  In this paper we discuss the requirements for a radio access network
architecture for ultra-dense networks for "smart city" applications, and show
that coordination is required between access points to overcome the effects of
interference. We propose a new paradigm, Fog Massive MIMO, based on a
combination of the "cell-free" massive MIMO concept and the Fog Radio Access
Network (F-RAN). In particular we analyze the potential benefit of improved
coordination between APs over different coordination ranges.
