Optimal Relay Selection Schemes For Secondary Users In Cognitive Radio Systems With Energy Harvesting

With the rapid growth of wireless communications business,the number of users and heterogeneous networks rise sharply,which not only leads to the increasingly scarce spectrum resources,but also causes the rise of the mobile communication network's energy consumption.In order to solve the problem of spectrum scarcity and the energy consumption at the same time,the energy harvesting cognitive network(EH-CRN)that combine the cognitive radio technology and energy harvesting technology has great significance.Bringing cooperative relay in EH-CRN,secondary users(SU)help primary users(PU)transmit in cooperative mode to improve transmission performance,and obtain their own transmission opportunities,at the same time,through energy harvesting supplement the energy consumption in cooperative transmission.So,the frontier research in recent years has begun to focus on the cooperative relay between PU and SU,and performance optimization in EH-CRN.In this thesis,based on the summary analysis of existing related research results,aiming at the existing problems in current cognitive radio energy harvesting system of cooperation between PU and SU,and combine the demand of the project,we carry out the research of optimal relay selection scheme aiming at SU in cognitive radio energy harvesting systems,the main work is as follows:In this thesis,we proposed a relay cooperative scheme based on SU's willingness and throughput.Unlike the traditional cooperative schemes,we considered the SU's willingness and assumed that SU can select PU with less traffic load to cooperate with,and specific cooperative strategy was proposed.In this scheme,we firstly designed an optimal scheme of energy harvesting time sharing factor to maximize the SU's throughput in cooperative mode and non-cooperative mode.Moreover,we derived the closed-form solution of energy harvesting time sharing factor in non-cooperative mode.Meanwhile,in cooperative mode,the optimal result can not be obtained directly through analytical algorithm,so the optimal problem was solved through ergodic searching solution.Finally,we conducted the simulation analysis,on the one hand,the results indicate that the proposed scheme has better performance compared with existed cooperative schemes,on the other hand,we simulated the impact on performance of proposed scheme which caused by different parameters.In this thesis,we also proposed a relay cooperative scheme based on SU's energy efficiency.Different from the simple system model and lack of specific energy management strategy in existing research,we considered multi-user system model,and assumed that the receiver has the energy storage devices,which can reasonable use the harvested energy so as to avoid being wasted.Firstly,the cognitive radio router(CRR)broadcast the data information carried by PU to SU,the SU that needed to access the primary channel sent the cooperative decision to CRR according to budget of transmission power.Then,we deduced the probability mass function(PMF)distribution of minimum data packet within fixed time slot,and proposed the specific cooperative strategy.Moreover,we designed a joint optimization algorithm of energy harvesting time sharing factor and secondary transmission power based on SU's energy efficiency,and deduced the optimal solution of energy harvesting time sharing factor and the closed-form solution of secondary transmission power.Finally,the designed algorithm and cooperative scheme were verified by the simulation analysis,which has performance advantages.