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-efficient resource allocation are of particular interests. In this chapter, the authors first provide a systematic study on Cooperative Cognitive Radio Networking (CCRN). As an effort to shed light on addressing spectrum-energy inefficiency at a low complexity, an orthogonal modulation enabled two-phase cooperation framework and an Orthogonally Dual-Polarized Antenna (ODPA) based framework, as well as their resource allocation problems are given and tackled.
Low-complexity energy-efficient resource allocation for delay-tolerant two-way orthogonal frequency-division multiplexing relays