KR101335363B1 - Method for allocating frequency band in a wireless communication system - Google Patents

Abstract

The present invention relates to a method for allocating a frequency band permitted for a communication system to each cell constituting a multi-cell communication system in a multi-cell wireless communication system, and more particularly to inter-cell interference (ICI). The present invention relates to a frequency division and frequency allocation method that is easy to use a partial frequency reuse method used to reduce the frequency.

According to the present invention, in a frequency band allocation method of a multi-cell communication system, dividing an entire frequency band into a center frequency band that does not overlap each other and a plurality of outer frequency bands, wherein the plurality of plurality of outer frequency bands are divided in a center region of a first cell. Allocating at least one of the at least one first outer frequency band and the center frequency band among outer frequency bands, and allocating the at least one first outer frequency band to an outer region of the first cell. A frequency band allocation method is provided.

According to the present invention, in a mobile communication system using a partial frequency reuse method, a change in distribution of a terminal in a cell or a change in data transmission bandwidth in a cell by changing a frequency band allocated to each cell without reassigning a frequency band to all cells. Can actively respond to

Partial Frequency Recycling, Frequency Band Division, Frequency Allocation, Fractional Frequency Reuse, Inter-Cell Interference

Description

Frequency allocation in wireless communication systems {METHOD FOR ALLOCATING FREQUENCY BAND IN A WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method for allocating a frequency band permitted for a communication system to each cell constituting a multi-cell communication system in a multi-cell wireless communication system, and more particularly to inter-cell interference (ICI). The present invention relates to an easier frequency division and frequency allocation method in using a partial frequency reuse method to reduce the frequency.

In general, a wireless communication system divides an entire service area provided by a wireless communication system into a plurality of cells. Each cell is provided with a base station providing a service to a terminal located in each cell.

In order to maximize the frequency efficiency of the wireless communication system (Frequency Efficiency), each cell of the wireless communication system may use all the frequency bands allowed for the wireless communication system. Since cells adjacent to each other use the same frequency band, a terminal in a specific cell receives a signal in the same frequency band as the specific cell from another cell.

Signals received from other cells cause intercell interference at the terminal. Inter-cell interference is not a problem because terminals existing in the center region of a specific cell have a weak strength of signals received from other cells, but terminals located in the outer region of a specific cell have strong strength of signals received from other cells. The interference greatly degrades communication performance.

In order to solve this problem, a partial frequency recycling method is used. In this method, data transmission with the terminal located in the center of the cell uses all the frequency bands allowed in the wireless communication system, while data transmission with the terminal located in the outer region of the cell uses only some frequency bands. Cells adjacent to each other transmit data to a terminal located in an outer region of each cell using different frequency bands. When a terminal located in an outer region of a cell receives only signals of a specific frequency band allocated to an outer region of a specific cell to which the terminal belongs, signals from other adjacent cells are not received, thereby reducing inter-cell interference.

However, in the conventional partial frequency recycling method, when the distribution of terminals in a specific cell changes and a frequency band allocated to a specific cell needs to be changed, the influence of the frequency band change also affects other cells. There was a downside to having to rebuild.

The present invention has been made to improve the prior art as described above, and an object of the present invention is to provide a frequency division method that is easy to reuse the partial frequency.

Another object of the present invention is to provide a method for allocating a data transmission frequency band to a terminal attempting to communicate with a base station of a cell in a frequency-divided cell.

It is still another object of the present invention to provide a frequency division method in a cell frequency allocated in consideration of partial frequency recycling, which does not cause additional inter-cell interference to other cells even when the frequency allocation is changed due to a change in the communication environment. The purpose.

In order to achieve the above object and to solve the problems of the prior art, the present invention provides a frequency band allocation method of a multi-cell communication system, in which the entire frequency band is divided into a center frequency band and a plurality of outer frequency bands that do not overlap each other. Allocating at least one or more first outer frequency bands of the plurality of outer frequency bands and the center frequency band to a center region of the first cell, and at least one of the at least one first regions to the outer region of the first cell It provides a frequency band allocation method comprising the step of assigning the outer frequency band.

