KR20070047136A - Wireless access point and call manager - Google Patents

Abstract

The present invention relates to an enterprise type one phone system, the system comprising:

The identification information of the one-phone terminal obtained from the inquiry and the received electric field strength level of the terminal are transmitted to the external device through the IP network, and roaming or handover is made by connecting the one-phone terminal designated by the external device to the serial port profile (SPP). Wireless access points for transmitting an associated message;

As the external device, receiving field strength (RSSI) information of one-phone terminals is collected from the wireless access points, and a roaming or handover time, a target terminal and an access point are determined based on the collected RSSI information. Roaming processing module for requesting the transfer to the corresponding one-phone terminal and a dynamic number management module for dynamically managing the VoIP number assigned to the terminals automatically connected to each access point by the determination of the roaming processing module Manager; characterized in that it comprises at least.

One phone, handover, roaming.

Description

WIRELESS ACCESS POINT AND CALL MANAGER}

1 is an exemplary system configuration for explaining the problems of roaming and handover in a general one-phone system.

Figure 2 is an exemplary configuration of a corporate one-phone system according to an embodiment of the present invention.

3 is a diagram illustrating a process of searching for and registering a terminal in a zone managed by an access point in an enterprise type one phone system according to an exemplary embodiment of the present invention.

4 is a view for explaining the process of the one-phone terminal is automatically connected to the access point (AP) in the enterprise-type one-phone system according to an embodiment of the present invention.

5 is a view for explaining a roaming service method in an enterprise-type one-phone system according to an embodiment of the present invention.

6 is a diagram illustrating a handover service method in an enterprise type one phone system according to an embodiment of the present invention.

The present invention relates to a OnePhone system, and more particularly, to an enterprise type onephone system and a wireless access point and call manager for constructing the system.

Onephone is a phone terminal that can be used as a wired telephone terminal and a mobile telephone terminal depending on time and place by having the functions of a landline telephone and a mobile telephone at the same time. The one-phone is a terminal adopting a cordless telephone profile (CTP), and the CTP is a profile for creating a wireless telephone system using Bluetooth.

On the other hand, the one-phone service refers to a wired / wireless integrated service that allows one-phone to receive telephone service through a PSTN as a landline telephone number in a designated zone and a mobile telephone number when outdoors. Since the one-phone service system is the same as the wireless telephone system, the terminal may be connected and used only to a specific access point (AP). When the distance is far from the AP, the connection is terminated and the call is terminated at the same time.

In order to compensate for these disadvantages, as shown in FIG. 1, there are techniques for securing mobility of one-phone terminals (also called CTP terminals) by installing several APs. As such, when using multiple APs, an important consideration is roaming and handover.

In a typical one-phone service system, a number is assigned to an access point (AP), not a terminal, and the call is made using a different number (AP number) according to the AP location of the one-phone terminal. Therefore, it does not matter in the case of outgoing calls, but in the case of incoming calls, there is a problem of which number should be called.

This problem in roaming can be easily solved by assigning a number to the one-phone terminal, registering the VoIP terminal with the corresponding number by recognizing the terminal in the access point (AP). For example, if the number of the one-phone terminal is set to 30003 and the terminal is connected to an access point A, the access point A registers the AP as 30003 in the call management server. If the terminal is connected to the access point B again, the access point A may release the number from the call management server and register and use the number 30003 again in the access point B to solve the above problem in roaming.

However, if the number is assigned to the one-phone terminal as described above, the handover cannot be applied. The reason is that the handover is made through the VoIP call transfer between access points. Since there is a number in the one-phone terminal, the call is made using 30003 in access point A and 30003 in access point B. As a result, VoIP call switching cannot be applied, and thus, handsets cannot be transferred because the calls of the access point A and the one-phone terminal cannot be transferred to the access point B.

Therefore, there is a need for a new technology that can normally roam and handover even in a one-phone service system.

Accordingly, an object of the present invention is to provide an enterprise-type one-phone system as a one-phone system capable of making a call without restriction on the positional movement of the one-phone terminal, terminals and call managers for constructing the system.

Furthermore, in order to solve the problem of roaming and handover that are not supported by standard Bluetooth, wireless access point terminals and calls that can be normally roamed and handed over in a one-phone system including a plurality of access points (APs). To provide managers and enterprise one phone systems that include them.

