Method and apparatus for utilizing a directional beam antenna in a wireless transmit/receive unit

• US 20050202859A1
• Filed: 11/24/2004
• Published: 09/15/2005
• Est. Priority Date: 11/24/2003
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Wang, Carl, Charlton, Gregg Arthur, Johnson, Kevin Peter, Lintelman, Ross L., Lynch, Michael James, Zangi, Kambiz Casey
• Granted Patent: US 7,460,834 B2
• Time in Patent Office: Days
• US Class Current: 455/575.700
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0695 using beam selection
• CPC Class Codes: H04B 7/088 using beam selection
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A method and apparatus for utilizing a switched beam directional antenna in a wireless transmit/receive unit (WTRU) is disclosed. A wireless communication system includes a serving cell, a neighbor cell and a WTRU. The WTRU is configured to generate and steer a directional beam in a plurality of directions. Once the WTRU registers with the wireless communication system, the WTRU receives messages transmitted by the serving cell. The WTRU measures signal quality of messages received in each of a plurality of predetermined directions while steering the directional beam antenna. The WTRU selects a particular one of the directions having the best signal quality. As the WTRU constantly moves, the WTRU monitors signal quality in the selected direction, and switches to another direction when the signal quality in a current direction drops below a predetermined threshold.

Claims

1. In a wireless communication system including a serving cell, at least one neighbor cell and at least one wireless transmit/receive unit (WTRU), a method for utilizing a directional beam antenna in the WTRU, comprising the steps of:

(a) the WTRU registering with the wireless communication system;

(b) the WTRU receiving signals transmitted by the serving cell and the neighbor cell;

(c) the WTRU measuring quality of the signals received in each of a plurality of predetermined directions while steering the directional beam antenna; and

(d) selecting a particular one of the directions having the best signal quality as an active beam.

2. The method of claim 1 further comprising the steps of:

(e) comparing the signal quality to a predetermined threshold; and

(f) maintaining the current position of the antenna if the signal quality is not below the predetermined threshold, and repeating steps (c) and (d) if the signal quality is below the predetermined threshold.

3. The method of claim 1 wherein the signal quality is measured in terms of at least one of a received signal strength indicator and a carrier-to-interference ratio.

4. The method of claim 1 wherein the quality of signals is measured in a dormant time slot.

5. The method of claim 1 wherein the WTRU receives signals from the serving cell in a different frame than the WTRU receives signals from the neighbor cell.

6. The method of claim 5 wherein the frame for receiving signals from the serving cell is determined to be same as the frames carrying a base station identity code on a broadcast control channel of the serving cell.

7. The method of claim 6 wherein the WTRU further obtains synchronization with the neighbor cell, whereby the frame for receiving signals from the neighbor cell is determined to be same as the frames carrying a base station identity code on a broadcast control channel of the neighbor cell.

8. The method of claim 5 wherein the WTRU decodes a base station identity code before changing the active beam.

9. The method of claim 5 wherein the WTRU does not decode a base station identity code before changing the active beam.

10. The method of claim 5 wherein the WTRU receives signals from the neighbor cell using an omni-directional beam.

11. The method of claim 1 wherein the signal quality is measured with messages transmitted from the serving cell via one of a pilot channel, a broadcast channel and a traffic channel.

12. The method of claim 1 wherein the quality of signals received from two different directions are compared with a midamble containing a data sequence, such that the quality of signals received from one direction is measured using a first half of the midamble and the quality of signals received from the other direction is measured using a second half of the midamble.

13. The method of claim 1 wherein one time slot is divided into a plurality of parts, and the quality of signals for each direction is measured in a different part of the time slot.

14. The method of claim 1 wherein the selection of the best directional beam is based on the average of some number of signal quality measurements made for each directional beam.

15. The method of claim 1 wherein the selection of the best directional beam is based on the differences between signal quality measurements made for each directional beam.

16. A wireless transmit/receive unit (WTRU) comprising:

(a) a switched beam directional antenna for generating a directional beam;

(b) a receiver/transmitter, electrically coupled to the switched beam directional antenna, for receiving and transmitting signals;

(c) a baseband processor, electrically coupled to the receiver/transmitter, for processing signals received by the receiver/transmitter;

(d) a beam steering unit, electrically coupled to the switched beam directional antenna, for steering the beam to a plurality of directions; and

(e) a controller, electrically coupled to the beam steering unit, the receiver/transmitter, and the baseband processor, the controller for steering the directional beam in a direction having the best quality of signal.

17. The WTRU of claim 16 wherein the controller constantly monitors signal quality in the selected direction and switches the beam steering unit to another predefined direction when the signal quality is below a predetermined threshold.

18. The WTRU of claim 17 wherein the signal quality is measured in terms of at least one of a received signal strength indicator and a carrier-to-interference ratio.

19. The WTRU of claim 16 wherein the quality of signals is measured in a dormant time slot.

20. The WTRU of claim 16 wherein the WTRU receives signals from the serving cell in a different frame than the WTRU receives signals from the neighbor cell.

21. The WTRU of claim 20 wherein the frame for receiving signals from the serving cell is determined to be same as the frames carrying a base station identity code on a broadcast control channel of the serving cell.

22. The WTRU of claim 21 wherein the WTRU further obtains synchronization with the neighbor cell, whereby the frame for receiving signals from the neighbor cell is determined to be same as the frames carrying a base station identity code on a broadcast control channel of the neighbor cell.

23. The WTRU of claim 20 wherein the WTRU decodes a base station identity code before changing the active beam.

24. The WTRU of claim 20 wherein the WTRU does not decode a base station identity code before changing the active beam.

25. The WTRU of claim 20 wherein the WTRU receives signals from the neighbor cell using an omni-directional beam.

26. The WTRU of claim 16 wherein the signal quality is measured with messages transmitted from the serving cell via one of a pilot channel, a broadcast channel and a traffic channel.

27. The WTRU of claim 16 wherein the quality of signals received from two different directions are compared with a midamble containing a data sequence, such that the quality of signals received from one direction is measured using a first half of the midamble and the quality of signals received from the other direction is measured using a second half of the midamble.

28. The WTRU of claim 16 wherein one time slot is divided into a plurality of parts, and the quality of signals for each direction is measured in a different part of the time slot.

29. The WTRU of claim 16 wherein the selection of the directional beam is based on the average of some number of signal quality measurements made for each directional beam.

30. The WTRU of claim 16 wherein the selection of the directional beam is based on the differences between signal quality measurements made for each directional beam.

31. An integrated circuit (IC) for use with an antenna array which generates a directional beam, the IC comprising:

a receiver/transmitter, electrically coupled to a switched beam directional antenna, for processing signals received and transmitted by the switched beam directional antenna;

a baseband processor, electrically coupled to the receiver/transmitter, for measuring the quality of the signals received by the switched beam directional antenna;

a beam steering unit, electrically coupled to the receiver/transmitter, for steering the beam to a plurality of directions; and

a controller, electrically coupled to the receive/transmitter, the beam steering unit and the baseband processor, the controller for steering the directional beam in a direction having the best quality of signal.