KR20050037325A - System and method for hand-off of mobile ip terminal in wireless network - Google Patents

Abstract

The present invention relates to a system and method for providing hand-off of a mobile IP terminal in a wireless system using mobile IP.

The present invention provides a system and method that can reduce the delay time when handoff of a mobile host in a wireless network, reduce power consumption during handoff, and prevent degradation of quality of service.

The system of the present invention is a system for handoff of a mobile IP terminal in a wireless network, which manages the wireless network, exchanges information between adjacent access routers, and a neighboring access router when a handoff request is requested from the mobile IP terminal. Access routers for transmitting information to the mobile IP terminal and the mobile IP terminal for performing a handoff to the handoff target access router using the information obtained from the access router.

Description

System and method for handoff of mobile IP terminal in wireless network {SYSTEM AND METHOD FOR HAND-OFF OF MOBILE IP TERMINAL IN WIRELESS NETWORK}

The present invention relates to a system and method for ensuring mobility of a terminal in a wireless system using mobile IP, and more particularly, to a system for providing hand-off of a mobile IP terminal in a wireless network; It is about a method.

Typically, a wireless system includes a system such as a cellular phone or a personal cellular system (PCS) mobile communication system, a system such as a wireless local loop (WLL) and a wireless LAN (WLAN). These systems have been developed as independent system domains, but the systems are currently being integrated using IP (Internet Protocol). As such, a proposed method for integrating systems using IP is a method of performing communication using Mobile IP in each system. As described above, when the mobile IP is used, the target of the terminal communicating with the wireless channel is an access router (AR). The most representative example of such an access router (AR) is a wireless LAN system.

Then, we will look at the case of using a mobile IP in a wireless LAN system. Basically, since the WLAN system communicates with the access router using a wireless channel, the mobility of terminals may be guaranteed within a range in which one access router performs communication. This mobility guarantee does not guarantee perfect mobility. That is, one terminal may move to another access router while performing communication in a specific access router area. In this case, as in the mobile communication system, handoff must be provided to ensure mobility. That is, the location of the terminal must be managed and seamless communication must be provided even during handoff. The technique used in the Internet to provide seamless communication even during handoff is Mobile IP technology. The IP (Internet Protocol) technology includes a version 4 mobile IPv4 and a version 6 mobile IPv6 technology depending on the version. In the following description, a terminal using a mobile IP regardless of a version will be referred to as a "mobile host".

In Version 4 of Mobile IPv4, a Home Agent (hereinafter referred to as "HA") and a Visitor Agent (hereinafter referred to as "FA") are defined to provide mobility of a mobile host. The location management of the mobile host is performed through HA and FA. The HA resides in the home network of the mobile host, and the FA resides in the network that the mobile host has handed off. First, whenever the mobile host performs a handoff, it informs the HA of its current location information. At that time, the HA records the location information of the mobile host, and when there is data destined for the mobile host, the HA intercepts and encapsulates the data, and delivers the data to the FA through a tunnel. The FA then receives the encapsulated data from the HA to the mobile host and forwards it to the mobile host in its network.

As described above, when data is delivered to the mobile host, the delivered data is always delivered via HA. This presents a problem that the delivery path of the data is not optimized. Therefore, in order to improve this, a route optimization (RO) technique has been proposed. The version 6 Mobile IPv6 scheme has been proposed to accept the advantages of the version 6 IPv6 scheme and to support mobile hosts in the version 6 IPv6 network. In this version 6 IP technique, RO is assumed by default when transferring data, so that the mobile host is the end of the tunnel to decapsulate.

On the other hand, the Mobile IP protocol is a method for handoff in the third layer (Layer 3: hereinafter referred to as "L3") of the model of the OSI 7 layer. However, the method for handoff in the second layer (Layer 2: hereinafter referred to as "L2") to be completed before communication is performed in L3 is not dealt with. In addition, since a large delay occurs during handoff of the mobile host, it is difficult for the mobile host to perform seamless communication. In order to compensate for this, techniques such as fast mobile IP or hierarchical mobile IP have been proposed. These methods reduce the delay time caused by handoff compared to mobile IP. However, the above methods are also techniques for dealing with handoff in L3, as with Mobile IP. That is, no consideration is given to L2 handoff. Therefore, there is no appropriate method for the optimization of the L2 handoff and the correlation between the L2 handoff and the L3 handoff at the time of the handoff (L2, L3).

Next, the cause of the delay in the L2 handoff process will be described. The delay in the L2 handoff process is basically due to the following characteristics of the wireless network.

First, even in the case of using one medium, the wireless network communicates using a different channel from the neighboring wireless network to avoid interference. Therefore, in order to handoff a mobile host, it is necessary to basically know the media information and channel information used in the wireless network to which the mobile host intends to handoff. In order to know this information, L2 of the mobile host must examine all the media and channels available in the wireless network. This process may be referred to as channel scanning. After performing such a channel scanning process, the mobile host selects an optimal medium and channel for handoff. After determining the optimal medium and channel as described above, the access router AR corresponding to the determination is selected, and then a handoff process is performed at L2.

This will be described with reference to FIG. 1. 1 is a diagram illustrating a moving path of an access router and a mobile host using an IP network.

