Cooperative Spectrum Sensing In Dense Network

With rapid development of wireless communication, dense network is emerged and regarded as a key step to enhance spectrum efficiency. However, the dense deployment may cause severe inter-cell interferences and degraded system performance. The exploding increase of wireless communications combined with the existing inefficient usage of the licensed spectrum gives a strong impetus to the development and standardization of cognitive radio networking and communications. Cognitive networking technology also has tremendous potential to improve network performance, even without considering dynamic spectrum use. Cognitive radio technologies provide an effective solution for the complex interference in dense network.In this dissertation, firstly overview the research status of dense network, cognitive radio, and mainly pay attention to the research of the cooperative spectrum sensing technologies in dense network compared with some traditional spectrum sensing techniques of cognitive radio network ,a framework for Cooperative spectrum sensing (CSS) is presented, which is the enabling technology for increasing the performance detection efficiency of wireless communications by reducing the number of sensing users. Based on that, Cognitive Radio (CR) can be developed as an enabling technology for supporting the CSS, which means that the wireless users are provided with enhanced capability for sensing the operating radio environment and for exploiting the network side information obtained from this sensing. The CSS concept means that the users of a wireless system are divided into clusters hierarchy with the primary users (PUs) entitled to protection and with cognitive radio capable secondary users (SUs). Secondly, the performance of cooperative spectrum sensing technology is analyzed by MATLAB tool and analyzed associated with the characteristics of dense network. Finally,we propose a new cooperative spectrum sensing scheme in emergency communication networks to enhance the robustness of spectrum sensing. The improved in detection of performance is obtained by reducing the number of sensing user (SUs) depends on applying fusion rule after the emergency case happened. After that deployed wireless emergency networks possess low spectrum efficiency that's will impact on the performance detection, similar to their civilian wireless counterparts. It's due to the traditional radio frequency partitioning where each service has uniquely assigned bandwidth. To alleviate this problem,we can adopt cognitive radio technology for physical and link layer design of future wireless emergency communication networks. Emergency Cognitive Radio Ad-hoc Networks(CRAHNs) require their sensing mechanism to be accurate, detection performance and have low latency in the delivery of packets. They should also be adaptive to varying number of SUs and SNR conditions. Cooperative spectrum sensing, where a number of SUs sense and exchange local spectrum sensing results, to achieve a more reliable decision on the presence of the legacy Primary Users(PUs),can be applied to emergency CRAHNS. An Emergency communication networks scheme proposed through CSS are divided into different clusters, each of them managed separately (clusters of fire fighters, police, rescue services, etc.) and created on an ad hoc basis. During the operation, each cluster will cooperate in helping other clusters to achieve their specific tasks. Such a cluster is called an Incident Area Network (IAN), which can enhance the cooperative sensing performance and reduce the number of sensing users compared with other traditional cooperative spectrum sensing in emergency case.