Space-time-power scheduling for wireless networks

• US 20040037258A1
• Filed: 11/27/2002
• Published: 02/26/2004
• Est. Priority Date: 08/26/2002
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Colubris Networks, Inc. (HP Inc.)
• Inventors: Scherzer, Shimon B., Worfolk, Patrick A.
• Granted Patent: US 7,031,336 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 88/12 Access point controller devices

Abstract

A technique is disclosed to schedule frame transmissions in a wireless network. The network includes a plurality of stations configured to communicate on the same frequency channel with a plurality of access points. A central controller examines the transmission characteristics between the various stations and access points and identifies frames that may be simultaneously transmitted by a subset of the access points to their intended stations.

Claims

1. A wireless network, comprising:

a plurality of M access point transceivers;

a plurality of N stations, wherein each station can communicate with all or a subset of the M access point transceivers; and

a central controller coupled to the plurality of M access point transceivers, wherein the central controller is configured to examine transmission characteristics between a subset of the stations and a subset of the multiple antenna elements for each access point transceiver, and based upon the transmission characteristics identify frames that may be scheduled for simultaneous transmission.

2. The wireless network of claim 1, wherein each access point transceiver has a multi-element antenna array.

3. The wireless network of claim 1, wherein the simultaneous transmission is from a subset of the access points to a subset of the stations.

4. The wireless network of claim 1, wherein the central controller schedules frames for simultaneous transmission based upon a likelihood of successful transmission and on the maximum aggregated data rate in the network as determined by the transmission characteristics.

5. The wireless network of claim 1, wherein the transmission characteristics comprise likelihood of station to station interference, access point transceiver to station path loss, and access point to access point path loss information.

6. The wireless network of claim 5, wherein the transmission characteristics further comprise station to station path loss information.

7. The wireless network of claim 3, wherein the transmission characteristics include a prediction of signal to interference ratios at the stations and access points.

8. The wireless network of claim 1, wherein the multi-element array in each of the access point comprises a multi-beam antenna.

9. The wireless network of claim 7, wherein the central controller is configured to command each station to transmit periodically so that the transmission characteristics may be updated.

10. The wireless network of claim 1, wherein the WLAN is an 802.11 network.

11. The wireless network of claim 1, wherein the medium access control (MAC) for each of the access point transceivers is controlled by the central controller.

12. The wireless network of claim 1, wherein the MAC for each of the access point transceivers is controlled by the respective access point transceiver.

13. The wireless network of claim 1, wherein the transmission characteristics include transmission characteristics derived from a cross correlation of packet transmissions from the stations.

14. The wireless network of claim 1, wherein the central controller is further configured to delay the subset of access points from transmitting the identified frames to the intended stations based on the transmission characteristics.

15. The wireless network of claim 1, wherein each of the access point transceivers transmits on the same frequency channel.

16. The wireless network of claim 15, further comprising an additional wireless network, wherein the additional wireless network comprises access point transceivers, each access point transceiver transmitting on the same frequency channel within the additional wireless network, the frequency channel within the additional wireless network being different than the frequency channel within the first wireless network.

17. The wireless network of claim 1, wherein the medium access control (MAC) for each of the access points is located in the central controller.

18. The wireless network of claim 1, wherein the transmission characteristics comprise a likelihood of interference from a first station to a second station determined by the spatial signature similarity between the first and second station and a comparison between the similarity and a fixed threshold.

19. The wireless network of claim 1, wherein the transmission characteristics comprise a likelihood of interference from a first station to a second station determined by the spatial signature similarity between the first and second station and a comparison between the similarity and a threshold that can be adjusted based on frame error and re-transmission rate.

20. The wireless network of claim 1, wherein the frames can be transmitted at different transmit powers based on a scheduling of the frames by the central controller.

21. The wireless network of claim 1, wherein the access point transceivers comprise conventional circuitry to measure received signal strength indicator (RSSI) information.

