KR20060118279A - Hand over method of mobile internet - Google Patents

Abstract

A handover method in the portable Internet is provided to enable a mobile terminal to reserve resources for a communication path in case of handover of a network layer in the portable Internet, thus the delay required in a resource reservation protocol can be reduced while handover delay is decreased. A mobile terminal transmits information about a target BS(Base Station) to a serving BS when handover occurs, in order to deliver the information to an RNC(Radio Network Controller). The RNC previously reserves resources to the target BS by using the information about the target BS. The RNC multicasts traffic to the serving BS and the target BS. The serving BS and the target BS store packets. If the handover to the target BS is successful, the terminal receives the multicasted traffic from the target BS. The RNC processes the handover of a network layer.

Description

Handover method of mobile Internet {HAND OVER METHOD OF MOBILE INTERNET}

1 is an operation flowchart of a handover method of a conventional portable Internet.

2 is a flowchart illustrating a handover method using a conventional basic resource reservation protocol.

Figure 3 is an exemplary network showing a configuration of a mobile communication system for explaining the present invention.

4 is a flowchart illustrating a handover method of the portable Internet according to an embodiment of the present invention.

5 is a flowchart illustrating a handover method using a resource reservation protocol according to an embodiment of the present invention.

6 is a flowchart illustrating an operation of multicasting traffic by resource reservation in a control station of FIG. 5;

The present invention relates to a handover method of the portable Internet, and more particularly, to a handover method of the portable Internet to reduce the handover delay by securing a path to the target base station to move to the mobile terminal in advance.

The portable Internet (WiBro) is a high-speed portable Internet service of 2.3 GHz frequency band and is an IP-based wireless data system having up and down asymmetric transmission characteristics using broadband wireless transmission technology.

In the mobile Internet, a mobile terminal is assigned a Care of Address (COA) in a mobile access network through a Mobile Internet Protocol (MIP) and is a home agent (HA) or a partner host (HA) of a home network. Register with CH: Correspondent Host and communicate through tunneling to ensure mobility. Mobility Support The Internet protocol provides mobility to an existing IP and continues to provide the service to the mobile terminal without changing the IP assigned initially regardless of where the mobile terminal moves. The mobile terminal uses a communication service while moving from a home network to an adjacent network. In this case, the mobile Internet performs network layer handover (L3 handover) for translating network addresses to ensure mobility in the mobile terminal.

When the mobile terminal moves from the serving cell to the neighbor cell, communication in the cell being served is impossible, so the mobile terminal tries to access the base station of the new cell out of the cell to which it belongs. The mobile terminal continues to use the communication service while moving from the serving cell to the neighboring cell. In this case, the mobile Internet performs data link layer handover (L2 handover) to ensure mobility in the mobile terminal.

As shown in FIG. 1, the handover operation of the portable Internet specified in the ICT group standard includes: a cell reselection step of selecting a cell for an adjacent base station from a terminal; A handover decision and initialization step of determining a handover at the base station; A target base station scanning step of scanning a target base station in a terminal; A network reentry step of starting a network reentry procedure at a terminal and a target base station; A service termination step of releasing all information related to the terminal connection from the serving base station; The handover canceling step of canceling the handover in progress in the terminal is performed.

In the cell reselection step, the mobile station selects a cell for the neighboring base station by using neighboring base station information obtained through the NBR-ADV message, performing a scan operation or performing ranging during a scan period or a sleep period. The NBR-ADV message includes information of a base station adjacent to the serving base station, and ranging adjusts a power offset between the terminal and the base station.

In the handover determination and initialization phase, the mobile terminal, serving base station, and network manager of the portable Internet determine and start a handover from the serving base station to the target base station. The serving base station manages the cell to which the mobile terminal currently belongs, and the target base station is a handover target of the serving base station.

In the target base station scanning step, the mobile terminal scans the target base station for synchronization with the uplink / downlink channel. The uplink / downlink channel is a communication channel of the mobile terminal and the base station, and the synchronization acquisition acquires synchronization for channel establishment between the mobile terminal and the base station.

In the network reentry step, the mobile terminal and the target base station perform ranging to start a network reentry procedure. The network reentry proceeds in the same way as the initial entry and the procedure can be simplified by using the terminal information received through the backbone network.

In the service termination step, the serving base station terminates the handover by terminating service to the mobile terminal and releases all connections and all related information associated with the mobile terminal.

