The methods, devices and systems that terminal switches at high speed between AP in wlan network
Technical field
The present invention relates to wireless communication field, the side that terminal switches at high speed between AP in a kind of wlan network is particularly related to
Method, device and system.
Background technique
In wlan network agreement, there are two types of basic network type, self wlan network and foundation structure type WLAN
Network.Wherein, in self wlan network, as shown in Figure 1 (in figure 1 be AP), in can Station in communication range
Between (can be multiple types) centralized management and forwarding of a central node, the net can be not necessarily to direct communication, data packet
Network type belongs to the scope of ad hoc network, is used for small-scale provisional communication;In foundation structure type wlan network, such as Fig. 2
Shown (1 is AP in figure, and 2 be interchanger), has a central access point to be responsible for all communications in network, some Station is such as
It needs to be communicated with other Station, it is necessary to data frame be first sent to access point, then transfer data frame by access point
Give purpose Station.
In above two network type, the service range of an AP (is known as BSS, basic service in 802.11 agreements
Collection), small office or family can be covered, wider region can not be serviced.802.11 agreements allow to connect several BSS
Extended service set (ESS), with the overlay area of this extended wireless network.So-called ESS is exactly that backbone network is utilized to go here and there several BSS
It is linked togather, as shown in figure 3, the AP in all ESS uses identical SSID (Service Set Identifier, services set
Mark).
Currently, in the hard handover being all analogous in cellular network that the switching of existing wlan network uses, after first disconnecting
Switching, Station is first disconnected and the physical connection of previous AP, then goes to be associated with new AP foundation again.But in Cellular Networks
Hard handover is to be initiated by network side, and the switching in wlan network is determined by station.When station discovery is current
The signal strength of the AP of connection is excessively weak, is not enough to maintain existing connection, it just will disconnect the connection with current AP, from searching
AP in selection one signal is best re-connects.Because when having the process of a disconnection reconnection leads to the switching of WLAN
Prolong all at 1 second or more.
And IEEE is directed to the demand of roaming switch, proposes IEEE802.11r agreement (Fast BSS Transition),
But the agreement is only for the cipher code renewal time improved in handoff procedure.New 802.11r standard is referred to as quickly basic
Service setting conversion (Fast Basic Service Set Transition).New key management mode is defined in agreement
And fast handoff mechanisms, while some information are increased, enable STA and target AP to establish secure connection in a relatively short period of time
And QoS resource distribution is completed, therefore can guarantee that transit time of the Wi-Fi equipment between two access points is less than 50 milliseconds, from
And meet the standard of voice roaming.
When carrying out roaming switch using 802.11r, can generally there be 50 milliseconds or so of delay, it is quicker to be unable to satisfy time delay
The application requirement of sense.AP and Station is needed all to support the function using 802.11r simultaneously.But it is most of currently on the market
AP is not carried out 802.11r agreement, causes lower deployment cost higher.Meanwhile 802.11r is not suitable for Station and is associated with original
The case where AP communication is deteriorated suddenly, but in high-speed mobile, due to the blocking etc. of building, this channel circumstance it is quick
Variation is recurrent.802.11r agreement is to provide the method for more efficient in terms of key updating in handoff procedure,
But the method for its hard handover does not change.
Summary of the invention
The technical problem to be solved in the present invention is to provide terminals in a kind of wlan network at low cost, switch speed is fast in AP
Between the methods, devices and systems that switch at high speed.
In order to solve the above technical problems, present invention offer technical solution is as follows:
A kind of method that terminal switches at high speed between AP in wlan network, comprising:
Obtain the information of attachable AP;
It is only authenticated and is established with attachable AP and be associated with;
When the signal strength of communicating AP is less than roaming switch threshold value, communication link is switched to, association has been established
An AP on.
Further, it is described authenticated and established with attachable AP be associated with further are as follows:
When the signal strength of attachable AP, which is greater than roaming, monitors threshold value, is authenticated and established with the AP and be associated with.
Further, further includes:
When the signal strength that associated AP has been established, which is less than roaming, to be monitored threshold value and be more than certain number, release and the AP
Association.
