Transmitting on the downlink using one or more weight vectors determined to achieve a desired radiation pattern

• US 6,154,661 A
• Filed: 12/10/1997
• Issued: 11/28/2000
• Est. Priority Date: 12/10/1997
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Goldburg, Marc H.
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US08/988,519
• Time in Patent Office: 1,084 Days
• Field of Search: 455/422, 455/522, 455/63, 455/560, 455/562, 455/525, 455/517, 370/277, 370/310, 370/334
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

This invention relates to a method and apparatus for transmitting one or more downlink signals simultaneously over the same conventional channel from a communication station to one or more subscriber units to achieve a desired overall radiation pattern (e.g., a near omnidirectional pattern) over a desired sector, the communication station including an array of antenna elements, determining means for determining weight vectors designed for the transmitting through the array to achieve the desired overall radiation pattern over the desired sector, one or more signal processors for weighting the downlink signals in phase and amplitude according to the weight vectors and adding the weighted signals to form a set of weighted downlink antenna signals, each summed and weighted downlink antenna signal having an intended antenna element in the array, a set of associated transmit apparatuses for transmitting the set of weighted downlink antenna signals using the array, each associated transmit apparatus including an input for receiving one of the summed and weighted downlink antenna signals, each antenna element coupled to the output of one of the associated transmit apparatuses.

Claims

1. A method for transmitting a downlink signal from a communication station to one or more subscriber units, the communication station including an array of antenna elements, each antenna element coupled to an associated transmit apparatus, the associated transmit apparatuses coupled to one or more signal processors for weighting the downlink signals in phase and amplitude according to a weight vector, the method comprising:

(a) determining a first weight vector designed for transmitting with low relative radiated power to achieve a desired radiation pattern over a desired sector without requiring pre-orthogonalizing the downlink signal;

(b) weighting the downlink signal with the selected first weight vector using the one or more signal processors to form a set of weighted downlink antenna signals, each weighted downlink antenna signal having an intended antenna element in the array; and

(c) transmitting the downlink signal by passing each weighted downlink antenna signal of the set of weighted downlink antenna signals to its intended antenna element through the intended antenna element'"'"'s associated transmit apparatus.

2. The method according to claim 1, further including

(d) receiving the downlink signal in at least one subscriber unit.

3. The method according to claim 1 wherein the desired sector includes a range of azimuths.

4. The method according to claim 3 wherein the desired sector includes a range of elevations.

5. The method according to claim 1 wherein the desired radiation pattern is a NOR pattern.

6. The method according to claim 1 wherein the weight vector determined in said step (a) is that weight vector that minimizes a cost function of the weight vector, the cost function including a first expression of variation of the radiation pattern resulting from transmitting using the weight vector from the desired radiation pattern over the desired sector.

7. The method according to claim 6 wherein the cost function includes an expression of the total power transmitted from the antenna elements by using the weight vector.

8. The method according to claim 6 wherein the cost function includes an expression of variations in transmitted power among the antenna elements when using the weight vector.

9. The method of claim 5 wherein said step (a) of determining further includes

(i) specifying a cost function of the weight vector, the cost function including an expression of variation of the radiation pattern resulting from transmitting using the weight vector from a NOR pattern over the desired sector;

and

(ii) selecting as the first weight vector that weight vector that minimizes the cost function.

10. The method according to claim 9 wherein the cost function includes an expression of the total power transmitted from the antenna elements by using the weight vector.

11. The method according to claim 10 wherein the cost function includes an expression of the variations in transmitted power among the antenna elements by using the weight vector.

12. The method according to claim 1 wherein the communication station is part of a FDMA/TDMA system.

13. The method according to claim 12 wherein the communication station operates according to a variant of the GSM communications protocol.

14. The method according to claim 12 wherein the communication station operates according to a variant of the PHS communications protocol.

15. The method according to claim 1 wherein the communication station is part of a CDMA system.

39. The method according to claim 1 wherein the antenna elements are approximately uniformly distributed, and wherein the steps (b) through (c) are periodically repeated using a plurality of shifted weight vectors in place of a plurality of desirable weight vectors, each shifted weight vector formed by shifting each desirable weight vector, the shift in each repetition dithered so that the average shift is zero.

