A method of supporting a hand-off decision for mobility service of dual mode terminal

A method of supporting a hand-off decision for mobility service of dual mode terminal

1 is a network construction diagram to which the present invention is applied;

2 is a flowchart illustrating a procedure for transmitting neighbor cell information in a control station of an asynchronous system during handoff according to an embodiment of the present invention;

3 is a flowchart illustrating a procedure for transmitting neighbor cell information in a control station of a synchronous system during handoff according to an embodiment of the present invention.

Explanation of symbols for the main parts of the drawing

10, 12: mobile terminal

<background-art><p>The present invention relates to a handoff determination support method for supporting mobility of a dual-mode terminal, and more particularly, provides a mobility service for a dual-mode terminal moving in an area in which a synchronous system and an asynchronous system are simultaneously serviced It relates to a handoff decision support method for</p><p>Due to the development of mobile communication technology and the evolution of communication networks, development and standardization of various types of mobile communication systems are in progress.</p><p>The mobile phone system, which has been developed centering on mobile phones, is now divided into the IS-95-based synchronous system led by the United States and the asynchronous GSM system developed by ETSI. It occupies more than 80%.</p><p>Currently, IMT-2000, a third-generation mobile communication system that is being standardized, is establishing a system design and frequency plan to support national roaming.</p><p>However, due to the interests of each country, it was impossible to establish a unified standard and system, and it was divided into the W-CDMA system led by Europe and Japan and the IS-2000 system led by the United States, development is in progress.</p><p>In Korea, the existing 2G mobile phone system adopts a synchronous method to provide services, and the commercialization of the CDMA 2000 system, which is an initial IMT-2000 system, is being promoted.</p><p>However, the future 3G system is highly likely to be adopted as an asynchronous W-CDMA system, and service providers are continuing efforts to introduce the W-CDMA system, and the domestic 3G system's mobile communication environment is Synchronous and asynchronous systems will coexist.</p><p>When the current 2nd generation mobile communication operators are determined as 3rd generation mobile communication operators, the handoff problem for mobility support between the asynchronous type system and the synchronous type system is raised.</p><p>Currently, a synchronous type mobile communication system and an asynchronous type mobile communication system have different types of channel structures and service capabilities. In the case of handoff, there is a method that can selectively accommodate the handoff according to the service capability of the terminal. necessary. Most of the conventional handoff studies mainly focus on the method of acquiring system synchronization necessary for handoff from an asynchronous system to a synchronous system, and little consideration is given to user data or service capability. have.</p><p>In other words, when most 2G mobile communication service providers are selected as 3G mobile communication service providers, it is very important to provide a handoff, particularly in terms of reduction of initial investment cost and recycling of pre-installed systems. The synchronous type mobile communication system and the asynchronous type mobile communication system operate according to different protocol structures and procedures. Therefore, in order to support smooth handoff, a method for determining handoff without affecting these procedures should be proposed.</p><p>The introduction of the asynchronous IMT-2000 system in the domestic communication environment in which the second generation system adopts the synchronous method has several problems in the efficient provision of services.</p><p>First, in order to introduce an asynchronous system, it is necessary to build a new mobile communication network that is different from the existing system. For this, a large initial investment cost and installation period are required.</p><p>In addition, a solution is required on how to utilize these two systems in a situation where the existing 2nd generation system and 3rd generation system coexist. The most commonly considered method is to build an asynchronous 3G mobile communication system from an area with a high service demand, and gradually expand these service areas. By doing this, the existing 2nd generation system is utilized as a replacement system outside the service area of the 3rd generation system.</p><p>However, for this, a method for supporting handoff for these two systems using different communication methods and protocols should be proposed. Major studies related to this are mainly focused on a method for acquiring system synchronization when handoff is performed from the asynchronous type 3G system service area to the synchronous type 2G system service area.</p><p>However, even if the synchronization problem is solved, the protocol inconsistency problem raised on the service protocol must be solved.</p></background-art><tech><p>The present invention has been devised in view of the above-described conventional circumstances, and in order to provide a mobility service between a synchronous system and an asynchronous system, the handoff is determined based on the service capability of the terminal and the state information of the system. An object of the present invention is to provide a method for supporting a handoff decision for supporting mobility of a dual-mode terminal, which is performed smoothly.</p></tech>