Further, described when the signal strength of communicating AP is less than roaming switch threshold value, communication link is cut
Change to have been established it is further on an associated AP are as follows:
When the signal strength of communicating AP is less than roaming switch threshold value and is more than certain number, communication link is cut
It changes to and has been established on an associated AP.
Further, described when the signal strength of communicating AP is less than roaming switch threshold value, communication link is cut
It changes to after having been established on an associated AP further include:
Data still are received from the AP of original connection whithin a period of time, but do not send data to former connection AP.
Further, described when the signal strength of communicating AP is less than roaming switch threshold value, communication link is cut
It changes to after having been established on an associated AP further include:
It triggers the interchanger connecting with the AP of present communications and carries out port address list update.
A kind of terminal, comprising:
Module is obtained, for obtaining the information of attachable AP;
Relating module is associated with for only being authenticated and being established with attachable AP;
Switching module, for when the signal strength of communicating AP is less than roaming switch threshold value, communication link to be cut
It changes to and has been established on an associated AP.
Further, the relating module is further used for:
When the signal strength of attachable AP, which is greater than roaming, monitors threshold value, is authenticated and established with the AP and be associated with.
Further, further includes:
De-association module, for monitoring threshold value and more than certain time when the signal strength that associated AP has been established is less than roaming
When number, releasing is associated with the AP's.
Further, the switching module is further used for:
When the signal strength of communicating AP is less than roaming switch threshold value and is more than certain number, communication link is cut
It changes to and has been established on an associated AP.
Further, which is characterized in that the switching module is also connected with receiving module, and the receiving module is used for:
Data still are received from the AP of original connection whithin a period of time, but do not send data to former connection AP.
Further, the switching module is also connected with trigger module, and the trigger module is used for:
It triggers the interchanger connecting with the AP of present communications and carries out port address list update.
A kind of WLAN communication system, including AP and above-mentioned terminal.
The invention has the following advantages:
The method that wlan network terminal of the invention switches at high speed between AP obtains the information of attachable AP first, and
It is authenticated and is established with attachable AP and be associated with, i.e., with the preparatory action that increases switching in the communication process of AP, found
After attachable AP, it is associated in advance with AP foundation, once the signal strength as communicating AP is not sufficient to ensure that normal number
When according to communication, communication link is just switched to the chain road that associated AP has been established, to realize that the fast roaming of link layer is cut
It changes.In the present invention, the information for obtaining attachable AP is carried out, and is authenticated and established associated movement consumption with attachable AP
When about 30-80ms, and the prior art be switching when just carry out above-mentioned movement, the present invention advances to above-mentioned movement before switching
It completes, handoff delay can be controlled within 10ms, can satisfy the requirement of major applications scene.With prior art phase
Than the present invention has the advantages that at low cost, switch speed is fast.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of independence wlan network in the prior art;
Fig. 2 is the structural schematic diagram of foundation structure type wlan network in the prior art;
Fig. 3 is the structural schematic diagram for the ESS that multiple AP in the prior art are constituted;
Fig. 4 is the flow diagram for the method that terminal switches at high speed between AP in wlan network of the invention;
Fig. 5 is complete connection procedure schematic diagram between Station and AP in the prior art;
Fig. 6 is that the process of the handoff preparation phase for the method that terminal switches at high speed between AP in wlan network of the invention is shown
It is intended to;
Fig. 7 is that the process of the roaming switch process for the method that terminal switches at high speed between AP in wlan network of the invention is shown
It is intended to;
Fig. 8 is that the triggering switch port for the method that terminal switches at high speed between AP in wlan network of the invention updates
Schematic diagram;
Fig. 9 is the structural schematic diagram of terminal of the invention.
Specific embodiment
To keep the technical problem to be solved in the present invention, technical solution and advantage clearer, below in conjunction with attached drawing and tool
Body embodiment is described in detail.
Name Resolution:
WLAN:Wireless LAN, WLAN.Wired connection is substituted by wireless radio-frequency to realize local
Data transmission in net.
AP:Access Point, access point.By wireless medium, network insertion service is provided for Station.
BSS:Basic Service Set, basic service set, the station being in communication with each other by one group are constituted.
The region that communication is able to carry out between station is known as primary service area.
