KR20080018675A - Method for reducing inter-cell interference - Google Patents

Abstract

A method for preventing inter-cell interference is provided to consider FRBs(Frequency Resource Blocks) in the edge of a cell and the inside of the cell, thereby reducing the inter-cell interference, improving the communication quality of a system, improving the throughput of a user of the cell edge and managing efficiently the power of a terminal. A method for preventing inter-cell interference comprises the following steps of: dividing the entire system bandwidth into plural FRBs; forming plural sub blocks by dividing a cell into plural bands and plural sectors; and allocating different FRBs to an adjacent sub block.

Description

Method for reducing inter-cell interference

1 illustrates a frequency spectrum of a cell according to an embodiment of the present invention.

2 illustrates a frequency allocation scheme of cells according to an embodiment of the present invention.

3 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

4 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

5 is an exemplary view showing a method of arranging multiple cells according to another embodiment of the present invention.

6 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

7 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

8 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

9 is an exemplary view showing a power allocation scheme according to an embodiment of the present invention.

The present invention relates to an intercell interference prevention method, and more particularly, to an intercell interference prevention method in a wireless communication system.

The wireless communication system has a cell structure for efficient system configuration. A cell is a subdivision of a large area into smaller areas in order to use frequency efficiently. In general, a base station is installed in a cell to relay a terminal.

The wireless communication system supports downlink and uplink for multiple terminals. Here, the downlink means communication from the base station to the terminal, and the uplink means communication from the terminal to the base station. Multiple terminals can transmit data simultaneously on the downlink or uplink. This is possible by multiplexing the data transmission. Multiplexing is achieved by orthogonally linking each other. Depending on how multiplexing is performed, orthogonality can be achieved in time, frequency, code domains, and the like. Orthogonality ensures that data transmission by each terminal does not interfere with data transmission by other terminals.

Multiple access systems generally include multiple cells. Data transmission by the terminal in the same cell prevents intra-cell interference through orthogonal multiplexing. However, data transmission by a terminal in different cells may not be orthogonal, and the terminal may experience inter-cell interference from another cell.

For example, orthogonal frequency division multiplexing (OFDM) is one of the techniques using multiple carriers. OFDM partitions the overall system bandwidth into a plurality of subcarriers with orthogonality and carries data on subcarriers for transmission. In a multi-cell environment, a system using multiple carriers such as OFDM may cause interference to users when adjacent cells use the same subcarrier.

One technique for reducing inter-cell interference is to use different frequencies between cells. For example, if the number of adjacent cells is three, the entire frequency band is divided into three parts so that the frequency bands do not overlap each other, thereby preventing inter-cell interference. However, this lowers the overall spectral efficiency.

Alternatively, a directional antenna may be arranged so that signals from one cell do not overlap with signals from other cells. However, directional antennas are not yet practical for use in portable terminals.

In order to improve communication quality, a technique for effectively reducing inter-cell interference is needed.

SUMMARY OF THE INVENTION The present invention provides a method for preventing inter-cell interference by allocating non-overlapping frequency resource blocks to adjacent cells in a cell.

According to an aspect of the present invention, a method for preventing intercell interference is provided. The inter-cell interference prevention method divides the entire system bandwidth into a plurality of frequency resource blocks, and divides one cell into a plurality of bands and a plurality of sectors to form a plurality of subblocks. Adjacent subblocks are allocated with different frequency resource blocks.

According to another aspect of the present invention, there is provided an inter-cell interference prevention method including a plurality of cells. The inter-cell interference prevention method divides the entire system bandwidth into a plurality of frequency resource blocks and divides the cell into a plurality of bands and a plurality of sectors to form a plurality of subblocks. Different frequency resource blocks are allocated to adjacent subblocks between adjacent cells.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout.

The following techniques can be used in various communication systems. Communication systems are widely deployed to provide various communication services such as voice, packet data, and the like. This technique can be used for downlink or uplink. The downlink means communication from a base station (BS) to a mobile station (MS), and the uplink means communication from a terminal to a base station. A base station generally refers to a fixed station that communicates with a terminal and may be referred to as other terminology, such as a node-B, a base transceiver system (BTS), or an access point. . The terminal may be fixed or mobile and may be referred to by other terms such as user equipment (UE), user terminal (UT), subscriber station (SS), wireless device (wireless device), and the like.