According to one aspect of the present invention, in a frequency band allocation apparatus of a multi-cell communication system, a divider for dividing an entire frequency band into a center frequency band that does not overlap each other and a plurality of outer frequency bands, and a center region of a first cell. And an allocator configured to allocate at least one or more first outer frequency bands and the center frequency band among the plurality of outer frequency bands, and to allocate the at least one first outer frequency band to an outer region of the first cell. Provided is a frequency band allocation apparatus.

According to the present invention, even in a mobile communication system in which each cell uses all frequency bands allowed in the mobile communication system in order to maximize frequency efficiency, the inter-cell interference of the terminal located at the outer side of each cell can be reduced. have.

According to the present invention, in a mobile communication system using a partial frequency reuse method, a change in distribution of a terminal in a cell or a change in data transmission bandwidth in a cell by changing a frequency band allocated to each cell without reassigning a frequency band to all cells. Can actively respond to

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a method for allocating respective frequency bands to a center region and an outer region of each cell in a multi-cell communication system according to the present invention. Hereinafter, a method of allocating a frequency band to each cell in a multi-cell communication system will be described in detail with reference to FIG. 1.

In step S110, the entire frequency band allowed for the multi-cell wireless communication system is divided into a center frequency band and a plurality of outer frequency bands. Each of the plurality of outer frequency bands does not overlap with each other, nor does it overlap with the center frequency band.

In step S120, each cell of the wireless communication system is divided into a central area and an outer area.

In operation S130, at least one or more outer frequency bands and a center frequency band of the plurality of outer frequency bands are allocated to the center region of the specific cell. According to an embodiment of the present invention, the outer frequency band may be a continuous frequency band or a discontinuous frequency band.

According to an embodiment of the present invention, a wireless communication system may transmit data using an Orthogonal Frequency Division Multiplex (OFDM) scheme. The frequency band may be a frequency band of a sub carrier of an orthogonal frequency division multiplexing scheme.

In step S140, an outer frequency band allocated to the center region among the plurality of outer frequency bands is allocated to the outer region of the specific cell allocated for the frequency in step S130.

The center frequency band is used only for communication with a terminal located in a center region of a specific cell, and the outer frequency band allocated to a specific cell may be used for communication with terminals located in all regions within a cell.

In step S150, at least one or more outer frequency bands and a center frequency band of the plurality of outer frequency bands are allocated to the center region of another cell adjacent to the cell allocated in the steps S130 and S140. The outer frequency band allocated in step S150 is determined not to overlap with the outer frequency band allocated to a specific cell in steps S130 and S140.

In step S160, the outer frequency allocated in step S150 is allocated to the outer region of the cell allocated with the frequency in step S150.

Since the outer frequencies allocated in the steps S150 and S160 do not overlap with the outer frequencies assigned to the adjacent cells in the steps S130 and S140, the outer frequencies that do not overlap with each other are used.

According to one embodiment of the present invention, steps S150 and S160 may be repeated until all frequencies of the plurality of cells constituting the wireless communication system are allocated to all cells. The outer frequency assigned to each cell is determined not to overlap with the outer frequency assigned to the adjacent cell.

According to an embodiment of the frequency band allocation method of the present invention, receiving radio channel state information from a terminal located in a specific cell, and based on the received radio channel state information, an area in which the terminal is located in the first cell; Estimating, and allocating at least one data transmission frequency band among the frequency bands allocated to the central region or the outer region to the terminal based on the estimation result.

According to an embodiment of the present invention, the wireless channel state information may include a received signal strength indicator (RSSI) or a signal to interference and noise ratio (SINR) measured by the terminal. have. When a base station of each cell transmits a reference signal of a constant intensity, and a terminal located in the center region or the outer region of each cell measures the strength of the reference signal or receives the reference signal and measures the signal-to-interference and noise ratio, An approximate distance from the base station of each cell to each terminal can be estimated based on the measured value.

Based on the estimated distance from the base station of each cell to each terminal, it is estimated whether each terminal is located in the center region or the outer region of each cell, and based on that, the terminal belonging to each region is assigned to each region. At least one data transmission frequency band may be allocated among the allocated frequency bands.