Wireless access point terminal according to an embodiment of the present invention for achieving the above object is basically an access point having a Bluetooth module and a Bluetooth CTP profile,

A serial port profile (SPP) for forming a channel for exchanging roaming or handover related messages with the one-phone terminal;

A received field strength detector for detecting a received field strength from radio frequency signals transmitted from nearby one phone terminals;

The identification information of the one-phone terminal obtained as a result of inquiry and the received electric field strength level of the terminal are transmitted to the call manager, and a channel is established with the one-phone terminal designated by the call manager through the serial port profile to send a roaming or handover related message. And a control unit for controlling the transmission.

The call manager according to another embodiment of the present invention is a call manager accessible through an IP network and access points capable of Bluetooth communication with a one-phone terminal,

A terminal information registration module for registering and managing the identification information, the VoIP number, and the registration request information of the terminals input through the manager interface in an internal DB;

A proxy module for performing all call processing related to incoming / outgoing / call forwarding;

Collects received field strength (RSSI) information of one-phone terminals from the access points, determines the time of roaming or handover, the target terminal and the access point based on the collected RSSI information, and transmits the information to the corresponding one-phone terminal. A roaming processing module;

And a dynamic number management module for dynamically managing VoIP numbers of terminals automatically connected to each access point by the determination of the roaming processing module.

Furthermore, the enterprise one-phone system according to another embodiment of the present invention,

The identification information of the one-phone terminal obtained from the inquiry and the received electric field strength level of the terminal are transmitted to the external device through the IP network, and roaming or handover is made by connecting the one-phone terminal designated by the external device to the serial port profile (SPP). Bluetooth access points for transmitting an associated message;

As the external device, receiving field strength (RSSI) information of one-phone terminals is collected from the Bluetooth access points, and a roaming or handover time, a target terminal and an access point are determined based on the collected RSSI information. Roaming processing module for requesting the transfer to the corresponding one-phone terminal and a dynamic number management module for dynamically managing the VoIP number assigned to the terminals automatically connected to each access point by the determination of the roaming processing module Manager;

In some cases, the SPP may be connected to the Bluetooth access point to receive roaming or handover related messages, and the one-phone terminals requesting CTP & SPP connection to the Bluetooth access point included in the received message may be further included.

According to the embodiments of the present invention as described above, in addition to the number used in the VoIP system, a virtual VoIP number is dynamically assigned to the one-phone terminal, while roaming between the one-phone terminal and the AP using a separate SPP channel. By transmitting the handover message, the roaming and handover service can be normally provided to the one-phone terminal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, a detailed description of related known functions or configurations will be omitted.

2 is a block diagram of a corporate one-phone system according to an embodiment of the present invention, wherein the corporate one-phone system performs a plurality of Bluetooth access accesses performing short-range communication with one-phone terminals 200 located in a zone. Points (AP1, AP2, ..) (100, 110), and each of the access points (100, 110) includes a call manager (Call Manager) 400 and the IP phone 300 connected to the call management through the IP network .

2, the one-phone terminal (also referred to as CTP terminal 200) according to an embodiment of the present invention is configured to add a SPP (Serial Port Profile) to the configuration of a general one-phone terminal that satisfies the standard Bluetooth standard and Bluetooth CTP profile Has For reference, the SPP is a channel that must be maintained for automatic access or for transmitting and receiving additional information between the terminal and the access point.

That is, the one-phone terminal 200 according to the embodiment of the present invention exchanges information with the access point (AP) through an additional SPP connection while maintaining a CTP connection with the access point (AP) to be described later. When the one-phone terminal 200 receives a roaming command from the access point (AP) through the SPP connection, it immediately terminates the current connection and attempts to connect with the access point (AP) of the provided information. In addition, when a handover command is received from an access point (AP), it immediately terminates the current connection, connects to the access point (AP) of information provided, and opens up the SCO channel so that the call can be maintained on the user side. In order to prevent a phone disconnection during handover, the one-phone terminal 200 preferably uses a scatternet.

 Meanwhile, the Bluetooth access points (APs) 100 and 110 are Bluetooth LAN access points and VoIP access points, and provide a LAN access service and a wireless VoIP service to the Bluetooth-based one-phone terminals 200 using a cordless telephony profile. It serves to provide. Such a Bluetooth access point basically has a configuration that satisfies the standard Bluetooth standard and the Bluetooth CTP profile. For reference, the Bluetooth access point according to the embodiment of the present invention has a basic configuration of the "premises switched network access point" already filed in 2001 by the applicant of the present application. In detail, an access point (AP) according to an embodiment of the present invention includes a Bluetooth module for wirelessly transmitting and receiving voice data at least with a one-phone terminal 200 equipped with a Bluetooth module, and a plurality of application programs operating on a real-time operating system. A control unit for controlling the overall operation of the access point, and a digital signal processing unit for compressing and outputting the voice data transmitted through the Bluetooth module according to the Internet phone standard or restoring the compressed data transmitted to the Bluetooth module. A memory unit for storing the control program data and the data generated during the system control operation, respectively; Ethernet controller for generating or receiving an Ethernet signal to be able to transmit and receive data connected to the IP-based network.

