《Space-time transmit precoding with imperfect feedback》.pdfVIP

2632 IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 47, NO. 6, SEPTEMBER 2001 Space–Time Transmit Precoding With Imperfect Feedback receiver, and can, therefore, perform spatial matched filtering or (in a multiuser context) interference suppression [4], [5]. Eugene Visotsky, Member, IEEE, and Upamanyu Madhow, Senior Member, IEEE These two strategies are based on two different, and extreme, as- sumptions regarding the channel feedback available at the transmitter: space–time coding requires no feedback, whereas beamforming Abstract— The use of channel feedback from receiver to transmitter is requires accurate feedback. Clearly, there are situations where neither standard in wireline communications. While knowledge of the channel at of these assumptions is valid, and one would expect that the transmitter the transmitter would produce similar benefits for wireless communica- strategy in such situations would be some blend of space–time coding tions as well, the generation of reliable channel feedback is complicated by the rapid time variations of the channel for mobile applications. The and beamforming. Our purpose in this correspondence is to make this purpose of this correspondence is to provide an information–theoretic intuition precise by providing information–theoretic insights into the perspective on optimum transmitter strategies, and the gains obtained by appropriate transmitter strategies when the c