Inter-technology handoff method in an IP-based wireless communication system

FIELD OF THE INVENTION The present invention generally relates to a mobile communication system, and more particularly, to an IP-based (IP-based) wireless access network including wireless access networks that use different wireless interface protocols. Internet Protocol) is a method of switching between technologies in mobile communication networks.

BACKGROUND With the rapid development of wireless communication technology, the demand for IP-based wireless data services is also increasing. The development of technology and user market demands have promoted the development and commercialization of wireless communication networks with different capacities, speeds and mobile support. Figure 1 is a schematic diagram illustrating a cellular environment with different overlapping radio access networks. In order to provide communication services in a cellular environment, a mobile station (MS) must have a local interface. Moreover, in order to provide the MS with uninterrupted communication services during roaming, an effective handover technology is required.

Mobile IP services on existing IP networks are available. Mobile IP services are designed to reset routing paths for MSs moving between networks of different sub-networks. By using mobile IP services, the MS detects a new IP sub-network (L3 mobile detection), generates a new IP address or assigns it, binds the IP address to the network, and sends data to the IP address. The mobile IP operation is performed when the physical connection (L2 connection) between the MS and a new base station (BS) is completed, and the physical connection includes authentication and login.

In other words, in order to perform handover between BSs or between networks with different characteristics due to their respective service providers, different characteristics including QoS (Quality of Service), cell size, and mobility support must be implemented to the new BS. The physical connection, the verification operation on the handover request from the MS and the continuous service support between the BS, and the operation of resetting the routing path for the seamless transmission of IP services.

Figure 2 is a flowchart illustrating a typical handover process between IP-based technologies. Referring to FIG. 2, in step S201, the MS actively or automatically searches for the BS according to the network policy, detects the handover situation, and decides to perform the handover. In step S202, a physical connection is established between the MS and a new BS,

200410103779.6 First, in step S203, messages about authentication, QoS negotiation, location and mobility management are exchanged between the new BS and the old BS. Then, according to the mobile IP convention, the IP routing path is reset in step S204.

However, due to the complexity of IP mobility operations, the mobile IP handover process may cause handover delays, thus reducing the quality of communication services.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and/or shortcomings and provide at least the following advantages. Therefore, an object of the present invention is to provide a check between IP ranges in advance during L2 connection establishment considering IP handover Mobile station movement-also known as IP movement-is a handover method to minimize the service delay involved in handover mobility operations on inter-technology handover.

Another object of the present invention is to provide a handover method based on whether the MS can connect to two BSs at the same time during the IP signaling process for handover between BSs to selectively set the signaling path to increase the reliability of handover .

A further object of the present invention is to provide a handover method generally applicable to BSs that provide different IP-based wireless access interfaces.

The above-mentioned purpose is achieved by providing a handover method in a communication system, in which a BS that provides MSs with different wireless access interfaces is connected to an IP-based network through a router. A decision is made for the MS to switch from the first BS to the second BS. The MS receives the IP service data from the first BS and establishes an L2 connection between the MS and the second BS. During the establishment of the L2 connection, the movement of the MS in the IP network is detected. Implement handover negotiation between the first and second BS through IP signaling. According to the negotiation, if the handover is available, the movement management is performed in consideration of the movement of the MS. The IP service data is sent to the MS in the network path reset to the second BS through mobility management, and the L2 connection between the MS and the first BS is released. Mobility management based on mobile IP is preferred.

In the L2 connection establishment step, the MS requests an L2 connection to the second BS in the L2 connection request message, and the second BS verifies the MS based on the L2 connection request message, and if the MS passes the verification, the second BS in the L2 success response message The BS notifies the MS to complete the L2 connection, and the L2 success response message contains the IP address of the second BS or the router connected to the second BS.

When the first BS receives the L2 connection success response message, it sends the same data as the IP service data sent to the MS to the second BS.

In the motion detection step, the IP address of the second BS or the router connected to the second BS is compared with the known IP address of the first BS or the router connected to the first BS to determine the operation of the MS.

200410103779.6 Whether the first move is in the same subnet or in a different subnet.

In the handover negotiation step, the MS determines whether the MS is likely to be connected to the first and second BSs at the same time, and sends a handover request message with a bypass flag set to true or false to the first BS according to the determination result. The first BS refers to the bypass flag, and if the received bypass flag indicates false, it sends a handover notification message with the bypass flag set to false to the second BS on the wired channel through the network. According to the bypass flag set to false in the handover notification message, the second BS sends a handover response message with the bypass flag set to false to the first BS on the wired channel through the network. The first BS sends a handover confirmation message to the MS.

