JP2008011184A - Wireless lan terminal and ip address continuous utilization method in handover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize stoppage of communication occurring at a time of a handover when the handover occurs from a wireless LAN access point of a wireless LAN terminal to another wireless LAN access point. <P>SOLUTION: When the wireless LAN access point of the handover destination belongs to the same subnetwork of the wireless LAN access point of the handover origin, the terminal does not acquire the IP address again from a DHCP (Dynamic Host Configuration protocol) server, and continuously uses the IP address which has been used until the time. Moreover, when continuously using it, a lease period of the IP address can be updated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless LAN terminal connected to a wireless LAN access point and a method for continuously using an IP address in handover between wireless LAN access points.

  A conventional data flow when a wireless LAN device terminal is handed over will be described with reference to FIG.

  When the wireless LAN is handed over, the wireless LAN terminal detects a handover destination wireless LAN access point, transmits a disconnection message to the connected wireless LAN access point, and disconnects the link. Next, data is exchanged with the handover destination wireless LAN access point, 802.11 authentication and association are performed, and a link is established. When the link establishment is completed, 802.1X authentication is performed when 802.1x authentication is required.

  Finally, the wireless LAN device terminal communicates data with the DHCP server to acquire IP address setting data.

Patent Document 1 describes a conventional technique in which a wireless LAN terminal connected to a wireless LAN access point roams to another wireless LAN access point adjacent to the wireless LAN access point.
Japanese Patent Laid-Open No. 2004-241937

  A wireless LAN terminal that uses the latter method because the method of automatically setting the IP address (applying IP address setting data from a DHCP server on the network) is more convenient than manually setting the IP address of the terminal. There are many.

  When such a wireless LAN device terminal moves between wireless LAN access points and performs connection handover, it applies the IP address setting data acquired by communicating data with the DHCP server, and then performs the handover destination wireless LAN access point. IP data communication becomes possible, and communication is interrupted until the application of the IP address setting data is completed after connection with the handover source wireless LAN access point. That is, since the IP address before the handover and the IP address after the handover are different, it is necessary to redo the connection between the IP layer (network layer) and the upper layer, and communication is interrupted during this redo period.

  In addition, since it is necessary to communicate data with the DHCP server in order to obtain the IP address setting, the power of the terminal is consumed.

  The present invention relates to a wireless LAN terminal capable of minimizing communication interruption that occurs during handover without acquiring IP address setting data from a DHCP server when the wireless LAN apparatus terminal performs handover, and an IP address in handover The purpose is to provide a method of continuous use.

  According to the present invention, when the first wireless LAN access point is handed over to the second wireless LAN access point, the first wireless LAN access point and the second wireless LAN access point belong to the same subnet. When it is determined that the subnet identity determination means for determining whether or not the first wireless LAN access point and the second wireless LAN access point belong to the same subnet, the first wireless LAN access point There is provided a wireless LAN terminal comprising: an IP address continuous use means for continuously using an IP address used when connected to the wireless LAN access point.

  In the wireless LAN terminal, the subnet identity determining means includes the second wireless LAN in a list of wireless LAN access points belonging to an adjacent subnet included in a wireless LAN frame received from the first wireless LAN access point. When no access point is included, it may be determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet.

  In the wireless LAN terminal, the subnet identity determining means includes the second wireless LAN in a list of wireless LAN access points belonging to the same subnet included in a wireless LAN frame received from the first wireless LAN access point. When an access point is included, it may be determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet.

In the above wireless LAN terminal, the subnet identity determining means adds the second identity to a list of MAC addresses of wireless LAN access points belonging to adjacent subnets included in a wireless LAN frame received from the first wireless LAN access point. If the MAC address of the wireless LAN access point is not included, it may be determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet. .
In the above wireless LAN terminal, when the second wireless LAN access point is handed over and the IP address used when connected to the first wireless LAN access point is continuously used, The lease time limit of the IP address may be updated.

In the wireless LAN terminal, when handing over to the second wireless LAN access point and continuing to use the IP address used when connected to the first wireless LAN access point, The lease term of the IP address may be updated only when the lease term of the IP address setting has not passed. In the wireless LAN terminal, the second wireless LAN access point is handed over, and the first When the IP address used when connected to one wireless LAN access point is continuously used, the remaining IP address setting lease term is less than a predetermined value, and the IP address setting lease The lease expiration date for the IP address may be renewed only if the time limit has not expired. Good.
In the wireless LAN terminal, when handover is made to the second wireless LAN access point, and it is determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet However, if the lease time limit for setting the IP address has passed, the IP address may be reset.