Several BSS are carried out series connection and are formed ESS, are exactly by ESS:Extended Service Set, extended service set
Several BSS are cascaded using backbone network.All access points positioned at the same ESS use identical SSID, usually
It is exactly the so-called network name of user.
Station: terminal, wireless Station are exactly a kind of wireless terminal accessing device for connecting wlan network, Ke Yijie
Wireless router, wireless aps are received, the wireless signal of wireless base station etc. refers in particular to the nothing for supporting 802.11a/b/g/n/ac agreement herein
Line Station.
WDS: wireless distribution system is wirelessly to a kind of method of distributed system network extension, it allows
It connects and connects other network equipments on the Station of AP.
Beacon frame: the management frame that AP is beacon by period transmission types informs presence and the energy of peripheral equipment AP
Power.
On the one hand, the present invention provides a kind of method that terminal switches at high speed between AP in wlan network, as shown in figure 4, packet
It includes:
Step S101: the information of attachable AP is obtained;
In this step, the beacon frame that Station can be sent by receiving surrounding AP, to obtain the letter of attachable AP
Breath, or Probe request claim frame can be periodically sent by Station, around active scan in wireless environment
AP, to obtain the information of attachable AP.
Step S102: it is only authenticated and is established with attachable AP and be associated with;
In the prior art, between Station and AP complete connection procedure as shown in figure 5, include scanning, link authentication,
Association, encryption certification, access authentication (not essential) and data transmission.In this step, Station and attachable AP is only carried out
Certification and establish association, certification herein and establish associated process refer to link authentication, association shown in dotted line frame in Fig. 5,
Encryption certification and access authentication (if any).Station is authenticated and is established with attachable AP be associated with after, without
The forwarding of data message, i.e., only maintain connection management, sends without data.
Step S103: when the signal strength of communicating AP is less than roaming switch threshold value, communication link is switched to
It has been established on an associated AP.
In this step, when the signal strength of communicating AP is less than roaming switch threshold value, then Station thinks its pass
The signal strength of the AP of connection is too low, is insufficient for normal data communication requirements, needs to attempt switching and is connected on new AP,
Preferably, communication link is switched on the highest AP of signal strength by Station.
Roaming switch threshold value: the effect for the roaming switch threshold value that the present invention is set is, when the signal of communicating AP is strong
When degree or transmission rate are less than the roaming switch threshold value of setting, then Station thinks that the signal strength of associated AP is too low.
The method that wlan network terminal of the invention switches at high speed between AP obtains the information of attachable AP first, and
It is authenticated and is established with attachable AP and be associated with, i.e., with the preparatory action that increases switching in the communication process of AP, found
After attachable AP, it is associated in advance with AP foundation, once the signal strength as communicating AP is not sufficient to ensure that normal number
When according to communication, communication link is just switched to the chain road that associated AP has been established, to realize that the fast roaming of link layer is cut
It changes.In the present invention, the information for obtaining attachable AP is carried out, and is authenticated and established associated movement consumption with attachable AP
When about 30-80ms, and the prior art be switching when just carry out above-mentioned movement, the present invention advances to above-mentioned movement before switching
It completes, handoff delay can be controlled within 10ms, can satisfy the requirement of major applications scene.With prior art phase
Than the present invention has the advantages that at low cost, switch speed is fast.
As an improvement of the present invention, step S102 is further are as follows:
When the signal strength of attachable AP, which is greater than roaming, monitors threshold value, is authenticated and established with the AP and be associated with.
In the present invention, although Station and AP establishes incidence relation, Station and AP are without datagram at this time
The forwarding of text, i.e., only maintain connection management, sends without data.
Threshold value is monitored in roaming: the effect for the roaming switch threshold value that the present invention is set is, when the AP's that Station is received
The signal intensity ratio roaming of beacon frame monitor threshold value it is strong when, then authenticated and established with the AP and be associated with.
As a further improvement of the present invention, further includes:
Step S301: when the signal strength that associated AP has been established, which is less than roaming, to be monitored threshold value and be more than certain number,
Releasing is associated with the AP's.
In the present invention, when the signal strength that associated AP has been established, which is less than roaming, to be monitored threshold value and be more than certain number,
Then think that the signal strength of the AP is excessively weak, do not have alternative switching condition, Station actively initiates de-association process, interrupt with
The association of AP.
