Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí sinh học đề tài : Multiuser MIMO downlink transmission with BEMbased limited feedback over doubly selective channels | Nguyen-Le et al. EURASIP Journal on Wireless Communications and Networking 2011 2011 138 EURASIP Journal on . http content 2011 1 138 Wireless Communications and Networking a Springerữpen Journal RESEARCH Open Access Multiuser MIMO downlink transmission with BEM-based limited feedback over doubly selective channels Hung Nguyen-Le1 Tho Le-Ngoc2 and Loic Canonne-Velasquez2 Abstract This article studies the problem of limited feedback design for heterogeneous multiuser MU transmissions over time- and frequency-selective doubly selective multiple-input multiple-output downlink channels. Under a doubly selective propagation condition a basis expansion model BEM is deployed as a fitting parametric model for capturing the time-variation of the MU downlink channels and for reducing the number of the channel parameters. The resulting dimension reduction in the time-variant channel representation in turn translates into a reduced feedback load of channel state information CSI to the base station BS . To produce limited feedback information vector quantization of the BEM coefficients is performed at mobile terminals under the assumption that perfect BEM coefficient estimation has been established by existing algorithms. Then the output indices of the quantized BEM coefficient vectors are sent to the BS via error-free zero-latency feedback links. To assess the feasibility of using the BEM-based limited feedback design in a MU network with an arbitrary number of active users the resultant sum-rate performance of the network is provided by employing the block-diagonalization precoding and greedy scheduling techniques at the BS. The relevant numerical results show that the BEM-based limited feedback scheme is able to significantly alleviate the detrimental effect of outdated CSI feedback which likely occurs as using the conventional block-fading assumption in MU transmissions over fast time-varying channels. Keywords limited feedback greedy scheduling .
