CN101521924B - Switching method and device of wireless local area network - Google Patents
Switching method and device of wireless local area network Download PDFInfo
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- CN101521924B CN101521924B CN2009101357320A CN200910135732A CN101521924B CN 101521924 B CN101521924 B CN 101521924B CN 2009101357320 A CN2009101357320 A CN 2009101357320A CN 200910135732 A CN200910135732 A CN 200910135732A CN 101521924 B CN101521924 B CN 101521924B
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Abstract
The invention discloses a switching method and a switching device of a wireless local area network. The method comprises the steps as follows: when a client end device detects that the signal intensity of a current access point is lower than a predetermined scan threshold, the client end device scans adjacent AP; when the client end device detects the adjacent AP the signal intensity of which is larger than or equal to the predetermined back-up AP threshold, the adjacent AP is added to a back-up AP list; and when a predetermined switching condition is satisfied, the client end device is switched to the adjacent AP in the back-up AP list from the current AP. In the invention, when moving, a wireless terminal device can start scan in time to acquire information of the adjacent AP according to parameters indicated by a network side AP, adjusts switching algorithm according to the parameters indicated by the network side AP to select the adjacent AP to carry out switching, and then is switched to a proper AP in real time when fast moving in a WLAN overlay area and obtains satisfied access service and communication effects.
Description
Technical field
The present invention relates to communication technical field, changing method and equipment in particularly a kind of WLAN (wireless local area network).
Background technology
WLAN (Wireless Local Area Network, WLAN (wireless local area network)) provides the wireless connections service of local area network (LAN), because wireless data access at a high speed can be provided, is one of popular at present technology.WLAN has been widely used in city, public place and has covered, and various places such as enterprise, building, family.
In the city covered, WLAN existed with the Mesh network mode more, and a kind of public access network is provided.The use of this public access network can be divided into static and the motion dual mode in form, and motion mode is exactly can realize wireless access in the vehicle that travels.The use of motion mode has brought very big challenge for wireless switching.In existing wlan standard, the switching of wireless client device (as wireless network card) between different AP (Access Point, access point) is by client device decision itself, and standard is without any regulation.At present, the handoff algorithms that each wireless client device producer realizes is not quite similar, but all is to search new AP again after being weaker than certain threshold value by the signal strength signal intensity of judging current connection AP basically.Find that in actual applications this handoff algorithms of wireless client device in any case dispose the AP network, all causes handoff procedure slow, has reduced the network result of use under the motion mode, especially about the application of real-time video aspect.
Application scenarios with WLAN shown in Figure 1 is an example.Suppose that a car-mounted terminal is along the fast moving of direction shown in the black line.Because the consideration of environment or other factors, in the covering to this road, AP1 has used directional antenna, and AP2 has used omnidirectional antenna.The coverage of AP1 and AP2 has been described among Fig. 1, expression be in this scope terminal equipment can and AP between communicate, satisfy the lowest signal intensity requirement of client device.Among Fig. 1:
The AP2 signal strength signal intensity minimum threshold point that client device can be communicated by letter with AP2 in the A point expression AP1 overlay area;
The AP1 signal strength signal intensity minimum threshold point that client device can be communicated by letter with AP1 in the B point expression AP2 overlay area.
When terminal equipment moves to the A point, because signal strength signal intensity is not lower than minimum threshold, so terminal equipment can not switch.In theory, terminal equipment can switch to AP2 smoothly at the B point.But in fact, terminal equipment needs a process to the signal strength detection of AP.Promptly when terminal equipment moved to the B point, because movement effects, terminal equipment can not detect AP1 at once and reach minimum threshold in this locational signal strength signal intensity.Possible situation is, when terminal equipment moves to the C point, could confirm that not in the service range of AP1, this moment, terminal equipment can scan several channels, until finding AP2 and switching to AP2.Terminal equipment finally switches to AP2 and also needs to spend a period of time from beginning to scan, and this moment terminal equipment the position farther than the C point.
Actual measured results shows that along with the difference of movement velocity, the drift distance between actual switching point and the B point also can be different.In addition, if the coverage of each AP is not very long, and that the client device movement velocity compares is higher, and client device can switch on the different AP, but the situation of switch-on and-off can appear in Radio Link, and wherein the time that can communicate by letter is very short.
Can find that based on above-mentioned analysis problems of the prior art are: wireless terminal device can't switch on the proper A P during fast moving in the WLAN coverage territory in real time, causes obtaining satisfied access service and communication efficiency.
Summary of the invention
The invention provides changing method and equipment in a kind of WLAN (wireless local area network), be used to make wireless terminal device in the WLAN coverage territory, can switch to proper A P in real time during fast moving.
For achieving the above object, the invention provides the changing method in a kind of WLAN (wireless local area network), comprising:
Client device receives the frame that current AP sends, and obtains the mobile service parameter collection of described current AP, and selects mobile service parameter to concentrate the corresponding mobile service parameter according to the rate travel of oneself;
When the signal strength signal intensity that described client device detects current access point AP is lower than scanning threshold value in the described mobile service parameter, carry out the scanning of neighbor AP;
When described client device detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, described neighbor AP is added backup AP tabulation;
When default switching condition satisfied, described client device was selected a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection.
Wherein, also comprise in the frame that described current AP sends: neighbor AP channel information, backup AP threshold value, each moves service parameter and comprises scanning threshold value, sweep spacing and switching threshold.
Wherein, when the signal strength signal intensity that described client device detects current access point AP was lower than scanning threshold value in the described mobile service parameter, the scanning of carrying out neighbor AP comprised:
When the signal strength signal intensity that described client device detects current access point AP is lower than scanning threshold value in the described mobile service parameter, carries out the scanning of neighbor AP according to described neighbor AP channel information, and in described sweep spacing, finish the scanning of neighbor AP.
