TRANSMITTER DIVERSITY TECHNIQUE FOR WIRELESS COMMUNICATIONS

• US 20080063107A1
• Filed: 10/30/2007
• Published: 03/13/2008
• Est. Priority Date: 09/16/1997
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Alamouti, Siavash, Tarokh, Vahid
• Granted Patent: US 7,587,007 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 1/02 Transmitters
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/04 using frequency diversity
• CPC Class Codes: H04L 1/0606 Space-frequency coding
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0631 Receiver arrangements
• CPC Class Codes: H04L 1/0643 block codes
• CPC Class Codes: H04L 1/0668 : Orthogonal systems, e.g. using Alamouti codes
• CPC Class Codes: H04L 1/08 : by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 25/0202 : Channel estimation

Abstract

A simple block coding arrangement is created with symbols transmitted over a plurality of transmit channels, in connection with coding that comprises only of simple arithmetic operations, such as negation and conjugation. The diversity created by the 5 transmitter utilizes space diversity and either time or frequency diversity. Space diversity is effected by redundantly transmitting over a plurality of antennas, time diversity is effected by redundantly transmitting at different times, and frequency diversity is effected by redundantly transmitting at different frequencies: Illustratively, using two transmit antennas and a single receive antenna, one of the disclosed embodiments provides the to same diversity gain as the maximal-ratio receiver combining (MRRC) scheme with one transmit antenna and two receive antennas. The principles of this invention are applicable to arrangements with more than two antennas, and an illustrative embodiment is disclosed using the same space block code with two transmit and two receive antennas.

Claims

1. An electronic circuit capable of receiving a wireless communication from first and second space diverse antennas, the wireless communication being further one of time diverse or frequency diverse, the electronic circuit comprising:

a channel estimator for estimating characteristics of a transmit channel received from at least one of said space diverse antennas and outputting said estimated channel characteristics to a signal combiner and to a detector, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

said signal combiner for combining signals received from said first and second space diverse antennas and outputting said combined signals to said detector as two output data signals responsive to said estimated transmit channel characteristics; and

said detector for detecting respective transmitted signals in the presence of noise responsive to said estimated channel characteristics and in accordance with a decision rule.

2. An electronic circuit capable of receiving a wireless communication as recited in claim 1, said signal combiner and said channel estimator initially receiving a known transmitted signal.

3. An electronic circuit capable of receiving a wireless communication as recited in claim 1, said detector feeding back the detected transmitted signals to said channel estimator for updating said transmit channel estimate.

4. An electronic circuit as recited in claim 1 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.

5. A method of receiving a wireless communication from first and second space diverse antennas, the wireless communication being further one of time diverse or frequency diverse, the method comprising:

estimating characteristics of a transmit channel received from one of said space diverse antennas and outputting said estimated characteristics to a signal combiner and a detector using a decision rule, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

combining signals received from said first and second space diverse antennas and outputting said combined signals to said detector as two output data signals responsive to said estimated channel characteristics;

and detecting respective transmitted signals in the presence of noise via said detector using said decision rule and being responsive to said estimated channel characteristics.

6. The method of receiving as recited in claim 5, further comprising initially receiving a known transmitted signal for distinguishing transmitted signals from noise.

7. The method of receiving as recited in claim 5 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.

8. An electronic circuit for decoding wireless communication signals, comprising:

a combiner adapted to receive one of an incoming time diverse or frequency diverse signal representing blocks of encoded symbols, wherein the blocks of symbols have been transmitted by a plurality of spatially diverse antennae, wherein the combiner is configured to combine the received encoded symbols, and wherein the received encoded symbols include negating selected symbols and conjugating selected symbols; and

a detector configured to recover one of a time diverse or a frequency diverse signal responsive to said combiner, the detector receiving the combined encoded signals and recovering a transmitted signal for feedback to said combiner.

9. An electronic circuit as recited in claim 8, the combiner initially receiving a known transmitted signal for distinguishing transmitted signals from noise.

10. An electronic circuit as recited in claim 8, the detector feeding back the recovered transmitted signals for evaluating signal estimates of the next sequence of signals.

11. An electronic circuit for decoding wireless communication signals, comprising:

a combiner adapted to receive one of an incoming time diverse or frequency diverse signal representing blocks of encoded symbols, wherein the blocks of symbols have been transmitted by a plurality of spatially diverse antennas, wherein the combiner is configured to combine the received encoded symbols and to output first and second signals, and wherein the received encoded symbols include negating selected symbols and conjugating selected symbols; and

a detector configured to recover one of a time diverse or a frequency diverse signal responsive to said combiner, the detector receiving the first and second output signals of said combiner and recovering a transmitted signal using one of a metric or decision rule.