As further improvement of the invention, step S103 is further are as follows:
When the signal strength of communicating AP is less than roaming switch threshold value and is more than certain number, communication link is cut
It changes to and has been established on an associated AP.
In the present invention, when the signal strength of communicating AP is less than roaming switch threshold value, then it is assumed that communicating
The signal strength of AP is too low, needs to carry out the switching between AP, to guarantee normal data communication.In the present invention, Station can be with
Communication link is switched to any one is higher than the signal strength of current communicating AP and have been established on an associated AP,
Preferably, communication link can be switched on the highest AP of signal strength by Station.
In above two improvement of the invention, by the way that associated signal strength (or the signal of communicating AP has been established
Intensity) with roaming monitor threshold value (or roaming switch threshold value) compared with when, need be more than certain number, then released again (or
Switching) operation." need be more than certain number " in the process is the fluctuation of signal strength in order to prevent and the Station occurred
It is operation associated that it is associated with reconciliation with AP frequent progress, that is, prevents " ping-pong ".Counter can be used when concrete application of the present invention
Accumulation operations are carried out, the number compared is counted, after counter reaches certain number, then takes subsequent operation.This
Invention can guarantee that the signal strength of AP is in metastable situation within a certain period of time, and just determination is associated with Station with AP
Or switching.
In the present invention, after step S103 further include:
Step S501: still receiving data from the AP of original connection whithin a period of time, but does not send data to former connection AP.
In the present invention, the partial data of terminal may have been cached before de-association in the message queue of original AP, after de-association
It still will continue to send, after terminal receives this partial data, judge data under normal circumstances and be not from and communicating AP just
It can lose, therefore, after Station completes roaming switch, the communication for connecting AP with original will not be stopped immediately, at this point, Station
It can receive the data from former connection AP, but not send data to former connection AP.After the time set by one,
Station stops receiving the data message from former connection AP.It by the mechanism, can prevent in after roaming switch, exchange
There may be the messages of undelivered to Station into the link of former connection AP for machine, to avoid losing due to caused by switching AP
Increase time delay because retransmitting data after packet.
In the present invention, after step S103 further include:
Step S601: the interchanger that triggering is connect with the AP of present communications carries out port address list update.
In the present invention, in station after an AP roaming switch to another AP, if be attached thereto by wired
Client (user) no data when externally sending, the MAC Address of the client remains recorded in the interchanger of former AP connection
In the address table of port, when there is data to be sent to client by the interchanger, data still can be passed through original AP by interchanger
The port of the interchanger of connection is externally sent, so, after station no longer monitors the data packet of original AP, it is sent to client
Data can lose.For this reason, it may be necessary to actively initiate the port address list update that can trigger interchanger by station
Process, to guarantee that subsequent data packet correctly can be sent to client by interchanger.
In the following, each step for the method that the present invention respectively switches at high speed terminal in wlan network AP carries out specifically
It is bright:
The one, present invention provides one embodiment for handoff preparation phase, and specific implementation step is as follows:
Compared with prior art, the present invention increases handoff preparation phase in the communication process of Station and some AP,
I.e. after discovery signal quality good AP, communication connection is set up with AP in advance, once meet switching condition, just by communication link
It is switched to the chain road for the AP having had connected, then disconnects the connection with previous AP again.To realize the quick unrestrained of link layer
Trip switching, enables the invention to that roaming switch process is rapidly completed.
Handoff preparation phase of the invention, as shown in fig. 6, AP and Station of the work in double layer network pass through wirelessly
The mode of bridge joint links together, and after Station normally accesses an AP, can be moved between each AP.
When Station is moved in the entire domain ESS, in the process of moving, Station can actively receive surrounding AP hair
The beacon frame sent.Fig. 6 shows the pretreatment movement that station is carried out for the non-signal for having connected AP.
