This is introductory course on Cognitive Radio. Cognitive Radio is a concept introduced to attack the upcoming spectrum crunch issue and make opportunistic use of spectrum. It is an emerging field. It is useful for BTech & MTech students to understand basic concepts about technology . There are various research opportunities and challenges in Cognitive Radio. The resource allocation & its optimization under various constraints is required to improve system performance. Any researcher who is beginner in this field can start with these basic concepts and explore various research opportunities. This Course is divided into three Sections. Section-1 Covers introduction to Cognitive Radio including Digital dividend, cognitive radio (CR) architecture, functions of cognitive radio, dynamic spectrum access (DSA), components of cognitive radio and potential applications of Cognitive Radio. Section-2 Covers Introduction to Spectrum Sensing including Spectrum sensing techniques, detection of spectrum holes (TVWS), collaborative sensing, geo-location database and spectrum sharing business models (spectrum of commons, real time secondary spectrum market). Transmitter detection based sensing techniques :Matched Filter, Energy Detection, Cyclostationary Feature Detection and Wavelet Detection are discussed in detail and compared with each other in terms of advantages and disadvantages.Section-3 Covers Research Challenges in Cognitive Radio: Network layer and transport layer issues, cross layer design for cognitive radio networks.