CN1992971A

CN1992971A - Method for avoiding data loss in switching process

Info

Publication number: CN1992971A
Application number: CNA2005101374629A
Authority: CN
Inventors: 杜汉美; 庄宏成
Original assignee: Huawei Technologies Co Ltd
Current assignee: XFusion Digital Technologies Co Ltd
Priority date: 2005-12-30
Filing date: 2005-12-30
Publication date: 2007-07-04
Anticipated expiration: 2025-12-30
Also published as: CN100512541C

Abstract

The invention relates to a method for avoiding losing data in switch process, wherein it is characterized in that: when receiver switches from local wireless access point AP into target AP, it will send buffer information to wireless access point AP; AP based on buffer information processes the data sent to the receiver, via the target AP sends processed data to the receiver. The invention can avoid losing data, confirm data integrality. And receiver STA can switch without complete data transmission by AP, to reduce time delay.

Description

In handoff procedure, avoid the method for loss of data

Technical field

The present invention relates to the communications field, relate in particular to the handoff procedure of WLAN (Wireless Local AreaNetwork, WLAN (wireless local area network)).

Background technology

WLAN compares with cable network, has characteristics such as easy deployment, port density height, mobility, is widely used at present.Along with the development of WLAN technology is perfect, WLAN will become the carrier-class public access wireless LAN as the mainstream technology and the mobile communication technology combination of broadband wireless network.Its mainly by wireless site (Station, STA), WAP (wireless access point) (Access Point, AP) and distributed system (Distributed System DS) waits composition.Wherein access terminal and can be in network move arbitrarily, WAP (wireless access point) is used to realize to comprise the cell management of sub-district in switching in, to the management and the bridging functionality of wireless access terminal, and distributed system is used to realize the management that accesses terminal at inter-network roaming.

When STA when current access point AP coverage cell moves to the sub-district that another access point AP covers, have the situation of lost data packets:

As shown in Figure 1, when STA switches to AP2, still exist data queue to wait on AP1 and send to STA, can cause losing of packet this moment.

As shown in Figure 2, when STA switches to AP2, because DS does not also react, still packet is issued AP1, this moment, AP2 did not receive this part packet, can cause losing of packet yet.

Packet lose the temporary transient interruption that can cause communication, this can affect to performance of system.In order to solve the problem that when STA switches, causes above-mentioned data-bag lost, the prior art relevant with the present invention proposed, its message flow schematic diagram as shown in Figure 3, handoff procedure comprises as shown in Figure 4:

At first as shown in Figure 4, STA authenticates by AP1 and AP2; After authentication success, as shown in Figure 5, STA sends " preparing to switch " (RTT, a Ready to transition) message and gives AP1, and AP1 gives AP2 with this forwards; After AP2 receives this message, as shown in Figure 6, send " remove and switch " (CTT, a Clear to transition) message and give AP1, after AP1 issues STA with all formation frames, just give STA the CTT forwards that receives; After STA receives CTT message, as shown in Figure 7, carry out relatedly with AP2 immediately, and collect the frame stay in advance, and carry out and switch.

Can reduce the possibility of above-mentioned two kinds of lost data packets to a certain extent by prior art, but it still exists following defective:

1, STA could switch with target AP after must waiting pending data to pass, and causes time delay like this.

2, because STA moves, in the process that the waiting list frame transmits,, so also can cause losing of data because signal weakening may break with current AP and be connected.

Summary of the invention

The purpose of this invention is to provide a kind of method of in handoff procedure, avoiding loss of data,, can avoid the loss of data in the handoff procedure, greatly guaranteed data integrity by the present invention; And among the present invention, STA needn't wait for just carrying out after current AP has transmitted data and switch, thereby reduce handover delay.

The objective of the invention is to be achieved through the following technical solutions:

The invention provides a kind of method of avoiding loss of data in handoff procedure, it comprises:

A, when receiving terminal when local wireless access point AP switches to target AP, cache information is sent to wireless access point AP;

B, described AP handle the data that the transmitting terminal that receives sends to described receiving terminal according to described cache information, and the data after will handling by described target AP send to described receiving terminal.