In addition to the basic configuration, the access point (AP) 100 and 110 according to an embodiment of the present invention may include a serial port profile (SPP) for forming a channel for exchanging roaming or handover related messages with the one-phone terminal 200. And a receiving field strength (RSSI) detector for detecting the received field strength from the radio frequency signal received through the Bluetooth module and outputting the received field strength to the controller. The received field strength detector may be implemented as a software module.

For reference, when the operation of the controller for controlling the overall operation of the Bluetooth access point is described in detail, the controller basically requests registration of its information (VoIP number) to the call manager 400 at boot time. Furthermore, the Bluetooth access point (AP) 100 and 110 periodically perform an inquiry procedure to transmit the collected information (MAC address) and RSSI information to the call manager 400 which will be described later, and the call manager ( Attempt to connect to the terminal 200 designated by the 400 through the SPP. In addition, the terminal 200 performs a role of exchanging roaming or other information using the SPP connection.

The above-described Bluetooth access point (AP) (100, 110) implements the CTP-VoIP gateway function for roaming and handover implementation proposed by the present invention. Since the CTP-VoIP gateway function means that it should perform VoIP terminal function by itself, the access point (AP) 100, 110 basically uses G.711 A-Law u-Law, G.729, and G.723.1 VoIP. It supports voice codec and related signal processing functions.

The call manager 400, which can be connected to a plurality of Bluetooth access points (APs) 100, 110,. Over an IP network, manages the entire enterprise type one phone system. The call manager 400 basically includes a SIP (Session Initiation Protocol) proxy module, a terminal information registration module, a roaming processing module, and a dynamic number management module.

The SIP proxy module performs all SIP call processing related to incoming and outgoing calls and call transfers. It is also responsible for assigning and managing VoIP numbers.

The terminal information registration module registers and manages information (MAC address and VoIP number) of terminals (VoIP phone, VoIP gateway, CTP phone) input through the manager interface in an internal DB.

The roaming processing module collects the RSSI information of the one-phone terminals 200 from the Bluetooth access points, and considers the collected RSSI and the number of terminals connected to the access point AP. And determine the target terminal and the access point and deliver the information to the terminal.

Finally, the dynamic number management module dynamically manages VoIP numbers of terminals automatically connected, roaming and handed over by the determination of the roaming processing module.

For reference, the IP phone 300 may also play a role of replacing a landline in a PBX environment.

Hereinafter, roaming and handover operations in the enterprise-type one-phone system based on the above-described configuration will be described in detail.

▶ Terminal Pre-registration and Authentication

First, the manager assigns VoIP numbers to VoIP terminals (VoIP phones, access points) and one-phone (CTP terminals) terminals 200 and registers each number in the internal DB of the call manager 400. That is, the terminal information registration module in the call manager 400 registers and manages information (MAC address and VoIP number) of terminals (VoIP phone, VoIP gateway, CTP phone) input through the manager interface unit in the internal DB. Information of the terminals registered in the internal DB can be illustrated as Table 1 below.

MAC ADDREESS TYPE Phone Number # 1 Phone Number # 1 Phone Number # 1 00: 07: 88: 10: 12: 11 2ch gateway 1000 1001 00: 07: 88: 16: 11: 34 Phone 2000 00: 07: 88: 54: 23: A3 AP 9001001 9001002 9001003 00: 07: 88: 80: 84: E3 CTP TL 3000 00: 07: 88: 11: 22: 33 CTP TL 3001

As shown in the above table, a terminal without a VoIP number is an unauthenticated terminal and cannot be used in the system.

▶ AP Location Registration

Each of the APs 100 and 110 connected to the IP network of the enterprise type one phone system transmits a REGISTER command to the call manager 400 so that its location (information) is changed to the call manager 400. ) Registered in internal DB.

▶ Search for devices in AP zone

First, each of the Bluetooth access points (APs) 100 and 110 registered in the call manager 400 searches for Bluetooth-enabled terminals by propagating an Inquiry message as shown in FIG. 3 and is transmitted from each terminal. The RSSI level of the signal is measured and the result (BdAddr, RSSI) is transmitted to the call manager 400.

