KR101206652B1 - Location information server, mobile equipment and periodic cell searching method in communication system - Google Patents

Abstract

Disclosed are a location information server, a mobile terminal, and a periodic cell search method to which a neighboring cell search optimization technique for cell selection / reselection is applied in a communication system. A location information server installed on a network in a system and communicating with a mobile terminal, comprising: a server communication unit for receiving a request message including terminal state information from the mobile terminal and transmitting a response message including neighbor cell search optimization information; A level dividing unit for dividing neighboring cells around a cell currently connected to the mobile terminal into a plurality of levels by using the terminal state information; And a discovery period adjustment parameter setting unit configured to set a discovery period adjustment parameter for adjusting a neighbor cell discovery period according to the levels distinguished by the level separator, wherein the mobile terminal in the LTE system is optimized. There is an effect of simplifying the neighbor cell search list and effectively adjusting the search period to perform conventional neighbor cell search.

Description

Location information server, mobile equipment and periodic cell searching method in communication system

The present invention relates to a location information server to which a neighbor cell search optimization technique for cell selection / reselection is applied in a mobile system, a mobile terminal, and a periodic cell search method.

The LTE (Long Term Evolution) system, which is currently being standardized, does not assume timing synchronization of a base station and thus performs a very complicated cell search step compared to a synchronous communication system.

As an example of a cell search method in a conventional wireless communication system, a method of generating complex sequences of a terminal type mapped to cell ID information for cell search, and a complex sequence mapped to a cell ID are included in every slot of a physical frame. There is a cell ID mapping method including transmitting to sync channels periodically transmitted every predetermined signal transmission interval. This reduces the complexity of hardware implementation by reusing the correlator and sequence generator for cell search at the receiving end, and reduces the complexity of the procedure by performing only two phases of synchronous channel search, but does not reduce the number of list of neighboring cells. There is a problem in that power consumption and delay time occur.

In another example of the conventional cell search method, a UE connected to a macro cell searches for a femtocell in an environment in which a large number of femtocells overlap in one macro cell. There is a method to search the femtocell using a dummy preamble to minimize. This reduces the MAC overhead by eliminating the neighboring femtocell list in the base station announcement message transmitted by the macro cell and confirms only the femtocell dummy preamble in the dedicated symbol of the macro cell. There is a problem in that the optimized search is difficult by efficiently reducing the list and searching all femtocells in the neighboring femtocell list at the same period.

In another example of the conventional cell search method, an energy calculation step of receiving a neighboring cell signal having a different phase and detecting a correlation value and calculating an energy of the detected correlation value, one or more candidate cells in order of magnitude of the calculated energy. There is a cell searching method including a candidate cell detecting step of detecting and a result output step of determining an energy ratio of the detected candidate cells and outputting a cell search result by comparing with a reference threshold ratio. According to this, although stable cell search results can be obtained even in a communication environment where external interference is severely changed, stable cell search results can be obtained by applying the same threshold ratio even when designers of the cell search apparatus are different. As in the conventional methods, power consumption and delay time due to unnecessary cell search are not generated because the number of neighbor cell lists is not reduced, and the optimized search is difficult by searching all neighbor cells in the list at the same period.

As another example of a conventional cell discovery method, a first step of searching for a cell using a primary synchronization signal (PSS) and a cyclic prefix after the first step in a synchronization and cell search method of a 3GPP LTE downlink system In the second step of selecting and the extended CP in the second step, after performing only one fast Fourier transform (FFT) using the extended CP, the second synchronization signal (SSS) detection and the broadcasting channel (BCH) detection are performed. There is a method of minimizing the complexity of the SSS detection during the initial synchronization and cell search in the 3GPP LTE system downlink including a third step of executing. According to this, it is possible to improve the performance that can reduce the computational complexity by up to 50%, but the power consumption and delay time due to unnecessary cell search can be reduced because the number of neighbor cells cannot be reduced as in the conventional methods described above. There is a problem that an optimized search is difficult by searching for all neighboring cells in the list at the same period.

The present invention provides a location information server, a mobile terminal, and a periodic cell search method for simplifying a neighbor cell search list and effectively adjusting a search period so that a mobile terminal in an LTE system can perform an optimized periodic neighbor cell search. It is for.

