KR100745086B1 - Resource Allocation Method in PFDMA Based Mobile Communication System - Google Patents

Abstract

The present invention relates to a resource allocation method in an orthogonal frequency division multiplexing (OFDM) based mobile communication system.

In an OFDM-based mobile communication system, cell coverage can be extended by arranging repeaters at cell boundaries, and interference effects between neighboring cells can be eliminated by allocating orthogonal resources to repeaters located at cell boundary regions. In addition, in operating the repeater maximizes resource efficiency by recycling the resources for the transmission and reception of the base station and the relay period to the resources necessary for the transmission and reception between the repeater and the user.

Description

Method for resource allocation in OFDM-based mobile communication systems

1 is an exemplary diagram illustrating a forward and reverse interference situation in a general cell boundary region.

2 is an exemplary diagram of an interference coordination method for reducing interference between users in a cell boundary region proposed by a general Alcatel.

3 is an analysis graph showing interference intensity according to the use of a general interference coordination technique.

4 is a conceptual diagram in which a fixed repeater is disposed in a general wireless mobile communication environment.

5 is an exemplary diagram of a repeater arrangement for reducing intercell interference according to an embodiment of the present invention.

6 is an exemplary diagram of interference according to a base station using an intersector omnidirectional antenna according to an embodiment of the present invention.

7 is an exemplary view showing a repeater frequency conversion for efficiency of resource use according to an embodiment of the present invention.

8 is a flowchart illustrating a repeater frequency resource allocation method according to an embodiment of the present invention.

9 is an exemplary diagram illustrating grouping of resources according to an embodiment of the present invention.

10A and 10B are diagrams illustrating resource allocation when a distribution of users is not uniform in a cell boundary area according to an exemplary embodiment of the present invention.

11 is an exemplary diagram of a method for avoiding inter-cell interference when a base station directly provides a service to a cell boundary area according to an embodiment of the present invention.

12 is a diagram illustrating a resource allocation method when there is a change in repeater arrangement of a cell boundary area according to an embodiment of the present invention.

13 is an exemplary view comparing the terminal reception performance of the OFDM-based mobile communication system and the terminal reception performance of the conventional OFDM-based mobile communication system according to an embodiment of the present invention.

The present invention relates to a mobile communication system, and more particularly, to a resource allocation method capable of improving resource efficiency of a mobile terminal in an orthogonal frequency division multiple access mobile communication system.

In the next generation mobile communication system, unlike the 1 to 2 GHz band used in the existing mobile communication system, a high frequency band of 3.5 GHz to 5 GHz is allocated and used. This high band propagation is similar to that of light and thus has a property of going straight rather than diffraction, thereby limiting the signal arrival area. Therefore, in urban areas where large and tall buildings are densely distributed, cell coverage is inevitably reduced.

In addition, since the next generation mobile communication system aims to provide a large capacity wireless link of 10Mbps or more per user, resource allocation per user increases. If the resource efficiency of the mobile communication system to which resources are allocated is not high, the service area that one base station can handle is significantly reduced compared to the previous one because the number of users that can be accommodated per base station is limited. Therefore, there is a problem that the installation cost of the base station increases.

In order to solve this problem, a claim has been made to introduce a relay, and research on this has been actively conducted. In fact, IEEE Communication Magazine. September 2004 “Relay-Based Deployment Concepts for Wireless and Mobile Broadband Radio” (WWRF) is conducting research based on the introduction of repeaters. The repeater receives a signal through an antenna having a better reception sensitivity than the terminal, and transmits a signal to the terminal using less power than the base station to cover the user in the shadow area or the cell boundary area as well as to expand the cell coverage as a whole. Effect.

However, this research attempt is a level that simply summarizes the use of repeaters in the classical sense, and is dominated by evaluation that it is difficult to see new ideas and to expect great usefulness. In addition, it has not been proposed a relay arrangement and associated resource allocation algorithm that can eliminate the inter-cell interference.

Accordingly, the present invention is to solve the above problems of the prior art, in the orthogonal frequency division multiple base mobile communication system to expand the cell coverage according to the base station / repeater and at the same time eliminate the inter-cell interference to maximize the resource efficiency It provides a radio resource allocation method that can be satisfied.

In the resource allocation method according to an aspect of the present invention for achieving the technical problem of the present invention, at least one repeater is disposed in a cell formed by a base station in a mobile communication system, the repeaters and the base station or the repeater In the method for allocating resources to terminals connected to the network,

The repeater is located in a cell boundary region of the base station, where the cell boundary region is divided into at least one region, and the method of allocating resources to the repeater or the terminal, (a) the mobile communication system Cell boundary region resources to provide all resources allocated to the cell boundary region of the base station and the inside of the cell, where the inside of the cell represents a region other than the cell boundary region adjacent to another cell in one cell. Dividing into intra-cell area resources to provide; (b) providing resources to be provided to the cell boundary region to the repeater located in the cell boundary region, wherein the resources provided are allocated to terminals distributed in the cell boundary region; And (c) providing resources to be provided inside the cell to the terminal located inside the cell.

