WO2015111816A1

WO2015111816A1 - Traffic load control device and method, and terminal device thereof

Info

Publication number: WO2015111816A1
Application number: PCT/KR2014/008574
Authority: WO
Inventors: 강창순
Original assignee: 창원대학교 산학협력단
Priority date: 2014-01-23
Filing date: 2014-09-15
Publication date: 2015-07-30
Also published as: KR20150088136A; KR101543145B1

Abstract

When an overload occurs in a serving cell, the present invention checks traffic load states of macro cells adjacent to the serving cell and then adjusts a load threshold value of the serving cell. Further, in the present invention, the serving cell transmits a message for adjusting handover threshold values of all terminals operating therein so that the terminals can adjust pre-configured handover threshold values. As a result, the terminals of the serving cell can be handed over to neighboring adjacent cells. Thus, the present invention, inducing a handover after considering first the traffic load states of the adjacent cells, can prevent the adjacent cells from being overloaded due to terminals unconditionally handed over from the serving cell.

Description

Traffic load control device and method, terminal thereof

The present invention relates to a traffic load control apparatus, and more particularly, when a traffic load of a serving cell reaches a specific threshold, adaptively adjusts the load threshold of the serving cell according to the traffic load of one or more neighboring cells. The present invention relates to a traffic load control apparatus and a method for improving a problem that may occur due to traffic overload of a serving cell.

The next generation of mobile communication systems such as LTE-A currently overlap small cells such as femtocells, picocells, and microcells and large cells such as macro cells that provide a wider service area. It provides a structure.

However, in recent years, the number of portable devices such as smart phones is increasing rapidly, so the traffic load on the mobile communication network is increasing. In particular, in the hierarchical cell structure of a mobile communication network in which small cells and large cells overlap, poor service quality, such as poor communication and data transmission rate, may be caused, resulting in a deterioration of network stability. have.

Accordingly, efforts have been actively made to efficiently manage traffic load in a hierarchical cell structure in which small and large cells overlap each other.

As an example for managing such traffic load, there is a Korean hand-held Patent No. 10-1335018, 'Handover method and system of the terminal' (filed earlier).

The preceding document is a method for handovering the terminal to another macro cell neighboring the serving cell or a femtocell superimposed with the serving cell by adjusting the handover parameter of the terminal operating in the overloaded cell.

However, although the prior document provides the effect of mitigating the traffic overload of the serving cell, this handovers the terminal belonging to the serving cell without considering the traffic load of the neighboring macro cell or the small cell femto cell at all. I'm making it.

Therefore, when the load of the serving cell and the neighboring macro cell or femto cell is overloaded, the macro cell or femto cell becomes more overloaded due to the handover terminals. Therefore, in this case, the probability that the terminal located in the serving cell is normally handed over to the macro cell or femto cell becomes low, and of course, even if the handover is successful, the call quality deteriorates to existing terminals due to the overload of the macro cell or femto cell. Can be.

Accordingly, an object of the present invention is to solve the above problems, and in the wireless communication system of a hierarchical hierarchical cell structure, the serving cell (ie, the macro cell) and the neighboring cells adjacent to the neighboring cells are checked in advance and then the serving cell The present invention provides a traffic load control apparatus and method for resolving a traffic overload condition by adjusting a load threshold of a cell to adjust coverage of cells.

Another object of the present invention is to provide a terminal device which is handed over from a serving cell to neighbor cells according to the traffic load state of the neighbor cell.

According to a feature of the present invention for achieving the above object, a check unit for checking the traffic load state for the serving cell and neighboring cells adjacent to the serving cell; A determination unit for determining an overload of the serving cell; And a load threshold adjuster configured to adjust a load threshold L _th set in the serving cell according to the traffic load state of the adjacent cells when the serving cell is overloaded.

And a message transmitter for transmitting a message to the terminal to adjust a handover threshold of at least one terminal located in the serving cell after the load threshold is adjusted.

According to the traffic load state, the load threshold L _th of the serving cell increases, decreases, or maintains the current load threshold by a predetermined value α.

The handover threshold includes a threshold (HOMM) for handover between macro cells and a threshold (HOMF) for handover from a macro cell to a femto cell.

The serving cell and the neighbor cell are macro cells.