Receive be not associated AP beacon frame after, it is alternative to first determine whether the AP has been added to roaming
In list of devices.If had been added to, judge whether the beacon frame signal intensity received is less than roaming and monitors threshold value.Such as
Fruit is less than, then counter 2 relevant to the AP carries out plus 1 operates;Otherwise, counter 2 is reset, and process terminates.Judge to count again
Whether more than one scheduled number limits (such as 10) to device 2.If being not above limitation, process terminates;Else if super
Cross limitation, then it is assumed that the signal strength of the AP is excessively weak, does not have alternative switching condition, and station actively initiates de-association process,
The connection with AP is interrupted, after the completion of process executes, Station deletes the AP from roaming optional equipment list, and process terminates.
If the AP in roaming optional equipment list, it is unrestrained not judge whether the beacon frame signal intensity of the AP is greater than
Threshold value is monitored in trip.If it is not greater, then process terminates.If it is greater, then Station actively initiate with the certification of the AP, be associated with
Process.If association failure, process terminate.If be successfully associated, the information of the AP is added to roaming optional equipment column
In table, then process terminates.Roaming alternate list has recorded but is not limited to the MAC Address of AP, signal strength, association status,
Switching state, last time information update time etc..In the process, although station with roaming optional equipment list in
AP equipment establishes incidence relation, but forwarding of the Station and AP without data message at this time.Namely only maintain connecting tube
Reason is sent without data.
When all not receiving the message of some AP in roaming optional equipment list in one section of specified duration, Station
Also de-association process can be actively initiated, and the AP is deleted from roaming alternate list.
The two, present invention provide one embodiment for roaming switch process, and specific implementation step is as follows:
Roaming switch process of the invention, as shown in fig. 7, firstly, the signal that Station will receive associated AP (may
It is beacon frame or data frame).Then judge whether signal strength is less than roaming switch threshold value.If it is not, then counter 1
It resets, process terminates.Otherwise, counter 1 carries out plus 1 operates.Judge again counter 1 value whether more than one scheduled number
It limits (such as 10).If being not above limitation, process terminates.Otherwise, then it is assumed that the signal strength of associated AP is too low, needs
The switching between AP is carried out, to guarantee normal data communication.Station first checks for roaming optional equipment list, if unrestrained
There are the better AP of signal strength in trip alternate list, then communication link is switched on the highest AP of signal strength by Station,
And the AP of original communication is put into peripatetic device alternate list.Meanwhile in order to which it is wired quickly to update the rear end AP after roaming switch
The mapping table of MAC Address and port in the network switch, Station meeting poll are connected to the user equipment of oneself, and will be every
The MAC Address of one user equipment sends two layer message, as source MAC to realize the quick update of double layer network topology.
If roaming optional equipment, list is empty (indicating without changeable AP), at this point, Station can periodical active transmission Probe
Request claim frame, the AP around active scan in wireless environment, to trigger the process of preparation stage shown in fig. 6.
In the present embodiment, the effect of counter 1 and counter 2 mainly prevents the fluctuation of signal strength and occurs
Station is associated with AP frequent progress conciliates operation associated namely ping-pong.After counter reaches certain number, just take
Subsequent operation, it is ensured that the signal strength of AP be within a certain period of time it is metastable, Station just determination is associated with AP
Or de-association.The selection of the two counters is related to the movement speed of Station in practical applications.Movement speed is faster
When, the time of Station from the overlay area that the overlay area of an AP is moved to another AP is shorter, when the switching needed
Between it is month faster, therefore the selection of times of counter is fewer.Under normal circumstances, when speed per hour is lower than 100 kilometers, it can choose meter
The number of number device is 10 or so;When speed per hour is higher than 100 kilometers, selection of times is 5 or so.It can guarantee handover delay control in this way
System is within 10ms.
In addition, after Station completes roaming switch, the communication that AP is connect with original will not be stopped immediately in the present embodiment,
At this point, Station can receive the data from former connection AP, but not send data to former connection AP.Over time,
Station stops receiving the data message from former connection AP.It by the mechanism, can prevent in after roaming switch, exchange
There may be undelivereds into the link of former connection AP for machine to Station message, to avoid the packet loss due to caused by switching AP.