Wherein, described steps A specifically comprises:

A1, when receiving terminal when local AP switches to target AP, cache information element buffer IE is sent to local AP, be provided with cache information among the described buffer IE;

Or,

A2, when receiving terminal when local AP switches to target AP, cache information element buffer IE is sent to target AP, be provided with cache information among the described buffer IE.

Wherein, described steps A 1 specifically comprises:

A11, when receiving terminal when local AP switches to target AP, with the target AP authentication success after, cache request FT Action buffer request message by quick switching sends to local AP with cache information element buffer IE, is provided with cache information among the described buffer IE;

Or,

A12, when receiving terminal when local AP switches to target AP, with the target AP verification process in, authenticate-acknowledge or request FT Action confirm or request message by quick switching send to local AP with cache information element buffer IE, are provided with cache information among the described buffer IE.

Wherein, described steps A 1 also comprises:

A13, carry out by reassociation requests Re association Req message described buffer IE being sent to target AP in the process of series of fortified passes connection, be provided with cache information among the described buffer IE in described receiving terminal and described target AP;

Or,

A14, carry out in the process of series of fortified passes connection in described receiving terminal and described target AP, by reassociation requests Re association Req message with described buffer IE, and the sequence information element S N IE of the data that receive sends to target AP, is provided with cache information among the described buffer IE.

Wherein, described steps A 2 specifically comprises:

A21, when receiving terminal when local AP switches to target AP, with target AP success series of fortified passes connection after, by request of data Data request message cache information element buffer IE is sent to target AP, be provided with cache information among the described buffer IE;

Or,

A22, when receiving terminal when local AP switches to target AP, after joining with target AP success series of fortified passes, with cache information element buffer IE, and the SN IE of the data that receive sends to target AP, is provided with cache information among the described buffer IE by request of data Data request message.

Wherein, be provided with data storage method in the described cache information, comprise data are sent to target AP buffer memory and data cached at local AP by distributed system DS.

Wherein, described step B specifically comprises:

B1, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, when the data storage method that is provided with in learning described cache information was " data cached at local AP ", the data that then transmitting terminal that receives sent to described receiving terminal were carried out buffer memory at local AP;

B2, when described receiving terminal and target AP are carried out the series of fortified passes connection, target AP is extracted described data in buffer from local AP, send to described receiving terminal then;

Or,

B3, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, when the data storage method that is provided with in learning described cache information was " data cached at local AP ", the data that then transmitting terminal that receives sent to described receiving terminal were carried out buffer memory at local AP;

The data storage method that B4, target AP are indicated according to the cache information that carries in the described Re association Req message extracts described data in buffer from local AP, send to described receiving terminal then;

Or,

B5, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, when the data storage method that is provided with in learning described cache information was " data cached at local AP ", the data that then transmitting terminal that receives sent to described receiving terminal were carried out buffer memory at local AP;

B6, target AP are according to the data storage method of indicating in the cache information that carries in the described Re association Req message, learn and extract described data in buffer from local AP, then the SN IE that will obtain from described Reassociation Req message sends to local AP;

B7, after local AP receives this message, the SN IE information that described SN IE information is corresponding with own data in buffer compares, and selects the data of inconsistent SN IE information correspondence then, and sends to target AP by DS;

B8, target AP send it to receiving terminal after getting access to described data.

Or,

B9, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, the data storage method that is provided with in learning described cache information is " data cached at local AP ", and the data that then transmitting terminal that receives sent to described receiving terminal are carried out buffer memory at local AP;

B10, target AP are extracted described data in buffer according to the data storage method of indicating in the cache information that carries in the described Re association Req message from local AP;

B11, described local AP send to target AP with the total data of its preservation;

B12, target AP compare local AP data cached SN IE information of sending and the SN IE information of obtaining from described Reassociation Req message, select the data of inconsistent SN IE information correspondence then, and send it to described receiving terminal;

Wherein, among step B1, B3, B5 or the B9, the described data that the transmitting terminal that receives sent to described receiving terminal also comprise in the process that local AP carries out buffer memory:

Simultaneously described data are sent to described receiving terminal.