According to another aspect of the invention, determining the traffic load state of neighboring cells neighboring the serving cell; Checking the traffic load status of the neighbor cells if the serving cell is overloaded; And adjusting a load threshold set in the serving cell according to the traffic load condition.

The traffic load state is divided into low (L _L ), normal, high (L _H ), the load threshold (L _th ) is reduced, maintained, and increased by a predetermined value (α) to correspond to the traffic load state, respectively. do.

The constant value α is a value smaller than 1, L _L <load threshold value L _th ≤ L _H , and L _H <1.

Here, the normal state is a state when the traffic load in the cell is less than a certain ratio, the low state is a state when the traffic load in the cell is less than the normal state, and the high state is the traffic load in the cell This is the state when it is larger than the normal state.

When the traffic load is low, the load threshold L _th is decreased by a predetermined value α, and a message for adjusting the handover threshold is transmitted to all terminals located in the serving cell.

If the traffic load is normal, a message for adjusting the handover threshold is transmitted to all terminals located in the serving cell.

According to the handover threshold, at least one terminal located in the serving cell is adjusted by adjusting a threshold value (HOMM) for handover between macro cells or a threshold value (HOMF) for handover from a macro cell to a femto cell. Alternatively, handover to the femto cell.

When the traffic load is high, the load threshold L _th is increased by a predetermined value α, and a message for adjusting the handover threshold is transmitted to all terminals located in the serving cell.

According to the handover threshold, a threshold value (HOMF) for handover from the macro cell to the femto cell is adjusted so that at least one terminal located in the serving cell is handed over to the femto cell.

According to another feature of the invention, the receiving unit for receiving a message for adjusting the handover threshold value from the serving cell is overloaded according to the traffic load state of the neighboring cell and the serving cell; And a handover threshold adjustment unit for adjusting the handover threshold according to the message.

The handover threshold includes at least one of a threshold value (HOMM) for handover between macro cells and a threshold value (HOMF) for handover from a macro cell to a femto cell.

The coverage of the serving cell is virtually enlarged or reduced in accordance with the handover threshold.

The terminal device is handed over to the macro cell when the threshold value HOMM is transmitted, and handed over to the femto cell when the threshold value HOMF is transmitted.

Such a traffic load control device and method according to the present invention, and its terminal device has the following effects.

According to the present invention, when the traffic load of the macro cell as the serving cell increases by a certain level or more, the traffic load state of the serving cell and the neighboring neighboring cells is first checked, and then the terminals located in the serving cell are selectively selected as the neighboring cells as the macrocell or femto. Handover to the cell.

Accordingly, by overloading the neighboring cells, the overload phenomenon of the neighboring cells is prevented by unilaterally inducing handover without considering the traffic load of the neighboring cells.

As a result, the call quality of the terminal may be reduced or the data rate may be lowered, and the stability of the mobile communication network may be greatly improved.

1 is a configuration diagram of a mobile communication system to which a hierarchical cell structure in which a femto cell and a macro cell are superimposed is used to explain the present invention.

2 is a block diagram of a traffic load control apparatus configured in a base station of a serving cell according to an embodiment of the present invention;

3 is a configuration diagram of a terminal handed over to an adjacent cell according to a control operation of a serving cell of the present invention

4 is a flowchart illustrating a traffic load control method according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a cell coverage configuration in which cell coverage is changed according to the traffic load control method of FIG.

According to the present invention, in the mobile communication system in which the macro cell and the femto cells overlap, the load threshold value of the serving cell is adjusted according to the load situation of the neighboring cells and the metro cell serving as the serving cell, and the handover threshold value of the terminal is adjusted. It is a basic technical point to prevent traffic overload by adjusting their virtual cell coverage.

Hereinafter, exemplary embodiments of a traffic load control apparatus and method according to the present invention and a terminal apparatus thereof will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a mobile communication system to which a hierarchical cell structure in which a femto cell and a macro cell are superimposed is applied to explain the present invention.

As shown in FIG. 1, a cell providing cell coverage having different sizes is configured. One is a femto cell 1 and the other two are first and

second macro cells

3 and 5. The femto cell 1 refers to an area in which a small wireless environment is provided to improve indoor serviceable area by installing a base station using an ultra-small, low power indoor / home office, and the first and second macro cells 3 ( 5) refers to an area serving a relatively wider area than the femto cell 1. That is, the cell coverage indicating the service area is determined by the transmission power of the base station, and the cell coverage is formed differently because the base station transmission powers of the macro cell and the femto cell are different from each other. For example, the base station transmit power of the

macro cells

3 and 5 is tens of watts or more, and the base station transmit power of the femto cell 1 is only a few hundred milliwatts. Meanwhile, all or part of the cell coverage of the femto cell 1 may be included in the cell coverage of the

macro cell

3, 5.