16. A method for transmitting a plurality of downlink signals from a communication station to a corresponding plurality of subscriber units over a conventional channel, each downlink signal having an intended subscriber unit, each intended subscriber unit having a location, each location being at least approximately known, the communication station including an array of antenna elements, each antenna element coupled to an associated transmit apparatus, the associated transmit apparatuses coupled to one or more signal processors for spatial multiplexing the downlink signals, the spatial multiplexing including weighting each downlink signal in phase and amplitude according to a weight vector and adding the weighted signals, the method comprising:

(a) determining a plurality of desirable weight vectors, each subscriber unit having an associated desirable weight vector in the plurality of desirable weight vectors, each associated desirable weight vector designed for downlink communication to its associated subscriber unit, the plurality of desirable weight vectors designed for producing an overall desirable radiation pattern over a desired sector;

(b) spatial multiplexing the plurality of downlink signals, the multiplexing including weighting each particular downlink signal with the desirable weight vector associated with the particular downlink signal'"'"'s intended subscriber unit, the spatial multiplexing by desirable weight vectors that are not associated desirable weight vectors in the plurality of desirable weight vectors being of one or more dummy signals, the spatial multiplexing using the one or more signal processors to form a set of summed and weighted downlink antenna signals, each summed and weighted downlink antenna signal having an intended antenna element in the array; and

(c) transmitting the plurality of downlink signals by passing each summed and weighted downlink antenna signal to its intended antenna element, the passing through the intended antenna element'"'"'s associated transmit apparatus.

17. The method according to claim 16 wherein the number of weight vectors in the plurality of desirable weight vectors is the same as the number of subscriber units so that all desirable weight vectors in the set of desirable weight vectors are associated desirable weight vectors.

18. The method according to claim 16, further including

(d) receiving the spatially multiplexed plurality of downlink signals at a particular one of the subscriber units.

19. The method according to claim 17 wherein the overall desirable radiation pattern is a NOR pattern.

20. The method according to claim 17 wherein the desired sector includes a range of azimuths.

21. The method according to claim 20 wherein the desired sector includes a range of elevations.

22. The method according to claim 16 wherein

the desired sector includes a set of corresponding regions, each corresponding region including at most one subscriber unit'"'"'s location, the union of all the corresponding regions substantially covering the desired sector,

in said determining step (a), each desirable weight vector is determined for transmission to one of the corresponding regions, and

the plurality of desirable weight vectors determined in said determining step (a) is the plurality of weight vectors that minimizes a cost function of possible weight vectors, the cost function including an expression of the variation from the desirable radiation pattern of the net overall radiation pattern resulting from transmitting using the plurality of weight vectors.

23. The method according to claim 22 wherein the number of weight vectors in the plurality of desirable weight vectors is the same as the number of subscriber units so that all desirable weight vectors in the set of desirable weight vectors are associated desirable weight vectors, and each subscriber unit'"'"'s location is in one of the corresponding regions.

24. The method according to claim 23 wherein the cost function includes an expression of the total power transmitted from the antenna elements using each weight vector.

25. The method according to claim 23 wherein the cost function includes an expression of the variations in transmitted power among the antenna elements using each weight vector.

26. The method according to claim 23 wherein the cost function includes an expression of the energy received in unintended corresponding regions for each weight vector.

27. A method for transmitting a plurality of downlink signals from a communication station to a corresponding plurality of subscriber units over a conventional channel with an overall desirable radiation pattern over a desired sector, each downlink signal having an intended subscriber unit, each intended subscriber unit having a location, each location being at least approximately known, the communication station including an array of antenna elements, each antenna element coupled to an associated transmit apparatus, the associated transmit apparatuses coupled to one or more signal processors for spatial multiplexing the downlink signals, the spatial multiplexing including weighting each downlink signal in phase and amplitude according to a weight vector and adding the weighted signals, the method comprising:

(a) partitioning the desired sector into a set of regions, the number of regions the same as the number of subscriber units, the union of all the regions substantially covering the desired sector;