Wherein, described step B specifically comprises:

B13, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, the data storage method that is provided with in learning described cache information is " data are sent to the target AP buffer memory by DS ", and the data that then transmitting terminal that receives sent to described receiving terminal send to target AP by DS and carry out buffer memory;

B14, when receiving terminal and target AP are carried out the series of fortified passes connection, target AP sends to receiving terminal with described data in buffer;

Or,

B15, after local AP receives described cache information, analyze and discern the data storage method that wherein is provided with, the data storage method that is provided with in learning described cache information is " data are sent to the target AP buffer memory by DS ", and the data that then transmitting terminal that receives sent to described receiving terminal send to target AP by DS and carry out buffer memory;

B16, when receiving terminal and target AP are carried out the series of fortified passes connection, target AP is according to the data storage method of indicating in the cache information that carries in the described Reassociation Req message, and the data of described storage are sent to receiving terminal;

Or,

B17, after local AP receives described buffer IE, analyze and discern the data storage method that is provided with among the described buffer IE, the data storage method that is provided with in learning described buffer IE information is " data are sent to the target AP buffer memory by DS ", and the data that then transmitting terminal that receives sent to described receiving terminal send to target AP by DS and carry out buffer memory;

B18, when receiving terminal and target AP are carried out the series of fortified passes connection, target AP is according to the data storage method of the buffer IE indication of carrying in the described Reassociation Req message, learn that transmitting terminal sends to the metadata cache of receiving terminal at oneself place, then SN IE information and the own data in buffer SN IE information that will obtain from described Re association Req message compares, and selects the data of inconsistent SN IE information correspondence to send to receiving terminal.

Wherein, among step B13, B15 or the B17, the described data that the transmitting terminal that receives sent to described receiving terminal send to the process that target AP is carried out buffer memory by DS, also comprise:

Simultaneously described data are sent to described receiving terminal.

As seen from the above technical solution provided by the invention, the present invention when receiving terminal when local wireless access point AP switches to target AP, cache information is sent to wireless access point AP; The transmitting terminal that described AP receives described AP according to described cache information sends to the data of described receiving terminal and handles, and the data after will handling send to described receiving terminal.By the present invention, can avoid the loss of data in the handoff procedure, greatly guaranteed data integrity; And among the present invention, needn't wait for just carrying out after current AP has transmitted data as the STA of receiving terminal and switch, thereby reduce handover delay.

Description of drawings

Fig. 1 is the situation schematic diagram of a kind of loss of data in the background technology;

Fig. 2 is the situation schematic diagram of another kind of loss of data in the background technology;

Fig. 3 is a message flow schematic diagram of the prior art;

Fig. 4 is that the message flow of pre-authentication process in the prior art is to schematic diagram;

Fig. 5 is that message flow when sending RTT message in the prior art is to schematic diagram;

Fig. 6 is the schematic diagram that flows to when the CTT frame is transmitted in the prior art;

Flow to schematic diagram during frame that Fig. 7 stays for the related also collection with AP2 of STA in the prior art;

Fig. 8 is the flow chart of first embodiment provided by the invention;

Fig. 9 is the flow chart of the 5th embodiment provided by the invention;

Figure 10 is the flow chart of the 6th embodiment provided by the invention.

Embodiment

The invention provides a kind of method of avoiding loss of data in handoff procedure, its core is: when receiving terminal when local wireless access point AP switches to target AP, cache information is sent to wireless access point AP; Described AP handles the data that the transmitting terminal that receives sends to described receiving terminal according to described cache information, and the data after will handling by described target AP send to described receiving terminal.

First embodiment provided by the invention is when switching to the process of purpose access point AP2 as the STA of receiving terminal from local access point AP1, and its flow process comprises as shown in Figure 8:

Step 101, successful session and transfer of data between STA and the AP1.

Step 102, the pre-authentication that STA switches fast by AP1 and AP2.

After the pre-authentication success, execution in step 103, promptly STA sends FT Action buffer request (cache request of change action fast) message and gives AP1, comprises Buffer IE (BufferInformation Element) unit information in the described message.Be provided with the cache way and the cache location of data in the described Buffer IE unit information.