The three, present invention provide one embodiment for triggering switch port renewal process, and specific implementation step is as follows:
In the present embodiment, (1 is AP1 in figure, and 1 ' is AP2, and 2 be interchanger, and 3 be Station, and 4 are as shown in Figure 8
Client, 5 be port 1,5 ' be port 4), in the case where double layer network, wireless bridging is served as before general AP and Station
Effect.Multiple AP are connected on the different port of interchanger, can be the different port of the same interchanger, are also possible to more
The different port of grade interchanger.Fig. 8 shows two AP (AP1 and AP2), is connect respectively at the different ends of the same interchanger
Network structure on mouth (port 1 and port 4).In this way, after Station is from AP1 roaming switch to AP2, if passed through
When wired client no data being attached thereto externally is sent, the MAC Address of the client remains recorded in the port 1 of interchanger
Address table in, have data by the interchanger be sent to client when, interchanger still can data by port 1 to outgoing
It send.Therefore, after station no longer monitors the data packet of AP1, the data for being sent to client can lose.Therefore, it is necessary to pass through
Station actively initiates the process that can trigger the port address list update of interchanger.After the completion of roaming switch, by
Station sends the data packet, such as ARP request of address etc. that a source MAC is client by AP2 immediately.In this way
Interchanger can update the MAC Address of the client into the address list of port 4 after receiving the data packet.To protect
Demonstrate,proving subsequent data packet correctly can be sent to client by interchanger.One, a station second line of a couplet of Fig. 8 signal
The case where client, naturally it is also possible to realize that multiple client's is same by one interchanger of wired connection at station
When connect.In this case, station just need to act on behalf of coupled each client by AP2 to interchanger send number
According to packet.
In conclusion the invention has the following advantages that
1. a Station, can be simultaneously in the case where being associated with to known AP and having transmitted data in WiFi network
The signal strength for monitoring other AP, when the signal strength of some AP, which is higher than roaming, monitors threshold value, foundation is associated with the AP's, and
The AP is stored in roaming optional equipment list.
2. Station has found that the signal strength of associated AP is lower than roaming switch threshold value in the bridge coil for opening WDS
When, data link can be switched to and be roamed on the optimal AP of the signal in optional equipment list, realize fast roaming.
3. acting on behalf of the method for sending two layer message by Station, end switch after realization AP after the completion of switching
MAC Address port mapping table quickly updates.
4. Station will not stop connecting the communication of AP with original immediately, but continue to from original after the completion of switching
The data message of AP avoids the packet loss due to caused by switching AP.
5. the station for acting on the fluctuation for mainly preventing signal strength and occurring and the AP frequency of counter 1 and counter 2
It is numerous be associated reconciliation it is operation associated, that is, prevent ping-pong.After counter reaches certain number, then take subsequent behaviour
Make, it is ensured that the signal strength of AP be within a certain period of time it is metastable, just determination is associated with or Xie Guan station with AP
Connection.
In addition, the present invention also has, existing net improvement cost is low, adapts to many advantages, such as scene is wide.Can be applied to it is various
The wireless data of high bandwidth, latency sensitive, high reliability in high-speed motion returns.Such as: driving school's examination, subway, bus, coal
Mine, train.
In each method of the present invention, the serial number of each step can not be used to limit the sequencing of each step, for
For those of ordinary skill in the art, without creative efforts, the successive of each step is changed also in this hair
Within bright protection scope.
On the other hand, the present invention also provides the devices that terminal in a kind of wlan network switches at high speed between AP, i.e. terminal, such as
Shown in Fig. 9, comprising:
Module 11 is obtained, for obtaining the information of attachable AP;
Relating module 12 is associated with for only being authenticated and being established with attachable AP;
Switching module 13, for when the signal strength of communicating AP be less than roaming switch threshold value when, by communication link
It is switched to and has been established on an associated AP.
The device that wlan network terminal of the invention switches at high speed between AP obtains the information of attachable AP first, and
It is authenticated and is established with attachable AP and be associated with, i.e., with the preparatory action that increases switching in the communication process of AP, found
After attachable AP, it is associated in advance with AP foundation, once the signal strength as communicating AP is not sufficient to ensure that normal number
When according to communication, communication link is just switched to the chain road that associated AP has been established, to realize that the fast roaming of link layer is cut
It changes.In the present invention, the information for obtaining attachable AP is carried out, and is authenticated and established associated movement consumption with attachable AP
When about 30-80ms, and the prior art be switching when just carry out above-mentioned movement, the present invention advances to above-mentioned movement before switching
It completes, handoff delay can be controlled within 10ms, can satisfy the requirement of major applications scene.With prior art phase
Than the present invention has the advantages that at low cost, switch speed is fast.
