KR102558207B1 - Method and apparatus for load balancing based on call admission control - Google Patents

Abstract

A method of operating a base station in a communication system including a plurality of base stations is disclosed. The method of operating a base station includes, when a new call is received from a first terminal, estimating resources required to accommodate the new call, comparing a first value, which is the sum of resources used by the base station and resources required to accommodate the new call, with a preset second value, estimating resources used by terminals capable of handover to another base station among terminals existing in the base station, when the first value is greater than the second value, estimating resources used by the base station when terminals capable of handover are handed over and the new call Comparing a third value, which is the sum of resources required to accommodate, with the second value, and when the third value is smaller than the second value, handing over handover-capable terminals.

Description

Call admission control based load balancing method and apparatus

The present invention relates to a load balancing method and apparatus in a communication system using a small cell, and more particularly, to a load balancing method and apparatus using a call admission control (CAC) algorithm.

A small cell base station can improve call quality by expanding indoor coverage. Small cell base station research has been discussed by standardization organizations since the second half of 2007. The concept of the small cell was established in ^3rd generation partnership project (3GPP) Release 8. In Release 9, a function for a femtocell (or home eNodeB (HeNB)) was added, and in Release 10, more HeNB functions were defined. Also, at the 2013 3GPP Summit meeting, small cell base stations were defined as an important technology element of 5G networks.

As a user equipment (UE) moves in a small cell network, the UE may access another cell from a serving cell currently being accessed. If the terminal moves away from the currently accessed serving cell, the connection to the serving cell may be disconnected, and the terminal may access a neighboring cell called a target cell. In this process, if the connection between the terminal and the serving cell is disconnected before the terminal accesses the target cell, the quality of service in the terminal may deteriorate. Therefore, it may be necessary to maintain QoS even when the terminal is moving using a handover technique. In particular, in a heterogeneous network (HetNet) in which small cells with narrow coverage are deployed, the problem of inter-cell movement of a terminal may be more important.

Load balancing can also be an issue in small cell networks. When the number of users existing in the network is large, a load balancing problem may occur when the user's access is concentrated in some cells. A lot of access requests and traffic may occur in some cells due to a large number of users, and some other cells may have enough resources due to a small number of users. That is, although there is a cell with free resources nearby, users may flock to the congested cell, and users may suffer performance degradation due to insufficient resources.

An object of the present invention to solve the above problems is to provide a load balancing method and apparatus using a call admission control (CAC) algorithm.

In order to achieve the above object, a method of operating a base station according to an embodiment of the present invention includes, when a new call is received from a first terminal, estimating resources required to accommodate the new call, comparing a first value, which is the sum of resources used by the base station and resources required to accommodate the new call, with a preset second value, estimating resources used by terminals existing in the base station capable of handover to another base station, when the first value is greater than the second value, estimating resources used by terminals capable of handover to another base station among terminals existing in the base station, In case of overrun, comparing a third value, which is the sum of the resources used by the base station and the resources required to accommodate the new call, with the second value, and if the third value is smaller than the second value, handover of terminals capable of handover may be included.

According to the present invention, when a base station receives a new call in a small cell network, when there is a concern that overall network performance (throughput) is degraded due to reception of the new call, MLB (mobility load-balancing) algorithm can be performed. The base station can secure resources for accommodating a new call by handing over terminals located at the edge of the cell to another cell, and can accept the new call after securing the resources. Since the base station can accept a new call after load balancing is achieved, network performance may not be degraded even if the base station accepts the new call. Accordingly, the performance of the communication system can be improved.

1 is a conceptual diagram illustrating an embodiment of a communication system.
2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
3 is a flowchart illustrating a load balancing method according to an embodiment of the present invention.
4 is a graph showing simulation results according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It should be understood that 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 exist in the middle. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprise" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but it should be understood that the presence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof is not excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and are not interpreted in an ideal or excessively formal sense unless explicitly defined in the present application.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

A communication system to which embodiments according to the present invention are applied will be described. A communication system to which embodiments according to the present invention are applied is not limited to the contents described below, and embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used in the same sense as a communication network.

1 is a conceptual diagram illustrating an embodiment of a communication system.

Referring to FIG. 1 , a communication system may include a plurality of communication nodes 110 , 111 , 112 , 113 , 114 , 120 , 121 , 130 , 131 , 140 , and 141 . In addition, an evolved packet core (EPC) 100 (eg, a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), a mobility management entity (MME), and a home subscriber server)) may be further included.

