KR102186325B1 - Device for allocationg pilot signal and method for allocationg pilot signal using the same - Google Patents

Abstract

In the method of allocating a pilot signal in a mobile communication system, the method of allocating a pilot signal according to the present invention comprises the steps of: base stations measuring a pilot signal transmitted by a terminal connected to each base station, and setting interference information and channel information for each base station, Receiving, by a first base station, the pilot signal, the interference information, or the channel information from neighboring base stations, and the first base station estimates a channel using at least one of the received pilot signal, the interference information, and the channel information And calculating an error, and allocating a pilot to a terminal connected to the first base station by the first base station using the calculated channel estimation error.

Description

Pilot signal allocation device and pilot signal allocation method using the same {DEVICE FOR ALLOCATIONG PILOT SIGNAL AND METHOD FOR ALLOCATIONG PILOT SIGNAL USING THE SAME}

The present invention relates to a pilot signal allocation apparatus and a pilot signal allocation method using the same.

Massive MIMO technology is being introduced to increase the amount of data transmission or channel capacity in a wireless section in a mobile communication system. Base stations to which such Massive MIMO technology is applied can reduce the effects of noise and interference in inverse proportion to the number of antennas by using many antennas, and increase the amount of data transmission in the wireless section by applying MU-MIMO and beamforming. have.

In a multi-cell environment, when a terminal belonging to one cell transmits a pilot signal to a base station, the signal acts as an interference to the base station of an adjacent cell. Therefore, in order to minimize interference due to a pilot signal, a pilot signal that is orthogonal to the number of terminals belonging to each cell plus the number of users of an adjacent cell is required.

However, due to the limit of the number of orthogonal pilots, it is not possible to allocate pilots to be orthogonal to terminals belonging to other cells. Accordingly, the cell receives not only a pilot signal sent by a UE belonging to its coverage, but also a signal sent by a UE using the same pilot signal in another cell, and estimates a channel based on these signals. Therefore, the estimated channel at this time is different from the existing channel due to interference from other cells, and pilot contamination occurs in which the signal transmitted by the base station acts as interference to a terminal using a non-orthogonal pilot of another cell. There is a difficulty.

The present invention is to propose a pilot signal allocation apparatus for allocating pilots and a pilot signal allocation method using the same in order to increase transmission capacity in a mobile communication system.

In the method of allocating a pilot signal in a mobile communication system, the method of allocating a pilot signal of the present invention includes the steps of: base stations measuring a pilot signal transmitted by a terminal connected to each base station, and setting interference information and channel information for each base station. 1 A base station receiving the pilot signal, the interference information, or the channel information from neighboring base stations, the first base station using at least one of the received pilot signal, the interference information, or the channel information to estimate a channel error And calculating, by the first base station, allocating a pilot to a terminal connected to the first base station by using the calculated channel estimation error.

The interference information may include a preset value for interference from a cell to which a pilot is not allocated from another cell.

The channel information may include a channel estimation error value set in a cell to which pilots are not assigned.

The channel information may include an average of covariance values of a channel between a base station of a specific cell and terminals connected to the specific cell.

The first base station may further include transmitting pilot allocation information allocated to a terminal connected to the first base station to a second base station.

The second base station calculating a channel estimation error using the pilot allocation information of the first base station, interference information or channel information of base stations other than the first base station, and the second base station calculates the channel estimation error. It may further include the step of allocating a pilot to the terminal connected to the second base station by using.

Allocating a pilot to a terminal connected to the second base station may include selecting, by the second base station, a terminal to use the same pilot signal as the terminal to which the pilot signal is assigned in the first base station.

When a plurality of base stations are adjacent, the plurality of base stations sequentially select a terminal, and the step of allocating the same pilot as the pilot allocated to the terminal connected to the first base station to the selected terminal.

