Researchs On Optimization Of Cognitive Relay Networks

With the continuous innovation and the rapidly changing in the research of wireless communication technology,the number of wireless users is gradlly increasing too.However,the wireless communication technology is still not perfect,there are still many problems to be solved.Due to the rapid development of wireless communication services,the spectrum resources tend to saturation,the existing technology has a very big limitation.Existing research shows that,although the spectrum resource is saturated,the existing spectrum is not fully utilized.How to solve the problem of spectrum resources,and use the network nodes to enhance network performance,which has aroused wide he attention and research of many scholars at home and abroad.The cognitive radio technology is considered as a promising technology to solve this problem.Cognitive radio is an intelligent wireless communication technology which has three aspects of abilities: first,it can detect the authorized and non authorized idle spectrum resources;second it is able to access the idle spectrum;third,the parameters of antenna can be changed based on their own wireless network environment,so as to achieve the corresponding communication performance.This technology can solve the problem of spectrum resource tension by improving the utilization of spectrum.At the same time,cooperative relay technology,which can resist the influence of channel transmission fading in wireless transmission,is an important technology to enhance the transmission range and improve QoS(Quality of Service)of wireless transmission system.This thesis is based on the combination of cognitive radio and relay technology,studies how to make the cognitive user can not only transmit their own data,but can help primary users improve the system transmission performance,and improve the utilization of resources in a wireless network.The main work and contributions of the thesis are as follows:First,according to the transmission distance of traditional dual-hop cognitive relay network is not enough,unable to implement two-way communication,we propose a new triple-hop relay communication model.This model can make full use of cognitive nodes to form the triple-hop network,improve the transmission distance,and achieve the two-way communication between cognitive users.Second,to solve the energy efficiency optimization problem of wireless equipment with battery,we put forward to reduce the consumption of resources through the network encoding two-way relaying,and utilize inter node transmission compensation to balance the energy consumption of a battery,so as to improve the total data transmission of system.Third,the power allocation of cognitive user is studied based on the cooperation of the OFDM sharing model.According to the characteristics of OFDM,we established the interference model between cognitive users and primary users,and the energy efficiency is optimized by a novel heuristic sub carrier matching method.Fourth,according to the node battery in wireless networks is often wasteful or starving,we proposed a energy transmission model for the time dimension and the node dimension in the network,and through the Lagrange optimal solution,to improve the node energy utilization rate and the total throughput.