Fast channel switching scheme for IEEE 802.11 WLANs

• US 7,352,728 B2
• Filed: 11/05/2002
• Issued: 04/01/2008
• Est. Priority Date: 03/07/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Soomro, Amjad
• Primary Examiner(s): Trost; William
• Assistant Examiner(s): SANTIAGO CORDERO, MARIVELISSE
• Application Number:
  US10/288,098
• Publication Number:
  US 20030171116A1
• Time in Patent Office: 1,974 Days
• Field of Search: 455/95, 455/452.1, 370/338, 370/437
• US Class Current: 370/338
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Disclosed is a method and system for switching at least one wireless node located within the coverage area of a basic-service set (BSS) or infrastructure-basic-service set (IBSS) in a wireless-local-area network (WLAN) from a first communication channel to a second communication channel. The method includes: determining whether the second communication channel to be used by at least one wireless node is needed; broadcasting by a source node a management frame to at least one of the wireless node when it is determined that the second communication channel is needed, the management frame including a channel-switch time and a second communication channel identifier; and switching, at least one wireless node receiving the management frame, from the first communication channel to a second communication channel within a countdown time corresponding to the channel switch time, wherein the channel-switch time is less than a beacon interval.

Claims

1. A method for switching at least two wireless nodes of a plurality of wireless nodes, located within the coverage area of a basic-service set (BSS1) or infrastructure basic-service set (IBSS) in a wireless-local-area network (WLAN), from a first communication channel to a second communication channel, the method comprising the steps of:

(a) determining whether said second communication channel to be used by said at least two wireless nodes is needed;

(b) broadcasting, by a source node, a management frame including a channel switch announcement element (CSAE) to said at least two wireless nodes when it is determined in step (a) that said second communication channel is needed, said CSAE including at least a channel-switch time and a second communication channel identifier;

(c) switching, at said at least two wireless nodes receiving said management frame including said CSAE, from said first communication channel to said second communication channel within a countdown time corresponding to said channel-switch time, wherein said channel-switch time is specified in microseconds independent of a beacon interval;

(d) determining, in a second node of said at least two wireless nodes, that said management frame including said CSAE was not received by a first node of said at least two wireless nodes; and

(e) re-transmitting, in dependence on said determination, said management frame including said CSAE from said second node of said at least two wireless nodes that received said management frame including said CSAE.

2. The method as claimed in claim 1, wherein said step (c) of switching said at least to wireless nodes further comprises the step of:

detecting the end of the received management frame at each of said at least two wireless nodes to initiate a countdown of said channel-switch time.

3. The method as claimed in claim 1, wherein said source node is selected from the group consisting of:

an access point (AP1) located in a coverage area of said BSS and a station (STA) located in a coverage area of said IBSS.

4. The method as claimed in claim 1, wherein said step (a) of determining whether said second communication channel is needed uses a criteria selected from the group consisting of:

interference to the channel quality in said first communication channel or meeting other regulatory requirements.

5. The method as claimed in claim 1, wherein said method further comnprises the step of:

allowing frame exchanges to continue in said first communication channel prior to the expiration of said channel-switch time.

6. A method for switching at least two wireless nodes of a plurality of wireless nodes, located within the coverage area of a basic-service set (BSS1) or infrastructure-basic-service set (IBSS), in a wireless-local-area network (WLAN) from a first communication channel to a second communication channel, the method comprising the steps of:

(a) determining whether said second communication channel to be used by said at least two wireless nodes is needed;

(b) broadcasting, by a source node, a first management frame including a channel switch announcement element (CSAE) to said at least two wireless nodes when it is determined in step (a) that said second communication channel is needed, said first management frame including said CSAE including a channel-switch time and a second communication channel identifier;

(c) upon receiving said broadcasted first management frame including said CSAE at said at least two wireless nodes, halting all further frame exchanges in said first communication channel to quiet said first communication channel during the duration of the channel-switch time;

(d) determining, in a second node of said at least two wireless nodes, that said first management frame including said CSAE was not received by a first node of said at least two wireless nodes; and

(e) re-transmitting, in response to said determination, said first management frame including said CSAE from said second node of said at least two wireless nodes that received said first management frame including said CSAE.

7. The method as claimed in claim 6, wherein the switching step further comprises the step of:

detecting the end of the first management frame including said CSAE, received at each of said at least two wireless nodes to initiate said countdown time.

8. The method as claimed in claim 6, wherein said source node is selected from the group consisting of:

an access point (AP) in said BSS and a STA in said IBSS located within said coverage area.

9. The method as claimed in claim 6, wherein said step (a) of determining whether said second communication channel is needed uses a criteria selected from the group consisting of:

interference to the channel quality in said first communication channel or meeting other regulatory requirements.

10. The method as claimed in claim 6, wherein said determining step further comprises the step of:

receiving a second management frame from said at least two wireless nodes receiving said first management frame.

11. A system for switching at least two wireless nodes of a plurality of wireless nodes located within the coverage area of a basic-service set (BSS1) or infrastructure-basic-service set (IBSS) in a wireless-local-area network (WLAN) from a first communication channel to a second communication channel, the system comprising:

means for determining whether said second communication channel to be used by said at least two wireless nodes is needed;

means for broadcasting, by a source node, a management frame including a channel switch announcement element (CSAE) to said at least two wireless nodes when it is determined that said second communication channel is needed, said management frame including said CSAE including a channel-switch time and a second communication channel identifier;

means for switching, at each of said at least two wireless nodes receiving said management frame including said CSAE, from said first communication channel to said second communication channel at the expiration of a countdown time corresponding to said channel-switch time, wherein said channel-switch time is independent of the beacon interval;

means for determining, at a second node of said at least two wireless nodes, that said management frame including said CSAE was not received by a first node of said at least two wireless nodes; and

means for re-transmitting said management frame including said CSAE from the second node of said at least two wireless nodes that received said management frame including said CSAE.

12. The system as claimed in claim 11, wherein said means for switching further comprises:

means for detecting the end of the received management frame at each of said at least two nodes to initiate a countdown of said channel-switch time.

13. A system for switching at least two wireless nodes of a plurality of wireless nodes located within the coverage area of a basic-service set (BSS) or infrastructure-basic-service set (IBSS) in a wireless-local-area network (WLAN) from a first communication channel to a second communication channel, the system comprising:

means for determining whether said second communication channel to be used by said at least two wireless nodes is needed;

means for broadcasting, by a source node, a first management frame including a channel switch announcement element (CSAE) to said at least two wireless nodes when it is determined that said second communication channel is needed, said CSAE including a channel-switch time and a second communication channel identifier;

means for halting all further frame exchanges in said first communication channel to quiet said first communication channel upon receiving said broadcasted first management frame including said CSAE at said at least two wireless nodes;

means for determining, at a second of node of said at least two wireless nodes, that said first management frame including said CSAE was not received by a first node of said at least two wireless nodes; and

means for re-transmitting said first management frame including said CSAE from the second node of said at least two wireless nodes that received said first management frame including said CSAE.

14. The system as claimed in claim 13, wherein said system further comprises:

means for switching from said first communication channel to second communication channel, at each of said at least two wireless nodes receiving said first management frame including said CSAE, within a countdown time corresponding to said channel-switch time, wherein said channel-switch time is at least one beacon interval and is independent of the beacon interval.