Software Defined Radio (SDR) terminals are crucial to enable seamless and transparent inter-working between fourth generation wireless access systems or communication modes. On the longer term, SDRs will be extended to become cognitive radios enabling efficient spectrum usage. Future communication modes will have heavy hardware resource requirements and switching between them will introduce dynamism in respect with timing and size of resource requests. In this paper, we propose a modeling framework that enables the simulation of such complex, dynamic hardware/software SDR designs. Thus, we can do an exploration, which can pinpoint the coarse grain platform component requirements for future SDR applications in a very early design phase. Our solution differs from existing ones by combining multiple simulation granularities in a way that is specialized for SDR simulation. Finally, we demonstrate the effectiveness of our approach with a case study for dimensioning the on-chip interconnect of a prospective SDR platform.