In the handover cancellation step, the mobile terminal may cancel the handover in progress at any time. When the mobile terminal cancels the handover, the portable Internet releases all information related to the handover.

When the mobile terminal moves from the home network to the neighbor network or from the serving cell to the neighbor cell, the quality of traffic (QoS) of the traffic may be degraded due to the change in the wireless environment, so the mobile terminal uses the resource reservation protocol (RSVP). By reserving resources for a path through which communication is performed, the service quality of traffic is guaranteed during handover. The resource reservation protocol requires complex signal packets for the resource reservation process and for continuous reservation updates.

In particular, in the application of wireless access point, the inter-cell movement of the mobile terminal adds a resource reservation step to the basic handover operation, which leads to an increase in handover delay resulting in a risk of worsening the quality of service. In order to lower the handover method using the resource reservation protocol to guarantee the quality of service and to reduce the performance degradation.

A method of implementing the resource reservation protocol (MIP-RSVP) over the mobility-supported Internet protocol attempts a new resource reservation for the session after network layer handover. Since the MIP-RSVP method can continuously receive the received traffic after the network layer handover is terminated and the resource reservation ends, the delay for resource reservation is added to the pure data link and network layer handoff delay. The delay is particularly long because the resource reservation as well as the registration of the secondary address must be performed to the home agent or the counterpart host of the mobile terminal. In addition, resource utilization is very inefficient because resources are allocated redundantly across the path across the backbone network for the same session. The resources allocated in the path before the mobile terminal moves are returned if no message arrives that periodically updates the end-to-end reservation status. The MIP-RSVP method has problems such as long handover delay, allocation of another resource for the handover session, and delay in returning resources.

A handoff method (RSVP-MP: Mobility Proxy), which implements a resource reservation protocol using hierarchical MIP, newly reserves a resource only in a changed path in a domain. The RSVP-MP method supports fast handoff by reducing the long address registration time which was a problem in hierarchical MIP.

The RSVP-MP method independently performs resource reservation according to a movement path within a domain and a host agent or a partner host, and a resource reservation centered on an MP that is responsible for movement and resource reservation of a mobile host in a domain. Since RSVP-MP method uses hierarchical MIP, it supports relatively fast network layer handover and can use resource efficiently by sending message to remove new resource reservation and existing resource reservation at the same time after moving. Since the time for reserving resources after the network layer handover needs to be additionally considered, the overall handover delay has a relatively long problem.

2 is a flowchart illustrating a handover method using a conventional basic resource reservation protocol. In the network layer handover operation defined in the ICT standard, when the mobile terminal moves from the home network to the neighboring network, the mobile terminal searches for neighboring base stations, selects a target base station to be handed over, performs network entry, and applies a basic resource reservation protocol. Activates a session by reserving resources for the path through which communication takes place.

The mobile terminal is disconnected from the serving base station during the scan period or the sleep period and determines whether to handover to the target base station in the normal operation state and is placed in the communication disconnection period. The mobile terminal does not receive a packet from the counterpart host in the communication disconnection period and selects a target base station and attempts a communication connection.

When the mobile terminal executes network reentry and completes the basic function configuration, it re-registers and establishes a reconnection to the mobile internet.The mobile internet assigns the IP address to the mobile terminal, registers the address, and checks the route from the partner host to the mobile terminal. Reserve a resource. During the communication disconnection period from network reentry to activation of the session, the mobile station does not receive the packet and receives the packet from the activation time of the session in which resource reservation for the path is completed.

When handover is performed from the mobile terminal to the target base station, there is a problem in that a long time delay for the entire handover required from the time point at which the packet is released because the connection with the serving base station is not received until the session is activated is received again.

Accordingly, the present invention has been made in view of the above-mentioned problems. When a handover of a network layer occurs, identifier information of an access point to which the mobile terminal moves to a domain agent managing its mobility before the handover of the data link layer starts from the mobile terminal It is an object of the present invention to provide a handover method of the portable Internet that transmits a signal to reserve a path to a new base station, thereby reducing handover delay and efficiently executing resource management.

The present invention for achieving the above object comprises the steps of transmitting the information of the target base station to the serving base station to the control station when the handover occurs in the mobile terminal; Pre-reserving a resource to a target base station by using the information of the target base station at the control station; Multicasting traffic from the control station to a serving base station and a target base station; Buffering packets at the serving base station and the target base station; Receiving multicasted traffic from a target base station upon successful handover from the mobile terminal to a target base station; And processing the handover of the network layer at the control station.