In FIG. 1, the Internet network 131 is a version 4 or version 6 IP network. The first router 121 and the second router 122 which are upper routers are connected to the network. A plurality of access routers 111, 112, 113, and 114 are connected below the first router 121 and the second router 122. In FIG. 1, a first access router 111 and a second access router 112 are connected to a lower part of the first router 121, and a third access router 113 is located below the second router 122. And the fourth access router 114 are connected.

It is assumed that the first access router 111 has a network channel of 802.11a standard of IEEE, and the second access router 112 is assumed to have a network channel of 802.11b standard of IEEE, and the third access router 113 ) Is assumed to have a network channel of IEEE 802.11a / b standard, and the fourth access router 114 is assumed to have a network channel of IEEE 802.11g standard. In addition, the mobile host 101 is connected to the lower part of the first access router 111 to perform communication through a wireless channel. The mobile host 101 is shown below the first access router 111 by reference numeral 101a, and the case where it exists below the second access router 112 is shown by reference numeral 101b. A case existing below the access router 113 is shown by reference numeral 101c.

In this way, the mobile host can move while changing the access router. That is, if there is only a lower part of a specific access router, there is no problem due to handoff. However, when moving to another access router, handoff should be performed. This case will be described in more detail.

For example, while performing communication in the network of the first access router 111 in which the current mobile host exists, the mobile host changes its area, that is, moves to the second access router 112 by moving as shown by reference numeral 10. Cases may occur. When the access router is changed as described above, the current network uses the IEEE 802.11a standard and the neighbor network performs the communication using the IEEE 802.11b technology. As a result, the following problems may occur by using different connection technologies.

First, since the mobile host 101a does not know which standard communicates with which neighbor network and which channel is used, the mobile host 101a needs to find out the technology and channel used. In order to know the standard and the channel used, the mobile host performs an inspection on all channels used in the standard by using IEEE 802.11a, which is a standard used in the currently connected network. However, the neighbor network uses the IEEE 802.11b standard network, so the information is not known. The mobile host then re-examines the channel using any other IEEE 802.11a-enabled access technology. If the mobile host can use all of the technologies of IEEE 802.11a, b, and g, then the channel is checked again by selecting either IEEE 802.11b or IEEE 802.11g. In this case, if the standard selected by the mobile host is IEEE 802.11b, it may be able to find out which channel is used in the neighbor network. If IEEE 802.11g is selected, all channels should be checked and then again checked using IEEE 802.11b.

When setting the standard and checking the channels one by one, the time required for this has a great effect on the communication. This is a problem not only for basic mobile IP, but also for fast hand-off and hierarchical mobile IP technology. In addition, when the mobile host uses a portable power source such as a battery, when such a large search time is required, the usage time is shortened. In addition, there is a problem that can cause a deterioration of the service quality because the fast handoff is not performed.

It is therefore an object of the present invention to provide a system and method that can reduce the delay time when handing off a mobile host in a wireless network.

Another object of the present invention is to provide a system and method for reducing power consumption during handoff of a mobile host in a wireless network.

It is still another object of the present invention to provide a system and method capable of preventing degradation of quality of service during handoff of a mobile host in a wireless network.

A system of the present invention for achieving the above objects is a system for handoff of a mobile IP terminal in a wireless network, which manages the wireless network, exchanges information between adjacent access routers, and handoffs from the mobile IP terminal. Access routers for transmitting adjacent access router information to the mobile IP terminal upon request, and the mobile IP terminal for performing a handoff to a handoff target access router using information obtained from the access router.

A method of the present invention for achieving the above objects is a handoff method of a mobile IP terminal in a wireless network, the process of exchanging information between adjacent access routers managing the wireless network, and the handoff request of the mobile IP terminal And transmitting time-contiguous access router information to the mobile IP terminal, and performing handoff to a handoff target access router using information obtained from the access router.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The method to be used in the present invention will then be outlined first. In order to solve the problems described in the prior art, the present invention uses a method in which geographically adjacent access routers periodically exchange media information and channel information used in their wireless networks, and notify the mobile host of this information. By using this method, the mobile host can complete the handoff in a short time by performing a check on a predetermined medium and a channel without having to perform a check on every medium and every channel. That is, the present invention proposes a protocol that can reduce the time required for handoff, reduce the power consumption of the mobile host, and prevent the degradation of the service quality. In the present invention, the concept of a protocol used to exchange information between access routers is an application level protocol.

First, a conceptual method of transferring information between routers in a network according to the present invention will be described first with reference to FIG. 2. 2 is a diagram illustrating a movement path of an access router and a mobile host using an IP network to which the present invention is applied. FIG. 2 is assumed to have the same configuration as that of FIG.

Accordingly, it is assumed that the first access router 211 has a network channel of IEEE 802.11a standard, and the second access router 212 is assumed to have a network channel of IEEE 802.11b standard, and the third access router ( 213 is assumed to have a network channel of the IEEE 802.11a / b standard, and the fourth access router 214 is an example of assuming that the network channel of the 802.11g standard of IEEE. In addition, the mobile host 201 is connected to the lower part of the first access router 211 and performs communication through a wireless channel. The mobile host 201 illustrates a case where it exists below the first access router 211 with reference numeral 201a, and a case where it exists below the second access router 212 as shown by reference numeral 201b. A case existing below the access router 213 is shown by reference numeral 201c.

