Michael M. Johnson

Simulation analysis of virtual geographic routing

Homeland defense applications will use large-scale ad-hoc networks of small devices. Routing is a crucial problem, for naive means do not scale well. Geographic routing (GR) (Karp 2000; Giordano, Stojmenovic, and Blazevic 2003) offers hope for scalability, under the assumption that every device knows its geographic coordinates, e.g., through GPS. This solution is unsuitable though when there is no easy means of establishing a devices physical location, indoors. To address this limitation we propose virtual geographic routing where we construct a virtual coordinate space and use GR within it. This paper describes VGR, compares the characteristics of paths VGR identifies with those that GR identifies, then presents theoretical and empirical evidence for its scalability.

The IDES framework: a case study in development of a parallel discrete-event simulation system

This tutorial describes considerations in the design and development of the IDES parallel simulation system. IDES is a Java-based parallel/distributed simulation system designed to support the study of complex large-scale enterprise systems. Using the IDES system as an example, the authors discuss how anticipated model and system constraints molded the design decisions with respect to modeling, synchronization, and communication strategies.

A geographically distributed enterprise simulation system

Abstract Sandia National Laboratories has the role of system integrator in the US Department of Energy’s Nuclear Weapons Complex (NWC) and the responsibility for maintaining the nuclear stockpile. Maintenance is a complex task that involves a great number of geographically distributed functions, and a variety of analysis tools and models are used to plan operations, assess capabilities and guide political decisions. We are developing a framework for modeling the NWC unde interactive human control. The framework consists of a simulation system whose users and components are distributed across the entire United States. The purpose of the system is to support decisions about questions ranging from low-level operational matters involving only a sub-component of the complex to high-level policy issues requiring simulation of the entire complex. The system integrates multiple domain-specific legacy models and policy models and allows simulation at varying levels of detail. To provide such a framework, we have had to address a number of technical problems, whose solution is the focus of this paper. The three most fundamental problems are • to provide geographically distributed, synchronized human participation in the simulation; • to provide distributed ownership and security in such a way that the facility hosting a domain-specific model retains all rights to provide or deny a user access to its information; and • to integrate legacy models written in a variety of tools or languages and executed on different platforms. Key features of our approach are the use of the Java language and the coordination of the simulation through a new parallel discrete-event simulation system.

Performance modeling of the IDES framework

The IDES project at Sandia National Laboratories is developing a large scale portable parallel simulator for use in stockpile stewardship. IDES will use the Breathing-Time-Buckets synchronization protocol; to support IDES development, this paper studies a performance model and describes performance experiments on expected work load and architectural parameters. A new parallel algorithm for terminating the window quickly is also described and analyzed.

Robust message routing for mobile (wireless) ad hoc networks.

This report describes the results of research targeting improvements in the robustness of message transport in wireless ad hoc networks. The first section of the report provides an analysis of throughput and latency in the wireless medium access control (MAC) layer and relates the analysis to the commonly used 802.11 protocol. The second section describes enhancements made to several existing models of wireless MAC and ad hoc routing protocols; the models were used in support of the work described in the following section. The third section of the report presents a lightweight transport layer protocol that is superior to TCP for use in wireless networks. In addition, it introduces techniques that improve the performance of any ad hoc source routing protocol. The fourth section presents a novel, highly scalable ad hoc routing protocol that is based on geographic principles but requires no localization hardware.

Understanding communication in counterterrorism crisis management.

This report describes the purpose and results of the two-year, Sandia-sponsored Laboratory Directed Research and Development (LDRD) project entitled Understanding Communication in Counterterrorism Crisis Management The purpose of this project was to facilitate the capture of key communications among team members in simulated training exercises, and to learn how to improve communication in that domain. The first section of this document details the scenario development aspects of the simulation. The second section covers the new communication technologies that were developed and incorporated into the Weapons of Mass Destruction Decision Analysis Center (WMD-DAC) suite of decision support tools. The third section provides an overview of the features of the simulation and highlights its communication aspects. The fourth section describes the Team Communication Study processes and methodologies. The fifth section discusses future directions and areas in which to apply the new technologies and study results obtained as a result of this LDRD.

Detection of nuclear material at border crossings using motion correlation

This paper considers the problem that arises when a vehicle carrying nuclear material is detected approaching a border crossing. As quickly as possible, and with automation we wish to identify which vehicle among all those in the area is likely to be carrying the source. We show that if the border crossing area has technology for tracking the position of vehicles, we can correlate observed movements with observed changes in levels of detected radiation - for as the vehicle carrying the material gets closer to the detector, the stronger will be the detected radiation. We use a simulation model that captures the stop-and-go dynamics of a border crossing area to evaluate our ideas, and find a highly successful technique that tracks which vehicles move just when detected radiation changes, coupled with fitting radiation intensity/distance observations to an inverse-square law. This method almost always isolates the sought vehicle just as soon as the minimum number of data observations is obtained

Nonlinear optimization for stochastic simulations.

This report describes research targeting development of stochastic optimization algorithms and their application to mission-critical optimization problems in which uncertainty arises. The first section of this report covers the enhancement of the Trust Region Parallel Direct Search (TRPDS) algorithm to address stochastic responses and the incorporation of the algorithm into the OPT++ optimization library. The second section describes the Weapons of Mass Destruction Decision Analysis Center (WMD-DAC) suite of systems analysis tools and motivates the use of stochastic optimization techniques in such non-deterministic simulations. The third section details a batch programming interface designed to facilitate criteria-based or algorithm-driven execution of system-of-system simulations. The fourth section outlines the use of the enhanced OPT++ library and batch execution mechanism to perform systems analysis and technology trade-off studies in the WMD detection and response problem domain.