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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 Channel Asymmetry in Cellular OFDMA-TDD Networks | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 121546 14 pages doi 10.1155 2008 121546 Research Article Channel Asymmetry in Cellular OFDMA-TDD Networks Ellina Foutekova 1 Patrick Agyapong 2 3 and Harald Haas1 1 Institute for Digital Communications School of Engineering Electronics The University of Edinburgh Edinburgh EH9 3JL UK 2 School of Engineering and Science Jacobs University Bremen 28759 Bremen Germany 3 Department of Engineering and Public Policy College of Engineering Carnegie Mellon University Pittsburgh PA 15213 USA Correspondence should be addressed to Ellina Foutekova e.foutekova@ed.ac.uk Received 17 January 2008 Revised 22 July 2008 Accepted 28 October 2008 Recommended by David Gesbert This paper studies time division duplex- TDD- specific interference issues in orthogonal frequency division multiple access- OFDMA- TDD cellular networks arising from various uplink UL downlink DL traffic asymmetries considering both line-of-sight LOS and non-LOS NLOS conditions among base stations BSs . The study explores aspects both of channel allocation and user scheduling. In particular a comparison is drawn between the fixed slot allocation FSA technique and a dynamic channel allocation DCA technique for different UL DL loads. For the latter random time slot opposing RTSO is assumed due to its simplicity and its low signaling overhead. Both channel allocation techniques do not obviate the need for user scheduling algorithms therefore a greedy and a fair scheduling approach are applied to both the RTSO and the FSA. The systems are evaluated based on spectral efficiency subcarrier utilization and user outage. The results show that RTSO networks with DL-favored traffic asymmetries outperform FSA networks for all considered metrics and are robust to LOS between BSs. In addition it is demonstrated that the greedy scheduling algorithm only offers a marginal increase in spectral efficiency as compared to .
