KR20100046755A - Wireless communication system in multi-cell and multi-antenna environments and method thereof - Google Patents

Abstract

PURPOSE: A wireless communication system in a multi cell and a multi antenna environment and a method thereof are provided to actively estimate interference information from a terminal to an adjacent cell in multi cell environment, thereby using the interference information to an interference control. CONSTITUTION: A high frequency processor(140) changes a high frequency signal of a transmission method realization unit(130) to baseband signal. A information restoration unit(170) restores the baseband signal. A scheduler(105) assigns each time-frequency resources to terminals. A transmission power decision unit(120) determines a transmission power of a broadcasting signal based on load information of corresponding cell of a load information calculator(110). A interference information estimator(230) estimates the interference information based on a input signal of a high frequency processing unit(220).

Description

Wireless communication system in multi-cell multi-antenna environment and its method {Wireless communication system in multi-cell and multi-antenna environments and method

The present invention relates to a wireless communication system and method thereof in a multi-cell multi-antenna environment. More specifically, in a multi-cell multi-antenna environment, each base station periodically transmits a signal using a predetermined time-frequency resource so that a terminal in another cell can estimate interference information from an adjacent cell. The present invention relates to a wireless communication system and method for estimating interference information using a signal in a terminal.

The present invention is derived from a study conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development. [Task management number: 2008-F-007-01, Task name: Intelligent wireless communication in a three-dimensional environment system].

Multiple transmit / receive antenna technology enables to increase the data rate and reliability of a wireless communication system by installing a plurality of antennas at the transmitting end and the receiving end and utilizing them. However, most of the conventional researches on the multiple transmit / receive antenna technology have a limitation in that only the single cell environment is considered, and the influence of interference between adjacent cells existing in the multi-cell environment, which is a practical wireless communication environment, is not sufficiently considered.

In a wireless communication system based on a multi-cell environment, it is very important to solve the problem of interference between adjacent cells. In particular, as the inter-cell frequency reuse rate increases, the effect of inter-cell interference is increasing, and inter-cell interference has become the biggest obstacle to achieving high-speed wireless data rate. Although multiple transmit / receive antenna technology has the potential as a means to solve the problem of inter-cell interference, the research that actively uses multiple antennas as a means to solve the problem of inter-cell interference is still in the beginning stage.

Conventional studies related to multiple antenna technology in a multi-cell environment are as follows. Jiwoong Kang, Hee-Won Je, and Kwang-Bok Lee proposed a transmission antenna selection method considering adjacent cell interference in a multi-cell environment (JW Kang, HW Je, and KB Lee, “Transmit Antennas Subset Selection for Downlink MIMO Systems”, in Proc. International Conference on Communications 2007 (ICC2007), June 2007). On the assumption that the transmitter does not know the channel information, Blum has proved that the optimal transmission scheme using multiple antennas can vary depending on the influence of interference between adjacent cells (RS Blum, “MIMO capacity with interference”, IEEE Journal on Selected). Areas in Communications, vol. 21, no. 5, pp. 793-801, June 2003). Ye proposed a technique for determining the transmission scheme of multiple antennas in consideration of the influence of interference between adjacent cells in a multi-cell environment (S. Ye, and RS Blum, “Optimized signaling for MIMO interference systems with feedback”, IEEE Transactions on Signal Processing, vol. 51, no. 11, pp. 2939-2848, Nov. 2003). However, in order to use the technique proposed by Ye, it is difficult to apply it to an actual system because each transmitting end must know the channel state of all the links existing in the system and the transmission method used by the transmitting end of the other cell.

Referring to FIG. 1, unlike a system in which only a single cell is considered, in a wireless communication system in a multi-cell environment, there is an interference signal received or received from neighbor cells when transmitting and receiving a signal in a corresponding cell. Therefore, when transmitting and receiving a signal without considering such interference, communication efficiency and performance are lower than actually expected, and this phenomenon becomes more severe as the size of the cell is smaller or the terminal is located in the edge region of the cell. . However, there is no concrete way to solve this problem. That is, conventional studies for actively responding to interference from or adjacent to neighboring cells in a multi-cell environment are still in their infancy, and research on this is very inadequate.

The present invention is designed to solve the problems as described above,

A method for actively responding to interference received from or adjacent to cells when transmitting and receiving a signal in a corresponding cell four. It is an object of the present invention to provide a system and a method for allowing each base station to periodically transmit a signal reflecting load information of a corresponding cell using a resource of a predetermined time-frequency and estimate interference information using the signal at a terminal. It is done.

In addition, the present invention uses a separate resource so that the terminal in a cell can estimate not only the channel of the cell but also the channel of the adjacent cell, and reflects the load information in the transmission power of the signal to be used for channel estimation. It is an object of the terminal of the cell to additionally know the load information of the adjacent cell and the channel information reflecting the load.

In a wireless communication system according to a first embodiment of the present invention, in a wireless communication system in a multi-cell multi-antenna environment, a base station includes one of channel information with the base station and load information of the base station with terminals of adjacent cells. It is characterized by transmitting a radio signal so that an abnormality can be estimated.

In particular, the base station, the load information calculation unit for calculating the load information of the cell; A transmission power determination unit which determines transmission power of the radio signal using the load information; And a transmission method implementation unit for adjusting and transmitting the transmission power of the wireless signal based on the transmission power determined by the transmission power determination unit.

The transmission power determining unit may determine the transmission power of the radio signal by using an increasing function having the load information as a variable.

In addition, the transmission method implementation unit, characterized in that for transmitting the transmission power determined by the transmission power determiner over the entire time-frequency resources allocated in the transmission of the radio signal.

In addition, the transmission method implementation unit divides the time-frequency resources allocated in transmitting the radio signal into two parts, one part of the transmission power determined by the transmission power determining unit, and the other part of the reference transmission. It is characterized by the transmission in power.

In addition, the transmission method implementation unit, if the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, characterized in that for transmitting the reference transmission power of the cell separately.

In addition, the transmission scheme implementation unit, characterized in that for periodically transmitting the radio signal using a pre-allocated time-frequency resources.

