Apparatus and method of enhancing transmit diversity

• US 6,594,226 B1
• Filed: 12/15/1999
• Issued: 07/15/2003
• Est. Priority Date: 12/15/1999
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Soni, Robert Atmaram, Benning, Roger David, Buehrer, R. Michael
• Primary Examiner(s): Vu, Huy D.
• Assistant Examiner(s): HO, DUC CHI
• Application Number:
  US09/464,615
• Time in Patent Office: 1,308 Days
• Field of Search: 370/203, 370/208, 370/209, 370/334, 370/335, 370/342, 375/267, 375/299, 375/144, 375/146, 375/347, 375/147, 375/145, 455/101, 455/269, 455/276.1, 455/562, 343/844, 342/354, 342/368, 342/373, 342/374, 342/375
• US Class Current: 370/208
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence

Abstract

Disclosed is a method and apparatus for enhancing diversity gain without reducing data rate by increasing the number of antenna elements and configuring the antenna elements for improving signal-to-noise ratio at a receiver. The antenna array comprise a first antenna group with at least two antenna elements and a second antenna group with at least one antenna element. The first and second antenna groups are spaced approximately ten carrier wavelengths or more apart from each other, and the antenna elements belonging to the first antenna group are spaced approximately a half carrier wavelength or less apart from each other. A plurality of data streams is generated from a signal and used to produce a first and second plurality of representative data streams. Each of the first plurality of representative data streams is phase-shifted and encoded using different orthogonal codes.

Claims

1. A method of signal processing for a wireless communications system employing an antenna array having at least a first antenna group with at least two antenna elements and a second antenna group with at least one antenna element, wherein the first and second antenna groups are spaced approximately ten carrier wavelengths or more apart from each other and the antenna elements belonging to the first antenna group are spaced approximately a half carrier wavelength or less apart from each other, the method comprising the steps of:

generating a plurality of data streams from a signal;

encoding each of at least two sets of a first plurality of representative data streams derived from the plurality of data streams using different orthogonal codes;

phase shifting a first set of the first plurality of representative data streams;

encoding each of at least one set of a second plurality of representative data streams derived from the plurality of data streams using different orthogonal codes, wherein different orthogonal codes are used to encode representative data streams of the first and second plurality of representative data streams derived from a same data stream in the plurality of data streams, the first and second plurality of representative data streams being representative data streams of the plurality of data streams that allow for the plurality of data streams to be recovered at a receiver after encoding;

transmitting an encoded and phase shifted first set of the first plurality of representative data streams over a first antenna element in the first antenna group;

transmitting an encoded second set of the first plurality of representative data streams over a second antenna element in the first antenna group; and

transmitting an encoded set of the second plurality of representative data streams over an antenna element in the second antenna group.

2. The method of claim 1, wherein D number of data streams are generated from the signal S and D is equal to a number of antenna groups rounded up to the nearest power of two.

3. The method of claim 1, wherein the first set of the first plurality of representative data streams are phase shifted such that the encoded and phase shifted first set of the first plurality of representative data streams arrive in-phase with the encoded second set of the first plurality of representative data streams at the receiver.

4. The method of claim 1, wherein the step of phase shifting comprises the step of:

measuring an angle-of-arrival of a signal transmitted by the receiver, the angle-of-arrival indicating a phase difference between signals transmitted over the first and second antenna elements in the first antenna group.

5. The method of claim 1, wherein the step of phase shifting comprises the step of:

receiving phase information from the receiver indicating a phase difference between signals transmitted over the first and second antenna elements in the first antenna group.

6. The method of claim 1, wherein the plurality of data streams are recoverable at the receiver when the first and second plurality of representative data streams are such that a summation of products between a first representative data stream encoded with an orthogonal code and a second representative data stream encoded with a same orthogonal code, for all orthogonal codes, result in a value of zero, the first representative data stream is a representative data stream belonging to the first plurality of representative data streams and the second representative data stream is a representative data stream belonging to the second plurality of representative data streams.

