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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 5.5 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.
Sendonaris A, Erkip E, Aazhang B: User cooperation diversity—part I: system description. IEEE Transactions on Communications 2003, 51(11):1927-1938. 10.1109/TCOMM.2003.818096 CrossRef
Kramer G, Marić I, Yates RD: Cooperative communications. Foundations and Trends in Networking 2006, 1(3-4):271-425. 10.1561/1300000004 CrossRef
Berger S, Wittneben A: Experimental performance evaluation of multiuser zero forcing relaying in indoor scenarios. Proceedings of the 61st IEEE Vehicular Technology Conference (VTC '05), May-June 2005, Stockholm, Sweden 2: 1101-1105.
Rice University WARP Project http://warp.rice.edu
Herhold P, Zimmermann E, Fettweis G: On the performance of cooperative amplify-and-forward relay networks. Proceedings of the 5th International ITG Conference on Source and Channel Coding (SCC '04), January 2004, Erlangen, Germany 451-458.
Tu Y-S, Pottie GJ: Coherent cooperative transmission from multiple adjacent antennas to a distant stationary antenna through AWGN channels. Proceedings of the 55th IEEE Vehicular Technology Conference (VTC '02), May 2002, Birmingham, Ala, USA 1: 130-134.
Brown DR III, Prince GB, McNeill JA: A method for carrier frequency and phase synchronization of two autonomous cooperative transmitters. Proceedings of the 6th IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC '05), June 2005, New York, NY, USA 260-264.
Anghel PA, Leus G, Kaveh M: Multi-user space-time coding in cooperative networks. Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP '03), April 2003, Hong Kong 4: 73-76.
Alamouti SM: A simple transmit diversity technique for wireless communications. IEEE Journal on Selected Areas in Communications 1998, 16(8):1451-1458. 10.1109/49.730453 CrossRef
IEEE Std 802.11a-1999 : Part 11: wireless LAN medium access control (MAC) and physical layer (PHY) specifications: high-speed physical layer in the 5 GHz band. 1999.
- On Building a Cooperative Communication System: Testbed Implementation and First Results
- Springer International Publishing
EURASIP Journal on Wireless Communications and Networking
Elektronische ISSN: 1687-1499
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