If the terminal is located in the outer region of a specific cell, the data transmission frequency band should be allocated among the outer frequency bands, but if the terminal is located in the central region, the data transmission frequency band should be allocated among the center frequency band or the outer frequency band allocated to the specific cell. Frequency band can be selected.

According to an embodiment of the present invention, when the total number of terminals located in a specific cell is smaller than a predetermined value, at least one data transmission frequency band among the allocated outer frequency bands may be allocated to a terminal located in a central area. have.

Since the outer frequency band allocated to the outer side of a specific cell is a superior channel with less inter-cell interference than the center frequency band, when the number of terminals existing in the cell is smaller than the predetermined number, all the terminals in the cell have the outer frequency band. Priority can be assigned to the data transmission frequency band. Each terminal transmits data using an outer frequency band with little interference between cells, thereby improving data transmission performance.

According to an embodiment of the present invention, when a terminal is located in a central region of a specific cell, at least one data transmission frequency band may be allocated to the terminal in preference to an outer frequency band.

By assigning a center frequency band to a terminal located in the center region of the cell, and assigning an outer frequency band to a terminal located in the outer region, the number of terminals allocated to each frequency band or the range of data transmission frequency bands used by the terminal can be adjusted. have. Data transmission capacity of each cell can be maximized by transmitting data to the maximum number of terminals within the range of the center frequency band and the outer frequency band allocated to each cell.

2 is a diagram illustrating allocation of outer frequency bands that do not overlap each other between adjacent cells according to an embodiment of the present invention. Hereinafter, a method of allocating frequency bands that do not overlap each other between cells adjacent to each other will be described in detail with reference to FIG. 2.

The total frequency band 210 allocated to the wireless communication system includes a center frequency band 211 allocated to the center regions 221, 231, and 241 of each cell 220, 230, and 240 and an outer region 222, of each cell. It consists of a plurality of outer frequency bands 212, 213, 214 assigned to 232, 242. Each frequency band 211, 212, 213, 214 is determined not to overlap each other.

Assume that the first outer frequency band 212 and the center frequency band 211 are allocated to the center region 221 of the first cell 220, and the first outer frequency band 212 is allocated to the outer region 222. lets do it.

A second outer frequency band 213 and a center frequency band 211 that do not overlap the first outer frequency band 212 are allocated to the central region 231 of the second cell 230 adjacent to the first cell 220. In the outer region 232, a second outer frequency band 213 is allocated.

The center region 241 of the third cell 240 adjacent to the first cell 220 and the second cell 230 does not overlap the first outer frequency band 212 and the second outer frequency band 213. Three frequency bands 214 and a center frequency band 211 are allocated. The outer zone 242 is assigned a third outer frequency band 214.

In FIG. 2, an embodiment in which the outer frequency bands 212, 213, and 214 are divided into three is illustrated, but according to an embodiment of the present invention, the outer frequency bands may be divided into four or more and allocated to each cell. When the entire area in which the wireless communication system provides a service is ideally cell planned, even if the outer frequency band is divided into three, different outer frequency bands may be used between adjacent cells. Three outer frequency bands may not be enough. In this case, the present invention may be implemented by dividing the outer frequency band into four or more.

3 is a diagram illustrating that inter-cell interference occurring in a terminal located outside a cell is reduced when each frequency band is allocated to a center region and an outer region of each cell according to the present invention. Hereinafter, the inter-cell interference is reduced in the terminal located outside the cell with reference to FIG. 3. FIG.

3A illustrates a cell structure of a multi-cell communication system. Terminal 340 is located within the coverage of a system consisting of a plurality of cells.

According to an embodiment of the present invention, a multi-cell communication system and a terminal may transmit data using an orthogonal frequency division multiplexing scheme.

Unlike code division multiple access (CDMA), which distinguishes signals transmitted from different cells by using different codes between different cells, orthogonal frequency division multiplexing uses different frequencies in each orthogonal frequency division multiplexing scheme. Identifies the signal transmitted from the cell.

According to an embodiment of the present invention, each cell may use the entire frequency band in order to maximize the performance of the multi-cell communication system. If each cell uses the entire frequency band, the frequency efficiency of the multi-cell communication system is 1.

