KR100827184B1 - Mobile node - Google Patents

Abstract

The mobile node 10, which has no communication interruption time and performs a high quality handover process for maintaining the continuity of communication satisfactorily, has an interface function for connecting to a network. The network quality monitoring unit 12 monitors the network quality based on at least one of the radio wave strength or the radio band received by the network devices 11-1 to 11-n. The handover control unit 13 transmits a temporary address to the address registration destination, changes the path of communication information, and switches the connection destination to a new network before the communication is disconnected in accordance with the state of network quality. Do it. The network control unit 14 receives a response indicating that the temporary address has been updated at the address registration destination, and maintains the reception function with the network before switching until the communication is disconnected.

Handover, Network, Connection, Address, Interruption, Quality Monitoring

Description

Mobile node {MOBILE NODE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mobile nodes, and more particularly to mobile nodes that communicate over mobile IP (Internet Protocol) networks.

In recent years, with the progress of multimedia, the demand for information networks has been advanced and diversified, and development is rapidly progressing toward the realization of a ubiquitous network society. Ubiquitous. " Ubiquitous networks have attracted attention as the next stage of the information society, aiming at an environment (ubiquitous computing) where computers can be used simply and whenever.

The important thing in a ubiquitous environment is that users can connect to the network at any timing. Therefore, the expectation regarding wireless communication in which the degree of freedom is not limited by the cable connection is the highest. Therefore, in recent years, the mobile node has been highly functionalized, and one mobile node is used for multiple networks (mobile IP networks). The environment of connecting in various ways has also been maintained.

On the other hand, there is a handover in the technology that is the key to the spread of mobile IP. Handover refers to a technology for automatically switching the connection destination of a network so that the mobile node can continue the communication even when the mobile node moves to another network during communication with the current network.

For example, at a cafe table, a person listening to music with a PDA (Personal Digital Assistant) equipped with a wireless LAN (Local Area Network) function moves to a neighbor's boutique equipped with another wireless LAN base station. In one case (all PDAs and wireless LANs correspond to mobile IP), if the user has a handover function, the user can continue to listen to streaming music even when moving to another network. Such handover control needs to be carried out instantaneously without the user's knowledge, but it becomes very important for data communication rather than communication only with voice information.

In the conventional handover technology, when disconnection with a network currently being connected is detected, a preset user policy and a network usable at that time are automatically selected to switch networks.

Moreover, the technique which measures received electric field strength, judges that it is used as the weak electric field strength when a measurement result becomes below a reference value, and performs the handover process to another base station is proposed. See, for example, Japanese Patent Application Laid-Open No. 2000-50337 (paragraphs [0005] to [0010], FIG. 2).

However, in the prior art as described above, in the former case, since the handover process is performed after detecting the disconnection of the connected network, communication is cut off midway until the switching of the network connection is completed after disconnection. Therefore, there is a problem that packet loss occurs when the network connection is switched during packet reception.

For example, when streaming broadcast is being listened to, images and audio are cut off, and in the meantime, when packets such as streaming data arrive, packet loss occurs.

On the other hand, with respect to the prior art (Japanese Patent Laid-Open No. 2000-50337), the handover is performed when the received electric field strength is lower than or equal to the reference value, not after disconnection of the network, but the mobile node accompanying the network switching is performed. Since the registration process is not considered at all, there is a problem that communication may not be resumed after the handover process.

That is, even after the network switching, if the registration process of the mobile IP accompanying it is not completed at the network side, communication cannot be normally started to the network of the new moving destination. Therefore, the mobile node needs to allow reception for a predetermined time even after handover processing of the packet via the old network before the movement.

In addition, a wireless network may be disconnected soon after a connection is established once (for example, when it is near the radio wave reception area boundary). Therefore, in order to prevent instability of the network connection, it is also important to perform the handover process after the network to be switched to becomes stable.

This invention is made | formed in view of such a point, and an object of this invention is to provide the mobile node which performs the high quality handover process in order to maintain the continuity of communication with no communication interruption time.

In this invention, in order to solve the said subject, in the mobile node 10 which communicates on a mobile IP network as shown in FIG. 1, the network device 11-1-11-n which has an interface function which connects with a network. ), The network quality monitoring unit 12 that monitors the network quality based on at least one of the radio wave strength or the radio band received by the network devices 11-1 to 11-n, and the state of the network quality. Therefore, before the communication is disconnected, the handover control unit 13 which transmits the temporary address to the address registration destination, changes the path of the communication information, and performs a handover for switching the connection destination to the new network, and the temporary address is the address. A network system that receives a response indicating that it has been updated at the registration destination and maintains the reception function with the network before switching until the communication is disconnected. The mobile node (10), characterized in that it has a part (14) is provided.

Here, the network devices 11-1 to 11-n have an interface function for connecting with a network. The network quality monitoring unit 12 monitors the network quality based on at least one of the radio wave strength or the radio band received by the network devices 11-1 to 11-n. The handover control unit 13 transmits a temporary address to the address registration destination, changes the path of communication information, and switches the connection destination to a new network before the communication is disconnected in accordance with the state of network quality. Do it. The network control unit 14 receives a response indicating that the temporary address has been updated at the address registration destination, and maintains the reception function with the network before switching until the communication is disconnected.

The above and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments as examples of the present invention.

According to the present invention, in the handover on the mobile IP network, the communication interruption time with the network is no longer, so that the occurrence of packet loss can be eliminated. Therefore, it is possible to provide a seamless handover of the network to the user without interrupting IP communication such as voice or video.

For example, when a user is making a call using an IP telephone implementing the function of the present invention, the user is not aware of the interruption of communication due to network switching. In addition, even when the user moves while watching streaming data such as a moving picture, the moving picture does not occur due to network switching.

Further, according to the present invention, the network connection in a stable state can be controlled by setting a drop threshold and a recovery threshold for each threshold of the radio wave strength / wireless band and performing network switching control. have. For this reason, even in an area where radio wave strength, such as in the vicinity of a boundary of a wireless network, changes, it is possible to minimize fluctuations in the network and generation of noise accompanying it, thereby providing a user with stable and stable communication. .

According to the state of network quality, the mobile node of the present invention transmits a temporary address to an address registration destination, changes the path of communication information, and performs a handover to switch the connection destination to a new network, before the communication is disconnected. Until the temporary address is updated at the address registration destination and communication is disconnected, the reception function with the network before switching is maintained. As a result, since no communication interruption time can be maintained and communication continuity can be maintained satisfactorily, it is possible to improve communication quality on the mobile IP network.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings. 1 is a principle diagram of a mobile node of the present invention. The mobile node 10 is a terminal device that communicates on a mobile IP network, and corresponds to a notebook personal computer, a PDA, a mobile phone, and the like. In addition, the function of the present invention can be applied to any of mobile IPv4 and mobile IPv6.