According to the present invention among the above-described configuration, the first access router 211 transfers the standard and channel information used by the first access router 211 to the second access router 212 through the first router 221 connected to the upper part. This delivery route is shown at 201. The second access router 221 also transmits the standard and channel information used by the second access router 221 to the first access router 211 through the first router 221 connected thereto. This route of delivery is shown at 202. The second access router 212 and the third access router 213 transfer data to the Internet 231 through the first router 221 connected to the upper part of the second access router 212, and thereafter. Information is transmitted to the third access router 213 through the second router 222 connected to the upper part of the third access router 213. Such information may be standard information, channel information quality of service (QoS) information, security information, and the like. The expression "information" or "standard information and channel information" or "standard and channel information" used in the following description are all representative of the above information, and other information required by the network is required. Information and other information needed for handoff may be further included. As such, the information required for the network and the information required for the handoff are information that can be known to those skilled in the art with reference to the present invention described below.

This path is shown at 203. In the opposite case, the third access router 213 and the second access router 212 transfer data to the Internet 231 through the second router 222 connected to the upper part of the third access router 213. Thereafter, the standard information and the channel information are transmitted to the second access router 212 through the first router 221 connected to the upper part of the second access router 213. This path is shown at 204. This is the case where the paths of the reference numeral 205 and the reference numeral 206 are also transmitted in the same manner.

In order to perform the operation described above, each access router should be able to transmit its information to a geographically adjacent access router. Each access router also needs information about what access routers exist around it. In the present invention, there may be two methods for a specific access router to know what access routers exist around it.

First, the administrator who manages the network explicitly defines the access routers adjacent to each access router. This is the simplest method and is useful unless your network configuration changes. However, this method has a disadvantage in that the administrator has to configure all access routers and change them manually when the access router is added or changed.

Secondly, there is a way for each access router to automatically know the information of the access router located in its vicinity by the mobile host. The second method is a method in which a mobile host performs handoff while informing the access router of the current network of information about the network before the handoff, and can use the information to know the information about the neighboring access router. Using this method, each access router can automatically grasp their information even if an access router is added.

3 is a flowchart of an operation performed at each access router when a mobile host performs a handoff according to a preferred embodiment of the present invention. Hereinafter, referring to FIG. 3, the overall process when a mobile host performs a handoff from a specific access router to another access router after transmission of information between respective access routers according to the present invention will be described. In addition, it is assumed that the mobile host 201a moves from the first access router 211 to the second access router 212 as an example.

First, since the first access router 211 and the second access router 212 are adjacent access routers, information about a standard and a channel used between the access routers was previously exchanged. In FIG. 3, it is assumed that this process has already been performed in step 300. However, if it is performed for the first time, it can be seen that there is a mutually adjacent access router after a handoff request from a specific mobile host. However, in general, since most of these things happen after the pre-made, step 300 is described as already performed. Therefore, the first access router 211 and the second access router 212 are in a state of knowing the information on the standard and the channel of the IEEE used mutually.

In this case, when a specific mobile host, that is, the mobile host 201a moves to the second access router 212 while moving with reference numeral 10, the mobile host 201a requests a handoff to the first access router 211. Done. At this time, the mobile host 201a requests the first access router 211 for information about an access router that is a target of the handoff. Upon receiving such a handoff request, that is, when a handoff is requested from a specific mobile host as a result of the check in step 310, the first access router 211 proceeds to step 320. In step 320, the first access router 211 transfers the specification and channel information used by the second access router 212, which is the access router requested by the mobile host 201a, to the mobile host 201a. The first access router 211 proceeds to step 330 to release a channel established with the mobile host 201a and to stop communication. This process is also performed in the mobile host 201a, and releases a channel with the first access router 211 and sets a channel with the second access router 212 to perform a handoff. Through this, the mobile host 201a moves and becomes the mobile host 201b existing under the second access router 212.

4 is a control flowchart of updating neighbor network information in an access router of a wireless network according to the present invention. Hereinafter, a control process for updating neighbor network information performed by an access router in a wireless network according to the present invention will be described in detail with reference to FIG. 4. In addition, the control process of FIG. 4 will be described as a process performed by the first access router 211 of FIG.

The first access router 211 maintains the standby state in step 400. In the standby state used in FIG. 4, a state in which the first access router 211 does not perform a special operation or a state in which an operation related to the present invention is not collectively referred to as a standby state.

While maintaining the standby state, the first access router 211 proceeds to step 410 to check whether an update period has arrived. In the present invention, it is assumed that the access routers have an update period of a predetermined time unit in order to transfer information between adjacent routers. Such an update period may be set to 30 seconds or more or less time. When the update cycle arrives as described above, the first access router 211 proceeds to step 440. However, if the update cycle does not arrive, the process proceeds to step 420.

In step 420, the first access router 211 determines whether its network configuration (or environment) has changed. Such a change in network configuration or environment may correspond to a change in a channel or a change in a standard used. In this case, the first access router 211 proceeds to step 430, and if not, proceeds to the standby state of 400. In step 430, the first access router 211 updates and stores the changed configuration information in its own network, and proceeds to step 440. When the first access router 211 proceeds from step 410 or step 430 to step 440, the first access router 211 transfers network configuration information to adjacent access routers. The adjacent access routers may be known through the method described with reference to FIG. 3.

