CN101202685B - Method for handing over in wireless area network and device of applying the method - Google Patents
Method for handing over in wireless area network and device of applying the method Download PDFInfo
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Abstract
The invention relates to a wireless area network transmission method and a device which applies the method. When a client is transmitting/receiving a grouping, the client switches between a data receiving and transmitting mode and a searching mode for every specific time interval. In the searching mode, the client selects a receiving access point to carry through transmission and rebuilds the link of the network according to the preset rule from the result of searching when the client searches out a plurality of channels every time.
Description
Technical field
The present invention relates generally to a kind of delivering method and uses the device of said method, in particular to a kind of device that is applied in the delivering method in the radio area network and uses said method.
Background technology
Along with radio area network (Wireless Local Area Network, popularizing WLAN), and the scope of application of radio area network constantly increases.(Voice overWLAN VoWLAN) will become the focus that another gets most of the attention in the radio area network voice service.But show that according to present resulting data the standard of IEEE802.11 can't satisfy the demand of radio area network voice service now, main cause comes from the long handover of radio area network (Handoff) and postpones.
Compared to other wireless systems, radio area network has more handover chance.This is that (Access Point, covering scope AP) are not very big (50～100 meters), have relatively just increased the number of times of each radio area network voice service user handover yet because of each reception access point in radio area network.Show that according to the data that correlative study proposed (Media Access Control, MAC) handover of layer postpones (latency) time greatly between 200 to 1000 milliseconds (millisecond) in the control of radio area network medium access.When beginning to carry out handover, (Mobile Station MS) switches between different working channels client, hunts out suitable reception access point by this.During this section is searched, if client is interrupted with the line that receives at present between access point, this will cause receiving and dispatching any grouping.For the radio area network voice service, continuous like this packet drop will cause conversation temporarily to stop, and make radio area network voice service speech quality descend significantly.
In traditional handover mechanism, the handover of radio area network medium access control layer postpones to be made up of search delay (probe delay), authentication delay (authentication delay) and connection delay (association delay).The handover that Fig. 1 is expressed as radio area network postpones part.Searching delay is exactly the delay that is being produced when client is being sought the reception access point that can supply handover in all available channels (channel).And authentication to postpone be exactly client with new delay when receiving the access point authentication.Connection delay then is that client follows new reception access point to rebulid the delay of line.
Search process when Fig. 2 is expressed as radio area network medium access control layer handover.Channel switch time (Channel Swit ch﹠amp; Transmission, CST), be exactly client from some channel switch to the required time of another channel.The smallest passage time (min channel time) represents respectively that with the largest passages time (max channel time) client is at a maximum and minimum time that channel is required of search.
Be the opportunity that the largest passages time takes place after client is sent search requirement (probe request), has what reception access points to exist on each channel because client can't be learnt.Therefore, if receive that in this channel receiving the search that access point responds responds (probe response), client just clamped on to the largest passages time and obtained the search response that institute might respond this moment.Say it on the contrary,, do not receive access point and respond the search response, at this moment the client awaits smallest passage time, search next channel with continuation if after client is sent the search response.
Fig. 3 is expressed as traditional radio area network delivering method schematic diagram.After the present signal quality of client terminal to discover is lower than certain threshold value, just begin to start handover mechanism.At this moment, client just can be searched all channels in regular turn, for example the diagram in from channel 1 to channel N.After searching end, client just judges that according to the criterion of setting in advance (as: best signal quality or best service quality) the reception access point in that channel is best selection, the channel that begins conversion client with that carries out handover, and rebulids the connection of network.
Said method is to carry out the channel switching of handover operation again after searching all channels in regular turn, and sets up new network connection.Because at channel search therebetween, client can't communicate with present reception access point.Therefore, the grouped data that sends will be lost when handover.Thus, will cause when searching, client can't be listened to any sound and cause temporary dropped calls, and then reduces the wish of user's use radio area network voice service.
In addition, this area has also proposed many different delivering methods.For example, for example the U.S. the 6th, 278, in No. 877 patents patent that name is called " Handover Method For Mobile WirelessStation " is proposed, above-mentioned patent is to allow client (MS) collect passively by the information that receives the beacon (beacon) that access point (AP) sent, and determines whether according to the power of beacon signal beginning to search contiguous AP has which.The power of the beacon signal of being sent according to contiguous AP decides wants handover to that reception access point.Above-mentioned patent is when handling the client handover, and what mainly adopt is passive signal detection scheme, and just client (MS) is exactly to collect the contiguous beacon signal that access point (AP) is sent that receives quietly.
