Towards Practical Store-Carry-Forward Networking: Examples and Issues

In the evolution of wireless networks such as wireless sensor networks, mobile ad-hoc networks, and delay/disruption tolerant networks, the Store-Carry-Forward (SCF) message relaying paradigm has been commonly featured and studied with much attention. SCF networking is essential for offsetting the deficiencies of intermittent and range limited communication environments because it allows moving wireless communication nodes to act as “mobile relay nodes”. Such relay nodes can store/carry/process messages, wait for a better opportunity for transmission, and finally forward the messages to other nodes. This paper starts with a short overview of SCF routing and then examines two SCF networking scenarios. The first one deals with large content delivery across multiple islands using existing infrastructural transportation networks (e.g., cars and ferries) in which mobility is uncontrollable from an SCF viewpoint. Simulations show how a simple coding technique can improve flooding-based SCF. The other scenario looks at a prototype system of unmanned aerial vehicle (UAV) for high-quality video surveillance from the sky in which mobility is partially controllable from an SCF viewpoint. Three requisite techniques in this scenario are highlighted - fast link setup, millimeter wave communications, and use of multiple links. Through these examples, we discuss the benefits and issues of the practical use of SCF networking-based systems

Effects of detailed ofdm modeling in network simulation

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Performance Estimation of Parallel Discrete Event Simulation Using Synchronous Conservative Algorithm

Exploiting an efficient scheme for parallel discrete event simulation requires precise information about simulation runs. However, the virtual time synchronization algorithm gives rise to a wide gap between simple estimation and the actual simulation. This paper proposes a new performance estimation model for parallel simulation using synchronous conservative algorithm. The model assumes an exponential distribution for virtual time intervals between events. The result shows that the estimated execution time using the model is practically exact compared with the actual one. 1 Introduction Parallel discrete event simulation [Fuj90, Fuj93] requires good performance estimation to analyze its problems and achieve efficient execution. However, the complexity of the virtual time synchronization algorithm [Fuj90] causes a simple estimation far from the actual simulation and keeps parallel simulation from putting it into practice. This paper presents a new performance estimation model of paral..

Abstract

In mobile ad hoc network (MANET) studies, it is imperative to use highly detailed device models as they provide high layer protocols with good prediction of underlying wireless communication performance. However, such studies often utilize abstract models for execution speed and simplicity. This paper first shows that physical layer variables including path loss, shadowing, multipath, Doppler have significant effects on the predicted overall networking performance. It then proposes an approach to simulate details of wireless propagation and radio characteristics in networking studies while still maintaining a reasonable simulation execution time. Through our runtime performance studies with detailed OFDM Simulink / MATLAB models and QualNet network simulator, it is shown that the proposed approach can improve the simulation runtime performance by three to four orders of magnitudes without compromising the fidelity of simulation results. 1