In order to exchange information between the access routers described above, there may be periodic information exchange. Alternatively, when a change occurs in the network, a method of informing the access router of the neighbor network may be used. Each has advantages and disadvantages and can be defined according to the network's management policy.

5 is a control flowchart when an access router receives network information from an adjacent access router according to an exemplary embodiment of the present invention. Hereinafter, a control process in the case of receiving network information from an adjacent access router in an access router according to an embodiment of the present invention will be described in detail. In addition, it is assumed that the above example is performed in the first access router 211 of FIG.

The first access router 211 maintains the standby state in step 500. In the standby state used in FIG. 5, a state in which the first access router 211 does not perform a special operation or a state in which an operation related to the present invention is not collectively referred to as a standby state.

The first access router 211 maintains the standby state as described above, and proceeds to step 510 to check whether information is received from an adjacent access router. In step 510, when the network information having the standard and the channel information is received from the adjacent access router, the first access router 211 proceeds to step 520 and compares it with the existing network information of the corresponding neighboring access router. Perform In operation 530, the first access router 211 proceeds to step 540 when the network information received from the adjacent access router is different from the existing access network information, that is, when it is changed, and proceeds to step 500. . In operation 540, the first access router 211 updates and stores network information of the corresponding access router received from the adjacent access router. As a result, when network information is changed from an adjacent access router, neighboring network information can be continuously updated and maintained accordingly.

6 is a control flowchart when handoff is performed in a mobile host of a network according to an exemplary embodiment of the present invention. Hereinafter, a control process for performing handoff in a mobile host of a network according to the present invention will be described in detail with reference to FIG. 6. In addition, the process will be described on the assumption that the mobile host 201a located in the first access router 211 moves to the second access router 212 as shown in FIG. 2.

The mobile host 201a performs a communication mode or a standby mode in step 600. Herein, the communication mode refers to a state of communicating with the first access router 211 which is the corresponding access router, and the standby mode refers to a state of not communicating with a specific access router. The mobile host 201a in this state proceeds to step 602 and checks whether a situation requiring handoff occurs. If a situation requiring handoff occurs in step 602, the flow proceeds to step 604. Here, the determination of whether or not a handoff is necessary may be performed by comparing a signal strength from the current access router with a signal strength from another access router, and the like.

In this case, when a handoff is required and the flow proceeds to step 604, the mobile host 201a requests neighbor network information to the first access router 211 that communicates with itself. After requesting the neighbor network information as described above, the mobile host 201a receives the neighbor network information from the first access router 211 in step 606. In this case, the received neighbor network information may be information of a plurality of access routers rather than information of one access router. This is easy to see if you consider adjacent cells in a cellular system. In step 606, when the first access router 211 receives the information of the neighbor network, the process proceeds to step 608 to determine the priority of the medium and the channel. In this case, a specific medium may be determined first, and then a channel may be set. If there are three neighbor access router information received from the first access router 211, three neighboring access routers having a network environment of 802.11a of the IEEE standard, 802.11g neighbor access router of the IEEE standard Assume one case. In addition, the channel information used by each neighboring access router, that is, the channel information used by two neighboring access routers having the 802.11a network environment of the IEEE standard can be found. Know channel information to use. Therefore, after determining a specific standard, using the method of checking corresponding channels, it is possible to determine an access router that can perform handoff without checking all channels.

In the present invention, the method of determining the priority will not be described in detail. When the priority is determined in this way, the mobile host 201a proceeds to step 610 to search for channels according to the priority. Whenever a specific channel is searched for, a process proceeds to step 612 to check whether a target network for handoff is searched. In step 612, if the target network is searched, the mobile host 201a proceeds to step 614. FIG. However, if the target network is not searched in step 612, the mobile host 201a proceeds to step 610 to change the channel or specification according to the next priority and perform a new search as the changed.

When the search for the specific network to perform the handoff is completed through this process, the mobile host 201a performs the L2 handoff. After that, the handoff process is performed on the upper layer. When the handoff process is completed, that is, when the mobile host 201a moves to the lower part of the second access router 212 of FIG. 2, the mobile host 201a performs the communication mode or the standby mode of step 600 again.

As described above, the process when the mobile host performs the handoff will be described once again with reference to FIG. 2. When the mobile host 201a moves from the lower side of the first access router 211 to the lower side of the second access router 212, the mobile host is about to perform a handoff using the signal strength of the current network. Will be detected. The mobile host then requests the first access router 211 of the current network for information about the neighboring wireless network of the current network. Using this information, the mobile host can obtain the following information. First, it is possible to know in which administrative domain the mobile host exists, and the distance between neighboring access routers (Hop Distance). You can also find out what features an access router can provide. The mobile host can use this information to know the information about the surrounding wireless network, and can select and hand off an access router that is most suitable for communication of the mobile host among various access routers.

However, current mobile IP technology does not provide a technology for a mobile host to select a suitable access router. Therefore, to this end, the present invention proposes a method of performing an efficient handoff using an Access Router Information Protocol (ARIP) packet. As such, when the ARIP packet proposed by the present invention is used, handoff between heterogeneous networks can be applied. Next, a case of using an ARIP packet will be described below.

