Patent Publication Number: US-2023164522-A1

Title: Grouping method and system using bluetooth-based star network

Description:
TECHNICAL FIELD 
     An embodiment of the present invention relates to grouping method and system using a Bluetooth-based star network. 
     BACKGROUND ART 
     The contents described below merely provide only background information related to the present embodiment and do not constitute the prior art. 
     With the recent increase in the use of multi-use facilities and group outdoor activities, the incidence of disappearance of objects (infants, the elderly, intellectual disabilities, etc.) in need of protection and management is gradually increasing. There are many cases of occurring in multi-use facilities crowded with people such as large marts, amusement parks, and terminals in family units. 
     Since infants and persons with intellectual disabilities have short attention span at the time of the group activities in the form of nature learning and field trips in kindergartens and welfare facility groups, there are frequent cases of group departure due to distraction and sudden behavior. In addition, the elderly (including the elderly with dementia) often break away from the group due to their own actions during group tours and viewings at home and abroad. When breaking away from the group, they may not be aware whether to break away from the group. 
     In the event of group activities, when a person break away from a group&#39;s allowable range, there is a need for a system for not only alerting parents and managers immediately through notification (sound and vibration), but also notifying all persons subject to protection management, including the breakaway person of the occurrence of the breakaway person to find the breakaway person early, thereby preventing the disappearance. 
     Techniques for detecting the breakaway person have been variously researched, but there is a technique capable of checking a movement path of the other party away from a group by calculating a self-position between the respective devices using a plurality of devices connected with a conventional short-range wireless network, calculating a distance by exchanging the calculated self-position, and designating a current position as an absolute position while outputting an alarm when the self-position exceeds a set reference distance to calculate a self-moving distance. 
     In addition, as a technique for recognizing breakaway persons from the group in the related art, there is a technique in which each of a plurality of member terminals performing group activities receives radio waves transmitted from each other to detect the intensities of the radio waves, obtains a distance between a plurality of member terminals from the detected intensities of the radio waves, and outputs a warning when there is a terminal having a distance between the member terminals of a reference distance or more among the plurality of member terminals after acquiring the reference distance based on the acquired distance between the member terminals. 
     Most of the above-described prior arts use a method of measuring a distance or detecting a breakaway person through a communication distance of a protector terminal. When the breakaway person is detected through the communication distance of the protector terminal, there may be a situation in which it is determined as a breakaway person even if not break away. Accordingly, there is a need for a technique to determine the breakaway between moving nodes through a star network connected between the respective terminals instead of performing communication between terminals centered on the protector terminal. 
     DISCLOSURE 
     Technical Problem 
     An object of the present embodiment is to provide grouping method and system using a Bluetooth-based star network, which group an instructor and members into a primary group by using a star network so that the instructor can detect the breakaway of a moving group in the outdoors, without using a direction finding technology of a beacon that requires the use of fixed transmitter and receiver, and allow some members of the primary group to be instructors and members, and then use the star network to allow some members to be grouped into subordinate members and secondary groups, so that a leading instructor is notified of moving farther away from the group by using messages sent therebetween. 
     Technical Solution 
     According to an aspect of the present invention, there is provided a grouping system using a Bluetooth-based star network including: a primary instructor terminal that is paired with a plurality of member terminals by a predetermined number based on Bluetooth to form a primary group constituting a star network; a secondary instructor terminal in which some members of the primary group are paired with a predetermined number of other member terminals based on Bluetooth, which are not paired with the primary instructor terminal among the plurality of member terminals as the instructor and the member to form a secondary group constituting a subordinate star network of the primary group; and a management terminal which is paired with the primary instructor terminal to visually display tags of the member terminals breaking away from or joined in the primary group and the secondary group. 
     According to another aspect of the present invention, there is provided a grouping method using a Bluetooth-based star network including: a process of pairing a primary instructor terminal with a plurality of member terminals by a predetermined number based on Bluetooth to form a primary group constituting a star network; process of pairing, by a secondary instructor terminal, some members of the primary group with a predetermined number of other member terminals based on Bluetooth, which are not paired with the primary instructor terminal among the plurality of member terminals as the instructor and the member to form a secondary group constituting a subordinate star network of the primary group; and a process of visually displaying, by a management terminal which is paired with the primary instructor terminal, tags of the member terminals breaking away from or joined in the primary group and the secondary group. 
