Raphael Hunger David A. Schmidt Wolfgang Utschick Sum-Capacity and MMSE for the MIMO Broadcast Channel without Eigenvalue Decompositions. 776-780 2007 ISIT https://doi.org/10.1109/ISIT.2007.4557107 conf/isit/2007 db/conf/isit/isit2007.html#HungerSU07