12. An electronic circuit as recited in claim 11, the combiner initially receiving a known transmitted signal.

13. An electronic circuit as recited in claim 11, the detector feeding back the recovered transmitted signals to said combiner.

14. An electronic circuit as recited in claim 11, the channel transfer function being multiplied times a transmitted symbol.

15. A method for decoding wireless data communication signals, the method comprising:

combining first and second received space diverse transmit data channels to receive one of an incoming time diverse or frequency diverse signal representing blocks of encoded symbols, wherein the blocks of encoded symbols have been transmitted by a plurality of spatially diverse antennas and wherein the received encoded symbols include negating selected symbols and conjugating selected symbols; and

detecting the combined encoded signals and recovering a transmitted signal using one of a metric or a decision rule to recover decoded blocks of symbols.

16. A decoding method as recited in claim 15, further comprising initially receiving a known transmitted wireless data communication signal.

17. A decoding method as recited in claim 15, further comprising feeding back the recovered transmitted signal.

18. A decoding method as recited in claim 15, further comprising feeding back the recovered transmitted signal to a channel estimator, the channel estimator for updating a channel estimate.

19. A decoding method as recited in claim 15, wherein said transmitted symbol blocks are distorted by a complex multiplication distortion factor composed of a magnitude and a phase response, a channel transfer function used in said detecting being related to said complex multiplication distortion factor.

20. An electronic circuit for receiving wireless communications of unequal power from first and second space diverse antennas, the wireless communication being further one of time diverse or frequency diverse, the electronic circuit comprising:

a channel estimator for estimating characteristics of at least one transmit channel received from said space diverse antennas and outputting said estimated characteristics to a signal combiner and a detector, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

said signal combiner for combining signals received from said first and second space diverse antennas and outputting said combined signals to said detector as two output data signals responsive to said estimated channel characteristics; and

said detector for detecting respective transmitted signals in the presence of noise responsive to said estimated channel characteristics, said detector for feeding back the detected transmitted signals to said channel estimator.

21. An electronic circuit as recited in claim 20 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.

22. A method of receiving a wireless communication from first and second space diverse antennas, the wireless communication comprising symbols of unequal power, the wireless communication being transmitted over first and second sequential time intervals, the method comprising:

combining signals received from said first and second space diverse antennas and outputting said combined signals to a detector as two output data signals;

estimating characteristics of a detected transmit channel and outputting said estimated characteristics to a signal combiner and to said detector, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

detecting respective transmitted signals in the presence of noise via said detector responsive to said estimated channel characteristics to recover the transmitted signals; and

feeding back the recovered transmitted signals for updating channel estimates.

23. A method of receiving a wireless communication as recited in claim 22, comprising initially receiving a known transmitted signal for use in estimating characteristics of a corresponding transmit channel.

24. A method of receiving a wireless communication as recited in claim 22 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.

25. An electronic circuit for receiving a wireless communication transmitted from first and second space diverse antennas, the wireless communication being further one of time diverse or frequency diverse, the electronic circuit comprising:

first and second channel estimators for receiving said wireless communication via first and second space diverse receive antennae respectively and for estimating characteristics of a transmit channel received from said space diverse antennas and outputting said estimated characteristics to a signal combiner and a detector, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

a signal combiner for combining signals received from said first and second space diverse antennas and outputting said combined signals to said detector as two output data signals responsive to said estimated channel characteristics; and

said detector for recovering respective transmitted signals in the presence of noise responsive to said estimated channel characteristics and said two output data signals received from said signal combiner.

26. An electronic circuit as recited in claim 25 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.

27. A method of receiving a wireless communication transmitted from first and second space diverse antennas, the wireless communication being further one of time diverse or frequency diverse, the electronic circuit comprising:

receiving said wireless communication via first and second space diverse receive antennae at first and second channel estimators respectively;

estimating characteristics of a transmit channel received from said space diverse antennas and outputting said estimated characteristics to a signal combiner and a detector, the characteristics being related to a time difference between sequential transmissions from said space diverse antennas;

combining signals received from said first and second space diverse antennas and outputting said combined signals to said detector as two output data signals responsive to said estimated channel characteristics; and

recovering respective transmitted signals at said detector in the presence of noise responsive to said estimated channel characteristics and said two output data signals.

28. The method of receiving as recited in claim 27 wherein said sequential transmissions comprise blocks of encoded symbols, said blocks of encoded symbols including one of negated symbols and conjugates of symbols.