Software Defined Radio
Software-defined radio (SDR) refers to a radio device whose function is not fixed in hardware, but rather can be programmed by software using digital signal processing techniques. The analog portions of the software-defined radio are kept to a minimum, allowing the radio to become a cellular telephone, a GPS receiver, an amateur packet radio, or any other sort of radio transmitting or receiving device. Three excellent starting points for further information on radio are:

* Software-Defined Radio Forum: http://sdrforum.org/
* GNU Software Radio Project: http://www.gnu.org/software/gnuradio/
* Amateur Radio Relay League: http://www.arrl.org/tis/info/sdr.html

The GNU Software Radio is a code base of free software that performs digital signal processing using a personal computer and freely available RF receiver front-end designs. Since the system utilizes open-source software and a standard PC under Linux, the GNU Software Radio receiver is an ideal platform for learning and experimenting with SDR concepts.

The NCASSR SDR Project at NCSA has extended the GNU Software Radio receiver design into a 900MHz narrowband software-defined radio transceiver—that is, a radio capable of transmitting and receiving. The project team developed the SDR transceiver to facilitate further research and development of SDR, including new front-end hardware, algorithms, protocols, security, and operational visualization.

An ideal SDR can operate in any radio frequency band, limited only by national regulatory agencies and the characteristics of its RF "front-end" analog hardware and antenna.The researchers' current approach to the front-end analog hardware is to support a common Intermediate Frequency (IF) and design RF hardware to fit between the antenna and the common IF. Dr. Jennifer Bernhard of the University of Illinois at Urbana-Champaign Electrical and Computer Engineering department is leading an effort to design a antenna for the extensible sensor platform that would cover a wide band from 50MHz-2.4GHz—wider than any antenna commercially available today.

One area of SDR research already underway at NCSA is the SDR operational visualization software that serves as both an educational tool for introducing concepts of radio communications to novice users, and an architectural overview of our SDR system. This real-time visualization provides a qualitative, high-level block diagram of the operation of the SDR as it receives a still image. The visualization software taps into an active SDR, extracts the signal after each stage of reception, and superimposes an image of the signal onto the block diagram.

Another new application is a reconfigurable communication protocol stack. Reminiscent of the Unix System V streams architecture, the transmit and receive data paths are composed of processing blocks that may be dynamically swapped in and out of the flow at run-time. Currently, the communication stack elements are discrete blocks that handle the network transport protocol, security processing, end-user applications, and the radio hardware management.

An example of the flexibility and usefulness of this architecture is a simple security application. The security processing block in the receiver data stream is using the DES algorithm to decrypt the received data. An authenticated command to change to the AES algorithm is received by the radio. The radio management software swaps out the security block implementing DES and replaces it with the security block implementing AES. Data processing continues seamlessly.

To provide security for SDR, the NCSA SDR Project team is developing a voice authentication application that identifies and authorizes SDR users, allowing specific radio capabilities to be unlocked depending on the user. For example, imagine a software-defined radio for emergency response with this voice authentication application—an ordinary citizen could be allowed to use the radio to contact authorities to report incidents (a form of 911 service), while an identifier response commander could use the radio to communicate on a number of private bands reserved for responding teams—police, fire, medical, etc.
 
Project Leads
Randy Butler, NCSA
Donna Cox, NCSA
Matt Hall, NCSA
Volodymyr Kindratenko, NCSA
Meenal Pant, NCSA
David Pointer, NCSA
 
Project Contributors
Tom Rimvosky, NCSA
Von Welch, NCSA
Paul Zawada, NCSA

Return to Projects list


The National Center for Advanced Secure Systems Research NCASSR) at the University of Illinois at Urbana-Champaign (UIUC) is a multi-institutional cybersecurity research team. NCASSR focuses basic and applied research necessary to develop next generation information security technologies that address national cybersecurity needs. NCASSR is led by the National Center for Supercomputing Applications (NCSA) and supported by funding from the Office of Naval Research (ONR).


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