The present invention can be applied to any multiple access scheme that requires frequency division for multiple access. Multiple access schemes include frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), multi-carrier code division multiple access (MC-CDMA), and combinations thereof.

1 illustrates a frequency spectrum of a cell according to an embodiment of the present invention.

Referring to FIG. 1, the total frequency bandwidth is divided into a plurality of frequency resource blocks (FRBs) according to channel environments. The FRB may be configured in the form of time x frequency. In a multiple access system such as OFDMA using multiple subcarriers, the FRB may be a subset of subcarriers divided from the entire set of subcarriers.

The number or size of the FRBs is not limited and is not necessarily limited to the number or type shown. The size of the FRB may not be constant and may vary in size depending on the channel environment. The FRB is a logical division, and the physical spectral bands that are actually allocated may not have a zero shared set among each other.

Each FRB may have a different transmit power level. That is, interference can be reduced by varying the transmission power level of the subband according to the channel environment.

2 illustrates a frequency allocation scheme of cells according to an embodiment of the present invention.

Referring to FIG. 2, one cell divides into four bands from the edge to the center, and one cell divides into three sectors radially. Therefore, 12 sub blocks are formed in one cell.

The cell shapes shown in the figures indicate a bundle of users with similar channels or interference in one cell or sector. This may or may not match the physical cell shape. That is, when the physical cell shape and the definition of the user group are the same, the change by the feature in the cell is the same in all directions and positions, and the influence in the adjacent cell is the same in all the positions. On the other hand, if the physical conditions are not the same at every location, the band definition by the user group may take a different form than the band in the physical cell.

The number of bands is not limited and may be two or more. In addition, the shape of the band is not limited and various forms are possible. For example, it is possible to increase the size of the band near the edge of the cell and to reduce the size of the band toward the center. Alternatively, the size of the band can be reduced near the edge of the cell, and the size of the band can be increased toward the center. In addition, the size or number of bands can be adaptively changed according to the channel environment.

The number of sectors is not limited and may be two or more. The shape of the sector is not limited, and the size may be the same for each sector, and the size may be different for each sector. In addition, the size or number of sectors may be adaptively changed depending on the channel environment.

Each FRB is allocated to an adjacent subblock. FRBs allocated to adjacent subblocks are different. That is, adjacent subsectors are allocated with FRBs that do not overlap each other. For example, divide the total bandwidth into four FRB groups according to the number of bands. Each FRB group includes three FRBs as many as sectors. An FRB group is allocated to each band, and an FRB of an FRB group corresponding to each sector is allocated.

In the figure, different FRBs are allocated to each subblock, but non-adjacent subblocks may allocate the same FRB.

According to the present invention, FRBs that do not overlap each other are allocated to adjacent cells and sectors in the set and sectors for users divided into groups according to the channel environment. By assigning the divided FRBs to the divided subblocks in the cell, users use the FRBs that do not overlap with users of adjacent cells and sectors. Thus, the interference from the same FRB can be reduced to improve the performance of the entire system.

On the other hand, in the case of using the multiple subcarriers by assigning different subcarriers between adjacent FRBs, it is possible to reduce the interference that can occur by using the same subcarriers in the cell and sector. In assigning frequency groups to FRBs divided by cells or sectors, frequencies may be partially overlapped or not overlapped depending on the degree of influence or reception to neighboring cells.

3 illustrates a method of arranging multiple cells according to an embodiment of the present invention.

Referring to FIG. 3, one cell has four bands and three sectors, and each band and sector is assigned an FRB that does not overlap adjacent bands and sectors. In addition, FRBs that do not overlap not only within the cell but also between bands and sectors of adjacent cells are allocated. This is a multi-cell environment consisting of one tier containing seven cells, but the present invention can be extended to two stages (19 cells) or more.

One cell has four bands and is further divided into three sectors. Twelve sub-blocks divided by band by sector are allocated with FRBs so as not to overlap each other. That is, sectors in the same cell have different FRB groups in the band. This method, when applied to other cells, has a FRB that does not overlap between adjacent cells.