Since each cell transmits data using the same frequency band, the terminal receives all the signals transmitted from each cell, and as a result, the inter-cell interference (ICI) measured by the terminal increases, resulting in an increase in the terminal. Data transmission performance is reduced.

In the orthogonal frequency division multiplexing scheme, the signal-to-interference and noise ratio (SINR) measured at the terminal may be defined as the ratio of the bandwidth of the interference signal received by the terminal from another cell to the bandwidth used by the terminal for data transmission.

If the partial frequency recycling is not performed, since each cell uses the same frequency band 350, the terminal 340 receives all the signals transmitted from each cell and receives the signals of the entire frequency band 350. The signal-to-interference and noise ratio measured by the terminal are deteriorated due to the inter-cell interference generated by the cell.

Figure 3 (b) is a view showing a conventional frequency division method and a partial frequency recycling method according to the prior art and the frequency division method according to the partial frequency recycling method according to the present invention does not perform partial frequency recycling.

When partial frequency recycling is not performed, the entire frequency band 350 is allocated to each cell.

In order to prevent performance degradation due to intercell interference, the IEEE 802.20 standard does not allocate the entire frequency band 360 to each cell, but allocates the center frequency band 361 to the center region of each cell. In the outer region of the cell, a partial frequency recycling method for allocating at least one of the plurality of outer frequency bands 365 is proposed.

According to the partial frequency recycling method according to the IEEE 802.20 standard, a center frequency band 361 is provided in the center region 310 of each cell in which a '1' is indicated in the center region of the cell, and a first outer frequency is formed in the outer region 311. 362 is assigned. A center frequency band 361 is allocated to the center region 320 of each cell in which '2' is indicated in the center region of the cell, and a second outer frequency 363 is allocated to the outer region 321. A center frequency band 361 is allocated to the center region 330 of the cell in which '3' is displayed in the center region of the cell, and a third outer frequency 364 is allocated to the outer region 331.

If the terminal accessing the multi-cell communication system and transmitting data is located in the central regions 310, 320, and 330 of a specific cell, the terminal transmits data using the center frequency band 361. Since the center frequency band 361 is allocated to the center regions 310, 320, and 330 of each cell, the data transmission performance of the terminal is dependent on the inter-cell interference generated by the signal of the center frequency band 361 transmitted in each cell. Is lowered.

When the terminal is located outside the cells 311, 321 and 331, the terminal transmits data using the outer frequency bands 362, 363 and 364 allocated to each cell. A cell using the same outer frequency bands 362, 363, 364 assigned to the outer frequency bands 362, 363, 364 allocated to the cell where the terminal is located is about one third of all cells. The data transmission performance of the terminal is degraded by intercell interference caused by signals in specific frequency bands 362, 363 and 364 transmitted from about one third of the cells.

On the other hand, in order to prevent performance degradation due to inter-cell interference, the WiMax standard allocates the entire frequency band 370 in the central regions 310, 320, and 330 of each cell, and in the outer region of each cell. A partial frequency recycling method for allocating at least one of a plurality of frequency bands 371, 372. 373 has been proposed.

The first frequency band 371 is in the outer region 311 of each cell marked '1' in the center region of the cell, and in the outer region 321 of each cell in which the '2' is marked in the middle region of the cell. In the second frequency band 372, a third frequency band 373 is allocated to the outer region 331 of each cell in which '3' is marked in the center region of the cell.

If the terminal accessing the multi-cell communication system and transmitting data is located in the central region 310, 320, 330 of a specific cell, the terminal 340 transmits data using the entire frequency band 370. Since the center region 310, 320, 330 of each cell uses the entire frequency band 370, the data transmission performance of the terminal 340 is generated by the signal of the entire frequency band 370 transmitted in each cell. It is degraded by intercell interference.

If the terminal accessing the multi-cell communication system and transmitting data is located in the outer regions 311, 321, and 331 of the specific cell, the terminal transmits data using the specific frequency bands 371, 372, and 373. . Since the specific frequency bands 371, 372, and 373 used by the terminal are used by all other cells, the data transmission performance of the terminal is degraded by the inter-cell interference generated by the signals received from all other cells.

