Adaptive beam-forming system using hierarchical weight banks for antenna array in wireless communication system

• US 20050206564A1
• Filed: 03/04/2005
• Published: 09/22/2005
• Est. Priority Date: 03/19/2004
• Status: Active Grant

• Current Assignee: Comware Incorporated
• Original Assignee: Comware Incorporated
• Inventors: Somerlock, Oscar Frederick III, Mao, Jian
• Granted Patent: US 7,312,750 B2
• Time in Patent Office: Days
• US Class Current: 342/377
• 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 3/2682 Time delay steered arrays

Abstract

An adaptive beam-forming system using hierarchical weight banks for antenna arrays in wireless communication systems is disclosed. The present invention can be applied for both reception and transmission beam-forming. The hierarchical weight banks contain weights that are pre-calculated based on pre-set beam look directions. By comparing measurements of chosen signal quality metrics for pre-set look directions, the best weights, and thus the best beam look direction, can be selected from the weight banks.

Claims

1. A wireless communication system, comprising:

an antenna array structure having a plurality of antenna elements that receive and transmit radio-frequency signals;

a plurality of radio-frequency units and frequency converters configured to transform received RF signals to receive analog base-band signals and transform analog transmit base-band signals into a transmit RF signals;

a plurality analog-to-digital converters configured to convert the receive analog base-band signals into a receive digital base-band signals and a plurality of digital-to-analog converters configured to convert transmit digital base-band signals into transmit analog base-band signals;

a multipath delay profile estimation unit configured to estimate delays of multipath signal components based on the receive digital base-band signals; and

a plurality of beam-forming units configured to process the multipath signal components, wherein each of the beam-forming units comprise;

a set of hierarchical weight banks that store pre-calculated weights in accordance with pre-specified beam look directions;

a digital processing unit configured to estimate a signal metric, select the best weights from weight banks based on the estimated signal metric, and apply the selected weights to the received digital signal to shift a beam pattern to point to the best beam look direction.

2. The wireless communication system of claim 1, further comprising:

a combining mechanism configured to combine signal components from the beam-forming units in the presence of the multipath signal components.

3. The wireless communication system of claim 1, wherein the antenna elements are configured as at least one of omni-directional and/or sectorized elements.

4. The wireless communication system of claim 1, wherein the pre-calculated weights are applied to the digital receive base-band signal.

5. The wireless communication system of claim 1, wherein the antenna array structure comprises at least one linear array.

6. The wireless communication system of claim 5, wherein a mirror beam is used to support searching of an azimuth angle greater than 180 degrees.

7. The wireless communication system of claim 1, wherein the antenna array structure comprises at least one two dimensional antenna array.

8. The wireless communication system of claim 1, wherein the antenna array structure comprises at least one three dimensional antenna array.

9. The wireless communication system of claim 1, wherein pre-calculated weights are stored in a hierarchical weight bank structure.

10. The wireless communication system of claim 9, wherein the hierarchical weight bank structure comprises a binary tree.

11. The wireless communication system of claim 9, wherein the hierarchical weight bank structure comprises a B+ tree.

12. The wireless communication system of claim 1, wherein the multipath delay profile estimation unit detects multipath signal components of multiple received digital signals, separate the multipath signal components in the time domain, and distribute received multipath signal components to one or more beam-forming units.

13. The wireless communication system of claim 12, wherein each beam-forming unit processes a separate multipath signal component.

14. The wireless communication system of claim 1, wherein the signal metric comprises at least one of instant received power, bit error rate, frame error rate, signal-to-noise ratio, and signal-to-interference plus noise ratio.

15. The wireless communication system of claim 1, wherein the beam-forming units process the transmit digital base-band signals.

16. The wireless communication system of claim 14, wherein the beam-forming units apply the weights that correspond to the best received beam look direction to the transmit digital base-band signals.

44. The wireless communication system of claim 1, further comprising an electronically controlled switch configured to multiplex receive signals from multiple antenna elements through one of the radio-frequency units, one of the frequency converters, and one or more of the analog-to-digital converters.

17. A wireless communication method, comprising:

transmitting and receiving radio-frequency signals through an antenna array structure having a plurality of antenna elements;

transforming received RF signals into receive analog base-band signals;

transforming transmit analog base-band signals into a transmit RF signals;

converting the receive analog base-band signals into receive digital base-band signals;

converting transmit digital base-band signals into transmit analog base-band signals;

estimating delays of multipath signal components based on the receive digital base-band signals;

pre-specifying beam look directions and calculating the weights associated with each look direction; and

processing the multipath signal components via a plurality of beam-forming units, wherein each of the beam-forming units operate by;

referencing banks of pre-calculated weights in accordance with the pre-specified beam look directions;

estimating a signal metric from the multipath signal components,

selecting the best weights from weight banks based on the estimated signal metric, and

applying the selected weights to the received digital signal to shift a beam pattern to point to the best beam look direction.

18. The method of claim 17, further comprising:

combining signal components from the beam-forming units in the presence of the multipath signal components.

19. The method of claim 17, wherein the pre-calculated weights are applied to the digital receive base-band signal.

20. The method of claim 17, wherein the antenna array structure comprises at least one linear array.

21. The method of claim 20, wherein a mirror beam is used to support searching of an azimuth angle greater than 180 degrees.