22. The wireless network of claim 1, wherein the frames each comprise a preamble, and wherein the access point transceivers each comprise a matched filter to perform a detection on the preamble.

51. The wireless local network of claim 1, wherein the wireless local network is a wireless local area network.

23. A method of scheduling frame transmissions in a wireless network, wherein the wireless network includes a plurality of M access points, and a plurality of N stations, wherein each station can communicate with all or a subset of the M access points, comprising:

receiving a set of frames for transmission to intended stations within the plurality of N stations;

examining transmission characteristics between a subset of the stations and a subset of the antenna arrays for the access points; and

based upon the transmission characteristics, identifying frames within the set of frames that may be simultaneously transmitted.

24. The method of claim 23, wherein each access point comprises an antenna array.

25. The method of claim 23, further comprising transmitting the identified frames from a subset of the access points to their intended stations.

26. The method of claim 23, wherein the network is an 802.11 network.

27. The method of claim 23, further comprising transmitting the set of frames on the same frequency channel.

28. The method of claim 23, wherein the antenna arrays are multi-beam antennas.

29. The method of claim 23, wherein the transmission characteristics comprise channel gains between the access points and stations and between one access point and remaining ones of the access points.

30. The wireless local area network of claim 23, wherein the transmission characteristics comprise likelihood of station to station interference, access point transceiver to station path loss, access point to access point path loss, and station to station path loss information.

31. The method of claim 23, further comprising adjusting transmit power in transmitting the frames from the subset of access points based on the transmission characteristics.

32. The method of claim 23, further comprising sequentially transmitting the frames based on the transmission characteristics.

33. The method of claim 23, further comprising delaying transmitting one of the subset of frames based on the transmission characteristics.

34. The method of claim 23, wherein examining the transmission characteristics comprises examining interference information between station and station and path loss information between access point and station for each access point and station.

35. The method of claim 34, wherein the interference information is related to the channel gain between station and station.

36. The method of claim 28, wherein the beams of the multi-beam antennas are orthogonal or nearly orthogonal to each other.

37. The method of claim 23, wherein examining the transmission characteristics comprises predicting the signal to interference ratio at the subset of the stations.

38. The method of claim 23, further comprising queuing a sequence of frames to be transmitted by the access points.

39. The method of claim 23, further comprising polling the stations when an uplink transmission has not occurred for a specified period of time.

40. The method of claim 23, further comprising routing the frames to one of the subset of stations from a plurality of access points, based on whether the one station acknowledges a downlink frame.

41. The method of claim 23, further comprising utilizing 802.11 Point Coordination Function (PCF) mode to force transmissions from the stations.

42. The method of claim 23, further comprising utilizing 802.11 Distributed Coordination Function (DCF) mode during transmissions from the stations to the access points.

43. The method of claim 23, wherein the examining comprises determining a likelihood of interference from a first station to a second station by determining a spatial signature similarity between the first and second station and comparing the similarity against a fixed threshold.

44. The method of claim 23, wherein the examining comprises determining a likelihood of interference from a first station to a second station by determining a spatial signature similarity between the first and second station and comparing the similarity against a threshold that can be adjusted based on frame error rate.

45. The method of claim 44, wherein the similarity is a correlation.

46. The method of claim 23, wherein the examining comprises measuring the rate of failed or successful frames transmission from a first station to a second station or from a first access point to a second access point, and based on the measuring, adapting a threshold, wherein the threshold is used to determine a spatial signature similarity between the first and second station.

47. The method of claim 23, further comprising transmitting individual ones of the frames at different transmit powers based on a scheduling of the frames.

48. The method of claim 45, wherein the transmitting and the scheduling is from the access point transceivers to the stations.

49. The method of claim 23, wherein the examining comprises measuring received signal strength indicator (RSSI) information with conventional access point circuitry.

50. The method of claim 23, wherein the examining comprises performing a fast correlation on the preamble of the received frame utilizing a matched filter.

52. The method of claim 23, wherein the wireless local network is a wireless local area network.