Browsing by Author "Rudra Dutta, Committee Member"

Now showing 1 - 11 of 11

Adaptive Transmission Using Channel Inversion for Multiple-Antenna Systems
(2005-04-07) James, Chris Mary; Brian L. Hughes, Committee Chair; J. Keith Townsend, Committee Member; Rudra Dutta, Committee Member
Adaptive modulation often achieves a significantly higher capacity than nonadaptive modulation in multiple-antenna wireless communication systems, particularly when the transmit antennas outnumber the receive antennas. Adaptive modulation generally involves varying signal power, constellation and coding in response to changing channel conditions, which adds considerable system complexity. This thesis examines simpler adaptive transmission schemes based on channel inversion (CI) and truncated channel inversion (TCI) in combination with multi-dimensional eigen-beamforming. Optimal CI and TCI schemes for multiple-antenna systems are derived and it is shown that these schemes suffer a small loss in capacity relative to optimal adaptive modulation, even for relatively small antenna arrays. This thesis also considers a practical coding scheme, turbo trellis-coded modulation (TTCM) in conjunction with CI. The results indicate that this scheme can perform within 4 dB of the optimal adaptive capacity.
Cache Aided Video Coding.
(2010-12-09) Gokare Somashekhar, Kumar; Injong Rhee, Committee Chair; Rudra Dutta, Committee Member; Khaled Abdel Harfoush, Committee Member
Congestion Control and Quality-of-Service (QoS) on Jumpstart Optical Burst Switched Environment
(2006-07-16) Yang, Li; Wenye Wang, Committee Member; Khaled Harfoush, Committee Member; Rudra Dutta, Committee Member; George N Rouskas, Committee Chair
This thesis studies the congestion control and Quality-of-Service (QoS) problems in Optical Burst Switched (OBS) networks. It consists of three parts. In the first part, we consider path switching as a congestion control mechanism at the edge of the network. We study a suite of path-switching strategies, each of which gives a different method to estimate the path congestion online. We also develop a framework for combining several path switching strategies into hybrid strategies whose results are based on the decisions of multiple individual methods. We demonstrate the effectiveness and benefits of adaptive path selection via simulation. In the second part of the thesis, we develop a general framework for absolute service guarantees for an OBS network in terms of the end-to-end burst loss. We first present a parameterized model for wavelength sharing. Then, we develop a heuristic for optimizing the policy parameters to support per-link absolute QoS guarantees. Finally, we present a methodology for acquiring the per-link parameters from the end-to-end QoS requirements so as to provide network-wide guarantees. We present numerical results to validate our approach. In the third part, we present a per-link wavelength provisioning scheme based on Constrained Markov Decision Processes (CMDP) theory to provide service differentiation. Service differentiation is evaluated with two objectives on OBS networks: to maximize the constrained throughput; and to minimize the loss of the best effort traffic subject to the constraints on the priority traffics. The randomized threshold policies we obtain are simple to implement and operate, and make effective use of statistical multiplexing.
Economic Models for Tiered Network Services
(2010-04-12) Lv, Qian; Wenye Wang, Committee Member; Rudra Dutta, Committee Member; Khaled Harfoush, Committee Member; George N Rouskas, Committee Chair
Tiered network services have been prevalent in current networking industry. The term tiered service means that the network operator only provides a small set of tiers (levels) - which offer progressively higher levels of service - to the customers each of whom will be mapped to one of the given tiers. In this thesis we focus on the economic issues for tiered network service. We first formulate the problem of selecting service tiers from three perspectives: one that considers the users interests only, one that considers only the service providerâ€™s interests, and one that considers both simultaneously. We consider the solution to this problem under two cases: 1) the discrete case, i.e., each user demand is known to the service provider; 2) the stochastic case, i.e., the service provider only knows the probability distribution of the user demands. For both cases, we present accurate and efficient algorithms based on dynamic programming. After finding the set of (near-) optimal service tiers, we then employ game-theoretic techniques to find an optimal price for each service tier that strikes a balance between the conflicting objectives of users and service provider. This work provides a theoretical framework for reasoning about and pricing Internet tiered services, as well as a practical toolset for network providers to develop customized menus of service offerings. We further consider some advanced economic topics in tiered network service. We notice that some network services may tend to be elastic, i.e., the users may value a given service differently and show different willingness to pay for the service. In this thesis, we assume that users are partitioned into some distinct classes. We develop an optimal algorithm to select jointly the set of service tiers and their prices so as to maximize the provider profits. Our research shows that introducing multiple tiers can be an effective market segmentation strategy that may lead to an increase in profits. Another advanced topic in tiered network service is service bundling, which means the network providers combine several services together and sell them as a single package at a lower price than that if the services are sold separately. Based on tools from microeconomics and utility theory, we developed an efficient method to find tiered structures for bundles of network services with the objective of maximizing provider profits under user constraints.