In order for a current mobile host to hand off a wireless network, a search for all channels must be performed for each wireless network as described in the related art. This selects the appropriate access router for the mobile host and only then starts the L2 handoff. When ARIP is applied to it, the mobile host can know the information about the neighboring wireless network, and thus can search only the channel used by the neighboring network, thereby reducing the time required for handoff.

This ARIP packet has a configuration as shown in Table 1 below.

MAC Header (14 bytes) IPv6 Header (20 bytes) UDP Header (8 bytes) ARIP Information (64 bytes + option length)

In addition, the information type and configuration of the ARIP information region located at the end of the ARIP packet can be configured as shown in Table 2 below.

Address of Access Router Medium Info. Channel Info. OoS Info. Flags Authentication Info. Address prefix Options

The length of each region used in Table 2 is as follows: Address of Access Router is 128 bits, Medium Info. Is 32 bits, Channel Info. Is 32 bits, OoS Info. Is 32 bits, and Flags is It is 32 bits, Authentication Info. Is 128 bits, Address Prefix is 128 bits, and Options is variable size.

In the ARIP according to the present invention, information exchanged between each access router is as follows. First, the L2 information is transmitted in order to reduce the delay time for the L2 handoff of the mobile host. For example, different information is included according to a medium used in a wireless network. If IEEE 802.11 is used, extended service set ID (ESSID) and channel information are included. In addition, in <Table 2>, the Address of Access Router indicates an address of the access router, Medium Info., Channel Info. And the like indicate which wireless access medium is used and which channel is used. Flags indicate information on whether an access router currently transmitting this packet supports Fast Handoff, Paging, and the like. Authentication Info. And QoS Info. Indicate QoS information provided by the corresponding access router and information on which authentication is used. Address Prefix indicates the prefix of the address currently used by the network managed by this access router. Finally, if there is more need depending on the presence or absence of each information, Options are used to convey the information.

For example, when using an 802.11 WLAN, information such as ESSID is transmitted. In addition, the L3 information may be included to reduce the delay time in the L3 handoff. And application information for supporting handoff of other mobile hosts.

7 is a signal flow diagram when performing Predictive Fast Handover by using an ARIP packet according to the present invention. Hereinafter, with reference to FIG. 7, the signal flow and operation of the mobile host and the access router during the predicate fast handover using the ARIP packet according to the present invention will be described in detail.

The mobile node (MN) 201 of FIG. 7 illustrates the mobile host of FIG. 2 as an example, and when the handoff is performed in the first access router 211 in FIG. (PAR: Previous Access Router), so we put it together. In addition, since the second access router 212 becomes a new access router (NAR) serving as a target for handoff, the second access router 212 is described together.

The mobile host 201 is in a state of receiving data from the first access router 211 in step 700. As described above, a case in which handover is performed while receiving data will be described. In addition, step 702 of FIG. 7 is a process of exchanging network information between the first access router 211 and the second access router 212 which is an adjacent access router using the ARIP packet according to the present invention. In this case, the contents of the exchange are exchanged as described above.

In this state, there is a case where the previous second layer trigger (Pre-L2 Trigger) occurs while the mobile host 201 performs communication with the first access router 211. This second layer trigger is a case of requesting handover of the second layer. That is, when the signal strength is weak and the like to inform the upper layer of the mobile host that communication should be performed through another access router. The mobile host 201 proceeds to step 706 and requests the neighbor network information by transmitting an ARIP packet according to the present invention to obtain the neighbor network information to the first access router 211. Here, the previous second layer trigger (Pre-L2 Trigger) is a second layer trigger (L2 Trigger-Layer 2) from the second layer (layer 2) to perform the actual handoff after the mobile host 201 enters the network. Layer 3) can be any time from indication to), which is determined by network management or other factors.

If the information of the neighbor access network is requested, the first access network 211 transfers the information of the networks adjacent to the first access network to the mobile host 201 in step 708. Then, the mobile terminal generates a second layer trigger (L2 trigger) in step 710, and proceeds to step 712 to request information for latent fast handover to the first access router 211. Send a Router Solicitation for Proxy (RtSolPr). In operation 714, the first access router 211 transmits access router information to the mobile host 201 using a proxy router advertisement (PrRtAdv).

The mobile host 201 then generates a prospective new care of address (NCoA). In operation 716, the mobile host 201 transmits a fast binding update message (FBU) to the first access router 211 with the generated NCoA. The FBU is a message indicating that the mobile host 201 should redirect traffic to the second access router 212 to the first access router 211. Accordingly, the FBU may bind a previous valid address (PCoA), that is, a valid address (CoA) at a first access router 211 that is a previous access router and a valid address (CoA) at a second access router, that is, a new access router. The authority is given to the first access router 211. This is to allow the packet to be delivered to the mobile host 201 to be tunneled to a location where the location of the mobile host 201 is changed.

Accordingly, the first access router 211 receiving the FBU message sends a hand-over initiate message (HI) to the second access router 212, which is a new access router received from the mobile host 201 in operation 718. send. The HI is to initiate a handover by being sent from the first access router 211 to the second access router 212, which is a new access router. The second access router 212 then sends a hand-over acknowledgment (HACK) handover acknowledgment (HACK) as a result in step 720 according to the HI received from the first access router 211. Send to 211. The process of delivering HI and HACK is to verify whether the expected NCoA can be used.