  According to the present invention, it is possible to minimize the interruption of communication that occurs during handover.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

[Embodiment 1]
The present invention handovers a connection from a wireless LAN access point to which a wireless LAN client is connected to another wireless LAN access point in an IEEE 802.11 network (wireless LAN) that automatically assigns an IP address using a DHCP server. In this case, the IP address is quickly acquired while suppressing the power consumption of the wireless LAN client, and the communication interruption at the time of handover is reduced.

  In FIG. 2, before handing over the connection from the wireless LAN access point 105-1 to which the wireless LAN terminal 107 is connected to the adjacent wireless LAN access point 105-2, the wireless LAN terminal 107 is connected to the wireless LAN access point 105-2. Is received from the connected wireless LAN access point 105-1, indicating whether or not is in the same subnet as the wireless LAN access point 105-1.

  When the wireless LAN access point 105-2 is a wireless LAN access point on the same subnet as the wireless LAN access point 105-1, when the connection is handed over to the wireless LAN terminal 107 wireless LAN access point 105-2, DHCP is used before. The lease period of the current IP address setting data (device IP address, DNS server IP address, etc.) assigned by the server 101 is checked. If the lease period is still valid, a new DHCP server 101 is created when the handover is completed. The IP address used when connected to the wireless LAN access point 105-1 is continuously used without requesting the IP address setting data lease to the user.

  FIG. 2 shows an example of a network composed of an IEEE 802.11 network and an IEEE 802.3 network.

  In FIG. 2, a wireless LAN access point 105-1 and a wireless LAN access point 105-2 represent wireless LAN access points connected on the same IP subnet. The figure shows that the wireless LAN access point 105-1 connected to the wireless LAN terminal 107 periodically sends out a broadcast message. The broadcast message is a message that describes a list of wireless LAN access points adjacent to the wireless LAN access point that transmits the broadcast message while existing in a different subnet from the wireless LAN access point that transmits the broadcast message. It is.

  An example of a broadcast message is shown in FIG.

  In FIG. 3, the wireless LAN access point list is a wireless LAN access point that satisfies the above conditions (that is, a wireless LAN that transmits the broadcast message while existing in a different subnet from the wireless LAN access point that transmits the broadcast message. This is data for storing a list of wireless LAN access points adjacent to the access point. The first field of the wireless LAN access point list (“number of wireless LAN access points” field) indicates the number of wireless LAN access points in the list, and thereafter, there are fields corresponding to the number of wireless LAN access points. The field of represents the MAC address of the wireless LAN access point. In order to distinguish the wireless LAN access point list from other protocol data, an ID is assigned to the protocol of the wireless LAN access point list, and the ID is stored in the protocol ID in the 802.2 LCC header. The wireless LAN access point list is uniquely defined according to the present invention.

  FIG. 4 shows a handover operation of the wireless LAN terminal.

  In FIG. 1, when a connection is handed over from the wireless LAN access point AP11 to which the wireless LAN terminal is connected to the AP12, the IP address setting used during the connection with the AP11 is applied without requesting the IP address setting data to the DHCP server. .

  In this way, in the present invention, when the handover is performed, the IP address is not acquired from the DHCP server, and the IP address setting data before the handover is continuously used. Communication interruption intervals when acquiring IP address setting data from the server can be reduced. Further, since the wireless LAN terminal does not transmit a DHCP packet for acquiring IP address setting data at the time of handover, power consumption of the apparatus can be suppressed.

  Next, the operation of the wireless LAN terminal at the time of handover will be described using the chart shown in FIG.

  In FIG. 4, step S <b> 301 indicates that the wireless LAN terminal 107 starts connection to the wireless LAN access point 105.

  After the MAC link is established and authentication is normally completed, the wireless LAN terminal 107 communicates data with the DHCP server 101. IP address setting data is acquired and applied to the network adapter (step S303). Step S305 shows a state in which the connection is being made and Internet protocol communication is possible.

  When the wireless LAN terminal 107 and the wireless LAN access point 105 are connected, the wireless LAN terminal 107 receives a broadcast message including the wireless LAN access point list from the wireless LAN access point 105, and the wireless LAN access is in progress during connection. It is determined whether a wireless LAN access point adjacent to the point exists in the same subnet.

  Step S307 in FIG. 4 indicates that the DHCP server 101 is requested to update the IP address setting data when the lease term of the IP address setting data used by the wireless LAN terminal 107 during connection is near. Yes.

  Step S309 in FIG. 4 indicates that handover is performed when the wireless LAN terminal 107 moves and moves away from the connected wireless LAN access point 105-x and enters the coverage area of another wireless LAN access point 105-y. Show.

