JP4279046B2 - Wireless terminal device having high-speed roaming processing means for wireless LAN - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless terminal device, and particularly, when there is a wireless terminal device that roams between access points on a communication network to which a plurality of bridge-type wireless access points are connected under the control of a server device, wireless roaming at high speed The present invention relates to a wireless terminal device provided with means for performing processing, that is, promptly recognizing movement of a wireless terminal device and resuming communication between the wireless terminal device and a server device.
[0002]
[Prior art]
With recent advances in wireless technology, an increasing number of wireless terminal devices join the LAN system while performing wireless communication instead of wired communication. When connecting via a wireless LAN, the wireless terminal device is always moving during wireless communication, and may be out of the wireless communicable area during communication. Furthermore, since the battery is used as a power source, a sudden power interruption may occur. In addition, such a system is used in, for example, a physical distribution system, and has a characteristic that data to be held is regarded as important even when the wireless terminal device is used in a relatively poor environment.
[0003]
On the other hand, in recent years, when a LAN is configured, it is common to reduce restrictions on the load and distance of the entire communication network by using a learning type multi-port bridge such as a switching hub.
[0004]
The learning type bridge knows the address (MAC Address) of the terminal connected to the port by learning, and only the data related to the subordinate address is sent to the port so that excess data is transferred to the communication network. The flow is suppressed. This effect reduces the load on the entire LAN.
[0005]
Although a plurality of bridge-type wireless access points are often connected on this communication network, when the wireless terminal device moves (roams), as seen from the bridge, as shown in FIG. The terminal will move between ports. Therefore, when roaming, the bridge must relearn the address of the terminal connected to the port by some means.
[0006]
Therefore, conventionally, when the wireless terminal device (7) recognizes movement, a signal called a roaming packet is sent to the bridge-type wireless access point (6) (hereinafter referred to as wireless AP 2) that has newly started communication. The signal arrives from the wireless AP 2 (6) via the learning bridge (2) to the bridge wireless access point (5) (hereinafter referred to as wireless AP 1) that has been communicating, so that the learning bridge (2) and Each bridge type wireless access point (5), (6) (wireless AP1, wireless AP2) recognizes the movement of the wireless terminal device (7) and re-learns (rewrites the MAC address table). The bridge (2) flows data from the server device (1) only to the wireless AP 2 (6) that has newly started communication, and no longer sends data to the wireless AP 1 (5) that has been communicating.
[0007]
Note that when the wireless AP 2 (6) that has newly started communication recognizes the movement of the wireless terminal device (7), the wireless AP 2 (6) wirelessly communicates until then via the learning bridge (2). A roaming packet may be sent to AP1 (5).
[0008]
However, re-learning for a conventional learning bridge is based on the assumption that the computer used at one desk is taken (moved) to another desk and reconnected at the destination (this In such a case, when the power of the personal computer is turned on again, the bridge is re-learned), and it is not assumed that the terminal roams frequently like a handy terminal with wireless communication.
[0009]
Therefore, the master station has a slave station registration MAC address table that stores the MAC address of the slave station to be registered at least, and is roaming when the slave station moves to a certain service area and registers with a new master station. When the new master station completes registration of the slave station, it broadcasts the fact to the original master station in a UDP / IP packet, and the corresponding original master station sends a packet. Is known to have moved to another service area, and is deleted from the original MAC address table of the master station (see Patent Document 1).
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-317744
[Problems to be solved by the invention]
When a wireless terminal device moves (roams) in a communication network having a learning type bridge, the following problems occur.
[0012]
(A) Once a learning bridge learns, it keeps flowing data to the learned port (access point) until it is forgotten or re-learned. However, the forgotten time (aging time) is usually on the order of a few minutes. For example, even when the wireless terminal device (7) moves from (A) to (B) on the communication network shown in FIG. 2, until the bridge A (2) re-learns,
Server device (1)-> Bridge A (2)-> Bridge B (3)-> Wireless AP1 (5) The useless communication does not stop and the route of Bridge A (2)-> Bridge C (4) remains closed Therefore, the wireless terminal device (7) under the control of the wireless AP 2 (6) cannot receive data.
[0013]
(Ii) Many bridges relearn when there is communication from outside the learned port. Many wireless LAN systems send out packets by roaming, so that they can be relearned. However, in a wireless space with a high load or a low reliability as a transmission path, packets cannot always be sent (received).
[0014]
(Iii) When there are a plurality of communication paths for load distribution or a redundant configuration, a bridge that cannot be re-learned may be generated. For example, in the case of FIG.
