Device-to-device data storage for mobile cellular systems

As an alternative to downloading content from a cellular access network, mobile devices could be used to store data files and distribute them through device-to-device (D2D) communication. We consider a D2D-based storage community that is comprised of mobile users. Assuming that transmitting data from a base station to a mobile user consumes more energy than transmitting data between two mobile users, we show that it can be beneficial to use redundant storage to ensure that data files stay available to the community even if some of the storing users leave the network. We derive a tractable closed-form equation stating when redundancy should be used in order to minimize the expected energy consumption of data retrieval. We find that replication is the preferred method of adding redundancy as opposed to regenerating codes. Our findings are verified by computer simulations.