Relay-based cooperative spectrum sensing framework under imperfect channel estimation

To reduce interference to primary user and improve channel capacity with an acceptable detection probability in cognitive radio networks, we propose a relay-based cooperative spectrum sensing framework. Different from conventionally cognitive radio network, where spectrum sensing and signal transmission are performed separately, the proposed framework integrates spectrum sensing into signal transmission by assigning different signal types to primary user and cognitive users, i.e., sinusoidal signal and chirp signals for primary user and cognitive users, respectively. Thanks to the energy concentration property of chirp signals in the fractional Fourier transform (FrFT) domain, the separation of primary user and cognitive users can be realized easily. In this proposed framework, interference to primary user can be reduced because of the simplified time slot structure, and channel capacity can also be improved by removing the separate spectrum sensing process. Moreover, by using the energy accumulation of the primary user in the signal transmission process, the detection probability of the proposed framework can also be improved even with channel estimation error and signal separation error.