Wireless AP2 (6) ⇒ Bridge C (4) ⇒ Bridge B (3)
The bridge A (2) does not reach and the bridge A (2) is not relearned. If the bridge A (2) cannot be learned, the wireless terminal device (7) under the wireless AP 2 (6) connected to the bridge C (4) cannot receive data.
[0015]
In general, data does not flow between the bridge B (3) and the bridge C (4) in the same hierarchy by a protocol called STP (Spanning-Tree Protocol) (to avoid a network loop). There are many cases. This is to prevent data from circulating and increasing the load on the communication network. For this reason, even if the bridge B (3) and the bridge C (4) are relearned by the roaming packet,
Server device (1)-> Bridge A (2)-> Bridge B (3)-> Bridge C (4)-> Wireless AP2 (6)
Data does not flow along the route.
[0016]
By the above (a) to (u), in the case of an application for a wireless handy terminal that is expected to frequently roam, it may happen that communication cannot be performed for a while after roaming. This appears as a variation in response time between terminals.
[0017]
Further, in the method disclosed in Patent Document 1, since it is unknown where the original master station is, a MAC address deletion request is sent by UDP / IP. If there is no guarantee that the address deletion request will arrive, and if it does not, useless packets will continue to be discharged from the original master station onto the communication network, further increasing the communication load.
[0018]
An object of the present invention is to overcome the above-mentioned problems, and even when there is a wireless terminal device that moves frequently, it is possible to promptly re-learn the learning bridge in a timely manner and to distribute the load on the communication network. An object of the present invention is to provide a wireless terminal device provided with roaming processing means.
[0019]
[Means for Solving the Problems]
And a server device on the communication network including a plurality of bridge-type wireless access point, the wireless terminal device roaming between the bridge wireless access point, a detection means for detecting roaming, said detecting means, after roaming When a bridge type wireless access point that performs communication is detected, the server apparatus is provided in advance for line connection monitoring to the server apparatus via the bridge type wireless access point that performs communication after the roaming . Transmitting means for sending a signal for monitoring the line connection.
[0020]
The wireless terminal device according to the present invention further comprises receiving means for receiving a response from the server device that has received the signal for monitoring the line connection, and the server device receives the response until the receiving device receives the response. The transmission means sends a signal for monitoring the line connection a plurality of times.
[0021]
Further, the signal for monitoring the line connection is a line connection monitoring packet.
[0022]
That is, in order to solve the above-described problem, the wireless terminal device according to the present invention
(A) A wireless terminal device that has detected roaming by a change in a connection access point sends a line connection monitoring packet (confirmation signal) to a communication partner (for example, a server device),
(B) Upon receiving the line connection monitoring packet, the communication partner (for example, the server device) of the wireless terminal device sends a response back to the wireless terminal device,
(C) The wireless terminal device continues to send line connection monitoring packets until a response is received from the communication partner,
(D) Re-learn all necessary bridges on the new communication path by exchanging this packet.
By performing such a series of processing, high-speed roaming processing becomes possible.
[0023]
As described above, there is a feature that communication with the server device can be resumed without waiting for the aging time even after roaming of the wireless terminal device.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The wireless terminal device of the present invention will be described in detail with reference to FIG.
[0025]
FIG. 3 is a diagram showing a configuration of a network system such as a (wired or wireless) LAN according to an embodiment of the present invention.
[0026]
In FIG. 3, 1 is a server device, 2 to 4 are learning-type bridges, 5 and 6 are bridge-type wireless access points (wireless AP1 & wireless AP2), and 7 is a wireless portable terminal corresponding to a terminal device. The bridges (2) to (4) perform wireless communication with the wireless terminal device (7) via the wireless AP1 (5) or the wireless AP2 (6), and between the bridge and the server device (1) via the network. connect.
[0027]
An outline of roaming in the wireless LAN will be described with reference to FIG.
[0028]
The server device (1) processes and controls communication and data in the wireless LAN. The bridges (2) to (4) compare the destination of the received packet with the address table in which the MAC address is registered, and relay the packet to the port (access point) where the corresponding terminal exists. If there is a destination terminal at the same port as the received port, the packet is discarded, and unnecessary packets are not relayed to the segment beyond the bridge. The wireless terminal device (7) receives data from the server device (1) via the bridges (2) to (4), the wireless AP1 (5), and the wireless AP2 (6), or the operator Data is input to the wireless terminal device (7) and sent to the server device (1) via the LAN. The wireless terminal device (7) may be carried by an operator or may be mounted and operated on a vehicle such as a forklift that moves in a warehouse.
[0029]
The operation of each unit when the wireless terminal device (7) moves from (a) to (b) on the communication network shown in FIG. 3 will be described with reference to FIG.