According to the partial frequency recycling method according to the present invention, at least one frequency band 382, 383, 384 in the central region 310, 320, 330 of each cell in the center frequency band 381 and the outer frequency band 385. ) Is allocated, and the outer frequency bands 382, 383, and 384 allocated to the center region are allocated to the outer regions 311, 321, and 331 of each cell.

A center frequency band 381 and a first outer frequency band 382 are allocated to the center region 310 of each cell in which the center region of the cell is marked with '1', and the outer region 311 has a first outer frequency band. 382 may be assigned. A center frequency band 381 and a second outer frequency band 383 are allocated to the center region 320 of each cell in which the center region of the cell is marked with '2', and the outer region 321 has a second outer frequency band. 383 may be assigned. A central frequency band 381 and a third outer frequency band 384 are allocated to the center region 330 of each cell in which the center region of the cell is marked with '3', and the outer region 331 has a third outer frequency band. 384 may be assigned.

If the terminal accessing the multi-cell communication system and transmitting data is located in the central region 310, 320, 330 of a specific cell, the terminal may include a center frequency band 381 and an outer frequency band 382, 383, 384. Send data using. Since the center frequency band 381 is allocated to the center regions 310, 320, and 330 of each cell, the data transmission performance of the terminal is dependent on the inter-cell interference generated by the signals of the center frequency band 361 transmitted in each cell. Is lowered. Since the outer frequency bands 382, 383, and 384 are allocated to about one third of all cells, the data transmission performance of the terminal is based on the outer frequency bands 382, 383, It is further degraded by the intercell interference generated by the signal of 384).

According to the present invention, in the case of a terminal located in the center region of a specific cell, the strength of the interference signal from another cell also increases in the outer frequency band. However, since the data transmission bandwidth used by the terminal increases more than the increase of the interference signal, the signal-to-interference and noise ratio measured by the terminal is improved.

If a terminal accessing a multi-cell communication system and transmitting data is located in an outer region 311, 321, 331 of a specific cell, the terminal transmits data using the outer frequency bands 382, 383, 384. . Since each outer frequency band is allocated to about one third of all cells, data transmission performance of the terminal is applied to signals of outer frequency bands 382, 383, and 384 transmitted from about one third of all cells. It is degraded by the inter-cell interference generated by it.

According to the partial frequency allocation method according to the conventional method, since the terminal located in the outer region of each cell reduces the frequency band of the signal transmitted from the other cell, the signal band of the radio channel between the base station and the terminal of each cell is consequently reduced. The interference and noise ratios are improved.

According to the partial frequency allocation method according to the present invention, in the case of a terminal located in the outer region of each cell, the signal-to-interference of the radio channel between the base station and the terminal of each cell, like the partial frequency allocation method according to the conventional method And the noise ratio is improved.

4 is a diagram illustrating allocating a portion of an outer frequency band allocated to a cell outer region to a center region according to an embodiment of the present invention. Hereinafter, the allocation of a portion of the outer frequency band to the central region will be described in detail with reference to FIG. 4.

According to an embodiment of the present invention, a center frequency band 411 and at least one outer frequency band 412, 413, 414 in a central region of each cell among the total frequency bands 410 allowed for a multi-cell communication system. Is allocated, and the outer frequency bands 412, 413, and 414 allocated to the central region are allocated.

In the embodiment shown in FIG. 4, the common frequency band 411 and the first outer frequency band 412 are allocated to the central region of the first cell. The common frequency band 411 and the second outer frequency band 413 are allocated to the center region of the second cell adjacent to the first cell, and the common frequency band is assigned to the center region of the third cell adjacent to the first cell and the second cell. 411 and a second outer frequency band 414 are allocated.

According to an embodiment of the present invention, the center frequency band 421 and the first outer frequency band 422 allocated to the first cell are not changed, but the second outer frequency band 413 of the second outer frequency band 413 assigned to the second cell is not changed. The allocation of some frequency bands 433 can be changed. Among the second outer frequency bands 413 allocated to the outer region of the second cell, some frequency bands 433 may be allocated only to a terminal located in the central region, such as the center frequency band 421.

According to the present invention, since only a specific frequency band 432 is allocated to a data transmission frequency band for a terminal located in an outer region, additional intercell interference is not generated in another cell.

