Ahmed S. Ibrahim 0001 Ahmed K. Sadek Weifeng Su K. J. Ray Liu Relay Selection in Multi-Node Cooperative Communications: When to Cooperate and Whom to Cooperate with? 2006 conf/globecom/2006 GLOBECOM https://doi.org/10.1109/GLOCOM.2006.601 db/conf/globecom/globecom2006.html#IbrahimSSL06