The pilot signal allocation apparatus of the present invention uses at least one of a transmission/reception unit for receiving pilot allocation information from base stations, interference information and channel information, the pilot allocation information, the interference information, or the channel information. And a pilot allocation unit for allocating a pilot to a terminal connected to a base station of a specific cell by using the calculated channel estimation error.

The transceiver may receive the pilot allocation information from a base station to which a pilot is allocated, or may receive the interference information and the channel information from a base station to which a pilot is not allocated.

The pilot allocator may select a terminal to use the same pilot signal as the pilot allocated by the base station to which the pilot is allocated.

The pilot allocator may select a terminal having the smallest value of the calculated channel estimation error among terminals connected to a base station of a specific cell as a terminal to use a specific pilot.

The interference information may include a preset value for interference from other base stations to a base station to which a pilot is not assigned.

The channel information may include a channel estimation error value set by a base station to which a pilot is not assigned, or an average of covariance values of a channel between a base station of a specific cell and terminals connected to the specific cell.

According to the present invention, an environment in which pilot contamination that occurs when pilots are allocated in a mobile communication system using Massive MIMO can be mitigated and transmission capacity can be increased.

1 is a schematic diagram of a pilot signal allocation apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart schematically illustrating a process of allocating pilot signals by a pilot signal allocation apparatus arranged in base stations according to an embodiment of the present invention.
3 is a diagram illustrating an example of allocating a pilot signal in a first base station according to an embodiment of the present invention.
4 is a diagram illustrating an example of allocating a pilot signal in a second base station according to an embodiment of the present invention.
5 is a diagram illustrating an example of allocating a pilot signal in a third base station according to an embodiment of the present invention.
6 is a diagram showing a test result of a pilot signal allocation method according to the prior art and an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the embodiments of the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

Throughout the specification, a terminal is a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), and an access terminal. terminal, AT), user equipment (UE), and the like, and may include all or part of the functions of a terminal, MT, SS, PSS, AT, UE, and the like.

In addition, the base station (BS) is a node B (node B), an advanced node B (evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a transceiver base station It may refer to (base transceiver station, BTS), mobile multihop relay (MMR)-BS, and the like, and may include all or part of functions such as NodeB, eNodeB, AP, RAS, BTS, MMR-BS.

Now, a pilot signal allocation apparatus according to an embodiment of the present invention and a pilot signal allocation method using the same will be described in detail with reference to FIGS. 1 to 5.

1 is a schematic diagram of a pilot signal allocation apparatus according to an embodiment of the present invention. In this case, the apparatus for allocating a pilot signal only shows a schematic configuration necessary for description according to an embodiment of the present invention, but is not limited thereto.

Referring to FIG. 1, a pilot signal allocation apparatus 100 according to an embodiment of the present invention includes pilot contamination occurring in a mobile communication system using massive multiple input/output (hereinafter, Massive MIMO, multiple-input and multiple-output). It is a device that allocates a pilot to alleviate the phenomenon of pilot contamination and increase the transmission capacity. Here, the pilot is a reference signal promised between the base station and the terminal in order to obtain channel state information (CSI) between the terminal and the base station, and a pilot signal, a pilot sequence, or a reference signal signal).

In addition, the pilot signal allocation apparatus 100 includes a transmission/reception 110, a calculation unit 120, a pilot allocation unit 130, and a control unit 140 according to an embodiment of the present invention.

The transmission/reception 110 receives pilot allocation information from base stations or receives interference information and channel information. Here, the pilot allocation information includes information on which a specific base station has allocated a specific pilot to a specific terminal.

In addition, the interference information includes pre-determined interference (PDI), which is a preset interference, which includes a preset value of interference transmitted from a base station to which a pilot is not assigned to a cell of a base station to which a current pilot is assigned.

In addition, the channel information is a covariance value of a channel obtained by measuring a pilot signal transmitted by each terminal at each base station corresponding to a cell to which the terminal belongs and an adjacent cell, and channel estimation set by a base station to which no pilot is assigned. Contains the error value. And, the channel information includes a PDD (pre-detemined desired-term). Here, the PDD is an average of the covariance values of the channels of terminals connected to the own cell measured by the base station.

