KR20080032991A - Cell arrangement method for wireless telecommunication system based on bandwidth and power tradeoff, and frequency reuse method using it - Google Patents

Abstract

A cell arrangement method for considering optimal allocation of power and bandwidths in a wireless communication system and a frequency reuse method using the arrangement method are provided to allocate high transmission power and narrow bandwidths to users located in a cell border, and to allocate low transmission power and wide bandwidths to users located in the center of a cell, thereby improving system performance. Frequency areas are divided into a frequency area having little interference of peripheral cells with high transmission power and a frequency area having large interference of peripheral cells with low transmission power. Transmission power and the number of terminals are differently allocated to each of the divided frequency areas. When the frequency areas are divided, the frequency areas are divided into an area having narrow bandwidths with a high SNR(Signal to Noise Ratio) and an area having wide bandwidths with a low SNR.

Description

Cell arrangement method for considering bandwidth and power optimal allocation in wireless communication system and frequency reuse method using same {} cell arrangement method for wireless telecommunication system based on bandwidth and power tradeoff, and frequency reuse method using it}

1 is an exemplary configuration diagram of a system using a frequency reuse method considering optimal allocation of bandwidth and power in a downlink OFDMA system according to the present invention;

2 is an explanatory diagram showing a system using frequency reuse efficiency 1 that is the basis of the present invention;

3 is an explanatory diagram showing a system using the frequency reuse efficiency 1 / K underlying the present invention,

4 is an explanatory diagram showing a system using frequency reuse efficiency (K-1) / K, which is the basis of the present invention;

5 is an exemplary diagram of allocation of bandwidth and power according to SNR;

6 is a diagram illustrating an embodiment of a system to which bandwidth and power allocation are applied based on frequency reuse efficiency 1/3 according to the present invention;

7 is a diagram illustrating an embodiment of a system to which bandwidth and power allocation are applied based on frequency reuse efficiency 2/3 according to the present invention;

8 is an explanatory diagram showing a transmission rate according to a signal-to-noise ratio to explain characteristics of a frequency reuse method;

9 is an explanatory diagram showing transmission rates according to distances from a base station in order to explain the characteristics of the frequency reuse method.

The present invention relates to a cell arrangement method considering an optimal allocation of bandwidth and power in a wireless communication system, a frequency reuse method using the same, and a computer-readable recording medium recording a program for implementing the methods. In a downlink Orthogonal Frequency Division Multiple Access (OFDMA) communication system, a cell arrangement method based on bandwidth and power exchange, a frequency reuse method using the same, and a computer recording a program for realizing the methods. The present invention relates to a readable recording medium.

In particular, the present invention relates to a new frequency reuse method for an OFDMA system by combining the concept of bandwidth and power exchange with a frequency reuse method, more specifically, rather than allocating the same bandwidth and the same power to users in a cell. In other words, performance is improved by assigning high transmit power and narrow bandwidth to users at cell boundaries and low transmit power and wide bandwidth to users at cell centers.

OFDMA is a concept in which a plurality of users divide subcarriers of an orthogonal frequency division multiplexing (OFDM) system to share resources, and is considered as a new multiple access method for next generation mobile communication. In the OFDMA scheme, subcarriers allocated to a user are not fixed and are dynamically allocated to each transmission by scheduling.

In a typical cellular system, a frequency reuse method divides a frequency into a plurality of channels and allocates channels in units of cells according to a predetermined frequency allocation pattern so as to maintain interference between the same channels below a specific level. However, the frequency reuse method in the OFDMA system is a problem of assigning subcarriers without changing the carrier frequency, and each terminal can be allocated to a different frequency region for each transmission by scheduling without handover or the like. Therefore, the frequency reuse in the OFDMA system is not limited to the frequency allocation problem of the cell, but results in the dynamic resource allocation problem in which the frequency domain to which the terminal belongs is determined by real-time information such as the location of the terminal, the channel state, and the amount of interference.