In addition, the transmission method implementation unit, in transmitting the radio signal, characterized in that for transmitting the radio signal while sharing the same time-frequency resources with each base station of the adjacent cell.

In addition, the transmission method implementation unit is characterized in that for transmitting the radio signal by transmitting a time-frequency resource different from each base station of an adjacent cell.

In addition, the transmission scheme implementation unit, characterized in that for transmitting the radio signal using the time-frequency resources allocated for channel estimation with the terminal of the cell.

In addition, the transmission method implementation unit, if the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, characterized in that for transmitting the reference transmission power of the cell separately.

In a terminal according to the first embodiment of the present invention, each base station sharing the same time-frequency resource in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, and determines the determined transmission. Receiving unit for receiving the radio signal transmitted by using different codes to reflect the power to the radio signal; And an interference information estimator for estimating interference information from an adjacent cell using the radio signal.

In particular, the interference information estimator calculates a covariance matrix using the received signal vector of the radio signal, removes a component corresponding to a channel with a base station of the corresponding cell from the covariance matrix, and removes an interference covariance matrix ( The interference information is estimated by calculating an interference covariance matrix.

In a terminal according to a second embodiment of the present invention, each base station using different time-frequency resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of a corresponding cell, A receiver for dividing a resource into two parts, one part transmitting at the determined transmission power, and the other part receiving a radio signal transmitted at a reference transmission power; And an interference information estimator for estimating interference information from an adjacent cell using the radio signal.

In particular, the interference information estimator may estimate the interference information based on the transmission power of each part of the received radio signal.

The interference information estimating unit may estimate the interference information by calculating a ratio of the transmission power of each portion.

In the terminal according to the third embodiment of the present invention, each base station using different resources in a multi-cell environment determines the transmission power of a radio signal to be transmitted using load information of the corresponding cell, A receiving unit which receives a radio signal transmitted at the determined transmission power over; And an interference information estimator for estimating interference information from an adjacent cell using the radio signal.

In particular, the interference information estimator estimates channel information from the radio signal, and calculates an interference covariance matrix using the same to estimate the interference information.

The wireless communication method according to the first embodiment of the present invention is a wireless communication method for allowing terminals of other cells adjacent to a base station to estimate load information of a cell to which the base station belongs in a multi-cell multi-antenna environment. Calculating load information of the corresponding cell; Determining a transmission power of a radio signal to be transmitted using the load information; And adjusting and transmitting a transmission power of the radio signal based on the determined transmission power.

In particular, the step of determining the transmission power, characterized in that using the increasing function (increasing function) having the load information as a variable.

In addition, the increasing function is characterized in that the linear function (linear function).

The transmitting may include transmitting at the determined transmission power over the allocated time-frequency resource.

The transmitting may include: dividing the allocated time-frequency resource into two parts, one part transmitting the transmission power determined by the transmission power determining unit, and the other part transmitting the reference transmission power. do.

The transmitting may include transmitting the reference transmission power of the cell separately if the reference transmission power of the neighboring cell is different from the reference transmission power of the cell.

The transmitting may include transmitting the radio signal periodically using a pre-allocated time-frequency resource.

The transmitting may include transmitting the radio signal while sharing the same time-frequency resource with each base station of an adjacent cell.

The transmitting may include transmitting a radio signal by receiving a different time-frequency resource from each base station of an adjacent cell.

The transmitting may include transmitting the radio signal using a time-frequency resource allocated for channel estimation with a terminal of a corresponding cell.

A wireless communication method according to a second embodiment of the present invention is a wireless communication method performed by a terminal in estimating interference information from an adjacent cell in a multi-cell multi-antenna environment, wherein the terminal shares the same time-frequency resource. Determining, by each base station, transmission power of a radio signal to be transmitted using load information of a corresponding cell, and receiving the radio signal transmitted using different codes by reflecting the determined transmission power in the radio signal; And estimating interference information from an adjacent cell using the radio signal.

In particular, the estimating of the interference information may include calculating a covariance matrix using the received signal vector of the radio signal, removing a component corresponding to a channel with a base station of the cell from the covariance matrix, and then interfering with the interference signal. The interference information is estimated by calculating an interference covariance matrix.

The wireless communication method according to the third embodiment of the present invention is a wireless communication method performed by a terminal in estimating interference information from an adjacent cell in a multi-cell multi-antenna environment, wherein the terminals are different from each other in a multi-cell environment. Each base station using time-frequency resources determines transmission power of a radio signal to be transmitted using load information of a corresponding cell, divides a given resource into two parts, and transmits one part at the determined transmission power, The other part comprises: receiving a radio signal transmitted at a reference transmission power; And estimating interference information from an adjacent cell using the radio signal.

In particular, the estimating of the interference information may include estimating the interference information based on the transmission power of each part of the received radio signal.

The estimating of the interference information may include estimating the interference information by calculating a ratio of transmission power of each portion.

A wireless communication method according to a fourth embodiment of the present invention is a wireless communication method performed by a terminal in estimating interference information from a neighbor cell in a multi-cell multi-antenna environment, wherein the terminal is configured to have different resources in a multi-cell environment. Determining, by each base station using, load power of a radio signal to be transmitted using load information of a corresponding cell, and receiving a radio signal transmitted at the determined transmit power over a given resource; And estimating interference information from an adjacent cell using the radio signal.

In particular, the estimating of the interference information may include estimating channel information from the radio signal and estimating the interference information by calculating an interference covariance matrix.

According to the present invention has the following effects.

In a multi-cell environment, terminals can actively estimate interference information from neighbor cells and use it for interference control. In addition, in a multi-cell environment, each base station transmits the load information of the corresponding cell to the transmission power of the radio signal to be transmitted, and the terminals of the neighboring cells can estimate the interference information from the neighboring cell through this signal. Each base station in a multi-cell environment has an advantage of not having to use a separate resource in order for terminals of neighboring cells to estimate interference information from neighboring cells.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same components, and repeated descriptions and detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity.