As an improvement of the present invention, relating module 12 is further used for:
When the signal strength of attachable AP, which is greater than roaming, monitors threshold value, is authenticated and established with the AP and be associated with.
In the present invention, although Station establishes incidence relation with the AP equipment in roaming optional equipment list, at this time
Forwarding of the Station and AP without data message, i.e., only maintain connection management, sends without data.
As a further improvement of the present invention, further includes:
De-association module, for monitoring threshold value and more than certain time when the signal strength that associated AP has been established is less than roaming
When number, releasing is associated with the AP's.
In the present invention, when the signal strength that associated AP has been established, which is less than roaming, to be monitored threshold value and be more than certain number,
Then think that the signal strength of the AP is excessively weak, do not have alternative switching condition, Station actively initiates de-association process, interrupt with
The association of AP.
As further improvement of the invention, switching module 13 is further used for:
When the signal strength of communicating AP is less than roaming switch threshold value and is more than certain number, communication link is cut
It changes to and has been established on an associated AP.
In the present invention, when the signal strength of communicating AP is less than roaming switch threshold value, then it is assumed that communicating
The signal strength of AP is too low, needs to carry out the switching between AP, to guarantee normal data communication.In the present invention, Station can be with
Communication link is switched to any one is higher than the signal strength of current communicating AP and have been established on an associated AP,
Preferably, communication link can be switched on the highest AP of signal strength by Station.
In the present invention, switching module 13 is also connected with receiving module, and receiving module is used for:
Data still are received from the AP of original connection whithin a period of time, but do not send data to former connection AP.
In the present invention, after Station completes roaming switch, the communication that AP is connect with original will not be stopped immediately, at this point,
Station can receive the data from former connection AP, but not send data to former connection AP.By one section setting when
Between after, Station stops receiving the data message from former connection AP.By the mechanism, can prevent in after roaming switch,
There may be the messages of undelivered to Station into the link of former connection AP for interchanger, to avoid causing due to switching AP
Packet loss.
In the present invention, switching module 13 is also connected with trigger module, and trigger module is used for:
It triggers the interchanger connecting with the AP of present communications and carries out port address list update.
In the present invention, in station after an AP roaming switch to another AP, if be attached thereto by wired
Client (user) no data when externally sending, the MAC Address of the client remains recorded in the interchanger of former AP connection
In the address table of port, when there is data to be sent to client by the interchanger, data still can be passed through original AP by interchanger
The port of the interchanger of connection is externally sent, so, after station no longer monitors the data packet of original AP, it is sent to client
Data can lose.For this reason, it may be necessary to actively initiate the port address list update that can trigger interchanger by station
Process, to guarantee that subsequent data packet correctly can be sent to client by interchanger.
In another aspect, the present invention also provides the system that terminal in a kind of wlan network switches at high speed between AP, i.e. WLAN
Communication system, including AP and above-mentioned terminal.
The system that wlan network terminal of the invention switches at high speed between AP obtains the information of attachable AP first, and
It is authenticated and is established with attachable AP and be associated with, i.e., with the preparatory action that increases switching in the communication process of AP, found
After attachable AP, it is associated in advance with AP foundation, once the signal strength as communicating AP is not sufficient to ensure that normal number
When according to communication, communication link is just switched to the chain road that associated AP has been established, to realize that the fast roaming of link layer is cut
It changes.In the present invention, the information for obtaining attachable AP is carried out, and is authenticated and established associated movement consumption with attachable AP
When about 30-80ms, and the prior art be switching when just carry out above-mentioned movement, the present invention advances to above-mentioned movement before switching
It completes, handoff delay can be controlled within 10ms, can satisfy the requirement of major applications scene.With prior art phase
Than the present invention has the advantages that at low cost, switch speed is fast.
The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art
For, without departing from the principles of the present invention, it can also make several improvements and retouch, these improvements and modifications
It should be regarded as protection scope of the present invention.