(b) determining a plurality of desirable weight vectors, each desirable weight vector designed for downlink communication to one of the regions, the plurality of desirable weight vectors designed for producing the overall desirable radiation pattern over the desired sector, the plurality of desirable weight vectors and the set of regions defining a situation;

(c) storing the desirable weight vectors in a memory;

(d) repeating the steps (a) through (c) for different sets of regions until a sufficient number of situations is stored;

(e) recalling from the memory the plurality of desirable weight vectors of the situation appropriate f or the locations of the subscriber units;

(f) spatial multiplexing the plurality of downlink signals, the multiplexing including weighting each particular downlink signal with the recalled desirable weight vector designed to transmit to the region that includes the location of the particular downlink signal'"'"'s intended subscriber unit, the spatial multiplexing using t he one or more signal processors to form a set of summed and weighted downlink antenna signals, each summed and weighted downlink antenna signal having an intended antenna element in the array; and

(g) transmitting the plurality of downlink signals by passing each summed and weighted downlink antenna signal to its intended antenna element, the passing through the intended antenna element'"'"'s associated transmit apparatus.

28. The method according to claim 27 wherein the plurality of desirable weight vectors determined in said step (b) is the plurality of weight vectors that minimizes a cost function of possible weight vectors, the cost function including an expression of the variation from the desirable radiation pattern of the net overall radiation pattern resulting from transmitting using the plurality of weight vectors.

29. The method according to claim 28 wherein the cost function includes an expression of the total power transmitted from the antenna elements using each weight vector.

30. The method according to claim 28 wherein the cost function includes an expression of the variations in transmitted power among the antenna elements using each weight vector.

31. The method according to claim 28 wherein the cost function includes an expression of the energy received in unintended corresponding regions for each weight vector.

32. A method for transmitting a plurality of downlink signals from a communication station to a corresponding plurality of subscriber units over a conventional channel with an overall desirable radiation pattern over a desired sector, each downlink signal having an intended subscriber unit, each intended subscriber unit having a location, each location being at least approximately known, the communication station including an array of antenna elements, the antenna elements approximately uniformly distributed, each antenna element coupled to an associated transmit apparatus, the associated transmit apparatuses coupled to one or more signal processors for spatial multiplexing the downlink signals, the spatial multiplexing including weighting each downlink signal in phase and amplitude according to a weight vector and adding the weighted signals, the method comprising:

(a) partitioning the desired sector into a set of regions, the number of regions being at least the number of subscriber units, the union of all the regions substantially covering the desired sector;

(b) determining a plurality of desirable weight vectors, each desirable weight vector designed for downlink communication to one of the regions, the plurality of desirable weight vectors designed for producing the overall desirable radiation pattern over the desired sector, the plurality of desirable weight vectors and the set of regions defining a situation;

(c) determining a translation of the set of regions using the locations of the subscriber units to ensure that there is no more than one subscriber unit per translated region and that the locations of the subscriber units are adequately separated;

(d) shifting each determined desirable weight vector to form a plurality of shifted weight vectors, each shift corresponding to the translation determined in the step (c);

(e) spatial multiplexing the plurality of downlink signals, the multiplexing including weighting each particular downlink signal with the shifted weight vector designed to transmit to the translated region that includes the location of the particular downlink signal'"'"'s intended subscriber unit, the spatial multiplexing by any shifted weight vectors that are designed to transmit to any translated regions that have no subscriber unit being of one or more dummy signals, the spatial multiplexing using the one or more signal processors to form a set of summed and weighted downlink antenna signals, each summed and weighted downlink antenna signal having an intended antenna element in the array; and

(f) transmitting the plurality of downlink signals by passing each summed and weighted downlink antenna signal to its intended antenna element, the passing through the intended antenna element'"'"'s associated transmit apparatus.

33. The method according to claim 32 wherein each shifted region has a subscriber unit, and wherein the plurality of desirable weight vectors determined in said step (b) is the plurality of weight vectors that minimizes a cost function of possible weight vectors, the cost function including an expression of the variation from the desirable radiation pattern of the net overall radiation pattern resulting from transmitting using the plurality of weight vectors.

