KR101988990B1 - Handover method in base station - Google Patents

Abstract

The present invention relates to a handover method in a base station apparatus, comprising: receiving a measurement report message from a plurality of terminals existing in a serving cell; Calculating an optimal A3 parameter considering a state of a communication channel in a RAN shared environment based on the UE measurement information included in the measurement report message; And determining a handover to an adjacent cell using the optimal A3 parameter.

Description

[0001] HANDOVER METHOD IN BASE STATION [0002]

The present invention relates to a handover method in a base station, and more particularly, to a method for determining an optimal handover parameter for extending network coverage while maintaining network quality in a mobile communication system employing RAN sharing technology .

Public Safety Network refers to the disaster safety communication network (PS-LTE), the LTE-R and the maritime mobile communication network (LTE-M). Each public safety network includes a pilot network, And so on.

As shown in FIG. 1, each public safety network uses co-channel interference (CCI) because the same frequency band of 700 MHz is used for different purposes. RAN (Radio Access Network) sharing technology is needed to solve this same channel interference problem and to maximize the service area.

The RAN sharing technology shares the access network of the network and not only the sites, antennas, and steel towers, but also the eNB (Evolved Node B), which is the radio access equipment immediately before the core network access point, (Evolved Packet Core) to the service network.

RAN sharing technology can be divided into passive mode and active mode. Among them, Multi-Operator RAN (MORAN), Multi-Operator Core Network (MOCN) and Gateway Core Network (GWCN) are available. For example, as shown in FIG. 2, the MORAN scheme shares only base station equipment, the MOCN scheme shares both spectrum and base station equipment, and the GWCN scheme shares some elements of RAN and Core Network (CN) .

Among the above-described RAN sharing technologies, the public safety network will use the backhaul sharing type MOCN scheme, which is a method of sharing a base station by opening a call path from a backbone switch. 3, the PS-LTE, the LTE-R, and the LTE-M share the spectrum and base station equipments, Communication service can be provided.

Meanwhile, in this RAN shared environment, network quality and network coverage are in a trade-off relationship with each other. That is, if the handover parameter is large, there is a problem that the network coverage is increased but the network quality is deteriorated. If the handover parameter is small, there is a problem that the network quality is improved but the network coverage is reduced. Therefore, there is a need to determine an optimal handover parameter for extending network coverage while maintaining network quality in a RAN shared environment.

The present invention is directed to solving the above-mentioned problems and other problems. Another object of the present invention is to provide a method and apparatus for determining optimum handover parameters for extending network coverage while maintaining network quality in a mobile communication system employing RAN sharing technology.

Another object of the present invention is to provide a method and apparatus for determining an optimal handover parameter in consideration of a current communication channel state in a mobile communication system employing RAN sharing technology.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

According to an aspect of the present invention, there is provided a method for receiving a measurement report message from a plurality of terminals in a serving cell, Calculating an optimal A3 parameter considering a state of a communication channel in a RAN shared environment based on the UE measurement information included in the measurement report message; And determining a handover to an adjacent cell using the optimal A3 parameter.

를 이용하여 최적의 A3 파라미터를 계산할 수 있다. 상기 수학식에서

의 간섭 성분은 RAN 공유 환경에서의 셀 간 간섭을 포함할 수 있다. 또한, 복수의 단말들로부터 수신되는 단말 측정 정보는 RSSI 정보, RSRP 정보, RSRQ 정보, SINR 정보 중 적어도 하나를 포함할 수 있다.In this embodiment,

Can be used to calculate the optimal A3 parameter. In the above equation

May include inter-cell interference in a RAN shared environment. In addition, the UE measurement information received from a plurality of UEs may include at least one of RSSI information, RSRP information, RSRQ information, and SINR information.

을 통해 정의될 수 있다. In another embodiment, the handover determination step may further include confirming whether the event A3 condition is satisfied using the optimal A3 parameter. The event A3 condition is expressed by Equation

Lt; / RTI >

In another embodiment, the handover determination step may include: proceeding with a handover to an adjacent cell when the event A3 condition is satisfied; If the event A3 condition is not satisfied, the method may further include the step of continuously maintaining the serving cell.

