Computer Science Theses

Efficient GTS Allocation Schemes for IEEE 802.15.4

Syed E. Haque — Tue, 17 Apr 2012 10:26:24 PDT

IEEE 802.15.4 is a standard defined for wireless sensor network applications with limited power and relaxed throughput needs. The devices transmit data during two periods: Contention Access Period (CAP) by accessing the channel using CSMA/CA and Contention Free Period (CFP), which consists of Guaranteed Time Slots (GTS) allocated to individual devices by the network coordinator. The GTS is used by devices for cyclic data transmission and the coordinator can allocate GTS to a maximum of only seven devices. In this work, we have proposed two algorithms for an efficient GTS allocation. The first algorithm is focused on improving the bandwidth utilization of devices, while the second algorithm uses traffic arrival information of devices to allow sharing of GTS slots between more than seven devices. The proposed schemes were tested through simulations and the results show that the new GTS allocation schemes perform better than the original IEEE 802.15.4 standard.

Attacking and Securing Beacon-Enabled 802.15.4 Networks

SANG SHIN JUNG — Thu, 28 Apr 2011 12:46:32 PDT

The IEEE 802.15.4 has attracted time-critical applications in wireless sensor networks (WSNs) because of its beacon-enabled mode and guaranteed timeslots (GTSs). However, the GTS scheme’s security still leave the 802.15.4 MAC vulnerable to attacks. Further, the existing techniques in the literature for securing 802.15.4 either focus on non beacon-enabled 802.15.4 or cannot defend against insider attacks for beacon-enabled 802.15.4. In this thesis, we illustrate this by demonstrating attacks on the availability and integrity of the beacon-enabled 802.15.4. To proof the attacks, we implement the attacks using Tmote Sky motes for a malicious node along with regular nodes. We show that the malicious node can freely exploit the beacon frames to compromise the integrity and availability of the network. For the defense, we present beacon-enabled MiniSec (BCN-MiniSec) and analyze its cost.

Computing with Granular Words

Hailong Hou — Mon, 25 Apr 2011 06:55:49 PDT

Computational linguistics is a sub-field of artificial intelligence; it is an interdisciplinary field dealing with statistical and/or rule-based modeling of natural language from a computational perspective. Traditionally, fuzzy logic is used to deal with fuzziness among single linguistic terms in documents. However, linguistic terms may be related to other types of uncertainty. For instance, different users search ‘cheap hotel’ in a search engine, they may need distinct pieces of relevant hidden information such as shopping, transportation, weather, etc. Therefore, this research work focuses on studying granular words and developing new algorithms to process them to deal with uncertainty globally. To precisely describe the granular words, a new structure called Granular Information Hyper Tree (GIHT) is constructed. Furthermore, several technologies are developed to cooperate with computing with granular words in spam filtering and query recommendation. Based on simulation results, the GIHT-Bayesian algorithm can get more accurate spam filtering rate than conventional method Naive Bayesian and SVM; computing with granular word also generates better recommendation results based on users’ assessment when applied it to search engine.

Assessing the Physical Vulnerability of Backbone Networks

Vijetha Shivarudraiah — Mon, 25 Apr 2011 06:55:47 PDT

Communication networks are vulnerable to natural as well as man-made disasters. The geographical layout of the network influences the impact of these disasters. It is therefore, necessary to identify areas that could be most affected by a disaster and redesign those parts of the network so that the impact of a disaster has least effect on them. In this work, we assume that disasters which have a circular impact on the network. The work presents two new algorithms, namely the WHF-PG algorithm and the WHF-NPG algorithm, designed to solve the problem of finding the locations of disasters that would have the maximum disruptive effect on the communication infrastructure in terms of capacity.

Covert DCF - A DCF-Based Covert Timing Channel In 802.11 Networks

Russell Holloway — Tue, 30 Nov 2010 13:11:37 PST

Covert channels are becoming more popular as security risks grow in networks. One area that is promising for covert channels is wireless networks, since many use a collision avoidance scheme such as carrier sense multiple access with collision avoidance (CSMA/CA). These schemes often introduce randomness in the network, which provides good cover for a covert timing channel. In this thesis, we use the 802.11 standard as an example to demonstrate a wireless covert channel. In particular, most 802.11 configurations use a distributed coordinated function (DCF) to assist in communications. This DCF uses a random backoff to avoid collisions, which provides the cover for our covert channel. Our timing channel provides great improvements on other recent covert channels in the field of throughput, while maintaining high accuracy. We are able to achieve throughput over 8000 bps using Covert DCF, or by accepting a throughput of 1800 bps we can achieve higher covertness and 99% accuracy as well.

