Method and system for reducing channel interference in a frame-synchronized wireless communication system

• US 7,177,598 B2
• Filed: 09/05/2001
• Issued: 02/13/2007
• Est. Priority Date: 11/15/2000
• Status: Expired due to Fees

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Klein, Israel Jay, Stanwood, Kenneth L., Price, Frederick W., Behar, Jacques, Gilbert, Sheldon L., Gazelle, David
• Primary Examiner(s): Nguyen; Duc M.
• Assistant Examiner(s): GENACK, MATTHEW W
• Application Number:
  US09/947,650
• Publication Number:
  US 20020058513A1
• Time in Patent Office: 1,987 Days
• Field of Search: 455/63, 455/63.1, 455/63.2, 455/67.11, 455/423, 455/446, 455/447, 455/449, 370/277, 370/281, 370/296, 370/328, 370/329, 370/330, 370/337, 370/347, 370/436, 370/478
• US Class Current: 455/63.1
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/12 Fixed resource partitioning
• CPC Class Codes: H04W 16/24 Cell structures

Abstract

Base stations having potentially interfering terminal stations that are geographically located on the same or similar diagonal or Line of Sight (relative to the base station) operate on a first set of time frames (e.g., “even” time frames). Similarly, base stations having potentially interfering terminal stations that are not geographically located on the same or similar diagonals operate on a second set of time frames (e.g., “odd” time frames). By alternating in their use of the even and odd frames, the potential for co-channel interference between terminal stations is minimized. Systems and methods are disclosed which reduce co-channel and adjacent channel interference between terminal stations of different cells as well as adjacent channel interference between terminal stations of adjacent cells. The methods and systems so described can be used during the deployment or expansion of a communication system in a region.

Claims

1. A method of reducing co-channel interference in a communication system having base stations and terminal stations with each terminal station associated with one base station sector, each base station has an associated and corresponding cell, each cell includes a plurality of associated and corresponding sectors, each sector of each cell having a different channel than the other sectors of the same cell, the communication system comprises an uplink and a downlink with each including at least one slot, and the uplink comprises an uplink signal divided in the frequency domain into a plurality of channels, the method comprising:

determining a set of terminal stations that may potentially interfere with each other at a selected base station sector if they use the same channel;

determining a first subset of the set of terminal stations such that the subset communicates with a first set of associated and corresponding base station sectors that are arranged along a first line of sight that includes the selected base station;

determining a second subset of the set of terminal stations, wherein the subset communicates with a second set of associated and corresponding base station sectors that are arranged along a second line of sight which is parallel with the first line of sight;

allocating a first up link channel for the first subset of terminal stations; and

allocating a second uplink channel for the second subset of terminal stations.

2. The method of claim 1, further comprising transmitting on said first uplink channel from the terminal stations associated with the first set of base stations and transmitting on said second uplink channel from the terminal stations associated with the second set of base stations.

3. The method of claim 1, further comprising separating the uplink and downlink into frames for use in a time division duplex communication system.

4. The method of claim 1, further comprising using a first frequency for the uplink and a second frequency for the downlink, both for use in a frequency division duplex communication system.

5. The method of claim 1, wherein the method is used with a single frequency set and four sectors per cell.

6. The method of claim 1, further comprising separating the first uplink channel into a first polarization upper sub-channel, a second polarization upper sub-channel, a first polarization lower sub-channel, and a second polarization lower sub-channel, all of which are used within a four sector cell.

7. The method of claim 1, further comprising separating the second uplink channel into a first polarization upper sub-channel, a second polarization upper sub-channel, a first polarization lower sub-channel, and a second polarization lower sub-channel, all of which are used within a four sector cell.

8. The method of claim 1, further comprising adjusting the number of the at least one slots in the downlink to compensate for differences in spectrum efficiency of the downlink as compared to the uplink.

9. The method of claim 8, further comprising calculating the number of the at least one slot in the downlink using equation Rd=1/[(Sd/Su)/(Td/Tu)+1], wherein Sd=spectrum efficiency for the downlink, Su=spectrum efficiency for the uplink, Td=time slots allocated by the system on the downlink, and Tu=time slots allocated by the system on the uplink.

10. The method of claim 9, further comprising calculating the number of the at least one slot in the uplink using the equation Ru=1−

Rd.

