QoE-driven social aware caching placement for terrestrial-satellite networks

In remote terrestrial-satellite networks, caching is a very promising technique to alleviate the burden of space cloudlet (e.g., cache-enabled satellite user terminal) and to improve subscribers' quality of experience (QoE) in terms of buffering delay and achievable video streaming rate. In this paper, we studied a QoE-driven caching placement optimization problem for video streaming that takes into account the required video streaming rate and the social relationship among users. Social ties between users are used to designate a set of helpers with caching capability, which can cache popular files pro-actively when the cloudlet is idle. We model the utility function of QoE as a logarithmic function. Then, the caching placement problem is formulated as an optimization problem to maximize the user's average QoE subject to the storage capacity constraints of the helpers and the cloudlets. Furthermore, we reformulate the problem into a monotone submodular optimization problem with a partition matroid constraint, and an efficient greedy algorithm with 1 − 1/6 approximation ratio is proposed to solve it. Simulation results show that the proposed caching placement approach significantly outperforms the traditional approaches in terms of QoE, while yields about the same delay and hit ratio performance compare to the delay-minimized scheme.