In the handover negotiation step, if the bypass flag in the handover request message is true, the first BS sends a handover communication message with the bypass flag set to true on the wireless channel to the second BS through the MS. When receiving the handover notification message with the bypass flag set to true, the second BS sends a handover response message with the bypass flag set to true to the first BS on the wireless channel through \43.

In the handover negotiation step, if the bypass flag in the handover request message is true, the first BS determines whether the number of hops between the first BS and the second BS is greater than a predetermined value, or whether the number of hops is not measurable . If the number of hops is less than the threshold, the first BS sends a handover notification message with a bypass flag set to false to the second BS on the wired channel through the network. Then, the second BS sends a handover response message with a bypass flag set to false to the first BS on the wired channel through the network.

If the number of hops is greater than the threshold or is not measurable, the first BS sends a handover notification message with the bypass flag set to true to the second BS on the wireless channel through the MS. Then the second BS sends a handover response message with the bypass flag set to true to the first BS on the wireless channel through the MS.

BRIEF DESCRIPTION OF THE DRAWINGS The following detailed description with reference to the accompanying drawings will make the above and other objects, features and advantages of the present invention more obvious, in which: Figure 1 is a schematic diagram illustrating different overlapping communication cellular environments; Figure 2 is A flowchart illustrating a typical handover process between IP-based technologies; Fig. 3A is a conceptual diagram illustrating handover between different BSs in the same IP sub-network according to the present invention; Fig. 3B is a conceptual diagram illustrating handover between different IP sub-networks according to the present invention; The concept of handover between different BSs in the network

200410103779.6 Figure; Figure 4 is a flowchart illustrating the signal flow for IP-based inter-technology handover according to a preferred embodiment of the present invention; Figure 5 is a flowchart illustrating the detailed signal flow for L2 connection establishment illustrated in Figure 4 Figures: Figure 6 is a flowchart illustrating the signal flow when the MS determines the signaling path according to a preferred embodiment of the present invention; Figure 7 is a flowchart illustrating the situation where the signaling path is determined at the BS according to the preferred embodiment of the present invention The flow chart of the signal flow under.

DETAILED DESCRIPTION Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, since unnecessary details on well-known functions or structures may cause obscure inventions, detailed descriptions thereof will not be given.

In an IP-based wireless network environment, there are two scenarios for switching between technologies: switching between technologies in the same IP sub-network and switching between technologies in different IP sub-networks. In the latter case, the service provider or network configuration may be different. However, it is presupposed that each different IP sub-network has a transport layer.

FIG. 3A is a conceptual diagram illustrating vertical handover (VHO) between different BSs in the same IP sub-network according to the present invention. Referring to FIG. 3A, two IP sub-networks 310 and 320 are connected to the Internet 300 through their respective sub-network routers and gateway routers (not shown). Each of the IP sub-networks 310 and 320 includes multiple BSs with their respective service areas. In this network environment, the MS 10 tries the VHO from the old BS 313 to the new BS 315 in the first ip sub-network 310.

FIG. 3B is a conceptual diagram illustrating VHO between different BSs in different IP sub-networks according to the present invention. Referring to FIG. 3B, the MS 10 attempts a VHO from the old BS 315 in the first IP sub-network 310 to the new BS 323 in the second IP sub-network 320.

The handover method of the present invention can be equally applied to VHO between different BSs in the same IP sub-network and VHO between different BSs in different IP sub-networks_o For the purpose of handover, the MS completes the L3 information (the IP address of the BS or the router connected to the BS) required for the VHO during the establishment of the L2 connection with the BS. When VHO is determined through negotiation between BSs, the L3 information is used to quickly perform VHO.

The inter-technology handover method of the present invention provides support by MS using different parameters or according to network policy

200410103779.6 The signaling scheme for handover between IP-based technologies. The MS, which already knows that the BS sends receivable signals in its cell, decides the VHO according to the handover policy considering cost, QoS, and mobility, and tries an L2 connection to the new BS. After the authentication and login of the MS, the new BS sends a message indicating the success of the L2 connection to the MS. The message contains the IP address of the new BS or the IP address of the access router connected to the new BS. Then, the MS sends a VHO request message containing the IP address to the old BS. The old BS sends a handover message to the IP address through the IP network. After negotiation between the two networks or BSs, the old BS informs the MS of the exchange result and the required information. This IP-based handover signaling can be applied to any IP-based network, so it has good scalability. Once the handover result is received, the MS continuously receives IP data services.

