3. Challenges

The large-scale deployment of small cells brings with it a number of challenges. These relate to the fact that SCNs act as a bridge between fully centralized (cellular) and fully decentralized (ad-hoc) networks, implying a major break between managed and administered systems on the one hand, and self-organizing networks (SONs), in which nodes learn their environment and make intelligent decisions, on the other. It is widely recognized, for example, that a massive increase in the density of a small-cell network would only be financially viable if the manpower requirements for controlling these networks were significantly reduced. Other challenges are posed by interference and mobility management, performance prediction, network coverage and security issues, detailed below.

• Self-organization

  The self-organization process...