Study On Spectrum Handoff Mechanism Of Cognitive Radio System

Cognitive radio technology can efficiently use existing spectrum holes to avoid interference with the primary user to work under the premise by introducing opportunistic cognitive user access services, thus greatly improving network efficiency. As an important branch of the spectrum handoff technology by many researchers at home and abroad, cognitive radio technology has caused continuous and widespread attention, and in this article we will conduct in-depth study.This paper studies the spectrum of cognitive radio network handoff technology and the paper’s main contents are as follows.Chapter Ⅰ introduces the background of cognitive radio, including the concept of cognitive radio, the advantages and problems of cognitive radio technology, as well as cognitive radio key technologies and application prospects.Chapter Ⅱ describes the spectrum handoff as an important part of the concept of the cognitive radio technology. And then introduces the key technologies of the spectrum handoff and current research status. Finally it introduces the performance indicators of spectrum handoff as the algorithm reference in later chapters.Chapter Ⅲ presents a probability-based prediction spectrum handoff algorithm. Based on the ON-OFF channel model, we compare the relationship between the elapsed time of the idle channel and the already past service time of the cognitive user to reach the final formula as the key judging condition. The simulation also proved that the probability-based prediction algorithm can effectively reduce the handoff rate while slightly improves the throughput of cognitive radio system.Chapter IV presents a dynamic channel reservation algorithm. Previous study focus on the fixed number channels, but when all the reserved channels are occupied the new arrived primary user may cause more spectrum handoffs in non-reserved channels which will enhance handoff probability, and when all non-reserved channels are occupied the system can’t accept new cognitive users even there exist idle reserved channels. We use a dynamic run-time model to do the simulation and the results show that under the system most tolerant probabilities the dynamic spectrum reservation algorithm can accept more user traffic than previous fixed number channels algorithm, thus will significantly improve the system performance.