The U.S. the 6th, 980, in No. 535 patents patent that name is called " Handover Method For MobileWireless Station " is proposed, above-mentioned patent is that the AP that connected at present sends to search and requires (proberequest) to give contiguous AP, and client to be exactly the search of collecting contiguous AP quietly and being sent respond.
And the open middle patent that name is called " System AndMethod For Performing A Fast Handoff In A Wireless Local Area Network " that proposes of No. 2004054283 patent application of PCT patent WO, above-mentioned patent is to be used for reducing the time that client (MS) is searched, and mainly is to come channel search (channel) according to the order after the ordering.Above-mentioned patent is similar to the practice of consecutive points curve chart (neighborgraph).All there is a nearest neighbor point table (nearest-neighbortable) at each MS, and the AP in the nearest neighbor point table is done an ordering according to previous experience, and search AP according to the order of ordering.
Also have No. the 20060092883rd, U.S. Patent Application Publication in addition, name is called " Probing methodfor fast handoff in WLAN ", or No. the 20050282546th, U.S. Patent Application Publication, name is called " Method and system for providing fast handoff in a WLAN-likecommunication system using active neighboring sets ", or No. the 20060062183rd, U.S. Patent Application Publication, name is called " Methods and systems for reducing MAClayer handoff latency in wireless networks ", or No. the 20040224690th, U.S. Patent Publication, name is called " Handoff method in wireless LAN; and access pointand mobile station performing handoff method ", or patent No. US2006072507 number, name is called case content before the related application of " Minimizing handoffs and handoff times inwireless local area networks " or the like.The disclosed content of these patent application cases is in order to shorten the time of client channel search.
Summary of the invention
The present invention proposes a kind of delivering method, is applied to the radio area network communication system and carries out the gapless handover.Above-mentioned radio area network communication system comprises client and a plurality of reception access point.This delivering method comprises that every a predetermined time interval, this client is switched when client sends/receive grouping between data transmit-receive pattern and seek mode.Select the channel search to receive access point in the time of in seek mode, obtain the signal quality numerical value that receives access point, and select a reception access point to carry out handover, rebulid the link of network according to prior setting criterion.
The present invention proposes a kind of delivering method of radio area network.Above-mentioned radio area network communication system comprises a client and a plurality of reception access point.This delivering method comprises the search pattern of client with a noncontinuity, selects one to receive the search of access point to several channels at every turn, and the received signal intensity of the reception access point that searched of record.When client when carrying out handover, when the signal quality numerical value that detects the reception access point that is linked at present is lower than a minimum acceptable signal quality numerical value, select a temporary access point in the reception, temporarily move on to this access point in the reception temporarily from the present reception access point that links, and continue to search the channel of not searching as yet.After finishing all channels of search, client selects a reception access point to carry out handover according to setting criterion in advance.
The present invention also proposes a kind of device that carries out handover in wireless local area network communication system, and this wireless local area network communication system comprises a plurality of access points, and this device comprises a transceiver module and a search module.Transceiver module is in order to transmit/to receive grouping, search module is in order to search above-mentioned a plurality of access point, wherein when device carries out a handover function, transceiver module and search module switch every a predetermined time interval, and wherein search module searches one to several channels at every turn when searching, from the result who searches, according to a prior criterion of setting, from described access point, select one of them to carry out handover, rebulid the link of network.
Description of drawings
For technology of the present invention, feature can be become apparent, examples of implementation cited below particularly, and conjunction with figs. are described in detail as follows.
The handover that Fig. 1 is expressed as radio area network postpones part.
Search process when Fig. 2 is expressed as radio area network medium access control layer handover.
Fig. 3 is expressed as traditional radio area network delivering method schematic diagram.
Fig. 4 is expressed as the delivering method schematic diagram of the embodiment of the invention.
Fig. 5 is expressed as the delivering method flow chart of steps of the embodiment of the invention.
Fig. 6 is expressed as the delivering method flow chart of steps of the embodiment of the invention.
