Hyungsik Ju Rui Zhang 0006 User cooperation in wireless powered communication networks. 1430-1435 2014 GLOBECOM https://doi.org/10.1109/GLOCOM.2014.7037009 https://www.wikidata.org/entity/Q58024480 conf/globecom/2014 db/conf/globecom/globecom2014.html#JuZ14