Method for scanning access points during station's handoff procedure in wireless communication system and station performing the method, and network interface supporting the method and wireless communication system enabling the method

• US 20080056211A1
• Filed: 02/16/2007
• Published: 03/06/2008
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Original Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Inventors: Jang, Kyung Hun, Hwang, Hyo Sun, Choi, Munhwan, Kim, Youngsoo, Choi, Sunghyun, Jin, Sunggeun
• Granted Patent: US 8,194,606 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 2101/677 Multiple interfaces, e.g. multihomed nodes
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A wireless communication system includes at least one AP assigned with a unique MAC address and a shared virtual MAC address; and at least one mobile station to search the at least one AP, receive AP information from the retrieved AP, and perform a handoff, wherein the mobile station transmits query data to the shared virtual MAC address, receives response data from the AP, determines whether the AP exists on a predetermined channel, and when the AP exists on the channel, requests the AP having the shared virtual MAC address for AP information, and receives the AP information from the AP.

Claims

1. A method of scanning an access point (AP) during a handoff procedure of a mobile station in a wireless communication system, the method comprising:

transmitting query data to at least one AP on a predetermined channel;

receiving response data about the query data from the AP on the predetermined channel;

requesting AP information from the AP that has transmitted the response data; and

receiving the AP information from the AP.

2. The method according to claim 1, wherein the receiving of the response data comprises:

switching from the predetermined channel to another channel to transmit the query data, when the response data was not received from the AP via the predetermined channel.

3. The method according to claim 1, wherein the AP information comprises at least one of a Media Access Control (MAC) address of the AP, a beacon interval, and a supported data rate.

4. The method according to claim 1, wherein the at least one AP has a shared virtual MAC address.

5. The method according to claim 4, wherein the shared virtual MAC address is known to the mobile station.

6. The method according to claim 4, wherein:

the transmitting the query data comprises transmitting a Reset-to-Send (RTS) control frame from the mobile station to the shared virtual MAC address; and

the receiving the response data comprises receiving a Clear-to-Send (CTS) control frame from the AP.

7. The method according to claim 4, further comprising:

transmitting the query data to the predetermined channel and at least one other channel at a predetermined minimum data rate value;

re-transmitting the query data by increasing the minimum data rate value, when the response data about the query data is received from the AP; and

repeating the re-transmitting until the response data is not received from the AP; and

determining a data rate of previous query data as a maximum achievable data rate with respect to a corresponding channel, when the response data is not received from the AP.

8. The method according to claim 7, wherein the wireless communication system is a wireless local area network (WLAN) according to an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, and, in the re-transmitting, the data rate is any one of 6 Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 24 Mbps, 36 Mbps, 48 Mbps, and 54 Mbps.

9. The method according to claim 7, further comprising:

recording an average signal-to-noise ratio (SNR) in a predetermined table, based on the maximum achievable data rate determined for each channel and the response data received via the predetermined channel,

wherein the AP is determined according to predetermined criteria.

10. The method according to claim 9, wherein the predetermined criteria comprise:

having a maximum value from the maximum achievable data rate that is stored in the predetermined table; and

having the highest average SNR when the maximum achievable data rate is identical.

11. The method of claim 4, further comprising:

transmitting the query data to the channel and at least one other channel at a predetermined minimum data rate value;

re-transmitting the query data by increasing a minimum data rate value, when the response data about the query data is received from the AP; and

repeating the re-transmitting until the response data is received, and requesting AP information from the AP when the increased data rate is greater than a predetermined minimum data rate.

12. The method of claim 4, wherein:

the requesting the AP information comprises transmitting a Probe Request to the shared virtual MAC address; and

the receiving the AP information comprises receiving a Probe Response from the AP.

13. The method of claim 12, further comprising:

waiting to receive the Probe Response for a first MaxChannelTime by the mobile station after transmitting the Probe Request.

14. The method of claim 13, further comprising:

waiting to receive the Probe Response for a second MaxChannelTime by the mobile station, when the mobile station did not receive the Probe Response after the first MaxChannelTime has elapsed.

