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There are a large number of redundant transmissions in current D2D multicast content delivery systems, which seriously reduces the utilization efficiency of resources. This paper designs a novel user-information-aware D2D video distribution mechanism. More specifically, by predicting users’ video requests, the video can be pushed to potential service requesters while distributing video for service requesters. Firstly, the willingness of potential requesters to accept the pushed video is estimated based on the users’ interests, the popularity of the videos and the residual-energy of the users’ devices, and the user-demand-aware clustering algorithm is proposed. Secondly, considering social and interference information, the utility metric of D2D multicast is proposed to measure the value of content distribution service. Finally, this paper proposes a D2D video distribution mechanism to optimize the utility value. Simulation results show that the proposed mechanism significantly improves throughput, energy and spectrum efficiency compared to the traditional distribution mechanism.

Relay-assisted Device-to-Device (D2D) communication, one of the important transmission modes in mobile health systems, can provide high transmission quality for servicing users at the edge of system coverage. However, the quality of the D2D relay communication is largely limited by the relay nodes. When a poor node is selected to assist the source node in the data transmission, it is likely to result in the loss of medical data and inaccurate transmission. Therefore, this paper focuses on how to select relay modes and relay nodes to improve the reliability of medical data transmission. Firstly, in order to eliminate the relay nodes with low energy or poor willingness, the acceptable energy consumption metric of relay nodes is proposed in this paper. The relay mode of each relay node is determined by the acceptable energy consumption metric, which can ensure the physical reliability of the relay communication links. Then a trust metric is proposed to measure the social reliability of each relay link, further excluding the malicious relay nodes. Finally, this paper proposes a relay selection algorithm based on compromise factors (RSCF). With the help of the proposed algorithm, the reliability of the relay communication can be guaranteed, and the spectrum efficiency can be promoted greatly. The simulation results show that the relay nodes selected by RSCF algorithm can greatly improve transmission rate and reliability compared with the traditional relay-assisted D2D communication schemes.

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The rapid development of mobile multimedia services integrated with online and offline social networks has made the mutual transmission of smart devices more frequent. Device to Device relay communication (D2D relay communication) can extend the transmission range of shared multimedia services, further reducing the burden on the base stations. However, when multimedia services are transmitted by D2D relay communication, the selfishness of the relay nodes affects the quality of the transmission. In order to solve this problem, the integration of social factors has become a common research topic. However, social factors generally come from multi-dimensional information. The more kinds of information, the more hidden information, and the measurement of social relations will become extremely difficult. Hence, this paper focuses on the measurement of social relationships based on multi-dimensional information and then combines physical domains to choose relay nodes. Firstly, the transmission performance of D2D relay communication is analyzed in the physical domain. Then, in order to better integrate multi-dimensional information, we construct a hypernet architecture based on spatiotemporal-user-location-category and quantify the edge weights. Three categories of weighted super-edge structures are defined to capture a variety of hidden social relationships, and the social relationship strength of any two users is measured. Finally, a relay selection algorithm that maximizes the social rate is proposed, which combines social relationships of multi-dimensional information and quality of physical transmission. The simulation results show that the Based on Maximum Social Rate for Relay Selection Algorithm (MSRRS) proposed in this paper has a significant improvement in transmission quality and transmission stability for multimedia application compared with the traditional relay selection algorithm. INDEX TERMS D2D, relay communication, social awareness, hypernet, multimedia transmission. How to meet people's growing demand for communication services with limited resources is an urgent problem to be solved [5]. D2D communication is a technology for communication of adjacent terminals [6], [7]. After the establishment of the D2D communication link between two adjacent terminals, data communication among devices will no longer need the core network's support or intermediate equipment [8], [9].