[0030]
The wireless terminal device (7) includes means for detecting that the wireless access point for communication has changed from the wireless AP1 (5) to the wireless AP2 (6). When the change of the wireless access point is detected by the detecting means (S1), a line connection monitoring packet (P) which is a signal for monitoring the line connection is sent to the server apparatus (1) (S2). This packet (P)
Wireless AP2 (6) ⇒ Bridge C (4) ⇒ Bridge A (2) ⇒ Server device (1) flows and each packet should relearn when packet (P) passes through each bridge on the route .
[0031]
However, as described above, in a wireless space with a high load or a low reliability as a transmission path, a packet cannot always be sent (received), so a response signal (Q) is sent from the server device (1). Try to ask. Until the wireless terminal device (7) receives the response signal (Q) (S3), the line connection monitoring packet (P) is continuously sent to the server device (1) periodically or irregularly (S2), When the response signal (Q) is received, transmission of the line connection monitoring packet (P) is stopped (S4).
[0032]
The response signal (Q) from the server device (1) is also
Server device (1)-> Bridge A (2)-> Bridge C (4)-> Wireless AP2 (6)-> Wireless terminal (7) (A)
Therefore, each bridge can be re-learned at this time, and the certainty of re-learning is increased.
[0033]
Note that a normal server device has a function of responding to a command called ping as a standard feature.
[0034]
This is the most basic command used to check whether an IP packet reaches the communication destination and whether it is reachable in IP in a TCP / IP network that performs reliable session-oriented communication. Yes, using the echo command of ICMP (Internet Control Message Protocol).
[0035]
Since this function is provided as standard on the server device side, only the software on the wireless terminal device (7) side needs to be changed in order to realize the above embodiment. That is, in order to send a response signal (Q) from the server apparatus (1), it is only necessary to send a ping (line connection monitoring packet (P)) to the server apparatus (1). There is no need to change the hardware / software of the server device (1) that responds or each bridge.
[0036]
In addition, as a method for the wireless terminal device to detect the change of the access point,
Receive beacons that are packets sent at regular intervals from the access point to synchronize the wireless network,
An inquiry is sent from the wireless terminal device at a constant time period, and communication is made with a high RSSI (Received Signal Strength Indicator).
However, in the present invention, high-speed roaming processing is always possible without being affected by the method.
[0037]
【The invention's effect】
When the wireless terminal device moves and detects a change in the wireless access point (roaming), the learning bridge can be re-learned by simply sending a confirmation signal (line connection monitoring packet) to the server device. Further, the server device that has received the confirmation signal returns a response to the wireless terminal device, thereby prompting the learning bridge again to learn again. As a result, in a LAN including a bridge-type access point that receives access from a wireless terminal device that moves at high speed, even if the wireless terminal device moves at high speed, the route including the learning-type bridge is hardly subjected to a load. Allows the learning bridge to relearn.
[Brief description of the drawings]
FIG. 1 is a diagram related to a conventional LAN configuration. FIG. 2 is a diagram related to a LAN configuration using conventional technology. FIG. 3 is a diagram related to a LAN configuration using the present invention. Flow chart shown [Explanation of symbols]
1-server device 2-4-learning bridge 5, 6-bridge wireless access point 7-wireless terminal device P-line connection monitoring packet Q-response signal

Claims (4)

In a wireless terminal device that roams between the bridge wireless access points on a communication network composed of a server device and a plurality of bridge wireless access points,
Detection means for detecting roaming;
When the detection unit detects a bridge type wireless access point that performs communication after roaming , the server apparatus monitors the connection of the line to the server apparatus via the bridge type wireless access point that performs communication after the roaming. Transmitting means for sending a signal for monitoring the line connection provided in advance ,
A wireless terminal device comprising: The wireless terminal device according to claim 1,
Receiving means for receiving a response from a server device that has received a signal for monitoring the line connection;
A wireless terminal device, wherein the transmitting unit sends a signal for monitoring line connection to the server device a plurality of times until the receiving unit receives the response.   3. A radio terminal apparatus according to claim 1, wherein the signal for monitoring line connection is a line connection monitoring packet. In a wireless communication system including a wireless terminal device capable of roaming between a bridge type wireless access point on a communication network composed of a server device and a plurality of bridge type wireless access points,
  When the wireless terminal device detects roaming, the server device previously provides a line for monitoring the connection of the line to the server device via a bridge type wireless access point that performs communication after roaming based on the detection. Send a signal to monitor the connection,
  A wireless communication system in which the bridge wireless access point that performs communication after roaming performs re-learning of a communication path based on a signal for monitoring a line connection transmitted from the wireless terminal device.

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