Study On Opportunistic Carrier Aggregation In LTE-Advanced System

Spectrum resource is a kind of limited natural resource,with the rapid development of mobilecommunication technology,shortage of spectrum is more and more serious.The technology ofCarrier Aggregation in LTE-Advanced can polymerize several authorized spectrum band to increasethe system bandwidth available.However,the authorized spectrum assigned to LTE-Advancedsystem is limited.With the technology of Opportunistic Spectrum Access based on CognitiveRadio,a system can dynamically access the spectrum hole of unauthorized spectrum to share theunauthorized spectrum with other system.Opportunistic Carrier Aggregation can combine thecharacteristics of Carrier Aggregation and Opportunistic Spectrum Access to increase systemavailable bandwidth in great degree,and support the service of high rate.First,taking LTE-Advanced system as the research background,the paper discusses thetechnology of Carrier Aggregation,including the basic characteristics and the latest researchprogress,and studies Opportunistic Spectrum Access based on Cognitive Radio in deep,specifically,the technology of temporal Opportunistic Spectrum Access is modeled and the mechanism oftemporal spectrum concession is analyzed.Then the paper especially introduces the basic conceptsof Opportunistic Carrier Aggregation and designs a scheme to realize the technology,includingspectrum access and spectrum concession,as well as simulation and research on performance of thesecondary user system.In addition,this paper puts forward an improved proportional fairness (PF) algorithm CQI-PF,by adding CQI factor,the algorithm can increase the scheduling factors of cell edge users,and thenincrease the possibility of being scheduled,make resource allocation a little incline to the cell edgeusers,and improve the fairness between the users overall.Then,this paper designs a new resourcescheduling scheme under Opportunistic Carrier Aggregation,by using CQI-PF algorithm in thespectrum hole,and using the traditional PF algorithm in the original component carrier,in this way,itcan only sacrifice part throughput on the free spectrum to improve the edge users throughput andfairness,from the perspective of the secondary user system,it realizes a good balance between thesystem throughput and fairness by accessing free spectrum opportunities.Simulation results and analysis show that Opportunistic Carrier Aggregation can in further increase the average throughput of the system,compared with Carrier Aggregation.CQI-PFalgorithm can improve fairness between users with little sacrifice of average throughput.Under thescenario of Opportunistic Carrier Aggregation,the improved resource scheduling scheme canimprove the edge throughput and overall fairness largely by little sacrifice of average throughput.