According to the present invention, inter-cell interference is allocated by assigning FRBs that do not overlap each other between adjacent cells. Inter-cell interference can be reduced by selecting an FRB in which inter-cell interference is minimized by band and sector.

4 illustrates a method of arranging multiple cells according to another embodiment of the present invention.

Referring to FIG. 4, in the cell divided into three sectors, the FRB is allocated differently for each band. Sectors use the same FRB in the same band. The band located at the cell edge uses a different FRB from the band located at the adjacent cell edge. However, the band located inside the cell may use the same FRB as the band located inside the adjacent cell.

That is, one cell is divided into at least two bands, and an edge band is assigned an FRB that does not overlap with an edge band of an adjacent cell. The inner bands may be assigned the same FRB as the same band of adjacent cells. The terminal located in the center of the cell can use the entire frequency band except the FRB of the edge band and the FRB of the inner band. Alternatively, the center of the cell may use the entire frequency band except for the FRB of the inner band. Although two bands are shown here, this is not a limitation and three or more bands are possible.

Inter-cell interference is reduced by using two bands using different FRBs in one cell.

5 shows a layout method of multiple cells according to another embodiment of the present invention.

Referring to FIG. 5, in a cell divided into three sectors, the FRB is allocated differently for each band. Sectors use the same FRB in the same band. The band located at the cell edge uses a different FRB from the band located at the adjacent cell edge. Similarly, a band located inside a cell uses a different FRB than a band located inside an adjacent cell.

That is, one cell is divided into at least two bands, and an edge band (first band) and an inner band (second band) are each assigned the same band of adjacent cells and FRBs that do not overlap each other. The terminal located in the center of the cell can use the entire frequency band except the FRB of the edge band and the FRB of the inner band. Alternatively, the terminal located in the center of the cell may use the entire frequency band except for the FRB of the inner band. Although two bands are shown here, this is not a limitation and three or more bands are possible.

Inter-cell interference is reduced by varying the inner band FRB as well as the edge band FRB between adjacent cells.

6 illustrates a method of arranging multiple cells according to another embodiment of the present invention.

Referring to FIG. 6, in a cell divided into two bands and three sectors, a band located at a cell edge uses the same FRB for each sector. However, the band located at the cell edge uses a different FRB from the band located at the adjacent cell edge. The band located inside the cell uses a different FRB for each sector, and uses a FRB that does not overlap with neighboring sectors of an adjacent cell.

The inner bands use FRBs that do not overlap between sectors within the same cell. In other words, the edge band uses a FRB that does not overlap with an adjacent cell, and the inner band located inside the cell uses a different FRB for each sector. Although two bands are shown here, this is not a limitation and three or more bands are possible.

The edge band uses the same FRB for each sector, but the inner band uses different FRBs for each sector to reduce inter-cell interference.

7 illustrates a method of arranging multiple cells according to another embodiment of the present invention.

Referring to FIG. 7, bands located at cell edges in cells divided into three sectors use different FRBs for each sector. The band located at the cell edge uses a different FRB from the band located at the adjacent cell edge. In addition, the edge band uses FRBs that do not overlap each other with neighboring sectors of adjacent cells for each sector. Bands located inside the cell use the same FRB between sectors.

That is, the edge band is divided into three sectors and assigned different FRBs from adjacent cells. In the inner band, all cells may be allocated the same FRB regardless of the cell. Although two bands are shown here, this is not a limitation and three or more bands are possible.

The edge band uses different FRBs for each sector, but the inner band uses the same FRBs for each sector to reduce inter-cell interference.

8 is an exemplary view showing a multi-cell arrangement according to another embodiment of the present invention.

Referring to FIG. 8, bands located at cell edges in a cell divided into two bands and three sectors use different FRBs for each sector. The band located at the cell edge uses a different FRB from the band located at the adjacent cell edge. In addition, the edge band uses FRBs that do not overlap each other with neighboring sectors of adjacent cells for each sector. Bands located inside the cell use the same FRB regardless of sector. However, the band located inside the cell uses a different FRB from the same band of the adjacent cell.

