Receiver architecture employing space time spreading and...

Details Receiver architecture employing space time spreading and... Receiver architecture employing space time spreading and...

1999-09-13

2001-11-13

Olms, Douglas (Department: 2661)

Multiplex communications

Generalized orthogonal or special mathematical techniques

C370S342000

Reexamination Certificate

active

06317410

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to wireless communication systems and, in particular, to wireless communication employing transmit diversity.
BACKGROUND OF THE RELATED ART
Several third generation wireless communication systems are being developed. One such third generation wireless communication system is known as CDMA 2000. In CDMA 2000, a variety of techniques are being incorporated for improving call quality. Open loop transmit diversity is one Such technique in which user signals are transmitted using two antennas. In a first phase of CDMA 2000, open loop transmit diversity is currently being implemented in a form of orthogonal transmit diversity (OTD). In OTD, separate antennas are used to transmit even data bits and odd data bits to achieve transmit diversity and improved call quality.
In a second phase of CDMA 2000, open loop transmit diversity may be implemented in a for in of space time spreading (STS) using Walsh functions or codes. STS enhances call quality by providing variable gain over OTD depending on the coding rate being used. Specifically, in STS, odd data bits and even data bits are jointly, not separately, transmitted over two antennas. However, the manner in which tile odd and even data bits are modulated/processed before being transmitted over one antenna will be different from the manner in which the odd and even data bits are modulated/processed being transmitted over the other antenna.
There has been some concern that including both open loop transmit diversity schemes as options in CDMA 2000 would be very complex in terms of implementing them into a common transmitter architecture. Accordingly, there exists a need for a simple to implement common receiver architecture that has incorporated orthogonal transmit diversity and space time spreading schemes.
SUMMARY OF THE INVENTION
The present invention is a common receiver architecture having incorporated both open loop transmit diversity schemes using a plurality of binary switches. Employment of binary switches allows for the sharing of certain components whether the receiver is utilizing a orthogonal transmit diversity (OTD) scheme or a space time spreading (STS) scheme. Accordingly, the number of components in the receiver is minimized and the complexity of the receiver is simple enough to be implemented into a single application specific integrated chip.
The receiver operates in an OTD and a STS mode, and comprises mixers and adders. The mixers mix a received signal with a first function to produce a first mixed signal, and the received signal with a second function to produce a second mixed signal, wherein the second function is a complement of the first function. The first mixed signal is mixed with a conjugate of a first channel estimate to produce a third mixed signal, and with a conjugate of a second channel estimate to produce a fourth mixed signal. The second mixed signal is mixed with the conjugate of the second channel estimate to produce a fifth mixed signal. A conjugate of the second mixed signal is mixed with the first channel estimate to produce a sixth mixed signal. In OTD mode, the third and fifth mixed signals are time multiplexed together to produce a version of the transmitted signal. In STS mode, the third mixed signal and a conjugate of the fifth mixed signal are added together by an adder to produce a first added signal, and the fourth mixed signal and an inverted sixth mixed signal are added together by an adder to produce a second added signal, wherein the first and second added signals are time multiplexed together to produce a version of the transmitted signal.


REFERENCES:
patent: 6154485 (2000-11-01), Harrison
patent: 6173005 (2001-01-01), Kotzin et al.
patent: 6185266 (2001-02-01), Kuchi et al.

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