The network devices 11-1 to 11-n each have an interface function for connecting to a network, and correspond to, for example, a NIC (network interface card). The mobile node 10 is equipped with a plurality of network devices connected to a network such as a wireless LAN or FOMA (registered trademark, hereinafter omitted) of a third generation cellular telephone network, and can be connected to a plurality of networks from one terminal.

The network quality monitoring unit 12 monitors the network quality based on at least one of the radio wave strength or the radio band received by the network devices 11-1 to 11-n.

The handover control unit 13 transmits a temporary address (CoA: Care of Address) to an address registration destination (home agent, etc.) before the communication is disconnected in accordance with the state of the network quality, so that the path of the communication information (IP packet). Is changed and handover is performed to switch the connection destination to the new network. As connection switching of a network, switching from the mobile IP network currently communicating with a new mobile IP network is performed.

In addition, the temporary address refers to an IP address which the mobile node 10 temporarily uses in the network of the moving destination. A home agent (HA) is a node that exists in the home network of the mobile node 10 and distributes information to the mobile node 10 or recognizes the location of the mobile node 10.

In addition, regarding the network selection of the connection destination, the handover control unit 13 stores a user priority that can be set by the user (priority of network connection), and according to the change in network quality, the handover control unit 13 sends a hand to a network having a high priority. Over is made. Alternatively, handover is performed based on the network quality index described later managed by the network quality monitoring unit 12.

The network control unit 14 receives a response indicating that the temporary address has been updated at the address registration destination, and maintains the packet reception function with the network before switching until the communication with the network before switching is cut off.

Here, when the mobile node 10 communicates with the network N1 for the first time and moves to the network N2, when the mobile node 10 recognizes that the network quality of the network N1 is degraded, the handover process is performed (that is, the network). If handover is detected before network is disconnected, handover is performed), and communication with the network N2 is continued. At this time, the packet transmitted from the network N1 is received until the communication with the network N1 before switching is cut off. This enables handover without packet loss (no communication interruption time).

Next, the entire operation will be described using the sequence diagram. 2 is a sequence diagram illustrating the operation of the mobile node 10. First, the mobile node 10 communicates via a wireless LAN, moves to a cellular telephone network (FOMA, etc.) side, and then communicates via a cellular telephone network.

[S1] When the mobile node 10 is communicating via a wireless LAN, the mobile node 10 moves to the cellular phone network side and moves away from the wireless LAN, thereby degrading network quality with the wireless LAN. In addition, the state change of the network quality is actually detected at the mobile node 10 regardless of the movement of the mobile node 10.

[S2] The mobile node 10 detects an event indicating a decrease in network quality with the wireless LAN currently communicating, and activates the handover process.

[S3] The mobile node 10 transmits a router solicitation (RS) to an access router (AR) via a cellular phone network. RS refers to a request for acquiring the prefix information (if it is IPv6, the network identifier of the upper 64 bits of the 128-bit IPv6 address), and the AR refers to a router that performs traffic routing between the IP network and the cellular phone network. .

[S4] AR returns RA (Router Advertisement) to the mobile node 10 via the cellular phone network.

[S5] The mobile node 10 transmits a BU (Binding Update) to the HA via the cellular phone network.

[S6] The HA returns a BA (Binding Acknowledgment) to the mobile node 10 via the cellular phone network.

[S7] The mobile node 10 continues the communication performed in the wireless LAN through the cellular phone network, AR, and HA.

[S8] Communication between the mobile node 10 and the wireless LAN is disconnected. In addition, from the deterioration of the network quality in step S1 to the disconnection in step S8, the mobile node 10 continues to receive packets from the wireless LAN.

Next, the configuration of the mobile node 10 will be described. 3 is a diagram illustrating a configuration of the mobile node 10. In the figure, a thick solid line arrow indicates data, and a thin solid line arrow indicates a control signal. The mobile node 10 includes a network device 11, a network quality monitoring unit 12, a mobile IP control unit (corresponding to the handover control unit of the present invention) 13, a network control unit 14, an application 15, and a packet. An input unit 16 and a packet output unit 17 are provided.

The application 15 is an upper application and is software that communicates with other nodes or provides a service to a user. The application 15 includes an application that performs link disconnection processing such as stopping (down) processing of the communication interface of the network device 11 or dial-up of dial-up, and the network control unit ( 14), interface down processing or link breaking processing is required.

The mobile IP control unit 13 is composed of a network state management unit 13a, a network switching control unit 13b, a handover execution unit 13c, and a terminal management unit 13d. Control is performed.

Upon receiving the network quality change event from the network quality monitoring unit 12, the network state management unit 13a notifies the network switching control unit 13b of the network switching request in accordance with the quality situation.

The network switching control unit 13b executes handover in response to changes in network quality (e.g., decrease / restoration of radio wave strength, lack / restoration of radio band, disconnection / establishment of network connection) in accordance with network switching request. A handover request is output to the unit 13c, and an instruction for network switching is output to the network control unit 14.

The handover execution unit 13c executes mobile IP handover based on the handover request. The terminal manager 13d manages the mobile node information, and outputs a network switch request to the network switch control unit 13b as required by the mobile node 10 for communication control and if necessary. The packet data output request is also sent to the packet output unit 17.

The packet input unit 16 performs input processing of packet data received through the network device 11. The packet output unit 17 transmits the packet data to the network via the network device 11 in accordance with the packet data output request.

The network control unit 14 is composed of a packet transmission and reception control unit 14a, an interface processing unit 14b, and a link control unit 14c, and performs management of the network device 11 and overall management of packet transmission and reception.

The packet transmission / reception control unit 14a performs packet transmission / reception control, and performs network transmission / reception with the new network after the switching while maintaining the packet reception function with the old network before the switching.

The interface processing unit 14b performs state management control of the packet input / output interface of the network device 11. In addition, when performing the interface down process according to the request of the application 15, if the communication interface of the target network device is currently connected, a network switching request is executed by the network switching control section 13b to execute the hand. The over is executed, and then the down process is performed (after completion of network switching). When the interface of the network device is up (started up), the network switching control unit 13b notifies that the network device becomes valid.

The link control unit 14c performs state management control of the link of the network with which the network device 11 communicates. At the start of the link disconnection process according to the instruction of the application 15, if the target link is currently connected, a network switching request is made to the network switching control section 13b to execute a handover. The link cutting process is performed later (after completion of network switching). In addition, when the link of the network device is up (connection establishment), the network switching control unit 13b notifies that the connection of the network is established.

