Software Defined Radios (SDRs) require architectures with a high flexibility to support multi-mode and multi-standard receivers and transmitters. In addition, these architectures need to fulfill the contradicting requirements of high performance for processing high data rates and low power consumption to be deployable in mobile devices. As the market for SDR is evolving, a scalable and adaptive architecture is desired to be able to upgrade the architecture to provide the needed computing performance for future use cases. This chapter highlights the requirements of high flexibility, high performance, low power, and high scalability and presents a solution to fulfill these requirements using runtime reconfigurable Multi-Processor Systems-on-Chip (MPSoCs).