In the present invention, a wireless communication system in a multi-cell environment means that a plurality of base stations exist, each base station manages one cell, and a plurality of terminals communicate with each cell. A wireless communication system in a multi-antenna environment refers to a system in which each base station and terminals have one or more antennas.

In the drawings for explaining a wireless communication system in a multi-cell multi-antenna environment according to the present invention, the mobile station and the base station have three antennas. However, this is for understanding and the number of antennas is not limited thereto. In addition, although only one base station and one terminal are shown in FIG. 2, this is for clarity, and as described above, a wireless communication system in a multi-cell environment according to the present invention includes a plurality of base stations each including one base station. There is a cell, and there are a plurality of terminals in each cell.

2 is a wireless communication system in which a terminal of a cell estimates load information of a cell in a multi-cell multi-antenna environment or terminals of a cell adjacent to a cell can estimate load information of a cell adjacent to a cell A diagram for explaining.

In FIG. 2, there is shown that there is one base station 100 and one terminal 200, but for the sake of understanding, as described above, a plurality of cells exist and each cell has one base station and a plurality of cells. It is a multi-cell environment in which a terminal exists. In addition, the terminal 200 illustrated in FIG. 2 may be a terminal belonging to the same cell as the base station 100 or a terminal belonging to a cell different from the base station 100.

Hereinafter, for convenience of description, as shown in FIG. 2, only one base station 100 and one terminal 200 will be described as an example.

라고 가정 한다. 이 경우 i번째 셀의 k번째 단말기가 받는 신호는 수학식 1과 같이 표현할 수 있다. Hereinafter, in the present invention, downlink communication means that the base station transmits signals to the terminals. In addition, it is assumed that there are a total of M cells, each base station has Nb antennas, and each terminal has Nu antennas. And, load information of the i-th cell

Assume that. In this case, the signal received by the k-th terminal of the i-th cell may be expressed as Equation 1.

는 m번째 셀의 기지국으로부터 n번째 셀의 k번째 단말기로의 채널응답 행렬(Nu x Nb)를,

는 m번째 셀의 기지국이 송신하는 방송신호벡터(Nb x 1)를,

는 m번째 셀의 k번째 단말기의 수신신호 벡터(Nu x 1)를,

는 m번째 셀의 k번째 단말기의 수신잡음 벡터(Nu x 1)를 의미한다.here,

Denotes a channel response matrix (Nu x Nb) from the base station of the mth cell to the kth terminal of the nth cell,

Is a broadcast signal vector (Nb x 1) transmitted by the base station of the m-th cell,

Is the received signal vector (Nu x 1) of the k-th terminal of the m-th cell,

Denotes a reception noise vector Nu x 1 of the k th terminal of the m th cell.

을 송신한다. 이 신호는 기지국(100)이 주기적으로 송신하게 되는데, 기지국(100)은 미리 할당받은 시간-주파수 자원을 이용하여 방송신호

을 송신하게 된다. 예컨대, 도 3에 도시한 바와 같이, IEEE 802.16의 프리앰블(preamble)처럼 미리 정해진 위치(예를 들어, 하향링크 프레임의 첫 심볼 또는 마지막 심볼)에 인접하는 다른 셀의 기지국과 동일한 시간- 주파수 자원을 공유 또는 분할하여 상기한 방송신호를 송신할 수 있다. 기지국(100)이 이 방송신호를 보낼 때 사용하는 시간-주파수 자원의 위치는 다중 셀 환경에서 인접하는 다른 셀의 기지국과 동일할 수도 있고, 다를 수도 있다. 즉, 다중 셀 환경에서 각각의 기지국이 방송신호를 보낼 때 사용하는 시간-주파수 자원의 위치는 셀 마다 동일할 수도 있고, 다를 수도 있다. 하지만, 이 방송신호를 수신하는 단말기(100)는 기지국(100)에게 할당된 시간-주파수 자원의 위치는 알고 있다. The base station 100 according to the present invention is a broadcast signal so that the terminals of the cell or another neighboring cell can estimate the channel response matrix, the load information of the cell, or the interference covariance matrix between the base station and the terminal of the cell.

Send. The signal is periodically transmitted by the base station 100, the base station 100 is a broadcast signal using the time-frequency resources allocated in advance

Will be sent. For example, as shown in FIG. 3, the same time-frequency resource as that of the base station of another cell adjacent to a predetermined position (for example, the first symbol or the last symbol of a downlink frame), such as a preamble of IEEE 802.16. The broadcast signal may be transmitted by sharing or splitting. The location of the time-frequency resource used by the base station 100 to transmit this broadcast signal may be the same as or different from that of the neighboring cells in a multi-cell environment. That is, in a multi-cell environment, the location of time-frequency resources used when each base station transmits a broadcast signal may be the same for each cell or may be different. However, the terminal 100 receiving the broadcast signal knows the location of the time-frequency resource allocated to the base station 100.

의 송신전력은 해당 셀의 부하정보를 반영한다. 이를 위해, 본 발명의 기지국(100)은 스케쥴러(105), 부하정보 산출부(110), 송신전력 결정부(120), 송신방식 구현부(130), 고주파 처리부(140,160), 스위치(150), 및 정보 복원부(170)를 구비한다.Broadcast signal transmitted by the base station 100

The transmit power of reflects the load information of the corresponding cell. To this end, the base station 100 of the present invention is a scheduler 105, load information calculation unit 110, transmission power determination unit 120, transmission method implementation unit 130, high frequency processing unit 140, 160, switch 150 And an information reconstruction unit 170.

The high frequency processor 140 converts the high frequency signal received from the transmission method implementation unit 130 into a baseband signal and transmits the signal to the switch 150.

The switch 150 receives the high frequency signals from the terminals of the cell through the antenna and transmits the high frequency signals to the high frequency processor 160, and receives the baseband signals from the high frequency processor 140 to transmit the signals through the antenna.

The high frequency processor 160 converts the high frequency signal received from the switch 150 into a baseband signal and transmits the signal to the information reconstruction unit 170.

