# FollowMe: One Social Importance-Based Collaborative Scheme in MONs
## 2 Related Works  
The incentive model used in MONs can be classified into three types: the reputation system, the virtual money mechanism, and the tit-for-tat method. In the reputation system, packets are forwarded to nodes with a more favorable reputation. The value of the reputation is calculated from the historical behavior of nodes [2]. The authors of [8] use the number of forwarding times and success rate to estimate the reputation of nodes. A node aiming to enhance its reputation score has to receive/forward packets from/to other nodes; otherwise, it would be excluded from the network if its reputation is below a threshold. The reputation system is effective in situations in which the difference among nodes' reputation scores is large. In contrast, the improvement in collaborative behavior among nodes with similar scores is not obvious. The virtual currency mechanism enables nodes to gain a certain amount of income if they assist others to forward packets, and the income is paid by the node-sending packets [3]. Other researchers proposed Nuglet [9], which installs anti-modified hardware on nodes as a security measure to protect the currency swapping process. The virtual currency mechanism generally requires a central control node in networks and the realization of this mechanism is also extremely complex. Both of these features limit the applicability and scalability of this solution. The tit-for-tat method is based on the principle of equivalent exchange and uses game theory to construct the knowledge model. In each round, the participants in the game initially adopt a cooperation strategy, after which they imitate their opponent's recent behavior. If the game player in the latest round adopts the cooperation strategy, then the node chooses the cooperation strategy; otherwise, it chooses the betrayal strategy [4]. From the perspective of a non-cooperative game, the authors of [10] present a cooperation model with asymmetric information. This model reduces the cheating behavior of rational nodes, which use forged feedback information to increase their income. Although the tit-for-tat method seems to be fair, it may in fact weaken the forwarding efficiency. Imagine a situation in which a node attempts to send additional packets to the receiver, but the node is unable to do this if it only obtains a few packets from the receiver. Apart from the above mechanisms, some researchers use evolutionary game theory to study the cooperative behavior of bounded rational nodes in different systems and networks [11]. In an evolutionary game, nodes decide their own strategy by observing others' behavior; therefore, designing the game strategy is of key importance. A cautious idea was put forward [12], and properly introduced into the prisoner's dilemma model, and then the random Fermi update rule was used to describe the way in which the prudent idea affects the evolution of cooperative behavior. [PERSON] et al. [13] proposed a repeated game model to search the services in complex networks,and they used the random walk strategy to forward messages to neighbors. [PERSON] et al. [14] investigated the evolution of cooperation in a memory-based prisoner's dilemma game (PDG) on interdependent networks. Similarly, [PERSON] et al. [15] studied the influence of the neighborhood size and individual density on two interdependent lattices with the PDG model. Note that none of these researchers considered the influence of the sociality of a node on the collaborative behavior (Many routing algorithms such as Bubble and Hotent [16] employ the social property of nodes; however, to the best of our knowledge, currently incentive works do not evaluate the influence of social importance on the incentive process. ), i.e., in each updating round, nodes select strategies randomly from their neighbors to use in the game. In fact, nodes in MONs are always carried by people or installed in vehicles and show strong sociality. They tend to approach other nodes with higher importance in the virtual space similar to human beings in the physical world.