KR101581045B1 - FEMTO BASE STATION AND Dynamic Bandwidth Coordination METHOD - Google Patents

Abstract

The present disclosure provides a method for transmitting a synchronization signal and a system information signal at a femto base station. The transmission method receives a synchronization signal and a system information signal of a macro base station in a frame. Wherein the frame structure includes one or more subframes, and the subframe includes one or more slots. Then, based on the synchronization signal and the system information signal, a position of a synchronization signal and a system information signal of the femto base station is determined in the frame. Here, the positions of the synchronization signal and the system information signal of the femto base station are the same as the positions of the synchronization signal and the system information signal of the macro base station and the frequency axis, but are determined so as to be spaced apart in the slot unit or the subframe unit. Then, the synchronization signal and the system information signal of the femto base station are transmitted at the determined position.

Description

[0002] FEMTO BASE STATION AND DYNAMIC BANDWIDTH COORDINATION METHOD [

The present invention relates to a mobile communication system, and more particularly, to a femto base station in a mobile communication system.

Second generation mobile communication refers to digital transmission and reception of voice, including CDMA and GSM. In addition to the GSM, GPRS has been proposed, which is a technique for providing a packet switched data service based on the GSM system.

Third Generation Partnership Project (3GPP) has developed a mobile communication system (IMT-2000) technology and developed a radio access technology (Radio Access) Technology: RAT). As such, the IMT-2000 technology and the radio access technology (RAT), for example, WCDMA, are collectively referred to as Universal Mobile Telecommunication System (UMTS) in Europe. UTRAN is an abbreviation of UMTS Terrestrial Radio Access Network.

Meanwhile, the third generation mobile communication has evolved into a fourth generation mobile communication.

The 4G mobile communication technology has been proposed as a Long-Term Evolution Network (LTE) technology standardized by 3GPP and IEEE 802.16 technology standardized by IEEE. In the LTE, the term Evolved-UTRAN (E-UTRAN) is used.

In the 4th generation mobile communication technology, Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) has been introduced. OFDM uses a plurality of orthogonal subcarriers. OFDM utilizes the orthogonality property between IFFT (inverse fast Fourier transform) and FFT (fast Fourier transform). The transmitter performs IFFT on the data and transmits it. The receiver performs an FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

Meanwhile, attempts have been made to increase the cell capacity to support high-capacity services and interactive services such as multimedia contents and streaming in the third or fourth generation mobile communication systems.

There has been an approach to increase the cell capacity by using higher frequency bands and decreasing the cell radius. When a cell having a small cell radius, such as a pico cell, is applied, a higher frequency band than that used in the conventional cellular system can be used, and more information can be transmitted. However, there is a disadvantage that it requires a lot of base stations in the same area, which is costly.

Recently, a femto base station (femtocell) has been proposed as an approach to increase the cell capacity using such a small cell.

The femto base station means to provide a small wireless environment by installing a base station using an ultra small size and low power in a house / office. It is expected that the femto base station can improve the quality of service by improving the indoor coverage area and capacity, and it is expected that the femto base station can completely settle the next generation mobile communication system by providing data service.

The femto base station is being standardized as a Home eNodeB in the 3GPP WCDMA and LTE groups, and research on femtocell is underway in 3GPP2.

Various schemes for implementing such a femto base station in an existing mobile communication network have been proposed as shown in FIG.

1 (a) is a diagram illustrating a network structure of a femto base station based on the prior art.

As shown in FIG. 1 (a), a macro base station (M-BS) serving as a wide area and a femto-BS (f-BS) ).

The femto base station (f-BS) is connected to a femto base station control station (FNC) through the Internet and is controlled by the femto base station (f-BS).

The terminal measures a signal of neighboring cells and transmits the signal to its femto base station. The femto base station recognizes and manages the neighboring cell through the neighboring cell. The femto base stations exchange information through a direct link or an indirect link through the FNC. Information is exchanged between the femto base station and the macro base station through an FNC and an RNC (Radio Network Controller) or a Mobility Management Entity (MME) for controlling the femto base station in a mobile communication network.

FIG. 1 (b) is another example of a network structure based on a femto base station according to the related art.

As shown in FIG. 1 (b), the femto BSs (f-BSs) exchange information through a direct link or an MME, unlike FIG. Also, the macro base station (M-BS) and the femto base station (f-BS) exchange information through the MME.

