Research On Optimal Allocation Of Downlink Resources In Wireless Cognitive Cellular Networks

With the progress of science and technology,communication technology has been greatly developed after entering the 21st century.Information age rapidly developed from 1G to 4G,and "Internet +"was put on the agenda as an important strategy for national development.Communication network technology has been paid more and more attention,and spectrum resources are constantly divided into a variety of communication systems.Cognitive radio technology emerged with the scarcity of spectrum resources.Cognitive radio technology allows the secondary user(SU)to use the authorized spectrum without interfering with the communication of the primary user(PU).The first chapter talks about the research background of the research topic and overseas and domestic research status and expounds the significance of the research in the face of the lack of spectrum resources.Then,this paper introduces the cognitive radio network from three aspects:the concept,key technology,characteristics and application prospect of cognitive radio network.The second chapter summarizes the downlink resource allocation for wireless cognitive cellular networks.In the traditional cellular network,we usually segment the spectrum with fixed division,which makes the spectrum utilization is low,and it can be solved by using dynamic and constrained authorized spectrum of cognitive radio technology.Then,it introduces the resource allocation technology in wireless cognitive cellular network.When the secondary user is a single user,the secondary user occupies all the available spectrum resources;and in the case of multi-user,the spectrum resource is allocated among multiple users,taking into account the fairness of each user and the optimal spectrum distribution.Finally,theoretical basis,common methods and existing algorithms of downlink resource allocation are introduced and analyzed according to the published literature.This is the rationale for the downlink resource allocation problem in wireless cognitive cellular below.In the third chapter,we not only need to consider the fairness of each user and the optimal allocation of spectrum,but also need to consider the main user protection when the cognitive user is a multi-user.Thus,this paper proposes a downlink resource allocation algorithm in wireless cognitive cellular networks:when subchannel allocation is performed,the minimum rate requirement of the cognitive user is used as a constraint,as long as the cognitive user reaches the required rate,it is no longer assigned to the subcarrier,so that the subcarrier that is saved to the new access to the user to use.Use the Hungarian algorithm to optimize the allocation of subchannels based on cost.After the subcarrier allocation is complete,we perform power allocation.According to the subcarrier allocation,the power allocation is carried out by using the water injection algorithm for each subcarrier,and the algorithm is improved according to the constraint condition and the power allocation.In the fourth chapter,use MATLAB simulation platform to verify the performance of the algorithm through four different test programs.First,the complexity of the algorithm is analyzed from the theoretical point of view.Then,according to the existing literature,the channel is modeled as an ITU general fading channel and a simulation parameter is.given.Finally,the simulation results of the algorithm are analyzed in detail and good performance of the algorithm is verified.