Cognitive Radio oriented wireless networks: Challenges and solutions

Existing wireless networks are unable to fulfill the insatiable demand of radio spectrum by emerging wireless services and applications. To address the current spectrum scarcity problem, next generation wireless networks are required to be comprising of intelligent and reconfigurable radios (popularly known as Cognitive Radios (CRs)) that can interact with their continuously changing environment to capture real time spectrum awareness and avail any spectrum usage opportunity. Dynamic and opportunistic spectrum access is identified as an enabling technology for Cognitive Radio Oriented Wireless Network (CROWN) wherein low-priority secondary users (CRs) are allowed to communicate over licensed frequency bands when the legacy users of that spectrum are not fully utilizing it. As most of the spectrum is already allocated to primary users with exclusive legacy rights of the frequency bands, the key challenge for CROWN is to reuse/share licensed spectrum without interfering with primary transmissions. This paper highlights fundamental challenges in getting multi-dimensional spectrum awareness under practical constraints and provides viable solutions. Furthermore, limitations of both transmitter detection based non-cooperative spectrum sensing techniques and cooperative sensing strategies are discussed, open research challenges are investigated and possible solutions are presented.