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 Effects of Channel Estimation on Multiuser Virtual MIMO-OFDMA Relay-Based Networks | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2010 Article ID 764784 13 pages doi 2010 764784 Research Article Effects of Channel Estimation on Multiuser Virtual MIMO-OFDMA Relay-Based Networks Victor P. Gil Jimenez 1 Carlos Ribeiro 2 3 Atilio Gameiro 2 and Ana García Armada1 1 Universidad Carlos III de Madrid Avenida de la Universidad 30 Leganes 28911 Madrid Spain 2Instituto de Telecomunicacoes Campus Universitario de Santiago 3810-193 Aveiro Portugal 3Instituto Politecnico de Leiria Campus 2 Morro do Lena Alto do Vieiro 2411-901 Leiria Portugal Correspondence should be addressed to Victor P. Gil Jimenez vgil@ Received 22 February 2010 Revised 1 July 2010 Accepted 7 November 2010 Academic Editor Jean-Marie Gorce Copyright 2010 Victor P. Gil Jimenez et al. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. A practical multiuser cooperative transmission scheme denoted as Virtual Maximum Ratio Transmission VMRT for multipleinput multiple-output-orthogonal frequency division multiple access MIMO-OFDMA relay-based networks is proposed and evaluated in the presence of a realistic channel estimation algorithm and using low-density parity-check LDPC codes. It is shown that this scheme is robust against channel estimation errors. It offers diversity and array gain keeping the complexity low with a multiuser and multiantenna channel estimation algorithm that is simple and efficient. In addition the combination with LDPC codes provides improved gains diversity gains larger than 6 dB can be easily obtained with a reduced number of relays. Thus this scheme can be used to extend coverage or increase system throughput by using simple cooperative OFDMA-based relays. 1. Introduction The idea of increasing reliability coverage and or capacity in future .