The first access router receiving the handover response message as described above transfers a fast binding acknowledgment (FBACK) message to the mobile host 201 and the second access router 212 in steps 722a and 722b. The mobile host 201 must then use the available NCoA-sent to HI and verified by the new access router or assigned by the new access router-when accessing the new access router, the second access router 212. . Accordingly, the mobile host 201 disconnects the channel connected to the first access router 211 in step 724.

In operation 726, the first access router 211 forwards the data to be delivered to the mobile host to the second access router 212, which is a new access router. In addition, in step 728, the mobile host 201 determines a priority according to the received neighbor network information according to the information, and checks a channel. When the mobile host 201 searches the neighboring network to perform the handoff as described above, the mobile host 201 searches only a limited number of channels using the information by the ARIP according to the present invention, and performs a search for the neighboring network. When this channel check is completed, the mobile host 730 prepares for a connection.

The mobile host 201 transmits a fast neighbor advertisement (FNA) to the second access router 212, which is a new access router. The FNA is a message sent from the mobile host to the second access router to confirm the NCoA when the mobile host 201 receives the FBACK and to inform that it is connected to the new access router. As such, the second access router 212 receiving the FNA message transmits the data received from the first access router 211, which is the previous access router, to the mobile host 201.

8 is a signal flow diagram when performing Reactive Fast Handover by using an ARIP packet according to the present invention. Hereinafter, with reference to FIG. 8, the signal flow and the operation of a mobile host and an access router in a reactive fast handover using an IAPR packet according to the present invention will be described in detail.

The mobile node (MN) 201 of FIG. 8 illustrates the mobile host 201 of FIG. 2 as an example, and when the first access router 211 performs handoff in FIG. 8, It became a previous access router (PAR), so we put it together. In addition, since the second access router 212 becomes a new access router (NAR) serving as a target for handoff, the second access router 212 is described together.

The mobile host 201 is in a state of receiving data from the first access router 211 in step 800. As described above, a case in which handover is performed while receiving data will be described. In addition, step 802 of FIG. 8 is a process of exchanging network information between the first access router 211 and the second access router 212 which is an adjacent access router using the ARIP packet according to the present invention. In this case, the contents of the exchange are exchanged as described above.

In this state, there is a case where the previous second layer trigger (Pre-L2 Trigger) occurs while the mobile host 201 performs communication with the first access router 211. This previous second layer trigger is a case of requesting handover of the second layer. That is, the second layer of the mobile host informs the third layer that the signal strength is weakened and thus communication should be performed through another access router. The mobile host 201 proceeds to step 806 and requests the neighbor network information by transmitting an ARIP packet according to the present invention to obtain the neighbor network information to the first access router 211. Here, the previous second layer trigger (Pre-L2 Trigger) is a second layer trigger (L2 Trigger-Layer 2) from the second layer (layer 2) to perform the actual handoff after the mobile host 201 enters the network. Layer 3) can be any time from indication to), which is determined by network management or other factors.

When the information of the neighbor access network is requested, the first access network 211 transmits the information of the networks adjacent to the first access network to the mobile host 201 in step 808. Then, the mobile terminal generates a second layer trigger (L2 Trigger) in step 810, and proceeds to step 812 to request for information for latent fast handover to the first access router 211. Send a Router Solicitation for Proxy (RtSolPr). In operation 814, the first access router 211 transmits access router information to the mobile host 201 using a proxy router advertisement (PrRtAdv).

After performing step 814, the mobile host 201 proceeds to step 816 to disconnect the channel from the first access router 211. In step 818, the mobile host 201 searches for a neighboring network to perform a handoff. In this case, the mobile host 201 searches only a limited number of channels using the information of the ARIP and searches for the neighboring network. If the mobile host 210 does not receive a FBACK from the first access router 201, which is a previous access router, for example, it does not send an FBU or if it leaves the first access router 211 before sending the FBU and receiving the FBACK. The host 201 proceeds to step 822 to encapsulate the FBU to the second access router 212, which is the next access router, and transmits a fast neighbor advertisement (FNA). Step 822 is for the second access router 212 to verify that NCoA can be used. If NCoA is in use, it should discard the FBU packet inside and send an alternative NCoA to the Router Advertisement by setting the Neighbor Advertisement acknowledge (NAACK) option. The FNA is a message sent from the mobile host 201 to the second access router 212 to confirm a new care of address (NCoA) and to inform that the second access router 212 is connected.

The mobile host 201 then connects to the second access router 212 and sends a FBU message to the first access router 211. The FBU is a message indicating that the MN should redirect traffic to the first access router 211 to the second access router 212. Therefore, the FBU binds a new effective address (NCoA) from the previous effective address (PCoA) of the first access router 211 that is the previous access router and the second access router 212 that is the new access router. This is to give the second access router 212 the right to do so that the packet is tunneled to the location where the mobile host 201 is moved.

The first access router 211 then sends a FBACK message to the second access router 212 in response to the FBU. Accordingly, the first access router 211 forwards data to be transmitted to the mobile host 201 to the second access router 212. The second access router 212 then sends the data received from the first access router 211 to the mobile host 201.