     Advantageous Effects 
     As described above, according to the present embodiment, it is possible to notify a leading instructor of moving farther away from the group by using messages sent therebetween by grouping an instructor and members into a primary group by using a star network so that the instructor can detect the breakaway of a moving group in the outdoors, without using a direction finding technology of a beacon that requires the use of fixed transmitter and receiver, and allowing some members of the primary group to be instructors and members, and then using the star network to allow some members to be grouped into subordinate members and secondary groups. 
     According to the present embodiment, it is possible to allow an instructor to easily detect the breakaway of members of a moving group on board a school bus or a school bus. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram schematically illustrating a grouping system using a Bluetooth-based star network according to the present embodiment. 
         FIG.  2    is a diagram illustrating a grouping method using a Bluetooth-based star network according to the present embodiment. 
         FIG.  3    is a diagram illustrating a star network topology according to the present embodiment. 
         FIG.  4    is a diagram illustrating a relationship between an instructor terminal and a member terminal according to the present embodiment. 
         FIG.  5    is a diagram for describing disconnection between an instructor terminal and a member terminal according to the present embodiment. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS FOR MAIN PARTS OF DRAWINGS 
       110 : Primary instructor terminal 
       120 : Member terminal 
       130 : Management terminal 
       210 : Secondary instructor terminal 
       220 : Additional secondary instructor terminal 
     MODES FOR THE INVENTION 
     Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a diagram schematically illustrating a grouping system using a Bluetooth-based star network according to the present embodiment. 
     The grouping system using a Bluetooth-based star network according to the present embodiment includes a primary instructor terminal  110 , a member terminal  120 , and a management terminal  130 . Components included in the grouping system using the Bluetooth-based star network are not necessarily limited thereto. 
     The primary instructor terminal  110 , the member terminal  120 , and the management terminal  130  according to the present embodiment refer to devices capable of tracking a position based on BLE 5. 
     The primary instructor terminal  110  is a wearable device implemented in the form of a bracelet, a necklace, a watch, and the like, and preferably refers to an electronic device supporting a BLE 5-based position tracking function. 
     The member terminal  120  is a wearable device implemented in the form of a bracelet, a necklace, a watch, and the like, and preferably refers to an electronic device supporting a BLE 5-based position tracking function. 
     The primary instructor terminal  110  and the member terminal  120  may include a microphone and a speaker to transmit and receive audio signals to and from each other. The primary instructor terminal  110  may broadcast a message to all member terminals  120  included in a member group. The primary instructor terminal  110  may individually send a direct message using a unique ID (virtual ID) of the member terminal  120 . 
     The management terminal  130  refers to an electronic device that communicates with the primary instructor terminal  110  via a short-range network according to a user&#39;s key manipulation. The management terminal  130  includes a memory for storing a program or protocol for communicating with the primary instructor terminal  110  via a short-range network, a microprocessor for executing and controlling the corresponding program, and the like. 
     The management terminal  130  may be an electronic device such as a smart phone, a tablet, a laptop, a personal computer (PC), a personal digital assistant (PDA), and a portable multimedia player (PMP), a wireless communication terminal, and a media player. 
     The management terminal  130  is various devices including (i) a communication device such as a communication modem for performing communication with various devices or wired and wireless networks, (ii) a memory for storing various programs and data, (iii) a microprocessor for operation and control by executing the program, and the like. According to at least one embodiment, the memory may be a computer readable recording/storage medium, such as a random access memory (RAM), a read only memory (ROM), a flash memory, an optical disk, a magnetic disk, a solid state disk (SSD), etc. According to at least one embodiment, a microprocessor may be programmed to selectively perform one or more of operations and functions described herein. According to at least one embodiment, the microprocessor may be implemented in whole or in part as hardware such as an application specific integrated circuit (ASIC) of a specific configuration and the like. 
     The management terminal  130  is paired with the primary instructor terminal to visually display tags of the member terminals breaking away from or joined in a primary group and a secondary group. 
     For example, as illustrated in  FIG.  1   , when a teacher leads about 20 students in a kindergarten to visit an amusement park, the students need to frequently check the breakaway while moving. If a breakaway person occurs, it is necessary to quickly find the position of the breakaway person. 
     Accordingly, it is preferable to determine how much the students are far away from the teacher and where the students are located based on the position using the primary instructor terminal  110 , the member terminal  120 , and the management terminal  130  that support BLE 5. 