Meanwhile, in the 3GPP LTE standard, a FDD system of a Type 1 frame structure and a TDD system of a Type 2 frame structure are both proposed, and researches on an efficient bandwidth allocation problem suited to the structure of each system are underway.

When there are a plurality of femto base stations in a macro cell, it is systematically unreasonable for the central controller, e.g., the FNC / MME, to adjust the bandwidths of the entire femto base stations, It is natural that dynamic adjustments should be possible without. Although there are studies on the distributed dynamic bandwidth control technology, there are still disadvantages.

It is an object of the present invention to enable bandwidth control dynamically between femto base stations. In particular, it is an object of the present invention to minimize the interference between the femto base stations and the macro base station while maximizing the utilization efficiency of the bandwidth given to the macro base station and the femto base station.

In addition, the present invention is capable of adjusting the dispersion bandwidth between the femto base stations in a dense region of the femto base stations.

In order to achieve the above object, the present invention provides a method for transmitting a synchronization signal and a system information signal in a femto base station.

The transmission method receives a synchronization signal and a system information signal of a macro base station in a frame. Wherein the frame structure includes one or more subframes, and the subframe includes one or more slots. Then, based on the synchronization signal and the system information signal, a position of a synchronization signal and a system information signal of the femto base station is determined in the frame. Here, the positions of the synchronization signal and the system information signal of the femto base station are the same as the positions of the synchronization signal and the system information signal of the macro base station and the frequency axis, but are determined so as to be spaced apart in the slot unit or the subframe unit on the time axis. Then, the synchronization signal and the system information signal of the femto base station are transmitted at the determined position.

In the determining step, the positions of the synchronization signal and the system information signal of the femto base station may be determined to be a specific slot or a specific subframe according to an index in a group allocated to the femto base station. The determining step is performed at a predetermined frame period.

The group includes one or more adjacent femto base stations that interfere with the femto base station.

The method includes receiving a synchronization signal and a system information signal from an adjacent femto base station; And performing at least one of shifting, reducing, expanding, and time-sharing the frequency bandwidth of the femto base station according to the synchronization signal and the system information signal from the adjacent femto base station.

The femto base station has a cluster index and a frequency band is allocated according to the cluster index.

The cluster may include an adjacent femto base station causing a large interference with the femto base station.

According to another aspect of the present invention, there is provided a method of selecting a macro base station and a femto base station in a terminal.

According to the connection method, the terminal receives a synchronization signal and a system information signal of a macro base station in a radio frame. The synchronous signal and the system information signal of the femto base station are received at a position that is the same as the position and the frequency axis of the synchronous signal and the system information signal of the macro base station but spaced apart in the slot unit or subframe unit within the frame on the time axis do. Then, one of the macro base station and the femto base station is selected and connected based on the synchronization signals and the system information signals.

In order to achieve the above object, the present invention provides a femto base station. The femto base station includes a transmitting and receiving unit for receiving a synchronization signal and a system information signal of a macro base station in a frame. Wherein the frame structure includes one or more subframes, and the subframe includes one or more slots. Wherein the femto base station determines a position of a femto base station synchronization signal and a system information signal in the frame based on the synchronization signal and the system information signal and outputs a synchronization signal and a system information signal of the femto base station at the determined position And a processor for transmitting the data through the transceiver. Here, the positions of the synchronization signal and the system information signal of the femto base station are the same as the positions of the synchronization signal and the system information signal of the macro base station and the frequency axis, but are determined to be spaced in the time axis by the slot unit or the subframe unit.

According to the embodiment of the present invention, the bandwidth adjustment can be performed in a distributed manner while minimizing the collision according to the change of the traffic amount of the macro base station and the femto base station. Also, the bandwidth allocation efficiency of the macro base station and the femto base station is increased, the interference between the femto base stations is minimized, and the interference between the femto base station and the macro base station is minimized.

The present invention is applied to a femto base station. However, the present invention is not limited to this and can be applied to all communication systems and methods to which the technical idea of the present invention can be applied.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "comprising" or the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

When an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may be present in between. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings. The spirit of the present invention should be construed as extending to all modifications, equivalents, and alternatives in addition to the appended drawings.

Hereinafter, the term 'terminal' is used, but the terminal may be referred to as a UE (User Equipment), ME (Mobile Equipment), or MS (Mobile Station). The UE may be a portable device having a communication function such as a cellular phone, a PDA, a smart phone, a notebook, or the like, or a non-portable device such as a PC or a vehicle-mounted device.

Also, the term femto base station is used below, but the femto base station may be called a home node B.