A plurality of communication nodes may support 4G communication (eg, long term evolution (LTE), advanced (LTE-A)), 5G communication, and the like specified in the 3rd generation partnership project (3GPP) standard. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less. For example, for 4G communication and 5G communication, a plurality of communication nodes are code division multiple access (CDMA)-based communication protocol, WCDMA (wideband CDMA)-based communication protocol, TDMA (time division multiple access)-based communication protocol, FDMA (frequency division multiple access)-based communication protocol, OFDM (orthogonal frequency division multiplexing)-based communication protocol, filtered OFDM-based communication protocol, CP (cyclic prefix)-OFDM-based communication protocol, DFT-s-OF DM (discrete Fourier transform-spread-OFDM) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (non-orthogonal multiple access), GFDM (generalized frequency division multiplexing) based communication protocol, FBMC (filter bank multi-carrier) based communication protocol, UFMC (universal filtered multi-carrier) based communication protocol, SDMA (space division multiple access)-based communication protocols may be supported. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2 , a communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 to communicate with each other.

However, each component included in the communication node 200 may be connected through an individual interface or an individual bus centered on the processor 210 instead of the common bus 270 . For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface.

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260 . The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1 , a communication system may include a plurality of base stations 110, 120, 130, and 140, and a plurality of terminals 111, 112, 113, 114, 121, 131, and 141. A communication system including base stations 110 , 120 , 130 , and 140 and terminals 111 , 112 , 113 , 114 , 121 , 131 , and 141 may be referred to as a “small cell network”. The first base station 110 , the second base station 120 , the third base station 130 , and the fourth base station 140 may form a small cell. The first terminal 111, the second terminal 112, the third terminal 113, and the fourth terminal 114 may belong to the cell coverage of the first base station 110. The third terminal 113, the fourth terminal 114, and the fifth terminal 121 may belong to the cell coverage of the second base station 120. The sixth terminal 131 may belong to the cell coverage of the third base station 130 . The seventh terminal 141 may belong to the cell coverage of the fourth base station 140 .

Here, each of the plurality of base stations 110, 120, 130, and 140 includes a small cell, a NodeB, an evolved NodeB, a gNB, an ng-eNB, a base transceiver station (BTS), a radio base station, a radio transceiver, an access point, an access node, a road side unit (RSU), a radio remote head (RRH), It may be referred to as a transmission point (TP), a transmission and reception point (TRP), a flexible (f)-TRP, and the like. Each of the plurality of terminals 111, 112, 113, 114, 121, 131, and 141 supports functions of a user equipment (UE), a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, and an internet of things (IoT). It may be referred to as a device, a mounted module/device/terminal, an on board unit (OBU), and the like.

Meanwhile, each of the plurality of base stations 110, 120, 130, and 140 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110, 120, 130, and 140 may be connected to each other through an X2 interface. The plurality of base stations 110, 120, 130, and 140 may exchange information with each other through the X2 interface and may perform functions such as handover. Each of the plurality of base stations 110, 120, 130, and 140 may be connected to the EPC through an S1 interface. Specifically, the plurality of base stations 110, 120, 130, and 140 may be connected to the MME through an S1-MME interface and connected to the S-GW through an S1-U interface. Each of the plurality of base stations 110, 120, 130, and 140 may transmit signals received from the EPC to the corresponding terminals 111, 112, 113, 114, 121, 131, and 141, and may transmit signals received from the corresponding terminals 111, 112, 113, 114, 121, 131, and 141 to the EPC. .

In addition, each of the plurality of base stations 110, 120, 130, and 140 transmits MIMO (eg, single user (SU)-MIMO, multi-user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, direct device to device communication (D2D) (or, Proximity services (ProSe)) may be supported. Here, each of the plurality of terminals 111, 112, 113, 114, 121, 131, and 141 may perform an operation corresponding to the base station 110, 120, 130, and 140, and an operation supported by the base station 110, 120, 130, and 140. For example, the first base station 110 may transmit a signal to the first terminal 11 based on the SU-MIMO scheme, and the first terminal 111 may receive a signal from the first base station 110 by the SU-MIMO scheme.