The network device 11 performs interface connection control with a network and management of a connection state according to the network type. For example, as the network type, network devices such as wireless LAN 11-1, FOMA l1-2, Bluetooth 11-3, and PDC (Personal Digital Cellular) l1-4 (NIC's) (In addition, the device having the wired interface may be provided as well as the device of the wireless interface).

The network quality monitoring unit 12 includes a radio wave strength monitoring unit 12a and a radio band monitoring unit 12b. The radio wave strength monitoring unit 12a monitors the radio wave strengths of various network devices 11 at fixed or variable periods or based on packet reception (both of periodic monitoring and monitoring using packet reception). You may use). When a change in network quality is detected, a network quality change event is sent to the network state management unit 13a.

The radio band monitoring unit 12b monitors the radio band state of various network devices 11 at fixed or variable intervals or by packet reception (both of periodic monitoring and monitoring using packet reception). May be used). When a change in network quality is detected, a network quality change event is sent to the network state management unit 13a.

Next, the handover of the present invention when the network quality is lowered will be described in detail. 4 is a diagram illustrating handover due to network quality deterioration. First, the system configuration of the network (the system shown in the drawing is an example) will be described.

The IP network 101 is connected to an HA 20, a correspondent node (CN) 104, and an AR (access router) 31, 41. An AR 31 and an access point (AP) 32 are connected to the wireless LAN 102, and an AR 41 and a wireless base station (BS: Base) are connected to the cellular phone network (FOMA, etc.) 103. Station 42 connects.

For the network system as shown in the figure, the mobile node 10 assumes handover between heterogeneous networks from the wireless LAN 102 to the cellular phone network 103.

[S11] The mobile node 10 uses the network device 11-1 (NIC for a wireless LAN) to connect the CN 104, the IP network 101, the AR 31, the wireless LAN 102, Communication is performed via the AP 32, and a packet is transmitted from the CN 104 toward the mobile node 10.

[S12] When the decrease in the radio wave strength received by the NIC 11-1 or the shortage of the radio band occurs, the mobile node 10 detects a decrease in network quality before the network connection to which communication is currently being made is disconnected. Changes the main interface to network device 11-2 (NIC for mobile telephone network), and transmits RS from NIC 11-2 to AR 41 on mobile phone network 103 that can communicate. .

[S13] The AR 41 immediately returns the RA to the mobile node 10 upon receiving the RS.

[S14] The mobile node 10, upon receiving the RA, generates a temporary address for use in the cellular phone network 103, and selects the AR 41 as the default router. Then, uplink packet transmission from the path using the NIC 11-1 is inhibited. Thereafter, the HA 20 transmits a BU (transmission of a temporary address).

In addition, the default router is difficult to set a route to all routers, for example, to all hosts or networks on the Internet in advance, so that a router that routes the most common general route (default route) is used. Say.

[S15] When the HA 20 receives the BU from the mobile node 10, the HA 20 updates a database corresponding to the home address and the temporary address of the mobile node 10 (that is, updates the temporary address), and sends a BA as a response. Reply.

[S16] The mobile node 10 also transmits a BU to the CN 104 that was in communication.

[S17] The CN 104 then transmits the packet to the mobile node 10 via the IP network 101, the AR 41, the cellular phone network 103, and the BS 42, which are new paths.

In addition, since the NIC 11-1 maintains the connection state with the wireless LAN 102 in the above-described sequence, since the packet reception is continued, the mobile node (before the CN 104 receives the BU) is used. Even when a packet is transmitted via the wireless LAN 102 toward 10, it can be received using the NIC 11-1. Therefore, it is possible to handover without generating a packet loss.

Next, the handover of the present invention accompanying the restoration of network quality will be described in detail. 5 is a diagram illustrating handover by network quality recovery. In the handover described above in Fig. 4, when the mobile node 10 is communicating with the CN 104 via the cellular phone network 103, it is assumed that the network quality of the wireless LAN 102 side is restored.

[S21] The mobile node 10 communicates with the CN 104 via the CN 104, the IP network 101, the AR 41, the cellular phone network 103, and the BS 42 using the NIC 11-2. The packet is transmitted from the CN 104 toward the mobile node 10.

[S22] When the network quality of the NIC 11-1 direction (wireless LAN 102) is restored, the mobile node 10 detects the effect, and transfers the main interface from the NIC 11-2 to the NIC 11-. 1), RS is transmitted to the AR 31 on the wireless LAN 102.

[S23] The AR 31 returns the RA to the mobile node 10 immediately upon receiving the RS.

[S24] When receiving the RA, the mobile node 10 generates a temporary address used by the wireless LAN 102, and sets the path in the direction of the NIC 11-1 selected as the main interface as the default route. In addition, uplink packet transmission from the path using the NIC 11-2 is inhibited. Thereafter, the HA 20 notifies the temporary address newly generated by the BU.

[S25] When the HA 20 receives the BU, the HA 20 updates a database corresponding to the home address and the temporary address of the mobile node 10 and returns a BA as a response.

[S26] The mobile node 10 also transmits a BU to the CN 104 that was in communication.

[S27] The CN 104 transmits the packet to the mobile node 10 via the IP network 101, the AR 31, the wireless LAN 102, and the AP 32, which are new paths.

In addition, since the NIC 11-2 maintains the connection state with the cellular phone network 103 in the above-described sequence, packet reception is continued, so that the CN 104 receives the mobile node (before receiving the BU). Even when the packet is transmitted through the cellular phone network 103 toward 10, it can be received using the NIC 11-2. Therefore, it is possible to handover without generating a packet loss.

In addition, regarding handover accompanying the restoration of the network quality here, it is assumed that the priority of the network in the direction of the wireless LAN 102 is higher than that of the cellular phone network 103, and thus, the cellular LAN network 103 is used from the wireless LAN. Although network switching to 102 is performed, if the network quality of the cellular phone network 103 and the wireless LAN 102 are about the same level, the network quality of the cellular phone network 103 does not deteriorate. It is not necessary to perform a handover accompanying the recovery.

In addition, although the handover demonstrated above showed about the handover between a wireless LAN and a mobile telephone network, the network used as a switching destination accompanying the fall of the radio wave strength of a wireless LAN is a wired type like Ethernet (registered trademark), for example. It may be a network. In addition, although the radio wave intensity and the radio band are measured as network quality, in the case of a wired network or the like, the connection establishment of the network is an opportunity and the handover process to the wired network is detected by detecting this network connection establishment. It is also possible to do this.