Fig. 7 is the overall operation flow chart of the radio area network gapless delivering method of the embodiment of the invention.
Fig. 8 is the explanation embodiment schematic diagram with radio area network handover device proposed by the invention.
The main element symbol description
S51～S55, S61～S66, S710～S760: step
800: the radio area network communication system
820,830,840 and 850: access point
822,832,842 or 852: connecting line
810: device
812: transceiver module
814: search module
816: decision mechanism
Embodiment
Because the delivering method of prior art is once to search all passages, after search finished, client selective reception access point was again carried out handover.In the search process of channel, can cause the once a large amount of loss of grouping, and then cause when searching, client can't be listened to any sound, causes temporary dropped calls, and then reduces the wish of user's use radio area network voice service.
And the present invention proposes mechanism and the method for a kind of radio area network gapless handover (WLAN seamless handoff), comprises noncontinuity search (Discontinuous Probe) mechanism, stops and restarting (Stop-then-resume) mechanism and link (Early connecting) mechanism ahead of time.Implement in the example one, the mechanism and the method for a kind of radio area network gapless handover that the present invention proposes, can send at MS and just authentication information (AuthenticationInformation) embedding of MS be searched in the requirement when search requires (Probe Request), with the time of minimizing authentication.The mechanism and the method for radio area network gapless handover proposed by the invention, handover at the medium access control layer of radio area network voice service (VoWLAN) postpones, comprise search postpone (Probe Delay), authentication postpones (Authentication Delay) and connection delay (Association Delay) can improve to reduce the time of handover effectively.
And above-mentioned noncontinuity search mechanism is exactly to allow client (Mobile Station, under abbreviate MS as) after starting seek operations, searches one at set intervals to several channels (Channel).Stop and the mechanism of restarting then be when MS in the process that noncontinuity is searched, find reception access point (the Access Point that a ratio is more suitable at present, under be called AP) and the quality received signal intensity of MS indication (Reeeived Signal Strength Indicator, the beneath RSSI that is called for short) when value has been lower than the minimum standard that can receive and dispatch grouping soon, with regard to first handover AP so far, restart the noncontinuity search afterwards and remove to search the channel of not searching as yet.Because client is temporary transient handover AP so far, therefore with this AP called after access point in the reception temporarily.Thereafter if during the AP that finds to be more suitable for, more again handover to this AP.In case ahead of time linking mechanism then is when MS in the process that noncontinuity is searched, finds an AP who quite is fit to, with regard to the AP so far of handover immediately, and the operation that stops to search.
Below just the present invention is described to implement example.
Fig. 4 is expressed as delivering method schematic diagram of the present invention.Preferable some start-up time of this example delivering method, after being that signal quality threshold that signal quality numerical value when client is lower than prior conclusion continuously reaches threshold number, just begin to start the noncontinuity search, this signal quality threshold is called noncontinuity and searches threshold value (Discontinuous Probe Threshold).This noncontinuity search is that client is every a predetermined time interval, hocket transmission/reception grouping (being called the data transmit-receive pattern) with search one to several channels (being called seek mode) with noncontinuity search (Discontinuous Probe) at every turn, and from the result who searches, set criterion (as: best signal quality or best service quality) in advance according to one and select a reception access point to carry out handover.
For example among Fig. 4, after jumping to channel 1 and search (client enters seek mode) from original channel, the rebound original channel sends/receives grouping (client enters transceiver mode) again, after then jumping to channel 2 and search (client enters seek mode once more) from original channel again, the rebound original channel sends/receives grouping (client enters transceiver mode once more) again.In addition, on the preferable application opportunity of present embodiment delivering method, be when client sends/receive grouping.Use present embodiment this moment, can reduce the packet drop number, improves voice communication and on average evaluate score, obtains communication quality preferably.
In the above-mentioned accompanying drawing, transmission/reception grouping is by orders such as original channel, channel 1, original channel, channels 2 with searching sequence until till the channel number of presetting hockets.And in an other embodiment, also can send/receive grouping at original channel after, carry out the search of a plurality of channels such as channel 1, channel 2 and channel 3 continuously after, the rebound original channel sends/receives grouping again.And in an other embodiment, also can send/receive grouping at original channel after, carry out the search of a plurality of odd number channels such as channel 1, channel 3 and channel 5 continuously, or the search of a plurality of even number channels such as channel 2, channel 4 and channel 6, the rebound original channel sends/receives grouping again.Just channel order also can be adjusted according to the needs in the design, but not searches in regular turn from 1 to N.
