Method and wireless communications system using coordinated transmission and training for interference mitigation

• US 6,377,636 B1
• Filed: 11/02/1999
• Issued: 04/23/2002
• Est. Priority Date: 11/02/1999
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Iospan Wireless, Inc. (Intel Corporation)
• Inventors: Heath, Robert W. Jr., Tellado, Jose, Paulraj, Arogyaswami J., Sebastian, Peroor K.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Liu, Shuwang
• Application Number:
  US09/432,295
• Time in Patent Office: 903 Days
• Field of Search: 375/347, 375/260, 375/346, 342/457, 455/78, 455/503, 370/342
• US Class Current: 375/346
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

A method for interference mitigation in a wireless communication system having multiple transmitters and receivers by introducing transmission time delays between the transmission of signals from the individual transmitters to ensure coherent reception of the signals at a specific point in the coverage area, such as at a center of distribution of the receivers. To further aid in interference mitigation the signals are assigned training patterns chosen to be distinguishable by the receiver and to optimize interference mitigation. The training patterns can be selected based on a feedback parameter, e.g., a measure of the quality of interference mitigation obtained from the receiver. The present method can be used in wireless communication systems which re-use frequencies including TDMA, CDMA, FDMA, OFDMA or other multiplex communication systems using a multiple access method or a combination of such methods.

Claims

1. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point,

whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein a number of receivers including said receiver are present in said coverage area, said number of receivers having a center of distribution, said predetermined point substantially coinciding with said center of distribution.

2. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said predetermined point is located along an axis of symmetry of said coverage area.

3. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said first signal S₁ is a useful signal and said second signal S₂ is an interfering signal and said method further comprises estimation of the channel of signal S₁ and of the channel of signal S₂, and of applying a method of interference mitigation in recovering said first signal S₁.

4. The method of claim 3, wherein said method of interference mitigation is selected from a group of methods consisting of beamforming, joint detection, successive interference canceling, space-time filtering and space-frequency filtering.

5. The method of claim 3, further comprising the step of assigning a first training pattern to said first signal S₁ and a second training pattern to said second signal S₂, said first training pattern and said second training pattern being distinguishable by said receiver.

6. The method of claim 5, wherein said first training pattern and said second training pattern are selected to optimize interference mitigation.

7. The method of claim 5, wherein said first training pattern and said second training pattern are selected based on a communication traffic volume.

8. The method of claim 5, wherein said first training pattern and said second training pattern are selected based on a feedback parameter from said receiver.

9. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said wireless communication system re-uses frequencies such that said first transmitter transmits at predetermined frequencies f₁, . . . f_n and said second transmitter also transmits at said predetermined frequencies f₁, . . . f_n.

10. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said first transmitter is a first base station located in a first cell and said second transmitter is a second base station located in a second cell in close proximity to said first cell and said first receiver is a wireless subscriber device.

11. The method of claim 10, wherein said second cell is adjacent said first cell.

12. The method of claim 10, wherein said first base station and said second base station are controlled by a base station control and said base station control introduces said transmission delay τ

.

13. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said first transmitter is a first wireless subscriber device, said second transmitter is a second wireless subscriber device, and said receiver is a first base station located in a first cell.

14. A method of interference mitigation by coordinated transmission in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) determining a time delay between reception at a predetermined point in said coverage area of a first signal S₁ transmitted from said first transmitter at a first frequency f₁ and a second signal S₂ transmitted from said second transmitter at said first frequency f₁;

b) introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said receiver, said first transmitter and said second transmitter have antenna arrays for interference mitigation.

15. A wireless communication system comprising:

a) at least a first transmitter and a second transmitter, said first transmitter transmitting a first signal S₁ at a first frequency f₁ and said second transmitter transmitting a second signal S₂ at said first frequency f₁;

b) a receiver located in a coverage area for receiving said first signal S₁ and said second signal S₂;

c) a means for determining a time delay between reception at a predetermined point in said coverage area of said first signal S₁ and of said second signal S₂; and

d) a coordinating means for introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

further comprising an analyzer for analyzing the interference between said first signal S₁ and said second signal S₂ at said receiver.

16. The wireless communication system of claim 15, wherein said coordinating means is a base station control, and said receiver further comprises said analyzer.

17. A wireless communication system comprising:

a) at least a first transmitter and a second transmitter, said first transmitter transmitting a first signal S₁ at a first frequency f₁ and said second transmitter transmitting a second signal S₂ at said first frequency f₁;

b) a receiver located in a coverage area for receiving said first signal S₁ and said second signal S₂;

c) a means for determining a time delay between reception at a predetermined point in said coverage area of said first signal S₁ and of said second signal S₂; and

d) a coordinating means for introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

further comprising a training unit for assigning a first training pattern to said first signal S₁ and a second training pattern to said second signal S₂, said first training pattern and said second training pattern being distinguishable by said receiver.

18. The wireless communication system of claim 17, further comprising an analyzer for analyzing the interference between said first signal S₁ and said second signal S₂ at said receiver, said analyzer being in communication with said training unit.

19. The wireless communication system of claim 18, wherein said analyzer is in feedback communication with said training unit, said analyzer generating a feedback parameter and said training unit using said feedback parameter in assigning said first training pattern and said second training pattern.

20. A wireless communication system comprising:

a) at least a first transmitter and a second transmitter, said first transmitter transmitting a first signal S₁ at a first frequency f₁ and said second transmitter transmitting a second signal S₂ at said first frequency f₁;

b) a receiver located in a coverage area for receiving said first signal S₁ and said second signal S₂;

c) a means for determining a time delay between reception at a predetermined point in said coverage area of said first signal S₁ and of said second signal S₂; and

d) a coordinating means for introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said first transmitter is a first base station, said second transmitter is a second base station and said receiver is a wireless subscriber device.

