Cognitive radio: Emerging trend of next generation communication system

The 4 G communication systems are expected to become intelligent enough for communication between different entities. The idea is to extend Shannon's idea of perfect communication system to artificial agent for wireless communication. The internetworking of 3G communication system, cognitive radio, and software defined radio are candidate of 4G communication system. The difference in performance of 4G communication system is achieved through incorporating intelligence in wireless communication device. The various streams are studied to have in-built intelligence in communication devices. In this paper we focused on cognitive radio which works on basic idea of effectively managing available spectrum for different wireless communication systems. Paper explains cognitive radio as 4G communication system candidate and discusses design challenges of cognitive radio.