Wherein, the mobile service parameter of described current AP is a plurality of, described each to move service parameter corresponding with a rate travel.
Wherein, client device receives the frame that current AP sends, and obtains the mobile service parameter collection of described current AP, and selects the corresponding mobile service parameter to comprise according to the rate travel of oneself:
Under the known situation of self rate travel, described client device is chosen the minimum rate travel greater than self rate travel of rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP;
Under self rate travel condition of unknown, described client device is chosen the minimum rate travel of each rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP.
Wherein, also comprise:
Under self rate travel condition of unknown, the backup AP tabulation after some cycles of scanning under the current sweep spacing of described client device still be a sky, and then described client device reduces the scanning that neighbor AP is carried out in sweep spacing again;
Under the unknown or known situation of self rate travel, if the signal strength signal intensity of current AP has been lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and described client means scans backs up the AP tabulation after some cycles still be empty, then described client device is ignored current mobile service parameter, carries out the scanning of neighbor AP again according to the scan mechanism in other handoff algorithms.
Wherein, also carry Same Vendor indication in the frame that described current AP sends, when described Same Vendor indication set, when described client device detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, further comprise:
Whether the BSSID that judges the basic service set identification BSSID of described neighbor AP and described current AP has the identical unique identification OUI that organizes, and described judged result adds backup AP tabulation with described neighbor AP when being.
Wherein, described when default switching condition satisfies, client device is selected a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection, comprising:
When the difference in the described backup AP tabulation between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP met or exceeded described switching threshold, described client device selected a neighbor AP also to switch on the described neighbor AP; Or
When the signal strength signal intensity of described current AP was lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device or satisfies switching condition in other handoff algorithms that are provided with in the described client device, described client device selected a neighbor AP also to switch on the described neighbor AP.
Wherein, described client device also comprises switch on the neighbor AP of selection from current AP after:
Described client device receives the described frame that back AP sends that switches, and obtains the neighbor AP channel information, backup AP threshold value and the described mobile service parameter that switches back AP that carry in the described frame; The mobile service parameter of AP before the neighbor AP channel information of storage, backup AP threshold value and the switching before covering.
The present invention also provides a kind of client device, comprising:
The frame receiving element is used to receive the frame that current AP sends, and obtains the mobile service parameter collection of described current AP;
Whether detecting unit, the signal strength signal intensity that is used for detecting current AP are lower than the scanning threshold value of the mobile service parameter that scanning element selects;
Scanning element, be used for selecting mobile service parameter to concentrate the corresponding mobile service parameter according to the rate travel of described client device, when the signal strength signal intensity that detects current AP when described detecting unit is lower than scanning threshold value in the described mobile service parameter, carry out the scanning of neighbor AP;
The tabulation maintenance unit is used for described neighbor AP being added backup AP tabulating when described scanning element detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value;
Switch unit is used for when default switching condition satisfies, and selects a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection.
Wherein, also comprise in the frame that described current AP sends: neighbor AP channel information, backup AP threshold value, each moves service parameter and comprises scanning threshold value, sweep spacing and switching threshold.
Wherein, described scanning element comprises the first scanning subelement, when the signal strength signal intensity that is used for detecting current access point AP is lower than the scanning threshold value of described mobile service parameter, carries out the scanning of neighbor AP according to described neighbor AP channel information, and in described sweep spacing, finish the scanning of neighbor AP.
Described scanning element comprises:
The second scanning subelement, be used under the known situation of self rate travel, choose the minimum rate travel of rate travel in each described mobile service parameter greater than self rate travel, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the described mobile service parameter, carry out the scanning of neighbor AP according to described neighbor AP channel information, in described sweep spacing, finish the scanning of neighbor AP;
The 3rd scanning subelement, be used under self rate travel condition of unknown, choose the minimum rate travel of each rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the described mobile service parameter, carry out the scanning of neighbor AP according to described neighbor AP channel information, in described sweep spacing, finish the scanning of neighbor AP.
Wherein, the described second scanning subelement, also be used under the known situation of self rate travel, if the signal strength signal intensity of current AP is lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again;
Described the 3rd scanning subelement also is used under self rate travel condition of unknown, and backup AP tabulation still is empty after some cycles of scanning under the current sweep spacing, then reduces the scanning that neighbor AP is carried out in sweep spacing again; Afterwards if the signal strength signal intensity of current AP has been lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again.
Wherein, when also carrying Same Vendor indication and described Same Vendor indication set in the frame that the current AP that described frame receiving element receives sends, described tabulation maintenance unit also is used for:
When described scanning element detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, whether the BSSID that further judges the basic service set identification BSSID of described neighbor AP and described current AP has the identical unique identification OUI that organizes, and described judged result adds described neighbor AP when being and backs up AP and tabulate.
Wherein, described switch unit comprises:
First switches subelement, is used for tabulating difference between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP when meeting or exceeding described switching threshold as described backup AP, selects a neighbor AP and switches on the described neighbor AP; Or
Second switches subelement, when being used for signal strength signal intensity as described current AP and being lower than the minimum signal strength threshold value in other handoff algorithms that described client device is provided with or satisfying switching condition in other handoff algorithms that are provided with in the described client device, select a neighbor AP and switch on the described neighbor AP.
