The design of 5G communications must take moving networks into account. Among scenarios considered in 5G, a moving network refers to a moving node with advanced network capabilities or such nodes gathered together to form a movable network that can communicate with its environment. In this paper, we review the key performance indicators introduced by pioneer 5G projects, such as METIS and NGMN, and the technical challenges faced in bridging the gap between current and expected 5G moving network performance. The architectures used in moving networks are also introduced. The promising technologies are grouped into clusters including high mobility, resource orchestration, and network sharing to shed the light in tackling the technical challenges.