Nowadays, Internet of things is one of the hottest topics in ICT and one of the six emerging technologies in the world. In general, things are referred to network-enabled and resource-constrained devices that are heterogeneous from different aspects. So, interoperability (working integrated) is one of the major challenges in IoT. There are thing-to-thing (T2T) and thing-to-gateway (T2G) communications between different things. These communications can be intra-domain or inter- domain (multi-domain). Indeed, the IoT can be considered as a set of multi-domain networks that co-exist in the same geographical locations, but run by different authorities. The things are monitoring the environment periodically and send their sensed data towards the gateway (sink) possibly via multiple hops. This problem can be investigated in two scenarios: common sink and separate sink scenario. In separate scenario the sinks belong to different authorities, but they are common resources used by all authorities in common scenario. In this thesis, we intend to study T2T communications with a new perspective of heterogeneity in both scenarios. Criteria of this heterogeneity is defined based on the preprocessing costs for the things in each domain which is now applied in Fog computing. Additionally, these things often have a direct relationship, they usually have built-in security mechanisms. On the other hand, we assume that each thing is capable to make malicious packets and propagate them in network. In other words, we are interested in investigating interoperability in multi-domain interactions. There are some trade-offs between energy consumption, lifetime and security level of domains in these situations. We will propose a non-cooperative game theoretic model, which is a repeated and complete information game. Then we will find the effective factors on cooperative behavior, including number of things per domain, path loss exponent and communication range. In defined settings, we will show the average lifetime of each domain if the things cooperate, also forward packets from other domains. Keywords: Internet of Things, Heterogeneous Things, Cooperative Behavior, Game Theory
