Modern radio communications include wireless networks and mobile communications of all types, from cellular networks to the radios used by police and fire departments around the country. Americans will talk for trillions of minutes and send trillions of text messages through wireless radio spectrums in 2012, generating revenue of $202 billion. In the public safety sphere, police and firefighters responding to 9/11 were operating on separate bands and could not coordinate efficiently. The White House has marked these issues as priorities with an initiative to nearly double the availability of radio spectrum for mobile devices and develop a nationwide, interoperable wireless network for public safety so that crisis response teams from different cities and agencies can communicate freely in an emergency.
Cognitive radio is a technology that is poised to realize these national expectations with dynamic spectrum access that scans for the clearest bands and switches seamlessly, establishing intelligent and efficient utilization of radio spectrum while securing users from abuse and malicious attacks. The IEEE Communications Society has put together a list of best relevant papers titled "Best Reading Topics in Cognitive Radio," and the Information Networks and Security Lab (iNFINITY) at Stevens Institute of Technology was strongly represented with four papers featured from associated faculty and researchers including Dr. Chandramouli, Dr. K. P. Subbalakshmi, and PhD candidate Yiping Xing. A journal special issue on dynamic spectrum access wireless communications, edited by Dr. Subbalakshmi and Dr. Chandramouli with colleagues from MIT and the U.S. Army Research Lab, is also featured.
“These Stevens researchers loom large in the literature of a disruptive technology that will potentially transform a telecommunications market worth hundreds of billions of dollars, touching all of our lives,” says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. “Their multifaceted research on the subject establishes efficient use of radio spectrum without compromising security.”
The Federal Communications Commission originally reserved spectrums for military, amateur radio, and pager use. Spectrums dedicated to cellular networks eventually became overloaded while the former spectrums were underutilized. Furthermore, researchers discovered that secondary users could transmit on a spectrum without interfering with the primary users’ signals as long as the power of the secondary transmissions were below a certain threshold known as the interference temperature. A highly cited article by the Stevens researchers established a method to optimally compute interference temperature. A higher threshold means more utility for secondary users, but an excessively high threshold can cause interference for primary users. Thus the report is helping to alter government policy for optimal efficiency of the system and maximum benefit to society.
To protect the primacy of licensed users on their designated spectrum beyond the advent of software-defined radio, Dr. Subbalakshmi contributes her network security expertise. She is eliminating the potential for malicious behavior such as primary user emulation, in which an unlicensed user takes a vacant spectrum and pretends to be the primary user by playing with the transmission parameters, resulting in unauthorized monopolization of the spectrum.
Dr. Chandramouli entered the field from the angle of making a mobile router with interoperability of radios for first responders, in order to prevent problems such as those experienced by 9/11 responders from different agencies. With Dr. Subbalakshmi, he received a Department of Justice grant for research into a low-cost mobile gateway with a router and intelligence in a wireless cloud. The cloud senses an emergency situation and instructs the router to reconfigure its parameters to operate on multiple bands simultaneously. The various agencies connect to the cognitive radio router, which then translates and authenticates between frequencies and bands seamlessly, in real time. The technology has had wider benefits in that that it suggested the possibility of making wireless standards agnostic, so that people using different carriers could talk to each other seamlessly. The “cognitive” technology senses radio channels to find best signal and reconfigures the network in real time so that users can take advantage of the strongest channel.
The Stevens collaborators have brought versatility and security to the technology, respectively, and they have started a company named Dynamic Spectrum, LLC with the aim of commercializing their innovations.