Wherein, described frame receiving element, also be used for receiving the described frame that back AP sends that switches after on the neighbor AP that switches to described backup AP tabulation from current AP, obtain the mobile service parameter of AP behind neighbor AP channel information, backup AP threshold value and described switching of carrying in the described frame; The mobile service parameter of AP before the neighbor AP channel information of storage, backup AP threshold value and the switching before covering.
Compared with prior art, the present invention has the following advantages:
Wireless terminal device is under situation about moving, can in time start scanning to obtain neighbor AP information according to the parameter of network side AP indication, and select neighbor AP to switch according to the parameter adjustment handoff algorithms of network side AP indication, thereby in the WLAN coverage territory, switch in real time on the proper A P during fast moving, obtain satisfied access service and communication efficiency.
Description of drawings
In order to be illustrated more clearly in the technical scheme of the embodiment of the invention, the accompanying drawing of required use is done to introduce simply in will describing embodiment below, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.
Fig. 1 is the application scenarios schematic diagram of WLAN in the prior art;
Fig. 2 is the changing method flow chart in the WLAN (wireless local area network) among the present invention;
Fig. 3 is the changing method flow chart in the WLAN (wireless local area network) in the application scenarios provided by the invention;
Fig. 4 is the structural representation of the client device that provides among the present invention;
Fig. 5 is another structural representation of the client device that provides among the present invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is a part of embodiment of the present invention, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.
The invention provides the changing method in a kind of WLAN (wireless local area network), as shown in Figure 2, comprising:
When the signal strength signal intensity that step s201, client device detect current access point AP is lower than default scanning threshold value, carry out the scanning of neighbor AP.
When step s202, client device detect signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, neighbor AP is added backup AP tabulation.
Step s203, when default switching condition satisfies, client device is on current AP switches to a neighbor AP the backup AP tabulation.
The embodiment of changing method in the WLAN (wireless local area network) that provides among the present invention is described below in conjunction with concrete application scenarios.
For AP involved in the present invention, need in the Beacon frame, carry the channel information of neighbor AP, the mode of carrying can be followed the agreement among prior art such as the 802.11k.But the Beacon frame (or other frames) that requires these neighbor AP and current AP to be sent has identical SSID (Service Set Identifier, service set), client device can carry out the scanning of neighbor AP fast according to the channel information of this neighbor AP.
In addition, AP among the present invention passes through IE (the Information Element of Vendor Specific (manufacturer's customization) type in Beacon frame (or other frames), information element) carries the MSP (Moving Service Parameter, mobile service parameter) that backs up AP threshold value and AP self.Should be with in the scene, the format sample of the IE of Vendor Specific type is as shown in table 1 below:
The format sample of the IE of table 1.Vendor Specific type
| Element?ID | Length | OUI | Type | Version | Flag | Backup?Threshold | MSP 1 | … | MSPn |
Element ID and Length (cell ID and length): meet in the prior art implication and form about IE.
OUI (Organization Unique Indication organizes unique identification): the i.e. manufacturer of AP; OUI generally is preceding 24 of MAC Address of an equipment, and it has identified the manufacturer of equipment.
Type: the types value that distributes for the handoff algorithms of supporting to provide among the present invention under this OUI.
Version: the version of this algorithm.
Flag: flag bit.The definition the highest-order bit is " Same Vendor (a same manufacturer) " among the present invention, if this position is 1, when expression requires client device to switch to different AP, the BSSID (Basic Service Set Identifier, basic service set identification) that must detect this AP has identical OUI with the BSSID of original AP.
Backup Threshold: backup AP threshold value.When the signal strength signal intensity that detects certain neighbor AP of current AP when client device is worth greater than this, this neighbor AP is joined in the backup AP tabulation.
MSP (Moving Service Parameter, mobile service parameter): ScanThreshold (scanning threshold value), the Scan Interval (sweep spacing) and the Switch Threshold (switching threshold) that comprise current AP.For each AP, the MSP of an acquiescence can be set, the form of the MSP of acquiescence can for＜scanning threshold value, sweep spacing, switching threshold.This moment, the format sample of MSP can be as shown in table 2 below:
The format sample of table 2.MSP
| Scan?Threshold | Scan?Interval | Switch?Threshold |
Wherein:
Scan Threshold: scanning threshold value.When the signal strength signal intensity that detects current AP when client device is lower than this scanning threshold value, the sweep spacing scanning neighbor AP that beginning is set according to Scan Interval.
Scan Interval: sweep spacing.Client device should be finished in a sweep spacing having the scanning of all channels of identical SSID with current AP.
Switch Threshold: switching threshold.If the difference in signal strength in the backup AP tabulation between a neighbor AP and the current AP is during more than or equal to switching threshold, client device should switch on this neighbor AP in the backup AP tabulation.If value is 0, expression is switched the difference no requirement (NR) to the signal between two AP, in case backup AP is arranged, should switch to immediately on the backup AP.
AP can also adopt the mode of carrying a plurality of MSP except can carry an acquiescence MSP in the frame that sends.Each MSP among a plurality of MSP is corresponding with a rate travel respectively.At this moment, each MSP is the four-tuple of being made up of Rate, Scan Threshold, Scan Interval, Switch Threshold field.The form of MSP can be＜rate travel, scanning threshold value, sweep spacing, switching threshold 〉.This moment, the format sample of MSP can be as shown in table 3 below:
The format sample of table 3.MSP
| Rate | Scan?Threshold | Scan?Interval | Switch?Threshold |
Wherein:
Rate: rate travel.Show when being lower than this rate travel that client device can switch with reference to parameter S can Threshold, Scan Interval and the Switch Threshold of back.
Scan Threshold: scanning threshold value.When the signal strength signal intensity that detects current AP when client device is lower than this scanning threshold value, the sweep spacing scanning neighbor AP that beginning is set according to Scan Interval.
