KR20070073466A - Method and apparatus for handoff of mobile terminal in complex network - Google Patents

Abstract

A handoff method of a wireless terminal in heterogeneous networks and an apparatus thereof are provided to prevent service interruption and a loss of data and improve communication service quality by providing a middle process for handoff between networks of the same kind. If a wireless terminal, connected to the second network, accesses a handoff-possible point(S400), the wireless terminal enables a handoff-possible interface(S402). Then, the wireless terminal determines each interface access weight in consideration of bandwidths of each network(S404). The wireless terminal selects a network and judges whether the selected network is the same kind as the presently connected network(S406). If not, the wireless terminal acquires an IP address from the selected network and executes handoff to the selected network(S410). In case the selected network is the same kind as the presently connected network, however, the wireless terminal selects an interface for access to the third network, the best alternative network as a middle process, acquires an IP address from the third network, and executes handoff to the third network(S420-S424). Then, the wireless terminal acquires a new IP address from the selected network using the interface used for the connection with the second network and executes handoff to the selected network(S426,S428).

Description

METHOD AND APPARATUS FOR HANDOFF OF MOBILE TERMINAL IN COMPLEX NETWORK}

1 is a schematic diagram of a heterogeneous network;

2 is a schematic block diagram of a dual mode terminal including a plurality of interfaces according to an embodiment of a wireless terminal to which the present invention is applied;

3 is a conceptual diagram illustrating handoff in a heterogeneous network according to the present invention.

4 is a flow chart illustrating a handoff process in a heterogeneous network according to the present invention.

The present invention relates to a method and apparatus for handoff of a wireless terminal in a heterogeneous network.

Previous wireless networks were implemented with only one wireless communication technology. However, the current wireless network is changing in the form of connecting a plurality of wireless communication networks each implemented by different wireless communication technologies. Of course, a wireless network and a wired network may be connected.

A network in which a plurality of networks connected to each other by different communication technologies is generally referred to as a heterogeneous network. In contrast, a network implemented with only one communication technology is called a “single network”. Networks implemented by various wireless technologies such as 3G (3rd generation), wireless local area network (WLAN), Wibro, and Ethernet may be connected to form a heterogeneous network. In response to the advent of heterogeneous networks, the development of dual-mode handsets supporting 3G systems and two or more wireless technologies, including WLAN, Ethernet and WLAN, is also accelerating.

One of the key technologies in mobility-oriented wireless networks is handoff, also known as handover. Handoff in heterogeneous networks should also be considered to support seamless service for users. do. Handoff in heterogeneous networks is becoming more effective due to the emergence of wireless technologies, such as Wibro, that add mobility.

A dual mode terminal capable of receiving a communication service while moving between different networks includes a plurality of interfaces for connecting to a plurality of networks implemented by different communication technologies. When a handoff is required, a dual mode terminal in a heterogeneous network is provided with a service by accessing a first network using an interface capable of accessing a new network to be handed off from among its own interfaces. The handoff is performed by terminating the connection to the network.

However, even in a handoff in a heterogeneous network, there may be a case where the new network is the same network as the existing network. In this case, the wireless terminal to be handed off must first terminate the connection with the existing network and then connect with the new network. The reason is that a wireless terminal handing off a network that is the same as the existing network must use the interface used for the connection with the existing network again for connection with the new network. Since a wireless terminal cannot access a plurality of networks at the same time using a single interface, in order to access two plurality of networks using a single interface, the wireless terminal must disconnect from an existing network and connect to a new network.

Therefore, in the case of horizontal handoff between networks of the same type, latency due to connection of Layer 2 (L2) and IP (Internet Protocol) resetting is inevitably present. Especially during macro-handoff, when handoff is performed between homogeneous networks, connection disconnection occurs due to reconnection of two layers and new IP configuration. As a result, there is a problem that the communication service is disconnected at the time of handoff.

Accordingly, an object of the present invention is to provide a method and apparatus for handoff of a wireless terminal in a heterogeneous network which can reduce service interruption and data loss during handoff.

In the handoff method of a wireless terminal in a heterogeneous network according to an aspect of the present invention for achieving the above object, a process of determining whether a handoff is necessary, and if it is determined that a handoff is necessary, a network capable of handoff is possible. Searching a network, selecting a first network that provides the best communication quality among the searched networks, and whether the first network is the same network as the second network that the wireless terminal is previously connected to. Determining and if the two networks are homogeneous, selecting a third network that is heterogeneous and a second network that provides the best communication quality among the searched networks, and handing off to the selected third network. It may include.