Data Aggregation through Web Service Composition in Smart Camera Networks

Jayampathi S. Rajapaksage — Mon, 29 Nov 2010 08:05:29 PST

Distributed Smart Camera (DSC) networks are power constrained real-time distributed embedded systems that perform computer vision using multiple cameras. Providing data aggregation techniques that is criti-cal for running complex image processing algorithms on DSCs is a challenging task due to complexity of video and image data. Providing highly desirable SQL APIs for sophisticated query processing in DSC networks is also challenging for similar reasons. Research on DSCs to date have not addressed the above two problems. In this thesis, we develop a novel SOA based middleware framework on a DSC network that uses Distributed OSGi to expose DSC network services as web services. We also develop a novel web service composition scheme that aid in data aggregation and a SQL query interface for DSC net-works that allow sophisticated query processing. We validate our service orchestration concept for data aggregation by providing query primitive for face detection in smart camera network.

A Novel Stable Model Computation Approach for General Dedcutive Databases

Komal Khabya — Wed, 15 Sep 2010 11:41:12 PDT

The aim of this thesis is to develop faster method for stable model computation of non-stratified logic programs and study its efficiency. It focuses mainly on the stable model and weak well founded semantics of logic programs. We propose an approach to compute stable models by where we first transform the logic program using paraconsistent relational model, then we compute the weak-well founded model which is used to generate a set of models consisting of the true and unknown values, which are tested for stability. We perform some experiments to test the efficiency of our approach which incurs overhead to eliminate negative values against a Naïve method of stable model computation.

STCP: A New Transport Protocol for High-Speed Networks

Ranjitha Shivarudraiah — Tue, 08 Jun 2010 10:24:44 PDT

Transmission Control Protocol (TCP) is the dominant transport protocol today and likely to be adopted in future high‐speed and optical networks. A number of literature works have been done to modify or tune the Additive Increase Multiplicative Decrease (AIMD) principle in TCP to enhance the network performance. In this work, to efficiently take advantage of the available high bandwidth from the high‐speed and optical infrastructures, we propose a Stratified TCP (STCP) employing parallel virtual transmission layers in high‐speed networks. In this technique, the AIMD principle of TCP is modified to make more aggressive and efficient probing of the available link bandwidth, which in turn increases the performance. Simulation results show that STCP offers a considerable improvement in performance when compared with other TCP variants such as the conventional TCP protocol and Layered TCP (LTCP).

A GPU Stream Computing Approach to Terrain Database Integrity Monitoring

Sean Patrick McKeon — Mon, 08 Feb 2010 16:58:11 PST

Synthetic Vision Systems (SVS) provide an aircraft pilot with a virtual 3-D image of surrounding terrain which is generated from a digital elevation model stored in an onboard database. SVS improves the pilot's situational awareness at night and in inclement weather, thus reducing the chance of accidents such as controlled flight into terrain. A terrain database integrity monitor is needed to verify the accuracy of the displayed image due to potential database and navigational system errors. Previous research has used existing aircraft sensors to compare the real terrain position with the predicted position. We propose an improvement to one of these models by leveraging the stream computing capabilities of commercial graphics hardware. "Brook for GPUs," a system for implementing stream computing applications on programmable graphics processors, is used to execute a streaming ray-casting algorithm that correctly simulates the beam characteristics of a radar altimeter during all phases of flight.

Batch Scheduling in Optical Burst Switching Networks

Yichuan Wang — Mon, 08 Feb 2010 16:58:10 PST

Optical Burst Switching (OBS) is an emerging technology for bearing bursty IP traffic directly over Wavelength Division Multiplexing (WDM) links. In OBS network, a key challenge is to reduce the data loss rate with efficient scheduling algorithms. In this work, we first propose a novel traffic aggregation algorithm, namely Tree-based Burst Aggregation (TBA), which aggregates bursts that are routed within a common tree topology into a composite burst and switch them as a single unit whenever possible. Then we propose another set of algorithms are batch scheduling using interval graphs in the core nodes. The algorithms effectively consider the strong correlations among the multiple bursts, and employ the proposed interval graphs and min-cost circular flow techniques to achieve optimized network performance in terms of data loss rate in OBS networks.