Scan Interval: sweep spacing.Client device should be finished in a sweep spacing having the scanning of all channels of identical SSID with current AP.
Switch Threshold: switching threshold.If the difference in signal strength in the backup AP tabulation between a neighbor AP and the current AP is during more than or equal to switching threshold, client device should switch on this neighbor AP in the backup AP tabulation.If value is 0, expression is switched the difference no requirement (NR) to the signal between two AP, in case backup AP is arranged, should switch to immediately on the backup AP.
When carrying a plurality of MSP, AP can carry the quaternary group information of a plurality of MSP according to application demand, and different quaternary group informations can be arranged according to the value ascending order of rate travel Rate, can certainly adopt other modes to arrange.AP obtains these methods that move service parameter information and can comprise by human configuration etc., does not limit in the present invention.
In the application scenarios of the present invention, suppose that the backup AP threshold value of having carried the neighbor AP channel information in the frame that AP sends, having carried is-68dBm, and carried four mobile service parameters that are used for different rate travels in the frame, supposed that these four mobile service parameter MSP are specific as follows:
The MSP of current AP
1:＜20km/h ,-70dBm, 20ms, 5dBm 〉
1
The MSP of current AP
2:＜40km/h ,-68dBm, 20ms, 4dBm 〉
2
The MSP of current AP
3:＜60km/h ,-67dBm, 10ms, 3dBm 〉
3
The MSP of current AP
4:＜80km/h ,-65dBm, 10ms, 2dBm 〉
4
Mobile service parameter MSP with AP1
1Be example, its implication is: the highest suitable rate travel is 20km/h, when promptly the rate travel of wireless client is smaller or equal to 20km/h, can use the mobile service parameter MSP of this AP1
1The scanning threshold value is-70dBm when promptly the signal strength signal intensity of current AP is less than-70dBm, to begin to carry out the scanning of neighbor AP; Sweep spacing is 20ms, promptly need finish the scanning of neighbor AP in 20ms according to the neighbor AP channel information; In this scanning process, if scan signal strength signal intensity greater than backup AP threshold value promptly-neighbor AP of 68dBm, this neighbor AP is added backup AP tabulation; Switching threshold is 5dBm, and promptly when the difference in signal strength between one or more neighbor AP and the current AP during more than or equal to 5dBm, client device should switch on the neighbor AP.
For client device STA, client device is after connecting certain SSID, and whether the Beacon frame (or other frames) that should detect the AP transmission has carried mobile service parameter.If have, can inquire the user or learn whether need to support the changing method that provides among the present invention by other modes (as detecting the number that switches AP in the certain hour).If do not support, then keep other changing methods that dispose on the client device; Otherwise the fast moving changing method that provides among use the present invention is handled, and below this is described in detail.This method may further comprise the steps as shown in Figure 3:
Step s301, client device resolve the mobile service parameter of the AP that carries in the frame that AP sends, obtain each and move " rate travel " in the service parameter, and select one to move the scanning that service parameter is used for neighbor AP according to the rate travel of self.Concrete:
Client device is chosen each and is moved the minimum rate travel greater than self rate travel of rate travel in the service parameter under the known situation of self rate travel, the mobile service parameter of this minimum rate travel correspondence is used for the scanning of neighbor AP.Client device is chosen each and is moved the minimum rate travel in each rate travel in the service parameter under self rate travel condition of unknown, the mobile service parameter of this minimum rate travel correspondence is used for the scanning of neighbor AP.
With known its rate travel of client device is that 35km/h is an example, and then according to four mobile service parameter MSP of above-mentioned current AP, it is 40km/h that client device should be selected the minimum rate travel greater than self rate travel (35km/h); The MSP that it is corresponding
2:＜40km/h ,-68dBm, 20ms, 4dBm 〉
2Be used for the scanning of neighbor AP.Do not know that with client device the rate travel of self is an example again,, choose each and move that the minimum rate travel in each rate travel is 20km/h in the service parameter, the MSP that it is corresponding then according to the mobile service parameter MSP of above-mentioned four current AP
1:＜20km/h ,-70dBm, 20ms, 5dBm 〉
1Be used for the scanning of neighbor AP.
The situation that is 35km/h with known its rate travel of client device in the following steps is that example describes, and promptly client device uses MSP
2:＜40km/h ,-68dBm, 20ms, 4dBm 〉
2Be used for the scanning of neighbor AP.For other situations similarly, do not repeat to introduce at this.
The signal strength signal intensity that step s302, client device detect current AP is lower than when scanning threshold value, carries out the scanning of neighbor AP.Concrete:
Client device uses MSP
2:＜40km/h ,-68dBm, 20ms, 4dBm 〉
2When being used for the scanning of neighbor AP, the signal strength signal intensity that detects current AP when client device is during less than-68Bm, and the neighbor AP channel information that carries in the frame that beginning sends according to AP carries out the scanning of neighbor AP.
When step s303, client device detect signal strength signal intensity more than or equal to the neighbor AP of backup AP threshold value, neighbor AP is added backup AP tabulation.Concrete:
Owing to should be-68dBm, when then client device detects signal strength signal intensity more than or equal to the neighbor AP of-68dBm, this neighbor AP is joined backup AP tabulation, and this scanning is at above-mentioned MSP with the backup AP threshold value of carrying in the frame that hypothesis AP sends in the scene
2Finish in the sweep spacing 20ms of middle regulation.
