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 On Building a Cooperative Communication System: Testbed Implementation and First Results | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2009 Article ID 972739 9 pages doi 2009 972739 Research Article On Building a Cooperative Communication System Testbed Implementation and First Results Patrick Murphy Ashutosh Sabharwal and Behnaam Aazhang Department of Electrical and Computer Engineering Rice University 6100 S. Main St. Houston TX 77005 USA Correspondence should be addressed to Ashutosh Sabharwal ashu@ Received 1 November 2008 Revised 24 March 2009 Accepted 5 June 2009 Recommended by Alejandro Ribeiro We present the results from over-the-air experiments of a complete implementation of an amplify and forward cooperative communications link. Our custom OFDM-based physical layer uses a distributed version of the Alamouti block code where the relay sends one of the branches of Alamouti-encoded symbols. First we show analytically and experimentally that amplify and forward protocols are unaffected by carrier frequency offsets at the relay. This result allows us to use a conventional Alamouti receiver without change for the distributed relay system thereby allowing cooperative systems to reuse components of current noncooperative systems. Our full system implementation shows gains of up to dB in peak power constrained networks. Thus we can conclusively state that even the simplest form of relaying can lead to significant gains in practical implementations. Copyright 2009 Patrick Murphy 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. 1. Introduction Cooperative communications 1 2 and references therein has emerged as a significant concept to improve reliability and throughput in wireless systems. In cooperative communications the resources of distributed nodes are effectively pooled for the collective benefit of all nodes.