Hereinafter, prior to description with reference to the drawings, the concept proposed in the present specification will be briefly described as follows.

This specification provides a method for adjusting the distributed dynamic bandwidth. In the 3GPP LTE environment, when the femto base station network is configured, the dynamic dynamic bandwidth adjustment method dynamically adjusts the bandwidth of the femto base stations according to the increase and decrease of the traffic using the time shift center frequency. The dynamic adjustment of the bandwidth is based on a bandwidth shift (BE), a bandwidth shift (Shift), a time division (TDB), a bandwidth reduction (BR) And the bandwidth is determined by each femto BS in a distributed manner.

The present specification also provides a method for dynamically arranging / changing the order of bandwidth used by each base station. The sorting / changing method includes an Ascending Bandwidth Coordination Algorithm and a bandwidth ordering algorithm for minimizing interference between a macro cell and a femto base station when a small number of femto BSs are distributed in one macro cell (Bandwidth Swapping Algorithm).

2 is an exemplary illustration of a system and bandwidth for illustrating embodiments of the present invention.

2, a terminal 100, a plurality of femto base stations 201, 202 and 203 (hereinafter referred to as 200), a macro base station 300 and a central controller (e.g., a gateway, FNC, .

The terminal 100, the plurality of femto base stations 200, the macro base station 300 and the like follow the 3GPP LTE system.

The femto base station 200 is located in a cell region of the macro base station 300 and the femto base station 200 uses a small amount of resources compared to the macro base station 300 to transmit a small data rate to a small number of users. Service.

However, interference occurs between the femto base stations 200 and between the femto base station 200 and the macro base station 300.

In FIG. 2, a radio resource is represented by an LTE Type 1 frame structure.

In the LTE Type 1 frame structure, the macro base station 300 transmits synchronization information of PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal) through six resource blocks (RB) Signal and a system information signal of a PBCH (Physical Broadcast Channel).

However, the concept of the present invention is not limited to the LTE Type 1 frame structure, but can be applied to a frame structure conforming to IEEE 802.16m. In the IEEE 802.16m, the PSS and the SSS are respectively referred to as a PA-Preamble (SA) and an SA-Preamble (Secondary Advanced-Preamble).

However, the femto base stations 200 are located at the center frequency for the normal data on the frequency axis through the six RBs of the macro base station 300 And transmits a synchronization signal such as its own PSS and SSS and a system information signal such as the PBCH.

therefore. The femto base stations 200 and the macro base station 300 interfere with each other with a synchronization information signal and a system information signal.

In order to solve such an interference, the present invention proposes a dynamic bandwidth adjustment for the femto base station and the macro base station.

The dynamic bandwidth adjustment will be briefly described as follows.

The femto base station and the macro base station time shift the center frequency for the synchronization signal and the signal of the system information. Using the time shift center frequency, the macro base station 300 and the femto base stations 200 can transmit a synchronization information signal and a system information signal to six resource blocks, Can be transmitted without collision.

At this time, the bandwidth re-adjustment between the femto base stations may be performed with a predetermined fixed frame period.

FIG. 3A shows a concept in which each femto base station moves center frequencies in units of slots according to the first embodiment of the present invention. FIG. 3B shows the concept shown in FIG. 2 in more detail.

3A and 3B, according to the first embodiment of the present invention, in order to distinguish between the synchronization information signal and the system information signal of the femto base station and the macro base station, a time shift center frequency ) In units of slots.

The horizontal axis of the illustrated frame structure corresponds to the time axis, and the vertical axis corresponds to the frequency axis. The illustrated frame structure follows the LTE Type 1 frame structure. The LTE Type 1 frame includes 10 subframes, each subframe having a length of 1 ms and including two slots. Each slot has a length of 0.5 ms and includes 7 OFDM symbols.

The LTE Type 1 frame structure includes a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS) synchronization information signal and a PBCH (Physical Broadcast Channel) through six resource blocks (RBs) ) System information signal. At this time, the PSS and the SSS are transmitted in five subframe periods, and the PBCH is transmitted in every frame period.

As shown in FIG. 3, each femto base station moves its center frequency on a time axis in a slot unit. Therefore, the PSS, the SSS, and the PBCH are moved on a slot basis for each femto BS. At this time, the femto base stations are grouped, and the indexes within each group are shown.

