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Abstract-Unstructured mobile networks (UMNs) are mobile networks in which there is little or no pre-installed infrastructure (access points, antennas), and as such message forwarding is performed among the mobile nodes or within the wireless infrastructure. Routing in those networks occurs either using MANET approaches, where nodes build and end-to-end path among source and destination, or DTN routing, where nodes exchange cached messages whenever they enter in radio range with one another. One open question in the field, however, is when to use each of the approaches. Most UMN deployments lie on a gray zone, where it is hard to determine the most suitable protocol. This paper presents a performance evaluation of both approaches, in an attempt to identify when to employ each protocol.

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Opportunistic Networks (ONs) are mobile networks that support intermittent links and long delays. ON nodes exchange data in brief moments called contacts, when another node is within radio range. Contacts are ephemeral and unpredictable, thus they must be implemented as efficiently as possible. However, most previous work rely on simplistic assumptions such as unlimited bandwidth and contentionfree transmissions. This paper presents a more realistic evaluation of ON contacts. Simulations show that, on opposition to the consensus in the literature, routing protocols that forward more copies and those that determine a subset of nodes to receive the Bundles using a certain criteria outperform flooding-based protocols, because the latter generates too much medium contention. Finally, buffer management and forwarding prioritization may influence the performance of the network by up to 30%.

This study takes an approach to reliability-based topology optimization (RBTO) for 3D structures by applying an expansion of smoothing evolutionary structural optimization (SESO) and sequential element rejection and admission (SERA) for three-dimensional optimization. In the search for the stable optimal solution, and a more reliable structure, we present a performance index with the ability to monitor the evolutionary optimization procedure and adopt the filtering scheme usually applied in solid isotropic material with penalization (SIMP). The limit state functions are the maximum displacement constraints imposed in the topology optimization procedure and a structure’s performance control; a comparative analysis of the deterministic topology optimization (DTO) with the RBTO models is also explored. The obtained results suggest the importance of using the RBTO concept in 3D structures as part of the design analysis process.

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