Massive MIMO for (B)5G - lessons learned and some thoughts about the future

In about a decade, Massive MIMO technology has evolved from a wild academic idea to a commercial reality, and it is likely to be a main component of any future wireless system.   In this talk I will discuss some important lessons learned during the development of the fundamental theory behind this technology. Furthermore I will discuss some emerging ideas and current research, including cell-free Massive MIMO, massive machine-type communications (mMTC), grant-free random access, and more.