As described above, when the macro base station 300 or the femto base station 200 receives the PSS, the SSS, and the PBCH of the macro base station or the femto base stations belonging to one group, the macro base station 300 or the femto base station 200 can receive the packets without collision.

When the center frequency is shifted in the LTE Type 1 frame structure in units of slots, a maximum of eight femto BSs can form one group as shown in FIG. 3A and FIG. 3B, and the number of femto BSs forming a group is femto BS Femto base stations.

3A and 3B, since the center frequencies of six RBs are used in units of slots according to the LTE Type 1 frame structure, the macro base station 300 determines whether the femto BSs 200 have received the PSS, SSS, It knows how to transmit the PBCH information to the second symbol. Therefore, symbols that are not used because the femto base stations 200 do not send the PSS, SSS, and PBCH information can be further utilized by the macro base station 300. The macro base station 300 may use the symbols for its own terminals to use the bandwidth more densely and efficiently.

FIG. 4 is a diagram illustrating an example of grouping femto base stations interfering with each other and moving a center frequency in units of slots according to the first embodiment shown in FIG.

4, the vertical axis represents time and the horizontal axis represents frequency.

As can be seen from FIG. 4, the femto base stations that interfere with each other are grouped, and the center frequency of the femto base stations is moved in units of slots to minimize the interference. In this case, the slots used by the femto BSs are allocated such that the distance between the slots is maximized so that the interference between the femto BSs is minimized. In addition, each femto base station is assigned a group index in said group to from 1 N _Group (= 7).

That is, the femto base stations are grouped, and the center frequency of the femto base stations is moved in units of slots. At this time, as shown in FIG. 3B, a group is formed with a maximum number of femto base stations of 8 or less. When a femto base station in a group is assigned a group index, the femto base stations determine the number of slot movements from the macro base station according to the index. Therefore, each femto base station can transmit a synchronization information signal and a system information signal without collision with the macro base station 300 or another femto base station.

FIG. 5A illustrates a concept in which each femto BS moves a center frequency in units of subframes according to a second embodiment of the present invention. Figure 5b shows the concept shown in Figure 5a in more detail.

5A and 5B, according to the second embodiment of the present invention, in order to distinguish between the synchronization information signal and the system information signal of the femto base station and the macro base station, . The illustrated frame structure follows the LTE Type 1 frame structure.

As shown in FIGS. 5A and 5B, femto base stations interfering with each other are grouped, and femto base stations in each group move PSS, SSS, and PBCH on a time axis in units of subframes. Then, the MSs 100 receiving the service from the macro base station 300 or the femto BS 200 can receive the PSS, SSS, and PBCH of the macro base station or the femto BSs belonging to one group without collision.

As described above, when the center frequency is shifted in units of subframes in the LTE Type 1 frame, a maximum of four femto BSs can form one group as shown in FIGS. 5A and 5B. At this time, the number of femto base stations forming a group is determined according to interference between the femto base station and the femto base station.

As described above, since the femto base stations use the center frequency by moving in the subframe unit, the macro base station knows how many symbols the respective femto base stations transmit PSS, SSS and PBCH information. Therefore, if there are symbols that are not used because the femto BSs do not send PSS, SSS, and PBCH information, the macro base station 300 can further utilize the symbols. By using these symbols, the macro base station can further serve the user of the macro base station and use the bandwidth more densely.

FIG. 6 is a diagram illustrating an example of grouping femto base stations interfering with each other and moving a center frequency in units of subframes according to the second embodiment shown in FIG.

At this time, the subframes used by the femto BSs are allocated such that the distance between the subframes is maximized such that the interference between them is minimized. In addition, each femto base station is assigned a group index in said group to from 1 N _Group (= 4).

That is, the femto base stations are grouped, and the center frequency of the femto base stations is moved in units of subframes. At this time, as shown in FIG. 5B, groups of four or less are formed as the maximum number of femto base stations. When a femto base station in a group is assigned a group index, the number of subframe moves from the macro base station is determined according to the index. Therefore, each femto base station can transmit a synchronization information signal and a system information signal without collision with the macro base station 300 or another femto base station.

7 is an exemplary view showing a relationship between a cluster and a group according to the third embodiment of the present invention.

In FIG. 7, it is assumed that each femto BS moves the center frequency according to the first embodiment.

As described above, the femto base stations interfering with each other are grouped into one group, and the femto base stations in the group use their center frequency by moving them in the slot unit.