In addition, if " the Same Vendor " of Flag field is 1 in the frame that AP sends, then only when the BSSID of the BSSID of this neighbor AP and current AP has identical OUI, client device just joins neighbor AP in the backup AP tabulation, by this parameter, can guarantee that client device can both be positioned on the AP of same producer before and after switching, because the AP of same producer can both support the mobile handoff algorithms among the present invention, make the mobile handoff algorithms of client device in all the time can be implement AP and switch according to the present invention.And as " the Same Vendor " of Flag field when being 0, when no matter whether the BSSID of the BSSID of neighbor AP and current AP had identical OUI, client device all joined neighbor AP in the backup AP tabulation.After the step that switches to the neighbor AP the backup AP tabulation from current AP in, the neighbor AP that can preferentially select to have identical OUI with the BSSID of current AP is switched, and also can not consider whether have this factor of identical OUI with the BSSID of current AP when selecting neighbor AP to switch.
Need to prove, may have the situation of scanning in this step less than qualified neighbor AP.For this situation, processing method can for:
(1) client device is under the known situation of self rate travel, if the signal strength signal intensity of current AP be lower than minimum signal threshold in other handoff algorithms that dispose on the client device (as-70dBm), and back up the AP tabulation at the some all after dates of client means scans still for empty, then client device should be ignored current mobile service parameter, scans again and switches according to the scan mechanism in other handoff algorithms that dispose on the client device.For using scene, promptly ignore current mobile service parameter MSP
2, the scan mechanism in other handoff algorithms that dispose on the use client device scans again and switches.
(2) client device is under self rate travel condition of unknown, can suitably reduce the scan period according to backup AP tabulation situation, if under current sweep interval, scanned several all after dates, if also do not find any backup AP, then can suitably reduce sweep interval.For using scene, promptly sweep interval can be reduced to 15ms or 10ms, carry out the step of the described scanning neighbor AP of step s302 once more.If afterwards the signal strength signal intensity of current AP be lower than minimum signal threshold in the former algorithm of client device (as-70dBm), and back up the AP tabulation at the some all after dates of client means scans still for empty, then client device should be ignored current mobile service parameter, scans again and switches according to the scan mechanism in other handoff algorithms of configuration.For using scene, promptly ignore current mobile service parameter MSP
2, the scan mechanism in other handoff algorithms that dispose on the use client device scans again and switches.
Step s304, client device switch on the neighbor AP that backs up the AP tabulation from current AP.Concrete, should be with in the scene, when satisfying one of following condition, client device should switch on the neighbor AP that backs up the AP tabulation from current AP:
When (1) difference between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP met or exceeded switching threshold in the backup AP tabulation, client device switched on one of them neighbor AP according to the selection algorithm of oneself.For should be for scene, when the difference between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP met or exceeded 4dBm, client device need switch on one of them neighbor AP from current AP.When qualified neighbor AP has when a plurality of, client device can be selected one of them neighbor AP according to the selection algorithm of self, for example select, should not limit at this with scene according to standards such as detected sequencing, instantaneous signal strength size, signal strength signal intensity mean value sizes.As above a step is described in addition, when selecting neighbor AP, whether the BSSID of neighbor AP can also be had this factor of identical OUI as choice criteria with the BSSID of current AP, and preferential the selection has the neighbor AP of identical OUI with the BSSID of current AP.
(2) signal strength signal intensity of current AP is lower than the minimum signal threshold in other handoff algorithms of client device configuration, when perhaps satisfying other switching conditions in the former algorithm of client device, then client device switches on the neighbor AP that backs up in the AP tabulation according to the selection algorithm of oneself.For should be for scene, though the difference between the signal strength signal intensity of each neighbor AP and the signal strength signal intensity of current AP is all less than 4dBm, if but according to other handoff algorithms of client device configuration, client device need the signal strength signal intensity of current AP less than minimum signal threshold (as-switch 70dBm) time, then client device still will switch to according to other handoff algorithms of configuration on the neighbor AP in the backup AP tabulation.When the neighbor AP in the backup AP tabulation has when a plurality of, client device can be selected one of them neighbor AP according to the handoff algorithms of self, for example select, should not limit at this with scene according to standards such as detected sequencing, instantaneous signal strength size, signal strength signal intensity mean value sizes.As above a step is described in addition, when selecting neighbor AP, whether the BSSID of neighbor AP can also be had this factor of identical OUI as choice criteria with the BSSID of current AP, and preferential the selection has the neighbor AP of identical OUI with the BSSID of current AP.
When the AP that step s305, client device connect changes, by neighbor AP channel information, backup AP threshold value and the mobile service parameter of Beacon frame or other frames reception switching back AP transmission, and the parameter of use switching back AP transmission covers from switching the parameter of preceding AP reception.
Above application scenarios has been described AP and carried neighbor AP channel information, backup AP threshold value (the specific embodiment of the present invention 68dBm), and when having carried four MSP that are used for different rate travels in the frame in the frame that sends.Be understandable that when AP only carried an acquiescence MSP in the frame that sends, its embodiment was with above-mentioned similar when carrying a plurality of MSP that is used for different rate travels.Below AP is only carried an acquiescence MSP in the frame that sends situation be introduced:
Suppose that the backup AP threshold value of having carried the neighbor AP channel information in the frame that AP sends, having carried is-68dBm, and the acquiescence MSP that carries in the frame for＜-70dBm, 20ms, 5dBm.That is: the scanning threshold value is-70dBm, when promptly the signal strength signal intensity of current AP is less than-70dBm, begins to carry out the scanning of neighbor AP; Sweep spacing is 20ms, promptly need finish the scanning of neighbor AP in 20ms according to the neighbor AP channel information; In this scanning process, if scan signal strength signal intensity greater than backup AP threshold value promptly-neighbor AP of 68dBm, this neighbor AP is added backup AP tabulation; Switching threshold is 5dBm, and promptly when the difference in signal strength between one or more neighbor AP and the current AP during more than or equal to 5dBm, client device should switch on the neighbor AP.