Each cell coverage is configured with a base station. That is, the base station is a femto base station 6, the first macro base station 7, the second macro base station 8, each of these base stations (6) (7) (8) is in a position that can provide a proper communication service It is composed. That is, the

base stations

6, 7, and 8 are installed at appropriate locations capable of sufficiently performing a mobility management function for supporting or controlling communication services of terminals located in respective cell coverages. The cell coverage is determined by the installation location of the

base stations

6, 7 and 8.

In the service area of the mobile communication system, there is a space where cell coverage overlaps each other. The overlapping space includes a first region where the coverage of the femto cell 1 overlaps with the coverage of the first macro cell 3, and the coverage of the first macro cell 3 and the coverage of the second macro cell 5 overlap. It is a 2nd area | region which becomes.

Terminals

10 and 11 are located in the first area and the second area. In this case, the first terminal 10 is located in the first area and the second terminal 11 is located in the second area.

Meanwhile, in the present embodiment, when the traffic load of the macro cell (hereinafter, referred to as a 'serving cell') 3 in which the first macro base station is located reaches a specific threshold (called a 'load threshold'), the current serving cell The traffic load of the serving cell 3 is adjusted by handing over the terminal receiving the service of (3) to another neighboring cell. At this time, the traffic load state of the serving cell 3 and the neighboring

neighbor cells

1 and 5 is first considered, and then the

terminals

10 and 11 are selectively handed over.

The necessary components for this purpose will be described with reference to FIGS. 2 and 3.

2 is a configuration diagram of a traffic load control apparatus configured in a base station of a serving cell according to an exemplary embodiment of the present invention, and FIG. 3 is a configuration diagram of a terminal handed over to an adjacent cell according to the control operation of the serving cell of the present invention.

First, look at FIG. Referring to FIG. 2, the traffic load control apparatus 20 includes a determination unit 21 for determining an overload of the serving cell 3. The overload determination can be seen by comparing whether the traffic load of the serving cell 3 has reached a threshold.

And a check unit for checking the traffic load status of the neighboring cells (1) (5) neighboring the serving cell (3) is configured. The check unit checks the downlink traffic load of the serving cell 3 and the first check unit 23 and at least one other macro cell (ie, the second macro cell) 5 neighboring the serving cell 3. A second check unit 25 for checking a downlink load state, respectively. At this time, the first check unit 23 and the second check unit 25 may check the traffic load state of cells in a state configured together with the traffic load control device 20, or adjacent cells (1) (5) Each of the second check units 25 may be configured, and the serving cell 3 may receive and check the traffic load state checked by the second check unit 25. In addition, the traffic load state checked by the first checker 23 and the second checker 25 is three steps, such as a low-load state, a normal-load state, and a high-load state. It will be divided into. However, it is not necessarily limited thereto. You may want to further refine or simplify your traffic load. That is, the traffic load state may be provided to be freely changed depending on the communication environment of the neighbor cells.

When the serving cell 3 is overloaded, a load threshold adjusting unit 27 is configured to adjust the load threshold of the serving cell 3 according to the traffic load. The load threshold adjustment unit 27 increases or decreases the load threshold in accordance with the traffic load condition.

The message transmitter 29 is configured to transmit a message to the terminals to adjust the handover threshold of the terminals located in the serving cell 3 according to the traffic load of the neighbor cell 5. The handover threshold transmitted by the message transmitter 29 includes a handover margin for macrocell (HOMM) and a handover margin for handover from a macro cell to a femto cell (HOMF). for Femtocell).

By adjusting the load threshold and the handover threshold in this way, it is possible to virtually adjust (ie, enlarge or reduce) the coverage of the serving cell 3 and the coverage of the

adjacent cells

1 and 5. In other words, some or all of the terminals located in the serving cell 3 are handed over to the macro cell 5 or the femto cell 1, which are adjacent cells.

Next, referring to FIG. 3, the

terminals

10 and 11 become portable devices such as smart phones that are located in cell coverage and perform various communication services.