On the other hand, femto base stations with large interference form one cluster again. At this time, the number of femto base stations forming the cluster is smaller than the number of femto base stations forming the group. Here, groups and clusters have independent relationships, not dependency relations. That is, a cluster can be formed with a femto base station of another group instead of a cluster within a group.

In the example of FIG. 7, one group is composed of seven femto base stations, and one cluster is composed of three femto base stations.

One cluster uses the entire femto base station allocation bandwidth of FIG. 2, and the femto base stations belonging to one cluster divide and use the entire femto base station bandwidth according to a required QoS in its own cell. The femto base stations are allocated a position on a time axis, which is a position of a slot through which the center frequency is to be used, through a group index, and are allocated frequency bandwidths through a cluster index.

FIG. 8 is an exemplary view showing an embodiment of the third embodiment shown in FIG. 7, and FIG. 9 is an exemplary view showing another embodiment of the third embodiment shown in FIG.

8 and 9, the femto base stations 200 having the group indices 1, 3 and 4 constitute one cluster, and each femto base station 200 moves the center frequency for the synchronization signal and the system information signal in units of slots Respectively.

Therefore, even in the femto base station existing in the same group, the interference is reduced due to the movement in the slot unit, and the service can be performed without collision.

As shown in FIG. 8, when the traffic of the femto BS 200 is small, the initial bandwidth allocation of the femto BS 200 is allocated with an empty bandwidth. If there is no increase in the amount of traffic thereafter, Bandwidth expansion is possible.

9, when the traffic of the femto base station 200 is large, the initial bandwidth allocation of the femto base station 200 is allocated without an empty bandwidth, and a service with a higher data rate can be provided none.

FIG. 10 is an exemplary view illustrating an exemplary situation assumed to explain a fourth embodiment of the present invention, FIG. 11 is a conceptual diagram illustrating a band extension method according to a fourth exemplary embodiment of the present invention, 12 is an exemplary diagram showing the concept of FIG. 11 in terms of a frequency axis and a time axis.

10 shows a case where an arbitrary terminal accesses a femto base station. An arbitrary terminal receives a pilot signal from femto base stations and predicts channel information through the received pilot signal. The terminal selects a femto base station having the best channel condition through prediction of the channel information, and receives a service from the femto base station.

At this time, if the selected femto base station already has a lot of traffic and the resources are insufficient (the femto base station transmitting and receiving such a large amount of traffic is called a hot spot area), the femto base station sets the bandwidth Expand.

Referring to FIG. 11, when a surplus bandwidth is sufficient in a cluster, a femto base station transmitting and receiving a large amount of traffic performs a bandwidth expansion (BE) as shown in the figure.

That is, when the femto base station having the cluster index C is in the hot spot area, the bandwidth extension is performed with the surplus bandwidth of the adjacent femto base station (cluster index B).

FIG. 12 shows the example of FIG. 11 along the frequency axis and the time axis. It shows that the bandwidth remaining in the adjacent femto base station B is extended to its own bandwidth to guarantee QoS of users.

FIG. 13 is a conceptual diagram illustrating a band extending method according to a fourth embodiment of the present invention in accordance with other circumstances, and FIG. 14 is an exemplary diagram illustrating the concept of FIG. 13 along a frequency axis and a time axis.

13 shows a case where there is an excess bandwidth in the cluster but collides with the bandwidth of the adjacent femto base station B.

In order to prevent such collision, when the femto base station C performs the bandwidth extension, the neighbor femto base station B pushes its bandwidth on the frequency axis.

That is, the femto base station B determines whether or not the bandwidth of the femto base station C is extended based on the center frequency (center frequency), and thus the bandwidth of the femto base station B is shifted to the remaining bandwidth of the adjacent femto base station A. do.

FIG. 14 shows the example of FIG. 13 along the frequency axis and time axis. As can be seen from FIG. 14, the adjacent femto base station B performs a bandwidth movement to another adjacent femto base station A having an excess bandwidth And the remaining bandwidth is extended to the bandwidth of the femto base station C in which the new user is generated.

FIG. 15 is a conceptual diagram illustrating another embodiment of the band extending method according to the fourth embodiment of the present invention, and FIG. 16 is an exemplary view showing the concept of FIG. 15 along the frequency axis and the time axis.

FIG. 15 shows a case where there is not a sufficient surplus bandwidth in the cluster.

In this case, bandwidth time division is performed as shown in FIG.

