High-speed roaming method of wireless LAN

• US 6,917,804 B2
• Filed: 07/10/2001
• Issued: 07/12/2005
• Est. Priority Date: 07/11/2000
• Status: Active Grant

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Clarion Co., Ltd. (Faurecia SA)
• Inventors: Sato, Kiyotaka, Takayama, Takashi
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): PEREZ, ANGELICA
• Application Number:
  US09/901,134
• Publication Number:
  US 20020025810A1
• Time in Patent Office: 1,463 Days
• Field of Search: 455/403, 455/432.1, 455/432.2, 455/432.3, 455/434, 455/43, 370/338, 370/329
• US Class Current: 455/432.1
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 48/20 Selecting an access point

Abstract

All access points are operated synchronously, and monitor the beacon to mate with the hopping frequency of the neighboring access point. Accordingly, the station can grasp the up-to-date radio situation of the neighboring access point to be entered subsequently, and constructs the information as the database. As a result, when the beacon quality of the current subscription (connected) access point is reduced lower than the threshold value, the hopping channel and the hopping pattern are fitted to the neighboring access point having the best communication environment by referring the database, and then the subscription operation is applied directly.

Claims

1. A high-speed roaming method of a wireless LAN comprising:

a network;

a plurality of access points provided in the network; and

a mobile terminal that is radio-connected to one of said plurality of access points via a communication system using a frequency hopping,

wherein each of said access points;

registers previously a predetermined number of access points out of respective neighboring access points as neighboring access points;

sends out hopping information thereof periodically to the network at mutually different timings;

receives the hopping information of the neighboring access points out of the respective neighboring access points to construct a database; and

synchronizes all of said access points in a same subnet of the network and sends out radio beacons synchronously from said access points; and

wherein said mobile terminal;

monitors said radio beacons of a connected access point and downloads hopping information of the neighboring access points from said connected access point;

monitors radio beacons of said neighboring access points based on the hopping information;

constructs the hopping information as a mobile terminal database to continuously compare radio environments; and

selects and connects an access point having a best radio situation by referring the mobile terminal database of said neighboring access points when a quality of the radio beacon of said connected access point is reduced lower than a predetermined value,

wherein, when said mobile terminal is not connected to said access point having said best radio situation, said mobile terminal is connected subsequently to an access point having a second best radio situation.

2. The high-speed roaming method of a wireless LAN according to claim 1, wherein

each of said access points sets one access point of said access points as a master access point, and sets the access points other than said master access point as slave access points,

said master access point sends out a master beacon containing time information to the network at a predetermined time interval, and

said slave access points are operated in synchronism with said master access point by receiving said master beacon and comparing time information contained in said master beacon with time information of each of said slave access points.

3. The high-speed roaming method of a wireless LAN according to claim 2, wherein

when an operation of said master access point is stopped because of a predetermined reason, a backup access point connected to the same subnet backs-up said master access point in place of said master access point.

4. The high-speed roaming method of a wireless LAN according to claim 1, wherein

said mobile terminal is not connected to all of said neighboring access points, said mobile terminal is connected to said access point having a good communication situation by scanning all frequency channels.

5. The high-speed roaming method of a wireless LAN according to claim 1, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

6. The high-speed roaming method of a wireless LAN according to claim 2, wherein

when said mobile terminal is not connected to all neighboring access points, said mobile terminal is connected to said access point having a good communication situation by scanning all frequency channels.

7. The high-speed roaming method of a wireless LAN according to claim 3, wherein

when said mobile terminal is not connected to all neighboring access points, said mobile terminal is connected to said access point having a good communication situation by scanning all frequency channels.

8. The high-speed roaming method of a wireless LAN according to claim 1, wherein

when said mobile terminal is not connected to all neighboring access points, said mobile terminal is connected to said access point having a good communication situation by scanning all frequency channels.

9. The high-speed roaming method of a wireless LAN according to claim 2, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

10. The high-speed roaming method of a wireless LAN according to claim 3, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

11. The high-speed roaming method of a wireless LAN according to claim 1, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

12. The high-speed roaming method of a wireless LAN according to claim 4, wherein

said mobile, terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

13. The high-speed roaming method of a wireless LAN according to claim 5, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

14. The high-speed roaming method of a wireless LAN according to claim 7, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

15. The high-speed roaming method of a wireless LAN according to claim 8, wherein

said mobile terminal is connected to said access point having a best communication situation, by scanning all connectable access points out of said access points provided in the network at a rising time.

16. The high-speed warning method of a wireless LAN according to claim 3, wherein said backup access point comprises:

an access point having a smallest hopping set number.

17. The high-speed roaming method of a wireless LAN according to claim 3, wherein said backup access point is set based on a set alias name.

18. The high-speed roaming method of a wireless LAN according to claim 3, wherein said backup access point is set based on a MAC identification.

19. The high-speed roaming method of a wireless LAN according to claim 1, wherein said mobile terminal monitors said radio beacons to mate with the hopping information of the neighboring access point since said access points are operated synchronously.

20. The high-speed roaming method of a wireless LAN according to claim 1, wherein said mobile terminal fits a hopping channel and a hopping pattern to one the neighboring access point having the best radio situation.

21. The high-speed roaming method of a wireless LAN according to claim 19, wherein said mobile terminal transmits a probe request frame.

22. The high-speed roaming method of a wireless LAN according to claim 21, wherein said mobile terminal receives a probe response frame from said neighboring access point having the best radio situation.

23. The high-speed roaming method of a wireless LAN according to claim 22, wherein said mobile terminal decides the neighboring access point having the best radio situation and transmits an authentication request frame to the neighboring access point having the best radio situation.