Research On Energy-efficient Spectrum Sensing And Spectrum Access In Cognitive Radio Networks

The cognitive radio(CR)is one of the key technologies of the fifth generation mobile communication system(5G)to solve the spectrum scarcity.It can provide higher bandwidth and efficient spectrum usage by reusing the licensed spectrum in unlicensed manner or opening the licensed bands to unlicensed users to use them without causing any interference to the licensed user.Different cognitive radio systems concerns different performance indexes: the system with high data transmission efficiency usually concentrates the improvement of the throughput,while the energy efficiency(EE)is always studied in the system with energy-constrained nodes.This thesis focuses on the effects of spectrum sensing and access on the energy efficiency of the cognitive radio network(CRN)in sequential multichannel spectrum sensing.The main contents and achievements are as follows:(1)The relationship between the number of the sensing channel in sequential multichannel spectrum sensing and the EE is studied.Aiming at solving the issue how many channels should be sensed in CRN from the energy efficiency perspective,two spectrum sensing and accessing schemes are proposed.The EE of CRN under different schemes is firstly modeled as the mean of throughput-to-power ratio.Based on the model,an optimization problem is further set up to explore the effects of the number of sensing channels on the EE of CRN.Theoretical and simulated results finally indicate some interesting results: the number of sensing channels has nearly no effect on the EE of CRN under sequential channels sensing and instant channel access at a time finding an idle channel.However,the number of sensing channels has an obvious effect on the throughput of CRN.In the theme that secondary user(SU)senses fixed number of channels then selecting an idle channel for transmission,theoretical and simulated results indicate that the EE decreases monotonously with the number of sensing channels.(2)An energy-efficient hybrid spectrum accessing scheme for QoS provisioning is proposed.In the proposed theme,the SU first sorts the sensing channel according to the channel interference gain between different the primary users(PU)in ascending order then senses channels sequentially in this order.According to the SU could access the idle/busy channel in Overlay/Underlay mode,a joint optimization algorithm of access channel selection and power control with the consideration of sensing results and the QoS constraint is designed.Simulated results finally indicate the relationship between the EE and QoS as well as the number of PU,and summarize the best scenario for the scheme.In this thesis,it is shown that the reasonable design of spectrum sensing scheme and slot scheduling strategy,joint optimization of access channel selection and power control are all helpful to improve the energy efficiency of cognitive systems,which has instructive significance for solving the problem of efficient transmission of cognitive system with limited energy.