7 and 8 described above have described a method of applying ARIP to a fast handoff process. The ARIP packet according to the present invention can operate like a fast handoff, and is required for handoff than when only fast handoff is used because the exchange of messages and information is performed in advance. You can save time. That is, since the search for the channel search in L2 is performed only for a limited channel, not for the entire channel, the time required can be reduced. In addition, the mobile host 201 searches the network in order to perform the handoff, and may use the above information to determine the priority according to the state of the mobile host 201. In other words, the mobile host 201 may perform a handoff to a desired network.

In this way, the mobile host can perform the handoff to the desired network may be a factor to increase the performance of the network. For example, if the mobile host supports fast handoff and the current access router supports fast handoff, it is better for the mobile host to handoff to a network that supports fast handoff when attempting to handoff. Such information can be known using the information contained in the ARIP packet. QoS information is also available to the mobile host for the same reason.

9 is a signal flowchart according to another embodiment when performing a fast handover using an ARIP packet of the present invention. Hereinafter, with reference to FIG. 9, the signal flow and the operation of the mobile host and the access routers during the handover using the ARIP packet according to the present invention will be described in detail.

The mobile node (MN) 201 of FIG. 9 illustrates the mobile host 201 of FIG. 2 as an example, and the first access router 211 performs a handoff in describing FIG. 9. If it becomes a previous access router (PAR), it is written together. In addition, since the second access router 212 becomes a new access router (NAR) as a target for handoff in the description of FIG. 9, the second access router 212 is described together.

The mobile host 201 is in a state of receiving data from the first access router 211 in operation 900. As described above, a case in which handover is performed while receiving data will be described. In addition, step 902 of FIG. 9 is a process of exchanging network information between the first access router 211 and the second access router 212 which is an adjacent access router using the ARIP packet according to the present invention. In this case, the exchange is made of the information as described above.

In this state, while the mobile host 201 is communicating with the first access router 211, a previous second layer trigger (Pre-L2 Trigger) may occur as shown in step 904. Here, the previous second layer trigger (Pre-L2 Trigger) is a second layer trigger (L2 Trigger-Layer 2) from the second layer (layer 2) to perform the actual handoff after the mobile host 201 enters the network. It can be any time from-to indication 3). The previous second layer trigger generation time is determined by network management or other factors. In step 906, the mobile host 201 requests the neighbor network information by transmitting an ARIP packet according to the present invention to obtain the neighbor network information to the first access router 211.

If the information of the neighbor access network is requested, the first access router 211 proceeds to step 908 to transfer the information of the access routers of the network adjacent to the first access router 211 to the mobile host 201. The mobile host 201 then determines priorities for the wireless medium and channel to use according to its preferences. In the present invention, priority determination according to the preference will not be discussed in detail. If the priority is determined, the mobile host 201 transmits the RtSolPr to the first access router 211 to request information for performing hand-over in step 910.

In operation 912, the first access router 211 transmits information of neighboring access routers to the mobile host 201 using a proxy router advertisement (PrRtAdv). Accordingly, the mobile host 201 receives the router advertisement message in step 912. The mobile host 201 then generates a prospective new care of address (NCoA) for use in the selected neighboring access router. In operation 914, the mobile host 201 generates a prepare fast binding update message (PFBU) including the generated expected NCoA and transmits the generated fast binding update message to the first access router 211. The PFBU is a message indicating that the mobile host 201 should redirect traffic to the second access router 212 to the first access router 211.

Accordingly, the PFBU binds a previous valid address (PCoA), that is, a valid address (CoA) at a first access router 211 that is a previous access router and a valid address (CoA) at a second access router, that is, a new access router. The authority is given to the first access router 211. This is to allow the packet to be delivered to the mobile host 201 to be tunneled to a location where the location of the mobile host 201 is changed.

Accordingly, the old access router 211 that receives the PFBU for the access router from the mobile host 201 transmits a handover initiation message (HI) to the second access router 212, which is a new access router. . In an embodiment of the present invention, the first access router 211 receiving the PFBU message transmits a handover initiation message (HI) to the second access router 212, which is a new access router (916). The HI is to initiate a handover by being sent from the first access router 211 to the second access router 212, which is a new access router.

Then, the second access router 212 performs a duplicate address detection (DAD) in step 918 in response to the HI received from the first access router 211, and as a result, a handover response message (HACK). hand-over acknowledgment) is transmitted to the first access router 211 that is the previous access router. The process of delivering HI and HACK is to verify whether the expected NCoA can be used. The first access router, the previous access router that received the handover response message from the access router, binds to the freeze state for the PCoA (CoA used in the PAR) and the NCoA (CoA used in the NAR) of the mobile host 201. Create an entry. The binding entry in the freeze state is not activated until a fast binding update message (FBU) is received from the mobile host, and the first access router that is the previous access router for the binding entry in the inactive state. 201 does not forward traffic to the second access router 202.

When the first access router 211, which is the previous access router, receives the HACK message, the first access router 211 transmits a prepare fast binding acknowledgment (PFBack) message to the mobile host 201 in step 920. In this case, the mobile host 201 actually transmits the handover response message to the access router 201 by using the mapping of the second layer and the third layer information (L2: L3 mapping). Select a channel to be scanned. According to an embodiment of the present invention, when a first access router 211, which is a previous access router, receives a handover response message from a second access router 212, generates a prepare fast binding acknowledgment (PFBack) message. To the mobile host 201.