According to another aspect of the present invention, there is provided a resource allocation method, wherein at least one repeater is disposed in a base station in a mobile communication system, the relays are connected to the base station or the repeaters. In a method of allocating resources in the terminal,

The repeater is located in a cell boundary region of the base station, and the method for allocating resources to the repeater or the terminal includes: (a) dividing the cell boundary region divided into the at least one region into a predetermined number of sub regions; step; (b) resources to provide the entire resource allocated to the mobile communication system to a cell boundary area divided into the predetermined number of sub-areas and the inside of the cell, where the inside of the cell is a cell adjacent to another cell; Dividing into regions to be provided except for the boundary region; And (c) providing a resource divided into resources to be provided to the cell boundary region to the repeater located in the cell boundary region, and providing a resource divided into resources to be provided inside the cell to the terminal located inside the cell. It includes a step.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

In the next generation mobile communication system, the frequency reuse rate is 1, and the interference problem between users in the cell boundary area is emerging. The interference situation in the cell can be considered to be divided into forward and reverse directions, which will be described with reference to FIG. 1.

1 is an exemplary diagram illustrating a forward and reverse interference situation in a general cell boundary region.

1, the interference in the forward direction is applied from the base station to the terminal, it can be seen that the interference strength received by the terminal B from the other base station than the terminal A is greater. That is, the farther away from the base station, the more severe interference caused by a cell, which is a signal transmission / reception area of another base station. In particular, in a terminal located at the boundary between two cells, a problem occurs that the signal strength from its base station is the smallest and the interference strength from another base station is the largest. ”

In contrast to the forward direction, interference in the reverse direction causes the terminal to affect the base station. In the reverse direction, since a terminal located far from the base station increases the signal strength and transmits the corresponding signal to the base station through a power control scheme, the signal strength received by the base station is constant regardless of the position of the terminal. In the case of other cell interference, the power of the user in the boundary region of the cell acts as a large interference signal. In this case, the base station usually uses multiple reception antennas, and the interference problem is less serious when compared to the forward case because the antenna has excellent reception sensitivity and signal processing capability.

Next, an interference coordination method for reducing interference between users in the cell boundary region according to the forward or reverse direction described with reference to FIG. 1 will be described with reference to FIG. 2.

2 is an exemplary diagram of an interference coordination method for reducing interference between users in a cell boundary region proposed by a general Alcatel.

Alcatel uses interference coordination to reduce the interference between users located at the cell boundary area. It groups the entire frequency domain into non-contiguous frequencies and assigns the frequency groups to specific regions.

As shown in FIG. 2, the same frequency group is allocated to an adjacent cell boundary region of a target cell. Then, in the target cell, the inter-cell interference effect will be limited to the first frequency group, so if only the frequency of the first frequency group is avoided, the inter-user interference effect can be reduced. Assuming isotropic propagation in the planar zone and indicating strips from other cells with assigned frequency block numbers, all frequencies across the zone with full symmetry using the full resource usage as shown in FIG. (1-9) is used evenly. In this case, if resources for frequencies other than frequency 1 are allocated to a terminal adjacent to a target cell using frequency 1 and located in a cell boundary region, the influence of interference between users may be reduced.

Next, the interference intensity when the interference adjustment method is used as described above with reference to FIG. 2 and the interference intensity when not the case will be compared with reference to FIG. 3.

3 is an analysis graph showing interference intensity according to the use of a general interference adjustment method.

Referring to FIG. 3, when the interference coordination method is not used, as shown in a graph indicated by the reference numeral 50, the influence of the interference evenly spread in all frequency domains. However, when the interference adjustment method is used, all interference effects are limited to the frequency group 1 as described in FIG. 2, and the interference effects in the remaining frequency groups are greatly reduced.

Ideally, as in the graph indicated by the reference numeral 52, there is no interference effect in all frequency domains except the frequency group 1, but the interference effect is influenced not only by neighboring cells but also by other cells, so that other frequency domains are actually different. Interference effects also occur at. However, the size is considerably reduced, subject to interference such as the graph indicated by reference numeral 51.

Next, the arrangement of the fixed relay in the wireless mobile communication environment described in the WWRF will be described with reference to FIG. 4.

4 is a conceptual diagram in which a fixed repeater is disposed in a general wireless mobile communication environment.

As shown in FIG. 4, (a) illustrates a case where both the base station and the repeater use the same frequency, f1, in the time axis in order to relay the signal. (b) illustrates a case where the base station receives information using the frequency f1 and converts the frequency to f2 to provide a service to repeater users. This is a case where resources are divided and used on a frequency.

