Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Downlink Assisted Uplink Zero Forcing for TDD Multiuser MIMO Systems | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2009 Article ID 894726 11 pages doi 2009 894726 Research Article Downlink Assisted Uplink Zero Forcing for TDD Multiuser MIMO Systems Petri Komulainen Antti Tolli Matti Latva-aho and Markku Juntti Centre for Wireless Communications University of Oulu . Box 4500 90014 Oulu Finland Correspondence should be addressed to Petri Komulainen Received 1 February 2009 Revised 11 May 2009 Accepted 19 July 2009 Recommended by Bruno Clerckx This paper proposes practical coordinated linear transmit-receive processing schemes for the uplink UL of multiuser multipleinput multiple-output MIMO systems in the time division duplex TDD mode. The base station BS computes the transmission parameters in a centralized manner and employs downlink DL pilot signals to convey the information of the beam selection and beamformers to be used by the terminals. When coexisting with the DL transmit-receive zero forcing the precoded DL demodulation pilots can be reused for UL beam allocation so that no additional pilot overhead is required. Furthermore the locally available channel state information CSI of the effective MIMO channel is sufficient for the terminals to perform transmit power and rate allocation independently. In order to reduce the UL pilot overhead as well we propose reusing the precoded UL demodulation pilots in turn for partial CSI sounding. The achievable sum rate of the system is evaluated in time-varying fading channels and with channel estimation. According to the results the proposed UL transmission strategy provides increased rates compared to single-user MIMO transmission combined with user selection as well as to UL antenna selection transmission without being sensitive to CSI uncertainty. Copyright 2009 Petri Komulainen et al. This is an open access article distributed under the Creative Commons Attribution License which permits .