Fig. 5 is expressed as delivering method step exemplary flowchart of the present invention.Please also refer to Fig. 4 and Fig. 5, execution in step S51 at first behind client terminal start-up, client can continual passive type ground be monitored the variation of (Passive Scan) signal quality numerical value.Then at step S52, judge whether the signal quality numerical value of client is lower than the signal quality threshold of prior decision continuously, just aforesaid noncontinuity is searched threshold value (Discontinuous Probe Threshold), and number of times reaches the predetermined threshold value number of times, if, just begin execution in step S53, when client sends/receives grouping at present, the just noncontinuity search of setting up procedure S54.
In the noncontinuity of step S54 was searched, client can be every a predetermined time interval, and the transmission that hockets/reception is divided into groups and with a noncontinuity method for searching, each sequential hunting one is to several channels.At step S55, client can select a reception access point to carry out handover according to prior setting criterion (as: best signal quality or best service quality) from the result who searches, and rebulids the link of network.
In order to be described in more detail, at this delivering method step exemplary flowchart of the present invention is proposed further, please refer to shown in Figure 6.At first at step S61, client is carried out passive type earlier and is scanned (Passive Scan) to obtain signal quality numerical value.At step S62, whether the signal quality numerical value that client determining step S61 obtains is lower than signal quality threshold continuously reaches threshold number, if, then carry out next step S63, if not, then get back to the variation of the continual monitor signal quality of step S61 numerical value.When being lower than signal quality threshold continuously, signal quality numerical value reaches threshold number, then as step S63, client judges whether to send/receive grouping, if, then carry out the noncontinuity search of step S64, if not, then carry out all channels of continuity ground search that step S65 noncontinuity is searched, just search all channels in regular turn, and write down the signal quality numerical value of the reception access point on these channels.
The step S64 of noncontinuity search can be divided into several sub-steps, comprises that step S641 as shown in Figure 6 arrives step S644.In step S641, in a predetermined time interval, be transformed into to noncontinuity one or more channel; In step S642, search reception access point at the described channel of step S641.In step S643, the signal quality numerical value of the reception access point that record step S642 was searched, at step S644, get back to original channel and continue transmission/reception grouping,, judge whether to search the reception access point of finishing on all channels at step S645, if, then proceed next step S66, if not, resumes step S641 then.
At step S66, client will select a reception access point to carry out handover according to prior setting criterion among the reception access point on the channel of being searched.
Noncontinuity is searched (Discontinuous Probe) parameter setting
In the top enforcement example, the signal quality threshold of the prior decision of mentioning, threshold number, set the signal quality of criterion such as the best or best service quality, noncontinuity predetermined time interval and channel search quantity or the like in searching in advance, it all is the selection in the design, can determine that these changes all belong to category of the present invention according to the communication protocol (Protocol) of the communication system of being used, employing, the environment for use of communicating by letter or the like parameter.Signal quality described herein can be in radio area network quality received signal intensity indication (Received Signal Strength Indicator, RSSI).
In the noncontinuity seek operations, the enforcement example that each parameter is worked out can be with reference to beneath explanation, right and unrestricted parameter setting scope of the present invention.In this noncontinuity search mechanism, it is as starting the point that noncontinuity is searched that noncontinuity is searched threshold value (Discontinuous Probe Threshold, beneath abbreviation DPT).DPT will be according at that time translational speed of the design of every money radio area network (WLAN) chipset and client MS and is different, and this threshold value can still can be received and dispatched allowed signal quality numerical value of when grouping greater than WLAN, for example minimum RSSI measuring value, this claim for RSSI
MinWherein, the translational speed of MS (under be called MS_Speed) then can be inferred out according to the variable quantity of RSSI in the unit interval, shown in following formula:
Wherein, DS () letter formula is represented the distance transform between RSSI value and MS and AP distance, and the input value of DS () is the RSSI value, and output then is the distance between MS and AP distance.DS () letter formula will be according to the design of every money WLAN chipset and is different.RSSI
tWith RSSI
T-M_interalRSSI value when difference express time t and t-M_interal, the time interval of M_interal value representation RSSI sampling.