Each of the first base station 110, the second base station 120, the third base station 130, and the fourth base station 140 may transmit signals to the terminals 111, 112, 113, 114, 121, 131, and 141 based on the CoMP scheme, and the terminals 111, 112, 113, 114, 121, 131, and 141 can receive signals from the first base station 110, the second base station 120, the third base station 130, and the fourth base station 140 by the CoMP method. Each of the plurality of base stations 110, 120, 130, and 140 may transmit/receive signals based on the CA scheme with the terminals 111, 112, 113, 114, 121, 131, and 141 within their cell coverage.

Next, a load balancing method using a call admission control (CAC) algorithm will be described.

3 is a flowchart illustrating a load balancing method of a base station according to an embodiment of the present invention.

Referring to FIG. 3 , the communication system of FIG. 3 may be the same as or similar to the communication system of FIG. 1 . The base station performing the load balancing operation in FIG. 3 may be the first base station 110 of FIG. 1 . The base station 110 may provide a communication service to the terminals 111, 112, 113, and 114 based on a communication protocol (eg, 4G communication protocol, 5G communication protocol).

When overload occurs due to a large number of terminals accessing a cell, service may not be properly provided. Therefore, in order to protect the service provided by the network, load balancing may be required to properly distribute the load of the cell.

Load balancing methods applicable to small cell networks include handover mobility load balancing (MLB), which controls load balancing in a radio resource control (RRC)-connected state, and cell reselection MLB, which controls load balancing in an RRC-idle state.

Using the handover MLB, the base station can forcibly handover terminals located at the boundary of a cell with a high load to neighboring cells with a low load by controlling handover conditions. Handover MLB may conflict with mobility robust optimization (MRO), one of the self-optimization network (SON) functions. Since both handover MLB and MRO control handover parameters, conflicts may occur in controlling handover parameters. When cell reselection handover is used, the base station can hand over UEs existing in a cell with a high load to a cell with a low load by controlling cell reselection conditions. Cell reselection handover may be performed when the UE is in an RRC-idle state. Hereinafter, a load balancing method using a call admission control algorithm, which is performed when the terminal is in an RRC-connected state, will be described.

When a call is received, the base station 110 may check whether the received call is a new call (S301). If the received call is not a new call, it does not affect the load of the cell and thus the load balancing operation can be terminated.

If the received call is a new call, the base station 110 can estimate the amount of resources (R _req ) required for a service requested by the new call (S302). Shannon's channel capacity equation can be used to estimate the amount of resources required for a new call. The channel capacity C that the UE can receive according to the signal-to-interference ratio (SINR) of the cell i signal measured by the UE can be calculated by Equation 1, Shannon's channel capacity equation.

Referring to Equation 1, C may mean channel capacity, B may mean bandwidth (Hz), and S/N may mean signal-to-interference ratio. When B is the bandwidth of one resource block, C may mean the channel capacity of one resource block. If the data rate required by the new call is φ, the number of resource blocks RB required by the new call can be determined by Equation 2.

Referring to Equation 2, C may mean the channel capacity of one resource block. Therefore, the required number of resource blocks (RB) can be obtained by dividing the required data rate φ by the channel capacity of one resource block.

For example, when the scheduling unit (transmission time interval, TTI) is 1 ms, a resource block ratio (R _req ) required for a new call may be calculated by Equation 3.

Referring to Equation 3, 1000N _PRB may mean the total number of physical resource blocks for unit time. RB may mean the number of resource blocks required according to the new call calculated in Equation 2. A value obtained by dividing the number of required resource blocks by the total number of physical resource blocks may mean a block ratio (R _req ) required according to a new call.

The base station 110 may check whether there are resources capable of accommodating a new call without deteriorating the quality of service currently being provided. In order to determine whether there are enough resources to accommodate a new call, the base station 110 can calculate the amount of resources currently used by the cell (ie, cell load). The base station 110 may calculate the load of the cell through the average resource block usage ratio. The average resource block usage rate may be calculated based on a physical resource block (PRB) of the physical layer. The average resource block usage ratio (R _now ) can be calculated by Equation 4.

Referring to Equation 4, for a given time T, an average resource block use ratio (R _now ) of an arbitrary cell i at the current time t can be obtained. N- _PRB may mean the number of physical resource blocks on the frequency axis, and RB _{i -} ^τ may mean the number of blocks used for time τ in an arbitrary cell i.

The base station 110 may compare the sum of the average resource block usage ratio (R _now ) and the resource block ratio (R _req ) required by a new call with a preset threshold (S303). When the sum of the average resource block usage ratio (R _now ) and the required resource block ratio (R _req ) is less than or equal to a preset threshold value, the base station 110 may accept the call (S309).