Further, the transmission/reception 110 receives pilot allocation information from a base station to which a pilot is allocated, or receives the interference information and the channel information from a base station to which a pilot is not allocated. In addition, the transmission/reception 110 may measure a pilot signal transmitted by a terminal connected to a corresponding base station in a base station in which the pilot signal allocation apparatus 100 according to an embodiment of the present invention is disposed.

The calculation unit 120 calculates a channel estimation error using at least one of pilot allocation information, interference information, or channel information received by the transmission/reception 110. The calculation unit 120 may calculate a PDI value or a PDD value using a pilot signal measured by the transmission/reception 110 and may set the calculated PDI value and PDD value as interference information or channel information for a corresponding base station.

The pilot allocator 130 allocates a pilot to a terminal connected to a base station of a specific cell by using the channel estimation error calculated by the calculator 120.

At this time, the pilot allocator 130 may select a terminal to use the same pilot signal as the terminal selected by the corresponding base station when there is already a base station to which a specific pilot is assigned.

In addition, the pilot allocator 130 may select a terminal having the smallest value of the calculated channel estimation error among terminals connected to a base station of a specific cell as a terminal to use a specific pilot.

In addition, the control unit 140 controls the transmission/reception 110, the calculation unit 120, and the pilot assignment unit 130 to smoothly operate. In addition, the control unit 140 allows the base stations to which the pilot signal allocation apparatus 100 according to an embodiment of the present invention is disposed to sequentially transmit pilot allocation information, interference information, or channel information, and sequentially allocate pilot signals. Can be controlled.

Hereinafter, a process of calculating a channel estimation error and allocating a pilot signal in a mobile communication system by the pilot signal allocation apparatus 100 according to an embodiment of the present invention will be described in detail.

In one embodiment of the present invention, a network system in which there are L cells and each cell consists of 1 base station and K terminals is considered. In each cell, a group can be created by selecting one terminal at a time, a total of L terminals, and terminals belonging to this group use the same pilot.

에 대한 채널 공분산(covariance)값은

로 나타낼 수 있다. 여기서

는 1번째 셀에 속해있는 k번째 단말이 전송한 파일럿을 i번째 셀에서 수신하여 추정한 채널 벡터이다. In addition, each cell has a base station having M antennas, and there are K terminals having one antenna. Also, the channel

The channel covariance for is

It can be expressed as here

Is a channel vector estimated by receiving the pilot transmitted by the k-th terminal belonging to the first cell in the i-th cell.

라고 하면, k번째 파일럿 신호

를 사용하는 l번째 셀 안의 단말의 인덱스

가 된다. 그리고, k번째 파일럿 신호

를 보내는 단말들의 그룹을

라고 정의한다. 그러면 주어진 단말들의 그룹에 대한 정규화(normalize)된 채널 추정 오류는 다음의 수학식 1과 같다.And,

, The k-th pilot signal

The index of the terminal in the l-th cell using

Becomes. And, the k-th pilot signal

Group of terminals sending

Is defined as. Then, the normalized channel estimation error for a given group of terminals is expressed in Equation 1 below.

Here, the mean square error (MSE) in the base station of the j-th cell is defined as in Equation 2 below.

는 j번째 셀의 기지국과 j번째 셀의

단말과의 채널의 공분산(covariance)값이다. And,

Is the base station of the j-th cell and the j-th cell

This is the covariance value of the channel with the terminal.

Here, there are two methods of allocating a terminal to use the same pilot, an exhaustive search method and a greedy search method.