According to MS_Speed and RSSI
Min, we just can release DPT:
DPT＝RSSI
min+DS
-1(MS_Speed×(Disprobe_Time+M_interval×α))
Wherein, DS
-1() letter formula is also represented the conversion between RSSI value and MS and AP distance, DS
-1() is the inverse function of DS ().DS just
-1The input of () is the distance between MS and AP distance, and output then is the RSSI value.α then represent when the RSSI of MS value is continuous be lower than DPT α time after, just can begin to start the noncontinuity search.Disprobe_Time represents to use the noncontinuity search and searches the required time of all channels.
The value of Disprobe_Time then can be represented by following formula:
Disprobe_Time＝(MaxChannelTime+RTT+2×CST)×TotalChannel
+MinWaitTime×(TotalChannel-1)
Wherein, MaxchannelTime represents that respectively MS is searching the maximum time that channel is required.RTT (Round Trip Time) searches the grouping turnaround time.CST represents channel switch time (Channel Switch﹠amp; Transmission), be exactly MS from some channel switch to the required time of another channel.TotalChannel represents when handover takes place, the channel number of the required search of MS.MinWaitTime then represents, gets back to channel wait originally and receive the required minimum time of grouping after MS has searched a channel.
According to shown in Figure 6, in case MS decision begin to do the noncontinuity search, then MS must arrange those channels be need to be searched earlier, the time every how long search once, and once can search several channels.For the order that channel is searched, then can do ordering according to searching the probability of using.For example, in IEEE 802.11b standard, be exactly first channel search 1,6,11 these three channels.Because these three channel is the most normal is used, just might obtain more information so search these three channels.Remaining channel then is that ascending mode is searched in regular turn.The time interval of searching then is to depend on Simulation result.Because the time interval of too small search will be caused the loss of grouping; The time interval of long search then can cause noncontinuity to search to such an extent that spend the long time just can finish, and this may with cause MS do several times handover more.Show according to Simulation result at present, when the time interval of searching at 250ms, almost do not have the situation of packet drop.As for each channel number of searching also is to depend on Simulation result, just depends on the maximum duration that wlan system can be allowed the temporary transient not contracture group of MS and be divided into groups can not lose.Show according to Simulation result at present, when the channel number of each search is 1, can obtain goodish result.
Stop and restarting the operating mechanism of (Stop-then-resume)
Employing stops and the main cause of restarting (Stop-then-resume) mechanism is that the time of whole search will be elongated when MS uses the noncontinuity search, and this will increase MS and has little time to have searched the operation that just is forced to do handover before all channels.Stop-then-resume mechanism is to work as MS in the process that noncontinuity is searched, when the RSSI value of finding reception access point (AP) that a ratio is more suitable at present and MS has been lower than the minimum standard that can receive and dispatch grouping soon, with regard to first handover AP (be called temporarily access point) so far, restart the noncontinuity search afterwards and remove to search the channel that does not carry out as yet in the reception.Thereafter if during the AP that finds to be more suitable for, more again handover to this AP that is more suitable for.If when not finding proper A P as yet before the RSSI of MS value has been lower than the minimum standard that can receive and dispatch grouping, the method that MS will adopt tradition to search has been searched all channels as early as possible.
Link the operating mechanism of (Early connecting) ahead of time
Link (Early connecting) ahead of time in case mechanism then be when MS in the process that noncontinuity is searched, find one when being greater than or equal to predefined value, so far receive access point (AP) with regard to handover immediately, and the operation that stops to search.Claim that at this preset value is B threshold value (B_threshold).The selected of B_threshold then is to decide according to the specification of system, allows MS can be in the signal quality of fast transmission speed.Early connecting mechanism can reduce the search that there is no need.
Overall operation mechanism
Fig. 7 is the overall operation exemplary flowchart of radio area network gapless handover of the present invention (WLAN seamless handoff) method.As step 710, when MS began to carry out the noncontinuity search, MS also can constantly detect and present just quality received signal intensity indication (RSSI) value between the reception access point (AP) of line, and notes down which channel and search.Step 720 confirms whether the resulting RSSI value of MS is greater than or equal to B threshold value (B_threshold).In case when finding to be greater than or equal to the AP of B threshold value, just handover AP so far immediately, and the operation that stops to search, as step 760, just this to receive access point be suitable reception access point.If no, then carry out step 730, confirm whether the resulting RSSI value of MS is less than or equal to minimum permissible communication quality.If not, then carry out follow-up step, as step 732, MS continues to carry out the operation of noncontinuity search till all channels were all searched.Step 734, whether MS has searched proper A P.If then as step 760, handover is AP so far.If not, then as step 736, the still uncompleted channel of lasting search, just MS can do the noncontinuity search constantly, till searching available AP, or just is left intact, and just allows MS interrupt network line.