For reference, in FIG. 3, the virtual VoIP number assigned to the one-phone terminal 200 is 3001, the MAC address of the terminal is 00: 07: 88: 11: 22: 33, and the VoIP number of the access point AP1 is 1017. It is shown. As shown in FIG. 3, when each access point retrieves information of one-phone terminals in a zone and delivers the information to the call manager 400, the call manager 400 registers the received information in an internal DB. For example, the terminal search information registered as described above may be as shown in Table 2 below.

TL AP RSSI 00: 07: 08: 88: 11: 22: 33 AP1 (1017) 33 00: 07: 08: 88: 11: 22: 33 AP2 (1018) 2 00: 07: 08: 88: 11: 22: 33 APn (1203) -65

As described above, the call manager 400 determines roaming using the terminal search information collected through the AP. The conditions of roaming may be determined through experimentation during the development process.

▶ Automatic connection of terminal in AP zone

As described above, when a terminal in the AP zone is searched, the call manager 400 causes the access point having the largest RSSI level between the one-phone terminal 200 and the AP to refer to the terminal search information registered in the internal DB. Command to connect with terminal. That is, as shown in FIG. 4, the connection message (Connect TL) containing the identification information (BdAddr) of the one-phone terminal is transferred to the access point AP1 100 to instruct the one-phone terminal 200 to connect. Then, the access point (AP1) 100 transmits an SPP Connect Request message to the connected one-phone terminal 200, and the one-phone terminal 200 having received the SPP connection request message responds thereto. The SPP connection response message (Accept SPP Connection Req) is transmitted to the access point 100 side. When the one-phone terminal 200 requesting the connection transmits a CTP connection request message to the access point 100 and requests a CTP connection, the access point 100 responds to the CTP connection response message (Accept CTP Connection). Req) is returned to the one-phone terminal 200 side. According to such a procedure, the CTP connection is made between the one-phone terminal 200 and the access point 100. As a result, the one-phone terminal 200 is automatically connected to the enterprise-type one-phone system.

When the CTP connection is made with the one-phone terminal 200, the corresponding access point 100 transmits a register message including identification information BdAddr of the CTP-connected terminal and its VoIP number to the call manager 400. . Then, the dynamic number management module in the call manager 400 registers and manages the virtual VoIP number assigned to the one-phone terminal 200 automatically connected to the access point 100 to the access point. In this case, the internal DB data can be seen to be dynamically updated as shown in Table 3 below.

End Point IP VoIP CTP number 192.168.10.9 1017 (AP1) 3001 192.168.10.73 1018 (AP2) 192.168.10.127 1203 (APn)

Hereinafter, a roaming method in an enterprise one-phone system according to an embodiment of the present invention will be described with reference to FIG. 5.

▶ Roaming Service Method

Referring to FIG. 4, first, it may be assumed that the one-phone terminal 200 is connected to the access point AP1 100 through the terminal searching process in the AP zone and the automatic connection process of the terminal in the AP zone. In this case, the access point AP1 100 transmits a register message indicating that the access point AP1 is connected to the one-phone terminal 200 to the call manager 400 (S2), so that the internal DB of the call manager 400 is automatically transmitted to the access point AP1 100. Information of the connected one-phone terminal 200 is registered (S3).

In this state, if the one-phone terminal 200 moves (S4) to the zone in which the access point AP2 110 is located by the user movement, the call manager 400 collects the terminals from the access points 100 and 110. It is determined whether the one-phone terminal 200 should receive a roaming service by using the RSSI information of these.

When it is determined that the one-phone terminal 200 needs to receive the roaming service, the call manager 400 sends the roaming request message containing the connection information (Target GW's BDADDR) of the destination access point through the access point AP1 (100). Transfer to the (200) side (S5, S6). The roaming request message is transmitted from the access point AP1 100 to the one phone terminal 200 through the SPP channel.

Meanwhile, the one-phone terminal 200 receiving the roaming request message releases the connection (CTP & SPP Link Disconnected) (S7) with the access point AP1 110 currently being accessed. In addition, the CTP & SPP connection request message (CTP & SPP Link Request) containing the newly received access point connection information is transmitted (S8) and attempts to connect to the access point AP2 (110). In addition, the access point AP2 110 transmits (S9) the CTP & SPP connection response message in response to the CTP & SPP connection request message to the one phone terminal 200, thereby providing the one phone terminal 200 and the access point AP2 110. ) Is automatically connected.