A Browser-Based Collaborative Multimedia Messaging System

Susan Gayle Gentner — Mon, 08 Feb 2010 16:58:09 PST

Making a communication tool easier for people to operate can have profound and positive effects on its popularity and on the users themselves. This thesis is about making it easier for people to publish web-based documents that have sound, video and text. Readily available software and hardware are employed in an attempt to achieve the goal of providing a software service that enables users to compose audio-video documents with text.

Implementing Energy-Saving Improvements to the IEEE 802.15.4 MAC Protocol

Marco Valero — Mon, 08 Feb 2010 16:58:08 PST

IEEE 802.15.4 is a standard designed for low data rate wireless personal area networks (WPANs) intended to provide connectivity to mobile devices. Such devices present considerable storage, energy, and communication constraints. However, they can be used in a variety of applications like home/office automation, environmental control and more. In order to extend the lifetime of the WPAN, we propose some changes to the standard including modifications to the Superframe Guaranteed Time Slot (GTS) distribution which can be optimized to reduce energy consumption. We implemented the proposed improvements to the IEEE 802.15.4 protocol using real sensor nodes. Specifically, we conducted an energy study of the proposed acknowledgment-based GTS descriptor distribution scheme and compared the results with the standard implementation. Experiments show that the proposed changes reduce energy consumption up to nearly 50% when 7 devices allocate guaranteed time slots descriptors during normal communication.

A Convert Channel Using 802.11 LANS

Telvis Eugene Calhoun — Mon, 08 Feb 2010 16:58:07 PST

We present a covert side channel that uses the 802.11 MAC rate switching protocol. The covert channel provides a general method to hide communications in an 802.11 LAN. The technique uses a one-time password algorithm to ensure high-entropy randomness of the covert messages. We investigate how the covert side channel affects node throughput in mobile and non-mobile scenarios. We also investigate the covertness of the covert side channel using standardized entropy. The results show that the performance impact is minimal and increases slightly as the covert channel bandwidth increases. We further show that the channel has 100% accuracy with minimal impact on rate switching entropy. Finally, we present two applications for the covert channel: covert authentication and covert WiFi botnets.

An Adaptive Mesh MPI Framework for Iterative C++ Programs

Karunamuni Charuka Silva — Mon, 08 Feb 2010 16:58:07 PST

Computational Science and Engineering (CSE) applications often exhibit the pattern of adaptive mesh applications. Adaptive mesh algorithm starts with a coarse base-level grid structure covering entire computational domain. As the computation intensified, individual grid points are tagged for refinement. Such tagged grid points are dynamically overlayed with finer grid points. Similarly if the level of refinement in a cell is greater than required, all such regions are replaced with coarser grids. These refinements proceed recursively. We have developed an object-oriented framework enabling time-stepped adaptive mesh application developers to convert their sequential applications to MPI applications in few easy steps. We present in this thesis our positive experience converting such application using our framework. In addition to the MPI support, framework does the grid expansion/contraction and load balancing making the application developer’s life easier.

An Interactive Wildfire Spread and Suppression Simulation Environment Based on Devs-Fire

Fei Song — Mon, 08 Feb 2010 16:58:06 PST

Wildfires pose serious threats to the society and environment. Simulation of wildfire spread and fire suppression remains a challenging task due to the complexity of wildfire behavior and fire suppression tactics. In previous work, a wildfire spread and suppression simulation model called DEVS-FIRE has been developed. Based on that model, this thesis develops a graphic user interface to support an interactive simulation environment for surface wildfire spread and suppression simulation. The developed environment allows users to dynamically set up fire spread simulations, and to interacticaly deploy firefighting agents to experiment different fire suppression tactics. This graphic user interface is implemented using the Java Swing framework, and is intergrated with the DEVS-FIRE model in a well-designed manner. The software architecture is described and the simulation environment and experiment results with different fuel, terrain and weather data are presented.