According to another aspect of the present invention, there is provided a mobile communication system including: a measurement information detector for analyzing a measurement report message received from a plurality of terminals existing in a serving cell to detect terminal measurement information; An A3 parameter calculation unit for calculating an optimal A3 parameter considering a communication channel state in an RAN shared environment based on the terminal measurement information provided from the measurement information detection unit; And a handover execution unit for confirming whether the event A3 condition is satisfied using the A3 parameter determined through the A3 parameter calculation unit and for determining a handover to an adjacent cell based on whether the event A3 condition is satisfied or not do.

A handover method in a base station according to embodiments of the present invention and effects of the apparatus will be described as follows.

According to at least one embodiment of the present invention, network coverage can be extended while maintaining network quality by performing handover using A3 parameters adaptively changeable according to the current communication channel conditions.

According to at least one of the embodiments of the present invention, when there are various service providers (PS-LTE / LTE-M / LTE-R) using the same frequency band, By performing the handover using the A3 parameter, resources can be efficiently allocated and the coverage gain can be obtained.

However, the effects of the handover method and the apparatus according to the embodiments of the present invention are not limited to those described above, and other effects not mentioned are not described in the description of the present invention It will be understood by those of ordinary skill in the art.

1 shows a communication system in which co-channel interference occurs in a public safety network having different operating entities;
2 is a diagram illustrating a method of RAN sharing technology;
3 is a view for explaining a RAN sharing technique used in a public safety network;
4 is a configuration diagram of a mobile communication system according to an embodiment of the present invention;
5 is a diagram illustrating a mobile communication system performing a handover when an event A3 is satisfied;
6 is a signaling flowchart between a terminal apparatus and a base station apparatus performing a handover procedure according to an embodiment of the present invention;
7 is a configuration diagram of a base station apparatus according to an embodiment of the present invention;
8 is a flowchart illustrating a handover method of a base station apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

The present invention proposes a method for determining an optimal handover parameter for extending network coverage while maintaining network quality in a mobile communication system employing RAN sharing technology. In addition, the present invention proposes a method for determining an optimal handover parameter that can be adaptively changed according to the current communication channel state in a mobile communication system to which RAN sharing technology is applied.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings.

4 is a block diagram of a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 4, the mobile communication system 100 according to the present invention uses an MOCN RAN sharing technology to solve co-channel interference between a public safety net or a public safety net and a commercial net. In the mobile communication system 100, a service provider (e.g., PS-LTE, LTE-R, or LTE-M) with a service provider can provide a communication service by sharing spectrum and base station equipment.

The mobile communication system 100 may include a user equipment 110, a serving base station 120, and a target base station 130 (Target eNB). The serving base station 120 and the target base station 130 may be connected to a core network of a provider network.

The terminal device 110 is a terminal supporting a multi-carrier system that provides mobile communication services using different frequency bands. Base station apparatuses 120 and 130 are base stations that support a multicarrier system.

The terminal apparatus 110 can use the communication service through communication with the base station apparatuses 120 and 130 by connecting to the base station apparatuses 120 and 130 using any one frequency band among the different frequency bands. Here, the different frequency bands may be a plurality of frequency bands used in one communication network, for example, an LTE network, but are not limited thereto.

The terminal apparatus 110 and the serving base station 120 may perform handover in order to maintain the current communication service when the terminal apparatus 110 moves between the cells while the terminal apparatus 110 is connected to the serving base station 120. [ Procedure.

For example, the terminal device 110 measures surrounding signals, selects candidate base stations (i.e., candidate cells) suitable for handover based on the measurement result, and reports the selected candidate base stations to the serving base station 120. At this time, the terminal device 110 may transmit a measurement report message to the serving base station 120.

The serving base station 120 selects a target base station to perform a handover based on the measurement information reported by the terminal device 110 and transmits a command to the terminal device 110 to instruct the selected target base station to perform handover Lt; / RTI > In response to this, the terminal device 110 can terminate the connection with the serving base station 120 and then connect to the target base station 130.

In this handover procedure, if the base station periodically transmits the signals measured by the terminal apparatuses existing in the specific cell, the base station may allocate a large amount of resources to process the measurement information received from the terminal apparatuses in real time Consuming, and there is a problem in that the terminal consumes a lot of battery to periodically measure and report peripheral signals. Accordingly, it is necessary to set the appointment of each other so that the information measured by the terminal device is reported only at a specific point in time, and the base station device can issue a handover command based on the information. This promise is defined as an "LTE event" in the 3GPP standard.

The handover event type defined in 3GPP is shown in Table 1 below.