(c) divides the resources from each other on the frequency resources in the same manner as in (b), but uses another repeater (referred to as a “converted repeater” for the convenience of description) to perform frequency conversion between the base station and the repeater. The case is illustrated. At this time, the conversion repeater is not used to service users, unlike general repeaters, and is used only for frequency conversion.

As the next-generation mobile communication system has a serious problem of cell coverage reduction and interference at the cell boundary area, the only method that can extend the cell coverage currently available is to use a repeater. As described above, a repeater arrangement method capable of extending cell coverage using a repeater and reducing inter-cell interference will be described in detail with reference to FIG. 5.

5 is an exemplary diagram of a repeater arrangement for reducing intercell interference according to an embodiment of the present invention.

Prior to describing an arrangement method according to an embodiment of the present invention, some terms are first defined as follows.

Base station threshold: means a signal level (Signal to Interference and Noise Ratio, signal-to-interference and noise ratio, hereinafter referred to as "SINR") of a certain quality received by the terminal from the base station. A terminal may provide a service to a user only after receiving a signal level higher than a base station threshold value, and the base station threshold value may be set differently according to a system.

Repeater Threshold: The SINR, which is a signal level of a certain quality received by the terminal from the repeater. The terminal may provide a service to the user only after receiving a signal level higher than the repeater threshold, and the repeater threshold may be set differently according to the system.

Cell radius: means the distance to the point where the signal transmitted from the base station becomes equal to the base station threshold.

Repeater Radius: The distance from the repeater to the point where the signal transmitted equals the heavy machinery threshold.

Inner radius: It means the value subtracted from the radius of the cell by the radius of the repeater.

Outer radius: The radius of the cell plus the radius of the repeater.

Cell boundary area: the area between the inner and outer radius.

Based on the terms defined above, the base station and the repeater are arranged under the following three conditions.

First, base stations are arranged such that the distance between two base stations is less than twice the outer radius and greater than twice the cell radius.

Second, the repeaters are arranged in the cell radius, the distance between the repeaters in the same base station is arranged to be equally spaced from each other within a distance less than twice the radius of the repeater.

Third, the terminals communicate with the base station or repeater that sends the best signal at the current location. In this case, the quality of the signal may be generally determined by the strength of the pilot signal, but is not necessarily limited thereto.

Here, information about the outer radius, the cell radius, or the repeater radius is provided to the system designer with specifications according to the performance of the base station or repeater to be designed before the mobile communication system is designed, and the system designer arranges the base station or repeater based on the information. .

When arranging the base station and the repeater under such conditions, since the general cell arrangement is made of a geometric shape, the shape of the cell radius may also be assumed as a specific geometric figure. In the embodiment of the present invention, it was regarded as a regular hexagon, and even in this case, the base station and the repeater may be arranged under the above conditions, but are not necessarily limited thereto.

In the conventional resource allocation method using a repeater, a method of avoiding interference by allocating resources to terminals so as to ensure orthogonality with each other in a cell boundary region has been used. However, in the embodiment of the present invention, even when the same resource is allocated to a repeater, the resource is allocated in the cell boundary region. Ensure orthogonality between

As shown in FIG. 5, the portion denoted by the circle 100 means the reach of the repeater signal, and the portion filled with the same pattern means an area using the same frequency. Arrow 110 also shows that the repeater signals are likely to cause interference with each other.

As described above, since the reach range of the signal transmitted from the repeater is limited, orthogonality can be obtained according to the arrangement of the repeater even if the same resource is allocated to the entire cell boundary region. That is, even if the same resource is allocated to the cell boundary region, interference can be avoided.

When the base station and the repeater are arranged in the method shown in FIG. 5 and resources are allocated using the base station and the repeater, the resources used in the cell boundary region and the resources used inside the cell are different from each other. Therefore, the in-cell users are not affected by interference at all, and since the interference occurs only between repeaters assigned the same resources in the cell boundary area, the strength of the interference is considerably reduced as a whole. In this case, the inside of a cell means a region except for a border region adjacent to another cell in one cell.

Next, an example of interference expected when the omnidirectional antenna is used in the base station when the base station and the repeater are installed according to an embodiment of the present invention will be described with reference to FIG. 6.

6 is an exemplary diagram of interference according to a base station using an intersector omnidirectional antenna according to an embodiment of the present invention.

Referring to FIG. 6, the arrow 120 indicated by the dotted line represents the interference described with reference to FIG. 5, and the solid line arrow 130 illustrates the interference effect that will additionally occur when the omnidirectional antenna is used. The cause of the interference, such as the solid arrow 130, is caused because the signal transmitted for communication between the base station and the relay period in the adjacent cell interferes with the user at the cell boundary region.