11. A communication system with reduced co-channel interference for use in a communication system having base stations and terminal stations, the system comprising:

a set of terminal stations that may potentially interfere with each other at a selected base station sector, each terminal station being associated with at least one base station sector, each base station having an associated and corresponding cell which includes a plurality of associated and corresponding sectors, each sector of each cell having a different channel than the other sectors of the same cell, wherein the communication system comprises an uplink and a downlink, the uplink comprising an uplink signal divided in the frequency domain into a first uplink channel and a second uplink channel;

a first set of base station sectors associated with a first subset of the set of terminal stations and are arranged along a first line of sight which includes the selected base station sectors; and

a second set of base station sectors associated with a second subset of the set of terminal stations and are located along a second line of sight which is parallel to the first line of sight, the terminal stations associated with the first set of base station sectors are configured to transmit on the first uplink channel and the terminal stations associated with the second set of base station sectors are configured to transmit on the second uplink channel.

12. The system of claim 11, wherein the first uplink channel includes a first polarization upper sub-channel, a second polarization upper sub-channel, a first polarization lower sub-channel, and a second polarization lower sub-channel, all for use in a four sector cell.

13. The system of claim 11, wherein the second uplink channel includes a first polarization upper sub-channel, a second polarization upper sub-channel, a first polarization lower sub-channel, and a second polarization lower sub-channel, all for use in a four sector cell.

14. The system of claim 11, wherein the uplink and downlink are separated into frames in the time domain to operate in a time division duplex manner.

15. The system of claim 11, wherein the uplink and downlink are separated in the frequency domain to operate in a frequency division duplex manner.

16. A system for reducing co-channel interference that includes base stations and terminal stations where each terminal station is associated with a base station and where the base stations and the terminal stations communicate during a first frame and a second frame of an uplink channel, the system comprising:

a selected base station that is susceptible to receiving co-channel interference from a set of terminal stations and is configured to receive the uplink channel at a first frequency and to transmit a downlink channel at a second frequency;

a first subset of the set of terminal stations, wherein the first subset comprises at least two terminal stations, the first subset of terminals that lie along a geographical diagonal line of sight passing through the selected base station; and

a second subset of the set of terminal stations, wherein the second subset comprises at least two terminal stations, the second subset of terminals lie outside the geographical diagonal line of sight, wherein the first subset of the set of terminal stations is configured to transmit at the first frequency to an associated first set of base stations during the first frame of an uplink channel and wherein the second subset of the set of terminal stations is configured to transmit at the first frequency to an associated second set of base stations during the second frame of the uplink channel.

17. The system of claim 16, wherein the first set of base stations lie along the geographic diagonal line.

18. The system of claim 16, wherein the system is configured to operate in a frequency division duplex communication system.

19. A method for reducing co-channel interference in a communication system that includes base stations and terminal stations where each base station has an associated cell, each cell includes a plurality of sectors, and each sector of each cell uses a different uplink channel than the other sectors of the same cell, each terminal station is associated with a base station and with a sector of its associated base station, and an uplink signal is divided in the frequency domain into a first uplink channel and a second uplink channel, the method comprising:

determining a set of terminal stations that may potentially interfere with each other at a selected base station sector;

determining a first subset of the set of terminal stations, wherein the first subset comprises at least two terminal stations, the first subset of terminals having a first set of associated and corresponding base station sectors which lie along a geographical diagonal line of sight passing trough the selected base station;

determining a second subset of the set of terminal stations, wherein the second subset comprises at least two terminal stations, the second subset of terminals having a second set of associated and corresponding base station sectors that lie outside the geographical diagonal line of sight;

allocating the first uplink channel for the first subset of terminal stations to communicate with their associated base station sectors; and

allocating the second uplink channel for the second subset of terminal stations to communicate with their associated base station sectors.

20. The method of claim 19, further comprising transmitting on the first uplink channel by the first set of terminal stations to their associated base stations and transmitting on the second uplink channel by the second set of terminal stations to their associated base stations.

21. The method of claim 19, further comprising separating the uplink and downlink into frames for use in a time division duplex communication system.

22. The method of claim 19, further comprising using a first frequency for the uplink and a second frequency for the downlink, both for use in a frequency division duplex communication system.

