Preemptive packet for maintaining contiguity in cyclic prioritized multiple access (CPMA) contention-free sessions

• US 9,319,906 B2
• Filed: 09/09/2013
• Issued: 04/19/2016
• Est. Priority Date: 11/02/2001
• Status: Expired due to Fees

• 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:
  US14/021,978
• Publication Number:
  US 20140010226A1
• Time in Patent Office: 953 Days
• US Class Current: 1/1
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• 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

An access point transmits a preemptive peg packet when it has no data to transmit in order to maintain the contiguity of its transmission timing position with respect to the timing position of other contention-free sessions (CFS) transmitted by other access points in an existing, periodic sequence. The cyclic prioritized multiple access (CPMA) method establishes the transmission timing position of contention-free sessions (CFS) between overlapping first and second wireless LAN cells contending for the same medium. Each cell includes a respective plurality of member stations. If an access point has no traffic, it will transmit a short, preemptive pegging packet and reset its backoff timer. In this manner, no gaps longer than the distributed coordination function (DCF) Interframe Space (DIFS) are left idle. This prevents other stations from using DCF contention to seize the channel, until all access points have completed one contention-free session (CFS) per periodic cycle.

Claims

1. A method, comprising:

coordinating, by a processor of a first access point station in a first wireless local area network cell, a first contention-free session comprising multiple bursts with member stations in the first wireless local area network cell;

transmitting, by the processor of the first access point station, a preemptive peg packet to maintain a contiguity of a transmission timing position of the first access point station with respect to a timing position of a second contention-free session transmitted by a second access point station; and

wherein the preemptive peg packet is for preventing a gap to be left idle for longer than a distributed coordination function interframe space;

whereby other access point stations and other member stations are prevented from using the distributed coordination function interframe space to seize a medium, until the first access point station has completed the first contention-free session and the second access point station has completed the second contention-free session in a periodic cycle.

2. The method of claim 1, further comprising:

setting by the first access point station a backoff timer to a fixed deterministic post-backoff delay, which has a value of Bkoff times a fixed number of idle time slots, the value of Bkoff being greater than a number of overlapping wireless local area network cells;

counting down the backoff timer by the first access point station;

transmitting another one of the first contention-free session by the first access point station when the backoff timer expires; and

resetting the backoff timer to the value of Bkoff to start a new cycle.

3. The method of claim 2, further comprising:

the backoff timer being counted down using an interframe space.

4. The method of claim 3, wherein the interframe space being a priority interframe space.

5. The method of claim 3, wherein the interframe space being a minimum arbitration interframe space.

6. The method of claim 2, further comprising:

listening, by a processor of the second access point station in a second wireless local area network cell, to an activity in the medium and detecting an end to the first contention-free session indicated by an interval longer than a priority interframe space idle interval following an end to the activity in the medium;

setting a second post-backoff delay by the processor of the second access point station to transmit a minimal interval after the first contention-free session of the first access point station; and

coordinating by the processor of the second access point station in the second wireless local area network cell the second contention-free session, the second contention-free session including multiple bursts with other member stations in the second wireless local area network cell.

7. The method of claim 6, wherein the second post-backoff delay being a minimum arbitration interframe space.

8. The method of claim 6, further comprising:

initiating by the second access point station another one of the second contention-free session when the second post-backoff delay is counted down to zero; and

resetting the second post-backoff delay to start a new cycle.

9. The method of claim 6, further comprising:

separating consecutive ones of the first and second contention-free sessions by idle gaps which are less than a priority interframe space.

10. The method of claim 9, where the setting the second post-backoff delay further comprises:

detecting an idle period X=priority interframe space +x, x>

0 at time t; and

setting the second post-backoff delay at time t, to a value of Bkoff-x.

11. A first access point station, comprising:

a processor in a first wireless local area network cell, the processor performing operations comprising;

coordinating in the first wireless local area network cell a first contention-free session comprising multiple bursts with member stations in the first wireless local area network cell;

transmitting a preemptive peg packet to maintain a contiguity of a transmission timing position of the first access point station with respect to a timing position of a second contention-free session transmitted by a second access point station comprising a processor; and

wherein the preemptive peg packet is for preventing a gap to be left idle for longer than a distributed coordination function interframe space;

whereby other access point stations and other member stations are prevented from using the distributed coordination function interframe space to seize a medium, until the first access point station has completed the first contention-free session and the second access point station has completed the second contention-free session in a periodic cycle.

12. The first access point station of claim 11, the operations further comprising:

setting a backoff timer to a fixed deterministic post-backoff delay, which has a value of Bkoff times a fixed number of idle time slots, the value of Bkoff being greater than a number of overlapping wireless local area network cells;

counting down the backoff timer;

transmitting another one of the first contention-free session when the backoff timer expires; and

resetting the backoff timer to the value of Bkoff to start a new cycle.

13. The first access point station of claim 12, wherein the backoff timer is counted down using an interframe space.

14. The first access point station of claim 13, wherein the interframe space being a priority interframe space.

15. The first access point station of claim 13, wherein the interframe space being a minimum arbitration interframe space.

16. A system comprising:

a first access point station in a first wireless local area network cell, the first access point station performing operations comprising;

coordinating in the first wireless local area network cell a first contention-free session comprising multiple bursts with member stations in the first wireless local area network cell;

transmitting a preemptive peg packet to maintain a contiguity of a transmission timing position of the first access point station with respect to a timing position of a second contention-free session transmitted by a second access point station, wherein the preemptive peg packet is for preventing a gap to be left idle for longer than a distributed coordination function interframe space, whereby other access point stations and other member stations are prevented from using the distributed coordination function interframe space to seize a medium, until the first access point station has completed the first contention-free session and the second access point station has completed the second contention-free session in a periodic cycle;

setting a backoff timer to a fixed deterministic post-backoff delay, which has a value of Bkoff times a fixed number of idle time slots, the value of Bkoff being greater than a number of overlapping wireless local area network cells;

counting down the backoff timer;

transmitting another one of the first contention-free session when the backoff timer expires; and

resetting the backoff timer to the value of Bkoff to start a new cycle; and

the second access point station in a second wireless local area network cell, the second access point station performing operations comprising;

listening in the second wireless local area network cell to an activity in the medium and detecting an end to the first contention-free session indicated by an interval longer than a priority interframe space idle interval following an end to the activity in the medium;

setting a second post-backoff delay to transmit a minimal interval after the first contention-free session of the first access point station; and

coordinating in the second wireless local area network cell the second contention-free session, the second contention-free session including multiple bursts with other member stations in the second wireless local area network cell.

17. The system of claim 16, wherein the second post-backoff delay is a minimum arbitration interframe space.

18. The system of claim 16, wherein the operations performed by the second access point station further comprise:

initiating another one of the second contention-free session when the second post-backoff delay is counted down to zero; and

resetting the second post-backoff delay to start a new cycle.

19. The system of claim 16, wherein the operations performed by the second access point station further comprise:

separating consecutive ones of the first and second contention-free sessions by idle gaps which are less than a priority interframe space.

20. The system of claim 19, wherein the setting the second post-backoff delay further comprises:

detecting an idle period X=priority interframe space +x, x>

0 at time t; and

setting the second post-backoff delay at time t, to a value of Bkoff-x.