The terminal 10 (11) is configured with a receiver 32 for receiving a message transmitted by the traffic load control device 20 of the serving cell (3). Since the message is transmitted randomly at any time, the receiver 32 should always maintain a state in which the message can be received. The receiver 32 may be used together with a receiver (not shown) that receives a series of high quality multimedia data or may be separately configured. Meanwhile, if the receiver 32 is used together with a receiver that receives multimedia data, priority may be given when receiving the message and the multimedia data. For example, the reception of the multimedia data may be temporarily stopped while the message is being received, or conversely, the reception of the message may be temporarily stopped while the multimedia data is being received.

In addition, the terminal 10 (11) is configured with a handover threshold adjustment unit 34 for adjusting the preset handover threshold in accordance with the message. According to the handover threshold, the

terminals

10 and 11 are handed over to the macro cell 5 or the femto cell 1.

Next, a method of adjusting traffic loads between cells using a traffic load control device having the above configuration will be described. This will be described with reference to FIG. 4 which illustrates a traffic load control method according to a preferred embodiment of the present invention, and FIG. 5 which shows an example in which cell coverage is changed.

As shown in FIG. 1, a cell constituting a mobile communication system includes a femto cell 1, a serving cell 3, and a second macro cell (hereinafter referred to as a 'macro cell') 5. In addition, a first region and a second region overlapping each other are formed between the cells. At least one terminal 10 (11) is positioned in the first area and the second area, respectively, and a communication service is normally performed.

In this state, the serving cell 3 and the macro cell 5 respectively check the traffic load by the first checker 23 and the second checker 25 while providing communication services in their service areas (s10). ). That is, the base station of the serving cell 3 checks the downlink traffic load L _K in its cell area, and the base station of the macro cell 5 also checks the downlink traffic load L _j in its cell area. It is. Of course, the checking of such traffic load is continuously performed during the communication service, and when there are two or more macro cells, all macro cells check their downlink traffic load.

While the traffic load is checked, the determination unit 21 of the serving cell 3, which is a macro cell, continuously determines whether its cell is overloaded (s12). This is done by comparing the downlink traffic load L _K with a preset load threshold L _th . The load threshold L _th is used as a measure for overload determination of the serving cell 3. Therefore, when the downlink traffic load L _K is greater than the load threshold value L _th , the determination unit 21 determines that the serving cell is in a traffic overload condition.

Here, the load threshold value L _th has a constant value α that decreases or increases according to the traffic load L _j of the macro cells 5, which are all neighboring neighbor cells, and the constant value is smaller than 1. It is set to a value. In addition, the traffic load state is represented by L _L when low and L _H when high, wherein the load threshold L _th is set to a value greater than L _L and less than or equal to L _H as shown in Equation 1 below. In addition, L _H is set smaller than 1 as in the following formula (2).

[Equation 1]

L _L <Load Threshold (L _th ) ≤ L _H

[Equation 2]

L _H <1

On the other hand, when the serving cell 3 is overloaded, the call quality and data rate of the terminals in the serving cell 3 are inevitably deteriorated. Therefore, the overload condition of the serving cell 3 must be solved. This can be solved by virtually adjusting (ie, zooming in / out) the coverage of the serving cell 3 and the

adjacent cells

1, 5.

Next, a process of resolving an overload state according to the traffic load state of the serving cell 3 and neighboring neighboring

cells

1 and 5 will be described.

First, the traffic load L _j of at least one macro cell 5, which is an adjacent cell, is low (load state) (S14). That is, L _j <L _L.

In this case, since the traffic load of the neighboring cell 5 is relatively low, the neighboring cell 5 can sufficiently handle this even if the at least one terminal located in the serving cell 3 is handed over. Therefore, the load threshold adjusting unit 27 decreases the load threshold L _th set in advance in the serving cell 3 by a predetermined value α (s15).

Thereafter, when the load threshold L _th is adjusted, the message transmitter 29 transmits a message to decrease the handover threshold of all terminals located in the service area of the serving cell 3 (S16). Since the message transmission is uniformly transmitted to all terminals, the broadcasting scheme can be applied.

If so, the terminal 10 (11) adjusts the preset handover threshold (s17). At this time, the handover threshold is divided into a HOMM value and a HOMF value, and the terminal 11 receiving the HOMM value adjusts a threshold value for handover between the

macro cells

3 and 5 and transmits the HOMF value. The received terminal 11 adjusts a threshold for handover between the macro cell 5 and the femto cell 1.

