KR20050032812A - Packet link setting method at the time of handoff for mobile communication system - Google Patents

Abstract

A method for setting a packet path during handoff of a mobile communication system is provided to minimize a waste of wire resources, which can be caused during a handoff, and to prevent a packet loss, when a packet path of the wire resources is reset by the handoff between MSCs of MTs(Mobile Terminals). An MT for performing an HO(Handoff) simultaneously transmits an HO signal to a present BS(BS_P) and a target BS(BS_C). An MSC(MSC_C) of the target BS(BS_C) carries out a procedure of extending a connection with a previous MSC(MSC_P), so that the MT can quickly perform the HO through an extended path. The present BS(BS_P) informs an upper COS(Crossover Switch) to execute an optimum path rerouting process toward an HO target, so that the COS can reset an optimum path to the MSC(MSC_C). The MSC(MSC_C) releases a path with the previous MSC(MSC_P), and resets a connection with the new optimum path.

Description

PACKET LINK SETTING METHOD AT THE TIME OF HANDOFF FOR MOBILE COMMUNICATION SYSTEM}

The present invention relates to a method for establishing a packet path during handoff of a mobile communication system. In particular, when resetting a packet path of a wired resource due to handoff between an exchange (MSC) of a mobile communication terminal, it may occur during handoff. The present invention relates to a packet routing method during handoff of a mobile communication system for minimizing packet loss while minimizing waste of wired resources.

In general, re-establishing a connection between wired resources (MSCs) for handoff of a mobile communication terminal is referred to as rerouting. This rerouting quickly reestablishes a connection to a mobile area of the terminal. In addition, the increase in signal traffic and burden of network nodes due to the establishment and release of the connection should be less.

In addition, since the support of the wired section in the wireless network is relatively rich compared to the wireless section, it is important to prevent the loss of the cell being transmitted and to ensure the order rather than the resource efficiency.

A redirection scheme proposed for mobility support of a mobile communication terminal can be largely classified into a path extension method and a path rerouting method as shown in FIG. 1.

First, the path extension method is a method of continuously extending an additional path of a virtual connection from an old base station to a new base station during handoff as shown in FIG. The switch currently serving the mobile communication terminal (MSC) becomes a crossover switch (COS), a top-level connection switch that manages the packet exchange of the mobile communication terminal, and continues to the destination access point where the mobile communication terminal moves. This is a way to extend the path.

In the path extension scheme, signaling for connection reconfiguration is performed at the local level between the exchanges and can be easily implemented in the existing No. 7 network. This short, fast handover is possible, and cell loss prevention and order can be easily guaranteed.

Next, the path rerouting method selects an appropriate switch on a previously set path as a COS (Crossover Switch) as shown in FIG. 1 (b), and maintains only the section from the COS to the new base station while maintaining the path of the COS in the opposite terminal. Rerouting is done by rerouting.

The path rerouting schemes are developed from handoffs by an anchor used in existing IS-41 and GSM cellular telephone networks. In the path rerouting method, characteristics such as handover delay and path optimization vary greatly according to the COS selection algorithm. Various COS selection algorithms for handover in a wireless network have been proposed. A typical dynamic COS selection algorithm is HOS (HandOff Switch), a handover technique of NEC's WATMnet.

However, the path extension method may cause unnecessary waste of connection resources due to continuous connection of wired resources, as well as a problem of delay of data transmission due to the extension path, and when the terminal reconnects to a previously visited base station, a loop on the path may occur. Since a loop may occur, frequent use of resources may cause redundant use of resources, thereby eliminating the loop.

In addition, the path rerouting method may set the original path from the new base station to be close to the optimum, thereby preventing end-to-end data delay and increasing the efficiency of network resources. However, there is a problem that the transmission of information can be interrupted due to an increase in the overall handoff control time due to the COS selection process, which is the core of the optimal path selection, and the new path selection according to the selected COS.

In order to guarantee packet order during handoff, packets that have already been transmitted must be retransmitted from the current switch to the COS when switching occurs in the COS. Therefore, the farther the COS is from the current switch, the greater the amount of packets that need to be transmitted, and packet loss may occur due to overflow of the COS buffer. In addition, there is a problem that the packet delay increases before and after the start of the handoff and the algorithm for guaranteeing the order of the packets becomes very complicated.