Next, the operation of the network quality monitoring unit 12 will be described. The network quality monitoring unit 12 has a timer for quality monitoring, and the monitoring cycle can be rewritten from the application. In addition, the quality monitoring starts processing every cycle set in the timer. In addition to starting the timer, the network quality monitoring function is also called when the network device which is the object of quality measurement receives the packet.

Periodic monitoring starts this function with a timer handler that operates when the timer expires, and hardware interrupt handler starts monitoring with a packet reception. In order to identify which process has been activated, the handler of the originator sets the ID for identifying itself as a parameter at the time of the network quality monitoring part 12 to start.

In addition, in order to prevent the quality monitoring from being excessively started and affecting the performance of the system (that is, to prevent the processing from being overloaded), an over surveillance prevention timer is provided so that the monitoring processing is not executed more than necessary. do. When the network quality monitoring function is activated, after the excess monitoring prevention timer is checked, the radio wave strength monitoring unit 12a and the radio band monitoring unit 12b for all the mounted network devices 11-1 to 11-n. ) To measure network quality.

6 is a flowchart showing the operation of the network quality monitoring unit 12.

[S31] It is determined whether or not the excess prevention timer has expired. If it is expired (time count end), the flow advances to step S32. Otherwise, the process ends. In addition, when the excess prevention timer time-counts, network quality is not measured.

[S32] The corresponding processes of steps S32a to S32e are performed for all the network devices 11-1 to 11-n to be mounted.

[S32a] It is determined whether the device state is connected (whether or not the network device 11 is connected to the apparatus). If it is the connection, the process proceeds to step S32b, and if it is disconnected, the process proceeds to step S33.

[S32b] It is determined whether or not the network state is connected (whether or not the network device 11 is currently communicating). If it is the connection, the process proceeds to step S32e, and if it is disconnected, the process proceeds to step S33.

[S32c] The process of the radio wave intensity monitoring unit 12a is started.

[S32d] If the propagation intensity is in a normal state, the flow advances to step S32e, and if it is in a low state, the flow advances to step S33.

[S32e] The process of the radio band monitoring unit 12b is started.

[S33] It is determined whether or not there is a timeout call. If there is a call, the process returns to the start after the time set by the watchdog timer value. If no call is made, the process proceeds to step S34 because the network quality measurement is started by the packet receiving instrument.

[S34] The excessive monitoring prevention timer is started to stop the network quality measurement process.

Next, the operation of the radio wave intensity monitoring unit 12a will be described. 7 is a diagram illustrating an operation concept of the radio wave intensity monitoring unit 12a. The vertical axis represents the propagation intensity and the horizontal axis represents the time, representing the waveform of the received radio waves.

The radio wave intensity monitoring unit 12a has two threshold values for determining the decrease and recovery of the radio wave state. One is a fall threshold (outside threshold) for determining that the propagation intensity has fallen, and the other is a recovery threshold (intra-zone threshold) for determining that the propagation strength has been restored. The setting of these thresholds can be arbitrarily changed by the operation of the application 15.

Here, if only one threshold value is set, when a small change in the radio wave intensity over the threshold occurs frequently, if control is switched each time, the processing load of the system increases. Therefore, in the present invention, two kinds of threshold values of reduction and recovery are set to prevent an increase in the processing load of the system. In addition, the measurement of the radio wave intensity | strength has shown the state measured in 200 ms unit in the case of drawing.

The radio wave strength monitoring unit 12a first reads the radio wave strength of the radio channel during communication. In order to read the radio wave strength, there is a method of inquiring the radio wave state using, for example, an interface with a wireless LAN card.

The decrease in the propagation intensity is detected by the read propagation intensity being lower than the lower threshold value, and handover is executed in that case. However, like the level L1, even if the drop threshold is lower than the drop threshold, if the drop threshold is exceeded in a short time, no handover is performed. This is because, if the handover is performed in a state in which the radio wave state is shaking near the deterioration threshold value, a change in network switching occurs and stable connection control cannot be performed.

Therefore, in the present invention, when the quality of the received radio wave is lower than the lowering threshold value, for example, for a certain period of time, it is recognized that the lowering of the network quality is performed and the handover is finally executed. For example, in the case of the drawing, handover is performed at the level L2 below the degradation threshold for approximately 600 ms.

Moreover, when the fall of the radio wave intensity is detected, the radio wave intensity monitoring part 12a notifies the network state management part 13a of the radio wave intensity fall, and sets its propagation state to fall. Since radio wave intensity fell, it does not carry out about other quality monitoring (radio band). Then, when this function is activated by timeout, the timer for next start is set.

On the other hand, the restoration of the propagation intensity is detected when the propagation intensity subsequently read out from the state where the propagation intensity is lower than the restoration threshold value is detected, in which case handover is executed. However, like the level L3, even if the recovery threshold value is exceeded, the handover is not performed when the recovery threshold value is lowered in a short time. This is because, for the same reason as described above, if the handover is performed in a state where the radio wave state is shaking near the recovery threshold value, a change occurs in network switching, and stable connection control cannot be performed.

Therefore, in the present invention, when the quality of the received radio wave exceeds the recovery threshold value, for example, for a certain period of time, it is recognized that the quality of the network is to be restored and then handover is executed. For example, in the case of the figure, handover is performed at a level L4 above the recovery threshold for approximately 600 ms.

In addition, when the radio wave strength is restored, the radio wave strength monitoring unit 12a notifies the network state management unit 13a of the radio wave strength recovery, sets its radio wave strength state to normal, and thereafter monitors the radio band. Will run. In addition, by using a statistical method such as a moving average to the value of the radio wave strength, the influence of the strength and weakness of the temporary wave strength can be further reduced.

8 is a flowchart showing the operation of the radio wave intensity monitoring unit 12a.

[S41] Radio wave strength is read.

[S42] The radio wave intensity state is determined. If normal, the flow advances to step S43, and if low, shifts to step S46.

[S43] It is determined whether or not the radio wave intensity is lower than the drop threshold value continuously for a predetermined time, for example. If it is less, the process returns to step S44, otherwise, the process ends.

[S44] The network state management unit 13a is notified of the decrease in the radio wave strength.

[S45] The radio wave strength state is set to a drop in the network state management unit 13a.

[S46] It is determined whether or not the radio wave strength exceeds the recovery threshold for a predetermined time, for example. If above, the process proceeds to step S47, otherwise, the process ends.

[S47] The network state management unit 13a is notified of the radio wave strength recovery.

[S48] The radio wave strength state is normally set for the network state management unit 13a.

Next, the case where handover is performed by recognizing the fall of the propagation intensity using the sudden deterioration threshold is described. 9 is a diagram illustrating an operation concept of the radio wave intensity monitoring unit 12a using the sudden deterioration threshold. The vertical axis represents propagation intensity and the horizontal axis represents time.

