Cognitive Radio Spectrum In The Switch Study

The rapid progress of wireless applications results in the scarcity of radio resources and demands higher efficiency of radio resource management mechanisms. As a big breakthrough in improving the utilization of radio resources, cognitive radio techniques has been one important research topic in wireless networks. However, it needs deep-research in a variety of areas, among which, spectrum handoff algorithm and protocol design in cognitive radio network is a widely-discussed key technique.To deal with the mobility of spectrum used by cognitive users in cognitive radio network, we need a new handoff mechanism, we called spectrum handoff, which enable cognitive users transferring connection among different spectrums. This thesis carries out a deep-research in spectrum handoff algorithms and corresponding protocols under the context of cognitive networks. Through analyzing the characteristics of cognitive radio and spectrum handoff, the spectrum handoff algorithms and protocols which adapt them well to the cognitive radio environment are proposed. Besides, their corresponding simulation performances are also illustrated in this thesis.This thesis first introduces the cognitive radio concepts, the research status on cognitive radio techniques. The characteristics of cognitive radio and possible issue to confront are analyzed and concluded in follow. We give the definition of the spectrum handoff include its class and flow based on the presentation of the research of handoff management in the next-generation. And then existing spectrum handoff algorithms and protocols are generally also analyzed so as to specify the focus in this thesis.Focusing on the two aspects: 1, cognitive radio system has a high handoff rate because of the spectrum dynamic; 2, call drop rate of cognitive radio system is increased on peak of primary users. The spectrum handoff algorithms and protocols which adapt them well to the cognitive radio environment are proposed. Chapter 3 proposes a spectrum allocation algorithm which enables each cognitive user to distributive choose the best channel to optimize the performance of handoff by minimizing handoff rate and handoff latency. Chapter 4 designs a handoff retrieval protocol which saves the call drop based on the Hierarchical Spectrum Sharing Network, theory and simulation results all show that this protocol can reduce the call drop rate on a big scale.