Cognitive radio is an emerging technology for advance communication,it has many functions and aspects like spectrum sensing,spectrum management,spectrum decision and spectrum analysis.This book will provide a simple and short way for researchers and students to understand the spectrum sensing techniques in summarize. Meanwhile fuzzy logic technique has been discussed as a complete example which will provide help to design a project hardware in future. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------"Knowing you'll be in all my tomorrows,makes my today so wonderful!"