That is, since there is no surplus bandwidth, the femto base station (cluster index C) in which a new user has occurred uses the bandwidth and the femto base station (cluster index B) using the adjacent bandwidth by time division (Time Division Bandwidth: TDB) . Here, the determination of the femto base station using the TDB is determined according to the degree of QoS guarantee of each cell. If the QoS of the femto base station A and the femto base station B is better assured, (C) performs the BE, and the femto base station (A) and the femto base station (B) can perform the TDB.

FIG. 16 shows an example of bandwidth time division on the frequency axis and time axis in the example of FIG. 15, in which the adjacent femto base station B and the femto base station C in which a new user has occurred can not perform bandwidth extension or movement, , And thus all the femto base stations guarantee QoS of users.

17 is an exemplary diagram illustrating a frequency band and a time axis according to yet another embodiment of the method of extending a band according to the fourth embodiment of the present invention.

17, when the number of the terminals 100 connected to the macro base station 300 increases, when attempting to expand the bandwidth of the macro base station 300, the femto base stations 200, Resets the bandwidth.

When the number of users served by the macro base station 300 increases or decreases, the macro base station 300 dynamically increases or decreases the bandwidth.

As the macro base station 300 dynamically expands or narrows the bandwidth, each femto base station 200 in the cluster can listen to the center frequency from the macro base station 300, .

The femto base stations 200 can calculate a usable bandwidth based on the bandwidths of other femto base stations in the cluster using the center frequency, the synchronization signal, and the system information signal from the macro base station 300 have.

Then, the femto base stations 200 perform bandwidth reset based on the calculated bandwidth, such as the bandwidth extension, the movement of the center frequency, and the time division of the bandwidth.

The bandwidth resetting may be performed at a predetermined frame unit cycle as described above.

18 is a diagram illustrating a method of aligning a bandwidth of a femto base station on a frequency axis according to a fifth embodiment of the present invention.

18, when a plurality of femto base stations are distributed in a cell region of one macro base station, the macro base station and the femto base station organize the bandwidths in ascending order to minimize interference between the macro base stations and the femto base stations An Ascending Bandwidth Coordination Algorithm is shown.

18 (a) is an example of a bandwidth when the amount of traffic of the femto base stations is small.

In this way, according to the fifth embodiment of the present invention, the femto base stations are arranged in ascending order according to the bandwidth in the direction of the bandwidth sufficiently short of the bandwidth of the macro base station on the frequency axis. That is, the bandwidth of the femto base station B with the highest traffic is aligned on the frequency axis to the furthest away from the macro base station.

Meanwhile, FIG. 18 (b) is an example of the bandwidth when the amount of traffic of the femto base stations is large.

In this manner, according to the fifth embodiment of the present invention, when the amount of traffic is large, the femto base stations sort the bandwidths in ascending order of traffic size in a direction closely located to the macro base station bandwidth. That is, the bandwidth of the femto base station A with the smallest traffic is arranged to be densely located on the frequency axis of the macro base station.

FIG. 19 is an exemplary view of the fifth embodiment shown in FIG. 18; FIG.

Referring to FIG. 19, when a plurality of femto base stations are distributed in a cell region of a macro base station, the femto base station B determines the position of the bandwidth on the frequency axis as the traffic of the specific femto base station B increases Are arranged in ascending order in a direction sufficiently lower than the bandwidth of the macro base station.

For example, the femto base stations A, C, and B are rearranged in the order of femto base stations A, C, and B while the bandwidth of the femto base stations A, B, do.

Each femto base station can determine the bandwidth position of its neighboring femto base station by knowing the location of the bandwidth used by the adjacent femto base station through the system information of the adjacent femto base station.

All of the above-described methods can be performed dispersively in each femto base station since each femto base station can listen to the center frequencies of the macro base station and the surrounding femto base stations.

Such a distributed dynamic bandwidth adjustment method may be performed in a predetermined frame unit as follows.

Also, each femto base station performs grouping and clustering mentioned above, and moves the center frequency for the synchronization signal and the system information signal in the slot unit or the subframe unit through the group index.

Each femto base station checks the bandwidth of each macro base station through the system information received through the center frequency, and calculates the bandwidth that can be allocated to the femto base station.

Each femto base station determines the bandwidth according to the amount of traffic in its own cell through the cluster index. Here, each femto base station designates an initial bandwidth, and determines the bandwidth in such a manner as to expand or contract from the bandwidth.

Next, each femto BS checks the bandwidth conditions determined by the neighboring femto BSs, and if a collision occurs with the bandwidth of the neighboring femto BSs, a bandwidth expansion (BE), a bandwidth shift (Shift) And performs Time Division Bandwidth (TDB).