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

3 is an exemplary network illustrating a configuration of a mobile communication system for explaining the present invention.

The mobile terminal 10 is currently connected to the serving base station 21 to use a communication service, and performs a scan operation during a scan period or a sleep period and adjusts a power offset using neighboring base station information obtained through an NBR-ADV message. Perform ranging.

The mobile terminal 10 and the serving base station 21 perform power ranging by adjusting the power offset, and compare the power level of the serving base station 21 with the power level of the neighboring base station 22 to adjust the power level of the neighboring base station 22. When it is high handover is determined.

The mobile terminal 10 scans the neighboring base station 22 to select the target base station 23 to be handed over and requests a handover to the control station 31. The control station 31 determines that the target base station 23 is connected to the home network. It determines that it belongs to an adjacent network that does not belong and checks the handover occurrence of the network layer.

The mobile terminal 10 transmits the information of the target base station 23 to the serving base station 21, the serving base station 21 to the control station 31 and the control station 31 to the upper control station 40 mobile terminal. Information of the target base station 23 corresponding to the handover request of (10) is transferred.

The control station 31 and the upper control station 40 newly reserve a resource for the path to the target base station 23, determine whether the reserved resource is used, and return the reserved resource if it is not used for a predetermined time. The control station 31 and the upper control station 40 determine whether the path to the mobile terminal via the serving base station 21 and the path to the mobile terminal 10 via the target base station 23 are connected and connected. Multicast traffic to both base stations.

The serving base station 21 and the target base station 23 store the received packet in a buffer, and upon successful handover, the target base station 23 transmits the buffered packet to the mobile terminal 10 by CID (Connection ID). The mobile terminal 10 receives a packet from the new target base station 23 upon successful handover.

4 is an operation flowchart of a handover method of a portable Internet according to an embodiment of the present invention, as shown in this step, selecting an initial cell from a mobile terminal and registering with a serving base station to establish an IP connection; Searching for a neighbor base station in the mobile terminal to determine a handover when the power level of the neighbor base station is increased; Pre-reserving resources from the control station to the target base station when a handover of the network layer occurs; Performing network reentry at the mobile terminal; Receiving multicasted traffic from a target base station if the mobile terminal succeeds in handover; And processing the handover of the network layer at the control station.

The mobile terminal selects an initial cell, acquires synchronization, performs ranging on downlink and uplink, registers with a serving base station, establishes an IP connection, and transmits operation parameters to establish a connection. Subsequently, the mobile terminal performs a scan operation during a scan period or a sleep period using the neighbor base station information obtained through the NBR-ADV message in cell reselection and searches for the neighbor base station.

The mobile terminal and the serving base station adjust the power offset and compare the power level of the serving base station with the power level of the neighboring base station while performing ranging, and determine the handover when the power level of the neighboring base station increases.

When the mobile terminal scans the neighbor base station to select a target base station to be handed over and requests a handover to the control station, the control station determines that the target base station belongs to an adjacent network not belonging to the home network, and handovers the network layer to the mobile terminal. Notify the occurrence.

The mobile terminal notifies the occurrence of handover and is disconnected from the serving base station and is placed in a communication interruption section in which a packet is not received. At this time, the control station reserves the resource for the path to the target base station by using the information of the target base station received from the mobile terminal.

When the handover of the network layer occurs, the control station uses the information of the data link layer to secure a path to the target base station to which the mobile terminal is to move in advance, and multicasts traffic to the serving base station and the target base station by IP tunneling. The mobile terminal performs network reentry to perform handover of the data link layer, and upon successful handover, receives the multicasted traffic from the target base station. This will be described in detail as follows.

5 is an operation flowchart of a handover method using a resource reservation protocol according to an embodiment of the present invention, as shown therein, transmitting information of a target base station from a mobile terminal to a serving base station; Transmitting information of a target base station from the serving base station to a control station; Newly reserving a resource for a path from the control station to a target base station; Multicasting traffic from the control station to a serving base station and a target base station; Buffering packets at the serving base station and the target base station; Receiving a packet with a new CID from a target base station if the mobile terminal succeeds in handover; If the handover fails, the mobile terminal receives the buffered packet from the serving base station.

The mobile terminal determines the handover to the target base station and transmits the information of the target base station to the base station currently serving when the handover of the network layer occurs. The serving base station transmits the information of the target base station to the control station.

The control station has information of all base stations existing in its network, and the control station or higher control station of the serving base station newly reserves resources for the path to the target base station. This will be described in detail as follows.