In the step 103, FT Action buffer request message adopts Action frame frame format, and its formal definition is as shown in table 1:

Category

Action

Target Address

Status Code

Count IE

Other IEs

Table 1

Target Address is the address of current AP in the table 1.

The frame structure of FT Action buffer request message is as shown in table 2:

Order	1	2	3	4	5
Order	1	2	3	4	5	Information	TIE(Reassociaton)	FT IE	RSN IE	EAPK IE	Buffer IE

Table 2

The form of the Buffer IE unit information in the table 2 is as shown in table 3:

Element ID

Length

Buffer identify

Table 3

Being provided with of Buffer Identify in the table 3 is as shown in table 4:

00	No buffer memory
00	No buffer memory	01	Data are sent to the target AP buffer memory by DS
10	Data cached at local AP	01	Data are sent to the target AP buffer memory by DS
10	Data cached at local AP	……	Keep

Table 4

As can be seen from Table 4, when the Buffer Identify in Buffer IE unit information is set to " no buffer memory " mode, be for compatible prior art.

Step 104, receive the FT Action buffer request message of STA transmission as AP1 after, the message that sends FT Action buffer response is to STA, obtain simultaneously and identification message in the BufferIE unit in information, and data are handled according to the information in the described Buffer IE unit.

If the setting among the Buffer Identify in the Buffer IE unit information in the described message is designated as the mode of " data are sent to the target AP buffer memory by DS ", so this moment the current wireless access point, after receiving this information as AP1, send FT Action buffer response message to STA, simultaneously data are issued STA, and send to the AP2 buffer memory by DS simultaneously.

If the setting among the Buffer Identify in the Buffer IE unit information in the described message is designated as the mode of " data cached at local AP ", so this moment the current wireless access point, after receiving this information as AP1, the message that sends FT Action buffer response is to STA, simultaneously data are issued STA, and simultaneously data are got up at local cache.

Step 105, STA and Target Wireless access point AP2 carry out the series of fortified passes connection.

When in AP1 when data cached, the processing procedure of step 105 is as follows:

STA sends Re association Req (reassociation requests) message and gives Target Wireless access point AP2; After described AP2 receives described Re association Req message, send Pick updata request (request of fetching data) message to AP1 and give described AP1; After described AP1 receives described Pick updata request message, return feedback Pick up data response (response of fetching data) message and give described AP2, and send corresponding data to described AP2, behind Data Transfer Done, send Pick up dataACK (affirmation of fetching data) message and give described AP2; After described AP2 AP2 receives this message, confirm that data all receive, then send the data to described STA, and simultaneously to STA loopback Re associationResp (re-association response) message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

When in AP2 when data cached, need not extracting data this moment in AP1, and the processing procedure of step 105 is as follows like this:

STA sends Re association Req (reassociation requests) message and gives Target Wireless access point AP2; After described AP2 receives described Re association Req message, give described STA, and send the data of preserving to STA simultaneously to STA loopback Reassociation Resp (re-association response) message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

Step 106, STA and Target Wireless access point AP2 carry out session and transfer of data.

Second embodiment provided by the invention, the difference of itself and first embodiment is:

In step 105, STA sends to the Buffer IE information element that also carries in the Re association request message of AP2 as describing among first embodiment.The configuration information of indicating among the Buffer IE that carries in the configuration information of indicating among the Buffer IE that carries in the described Re association request message and the FT Action buffer request message is consistent.

After AP2 receives this request message, obtain and identification message in information in the Buffer IE unit, and handle accordingly according to the information after the identification:

If the setting among the Buffer Identify in the Buffer IE information element in the described message is designated as " data cached at local AP ", after then AP2 receives " Re associationrequest " message that STA sends to, send " Pick up data request " message and give AP1; After AP1 receives this message, send " pick up data response " message and give AP2, and send to AP2 with data cached by DS simultaneously.After transmission finished, AP1 sent acknowledge message " pick up data ACK " and gives AP2.After AP2 receives this message, confirm that data all receive, then described data are sent to STA, and respond simultaneously and give a Re association of STA response message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

If the setting among the Buffer Identify in the Buffer IE information element in the described message is designated as " data are sent to the target AP buffer memory by DS ", this moment, AP2 directly sent to STA with data in buffer, and a Re association of STA response message is given in loopback simultaneously.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

Other process in the present embodiment and the associated description among first embodiment are identical, are not described in detail here.