In order to describe the above handover process in more detail, in the case of VH0 between different BSs in the same IP sub-network, once the VHO is decided by handover signaling, the data transmitted from the old BS to the new BS does not pass the data defined in the network. The routing method sends data to the new BS. In the case of VHO between different BSs in different IP sub-networks, the MS tells the old BS that it needs to move 11> operations through the VHO request message, or the old BS that received the VHO request message compares its IP address with that of the new BS. IP address to identify the requirements of mobile IP operations. After the VHO is determined through the handover signaling between the two BSs, the mobile IP operation is performed to transmit data from the old BS to the new BS or the router connected to the old BS, receive the handover information, and transmit the data to the router connected to the new BS . Therefore, the MS continuously receives IP data services during the handover.

Briefly, during the ongoing IP data service during the VHO handover to a different BS, the L2 connection between the MS and the new BS and the handover negotiation between the old BS and the new BS through IP signaling, once the old BS It is determined that the VHO to the new BS is successful, and when the old BS or the new BS is re-routed through the mobile IP operation, the data transmission between the MS and the new BS is available. Therefore, the service delay involved in the mobile IP operation is reduced. The handover signaling process of the present invention is configured to realize the operation for supporting mobility at the 1P layer and reduce the service delay of the operation. Because the mobile Internet Protocol version 6 (MIPνό) standardization has not yet been completed, and various algorithms for mobility support can be applied to the network, the BS implements IP mobility support operations during the handover signaling, so that during the handover signaling During the transmission or sending of data at the appropriate time.

Fig. 4 is a flowchart illustrating a signal flow for switching between IP-based technologies according to a preferred embodiment of the present invention.

Referring to FIG. 4, it is presupposed that the MS terminal 41 is in a handover state from the old BS 43 (BS1) to the new BS 45 (BS2) with a different wireless interface.

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MS 41 detects L3 movement through the L2 connection to BS2. When accepting handover through negotiation between BS1 and BS2, MS 41 determines whether a rerouting operation such as mobile IP operation is required. BS1 and 852 can determine whether 541 will invoke the mobile IP operation through the "day 0 signaling". The routing path of Roots MS 41 is reset, and the two BSs operate on two paths.

In the case of VHO between BS1 and BS2 in the same IP sub-network, when VHO between them is allowed through the handover signal 4, BS1 sends data to BS2, or transmits data through a method defined in the network for data Arrive at the new BS.

In the case of VHO between BS1 and BS2 in different IP sub-networks, after the VHO is allowed through handover signaling, when MS 41 receives the VHO ACK message, BS1 transmits data to BS2 or BS1 transmits data to MS 41 and BS2 , And perform routing reset operations such as mobile IP operations.

Referring to FIG. 4, MS 41 is receiving IP services from BS1 in step S401. In step S40?, when the MS 41 decides VHO due to a change in the communication environment during the IP service, an L2 connection to BS2 is established in step S403. In step S404, the MS 41 detects the L3 movement from the received IP-related information during the establishment of the L2 connection. BS1 and BS2, which are connected by the VHO request message sent from MS 41 in step S405, implement VHO negotiation in step S406. In step 8407, the BS1 sends a VHOACK message to the MS 4L. In step S408, the MS 41 determines whether VHO is possible through the VHO ACK message. If VHO is not possible, MS 41 keeps the ongoing IP service. On the contrary, if VHO is possible, the MS 41 performs an IP mobility control operation considering the detected L3 motion state in step S409, and receives an IP service from BS2 in step S410. In step S411, the MS sends an L2 connection release request message to BS1, thereby completing VHO.

According to the handover method of the present invention, for fast handover, during the establishment of the L2 connection, the old BS and the new BS each send to the MS the L3 information including their IP address or the 1P address of the router to which they are connected.

After the new BS verifies that the MS requests a connection, the BS sends a message to the MS indicating that the L2 connection is successful, and the message contains its IP address or the IP address of the router to which it is connected. Therefore, the MS can identify the IP subnet of the new BS. This L2 connection establishment process can speed up IP-based VHO signaling and motion detection in the IP layer. Therefore, the MS can predict and prepare operations for supporting motion in the IP layer.

FIG. 5 is a flowchart illustrating the signal flow for L2 connection establishment illustrated in FIG. 4. Referring to FIG. 5, MS 41 sends an L2 connection request message to BS1 or BS2 in step S501. BS2 verifies the MS in step S502. 41. If the verification fails in step S504, then BS2 in step S503

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MS 41 sends an L2 connection failure response message. On the other hand, if the verification is passed, the BS2 sends an L2 connection success response message to the MS 41 in step S505, and registers the MS 41 in step S506. The L2 connection success response message includes IP information including the IP address of BS2 or the router connected to BS2. In step S507, the MS 41 uses the IP information to detect the IP subnet and L3 movement.