When the CTP & SPP connection is made with the one-phone terminal 200, the access point AP2 110 sends a call manager (Register) message containing the identification information (BdAddr) and its own VoIP number of the CTP & SPP-connected terminal. 400) (S11). Then, the dynamic number management module in the call manager 400 updates the internal DB by registering a virtual VoIP number assigned to the one-phone terminal 200 automatically connected to the access point AP2 110 to the corresponding access point (S12). The series of roaming procedures is terminated by sending a 200 OK message.

▶ Handover Service Method

Unlike the roaming service, the handover service is best connected to a user's one-phone (CTP) terminal through Bluetooth communication, and the user does not terminate the connected call when the user moves through the location using the connected one-phone terminal. A service that automatically connects to an access point capable of making a call service so that a call can be continued. Hereinafter, a handover service method according to an embodiment of the present invention will be described in detail with reference to FIG. 6.

First, the one-phone terminal 200 is connected to the access point AP1 100 through the terminal discovery process in the AP zone and the automatic connection process of the terminal in the AP zone, as shown in FIG. 6 to the call of the VoIP phone 2088 user. It can be assumed that the VoIP call is made between the one-phone terminal 200 and the VoIP phone.

As the user of the one-phone terminal 200 moves to the zone where the access point AP2 110 is located, the call manager 400 uses the one-phone terminal (RSI) information of the terminals collected from each of the access points 100 and 110. 200 determines whether to receive the handover service.

If it is determined that the one-phone terminal 200 needs to receive the handover service, the call manager 400 transmits a handover request message containing the connection information (Target GW's BDADDR) of the destination access point to the access point AP1 (100). Transfer to the one-phone terminal 200 through). The handover request message is transmitted from the access point AP1 100 to the one phone terminal 200 through the SPP channel.

Meanwhile, the one-phone terminal 200 receiving the handover request message requests a disconnection of the SPP channel to the access point AP1 (110) currently connected (SPP). If there is a response (SPP: Disconnect Ack), the newly transmitted access point AP2 (110) requests the connection of the SPP channel and the CTP channel (SPP: Connect request) to connect the access point AP2 (110) and the SPP & CTP channel. Form. When the SPP & CTP channel is formed between the one-phone terminal 200 and the access point AP2 110, the two parties later transmit messages (SETUP, ALERTING) to establish an SCO link through the CTP channel.

In order to minimize the disconnection time during handover, the one-phone terminal 200 and the access points 100 and 110 according to an embodiment of the present invention are preferably configured to establish a scatternet. Experimental results show that in case of applying scatternet, it takes about 400ms to connect the next access point and CTP after the end of CTP, and about 1 second when scatternet is not applied. Therefore, in order to minimize the disconnection time during handover, applying a scatternet is a preferable method.

When using the scatternet as described above, messages (DISCONNECT, RELEASE) for SCO Link Disconnected are transmitted between the one-phone terminal 200 and the access point AP1 100, and as a result, the one-phone terminal 200 The CTP ACL Link of the access point AP1 100 currently connected with the CTP ACL Link Disconnected.

As described above, between the access points 100 and 110 for supporting the handover and the VoIP phone 2088 as the call counterpart during the process of disconnecting and forming the link between the one-phone terminal 200 and the access points 100 and 110 as follows. The same call transfer procedure is followed.

First, the access point AP1 100, which is in the connected state with the one-phone terminal 200, transmits a SIP INVITE message to the VoIP phone 2088, which is a call counterpart, and requests a call holding. In response to the request, the VoIP phone 2088 transmits a response message 200 OK to the access point AP1 100, and the access point AP1 100 transmits a SIP REFER message back to the VoIP phone 2088 for access. A request is made to establish a new call with point AP2 110.

The VoIP phone 2088 receiving the new call setup request then sends a SIP INVITE message to the access point AP2 110 to request a new call setup. In response to the call setup request, when the access point AP2 110 transmits a response message 200 OK to the VoIP phone 2088, the VoIP phone 2088 indicates that the new call setup is completed to the access point AP1 100. Send SIP NOTIFY message. Accordingly, the access point AP1 100 transmits a SIP BYE message for terminating a previous call to the VoIP phone 2088, so that the call between the access point AP1 100 and the VoIP phone 2088 is changed to the access point AP2 110. And a call between the VoIP phone 2088 is switched.

