Spectrum sensing and opportunistic medium access control protocol design for cognitive radio wireless networks

The explosive growths in the wireless communication field require more spectral resources, while the radio spectrum is a finite natural source. On the other hand, usable frequency bands are nearly fully occupied by the licensed users by the static allocation strategy and it is also known that most of the radio spectrum is inefficiently used. In cognitive radio (CR), frequency allocation and the access to radio spectrum is not assumed fixed but dynamic and thus cognitive radio technology utilizes this dynamic structure to improve spectrum efficiency and network performance. The primary objective of the thesis is to study spectrum sensing duty of cognitive radio attached with proper medium access control (MAC) design. A new wireless network scheme where the intentional background noise is added to the wireless region is proposed. With the proposed scheme, a blind sensing algorithm is introduced. The proposed scheme mainly addresses the sensing problem of secondary users as well as the primary users without any prior knowledge. Moreover, the problems coming from noise uncertainty and different kind of noise types are diminished because of added dominant noise characteristics. The performance analysis has been conducted using real data and the experimental observations have been obtained. The experimental results show that the proposed sensing algorithm outperforms the existing methods and is robust on noisy environments. By the novel method presented here, 90% true detection performance is achieved on the orders of nearly -10 dB SNR values. With nearly perfect sensing performance, the proposed CR-MAC provides simple, fast and accurate operating conditions.