Vignesh Sethuraman Ligong Wang Bruce E. Hajek Amos Lapidoth Low-SNR Capacity of Noncoherent Fading Channels. 1555-1574 2009 55 IEEE Transactions on Information Theory 4 http://dx.doi.org/10.1109/TIT.2009.2012995 db/journals/tit/tit55.html#SethuramanWHL09