23. A method for reducing channel interference in a communication system that includes base stations and terminal stations with each terminal station associated with a base station, and each base station is associated with a cell, the method comprising:

determining a first set of terminal stations in a first cell that may potentially interfere with a second set of terminal stations in a second cell;

determining a subset of the first set of terminal stations, wherein said subset comprises at least two terminal stations, that lie along a line of sight that passes trough a base station in the second cell;

determining a subset of the second set of terminal stations that uplink using a less robust modulation technique than is available;

selecting a more robust modulation technique for the subset of the second set of terminal stations; and

coordinating uplink transmissions by the subset of the first set of terminal stations with uplink transmissions by the subset of the second set of terminal stations so that the subset of the second set of terminal stations utilize the more robust modulation technique when terminals in the subset of the first set of terminal stations are transmitting to decrease the effect of channel interference at the base station in the second cell.

24. The method of claim 23, wherein the first set of terminal stations and the second set of terminal stations both uplink using a first channel.

25. The method of claim 23, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

26. The method of claim 23, further comprising measuring signal to noise ratios at the base station in the second cell for the uplink transmissions from the first set of terminal stations to determine the first subset of the first set of terminal stations.

27. A method for reducing channel interference in a communication system that includes base stations and terminal stations, each base station is associated with a cell, each cell includes a plurality of sectors, each terminal station is associated with a base station and with a sector of its associated base station, the method comprising:

determining a first set of terminal stations in a sector of a first cell that may potentially interfere with a second set of terminal stations in a sector of a second cell;

determining a subset of the first set of terminal stations, wherein said subset comprises at least two terminal station, that lie along a line of sight that passes through a base station in the second cell;

determining a subset of the second set of terminal stations that uplink using a less robust forward error correction technique than is available;

selecting a more robust forward error correction technique for the subset of the second set of terminal stations when terminal stations in the subset of first terminal stations are transmitting; and

coordinating uplink transmissions by the subset of the first set of terminal stations with uplink transmissions by the subset of the second set of terminal stations, the subset of the second set of terminal stations utilizing the more robust forward error correction technique to reduce channel interference at the base station in the second cell.

28. The method of claim 27, wherein the first set of terminal stations and the second set of terminal stations both uplink using a first channel.

29. The method of claim 27, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

30. The method of claim 27, further comprising measuring signal to noise ratios at the base station in the second cell for the uplink transmissions from the first set of terminal stations to determine the first subset of the first set of terminal stations.

31. A system for reducing channel interference in a communication system that includes base stations and terminal stations with each terminal station associated with a base station, and each base station is associated with a cell, the system comprising:

a first set of terminal stations located in a first cell that may potentially interfere with a second set of terminal stations in a second cell;

a subset of the first set of terminal stations, wherein said subset comprises at least two terminal station, that lie along a line of sight that passes through a base station in the second cell; and

a subset of the second set of terminal stations that are configured to select a more robust modulation technique for their uplink transmissions, wherein the uplink transmissions by the subset of the first set of terminal stations are coordinated with uplink transmissions by the second set of terminal stations, the second set of terminal stations utilizing the more robust modulation technique when the first subset of the first set of terminal stations are transmitting to reduce channel interference at the base station in the second cell.

32. The system of claim 31, wherein the first set of terminal stations and the second set of terminal stations both uplink using a first channel.

33. The system of claim 31, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

34. The system of claim 31, wherein the base station in the second cell is configured to measure signal to noise ratios for uplink transmissions from the first set of terminal stations to determine the subset of the first set of terminal stations.

35. A system for reducing channel interference in a communication system that includes base stations and terminal stations with each terminal station associated with a base station, and each base station is associated with a cell, the system comprising:

a first set of terminal stations located in a first cell that may potentially interfere with a second set of terminal stations in a second cell; and

a subset of the first set of terminal stations, wherein said subset comprises at least two terminal station, that lie along a line of sight that passes through a base station in the second cell, where the second set of terminal stations that are configured to select a more robust forward error correction technique for their uplink transmissions, when terminal stations in the subset of first set of terminal stations is transmitting, wherein the uplink transmissions by the subset of the first set of terminal stations are coordinated with uplink transmissions by the second set of terminal stations, the second set of terminal stations utilizing the more robust forward error correction technique to reduce channel interference at the base station in the second cell.

36. The system of claim 35, wherein the first set of terminal stations and the second set of terminal stations both uplink using a first channel.

37. The system of claim 35, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

38. The system of claim 35, wherein the base station in the second cell is configured to measure signal to noise ratios for uplink transmissions from the first set of terminal stations to determine the subset of the first set of terminal stations.