According to an embodiment of the present invention, if some frequency bands 433 of the second outer frequency band 413 are allocated only to a terminal located in a central area, it is not necessary to transmit a signal of some frequency bands 433 to the outside of the cell. The transmit power of some frequency bands 433 may be reduced to be equal to or less than the transmit power of the center frequency band 431. In one embodiment of the present invention, the change of the frequency allocation in the center region and the outer region merely reduces the transmission output of some frequency bands 433 and changes the terminal to which the frequency band is allocated, and thus the adjacent to the second cell. It does not cause additional intercell interference to the first cell or the third cell. Some of the remaining frequency bands 432 of the second outer frequency band 413 are allocated to terminals located in the outer region of the second cell.

The allocation of some frequency bands 443 of the third outer frequency band 414 allocated to the outer region of the third cell may be changed. Additional inter-cells are added to the first and second cells adjacent to the third cell even when some frequency band 443 is allocated only to a terminal located in the center region, such as the center frequency band 441 allocated to the center region of the third cell. Does not cause interference Some of the remaining frequency bands 442 of the third outer frequency band 414 are allocated to a terminal located in the outer region of the third cell.

In addition to the center frequency bands 421, 431, and 441 assigned to each cell, the frequency bands 433 and 443 that can be allocated only to the central region are increased. Even if the number of terminals distributed in the central region of each cell increases or the sum of frequency bands used by terminals located in the central region increases, additional frequency bands 433 and 443 are allocated to actively change the communication environment. Can cope

In the partial frequency allocation method according to the prior art, when the frequency band allocated to a specific zone is allocated to another region, additional inter-cell interference is generated in another cell. Therefore, in order to cope with changes in the communication environment in a specific cell, there is a disadvantage in that frequency division and frequency allocation of the entire cell must be redone.

According to the present invention, after a frequency band is allocated to each cell constituting a multi-cell communication system, even if the frequency bands are individually assigned to each cell according to a change in the communication state of each cell, the communication of other cells is not possible. Does not affect There is no need to redo frequency division and frequency allocation in order to change the frequency band assigned to each cell.

FIG. 5 is a flowchart illustrating a step-by-step method of allocating a portion of an outer frequency band allocated to a cell outer region to a center region according to an embodiment of the present invention. Hereinafter, a method of allocating a part of the outer frequencies to the central region will be described in detail with reference to FIG. 5.

In step S510, the entire frequency band available to the multi-cell wireless communication system is divided into a center frequency band and a plurality of outer frequency bands.

In step S520, each cell of the wireless communication system is divided into a central area and an outer area.

In step S530, at least one outer frequency band and the center frequency band of the plurality of outer frequency bands are allocated to the center region of the specific cell.

In step S540, an outer frequency band allocated to the center region among the plurality of outer frequency bands is allocated to the outer region of the specific cell allocated in the frequency S530.

In step S550, a third outer frequency band is determined from the specific outer frequency band allocated in step S530.

The ratio of the center frequency band divided into the plurality of outer frequency bands divided in step S510 is a distribution of terminals in the center region and the outer region of each cell, or a frequency used by each terminal located in each region of each cell. It may not be determined corresponding to the sum of the bands. In addition, when determining the ratio of the center frequency band and the plurality of outer frequency bands in step 510, it is determined according to the distribution of the terminal or the sum of the frequency bands. The sum of the frequency bands used by the terminal may vary. In this case, maintaining the ratio of the divided center frequency band and the plurality of outer frequency bands in step S510 is not appropriate to maximize the performance of the multi-cell communication system.

In step S560, the third outer frequency band determined in step S550 is not allocated to the data transmission frequency band for the terminal located in the outer region of the specific cell. As a result, the third outer frequency band selected from the outer frequency bands that can be allocated to all the terminals located in the center region and the outer region in the cell is not assigned to the terminal located in the outer region as the data transmission frequency band, but only to the terminal located in the central region. It is assigned to the data transmission frequency band. Since the outer frequency band that can be allocated to all terminals is not allocated to the terminals located in a specific region, it does not cause a large change in the existing frequency allocation and does not cause additional inter-cell interference to other cells. In order to change the frequency band allocated to each cell, there is an effect of changing the frequency band without having to perform frequency division and frequency allocation again.