개의 조합에 대해서 계산을 한 후 비교해야 하므로, 비교해야 하는 단말의 수와 협력해야 하는 셀의 수에 따라 복잡도가 지수적으로 증가하는 문제가 있다.First, in the excessive search method according to the prior art, a channel estimation error is calculated for all possible combinations of terminals, and the same pilot is allocated to a combination having the smallest channel estimation error. However, since the channel estimation error must be calculated for all possible combinations, the complexity is high. In other words,

Since a combination of dogs must be compared after calculation, there is a problem that the complexity increases exponentially according to the number of terminals to be compared and the number of cells to be cooperated.

의 크기가 L로 일정하지 않다. 그러므로, 그리디 검색 방법에서는 j번째 단계에서의 정규화(normalize)된 다음 수학식 3을 이용하여 계산한다.In addition, the greedy search method is a method of sequentially selecting a terminal to use the same pilot in each cell from the first cell to the L-th cell one by one. At this time, it is assumed that there are K terminals in each cell. And, unlike the excessive search method, the greedy search method is a method of adding terminals to be used one by one.

The size of L is not constant. Therefore, in the greedy search method, it is normalized in the j-th step and then calculated using Equation 3.

Here, the MSE at the base station of the j-th cell is calculated as shown in Equation 4 below.

개의 조합을 고려하게 된다. 즉, 과도한 검색 방법은 채널 추정 오류를 최소로 낮출 수 있지만 셀 개수가 증가할수록 복잡도가 지수적으로 증가하는 단점이 있다.Therefore, an excessive search method that considers a combination of all possible terminals can minimize a channel estimation error. However, since the combination of all terminals is considered, the complexity is very high. The excessive search method is that there are L cells with K names in each cell.

The combination of dogs is considered. That is, the excessive search method can reduce the channel estimation error to the minimum, but has a disadvantage in that the complexity increases exponentially as the number of cells increases.

In addition, since the greedy search method sequentially selects terminals, it has an advantage of lower complexity than an excessive search method that considers all possible groups of users. However, the greedy search method selects the terminal of the current cell by considering only interference from the terminal selected in the previous cell.

Therefore, which terminal is selected in the previous cell has a great influence on the channel estimation error. In particular, when selecting a terminal in each cell, there is a limit to lowering the channel estimation error because only interference from a previous cell is considered and interference from a subsequent cell is not considered.

In addition, unlike the excessive search method, the greedy search method considers K terminals sequentially in each cell, so a total of KL combinations are considered. That is, although the greedy search method has the advantage of linearly increasing the complexity as the number of cells increases, there is a limit to lowering the channel estimation error.

Accordingly, a pilot allocation method according to an embodiment of the present invention provides a method capable of further reducing a channel estimation error while having the same complexity as a greedy search method.

A pilot allocation method according to an embodiment of the present invention uses a method of dividing the sum of the mean square errors (MSE) by the sum of the covariances of each channel as shown in Equation 5 below.

Here, the MSE at the base station of the j-th cell is calculated in the same manner as in Equation 4 above.

In the pilot allocation method according to an embodiment of the present invention, a terminal is sequentially selected for each cell through inter-cell cooperation, as in the greedy search method, but additionally, interference (PDI) and PDD from a cell that has not yet been assigned a pilot are The influence of interference from a user to which a pilot is assigned by setting in advance to a cell to which a pilot is not yet assigned is considered.

In the greedy search method, only interference from a previous cell was considered when selecting a user in each cell, but the pilot allocation method according to an embodiment of the present invention considers interference from a subsequent cell and interference affecting a subsequent cell. do. Here, taking into account both interference from each UE of a subsequent cell and interference affecting a subsequent cell has a complexity similar to that of an excessive search method.

Therefore, in the pilot allocation method according to an embodiment of the present invention, interference from a cell to which a pilot is not yet allocated and a desired condition (desired-term) in a cell to which a pilot is not yet allocated are calculated in advance or measured. By using a preset value, such as a value, the user takes into account interference that is affected or received by subsequent cells.