The influence of such interference can be completely solved when the base station uses a beamforming antenna. Accordingly, only interference as described in FIG. 5 exists.

Next, a method of increasing the efficiency of frequency resources when using a beamforming antenna will be described with reference to FIG. 7.

7 is an exemplary view showing a repeater frequency conversion for efficiency of resource use according to an embodiment of the present invention.

Using the beamforming antenna as shown in Figure 7, there is an advantage that the resources for the transmission and reception of the base station and the relay period can be recycled as resources for the transmission and reception between the repeater and the user. Since the repeater cannot transmit and receive the same frequency at the same time because of the feedback phenomenon of the received signal unless the isolation between the transmitted and received signals is not perfect, frequency conversion is essential.

Therefore, when the beamforming antenna is not used, resources between the base station and the relay period and resources between the repeater and the terminal should be used separately. Otherwise, the resources between the two links will interfere with each other.

However, when the beamforming antenna is used, since the range of the transmission signal is limited to one repeater, there is no interference effect on neighboring repeaters. Therefore, even if the frequency conversion of the repeater is essential, when receiving the resource from the base station and performing the frequency conversion, the transceiving resource between the base station and the relay period is transmitted to the user by converting the frequency into the resource received from the base station. It can be used as a resource for transmitting and receiving between the repeater and the terminal.

That is, as shown in Figure 7, the signal output from the base station to the repeater FFT (Fast Fourier Transform) processing to convert the signal into the frequency domain signal processing the signal of the transformed frequency region to form a beam forming in the desired direction Do it. Using such a method, the repeater-terminal use frequency resource transmitted in the repeater region indicated by 311 may be used as the base station-relay period frequency resource denoted by 302.

Similarly, the repeater-terminal use frequency resource transmitted in the repeater region indicated by 301 may also be used as the base station-relay period frequency resource denoted by 322. In addition, the repeater-terminal use frequency resource transmitted in the repeater region indicated by 321 may be used as the base station-relay period frequency resource denoted by 312. Therefore, the efficiency of the recycling of frequency resources is improved. Here, the method of allocating resources to the repeater by forming the beam forming is already known, and detailed descriptions thereof will be omitted in the embodiments of the present invention.

Next, a method of allocating a frequency resource for increasing the efficiency of resource allocation described with reference to FIG. 7 will be described with reference to FIG. 8.

8 is a flowchart illustrating a repeater frequency resource allocation method according to an embodiment of the present invention.

The step of allocating frequency resources according to an embodiment of the present invention can be divided into three parts. First, the first step is an initialization step (S100), which divides the entire resources given to the mobile communication system into resources to be used in the cell and resources to be used in the cell boundary region.

The second step is a resource allocation step of allocating resources to users in the cell boundary region (S200). The base station and the repeater are connected to each other to find the most efficient resource allocation according to the amount of resources required in the cell boundary region. The last step is an internal user resource allocation step (S300) for allocating resources to users in a cell. The second step is to allocate resources to users in the cell boundary area and close to users based on the distribution of remaining resources. Allocates resources first.

In this case, the base station and the repeater first allocate frequency resources to cell-centric users in association with each other, and then allocate frequency resources to users within the cell. This indicates that the use efficiency of resources can be maximized.

In other words, when the frequency resources are allocated to the users at the cell center after the frequency resources are allocated to the users located at the cell boundary region, the interference strength of the frequency resources is somewhat larger than the interference strength felt by the users at the cell boundary region. However, the efficiency of resources can be increased without wasting extra resources. Here, the interference felt by the cell-centric users means interference occurring between users in the boundary region of another cell.

In addition, as described above, the repeater somewhat reduces the signal strength of resources used by the users located in the cell boundary area and reassigns them to the users in the cell. This increases the strength of the interference somewhat, but has the advantage that the reuse rate of the frequency resource can be set to 1 or more. Interference here refers to interference occurring between a user inside a cell and a user located in a cell boundary region.

The reason why the resources used by the users located in the cell boundary region can be reassigned to the users located in the cell center or the users located inside the cell is because the resources allocated to the users are allocated through beamforming. Beamforming for resource allocation is performed regardless of whether the distribution of users located in the cell boundary region is uniform. That is, when the distribution of users is uniform, resources may be allocated without an optimal bandwidth calculation process. If the distribution is not uniform, resources are allocated to users after a separate bandwidth calculation process. Beamforming is used to minimize system complexity and system interference.

As described above, after all users have been allocated resources, the service starts. If there is a change in resources required by the cell boundary region, the user distribution of the cell boundary region is checked again to allocate resources. Looking at the resource allocation method divided into three steps as described in more detail as follows.

