Software-defined-radio (SDR) technology at one time was automatically associated with the type of secure communications needed by the Armed Forces. But, as with many things based on electronic components, that has changed a great deal in recent years. SDR-based products are now available for amateur-radio operators, as well as for commercial and consumer radio users. In fact, as some of the critical components for SDR systems—such as analog-to-digital converters (ADCs) and digital-to-analog converters (DACs)—have improved in performance and dropped in price, the market for SDR-based products has seemingly expanded to the consumer level. It appears that SDR technology will be embraced by healthy markets in commercial, military, and even industrial areas.

An ideal SDR configuration can be as simple as an antenna, ADC, DAC, and programmable processor (to control the data converters). The concept of changing the characteristics of a radio through software has actually been around for almost 30 years, with the possibility of using software and hardware together in this way coming from a laboratory at defense contractor E-Systems (now part of Raytheon Co.). With the security inherent in the programmability of these radios, it is easy to see why so many military radio architects would become entranced by the technology, especially with the growing availability of affordable data converters capable of supporting broadband communications.

At the same time, with the modern consumer’s appetite for instant communications and high-data-rate wireless communications, SDR technology represents a viable approach for commercial service providers wanting to field equipment that can adapt to ever-changing wireless standards. Organizations such as the Wireless Innovation Forum (WIF) have registered their support for SDR technology, as well as their desire for this technology to achieve a strong position in both commercial and military communications applications.

One of the more visible users of SDR technology is NASA on the International Space Station. Earlier this year, NASA began using its Space Communications and Navigation (SCaN) test bed for experiments to develop advanced communications, networking, and navigation functions in space. The SCaN test bed uses a new generation of SDR technology that promises to bring new cost savings and efficiency to NASA as it develops high-speed data communications solutions for the future. SDRs for the platform have already been developed under cooperative agreements with NASA by General Dynamics and Harris Corp.

According to International Space Station Program Manager Michael Suffredini, “The space station serves as a dynamic test bed for the technologies needed for future human and robotic exploration. SCaN is an example of the technologies that are being matured in low-Earth orbit and used to increase science return of many different types of spacecraft.” John Rush, Technology and Standards Director for SCaN at NASA Headquarters in Washington, DC, adds: “With the development and deployment of this test bed, NASA has enabled significant future advancements by gaining knowledge and understanding of SDR development.”

The test bed has been applied to learning more about communications in space using S- and Ka-band frequencies. It will also be used for an experiment with NASA’s latest Tracking and Data Relay Satellite (TDRS), to demonstrate a TDRS spacecraft acquiring and successfully auto-tracking a Ka-band user in low-Earth orbit. This test bed is expected to be operational for as long as six years aboard the space station. It is meant to offer experimental opportunities to NASA, industry, academia, and other government agencies. The experiments contribute data to the Space Telecommunications Radio Standard Compliant repository; they enable future hardware platforms to use common, reusable software modules to reduce development time and costs.