Defense Notices

Multi-agent systems are a common paradigm for building distributed systems in different domains such as networking, health care, swarm sensing, robotics, and transportation. Performance goals can vary from one application to the other according to the domain's specifications and requirements. Yet, performance goals can vary over the course of task execution. For example, agents may initially be interested in completing the task as fast as possible, but if their energy hits a specific level while still working on the task, they might, then need to switch their goal to minimize energy consumption. Previous studies in multi-agent systems have observed that varying the type of information that agents communicate, such as goals and beliefs, has a significant impact on the performance of the system with respect to different, usually conflicting, performance metrics, such as speed of solution, communication efficiency, and travel distance/cost. Therefore, when designing a communication strategy for a multi-agent system, it is unlikely that one strategy can perform well with respect to all of performance metrics. Yet, it is not clear in advance, which strategy or communication decisions will be the best with respect to each metric. Previous approaches to communication decisions in multi-agent systems either manually design a single/multiple fixed communication strategies, extend agents' capabilities and use heuristics, or allow learning a strategy with respect to a single predetermined performance goal. To address this issue, this research introduces goal-oriented communication strategy, where communication decisions are determined based on the desired performance goal. This work proposes an evolutionary approach for learning a goal-oriented communication strategy in multi-agent systems. The approach enables learning an effective communication strategy with respect to simple or complex measurable performance goals. The learned strategy will determine what, when, and to whom the information should be communicated during the course of task execution.

Program slicing is a popular program decomposition and analysis technique 
that extracts only those program statements that are relevant to particular points 
of interest. Executable slices are program slices that are independently executable 
and that correctly compute the values in the slicing criteria. Executable slices 
can be used during debugging and to improve program performance through 
parallelization of partially overlapping slices. 

While program slicing and the construction of executable slicers has been 
studied in the past, there are few acceptable executable slicers available, 
even for popular languages such as Java. 
In this work, we provide an extension to the T. J. Watson Libraries for 
Analysis (WALA), an open-source Java application static analysis suite, to 
generate fully executable slices. 

We analyze the problem of executable slice generation in the context 
of the capabilities provided and algorithms used by the WALA library. 
We then employ this understanding to augment the existing WALA static SSA slicer 
to efficiently track non-SSA datapendence, and couple this component with 
our exectuable slicer backend. 
We evaluate our slicer extension and find that it produces accurate 
exectuable slices for all programs that fall within the limitations of the 
WALA SSA slicer itself. 
Our extension to generate executable program slices facilitates one of the 
requirements of our larger project for a Java application automatic 
partitioner and parallelizer.

Software engineering and mission command are two separate but similar fields, as both are instances of complex problem solving in environments with ever changing requirements. Both fields have followed similar paths from using industrial age decomposition to deal with large problems to striving to be more agile and resilient. Our research hypothesis is that modifications to agile software development based on inspirations from mission command can improve the software engineering process in terms of planning, prioritizing, and communication of software requirements and progress, as well as improving the overall software product. Targeted Scrum is a modification of Traditional Scrum based on three inspirations from Mission Command: End State, Line of Effort, and Targeting. These inspirations have led to the introduction of the Product Design Meeting and modifications of some current Scrum meetings and artifacts. We tested our research hypothesis using a semester-long undergraduate level software engineering class. Students in teams developed two software projects, one using Traditional Scrum and the other using Targeted Scrum. We then assessed how well both methodologies assisted the software development teams in planning and developing the software architecture, prioritizing requirements, and communicating progress. We also evaluated the software product produced by both methodologies. It was determined that Targeted Scrum did better in assisting the software development teams in the planning and prioritization of the requirements. However, Targeted Scrum had a negligible effect on improving the software development teams’ external and internal communications. Finally, Targeted Scrum did not have an impact on the product quality by the top performing and worst performing teams. Targeted Scrum did assist the product quality of the teams in the middle of the performance spectrum.

In software engineering, altering a program's original implementation disconnects it from the model that produced it. Reconnecting the model and new implementations must be done in a way that does not decrease confidence in the design's correctness and performance. This thesis demonstrates that it is possible, in practice, to connect the model of Conway’s Game of Life with new implementations, using the worker/wrapper transformation theory. This connection allows development to continue without the sacrifice of re-implementation. 

HERMIT is a tool that allows programs implemented in Haskell to be transformed during the compilation process, and has features capable of performing worker/wrapper transformations. Specifically in these experiments, HERMIT is used to apply syntax transformations to replace Life's linked-list based implementation with one that uses other data structures in an effort to explore alternative implementations and improve overall performance. 

Previous work has successfully performed the worker/wrapper conversion on an individual function using HERMIT. This thesis presents the first time that a programmer-directed worker/wrapper transformation has been attempted on an entire program. From this experiment, substantial observations have been made. These observations have led to proposed improvements to the HERMIT system, as well as a formal approach to the worker/wrapper transformation process in general.

Active is a Haskell library for creating animations driven by time. The key concept is that every animation has its own starting and ending time and the motion of each element can be defined as a function of time. This underlying idea is intuitive and simple enough for the users to understand that it has created a space for simple animations, called “Functional Active programming”. Although there are many FRP libraries available, FRP libraries are often challenging to use for simple animations. 
In this project, we have added some reactive features to the Active library as an attempt to enhance the active programming space without complicating the underlying principles. This will let Active elements to detect collisions, or a mouse click event, and change their behavior accordingly. Having built-in reactive features equips the Active programmers with extra tools at their disposal and significantly reduces the efforts needed to code such reactions. These reactive features have been implemented on top of the Blank Canvas. 