The radio wave intensity monitoring unit 12a has a sudden deterioration threshold at a value lower than the drop threshold. When measuring the radio wave strength, when the radio wave intensity falls below the sudden deterioration threshold, it is determined that the connection with the network currently being communicated cannot be maintained, and the handover is immediately started. For example, in the case of the drawing, handover is performed at the level L5 exceeding the abrupt deterioration threshold twice in succession in 200 msec units.

As described above, when the radio wave currently in use is suddenly deteriorated due to an unexpected event such as a failure of the access point of the wireless LAN, there is a possibility that the connection of the network is cut off. Therefore, in the present invention, the communication interruption time is minimized by setting a sudden deterioration threshold and performing a handover in an instant in preparation for such a case.

Next, the operation of the radio band monitoring unit 12b will be described. Similar to the radio wave intensity monitoring unit 12a, the radio band monitoring unit 12b detects using two threshold values of lack of radio band (increase in the number of users using a certain radio band) and recovery. That is, the threshold value for determining the band shortage has a lack threshold and a recovery threshold as the threshold for band recovery determination.

The comparison between the radio band and the threshold is the same as in the case of radio wave strength monitoring. In addition, as a means of reading the radio band, a method of always monitoring the average transmission speed of actually transmitted and received packets, accumulating the results, reading the information, and a method of viewing the control information implemented by the communication service provider in its own protocol, etc. There is this.

10 is a flowchart showing the operation of the radio band monitoring unit 12b.

[S51] The available radio band is read.

[S52] The wireless band state is determined. If normal, the flow advances to step S53, and if insufficient, proceeds to step S56.

[S53] It is determined whether or not the radio band is lower than the under threshold, for example, continuously for a predetermined time. If it is less, the process returns to step S54, otherwise, the process ends.

[S54] The network state management unit 13a notifies the radio band shortage.

[S55] For the network state management unit 13a, the radio band is set short.

[S56] It is determined whether or not the radio band exceeds the recovery threshold, for example, continuously for a predetermined time. If above, the process goes to step S57, otherwise, the process ends.

[S57] The network state management unit 13a is notified of the radio band recovery.

[S58] The radio band state is normally set for the network state management unit 13a.

Next, a quality control table managed by the network quality monitoring unit 12 will be described. 11 is a diagram illustrating a quality control table. The quality control table T1 is provided corresponding to the network devices 11-1 to 11-n.

For each item of the quality management table T1, the device identifier is an identifier indicating whether the corresponding network device is a wireless LAN or a cellular telephone network. The propagation state is the intensity of radio waves in current communication. Band state is the radio band quality in current communications. The device state indicates whether the corresponding network device is unavailable or unavailable (whether or not it is connected to the apparatus). The network state indicates whether or not it is currently used for communication as the main interface.

The propagation intensity drop threshold is a set value of the drop threshold. The propagation strength recovery threshold is a set value of the recovery threshold. The out of band threshold is a set value of the out of band threshold. The band recovery threshold is a set value of the band recovery threshold. The monitoring period is set to 200 ms or the like, for example.

The network quality index refers to an index calculated by weighting network quality and user priority. The network quality and priority are quantified, respectively, and the network quality index is calculated as α x network quality + β x priority (α and β are constants).

If a handover is performed based on such a network quality index, more flexible handover is possible. For example, if the network N1 has a high user priority and the network N2 has a medium user priority, the network N1 is always selected when the network to be switched only by the priority is selected.

On the other hand, in the case where the priority is high for network N1, the quality is low, and the priority is medium and the quality is high for network N2, when the network quality indicators are calculated for networks N1 and N2, network N2 should be switched. The choice is made (ie, the choice of network quality and priority). In the present invention, both network switching based on user priority or network switching based on network quality index can be supported.

Next, the operation of the network state management unit 13a will be described. The network state management unit 13a maintains the interface (network device) currently being used as the main and the network quality state (normal and reduced) for each interface.

When receiving the notification of the radio wave strength drop from the radio wave intensity monitoring unit 12a, if the radio wave state of the interface is normal, the set value is changed to the quality degradation state. If the target interface is used as the main, the network switching request is sent to the network switching control section 13b.

When the restoration strength is notified from the radio wave strength monitoring unit 12a, if the radio wave intensity of the target interface is in a low state, the quality is returned to normal, and the network switching request is sent to the network switching control unit 13b. In addition, the same control as above is performed with respect to the radio band quality.

12 is a flowchart showing the operation of the network state management unit 13a.

[S61] It is determined whether or not a network quality monitoring event has been received. If received, branches to the event type.

[S62] Upon receiving a radio wave intensity deterioration event, it is determined whether the quality of the current interface (network device) that is the event target is in a deteriorated state or a normal state. If it is in the lowered state, since the setting remains the same, the process returns to step S61 without changing. In the normal state, the flow advances to step S63.

[S63] The setting of the network device as the event target is set from the normal state to the degraded state.

[S64] It is determined whether the network device which is the event target is the main interface. If not, the flow returns to step S61, and if it is main, the flow goes to step S65.

[S65] The network switching request is sent to the network switching control section 13b.

[S66] When the radio band shortage event is received, it is determined whether the quality of the current interface (network device) that is the event target is a band shortage state or a normal state. If the bandwidth is low, the setting remains as it is, without changing, and the flow returns to step S61. In the normal state, the flow advances to step S67.

[S67] The setting of the network device that is the event target is set from the normal state to the out of band state, and the flow proceeds to step S64.

[S68] When the radio wave strength recovery event is received, it is determined whether the quality of the current interface (network device) that is the event target is in a degraded state or a normal state. In the normal state, since the setting remains the same, the process returns to step S61 without changing. If it is in the lowered state, the flow proceeds to step S69.

[S69] The setting of the network device as the event target is set from the degraded state to the normal state, and the flow proceeds to step S65.

[S70] When the radio band recovery event is received, it is determined whether the quality of the current interface (network device) that is the event target is low or normal. In the normal state, since the setting remains the same, the process returns to step S61 without changing. If there is a band shortage condition, the flow proceeds to step S71.

[S71] The setting of the network device as the event target is set from the low state to the normal state, and the flow proceeds to step S65.

Next, the operation of the network switching control section 13b will be described. The network switching control unit 13b sets and manages priorities of the mounted network devices. When the network switching control unit 13b receives the network switching request, the network state of the mounted network device is searched in ascending order of priority, and the interface of the normal state which is the most preferred is designated as the main interface. .