  In step S311 in FIG. 4, the wireless LAN terminal 107 disconnects the link with the handover source wireless LAN access point 105-x, establishes a new link with the handover destination wireless LAN access point 105-y, and performs authentication. Is shown.

  When the link is established with the handover destination wireless LAN access point 105-y and the authentication is normally completed, the wireless LAN terminal 107 continues to use the IP address setting data before the handover or newly establishes a connection to the DHCP server 101. Whether IP address setting data is requested or not is determined by the following conditions (A) and (B).

  When the conditions (A) and (B) are satisfied, the IP address setting data used before the handover is continuously used. If not, it requests the DHCP server 101 for IP address setting data.

  Condition (A) The lease time limit of the IP address setting data before the handover is still valid.

  Condition (B) Before handover, a broadcast message including a list of wireless LAN access points is received from the handover source wireless LAN access point 105-x, and the broadcast message is transmitted to the handover destination wireless LAN access point and the handover. Indicates that the original wireless LAN access point is in the same subnet.

[Embodiment 2]
The second embodiment is basically the same as the first embodiment, but the second embodiment shows the operation of the wireless LAN terminal in more detail than the first embodiment.

  Referring to FIG. 5, first, a connection is attempted by searching for a wireless LAN access point (AP) to be connected (step S401).

  Next, it is checked whether or not the connection is successful (step S403).

  If the connection is not successful ("NO" in step S403), after waiting for about 10 to 60 seconds (step S405), connection is attempted again (step S401).

  If the connection is successful (“YES” in step S403), a process of periodically detecting whether the handover condition is satisfied is started (step S407). As the handover condition, for example, the electric field strength of the received signal from the connected wireless LAN access point is less than a predetermined value, or the communication quality (for example, bit error rate, frame error rate, carrier / noise ratio) is predetermined. That is, the wireless LAN access point to be connected to is in the vicinity, and the electric field strength of the received signal from the wireless LAN access point is a predetermined value or more.

  Next, a process for monitoring a broadcast message including a list of wireless LAN access points is started (step S409).

  Next, an operation for acquiring an IP address, lease expiration information, and the like from the DHCP server 101 is attempted (step S411).

  Next, it is determined whether or not the handover condition is currently satisfied (step S413).

  If not satisfied ("NO" in step S413), it is determined whether 20 seconds have elapsed from step S411 and whether the previous step S411 was not successful (step S415). If unsuccessful (“YES” in step S415), the process returns to step S411 and tries step S411 again.

  If it has succeeded (“No” in step S415), it waits for one second (step S417), returns to step S413, and determines again whether the handover condition is satisfied. Therefore, once step S411 is successfully performed, it is determined whether or not the handover condition is satisfied every second. However, this determination may be made at a cycle other than 1 second.

  If the handover condition is satisfied (“YES” in step S413), an operation of handing over the connection to a new wireless LAN access point is attempted (step S419).

  If the operation (handover) in step S419 is not successful (“NO” in step S421), after waiting for about 1 second (step S423), the process returns to step S413 to determine again whether the handover condition is satisfied. . However, the waiting time of 1 second may be changed to a waiting time other than 1 second.

  If the operation (handover) of step S419 is successful (“YES” in step S421), a broadcast message including a wireless LAN access point list is received from the handover source wireless LAN access point 105-x. In step S425, it is determined whether or not the condition that there is no handover destination wireless LAN access point is satisfied.

  Referring to FIG. 6, when the condition in step S425 is not satisfied (“NO” in step S425), the handover destination wireless LAN access point 105-y is the handover source wireless LAN access point 105-x. (Step S427), the process returns to Step S411, and the IP address is reacquired. The IP address reacquisition is the same as in the prior art.

  When the condition in step S425 is satisfied (“YES” in step S425), the handover destination wireless LAN access point 105-y belongs to the same subnet as the handover source wireless LAN access point 105-x. Judge that

  In this case, if the IP address setting refresh condition is satisfied (“YES” in step S429) and the lease time limit of the IP address setting has not passed (“YES” in step S431), the IP address refresh operation is performed. (Step S433). That is, the DHCP server 101 is requested to update the lease period of the IP address.

  The satisfaction of the IP address setting refresh condition means that the remaining lease time limit of the IP address is equal to or less than a predetermined value. If the remaining lease time limit of the IP address exceeds a predetermined value (“NO” in step S429), it is not necessary to renew the lease time limit of the IP address in step S433. Then, it is determined whether or not the handover condition is satisfied (step S413). The remaining lease term of the IP address is equal to or less than a predetermined value is, for example, that the IP address is set last or the time when the lease term is updated is T1, the acquired lease term is LT, and the current time is T2. In this case, the difference between T1 and T2 is LT / 5 or less, or the difference between T1 and T2 is 5 minutes or less.

