station apparatus,

And the at least one third base station apparatus controls the transmission of the data signal of the at least one second base station apparatus to transmit the data signal to the terminal apparatus.
The method of claim 11,

The first base station apparatus

Receiving a first feedback signal from the terminal device, the first feedback signal including information on the strength of a radio signal transmitted by the at least one second base station device to the terminal device;

And select the at least one third base station apparatus based on the first feedback signal.
In a multi-cell cooperative communication system,

A plurality of base station apparatuses having at least one first antenna and receiving data signals transmitted from a terminal apparatus having at least one second antenna using the at least one first antenna.

Including,

The plurality of base station apparatus includes a serving cell base station apparatus and at least one neighbor cell base station apparatus,

The serving cell base station apparatus receives a first data signal, the at least one neighbor cell base station apparatus receives a second data signal,

The at least one neighbor cell base station apparatus transmits at least one of the second data recovered from the second data signal and the information about the second data signal to the serving cell base station apparatus,

And the serving cell base station apparatus restores first data from the first data signal using at least one of the second data and information about the second data signal.
The method of claim 13,

And wherein the information about the second data signal is quantized of the second data signal.
The method of claim 13,

The second data signal includes a plurality of second data symbols,

The information about the second data signal includes a soft decision value for each of the plurality of second data symbols and an effective noise variance value for each of the plurality of second data symbols. Cell cooperative communication system.
The method of claim 13,

The second data signal includes a plurality of second data symbols,

And wherein the information about the second data signal comprises a soft decision value for each of the plurality of second data symbols and an average value of effective noise variance values for each of the plurality of data symbols.
The method of claim 13,

The second data signal comprises a plurality of second data bits,

And wherein the information about the second data signal comprises a soft decision value for each of the plurality of second data bits.
The method of claim 13,

The serving cell base station apparatus transmits a request for information on the second data signal to the at least one neighboring cell base station apparatus;

The at least one neighbor cell base station apparatus, upon receiving the request command, transmits at least one of the information about the second data and the second data signal to the serving cell base station apparatus.
The method of claim 13,

The at least one neighbor cell base station apparatus

If the restoration of the second data is successful, transmit the second data to the serving cell base station apparatus;

And if the restoration of the second data fails, transmitting information on the second data signal to the serving cell base station apparatus.
A terminal apparatus for performing multi-in multi-out (MIMO) communication with a multi-cell cooperative communication system including a plurality of base station apparatuses,

A storage unit for storing a codebook including at least one precoding matrix composed of a plurality of precoding vectors;

A receiver which receives a radio signal from the plurality of base station apparatuses;

A channel estimating unit estimating a state of a plurality of channels formed between the plurality of base station apparatuses and the terminal apparatus based on the radio signal;

Select one precoding matrix from the at least one precoding matrix based on the estimated state of the plurality of channels, and at least one precoding vector from among a plurality of precoding vectors constituting the one precoding matrix. A selection unit for selecting; And

Transmitter for transmitting a second feedback signal including information on the selected at least one precoding vector to at least one base station device of the plurality of base station devices

Terminal device comprising a.
The method of claim 20,

An intensity measuring unit measuring intensity of the plurality of wireless signals

More,

The transmitter further transmits a first feedback signal including the strengths of the plurality of wireless signals.
The method of claim 20,

The plurality of base station apparatuses include a first base station apparatus and at least one second base station apparatus,

The receiving unit

Receiving information on the at least one second base station apparatus from the first base station apparatus,

Terminal device for receiving only a radio signal transmitted from the at least one second base station device.