The method may further include handing off to the first network after handing off to the third network.

The handoff to the first network may include setting an interface with the first network, connecting with the first network using the set interface, and terminating the connection with the third network. It may include.

The setting of the interface with the first network may include receiving a new IP (Internet Protocol) from the first network.

The method may include comparing the quality of service of the first network and the third network, determining whether the difference in quality of service of the two networks is greater than a predetermined setting value, and the difference in quality of service of the two networks is predetermined. If it is determined that the value is greater than the set value, after handing off to the third network, the method may further include handing off to the first network.

Each of the first network, the second network, and the third network may include at least one of a 3rd generation (3G) network, a wireless LAN network, a WiBro network, and an Ethernet network.

The quality of service may be determined by at least one of a signal to noise ratio (SNR) and a bandwidth provided by each network to a wireless terminal accessing the corresponding network.

In order to achieve the above object, a handoff apparatus for a wireless terminal in a heterogeneous network according to another aspect of the present invention is a target capable of handoff when it is determined that a handoff and a plurality of interfaces connectable to different networks are required. If the first network that searches for the networks and provides the best communication quality among the searched networks is the same network as the second network that is the network to which the wireless terminal has previously connected, the second network among the searched networks Select a third network that is heterogeneous to the network and provides the best communication quality, and connect to the third network and connect with the second network using an interface capable of accessing the third network among the interfaces; Hand to the third network to terminate It may comprise a control unit for performing a program.

The control unit, after the handoff to the third network, connects to the first network by using an interface that can connect to the first network among the interfaces, and terminates the connection with the third network. Handoff may be performed.

The controller compares the quality of service of the first network and the third network, and if it is determined that the difference between the quality of service of the two networks is greater than a predetermined setting value, after the handoff to the third network, the first network Handoff may be performed.

Here, the “first network” refers to a network that can provide the best communication quality of service to the wireless terminal among the networks that can be the target of handoff of the wireless terminal. "Second network" refers to a network to which a wireless terminal to be handoff is previously connected. The “third network” refers to a network capable of providing a best communication quality of service to a corresponding wireless terminal among networks that may be subject to handoff of the wireless terminal, among networks that are not the same as the second network.

The present invention provides a handoff to a third network when the first network is a homogeneous network, in order to prevent latency caused by a layer 2 connection and an IP reset during handoff between homogeneous networks in a heterogeneous network. By setting it as an intermediate step, it prevents handoff between homogeneous networks. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of a heterogeneous network.

1 is a heterogeneous network connected to a 3G network, a WiBro network, and a WLAN network. In FIG. 1, a wireless LAN including a WiBro network including a radio access station (RAS) 110 and an access control router (ACR) 112, an access point 120, and a router 122. The network is connected to the home agent (HA) 130 and the core network (CN) 140 through the Internet.

The terminal 100 is a dual mode terminal and may be connected to the RAS 110 to receive a WiBro service or may be connected to the AP 120 to receive a wireless LAN service. The terminal connected to the RAS 110 or the AP 120 may access the Internet through the ACR 112 or the router 122. Meanwhile, the terminal 100 may be provided with a 3G service by accessing a 3G network or may be provided with a communication service through a corresponding network by accessing another network. The terminal 100 may include a plurality of interfaces for connecting to the plurality of networks.

2 is a block diagram of a dual mode terminal including a plurality of interfaces according to an embodiment of a wireless terminal to which the present invention is applied.

The wireless terminal illustrated in FIG. 2 includes a controller 200 and a plurality of interfaces, that is, a first interface 210 and a second interface 212. These controllers 200 and the plurality of interfaces 210, 212,... Are used for handoff of a wireless terminal in a heterogeneous network according to the present invention, and therefore, these controllers 200 and the plurality of interfaces 210. , 212, ...) may be considered as constituent elements of the apparatus of the present invention.

The interfaces can each be used for connection to one network. For example, the first interface may be used for connection to a WiBro network and the second interface may be used for connection to a WLAN network. Of course, other interfaces may be included in the wireless terminal.

The controller 200 determines whether the wireless terminal needs to be handed off, searches for a network to be handed off, selects one network among the searched networks, connects to the selected network, and connects to an existing network. Control processes throughout the handoff, such as terminating a. The controller 200 may control the interface for accessing the network and terminating the connection.

Consider a handoff of a wireless terminal connected to a heterogeneous network and receiving a communication service. In general, handoff occurs while the wireless terminal is moving. Handoff involves the process of connecting to a new network and terminating the connection to an existing network while the wireless terminal is moving from one area of the network to another.