Accordingly, the pilot allocation method according to an embodiment of the present invention uses PDI and PDD, and selects a terminal that reduces a channel estimation error using Equation 6 below.

Here, the MSE at the base station of the j-th cell is calculated using Equation 7 below.

는 j번째 셀의 기지국에 간섭으로 작용하는 번째 l셀의 PDI 값이며,

는 j번째 셀의 PDD 값이다.here

Is the PDI value of the l-th cell acting as interference to the base station of the j-th cell,

Is the PDD value of the j-th cell.

인 경우, 첫 번째 셀부터

번째 셀까지 (예를 들어, 이미 파일럿을 할당한 셀 및 현재 파일럿을 할당하고 있는 셀)와

인 경우,

번째 셀부터 마지막 셀까지(예를 들어, 아직 파일럿을 할당하지 않은 셀)로 두 가지로 나누어서 계산한다. In the present invention, the MSE value

, From the first cell

To the first cell (e.g., a cell that has already assigned a pilot and a cell that is currently assigning a pilot) and

If is,

It is calculated by dividing into two cells from the first cell to the last cell (for example, a cell that has not yet assigned a pilot).

인 경우에는 수학식 4에다가 추가로 PDI값을 고려해준다. 즉, 이미 파일럿이 할당된 셀에서부터 오는 간섭에 아직 파일럿이 할당되지 않은 셀에서부터 오는 간섭

을 추가로 고려하여 MSE 값을 수식학 7과 같이 계산한다.

In the case of, the PDI value is additionally considered in addition to Equation 4. In other words, interference from a cell to which a pilot is already assigned is interference from a cell that has not yet been assigned a pilot.

In consideration of additionally, the MSE value is calculated as in Equation 7.

보다 큰 경우에 기존의 방법에서는 j번째 셀에서의 희망 조건(desired-term)이 정의되지 있지 않으므로 j셀에서의 MSE 값을 정의할 수 없었다. And, j is

In the larger case, since the desired-term in the j-th cell is not defined in the existing method, the MSE value in the j-th cell cannot be defined.

로 정의한다. 그러므로, 본 발명의 한 실시예 따른 파일럿 신호 할당 방법에서는

경우에 MSE 값을 수학식 7과 같이 정의한다. 이때, 파일럿을 할당할 때 계산하여 비교하는 채널 추정 오류는 총 L개의 MSE 값을 모두 고려한 수학식 6을 통해 도출할 수 있다.However, in the pilot signal allocation method according to an embodiment of the present invention, a desired condition in the j-th cell is considered as a predetermined value or a measured value calculated in advance, and the value is

Is defined as Therefore, in the pilot signal allocation method according to an embodiment of the present invention

In this case, the MSE value is defined as in Equation 7. In this case, the channel estimation error calculated and compared when allocating pilots may be derived through Equation 6 in which all L MSE values are considered.

FIG. 2 is a flowchart schematically illustrating a process of allocating pilot signals by a pilot signal allocation apparatus arranged in base stations according to an embodiment of the present invention.

In the pilot signal allocation method according to an embodiment of the present invention, a pilot signal transmitted by each terminal is measured in each cell to obtain a channel covariance value (or channel information corresponding thereto) for each antenna of the terminal. In addition, this can be performed with a much longer period than channel estimation performed every time for data transmission. In addition, the PDI value and the PDD value may be measured and set together when measuring the pilot signal or may be preset by the network operator.

Here, a method of setting the PDI value through measurement at the base station is as follows. The base station separately allocates a resource block and transmits a pilot signal at the same transmission power as that of the terminal using one of the antennas of the base station. At this time, the transmitted pilot should be orthogonal to other pilots. The transmitted pilot is measured by another base station to obtain a covariance value, or a channel is estimated and set as a PDI value. This value is obtained in the same way as when the terminal transmits a pilot to obtain a channel covariance value.

