Awais Salman Qazi; Muhammad Shoaib; Muhammad Shahan Saleem , pp. 88. ING/School of Engineering, 2012.
Nowadays, the world has observed a tremendous increase in the demand of radio spectrum in wireless communication. Services like broadband internet, telecommunication, videoconferencing, mobile IP, online multimedia gaming and other applications have been deployed using wireless services. All of this has put an immense pressure on the companies offering radio resources such as bandwidth and power to raise the data rates in order to provide a guaranteed quality of service and quality of experience for the users. The shortage of radio spectrum and power have led to an emerging of the need-based concept of Cognitive Radio to economize the exceeding utilization of spectrum in order to accommodatea rising demand of higher data rates for using wireless services by applying the concept of cooperative communication in cognitive radio networks. Multiple-input multiple-output (MIMO) antenna systems have practically been considered as a way forward to address these challenging demands by actually conceptualizing the advancement of cooperative communication in cognitive radio networks. MIMOs have the capacity to be implemented in mobile cellphones. This capacity can be harnessed by using the major idea of forming a virtual station of MIMOs antenna system by invoking a terminal known as relay station. The relay schemes of cooperative communication that run on this relay station to gauge all the wireless traffic are Amplify-Forward and Detect-Forward. We have proposed a model to study the hybrid form of Decode-Amplify-Forward, to see the drastic and rapid increase in the usability of the cooperative spectrum. This system typically consists of the Primary User, the Cognitive Relays, the Cognitive Controller and the Secondary User. The PU transmits data to the CRs and CRs decode and re-encode the transmitted data by using Maximum Likelihood estimation and 2 x 2 Alamouti OSTBC techniques and later amplify the data by squaring the Alamouti OSTBC (re-encoded) data at the relays. All the relays in the system forward their collective decision to CC to finalize its decision on the basis of the information provided by the relays. This system is simulated by MATLAB and results are validated using MATLAB to accomplish transmit diversity, spatial diversity, cooperative diversity and diversity gain in cognitive radio environment in handling detection probability of licensed (primary user) for the unlicensed user (secondary user) to use cooperative spectrum.
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