Energy efficient coded cooperative data exchange for mobile users

In this paper, we generalize the problem of network coded cooperative data exchange from a fixed broadcast topology to dynamic networks with mobile peers. In this problem a group of wireless clients are interested in obtaining a set of packets through cooperation, where each client initially holds a subset of packets. Unlike recent studies where cooperation is enabled through a fixed error free broadcast channel among fixed or stationary peers, we assume that peers move randomly between transmission rounds, have a limited transmission range and suffer from packet erasures. In this case giving an exact solution to the problem of minimum number of transmissions is difficult, if not impossible. Therefore, we propose two different heuristic transmission strategies to decrease the total number of transmissions compared to uncoded transmissions. We compare the performance of these two strategies in terms of energy consumption (total number of transmissions) by analysis and simulations. In particular, we show that when packet delivery delay is not an issue, the total number of transmissions can be dramatically decreased at the price of a small overhead.