In addition, the present invention provides a location information server, a mobile terminal, and a periodic cell search method that can reduce power consumption and search delay time due to unnecessary search since the number of neighboring cells to be periodically searched is limited according to the location of the mobile terminal. It is to.

In addition, the present invention is to improve the handover performance due to the selection of the mobile cell at the appropriate moment by reducing the search period of the neighboring cell having a high probability of selection by adjusting the neighbor cell search period according to the level of the neighboring cell. To provide an information server, a mobile terminal and a periodic cell search method.

Other objects of the present invention will be readily understood through the following description.

According to an aspect of the present invention, a location information server installed on a network in a system and communicating with a mobile terminal, receiving a request message including terminal state information from the mobile terminal and including neighbor cell search optimization information; Server communication unit for transmitting a response message; A level dividing unit for dividing neighboring cells around a cell currently connected to the mobile terminal into a plurality of levels by using the terminal state information; And a search period adjustment parameter setting unit for setting a search period adjustment parameter for adjusting the neighbor cell search period according to the levels separated by the level separator.

The neighbor cell search optimization information may include information of neighbor cells belonging to each of the plurality of levels and the search period adjustment parameter information.

The terminal state information may include one or more of an ID, location information, currently connected cell information, and supportable access technology type information of the mobile terminal.

The location information server has connection point location information of all cells, transmission range related information, and neighbor cell information of each cell for all access technologies in the communication system, and the level divider is configured according to the mobility of the mobile terminal. A speed related parameter may be defined, and levels of the neighbor cells may be classified according to the speed related parameter and the supportable access technology type information.

The level separator may classify the levels of the neighbor cells into levels 1 to 3 according to the following equation.

Here, Dist (MN, Neighbor_PoA) is the distance between the current location of the mobile terminal and the location of the connection point of the neighboring cell, R _type is the transmission range radius according to the access technology type, T _period exchanges the request message or the response message The message exchange period, V _high , represents the average speed of a terminal having relatively fast mobility, V _medium represents the average speed of a terminal having normal mobility, and V _low represents the average speed of a terminal having relatively slow mobility. .

The search period parameter setting unit may set the search period parameter according to the following equation.

Here, F _L1 , F _L2 , and F _L3 are search period adjustment parameters for neighbor cells belonging to level 1, level 2, and level 3, respectively.

Meanwhile, according to another aspect of the present invention, a mobile terminal for performing a periodic search for a neighbor cell on a network in a system, the mobile terminal comprising: a GPS for identifying the location of the mobile terminal and generating location information; A terminal communication unit transmitting a request message including terminal state information to a location information server and receiving a response message including neighbor cell search optimization information generated at the location information server; A search list simplification unit for simplifying a neighbor cell search list by using the neighbor cell search optimization information; And a search period adjusting unit configured to adjust a search period for a neighbor cell belonging to the neighbor cell search list by using the neighbor cell search optimization information.

The terminal state information may include one or more of an ID, location information, currently connected cell information, and supportable access technology type information of the mobile terminal.

The neighbor cell search optimization information may include information of neighbor cells belonging to each of the plurality of levels and the search period adjustment parameter information.

The search list simplifier may exclude, from the neighbor cell search list, neighbor cells that are not related to information of neighbor cells belonging to each of the plurality of levels among all neighbor cells around the cell to which the mobile terminal is currently connected.

The search period adjusting unit may adjust the search period by using the search period adjustment parameter information and period information for searching for each access technology type.

The search period controller may adjust the search period according to the following equation.

,

,

는 각각 레벨 1, 레벨 2, 레벨 3에 따른 탐색 주기이고, F_L1, F_L2, F_L3는 각각 레벨 1, 레벨 2, 레벨 3에 따른 탐색 주기 조절 파라미터이며,

는 접속 기술 타입 별로 탐색을 수행하는 주기 정보이다.here,

,

,

Are search periods according to level 1, level 2 and level 3, and F _L1 , F _L2 and F _L3 are search period adjustment parameters according to level 1, level 2 and level 3, respectively.

Is period information for searching for each access technology type.

