The advantages provided by Software Defined Radios (SDRs) have made them useful tools for communication engineers and academics alike. The ability to support a wide range of communication waveforms with varying modulation, encoding, or frequencies on a single hardware platform can decrease production costs while accelerating wave-form development. SDR applications are expanding in military and commercial environments as advances in transistor technology allow greater computational density with decreased power-consumption, size, and weight. As the demand for greater performance continues to increase, some SDR manufacturers are experimenting with heterogeneous processing platforms to meet these requirements. Heterogeneous processing, a method of dividing computational tasks among dissimilar processors, is well-suited to the data flow programming paradigm used in many common SDR software frameworks. Particularly on embedded platforms, heterogeneous processing can offer significant gains in computational power while maintaining low power-consumption, opening the door for affordable and useful mobile SDR platforms. Many past SDR hardware implementations utilize a partially heterogeneous processing approach. A field programmable gate array (FPGA) is often used to perform high-speed processing (DDC, decimation) near the radio front-end while another processor (GPP, DSP or FPGA) performs the rest of the SDR application signal processing (gain control, filtering, demodulation). A few recent SDR hardware platforms are designed to allow the use of multiple processor types throughout the SDR application's processing chain. This can result in significant benefit to SDR software that can take advantage of the greater heterogeneous processing now available. This thesis will present a new method of heterogeneous processing in the framework of GNU Radio. In this implementation a software wrapper allows a DSP to participate seamlessly in GNU Radio applications. The DSP can be directly substituted for existing GNU Radio signal processing blocks—significantly expanding the platform's capabilities while maintaining the benefits of the component-based design methodology. A similar approach could be applied to additional processing elements (e.g. FPGAs and co-processors) and to other SDR software frameworks. As the capabilities of this heterogeneous framework increase users will be required to assign hardware resources to signal processing tasks to maximize performance. To remove this burden, a method of predicting GNU Radio application performance and a heuristic resource mapping algorithm, which seems to perform well in practice, are presented. / Master of Science