Event ID Description A1 Serving becomes better than threshold A2 Serving becomes worse than threshold A3 Neighbor becomes offset better than serving A4 Neighbor becomes better than threshold A5 Serving becomes worse than threshold 1 and neighbor becomes better than threshold 2 A6 Neighbor becomes offset secondary cell

Referring to Table 1, Event A1 is an event that satisfies a condition that a signal of the serving base station becomes larger than a threshold value, Event A2 is an event that satisfies a condition that a signal of the serving base station becomes smaller than a threshold value, Event A3 is an event Is larger than the signal of the serving base station by an offset.

Event A4 is an event that satisfies the condition that the signal of the adjacent base station becomes larger than the threshold value. Event A5 is an event that satisfies the condition that the signal of the serving base station becomes smaller than the first threshold value and the signal of the adjacent base station becomes larger than the second threshold value. Event A6 is an event that satisfies the condition that the signal of the adjacent base station becomes larger than the signal of the SCELL (Secondary Cell) by an offset.

In the mobile communication system 100 according to the present invention, handover (hereinafter referred to as "A3 handover") is started based on Event A3 defined in the 3PP standard. 5, when the signal of the neighboring base station becomes larger than the signal of the serving base station, the terminal 110 measures neighboring signals and selects candidate base stations suitable for handover based on the measurement result And reports it to the serving base station 120. The serving base station 120 selects a target base station to perform handover based on the measurement information reported by the terminal device 110 and transmits a command to the selected target base station to the terminal device 110 have.

On the other hand, in the 3PP standard, it is recommended to select one of the values from -15 dB to 15 dB with respect to the offset value of the event A3, and defines a default value of 3 dB. Therefore, in the conventional mobile communication system, it is confirmed whether the event A3 condition is satisfied by using the offset value (3 dB) defined as the default, and the handover is determined based on this. Here, the event A3 condition can be expressed by Equation 1 below.

은 서빙 셀로부터 수신되는 RSRP(Reference Signal Received Power),

는 인접 셀로부터 수신되는 RSRP,

는 이벤트 A3 Offset 값(-15 dB ~ 15dB) 중 3GPP 권고 Default Value(3dB)임.here,

(RSRP) received from the serving cell,

RSRP received from the neighbor cell,

Is the 3GPP Recommendation Default Value (3dB) among the event A3 offset value (-15 dB ~ 15dB).

However, in the mobile communication system according to the present invention, instead of using a fixed offset value (for example, 3 dB) at the time of handover based on the event A3, an optimal A3 parameter Offset), and determine whether to proceed with the handover based on the calculated A3 parameter.

6 is a signaling flowchart between a terminal device and a base station device performing a handover procedure according to an embodiment of the present invention.

Referring to FIG. 6, the terminal device 110 may measure signal strength and quality of serving cells and neighbor cells (S610).

The terminal device 110 can measure a reference signal received power (RSRP) and a reference signal received quality (RSRQ) with respect to a reference signal. Here, RSRP denotes a power of a reference signal received in the terminal device 110, and RSRQ denotes a quality of a reference signal received in the terminal device 110.

In addition, the terminal device 110 can measure RSSI (Received Signal Strength Index) and SINR (Signal to Interference Noise Ratio) for the received signal. Here, RSSI means the strength of all signals received by the terminal device 110, and SINR means the received signal-to-interference and noise ratio.

The SINR value of the signal received by the terminal device 110 may be defined as: < EMI ID = 2.0 >

Where TP is the transmission power of the base station, PL is the path loss, and IN is the interference and noise.

The intensity of interference and noise IN used in Equation (2) can be defined as Equation (3) below.

Here, the interference is all interference in the LTE environment, interference ^* _{cell in RAN sharing} is inter-cell interference in the RAN shared environment, and noise is noise.

)을 측정할 수 있다.Thus, the terminal device 110 is substantially SINR value considering the inter-cell interference (Interference ^* _{cell in RAN Sharing)} in general, as well as interference in the LTE RAN environment the shared environment (

) Can be measured.

The terminal device 110 may select one or more candidate base stations (i.e., candidate cells) suitable for handover based on the measurement result of the neighbor signal (S620).

The terminal device 110 may transmit a measurement report message including at least one of the measurement information and the candidate cell information to the serving base station 120 (S630).

The serving base station 120 may calculate the A3 parameter based on the measurement information reported by the terminal device 110 (S640). At this time, the serving base station 120 can calculate the optimal A3 parameter considering the current communication channel state.

)를 계산할 수 있다.The serving base station 120 uses the following equation (4) to calculate the optimal A3 parameter

) Can be calculated.

