Method and apparatus for a multi-beam antenna system

• US 20050101352A1
• Filed: 11/10/2003
• Published: 05/12/2005
• Est. Priority Date: 11/10/2003
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Logothetis, Andrew, Astely, David
• Granted Patent: US 7,664,533 B2
• Time in Patent Office: Days
• US Class Current: 455/562.100
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 25/002 providing at least two patterns of different beamwidth; Variable beamwidth antennas
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 3/40 with phasing matrix

Abstract

An antenna array in a radio node includes multiple antenna elements for transmitting a wider beam covering a majority of a sector cell that includes a common signal and a narrower beam covering only a part of the sector cell that includes a mobile user-specific signal. Transmitting circuitry is coupled to the antenna array, and processing circuitry is coupled to the transmitting circuitry. The processing circuitry ensures the user-specific signal and the common signal in a mixed beam embodiment are in-phase and time-aligned at the antenna array. In a steered beam embodiment, the processing circuitry ensures the user-specific signal and the common signal are time-aligned and have a controlled phase difference when received at mobile stations in the sector cell. In both embodiments, distortions in the common signal and the user-specific signal associated with their conversion from baseband frequency to radio frequency are also compensated. And in the steered beam embodiment, beam forming weights are used not only to radiate a narrower beam to the desired mobile user but also to direct a wider common signal beam to reach all mobile users in the cell.

Claims

1. Apparatus comprising:

an antenna array including multiple antenna elements for transmitting a wide beam covering a majority of a sector cell that includes a common signal and at least one narrow beam covering only a part of the sector cell that includes a mobile user-specific signal;

transmitting circuitry coupled to the antenna array; and

circuitry, coupled to the transmitting circuitry, for ensuring that the user-specific signal and the common signal are substantially in-phase and substantially time-aligned at the antenna array.

2. The apparatus in claim 1, wherein the circuitry includes filtering circuitry configured so that the common signal is transmitted only from a center antenna element in the antenna array.

3. The apparatus in claim 1, wherein the circuitry is configured to ensure that the user-specific signal is in-phase and time-aligned with the common signal at a center antenna element in the antenna array.

4. The apparatus in claim 1, wherein the circuitry includes filtering circuitry configured to compensate distortions in the common signal and the user-specific signal associated with conversion of the common signal and the user-specific signal from baseband frequency to radio frequency.

5. The apparatus in claim 1, wherein the antenna array includes an odd number N of antenna elements, where N is a positive integer greater than 1, the apparatus further comprising:

a beam forming network, coupled between the antenna array and transmitting circuitry, for receiving the user-specific signal and the common signal and generating N narrow beams to be provided to the antenna array.

6. The apparatus in claim 5, wherein the beam forming network is configured to transmit the common signal simultaneously on the N beams with equal or approximately equal power.

7. The apparatus in claim 6, wherein the beam forming network is configured to transmit the user-specific signal simultaneously on the N beams with a power that is determined using N user-specific beam weights, each user-specific beam weight corresponding to one of the N beams, such that a beam narrower than a beam radiating the common signal is radiated in a direction of the user.

8. The apparatus in claim 7, wherein each user-specific beam weight is proportional to a function of an uplink average signal power received on the corresponding beam.

9. The apparatus in claim 1, further comprising:

beam weighting circuitry for weighting the user-specific signal with a user-specific signal beam filter weight corresponding to each beam and providing each weighted user-specific signal to a corresponding beam filter.

10. The apparatus in claim 9, wherein the user-specific signal beam filter weights are configured so that radiated energy from the antenna elements is directed to a desired mobile user.

11. The apparatus in claim 5, further comprising:

receiving circuitry coupled to the beam forming network;

a signal processor, coupled to the receiving circuitry, for processing signals received on the N beams to estimate a received signal and for determining an average uplink received signal power for each beam.

12. The apparatus in claim 6, further comprising:

first and second antenna arrays each including an odd number N of antenna elements, where N is a positive integer greater than 1, for transmitting a wider beam covering a majority of a sector cell that includes the common signal and at least one narrower beam covering only a part of the sector cell that includes a mobile user-specific signal;

first transmitting circuitry coupled to the first antenna array;

second transmitting circuitry coupled to the second antenna array;

a first beam forming network, coupled between the first antenna array and the first transmitting circuitry, for receiving the user-specific signal and the common signal and generating N narrow beams to be provided to the first antenna array;

a second beam forming network, coupled between the second antenna array and the second transmitting circuitry, for receiving the user-specific signal and the common signal and generating N narrow beams to be provided to the second antenna array;

first circuitry, coupled to the first transmitting circuitry, for ensuring that the user-specific signal and the common signal at the first antenna array elements are in-phase and time-aligned; and

second circuitry, coupled to the second transmitting circuitry, for ensuring that the user-specific signal and the common signal at the second antenna array are in-phase and time-aligned.

