CN101909339A - Method and device for roaming in wireless local area network - Google Patents

Abstract

The invention provides a method and a device for roaming in a wireless local area network. The method and the device for roaming in the wireless local area network take all types of frames sent by the connected access points as the basis for updating the received signal strength indicating value. In addition, the device also actively sends an invalid frame to the connected access point and updates the RSSI according to the ACK frame returned by the access point.

Description

Method and device for roaming in wireless local area network

technical field

The invention relates to a communication system, in particular to a method and device for roaming in a wireless local area network.

Background technique

With the increasing popularity of wireless local area network (WLAN), various applications are also developing rapidly, and many teams have also invested in research on improving the quality of data transmission in wireless networks. In a wireless local area network, a mobile wireless transmit/receive unit (Wireless Transmit/ReceiveUnit, WTRU) may be within the signal transmission range of multiple access points (Access Point, AP) at the same time. When the WTRU is roaming among multiple access points, the connected access point may need to be adjusted according to the location and signal quality.

FIG. 1 describes the situation where a station 13 roams from the transmission range of one access point 11 to the transmission range of another access point 12 in a wireless local area network. FIG. 2 shows that under ideal conditions, the station 13 moves from left to right with time, and the received signal strengths of the access point 11 and the access point 12 are shown in curves 21 and 22 respectively. The signal strength detected by the station 13 is determined according to the periodic beacons (beacons) sent by the access point 11 and the access point 12, and the period is about 50 ms. The station 13 can decide who to connect to based on the strength of its received signal. For example, station 13 remains connected to access point 11 until time Ts. After the time Ts, since the strength of the signal received by the station 13 from the access point 11 is already lower than the signal strength of the access point 12, the connection object of the station 13 changes to the access point 12. However, in some cases, the signal strength of the originally connected access point 11 may be instantly and greatly reduced due to the change of the use environment, rather than being gradually reduced. For example, the access point 11 is an access point configured in a meeting room. The user leaves the meeting room with the station 13 and closes the door, and moves towards the access point 12 outside the meeting room. FIG. 3 shows the signal strength of the access point 11 and the access point 12 changing with time in this situation. In FIG. 3 , when the door is closed (time T0 ), the signal of the access point 11 has dropped significantly, and the station 13 should switch the connection object to the access point 12 at this time. However, because the current mechanism is to update the signal strength of AP 11 according to the periodic beacon signal of AP 11, when station 13 finds that the signal of AP 11 is quite weak at time T1, it has already been T1 The time of -T0 cannot receive the signal normally. During this delay period, in addition to being unable to transmit and receive frames, important frames may also be lost. Therefore, how to update the signal value of the access point more quickly to achieve seamless roaming has become a direction of industry efforts.

Contents of the invention

The method and device for roaming in the wireless local area network of the present invention use all frames sent by the connected access point as the basis for updating the received signal strength indicator value. In addition, an invalid frame is also actively sent to the connected access point, and the RSSI value is updated according to the acknowledgment frame replied by the access point.

One aspect of the present invention discloses a method for roaming in a wireless local area network, the method comprising the steps of: receiving a plurality of frames sent by a first access point; updating at least one received signal according to any one of the plurality of frames a strength indicator value; and if the at least one received signal strength indicator value is less than a threshold or the time from receiving the previous frame exceeds a set time, connect to the second access point.

Another aspect of the present invention discloses a method for roaming in a wireless local area network, the method comprising the steps of: periodically sending an invalid frame to a first access point; receiving at least one frame sent by the first access point ; update at least one received signal strength indicator value according to the at least one frame; and if the at least one received signal strength indicator value is less than a threshold or the time from receiving the previous frame exceeds a set time, connect to the second access point.

Another aspect of the present invention discloses a frame receiving device, which includes a sending unit, a receiving unit, an updating unit, a judging unit, and a switching connection unit. The sending unit is used for periodically sending at least one invalid frame to the first access point. The receiving unit is used for receiving a plurality of frames sent by the first access point. The updating unit is used for updating at least one RSSI value according to any one of the plurality of frames. The judging unit is used for judging whether the at least one RSSI value is smaller than a threshold or whether the time from receiving the previous frame exceeds a set time. The switch connection unit connects to the second access point according to the determination result of the determination unit.

Description of drawings

Fig. 1 has described the situation that the station roams in the wireless network;

Fig. 2 shows the situation that the received signal strength indication value changes with time;

Figure 3 shows another RSSI value over time:

FIG. 4 shows a flowchart of a method for roaming in a wireless local area network according to an embodiment of the present invention;

FIG. 5 shows a flowchart of a method for roaming in a wireless local area network according to another embodiment of the present invention; and

FIG. 6 depicts a block diagram of an apparatus for roaming in a WLAN according to yet another embodiment of the present invention.