은 A3 Offset 값(-15 dB ~ 15dB) 중 3GPP 권고 Default Value(3dB),

는 특정 단말을 통해 측정된 실질적인 SINR 값,

은 서빙 셀 내에 존재하는 복수의 단말들로부터 수신되는 SINR 값들 중 최소값,

은 서빙 셀 내에 존재하는 복수의 단말들로부터 수신되는 SINR 값들 중 최대값임.here,

Is the 3GPP Recommendation Default Value (3dB) of A3 Offset value (-15 dB ~ 15dB)

A real SINR value measured through a particular terminal,

A minimum value of SINR values received from a plurality of terminals existing in a serving cell,

Is a maximum value among SINR values received from a plurality of terminals existing in a serving cell.

)를 이용하여 3GPP 표준에서 정의하고 있는 이벤트 A3 조건을 만족하는지를 확인할 수 있다. 상기 이벤트 A3 조건은 아래 수학식 5와 같이 표현될 수 있다.The serving base station 120 may determine the optimal A3 parameter

) Can be used to confirm whether the event A3 condition defined in the 3GPP standard is satisfied. The event A3 condition can be expressed by Equation (5) below.

은 서빙 셀로부터 수신되는 RSRP,

는 인접 셀로부터 수신되는 RSRP,

는 현재의 통신 채널 상태를 고려한 최적의 A3 파라미터임.here,

RSRP received from the serving cell,

RSRP received from the neighbor cell,

Is an optimal A3 parameter considering current communication channel conditions.

)가 서빙 셀의 신호(

)보다 최적의 오프셋(

)만큼 커지는 경우), 해당 조건을 만족하는 인접 셀을 타겟 셀로 선택하고, 상기 선택된 타겟 셀로 핸드오버를 결정할 수 있다(S650).When the event A3 condition is satisfied (i.e., the signal of the adjacent cell (

) ≪ / RTI > of the serving cell (

) Than the optimal offset (

), The target cell is selected as the neighboring cell satisfying the condition, and handover to the selected target cell can be determined (S650).

The serving base station 120 may transmit a command to the target base station 130 to instruct the terminal device 110 to perform the handover (S660). In response to this, the terminal device 110 can perform a handover procedure of terminating the connection with the serving base station 120 and then accessing the target base station 130 (S670).

As described above, in the mobile communication system according to the present invention, the network coverage can be extended while maintaining the network quality by performing the handover using the A3 parameter adaptively changeable according to the current communication channel state. In addition, when there are various service providers (PS-LTE / LTE-M / LTE-R) using the same frequency band, handover is performed using A3 parameters considering inter- The resources can be efficiently allocated and the coverage gain can be obtained.

7 is a configuration diagram of a base station apparatus according to an embodiment of the present invention.

Referring to FIG. 7, the base station 200 according to an embodiment of the present invention may include a measurement information detector 210, an A3 parameter calculator 220, and a handover implementer 230. The components shown in FIG. 7 are not essential for implementing a base station device, so that the base station device described herein can have more or less components than the components listed above.

The measurement information detection unit 210 can detect terminal measurement information by analyzing a measurement report message received from the terminal apparatus 110. [ The UE measurement information may include information on the signal strength and quality of the serving cell and neighboring cells. For example, the UE measurement information may include at least one of RSSI information, RSRP information, RSRQ information, and SINR information.

The A3 parameter calculation unit 220 may calculate the A3 parameter based on the measurement information provided from the measurement information detection unit 210. [ That is, the A3 parameter calculating unit 220 can calculate the optimal A3 parameter considering the current communication channel state using Equation (4).

The handover execution unit 230 can confirm whether the event A3 condition defined in the 3GPP standard is satisfied by using the A3 parameter determined through the A3 parameter calculation unit 220. [

When the event A3 condition is satisfied, the handover execution unit 230 selects a neighboring cell satisfying the condition as a target cell, and performs handover to the selected target cell.

8 is a flowchart illustrating a handover method of a base station apparatus according to an embodiment of the present invention.

Referring to FIG. 8, the base station apparatuses 120 and 200 may receive a measurement report message from a plurality of terminals existing in a specific cell (S810). At this time, the measurement report message may include at least one of measurement information and candidate cell information about the serving cell and neighboring cells.

The base station apparatuses 120 and 200 may detect terminal measurement information required for handover based on the measurement report message received from the terminals. At this time, the UE measurement information may include at least one of RSSI information, RSRP information, RSRQ information, and SINR information.

