Bingxuan ZHAO Wireless Communication and Satellite Communication Project II Shimamoto Laboratory, GITS Waseda University Ph.D Academy Spectrum Sensing for Wireless Networks 1

Outline Introduction Cooperative Spectrum Sensing Conclusion of the Dissertation 2

Current Status of Wireless Spectrum Limited Supply vs. Growing Demand 3

Current Status of Wireless Spectrum Scarcity vs. Largely Underutilized 4 Cognitive Radio: improve spectrum utilization mch_m/mch_m_slides.pdf

Research Question Cooperative Spectrum Sensing Effectively find the White Spaces: decrease P FA Avoid interference with the PUs: decrease P MD  How to address the power uncertainty problem to decrease P FA and P MD 5 Noise Power Uncertainty

Local Sensing Techniques 6 Simplicity No prior-knowledge required Most widely used Energy Detection mechanism Time Domain Frequency Domain

Cooperative Spectrum Sensing 7 Data Collocation Data Processing Data Reporting Infer Presence Absence Soft Combing: Data fusion, high performance, high BW requirement Hard Combing: Decision fusion, low performance, low BW requirement

Model of Inter-Channel Interference 8 Superposed Power

Power Decomposition 1/3 9  d is the distance between tx and r.  P t is the transmission power  beta is the path loss exponent  I(u,v) is the interference factor  is constant The received power of the receiver, r, working on channel u produced by the transmitter, tx, working on channel v can be represented by: ACM Sigmetrics (2006)

Power Decomposition 2/3 10 The total received power by a secondary user s(i,j): Mathematical Transform

Performance Evaluation of Power Decomposition 11  Power decomposition works well in low SINR with conventional method can not.  Soft combination can achieve better performance than hard combination.  Power decomposition can cope with the increase of the inter-channel interference.  Power decomposition can achieve lower P FA, i.e., higher spectrum utilization.  Power decomposition can achieve higher P D, lower interference with PUs

Conclusion of Chapter 3 Proposed a power decomposition method: Non-coherent: depends only on distances Improve spectrum utilization Decrease interference with PUs 12