21. A wireless communication system comprising:

a) at least a first transmitter and a second transmitter, said first transmitter transmitting a first signal S₁ at a first frequency f₁ and said second transmitter transmitting a second signal S₂ at said first frequency f₁;

b) a receiver located in a coverage area for receiving said first signal S₁ and said second signal S₂;

c) a means for determining a time delay between reception at a predetermined point in said coverage area of said first signal S₁ and of said second signal S₂; and

d) a coordinating means for introducing a transmission delay τ

between the transmission of said first signal S₁ and the transmission of said second signal S₂ such that said first signal S₁ and said second signal S₂ are received coherently at said predetermined point, whereby said first signal S₁ and said second signal S₂ are received substantially coherently by said receiver, thereby aiding in interference mitigation;

wherein said first transmitter is a first wireless subscriber unit, said second transmitter is a second wireless subscriber unit, and said receiver is a base station.

22. A method for interference mitigation in a wireless communication system having at least a first transmitter, a second transmitter and a receiver, said receiver being located within a coverage area, said method comprising the following steps:

a) transmitting to said receiver a first signal S₁ from said first transmitter at a first frequency f₁ and a second signal S₂ from said second transmitter at said first frequency f₁;

b) assigning to said first signal S₁ a first training pattern;

c) assigning to said second signal S₂ a second training pattern; and

d) coordinating the reception of said first training pattern and said second training pattern at said receiver, such that said first training pattern and said second training pattern are received coherently at said predetermined point, whereby said first pattern and said second pattern are received substantially coherently by said receiver, thereby aiding in interference mitigation.

23. The method of claim 22, wherein said predetermined point is located at the position of said receiver.

24. The method of claim 22, wherein said predetermined point is determined by ranging.

25. The method of claim 22, further comprising the step of indicating said training patterns.

26. The method of claim 22, wherein a number of receivers comprising said receiver are present in said coverage area, said number of receivers having a center of distribution, said predetermined point substantially coinciding with said center of distribution.

27. The method of claim 22, wherein said predetermined point is located along an axis of symmetry of said coverage area.

28. The method of claim 22, wherein said coverage area comprises a sector of a cell.

29. The method of claim 22, wherein said first signal S₁ is a useful signal and said second signal S₂ is an interfering signal and said method further comprises estimation of the channel of signal S₁ and of the channel of signal S₂ and of applying a method of interference mitigation in recovering said first signal S₁.

30. The method of claim 29, wherein said method of interference mitigation is selected from a group of methods consisting of beamforming, joint detection, successive interference canceling, space-time filtering and space-frequency filtering.

31. The method of claim 29, wherein said first training pattern and said second training pattern are selected to optimize interference mitigation.

32. The method of claim 29, wherein said first training pattern and said second training pattern are selected based on a communication traffic volume.

33. The method of claim 29, wherein said first training pattern and said second training pattern are selected based on a feedback parameter from said receiver.

34. The method of claim 22, wherein said wireless communication system re-uses frequencies such that said first transmitter transmits at predetermined frequencies f₁, . . . f_n and said second transmitter also transmits at said predetermined frequencies f₁, . . . f_n.

35. The method of claim 22, wherein said first transmitter is a first base station located in a first cell and said second transmitter is a second base station located in a second cell in close proximity to said first cell and said first receiver is a wireless subscriber device.

36. The method of claim 35, wherein said second cell is adjacent said first cell.

37. The method of claim 35, wherein said first base station and said second base station are controlled by a base station control and said base station control performs said step of coordinating the reception of said first training pattern and said second training pattern at said receiver.

38. The method of claim 22, wherein said first transmitter is a first wireless subscriber device, said second transmitter is a second wireless subscriber device, and said receiver is a first base station located in a first cell.

39. The method of claim 22, wherein said receiver, said first transmitter and said second transmitter have antenna arrays for interference mitigation.

40. A wireless communication system comprising:

a) at least a first transmitter and a second transmitter, said first transmitter transmitting a first signal S₁ at a first frequency f₁ and said second transmitter transmitting a second signal S₂ at said first frequency f₁;

b) a training unit for assigning to said first signal S₁ a first training pattern and to said second signal S₂ a second training pattern;

c) a receiver located in a coverage area for receiving said first signal S₁ and said second signal S₂; and

d) a coordinating means for coordinating the reception of said first training pattern and said second training pattern at said receiver, such that said first training pattern and said second training pattern are received coherently at said predetermined point, whereby said first pattern and said second pattern are received substantially coherently by said receiver, thereby aiding in interference mitigation.

41. The wireless communication system of claim 40 selected from a group consisting of TDMA systems, CDMA systems, FDMA systems and OFDMA systems.

42. The wireless communication system of claim 40, further comprising a means for indicating said training patterns.

43. The wireless communication system of claim 40, wherein said coordinating means is a base station control.

44. The wireless communication system of claim 40, further comprising an analyzer for analyzing the interference between said first signal S₁ and said second signal S₂ at said receiver.

45. The wireless communication system of claim 44, wherein said coordinating means is a base station control, and said receiver further comprises said analyzer.

46. The wireless communication system of claim 45, wherein said analyzer is in feedback communication with said training unit, said analyzer generating a feedback parameter and said training unit using said feedback parameter in assigning said first training pattern and said second training pattern.

47. The wireless communication system of claim 40, wherein said first transmitter is a first base station, said second transmitter is a second base station and said receiver is a wireless subscriber device.

48. The wireless communication system of claim 40, wherein said first transmitter is a first wireless subscriber unit, said second transmitter is a second wireless subscriber unit, and said receiver is a base station.