     The students wear the member terminal  120  that is a wearable device (e.g., bracelet, and necklace) capable of BLE 5-based position tracking. The teacher performs BLE 5-based short-range communication with each member terminal  120  using the primary instructor terminal  110 . Here, the primary instructor terminal  110  is connected to the management terminal  130  to display the center like a radar. 
     The wearable member terminal  120  worn by about  20  students is connected to the primary instructor terminal  110  through short-distance communication. 
     The primary instructor terminal  110  communicates with the management terminal  130  to display, on the management terminal  130 , how much the member terminals  120  connected to the primary instructor terminal  110  are separated from the center and where the member terminal  120  is located, in the form of a tag of S1, S2, S3 . . . S20 of identification numbers assigned to each member terminal  120 . 
     The primary instructor terminal  110  and the member terminal  120  can communicate with each other at a maximum distance of about 1 km. Since BLE 5-based communication is performed using the primary instructor terminal  110  and the member terminal  120 , the instructor may quickly identify the breakaway of the member when taking out the member or going to and from school. 
       FIG.  2    is a diagram illustrating a grouping method using a Bluetooth-based star network according to the present embodiment. 
     A grouping system using a Bluetooth-based star network according to the present embodiment may notify a leading instructor of moving farther away from a group by using messages sent therebetween by grouping an instructor and members into a primary group by using a star network so that the instructor can detect the breakaway of a moving group in the outdoors, without using a direction finding technology of a beacon that requires the use of fixed transmitter and receiver, and allowing some members of the primary group to be instructors and members (multi rolls), and then using the star network to allow some members to be grouped into subordinate members and secondary groups. 
     The grouping system using the Bluetooth-based star network according to the present embodiment does not use the direction finding technology of the beacon to enable transmission and reception between the primary instructor terminal  110  and the member terminals in the primary group or the secondary group by loading a large amount of data (e.g., voice signal, etc.) in an advertising packet. 
     First, the primary instructor terminal  110  is set. The primary instructor terminal  110  operates in a standby state. The primary instructor terminal  110  is paired with a plurality of member terminals  120  for configuring the star network based on Bluetooth. The member terminal  120  is paired with the primary instructor terminal  110  in the standby state when a provided button is input. The primary instructor terminal  110  forms a primary group when the plurality of paired member terminals  120  are connected. 
     The primary instructor terminal  110  checks discovery names of the plurality of member terminals  120  to be paired, and allows only terminals having names matching predetermined names among the discovery names to be paired so as to form the primary group. 
     Thereafter, the primary instructor terminal  110  sets one of the members of the primary group as the secondary instructor terminal  210  which is the instructor and the member. The secondary instructor terminal  210  is paired with a plurality of member terminals  120  for configuring a subordinate star network based on Bluetooth. The member terminal  120  is paired with the secondary instructor terminal  210  in the standby state when a provided button is input. The secondary instructor terminal  210  constitutes a secondary group when the plurality of paired member terminals  120  are connected. 
     The secondary instructor terminal  210  checks discovery names of the plurality of member terminals  120  to be paired, and allows only terminals having names matching predetermined names among the discovery names to be paired so as to form the secondary group. 
     When the plurality of member terminals  120  are paired with the primary instructor terminal  110 , if there is a member terminal  120  requiring the paring with the primary instructor terminal  110  even after a predetermined number (e.g., 20) of member terminals  120  have been all paired with the primary instructor terminal  110  in the time order, the primary instructor terminal  110  sets one of the members of the primary group as the secondary instructor terminal  210  which is an instructor and a member. 
     In other words, the member terminal  120  that is located closer to the primary instructor terminal  110  is first paired with the primary instructor terminal  110 , and the member terminal  120  that is located further away from the primary instructor terminal  110  is not paired with the primary instructor terminal  110 . The primary instructor terminal  110  is paired with the member terminals  120  in the order of increasing RSSI or the time order of requesting a connection to form the primary group. 
     Thereafter, if there is a member terminal  120  requesting pairing even after all the plurality of member terminals  120  have been paired by a predetermined number (e.g., 20) in the time order, the primary instructor terminal  110  sets one of the members of the primary group as the secondary instructor terminal  210  which is an instructor and a member. 
     When the member terminal  120  is connected to the primary instructor terminal  110 , the member terminal  120  transmits its own discovery name to the connected primary instructor terminal  110 . 
