Research On D2D Cooperative Transmission Mechanism Based On Social Characteristics

With the rapid growth of the number of mobile users and wireless data services,the limited spectrum resources and the growing demand for data services have become the main contradiction in mobile communication.In order to meet the new need of future users,services,and networks,5G has proposed many key technologies to improve the spectrum efficiency,increase the bandwidth capacity,and enhance the coverage of base stations and user experience.In particular,D2 D communications,as one of the key enabling technologies of 5G,allows the user equipment to communicate directly.This technology not only can alleviate the pressure of cellular network access and transmission but also can effectively improve spectrum utilization,increase network throughput,and reduce energy consumption and transmission delay.Therefore,It has become the focus of the industry.Besides,affected by social network characteristics,the user equipment carried by mobile users is indirectly endowed with social attributes,which presents some social characteristics,such as social relations,community,trust,and selfish behavior.The social characteristics among mobile users are the important factors for driving content sharing and user cooperation.Therefore,mining and utilizing the features of social networks to assist in solving the D2 D cooperative transmission problem has attracted extensive attention and produced research results.In this context,this thesis studies the D2 D cooperative transmission mechanism by considering the characteristics of the social community structure,social trust,and selfish behavior.Details of the main work are as follows:(1)Aiming at the problem of user content caching and user differentiated service requirements,D2 D cooperative cache strategy based on social community structure and multi-D2 D multi-point cooperative transmission is studied.D2D users can serve as mobile service providers to reduce the load of base stations and enhance network performance through D2 D cooperative transmission.However,when the quality of D2 D links between users is low,the current one-to-one unicast or one-to-many multicast transmission mechanisms cannot always meet the requirements of D2 D users.In this thesis,a many-to-one multi-D2 D cooperative transmission mechanism is proposed.Firstly,to improve the efficiency of D2 D collaborative caching,a community structure aware D2 D collaborative caching strategy is proposed.Then,a non-cooperative game model is proposed for multi-D2 D multi-point cooperative transmission,which can maximize the benefit function of users while ensuring the service quality of users.The simulation results show that compared with the D2 D transmission mechanism based on cache location,the content hit rate and unload rate of the proposed multi-D2 D multi-point cooperative transmission mechanism are increased by 37.5% and 28.5% respectively.Therefore,the proposed mechanism can not only improve the efficiency of D2 D user cooperative caching,but also improve the efficiency of D2 D cooperative transmission.(2)Aiming at the problem of non cooperative transmission caused by subjective factors,a trust oriented D2 D cooperative transmission mechanism is studied.In order to improve the reliability of D2 D cooperative transmission,this thesis proposes a trust oriented cooperative transmission mechanism based on the subjective reasons of users.Particularly in the trust calculation process,the multi-dimensional trust relationship between D2 D users is constructed from the perspective of the cognition,emotion,and behavior in the interaction process.In addition,according to the multi-dimensional trust relationship between D2 D sending users and cooperative users,and the decision-making rough set theory based on Naive Bayes formula,D2 D cooperative users are divided into three categories: trusted users,users to be observed,and untrusted users.Finally,considering the trust relationship among and transmission rate of users,the optimal cooperative user is selected.The simulation of the measured social network statistical data shows that the cooperation success rate of the proposed cooperative transmission mechanism is 36.4% higher than that of the cooperative transmission mechanism based on social relationship strength.Thus,we can see that the proposed mechanism can not only improve the efficiency of D2 D user cooperative transmission,but also improve the reliability of D2 D cooperative transmission.(3)Aiming at the problem of non cooperative transmission caused by objective factors,this thesis studies competitive relationship aware D2 D cooperative transmission mechanism.In order to stimulate the enthusiasm of D2 D users,this thesis proposes a competitive relationship aware D2 D incentive cooperative transmission mechanism based on the objective reasons.In particular,according to the different modes of service supply,there will be a variety of competitive relationships among service providers,namely,the unequal competitive relationship between base stations and D2 D cooperative users and the fair competitivev relationship among multiple D2 D cooperative users.To maximize the utility function of service providers under different competitive relationships,a D2 D incentive pricing mechanism based on Stackelberg and Nash game is proposed,and the optimal solution is obtained using the backstepping induction method and the step-by-step iterative algorithm.The simulation results show that compared with the incentive mechanism which only considers the interests of users,the proposed D2 D incentive cooperation mechanism based on Nash and Stackelberg game yields a 12.4% higher benefit of cooperative users and a 32.8% higher benefit of base stations respectively.Therefore,the proposed mechanism can effectively encourage the D2 D cooperative users and then improve the reliability of D2 D cooperative transmission.