First, an initializing step (S100) is a step in which the base station is contoured to divide and allocate the resources to the repeater or the terminal, respectively, sub-carrier ordering step (S110) and frequency resource grouping (Frequency) Grouping) step (S120). Here, the sub-carrier sequencing step (S110) is a process of randomly selecting any resource to allocate to a repeater or a terminal, not a continuous resource allocation, for all resources allocated to the base station.

The randomly selected resources are divided into a base station-relay resource region and a base station-terminal resource region through a frequency resource grouping step (S120). In this way, the frequency resource grouping step (S120) simply distinguishes resources to be used inside the cell (or also referred to as base station-terminal resources) and resources to be used in a cell boundary region (or also referred to as base station-relayer resources). Here, the first step is to classify resources on the assumption that all users who will receive services using the resources are uniformly distributed.

The next second step (S200) is a part of allocating resources to a plurality of users substantially distributed in the cell boundary region, unlike the first step (S100), the case where the distribution of users is uniform and not uniform. Allocate resources with consideration. When the frequency resources are grouped through the step S120, the base station checks the distribution of users in the cell boundary region (S210).

If it is determined that the distribution of the users is not uniformly determined, the optimal bandwidth is calculated (S220), and the repeater performs beamforming (S230) to successfully allocate resources to the users based on the calculated bandwidth. After performing beamforming (S230), the base station allocates resources to the repeater (S240). However, if it is determined that the users are uniformly distributed, the repeater immediately performs beamforming for resource allocation to the users (S230). As described above, beamforming for resource allocation may be performed regardless of whether a distribution degree of users located at a cell boundary region is uniform.

At this time, the criteria for determining whether the distribution degree of the user performed in step S210 is uniform or not is as follows. First, when designing a system, a predetermined uniformity is set, and when a base station receives a signal from a user's terminal, the distribution of users is uniform when the received signal from a specific area is not greater or smaller than a predetermined predetermined uniformity. To judge. If the received signal is larger than the predetermined uniformity, it is determined that the distribution of users is concentrated in the corresponding area. If the number of received signals is smaller than the uniformity, it is determined that the distribution of users is small.

Next, a third step (S300) of allocating resources to users in a cell is performed, and the third step is divided into the following steps. After allocating the resources to the repeater in the base station to check the remaining frequency resources (S310), and assigns the frequency resources to the users in the center of the cell (S320).

Here, the user at the center of the cell means a user located within a set distance from the base station. First, frequency resources are allocated to the users at the cell center (S320), and then, frequency resources are allocated to the users who have not been allocated the resources in the cell (S330).

When allocating the resources up to the third step as described above, it is determined whether there are more resource requests from the repeater or the presence of resources continuously returned (S400). This can be confirmed by the presence or absence of resources returned when a user who has been allocated and used resources at base station A stops using resources or moves to base station B. In addition, when there is a change in resources required in the cell boundary region or a change in user distribution in the cell boundary region, it may be determined by determining whether there are more resource requests from the repeater. After the determination, step S210 or step S240 is performed.

Next, a method of grouping resources in order to avoid interference with the neighboring cell described with reference to FIG. 8 will be described in detail with reference to FIG. 9.

9 is an exemplary diagram illustrating grouping of resources according to an embodiment of the present invention.

As shown in FIG. 9, the total resources given to the system are divided into resources for users in the cell boundary region and resources for users in the cell. The resource portion for the cell boundary region is divided into as many resources as the cell boundary region is divided, and the resource for the user inside the cell is divided into three portions. In an embodiment of the present invention, the resources of the cell boundary region are divided into three parts, and the number of dividing the resources of the cell boundary region and the resources within the cell is not necessarily limited thereto.

This grouping of resources and dividing the resources into a plurality of numbers is for allocating resources more efficiently in the repeater resource allocation portion, which will be described with reference to FIG. 12 below. As illustrated in FIG. It is also related to the division of the terminal resource area. As described above with reference to FIG. 8 in all cells, resources are allocated, and users are allocated a service from a resource quota allocated to their region. In this case, a subcarrier having a good channel state is first allocated to the allocated resource by using a frequency hopping technique and channel information fed back through an uplink.

Next, when it is determined that the distribution of users located in the cell boundary region is not uniform through the step S210 described above with reference to FIG. 8, a method of performing effective resource allocation will be described in detail with reference to FIGS. 10A and 10B. do.

10A and 10B are diagrams illustrating resource allocation when a distribution of users is not uniform in a cell boundary area according to an embodiment of the present invention.

As described above, the resource allocation method proposed through the embodiment of the present invention recycles resources used for transmission and reception between the base station and the repeater as resources for transmission and reception between the base station and the repeater in order to increase the efficiency of the resource. At this time, if the distribution of users in the cell boundary region is uniform, no problem occurs. If the distribution is uneven, resource waste may be severe.