<p>In order to achieve the above object, a method for supporting handoff determination for mobility support of a dual-mode terminal according to a preferred embodiment of the present invention is provided in a network in which a service area of a synchronous system and a service area of an asynchronous system are mixed. A method for supporting handoff determination according to movement of a dual-mode terminal capable of supporting both the synchronous system and the asynchronous system, the method comprising:</p><p>a first step of simultaneously transmitting service capability information of dual-mode terminals in the synchronous system and the asynchronous system to the network regardless of a system corresponding to a current service area; and a second step of selectively transmitting, to the dual-mode terminal, optimal neighbor cell information according to the movement of the dual-mode terminal, based on the service capability information of the dual-mode terminal in the network.</p><p>In addition, the method for supporting handoff determination for mobility support of a dual-mode terminal according to another embodiment of the present invention includes the synchronous system and the asynchronous system in a network in which a service area of a synchronous system and a service area of an asynchronous system are mixed. A method for supporting handoff determination according to movement of a dual-mode terminal capable of supporting all asynchronous systems, the method comprising:</p><p>a first step of simultaneously transmitting service capability information of dual-mode terminals in the synchronous system and the asynchronous system to the network regardless of a system corresponding to a current service area; When the dual-mode terminal operates in the service area of the synchronous system, the control station built in the synchronous system determines whether the asynchronous system is supported based on the service capability information from the dual-mode terminal and supports the asynchronous system. a second process of transmitting neighbor cell information of an asynchronous system to the dual-mode terminal; and if the dual-mode terminal operates in the service area of the asynchronous system, the control station built in the asynchronous system determines whether to support the synchronous system based on service capability information from the dual-mode terminal and supports it. and a third step of transmitting the neighbor cell information of the synchronous system to the dual-mode terminal.</p><p>Hereinafter, a method for supporting a handoff decision for supporting mobility of a dual-mode terminal according to an embodiment of the present invention will be described with reference to the accompanying drawings.</p><p>1 is a network construction diagram to which the present invention is applied, wherein the mobile terminals 10 and 12 may be dual-mode terminals capable of supporting both a synchronous system and an asynchronous system, or a terminal dedicated to a third-generation asynchronous system or a second-generation terminal. It may be a terminal dedicated to a synchronous system.</p><p>When the mobile terminals 10 and 12 are terminals capable of supporting both a synchronous system and an asynchronous system, each of the synchronous system and the asynchronous system independently has a protocol stack and supports one air interface at a time It becomes a dual-mode terminal. That is, the asynchronous service is provided within the service area of the asynchronous system (3rd generation mobile communication system), and the synchronous service is provided within the service area of the synchronous system (2nd generation mobile communication system).</p><p>As shown in FIG. 1, the asynchronous system will be rescued step by step to form a service area, and the service area in the existing synchronous mobile communication system (2nd generation mobile communication system) will include it.</p><p>In the network form as described above, in the case of the mobile terminal 10, since it is currently located in cell B of the 3rd generation system, the asynchronous IMT-2000 system is selected in the system selection process, and the appropriate protocol is driven. In the case of the mobile terminal 12, since it is currently located in cell E of the 2nd generation system, the 2nd generation synchronization system is selected in the system selection process, and a corresponding protocol is driven.</p><p>When the mobile terminal 10 moves in the direction of the arrow, the service area is changed from the 3rd generation asynchronous IMT-2000 system to the synchronous system. In this case, intersystem handoff occurs from the asynchronous system to the synchronous system. will do</p><p>For handoff, the mobile terminal 10 needs to inform the mobile terminal 10 of neighboring cell information on the neighboring second-generation system from the third-generation control station, and the standard of the current asynchronous system defines this in a system information message. Similarly, in the case of the mobile terminal 12, information on neighboring cells in the 3rd generation system is received from the 2nd generation control station.</p><p>For handoff between systems, power measurement is performed based on information on these adjacent cells, and a handoff cell is determined through this, and then the handoff is performed. However, in such a system environment, several types of mobile terminals may exist, and accordingly, it is determined whether handoff is possible. That is, when the mobile terminal 12 is a dedicated terminal capable of supporting only the 2G synchronization system, the 2nd generation control station only performs inter-cell handoff for cell F of the 2nd generation synchronization system, not the intersystem handoff. carry out In addition, when the mobile terminal 10 is a terminal dedicated to the 3rd generation asynchronous IMT-2000 system, there is no need to perform intersystem handoff of the 2nd generation synchronous system to Cell A. In order to support this, the network needs to know the service capability information of the mobile terminal before handoff. When the network can know the service capability information of the mobile terminal, it selectively transmits information on neighboring cells, thereby reducing the signal load on the system and preventing unnecessary handoff attempts.