  Software defined radio (SDR) has become a popular tool for the implementation
and testing for communications performance. The advantage of the SDR approach
includes: a re-configurable design, adaptive response to changing conditions,
efficient development, and highly versatile implementation. In order to
understand the benefits of SDR, the space telecommunication radio system (STRS)
was proposed by NASA Glenn research center (GRC) along with the standard
application program interface (API) structure. Each component of the system
uses a well-defined API to communicate with other components. The benefit of
standard API is to relax the platform limitation of each component for addition
options. For example, the waveform generating process can support a field
programmable gate array (FPGA), personal computer (PC), or an embedded system.
As long as the API defines the requirements, the generated waveform selection
will work with the complete system. In this paper, we demonstrate the design
and development of adaptive SDR following the STRS and standard API protocol.
We introduce step by step the SDR testbed system including the controlling
graphic user interface (GUI), database, GNU radio hardware control, and
universal software radio peripheral (USRP) tranceiving front end. In addition,
a performance evaluation in shown on the effectiveness of the SDR approach for
space telecommunication.
