Recent research shows that 70% of the available spectrum is not utilized efficiently. The bandwidth gets expensive owing to shortage of frequencies. For efficient utilization of spectrum, we need to sniff the spectrum to determine whether it is used by primary user or not. The term cognitive radio refers to the adoption of radio parameters using the sensed information of the spectrum. There are three major categories of spectrum sensing techniques; transmitter detection, receiver detection and interference temperature detection. This book presents a survey of techniques suggested in the literature for spectrum sensing with a performance analysis of transmitter-based detection techniques. A Fuzzy logic based technique for primary user detection has also been proposed. In comparison with transmitter detection techniques purposed technique provides good results under low SNR values.