And, the method of setting the PDD value is as follows. The average of the channel covariance values between the base station of the cell and the user belonging to the cell is set as the PDD value in the cell. When the PDI value and PDD value are set in advance by the network operator, the network operator may measure separately or set according to a separate policy.

Referring to FIG. 2, each of the base stations (first base station to Lth base station) measures a pilot signal and sets a PDI value and a PDD value (S100).

Then, the second base station to the Lth base station respectively transmit the PDI value and the PDD value to the first base station, and the first base station receiving the same calculates a channel estimation error and allocates a pilot to the terminal of the corresponding cell (S102, S104. ).

Then, the first base station delivers the pilot allocation information and the pilot measurement value to the second base station (S106).

Also, as above, the second base station receives the PDI value and the PDD value from the third base station to the Lth base station, respectively, calculates a channel estimation error of the corresponding cell, and allocates a pilot to the terminal of the corresponding cell (S108, S110).

In addition, in the pilot signal allocation method according to an embodiment of the present invention, the above procedure is sequentially repeated from branch station 3 to the L-th base station, allocating a pilot to the terminal of the corresponding cell, and transferring the pilot allocation information of the corresponding cell to the next cell. It transmits (S112 to S118).

3 is a diagram illustrating an example of allocating a pilot signal in a first base station according to an embodiment of the present invention.

First, in the pilot signal allocation method according to an embodiment of the present invention, when a pilot is allocated to a terminal in a first cell, it is assumed that interference occurs from cells other than the first cell, and the value is determined by using the PDI value described above. MSE is obtained from the equation above Equation 7.

In addition, the MSE of the remaining cells other than the first cell is also calculated from the following equation of Equation 7 using the PDD value described above. At this time, the PDD value is designated as the average of the covariance values of the terminals distributed in each cell. Substituting the obtained MSE into Equation 6, the channel estimation error can be obtained.

Referring to FIG. 3, a pilot signal allocation method according to an embodiment of the present invention is specified in consideration of a signal from terminals in a first cell of a first base station and a PDI value and a PDD value from cells other than the first cell. Select a terminal to use the pilot. In this case, the first base station selects the terminal having the smallest value obtained using Equation 6 as the terminal to use a specific pilot in the first cell.

4 is a diagram illustrating an example of allocating a pilot signal in a second base station according to an embodiment of the present invention.

4, interference from a UE selected in a first cell, a PDI value and a PDD value coming from a cell other than the first cell and a second cell, and signals from the UEs in the second cell are all considered. A terminal to use the same pilot as the terminal selected in the cell is selected.

In the second cell, the MSE of the first cell and the second cell is determined from the above equation of Equation 7 using interference from the UE selected in the first cell and PDI values from the remaining cells excluding the first cell and the second cell. Seek.

In addition, in consideration of interference from the UE selected in the first cell and PDD values of cells excluding the first cell and the second cell, the MSE of the remaining cells other than the first cell is also calculated from the following equation of Equation 7. Then, the second base station substitutes this for Equation 6 to obtain a channel estimation error, and selects a terminal having the smallest value as a terminal to use the same pilot as the terminal selected in the first cell.

5 is a diagram illustrating an example of allocating a pilot signal in a third base station according to an embodiment of the present invention.

5, a pilot signal allocation method according to an embodiment of the present invention includes interference from terminals selected in a first cell and a second cell, and PDI values from other cells except for the first, second, and third cells. And PDD values, and signals coming from terminals in the third cell are all considered to select a terminal to use the pilots of the same first base station and the second base station. In the pilot signal allocation method according to an embodiment of the present invention, the pilot is allocated by performing this process up to the L-th cell.

6 is a diagram showing a test result of a pilot signal allocation method according to the prior art and an embodiment of the present invention.

Referring to FIG. 6, a graph showing a test result of a channel estimation error comparing a conventional excessive search method and a greedy search method with a pilot signal allocation method according to an embodiment of the present invention. It can be seen that a pilot signal allocation method according to an embodiment of the present invention has the same complexity as a conventional greedy search method, and improves performance by reducing a channel estimation error.

