Power allocation scheme for the underlay cognitive radio user with the imperfect channel state information

Interference control (IC) plays a key role in cognitive radio networks (CRNs). The secondary users (SUs) should limit the interference power under a predefined threshold. It is hard to design a IC scheme for the IC by the imperfect the channel state information (CSI). By the influence of the imperfect CSI, the actual interference power may exceed the interference threshold and disturb the primary system. In this paper, the reasons which leads to the imperfect CSI are summarized as two key factors: outdate and channel estimation error. And three different assumptions of the CSI which is used for the design of IC scheme in underlay CRNs with time-varying channel are discussed: (a) neither consider the influence of outdated CSI nor the measurement error in channel estimation, (b) consider the influence of the outdated CSI but without consider the measurement error in channel estimation, (c) both consider the influence of the outdated CSI and the measurement error in channel estimation. By considering influence of the imperfect CSI, a robust IC scheme with imperfect CSI is proposed to control the interference power in time-varying channel. The simulation results demonstrate that the proposed IC schemes effectively control the interference power in time-varying channel.