On the other hand, according to another aspect of the present invention, a method in which a mobile terminal performs a periodic neighbor cell search in a communication system, the method comprising the steps of: (a) the mobile terminal transmits the terminal status information as a request message to the location information server; (b) the location information server dividing a neighbor cell of a cell currently connected to the mobile terminal into a plurality of levels using the terminal state information; (c) setting, by the location information server, a search period adjustment parameter according to the plurality of levels; (d) the location information server transmitting neighbor cell information divided into the plurality of levels and the search period adjustment parameter information to the mobile terminal as a response message; (e) simplifying, by the mobile terminal, a neighbor cell search list to be periodically searched using neighboring cell information divided into the plurality of levels; And (f) adjusting, by the mobile terminal, a neighbor cell search period for neighbor cells included in the neighbor cell search list by using a search period adjustment parameter according to the plurality of levels. Is provided.

Steps (a) to (f) may be repeated every exchange period of the request message and the response message.

The terminal state information may include one or more of an ID, location information, currently connected cell information, and supportable access technology type information of the mobile terminal.

The location information server has connection point location information of all cells, transmission range related information and neighbor cell information of each cell for all access technologies in the communication system, and step (b) is based on the mobility of the mobile terminal. According to the present invention, a plurality of speed related parameters may be defined, and levels of the neighbor cells may be classified according to the speed related parameter and the supportable access technology type information.

Step (b) may divide the levels of the neighbor cells into levels 1 to 3 according to the following equation.

Here, Dist (MN, Neighbor_PoA) is the distance between the current location of the mobile terminal and the location of the connection point of the neighboring cell, R _type is the transmission range radius according to the access technology type, T _period exchanges the request message or the response message The message exchange period, V _high , represents the average speed of a terminal having relatively fast mobility, V _medium represents the average speed of a terminal having normal mobility, and V _low represents the average speed of a terminal having relatively slow mobility. .

Step (c) may set the search period parameter according to the following equation.

Here, F _L1 , F _L2 , and F _L3 are search period adjustment parameters for neighbor cells belonging to level 1, level 2, and level 3, respectively.

In step (e), neighboring cells not related to information of neighboring cells belonging to each of the plurality of levels among all neighboring cells around the cell to which the mobile terminal is currently connected may be excluded from the neighboring cell search list.

In step (f), the search period may be adjusted by using the search period adjustment parameter information and the period information for performing the search for each access technology type.

Step (f) may adjust the search period according to the following equation.

,

,

는 각각 레벨 1, 레벨 2, 레벨 3에 따른 탐색 주기이고, F_L1, F_L2, F_L3는 각각 레벨 1, 레벨 2, 레벨 3에 따른 탐색 주기 조절 파라미터이며,

는 접속 기술 타입 별로 탐색을 수행하는 주기 정보이다.here,

,

,

Are search periods according to level 1, level 2 and level 3, and F _L1 , F _L2 and F _L3 are search period adjustment parameters according to level 1, level 2 and level 3, respectively.

Is period information for searching for each access technology type.

Other aspects, features, and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

According to an embodiment of the present invention, there is an effect of simplifying the neighbor cell search list and effectively adjusting the search period so that the mobile terminal in the LTE system can perform the optimized periodic neighbor cell search.

In addition, since the number of neighboring cells to be periodically searched is limited according to the location of the mobile terminal, unnecessary discovery is required by reducing the neighboring cell search overhead of the mobile terminal in the LTE system due to the development of various access technologies and the increase of a small range of cells. This reduces power consumption and seek latency.

In addition, by adjusting the neighbor cell search period according to the level of the neighbor cell, the handover performance due to the selection of the mobile cell at an appropriate instant can be improved by reducing the search period of the neighboring cell having a high probability of selection.

1 is a diagram illustrating a message exchange including neighbor cell search optimization information between a mobile terminal and a location information server according to an embodiment of the present invention;
2 is a block diagram showing a schematic configuration of a location information server according to an embodiment of the present invention;
3 is a block diagram showing a schematic configuration of a mobile terminal according to an embodiment of the present invention;
4 is a diagram illustrating a periodic neighbor cell search optimization process in a communication system according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

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

1 is a diagram illustrating a message exchange including neighbor cell search optimization information between a mobile terminal and a location information server according to an embodiment of the present invention.