The wireless terminal determines that it is necessary to perform a handoff when the SNR value of the network, that is, the SNR value of the signal received from the base station (RAS, AP, etc.) decreases below a predetermined reference value. The wireless terminal intending to perform the handoff first searches for a network to be handed off. If the SNR value of the network is more than a predetermined reference value, the network may be regarded as a network to be handed off. A network to be handed off may also be referred to as a handoff candidate network.

The handoff candidate network may be one or plural. When only one handoff candidate network is found, the wireless terminal hands off the network. When only one handoff candidate network is found, the wireless terminal performs the same handoff process and performs handoff to the corresponding network, regardless of whether the corresponding network is the same or heterogeneous network. .

Meanwhile, when a plurality of handoff candidate networks are searched, the wireless terminal selects a network capable of providing the highest quality communication service among the searched handoff candidate networks, that is, the first network. In a single network, it was common for the SNR values of each network to be used as a measure of communication quality of service. That is, in a single network, the wireless terminal regarded the network with the highest SNR among handoff candidate networks as the network capable of providing the highest quality communication service. However, in heterogeneous networks, the bandwidth of each network may be used as a measure of communication quality of service of the corresponding network. For example, the wireless terminal may perform a handoff by selecting a network that provides a greater bandwidth among handoff candidate networks. In addition, various items may be used as a measure of communication service quality of the network according to the characteristics of the network.

The first network is a network capable of providing the best communication service quality to a wireless terminal to be handed off, and is the highest priority handoff target network of the wireless terminal. By the way, if the first network is a network that the wireless terminal has previously connected to, that is, a network of the same type as the second network, as described above, the handoff from the second network to the first network is performed by connection of the second layer and Cause latency due to IP reset.

The wireless terminal determines whether the first network and the second network are the same type of network, and if it is determined that the two networks are the same type of network, the wireless terminal does not directly handoff from the second network to the first network and goes through an intermediate step. This prevents latency caused by Layer 2 connections and IP resets.

In other words, when it is determined that the first network and the second network are the same network, the wireless terminal provides a third communication service providing the best communication quality of service without being the same network as the second network among the found handoff candidate networks. Select a network and hand off from the second network to the third network. The wireless terminal then hands off from the third network back to the first network. The handoff from the second network to the third network and the handoff from the third network to the first network are both handoffs between heterogeneous networks, and thus do not require connection and IP reconfiguration of the second layer.

On the other hand, the wireless terminal, if the difference between the communication service quality provided by the first network and the communication service quality provided by the third network is not large, after the handoff from the second network to the third network, the first network from the third network. It may be possible to continue to receive communication service from the third network without performing a handoff to the network.

If it is determined that the difference between the communication service quality provided by the first network and the communication service quality provided by the third network is equal to or less than a predetermined setting value, the wireless terminal determines that the third network after the handoff from the second network to the third network is determined. Can continue to receive communication services. In this case, it is preferable that the setting value, which is a criterion of the determination, is set to a value that can make up for the communication service quality which is degraded by performing the hand rope again.

That is, the wireless terminal can be determined from the third network only when it is determined that the difference between the communication service quality provided by the first network and the communication service quality provided by the third network exceeds the communication service quality degraded by performing the handoff once more. It may be possible to perform a handoff to the first network.

Hereinafter, the above-described processes will be briefly described with reference to FIG. 3.

3 is a conceptual diagram illustrating an embodiment of a handoff in a heterogeneous network according to the present invention.

3 illustrates a terminal 100, a first network 304, a second network 300, and a third network 302. Here, the first network 304 and the second network 300 are the same kind of network. The terminal 100 connected to the second network 300 searches for a handoff candidate network when handoff is requested. In the embodiment shown in FIG. 3, the first network 304 and the third network 302 may be searched as handoff candidate networks. The first network 304 is a network that can provide the best communication quality of service, but is the same kind of network as the second network 300. Therefore, the terminal 100 hands off from the second network 300 to the third network 302. Thereafter, the terminal 100 hands off from the third network 302 to the first network 304.

On the other hand, the terminal 100 compares the communication service quality provided by the first network 304 and the communication service quality provided by the third network 302, and if the difference between the two quality of service is not large, the third network 302 May continue to receive communication service from the third network 302 without performing a handoff from the first network 304 to the network.

4 is a flow chart illustrating a handoff process in a heterogeneous network according to the present invention.

