How Many Users should be Turned On in a Multi-Antenna Broadcast Channel?

Wei Dai Youjian Liu Brian Rider Wen Gao How Many Users should be Turned On in a Multi-Antenna Broadcast Channel? http://arxiv.org/abs/0805.1442 2008 CoRR abs/0805.1442 db/journals/corr/corr0805.html#abs-0805-1442 informal publication