The information recovery unit 170 receives the baseband signal transmitted from the high frequency processor 160 and restores the received baseband signal. When the request for the resource to be used for uplink is received from the terminals of the cell, the information restoration unit 170 transmits the request to the scheduler 105.

를 계산한다. 부하정보

는 0≤

≤1 또는 0≤

≤∞의 다양한 값으로 산출될 수 있으며, 시스템의 특성에 따라 달라질 수 있다.The scheduler 105 allocates time-frequency resources to the terminals of the cell according to resource allocation requests from the terminals of the cell. In this case, the scheduler 105 allocates time-frequency resources to terminals of the corresponding cell in consideration of downlink resources. In addition, the scheduler 105 transmits the details of allocating time-frequency resources to the load information calculator 110. Accordingly, the load information calculation unit 110 is to consider the load information to consider any one or more of the uplink and downlink of the cell based on the data input from the scheduler 105.

Calculate Load information

Is 0≤

≤1 or 0≤

It can be calculated with various values of ≤∞ and can vary depending on the characteristics of the system.

의 송신전력을 결정한다. m번째 셀의 기지국이 송신하는 방송신호

의 송신전력을

이라고 하면

은 수학식 2와 같이 표현될 수 있다.The transmission power determiner 120 may broadcast the broadcast signal based on the load information of the corresponding cell calculated by the load information calculator 110.

Determine the transmit power of Broadcast signal transmitted by base station of mth cell

Transmit power

Speaking of

May be expressed as in Equation 2.

은 m번째 셀의 부하정보를 나타내고

은 m번째 셀의 미리 설정되어 있는 기준 송신전력을 나타낸다. 여기서 기준 송신전력은 일반적인 통신시스템에서 채널 추정에 사용하는 신호의 송신전력을 의미한다. 그리고, 함수

는 일 반적으로

의 증가함수(increasing function)의 형태가 될 수 있다. 즉, 셀의 부하가 증가할수록 방송신호

의 송신전력은 증가한다.here

Represents load information of mth cell

Denotes a preset reference transmission power of the m-th cell. Here, the reference transmission power means transmission power of a signal used for channel estimation in a general communication system. And a function

Is generally

It can be in the form of an increasing function of. That is, the broadcast signal increases as the load of the cell increases

The transmit power of is increased.

There are three types of concrete functions of the increment function.

① linear function

의 송신전력은 선형적으로 비례하여 증가한다. 예컨대, 송신전력 결정부(120)에서는 아래 수학식 3과 같은 식을 통해 송신전력을 결정할 수 있다. In this case, the broadcast signal increases as the load of the cell increases.

Transmit power increases linearly and proportionally. For example, the transmission power determiner 120 may determine the transmission power through the equation (3) below.

을 수신하지 않은 단말기는, 통신시 그 특정 기지국이 속한 셀을 고려하여 통신할 필요가 없게 된다. 따라서 더 정확하게 채널추정 및 빔형성 등이 가능해진다. 이러한 특성들은 이하 후술되는 다 른 실시예들에서도 동일하거나 유사하게 적용된다. In the case of using Equation 3 in the transmission power determiner 120, if there is no load of the corresponding cell, the base station 100 does not transmit a broadcast signal (P _m = 0). Accordingly, the terminal 200 does not have to estimate this channel in a multi-cell environment, and does not have to consider interference to the base station 100 during uplink communication (eg, beamforming, etc.). That is, a broadcast signal from a specific base station in a multi-cell environment

The terminal that has not received the UE does not need to communicate in consideration of the cell to which the particular base station belongs. Therefore, more accurate channel estimation and beamforming are possible. These characteristics apply equally or similarly to other embodiments described below.

② convex function

의 송신전력은 볼록함수 형태로 증가한다. 예컨대, 송신전력 결정부(120)에서는 아래 수학식 4와 같은 식을 통해 송신전력을 결정할 수 있다. In this case, the broadcast signal increases as the load of the cell increases.

The transmit power of increases in the form of convex function. For example, the transmission power determiner 120 may determine the transmission power through the equation (4) below.

③ concave function

의 송신전력은 오목함수 형태로 증가한다. 예컨대, 송신전력 결정부(120)에서는 아래 수학식 5와 같은 식을 통해 송신전력을 결정할 수 있다.In this case, the broadcast signal increases as the load of the cell increases.

The transmit power of is increased in the form of concave function. For example, the transmission power determiner 120 may determine the transmission power through the following equation (5).

을 송신전력 결정부(120)에서 결정된 송신전력으로 전송할 때, 미리 할당된 시간-주파수 자원을 사 용한다. 이하 시간-주파수 자원을 '자원'이라고 칭하기로 한다. 송신방식 구현부(130)는 할당된 자원 전체에 걸쳐 송신전력 결정부(120)에서 결정된 송신전력

으로 송신하거나(도 4의(a) 참고), 할당된 자원을 두 부분으로 분할하여 한 부분은 미리 설정된 기준 송신전력

으로 송신하고 다른 한 부분은

으로 송신할 수 있다(도 4의(b) 참고). 이때, 기지국(100)이 다중 안테나를 사용하는 경우, 송신방식 구현부(130)는 도 5에 도시한 바와 같이, 안테나 별로 할당된 자원을 두 부분으로 분할하여 한 부분은 미리 설정된 기준 송신전력

으로 송신하고 다른 한 부분은

으로 송신할 수도 있다.Meanwhile, the transmission method implementation unit 130 transmits the broadcast signal at the transmission power determined by the transmission power determiner 120. Transmission method implementation unit 130 is a broadcast signal

When transmitting to the transmission power determined by the transmission power determiner 120, it uses a time-frequency resource allocated in advance. Hereinafter, time-frequency resources will be referred to as 'resources'. The transmission method implementation unit 130 transmits power determined by the transmission power determiner 120 over the allocated resources.

(Refer to (a) of FIG. 4) or by dividing the allocated resource into two parts, one of which is a preset reference transmission power.

And the other part

Can be transmitted (see FIG. 4B). In this case, when the base station 100 uses multiple antennas, as shown in FIG. 5, the transmission method implementation unit 130 divides the resources allocated for each antenna into two parts, one of which is a preset reference transmission power.