Accordingly, the

terminals

10 and 11 located in the serving cell 3 are handed over to the macro cell 5 or the femto cell 1 which are adjacent cells (s18). As a result, the serving cell 3 eliminates the overload, and the serving cell 3, the macro cell 5, and the femto cell 1 have load balancing effects among the cells, thereby making the call quality and data transmission possible without error. You will be served.

Second, the traffic load L _j of at least one macro cell 5, which is an adjacent cell, is in a normal-load state (S20).

In this case, the serving cell (3) is not adjusted to the currently set load threshold (L _th). In other words, the load threshold adjustment unit 27 is in an inoperative state.

However, the message transmitter 29 transmits a message to reduce the handover threshold of all terminals located in the service area of the serving cell 3 (S16). Then, the terminal adjusts its handover threshold according to the transmitted message (s17). At this time, the handover threshold is adjusted by dividing the HOMM value or the HOMF value according to the position of the terminal.

Third, the traffic load L _j of at least one macro cell 5, which is an adjacent cell, is in a high-load state (S22).

This is a case where the traffic load L _j is high in any one of the neighbor cells. As such, when the traffic load L _j is greater than the load threshold L _th even in at least one of the neighbor cells, the load threshold adjuster 27 sets the load threshold L _th to a predetermined value. Increase by (α) (s23).

When the load threshold L _th is increased, the message transmitter 29 transmits a message so that all terminals located in the service area of the serving cell 3 adjust the handover threshold (S24).

Accordingly, the terminal adjusts the preset handover threshold value, in which case only the HOMF value is adjusted (S25). That is, the terminals located in the serving cell 3 are handed over only to the femto cell 1. This is to prevent the terminal from being handed over to the macro cell 5 which is overloaded because the traffic load of the macro cell 5 which is an adjacent cell is overloaded.

As a result, the terminals of the serving cell 3 are handed over only to the femto cell 1 so that the femto cell 1 partially bears the traffic load of the serving cell 3 (S26).

This operation will continue until the traffic load of the macrocell 5 is not more than the load threshold (L _th).

As illustrated in FIG. 5, the cell coverage is changed according to the adjustment of the load threshold and the handover threshold.

5, the coverage 3 ′ of the serving cell 3 is reduced and conversely the coverages 5 ′ and 1 ′ of the macro cell 5 and the femto cell 1 are expanded. Accordingly, the first terminal 10 located in the first area is handed over from the serving cell 3 to the femto cell 1, and the second terminal located in the second area has the macro cell 5 in the serving cell 3. It can be seen that the handover to.

Meanwhile, the

terminals

10 and 11 adjust the handover threshold as follows according to the message transmitted by the message transmitter 29.

First, the handover threshold is reduced. This corresponds to the case where the traffic load L _j of the neighbor cell 5 is low, and is equal to Equations 3 and 4 below.

[Equation 3]

HOMM _adj = HOMM-△ HOM

In Equation 3, HOMM represents a handover margin required for handover from the serving cell 3 to the macro cell 5, and ΔHOM represents a decrease in the handover margin. Therefore, HOMM _adj represents a value of decreasing handover margin by ΔHOM in the originally planned HOMM.

[Equation 4]

HOMF _adj = HOMF-△ HOM

In Equation 4, HOMF represents a handover margin required for handover from the serving cell 3 to the femto cell 1, and ΔHOM represents a decrease in the handover margin. Therefore, HOMF _adj represents a value of decreasing handover margin by ΔHOM in the originally planned HOMF.

On the other hand, when the traffic load L _j of the neighbor cell 5 is high, the handover threshold is increased. This is the same as Equation 5 and Equation 6 below.

[Equation 5]

HOMM _adj = HOMM + △ HOM

[Equation 6]

HOMF _adj = HOMF + △ HOM

As shown in

Equations

5 and 6, the handover margin is increased by ΔHOM in the originally planned HOMM (or HOMF).

On the other hand, the handover process of the terminal 10 (11) is operated differently according to the received signal strength.