13. The apparatus in claim 12, further comprising:

first receiving circuitry coupled to the first beam forming network;

second receiving circuitry coupled to the second beam forming network;

a signal processor, coupled to the first and second receiving circuitry, for processing signals received on the N beams from the first beam forming network and on the N beams from the second beam forming network to estimate a received signal.

14. Apparatus comprising:

an antenna array including multiple antenna elements for transmitting a wider beam covering a majority of a sector cell that includes a common signal and at least one narrower beam covering only a part of the sector cell that includes a mobile user-specific signal;

transmitting circuitry coupled to the antenna array; and

circuitry, coupled to the transmitting circuitry, for ensuring that the user-specific signal and the common signal are substantially time-aligned and have a controlled phase difference when received at mobile stations in the sector cell.

15. The apparatus in claim 14, wherein the circuitry includes filtering circuitry configured so that the common signal is transmitted only from a center antenna element in the antenna array.

16. The apparatus in claim 14, wherein the circuitry is configured so that the wide beam carrying the common signal is generated using multiple antenna elements in the antenna array.

17. The apparatus in claim 14, wherein the circuitry includes filtering circuitry configured to compensate distortions in the common signal and the user-specific signal associated with conversion of the common signal and the user-specific signal from baseband frequency to radio frequency.

18. The apparatus in claim 14, further comprising:

beam weighting circuitry for weighting the user-specific signal with a user-specific signal beam filter weight corresponding to each antenna and providing each weighted user-specific signal to a corresponding antenna transmit filter.

19. The apparatus in claim 18, wherein the user-specific signal beam filter weights are configured so that radiated energy from the antenna elements is directed to a desired mobile user.

20. The apparatus in claim 18, further comprising:

beam weighting circuitry for weighting the common signal with a common signal beam filter weight corresponding to each antenna and providing each weighted common signal to a corresponding antenna transmit filter.

21. The apparatus in claim 20, wherein the common signal beam filter weights are configured so that radiated energy from the antenna elements is directed in a desired shape in the sector cell.

22. The apparatus in claim 20, wherein the user-specific signal and common signal beam weights are complex numbers used to phase-rotate and amplify the user-specific and common signals, respectively.

23. The apparatus in claim 18, wherein the user-specific beam filter weights are selected to match an average spatial signature which is a complex valued measure of an average received signal as a function of an angle at which the received signal is received.

24. The apparatus in claim 18, wherein the user-specific beam weights are selected to minimize a transmitted power allocated to a mobile user such that a standard deviation of a phase difference between the common and user-specific signals received by the mobile user is less than or equal to a target value that ensures a desired quality of service.

25. The apparatus in claim 14, further comprising:

a beam forming network coupled to the N antenna elements for generating N received beams;

receiving circuitry coupled to the beam forming network;

a signal processor, coupled to the receiving circuitry, for processing signals received on the N received beams to estimate a received signal and for determining statistics of a channel through which the received signals propagate.

26. The apparatus in claim 14, further comprising:

first and second antenna arrays each including N antenna elements for transmitting a wider beam covering a majority of a sector cell that includes a common signal and at least one narrower beam covering only a part of the sector cell that includes a mobile user-specific signal;

first transmitting circuitry coupled to the first antenna array for providing the user-specific signal and the common signal to the first antenna array;

second transmitting circuitry coupled to the second antenna array for providing the user-specific signal and the common signal to the second antenna array;

first circuitry, coupled to the first transmitting circuitry, for ensuring that the user-specific signal and the common signal from the first antenna elements are substantially time-aligned and have a controlled phase difference when received at mobile stations in the sector cell; and

second circuitry, coupled to the second transmitting circuitry, for ensuring that the user-specific signal and the common signal from the second antenna elements are substantially time-aligned and have a controlled phase difference when received at mobile stations in the sector cell.

27. The apparatus in claim 26, further comprising:

a first beam forming network coupled to the antenna array;

first receiving circuitry coupled to the first beam forming network;

a second beam forming network coupled to the antenna array;

second receiving circuitry coupled to the second beam forming network;

a signal processor, coupled to the first and second receiving circuitry, for processing signals received on the N beams from the first beam forming network and on the N beams from the second beam forming network to estimate a received signal.

