Overlap mitigation in wireless LANs using a central medium access control

• US 20030202498A1
• Filed: 04/10/2003
• Published: 10/30/2003
• Est. Priority Date: 04/10/2002
• Status: Active Grant

• Current Assignee: Nokia of America Corporation (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Teunissen, Harold Wilhelm, de Heer, Arie Johannes
• Granted Patent: US 7,349,366 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• 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 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 80/00 Wireless network protocols or protocol adaptations to wireless operation
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

The present invention relates to an access point for a wireless local area network. The access point is arranged to service its stations by using a Point Coordination Function protocol and to monitor overlap with neighbouring access points. To mitigate overlap, the access point and overlapping neigbouring access points synchronize in such a way that the access point can service its stations in an overlap areas during a certain servicing time, while the overlapping neighbouring access points are silent, and vice versa. A silence trade-off mechanism is used to assure that overlapping access points get their fair share of available bandwidth.

Claims

1. An access point for a wireless local area network, the access point being arranged to service at least one station by using a central medium access control protocol during a time period, and to monitor overlap with neighbouring access points, and to define one or more areas in which at least one first station experiences overlap, as being overlap areas, and one or more areas in which at least one second station does not experience overlap, as being non-overlap areas, and to define one or more neighbouring access points causing the overlap as being overlapping neighbouring access points, the accesspoint comprising:

a processor device operable such that the access point and the overlapping neighbouring access points synchronize in such a way that the access point can service the at least one first station in the overlap areas during a servicing time within the time period, while the overlapping neighbouring access points are silent, and vice versa, and said device further being operable such that the access point is further arranged to determine the amount of the servicing time by exchanging requests for silence with its overlapping neighbouring access points.

2. The access point according to claim 1, characterized in that the central medium access control protocol is a Point Coordination Function (PCF) protocol.

3. The access point according to claim 1, characterized in that the access point is arranged to execute a silence trade-off mechanism which includes:

(a) initialisation of an own supply for silence;

(b) determination of a total period of time available for resolving overlap;

(c) determination of an own demand for silence towards each overlapping neighbouring access point;

(d) exchanging of an amount of time which is available by the access point for resolving overlap with its neighbouring access points;

(e) combination of coincident demands using a predetermined combination rule;

(f) determination of an effective overlapping time according to a predetermined overlap time rule;

(g) setting the own supply for silence to the effective overlapping time;

(h) determination of a minimum of demands and supplies for silence according to a minimum determination rule;

(i) calculation of the own supply of silence;

(j) repeat the previous steps until a predefined criteria is met.

4. The access point according to claim 3, characterized in that the calculation of the own supply of silence includes:

(a) determination of a maximum claim for silence;

(b) selection of a smallest demand for silence, out of a set (Demands) which constitutes the demands for silence from all overlapping access points;

(c) removing the smallest demand for silence from the set (Demands);

(d) determination of a maximum supply/demand time by calculating the minimum of the maximum claim for silence and the amount of time corresponding to the smallest demand for silence from step (b);

(e) updating the own supply for silence if the smallest demand for silence corresponds with the access point;

(f) extract the maximum supply/demand time from the effective overlapping time;

(g) repeat the previous steps until the set (Demands) is empty.

5. The access point according to claim 1 included in a wireless local area network comprising at least two access points.

9. A computer program product to be loaded by an access point according to claim 1, the computer program product providing the access point with the capacity for determining the amount of the servicing time (31) by exchanging requests for silence by the access point (1) with its overlapping neighbouring access points (2, 3).

6. A method to be performed by an access point for a wireless local area network, the access point being arranged to service at least one station by using a central medium access control protocol during a time period, and to monitor overlap with neighbouring access points, and to define one or more areas in which at least one first stations (4) experiences overlap, as being overlap areas, and one or more areas in which at least one second station does not experience overlap, as being non-overlap areas, said method comprising the steps of:

defining one or more neighbouring access points causing the overlap as being overlapping neighbouring access points;

the access point and the overlapping neighbouring access points synchronizing in such a way that the access point can service the at least one first station in the overlap areas during a servicing time within the time period, while the overlapping neighbouring access points are silent, and vice versa; and

determining the amount of the servicing time by exchanging requests for silence by the access point with its overlapping neighbouring access points.

7. The method according to claim 6, characterized in that the central medium access control protocol is a Point Coordination Function (PCF) protocol.

8. The method according to claim 6, characterized by:

(a) initialisation of an own supply for silence;

(b) determination of a total period of time available for resolving overlap;

(c) determination of an own demand for silence towards each overlapping neighbouring access point;

(d) exchanging of an amount of time which is available by the access point for resolving overlap with its neighbouring access points;

(e) combination of coincident demands using a predefined combination rule;

(f) determination of an effective overlapping time according to a predefined overlap time rule;

(g) setting the own supply for silence to the effective overlapping time;

(h) determination of a minimum of demands and supplies for silence according to a predefined minimum determination rule;

(i) calculation of the own supply of silence;

(j) repeat the previous steps until a predefined criteria is met.