15. A method of scanning an access point (AP) during a handoff procedure of a mobile station in a wireless communication system, the method comprising:

receiving a beacon transmitted from at least one AP having a shared virtual Media Access Control (MAC) address;

determining whether the AP exists on a channel, based on an AP channel report (ACR) contained in the beacon;

transmitting a Probe Request frame to the shared virtual MAC address, when the AP exists on the channel; and

receiving a Probe Response frame from the AP.

16. The method of claim 15, wherein the shared virtual MAC address is known to the mobile station.

17. The method of claim 15, further comprising:

waiting to receive the Probe Response frame for a first MaxChannelTime by the mobile station after transmitting the Probe Request frame.

18. The method of claim 17, further comprising:

waiting to receive the Probe Response frame for a second MaxChannelTime by the mobile station, when the mobile station did not receive the Probe Response frame after the first MaxChannelTime has elapsed.

19. A network interface in an access point (AP) of a wireless communication system, the network interface comprising:

a Media Access Control (MAC) driver to record a shared virtual MAC address and a unique MAC address assigned to the AP;

a Physical Layer (PHY) controller to interface with a transmission media according to the wireless communication system; and

a scanning component to communicate with a mobile station, via the PHY controller, using the shared virtual MAC address and to scan APs during a handoff procedure.

20. The network interface of claim 19, wherein the wireless communication system is a wireless local area network (WLAN) according to IEEE 802.11 standards.

21. A mobile station to scan at least one access point (AP) of a wireless communication system, the mobile station comprising:

an address table to record a shared virtual Media Access Control (MAC) address assigned to the AP;

a PHY controller to interface with the AP via a transmission media according to the wireless communication system; and

a scanning component to communicate with the AP, via the PHY controller, using the shared virtual MAC address and to scan the at least one AP during a handoff procedure.

22. The mobile station of claim 21, wherein the wireless communication system is a wireless local area network (WLAN) according to IEEE 802.11 standards.

23. A wireless communication system comprising:

at least one access point (AP) assigned with a unique Media Access Control (MAC) address and a shared virtual MAC address; and

at least one mobile station to search for the at least one AP, receive AP information from the AP, and perform a handoff,

wherein the mobile station transmits query data to the shared virtual MAC address, receives response data from the AP, determines whether the AP exists on a predetermined channel, and, when the AP exists on the channel, requests AP information from the AP having the shared virtual MAC address, and receives the AP information from the AP.

24. The wireless communication system of claim 23, wherein the wireless communication system corresponds to a wireless local area network WLAN according to IEEE 802.11 standards, the query data corresponds to an RTS control frame, the response data corresponds to a Clear-to-Send (CTS) frame, the mobile station requests AP information from the AP using a Probe Request frame, and the AP transmits the AP information to the mobile station using the Probe Response frame.

25. A computer readable medium having computer-executable instructions to perform a method comprising:

transmitting query data to at least access point (AP) on a predetermined channel;

receiving response data about the query data from the AP on the predetermined channel;

requesting AP information from the AP that transmitted the response data; and

receiving the AP information from the AP.

26. A computer readable medium having computer-executable instructions to perform a method comprising:

determining whether an access point (AP) exists on a channel based on an AP channel report contained in a beacon transmitted from at least one AP having a shared virtual Media Access Control (MAC) address;

transmitting a Probe Request frame to the shared virtual MAC address, when the AP exists on the channel; and

receiving a Probe Response frame from the AP.

27. A method to reduce scanning latency during a handoff, the method comprising:

detecting at least one access point (AP) using a shared virtual Media Access Control (MAC) address recorded in each of the at least one APs; and

acquiring information about each detected AP.

28. A network interface comprising:

a detection component to detect at least one access point (AP) using a shared virtual Media Access Control (MAC) address recorded in each of the at least one APs; and

an information acquiring component to acquire information about each detected AP.