When assigning subcarriers to each user, it is not necessary to allocate the same power to all subcarriers. In general, a method of allocating high power to the user in the center of the cell may be used to increase the total data transmission amount of the cell. Power control can be used to allocate high power to users at cell boundaries.

However, in order to satisfactorily support both the user at the cell center and the user at the cell boundary, the allocation of subcarrier resources and power control should be considered at the same time. For example, it is advantageous for a user at the center of the cell to increase the number of subcarriers allocated rather than to increase the transmission power, and to increase the transmission power even if the number of subcarriers is reduced for the user at the cell boundary. Therefore, the overall performance can be improved by exchanging subcarrier resources and power resources between the user at the center of the cell and the user at the cell boundary.

Accordingly, the present invention proposes a new frequency reuse method capable of maximizing the throughput of an OFDMA system in consideration of bandwidth and power allocation at the time of frequency reuse.

SUMMARY OF THE INVENTION The present invention has been proposed to meet the above-mentioned requirements. In the downlink orthogonal frequency division multiple access (OFDMA) communication system, bandwidth and power allocation can be maximized by simultaneously considering bandwidth and power allocation in frequency reuse. SUMMARY OF THE INVENTION An object of the present invention is to provide a cell arrangement method based on power exchange, a frequency reuse method using the same, and a computer-readable recording medium recording a program for implementing the methods.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The present invention for achieving the above object, in the cell and frequency arrangement method in a wireless communication system, in order to allocate different resources according to the signal-to-interference ratio (SNR) for each frequency domain, the transmission power is high in the frequency domain and peripheral The cell and frequency arrangement is designed by dividing the cell into a frequency region having low interference of the cell and a frequency region having low transmission power and having high interference of neighboring cells.

In addition, the present invention relates to a frequency reuse method in a wireless communication system, in which a frequency domain is divided into a frequency region having a high transmission power and a low interference of a neighboring cell and a frequency region having a low transmission power and a large interference of a neighboring cell. Region division step; And a frequency reuse step of differently allocating the transmission power and the number of terminals in each of the divided frequency domains.

In addition, the present invention relates to a method for reusing a frequency in a wireless communication system, in which a terminal reduces transmission power in a cell center region, increases the number of subcarriers, and increases transmission power in a cell boundary region while reducing the number of subcarriers. It is characterized by.

On the other hand, the present invention, in order to allocate different resources according to the signal-to-interference ratio (SNR) for each frequency domain in a cell and frequency arrangement system having a processor, the frequency domain has a high transmission power and a low interference of neighboring cells The present invention provides a computer-readable recording medium recording a program for realizing a function of arranging a cell and a frequency by dividing it into a region and a frequency region having a low transmission power and having high interference of neighboring cells.

In addition, the present invention provides a frequency reuse system in which a frequency domain is divided into a frequency domain having a high transmission power and a low interference of a neighboring cell and a frequency domain having a low transmission power and a large interference of a neighboring cell in a frequency reuse system having a processor. function; And a computer-readable recording medium having recorded thereon a program for realizing a frequency reuse function for differently allocating transmission power and the number of terminals in each of the divided frequency domains.

In the conventional cellular system, the frequency reuse method divides frequencies and allocates terminals located in a specific cell to a specific frequency domain, while frequency reuse in an OFDMA system can be regarded as a subcarrier allocation problem determined by scheduling.

Accordingly, in the present invention, when allocating subcarriers to each user, instead of allocating a constant bandwidth and power to all users, the user in the center of the cell lowers transmission power and increases the number of subcarriers (ie, lowers SNR and widens bandwidth). For the users at the cell boundary, the overall performance can be improved by increasing the transmission power and reducing the number of subcarriers (ie, increasing the SNR and narrowing the bandwidth).

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a frequency reuse method of an OFDMA system will be described with reference to FIGS. 2 to 4 for better understanding, and a concept of switching bandwidth and power will be described with reference to FIG. 5.

2 shows a case of frequency reuse efficiency 1 in which each cell uses all subcarriers.

