The Necessity for Strong Reciprocators in Mobile Ad Hoc Networks

In civilian mobile ad hoc networks behaviour of network participants in accordance with the collective interest cannot be guaranteed. The cooperation in packet forwarding can emerge if the reciprocal tit-for-tat (TFT) principle is commonly used. This induces the nodes with self-regarding preferences to act cooperatively. However, as demonstrated in this paper, in certain conditions costs of using a reciprocal forwarding are greater than benefits. In such a case, the cooperation can emerge only if nodes with specific behaviour called strong reciprocity are present in the network. This paper analyses such conditions using a nature-inspired evolutionary approach. The computational experiments demonstrate that as soon as at least approximately 70% of nodes follow the TFT-principle in packet forwarding, benefits of its use exceed costs, regardless the forwarding behaviour of the remaining nodes. Consequently, strong reciprocators are not required for sustaining cooperative network. Below that threshold, the need for strong reciprocators depends on the composition of the remaining nodes. In particular, it is positively correlated with the number of unconditionally cooperative nodes as these nodes create incentives for free-riding behaviour.