The 3rd embodiment provided by the invention, the difference of itself and first embodiment is:

In step 105, STA sends to the Buffer IE information element that also carries in the Re association request message of AP2 as describing among first embodiment, also carries the sequence SN IE (sequence number information element) of the paid-in data of STA simultaneously.

The form of described SN IE is as shown in table 5:

Element ID

Length

SN

Table 5

If the setting among the Buffer Identify in the Buffer IE information element in the described message is designated as " data cached at local AP ", after then AP2 receives " Re associationrequest " message that STA sends to, this SN IE sequence information is included in " Pick up data request " message, and sends to AP1; After AP1 receives this message, send " pick up data response " message and give AP2, and simultaneously correspondence described SN IE information and data cached SN IE information are compared, the data of inconsistent SN IE information correspondence are sent to AP2 by DS, be about to the data that STA confiscates and send to AP2 by DS.After transmission finished, AP1 sent acknowledge message " pick up dataACK " and gives AP2.After AP2 receives this message, confirm that data all receive, then described data are sent to STA, and respond and give a Re association of STA response message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

Perhaps carry out according to following flow process:

AP2 directly sends " Pick up data request " message and gives AP1; After AP1 receives this message, send " pick up data response " message and give AP2, and simultaneously data in buffer is all issued AP2, and after transmission finishes, send acknowledge message " pick up data ACK " and give AP2; After AP2 receives this message, confirm that data all receive, then the data cached sequence information that the AP1 that receives is sent compares with the SN IE information of local data of preserving, select the data of inconsistent SN IE information correspondence then, and send it to STA, and respond and give a Reassociation response of STA message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

If the setting among the Buffer Identify in the Buffer IE information element in the described message is designated as " data are sent to the target AP buffer memory by DS ", this moment, AP2 compared the data sequence information among data in buffer sequence information and this SN IE, then will be simultaneously correspondence described SN IE information and data cached SN IE information be compared, select the data of inconsistent SN IE information correspondence then, and send it to STA, and respond and give a Re association of STA response message.Through said process, STA successfully joins with Target Wireless access point AP2 series of fortified passes.

In first three embodiment, WAP (wireless access point) is issued STA with data in data cached, can make full use of the resource of system like this, and can reduce the time delay that transmits data.

The 4th embodiment provided by the invention, its flow process still as shown in Figure 8, itself and first, second and the difference part of the 3rd embodiment be:

Receive " FT Action buffer request " message of STA transmission as AP1 after, send " FTAction buffer response " message and give described STA, and when sending " FT Action bufferresponse " message, no longer send data to STA, but, select corresponding cache way and cache location that data are carried out buffer memory according to the set-up mode that the buffer IE information of carrying in " FT Action bufferrequest " message is indicated.

Other process in the present embodiment and the associated description among first embodiment are identical, are not described in detail here.In the present embodiment, owing to when sending " FT Action buffer response " message, no longer send data to STA, and just carry out the process of buffer memory, thereby not as first three embodiment conserve system resources.

The 5th embodiment provided by the invention, the difference of itself and first embodiment is, in the present embodiment, is to carry Buffer IE unit information by the message in the verification process, indicates corresponding metadata cache mode.Its implementation process comprises as shown in Figure 9:

Step 301, successful session and transfer of data between STA and the AP1.

Step 302, the pre-authentication that STA switches fast by AP1 and AP2.In the process of authentication, STA sends in " FT Action ACK or response " message of AP1 and carries Buffer IE unit information; When described AP1 receives described message, according to the set-up mode of indicating in the described Buffer IE unit information, select corresponding cache way and cache location, and the data that send according to selected cache way and buffer memory location storage STA.Associated description among the concrete process of caching and first embodiment is identical, is not described in detail here.