According to an embodiment of the present invention, the third outer frequency band may be determined based on the ratio of the number of terminals located in the center region of each cell and the number of terminals located in the outer region. When the number of terminals located in the center region is greater than when determining the ratio of the center frequency band and the plurality of outer frequency bands in step S510, the terminal located in the center region of the third outer frequency band determined from the outer frequency bands. Can only be assigned to the data transmission frequency band.

According to an embodiment of the present invention, the third outer frequency band is a sum of frequency bands used by at least one terminal located in the center region of each cell, and a frequency band used by at least one terminal located in the outer region. It can be determined based on the sum of. When the frequency bands used by the terminals located in the central area become larger than when the ratio of the central frequency band and the plurality of outer frequency bands is determined in step S510, the third outer frequency band determined from the outer frequency bands is applied to the central area. Only the terminal located can be allocated to the data transmission frequency band.

6 is a diagram illustrating a structure of a frequency band allocation apparatus of a multi-cell communication system according to the present invention. Hereinafter, the operation of the frequency band allocating apparatus will be described in detail with reference to FIG. 6. The frequency band allocation apparatus 600 according to the present invention includes an allocator 610, a receiver 620, an estimator 630, a transmitter 640, and a divider 650.

The divider 650 divides the entire frequency band of the multi-cell communication system into a center frequency band and a plurality of outer frequency bands that do not overlap each other. Each of the plurality of outer frequency bands does not overlap each other, nor does it overlap with the center frequency band.

The allocator 610 allocates at least one or more outer frequency bands and the center frequency bands of the plurality of outer frequency bands to the center region of a specific cell, and allocates the outer frequency band to the center region of the specific cell. Allocate

According to an embodiment of the present invention, the allocator 610 may allocate another outer frequency band and a center frequency band that do not overlap with an outer frequency band allocated to the specific cell in a center region of another cell adjacent to the specific cell. have. An outer frequency band allocated to the center region of the other cell may be allocated to an outer region of another cell adjacent to the specific cell.

The receiver 620 receives radio channel state information from a terminal located in a specific cell. According to an embodiment of the present invention, the wireless channel state information may include a received signal strength indicator (RSSI) or a signal to interference and noise ratio (SINR) measured by the terminal. Can be.

The estimator 630 estimates an approximate distance from the base station of the specific cell to the terminal based on the radio channel state information received by the receiver 620. According to an embodiment of the present invention, when a base station transmits a reference signal having a constant intensity to a terminal and receives the reference signal from the terminal and measures the strength or signal-to-interference and noise ratio, the approximate distance from the base station to the terminal may be estimated. Can be.

According to an embodiment of the present invention, the estimator 630 estimates whether the area in which the terminal is located is a center area or an outer area of the cell based on the approximate distance from the base station to the terminal, and the allocation unit 610 determines the area of the cell. At least one data transmission frequency band among the frequency bands allocated to the central region or the outer region may be allocated to the terminal.

The transmitter 640 transmits data to the terminal based on the allocated frequency band.

According to an embodiment of the present invention, the divider 650 determines some frequency bands from the outer frequency bands allocated to the center region and the outer region of the specific cell, and the allocation unit 610 is located at the outer region of the specific cell. For the located terminal, some frequency bands selected by the divider 650 may not be allocated as the data transmission frequency band. As a result, some frequency bands are allocated only to terminals located in the central area, such as the center frequency band, and thus, the same effect as the increase of the center frequency band is obtained. When the number of terminals located in the central region increases or the sum of the bandwidths used by the terminals located in the central region increases, some frequency bands of the outer frequency bands may be allocated only to the terminals located in the central region. Even if the allocation of the frequency band is changed, inter-cell interference is not additionally generated in other cells adjacent to a specific cell, so that the frequency allocation of the multi-cell communication system does not need to be redone.

Embodiments of the present invention also include a computer readable medium having program instructions for performing various computer implemented operations. The computer readable medium may include a program command, a data file, a data structure, etc. alone or in combination. The program instructions may be those specially designed and constructed for the present invention or may be available to those skilled in the art. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. When all or a part of the operation of the mobile terminal or the base station described in the present invention is implemented by a computer program, the computer readable recording medium storing the computer program is also included in the present invention.