FIG. 6 is a flowchart illustrating an operation of multicasting traffic by resource reservation in a control station of FIG. 5, wherein the serving base station transmits information of the target base station to the control station as shown in FIG. 5; Transmitting information of a target base station from the control station to a higher control station; Newly reserving a resource for a path from the control station to a target base station; Newly reserving a resource for a path from the upper control station to a target base station; Multicasting traffic from the upper control station to a serving base station and a target base station.

The control station receives the information of the target base station from the serving base station, newly reserves a resource for the path to the target base station, determines whether the reserved resource is used, and returns the reserved resource if it is not used by the mobile terminal. The control station determines the network to which the target base station belongs, and if it belongs to another network, transmits information of the target base station to the higher control station.

The upper control station receives the information of the target base station from the serving base station or the control station, newly reserves a resource for the path to the target base station, determines whether the reserved resource is used, and returns the reserved resource if it is not used by the mobile terminal. do.

The upper control station determines whether the path to the mobile terminal via the serving base station and the path to the mobile terminal via the target base station is connected, and multicasts traffic to the serving base station and the target base station when connected. At this time, the upper control station multicasts the traffic by IP tunneling to the two base stations.

The serving base station and the target base station receive the packets multicasted by the upper control station and store them in a buffer.

The mobile terminal acquires synchronization for the target base station for performing network reentry, performs ranging on downlink and uplink, and attempts to form a basic function. In this case, when cell rejection occurs between the mobile terminal and the target base station, the mobile terminal selects another target base station and transmits information of the other target base station to the serving base station to newly reserve a resource for a path to the other target base station by the control station. .

When the mobile terminal completes network reentry and succeeds in handover corresponding to the target base station, and the session is activated, the mobile terminal receives the packet with the new CID from the target base station, and the target base station transmits the buffered packet to the mobile terminal with the new CID. If the handover fails, the mobile terminal receives a buffered packet from the serving base station.

The mobile terminal starts receiving the buffered packet from the target base station prior to the handover of the network layer. At the same time, the control station releases the resources reserved to the serving base station.

In addition, the serving base station terminates the service to the mobile terminal to terminate the handover and releases all connections associated with the mobile terminal and all related information.

The control station applies hierarchical MIP and handles handover of the network layer. The control station reregisters and reconnects the mobile terminal, assigns an IP address to the mobile terminal and registers the address. The control station handles the handover of the network layer by not only registering the auxiliary address but also performing resource reservation to the home agent or counterpart host of the mobile terminal.

As described in detail above, the present invention reduces the delay required by the resource reservation protocol by reserving a resource for a communication path in advance during handover in the mobile Internet, and reduces the handover delay, thereby preventing the mobile terminal from receiving a packet. By shortening the communication interruption period, there is an effect that the packet is normally received from the target base station to which the handover is performed.

In addition, by multicasting the traffic to the serving base station and the target base station to which the resource is reserved, the buffered packet is received from the target base station handed over by the mobile terminal before handover of the network layer, thereby ensuring the quality of traffic and minimizing the handover delay. This provides efficient service mobility and maximizes resource efficiency.

Claims (6)

Transmitting, by the mobile terminal, information of the target base station to the serving base station when the handover occurs; Pre-reserving a resource to a target base station by using the information of the target base station at the control station; Multicasting traffic from the control station to a serving base station and a target base station; Buffering packets at the serving base station and the target base station; Receiving multicasted traffic from a target base station upon successful handover from the mobile terminal to a target base station; And a step of processing handover of a network layer at the control station. The method of claim 1, wherein the mobile terminal receives a buffered packet from a serving base station when the handover fails. The handover method of claim 1, wherein the control station releases the reserved resources to the serving base station at the same time as the mobile station receives the traffic from the target base station. The method of claim 1, wherein the information transmission of the target base station is Transmitting information of the target base station from the mobile terminal to the serving base station; Transmitting information of a target base station from the serving base station to a control station; And determining, by the control station, a network to which the target base station belongs and transmitting information of the target base station to a higher control station when belonging to another network. The method of claim 1, wherein the traffic multicasting of the control station It is determined whether the path to the mobile terminal via the serving base station and the path to the mobile terminal via the target base station are connected to each other, and when connected, multi-casting traffic to the serving base station and the target base station. Over way. The method of claim 1, wherein the control station determines whether to use the reserved resource and returns the reserved resource if it is not used by the mobile terminal.

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