Efficient use of the vast spectrum offered by fiber-optic links by an end user with relatively small bandwidth requirement is possible by partitioning a high speed signal in a wavelength channel into multiple low-rate subcarriers. Multi-carrier systems not only ensure optimized use of optical and electrical components, but also tolerate transmission impairments. The purpose of this research is to theoretically and experimentally study mixing among subcarriers in Radio-Over-Fiber (RoF) and direct detections systems. 
For an OFDM-RoF system, we present a novel technique that minimizes the RF domain signal-signal beat interference, relaxes the phase noise requirement on the RF carrier, realizes the full potential of the optical heterodyne technique, and increases the performance-to-cost ratio of RoF systems. We demonstrate a RoF network that shares the same RF carrier for both downlink and uplink, avoiding the need of an additional RF oscillator in the customer unit. 
For direct detection systems, we propose theoretical and experimental investigation of impact of semiconductor optical amplifier nonlinearities on Compatible-SSB signals. As preliminary work, we present experimental comparison of performance degradation of coherent optical OFDM and single carrier Nyquist pulse modulated systems in a nonlinear environment. Furthermore, analysis of distribution properties of optical phases driving a dual-drive MZM and their dependence on scaling factor are proposed for Compatible-SSB modulation format through simulations and experimental results. An optimum scaling factor needs to be found that minimizes residual sideband and signal-signal beat interference in such systems. 

The WFG2013 project uses Analog Devices AD9915 DDS ICs at up to 2.5 GS/s as basic building blocks for a scalable,synchronous, multichannel DDS system. Four DDS ICs are installed on a daughterboard with an Altera Cyclone 5E FPGA as a controller. The daughterboard can run standalone (Solo), in conjunction with another daughterboard (Duo), or N daughterboards surfing a motherboard (Mucho). 

Synchronization between configured DDS ICs is achieved via the on-chip SYNC-IN and SYNC-OUT signals. The master DDS (only one per configuration) generates the SYNC_OUT signal, which is distributed to the SYNC_IN pins on all DDS ICs, including the master. The synchronization signal distribution network was designed to minimize skew such that the SYNC_IN signal reaches the all DDSs at virtually the same time. Even if some skew appears, the AD9915's SYNC_IN and SYNC_OUT signals have adjustable delay. The SYNC_IN signal causes the DDSs to assume a known state. Because all of the DDSs reach the same state at the same time, they are, by definition synchronized.

Websockets is a protocol that provides a full-duplex communication channel over a single TCP connection between a web server and web client. Kansas-comet is long polling solution that allows web servers written in the functional programming language Haskell to push data to browser clients. Implementing kansas-comet with websockets enables pushing data from web servers to clients with reduced data loads and network latency, which helps in scaling web applications. Other applications, like the graphics library blank canvas, use kansas-comet, so improving kansas-comet also improves these applications as well. 

In this project, we add websockets to kansas-comet for the sake of improving client-server communications by providing a modern full duplex communication channel. Modern web browsers support the websocket protocol but it is important for kansas-comet to also provide backward compatibility. So, the new kansas-comet now implements a mechanism that falls back to long polling strategy when browser does not support websocket or when applications using kansas comet does not implement websockets. We use JavaScript and the kansas-comet JavaScript library on client browsers, and we use websocket, wai-websockets and warp libraries on the server side to implement websockets in kansas comet.

Increasing focus on global warming has challenged the scientific community to develop ways to mitigate its adverse effects. This is more so important as different technologies become an integral part of daily human life. Mobile wireless networks and mobile devices form a significant part of these technologies. It is estimated that there are over four billion mobile phone subscribers worldwide and this number is still growing as more people get connected in developing countries. In addition to the growing number of subscribers, there is an explosive growth in high data applications among mobile terminal users. This has put increased demand on the mobile network in terms of energy needed to support both the growth in subscribers and higher data rates. The mobile wireless industry therefore has a significant part to play in the mitigation of global warming effects. To achieve this goal, there is a need to develop and design energy efficient communication schemes for deployment in future networks and upgrades to existing networks. This is not only done in the wireless communication infrastructure but also in mobile terminals. In this project a practical power consumption model which includes circuit power consumption from the different components in a transceiver chain is analyzed. This is of great significance to practical system design when doing energy consumption and energy efficiency analysis. The proposed power consumption model is then used to evaluate the energy efficiency in the context of cooperative Multiple Input Multiple Output(MIMO)systems.

The reliance of Unmanned Aerial Vehicles (UAVs) on Global Navigation Satellite System (GNSS) for autonomous operation represents a significant vulnerability to their reliable and secure operation due to signal interference, both incidental (e.g. terrain shadowing, ionospheric scintillation) and malicious (e.g. jamming, spoofing). An accurate and reliable alternative UAV navigation system is proposed that exploits Signals of Opportunity (SOP) thus offering superior signal strength and spatial diversity compared to satellite signals. Given prior knowledge of the transmitter's position and signal characteristics, the proposed technique utilizes triangulation to estimate the receiver's position. Dual antenna interferometry provides the received signals' Angle of Arrival (AoA) required for triangulation. Reliance on precise knowledge of the antenna system's orientation is removed by combining AoAs from different transmitters to obtain a differential Angles of Arrival (dAoAs). Analysis, simulation, and experimental techniques are used to characterize system performance; a path to miniaturized system integration is also presented.