If before MS has searched all channels, the RSSI value just has been lower than minimum permissible communication standard.This moment, MS just chose the AP that a ratio is more suitable at present from the channel of having searched as step 740.If MS does not find proper A P, then MS just directly uses the remaining channel of not searching as yet of successional sequential hunting, up to finding suitable AP.Do not adopt this moment the reason of noncontinuity search to be to save the time that MS searches.If the AP that finds than being more suitable for is at present arranged, then as step 750, MS to this AP, and proceeds the operation that noncontinuity is searched with regard to first handover, till MS has searched all channels.After having searched all channels, MS can select a reception access point to carry out handover according to setting criterion in advance, rebulids the link of network.
Please refer to Fig. 8, so that the enforcement example with radio area network handover device proposed by the invention to be described.Above-mentioned radio area network communication system 800 comprises a plurality of access points, and is for example illustrated 820,830,840 and 850, and these access points are respectively in wired or wireless mode, as shown in the figure 822,832,842 or 852 be connected to Local Area Network 805.And this device 810 comprises transceiver module 812 and search module 814.This transceiver module 812 is in order to sending/to receive grouping, and search module is in order to search these access points 820,830,840 and 850.When this device 810 carried out a handover function, then this transceiver module 812 switched every a predetermined time interval with search module 814.This search module searches one to several channels, from the result who searches at every turn when searching, set criterion in advance according to one, for example, from these access points 820,830,840 and 850, select one of them to carry out handover, rebulid the link of network according to the judgment mechanism 816 in the diagram.Above-mentioned search module is in the mode of a noncontinuity, each one or more channels of selecting are searched these access points 820,830,840 and 850, and the received signal intensity of record access point, this transceiver module 812 then with the channel continuation transmission/reception grouping of present use, for example continues transmission/reception grouping with the channel that access point 820 is set up.
This search module 814 requires (Probe Request) to require these access points 820,830,840 and 850 one of them answer to search, and judges the signal quality numerical value of access point according to the return signal that access point sent.During above-mentioned search requires, authentication information (Authentication Information) can be embedded this and search in the requirement.
In sum, though the present invention with the enforcement example openly as above, so it is not in order to limit the present invention.Those of ordinary skill under any in the technical field under the situation that does not break away from the spirit and scope of the present invention, can carry out various changes and modification.Therefore, protection scope of the present invention is as the criterion with the scope of the claim that proposed.
Claims (19)
1. the delivering method of a radio area network, the radio area network communication system comprises a client and a plurality of reception access point, above-mentioned delivering method comprises:
When above-mentioned client sends/receives grouping, every a predetermined time interval, above-mentioned client is switched between a data transmit-receive pattern and a seek mode, in the time of wherein in above-mentioned seek mode, above-mentioned client is each searches one to several channels, from the result who searches, set criterion in advance according to one, select a reception access point to carry out handover, rebulid the link of network
Wherein before above-mentioned client entered above-mentioned seek mode, above-mentioned client was carried out the passive type search, got the signal quality numerical value of the reception access point that is linked up till now; When the signal quality numerical value of the present reception access point that links was lower than a signal quality numerical threshold continuously and reaches a threshold number, above-mentioned client then carried out switching between above-mentioned data transmit-receive pattern and the above-mentioned seek mode.
2. delivering method as claimed in claim 1, wherein above-mentioned client comprises from switch step between above-mentioned data transmit-receive pattern and the above-mentioned seek mode:
In above-mentioned seek mode, above-mentioned client is in the mode of a noncontinuity, each one or more channels of selecting are searched above-mentioned a plurality of reception access point, and note down the received signal intensity of above-mentioned a plurality of reception access points, and in above-mentioned data transmit-receive pattern, then continue transmission/reception grouping with former use channel;
Carry out repeatedly between above-mentioned data transmit-receive pattern and the above-mentioned seek mode and switch, until finishing of the search of all channels for above-mentioned a plurality of reception access points; And
From above-mentioned a plurality of reception access points of having searched,, select a reception access point to carry out handover according to above-mentioned prior setting criterion.