However, if all the cells use the same frequency as shown in Figure 2, the terminal at the cell boundary is subjected to a large interference. Therefore, the frequency reuse efficiency may be lowered to reduce the interference.

In frequency reuse efficiency 1 / K, the frequency is divided into K regions as shown in FIG. 3, and a number between 1 and K is assigned to each cell so that adjacent cells have different numbers. Cell k reduces interference with adjacent cells by using only frequency domain k.

In the frequency reuse of the OFDMA system, since each terminal can determine the frequency domain only by subcarrier allocation without changing the carrier, the frequency region can be determined according to the position and state of the terminal.

Therefore, in the frequency reuse efficiency (K-1) / K, the frequency is divided into K regions as shown in FIG. 4 and a number is assigned to the cell in the same manner as the frequency reuse efficiency 1 / K, but the cell k is assigned to the frequency region k. Use only the remaining areas.

Referring to FIG. 4, each terminal in cell k measures the preamble of the neighboring cell to find a cell m (≠ k) having the largest intensity of the preamble (possibly having the largest interference), and not using the cell. Assigned to frequency domain m to avoid interference from cell m.

Here, the frequency region not used by each cell may be used as long as it transmits with weak power so that interference does not occur to adjacent cells. In this case, the performance may be further improved by not only considering a power allocation problem but also considering a bandwidth and power allocation problem as shown in FIG. 5.

Let's look at the concept of bandwidth and power exchange.

First, suppose that N terminals are allocated the same amount of power as the same number of subcarriers (method for allocating fixed bandwidth and power).

, 잡음 및 간섭의 전력을

라고 한다면 i번째 단말기의 데이터 전송 속도 R_i는 다음의 [수학식 1]과 같이 주어진다.The number of subcarriers of the symbol is B, the power allocated to each subcarrier is P, and the average channel power of the i-th terminal is

Power of noise, interference

In this case, the data rate R _i of the i-th terminal is given by Equation 1 below.

이다.In Equation 1, Γ is a Signal-to-Noise Ratio (SNR) gap,

to be.

Now, assume that different terminals are assigned different numbers of power and subcarriers.

When the number of subcarriers allocated to the i th terminal is B _i and the power allocated to each sub carrier is α _i P, the data transmission rate R _i of the i th terminal is given by Equation 2 below.

If the frequency and the total power used by the terminal in [Equation 2] is maintained, the following equations [Equation 3] and [Equation 4].

In order to maintain the performance of Equation 1 in Equation 2, the bandwidth may be increased when the power is reduced, and the power may be increased when the bandwidth is decreased. Due to the increase of the logarithmic function, the terminal having a high SNR is advantageous to increase the channel capacity rather than the power increase, and the terminal having a low SNR may reduce the bandwidth and increase the power. As illustrated in FIG. 5, the terminal having a high SNR and a low terminal can maximize overall yield by exchanging bandwidth and power.

For example, when there are two terminals and B ₁ subcarriers are used for the first terminal, the power of the subcarrier of the first terminal is equal to the following Equation 5 to maintain the performance of Equation 1 above. It can be decided together.

The data transmission rate of the second terminal at this time is as shown in Equation 6 below.

For example, if B = 10, SNR ₁ = -5 dB and SNR ₂ = 20 dB , the number of subcarriers of the terminal having a low SNR using B ₁ = 2 is lower than that of subcarriers equally divided by B ₁ = 5. Reducing the power and increasing the power improves the data transfer rate of the second terminal by about 34%.

Therefore, in the present invention, considering bandwidth and power allocation at the time of frequency reuse, instead of allocating a constant bandwidth and power to all users when allocating subcarriers to each user, the user in the center of the cell lowers transmission power and Increasing the number (i.e. lowering the SNR and increasing the bandwidth) and improving the overall performance for users at cell boundaries by increasing the transmission power and reducing the number of subcarriers (i.e. increasing the SNR and narrowing the bandwidth).

1, 6, and 7, a new frequency reuse method for maximizing the throughput of an OFDMA system by considering bandwidth and power allocation at the time of frequency reuse will be described in more detail. do.