     After the primary instructor terminal  110  sets one of the members of the primary group as the secondary instructor terminal  210  which is the instructor and the member, the primary instructor terminal  110  receives a report indicating that all the member terminals  120  have been paired by the predetermined number, from the secondary instructor terminal  210 . 
     The primary instructor terminal  110  sets the other one of the members of the primary group as the secondary instructor terminal  220  which is the instructor and the member. The primary instructor terminal  110  checks the discovery names of the plurality of member terminals  120  to be paired. The primary instructor terminal  110  extracts only terminals having names that match predetermined names among the discovery names. 
     The primary instructor terminal  110  additionally checks subnames of the discovery names to group only terminals having the same subnames to be paired so as to form the primary group. Here, the member terminal  120  changes the subnames of the discovery names by adjusting the number of input times of a button provided in a group setting step (e.g., subname A when the button is input 3 times, subname B when the button is input 4 times, and subname C when the button is input 5 times). 
     The secondary instructor terminal  210  checks the discovery names of the plurality of member terminals  120  to be paired. The secondary instructor terminal  210  extracts only terminals having names that match predetermined names among the discovery names. 
     The secondary instructor terminal  210  additionally checks subnames of the discovery names to group only terminals having the same subnames to be paired so as to form the secondary group. Here, the member terminal  120  changes the subnames of the discovery names by adjusting the number of input times of a button provided in a group setting step (e.g., subname A when the button is input 3 times, subname B when the button is input 4 times, and subname C when the button is input 5 times). 
     The primary instructor terminal  110  is connected with a terminal in the primary group. The primary instructor terminal  110  sets a member terminal (member ID S 2 ) and a member terminal (member ID S 20 ) among the terminals in the primary group as the secondary instructor terminals  210  and  220 . 
     In the primary instructor terminal  110 , when there are 20 terminals as the primary group, if a member terminal (member ID S7) breaks away, a disconnection event (GAP Event) occurs in which the connection between the primary instructor terminal  110  and the member terminal (member ID S7) is broken. When the disconnection event occurs, both the primary instructor terminal  110  and the member terminal (member ID S7) recognize that the connection therebetween is broken. 
     When it is recognized that the member terminal (member ID S7) breaks far away from the primary instructor terminal  110 , in both the primary instructor terminal  110  and the member terminal (member ID S7), a message to join the group may be output while an LED flashes. 
     When the member terminal (member ID S7) moves toward the primary instructor terminal  110 , the member terminal (member ID S7) switches to am advertising state from the state in which the disconnection event has occurred. 
     Thereafter, when the member terminal (member ID S7) joins toward the primary instructor terminal  110 , the member terminal (member ID S7) is again connected to the primary group, and the disconnection event is converted into a connection event. 
     When the member terminal (member ID S7) moves within a predetermined distance, the primary instructor terminal  110  generates a connection event to connect the member terminal (member ID S7) to the primary group. 
     When the member terminal (member ID S7) is connected to the primary instructor terminal  110  again, the member terminal (member ID S7) changes the discovery name to indicate a connected S7, and then switches to an advertising state that periodically transmits information necessary for network management. 
     Accordingly, the member terminal (member ID S7) changes the discovery name to be joined in the primary group so as not to be connected to another group. 
     The primary instructor terminal  110  generates a notification warning to the member terminals  120  of which RSSI falls below a predetermined threshold. That is, the primary instructor terminal  110  recognizes that the member of which the RSSI falls below the predetermined threshold is moving away to generate a breakaway prevention message (sound, text, etc.) as an alarm to the member terminal  120 . 
     When a member terminal (member ID S2) among the terminals in the primary group is set as a secondary instructor terminal T 1    210 , the secondary instructor terminal  210  (as the instructor and the member terminal) operates in the same manner as a primary instructor terminal T 0    110  when a connection event and a disconnection event occur in the secondary group. The secondary instructor terminal T 1  operates as a clone concept of the primary instructor terminal T 0    110 . 
     The primary instructor terminal T 0    110  is connected with the management terminal  130  to visually display tags of the member terminals to break away from or be joined in the member group on the management terminal  130 . 
       FIG.  3    is a diagram illustrating a star network topology according to the present embodiment. 