1 is a diagram illustrating a method for allocating respective frequency bands to a center region and an outer region of each cell in a multi-cell communication system according to the present invention.

2 is a diagram illustrating allocation of outer frequency bands that do not overlap each other between adjacent cells according to an embodiment of the present invention.

3 is a diagram illustrating that inter-cell interference occurring in a terminal located outside a cell is reduced when each frequency band is allocated to a center region and an outer region of each cell according to the present invention.

4 is a diagram illustrating allocating a portion of an outer frequency band allocated to a cell outer region to a center region according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating a step-by-step method of allocating a portion of an outer frequency band allocated to a cell outer region to a center region according to an embodiment of the present invention.

6 is a diagram illustrating a structure of a frequency band allocation apparatus of a multi-cell communication system according to the present invention.

Claims (14)

In the frequency band allocation method of a multi-cell communication system, Dividing the entire frequency band into a center frequency band and a plurality of outer frequency bands that do not overlap each other; Allocating at least one or more first outer frequency bands and the center frequency bands of the plurality of outer frequency bands to a central region of a first cell; Allocating the at least one first outer frequency band to an outer region of the first cell; Allocating at least one second outer frequency band and the center frequency band of the plurality of outer frequency bands that do not overlap the at least one first outer frequency band among the plurality of outer frequency bands in a central region of the second cell adjacent to the first cell; step; And Allocating the at least one second outer frequency band to an outer region of the second cell Frequency band allocation method comprising a. delete The method of claim 1, Receiving radio channel state information from a terminal located in the first cell; Estimating an area where the terminal is located in the first cell based on the received radio channel state information; And Allocating at least one data transmission frequency band among the frequency bands allocated to the central region or the outer region to the terminal based on the estimation result; Frequency band allocation method further comprising. The method of claim 3, wherein the wireless channel information, And a received signal strength indicator (RSSI) or a signal to interference and noise ratio (SINR) measured by the terminal. The method of claim 1, If the total number of terminals located in the first cell is smaller than a predetermined value, And assigning at least one or more data transmission frequency bands of the allocated first outer frequency bands to a first terminal located in the central area. The method of claim 1, If the terminal is located in the central region of the first cell, And assigning at least one data transmission frequency band from the center frequency band to the terminal in preference to the at least one first outer frequency band. The method of claim 1, Determining a third outer frequency band from the at least first outer frequency band Including, And not determining the determined third outer frequency band for the terminal located in the outer region of the first cell. The method of claim 7, wherein the determining the third outer frequency band, And determining the third outer frequency band based on a ratio of the number of terminals located in the central area and the number of terminals located in the outer area. The method of claim 7, wherein the determining the third outer frequency band, The third outer frequency band is determined based on a sum of frequency bands used by at least one terminal located in the central area and a frequency band used by at least one terminal located in the outer area. Frequency band allocation method. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 and 3 to 9. In the frequency band allocation apparatus of a multi-cell communication system, A divider for dividing the entire frequency band into a center frequency band and a plurality of outer frequency bands that do not overlap each other; And Allocating at least one or more first outer frequency bands and the center frequency band among the plurality of outer frequency bands to a central region of a first cell, and assigning the at least one first outer frequency band to an outer region of the first cell. Allocator to allocate Including, The allocation unit, Assigning at least one second outer frequency band and the center frequency band of the plurality of outer frequency bands that do not overlap with the at least one first outer frequency band among the plurality of outer frequency bands to a central region of the second cell adjacent to the first cell; And assigning the at least one second outer frequency band to an outer region of the second cell. delete 12. The method of claim 11, A receiver configured to receive radio channel state information from a terminal located in the first cell; And An estimator estimating an area in which the terminal is located in the first cell based on the received radio channel state information More, The allocation unit, And at least one data transmission frequency band among the frequency bands allocated to the central region or the outer region to the terminal based on the estimation result. 12. The method of claim 11, The division unit determines a third outer frequency band from the at least first outer frequency band, And the allocator does not allocate the determined third outer frequency band to a first terminal located in an outer region of the first cell.

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