When the sum of the average resource block usage ratio (R _now ) and the required resource block ratio (R _req ) is greater than a preset threshold, the base station 110 may search for a terminal that can move to another cell for load distribution instead of rejecting the call (S304). The base station 110 may calculate signal measurement values of terminals located at the edge of a cell in order to handover the terminal to another neighboring cell.

For example, the base station 110 may use a 3GPP standard LTE event to select a terminal located at a cell edge. The terminal may transmit related information (eg, received signal strength, information indicating that a specific event is satisfied) to the base station 110 when one of Events A1 to A6 is satisfied according to the current state. Event A1 may mean when the signal strength of the serving cell is greater than the A1 threshold, and Event A2 may mean when the signal strength of the serving cell is less than the A2 threshold. Event A3 may mean when the signal strength of the neighboring cell is greater than the signal strength of the serving cell by an A3 offset, and Event A4 may mean when the signal strength of the neighboring cell is greater than the threshold value. Event A5 may mean a case where the signal strength of the serving cell is less than the first threshold and the signal strength of the neighboring cell is greater than the second threshold, and Event A6 is the signal strength of the neighboring cell (SCell). It may mean when the signal strength is greater than the A6 offset.

For example, when receiving the Event A1 message from the first terminal 111, the base station 110 may determine that the first terminal 111 is not located at the edge of the cell but is located in the center of the cell, and upon receiving the Event A4 message from the third terminal 113, it may determine that the third terminal 113 is located at the edge of the cell.

The base station 110 sequentially calculates the resource block ratio used by the corresponding terminal, starting with the terminal located at the edge of the cell most among the terminals located at the edge of the cell (eg, the terminal having the weakest signal strength of the serving cell). The ratio of resource blocks used by any terminal j (R _edge - ^j ) can be calculated by Equation 5.

Referring to Equation 5, for a given time period T, a resource block usage ratio (R _edge - ^j ) of an arbitrary terminal j can be obtained. may mean the number of physical resource blocks allocated to a certain terminal j in a certain cell i at time τ.

The set of terminals located at the edge of the cell is U _e = {1, 2, 3, , J}, the ratio (R _edge ) of the resource block used by the movable terminal can be expressed as in Equation 6.

Referring to Equation 6, R _edge is the terminals located at the edge of the cell {1, 2, 3, , J} can represent the sum of the loads. When all terminals located at the edge of a cell move to neighboring cells, the load of the cell is obtained by subtracting the ratio of resource blocks in use by terminals located at the edge of the cell (R _edge ) from the average block use ratio (R _now ) of the entire cell (S305). That is, when terminals located at the edge of a cell move to another cell, the resource block ratio (R _est ) used in the cell can be expressed as in Equation 7.

The base station 110 compares the sum of the resource block ratio (R _est ) used in the cell and the resource block ratio (R _req ) required by the new call with a preset threshold when terminals located at the edge of the cell move to another cell (S306). When terminals located at the edge of a cell move to another cell and the sum of the resource block ratio (R _est ) used in the cell and the resource block ratio (R _req ) required by the new call is greater than a preset threshold value, the base station 110 may reject the call (S310). That is, when the load reduced through the movement of terminals at the cell edge is smaller than the load caused by the new call, the base station 110 may reject the new call.

When terminals located at the edge of a cell move to another cell, when the sum of the resource block ratio (R _est ) used in the cell and the resource block ratio (R _req ) required for a new call is less than or equal to a preset threshold value, the base station 110 can calculate the minimum number of mobile stations that must be moved to accommodate the new call. That is, when the load reduced through the movement of terminals at the cell edge is greater than or equal to the load caused by the new call, the base station 110 may move the minimum number of terminals required to accommodate the new call to another cell instead of moving all terminals at the cell edge to another cell (S307). The minimum number of terminals required to accommodate a new call can be calculated by Equation 8.

In Equation 8, N may mean the minimum number of terminals required to accommodate a new call. After the base station 110 moves the terminals located at the edge of the cell to another cell, the sum of the resource block ratio required by the new call (R _req ) and the resource block ratio currently in use (R _now ) can be compared with a preset threshold (S308). When the sum of the resource block ratio required by the new call (R _req ) and the resource block ratio currently in use (R _now ) is smaller than the threshold value, the base station 110 may accept the call (S309). When the sum of the resource block ratio required by the new call (R _req ) and the resource block ratio currently in use (R _now ) is greater than a threshold value, the base station 110 may reject the call (S310).