The VHO negotiation between BS1 and BS2 illustrated in FIG. 4 can be implemented directly between BS1 and BS2 with or without MS 41.

The signaling path used for VHO negotiation can be determined by MS41 or BS1.

According to the signaling path setting method of the present invention, considering the structure of the MS successfully connected to the new BS and the handover decision method, the MS successfully connected to the new BS determines whether it can connect to the old BA and the new BS at the same time, and sends to the old BS VHO request message, the request message contains a bypass flag indicating whether the MS uses two channels. If two channels are used, the bypass flag is set to true, otherwise the service is set to false. The old BS determines the VHO signaling path through the VHO request message. That is, the old BS determines whether to send a handover message to the new BS through the wireless MS or through the IP wired network based on the bypass flag indicating the IP address of the new BS and the channel status of the MS. In the previous situation, the old BS sends a handover message with the bypass flag set to true to the MS, and the MS sends a handover message to the new BS. This signaling setting saves resources according to the structure and channel state of the MS and reduces the time delay for VHO signaling.

Fig. 6 is a flowchart illustrating a signal flow in a case where an MS determines a signaling path according to a preferred embodiment of the present invention. Referring to FIG. 6, in step S60I of the VHO request step illustrated in FIG. 4, MS 41 determines whether it is possible to connect to both BS1 and BS2 at the same time according to the structure of MS 41 and the adopted handover decision method. In step S602, if it is possible, MS 41 sets the bypass flag to true, or if it is not possible, MS 41 sets the bypass flag to false, and in step S603 sends the bypass flag to BS1 VHO request message. In step S604, BS1 detects the bypass flag. If the bypass flag is true, BS1 sends a VHO notification message with the bypass flag set to true to MS 41 in step S605. In step S606, MS 41 transmits a VHO notification message to BS2 without other additional processing. In step S607, BS2 sends a VHO response message with a bypass flag set to true to MS 41, and MS 41 sends a VHO response message to BS1 in step S608 without other additional processing.

On the other hand, if the bypass flag is set to false in step S604, B9 sends a VHO notification message to BS2 via the IP network in step S612, and BS2 sends a VHO response message directly to BS1 via the IP network in step S614.

FIG. 7 is a diagram illustrating a signal in a case where a BS determines a signaling path according to a preferred embodiment of the present invention;

200410103779.6 Flow chart of the No. stream. Referring to FIG. 7, in step S701, the MS 41 determines whether it is possible to connect to both BS1 and BS2 at the same time according to the structure of the MS 41 and the adopted handover decision method. In BUJUN S702, if it is possible, MS 41 sets the bypass flag to true, or if it is impossible, MS 41 sets the bypass flag to false, and sends the bypass flag to BS1 in step S7O3 VHO request message. BS1 checks the bypass flag in step S704. If the bypass flag is false, BS1 sends a VHO notification message to BS2 through the IP network in step S705, and BS2 sends a VHO response message to BS1 through the IP network in step S706.

Conversely, if the bypass flag is true, in step S707, BS1 determines whether the number of hops between BS1 and BS2 is greater than a predetermined threshold or is not measurable. If the number of hops is measurable and less than the threshold, BS1 sends a VHO notification message to BS2 through the IP network in step S708, and BS2 sends a VHO response message to BS1 through the IP network in step S709.

In step S707, if the number of hops is greater than the threshold or is not measurable, then in step S710, BS1 sends a VHO notification message with a bypass flag set to true to MS 41. In step S7II, MS 41 transmits the VHO notification message to BS2 without other additional processing. In step 3712, BS2 sends a VHO response message with a bypass flag set to true to MS 41, and MS 41 sends the VHO response message to BS1 in step S713 without other additional processing.

In the handover method of the present invention as described above, the handover time is determined through handover negotiation, and the old BS sends the IP service data for the MS to the new BS, thereby minimizing the resetting of the routing path and the resetting of the routing path. The business delay of mobility operations.

In addition, the signaling path is selectively set depending on the possibility of the current connection between the MS and both the old and new BSs in the IP signaling used for handover between BSs. Therefore, fast and reliable switching can be performed.

Although the present invention is given and described with reference to its specific preferred embodiments, those skilled in the art should understand that they can be used without departing from the spirit and scope of the present invention as defined by the appended claims. Make various modifications in form and details.

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