10A and 10B, according to an embodiment of the present invention, in order to allocate resources to users when users are unevenly distributed in cell boundary regions, the amount of resources required by all users is the same and each cell is the same. It is assumed that the resource requirements g ₁ , g ₂ , and g ₃ are always the same.

When users are unevenly distributed in the cell boundary region as in the embodiment of the present invention, the minimum amount of resources required to provide services to users is as follows. The minimum resource requirement required in each region may be referred to as R (here, the minimum resource requirement may be defined as R ₁ , R ₂ , and R ₃ since the cell boundary region is divided into three parts according to an embodiment of the present invention). In this case, in order for the repeater to serve the user, the repeater must receive information on the minimum resource requirement from the base station.

In addition, since the frequency of the corresponding resource needs to be converted, 2R _Max resources, which are twice as large as the resource demand among the three regions, are needed. The reason for doubling the area where the resource demand is greatest is that the resources allocated by the base station to the repeater and the resources transmitted from the relay to the base station are the two values because the base station must support both values. . However, it is not necessarily limited in this way.

And to service all three regions, resources corresponding to “R ₁ + R ₂ + R ₃ ” are needed. As a result, the minimum resource requirement for smooth service corresponds to the maximum of the two values described above, that is, 2R _Max and R ₁ + R ₂ + R ₃ . In this way, the resource allocation method that can satisfy the minimum resource requirements can be divided into the following two cases.

First, as shown in FIG. 10A, consider a case where a requirement of a specific region is smaller than the sum of resource requirements of two other regions, that is, “R ₁ <R ₂ + R ₃ ”. In this case, the method of allocating resources is based on the region with the lowest resource demand among the three regions. Here, the reference is a criterion for calculating an optimized bandwidth, that is, a reference for the size of resources allocated to one area when the base station-relay resource area is divided into three areas. do.

As shown in FIG. 10A, 11 users are located in a cell denoted by reference numeral 301, 6 users are located in a cell denoted by reference numeral 311, and 7 users are located unevenly distributed in a cell denoted by reference numeral 321. have. Therefore, in the second region, that is, the cell indicated by reference numeral 311, 6, which is a resource requirement request for resource allocation, is the minimum requirement, and this resource amount is commonly allocated to the three regions.

If the minimum requirement is allocated to each of six areas in common, the resource allocation for the first area (cell area 301) continues. Since there are 11 users in the first region, the information of the first region users is transmitted from the base station to the repeater using g ₂ and g ₃ . Then, g ₁ is used to transmit to the users. Since g ₁ is 6, the insufficient amount of resources (11-6 = 5) is additionally allocated by the base station (g ₅ = 5) to serve the users.

In the third region (cell area 321), the resources are allocated as described above, and the insufficient amount of resources is also allocated to the resource by the base station (g ₄ = 3) to serve the user. In this way, the resources allocated to the cell boundary area as a whole are “g ₁ (6) + g ₂ (6) + g ₃ (6) + g ₄ (3) + g ₅ (5) = 24”. do. In this case, since 2R _Max is 22 and R ₁ + R ₂ + R ₃ is 24, the larger of 24 is the minimum resource requirement.

Next, an embodiment in which the resource requirement of a specific region is larger than the sum of the resource requirements of other regions, that is, R ₁ > R ₂ + R ₃ will be described with reference to FIG. 10B.

As shown in FIG. 10B, the amount of resources commonly allocated to the three regions becomes the amount of resources of the region that requires the least amount among the three regions. This is the same as described above with reference to FIG. 10A, and in the embodiment of the present invention, this is the amount of resources in the region indicated by 311. In this case, since the sum of the resource demands of the other two regions is smaller than that of the region that requires the most resources, the sum of the resources of these two regions does not provide all the information desired in the first region.

Therefore, an additional resource allocation (g ₄ = 3) for transmitting from the base station to the repeater is required, and also a resource (g ₅ = 7) for serving the users of this area must be additionally allocated. As a result, the resource allocation required to serve the cell boundary area is “g ₁ + g ₂ + g ₃ + g ₄ + g ₅ = 22”. This satisfies the minimum requirement of 2R _Max = 22.

Next, as shown in FIGS. 10A and 10B, when a base station according to an embodiment of the present invention directly provides a service to a cell boundary region, intercell interference may be avoided by guaranteeing orthogonality of intercell resources in the cell boundary region. The method will be described with reference to FIG. 11.

11 is an exemplary diagram of a method for avoiding inter-cell interference when a base station directly provides a service to a cell boundary area according to an embodiment of the present invention.

When a base station directly provides a service to users in a cell boundary area, it is difficult to provide a service using a beamforming technique. Thus, providing grouped resources for cell border area users results in interference with users in adjacent cell border areas. To solve this problem, as shown in FIG. 9, resources allocated for users in a cell are grouped into three parts. When the base station additionally allocates resources to users in the cell boundary region, as shown in FIG. 11, if the service is performed using a group of resources orthogonal to each other in the boundary region of each cell, resource orthogonality is guaranteed.

