Naouel Ben Salem, Levente Buttyan, Jean-Pierre Hubaux and Markus Jakobsson abstract: In multi-hop cellular networks, the existence of a communication link between the mobile station and the base station is not required: a mobile station that has no direct connection with a base station can use other mobile stations as relays. Compared with conventional (single-hop) cellular networks, this new generation can lead to a better usage of the available spectrum and to a reduction of infrastructure costs. However, these benefits would vanish if the mobile nodes did not properly cooperate and forward packets for other nodes. In this paper, we propose a charging and rewarding scheme to encourage the most fundamental operation, namely packet forwarding. We analyse the robustness of our protocols against rational and malicious attacks. We show that our protocols thwart rational attacks and detect malicious attacks. We also show that our solution makes collaboration rational for selfish nodes.