Proxy Module for System on Mobile Devices (SyD) Middleware

Joseph Gunawan — Mon, 08 Feb 2010 16:58:05 PST

Nowadays, users of mobile devices are growing. The users expect that they could communicate constantly using their mobile devices while they are also constantly moving. Therefore, there is a need to provide disconnection tolerance of transactions in the mobile devices’ platforms and its synchronization management. System on Mobile Devices (SyD) is taken as one of the examples of mobile devices’ platforms. The thesis studies the existing SyD architecture, from its framework into its kernel, and introduces the proxy module enhancement in SyD to handle disconnection tolerance, including its synchronization. SyD kernel has been extended for the purpose of enabling proxy module. SyDSync has been constructed for synchronization with the proxy. The timeout has been studied for seamless proxy invocation. A Camera application that tries to catch a stolen vehicle has been simulated for the practical purpose of using the proxy module extension.

802.11 Fingerprinting to Detect Wireless Stealth Attacks

Aravind Venkataraman — Mon, 08 Feb 2010 16:58:04 PST

We propose a simple, passive and deployable approach for fingerprinting traffic on the wired side as a solution for three critical stealth attacks in wireless networks. We focus on extracting traces of the 802.11 medium access control (MAC) protocol from the temporal arrival patterns of incoming traffic streams as seen on the wired side, to identify attacker behavior. Attacks addressed include unauthorized access points, selfish behavior at the MAC layer and MAC layer covert timing channels. We employ the Bayesian binning technique as a means of classifying between delay distributions. The scheme requires no change to the 802.11 nodes or protocol, exhibits minimal computational overhead and offers a single point of discovery. We evaluate our model using experiments and simulations.

P-Percent Coverage in Wireless Sensor Networks

Chaitanya Sambhara — Mon, 08 Feb 2010 16:58:03 PST

Coverage in a Wireless Sensor Network reflects how well a sensor network monitors an area. Many times it is impossible to provide full coverage. The key challenges are to prolong the lifetime and ensure connectivity to provide a stable network. In this thesis we first define p-percent coverage problem in which we require only p% of the whole area to be monitored. We propose two algorithms, Connected P-Percent Coverage Depth First Search (CpPCA-DFS) and Connected P-Percent Connected Dominating Set (CpPCA-CDS). Through simulations we then compare and analyze them for their efficiency and lifetime. Finally in conclusion we prove that CpPCA-CDS provides 5 to 20 percent better active node ratio at low density. At high node density it achieves better distribution of covered area however the lifetime is only 5 to10 percent shorter then CpPCA-DFS. Overall CpPCA-CDS provides up to 30 percent better distribution of covered area.

SenMinCom: Pervasive Distributed Dynamic Sensor Data Mining for Effective Commerce

Naveen Hiremath — Mon, 08 Feb 2010 16:58:03 PST

In last few years, the use of wireless sensor networks and cell phones has become ubiquitous; fusing these technologies in the field of business will open up new possibilities. To fill this lacuna, I propose a novel idea where the combination of these will facilitate companies to receive feedback on their products and services. System's unobtrusive sensors will not only collect shopping, mobile usage data from consumers but will also make effective use of this information to increase revenue, cut costs, etc.; the use of mobile agent based data mining allows analyzing the data from different dimensions, categorizing it on factors such as product positioning, promotion of goods, etc. as in the case of a shopping store. Additionally, because of the dynamic mining system the companies get on-the-scene recommendation of products rather than off-the-scene. In this thesis, a novel distributed pervasive mining system is proposed to get dynamic shopping information and mobile device usage of the customers.

WS-CDL Based Specification for Web Services Collaboration Testing

Ahmed A. Ugaas — Mon, 08 Feb 2010 16:58:01 PST

Service Oriented Computing(SOC) is becoming a major paradigm for developing next generation of software systems, and one of the major challenges of Service Oriented Computing is testing interactions and collaborations among the distributed and dynamically integrated web services. To support automated test of web service‟s collaborations, a formal specification is needed. This thesis proposes a specification of web services collaborations based on Web Services Choreography Description Language (WS-CDL). We identify the basic constructs that can be found in any web services collaboration, and we mapped them to the new WS-CDL based language (WS-CDL+). Finally, A scenario of web services collaboration is developed and specification in WS-CDL+ is provided. This work builds a foundation for automated web services testing in a service oriented computing environment.