3. delivering method as claimed in claim 1, wherein when above-mentioned client is switched between above-mentioned data transmit-receive pattern and seek mode, comprise that more carrying out one stops and restarting mechanism, above-mentioned stop and the mechanism of restarting comprises the signal quality numerical value that detects the present reception access point that links of above-mentioned client, if when being lower than a minimum acceptable signal quality numerical value, select a temporary access point in the reception, temporarily move on to above-mentioned access point in the reception temporarily from the present reception access point that links, and proceed uncompleted search.
4. delivering method as claimed in claim 3, wherein above-mentioned access point in the reception temporarily, for from above-mentioned a plurality of reception access points of having searched, select the reception access point of signal quality numerical value greater than the signal quality numerical value of the present reception access point that links of above-mentioned client.
5. delivering method as claimed in claim 4, wherein above-mentioned access point in the reception temporarily is not when existing, then above-mentioned client stops to switch to above-mentioned data transmit-receive pattern, and rest in the above-mentioned seek mode, continue to search the reception access point of not searched at present, up to the reception access point that finds signal quality numerical value greater than the signal quality numerical value of the present reception access point that links of above-mentioned client, and select as above-mentioned access point in the reception temporarily and carry out handover.
6. delivering method as claimed in claim 1, wherein when above-mentioned client is switched between above-mentioned data transmit-receive pattern and above-mentioned seek mode, comprise that more carrying out one does sth. in advance linking mechanism, wherein above-mentioned linking mechanism ahead of time comprises when the above-mentioned a plurality of reception access point of search, in case above-mentioned a plurality of signal quality numerical value one of them when being greater than or equal to a threshold value, then directly handover to the above-mentioned reception access point of above-mentioned signal quality numerical value correspondence.
7. delivering method as claimed in claim 1, in the time of wherein in above-mentioned seek mode, above-mentioned client requires one of them answer of above-mentioned a plurality of reception access point to search, and the return signal that is sent according to above-mentioned reception access point is judged the signal quality numerical value of above-mentioned reception access point.
8. delivering method as claimed in claim 7 during wherein above-mentioned search requires embeds the authentication information of above-mentioned client during above-mentioned search requires.
9. delivering method as claimed in claim 1, wherein above-mentioned signal quality numerical threshold can be learnt according to following formula:
DPT＝RSSI
min+DS
-1(MS_Speed×(Disprobe_Time+M_Interval×α))；
DS wherein
-1() letter formula is represented the conversion between above-mentioned signal quality numerical value RSSI value and above-mentioned client and above-mentioned reception access point distance, DS
-1() is the inverse function of DS (), just DS
-1The input of () is above-mentioned client and above-mentioned reception access point distance, and RSSI
MinReceive and dispatch the minimum value of the signal quality numerical value of grouping for above-mentioned client, M_Interal represents the time interval of signal quality numerical value sampling, MS_Speed is the translational speed of above-mentioned client, and Disprobe_Time represents above-mentioned noncontinuity search required time, and α then represents above-mentioned threshold number.
10. delivering method as claimed in claim 9, wherein the value of Disprobe_Time then can be represented by following formula:
Disprobe_Time＝(MaxChannelTime+RTT+2×CST)×TotalChannel
+Min?WaitTime×(TotalChannel-1)
Wherein, MaxchannelTime represents that respectively above-mentioned client searching the maximum time that channel is required, RTT (Round Trip Time) searches the grouping turnaround time, CST represents the channel switch time (Channel Switch and Transmission), be exactly above-mentioned client from some channel switch to the required time of another channel, TotalChannel represents when handover takes place, the channel number of the required search of above-mentioned client, MinWaitTime are then represented to get back to original use channel and are waited for the required minimum time of grouping that receives behind the intact channel of above-mentioned client search.
11. delivering method as claimed in claim 1, wherein above-mentioned prior setting criterion comprises the signal quality an of the best.
12. delivering method as claimed in claim 1, wherein above-mentioned prior setting criterion comprises a best service quality.
