Optimal file storing with cache memory in amorphous femto helper aided networks

In this paper, we consider a cellular network, where a macro BS serves a single user with the aid of helper nodes, and find the optimal way to save a file in the helper nodes. Storing a file into distributed storage affects both hitting probability and successful recovery of the data at a user. With MDS coding, cache equipped helper nodes can store small fragments to improve the hitting probability. When a file is relatively important, we show that the optimal way to save a file is to save either the whole file or the smallest MDS fraction constrained on the amount of fragments. For less important file, we show that the conventional replica storing is optimal in terms of hitting probability.