In a cellular system, the users (terminals) at the cell boundary have a low attenuation SNR because the signal attenuation is large and the interference from neighboring cells is high, whereas the users (terminals) at the center of the cell have a small signal attenuation and low interference. Therefore, the reception SNR is high.

Therefore, the SNR of the user at the cell boundary should be increased and the bandwidth reduced, while the SNR of the user at the center of the cell should be lowered and the bandwidth increased.

Here, in order to increase the SNR of the user at the cell boundary, the cell and frequency arrangement is designed to increase the transmission power and to receive less interference from neighboring cells. That is, when designing the cell and frequency arrangement, the frequency domain may be divided into a region having a high transmission power and a low interference of a neighboring cell, and a region having a low transmission power and a large interference of a neighboring cell. 1 illustrates that different resources are allocated according to SNR in two different frequency domains using different transmission powers.

As shown in FIG. 1, instead of allocating the same power to 12 (/) users (terminals), transmit to 8 (/) users (terminals) at the cell boundary while reducing the number of subcarriers. Designed to increase power and to reduce the interference of neighboring cells (assigned to the frequency region where the interference of neighboring cells is less), and to the four (/) users in the center of the cell Allocates to the area, lowers the transmit power and increases the number of subcarriers. That is, at the cell boundary, the SNR is increased and the bandwidth is narrowed, and at the cell center, the SNR is decreased and the bandwidth is widened.

In a cellular system, arbitrarily increasing the power of a specific subcarrier without negotiating with neighboring cells may change interference between cells, making interference control difficult.

Therefore, in order to perform independent interference control for each cell, it is preferable to use a predetermined power for each frequency domain.

Accordingly, in order to apply the tradeoff concept of bandwidth and power to frequency reuse, the present invention proposes a method of dividing each cell into several frequency domains and allocating different transmit powers and the number of users for each frequency domain.

In the downlink OFDMA system according to the present invention, the frequency reuse method considering the optimal allocation of bandwidth and power, first, when designing the cell and frequency arrangement, the frequency region is a region with high transmission power and low interference of neighboring cells (high SNR). And a region having a narrow bandwidth), and a region having a low transmission power and a large interference with neighboring cells (a region having a low SNR and a wide bandwidth). Here, in the cellular system, the users at the cell boundary have a high signal attenuation and high interference from neighboring cells, so the reception signal-to-noise ratio (SNR) is low, whereas the users in the center of the cell have low signal attenuation and interference. Since the received SNR is high, the frequency domain can be divided.

In this case, the region having the high SNR and the narrow bandwidth narrows the basic unit of the bandwidth constituting the region, and the region having the low SNR and the wide bandwidth sets the basic unit of the bandwidth constituting the region.

Thereafter, different transmit powers and the number of users are allocated to each frequency domain. Here, the user's SNR at the cell boundary is increased and bandwidth is reduced, while the user's SNR at the center of the cell is lowered and the bandwidth is increased to maximize the overall yield. At this time, in order to increase the SNR of the user at the cell boundary, the cell and frequency arrangements are designed to reduce the interference of the neighboring cells while increasing the transmission power.

In this way, the bandwidth is divided in advance and a user is allocated to the bandwidth. In the case of assigning a user, a user (terminal) located at a cell boundary that is far from the base station and has a low SNR in a region having a high SNR and a narrow bandwidth is allocated. It assigns a 'user (terminal) near the base station and having a high SNR and located in the center of the cell' to an area with low SNR and wide bandwidth.

In this way, performance can be improved by allocating high transmit power and a narrow bandwidth to a user at a cell boundary and low transmit power and a wide bandwidth to a user at a cell center.

Next, a method based on frequency reuse 1 / K will be described with reference to FIG. 6, and a method based on frequency reuse efficiency (K-1) / K will be described with reference to FIG. 7.

FIG. 6 illustrates an example of applying bandwidth and power allocation based on the frequency reuse efficiency 1/3 of FIG. 3.

