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 A Fair Opportunistic Access Scheme for Multiuser OFDM Wireless Networks | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2009 Article ID 726495 14 pages doi 2009 726495 Research Article A Fair Opportunistic Access Scheme for Multiuser OFDM Wireless Networks Cedric Gueguen and Sébastien Baey Universite Pierre et Marie Curie UPMC - Paris 6 Laboratoire d Informatique de Paris 6 LIP6 104 avenue du President Kennedy 75016 Paris France Correspondence should be addressed to Cedric Gueguen Received 2 July 2008 Revised 13 December 2008 Accepted 1 February 2009 Recommended by Zhu Han We propose a new access scheme for efficient support of multimedia services in OFDM wireless networks both in the uplink and in the downlink. This scheme further increases the benefits of opportunistic scheduling by extending this cross-layer technique to higher layers. Access to the medium is granted based on a system of weights that dynamically accounts for both the experienced QoS and the transmission conditions. This new approach enables the full support of multimedia services with the adequate traffic and QoS differentiation while maximizing the system capacity and keeping a special attention on fairness. Performance evaluation shows that the proposed access technique outperforms existing wireless access schemes and demonstrates that choosing between high fairness and high system throughput is no more required. Copyright 2009 C. Gueguen andS. Baey. 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. 1. Introduction Providing mobile multimedia transmission services with an adequate QoS is very challenging. In contrast with wired communications wireless transmissions are subject to many channel impairments such as path loss shadowing and multipath fading 1-4 . These phenomena severely affect the transmission capabilities and in .
