Vertical adaptive antenna array for a discrete multitone spread spectrum communications system

• US 20020159506A1
• Filed: 12/10/2001
• Published: 10/31/2002
• Est. Priority Date: 02/24/1997
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: Douglas Frank Stolarz, Joel E. Becker, Siavash Alamouti
• Inventors: Alamouti, Siavash, Becker, Joel E., Stolarz, Douglas Frank
• Granted Patent: US 6,584,144 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 5/026 using code division

Abstract

Two or more antenna elements are arranged in the vertical direction to give vertical spatial adaptivity to a wireless discrete multitone spread spectrum communications system. The system is based on a combination of Discrete Multitone Spread Spectrum (DMT-SS) and multi-element adaptive antenna array technologies. This enables the automatic positioning of a beam in the vertical direction to position nulls where interferers are located on the same azimuth but are separated in elevation.

Claims

1. A highly bandwidth-efficient communications method, comprising:

receiving a received spread signal at a base station having a multi-element antenna array with a first plurality of antenna elements arranged in a spaced vertical direction and a second plurality of antenna elements arranged in a spaced horizontal direction;

said received spread signal comprising a first data signal spread over a plurality of discrete tones in accordance with a remote spreading code assigned to a remote unit for a first time period;

adaptively despreading the signal received at the base station by using first despreading codes that are based on the characteristics of the received signals at the first plurality of antenna elements of said array and perform vertical beam steering; and

adaptively despreading the signal received at the base station by using second despreading codes that are based on the characteristics of the received signals at the second plurality of antenna elements of said array to perform horizontal beam steering.

2. The highly bandwidth-efficient communications method of claim 1, further comprising:

spreading a second data signal at the base station with first spreading codes derived from said first despreading codes, that distributes the second data signal over a plurality of discrete tones and the first plurality antenna elements of said array, forming a first spectrally spread signal that is spectrally and spatially spread vertically;

spreading the second data signal at the base station with second spreading codes derived from said second despreading codes, that distributes the second data signal over the plurality of discrete tones and the second plurality antenna elements of said array, forming a second spectrally spread signal that is spectrally and spatially spread horizontally; and

transmitting said first and second spread signals during a second time period.

3. The highly bandwidth-efficient communications method of claim 1, further comprising:

receiving at the base station during an initialization period, a pilot spread signal comprising a known data signal spread over a plurality of discrete tones;

correlating the known data signal from the pilot spread signal with a reference known data signal and forming said first despreading code that is based on the characteristics of the received signals at the first plurality of antenna elements arranged in the spaced vertical direction, where a given element of the first despreading code corresponds to a given one of the first antenna elements and a given one of the discrete tones; and

correlating a known data signal from the pilot spread signal with a reference known data signal and forming said second despreading code that is based on the characteristics of the received signals at the second plurality of antenna elements arranged in the spaced horizontal direction, where a given element of the second despreading code corresponds to a given one of the second antenna elements and a given one of the discrete tones.

4. The highly bandwidth-efficient communications method of claim 2, wherein both the first and the second spread signals have a spectral form of a discrete multitone signal transmitted on multiple elements in the array.

5. The highly bandwidth-efficient communications method of claim 1, wherein the despreading step is a multiplication of a complex number representation of the despreading codes times a complex number representation of the received spread signal.

6. The highly bandwidth-efficient communications method of claim 2, wherein the spreading step is a multiplication of a complex number representation of the second spreading codes times a complex number representation of the data signal to be transmitted.

7. The highly bandwidth-efficient communications method of claim 1, wherein the despreading steps determine values of complex despreading codes which are then multiplied with a complex number representation of the received signals, resulting in an estimate of the first data signal.

8. The highly bandwidth-efficient communications method of claim 1, wherein the despreading steps adaptively position the spatial direction of receive sensitivity towards a desired signal source and diminish receive sensitivity from interfering sources

9. The highly bandwidth-efficient communications method of claim 2, wherein the spreading steps adaptively position transmitted signal energy of the spread signals towards a source of the received spread signal and adaptively diminishes transmitted signal energy towards interferers.