Client device is resolved the acquiescence MSP that carries in the frame that AP sends, and no matter whether the rate travel of self is known, all uses this acquiescence MSP to be used for the scanning of neighbor AP.For the scanning step of this neighbor AP, neighbor AP is added the step of backup AP tabulation and the step of selecting a neighbor AP to switch from backup AP tabulation according to scanning result, similar to the description among step s302～step s305 in the above-mentioned flow process, be not repeated in this description at this.
Below again in conjunction with the method to set up of mobile service parameter among the scene description the present invention among above-mentioned Fig. 1.For the application scenarios shown in Fig. 1, the scanning threshold value should be a reference point with the point of the A among Fig. 1, sets according to the signal strength signal intensity of the AP1 at A point place.During actual set, the delay situation that needs consideration target rate travel that signal strength detection is brought can suitably improve the scanning threshold value.For switching point, if the target application of the service of moving is not had bandwidth requirement, switching point so at the latest should be the B point; If the target application of the service of moving is had certain bandwidth requirement, and (promptly there is requirement in the signal strength signal intensity of the AP that client device is inserted, high more to bandwidth requirement, then require the signal strength signal intensity of the AP that client inserts big more), should between A point and B point, select suitable switching point so, can regard the B point as and move to left.Switching threshold should be set according to the signal strength difference that B point (being switching point) located between AP2 and the AP1, and switching interval should be set according to the distance between rate travel, A point and the B point.
In the said method provided by the invention, wireless terminal device is under situation about moving, can in time start scanning to obtain neighbor AP information according to the parameter of network side AP indication, and select neighbor AP to switch according to the parameter adjustment handoff algorithms of network side AP indication, thereby in the WLAN coverage territory, switch in real time on the proper A P during fast moving, obtain satisfied access service and communication efficiency.In addition, wireless network designer can be according to the target bandwidth requirement of network design situation, translational speed, application service etc., allows AP issue corresponding mobile service parameter, thereby the moving target that satisfies wireless terminal device is used.And handoff algorithms provided by the invention can with other handoff algorithms compatibilities and the existing wlan standard compatibility that dispose on the wireless terminal device, this handoff algorithms does not need existing network is done upgrading on the hardware, only just can realize by software upgrading.
The present invention also provides a kind of client device, is used for implementing the changing method in the WLAN (wireless local area network) that the present invention provides, as shown in Figure 4, comprising:
Detecting unit 10, whether the signal strength signal intensity that is used to detect current AP is lower than default scanning threshold value.
Scanning element 20 is used for carrying out the scanning of neighbor AP when signal strength signal intensity that detecting unit 10 detects current AP is lower than default scanning threshold value.
In addition, as shown in Figure 5, in the client device provided by the invention, can also comprise:
Frame receiving element 50 is used to receive the frame that current AP sends, and obtains the mobile service parameter of the neighbor AP channel information, backup AP threshold value and the current AP that carry in the frame, and mobile service parameter comprises scanning threshold value, sweep spacing and switching threshold; Wherein:
The scanning threshold value is used to represent that client device carries out the scanning threshold value of neighbor AP, and when the signal strength signal intensity of current access point AP was lower than the scanning threshold value, client device carried out the scanning of neighbor AP;
Sweep spacing is used to represent that client device finishes the time interval of neighbor AP scanning;
Switching threshold, the difference of signal strength signal intensity that is used to represent the signal strength signal intensity of neighbor AP and current AP are during more than or equal to switching threshold, and client device just switches to neighbor AP.
In addition, when also carrying Same Vendor indication and Same Vendor indication set in the frame of the current AP transmission that frame receiving element 50 receives, tabulation maintenance unit 30 also is used for: when scanning element 20 detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, whether the BSSID that further judges the basic service set identification BSSID of neighbor AP and current AP has the identical unique identification OUI that organizes, and judged result adds neighbor AP when being and backs up AP and tabulate.
In addition, frame receiving element 50 also is used for receiving the frame that switches back AP transmission when switch on the neighbor AP that backs up the AP tabulation from current AP after, obtains neighbor AP channel information, backup AP threshold value of carrying in the frame and the mobile service parameter that switches back AP; The mobile service parameter of AP before the neighbor AP channel information of storage, backup AP threshold value and the switching before covering.
In addition, the scanning element 20 in this client device may further include:
The first scanning subelement 21 when the signal strength signal intensity that is used to detect current access point AP is lower than default scanning threshold value, carries out the scanning of neighbor AP according to described neighbor AP channel information, and finish the scanning of neighbor AP in described sweep spacing.
The mobile service parameter of the current AP that obtains from the frame that receives when frame receiving element 50 is a plurality of, and each moves service parameter and a rate travel at once, and scanning element 20 may further include:
The second scanning subelement 22, be used under the known situation of self rate travel, choose each and move the minimum rate travel of rate travel in the service parameter greater than self rate travel, the mobile service parameter of minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the mobile service parameter, carry out the scanning of neighbor AP according to the neighbor AP channel information, in sweep spacing, finish the scanning of neighbor AP;
The 3rd scanning subelement 23, be used under self rate travel condition of unknown, choose the minimum rate travel that each moves each rate travel in the service parameter, the mobile service parameter of minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the mobile service parameter, carry out the scanning of neighbor AP according to the neighbor AP channel information, in sweep spacing, finish the scanning of neighbor AP.
