Wireless LANs and neighborhood capture

• US 7,995,544 B2
• Filed: 09/28/2007
• Issued: 08/09/2011
• Est. Priority Date: 11/02/2001
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Inventors: Benveniste, Mathilde
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US11/864,313
• Publication Number:
  US 20080019343A1
• Time in Patent Office: 1,411 Days
• Field of Search: 370/338, 370/349, 370/350, 370/447, 455/443, 455/452.1
• US Class Current: 370/338
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/02 Hybrid access
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Overlapped wireless LAN cells in a medium have an equal chance at establishing a session on the medium. A first member station in the first cell transmits a timing packet containing a timestamp value, which is received at a second member station in the second cell. This synchronizes member stations in the first and second cells to interrupt transmissions at a global channel release instant corresponding to the timestamp value. The member stations in the first and second cells then have the opportunity to contend for access to the medium following the global channel release instant, using a slotted CSMA/CA access method. Each of the member stations in the first and second cells has a superframe clock that is synchronized based on the timestamp value, thereby establishing a periodic global channel release instant during each of a plurality of periodic superframes. The member stations can then periodically interrupt transmissions at the periodic global channel release instant to contend for the medium. The periodic global channel release instant occurs at intervals that are sufficiently close to meet delay and jitter restrictions for time-critical voice and video applications.

Claims

1. A method to enable overlapping first and second wireless local area network cells to have an equal chance at establishing a session on a medium, the first wireless local area network cell including a first plurality of member stations and the second wireless local area network cell including a second plurality of member stations, comprising:

transmitting by a first member station in the first wireless local area network cell, a timing packet containing a timestamp value;

receiving the timing packet at a second member station in the second wireless local area network cell;

interrupting transmissions by the first plurality of member stations in the first wireless local area network cell and by the second plurality of member stations in the second wireless local area network cell at a global channel release instant based on the timestamp value; and

permitting the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell to contend for access to the medium following the global channel release instant.

2. The method of claim 1, which further comprises:

synchronizing a superframe clock in the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell based on the timestamp value;

establishing the global channel release instant at the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell during each of a plurality of periodic superframes based on the superframe clock; and

periodically interrupting transmissions at the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell at the global channel release instant.

3. The method of claim 2, which further comprises:

periodically permitting the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell to contend for access to the medium following the global channel release instant.

4. The method of claim 3, which further comprises:

the global channel release instant occurring at intervals to meet delay and jitter restrictions for time-critical voice applications.

5. The method of claim 3, which further comprises:

the global channel release instant occurring at intervals to meet delay and jitter restrictions for time-critical video applications.

6. The method of claim 3, which further comprises:

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell contending for access to the medium using a slotted carrier sense multiple access with collision avoidance access method following the global channel release instant.

7. The method of claim 6, which further comprises:

conducting a distributed coordination function session by one of the first plurality of member stations in the first wireless local area network cell or one of the second plurality of member stations in the second wireless local area network cell that has successfully accessed the medium following the global channel release instant.

8. The method of claim 6, which further comprises:

conducting a tiered contention multiple access session by one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell that has successfully accessed the medium following the global channel release instant.

9. The method of claim 6, which further comprises:

conducting a point coordination function session by one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell that has successfully accessed the medium following the global channel release instant.

10. The method of claim 6, which further comprises:

requiring that the medium be free of all activity at a termination of a busy period;

detecting a completion of a busy period before a next global channel release instant; and

foreshortening a subsequent busy period in order to ensure a termination of the subsequent busy period at the next global channel release instant.

11. A multiple-cell wireless local area network including overlapping first and second wireless local area network cells, the first wireless local area network cell including a first plurality of member stations and the second wireless local area network cell including a second plurality of member stations, comprising:

a first member station in the first wireless local area network cell, transmitting a timing packet containing a timestamp value;

a second member station in the second wireless local area network cell receiving the timing packet;

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell interrupting transmissions at a global channel release instant based on the timestamp value; and

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell contending for access to a medium following the global channel release instant.

12. The network of claim 11, which further comprises:

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell synchronizing a superframe clock based on the timestamp value;

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell establishing the global channel release instant during each of a plurality of periodic superframes based on the superframe clock; and

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell periodically interrupting transmissions at the global channel release instant.

13. The network of claim 12, which further comprises:

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell periodically contending for access to the medium following the global channel release instant.

14. The network of claim 13, which further comprises:

the global channel release instant occurring at intervals to meet delay and jitter restrictions for time-critical voice applications.

15. The network of claim 13, which further comprises:

the global channel release instant occurring at intervals to meet delay and jitter restrictions for time-critical video applications.

16. The network of claim 13, which further comprises:

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell contending for access to the medium using a slotted carrier sense multiple access with collision avoidance access method following the global channel release instant.

17. The network of claim 16, which further comprises:

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell detecting a completion of a busy period before a next global channel release instant; and

the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell foreshortening a subsequent busy period in order to ensure a termination of the subsequent busy period at the next periodic global channel release instant.

18. The network of claim 16, which further comprises:

one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell conducting a distributed coordination function session, the one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell having successfully accessed the medium following the global channel release instant.

19. The network of claim 16, which further comprises:

one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell conducting a tiered contention multiple access session, the one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell having successfully accessed the medium following the global channel release instant.

20. The network of claim 16, which further comprises:

one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell conducting a point coordination function session, the one of the first plurality of member stations in the first wireless local area network cell and the second plurality of member stations in the second wireless local area network cell having successfully accessed the medium following the global channel release instant.