Adaptive antenna for use in same frequency networks

• US 6,518,920 B2
• Filed: 08/28/2001
• Issued: 02/11/2003
• Est. Priority Date: 12/11/1998
• Status: Expired due to Fees

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: Tantivy Communications Incorporated (InterDigital, Inc.)
• Inventors: Gainey, Kenneth M., Proctor, Jr., James A.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/942,257
• Publication Number:
  US 20020047800A1
• Time in Patent Office: 532 Days
• Field of Search: 342/154, 342/157, 342/357, 342/368, 342/372
• US Class Current: 342/367
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• 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: H04B 7/0874 using subgroups of receive antennas

Abstract

An antenna apparatus which can increase capacity in a cellular communication system. The antenna operates in conjunction with a mobile subscriber unit and provides a plurality of antenna elements, each coupled to a respective programmable phase shifter. The phase of each antenna element is programmed for optimum reception during, for example, an idle mode which receives a pilot signal. The antenna array creates a beamformer for signals to be transmitted from the mobile subscriber unit, and a directional receiving array to more optimally detect and receive signals transmitted from the base station. By directionally receiving and transmitting signals, multipath fading is greatly reduced as well as intercell interference. Various techniques for determining the proper phase of each antenna element are accommodated.

Claims

1. In a system for providing wireless communications among a plurality of subscribers using spread spectrum signaling for transmission of a plurality of desired traffic signals from a subscriber unit to a base station unit on a common carrier frequency within a defined transmission region, a method for operating a directional antenna array which includes a plurality of antenna elements having programmable phase shifters, the method comprising the steps of:

determining, from a received pilot signal transmitted on a forward link from the base station to the subscriber unit and a plurality of candidate positions, a set of phase shifts for the antenna array that optimize reception of the pilot signal; and

setting the phase shifts to the optimized set of values during transmission of a forward link traffic signal, the optimal phase shift settings determined as a function of the direction of the base station.

2. A method of transmitting and receiving wireless signals between a subscriber unit and a base station, the subscriber being in a particular direction in relation to the base station, comprising:

determining the direction of the subscriber unit in relation to the base station from a plurality of candidate positions;

computing, at the subscriber unit, optimal phase shift control settings corresponding to the determined direction, the optimal phase shift settings determined as a function of the direction of the base station; and

applying the phase shift control settings to a plurality of adjustable phase shifters, each of the adjustable phase shifters in communication with a respective wireless antenna element for transmitting and receiving the wireless signals in the determined direction, wireless signals transmitted in the determined direction operable to be received at an optimal signal strength.

3. The method of claim 2 wherein the subscriber unit determines the direction to the base station to compute the optimal phase shift control settings.

4. The method of claim 2 wherein transmitting and receiving in the determined direction further comprises transmitting substantially all transmitting power in the determined direction and transmitting at a relatively low power level in other directions.

5. The method of claim 2 wherein the wireless signals transmitted in other than the determined direction are of a substantially lower power level than the signal transmitted in the determined direction.

6. The method of claim 2 further comprising periodically recomputing and applying the phase shift control settings.

7. The method of claim 2 further comprising determining an idle time wherein periodically recomputing is performed during the idle time.

8. The method of claim 2 wherein determining the direction further comprises

transmitting a pilot signal from the base station to the subscriber unit;

receiving the pilot signal at a plurality of antenna elements at the subscriber unit; and

comparing the received pilot signal according to a link quality metric.

9. The method of claim 8 further comprising comparing the received pilot signal to pilot signals received at other phase shift control settings.

10. The method of claim 8 wherein the link quality metric further comprises computing at least one of a signal to noise ratio (SNR), bit error rate (BER) and a noise energy level per chip.

11. The method of claim 2 wherein computing the optimal phase shift control settings further comprises computing optimal phase shift control settings for each of a plurality of antenna elements.

12. The method of claim 2 wherein the optima phase shift control settings further comprise maximizing the received signal energy.

13. The method of claim 2 wherein computing the optimal phase shift control settings further comprises computing a phase control value for each of the plurality of antenna elements.

14. The method of claim 2 wherein computing the optimal phase shift control settings further comprises:

determining an idle phase of data traffic signals over the wireless link;

transmitting a pilot signal from the base station to the subscriber unit;

applying a predetermined phase setting to each of the plurality of antenna elements, the predetermined phase setting corresponding to a relative direction of the base station;

measuring a received signal strength of the pilot signal at the predetermined phase settings;

iterating through additional predetermined phase settings, each of the predetermined phase settings corresponding to one of a particular relative direction; and

determining, when a particular predetermined phase settings corresponds to an optimal setting, the predetermined phase settings as the optimal phase settings.

15. The method of claims 2 wherein computing the optimal phase shift control settings further comprises:

selecting one of the plurality of antenna elements;

applying a predetermined phase setting to each of the unselected antenna elements;

varying the phase setting of the selected antenna elements through a plurality of phase settings, each phase setting corresponding to a particular relative direction;

measuring a received signal strength of a pilot signal at each of the plurality of phase setting;

determining if the received signal strength corresponds to an optimal phase setting;

iterating, through phase settings corresponding to other relative directions, if the received signal strength does not correspond to an optimal phase setting; and

selecting another one of the plurality of antenna elements if the received signal strength corresponds to an optimal phase setting.

16. A system for providing wireless communications among a plurality of subscribers using spread spectrum signaling for transmission of a plurality of desired traffic signals from a subscriber unit to a base station unit on a common carrier frequency within a defined transmission region employing a directional antenna array comprising:

a plurality of antenna elements

a like plurality of programmable phase shifters at the subscriber unit, each of the programmable phase shifters in communication with a corresponding one of the antenna elements, the antenna elements responsive to the programmable phase shifters for adjusting the phase of wireless signals transmitted thereby;

a pilot signal operable to be transmitted over a forward link from the base station to the subscriber unit and received by the plurality of antenna elements; and

a control processor at the subscriber unit responsive to the received pilot signal and operable to compute optimal phase shift settings from a plurality of candidate positions, the optimal phase shift settings determined as a function of the direction of the base station and the programmable phase shifters responsive to the control processor and operable to apply the computed optimal phase shift settings.

17. The system of claim 16 further comprising a determined direction corresponding to the location of the subscriber in relation to the base station, the optimal phase shift settings computed from the determined direction.

18. The system of claim 17 wherein transmitting and receiving in the determined direction further comprises transmitting substantially all transmitting power in the determined direction and transmitting at a relatively low power level in other directions.

19. The method of claim 17 wherein the wireless signals transmitted in other than the determined direction are of a substantially lower power level than the signal transmitted in the determined direction.