Referring to FIG. 6, the cells are allocated in the same manner as the frequency reuse efficiency 1 / K. However, in the cell k, the frequency domain k has a narrow bandwidth (a small subcarrier group) and a large transmission power for each user. Frequency domain is allocated a wide bandwidth (large subcarrier group) and low transmission power for each user.

The terminal with low SNR allocates to region k to mitigate interference from neighboring cells, and the terminal with high SNR finds cell m (≠ k) with the weakest (lowest interference) strength of the most received preamble, Assign to

FIG. 7 illustrates an example of applying bandwidth and power allocation based on the frequency reuse efficiency 2/3 of FIG. 4.

Referring to FIG. 7, the cell is allocated in the same manner as the frequency reuse efficiency 1 / K, but the cell k allocates a low transmission power in the frequency domain k and a large transmission power in the remaining K-1 frequency domains.

A terminal with a low SNR finds a cell m (≠ k) having the largest preamble strength and assigns it to the frequency region m, and a terminal with a high SNR is allocated to the region k.

Now, the characteristics of the frequency reuse method will be described.

To examine the characteristics of the frequency reuse methods, simply compare the transmission rates according to the distance from the base station without considering fading or shadowing.

Each cell is assumed to be assigned a number in the method of frequency reuse efficiency 1/3 as shown in FIG. The terminal belongs to the cell numbered 1, and the received signal power of the terminal when transmitted at a power of 1 S, the interference from the cells numbered k number of the terminal (excluding signals from the base station to which it belongs) Let I _{k be} the terminal noise. When the frequency reuse efficiency 1 is used, if a given bandwidth is B and N terminals are equally divided, the data transmission rate may be defined as shown in Equation 7 below.

If the frequency reuse efficiency 1/3 is used, the data transmission rate is expressed by Equation 8 below.

In the case of using frequency reuse efficiency 2/3, if the frequency is allocated to frequency 2 because it is closer to cell 2, the data transmission rate is expressed by Equation 9 below.

보다 먼 단말기는 주파수 영역1을, 가까운 단말기는 주파수 영역2 또는 3을 사용할 것이다. 단말기가 1번 주파수 영역에 할당이 되었다면 데이터 전송 속도는 하기의 [수학식 10]과 같다. In the present invention, suppose that the power of the frequency domain 1 is α ₁ and N ₁ is equally divided, and the power of the frequency domain 2 (or 3) is α ₂ and N ₂ is shared (N ₁ + 2N ₂ = N). If the number of terminals is very large and uniformly distributed, the distance is determined by

Farther terminals will use frequency domain 1 and closer terminals will use frequency domain 2 or 3. If the terminal has been allocated to the first frequency domain, the data transmission rate is expressed by Equation 10 below.

If the terminal is located near the base station and closer to cell 2 and assigned to frequency 3, the data transmission rate is expressed by Equation 11 below.

8 shows the logarithms of Equations 7 to 11 according to SNR. The attenuation of the signal is proportional to the third power of the path, taking into account the interference of 2 tiers, Γ = 1, B = 30, η = 0, N = 30, N ₁ = 20, N ₂ = 5, α ₁ / α ₂ = -9 dB was used.

In FIG. 8, an indication such as "+", "X", "o", "∇", etc. indicates an SNR and a data transmission rate according to each scheme in a terminal located at a cell boundary. In FIG. 8, "Δ" corresponds to a case where the distance from the base station is farthest among terminals to which Equation 11 is applied.

In FIG. 8, as the bandwidth used by each terminal increases, the slope of the curve increases and the SNR experienced by the terminal decreases. [Equation 7] shows that the performance decreases because the SNR is low at the cell boundary (+), but the high transmission rate is obtained because the SNR is high and the bandwidth is large at the cell center. In addition, Equation (8) shows good performance due to low interference at the cell boundary (X mark). However, even though SNR is improved due to low bandwidth, the increase in transmission rate is limited. In addition, the property of [Equation 9] lies in the middle of [Equation 7] and [Equation 8]. In addition, although the performance of the Equation 10 is small because the interference is small at the cell boundary (∇), the performance improvement is limited even if the SNR is increased.

