Hybrid spectrum sharing with imperfect sensing in fading channels

This paper considers the hybrid spectrum sharing paradigm where a cognitive radio system first performs spectrum sensing to identify primary users´ (PU) status (idle/busy) and then adapts its transmit power according to sensing outcomes. To maximize ergodic throughput in fading environments, joint sensing and power allocation has to be considered. However, existing studies determine the optimal sensing time based on instantaneous channel state information (CSI) at each time slot, which imposes a stringent requirement in practice. In this paper, we obtained a statistical CSI-based optimal sensing time by exploring the ergodic rates of both overlay and underlay access in Rayleigh fading environments. Simulation results validate the derived analytic expressions, showing that significantly higher maximum throughput can be achieved by hybrid access compared with conventional overlay access.