Information Integration: The Semantic-Model Approach
(2008-09-15) Chen, Dongfeng; Ting Yu, Committee Member; Rudra Dutta, Committee Member; Rada Chirkova, Committee Chair; Fereidoon Fred Sadri, Committee Member
Localization and Mobility Modeling in Wireless Ad Hoc Networks
(2008-12-06) Peng, Rong; Mihail L. Sichitiu, Committee Chair; Do Young Eun, Committee Member; Arne A. Nilsson, Committee Member; Rudra Dutta, Committee Member
The availability of wireless devices and their increasing ability of sharing information has stimulated the emergence of the wireless ad hoc networks. In this dissertation, we focus on two topics related to wireless ad hoc networks. One is the localization in the static wireless sensor networks and the other one is the mobility modeling in the mobile ad hoc networks. Localization is a fundamental service for many applications of wireless sensor networks. In the first part, we consider a distributed, probabilistic localization approach, which is suitable for systems with inaccurate range measurements and a small number of beacons. Two solutions are provided: an RSS-based solution and an angle-based approach corresponding to the measurements used between neighbor nodes. The basic idea of these approaches is to restrict the possible locations of the nodes by using probabilistic constraints. The proposed probabilistic approach is evaluated through simulations based on real-world and simulated measurements; the results are compared with the Cramer-Rao lower bound and other RSS-based and angle-based localization algorithms. The results show that, with inaccurate range measurements, and a small number of beacons, the proposed probabilistic approach outperforms existing methods and approaches the optimum bound. Due to the scarcity of real mobile ad hoc deployments, most protocol evaluations are carried out through simulations. One of the core components or network simulations is the mobility model, which characterizes the mobility patterns of the mobile devices in a network and uses such patterns to reproduce trajectories of the mobile devices accurately. In the second part of this dissertation, we study several real world traces including wireless LAN and bus traces. The statistical properties of several features that primarily determine the behavior of the mobile users are extracted and thoroughly analyzed. Using the extracted statistical properties and the statistical similarities of those features, we propose a simple generalized mobility generator that can generate both realistic and diversified synthetic traces.
Managing Heterogeneity in Structured Peer-to-Peer Systems
(2007-07-15) Wang, Chih-Chiang; Rudra Dutta, Committee Member; Khaled Harfoush, Committee Chair; Injong Rhee, Committee Member; George Rouskas, Committee Member
Network Resource Scheduling and Management of Optical Grids
(2007-05-17) Tanwir, Savera; Harry G. Perros, Committee Chair; Rudra Dutta, Committee Member; Michael Devetesikiotis, Committee Member
Advance reservation of lightpaths in an optical network has become a popular concept of reserving network resources in support of Grid applications. In this thesis, we have evaluated and compared several algorithms for dynamic scheduling of lightpaths using a flexible advance reservation model. The main aim is to find the best scheduling policy that improves network utilization and minimizes blocking. The scheduling of lightpaths involve both routing and wavelength assignment. Our simulation results show that minimum cost adaptive routing where link costs are determined by the current and future usage of the link provides the minimum blocking. Moreover, searching for k alternate paths within the scheduling window significantly improves the performance. For wavelength assignment, we have used a scheme that reduces fragmentation by minimizing unused leading or trailing gaps. We have also analyzed approaches for failure recovery and lightpath re-optimization. Finally, an advance reservation scheme needs timely information regarding the status of the optical links. To this end, we have surveyed various monitoring tools and techniques and we have proposed a monitoring framework to support fast restoration.
Swarm Over Swarm.
(2010-12-09) Selvanayagam, Alphonse Hansel; Injong Rhee, Committee Chair; Khaled Abdel Harfoush, Committee Member; Rudra Dutta, Committee Member
TIAA: A Toolkit for Intrusion Alert Analysis
(2004-03-30) Hu, Yiquan; Rudra Dutta, Committee Member; Peng Ning, Committee Chair; Douglas S. Reeves, Committee Member
Intrusion Detection has been studied for about twenty years. Intrusion Detection Systems (IDSs) are usually considered to be the second line of defense to protect against malicious activities along with the prevention-based security mechanisms such as authentication and access control. However, traditional IDSs have two major limitations. First, they usually focus on low-level attacks or anomalies, and raise alerts independently, although there may be logical connections between them. Second, in a typical environment there are a lot of false alerts reported by traditional IDSs, which are mixed with true alerts. Thus, the intrusion analysts or the system administrators are often overwhelmed by the volume of alerts. To address the aforementioned problems and thus to improve the usability of the current IDSs, the Toolkit for Intrusion Alert Analysis (TIAA) [17] is developed. The primary goal of TIAA is to provide system support for interactive analysis of intrusion alerts reported by traditional IDSs. TIAA is based on the alert correlation techniques previously developed in [16] and [15]. In addition, several new utilities are developed to facilitate the analysis of potentially large sets of intrusion alerts. More specifically, these new utilities include alert aggregation/disaggregation, clustering analysis, frequency analysis, link analysis, and association analysis. Finally, TIAA includes two additional visual representations of analysis results besides the hyper-alert correlation graphs proposed in [16], making it easier for a human analyst to understand the analysis results. It is envisaged that a human analyst and TIAA form a man-machine team, with TIAA performing automated tasks such as intrusion alert correlation and execution of analysis utilities, and the human analyst deciding what sets of alerts to analyze and how the analysis utilities are applied. This thesis presents the implementation of TIAA, including several analysis utilities, an improved alert collection system, and an integrated analysis environment with a user-friendly graphical user interface (GUI). This thesis also reports several experiments that evaluate the TIAA system using DARPA 2000 datasets and Cyber Panel Grand Challenge Problem datasets. The experimental results show that the TIAA system can greatly improve the analysis of intrusion alerts, and can cooperate with general underlying IDSs.
A Video Coding Approach to Compressive Distributed System Monitoring.
(2010-08-27) Venkatesh, Vinay; Xiaohui Gu, Committee Chair; Xiaosong Ma, Committee Member; Rudra Dutta, Committee Member