However, at the center of the cell, it is changed to the above Equation (11), and thus has a high transmission rate when the SNR increases.

9 shows the data transmission rate of the terminal according to the distance from the base station when the cell radius is 1. The curve of the frequency reuse efficiency 1 has a high slope and performs well in the center of the cell, but may have a lot of outage due to a low transmission speed at the cell boundary. The curve of frequency reuse efficiency 1/3 has a small slope, which is excellent at the cell boundary, but a high transmission rate cannot be obtained at the cell center. At frequency reuse efficiency 2/3, the characteristics at cell boundary and cell center are between frequency reuse efficiency 1 and 1/3. The performance of the proposed method according to the present invention consists of two curves with different slopes and shows the best performance in most sections.

In the simulation, the base station and the terminal are generated, the signal-to-interference ratio (SIR) is calculated using the inter-cell interference and the channel value, and the data rate is calculated using the channel capacity formula. Variables used in the experiment are shown in Table 1 below.

In the simulation, we confirmed that the cell data rate is high and fairness is good for each method. Data rates were measured in bit / sec / Hz, and outage and time slots were measured to observe fairness along with data rates.

Outage was determined when the data rate of each terminal was below a certain standard, and time slot was defined as the time taken to transmit the same amount of data to all terminals except the lower 2%.

Scheduling takes into account users with low SNR and uses the given bandwidth evenly among each user.

The experiments compared the frequency reuse schemes for the following six cases.

Frequency Reuse Factor (FRF) 1 (FIG. 2)

FRF 1/3 (FIG. 3)

FRF 2/3 (FIG. 4)

FRF 1/3 + Low Power (high power mobiles: low power mobiles = 20:10) (Figure 6)

FRF 1/3 + Low Power (high power mobiles: low power mobiles = 16:14) (Figure 6)

FRF 2/3 + Low Power (high power mobiles: low power mobiles = 26: 4) (FIG. 7)

Experimental results are shown in the following [Table 2].

As shown in Table 2 below, in case of frequency reuse efficiency 1, the data transmission amount is high, but the fairness performance is deteriorated due to high interference.

In the case of 1/3 frequency reuse efficiency, interference is mitigated to improve fairness, but the amount of data used is reduced due to the reduced bandwidth used.

In addition, since the frequency reuse efficiency 2/3 allocates a frequency domain using information of the terminal, fairness and data transmission amount may be improved at the same time.

When the user and power allocation are applied by applying the concept of bandwidth and power exchange to the existing frequency reuse scheme, the performance is improved more than the conventional scheme. It is possible to increase the data transmission speed or improve fairness according to the user's adjustment to the two areas.

In Table 2, (Case 1) is a case where the ratio of the number of users allocated to high power and the number of users allocated to low power is 20:10.

Also, (Case 2) is an experiment in which the ratio of the number of users allocated to high power and the number of users allocated to low power is 16:14.

In addition, for the frequency reuse efficiency 2/3, the ratio of the number of users allocated to high power and the number of users allocated to low power is 26: 4.

As described above, rather than allocating the same bandwidth and the same power to the users in the cell, assigning high transmit power and narrow bandwidth to the users at the cell boundary, and low transmit power and wide bandwidth to the users at the center of the cell. This helps improve performance.

As shown in the experimental results, the present invention shows better performance than the conventional frequency reuse method.

However, in the present invention, although only two levels of transmission power are considered, when considering several levels of transmission power, better performance may be obtained.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention provides a high transmit power and a narrow bandwidth for a user at a cell boundary, a low transmit power and a wide bandwidth for a user at a cell center, rather than allocating the same bandwidth and the same power to users in a cell. By assigning, the system performance can be improved.