When the main interface is changed, the main interface change request is sent to the network control unit 14, and the RS transmission request is sent to the handover execution unit 13c, respectively, and its status is set as the RA reception wait. Then, the RS is transmitted to the AR of the network. RS is output from the modified main interface.

The RA reception from the AR passes through the terminal manager 13d from the packet input unit 16 and is notified to the network switching control unit 13b. Upon receiving the RA via the main interface, the network switching control unit 13b sends a path switching request to the network control unit 14, changes the default route, and requests the handover execution unit 13c to send a BU to the HA. do. Finally, by BA reception returned from HA, handover is completed.

13 is a flowchart showing the operation of the network switching control section 13b.

[S81] It is determined whether or not an event has been received. If received, branches to the event type.

[S82] When a network switching request is received, the corresponding processes of steps S82a to S82f are performed in order of high priority for all networks.

[S82a] It is determined whether the interface state is a normal state. If not normal, the process proceeds to step S81, and in the normal case, the process proceeds to step S82b.

[S82b] The network device is selected as the main interface.

[S82c] It is determined whether to change the main interface. If no change is made, the process proceeds to step S82d, and if no change is made, the process proceeds to step S81.

[S82d] The main interface change request is sent to the network control unit 14.

[S82e] The RS transmission request is sent to the handover execution unit 13c, and the process proceeds to step S82f.

[S82f] The status is set as the RA reception wait, and the flow returns to step S81.

[S83] If the event type is RA reception, it is determined whether the status is RA reception wait. If RA reception is waiting, the process proceeds to step S83a, otherwise, the process ends.

[S83a] It is determined whether the reception is from the main interface. In the case of reception from the main interface, the process proceeds to step S83b, otherwise, the process ends.

[S83b] The path switching request is sent to the network control unit 14.

[S83c] BU transmission is requested to the handover execution unit 13c.

[S83d] The status is set to BA reception wait, and the flow returns to step S81.

[S84] If the event type is BA reception, it is determined whether the state is BA reception waiting. If it is BA reception wait, execution proceeds to step S84a, otherwise, the operation ends.

[S84a] It is determined whether the reception is from the main interface. In the case of reception from the main interface, the flow proceeds to step S84b, and otherwise ends.

[S84b] The state is set to wait for the network switching request, and the flow returns to step S81.

14 is a flowchart showing the operation of the network switching control section 13b. It is a flowchart of switching control based on network quality indicators.

[S85] It is determined whether or not an event has been received. If received, branches to the event type.

[S86] When the network switching request is received, the corresponding processes of steps S86a to S86f are performed in order from ascending network quality index to all networks.

[S86a] It is determined whether the interface state is a normal state. If not normal, the process proceeds to step S85 and, if normal, the process proceeds to step S86b.

[S86b] The network device is selected as the main interface.

[S86c] It is determined whether to change the main interface. If no change is made, the process proceeds to step S86d, and if no change is made, the process proceeds to step S85.

[S86d] The main interface change request is sent to the network control unit 14.

[S86e] The RS transmission request is sent to the handover execution unit 13c, and the process proceeds to step S86f.

[S86f] The status is set to RA reception wait, and the flow returns to step S85.

[S87] If the event type is RA reception, it is determined whether the status is RA reception wait. If it is the RA reception wait, execution proceeds to step S87a, otherwise, the operation ends.

[S87a] It is determined whether the reception is from the main interface. In the case of reception from the main interface, the flow advances to step S87b, otherwise, the process ends.

[S87b] The path switching request is sent to the network control unit 14, and the flow returns to step S85.

[S87c] The handover execution unit 13c requests BU transmission.

[S87d] Set the state to BA reception standby.

[S88] If the event type is BA reception, it is determined whether the state is BA reception waiting. If it is BA reception wait, execution proceeds to step S88a, otherwise it ends.

[S88a] It is determined whether the reception is from the main interface. In the case of reception from the main interface, the flow advances to step S88b, otherwise, the process ends.

[S88b] The state is set to wait for the network switching request, and the flow returns to step S85.

Next, the operation of the network control unit 14 will be described. When the network control unit 14 receives the main interface change request, the network control unit 14 switches the main interface. When the network control unit 14 receives the path switching request, the network control unit 14 sets the default route to the designated interface direction and transmits to other interfaces. By invalidating the path, it is impossible to transmit packets outside the designated interface direction.

Fig. 15 is a diagram showing a router information list for path control. The router information list T2 is managed by the network control unit 14. In the drawing, the interface corresponding to the router information at the top is the main interface.

For each item of the router information list T2, the router list identifier is an identifier indicating whether the router list of the wireless LAN or the router list of the cellular phone network is used. The router address is an address of a router to be connected in the current communication of the network device. The device name is the name of the network device (whether it is a wireless LAN device or a cellular phone network device).

The radio wave strength state is a radio wave strength in current communication. The band state is the radio band quality in current communication. The device state indicates whether the corresponding network device is enabled or disabled. The network state indicates whether or not it is currently used as the main interface.

16 is a flowchart showing the operation of the network control unit 14.

[S91] It is determined whether or not an event has been received. If received, branches to the event type.

[S92] When the path switching request is received, the default route is set in the designated interface direction.

[S93] The transmission paths other than the designated interface are invalidated, and the flow returns to step S91.

[S94] When the main interface change request is received, the main interface is switched to the designated network interface, and the flow returns to step S91.

Next, the handover of the present invention with stopping and starting of the network device will be described. The operation of starting and stopping the network device 11 can be performed from the application 15. However, in the present invention, the handover process is performed at high speed by switching the interface in advance before the network device stops when a stop is requested. This can reduce the packet loss associated with stopping the interface during use.

In addition, when the network device 11 is in the stopped state, when the start is requested, switching is requested after performing the interface start process. This is because, if the switching request is sent before the startup process is completed, the network toward the network device to which communication cannot communicate becomes the default route, and packet loss may occur.

When the interface processing unit 14b in the network control unit 14 receives the request for stopping the interface, the interface processing unit 14b changes the quality of the network device to the stopped state, and then transmits the network switching request to the network switching control unit 13b.

In the network switching control section 13b, the one with the highest priority among network devices having a normal network quality is selected, and handover processing is performed for the network to which the device is directed.

Thereafter, the interface processor 14b cuts off the interface of the network device. When the device startup request is received, the network switching request is sent to the network switching control section 13b after the network device startup processing is executed.

17 is a flowchart showing the operation of the interface processor 14b.

[S101] It is determined whether or not an event has been received. If received, branches to the event type.

[S102a] When the start request is received, it is determined whether the device state is normal. If normal, the process returns to step S101, otherwise, the process proceeds to step S102b.