7. The method of claim 1, wherein the orthogonal codes are Walsh codes.

8. The method of claim 1 comprising the additional steps of:

transmitting a first pilot signal over the first antenna element in the first antenna group;

transmitting a second pilot signal over the second antenna element in the first antenna group; and

transmitting a third pilot signal over the antenna element in the second antenna group.

9. The method of claim 8, wherein the first, second and third pilot signals are encoded using an identical orthogonal code.

10. The method of claim 8, wherein the first, second and third pilot signals are unique pilot signals.

11. The method of claim 8, wherein the first and second pilot signals are encoded using an identical orthogonal code.

12. The method of claim 8, wherein the first and second pilot signals are unique pilot signals.

13. The method of claim 8, wherein the first, second and third pilot signals are associated with the receiver.

14. A wireless communications system comprising:

a plurality of antenna groups including a first antenna group having at least one antenna element and a second antenna group having at least two antenna elements, the first and second antenna groups spaced a distance apart from each other such that signals transmitted from the first antenna group experience fading independent of signals transmitted from the second antenna group, the two antenna elements of the second antenna group spaced a distance apart from each other such that signals transmitted from the antenna elements experience correlated fading; and

a transmitter for generating a plurality of data streams from a signal, for transmitting each of at least two sets of a first plurality of representative data streams derived from the plurality of plurality of data streams and encoded using different orthogonal codes over the first antenna group, and for transmitting each of at least one set of a second plurality of representative data streams derived from the plurality of plurality of data streams and encoded using different orthogonal codes over the second antenna group, wherein different orthogonal codes are used to encode representative data streams of the first and second plurality of representative data streams derived from a same data stream in the plurality of data streams, the first and second plurality representative data streams being representative data streams of the plurality of data streams that allow for the plurality of data streams to be recovered at a receiver after encoding, and a first set of the second plurality of representative data streams being phase shifted for transmission over an antenna element belonging to the second antenna group.

15. The wireless communications system of claim 14, wherein the transmitter generates D number of data streams from the signal S and D is equal to a number of antenna groups rounded up to the nearest power of two.

16. The wireless communications system of claim 14, wherein the transmitter phase shifts the first set of the first plurality of representative data streams such that the encoded and phase shifted first set of the first plurality of representative data streams arrive in-phase with the encoded second set of the first plurality of representative data streams at the receiver.

17. The wireless communications system of claim 14 further comprising:

a second plurality of antenna groups for measuring an angle-of-arrival of a signal transmitted by the receiver, the angle-of-arrival indicating a phase difference between signals transmitted over the first and second antenna elements in the first antenna group.

18. The wireless communications system of claim 14 further comprising:

a receiver for receiving phase information from the receiver indicating a phase difference between signals transmitted over the first and second antenna elements in the first antenna group.

19. The wireless communications system of claim 14, wherein the plurality of data streams are recoverable at the receiver when the first and second plurality of representative data streams are such that a summation of products between a first representative data stream encoded with an orthogonal code and a second representative data stream encoded with a same orthogonal code, for all orthogonal codes, result in a value of zero, the first representative data stream is a representative data stream belonging to the first plurality of representative data streams and the second representative data stream is a representative data stream belonging to the second plurality of representative data streams.

20. The wireless communications system of claim 14, wherein the orthogonal codes are Walsh codes.

21. The wireless communications system of claim 14 the transmitter transmits a first pilot signal over the first antenna element in the first antenna group, a second pilot signal over the second antenna element in the first antenna group, and a third pilot signal over the antenna element in the second antenna group.

22. The wireless communications system of claim 21, wherein the first, second and third pilot signals are encoded using an identical orthogonal code.

23. The wireless communications system of claim 21, wherein the first, second and third pilot signals are unique pilot signals.

24. The wireless communications system of claim 21, wherein the first and second pilot signals are encoded using an identical orthogonal code.

25. The wireless communications system of claim 21, wherein the first and second pilot signals are unique pilot signals.

26. The wireless communications system of claim 21, wherein the first, second and third pilot signals are associated with the receiver.