Methods and devices for coordinating the transmissions of access points in WLANs

• US 20050190701A1
• Filed: 03/01/2004
• Published: 09/01/2005
• Est. Priority Date: 03/01/2004
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Bejerano, Yigal, Bhatia, Randeep S.
• Granted Patent: US 7,477,610 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

The coordination of transmissions by access points (APs) in a wireless local area network (WLAN) is carried out by allowing APs to transmit during slots of a Contention Free Period (CFP). Prior to transmission, slots are assigned to APs using a 4-approximation technique. This technique allows an AP to transmit using multiple frequencies. The assignment of slots satisfies a maximal, lower bound of an AP slot-to-user ratio.

Claims

1. A method for coordinating transmissions of access points in a wireless local area network comprising the steps of:

estimating a number of slots for each access point associated with a contention free period (CFP);

generating estimated slot sequences, slot assignments and a transmission frequency for each access point based on the estimated number of slots and an interference graph associated with every access point;

determining a total number of slots used in the estimated slot assignments;

comparing the total number of slots to an available number of slots;

adjusting a slot-to-user ratio of each access point if the total number of slots does not equal the available number of slots; and

assigning each access point a number of slots and a slot sequence based on the estimated slot assignments and slot sequences and assigning each access point a transmission frequency when the total number of slots equals the available number of slots.

2. The method as in claim 1 wherein the adjustment step further comprises the steps of:

increasing the slot-to-user ratio of each access point when the total number of slots is less than the available number of slots; and

decreasing the slot-to-user ratio of each access point when the total number of slots is greater than the available number of slots.

3. The method as in claim 1 further comprising the steps of:

estimating a next number of slots for each access point based on each access point'"'"'s adjusted slot-to-user ratio; and

generating next, estimated slot sequences, slot assignments and a transmission frequency for each access point based on the next number of slots and the interference graph.

4. The method as in claim 1 wherein the generation step further comprises generating the estimated slot sequences, slot assignments and frequencies such that no two interfering access points are assigned the same transmission frequency during a given slot and such that a total number of assigned slots is minimized.

5. The method as in claim 1 when the adjusting step further comprises the step of adjusting the slot-to-user ratio of each access point until said ratios substantially equal a maximum, lower bound of all of the slot-to-user ratios.

6. The method as in claim 1 wherein the method comprises a 4-approximation technique.

7. A system for coordinating transmissions of access points in a wireless local area network operable to:

estimate a number of slots for each access point associated with a contention-free period (CFP);

generate estimated slot sequences, slot assignments and a transmission frequency for each access point based on the estimated number of slots and an interference graph associated with every access point;

determine a total number of slots used in the estimated slot assignments;

compare the total number of slots to an available number of slots;

adjust a slot-to-user ratio of each access point if the total number of slots does not equal the available number of slots; and

assign each access point a number of slots and a slot sequence based on the estimated slot assignments and slot sequences and assigning each access point a transmission frequency when the total number of slots equals the available number of slots.

8. The system as in claim 7 further operable to:

increase the slot-to-user ratio of each access point when the total number of slots is less than the available number of slots; and

decrease the slot-to-user ratio of each access point when the total number of slots is greater than the available number of slots.

9. The system as in claim 7 further operable to:

estimate a next number of slots for each access point based on each access point'"'"'s adjusted slot-to-user ratio; and

generate next, estimated slot sequences, slot assignments and a transmission frequency for each access point based on the next number of slots and the interference graph.

10. The system as in claim 7 further operable to:

generate the estimated slot sequences, slot assignments and frequencies such that no two interfering access points are assigned the same transmission frequency during a given slot and such that a total number of assigned slots is minimized.

11. The system as in claim 7 further operable to:

adjust the slot-to-user ratio of each access point until said ratios substantially equal a maximum, lower bound of all of the slot-to-user ratios.

12. The system as in claim 7 wherein the system is operable to coordinate the transmissions using a 4-approximation technique.

13. A system for coordinating transmissions of access points in a wireless local area network comprising:

means for estimating a number of slots for each access point associated with a contention free period (CFP);

means for generating estimated slot sequences, slot assignments and a transmission frequency for each access point based on the estimated number of slots and an interference graph associated with every access point;

means for determining a total number of slots used in the estimated slot assignments;

means for comparing the total number of slots to an available number of slots;

means for adjusting a slot-to-user ratio of each access point if the total number of slots does not equal the available number of slots; and

means for assigning each access point a number of slots and a slot sequence based on the estimated slot assignments and slot sequences and assigning each access point a transmission frequency when the total number of slots equals the available number of slots.

14. The system as in claim 13 further comprising:

means for increasing the slot-to-user ratio of each access point when the total number of slots is less than the available number of slots; and

means for decreasing the slot-to-user ratio of each access point when the total number of slots is greater than the available number of slots.

15. The system as in claim 13 further comprising:

means for estimating a next number of slots for each access point based on each access point'"'"'s adjusted slot-to-user ratio; and

means for generating next, estimated slot sequences, slot assignments and a transmission frequency for each access point based on the next number of slots and the interference graph.

16. The system as in claim 13 further comprising:

means for generating the estimated slot sequences, slot assignments and frequencies such that no two interfering access points are assigned the same transmission frequency during a given slot and such that a total number of assigned slots is minimized.

17. The system as in claim 13 further comprising:

means for adjusting the slot-to-user ratio of each access point until said ratios substantially equal a maximum, lower bound of all of the slot-to-user ratios.