The nodes in MSNs are electronic devices that have limited resources, such as buffer, energy, etc. Mobile nodes would exhibit selfishness to save their own resources. The node model is summarized as follows.
- • There are two categories of nodes in networks: cooperative nodes and selfish nodes. Since nodes get paid only when the destination receives the bundle, selfish nodes cannot get benefit if they drop bundles.
- • Without incentive strategies, if a node is selfish, it accepts no bundles from other nodes unless it is the destination of the bundles.
- • Selfish nodes are of limited rational. That is, with the incentive strategies, these nodes pursue for the maximum benefit if nodes have sufficient resources. Meanwhile, nodes only consider whether it is beneficial to accept bundles at this moment and do not consider whether they may break the pale when they want to buy other nodes relay services.
When a source node Src sends a message M to a destination Dst, Src first sets the message head with necessary information and then generates a bundle, as shown in Fig.4.2.
Specifically, the bundle is comprised of six components: its bundle sequence number ID, source Src, destination Dst, creating time stamp TS, time-to-live TTL, and message M.
Fig. 4.2 Formation of the bundle
Our design goals have two desirable objectives as follows: On one hand, our scheme should be effective in stimulating selfish nodes to participate in bundle delivery in MSNs. On the other hand, it should be efficient without introducing too much extra transmission delay.