Capacity Issues for Cognitive Radio Systems

The development of software radio toward the cognitive radio brought the hope that the spectrum scarcity would be finally an issue of the past. Due to the characteristics of the cognitive operation and environment (including spectrum sharing), the operation of such a system has to take into account the interference to and from other wireless systems. Interference exploited via cognition could also improve spectral utilization and end-to-end performance, and the interference channel model could provide a good choice when evaluating these systems. However, the determination of the capacity region for the interference channel has been an open problem for more than 30 years, showing that the fundamental questions about networks and interference is not well understood until now. In spite of that, some researchers have already presented capacity analysis for cognitive radio systems under certain conditions.