39. A method for reducing adjacent channel interference in a communication system that includes a base station and terminal stations with each base station having antenna arrays, and each terminal station associated with one antenna array for transmitting an uplink to the base station, the method comprising:

determining a first set of terminal stations that may potentially interfere with a second set of terminal stations, the first set of terminal stations being associated with a first antenna array and the second set of terminal stations being associated with a second antenna;

determining a subset of the first set of terminal stations, wherein said subset comprises at least two terminal stations, that lie along a line of sight that passes through the second antenna

determining a subset of the second set of terminal stations that uplink to the second antenna array using a less robust modulation technique than is available;

selecting a more robust modulation technique for the subset of the second set of terminal stations when terminal stations in the first set of terminal stations are transmitting; and

coordinating uplink transmissions by the first set of terminal stations with uplink transmissions by the subset of the second set of terminal stations, the subset of the second set of terminal stations utilize the more robust modulation technique for their uplink transmissions to reduce adjacent channel interference at the second antenna array.

40. The method of claim 39, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

41. The method of claim 39, further comprising measuring signal to noise ratios at the first antenna array for the uplink transmissions from the first set of terminal stations to determine the potential for interfering with the second set of terminal stations.

42. A method for reducing adjacent channel interference in a communication system that includes base stations and terminal stations with each base station having antenna arrays, and each terminal station associated with one antenna array for transmitting an uplink to a base station, the method comprising:

determining a first set of terminal stations that may potentially interfere with a second set of terminal stations, the first set of terminals being associated with a first antenna array and the second set of terminal stations being associated with a second antenna array;

determining a subset of the first set of terminal stations, wherein said subset comprises at least two terminal stations, that lie along a line of sight that passes through the second antenna array

determining a subset of the second set of terminal stations that uplink to the second antenna array using a less robust forward error correction technique than is available;

selecting a more robust forward error correction technique for the subset of the second set of terminal stations when terminal stations in the first set of terminal stations are transmitting; and

coordinating uplink transmissions by the first set of terminal stations with uplink transmissions by the subset of the second set of terminal stations, the subset of the second set of terminal stations utilize the more robust forward error correction technique for their uplink transmissions to reduce adjacent channel interference at the second antenna array.

43. The method of claim 42, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

44. The method of claim 42, further comprising measuring signal to noise ratios at the first antenna array for the uplink transmissions from the first set of terminal stations to determine the potential for interfering with the second set of terminal stations.

45. A system for reducing adjacent channel interference in a communication system that includes a base station and terminal stations with each base station having antenna arrays, and each terminal station associated with one antenna array for transmitting an uplink to the base station, the system comprising:

a first set of terminal stations associated with a first antenna array that may potentially interfere with a second set of terminal stations associated with a second antenna array, the first set of terminal stations having a subset, wherein said subset comprises at least two terminal stations, that lie along a line of sight that passes through the second antenna array, the second set of terminal stations are configured to select a more robust modulation technique for their uplink transmissions when terminal stations in the first set of terminal stations are transmitting, wherein the uplink transmissions by the first set of terminal stations are coordinated with uplink transmissions by the second set of terminal stations, the second set of terminal stations utilizing the more robust modulation technique to reduce adjacent channel interference at the second antenna array.

46. The system of claim 45, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

47. The system of claim 45, wherein the base station is configured to measure signal to noise ratios for uplink transmissions from the first set of terminal stations which are used to determine the potential for the first set of terminal stations to interfere with the second set of terminal stations.

48. A system for reducing adjacent channel interference in a communication system that includes base stations and terminal stations with each base station having antenna arrays, and each terminal station associated with one antenna array for transmitting an up link to a base station, the system comprising:

a first set of terminal stations associated with a first antenna array that may potentially interfere with a second set of terminal stations associated with a second antenna array, the first set of terminal stations having a subset, wherein said subset comprises at least two terminal stations, that lie along a line of sight that passes through the second antenna array, wherein the second set of terminal stations are configured to select a more robust forward error correction technique for their uplink transmissions when terminal stations in the first set of terminal stations transmit, wherein the uplink transmissions by the first set of terminal stations are coordinated with uplink transmissions by the second set of terminal stations, the second set of terminal stations utilizing the more robust forward error correction technique to reduce adjacent channel interference at the second antenna array.

49. The system of claim 48, wherein the first set of terminal stations uplink using a first channel and the second set of terminal stations uplink using a second channel, such that the first and second channels are adjacent channels.

50. The system of claim 48, wherein the base station is configured to measure signal to noise ratios for uplink transmissions from the first set of terminal stations which are used to determine the potential for the first set of terminal stations to interfere with the second set of terminal stations.