Description of main component symbols

11, 12 access point

13 Sites

S401～S407 steps

S501～S508 steps

601 sending unit

602 receiving unit

603 update unit

604 Judgment unit

605 Switch connection unit

Detailed ways

FIG. 4 shows a flowchart of a method for roaming in a WLAN according to an embodiment of the present invention. In order to enable those skilled in the art to implement the present invention through the instructions of this embodiment, the flow of the frame receiving method will be described below with reference to FIG. 1 and FIG. 4 . Assume station 13 completes a standard channel scan procedure. The AP candidate list generated according to the standard channel scanning procedure includes the AP 11 and the AP 12 , and the station 13 is currently connected to the AP 11 . The aforementioned access point 11, access point 12, and station 13 are all devices conforming to the 802.11 standard specified by the Institute of Electrical and Electronics Engineering. In step S401, the process of this embodiment starts. In step S402, it is determined whether any type of frame sent by the access point 11 is received. The frame type includes but not limited to: Data frame, Control frame and Management frame. The control frame includes, for example, a Request to Send (RTS) frame, a Clear to Send (CTS) frame, an Acknowledgment frame or a Power Saving Poll (PS-Poll) frame. Management frames include, for example, beacon (beacon) frames, authentication (Authentication) frames, de-authentication (De-authentication) frames, connection request (Association request) frames, connection response (Association response) frames, reconnection request (Re- Association request frame, Re-association response frame, Disassociation response frame, Probe request frame, Probe response frame or Announcement Traffic Indication Message, ATIM) frame. If not, it is judged in step S403 whether the time since the last frame reception exceeds the set time. The set time is less than or equal to 100ms, and in this embodiment, the set time is 100ms. If not, return to step S402. If yes, switch the connection to the access point 12 in step S406. In step S402, if any frame is received, in step S404 the station 13 updates the received signal strength indication (Received Signal Strength Indication, RSSI) value according to the frame. In step S405, it is judged whether the latest RSSI value is smaller than a threshold. If yes, switch the connection to the access point 12 in step S406. The process of this embodiment may end in step S407, or repeat steps S402 to S406 again.

FIG. 5 shows a flowchart of a method for roaming in a WLAN according to another embodiment of the present invention. In order to enable those skilled in the art to implement the present invention through the instruction of this embodiment example, the flow of the frame receiving method will be described below with reference to FIG. 1 and FIG. 5 . Assume that station 13 has completed the standard channel scanning procedure. The AP candidate list generated according to the standard channel scanning procedure includes the AP 11 and the AP 12 , and the station 13 is currently connected to the AP 11 . The aforementioned access point 11 , access point 12 , and station 13 are devices conforming to the 802.11 standard specified by the Institute of Electrical and Electronics Engineering. In step S501, the process of this embodiment starts. In step S502 , the station 13 actively periodically sends null (Null) frames to the access point 11 . The period is less than or equal to 50ms, and the period is set to 50ms in this embodiment. In step S503, it is determined whether the Acknowledgment frame sent by the access point 11 or other types of frames, such as data frames, control frames or management frames, are received. Control frames include request-to-send, clear-to-send, acknowledgment, or power-save poll frames. Management frames include beacon frames, authentication frames, deauthentication frames, connection request frames, connection response frames, reconnection request frames, reconnection response frames, disconnection response frames, probe request frames, probe response frames, or announcement flow indication information frames . If not, it is determined in step S504 whether the time since the last frame reception exceeds the set time. The set time is less than or equal to 100ms, and this embodiment sets the time to 100ms. If not, return to step S502. If yes, switch the connection to the access point 12 in step S507. In step S503, if any frame is received, then in step S505 the station 13 updates the RSSI value according to the frame. In step S506, it is judged whether the latest RSSI value is smaller than a threshold. If yes, switch the connection to the access point 12 in step S507. The process of this embodiment may end in step S508, or repeat steps S502 to S507 again.