And the other part

It can also be sent.

는, 다중 셀 환경에서 다른 셀의 기준 송신전력과 동일할 수도 있고, 이를테면

로 같은 수도 있고, 다를 수도 있다. 다를 경우에는 프리앰블이나 비컨(beacon), 메시지 등 시스템마다 미리 정의되어 있는 다른 방법을 통해 단말기(200)에게 알려줄 수 있고, 단말기(200)는 그 상기한 방법을 통해 얻은 정보를 가지고 정규화(normalization)시켜줄 수 있다. 이하 후술되는 설명에서는 다중 셀 환경에서 각 셀의 기준 송신전력이 다음 수학식 6과 같이 동일하다고 가정한다.Reference Transmit Power Used by Base Station 100

May be equal to the reference transmit power of another cell in a multi-cell environment, such as

May be the same or different. If different, the terminal 200 may be notified to the terminal 200 through another method predefined for each system, such as a preamble, a beacon, a message, and the terminal 200 may be normalized with the information obtained through the above method. I can let you. In the following description, it is assumed that the reference transmission power of each cell is the same as in Equation 6 in a multi-cell environment.

Hereinafter, the transmission method implementation unit 130 is a broadcast signal A method of reflecting the transmission power determined by the transmission method determination unit 120 will be described in detail with reference to FIGS. 6 to 8.

를 송신하는 방법과 다중 셀 환경에서 다른 셀의 각 기지국과 서로 다른 자원을 이용하며 방송신호

를 송신하는 방법이 있다. 각 기지국 별로 자원을 구분하는 것 이외에도, 각 기지국이 다중 안테나를 사용하는 경우 안테나 별로 자원을 구분하여 이용하는 방법도 필요할 수 있다. 하지만, 다중 안테나의 경우에는 해당 셀에 기지국이 다수 개인 상황과 동일하게 확장가능하기 때문에, 후술되는 내용에서는 다중 셀 환경에서 각각의 기지국들의 안테나는 하나인 것으로 가정하여 설명하기로 한다. In general, the transmission method implementation unit 130 of the base station 100 uses the same resources as each base station of another cell in a multi-cell environment and broadcast signals.

Broadcast signal using a different resource from each base station of a different cell in a multi-cell environment

There is a way to transmit. In addition to classifying resources for each base station, if each base station uses multiple antennas, a method for classifying resources for each antenna may be required. However, in the case of the multi-antenna, since the base station can be expanded in the same cell as in the case of having a large number of base stations, the following description will assume that there is only one antenna of each base station in the multi-cell environment.

① In a multi-cell environment, each base station uses the same time-frequency resource

를 송신하게 되는데, 이때 각 기지국은 서로 다른 코드(code)를 사용하여서 방송신호를 송신한다. 전술한 바와 같이, 기지국의 안테나가 다수 개일 경우에도 각 안테나 별로 코드를 할당하여 같은 방법으로 방송신호를 송신하게 된다.Referring to FIG. 6, when each base station shares the same resource with each other in a multi-cell environment, the base station m (m = 1, 2, ..., M) indicates that the terminal existing in the cell 1 to M belongs to the base station m. Broadcast signal to estimate cell load information

In this case, each base station transmits a broadcast signal using a different code. As described above, even when there are a plurality of antennas of the base station, a code is assigned to each antenna to transmit a broadcast signal in the same manner.

② Each base station uses different time-frequency resources in a multi-cell environment

를 전송하게 된다. 마찬가지로 다중 셀 환경의 각 기지국이 다중 안테나를 사용하고 있을 때에는 각 기지국 별로 Nb개씩 자원을 할당 받을 수 있고, 각 기지국은 안테나 한 개당 하나의 자원을 할당해 줄 수 있다. 이상 설명한 방법 이외에도 다른 할당 방법이 존재할 수도 있으며, 본 발명에 적용되는 분할 방법이 상기한 방법에 국한되는 것은 아니다.Referring to FIGS. 7 and 8, a method in which each base station divides and allocates allocated resources is as follows. For example, when Nb * M resources are given to a base station of M cells, each M cell divides Nb resources from each other, and each base station of M cells uses a broadcast signal through this resource.

Will be sent. Similarly, when each base station in a multi-cell environment uses multiple antennas, Nb resources may be allocated to each base station, and each base station may allocate one resource per antenna. Other allocation methods may exist in addition to the above-described methods, and the division method applied to the present invention is not limited to the above-described methods.

Meanwhile, in addition to separate resources for estimating load information, which are given the same or differently for each base station in a multi-cell environment, each base station may be configured with an existing resource (eg, preamble in) used to provide services to terminals of the cell. IEEE 802.16e) may be used to allow terminals of a cell to estimate load information of the cell or terminals of a neighboring cell to estimate load information of the cell. This is possible because the base station provides the load information of the cell to the terminal of the cell or the neighboring cell by adjusting the transmission power of the broadcast signal, so that the base station can estimate the load information of the cell In order to enable terminals of neighboring cells to estimate load information of the corresponding cell, there is an advantage of not using a resource separately. In this case, when the reference transmission power of the preamble is different for each base station in a multi-cell environment, each base station informs the reference transmission power through a separate method predefined for each system so that the terminal can normalize.

Hereinafter, a method for the terminal 200 of the present invention to receive a broadcast signal transmitted from a base station of a cell through the above-described method and estimate a channel response matrix, load information, or interference covariance matrix of any cell. Let's explain. Hereinafter, the channel response matrix, the load information, and the interference covariance matrix will be collectively referred to as 'interference information'. In this case, the interference information may be information on a corresponding cell and information on a neighboring cell to be considered when the terminal 200 communicates with a base station of a corresponding cell in a multi-cell environment.

To this end, the terminal 200 of the present invention includes a switch 210, a high frequency processing unit 220, 270, an interference information estimating unit 230, a transmission method implementation unit 240, and an information restoration unit 250. Here, the switch 210 and the high frequency processor 220 correspond to the 'receiver' of the terminal 200, and the switch 210 and the high frequency processor 270 correspond to the 'transmitter' of the terminal 200.

