Wireless LANs and neighborhood capture

• US 7,983,232 B2
• Filed: 09/28/2007
• Issued: 07/19/2011
• Est. Priority Date: 11/02/2001
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Benveniste, Mathilde
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US11/864,244
• Publication Number:
  US 20080013522A1
• Time in Patent Office: 1,390 Days
• Field of Search: 370/338, 370/346, 370/348, 370/444, 370/448, 370/449, 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 of distributed dynamic bandwidth allocation, comprising:

time-slotting a communications channel into superframes of a superframe duration, wherein the superframes comprise control frames, data frames and busy periods, wherein the busy periods comprise contention-free periods and contention-free bursts;

assigning each busy period an arbitration-time inter-frame space;

further assigning an enhanced distributed coordination function station arbitration-time inter-frame space values according to a priority classification of the enhanced distributed coordination function station;

further assigning contention-free periods and contention-free bursts a first arbitration-time inter-frame space value;

further assigning available channels to a plurality of cells;

polling stations within a cell of the plurality of cells by an access point to determine if the stations within the cell have communications traffic to transmit; and

attempting to gain access to one of the available channels by using a reservation packet by the access point if the access point determines that the stations within the cell have communications traffic to transmit.

2. The method of claim 1, further comprising:

performing frame exchanges if the access to the one of the available channels is gained;

gaining the access to the one of the available channels by waiting for a backoff period and re-attempting to gain the access to the one of the available channels in the event that a transmission by another cell is less than a full time slot if the access to the one of the available channels was not gained; and

performing a global channel release of all channels of the available channels at pre-specified intervals.

3. The method of claim 2, wherein the using the reservation packet is based on carrier-sensing.

4. The method of claim 2, wherein the busy periods are foreshortened to meet a global channel release requirement.

5. The method of claim 2, wherein the global channel release occurs less frequently than after each busy period if busy periods are shorter than the superframe duration.

6. The method of claim 2, further comprising:

providing a plurality of co-channel groups of cells an equal opportunity to contend for the one of the available channels.

7. The method of claim 2, wherein the global channel release is performed at regularly spaced intervals.

8. The method of claim 2, wherein communication traffic loads are balanced across the plurality of cells and a plurality of re-use groups.

9. The method of claim 2, wherein the plurality of cells in a multiple-cell wireless local area network are synchronized to avoid busy periods straddling a boundary of the superframe.

10. The method of claim 9, wherein stations within a cell of the plurality of cells are synchronized with an access point of the cell.

11. The method of claim 10, wherein synchronization between the plurality of cells is accomplished via a wired distribution system in communication with a plurality of access points of the plurality of cells.

12. The method of claim 9, wherein neighboring cells synchronize with frames sent by stations in an overlapping coverage area of the neighboring cells.

13. The method of claim 9, wherein time offsets are corrected by the stations transmitting a special frame carrying a timestamp field.

14. The method of claim 13, wherein each station updates a clock of the respective station upon a receipt of the special frame having the timestamp field.

15. A multiple-cell wireless local area network using distributed dynamic bandwidth allocation, comprising:

a wired distribution network; and

a plurality of cells, each cell having a plurality of stations, wherein one of the plurality of stations in each cell is an access point, and further wherein communications between the plurality of stations are via the access point and where the plurality of stations is within one of a same cell and a different cell, and further wherein communications between one of the plurality of stations and the wired distribution network is via the access point, and further wherein some of the plurality of stations are in different cells that overlap;

wherein the wired distribution network allocates time-slots of a communications channel into superframes of a superframe duration, wherein the superframes comprise control frames, data frames and busy periods, wherein the busy periods comprise contention-free periods and contention-free bursts;

further wherein the wired distribution network assigns each busy period an arbitration-time inter-frame space;

further wherein the wired distribution network assigns an enhanced distributed coordination function station arbitration-time inter-frame space values according to a priority classification of the enhanced distributed coordination function station;

further wherein the wired distribution network assigns contention free periods and contention free bursts a first arbitration-time inter-frame space value;

further wherein the stations within a cell are polled by the respective access point of the cell to determine if the stations within the cell have communications traffic to transmit;

further wherein the respective access point attempts to gain access to the communications channel by using a reservation packet if the respective access point determines that the stations within the cell have communications traffic to transmit.

16. The multiple-cell wireless local area network of claim 15,

further wherein when the respective access point gains the access to the communications channel, the respective access point performs frame exchanges with the wired distribution network;

further wherein when the respective access point that has communications traffic to transmit does not gain access to the communications channel, the respective access point re-attempts to gain access to the communications channel by waiting for a backoff period and attempting to gain access to the communication channel in the event that a transmission by another cell is less than a full time slot; and

further wherein each of the respective access point and the wired distribution network performs a global channel release of all channels at pre-specified intervals.

17. The multiple-cell wireless local area network of claim 16, wherein the using the reservation packet is based on carrier-sensing.

18. The multiple-cell wireless local area network of claim 16, wherein the busy periods are foreshortened to meet a global channel release requirement.

19. The multiple-cell wireless local area network of claim 16, wherein the global channel release occurs less frequently than after each busy period if busy periods are shorter than the superframe duration.

20. The multiple-cell wireless local area network of claim 16, further comprising:

providing a plurality of co-channel groups of cells an equal opportunity to contend for the communication channel.

21. The multiple-cell wireless local area network of claim 16, wherein the global channel release is performed at regularly spaced intervals.

22. The multiple-cell wireless local area network of claim 16, wherein communication traffic loads are balanced across the plurality of cells and a plurality of re-use groups.

23. The multiple-cell wireless local area network of claim 16, wherein the plurality of cells are synchronized to avoid busy periods straddling a boundary of the superframe.

24. The multiple-cell wireless local area network of claim 23, wherein stations within a cell of the plurality of cells are synchronized with the access point in the cell.

25. The multiple-cell wireless local area network of claim 23, wherein neighboring cells synchronize with frames sent by stations in an overlapping coverage area of the neighboring cells.

26. The multiple-cell wireless local area network of claim 23, wherein time offsets are corrected by the stations transmitting a special frame carrying a timestamp field.

27. The multiple-cell wireless local area network of claim 26, wherein each station updates its a clock of the respective station upon a receipt of the special frame having the timestamp field.

28. The multiple-cell wireless local area network of claim 27, wherein synchronization between the plurality of cells is accomplished via a wired distribution system in communication with the access point in each cell.