TRANSMITTER DIVERSITY TECHNIQUE FOR WIRELESS COMMUNICATIONS

• US 20110170635A1
• Filed: 03/28/2011
• Published: 07/14/2011
• Est. Priority Date: 09/16/1997
• Status: Active Grant

• Current Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Original Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Inventors: Alamouti, Siavash, Tarokh, Vahid
• Granted Patent: US 8,355,475 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• 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 simple arithmetic operations, such as negation and conjugation. The diversity created by the 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 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. A transmitter apparatus comprising:

a coder responsive to incoming symbols to form encoded sets of symbols, each of the encoded sets of symbols including an incoming symbol and a related symbol, the related symbol being a complex conjugate or a negative complex conjugate of the incoming symbol; and

an output stage to apply, for each encoded set, the incoming symbol and the related symbol to different transmit antennas to transmit the encoded set with transmit diversity, the encoded set being further transmitted with one of frequency diversity and time diversity.

2. A method comprising:

receiving first and second symbols at an encoder;

encoding the received first and second symbols, the encoding including generating a complex conjugate of the first symbol and generating a negative complex conjugate of the second symbol;

transmitting the first symbol and the complex conjugate of the first signal with space diversity;

transmitting the second symbol and negative complex conjugate of the second symbol with space diversity.

3. The method as recited in claim 2 further comprising transmitting the first symbol and the complex conjugate of the first signal with one of frequency diversity and time diversity.

4. The method as recited in claim 3 further comprising transmitting the second symbol and the negative complex conjugate of the second signal with one of frequency diversity and time diversity.

5. The method as recited in claim 4 further comprising:

transmitting the first symbol and the negative complex conjugate of the second symbol over a first antenna; and

transmitting the second symbol and the complex conjugate of the first symbol over a second antenna.

6. A method of receiving a wireless communication that includes a transmitted block of symbols transmitted from at least two space diverse antennas to a receiving device, comprising:

receiving the transmitted block of symbols at the receiving device over at least first and second transmit channels that couple the at least two space diverse antennas to the receiving device, the transmitted block including a first symbol and a complex conjugate of the first symbol and a second symbol and a negative complex conjugate of the second symbol, the first symbol and the complex conjugate of the first symbol being received over different transmit channels, and the second symbol and the negative complex conjugate of the second symbol being received over different transmit channels;

wherein the first symbol and the complex conjugate of the first symbol are received with one of frequency diversity and time diversity; and

wherein the second symbol and the negative complex conjugate of the second symbol are received with one of frequency diversity and time diversity.

7. The method as recited in claim 6 further comprising estimating channel characteristics of the at least first and second transmit channels.

8. The method as recited in claim 7 further comprising combining the received transmitted block of symbols in a combiner and supplying symbol estimates from the combiner using the estimated channel characteristics.

9. The method as recited in claim 8 further comprising supplying the symbols estimates to a maximum likelihood detector and recovering the first and second symbols.

10. A device for receiving a wireless communication that includes a transmitted block of symbols transmitted from space diverse transmit antennas to the receiving device, the device comprising:

a signal combiner coupled to receive the transmitted block of symbols transmitted over transmit channels that couple the space diverse transmit antennas to the receiving device, the transmitted block of symbols including a first symbol and a complex conjugate of the first symbol, and a second symbol and a negative complex conjugate of the second symbol, the first symbol and the complex conjugate of the first symbol being received over different transmit channels, and the second symbol and the negative complex conjugate of the second symbol being received over different transmit channels, the signal combiner configured to combine the received transmitted block of symbols to generate symbol estimates;

wherein the first symbol and the complex conjugate of the first symbol are received with one of frequency diversity and time diversity; and

wherein the second symbol and the negative complex conjugate of the second symbol are received with one of frequency diversity and time diversity.

12. The apparatus as recited in claim 10 further comprising a maximum likelihood detector coupled to receive the symbol estimates and to recover the first and second symbols.

11. The device as recited in claim 11 further comprising:

a channel estimator coupled to receive antennas to receive the symbols transmitted over the transmit channels, the channel estimator configured to generate estimated transmit channel characteristics of the transmit channels and supply the estimated transmit channel characteristics to the signal combiner; and

wherein the signal combiner is configured to generate the symbol estimates using the estimated transmit channel characteristics.