</titles> <publication_date> <month>05</month> <year>2007</year> </publication_date> <pages> <first_page>1089</first_page> <last_page>1089</last_page> </pages> <publisher_item> <item_number item_number_type='arNumber'>4200929</item_number> </publisher_item> <doi_data> <doi>10.1109/TCOMM.2007.896148</doi> <resource>http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=4200929</resource> </doi_data> </journal_article> <journal_article> <titles> <![CDATA[Orthogonalized Spatial Multiplexing for Closed-Loop MIMO Systems

In this paper, we propose a novel spatial multiplexing (SM) scheme for transmission over flat-fading multiple-input multiple-output (MIMO) channels, which allows simple maximum-likelihood decoding at the receiver with small feedback information. We begin with a real-valued representation of the complex-valued system model, and show that we can achieve orthogonality between transmitted signals by applying a proper rotation to transmitted symbols. Compared with other closed-loop methods, the proposed scheme significantly reduces the processing complexity at both transmitter and receiver as well as the feedback overhead. We also combine the proposed orthogonalization method with antenna-selection techniques, and then discuss a criterion based on the minimum Euclidean distance between received vectors for selecting the optimal subset of multiple transmit antennas. Using geometrical properties of the receive constellations, we also present a simple antenna-selection metric for the proposed SM systems. Simulation results demonstrate that our SM system performs close to the optimum closed-loop system with much-reduced complexity