13. the delivering method of a radio area network, radio area network communication system comprise a client and a plurality of reception access point, above-mentioned delivering method comprises:
Above-mentioned client is carried out the passive type search, gets the signal quality numerical value of the reception access point that is linked up till now;
When the signal quality numerical value of the present reception access point that links is lower than a signal quality numerical threshold continuously and reaches a threshold number, above-mentioned client is with the order of a noncontinuity, select one or more channels to search above-mentioned a plurality of reception access point, obtain the signal quality numerical value of above-mentioned a plurality of reception access points;
When the signal quality numerical value that detects the present reception access point that links of above-mentioned client is lower than a minimum acceptable signal quality numerical value, select a temporary access point in the reception, temporarily move on to above-mentioned access point in the reception temporarily from the present reception access point that links, and proceed uncompleted above-mentioned noncontinuity search; And
Finish and search all channels of above-mentioned client, and, select a reception access point to carry out handover according to a prior criterion of setting.
14. delivering method as claimed in claim 13, in the time of wherein in above-mentioned seek mode, above-mentioned client requires one of them answer of above-mentioned a plurality of reception access point to search, and the return signal that is sent according to above-mentioned reception access point is judged the signal quality numerical value of above-mentioned reception access point.
15. delivering method as claimed in claim 14 during wherein above-mentioned search requires embeds the authentication information of above-mentioned client during above-mentioned search requires.
16. a device that carries out handover in the radio area network communication system, above-mentioned radio area network communication system comprises a plurality of access points, and said apparatus comprises:
One transceiver module is in order to send/to receive grouping; And
One search module, in order to search above-mentioned a plurality of access point, wherein when said apparatus carried out a handover function, above-mentioned transceiver module and above-mentioned search module switched every a predetermined time interval, and wherein above-mentioned search module is when searching, each search one is to several channels, from the result who searches,, from above-mentioned a plurality of access points, select one of them to carry out handover according to a prior criterion of setting, rebulid the link of network
Wherein before carrying out above-mentioned search, above-mentioned search module carries out the passive type search, gets the signal quality numerical value of the reception access point that is linked up till now; And when the signal quality numerical value of the present reception access point that links is lower than a signal quality numerical threshold continuously and reaches a threshold number, switch between above-mentioned transceiver module and the above-mentioned search module.
17. device as claimed in claim 16, wherein above-mentioned search module is in the mode of a noncontinuity, each one or more channels of selecting are searched above-mentioned a plurality of access point, and note down the received signal intensity of above-mentioned a plurality of access points, above-mentioned transceiver module then continues transmissions/reception with the channel of former use and divides into groups.
18. device as claimed in claim 16, wherein above-mentioned search module requires one of them answer of above-mentioned a plurality of access point to search, and judges the signal quality numerical value of above-mentioned access point according to the return signal that above-mentioned access point sent.
19. device as claimed in claim 18, wherein above-mentioned search embeds authentication information in the above-mentioned search requirement in requiring.
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| CN2006101667588A CN101202685B (en) | 2006-12-14 | 2006-12-14 | Method for handing over in wireless area network and device of applying the method |
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| CN2006101667588A CN101202685B (en) | 2006-12-14 | 2006-12-14 | Method for handing over in wireless area network and device of applying the method |
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| CN101202685B true CN101202685B (en) | 2011-05-11 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0605989B1 (en) * | 1993-01-08 | 2000-03-01 | Lucent Technologies Inc. | Handover method for mobile wireless station |
| CN1568043A (en) * | 2003-07-01 | 2005-01-19 | 株式会社日立制作所 | Method for cross-region switching of wireless local area network |
| CN1723656A (en) * | 2002-12-11 | 2006-01-18 | 皇家飞利浦电子股份有限公司 | System and method for performing a fast handoff in a wireless local area network |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0605989B1 (en) * | 1993-01-08 | 2000-03-01 | Lucent Technologies Inc. | Handover method for mobile wireless station |
| CN1723656A (en) * | 2002-12-11 | 2006-01-18 | 皇家飞利浦电子股份有限公司 | System and method for performing a fast handoff in a wireless local area network |
| CN1568043A (en) * | 2003-07-01 | 2005-01-19 | 株式会社日立制作所 | Method for cross-region switching of wireless local area network |
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