In the present embodiment, the mobile terminal 200 periodically searches for neighbor cells in order to handover from a cell to which the mobile station 200 is currently connected. The location information server 100 is used to simplify the search list for these neighbor cells and adjust the search period accordingly.

Referring to FIG. 1, messages exchanged between a mobile terminal 200 and a location information server (LIS) 100 are defined.

SimpliedNLRequest message is a request message (S10) sent by the mobile terminal 200 to the location information server 100, the ID of the mobile terminal 200, location coordinates (for example, GPS coordinates), current connection cell information, the terminal Contains information about the connection technology types that can be supported.

After receiving the SimpliedNLRequest message from the mobile terminal 200, the location information server 100 classifies the levels of neighboring cells based on the current connection network of the mobile terminal 200 using the information included therein (S20). . This will be described later in detail with reference to related drawings.

The location information server 100 transmits to the mobile terminal 200 a SimpliedNLAcknowledge message including information on neighboring cells corresponding to each level and parameters for adjusting a cell search period (S30).

Hereinafter, the configuration and operation of each of the location information server 100 and the mobile terminal 200 to optimize the neighbor cell search will be described in detail.

2 is a block diagram showing a schematic configuration of a location information server according to an embodiment of the present invention.

The location information server 100 according to the present embodiment is installed on a network in the system, and connects to all cells of the system (for example, LTE, CDMA, WLAN, WiBro, etc.) to all cell connection points (PoA, Point of Attachment) It is assumed that it has location information, information on its transmission range (eg, transmission radius), and neighbor cell information of each cell. If there is addition, deletion, or change of cell connection point location information, transmission range related information, and neighbor cell information, the location information server 100 may need to update the information.

Referring to FIG. 2, the location information server 100 according to the present embodiment includes a server communication unit 110, a level separator 120, and a search period adjustment parameter setting unit 130.

The server communication unit 110 communicates with one or more mobile terminals in the LTE system, and ID, location information, currently connected cell information of the mobile terminal from the mobile terminal, and access technology type information supported by the mobile terminal 200. Receive a request message (SimpliedNLRequest message) including the terminal state information, such as. Here, it is assumed that the mobile terminal is equipped with GPS so that it can know the GPS coordinates corresponding to its location information.

The level separator 120 classifies neighboring cells of the current connected cell of the mobile terminal into a plurality of levels by using the location information of the mobile terminal received through the server communication unit 110 and the current connected cell information. In the present specification, it will be described on the assumption that it is divided into three levels, but it should be understood by those skilled in the art that the scope of the present invention is not limited thereto.

The method of classifying neighboring cells may be applied differently because the message transmission range is different according to the access technology type (eg, LTE, CDMA, WLAN, WiBro, etc.) of the neighboring cells.

The level divider 120 first defines three speed related parameters V _high , V _medium , and V _low in order to classify neighboring cells into three levels. V _high indicates an average speed of a terminal having relatively fast mobility, V _medium indicates an average speed of a terminal having normal mobility, and V _low indicates an average speed of a terminal having relatively slow mobility.

The level separator 120 divides levels of neighbor cells into levels 1 to 3 according to Equation 1 below.

[Equation 1]

Here, R _type represents a transmission range radius according to the access technology type (for example, R _WLAN , R _LTE, etc.), and as described above, the location information server 100 is a connection technology type and transmission range of all cells in the system. Contains radius information. The T _period is a message exchange _period in which the mobile station exchanges a message (SimpliedNLRequest or SimpliedNLAcknowledge) including information for optimizing neighbor cell search with the location information server 100.

Dist (MN, Neighbor_PoA) indicates the distance between the current location of the mobile station and the location of the connection point (PoA) of the neighbor cell, and the current location of the mobile station is (X _m , Y _m ), and the location of the connection point of the neighbor cell. Is (X _n , Y _n ), Dist (MN, Neighbor_PoA) may be represented by Equation 2 below.