[S102b] The device startup process is performed.

[S102c] The quality of the device is brought to the normal state.

[S102d] The network switching control unit 13b is notified of the network switching request, and the flow returns to step S101.

[S103a] When a stop request is received, it is determined whether the device state is normal. If normal, the process returns to step S101, otherwise, the process proceeds to step S103b.

[S103b] The quality of the device is placed in the stop reservation state.

[S103c] The network switching control unit 13b is notified of the network switching request, and the flow returns to step S101.

[S104] Upon receiving a switch completion notification, all devices in the stop reservation state are stopped, the state is stopped, and the flow returns to step S101.

As described above, when the interface down (stop) process from the higher-level application is requested, when the network to which the target interface is connected is the current network, the down (stop) process is not immediately performed. Network switching to the network and handover control are executed, and after the processing is completed, down (stop) processing is performed. Thereby, even if the mobile node 10 is in communication, it is possible to continue communication without interrupting communication by the interface down process.

Next, the handover of the present invention with the disconnection and connection of a link will be described. The operation of connection and disconnection of the network can be performed from the application 15. However, in the present invention, the network is switched in advance and the handover process is performed at high speed before link disconnection is requested and actually disconnected. This can reduce packet loss associated with stopping the network during use.

When the network device is in the disconnected state, and a link connection is requested, the switching is requested after the interface connection process is performed. This is because, if the switching request is sent before the link connection processing is completed, the network which cannot communicate becomes the default route, which may cause packet loss.

18 is a flowchart showing the operation of the link processing unit 14c.

[S111] It is determined whether or not an event has been received. If received, branches to the event type.

[S112a] Upon receiving a start request, it is determined whether the link state is a connection. If it is the connection, the process returns to step S111, otherwise, the process proceeds to step S112b.

[S112b] Link connection processing is performed.

[S112c] The link state is set to the normal state.

[S112d] The network switching control unit 13b is notified of the network switching request, and the flow returns to step S111.

[S113a] Upon receiving a disconnect request, it is determined whether the link state is a connection. If it is the connection, the process returns to step S111, otherwise, the process proceeds to step S113b.

[S113b] The state of the link is set to the cut reservation state.

[S113c] The network switching control unit 13b is notified of the network switching request, and the flow returns to step S111.

[S114] Upon receipt of the switch completion notification, all the networks in the cut reservation state are cut off, the state is cut, and the flow returns to step S111.

As described above, when link disconnection processing such as telephone disconnection from a higher-level application is requested, when the target link is the current network, link disconnection processing is not performed immediately, but network switching to another network is performed. Processing and handover control are executed, and after the processing is completed, link breaking processing is performed. Thereby, even if the mobile node is communicating, it is possible to continue the communication without interrupting the communication by the link disconnection process.

Next, the handover of the present invention by switching the access point will be described. 19 is a diagram for explaining handover of access point switching. The wireless LAN is connected to the access points 51 and 52. First, it is assumed that the mobile node 10 is communicating via the access point 51.

When the radio wave strength of the access point 51 decreases, the mobile node 10 performs a handover. In the above-described handover, handover between heterogeneous networks is targeted, but in this example, access points in the same network are switched.

In the case of the figure, when the radio wave intensity of the access point 51 falls, handover is performed using the switching destination as the access point 52. In this manner, when the radio wave strength of the wireless communication being connected is weakened, and a wireless LAN is selected as the next connection destination media candidate, the access point that can be connected is searched before the currently connected wireless communication becomes unavailable. When the connection with the wireless communication being connected cannot be maintained, handover is instantaneously realized to the previously searched access point and communication continues. In addition, since detailed control of the handover of such an access point is the same as the handover control between heterogeneous networks, description of detailed control is abbreviate | omitted.

In addition, in the above example, although the switching of the access point in the same wireless LAN was shown, you may change the access point between different wireless LANs (for example, the access point 51a on the wireless LAN 5a). ), To the access point 51b on the wireless LAN 5b).

The above merely illustrates the principles of the present invention. Also, many modifications and variations are possible to those skilled in the art, and the present invention is not limited to the exact construction and application examples shown and described above, and all corresponding modifications and equivalents are to the appended claims and their equivalents. By the scope of the present invention.

1 is a principle diagram of a mobile node of the present invention;

2 is a sequence diagram illustrating the operation of a mobile node;

3 is a diagram illustrating a configuration of a mobile node;

4 is a diagram illustrating handover due to network quality deterioration;

5 is a diagram illustrating handover by network quality recovery;

6 is a flowchart showing the operation of the network quality monitoring unit;

7 is a view showing an operation concept of a radio wave intensity monitoring unit;

8 is a flowchart showing an operation of a radio wave intensity monitoring unit;

9 is a diagram illustrating an operation concept of a radio wave intensity monitoring unit using a sudden deterioration threshold.

10 is a flowchart showing the operation of the radio band monitoring unit;

11 is a view showing a quality control table;

12 is a flowchart showing an operation of a network state management unit;

13 is a flowchart showing an operation of a network switching control unit;

14 is a flowchart showing an operation of a network switching control unit;

15 is a view showing a router information list for path control;

16 is a flowchart showing the operation of the network controller;

17 is a flowchart showing an operation of an interface processor;

18 is a flowchart showing an operation of a link processing unit;

19 is a diagram for explaining handover of access point switching.

<Explanation of symbols for the main parts of the drawings>

N1: Mobile IP Network N2: Mobile IP Network

10: mobile node 13: handover control unit

12: network quality monitoring unit 14: network control unit

11: network device 15: application

16: packet input section 17: packet output section

102: wireless LAN 103: mobile phone network

51, 52: access point

Claims (25)