  Therefore, the condition determination S429 may be omitted, and if “YES” in the step S425, if “YES” in the step S431, the process proceeds to a step S433 to refresh the IP address.

  If the lease time limit for setting the IP address has passed (“NO” in step S431), the process returns to step S411 to reset the IP address.

  If the IP address refresh operation is performed in step S433, it is determined whether the handover condition is currently satisfied (step S435).

  If not satisfied (“NO” in step S435), it is determined whether or not 20 seconds have elapsed from step S433 and the previous step S433 was not successful (step S437). If not successful (“YES” in step S437), the process returns to step S431, and step S433 is tried again. However, before that, in step S431, it is determined whether or not the lease time limit of the IP address setting has ended. If it has ended, the process returns to step S411 without proceeding to step S433, and the IP address is changed. Reset it.

  If successful ("NO" in step S437), wait for one second (step S439), return to step S435, and determine again whether the handover condition is satisfied. Therefore, once step S433 is successfully performed, it is determined whether or not the handover condition is satisfied every second. However, this determination may be made at a cycle other than 1 second.

  If the handover condition is satisfied (“YES” in step S435), an operation of handing over the connection to a new wireless LAN access point is attempted (step S441).

  If the operation (handover) in step S441 is not successful (“NO” in step S443), after waiting for about 1 second (step S445), the process returns to step S435 to determine again whether the handover condition is satisfied. . However, the waiting time of 1 second may be changed to a waiting time other than 1 second.

  If the operation (handover) of step S441 is successful (“YES” in step S443), the process returns to step S425, and a broadcast message including a wireless LAN access point list is received from the handover source wireless LAN access point 105-x. It is determined whether or not a condition that no handover destination wireless LAN access point exists in this list is satisfied.

  The list of wireless LAN access points in the broadcast message includes wireless LAN access points belonging to the same subnet, and when the handover destination wireless LAN access point is in this list, the handover destination wireless LAN It may be determined that the access point belongs to the same subnet as the handover source wireless LAN access point. However, since the number of wireless LAN access points belonging to the same subnet is larger than the number of wireless LAN access points belonging to adjacent subnets, the broadcast message can be shortened in the second embodiment, and wireless The amount of processing for the LAN terminal to determine whether or not the handover destination wireless LAN access point belongs to the same subnet as the handover source wireless LAN access point can be reduced.

  In addition to the step S433, the IP address setting refresh is also performed by steps not described in the prior art.

  As described above, according to the first and second embodiments, the following effects can be obtained.

  The first effect is that data communication at the time of handover is interrupted because the IP address setting data used before the handover is applied without communicating data with the DHCP server when the wireless LAN terminal hands over the connection. Communication quality can be improved.

  The second effect is that since data communication with the DHCP server is not performed every time a handover is performed, it is possible to avoid unnecessary operation of a transmission circuit that consumes a large amount of power and to suppress power consumption. In particular, in the case of a device with a low frequency of data transmission, such as a wireless LAN-equipped alarm device (a device that sends an alarm signal to a management center through a wireless LAN when an emergency occurs) Therefore, operating a transmission circuit with high power consumption when communicating with a DHCP server greatly affects the driving time.

It is a figure which shows the outline | summary of the operation | movement of the handover which a wireless LAN terminal performs between wireless LAN access points. It is a figure which shows the structure of the system containing a wireless LAN terminal, a wireless LAN access point, a gateway, and a DHCP server. It is a figure which shows the structure of the broadcast message by embodiment of this invention. 5 is a flowchart showing a handover operation of a wireless LAN terminal according to the first embodiment of the present invention. It is a flowchart (1/2) which shows the operation | movement of the wireless LAN terminal handover by Embodiment 2 of this invention. It is a flowchart (2/2) which shows the operation | movement of the wireless LAN terminal handover by Embodiment 2 of this invention.