&Quot; (2) "

After performing level classification on the neighbor cells, the search period adjustment parameter setting unit 130 transmits a search period adjustment parameter F _L1 , F _L2 to be transmitted to the mobile terminal to be used to adjust the search period of the neighbor cell according to the divided level. , F _L3 is set as in Equation 3 below.

&Quot; (3) "

The server communication unit 110 searches for information (ID, etc.) of neighboring cells belonging to each level (level 1, level 2, level 3) classified by the level separator 120, and the search period adjustment parameter setting unit 130. The neighbor cell search optimization information such as the period adjustment parameters F _L1 , F _L2 and F _L3 is included in the response message (SimpliedNLAcknowledge message) and transmitted to the mobile terminal.

3 is a block diagram illustrating a schematic configuration of a mobile terminal according to an embodiment of the present invention.

Referring to FIG. 3, the mobile terminal 200 includes a GPS 210, a terminal communication unit 220, a search list simplifying unit 230, and a search period adjusting unit 240.

The GPS (Global Positioning System) 210 detects the position of the mobile terminal 200 by using a satellite, and generates and outputs it as position information.

The terminal communication unit 220 communicates with the location information server, transmits the request message shown in FIG. 1 to the location information server, and receives a response message from the location information server. The request message is a SimpliedNLRequest message, the ID of the mobile terminal 200, location information generated by the GPS 210, cell information to which the mobile terminal 200 is currently connected, and access technology type information supported by the mobile terminal 200. It includes. The response message is a SimpliedNLAcknowledge message and includes neighbor cell information belonging to each level classified by the location information server and search period adjustment parameter information according to each level.

The search list simplifier 230 selects a neighbor cell for the mobile terminal 200 to perform a periodic search using the neighbor cell information for each level included in the response message received through the terminal communication unit 220. .

In the neighbor cell selection method, neighboring cells not included in three levels classified by the location information server among all neighboring cells of the cell to which the mobile terminal 200 is currently connected are excluded from the search list. That is, neighboring cells irrelevant to neighboring cell information for each level included in the response message received through the terminal communication unit 220 may be excluded from the search list, thereby preventing unnecessary searching, thereby reducing power consumption and search delay time.

Neighbor cells within three levels perform periodic discovery during the T _period , which is a message exchange period, and perform message exchange with the location information server again after the T _period , so that neighbor cells according to the position of the mobile terminal 200 at the corresponding time point. By resetting the level of the signals, neighbor cells to be periodically searched can be newly determined.

After the simplification of the neighbor cell list to be searched periodically by the search list simplifier 230, the search period controller 240 adjusts the search period of the neighbor cell according to each level.

시간 마다 일정하게 주기적으로 탐색을 수행하게 된다. 하지만, 본 발명에서는 이웃 셀의 레벨에 따라 탐색 주기를 조절하기 위해 위치 정보 서버로부터 전달받은 탐색 주기 조절 파라미터 F_L1, F_L2, F_L3를 더 이용한다. In the LTE system, the mobile terminal 200 is for each access technology type.

The search is performed periodically at regular intervals. However, the present invention further uses the discovery period adjustment parameters F _L1 , F _L2 , and F _L3 received from the location information server to adjust the discovery period according to the level of the neighbor cell.

,

,

는 하기 수학식 4를 통해 구할 수 있다. Search cycle according to level 1, level 2, level 3

,

,

Can be obtained through Equation 4 below.

&Quot; (4) "

The mobile terminal 200 according to the present embodiment performs a periodic search only for neighboring cells belonging to the simplified search list by the search list simplifying unit 230, and selects by adjusting the search period according to the level of neighboring cells. By reducing the search period of the neighboring cell near this high, handover performance can be improved by selecting a mobile cell at an appropriate moment.

4 is a diagram illustrating a periodic neighbor cell search optimization process in a communication system according to an embodiment of the present invention.

First, in step S310, the mobile terminal transmits terminal state information for periodic neighbor cell search optimization to the location information server. The terminal state information includes information on its own location required for neighbor cell discovery, information on the currently connected cell, ID of the corresponding mobile terminal, and supportable access technology type information.

