In Cooperative MIMO communication,major challenges are efficient use of bandwidth and link reliability.To achieve cooperative diversity in cognitive radio network,DF-protocol is implemented at CRs using OSTBC. The 2-hop communication between source and destination is completed with the help of CRs using MIMO technology within the network. To achieve spatial diversity and good code rate Alamouti 2x2 STBC is used for transmission. CR is using the decoding DF-strategy and without amplifying ability before forwarding data towards destination provide better performance. The main objective of this thesis is to detect PU- spectrum availability or non-availability for the use of SU. The Alamouti 2x2 STBC encoded data is broadcasted to wireless Rayleigh faded channel through transmitter having two transmitting antennas. The CRs are preferred to place close with PU to detect transmitted signal and because of having decoding capability CRs decode the collected data using ML-decoding technique then re-encode the decoded data for further transmission towards receiver.This book is useful for students and researchers working in the areas of Cognitive Radio and Cooperative Wireless Networks.