The high frequency processor 270 converts the high frequency signal received from the transmission method implementation unit 240 into a baseband signal and transmits the signal to the switch 210.

The switch 210 transmits the high frequency signal received through the antenna to the high frequency processor 220, receives the baseband signal from the high frequency processor 270, and transmits the signal through the antenna.

The high frequency processor 220 converts the high frequency signal received from the switch 210 into a baseband signal and transmits the converted high frequency signal to the information recovery unit 250 and the interference information estimator 230.

The information recovery unit 250 receives the baseband signal transmitted from the high frequency processor 220 and restores the received baseband signal.

The interference information estimator 230 estimates 'interference information' based on the signal input from the high frequency processor 220. Hereinafter, the interference information estimator 230 receives a broadcast signal transmitted from a base station of a cell through the above-described method, and interfers the interference information (ie, a channel response matrix, a load information, or an interference covariance matrix) of that cell. The estimation method will be described in detail.

The broadcast signal transmitted to the terminal by the base station according to the present invention may be divided into three cases as follows.

① Each base station sharing the same time-frequency resource in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, and reflects the determined transmission power to the radio signal to generate different codes. When transmitting a broadcast signal using.

(2) When each base station using different resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, and transmits with the determined transmission power over a given resource.

(3) Each base station using different time-frequency resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, and divides a given resource into two parts, one of which is described above. When transmitting at the determined transmission power, and transmitting the other part at the reference transmission power.

을 받게 된다. 이때 다중 셀 환경의 각 기지국이 다중 안테나를 사용하고 있다면

(L x 1)를 길이 L에 걸쳐 받게된다. 이때 신호

는

의 송신전력으로 송신된다. 다음 수학식 7은 4개의 기지국이 1개의 안테나를 가지고 있고 길이가 L인 코드를 사용하고 있을 때 2개의 안테나를 가진 단말기에서 받은 신호를 나타낸다. 그 리고 기지국 m은 부하정보

을 가지고 코드

를 사용하며, 그 코드의 기준 송신전력은

, 부하가 고려된 실제 송신전력은

이라고 가정한다.First, each base station sharing the same time-frequency resources in a multi-cell environment determines the transmission power of a radio signal to be transmitted using load information of the corresponding cell, and reflects the determined transmission power to the radio signal to thereby be different from each other. When transmitting a broadcast signal using a code, the interference information estimator 230 estimates an interference covariance matrix through the following method. For convenience of explanation, it is assumed that the code length is L and the antenna of the terminal receiving the signal has two antennas. The terminal is defined as (i, k). This means that it is the k-th terminal of the i-th cell. At this time, the terminal (i, k) is a signal from the other base stations m = 1, 2, ..., i-1, i + 1, ..., M, including the base station i being serviced

Will receive. If each base station in a multi-cell environment uses multiple antennas

(L x 1) over the length L. Signal

Is

Is transmitted at the transmit power of. Equation 7 shows a signal received from a terminal having two antennas when four base stations have one antenna and use a length L code. And base station m is load information

Have code

The reference transmit power of the code is

, The actual transmit power considering load

Assume that

가 되고(2 X 1),

은 n번째 기지국으로부터 단말기의 m번 안테나로의 채널응답(1 x 1)을 의미한다.

은 2개의 수신안테나중 1번 안테나가 받은 신호(L x 1),

는 2번 안테나가 받은 신호(L x 1)를 나타낸다. 그리고

는 n번째 기지국이 사용하는 코드(L x 1),

는 m번 안테나에서의 수신잡음벡터(L x 1)를 의미한다. 이 때 채널응답

인 시간/주파수상의 자원을 통해 n번째 기지국에서 단말기의 m번 안테나로 길이 L인 코드가 전송되는데, 그 동안

는 값이 변하지 않는 것을 가정한다. 이는 다중 셀 환경에서 각 기지국이 자원을 공유하여 길이 L인 서로 다른 코드를 각각 전송한다고 할 때 이 공유하고 있는 자원 내에서 각 안테나 간 채널의 채널응답은 변하지 않는 것을 의미한다.Here, one antenna of each base station in a multi-cell environment and two antennas of a terminal (i, k) are referred to as a channel.

Becomes (2 X 1),

Denotes a channel response (1 × 1) from the nth base station to the antenna m of the terminal.

Is the signal received by antenna 1 of the two receiving antennas (L x 1),

Denotes the signal (L x 1) received by antenna 2. And

Is the code used by the nth base station (L x 1),

Denotes a reception noise vector (L x 1) at antenna m. Channel response

The code of length L is transmitted from the nth base station to the m antenna of the terminal through the resource on time / frequency.

Assumes that the value does not change. This means that in a multi-cell environment, when each base station shares a resource and transmits a different code of length L, the channel response of the channel between antennas does not change in the shared resource.

 Assuming that the terminal accurately estimates the channel without errors when four base stations are located as above, an accurate covariance matrix is given by Equation 8 below.

In Equation 8 above, () ^H represents the conjugate-transpose of the matrix. In this case, the terminal may estimate the covariance matrix by the following equation (9).

Equation 9 can be estimated by Equation 9 by using Equation 10 as an example.

This is only an example and may vary depending on the definition of the load and how the load is reflected in the transmission power. Equation 10 represents a case where the load information value is 0 to 1 and the load is linearly reflected in the transmission power.

In Equation 10, when the load information of each base station is 1, the actual covariance matrix is the same. In the following description, it is assumed that each load information is 1.

In Equation 10, if the codes are perfectly orthogonal to each other, the part corresponding to the second cross-term does not appear. If the code is made of PN-code, the longer the length L of the code, the closer the second term is to zero, which is more accurately estimated.

If the interference covariance matrix observed by the terminal (i, k) is obtained, the component corresponding to the channel with the corresponding base station should be removed from the covariance matrix as shown in Equation 11 below. For convenience of explanation, it is assumed that the terminal (1, k) belongs to the first base station. Where (^) means estimate.