As described above, the pilot signal allocation apparatus and the pilot signal allocation method using the same according to an embodiment of the present invention alleviate and transmit a pilot contamination phenomenon that occurs when pilot is allocated in a mobile communication system using Massive MIMO. It provides an environment in which capacity can be increased.

The embodiments of the present invention described above are not implemented only through an apparatus and a method, but may be implemented through a program that realizes a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such a recording medium can be executed not only in the server but also in the user terminal.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (14)

In a method of allocating a pilot signal in a mobile communication system,
Each of a plurality of base stations measuring a pilot signal transmitted by a terminal connected to the corresponding base station, and setting interference information and channel information for each base station,
The first base station of the plurality of base stations receives pilot allocation information from a base station that has assigned a pilot to a terminal of a corresponding cell among the plurality of base stations, and does not allocate a pilot to a terminal of the corresponding cell among the plurality of base stations. Receiving the interference information or the channel information from a non-existent base station,
Calculating, by the first base station, a channel estimation error using at least one of the received pilot allocation information, the interference information, or the channel information, and
And allocating, by the first base station, a pilot to a terminal connected to the first base station using the calculated channel estimation error,
The interference information,
A method of allocating a pilot signal having a preset value due to interference from a base station to which a pilot has not been assigned to a base station to which a pilot is assigned. delete In claim 1,
The channel information,
A pilot signal allocation method including a channel estimation error value set in a cell to which pilots are not allocated. In claim 1,
The channel information,
A pilot signal allocation method including an average of channel covariance values between a base station of a specific cell and terminals connected to the specific cell. In claim 3 or 4,
Transmitting, by the first base station, pilot allocation information allocated to a terminal connected to the first base station to a second base station
Pilot signal allocation method further comprising. In clause 5,
The second base station calculating a channel estimation error using the pilot allocation information of the first base station, interference information or channel information of base stations other than the first base station, and
Allocating, by the second base station, a pilot to a terminal connected to the second base station using the channel estimation error
Pilot signal allocation method further comprising. In paragraph 6,
Allocating a pilot to a terminal connected to the second base station,
Selecting, by the second base station, a terminal to use the same pilot signal as the terminal to which the pilot signal is allocated from the first base station
Pilot signal allocation method comprising a. In claim 1,
When a plurality of base stations are adjacent, the plurality of base stations sequentially select a terminal, and allocating a pilot identical to a pilot allocated to a terminal connected to the first base station to the selected terminal
Pilot signal allocation method further comprising. Transmitting/receiving unit for receiving pilot assignment information from base stations or receiving interference information and channel information,
A calculation unit that calculates a channel estimation error using at least one of the pilot allocation information, the interference information, and the channel information, and
A pilot allocator for allocating a pilot to a terminal connected to a base station of a specific cell by using the calculated channel estimation error,
The transceiver unit,
A pilot signal allocation apparatus for receiving the pilot allocation information from a base station to which a pilot is allocated, or receiving the interference information and the channel information from a base station to which a pilot is not allocated. delete In claim 9,
The pilot assignment unit,
A pilot signal allocation apparatus for selecting a terminal to use the same pilot signal as the pilot allocated by the base station to which the pilot is allocated. In claim 9,
The pilot assignment unit,
A pilot signal allocation apparatus for selecting a terminal having the smallest value of the calculated channel estimation error among terminals connected to a base station of a specific cell as a terminal to use a specific pilot. In claim 9,
The interference information,
A pilot signal allocation apparatus including a preset value for interference from other base stations by a base station to which a pilot is not assigned. In claim 9,
The channel information,
A pilot signal allocation apparatus including an average of a channel estimation error value set by a base station to which pilots are not assigned or covariance values of a channel between a base station of a specific cell and terminals connected to the specific cell.

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