On exploiting polarization for energy-harvesting enabled cooperative cognitive radio networking

Radio spectrum underutilization and energy inefficiency become urgent bottleneck problems to the sustainable development of wireless technologies. The research philosophies of wireless communications have been shifted from balancing reliability-efficiency tradeoff in the link level to seeking spectrum-energy efficiency in the network level. Global spectrum-energy efficient designs attract significant attention to improving utilization and efficiency, wherein cognitive radio networks and energy scavenging related techniques are of particular interests. In this article, we first provide a systematic study on cooperative cognitive radio networking (CCRN), followed by the discussions on research issues and challenges in designing spectrum-energycomplexity efficient CCRN. As an effort to shed light on addressing spectrum-energy inefficiency at a low complexity, a novel CCRN paradigm exploiting polarization and energy harvesting capabilities is elaborated. Specifically, we present a novel polarization and energy harvesting based framework for achieving size-cost effective CCRN. We introduce polarization signal processing to avoid interference between secondary users and primary users in cooperation. We propose a weighted sum spectrum efficiency based problem formulation and multi-timescale dynamic programming based energy/power allocation policy to evaluate the cooperation performance, subject to energy levels, power, and throughput constraints.