Claims (17)

In the cell and frequency arrangement method in a wireless communication system, In order to allocate different resources according to the signal-to-interference ratio (SNR) for each frequency domain, the frequency domain is divided into a frequency domain with high transmission power and low interference of neighboring cells and a frequency domain with low transmission power and high interference with neighboring cells. Cell and frequency arrangement design. The method of claim 1, Assigns a terminal in a cell boundary region to a frequency region where the neighboring cell has little interference, And assigning a terminal in a cell center region to a frequency region in which the neighboring cell has a large interference. The method of claim 2, In the cell center region, since the signal attenuation is small and the interference is small, the reception SNR is high. In the cell boundary region, the reception SNR is high because the signal attenuation is large and the interference from neighboring cells is large. The cell arrangement method of claim 1, wherein the SNR of the terminal in the cell center region is lowered and bandwidth is increased, and the SNR of the terminal in the cell boundary region is increased and bandwidth is reduced. The method of claim 3, wherein For the terminal in the cell boundary region, transmission power is increased while reducing the number of subcarriers, The terminal of the cell center region, the cell placement method characterized in that the transmission power is lowered and the number of subcarriers is increased. The method according to any one of claims 1 to 4, Allocating different transmission power and the number of terminals for each of the divided frequency domains Cell placement method further comprising. The method of claim 5, wherein The wireless communication system, A cell arrangement method, characterized by a downlink orthogonal frequency division multiple access (OFDMA) system. In the frequency reuse method in a wireless communication system, A frequency domain division step of dividing the frequency domain into a frequency domain having a high transmission power and a low interference of a neighboring cell and a frequency domain having a low transmission power and a large interference of a neighboring cell; And Frequency reuse step of differently allocating the transmission power and the number of terminals in each of the divided frequency domain Frequency reuse method comprising a. The method of claim 7, wherein In the frequency domain division step, And dividing the frequency domain into a region having a high SNR and a narrow bandwidth and a region having a low SNR and a wide bandwidth according to a received signal-to-noise ratio (SNR). The method of claim 8, The region having the high SNR and the narrow bandwidth narrowly sets the basic unit of the bandwidth constituting the region, The region having a low SNR and a wide bandwidth sets a basic unit of bandwidth constituting the region wide. The method according to any one of claims 7 to 9, In the frequency reuse step, In areas with high SNR and narrow bandwidth, allocate terminals that are far from the base station and are in the cell boundary region, having low SNR, A method for frequency reuse, characterized by allocating terminals in a cell center region and close to the base station with high SNR in an area with low SNR and wide bandwidth. The method of claim 10, And reducing the SNR of the terminal in the cell center region and increasing the bandwidth, and increasing the SNR of the terminal in the cell boundary region and reducing the bandwidth. The method of claim 11, For the terminal in the cell boundary region, transmission power is increased while reducing the number of subcarriers, The terminal of the cell center region, the frequency reuse method characterized in that the transmission power is lowered and the number of subcarriers is increased. The method of claim 12, The wireless communication system, A downlink orthogonal frequency division multiple access (OFDMA) system. In the frequency reuse method in a wireless communication system, The method of claim 1, wherein the terminal communicates by increasing transmission power while decreasing transmission power in the cell center region and increasing the number of subcarriers and reducing the number of subcarriers in the cell boundary region. The method of claim 14, The terminal, And reducing the signal-to-noise ratio (SNR) and increasing the bandwidth in the cell center region, and increasing the SNR and reducing the bandwidth in the cell boundary region. In a cell and frequency placement system with a processor, In order to allocate different resources according to the signal-to-interference ratio (SNR) for each frequency domain, the frequency domain is divided into a frequency domain with high transmission power and low interference of neighboring cells and a frequency domain with low transmission power and high interference with neighboring cells. To design cell and frequency layouts A computer-readable recording medium having recorded thereon a program for realizing this. In a frequency reuse system with a processor, A frequency domain classification function for dividing a frequency domain into a frequency domain having a high transmission power and a low interference of a neighboring cell, and a frequency domain having a low transmission power and a large interference of a neighboring cell; And Frequency reuse function for differently allocating transmit power and the number of terminals in each of the divided frequency domains A computer-readable recording medium having recorded thereon a program for realizing this.

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