Accordingly, the present invention was created to solve the above-mentioned conventional problems, and when resetting the packet path of the wired resource by the handoff between the MSCs of the mobile communication terminal, it may occur during the handoff. It is an object of the present invention to provide a packet routing method during handoff of a mobile communication system to minimize packet loss while minimizing waste of wired resources.

In order to achieve the above object, the present invention provides a mobile communication terminal for performing a handoff, comprising: simultaneously transmitting a handoff signal to a base station (BS_P) and a target base station (BS_C) to move; Performing a procedure of extending a connection with a previous mobile communication exchange (MSC_P) in a mobile communication switch (MSC_C) to be moved to a base station to move the mobile station to perform a handoff quickly through an extended path; The previous base station (BS_P) notifies the upper crossover switch (COS) to perform the optimal path rerouting toward the handoff target area, and reestablishes the optimal path from the COS to the mobile communication switch (MSC_C); When a new connection is re-established by the rerouting, the mobile communication exchange MSC_C may include releasing a path from the previous mobile communication exchange MSC_P and reestablishing a connection to a new optimal path.

The present invention is in the area of one mobile communication exchange (MSC_P: mobile communication exchange in charge of the area currently serving the terminal service), the other mobile communication exchange (MSC_C: mobile communication exchange in charge of the destination area to which the terminal is moving) In order to efficiently use wired resources of a mobile communication terminal which performs a handoff to an area to be provided, it is an object of the present invention to provide a rerouting method in which a path rerouting method is mixed with an existing path extension method.

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

FIG. 2 is a conceptual diagram of a method for setting a packet path during handoff of a mobile communication system according to the present invention. When the mobile communication terminal MT in a service area 'A' hands off to a service area 'B', The base station (BS_P: base station currently serving the terminal) managed by the mobile communication exchange (MSC_P) currently serving and the mobile base station (BS_C: target base station to which the terminal is moving) managed by another mobile communication exchange (MSC_C) Announce handoff.

Accordingly, the target base station BS_C to be moved confirms the handoff intention of the mobile communication terminal from the other area A and transmits it to the higher level mobile communication exchange MSC_C. The upper mobile communication exchange (MSC_C) checks its resource allocation state and requests the mobile communication exchange (MSC_P) in charge of the entire mobile area to expand the connection to the mobile terminal (MT).

Accordingly, the previous mobile communication exchange (MSC_P) extends the existing connection, performs a fast connection extension handoff to the responsible mobile communication exchange (MSC_C) of the mobile area and transmits a wireless packet.

On the other hand, the base station BS_P that has received the handoff intention to the neighboring area B informs the mobile communication switchboard MSC_P in charge of which area the mobile terminal is handing off. The MSC_P also informs the higher level mobile communication exchange on the existing path and delivers it to the MSC serving as the final COS.

Next, in the mobile communication exchange (MSC) serving as a COS role, the terminal MT finds an optimal path to the mobile communication exchange (MSC_C) that is in charge of the area to be moved, and performs route rerouting.

Receiving that the new connection has been reestablished, the handoff target mobile communication exchange (MSC_C) disconnects the connection with the previous handoff mobile communication exchange (MSC_P) that has already extended the connection and is sending packets, and disconnects the connection with the new optimal path. Reset it and use it.

Next, FIG. 3 is a flowchart illustrating a packet path setting process during handoff of a mobile communication system according to the present invention. When a mobile communication terminal MT in a certain area wants to handoff to another service area, the terminal is currently present. A handoff is requested to a base station (BS_P) that manages a service area and a moving target base station (BS_C) that manages another service area (HO_Request), and the base station transmits a handoff request fact to a higher mobile communication exchange (MSC_P, MSC_C), respectively. To pass.

Accordingly, when the MSC_C of the target area to be moved checks its resource allocation state and requests the mobile communication switch MSC_P in charge of the pre-movement area to extend the connection to the mobile terminal MT (Exten_Setup). In response, the former MSC_P extends the existing connection in response (Exten_Connect), and requests the COS to reroute to the MSC_C in the target area to be moved (Rerout_Request), so that the connection extension handoff is performed. Proceed with preparation for rerouting before (HO_Exec).

