The SEMAFOUR project will design and develop a unified self-management system, which enables the network operators to holistically manage and operate their complex heterogeneous mobile networks. The ultimate goal is to create a management system that enables an enhanced quality of user experience, improved network performance, improved manageability, and reduced operational costs. SEMAFOUR aims at taking the operation and management of mobile wireless networks to the next level.The SEMAFOUR project will have two key objectives. The first objective is the development of multi-RAT / multi-layer SON functions that provide a closed control loop for the configuration, optimisation and failure recovery of the network across different RATs (UMTS, LTE, WLAN) and cell layers (macro, micro, pico, femto). Such coordinated adaptation of radio (resource management) parameters in different RATs and cell layers is imperative for the global optimisation of network performance.The second objective is the design and development of an integrated SON management system, which interfaces between operator-defined performance objectives and the set of multi-RAT / multi-layer SON functions. This will provide a unified view on the performance of the complex heterogeneous network environment and allow its efficient control and operation. This important new management system enables operators to move their operational focus towards a higher, more global level, which is more transparent to the specifics of the underlying network technologies and cellular layout.In order to assess the achievable improvements in terms of network performance and manageability, the developed solutions will be evaluated through extensive simulation experiments and visualised by a demonstration system.