That is, the edge band is divided into three sectors and assigned different FRBs. The inner band may be allocated different FRBs from the same band of adjacent cells. Although two bands are shown here, this is not a limitation and three or more bands are possible.

Edge bands use different FRBs for each sector, and inner bands use different FRBs for each sector, thereby reducing inter-cell interference.

Hereinafter, a method for preventing intercell interference using a frequency reuse technique will be described. That is, in the above, different FRBs are allocated to different bands and sectors in the cell to prevent interference between cells. Hereinafter, different transmission electricity is set for each band and sector to prevent inter-cell interference.

The FRB may have different transmission electricity for each subband. That is, below, the FRB has a band corresponding to the entire frequency band, but has a transmission frequency different from other frequency bands in a preset frequency band. For example, the preset frequency band has a relatively small electricity compared to the remaining frequency bands. In a multiple access system such as OFDMA using multiple subcarriers, the FRB includes all subcarriers corresponding to the entire frequency band, but the subcarriers of some frequency bands set can have relatively small power.

In the embodiment of FIG. 8, seven adjacent cells are considered for clarity of explanation. Each cell is divided into two bands and three sectors, and includes six sub blocks. One FRB is allocated to one sub block A, and there are three adjacent FRBs in the sub block A. FIG. In another sub-block B, there are three adjacent FRBs.

9 is an exemplary view showing a power allocation scheme according to an embodiment of the present invention. This is a case where the present invention is applied to a communication system using a multi-carrier, and indicates a FRB allocated to a sub block A and an FRB allocated to a sub block B, respectively.

Referring to FIG. 9, two sub blocks corresponding to edge bands of two cells adjacent to the sub block corresponding to the inner band of the corresponding cell are adjacent to the sub block A. FIG. The FRB assigned to the sub block A relatively reduces the transmission power of the frequency band (subcarrier) corresponding to three adjacent sub blocks. The transmission power of the remaining frequency bands is maximized.

Similarly to the sub block A, the sub block B is adjacent to the sub block corresponding to the inner band of the cell and two sub blocks corresponding to the edge bands of two cells adjacent thereto. The FRB allocated to the sub block B makes the transmission power of the frequency band corresponding to three adjacent sub blocks relatively small. The transmission power of the remaining frequency bands is maximized.

That is, each FRB includes the entire system bandwidth and can reduce the inter-cell interference by varying the transmission power of the frequency band corresponding to the adjacent sub-block for each band and sector.

The invention can be implemented in hardware, software or a combination thereof. In hardware implementation, an application specific integrated circuit (ASIC), a digital signal processing (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, and a microprocessor are designed to perform the above functions. , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

As described above, according to the present invention, the inter-cell interference can be reduced by considering the FRB inside the cell as well as the cell edge, and the communication quality of the system can be improved. In addition, the throughput of the cell edge user is improved and efficient power management of the terminal is possible.

Claims (8)

Dividing the total system bandwidth into a plurality of frequency resource blocks; Dividing a cell into a plurality of bands and a plurality of sectors to form a plurality of subblocks; Allocating different frequency resource blocks to adjacent sub-blocks. The method of claim 1, The frequency resource block is a method for preventing inter-cell interference by dividing the entire system bandwidth into sub-frequency bands. The method of claim 1, The frequency resource block has an inter-cell interference prevention method having different transmission power for each frequency band. The method of claim 1, The frequency resource block has an intercell interference prevention method having different transmission power for each subcarrier. In the inter-cell interference prevention method comprising a plurality of cells, Dividing the total system bandwidth into a plurality of frequency resource blocks; Dividing the cell into a plurality of bands and a plurality of sectors to form a plurality of subblocks; And allocating different frequency resource blocks to adjacent subblocks between adjacent cells. The method of claim 5, wherein Allocating the frequency resource block And a sub-block located at an edge of the cell, a frequency resource block different from the sub-block located at an edge of the adjacent cell. The method of claim 6, Allocating the frequency resource block And a different frequency resource block is allocated to a subblock located at the same position among the subblocks located inside the cells adjacent to each other. The method of claim 5, wherein Allocating the frequency resource block Inter-cell interference prevention method for allocating the same FRB to the sub-block belonging to the same band.

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