In addition, if the adjacent femto BS and its own femto BS can not avoid a collision with the hot spot area, the bandwidth reduction (BR) is performed on the line that guarantees the minimum QoS.

Each femto base station performs dynamic bandwidth rebalance at a predetermined frame period.

On the other hand, such dynamic bandwidth adjustment method may be performed in a centralized manner.

That is, the techniques used in the above-mentioned dynamic bandwidth adjustment method can be modified and used as a central type. Unlike the distributed type, the central type is different from the central type in that the central controller can view the entire situation and determine the bandwidths at once without having to repeatedly perform the techniques.

Techniques used in the centralized dynamic bandwidth adjustment method include bandwidth expansion (BE), bandwidth shift (Shift), time division (TDB), and bandwidth reduction (BR) same.

FIGS. 19 to 21 show examples of three cases in which three femto base stations dispersively reconfigure the bandwidth according to the embodiments of the present invention.

FIG. 19 is a diagram illustrating a case in which the femto base station B confirms the bandwidth information of the femto base stations C and A when the femto base station C is in the hot spot area, moves the center frequency for the synchronization signal and the system information signal in units of slots or subframes, And performs bandwidth extension while avoiding collision with the femto base station C.

Also, the femto base station A can perform a bandwidth operation without collision with the femto base station B, thereby performing bandwidth extension.

Thereafter, the bandwidth is readjusted every frame period.

That is, the femto base station C performs the bandwidth extension to allocate the remaining bandwidth, and the femto base station B moves the bandwidth to avoid the collision with the femto base station C.

If all femto base stations occupy the bandwidth fairly, the distributed bandwidth adjustment is finished, and in case of generation of new traffic or decrease of traffic, bandwidth rebalance is performed again.

20 shows a case where the femto base station C and the femto base station B have a large amount of traffic but can not afford to expand the bandwidth. At this time, the femto base stations C and B divide the bandwidth by time division and use it in a fair manner.

FIG. 21 shows a situation in which bandwidth collision occurs as well as bandwidth expansion is impossible, although traffic of all three femto base stations is large. At this time, the femto base stations A and B having more margin for QoS reduce the bandwidth (BR), and the femto base stations B and C time-share the bandwidth to guarantee the minimum QoS or more fairly.

FIG. 23 shows an example in which nine femto base stations dispersively reconfigure bandwidth according to the embodiments of the present invention. FIG. 24 shows an example in which 27 femto base stations dispersively adjust the bandwidth according to the embodiments of the present invention.

The example of FIG. 23 is an extension of FIGS. 19, 20, and 21 described above, and there is no difference in technique or order. Therefore, it will not be described in detail because it can be easily understood by those skilled in the art based on the above-mentioned contents.

However, the femto base station A in the center of FIG. 22 needs to consider all the bandwidth information of the neighboring femto base stations. That is, as the femto base station network is expanded, the number of adjacent cells to be considered by one femto base station is a maximum of six.

Similarly, FIG. 24 shows an example of a case in which 27 femto base stations dispersively reconfigure the bandwidth in the dynamic bandwidth adjustment method. 24 is only an extension of FIGS. 19, 20, and 21 described above, and there is no difference in technique or order. Therefore, it will be understood by those skilled in the art based on the above-mentioned contents, and will not be described in detail.

The method according to the present invention described so far can be implemented in software, hardware, or a combination thereof. For example, a method in accordance with the present invention may be implemented in software (e.g., flash memory, hard disk, etc.) that can be stored in a storage medium And may be implemented as codes or instructions within the program. This will be described with reference to FIG.

FIG. 25 is a configuration block diagram of a femto base station 200 and a macro base station 300 according to the present invention.

As shown in FIG. 25, the femto base station 200 includes a storage unit 210, a controller 220, and a transmitter / receiver unit 230. The macro base station 300 includes a storage unit 310, a controller 320, and a transmission / reception unit 330.

The storage means 210 and 310 store the method shown in FIGS.

The controllers 220 and 320 control the storage units 210 and 310 and the transceivers 230 and 330. Specifically, the controllers 220 and 320 execute the methods stored in the storage nodes 210 and 310, respectively. The controllers 320 and 320 transmit the above-described signals through the transceivers 230 and 330.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, May be modified, modified, or improved.

FIG. 1 is a diagram illustrating a network structure based on a femto base station according to the related art.

