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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 NAF, OAF, or Noncooperation: Which Protocol to Choose? | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2008 Article ID 546470 7 pages doi 10.1155 2008 546470 Research Article NAF OAF or Noncooperation Which Protocol to Choose Ahmed Saadani and Olivier Traore France Telecom Division of Research and Development 38-40 Rue du General Leclerc 92794 Issy les Moulineaux Cedex 9 France Correspondence should be addressed to Ahmed Saadani ahmed.saadani@orange-ftgroup.com Received 1 June 2007 Revised 20 September 2007 Accepted 1 November 2007 Recommended by G. K. Karagiannidis The two main Amplify and Forward cooperative protocols are the orthogonal OAF and the nonorthogonal one NAF . In this paper we consider a given source N relays a destination and a channel realization and we try to resolve the following problem what is the best way to communicate without cooperation or using one of the two cooperative protocols This is equivalent to a power-sharing problem on the cooperation frame between source and relays aiming to the short-term channel capacity maximization. The obtained solution shows that cooperative protocol choice depends only on the available power at the relays. However the decision to cooperate depends on the channel conditions. We show that our power allocation scheme with relay selection improves the outage probability compared to the selective OAF and the NAF protocols and has a significant capacity gain. Copyright 2008 A. Saadani and O. Traore. 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 Communications on wireless channels are limited by multiple impairment sources multipath fading shadowing and path loss . Many diversity techniques have been developed to fight the fast fading such as multiple antennas for the spatial diversity coding for the time diversity. Recently cooperative diversity .
