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 Experimental Evaluation of Adaptive Modulation and Coding in MIMO WiMAX with Limited Feedback | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2008 Article ID 837102 12 pages doi 2008 837102 Research Article Experimental Evaluation of Adaptive Modulation and Coding in MIMO WiMAX with Limited Feedback Christian Mehlfuhrer Sebastian Caban and Markus Rupp Institute of Communications and Radio-Frequency Engineering Vienna University of Technology Gusshausstrasse 25 389 1040 Vienna Austria Correspondence should be addressed to Christian Mehlfuhrer Received 22 June 2007 Revised 3 October 2007 Accepted 28 November 2007 Recommended by Ana Perez-Neira We evaluate the throughput performance of an OFDM WiMAX IEEE Section transmission system with adaptive modulation and coding AMC by outdoor measurements. The standard compliant AMC utilizes a 3-bit feedback for SISO and Alamouti coded MIMO transmissions. By applying a 6-bit feedback and spatial multiplexing with individual AMC on the two transmit antennas the data throughput can be increased significantly for large SNR values. Our measurements show that at small SNR values a single antenna transmission often outperforms an Alamouti transmission. We found that this effect is caused by the asymmetric behavior of the wireless channel and by poor channel knowledge in the two-transmit-antenna case. Our performance evaluation is based on a measurement campaign employing the Vienna MIMO testbed. The measurement scenarios include typical outdoor-to-indoor NLOS outdoor-to-outdoor NLOS as well as outdoor-to-indoor LOS connections. We found that in all these scenarios the measured throughput is far from its achievable maximum the loss is mainly caused by a too simple convolutional coding. Copyright 2008 Christian Mehlfuhrer 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