</p><p>A method of transmitting service capability information of a mobile terminal to a network is different between a synchronous 2G system and an asynchronous 3G system. That is, in the synchronous 2G system, the protocol revision number (MS_P_REV) is included in the outgoing message to notify the network of the overall support capability of the mobile terminal, and the provided service is adjusted through the service option negotiation procedure.</p><p>On the contrary, in the 3rd generation asynchronous IMT-2000 system, the mobile terminal notifies the network of the range of the service it can provide through a service capability message. Therefore, for a smooth handoff, the mobile terminal must be able to simultaneously transmit these two pieces of information. To this end, when the dual-mode terminal operates in the synchronous 2G system area, the service capability information of the terminal for the case of operating in the 3G asynchronous system with respect to a message including information related to the service capability of the terminal together with the outgoing message contains fields. Similarly, even when the dual-mode terminal operates in the service area of the asynchronous system, protocol revision number information necessary for operation in the synchronous system is included in the service capability message of the terminal.</p><p>2 and 3 are flowcharts showing a procedure for transmitting neighbor cell information to perform handoff based on these information. FIG. 2 is a flowchart illustrating a procedure for transmitting neighbor cell information in a 3G control station. , FIG. 3 is a flowchart illustrating a procedure for transmitting neighbor cell information in a second generation control station.</p><p>First, according to the flowchart of FIG. 2, when the 3G control station receives service capability information related to functions that it can provide from a mobile terminal ("Yes" in step S10), the 3G control station receives the information ("Yes" in step S10). The service capability information of the mobile terminal is stored (step S12). When the mobile terminal transmits an information message related to its own service capability to the 3G control station, it also transmits protocol revision number information necessary when operating in a 2G synchronous system.</p><p>If the 3G control station does not receive the service capability information from the mobile terminal, it proceeds directly to the following step S14 without going through the step S12.</p><p>The 3G control station determines whether a handoff for the corresponding mobile terminal is necessary (step S14), and if it is determined that a handoff is necessary ("Yes" in step S14), the 3G control station stores the Based on the service capability information of the corresponding mobile terminal, it is determined whether the service capability of the mobile terminal supports the synchronous system (step S16). </p><p>If the service capability of the mobile terminal supports the synchronous system ("Yes" in step S16), the 3G control station adds the neighboring cell information of the synchronous system to the neighboring cell list (step S18), and the neighboring cell The list information is transmitted as a system parameter message to the mobile terminal (step S20). If the service capability of the mobile terminal does not support the synchronous system in step S16, the 3G control station proceeds directly to step S20 and performs the operation of the synchronous system without adding neighbor cell information of the synchronous system.</p><p>According to the flowchart of FIG. 3, when the second generation control station receives service capability information related to the functions it can provide from the mobile terminal ("Yes" in step S30), the second generation control station sends the received mobile terminal The service capability information of the terminal is stored (step S32). When the mobile terminal transmits an information message related to its own service capability to the second-generation control station, it also transmits service capability information of the mobile terminal for operating in a third-generation asynchronous system.</p><p>If the second generation control station does not receive the service capability information from the mobile terminal, it proceeds directly to the following step S34 without going through the step S32.</p><p>The second generation control station determines whether a handoff for the corresponding mobile terminal is necessary (step S34), and if the determination result indicates that handoff is necessary ("Yes" in step S34), the second generation control station stores the Based on the service capability information of the corresponding mobile terminal, it is determined whether the service capability of the mobile terminal supports the asynchronous system (step S36). </p><p>When the service capability of the mobile terminal supports the asynchronous system ("Yes" in step S36), the second-generation control station adds the neighbor cell information of the asynchronous system to the neighbor cell list (step S38), and the neighbor cell The list information is transmitted as a neighbor cell list message to the mobile terminal (step S40). If the service capability of the mobile terminal does not support the asynchronous system in step S36, the second generation control station proceeds directly to step S40 without adding information on the adjacent cell of the asynchronous system and performs the operation.</p>

<p>As described in detail above, according to the present invention, based on service capability information and system status information from a mobile terminal, optimal neighboring cell information is selectively transmitted to the mobile terminal during handoff according to the movement of the mobile terminal. By giving, handoff between the synchronous system and the asynchronous system is smoothly performed.</p><p>In addition, unnecessary transmission of neighbor cell list information can be prevented, and in particular, a message load in a handoff process for a dual-mode terminal operating in a synchronous system to operate in an asynchronous system is reduced.</p><p>In addition, the method of the present invention can be used in selecting a base station to be handed off in case of a forward handoff under consideration in the future.</p><p>On the other hand, the present invention is not limited to the above-described embodiments, but can be implemented with modifications and variations within the scope without departing from the gist of the present invention, and the technical idea to which such modifications and variations are applied also falls within the scope of the following claims. have to see</p>