34. The method according to claim 33 wherein the cost function includes an expression of the total power transmitted from the antenna elements using each weight vector.

35. The method according to claim 33 wherein the cost function includes an expression of the variations in transmitted power among the antenna elements using each weight vector.

36. The method according to claim 33 wherein the cost function includes an expression of the energy received in unintended corresponding regions for each weight vector.

37. The method according to claim 33 wherein the steps (d) through (f) are periodically repeated, the shift in each repetition dithered around the translation determined in the step (c).

38. The method according to claim 37 wherein the dithering includes adding a randomized shift to the translation determined in the step (c).

40. A communication station for transmitting a downlink signal to one or more subscriber units, the communication station including

(a) an array of antenna elements;

(b) means for determining a first weight vector designed for transmitting through the array with low relative radiated power to achieve a desired radiation pattern over a desired sector without requiring pre-orthogonalizing the downlink signal;

(c) one or more signal processors coupled for weighting the downlink signal in phase and amplitude according to the determined first weight vector to form a set of weighted downlink antenna signals, each weighted downlink antenna signal having an intended antenna element in the array; and

(d) a set of associated transmit apparatuses for transmitting the set of weighted downlink antenna signals through the array, each antenna element coupled to the output of an associated transmit apparatus in the set of associated transmit apparatuses, each associated transmit apparatus including an input for receiving one of the weighted downlink antenna signals.

41. The communication station according to claim 40 wherein the desired sector includes a range of azimuths.

42. The communication station according to claim 41 wherein the desired sector includes a range of elevations.

43. The communication station according to claim 40 wherein the desired radiation pattern is a NOR pattern.

44. The communication station according to claim 40 wherein the means for determining selects as the first weight vector that weight vector that minimizes a cost function of the weight vector, the cost function including a first expression of variation of the radiation pattern resulting from transmitting using the weight vector from the desired radiation pattern over the desired sector.

45. The communication station according to claim 44 wherein the cost function includes an expression of the total power transmitted from the antenna elements by using the weight vector.

46. The communication station according to claim 44 wherein the cost function includes an expression of the variations in transmitted power among the antenna elements when using the weight vector.

47. A communication station for transmitting one or more of downlink signals to a one or more subscriber units over a conventional channel, each downlink signal having one or more intended subscriber units, each intended subscriber unit having a location, each location being at least approximately known, the communication station comprising:

(a) an array of antenna elements;

(b) means for determining a plurality of desirable weight vectors, each subscriber unit having an associated desirable weight vector in the plurality of desirable weight vectors, each associated desirable weight vector designed for downlink communication to its associated subscriber unit, the plurality of desirable weight vectors designed for producing an overall desirable radiation pattern over a desired sector;

(c) one or more signal processors for spatial multiplexing a plurality of downlink signals to form a set of summed and weighted downlink antenna signals, the multiplexing including weighting each particular downlink signal with the desirable weight vector associated with the particular downlink signal'"'"'s intended subscriber unit, the spatial multiplexing by desirable weight vectors that are not associated desirable weight vectors in the plurality of desirable weight vectors being of one or more dummy signals; and

(d) a set of associated transmit apparatuses for transmitting the set of summed and weighted downlink antenna signals through the array, each antenna element coupled to the output of an associated transmit apparatus in the set of associated transmit apparatuses, each associated transmit apparatus including an input for receiving one of the weighted downlink antenna signals.

48. The communication station according to claim 47 wherein the number of weight vectors in the set of desirable weight vectors is the same as the number of subscriber units so that all desirable weight vectors in the set of desirable weight vectors are associated desirable weight vectors.

49. The communication station according to claim 48 wherein

the desired sector includes a set of corresponding regions, each corresponding region including at most one subscriber unit'"'"'s location, the union of all the corresponding regions substantially covering the desired sector,

each desirable weight vector is determined for transmission to a corresponding region by the determining means (b), and

the plurality of desirable weight vectors determined by the determining means (b) is the plurality of weight vectors that minimizes a cost function of possible weight vectors, the cost function including an expression of the variation from the desirable radiation pattern of the net overall radiation pattern resulting from transmitting using the plurality of weight vectors.