Multiuser Cooperative Diversity for Wireless Networks
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Editorial Multiuser Cooperative Diversity for Wireless Networks George K. Karagiannidis,1 Chintha Tellambura,2 Sayandev Mukherjee,3 and Abraham O. Fapojuwo4 1 Department
of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece 2 Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada T6G2V4 3 Marvell Semiconductor, Santa Clara, CA 95054, USA 4 Department of Electrical and Computer Engineering, The University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N1N4 Received 24 September 2006; Accepted 24 September 2006 Copyright © 2006 George K. Karagiannidis 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.
Multihop relaying technology is a promising solution for future cellular and ad hoc wireless communications systems in order to achieve broader coverage and to mitigate wireless channels impairment without the need to use high power at the transmitter. Recently, a new concept that is being actively studied in multihop-augmented networks is multiuser cooperative diversity, where several terminals form a kind of coalition to assist each other with the transmission of their messages. In general, cooperative relaying systems have a source node multicasting a message to a number of cooperative relays, which in turn resend a processed version to the intended destination node. The destination node combines the signal received from the relays, possibly also taking into account the source’s original signal. Cooperative diversity exploits two fundamentals features of wireless medium: its broadcast nature and its ability to achieve diversity through independent channels. There are three advantages from this. (1) Diversity. This occurs because different paths are likely to fade independently. The impact of this is expected to be seen in the physical layer, in the design of a receiver that can exploit this diversity. (2) Beamforming gain. The use of directed beams should improve the capacity on the individual wireless links. The gains may be particularly significant if space-time coding schemes are used. (3) Interference mitigation. A protocol that takes advantage of the wireless channel and the antennas and receivers available could achieve a substantial gain in system throughput by optimizing the processing done in the cooperative relays and in the scheduling of retransmissions by the relays so as to minimize mutual inter-
ference and facilitate information transmission by cooperation. In response to the demand for novel ideas and results, this special issue presents a sample of current activities and up-to-date efforts in design, implementation, and performance analysis of cooperative diversity systems. A brief summary of each paper is listed as follows. In the first paper by Z. Yang and A. Høst-Madsen, the cooperation efficiency of the multiple-relay channel w
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