In operation S320, the location information server classifies neighboring cells of a network to which the mobile terminal is currently connected to a plurality of levels using the information received from the mobile terminal. A method of dividing the neighboring cells into a plurality of levels has been described in detail with reference to Equations 1 and 2, which will be omitted herein.

In operation S330, the location information server sets search period adjustment parameters according to a plurality of levels, and transmits neighbor cell search optimization information including neighbor cell information divided into a plurality of levels and search period adjustment parameter information to the mobile terminal. Here, the setting of the search period adjustment parameter has been described in detail with reference to Equation 3, which will be omitted herein.

In step S340, the mobile terminal simplifies the neighbor cell search list to be periodically searched based on the information received from the location information server. Among the neighboring cells of the cell to which the mobile terminal is currently connected, neighboring cells not included in neighboring cell information divided into a plurality of levels in the location information server are simplified by excluding them from the neighboring cell search list to be periodically searched.

In step S350, the mobile terminal adjusts the neighbor cell search period for the neighbor cell included in the neighbor cell search list using the search period adjustment parameter according to its level. The adjustment of the neighbor cell search period has been described in detail above with reference to Equation 4, which will be omitted herein. Neighbor cell search periods are adjusted to reduce the search periods of neighboring cells that have a high probability of selection so that mobile cell selection can be made at an appropriate moment.

Step S310 and subsequent steps are repeatedly performed for each T _period , which is a message exchange period between the mobile terminal and the location information server.

It is obvious that each step of the periodic cell search method described above may be performed by an automated procedure in a time series order by a software program embedded in each component in a system consisting of a mobile terminal and a location information server. The codes and code segments that make up the program can be easily deduced by a computer programmer in the field. In addition, the program is stored in a computer-readable information storage medium, and the program is read and executed by a computer to implement the method. The information storage medium includes a magnetic recording medium, an optical recording medium, and a carrier wave medium.

Although the above has been described with reference to embodiments of the present invention, those skilled in the art may variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. And can be changed.

100: geolocation server
110: server communication unit
120; Level separator
130: search cycle adjustment parameter setting unit
200: mobile terminal
210: GPS
220: terminal communication unit
230: navigation list simplification unit
240: search period control unit

Claims (18)

delete delete delete delete delete delete delete delete delete delete delete delete A method of performing periodic neighbor cell search by a mobile terminal in a communication system,
(a) the mobile terminal transmitting the terminal status information to the location information server as a request message;
(b) the location information server dividing a neighbor cell of a cell currently connected to the mobile terminal into a plurality of levels using the terminal state information;
(c) setting, by the location information server, a search period adjustment parameter according to the plurality of levels;
(d) the location information server transmitting neighbor cell information divided into the plurality of levels and the search period adjustment parameter information to the mobile terminal as a response message;
(e) simplifying, by the mobile terminal, a neighbor cell search list to be periodically searched using neighboring cell information divided into the plurality of levels; And
and (f) adjusting, by the mobile terminal, a neighbor cell search period for neighbor cells included in the neighbor cell search list by using a search period adjustment parameter according to the plurality of levels. The method of claim 13,
The steps (a) to (f) are repeated periodically every exchange period of the request message and the response message. The method of claim 13,
And the terminal state information includes one or more of an ID, location information, currently connected cell information, and supportable access technology type information of the mobile terminal. 16. The method of claim 15,
The location information server has connection point location information, transmission range related information, and neighbor cell information of each cell of all cells of all access technologies in the communication system.
In step (b), a plurality of speed related parameters are defined according to the mobility of the mobile terminal, and the levels of the neighbor cells are classified according to the speed related parameters and the supportable access technology type information. Cell navigation method. 17. The method of claim 16,
The step (b) is a periodic cell search method characterized in that the level of the neighboring cells divided into levels 1 to 3 according to the following equation.
[Mathematical Expression]

Here, Dist (MN, Neighbor_PoA) is the distance between the current location of the mobile terminal and the location of the connection point of the neighboring cell, R _type is the transmission range radius according to the access technology type, T _period exchanges the request message or the response message message exchange cycle, V _high represents the average speed of a UE having a relatively high mobility, V _medium indicates the average rate of having the normal of the mobile terminal, V _low is being the average speed of a UE having a relatively slower mobility . delete

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