Scalable Networks on Chips (NoCs) are needed to match the ever-increasing communication demands of large-scale Multi-Processor Systems-on-Chips (MPSoCs) for high-end wireless communications applications. The heterogeneous nature of on-chip cores, and the energy efficiency requirements typical of wireless communications call for application-specific NoCs which eliminate much of the overheads connected with general-purpose communication architectures. However, application-specific NoCs must be supported by adequate design flows to reduce design time and effort. In this paper, the authors survey the main challenges in application-specific NoC design, and they outline a complete NoC design flow and methodology. A case study on a high complexity SoC demonstrates that it is indeed possible to generate an application-specific NoC from a high level specification in a few hours.