The paper presents a system-level approach for the modeling and simulation of a paradigmatic wireless sensor network composed of two nodes using SystemC-AMS, an open-source C++ extension to the OSCI SystemC standard dedicated to the description of heterogeneous systems containing digital, analog, RF hardware IPs as well as embedded software. The paper is composed of three parts. The first part details the modeled WSN (physical sensor, sigma-delta ADC, ATMEGA128 8- bit microcontroller running the embedded application, QPSK-based 2.4 GHz RF transceiver), presents the corresponding implementation in SystemC-AMS, and gives an insight on how multi-frequency simulation is handled in SystemC-AMS. The second part shows how to introduce several RF designer specifications (noise figure, IIP3, ...) into models and how to express them in SystemC-AMS. The third part proves that the combination of C++ and RF baseband equivalent dramatically reduces simulation time while keeping excellent accuracy and code readability. The paper concludes on the possibilities offered by this approach in terms of validation and optimization of heteregeneous systems through open-source simulation.