Browsing by Author "Rentz, Nicolas"
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Item HYBRID NETWORKS WITH A SPACE SEGMENT - TOPOLOGY DESIGN AND SECURITY ISSUES(2005) Roy-Chowdhury, Ayan; Baras, John S.; Hadjitheodosiou, Michael H.; Rentz, Nicolas; Baras, Dr. John S.; ISR; CSHCNIn this paper we investigate a hybrid network topology that is suitable for supporting interplanetary communications. We define an architecture comprised of a network of sensor nodes on a remote planetary surface, connected to a hybrid terrestrial network of wired and wireless LANs through a series of satellite relays. All the nodes in the network are IPaddressable and support public and symmetric key cryptography. The resulting network forms a hierarchical hybrid mesh that connects users on Earth to networks on or around a remote planetary surface. We describe the design of the network and present preliminary simulation results illustrating the network performance for various parameters. We also discuss how algorithms for user authentication, message integrity and data confidentiality can be incorporated in the network infrastructure for secure end-to-end communication.Item Performance Metric Sensitivity Computation for Optimization and Trade-off Analysis in Wireless Networks(2008-02-26) Baras, John S.; Tabatabaee, Vahid; Papageorgiou, George; Rentz, NicolasWe develop and evaluate a new method for estimating and optimizing various performance metrics for multi-hop wireless networks, including MANETs. We introduce an approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model takes into account effects of the hidden nodes, scheduling algorithms, IEEE 802.11 MAC and PHY layer transmission failures and finite packet transmission retries at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models, and develop a methodology for sensitivity analysis, parameter optimization and trade-off analysis for key wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.Item Throughput Evaluation and Optimization in Wireless Networks(2007-12-10) Rentz, Nicolas; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While wireless communication is progressively replacing wired technology, methods for the implementation of Wireless Ad-Hoc Networks are currently under development. As these methods do not require centralized coordination, they are particularly adapted to environments such as disaster recovery and military communication and are, therefore, of great interest. Despite the potential advantages, no reliable methodologies for the design of Wireless Ad-Hoc Networks have been proposed. This condition is largely due to the complexity of analysis of a wireless channel in comparison to that of a wired channel. In this thesis, we discuss the implementation of a tool for wireless network design. Taking a set of nodes and the corresponding characteristics, this tool computes the routes between each source-destination pair. The tool then computes the throughput for each connection and, finally, proposes a method for the optimization of throughput based on probabilistic routing via sensitivity analysis.