2 is an exemplary illustration of a system and bandwidth for illustrating embodiments of the present invention.

FIG. 3A illustrates a concept in which each femto base station moves center frequencies in units of slots according to the first embodiment of the present invention.

FIG. 3B shows the concept shown in FIG. 2 in more detail.

3C is a partial enlarged view of FIG. 3B.

FIG. 4 is a diagram illustrating an example of grouping femto base stations interfering with each other and moving a center frequency in units of slots according to the first embodiment shown in FIG.

FIG. 5A illustrates a concept in which each femto BS moves a center frequency in units of subframes according to a second embodiment of the present invention. FIG. 5B shows the concept shown in FIG. 5A in more detail.

5C is a partially enlarged view of Fig. 5B. Fig.

FIG. 6 is a diagram illustrating an example of grouping femto base stations interfering with each other and moving a center frequency in units of subframes according to the second embodiment shown in FIG.

7 is an exemplary view showing a relationship between a cluster and a group according to the third embodiment of the present invention.

8 is an exemplary view showing an embodiment of the third embodiment shown in FIG.

9 is an exemplary view showing another embodiment of the third embodiment shown in Fig.

FIG. 10 is an exemplary view illustrating an exemplary situation assumed to explain the fourth embodiment of the present invention.

FIG. 11 is a conceptual diagram illustrating a band extending method according to a fourth embodiment of the present invention, according to a specific situation.

12 is an exemplary diagram showing the concept of FIG. 11 in terms of a frequency axis and a time axis.

FIG. 13 is a conceptual diagram illustrating a band extending method according to a fourth embodiment of the present invention, according to another embodiment.

Fig. 14 is an exemplary diagram showing the concept of Fig. 13 on the frequency axis and the time axis.

FIG. 15 is a conceptual diagram illustrating a band extending method according to a fourth embodiment of the present invention, according to another embodiment.

16 is an exemplary diagram showing the concept of FIG. 15 in terms of a frequency axis and a time axis.

17 is an exemplary diagram illustrating a frequency band and a time axis according to yet another embodiment of the method of extending a band according to the fourth embodiment of the present invention.

18 is a diagram illustrating a method of aligning a bandwidth of a femto base station on a frequency axis according to a fifth embodiment of the present invention.

FIG. 19 is an exemplary view of the fifth embodiment shown in FIG. 18; FIG.

20 to 22 show examples of three cases in which three femto base stations dispersively adjust the bandwidth according to the embodiments of the present invention.

FIG. 23 shows an example in which nine femto base stations dispersively reconfigure bandwidth according to the embodiments of the present invention.

FIG. 24 shows an example in which 27 femto base stations dispersively reconfigure the bandwidth according to the embodiments of the present invention.

FIG. 25 is a configuration block diagram of a femto base station 200 and a macro base station 300 according to the present invention.

Claims (14)

A method for signal transmission by a femto base station in a wireless communication system, The femto base station receiving a reference signal from a macro base station; Determining, by the femto base station, a transmission radio resource to which a transmission signal of the femto base station is to be transmitted based on the reference signal; And The femto base station transmitting the transmission signal through the transmission radio resource, Wherein the femto base station is grouped with at least one other femto base station causing interference, Wherein the transmission radio resource is determined so as to be spaced apart from the macro base station by a slot unit or a subframe unit on a time axis, Wherein the transmission radio resource is determined to be the same as a frequency axis of a transmission radio resource of the femto base station but spaced in a slot unit or a subframe unit in a time axis. The method according to claim 1, Wherein the transmission radio resource is determined based on an index allocated to the femto base station. The method according to claim 1, Wherein the reference signal includes at least one of a synchronization signal and a system information signal of the macro base station. The method according to claim 1, Wherein the transmission signal includes at least one of a synchronization signal and a system information signal of the femto base station. An apparatus for transmitting signals by a femto base station in a wireless communication system, A transceiver for receiving a reference signal from a macro base station and transmitting a transmission signal through a transmission radio resource; And A processor for determining, based on the reference signal, a transmission radio resource to which the transmission signal is to be transmitted, Wherein the femto base station is grouped with at least one other femto base station causing interference, Wherein the transmission radio resource is determined to be spaced apart from the macro base station by the subframe in the time axis, Wherein the transmission radio resource is determined to be the same as a frequency axis of a transmission radio resource of the femto base station but spaced by a slot unit or a subframe unit on a time axis. delete delete delete delete delete delete delete delete delete

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