Next, a method of allocating resources when a change occurs in a position of a repeater disposed in a cell boundary region will be described with reference to FIG. 12.

12 is a diagram illustrating a resource allocation method when there is a change in repeater arrangement of a cell boundary area according to an embodiment of the present invention.

While operating a mobile communication system, a repeater may be inevitably added or removed depending on geographical factors or the number of users. In this case, if the resource area is allocated and managed separately for each repeater, the addition / removal of the repeater may not be performed smoothly due to the interference problem with the resources used in the repeater of the adjacent cell and the change of the resource grouping.

Accordingly, in order to solve the above problems, in order to propose a method of adding or removing a repeater without changing the existing frequency allocation method or the interference environment between adjacent repeaters and cells, in the embodiment of the present invention, a region is used. The concept was introduced. In other words, the circle representing the range transmitted by the existing repeater is changed into a sub-region that is a local concept.

As shown in FIG. 12, if the base station allocates resources as described in FIGS. 10A and 10B after dividing the cell boundary region into three regions without depending on the number of repeaters in the cell boundary region, Therefore, the service can be continued without changing the operation method of the mobile communication system.

The following is an existing OFDM based mobile communication system for sequentially allocating resources to a terminal by FIFO (First Input First Output) method without a repeater, and OFDM based mobile according to a relay arrangement and resource allocation method according to an embodiment of the present invention. In the communication system, a reception performance of a terminal will be described with reference to FIG. 13.

13 is an exemplary view comparing the terminal reception performance of the OFDM-based mobile communication system and the terminal reception performance of the conventional OFDM-based mobile communication system according to an embodiment of the present invention.

As described in FIG. 6, there are a total of 19 base stations divided into 3 sectors for each base station (3 Tier scenario), each sector has 300 frequency resources and a total distribution of 30 km / s with a uniform distribution of 3000 users. Suppose you are moving at a speed of h. FIG. 13 illustrates a distribution of a signal to interference plus noise ratio (SINR) of a user in order to compare the performance of a terminal according to a general resource allocation method with that of a terminal according to an embodiment of the present invention.

As shown in FIG. 13, when the resource is allocated according to the general scheme, 50% or more users have a SINR of 5dB or less. However, when resources are allocated according to an embodiment of the present invention, 90% or more users have 11dB or more. SINR may be provided. That is, since the Y axis of the graph is a cumulative distribution function, when the area of the Y axis is regarded as the total system capacity, the resource is allocated according to a general method and according to an embodiment of the present invention. The difference in one case is obvious. That is, it can be seen that a much higher system capacity can be secured when allocating resources according to an embodiment of the present invention.

In addition, the fact that most users receive a high reception quality of 11 dB or more means that a large number of users in the cell boundary area receive high-quality signals from the repeater without interference. Therefore, as a whole, it can be seen that the targets, such as reducing inter-cell interference and securing a wide service area, have been successfully met.

In addition, the situation shown in FIG. 6 is a situation in which the base station uses an intersector omnidirectional antenna instead of using a beamforming antenna, which is affected by the interference caused by the use of the intersector omnidirectional antenna as described in FIG. It is an increasing situation. This is a situation in which the influence of interference may be most effective in an embodiment of the present invention. Nevertheless, ensuring a high reception quality of 11 dB or more means that higher reception quality can be ensured by using a beamforming antenna or introducing a frequency hopping scheme as needed.

Here, a program for realizing a function corresponding to the configuration of the above-described embodiment of the present invention or a recording medium on which the program is recorded is also included in the scope of the present invention.

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

According to the embodiment described above, cell coverage can be extended by using a repeater, and interference effects between adjacent cells can be eliminated by allocating resources orthogonal to each repeater in a cell boundary region.

In addition, in the operation of the repeater to maximize the resource efficiency by recycling the resources for the transmission and reception between the base station and the repeater and users to increase the efficiency of resource use.

In addition, by allocating resources between users in the cell and users in the cell boundary region to ensure orthogonality with each other, the strength of system-wide interference is greatly reduced.

In addition, even if the strength of interference increases slightly depending on the system operation method, the frequency band used in the cell boundary region can be used to serve the users near the base station by reducing the signal strength, thereby increasing the frequency reuse rate.