When the wireless terminal approaches the handoff-capable point (S400), the wireless terminal enables the handoffable interface (S402). The wireless terminal determines each interface connection weight considering the bandwidth of each network in order to use the bandwidth of each network as a selection criterion of a network to be handed off (S404). Here, the network having the largest weight value may be selected as the network to be handed off. Of course, the wireless terminal may use items other than bandwidth as a selection criterion of the network to be handed off.

The wireless terminal determines whether the selected network is the same network as the network to which it is currently connected (S406).

If the selected network is not the same network as the network to which it is currently connected, the wireless terminal acquires an IP from the selected network (S408), and hands off to the selected network (S410).

On the other hand, if the selected network is a network of the same type as the network to which it is currently connected, the wireless terminal is an intermediate step, and first selects an interface capable of accessing the third network, which is the next-highest network (S420), and selects an IP from the third network. Obtain (422) and handoff to the third network (S424). Thereafter, the wireless terminal acquires a new IP from the first network using the interface used for the connection with the second network, in which the connection is terminated (S426), and hands off to the first network (S428).

As described above, when the handoff between homogeneous networks is required, the present invention does not directly handoff from the second network to the first network, but puts the handoff from the second network to the third network as an intermediate process. In the third network, only handoff between heterogeneous networks from the third network to the first network is performed. Through this, the present invention can prevent latency caused by connection and IP reconfiguration of the second layer caused by handoff between homogeneous networks.

By providing an intermediate process for handoff between homogeneous networks as described above, the present invention can prevent service disconnection and data loss that occurs during handoff between homogeneous networks, and improve communication service quality.

Claims (12)

In the handoff method of a wireless terminal in a heterogeneous network, Determining whether a handoff is necessary; If it is determined that the handoff is necessary, searching for networks to which the handoff is possible; Selecting a first network that provides the best communication quality among the searched networks; Determining whether the first network is a network of the same type as a second network which is a network to which the wireless terminal is previously connected; And If the two networks are homogeneous, selecting a third network that is heterogeneous to the second network and providing the best communication quality among the searched networks, and handing off to the selected third network. A handoff method of a wireless terminal in a network. The method of claim 1, After handing off to the third network, handing off to the first network. The method of claim 2, Handoff to the first network, Establishing an interface with the first network; Connecting to the first network using the set interface; And The handoff method of a wireless terminal in a heterogeneous network comprising the step of terminating the connection with the third network. The method of claim 3, wherein The process of setting an interface with the first network may include: Handoff method of a wireless terminal in a heterogeneous network comprising the step of receiving a new Internet Protocol (IP) from the first network. The method of claim 1, Comparing the quality of service of the first network and the third network; Determining whether a difference in quality of service of the two networks is greater than a predetermined value; If it is determined that the difference between the quality of service of the two networks is greater than a predetermined value, handoff to the third network, and then handoff to the first network. . The method of claim 1, Each of the first network, the second network, and the third network includes at least one of a 3rd generation (3G) network, a wireless LAN network, a WiBro network, and an Ethernet network. The method of claim 1, The quality of service may be determined by at least one of a Signal to Noise Ratio (SNR) and a bandwidth provided by each network to a wireless terminal connected to the corresponding network. Handoff method. In the handoff device of a wireless terminal in a heterogeneous network, A plurality of interfaces connectable to different networks, respectively; and If it is determined that the handoff is necessary, the second network is a network to which the wireless terminal has previously connected is searched for networks to which the handoff is possible, and a first network providing the best communication quality among the searched networks. And a third network that is heterogeneous to the second network and provides the best communication quality among the searched networks, and uses an interface capable of accessing the third network from among the interfaces. And a control unit for performing a handoff to a third network connecting to a third network and terminating the connection with the second network. The method of claim 8, The control unit, After handoff to the third network, handoff to the first network connecting to the first network and terminating the connection with the third network using an interface capable of connecting to the first network among the interfaces. Handoff device of a wireless terminal in a heterogeneous network to perform. The method of claim 8, The control unit, Comparing the quality of service of the first network and the third network, and if it is determined that the difference in the quality of service of the two networks is greater than a predetermined setting value, after handoff to the third network, handoff to the first network Handoff device of a wireless terminal in a heterogeneous network to perform. The method of claim 8, Each of the first network, the second network, and the third network includes at least one of a 3rd generation (3G) network, a wireless LAN network, a WiBro network, and an Ethernet network. The method of claim 8, The quality of service may be determined by at least one of a Signal to Noise Ratio (SNR) and a bandwidth provided by each network to a wireless terminal connected to the corresponding network. Handoff device.

Images