# Analysis of the Most Relevant Factors for Routing in Internet of Space Things Networks
## 2 Related Work  
As mentioned in the introduction, the goals of this paper were: to introduce a methodology for the analysis of the routing task in ad hoc IoT networks; to study and identify the impact of critical factors in the performance of reactive and proactive routing approaches in ad hoc routing for IoT networks; and to provide a useful performance analysis baseline for the development of new routing protocols for ad hoc IoT networking. Thus, prior to introducing our proposed methodology, in this section, we review previous relevant work related to IoT networking. The IoT paradigm has been previously addressed in [10; 18; 19; 24; 41; 43; 53]. These works studied the feasibility of establishing inter-satellite communication links that extend the Internet of Things (IoT) concept towards networks where the nodes are satellites (or even other kinds of spacecraft), thus defining the IoT paradigm. The authors in [10] explored the IoT paradigm and conceptually discussed a system architecture that fulfills this paradigm. As well, they discussed the challenges and constraints that must be overcome to successfully deploy IoT applications. Among the main challenges identified in this work, we can mention limited on-board processing capabilities of the nodes; considerable delays in propagation; and constraints introduced in the network topology by temporal variations, which can render satellite links susceptible to interruptions. The conceptual analysis introduced in Ref. [10] was later expanded in [19]. In this contribution, the authors further studied (by means of simulation) the duration of inter-satellite links when satellites with different orbital altitudes are considered as nodes of an IoST system. Additionally, a comparison of the physical layer performance between mmWave and S-band carriers is presented in this work. In [19], the author's review of the main characteristics of the spacecraft that can potentially become nodes in an IoST network was provided. Based on this review, Ref. [53] further analyzed the feasibility of establishing inter-CubeSats communication links. The results in this work show that it is possible to establish effective communication links between CubeSats. Therefore, we can conclude that CubeSats can effectively participate as nodes in ad hoc IoST networks. In [41], the authors performed a comparative analysis of features suitable for IoST networking, provided by routing protocols previously developed for other kinds of networks and applications. Notably, this work analyzed the features of protocols developed for snapshot networks, MANETs, delay-tolerant networks, wireless sensor networks, and low earth orbit (LEO) satellite networks. Based on this analysis, a set of routing protocols that might be used for IoST networking was identified. However, it is essential to note that the recommendation was only based on identified protocol features, as no performance analysis was provided. Based on their analysis, the authors concluded that MANET protocols can potentially be used for ad hoc IoST networking. However, in this work, the factors that could affect the performance of these protocols when used for ad hoc IoST networking were not thoroughly studied. In a later work [24], the authors studied the use of MANET routing protocols to form ad hoc IoST networks. In particular, they studied using an ad hoc IoST network to provide connectivity for the polar regions. As the implemented routing protocol in [24] was OLSR, the simulated ad hoc IoST network used a proactive routing approach. The reported results for this experiment showed that providing intermittent muti-hop communication to the polar regions was feasible using ad hoc IoST networking, even with relatively low node densities. Nevertheless, the authors concluded that network disruption is an ad hoc IoST networking issue that must be addressed.