That is, when the signal strength RSRP _M of the macro cell 5 received by the terminal 10 or 11 is greater than the HOMM _adj than the signal strength RSRP _S of the serving cell 3, the terminal may transmit the macro cell ( Perform handover to 5). On the other hand, when the strongest signal received by the terminal 10 or 11 is the femto cell 1, the signal strength RSRP _F received from the femto cell 1 is greater than the signal strength RSRP _S of the serving cell. If greater than the HOMF _adj , the terminal performs a handover to the femto cell 1.

As described above, the present embodiment describes that the traffic load of the serving cell and the neighboring cell (ie, the macro cell) neighboring are first identified, and then the handovers of the terminals located in the serving cell are handed over to the macro cell or femto cell to balance the traffic load. Provide as a summary.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the invention It will be apparent that other variations, modifications and equivalents are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention can solve the traffic overload caused by the increase in the use of high-speed data services, high-quality video services, including voice services in the mobile communication network, thereby improving users' service quality and data rate, and also improve the mobile communication network It can be applied to a mobile communication system that can greatly improve the overall network stability.

Claims

A checker for checking a traffic load state of a serving cell and neighboring cells neighboring the serving cell;

A determination unit for determining an overload of the serving cell; And

And a load threshold adjuster configured to adjust a load threshold value L th set in the serving cell according to the traffic load state of the adjacent cells when the serving cell is overloaded.
The method of claim 1,

And a message transmitter for transmitting a message to the terminal to adjust a handover threshold of at least one terminal located in the serving cell after the load threshold is adjusted.
The method of claim 2,

And a load threshold value L th of the serving cell increases, decreases or maintains a current load threshold value according to the traffic load state.
The method of claim 3, wherein

The handover threshold is,

And a threshold (HOMM) for handover between macro cells and a threshold (HOMF) for handover from a macro cell to a femto cell.
The method of claim 2,

And the serving cell and the neighbor cell are macro cells.
Determining a traffic load state of neighboring cells adjacent to the serving cell;

Checking the traffic load status of the neighbor cells if the serving cell is overloaded; And

And adjusting a load threshold set in the serving cell according to the traffic load condition.
The method of claim 6,

The traffic load state is divided into a low (L L ) state, a normal state, a high (L H ) state,

And reducing, maintaining, and increasing the load threshold value L th by a predetermined value α to correspond to the traffic load state, respectively.
The method of claim 7, wherein

The constant value α is a value smaller than 1,

The load threshold is greater than the L L and less than or equal to L H ,

The L H is less than 1 traffic load control method.
The method of claim 7, wherein

The steady state is a state in which a traffic load in a corresponding cell is below a certain ratio,

The low state is a state when the traffic load in the cell is less than the normal state,

The high state is a traffic load control method when the traffic load in the cell is greater than the normal state.
The method of claim 7, wherein

When the traffic load is low, the traffic load control method for reducing the load threshold L th by a predetermined value α and transmitting a message for adjusting the handover threshold to all terminals located in the serving cell. .
The method of claim 7, wherein

And transmitting a message for adjusting a handover threshold to all terminals located in the serving cell when the traffic load state is normal.
The method according to claim 10 or 11,

According to the handover threshold, at least one terminal located in the serving cell is adjusted by adjusting a threshold value (HOMM) for handover between macro cells or a threshold value (HOMF) for handover from a macro cell to a femto cell. Or traffic load control method for handover to a femto cell.
The method of claim 7, wherein

When the traffic load condition is high, the traffic load control for increasing the load threshold L th by a predetermined value α and transmitting a message for adjusting the handover threshold to all terminals located in the serving cell Way.
The method of claim 13,

And controlling a threshold value (HOMF) for handover from the macro cell to the femto cell according to the handover threshold so that at least one terminal located in the serving cell is handed over to the femto cell.
A receiving unit for receiving a message for adjusting a handover threshold value from the serving cell in an overloaded state according to a traffic load state of a serving cell and a neighboring neighbor cell; And

And a handover threshold adjustment unit for adjusting the handover threshold according to the message.
The method of claim 15,

The handover threshold includes at least one of a threshold (HOMM) for handover between macro cells and a threshold (HOMF) for handover from a macro cell to a femto cell.
The method of claim 16,

The terminal device is virtually enlarged or reduced coverage of the serving cell according to the handover threshold.
The method of claim 16,

The terminal device is handed over to the macro cell when the threshold value (HOMM) is transmitted, and handed over to the femto cell when the threshold value (HOMF) is transmitted.