     As illustrated in  FIG.  3   , the primary instructor terminal  110  is a host, and the member terminal  120  is a client, and the primary instructor terminal  110  and the member terminal  120  communicate with each other using an IoT star network. A member of the IoT star network consists of either a host or a client. One host may host approximately 20 clients. The host can serve as a broadcaster and an observer at the same time. 
       FIG.  4    is a diagram illustrating a relationship between an instructor terminal and a member terminal according to the present embodiment. 
     The management terminal  130  sets the first connected terminal as the primary instructor terminal T 0    110 . The management terminal  130  defines a total connection link count N (maximum 64), and then sets the first connected terminal as the primary instructor terminal T 0    110 . The primary instructor terminal  110  transmits an observation message or a broadcasting message to a member terminal group. 
     As illustrated in  FIG.  4   , the primary instructor terminal  110  broadcasts an instructor message to a primary group of clients of 01 to 0C. The primary instructor terminal  110  observes the member messages of the terminals in the primary group. The primary instructor terminal  110  selects up to 12 member terminals of up to a total link count received from the management terminal  130 . 
     A member terminal (member ID No. 40) and a member terminal (member ID No. 50) as one of the terminals in the primary group connected with the primary instructor terminal  110  are set as the secondary instructor terminals  210  and  220 . 
     The additional secondary instructor terminal (member ID No. 40)  220  broadcasts an instructor message to client terminals 41 to 4C and observes the member message. The additional secondary instructor terminal (member ID No. 40)  220  may select an auxiliary client member link count of  01  (member ID No. 41) to 12 (member ID No. 41) in the connecting link order until the total link count is equal to the number defined by the instructor. 
     If the total link count is matched, the instructor sends a message to the primary group and the secondary group to stop the connection of peer members. When a disconnection or long-distance detection event occurs, the primary or secondary groups immediately report the event to the instructor terminal. 
     The star network illustrated in  FIG.  4    may have the same structure as that of a star network of the Internet of Things, and the function of each of nodes may be implemented through wearable devices. 
     For example, nodes serving as a hub, a switch, and a router at a central connection point of the star network include the primary instructor terminal  110 , the secondary instructor terminal  210 , and the additional secondary instructor terminal  220 . 
     The primary instructor terminal  110 , the secondary instructor terminal  210 , and the additional secondary instructor terminal  220  may serve as the hub, the switch, and the router at the central connection point and may operate according to an algorithm corresponding to data when receiving the data from the member terminal  120 . 
     The primary instructor terminal  110  on the star network is paired with the member terminal of the primary group, and determines a distance from the member terminal  120  based on the data transmitted from the paired member terminal. 
     The secondary instructor terminal  210  on the star network is paired with the member terminal of the secondary group, and determines a distance from the member terminal  120  based on the data transmitted from the paired member terminal. 
     The additional secondary instructor terminal  220  on the star network is paired with the member terminal of the secondary group, and determines a distance from the member terminal  120  based on the data transmitted from the paired member terminal. 
     For example, after a teacher creates data using the management terminal  130  at the center, the teacher may transmit the data to its own primary instructor terminal  110  to operate the primary instructor terminal  110 , and at the same time, operate a subordinate secondary instructor terminal  210  and an additional secondary instructor terminal  220  in the same manner, which is connected to the primary instructor terminal  110 . 
     A member terminal in the primary group may transmit data in the form of a message to the primary instructor terminal  110  connected by a short-range wireless communication method. The data may be interpreted as a set of commands for controlling by combining various commands in a time series. 
     The member terminal  120  in the primary group may notify its existence to the primary instructor terminal  110  through an advertising operation within a distance that enables short-range wireless communication with the primary instructor terminal  110 . 
     The primary instructor terminal  110  may transmit data received from the member terminals  120  in the primary group in a broadcasting manner to provide the management terminal  130  with the data. 
     The primary instructor terminal  110  may determine the number of the plurality of member terminals  120  currently in the vicinity through the advertising operation of the plurality of member terminals  120  in the primary group. 
     Thereafter, the plurality of member terminals  120  in the primary group receiving the data may reply a response message to the primary instructor terminal  110 . When the primary instructor terminal  110  broadcasts the data and replies all response messages from the plurality of member terminals  120  in the primary group, the primary instructor terminal  110  may broadcast a specific message in consecutive time slots. 
