Cooperative spectrum sensing using energy detection in cognitive radio technology

• Main Author: Ji, Qing
• Other Authors: Chong Han Joo Peter
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems
• Online Access: http://hdl.handle.net/10356/40037
• Institution: Nanyang Technological University

Spectrum sensing is the key enabling technology for cognitive radio networks. The main objective of spectrum sensing is to provide more spectrum access opportunities to cognitive radio users without interfering with the operations of the licensed network. The present literature for spectrum sensing is still in its early stages of development and a number of different spectrum sensing methods have been proposed for identifying the presence of signal transmissions. This research study focuses on the energy detector based sensing technique which requires no prior knowledge about primary user‟s signals. First, a theoretical framework is developed and performance metric is valued for energy detector based spectrum sensing system; second, a closed form solution for local optimal detection threshold for secondary users is derived. After shifting the local single user spectrum sensing system to cooperative spectrum sensing system, we propose a novel threshold selection scheme for OR and AND-rule based cooperative sensing systems. Unlike previous works on cooperative sensing where a common threshold is used for all secondary users under the assumption that they have identical average SNR and noise power levels, the proposed scheme is studied under the more general framework of possibly different average SNR and different noise power levels at each secondary user and it significantly outperforms the common-threshold approach in terms of the total probability of erroneous decisions in OR-rule based system. On the other hand, even when all the SUs have identical average SNR and noise power levels, the new scheme is still able to deliver similar performance compared to schemes using a common detection threshold. This iterative scheme is also shown to have fairly low implementation complexity. Finally, simulation models have been built and intensive simulation results show that the proposed sensing framework can achieve maximum sensing efficiency and opportunities in multi-user/multi-spectrum environments, satisfying interference constraints.