Step 303, STA and Target Wireless access point AP2 carry out the series of fortified passes connection.Associated description among the implementation process of step 303 and first embodiment is identical, is not described in detail here.

After the series of fortified passes is unified into merit, execution in step 304, promptly STA and Target Wireless access point AP2 carry out successfully session and transfer of data.

The 6th embodiment provided by the invention, its main thought is: STA by AP1 and AP2 successfully carry out related after, STA sends a Data request to AP2, this message contains Buffer IE, perhaps contain SN IE simultaneously, after described AP2 receives described message, take corresponding processing method, send a Data response simultaneously to STA.Specific implementation process comprises as shown in figure 10:

Step 401, successful session and transfer of data between STA and the AP1.

Step 402, the pre-authentication that STA switches fast by AP1 and AP2.

After the pre-authentication success, execution in step 403, STA and Target Wireless access point AP2 carry out the series of fortified passes connection.

Step 401 is not described in detail to the same prior art of the process of step 403.

Next execution in step 404, and STA sends Data request to AP2, and this message contains the BufferIE unit.

After AP2 receives Data request message, obtain and identification message in information in the Buffer IE unit, and handle accordingly according to the information after the identification.Associated description in processing procedure and the foregoing description is similar, just in the present embodiment: when the setting among the Buffer Identify in the Buffer IE information element is designated as " data cached at local AP ", data cached at AP2, do not need afterwards in AP1, to extract data, and directly send data to STA; And another kind of situation, then with metadata cache in AP1, then need in AP1, to extract data, then send to STA again; While execution in step 405, promptly loopback Data response message is given STA.

If not only contain Buffer IE unit in the described message, but also when containing SN IE information, processing procedure same with the foregoing description in associated description similar, just be that loopback Data response message is to STA here.Be not described in detail this process in the present embodiment.

Last execution in step 406, promptly STA and Target Wireless access point AP2 carry out successfully session and transfer of data.

By the specific embodiments of the invention described above as can be seen, the present invention when receiving terminal when local wireless access point AP switches to target AP, cache information is sent to wireless access point AP; The transmitting terminal that described AP receives described AP according to described cache information sends to the data of described receiving terminal and handles, and the data after will handling send to described receiving terminal.By the present invention, can avoid the loss of data in the handoff procedure, greatly guaranteed data integrity; And among the present invention, needn't wait for just carrying out after current AP has transmitted data as the STA of receiving terminal and switch, thereby reduce handover delay.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims

1, a kind of method of avoiding loss of data in handoff procedure is characterized in that, comprising:

2, method according to claim 1 is characterized in that, described steps A specifically comprises:

Or,

3, method according to claim 2 is characterized in that, described steps A 1 specifically comprises:

Or,

4, method according to claim 3 is characterized in that, described steps A 1 also comprises:

Or,

5, method according to claim 2 is characterized in that, described steps A 2 specifically comprises:

Or,

6, according to any described method in the claim 1 to 5, it is characterized in that:

Be provided with data storage method in the described cache information, comprise data are sent to target AP buffer memory and data cached at local AP by distributed system DS.

7, according to claim 1,2,3,4 or 5 described methods, it is characterized in that described step B specifically comprises:

Or,

B12, target AP compare local AP data cached SN IE information of sending and the SN IE information of obtaining from described Reassociation Req message, select the data of inconsistent SN IE information correspondence then, and send it to described receiving terminal.

8, method according to claim 7 is characterized in that, among step B1, B3, B5 or the B9, the described data that the transmitting terminal that receives sent to described receiving terminal also comprise in the process that local AP carries out buffer memory:

Simultaneously described data are sent to described receiving terminal.

9, according to claim 1,2,3,4 or 5 described methods, it is characterized in that described step B specifically comprises:

Or,

10, method according to claim 9 is characterized in that, among step B13, B15 or the B17, the described data that the transmitting terminal that receives sent to described receiving terminal send to the process that target AP is carried out buffer memory by DS, also comprise:

Simultaneously described data are sent to described receiving terminal.