4 is a graph showing simulation results according to an embodiment of the present invention.

Referring to FIG. 4 , the simulation experiment was conducted by setting a mobile terminal located at the edge of a cell as one. Cyclic load balancing algorithm without considering CAC (red) and only CAC algorithm (green) If a new cell is overloaded when a UE moves, overall network performance (throughput) drops due to call acceptance and call rejection. On the other hand, the algorithm according to an embodiment of the present invention can know that network performance is maintained even when the new cell is overloaded when the terminal moves.

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated.

Claims (10)

As a method of operating a base station in a communication system including a plurality of base stations,
When a new call is received from a first terminal, estimating a resource block ratio required for the new call calculated by dividing the number of resource blocks required for the new call by the total number of physical resource blocks as a resource required to accommodate the new call;
comparing a first value, which is the sum of an average resource block use rate, which is the amount of resources being used by the base station, and a resource block rate required to accommodate the new call, with a preset second value;
If the first value is greater than the second value, estimating resources used by terminals existing in the base station capable of handover to another base station having transmitted information indicating that Event A4 is satisfied;
comparing a third value, which is the sum of resources used by the base station and resources required to accommodate the new call, with the second value when the handover-capable terminals are handed over; and
When the third value is less than the second value, handing over the handover-capable terminals;
The average resource block usage rate is , where T is a given time, t is the current time, N _PRB is the number of physical resource blocks on the frequency axis, Means the number of blocks used at time τ in any cell i, the operating method of the base station. delete delete The method of claim 1,
As a result of comparing a first value, which is the sum of the resources being used by the base station and the resources required to accommodate the new call, with a preset second value, when the first value is less than or equal to the second value, accepting the new call. The method of claim 1,
If the first value is greater than the second value, estimating resources used by terminals capable of handover to another base station that have transmitted information indicating that Event A4 is satisfied among terminals existing in the base station,
If the first value is greater than the second value, receiving information indicating that a specific event is satisfied among Event A1 to Event A6 from terminals present in the base station;
determining terminals that have transmitted information indicating that the Event A4 is satisfied among information indicating that the specific event is satisfied among the received Event A1 to Event A6 as terminals capable of handover;
Calculating ratios of resource blocks of terminals capable of handover; and
and estimating resources used by terminals capable of handover by summing the ratios of the resource blocks. The method of claim 1,
When the terminals capable of handover are handed over, a result of comparing a third value, which is the sum of resources used by the base station and resources required to accommodate the new call, with the second value, If the third value is greater than the second value, rejecting the new call. The method of claim 1,
When the third value is smaller than the second value, the step of handing over the handover-capable terminals,
if the third value is less than the second value, determining the smallest terminal that must be moved to accommodate the new call; and
And handing over the determined minimum terminals among the terminals capable of handover. As a base station,
processor;
a memory that communicates electronically with the processor; and
Includes instructions stored in the memory;
When the instructions are executed by the processor, the instructions cause the base station to:
when a new call is received from the first terminal, estimating a resource block ratio required for the new call, calculated by dividing the number of resource blocks required for the new call by the total number of physical resource blocks, as resources required to accommodate the new call;
compares a first value, which is the sum of an average resource block usage rate, which is the amount of resources being used by the base station, and a resource block rate required to accommodate the new call, with a preset second value;
If the first value is greater than the second value, estimating resources used by terminals capable of handover to another base station that have transmitted information indicating that Event A4 is satisfied among terminals existing in the base station;
comparing a third value, which is the sum of resources used by the base station and resources required to accommodate the new call, with the second value when the handover-capable terminals are handed over; and
When the third value is smaller than the second value, operates to cause handover of terminals capable of handover;
The average resource block usage rate is , where T is a given time, t is the current time, N _PRB is the number of physical resource blocks on the frequency axis, means the number of blocks used at time τ in any cell i. delete The method of claim 8,
When the first value is greater than the second value, when estimating resources used by terminals capable of handover to another base station among terminals existing in the base station, the commands are sent by the base station,
When the first value is greater than the second value, receiving received signal strength information of a serving cell from terminals existing in the base station;
determining terminals capable of handover based on the received received signal strength information;
calculating ratios of resource blocks of terminals capable of handover; and
A base station operable to cause estimating resources in use by terminals capable of handover by summing the ratios of the resource blocks.

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