FIG. 6 depicts a block diagram of an apparatus for roaming in a WLAN according to yet another embodiment of the present invention. The present implementation example is described below with reference to FIG. 1 and FIG. 6 . The device 600 for roaming in a WLAN includes a sending unit 601 , a receiving unit 602 , an updating unit 603 , a judging unit 604 and a switching connection unit 605 . The sending unit 601 is configured to periodically send invalid frames to the access point 11 . The period is less than or equal to 50ms, and the period is set to 50ms in this embodiment. The receiving unit 602 is configured to receive frames sent by the access point 11 . The update unit 603 is used for updating the RSSI value according to the frame sent by the access point 11 . The judging unit 604 is used for judging whether the RSSI value is smaller than a threshold, or whether the time from receiving the previous frame exceeds a set time. The set time is less than or equal to 100ms, and this embodiment sets the time to 100ms. When the latest RSSI value is less than the threshold or the time from receiving the previous frame exceeds the set time, the switching connection unit 605 switches the connection to the access point 12 .

The method and device for roaming in the wireless local area network of the present invention use all frames sent by the connected access point as the basis for updating the received signal strength indicator value. In addition, an invalid frame is also actively sent to the connected access point, and the RSSI value is updated according to the acknowledgment frame returned by the access point. The method and device for roaming in the wireless local area network of the present invention can quickly update the connection status of the access point it is connected to, and switch when the received signal strength indicator value is less than the threshold or the time from receiving the previous frame exceeds the set time Connect to another access point.

The technical content and technical features of the present invention have been disclosed above, but those skilled in the art may still make various replacements and modifications based on the instructions and disclosures of the present invention without departing from the essence of the present invention. Therefore, the protection scope of the present invention should not be limited to the contents disclosed in the embodiments, but should include various replacements and modifications that do not deviate from the present invention, and are covered by the claims.

Claims (20)

1. method that roves WLAN comprises:

Receive a plurality of frames that first access point sends;

Upgrade at least one received signal strength indicator value according in these a plurality of frames any one; And

If this at least one received signal strength indicator value surpasses setting-up time less than the time of threshold value or the previous frame of distance reception, then be connected with second access point.

2. method according to claim 1, it further comprises and scans program according to the standard channel and produce to connect short-list.

3. method according to claim 2, wherein this connection short-list comprises this first access point and this second access point.

4. method according to claim 1, wherein the kind of these a plurality of frames comprises Frame, control frame and management frames.

5. method according to claim 4, wherein this control frame is request transmit frame, clear to send frame, acknowledgement frame or power-save poll frame.

6. method according to claim 4, wherein this management frames be beacon frame, authentication frame, releasing authentication frame, association request frame, connection response frame, again association request frame, again the connection response frame, remove connection response frame, probe request, probing response frame or bulletin traffic indication information frame.

7. method according to claim 1, wherein this setting-up time is less than or equal to 100ms.

8. method that roves WLAN comprises:

Periodically send invalid frame to the first access point;

Receive at least one frame that this first access point sends;

According at least one received signal strength indicator value of this at least one frame update; And

If this at least one received signal strength indicator value surpasses setting-up time less than the time of threshold value or the previous frame of distance reception, then be connected with second access point.

9. method according to claim 8, it further comprises and scans program according to the standard channel and produce to connect short-list.

10. method according to claim 9, wherein this connection short-list comprises this first access point and this second access point.

11. method according to claim 8, wherein this at least one frame is an acknowledgement frame.

12. method according to claim 8, wherein this at least one frame is Frame, control frame or management frames.

13. method according to claim 12, wherein this control frame is request transmit frame, clear to send frame or power-save poll frame.

14. method according to claim 12, wherein this management frames be beacon frame, authentication frame, releasing authentication frame, association request frame, connection response frame, again association request frame, again the connection response frame, remove connection response frame, probe request, probing response frame or bulletin traffic indication information frame.

15. method according to claim 8, wherein this cycle is less than or equal to 50ms, and this setting-up time is less than or equal to 100ms.

16. a device that is used to rove WLAN comprises:

Transmitting element is in order to periodically to send at least one invalid frame to the first access point;

Receiving element is in order to receive a plurality of frames that this first access point sends;

Updating block is in order at least one the received signal strength indicator value of any one frame update in these a plurality of frames of basis;

Whether whether judging unit receive the time of previous frame above setting-up time less than threshold value or distance in order to judge this at least one received signal strength indicator value; And

Switch linkage unit, switch according to the judged result of this judging unit and be connected to second access point.

17. device according to claim 16, wherein the kind of these a plurality of frames comprises Frame, control frame and management frames.

18. device according to claim 17, wherein this control frame is request transmit frame, clear to send frame, acknowledgement frame or power-save poll frame.

19. device according to claim 17, wherein this management frames be beacon frame, authentication frame, releasing authentication frame, association request frame, connection response frame, again association request frame, again the connection response frame, remove connection response frame, probe request, probing response frame or bulletin traffic indication information frame.

20. device according to claim 16, wherein should the cycle less than 50ms, this setting-up time is less than 100ms.

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