Research On D2D Communication Technology Based On Social Networks

As the explosion of mobile services, the traditional cellular network system has being facing unprecedented challenges, such as scarcity of spectrum resources, overloaded base-station, crowded transmission links, and so on, which greatly restricts the development of communication technology in the future. Therefore, the device-to-device(D2D) communication system in which terminals are allowed to communicate directly with each other has become a new research focus recently in the field of wireless communications. As one of the key technology of next-generation wireless communication, it brings a lot of benefits as well as promising prospects such as offloading of base station in cellular networks, improvement of energy efficiency, expansion of communication range, increasement of transmission rate, etc. In addition, the users holding mobile communication devices will spontaneously form a relatively stable social network model with some regularity of complex network. Thus, this thesis will integrate social network with D2 D communication and consider the network topology between users to research the D2 D communication technology. Our completed work includes the following:(1) First, we analyzed the key technologies in D2 D communication and summarized the advantages and disadvantages of D2 D communication comparing with the traditional cellular communication and the traditional point-to-point communication. At the same time, complex network theory and its mathematical expression as well as the characteristics of the social network were illustrated, which laid the foundation for the later theoretical research.(2) Then, we researched the peer discovery strategy based on social relationships. As the first step of establishing D2 D links, it aimmed to identify potential D2 D users. There are several problems in the existing methods such as slow rate and insecurity, etc. For these defects, we studied the user-demand peer discovery strategy based on social relationships, which identifies potential D2 D users according to the distribution of documents requested by users, social relationships feed-backing or updating by base stations. Besides, in order to avoid vandalism of malicious user nodes, we also considered users’ reputation in the system. Theoretical analysis and simulation results show that, the proposed strategy can effectively discover neighboring users, and at the same time, the security of constituting D2 D link between users has also been increased.(3) Finally, we researched file-sharing mechanism based on social networks. The existing methods are not comprehensive. For example, it do not fully consider the social status and trust degree of users as well as the simplicity of files sharing in system. Thus, we analyzed a file-sharing mechanism based on social networks underlaying cellular networks. In the proposed mechanism, all users are divided into several groups according to the documentation requirements. Then the D2 D communication links or the cellular communication links are built within each group by fully taking the users’ social status, trust degrees and the unitity function into account. The target files give priority to be shared through the D2 D mode. Additionly, in order to avoid self-interference, D2 D users can only handle(send or receive) one request. To solve this problem, our solution was sending files through multi-rounds. Theoretical analysis and extensive simulation results show clearly that the social network can affect the whole wireless networks significantly. Selecting a user with the largest social degree as a central user can greatly reduce the transmission delay, relieve the heavy burden of base stations and thus optimize the overall performance of cellular communication systems.Our study has important theoretical significance and practical value on solving the problem of shortage of wireless resource and ensuring the safety in files-sharing.