28. A method for use in a radio node including an antenna array including multiple antenna elements, comprising:

filtering a user-specific signal and a common signal to ensure that the user-specific signal and the common signal are substantially in-phase and substantially time-aligned at the antenna array, and

transmitting simultaneously from the antenna array a wider beam covering a majority of a sector cell that includes the common signal and at least one narrower beam covering only a part of the sector cell that includes the user-specific signal.

29. The method in claim 28, further comprising:

transmitting the common signal only from a center antenna element in the antenna array.

30. The method in claim 29, wherein the processing includes compensating distortions in the common signal and the user-specific signal associated with conversion of the common signal and user-specific signals from baseband frequency to radio frequency.

31. The method claim 29, wherein the processing includes weighting the user-specific signal to ensure that the user-specific signal are substantially in-phase and substantially time-aligned with the common signal at a center element of the antenna array.

32. The method in claim 29, wherein the antenna array includes an odd number N of antenna elements, where N is a positive integer greater than 1, and wherein a beam forming network in the radio base station receives the user-specific signal and the common signal and generates N narrow beams to be provided to the antenna array.

33. The method apparatus in claim 32, further comprising:

transmitting the user-specific signal simultaneously on the N beams with a power that is determined using N user-specific beam weights, each user-specific beam weight corresponding to one of the N beams, such that a beam narrower than a beam radiating the common signal is radiated in a direction of the user.

34. The method in claim 33, wherein each user-specific beam weight is proportional to a function of an uplink average signal power received on the corresponding beam.

35. The method in claim 33, further comprising:

processing signals received on the N beams to estimate a received signal, and

determining an average uplink signal power for each beam.

36. The method in claim 33 implemented in two transmit diversity branches.

37. The method in claim 33 implemented in two receive diversity branches, further comprising:

processing signals received on the N beams from the two receive diversity branches to estimate a received signal.

38. A method for use in a radio node including an antenna array including multiple antenna elements, comprising:

processing a user-specific signal and a common signal to ensure that the user-specific signal and the common signal are substantially time-aligned and have a controlled phase difference when received at mobile stations in the sector cell, and

transmitting simultaneously from the antenna array a wider beam covering a majority of a sector cell that includes the common signal and at least one narrower beam covering only a part of the sector cell that includes the user-specific signal.

39. The method in claim 38, further comprising:

transmitting the common signal from only one of the N antenna elements.

40. The method in claim 38, wherein the user-specific signal is transmitted simultaneously from the N antenna elements.

41. The method in claim 40, wherein the user-specific signal is transmitted with a power and a phase rotation that are determined using N user-specific antenna weights.

42. The method in claim 41, wherein the user-specific signal antenna weights are configured so that radiated energy from the antenna elements is directed to a desired mobile user in the sector cell.

43. The method in claim 41, wherein the common signal is transmitted with a power and a phase rotation that are determined using N antenna weights.

44. The method in claim 43, wherein the common signal beam weights are configured so that radiated energy from the antenna elements is directed in a desired shape in the sector cell.

45. The method in claim 43, wherein the user-specific and common signal beam weights are complex numbers used to phase-rotate and amplify the user-specific and common signals, respectively.

46. The method in claim 41, further comprising:

selecting the user-specific weights to match an average spatial signature which is a complex valued measure of an average received signal as a function of an angle at which the received signal is received.

47. The method in claim 41, further comprising:

selecting the user-specific beam weights to minimize a transmitted power allocated to a mobile user such that a standard deviation of a phase difference between the common and user-specific signals received by the mobile user is less than or equal to a target value that ensures a desired quality of service.

48. The method in claim 44, wherein the user specific and common signals are transmitted simultaneously from the N antenna elements with a power that is determined using N user-specific and N common signal beam weights, respectively, each user-specific beam weight and each common signal beam weight corresponding to one of the N antenna elements, further comprising:

selecting the user-specific beam weights to direct radiated energy from the antenna array to a desired mobile user, and

selecting the common signal beam weights to direct radiated energy from the antenna array in a desired shape.

49. The method in claim 38, wherein the processing includes compensating distortions in the common signal and user-specific signal associated with conversion of the common signal and user-specific signals from baseband frequency to radio frequency.

50. The method in claim 38 implemented in two transmit diversity branches.