In addition, the second scanning subelement 22, also be used under the known situation of self rate travel, if the signal strength signal intensity of current AP is lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again;
In addition, the 3rd scanning subelement 23 also is used under self rate travel condition of unknown, and backup AP tabulation still is empty after some cycles of scanning under the current sweep spacing, then reduces the scanning that neighbor AP is carried out in sweep spacing again; Afterwards if the signal strength signal intensity of current AP has been lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again.
In addition, the switch unit 40 in this client device may further include:
First switches subelement 41, is used for when the difference between the signal strength signal intensity of signal strength signal intensity that backs up the one or more neighbor AP of AP tabulation and current AP meets or exceeds switching threshold, and client device selects a neighbor AP also to switch on the neighbor AP; Or
Second switches subelement 42, when being used for signal strength signal intensity as current AP and being lower than the minimum signal strength threshold value in other handoff algorithms that client device is provided with or satisfying switching condition in other handoff algorithms that are provided with in the client device, select a neighbor AP and switch on the neighbor AP.
In the said equipment provided by the invention, wireless terminal device is under situation about moving, can in time start scanning to obtain neighbor AP information according to the parameter of network side AP indication, and select neighbor AP to switch according to the parameter adjustment handoff algorithms of network side AP indication, thereby in the WLAN coverage territory, switch in real time on the proper A P during fast moving, obtain satisfied access service and communication efficiency.In addition, wireless network designer can be according to the target bandwidth requirement of network design situation, translational speed, application service etc., allows AP issue corresponding mobile service parameter, thereby the moving target that satisfies wireless terminal device is used.And handoff algorithms provided by the invention can with other handoff algorithms compatibilities and the existing wlan standard compatibility of wireless terminal device configuration, this handoff algorithms does not need existing network is done upgrading on the hardware, only just can realize by software upgrading.
Above-mentioned module can be distributed in a device, also can be distributed in multiple arrangement.Above-mentioned module can be merged into a module, also can further split into a plurality of submodules.
Through the above description of the embodiments, those skilled in the art can be well understood to the present invention and can realize by hardware, also can realize by the mode that software adds necessary general hardware platform.Based on such understanding, technical scheme of the present invention can embody with the form of software product, it (can be CD-ROM that this software product can be stored in a non-volatile memory medium, USB flash disk, portable hard drive etc.) in, comprise some instructions with so that computer equipment (can be personal computer, server, the perhaps network equipment etc.) carry out the described method of each embodiment of the present invention.
It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferred embodiment, module in the accompanying drawing or flow process might not be that enforcement the present invention is necessary.
It will be appreciated by those skilled in the art that the module in the device among the embodiment can be distributed in the device of embodiment according to the embodiment description, also can carry out respective change and be arranged in the one or more devices that are different from present embodiment.The module of the foregoing description can be merged into a module, also can further split into a plurality of submodules.
The invention described above embodiment sequence number is not represented the quality of embodiment just to description.
More than disclosed only be several specific embodiment of the present invention, still, the present invention is not limited thereto, any those skilled in the art can think variation all should fall into protection scope of the present invention.
Claims (17)
1. the changing method in the WLAN (wireless local area network) is characterized in that, comprising:
Client device receives the frame that current AP sends, and obtains the mobile service parameter collection of described current AP, and selects mobile service parameter to concentrate the corresponding mobile service parameter according to the rate travel of oneself;
When the signal strength signal intensity that described client device detects current access point AP is lower than scanning threshold value in the described mobile service parameter, carry out the scanning of neighbor AP;
When described client device detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, described neighbor AP is added backup AP tabulation;
When default switching condition satisfied, described client device was selected a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection.
2. the method for claim 1 is characterized in that, also comprises in the frame that described current AP sends: neighbor AP channel information, backup AP threshold value, each moves service parameter and comprises scanning threshold value, sweep spacing and switching threshold.
3. method as claimed in claim 2 is characterized in that, when the signal strength signal intensity that described client device detects current access point AP was lower than scanning threshold value in the described mobile service parameter, the scanning of carrying out neighbor AP comprised:
When the signal strength signal intensity that described client device detects current access point AP is lower than scanning threshold value in the described mobile service parameter, carries out the scanning of neighbor AP according to described neighbor AP channel information, and in described sweep spacing, finish the scanning of neighbor AP.
4. method as claimed in claim 2 is characterized in that, the mobile service parameter of described current AP is a plurality of, described each to move service parameter corresponding with a rate travel.
5. method as claimed in claim 4 is characterized in that, described client device receives the frame that current AP sends, and obtains the mobile service parameter collection of described current AP, and selects the corresponding mobile service parameter to comprise according to the rate travel of oneself:
Under the known situation of self rate travel, described client device is chosen the minimum rate travel greater than self rate travel of rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP;
Under self rate travel condition of unknown, described client device is chosen the minimum rate travel of each rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP.
6. as claim 3 or 5 described methods, it is characterized in that, also comprise:
Under self rate travel condition of unknown, the backup AP tabulation after some cycles of scanning under the current sweep spacing of described client device still be a sky, and then described client device reduces the scanning that neighbor AP is carried out in sweep spacing again;
Under the unknown or known situation of self rate travel, if the signal strength signal intensity of current AP has been lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and described client means scans backs up the AP tabulation after some cycles still be empty, then described client device is ignored current mobile service parameter, carries out the scanning of neighbor AP again according to the scan mechanism in other handoff algorithms.