10. The highly bandwidth-efficient communications method of claim 2, wherein the first period and the second period are parts of a time division duplex period.

11. The highly bandwidth-efficient communications method of claim 1, wherein the antenna array has a planar symmetry.

12. The highly bandwidth-efficient communications method of claim 1, wherein the antenna array has a cylindrical symmetry.

14. The highly bandwidth-efficient communications system of claim 13, further comprising:

means for spreading a second data signal at the base station with first spreading codes derived from said first despreading codes, that distributes the second data signal over a plurality of discrete tones and the first plurality antenna elements of said array, forming a first spectrally spread signal that is spectrally and spatially spread vertically;

said means for spreading also spreading the second data signal at the base station with second spreading codes derived from said second despreading codes, that distributes the second data signal over the plurality of discrete tones and the second plurality antenna elements of said array, forming a second spectrally spread signal that is spectrally and spatially spread horizontally; and

means for transmitting said first and second spread signals during a second time period.

15. The highly bandwidth-efficient communications system of claim 13, further comprising:

means for receiving at the base station during an initialization period, a pilot spread signal comprising a known data signal spread over a plurality of discrete tones;

means for correlating the known data signal from the pilot spread signal with a reference known data signal and forming said first despreading code that is based on the characteristics of the received signals at the first plurality of antenna elements arranged in the spaced vertical direction, where a given element of the first despreading code corresponds to a given one of the first antenna elements and a given one of the discrete tones; and

said correlating means also correlating a known data signal from the pilot spread signal with a reference known data signal and forming said second despreading code that is based on the characteristics of the received signals at the second plurality of antenna elements arranged in the spaced horizontal direction where a given element of the second despreading code corresponds to a given one of the second antenna elements and a given one of the discrete tones.

16. The highly bandwidth-efficient communications system of claim 14, wherein both the first and the second spread signals have a spectral form of a discrete multitone signal transmitted on multiple elements in the array.

17. The highly bandwidth-efficient communications system of claim 13, wherein the despreading is a multiplication of a complex number representation of the despreading codes times a complex number representation of the received spread signal.

18. The highly bandwidth-efficient communications system of claim 14, wherein the spreading is a multiplication of a complex number representation of the second spreading codes times a complex number representation of the data signal to be transmitted.

19. The highly bandwidth-efficient communications system of claim 13, wherein the despreading determines values of complex despreading codes which are then multiplied with a complex number representation of the received signals, resulting in an estimate of the first data signal.

20. The highly bandwidth-efficient communications system of claim 13, wherein the despreading adaptively positions the spatial direction of receive sensitivity towards a desired signal source and diminishes receive sensitivity from interfering sources.

21. The highly bandwidth-efficient communications system of claim 14, wherein the spreading adaptively positions transmitted signal energy of the spread signals towards a source of the received spread signal and adaptively diminishes transmitted signal energy towards interferers.

22. The highly bandwidth-efficient communications system of claim 14, wherein the first period and the second period are parts of a time division duplex period.

23. The highly bandwidth-efficient communications system of claim 13, wherein the antenna array has a planar symmetry.

24. The highly bandwidth-efficient communications system of claim 13, wherein the antenna array has a cylindrical symmetry.

13. A highly bandwidth-efficient communications system, comprising:

means for receiving a received spread signal at a base station having a multi-element antenna array with a first plurality of antenna elements arranged in a spaced vertical direction and a second plurality of antenna elements arranged in a spaced horizontal direction;

said received spread signal comprising a first data signal spread over a plurality of discrete tones in accordance with a remote spreading code assigned to a remote unit for a first time period;

means for adaptively despreading the signal received at the base station by using first despreading codes that are based on the characteristics of the received signals at the first plurality of antenna elements of said array and perform vertical beam steering; and

said despreading means adaptively despreading the signal received at the base station by using second despreading codes that are based on the characteristics of the received signals at the second plurality of antenna elements of said array to perform horizontal beam steering.