Explanation of symbols

101 DHCP server 103 Gateway 105 Access point 107 Wireless LAN terminal

Claims (16)

When handing over from the first wireless LAN access point to the second wireless LAN access point, it is determined whether or not the first wireless LAN access point and the second wireless LAN access point belong to the same subnet Subnet identity determination means to
Used when the first wireless LAN access point is connected to the first wireless LAN access point when it is determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet. IP address continuous use means for continuously using the IP address that has been used;
A wireless LAN terminal comprising: The wireless LAN terminal according to claim 1,
The subnet identity determining means includes
If the second wireless LAN access point is not included in the list of wireless LAN access points belonging to the adjacent subnet included in the wireless LAN frame received from the first wireless LAN access point, the first wireless A wireless LAN terminal, wherein a LAN access point and the second wireless LAN access point are determined to belong to the same subnet. The wireless LAN terminal according to claim 1,
The subnet identity determining means includes
When the second wireless LAN access point is included in a list of wireless LAN access points belonging to the same subnet included in the wireless LAN frame received from the first wireless LAN access point, the first wireless LAN A wireless LAN terminal, wherein a LAN access point and the second wireless LAN access point are determined to belong to the same subnet. The wireless LAN terminal according to claim 1,
The subnet identity determining means includes
When the MAC address of the second wireless LAN access point is not included in the list of MAC addresses of wireless LAN access points belonging to adjacent subnets included in the wireless LAN frame received from the first wireless LAN access point A wireless LAN terminal that determines that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet. The wireless LAN terminal according to claim 1,
When handing over to the second wireless LAN access point and continuing to use the IP address used when connected to the first wireless LAN access point, the lease expiration date of the IP address is updated. A wireless LAN terminal. The wireless LAN terminal according to claim 5,
When handing over to the second wireless LAN access point and continuing to use the IP address that was used when connected to the first wireless LAN access point, the lease time limit for IP address setting is A wireless LAN terminal that renews the lease term of the IP address only when it has not passed. The wireless LAN terminal according to claim 5,
Lease of IP address setting that remains when handing over to the second wireless LAN access point and continuing to use the IP address that was used when connected to the first wireless LAN access point A wireless LAN terminal that updates a lease term of an IP address only when the term is less than a predetermined value and the lease term of the IP address setting has not passed. The wireless LAN terminal according to claim 1,
Even if it is determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet after handover to the second wireless LAN access point. A wireless LAN terminal that resets an IP address when a lease time for setting has expired. When handing over from the first wireless LAN access point to the second wireless LAN access point, it is determined whether or not the first wireless LAN access point and the second wireless LAN access point belong to the same subnet A subnet identity determination step,
Used when the first wireless LAN access point is connected to the first wireless LAN access point when it is determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet. IP address continuous use step for continuously using the IP address that has been used,
An IP address continuous use method in handover characterized by comprising: The method for continuously using an IP address in handover according to claim 9,
In the subnet identity determination step,
If the second wireless LAN access point is not included in the list of wireless LAN access points belonging to the adjacent subnet included in the wireless LAN frame received from the first wireless LAN access point, the first wireless A method for continuously using an IP address in handover, wherein it is determined that a LAN access point and the second wireless LAN access point belong to the same subnet. The method for continuously using an IP address in handover according to claim 9,
In the subnet identity determination step,
When the second wireless LAN access point is included in a list of wireless LAN access points belonging to the same subnet included in the wireless LAN frame received from the first wireless LAN access point, the first wireless LAN A method for continuously using an IP address in handover, wherein it is determined that a LAN access point and the second wireless LAN access point belong to the same subnet. The method for continuously using an IP address in a handover according to claim 9,
In the subnet identity determination step,
When the MAC address of the second wireless LAN access point is not included in the list of MAC addresses of wireless LAN access points belonging to adjacent subnets included in the wireless LAN frame received from the first wireless LAN access point A method for continuously using an IP address in a handover, wherein the first wireless LAN access point and the second wireless LAN access point are determined to belong to the same subnet. The method for continuously using an IP address in handover according to claim 9,
When handing over to the second wireless LAN access point and continuing to use the IP address used when connected to the first wireless LAN access point, the lease expiration date of the IP address is updated. A method for continuously using an IP address. The IP address continuous use method according to claim 13,
When handing over to the second wireless LAN access point and continuing to use the IP address that was used when connected to the first wireless LAN access point, the lease time limit for IP address setting is A method for continuously using an IP address, wherein the lease expiration date of the IP address is renewed only when it has not passed. The IP address continuous use method according to claim 13,
Lease of IP address setting that remains when handing over to the second wireless LAN access point and continuing to use the IP address that was used when connected to the first wireless LAN access point A method of continuing to use an IP address, wherein the lease term of the IP address is renewed only when the term is less than a predetermined value and the lease term of the IP address setting has not expired. In the IP address continuous use method according to claim 9,
Even if it is determined that the first wireless LAN access point and the second wireless LAN access point belong to the same subnet after handover to the second wireless LAN access point. A method for continuously using an IP address, characterized by resetting an IP address when a set lease term has passed.

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