)은 알고 있다고 가정한다.In this case, each terminal of the multi-cell environment is a channel with the corresponding cell base station through a method for channel estimation in a corresponding cell, such as a channel estimation method or a preamble, which will be described later.

) Is assumed to be known.

 Each channel can be estimated in a similar manner. For example, if the terminal knows the code used by each base station, the channel can be estimated using the received signal and the code. Equation 12 shows a process of estimating a channel between antenna # 1 and base station # 1 of the terminal.

 As with Covariance, if the codes are orthogonal to each other, the cross-terms are zero and all components except noise are zero. Therefore, the better the signal-to-noise ratio, the more accurately the channel response can be obtained.

Next, when each base station using different resources in a multi-cell environment determines the transmission power of the radio signal to be transmitted using the load information of the corresponding cell, and transmits at the determined transmission power over a given resource The interference information estimator 230 estimates the interference covariance matrix in the following manner.

로 나타낼 수 있다. 여기에서

는 n번째 셀의 부하정보,

는 n번째 셀의 기지국으로부터 m번째 셀의 단말기의 k번째 안테나로의 채널응답을 나타낸다. m번째 단말기의 모든 안테나가 n번째 셀의 기지국으로부터 수신한 신호로부터 추정한 채널정보는 다음의 수학식 13과 같이 나타낼 수 있다.The terminal may estimate channel information reflecting load information of each base station by receiving signals from different time-frequency resources allocated to each cell. Channel information estimated from the signal received by the k-th antenna of the terminal of the m-th cell from the base station of the n-th cell

It can be represented as. From here

Is load information of nth cell,

Denotes the channel response from the base station of the n-th cell to the k-th antenna of the terminal of the m-th cell. Channel information estimated from signals received by all antennas of the m-th terminal from the base station of the n-th cell may be expressed by Equation 13 below.

은 다음의 수학식 14와 같이 추정한다.Interference covariance matrix at terminal of cell m

Is estimated as in Equation 14 below.

Next, each base station using different time-frequency resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, and divides a given resource into two parts. Is transmitted at the determined transmission power, and the other part is transmitted at the reference transmission power, the interference information estimator 230 estimates the interference information in the following manner.

, 나머지 한 부분은

으로 전송하였을 경우 단말기에서는 각 부분에서 수신된 신호의 송신전력의 비율를 계산하여

를 추정할 수 있다.

로 송신된 부분을 수신한 신호를

,

으로 송신된 부분을 수신한 신호를

라고 하면 기지국 m의 부하정보

는 수학식 15와 같다.One part of a given resource by the base station of the m-th cell

, The other part

In case of transmitting by, the terminal calculates the ratio of transmit power of the signal received from each part.

Can be estimated.

Signal received from the part

,

Signal received from the

Speak load information of base station m

Is the same as (15).

In the above embodiment, the method of estimating the load information in the receiving terminal may be different according to the method in which the load is reflected in the transmission power when the load is reflected in a proportional manner.

The present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media may include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage. Also included are those implemented in the form of carrier waves (eg, transmission over the Internet). The computer readable recording medium can also be distributed over network coupled systems so that the computer readable code is stored and executed in a distributed fashion.

As mentioned above, although the preferred embodiment of this invention was shown and described, this invention is not limited to the specific embodiment mentioned above, Usually, in the technical field to which this invention pertains without deviating from the summary of this invention claimed in a claim. Various modifications may be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

1 is an exemplary diagram to help understand a wireless communication system in a multi-cell multi-antenna environment.

2 is a diagram illustrating a wireless communication system in a multi-cell multi-antenna environment according to the present invention.

3 to 8 are reference diagrams for explaining a wireless communication method in a multi-cell multi-antenna environment according to the present invention.

Claims (53)

