Cognitive Radio technology is used for efficient utilization of the spectrum. There are two types of users, one is the Primary user (PU), and the second one is the Secondary user (SU). In those users, PU is having the license to use the spectrum. The SU does not have the license to use the spectrum. Cognitive Radio comprises of Spectrum sensing, Spectrum Management and Spectrum Mobility. In cognitive radio, optimal power control in spectrum sharing is main research issues. In the spectrum, sharing both PU and SU can access the spectrum simultaneously as long as there is no interference to PU’s of Quality of service (QOS). So we have to handle this interference to the PU and we have to improve the performance of the SU. For that power control is the main consternate to improve the performance of SU. In our thesis, we are divided into two parts, the first one is we used ANFIS (Adaptive Neuro Fuzzy Inference System) for optimizing power control in cognitive radio network Users (SU) by optimization of SNR & SINR at Primary User (PU) to maintain QOS of PU and improve the performance of SU and Channel capacity computation for various ISR tolerance levels at PU. In second part, we used implementation of MIMO (Multiple Input Multiple output)-OFDM (Orthogonal Frequency Division Multiplexing) transmission technique in CRN (Cognitive Radio networks) for it is use in emergency conditions where transmission requires reliability and high data rate. Then it is tested BER (Bit error rate) performance on MATLAB. Key words: Cognitive Radio, Power Control, the Fuzzy Interference System (FIS), ANFIS, “MIMO” (“Multiple Input Multiple Output”), “OFDM” (“Orthogonal Frequency Division Multiplexing”), AWGN, BER, SNR, Eb/N0