7. method as claimed in claim 2, it is characterized in that, also carry Same Vendor indication in the frame that described current AP sends, when described Same Vendor indicates set, when described client device detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, further comprise:
Whether the BSSID that judges the basic service set identification BSSID of described neighbor AP and described current AP has the identical unique identification OUI that organizes, and described judged result adds backup AP tabulation with described neighbor AP when being.
8. as each described method in the claim 2 to 5, it is characterized in that described when default switching condition satisfies, client device is selected a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection, comprising:
When the difference in the described backup AP tabulation between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP met or exceeded described switching threshold, described client device selected a neighbor AP also to switch on the described neighbor AP; Or
When the signal strength signal intensity of described current AP was lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device or satisfies switching condition in other handoff algorithms that are provided with in the described client device, described client device selected a neighbor AP also to switch on the described neighbor AP.
9. method as claimed in claim 8 is characterized in that, described client device also comprises switch on the neighbor AP of selection from current AP after:
Described client device receives the described frame that back AP sends that switches, and obtains the neighbor AP channel information, backup AP threshold value and the described mobile service parameter that switches back AP that carry in the described frame; The mobile service parameter of AP before the neighbor AP channel information of storage, backup AP threshold value and the switching before covering.
10. a client device is characterized in that, comprising:
The frame receiving element is used to receive the frame that current AP sends, and obtains the mobile service parameter collection of described current AP;
Whether detecting unit, the signal strength signal intensity that is used for detecting current AP are lower than the scanning threshold value of the mobile service parameter that scanning element selects;
Scanning element, be used for selecting mobile service parameter to concentrate the corresponding mobile service parameter according to the rate travel of described client device, when the signal strength signal intensity that detects current AP when described detecting unit is lower than scanning threshold value in the described mobile service parameter, carry out the scanning of neighbor AP;
The tabulation maintenance unit is used for described neighbor AP being added backup AP tabulating when described scanning element detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value;
Switch unit is used for when default switching condition satisfies, and selects a neighbor AP from described backup AP tabulation, and switches to from current AP on the neighbor AP of selection.
11. client device as claimed in claim 10 is characterized in that, also comprises in the frame that described current AP sends: neighbor AP channel information, backup AP threshold value, each moves service parameter and comprises scanning threshold value, sweep spacing and switching threshold.
12. client device as claimed in claim 11, it is characterized in that, described scanning element comprises the first scanning subelement, when the signal strength signal intensity that is used for detecting current access point AP is lower than the scanning threshold value of described mobile service parameter, carry out the scanning of neighbor AP according to described neighbor AP channel information, and in described sweep spacing, finish the scanning of neighbor AP.
13. client device as claimed in claim 11 is characterized in that, described scanning element comprises:
The second scanning subelement, be used under the known situation of self rate travel, choose the minimum rate travel of rate travel in each described mobile service parameter greater than self rate travel, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the described mobile service parameter, carry out the scanning of neighbor AP according to described neighbor AP channel information, in described sweep spacing, finish the scanning of neighbor AP;
The 3rd scanning subelement, be used under self rate travel condition of unknown, choose the minimum rate travel of each rate travel in each described mobile service parameter, the mobile service parameter of described minimum rate travel correspondence is used for the scanning of neighbor AP, and when the signal strength signal intensity that detects current AP is lower than the scanning threshold value that is provided with in the described mobile service parameter, carry out the scanning of neighbor AP according to described neighbor AP channel information, in described sweep spacing, finish the scanning of neighbor AP.
14. client device as claimed in claim 13 is characterized in that,
The described second scanning subelement, also be used under the known situation of self rate travel, if the signal strength signal intensity of current AP is lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again;
Described the 3rd scanning subelement also is used under self rate travel condition of unknown, and backup AP tabulation still is empty after some cycles of scanning under the current sweep spacing, then reduces the scanning that neighbor AP is carried out in sweep spacing again; Afterwards if the signal strength signal intensity of current AP has been lower than the minimum signal strength threshold value in other handoff algorithms that are provided with in the described client device, and backup AP tabulation is still for empty after scanning some cycles, then ignore current mobile service parameter, carry out the scanning of neighbor AP according to the scan mechanism in other handoff algorithms again.
15. client device as claimed in claim 11 is characterized in that, when also carrying Same Vendor indication and described Same Vendor indication set in the frame that the current AP that described frame receiving element receives sends, described tabulation maintenance unit also is used for:
When described scanning element detects signal strength signal intensity more than or equal to the neighbor AP of default backup AP threshold value, whether the BSSID that further judges the basic service set identification BSSID of described neighbor AP and described current AP has the identical unique identification OUI that organizes, and described judged result adds described neighbor AP when being and backs up AP and tabulate.
16. client device as claimed in claim 11 is characterized in that, described switch unit comprises:
First switches subelement, is used for tabulating difference between the signal strength signal intensity of the signal strength signal intensity of one or more neighbor AP and current AP when meeting or exceeding described switching threshold as described backup AP, selects a neighbor AP and switches on the described neighbor AP; Or
Second switches subelement, when being used for signal strength signal intensity as described current AP and being lower than the minimum signal strength threshold value in other handoff algorithms that described client device is provided with or satisfying switching condition in other handoff algorithms that are provided with in the described client device, select a neighbor AP and switch on the described neighbor AP.
17. as claim 11 or 16 described client devices, it is characterized in that, described frame receiving element, also be used for after on the neighbor AP that switches to described backup AP tabulation from current AP, receive the described frame that back AP sends that switches, obtain the neighbor AP channel information, backup AP threshold value and the described mobile service parameter that switches back AP that carry in the described frame; The mobile service parameter of AP before the neighbor AP channel information of storage, backup AP threshold value and the switching before covering.
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