Analysis of cognitive radio dynamics

Abstract

The cognitive concept of a radio capable of adapting to the environment and of adjusting its operation as a function of both external and internal unpredictable events forms the conceptual basis for the design of future wireless communication systems. Designing and developing smart wireless devices able to sense the environment, and to modify accordingly spectral shape and other features of radiated signals is extremely appealing [1,2]. In particular, by defining and developing technologies that can enable a radio device to adapt its spectrum according to the operating environment, that is, to be aware of the scenario in which it operates, design innovation is taking its first step toward conceiving wireless networks that cooperatively coexist with other wireless networks and devices. The coexistence principle is intrinsic to innovative technologies such as ultra wide band (UWB) radio [3], although the concept has a rather broader acceptation. Cognitive radio focuses on improving efficiency in the use of the wireless resource and applies basically to the behavior of one node. By introducing cognitive principles in the logic of the wireless network one extends the cognitive concept to rules of interaction between nodes. In order to optimize the design one must therefore model the set of wireless nodes as a social network forming one single entity. Time scale is particularly important when conceiving adaptive mechanisms that should allow the update of system configuration. System operation is ruled by clocks, that must be tuned according to the granularity that is requested by a specific operation. In the case of spectrum sensing, for example, it might be desirable to force the system to being continuous, in order to incorporate the capability of detecting sudden and unpredicted changes in the environment. Conversely, it might be desirable for other operations to be ruled on different time scales. © 2007 Springer Science+Business Media, LLC.