A mobile node that communicates on a mobile IP network, A network device having an interface function for connecting to a network, A network quality monitoring unit that monitors network quality based on at least one of radio wave strength and radio band received by the network device; A handover control unit which transmits a temporary address to an address registration destination, changes the path of communication information, and performs a handover to switch the connection destination to a new network before the communication is disconnected in accordance with the state of the network quality; A network control unit for receiving a response indicating that the temporary address has been updated at an address registration destination, and maintaining a reception function with a network before switching, until communication is disconnected, The network quality monitoring unit has a lower threshold value and a sudden deterioration threshold value of a value lower than the lower threshold value as threshold values for detecting the deterioration of radio waves, and the received radio wave is higher than the sudden deterioration threshold value. When it is lower than the degradation threshold, the handover request is output only when the degradation threshold is continuously lowered for a predetermined period of time, and when the received radio wave falls below the sudden degradation threshold, the handover request is immediately output. Mobile node. The method of claim 1, And if the network quality monitoring unit recognizes a decrease in network quality of a network that is currently communicating, the handover control unit switches to a new network. The method of claim 1, And when the network quality monitoring unit recognizes that the network quality of the network before switching is restored, the handover control unit returns the connection destination to the original switching network. The method of claim 1, The handover control unit stores the priority of network connection, and performs handover to a network having high priority according to the change of network quality. The method of claim 1, The network quality monitoring unit has a recovery threshold for detecting a quality recovery, and the handover control unit performs a handover accompanying network quality deterioration when the quality of the received radio wave is lower than the degradation threshold. And when the quality of radio waves received exceeds the recovery threshold, handover accompanying network recovery. The method of claim 5, The network quality monitoring unit outputs a handover request by recognizing that the network quality is deteriorated for a certain period of time when the quality of the received radio wave is stably below the lowering threshold value, and the quality of the received radio wave is a recovery threshold value. The mobile node, characterized in that when a stable time exceeds a certain time, and outputs a handover request by recognizing that the network recovery. The method of claim 1, The network quality monitoring unit has a shortage threshold for detecting a shortage of currently available radio bands, and a recovery threshold for detecting the recovery of a shortage of wireless bands, and the handover controller is further configured to provide a radio shortage threshold. The mobile node characterized by performing a handover accompanying network quality degradation when it is less, and performing a handover accompanying network recovery when a radio band exceeds a recovery threshold. The method of claim 1, And the network quality monitoring unit performs at least one of monitoring network quality at a fixed or variable period, or monitoring network quality based on packet reception. The method of claim 1, When the network control unit detects a stop request of the network device, the handover control unit performs a handover before the network device stops, and when the network control unit detects a start request of the network device. And the handover control unit performs handover after completion of the startup process of the network device. The method of claim 1, When the network control unit detects a request for disconnection of a link with a network used by the network device, the handover control unit performs a handover before the link is disconnected, and the network control unit issues a connection request of the network device. When it detects, the said handover control part performs a handover after completion of the connection process of the said network device, The mobile node characterized by the above-mentioned. The method of claim 1, And the network quality monitoring unit manages a network quality index calculated by weighting network quality and priority, and the handover control unit performs a handover based on the network quality index. The method of claim 1, When there is a first access point and a second access point in the network, the network quality monitoring unit recognizes a decrease in network quality from the first access point that is currently communicating, and further accesses the second access from the network quality of the second access point. And the handover control unit performs a handover from the first access point to the second access point when it is determined that the connection with the point is possible. In the handover method for performing a handover for the communication on the mobile IP network, As a case where a mobile node mounts network devices of a plurality of interfaces, and the mobile node moves between a plurality of networks, Monitor the network quality based on at least one of radio wave strength or radio band received by the network device, In accordance with the state of the network quality, before the communication is disconnected, a temporary address is sent to the address registration destination, Receive a response indicating that the temporary address has been updated at the address registration destination, and maintain the reception function with the network before switching until the communication is disconnected, After the transmission of the temporary address, a path for communication information is changed and a handover is performed to switch the connection destination to a new network. As a threshold for detecting the deterioration of the radio wave, it has a deterioration threshold and a sudden deterioration threshold of a value lower than the deterioration threshold, and the received radio wave is higher than the abrupt deterioration threshold and lower than the deterioration threshold. And outputting a handover request only when the degradation threshold is continuously lowered for a predetermined time, and immediately outputting a handover request when the received radio wave falls below the sudden degradation threshold. The method of claim 13, And recognizing a deterioration in network quality of the currently communicating network, switching to a new network. The method of claim 13, And recognizing that the network quality of the network before switching is restored, returning the connection destination to the original network before switching. The method of claim 13, A handover method, wherein the priority of network connection is stored and handover is performed to a network having high priority according to the change of network quality. The method of claim 13, Having a recovery threshold for detecting a quality recovery, if the quality of the received radio wave is lower than the degradation threshold, a handover accompanying network degradation is performed, and the quality of the received radio wave exceeds the recovery threshold. In one case, a handover method is performed, which involves network recovery. The method of claim 17, When the quality of the received radio wave falls below the deterioration threshold for a certain amount of time, it is recognized that the network quality is deteriorated and a handover is performed. A handover method for performing handover by recognizing network recovery. The method of claim 13, A hand that has a deterioration threshold for detecting a lack of a currently available radio band and a recovery threshold for detecting a restoration of a lack of a radio band, and when the radio band falls below the lack threshold, a hand accompanying network deterioration. And a handover accompanying network recovery when the radio band exceeds the recovery threshold. The method of claim 13, A handover method comprising at least one of monitoring network quality at a fixed or variable period or monitoring network quality based on packet reception. The method of claim 13, When a stop request of the network device is detected, a handover is performed before the network device stops, and when a start request of the network device is detected, a handover is performed after completion of the start process of the network device. Handover method. The method of claim 13, When detecting the disconnection of the link with the network used by the network device, handover is performed before the link is disconnected, and when the connection request of the network device is detected, the hand is completed after the connection processing of the network device is completed. Handover method characterized in that the over. The method of claim 13, A handover method, characterized in that handover is performed based on a network quality index calculated by weighting network quality and priority. The method of claim 13, When the first access point and the second access point exist in the network, it is possible to recognize the degradation of the network quality from the first access point currently in communication, and to connect with the second access point from the network quality of the second access point. And if it is determined that the handover is performed, handover from the first access point to the second access point is performed. In a mobile IP system for communicating over a mobile IP network, A network device having an interface function for connecting to a network, a network quality monitoring unit that monitors network quality based on at least one of a radio wave strength or a radio band received by the network device, according to the state of the network quality Before the truncation, a handover control unit which transmits a temporary address to the address registration destination, changes the path of communication information, and performs a handover for switching the connection destination to a new first network, and the temporary address is updated at the address registration destination. A mobile node composed of a network control unit for receiving a response indicating that the connection is received and maintaining the reception function with the second network before switching, until communication is disconnected; A home agent receiving the temporary address to recognize delivery and location of information to the mobile node; Correspondence that connects with the default router that receives the temporary address, transmits the communication information through the second network until the communication is disconnected, and communicates with the mobile node through the first network after the handover process. Contains nodes, The network quality monitoring unit has a lower threshold value and a sudden deterioration threshold value of a value lower than the lower threshold value as threshold values for detecting the deterioration of radio waves, and the received radio wave is higher than the sudden deterioration threshold value. When it is lower than the degradation threshold, the handover request is output only when the degradation threshold is continuously lowered for a predetermined period of time, and when the received radio wave falls below the sudden degradation threshold, the handover request is immediately output. Mobile IP system.

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