Truthful and non-monetary mechanism for direct data exchange

In recent years, direct data transfer between mobile devices has attracted significant interest from the research community. In this paper, we focus on the scenario in which a group of clients need to exchange a set of files over a lossless broadcast channel. Initially, each client has a subset of files available to it as a side information and needs to obtain the some of the other files in the set. The clients employ the network coding technique to increase efficiency. We assume that each client is selfish, i.e., its goal is to minimize its own transmission rate while trying to receive as much information as possible from other clients. The process is mediated by a one of the clients, referred to as a broker, that obtains clients´ bids and determines their transmissions rates. Our goal is to design a truthful mechanism that provides incentives for the clients to report the true values of the requested packets. While mechanisms based on the Vickery-Clarke-Groves (VCG) auction are known to be truthful, they involve monetary transactions, and hence are not suitable for the problem at hand. Accordingly, we propose a simple non-monetary algorithm that guarantees truthfulness. Our analytical results and a numerical study indicate that the total utility of all clients under our algorithm is very close to the optimum.