22. The method of claim 17, wherein the antenna array structure comprises at least one two dimensional array.

23. The method of claim 17, wherein the antenna array structure comprises at least one three dimensional array.

24. The method of claim 17, wherein the hierarchical weight bank structure comprises a binary tree.

25. The method of claim 17, wherein the hierarchical weight bank structure comprises a B+ tree.

26. The method of claim 17, wherein each beam-forming unit processes a separate multipath signal component.

27. The method of claim 17, wherein the signal metric comprises at least one of instant received power, bit error rate, frame error rate, signal-to-noise ratio, and signal-to-interference plus noise ratio.

28. The method of claim 17, wherein the beam-forming units process the transmit digital base-band signals.

29. The method of claim 17, wherein the beam-forming units apply the weights that correspond to the best received beam look direction to the transmit digital base-band signals.

45. The method of claim 17, wherein the pre-calculated weights are applied to the digital transmission base-band signal.

48. The method of claim 17, further comprising multiplexing received signals from a plurality of antenna elements through a single radio-frequency unit and a single frequency converter via an electrically-controlled switch, wherein the electrically controlled switch is in synchronization with sample clock of one or more analog-to-digital converters.

30. A method for calculating a set of weights corresponding to a pre-determined look direction using a data independent technique.

31. A system for calculating one or more sets weights for pre-determined look directions, and storing those sets of weights in a hierarchical weight bank structure

32. A wireless communication system, comprising:

an antenna array structure having a plurality of antenna elements that receive and transmit radio-frequency signals, the plurality of antenna elements including at least one active antenna element and a plurality of parasitic antenna elements, wherein each of the parasitic antenna elements are coupled to either an adjustable impedance component or electrical ground;

one or more radio-frequency units and one or more frequency converters configured to transform the receive radio-frequency signals into receive analog base-band signals and transform transmit analog base-band signals into the transmit radio-frequency signals;

one or more analog-to-digital converters configured to convert the receive analog base-band signals into receive digital base-band signals and a plurality of digital-to-analog converters configured to convert transmit digital base-band signals into the transmit analog base-band signals;

a set of hierarchical weight banks that store pre-calculated weights in accordance with pre-specified beam look directions; and

a digital processing unit configured to estimate a signal metric, select the best weights from weight banks based on the estimated signal metric, and apply the selected weights to the adjustable impedance components attached to the parasitic antenna elements.

33. The wireless communication system of claim 32, wherein the antenna elements are configured as at least three omni-directional and/or sectorized antenna elements.

34. The wireless communication system of claim 32, wherein the pre-calculated weights are applied to the received analog radio-frequency signal by using the digital-to-analog converters to adjust the voltage levels of the adjustable impedance components coupled to the parasitic elements to control the beam pattern of the antenna array.

35. The wireless communication system of claim 32, wherein the antenna array structure comprises at least one linear array.

36. The wireless communication system of claim 32, wherein the antenna array structure comprises at least one two dimensional antenna array.

37. The wireless communication system of claim 32, wherein the antenna array structure comprises at least one three dimensional antenna array.

38. The wireless communication system of claim 32, wherein the antenna array structure comprises at least one parasitic antenna array having at least one active element and a plurality of parasitic antenna elements, each of the parasitic antenna elements being coupled to either an adjustable impedance component or electrical ground.

39. The wireless communication system of claim 32, wherein the pre-calculated weights are stored in a hierarchical weight bank structure.

40. The wireless communication system of claim 39, wherein the hierarchical weight bank structure comprises a binary tree.

41. The wireless communication system of claim 39, wherein the hierarchical weight bank structure comprises a B+ tree.

42. The wireless communication system of claim 32, wherein the signal metric comprises at least one of instant received power, bit error rate, frame error rate, signal-to-noise ratio, and signal-to-interference plus noise ratio.

43. The wireless communication system of claim 32, wherein beam-forming is applied to transmitted signals by using the weights that correspond to the best receiver beam look direction.

46. A wireless communication method, comprising:

transmitting and receiving radio-frequency signals through an antenna array structure having a plurality of antenna elements in which at least one of the antenna elements is a parasitic antenna element that is coupled to an adjustable impedance component;

transforming receive radio-frequency signals into receive analog base-band signals;

transforming transmit analog base-band signals into the transmit radio-frequency signals;

converting the receive analog base-band signals into receive digital base-band signals;

converting transmit digital base-band signals into the transmit analog base-band signals;

pre-specifying beam look directions;

calculating weights associated with each of the pre-specified look direction; and

processing the receive and transmit signals via a beam-forming unit, wherein the beam-forming unit operates by;

referencing banks of pre-calculated weights in accordance with the pre-specified beam look directions;

estimating a signal metric from receive signal components,

selecting best weights from the referenced banks of pre-calculated weights based on the estimated signal metric, and

applying the best weights to the adjustable impedance components in order to create a receive and a transmit beam in the desired look direction.

47. The method of claim 46, where the antenna array structure comprises at least one parasitic antenna array having at least one active element and a plurality of parasitic elements which are coupled to the adjustable impedance components.