The maximum capacity of fractal D2D (device-to-device) social networks with both direct and hierarchical communications is studied in this paper. Specifically, the fractal networks are characterized by the direct social connection and the self-similarity. Firstly, for a fractal D2D social network with direct social communications, it is proved that the maximum capacity is @math if a user communicates with one of his her direct contacts randomly, where @math denotes the total number of users in the network, and it can reach up to @math if any pair of social contacts with distance @math communicate according to the probability in proportion to @math . Secondly, since users might get in touch with others without direct social connections through the inter-connected multiple users, the fractal D2D social network with these hierarchical communications is studied as well, and the related capacity is further derived. Our results show that this capacity is mainly affected by the correlation exponent @math of the fractal structure. The capacity is reduced in proportional to @math if @math , while the reduction coefficient is @math if @math .
As a key component of future 5G cellular networks to improve throughput and spectral efficiency, D2D communication has been investigated in many contexts. Particularly, many literatures concerning with the D2D social networks have sprung up. For instance, @cite_5 analyzed the performance of relay-assisted multi-hop D2D communication where the decision to relay was made based on social comparison. In @cite_0 , the small size social communities were exploited for the resource allocation optimization in social-aware D2D communication. In order to alleviate the security issue in D2D social networks, a secure content sharing protocol was proposed in @cite_11 to meet the security requirements.
@cite_0 @cite_5 @cite_11
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Social-aware device-to-device (D2D) resource allocation utilizes social ties in human-formed social networks to allocate spectrum resources between D2D users and cellular users. In this letter, we consider the small size social communities formed by people with similar interests and exploit them to optimize the resource allocation of the communities. This results in an optimal graph matching problem among communities to solve the D2D resource allocation problem. Solutions are derived via bipartite graph matching and an effective small social community resource allocation algorithm corresponding to the cases of small and high D2D user loads. Device-to-device (D2D) communications are recognized as a key enabler of future cellular networks, which will help to drive improvements in spectral efficiency and assist with the offload of network traffic. Relay-assisted D2D communications will be essential when there is an extended distance between the source and the destination or when the transmit power is constrained below a certain level. Although a number of works on relay-assisted D2D communications have been presented in the literature, most of those assume that relay nodes cooperate unequivocally. In reality, this cannot be assumed, since there is little incentive to cooperate without a guarantee of future reciprocal behavior. To incorporate the social behavior of D2D nodes, we consider the decision to relay using the donation game based on social comparison, characterize the probability of cooperation in an evolutionary context and then evaluate the network performance of relay-assisted D2D communications. Through numerical evaluations, we investigate the performance gap between the ideal case of 100 cooperation and practical scenarios with a lower cooperation probability. It shows that practical scenarios achieve lower transmission capacity and higher outage probability than idealistic network views, which assume full cooperation. After a sufficient number of generations, however, the cooperation probability follows the natural rules of evolution and the transmission performance of practical scenarios approach that of the full cooperation case, indicating that all D2D relay nodes adapt the same dominant cooperative strategy based on social comparison, without the need for external enforcement. With the increasing of mobile devices, Device-to-Device(D2D) communication is considered as a promising technology for achieving direct communication of devices. But the security issues still remain to be solved. In this paper, We utilize D2D communication between UEs in proximity to share epidemic media contents. We propose a Secure Content Sharing Protocol(SCSP) that combine with the credibility between users. The credibility involves user's interest, interaction and geographical location. By means of encryption, signature and authentication in SCSP, the data confidentiality, non-repudiation and mutual authentication can be guaranteed. Furthermore, the user's privacy can be protected based on Pallier Homomorphic Encryption. At last, it is shown that the proposed SCSP can meet the security requirements and have lower computation cost in comparison with other related works through security analysis and quantitative evaluation.