Accordingly, a user using the one-phone terminal 200 connected to the access point AP2 110 and the CTP and SPP channels can perform a seamless phone call with the user of the VoIP phone 2088 through the access point AP2.

As described above, the present invention dynamically manages by assigning a virtual VoIP number to the one-phone terminal in addition to the number used in the VoIP system, and transmits a roaming and handover message between the one-phone terminal and the AP using a separate SPP channel. By zooming, roaming and handover services can be normally provided to one-phone terminals (CTP terminals).

In addition, by allowing one-phone terminals and access points to establish a scatternet, it is also possible to minimize the disconnection time during handover.

On the other hand, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. For example, the embodiment of the present invention assumes terminals equipped with a Bluetooth module, but the present invention may also be implemented in terminals equipped with a short range wireless communication module such as a Zigbee module. Therefore, the true technical protection scope of the present invention should be defined only by the appended claims.

Claims (8)

In the one-phone terminal equipped with a short-range wireless communication module and an access point terminal having a CTP profile and a wireless communication module for performing wireless transmission and reception of voice data, A serial port profile (SPP) for forming a channel for exchanging roaming or handover related messages with the one-phone terminal; A received field strength detector for detecting a received field strength from radio frequency signals transmitted from nearby one phone terminals; The identification information of the one-phone terminal obtained as a result of inquiry and the received electric field strength level of the terminal are transmitted to the call manager, and a channel is established with the one-phone terminal designated by the call manager through the serial port profile to send a roaming or handover related message. And a control unit for controlling the transmission. The method of claim 1, wherein when the CTP & SPP connection request message is received from neighboring one-phone terminals, the controller controls the CTP & SPP connection with the corresponding one-phone terminal and transmits and controls the register message containing the identification information of the one-phone terminal to the call manager. Wireless access point terminal, characterized in that. The method according to claim 1 or 2, when the CTP & SPP connection request message is received from the peripheral one-phone terminal, the control unit controls the SPP & CTP connection with the corresponding one-phone terminal and in response to receiving the setup message and the call channel with the corresponding one-phone terminal (SCO link) is controlled to form a wireless access point terminal. The method of claim 1 or 2, wherein when the SPP disconnect request message is received from the one-phone terminal having the call channel, the controller transmits a call holding request message to the call counterpart terminal and requests to establish a new call with another access point terminal. Wireless access point terminal, characterized in that. In a call manager accessible via an IP network and access points capable of short-range wireless communication with a one-phone terminal, A terminal information registration module for registering and managing the identification information, the VoIP number, and the registration request information of the terminals input through the manager interface in an internal DB; A proxy module for performing all call processing related to incoming / outgoing / call forwarding; Collects received field strength (RSSI) information of one-phone terminals from the access points, determines the time of roaming or handover, the target terminal and the access point based on the collected RSSI information, and transmits the information to the corresponding one-phone terminal. A roaming processing module; And a dynamic number management module for dynamically managing VoIP numbers of terminals automatically connected to each access point by the determination of the roaming processing module. In the enterprise one phone system, The identification information of the one-phone terminal obtained from the inquiry and the received electric field strength level of the terminal are transmitted to the external device through the IP network, and roaming or handover is made by connecting the one-phone terminal designated by the external device to the serial port profile (SPP). Wireless access points for transmitting an associated message; As the external device, receiving field strength (RSSI) information of one-phone terminals is collected from the wireless access points, and a roaming or handover time, a target terminal and an access point are determined based on the collected RSSI information. Roaming processing module for requesting the transfer to the corresponding one-phone terminal and a dynamic number management module for dynamically managing the VoIP number assigned to the terminals automatically connected to each access point by the determination of the roaming processing module Manager; corporate one-phone system comprising at least. The mobile terminal of claim 6, further comprising: one-phone terminals for receiving a roaming or handover message by SPP connection with the wireless access point and requesting a CTP & SPP connection with the wireless access point included in the received message. Enterprise One Phone System. The method of claim 6 or 7, wherein the wireless access point is a Bluetooth access point terminal having a CTP profile, A serial port profile (SPP) for forming a channel for exchanging roaming or handover related messages with the one-phone terminal; A received field strength detector for detecting a received field strength from radio frequency signals transmitted from nearby one phone terminals; The identification information of the one-phone terminal obtained as a result of inquiry and the received electric field strength level of the terminal are transmitted to the call manager, and a channel is established with the one-phone terminal designated by the call manager through the serial port profile to send a roaming or handover related message. And a control unit for controlling the transmission.

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