Study On Cooperative Spectrum Sensing For The Cognitive Radio

Cognitive radio (CR) is the idea of wireless architecture which doesn't have a fixed operation frequency band. CR system searches the unused frequency spectrum and uses them to solve the problem of spectrum scarcity and meet the demand of more communication device. Here we discussed the various techniques for the spectrum sensing which made it possible to implement in practice. And we took consideration of the interference to the primary user and the fundamental requirements to implement such a system in the real world.Here we showed the SNR as the proxy of the distance and the maximum allowable power for the secondary system in order to guarantee that there won't be the unacceptable amount of the interference to the legacy user.Mainly we focus on the spectrum sensing techniques with their benefits and their feasibility on the implementation on the cognitive radio. We discussed the cooperative spectrum sensing technique with Decode and Forward (DF) Protocol using the energy detection method to ensure that it will improve on the detection method even with the simplest method we have for detecting the primary signal and its impact on the overall system performances. This makes possible of the concept of using the unused frequency band by the secondary user with the minimum acceptable interference to the legacy user, known as the "Cognitive Radio".We examine the case of two cognitive radio one acting as a relay for another and analyze the parameters like probability of detection, agility gain, time interval using DF protocol and compare it without the cooperation scheme, shown how it can improve the spectrum sensing techniques and handle the problem of shadowing and hidden node.And next we examine the case of multi-user cognitive network and seen how the cooperation can be obtained by the clustering method, and defining dedicated relay cluster for the normal CR cluster which need the relay in order to increase the detection of the primary user and the basic frame format for obtaining the cooperation from the relay user so that the overall probability of detection will be increased. Beside these we have shown that how the task of assigning dedicated relay with the optimum probability of detection is done and how this help on the sensing technology and make almost independent of the order in the TDMA mode and hence the time interval required for the sensing the primary user can be minimized.