Tactical Wireless Communications and Networks: Design Concepts and Challenges

7.3 Cognitive Radios in Tactical Environments

The Defense Advanced Research Projects Agency (DARPA) generated its own CR initiative, the XG initiative, to define an architectural framework where radios can be controlled using policy rules. A CR can be deployed anywhere in the world with only a change in policy rules. This radio can sense for spectrum opportunities, use the policies to decide which channels to use among a domain of CRs (in the DARPA initiative, this is referred to as the “XG domain”). A collection of centralized and distributed protocols are used to achieve the three steps necessary to have a functioning radio: spectrum awareness, spectrum allocation, and spectrum use.

The DARPA XG initiative is technically not limited to the tactical use of CRs, although the concept of universal deployment is certainly applicable to military deployment. Tactical CRs are thought of as machines that sense their environment (the radio spectrum) and respond intelligently to it. They seek other radios with which they want to communicate while avoiding or outwitting enemies (interfering radios). They conform to the etiquette defined by the FCC and deliver services to the user. They can deal with entirely new situations and learn from such experiences.

At the time of writing this book, it is hard to predict the magnitude of the impact that CRs will bring to tactical communications. The US Department of Defense realizes the drawback of SPR. It also realizes the time and fiscal investment ...