     The time slots of the primary instructor terminal  110  and the member terminals  120  in the primary group are synchronized in time. The primary instructor terminal  110  instructs a reset of the time slot by transmitting a signal for resetting the time slot, and the member terminal  120  in the primary group during advertising may reset a timer and a phase when receiving the signal for resetting from the primary instructor terminal  110 . 
     The primary instructor terminal  110  is paired with the plurality of member terminals by a predetermined number based on Bluetooth to form a primary group constituting a star network. 
     When there is a terminal which is moving far away from a predetermined threshold or more by exchanging the message between the primary instructor terminal  110  and the member terminals of the primary group and using received signal strength indication (RSSI), a notification is generated to the terminal far away from the predetermined threshold or more and the primary instructor terminal  110 . 
     The primary instructor terminal  110  is paired with the plurality of member terminals to be paired in the order of increasing RSSI or the time order of requesting a connection to form the primary group. 
     The primary instructor terminal  110  checks discovery names of the plurality of member terminals  120  to be paired, and allows only terminals having names matching predetermined names among the discovery names to be paired so as to form the primary group. 
     The primary instructor terminal  110  additionally checks subnames of the discovery names to group only terminals having the same subnames to be paired so as to form the primary group. 
     The primary instructor terminal  110  receives a report indicating that all the member terminals  120  have been paired by the predetermined number, from the secondary instructor terminal  210  and sets the other one of the members of the primary group as the additional secondary instructor terminal  220  which is the instructor and the member. 
     In the secondary instructor terminal  210 , some members of the primary group are paired with a predetermined number of other member terminals based on Bluetooth, which are not paired with the primary instructor terminal among the plurality of member terminals as the instructor and the member to form a secondary group constituting the subordinate star network of the primary group. 
     When there is a terminal which is moving far away from a predetermined threshold or more by exchanging the message between the secondary instructor terminal  210  and the member terminals of the secondary group and using RSSI, a notification is generated to the terminal moving far away from the predetermined threshold or more and the primary instructor terminal  110  that is the leading instructor. 
     The secondary instructor terminal  210  checks discovery names of the plurality of member terminals  120  to be paired, and allows only terminals having names matching predetermined names among the discovery names to be paired so as to form the secondary group. 
     The secondary instructor terminal  210  additionally checks subnames of the discovery names to group only terminals having the same subnames to be paired, so as to form the secondary group. 
       FIG.  5    is a diagram for describing disconnection between an instructor terminal and a member terminal according to the present embodiment. 
     The primary instructor terminal  110  or the secondary instructor terminal  210  generates a disconnection event (GAP Event) when there is a breakaway terminal which is moving far away from a threshold distance or more among the member terminals of the primary group or the secondary group. 
     When the breakaway terminal enters within the threshold distance, the primary instructor terminal  110  or the secondary instructor terminal  210  switches the disconnection event to a connection event after connecting the breakaway terminal to the primary group or the secondary group. When the breakaway terminal is connected to the primary group or the secondary group, the breakaway terminal changes the discovery name to indicate whether a connection exists, and then switches to an advertising state. 
     In a star network topology illustrated in  FIG.  5   , when a link is broken when a plurality of clients are connected to one host, the host immediately recognizes the disconnection of each client. 
     When member 02 sends a lock message to client 02 (member ID 02) by pressing a button, client 02 (member ID 02) transmits a lock message to the primary instructor terminal  110 . 
     The secondary instructor terminal  210  (member ID No. 30) reports to the primary instructor terminal  110  the fact that the link with 3C of the member group is broken. The secondary instructor terminal  210  (member ID No. 30) simultaneously broadcasts a message to terminals in all member groups or observes a client message. 
     When the RSSI of a member terminal (member ID No. 33) connected with the secondary instructor terminal  210  (member ID No. 30) is lower than −90 dBm, the secondary instructor terminal  210  (member ID No. 30) notifies the member terminal (member ID No. 33) of the fact that the signal intensity is lowered. 
     The above description just illustrates the technical spirit of the present invention and various changes and modifications can be made by those skilled in the art to which the present invention pertains without departing from an essential characteristic of the present invention. Accordingly, the various embodiments disclosed in the present invention are not intended to limit the technical spirit but describe the present invention and the technical spirit of the present invention is not limited by the following embodiments. The protection scope of the embodiment should be interpreted by the appended claims and all technical spirit in the equivalent range thereto should be interpreted to be embraced by the claims of the embodiment.