File distribution via proximity group communications in LTE-advanced public safety networks

A primary technological challenge after a disaster is rapid deployment of temporary infrastructure to provide communications for disaster management workers. 3GPP Release 12 defines proximity service (ProSe) to allow direct communications within users for Long Term Evolution-Advanced (LTE-A) public safety. To support group communications, each group members have to receive data sent from the group application server (GAS) maintained in ProSe. This paper discusses the use of vehicle-mounted mobile base station to provide group communications over a two-tier heterogeneous architecture with the aid of GAS and ProSe links. In this method, each vehicle-mounted mobile base station (BS) works in a cell breathing manner to expand or shrink the cell coverage periodically. This way can ensure GAS having the up-to-date proximity knowledge of all users while the part of high-cost group data traffic due to the users located far from the BS can be offloaded to low-cost ProSe links instead. We formulate the minimum cost problem of the ProSe-based File Distribution (PFD) in such architecture. We prove the minimum PFD problem is NP-complete and then proposes three sources selection algorithms for PFD, namely Greedy algorithm, Defer algorithm, and Recursive algorithm. Extensive simulation study is conducted to evaluate performance of the proposed algorithms.