  There have been active research activities worldwide in developing the
next-generation 5G wireless network. The 5G network is expected to support
significantly large amount of mobile data traffic and huge number of wireless
connections, achieve better cost- and energy-efficiency as well as quality of
service (QoS) in terms of communication delay, reliability and security. To
this end, the 5G wireless network should exploit potential gains in different
network dimensions including super dense and heterogeneous deployment of cells
and massive antenna arrays (i.e., massive multiple input multiple output (MIMO)
technologies) and utilization of higher frequencies, in particular millimeter
wave (mmWave) frequencies. This article discusses potentials and challenges of
the 5G heterogeneous wireless network (HetNet) which incorporates massive MIMO
and mmWave technologies. We will first provide the typical requirements of the
5G wireless network. Then, the significance of massive MIMO and mmWave in
engineering the future 5G HetNet is discussed in detail. Potential challenges
associated with the design of such 5G HetNet are discussed. Finally, we provide
some case studies, which illustrate the potential benefits of the considered
technologies.