In a wireless communication system of a multi-cell multi-antenna environment, The base station transmits the radio signal by adjusting a transmission power of a radio signal to be transmitted so that terminals of other neighboring cells can estimate one or more of channel information with the base station and load information of the base station. Wireless communication system. The method according to claim 1, The base station comprises: A load information calculator configured to calculate load information of a corresponding cell; A transmission power determining unit which determines a transmission power of the radio signal using the load information; And And a transmission method implementation unit for adjusting and transmitting the transmission power of the wireless signal based on the transmission power determined by the transmission power determination unit. The method according to claim 2, The transmission method implementation unit, And periodically transmitting the radio signal using a pre-allocated time-frequency resource. The method according to claim 2, The transmission power determiner, And a transmission power of the radio signal is determined using an increasing function having the load information as a variable. The method according to claim 4, And said increasing function is a linear function. The method according to claim 4, And the increasing function is a convex function. The method according to claim 4, The increasing function is a concave function (concave function). The method according to claim 2, The transmission method implementation unit, And transmitting at the transmission power determined by the transmission power determining unit over the allotted time-frequency resources in transmitting the radio signal. The method according to claim 2, The transmission method implementation unit, In the transmission of the radio signal, the allocated time-frequency resource is divided into two parts, one part of the transmission power determined by the transmission power determining unit, and the other part of the transmission power, characterized in that the transmission Wireless communication system. The method according to claim 2, The transmission method implementation unit, If the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, the wireless communication system characterized in that for transmitting the reference transmission power of the cell separately. The method according to claim 2, The transmission method implementation unit, In transmitting the radio signal, the radio communication system is configured to transmit the radio signal while sharing the same time-frequency resource with each base station of an adjacent cell. The method according to claim 11, The transmission method implementation unit, the wireless communication system, characterized in that for transmitting the wireless signal using a code (code). The method according to claim 12, The code is different from the code used by each base station of the adjacent cell. The method according to claim 11, The transmission method implementation unit, And transmitting the radio signal using a plurality of antennas to which codes are assigned. The method according to claim 14, And a different code is assigned to the plurality of antennas. The method according to claim 2, The transmission method implementation unit, And transmitting the radio signal by allocating a different time-frequency resource to each base station of an adjacent cell in transmitting the radio signal. 18. The method of claim 16, The transmission method implementation unit, And transmitting the radio signal using a plurality of antennas allocated with different time-frequency resources. The method according to claim 2, The transmission method implementation unit, And transmitting the radio signal using a time-frequency resource allocated for channel estimation with a terminal of a corresponding cell. 19. The method of claim 18, The transmission method implementation unit, If the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, the wireless communication system characterized in that for transmitting the reference transmission power of the cell separately. Each base station sharing the same time-frequency resources in a multi-cell environment determines the transmission power of a radio signal to be transmitted using load information of the cell, and reflects the determined transmission power to the radio signal to generate different codes. Receiving unit for receiving a wireless signal transmitted by using; And And an interference information estimator for estimating interference information from an adjacent cell using the radio signal. The method of claim 20, The interference information estimator, The covariance matrix is calculated using the received signal vector of the radio signal, the component corresponding to the channel with the base station of the cell is removed from the covariance matrix, and the interference covariance matrix is calculated to calculate the interference covariance matrix. Terminal for estimating interference information. 23. The method of claim 21, The interference information estimator, And estimating a channel with each base station using a code corresponding to each base station. Each base station using different time-frequency resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, divides a given resource into two parts, and determines one part of the base station. A receiving unit for transmitting at a transmission power and receiving a wireless signal transmitted at a reference transmission power; And And an interference information estimator for estimating interference information from an adjacent cell using the radio signal. The method according to claim 23, The interference information estimator, And estimating the interference information based on the transmission power of each part of the received radio signal. 27. The method of claim 24, The interference information estimator, And estimating the load information by calculating a ratio of transmission powers of the respective parts. Each base station using different resources in a multi-cell environment determines the transmission power of a radio signal to be transmitted using load information of the cell, and receives the radio signal transmitted at the determined transmission power over a given resource. A receiving unit; And And an interference information estimator for estimating interference information from an adjacent cell using the radio signal. The method of claim 26, The interference information estimator, And estimating channel information from the radio signal and estimating the interference information by calculating an interference covariance matrix. In a multi-cell multi-antenna environment, a terminal of another cell adjacent to a base station estimates load information of a cell to which the base station belongs. Calculating load information of a corresponding cell; Determining a transmission power of a radio signal to be transmitted using the load information; And Adjusting and transmitting transmission power of the wireless signal based on the determined transmission power. The method according to claim 28, The transmitting step, And periodically transmitting the radio signal using a pre-allocated time-frequency resource. The method according to claim 28, Determining the transmission power; And using an increasing function having the load information as a variable. The method of claim 30, And said increasing function is a linear function. The method of claim 30, The increasing function is a convex function (convex function). The method of claim 30, And said increasing function is a concave function. The method according to claim 28, The transmitting step, And transmitting at the determined transmit power over the allocated time-frequency resource. The method according to claim 28, The transmitting step, And dividing the allocated time-frequency resource into two parts, one part transmitting at the transmission power determined by the transmission power determining unit, and the other part transmitting at the reference transmission power. The method according to claim 28, The transmitting step, If the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, the wireless transmission method characterized in that for transmitting the reference transmission power of the cell separately. The method according to claim 28, The transmitting step, And transmitting the radio signal while sharing the same time-frequency resource with each base station of an adjacent cell. The method of claim 37, The transmitting step, And transmitting the radio signal using a code. The method of claim 38, The code is different from the code used by each base station of the adjacent cell. The method of claim 37, The transmitting step, And transmitting the radio signal using a plurality of antennas to which codes are assigned. The method of claim 40, And a different code is assigned to the plurality of antennas. The method according to claim 28, The transmitting step, And transmitting a radio signal by assigning a different time-frequency resource to each base station of an adjacent cell. The method of claim 42, And transmitting the radio signal using a plurality of antennas allocated with different time-frequency resources. The method according to claim 28, The transmitting step, And transmitting the radio signal using a time-frequency resource allocated for channel estimation with a terminal of a corresponding cell. The method of claim 44, The transmitting step, If the reference transmission power of the adjacent cell is different from the reference transmission power of the cell, the wireless communication method characterized in that for transmitting the reference transmission power of the cell separately. A wireless communication method performed by a terminal for estimating interference information from an adjacent cell in a multi-cell multi-antenna environment, the terminal comprising: Each base station sharing the same time-frequency resource determines transmission power of a radio signal to be transmitted using load information of a corresponding cell, and transmits the transmission signal using different codes by reflecting the determined transmission power in the radio signal. Receiving a radio signal; And Estimating interference information from an adjacent cell using the radio signal. The method of claim 46, Estimating the interference information, The covariance matrix is calculated using the received signal vector of the radio signal, the component corresponding to the channel with the base station of the cell is removed from the covariance matrix, and the interference covariance matrix is calculated to calculate the interference covariance matrix. A wireless communication method comprising estimating interference information. The method of claim 46, Estimating the interference information, And estimating a channel with each of the base stations using a code corresponding to each of the base stations. A wireless communication method performed by a terminal for estimating interference information from an adjacent cell in a multi-cell multi-antenna environment, the terminal comprising: Each base station using different time-frequency resources in a multi-cell environment determines transmission power of a radio signal to be transmitted using load information of the corresponding cell, divides a given resource into two parts, and determines one part of the base station. Transmitting at a transmission power and receiving another portion of the wireless signal at the reference transmission power; And Estimating interference information from an adjacent cell using the radio signal. The method of claim 49, Estimating the interference information, And estimating the interference information based on transmission power of each portion of the received radio signal. The method of claim 50, Estimating the interference information, And estimating the load information by calculating a ratio of transmission powers of the respective parts. A wireless communication method performed by a terminal for estimating interference information from an adjacent cell in a multi-cell multi-antenna environment, the terminal comprising: Each base station using different resources in a multi-cell environment determines the transmission power of a radio signal to be transmitted using load information of the cell, and receives the radio signal transmitted at the determined transmission power over a given resource. Making; And Estimating interference information from an adjacent cell using the radio signal. The method of claim 52, wherein Estimating the interference information, And estimating channel information from the radio signal, and estimating the interference information by calculating an interference covariance matrix.

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