The base station apparatuses 120 and 200 can calculate the A3 parameter based on the measurement information reported by the terminal apparatus (S820). That is, the base station apparatuses 120 and 200 can calculate the A3 parameter considering the current communication channel state using Equation (4).

For example, Table 2 below shows A3 parameters adaptively changeable according to the current communication channel conditions. When the current communication channel state is good, the A3 parameter calculated by the base station apparatuses 120 and 200 increases, and when the current communication channel state is bad, the A3 parameter calculated by the base station apparatuses 120 and 200 is .

RF Condition Adaptive A3 parameter Excellent (> = 80) 4.83 Good (-80 to -90) 4.66 Mid Cell (-90 to -100) 3.98 Cell Edge (<-100) 2.15

The base station apparatuses 120 and 200 can confirm whether the event A3 condition defined in the 3GPP standard is satisfied using the optimal A3 parameter (S830). The event A3 condition can be expressed as Equation (5).

If it is determined that the event A3 condition is satisfied, the base station apparatus 120 or 200 selects a neighboring cell satisfying the condition as a target cell and performs handover to the selected target cell in operation S840.

Meanwhile, if it is determined that the event A3 condition is not satisfied, the base station apparatuses 120 and 200 can continue to maintain the current serving cell without starting the handover to the neighboring cell.

As described above, in the base station apparatus according to the present invention, the network coverage can be extended while maintaining the network quality in the RAN shared environment by performing the handover using the optimal A3 parameter considering the current communication channel state .

The present invention described above can be embodied as computer-readable codes on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer readable medium include a hard disk drive (HDD), a solid state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, , And may also be implemented in the form of a carrier wave (e.g., transmission over the Internet). Also, the computer may include a control unit 180 of the terminal. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

100: mobile communication system 110: terminal device
120: serving base station 130: target base station
210: measurement information detection unit 220: A3 parameter detection unit
230: handover execution unit

Claims (8)

Receiving a measurement report message from a specific terminal in a serving cell;
Calculating an A3 offset parameter considering a state of a communication channel in a RAN (Radio Access Network) shared environment based on the UE measurement information included in the measurement report message; And
Determining a handover to a neighboring cell using the A3 offset parameter,
Wherein the A3 offset parameter is calculated using SINR (Signal to Interference Noise Ratio) information including an inter-cell interference component in the RAN shared environment. The method according to claim 1,
The UE measurement information includes at least one of Received Signal Strength Index (RSSI) information, Reference Signal Received Power (RSRP) information, Reference Signal Received Quality (RSRQ) information, and Signal to Interference Noise Ratio (SINR) Wherein the handover method comprises: The method according to claim 1,
Wherein the A3 offset parameter is calculated using the following equation.
[Mathematical Expression]

here,

Is a default value defined by the 3GPP standard,

A real SINR value measured through a particular terminal,

A minimum value of SINR values received from a plurality of terminals existing in a serving cell,

Is a maximum value among SINR values received from a plurality of terminals existing in a serving cell. The method of claim 3,
remind

Wherein the interference component in the RAN shared environment includes an inter-cell interference component in the RAN shared environment. 2. The method of claim 1,
Further comprising checking whether the event A3 condition is satisfied by using the A3 offset parameter. 6. The method of claim 5,
Wherein the event A3 condition is defined by the following equation.
[Mathematical Expression]

here,

RSRP received from the serving cell,

RSRP received from the neighbor cell,

Is an optimal A3 offset parameter considering the current communication channel state. 6. The method of claim 5,
Performing a handover to the neighbor cell if the event A3 condition is satisfied;
And if the event A3 condition is not satisfied, continuing the serving cell. A measurement information detector for detecting terminal measurement information by analyzing a measurement report message received from a specific terminal in a serving cell;
An A3 parameter calculation unit for calculating an A3 offset parameter considering a state of a communication channel in a RAN (Radio Access Network) shared environment based on the terminal measurement information provided from the measurement information detection unit; And
And a handover execution unit for confirming whether the event A3 condition is satisfied using the A3 offset parameter determined through the A3 parameter calculation unit and for determining a handover to a neighboring cell based on whether the event A3 condition is satisfied ,
Wherein the A3 parameter calculator calculates the A3 offset parameter using SINR (Signal to Interference Noise Ratio) information including an inter-cell interference component in the RAN shared environment.

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