When the mobile host receives the ready fast binding response message, the mobile host proceeds to step 922 to generate a second layer trigger (L2 trigger). The mobile host 201 selects a second access router 212, which is a target access router to be handed off by performing a search on a channel used by the access router selected in step 920, and then moves the previous access router, that is, the first access in step 924. A fast binding update message (FBU) is transmitted to the router 211.

Thereafter, the first access router 211 transmits a fast binding acknowledgment (FBACK) message to the mobile host 201 and the second access router 212 in steps 926a and 926b. In addition, the binding entry in the corresponding freeze state is activated, and the remaining binding entries in the freeze state can be automatically erased by a timeout. The mobile host 201 must then use the available NCoA-sent to HI and verified by the new access router or assigned by the new access router-when accessing the new access router, the second access router 212. .

Accordingly, the mobile host 201 disconnects the channel connected to the first access router 211 in step 928. In operation 930, the first access router 211 forwards data to be delivered to the mobile host to the second access router 212, which is a new access router. When the mobile host 201 searches for a neighbor network to perform a handoff in step 932, the mobile host 201 searches only a limited number of channels using the information by the ARIP according to the present invention, and performs a search for the neighbor network. . When the channel check is completed, the mobile host 201 prepares for a connection in step 934.

The mobile host 201 transmits a fast neighbor advertisement (FNA) to the second access router 212, which is a new access router. The FNA is a message sent from the mobile host 201 to the second access router 212 to confirm the NCoA when the mobile host 201 receives the FBACK and to inform that it is connected to the new access router. In step 938, the second access router 212 receiving the FNA message transmits data received from the first access router 211, which is the previous access router, to the mobile host 201.

In this way, when using the ARIP handoff has the following advantages. First, reverse address translation (mapping of L2 identifiers to L3 identifiers) may be omitted. Second, the DAD process can be performed using this method. Finally, channel scanning is performed only on the selected access routers and the access routers whose reverse address conversion is successful, thereby reducing the time for channel scanning. Such a method can be selectively used by comparing the overhead of performing DAD in a candidate access router to be handed off by the mobile host. That is, whether to use ARIP in conjunction with Fast Handover or to use the method of performing DAD in advance in the above manner can be selectively used according to the importance of traffic. In addition, when using ARIP in conjunction with Fast Handover, Predictive Fast Handover occurs mainly, and Reactive Fast Handover is unlikely.

As described above, the present invention exchanges information between geographically adjacent access routers using ARIP when the mobile host hands off the wireless network and delivers it to the mobile host. In this way, when the mobile host performs L2 handoff, only a limited number of channels need to be searched using the information transmitted from the access router without having to search for all channels. Thus, the delay time for L2 handoff can be reduced. Through this, the present invention helps the mobile host to perform a fast handoff, thereby improving the performance of the network. In order for the mobile host to handoff, it must perform a search for all channels for each wireless network. Since the ARIP of the present invention can be applied to handoffs between heterogeneous networks, the mobile host can know information about a neighboring wireless network when the ARIP is applied. Therefore, only the channel used in the neighboring network is searched. This can reduce the time required for handoff. That is, since the search for the channel search in L2 is performed only for a limited channel, not for the entire channel, the time required can be reduced. This is a factor that enables handoff to be performed quickly or not when ARIP is applied to fast handoff. In addition, since the current Mobile IP technology does not provide a technology for the mobile host to select a suitable access router, if the ARIP described in the present invention is used, more efficient handoff may be provided.

As described above, the present invention has an advantage that a handoff speed of a mobile host can be performed quickly. In addition, there is an advantage that can perform a fast handoff in hetero manganese. In addition, since the terminal capable of performing the fast handoff from the network point of view may select an access router supporting the fast handoff, there is an advantage of increasing network efficiency.

1 is a diagram illustrating a moving path of an access router and a mobile host using an IP network,

FIG. 2 is a diagram illustrating a movement path of an access router and a mobile host using an IP network to which the present invention is applied;

3 is a flowchart of an operation performed in each mobile access router when the mobile host performs a handoff according to an embodiment of the present invention;

4 is a control flowchart of updating neighbor network information in an access router of a wireless network according to the present invention;

5 is a control flowchart when an access router receives network information from an adjacent access router according to an exemplary embodiment of the present invention;

6 is a control flowchart when handoff is performed in a mobile host of a network according to an embodiment of the present invention;

7 is a signal flow diagram when performing Predictive Fast Handover using ARIP packet according to the present invention;

8 is a signal flow diagram when performing Reactive Fast Handover using ARIP packet according to the present invention;

9 is a signal flowchart according to another embodiment when performing a quick handover using an ARIP packet of the present invention.

Claims (2)

In the handoff method of a mobile IP terminal in a wireless network, Exchanging information between adjacent access routers managing the wireless network; Transmitting adjacent access router information to the mobile IP terminal when a handoff request is made by the mobile IP terminal; And performing a handoff to a handoff target access router using information obtained from the access router. A system for handoff of a mobile IP terminal in a wireless network, Access routers for managing the wireless network, exchanging information between adjacent access routers, and transferring adjacent access router information to the mobile IP terminal upon a handoff request from the mobile IP terminal; And the mobile IP terminal performing a handoff to a handoff target access router by using the information obtained from the access router.