Claims (12)

In a method for allocating resources to a terminal formed in a cell formed by a base station in a mobile communication system, the repeaters and the terminal connected to the base station or the repeaters, The repeater is located in a cell boundary region of the base station, where the cell boundary region is divided into at least one region, and the method for allocating resources to the repeater or the terminal, (a) a cell boundary region resource to provide all resources allocated to the mobile communication system to a cell boundary region of the base station and the inside of the cell, where the inside of the cell excludes a cell boundary region adjacent to another cell in one cell; Dividing into an in-cell area resource to provide to the remaining area; (b) providing resources to be provided to the cell boundary region to the repeater located in the cell boundary region, wherein the resources provided are allocated to terminals distributed in the cell boundary region; And (c) providing resources to be provided inside the cell to the terminal located inside the cell; Resource allocation method comprising a. The method of claim 1, In step (a), A subcarrier sequencing step of randomly selecting a cell boundary region resource or a resource for allocating into a cell with respect to all resources allocated to the base station; And A frequency resource grouping step of grouping and classifying a cell boundary region resource and an internal cell resource using the randomly selected resource Resource allocation method comprising a. The method of claim 2, In step (b), (i) receiving a signal from a terminal located in the cell boundary region, where the terminal is provided with resources in the cell boundary region, and whether the number of received signals is within a predetermined predetermined uniformity number range; Determining; (ii) calculating a bandwidth for the base station-relay resource region when the number of signals received from the terminal located in the cell boundary region is larger or smaller than the range of the uniformity number; (iii) performing beamforming on the resources so that the repeater can allocate resources to the terminal based on the calculated bandwidth; And (iv) allocating the beamformed resource to the repeater Resource allocation method comprising a. The method of claim 3, Step (ii), (ii-1) comparing the sizes of the plurality of resource requirements requested from the plurality of terminals located in the cell boundary region divided into the one or more regions; (ii-2) setting a resource requirement of the specific area as a criterion of the bandwidth calculation if the resource requirement of the specific area among the plurality of resource requirements is smaller than the sum of the resource requirements of the remaining areas; And (ii-3) comparing a resource multiplied by a predetermined number with a resource requirement of an area that has requested the largest resource among the plurality of resource requirements, and setting a large number as a minimum resource requirement by comparing a resource requirement set based on the bandwidth calculation; step Including, And in step (iv), allocates resources to the divided cell boundary regions based on the minimum resource requirements. The method of claim 4, wherein In step (ii-2), if the resource requirement of the specific region is greater than the sum of the resource requirements of the remaining regions, Setting a resource requirement of the specific region as a reference of the bandwidth calculation; And Setting a large number as a minimum resource requirement by comparing a resource multiplied by a predetermined value to a resource requirement of an area that has requested the largest resource among the plurality of resource requirements and a resource requirement set as a basis of the bandwidth calculation; Resource allocation method comprising a. The method of claim 5, The resource allocation method of allocating the resource requirement of the area which requested the smallest resource among the size of the plurality of resource requirements to the plurality of cell boundary areas in common. The method of claim 1, In step (c), Allocating the divided resources to the repeater or the terminal, and then determining whether there are any remaining resources; Allocating resources to a terminal in a cell center of the base station when resources remain without being allocated to the relay or the terminal; And Allocating a resource to a terminal in the cell center, where the cell center means an area within a predetermined distance set from the base station, and allocating the remaining resource to the terminal in the cell. Resource allocation method comprising a. The method of claim 7, wherein If there is no remaining resource, the step of preferentially allocating resources to the terminal in the cell Resource allocation method comprising a. The method of claim 1, Determining whether there is a resource recovered from the repeater or if there is an additional resource allocation request from the repeater; And If there is a resource to be recovered or an additional resource allocation request, performing step (b) Resource allocation method comprising a. The method of claim 9, The cell boundary region is an inner radius, where the inner radius means a value subtracted by a repeater radius from a cell radius indicating a distance to a point at which a signal transmitted from the base station becomes equal to a threshold of the base station. Where outer radius is the radius of the cell plus the radius of the repeater. In the method for allocating resources to the repeaters and the base station or a terminal connected to the repeaters when at least one repeater is disposed in a base station in a mobile communication system, The repeater is located in a cell boundary region of the base station, the method for allocating resources to the repeater or the terminal, (a) dividing a cell boundary area divided into at least one area into a predetermined number of sub areas; (b) resources to provide the entire resource allocated to the mobile communication system to a cell boundary area divided into the predetermined number of sub-areas and the inside of the cell, where the inside of the cell is a cell adjacent to another cell; Dividing into regions to be provided except for the boundary region; And (c) providing a resource divided into resources to be provided to the cell boundary region to the repeater located in the cell boundary region, and providing a resource divided into resources to be provided inside the cell to the terminal located inside the cell; step Resource allocation method comprising a. The method of claim 11, In step (c), Grouping terminals located in the cell boundary region by a predetermined number; And Allocating resources allocated to a terminal located in the cell boundary region of the portion of the resources to be orthogonal to each other in the cell boundary region Resource allocation method comprising a.

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