Next, when a connection extension handoff is performed (HO_Exec), a procedure (Radio_Release, Radio_Release_Ack) for disconnecting a connection between the terminal MT and the previous base station BS_P is performed, and the terminal MT communicates with the base station BS_C in the new area. It is connected (HO_Complete).

As described above, when the handoff between the terminal MT and the base station BS_C in the new area is performed, a procedure of disconnecting the path between the previous base station BS_P and the switch MSC_P proceeds with release and release_Ack. The setup procedure for rerouting is performed between the exchanges MSC_2 and MSC_C in the region, and rerouting is performed (Connect_Switching).

When the re-routing is performed, the new base station MSC_C and the old base station MSC_P are kept disconnected (Exten_Release), and the resources required for routing from the old base station MSC_P are transferred to the COS, and the old mobile communication exchange Release the route with (MSC_P) completely and re-establish the connection with the new optimal route.

As described above, according to the present invention, the mobile station simultaneously transmits a handoff signal to the previous base station BS_P and the target base station BS_C, thereby extending the connection with the previous mobile communication exchange MSC_P in the mobile base station MSC_C. The mobile station to handoff quickly through the extended path, and the previous base station (BS_P) informs the upper COS to perform optimal route rerouting toward the handoff target area. After the handoff is performed, the optimal path is reset from the COS to the mobile communication switch (MSC_C) to prevent looping due to efficiency of network resource use and path extension.

As described above, the method for setting a packet path during handoff in the mobile communication system of the present invention may occur during handoff when reconfiguring a packet path of a wired resource due to handoff between exchanges (MSCs) of the mobile communication terminal. Mobile communication that is currently in service to minimize waste of wired resources, to prevent looping that may occur when re-visiting a previously visited base station in a conventional path extension method, and to guarantee packet transmission in a conventional path rerouting method. By reducing the amount of packets retransmitted from the exchange to the COS, packet loss prevention and ordering can be guaranteed.

1 is an exemplary diagram for explaining a conventional general path connection expansion method and a connection rerouting method.

2 is a conceptual diagram for a packet path setting method during handoff in a mobile communication system according to the present invention;

3 is a flowchart illustrating a packet path setting process during handoff of a mobile communication system according to the present invention.

Claims (4)

The mobile terminal to perform the handoff sends a handoff signal to the current base station BS_P and the target base station BS_C simultaneously; Performing a procedure of extending a connection with a previous mobile communication exchange (MSC_P) in a mobile communication switch (MSC_C) to be moved to a base station to move the mobile station to perform a handoff quickly through an extended path; The previous base station (BS_P) notifies the upper crossover switch (COS) to perform the optimal path rerouting toward the handoff target area, and reestablishes the optimal path from the COS to the mobile communication switch (MSC_C); And when the new connection is reestablished by the rerouting, the mobile communication exchange (MSC_C) comprises releasing the path with the previous mobile communication exchange (MSC_P) and reestablishing the connection to the new optimal path. How to set up packet path during handoff of communication system The method of claim 1, wherein the connection extension procedure transmits a virtual connection setup signal (VC_Setup) to a higher mobile communication exchange (MSC_C) at a mobile base station (BS_C) that has received a handoff signal, and at a higher mobile communication exchange (MSC_C). The mobile communication exchange (MSC_P) is required to extend the connection to the terminal MT, and the mobile communication exchange (MSC_P) from the previous mobile communication exchange (MSC_P) to extend the connection to the mobile communication switch (MSC_C) of the area to be carried out that the handoff is performed quickly A method for establishing a packet path during handoff of a mobile communication system, characterized by the above-mentioned. The mobile communication according to claim 1, wherein the rerouting is performed by a mobile communication switch (MSC_P) through a higher mobile communication exchange (MSC_P) to determine in which area the mobile station is handed off from a previous base station (BS_P). The mobile communication exchange (MSC), which delivers up to the switching center (MSC) and performs a role of COS, is configured to find the optimal path to the mobile communication exchange (MSC_C) of the area to which the terminal MT moves, and perform rerouting. Packet routing method in handoff of mobile communication system. The method of claim 1, wherein the rerouting is configured to request rerouting from the previous mobile communication exchange (MSC_P) to the mobile communication exchange (MSC_C) of the area to be moved to the COS before the connection extension handoff is performed. Packet routing method in handoff of mobile communication system.