Browsing by Author "Dr. Injong Rhee, Committee Member"

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Differential Capacity p-Cycles
(2009-03-05) Jaikumar, Prashant; Dr. David Thuente, Committee Member; Dr. Injong Rhee, Committee Member; Dr. Rudra Dutt, Committee Chair
Survivability has become a central part of modern optical network design as the hundreds of wavelengths get multiplexed on fibers carrying data at Tbps speeds in DWDM networks. Provisioning for 100% restoration on failure using minimum amount of resources has become an important design problem. p-Cycles have emerged as a useful fault tolerance mechanism that operate at the speed of SONET rings, but also have low mesh-like spare capacity requirement. In this thesis, a modified version of p-cycle, called differential capacity p-cycle, is proposed that improve spare capacity efficiency beyond what is provided by a set of traditional p-cycles. Different variants of differential capacity p-cycles are proposed, analogous to some of the traditional p-cycle variants. The designs of the various types of differential capacity p-cycles are formulated using integer linear programs, and the spare capacity usage of these new structures are compared with that of traditional p-cycles and their variants.
Protection in survivable WDM grooming network.
(2004-05-05) Tiyachate, Ruarob; Dr. Rudra Dutta, Committee Chair; Dr. Mladen A. Vouk, Committee Member; Dr. Injong Rhee, Committee Member
Optical networks have been widely expected to fill the need for tomorrow's backbone networks because of the high bandwidth and highly predictable performance they promise. However, in recent years, the downturn of the economy has made the deployment of costly equipment to obtain very high bandwidth less immediately attractive. In the current context, research must address these realistic conditions, and this is part of the motivation for the area in which the research in this thesis is performed. We propose a two-step approach to design, and show how this approach is suitable from both the grooming and the protection points of view. We adopt well-known heuristics from literature to perform stand-alone grooming and stand-alone protection at the virtual link level, enhancing the protection algorithm by adotping a failure independent routing but failure-specific wavelength assignment for protection virtual links. We show that in relative terms, the grooming performance of the protection design is already quite good due to this approach. However, protecting at the virtual link level invariably increases the grooming cost of the protection solution, and this cost can be significant at the node at which it is maximum. We go on to show how this can be countered by performing sub-wavelength protection. All our theoretical expectations are validated by numerical simulations. Our results are as follows. Subwavelength protection can effectively use unutilized capacity in existing virtual topology. Proposed protection results in protection solution with less total amount of electronic processing from both individual traffic component and overall traffic component point of view. Proposed algorithm not only decreases the amount of electronic processing from protection solution, but also decreases amount of virtual link setup for protection. The implementation of the two-phase approach help reduce the computation time to find an effective protection solution. Numerical results show that proposed algorithm has performed well and produces similar effects on different traffic patterns and topologies.
RaPTEX: Rapid Prototyping Tool for Embedded Communication Systems
(2007-05-17) Lim, Jun Bum; Dr. Laurie Williams, Committee Member; Dr. Injong Rhee, Committee Member; Dr. Mihail L. Sichitiu, Committee Chair
Advances in microprocessors, memory, and radio technology have enabled the emergence of embedded systems that rely on communication systems to exchange information and coordinate their activity in spatially distributed applications. Developing embedded communication systems that are efficient and reliable, is a challenge due to the trade-offs imposed by the conflicts between application requirements and hardware constraints. In this thesis, we present RaPTEX, an integrated development environment (IDE) for embedded communication systems. RaPTEX consists of three major subsystems: a graphical module to facilitate component composition, code generation with access to component-level parameters, and a performance evaluation framework for allowing system designers to explore what-if scenarios and clearly expose the trade-offs of their choices. We also present two case studies of developing wireless sensor network applications using RaPTEX.
Testbed Implementation and Performance Evaluation of the Tiered Service Fair Queuing (TSFQ) Packet Scheduling Discipline.
(2008-05-16) Khare, Shrikrishna Girish; Dr. George Rouskas, Committee Chair; Dr. Rudra Dutta, Committee Member; Dr. Injong Rhee, Committee Member
In packet-switched networks, the scheduling algorithm implemented by the routers must possess three important properties: fairness, to provide isolation among competing flows and ensure that each flow receives its fair share of the link bandwidth; bounded delay, so as to guarantee a bounded end-to-end delay to interactive applications; and low complexity, so as to be possible to operate at wire speeds even for large number of flows. Although many fair queuing disciplines have been proposed, the best among them have worst-case time complexity of O(log n) for a link with n flows. Tiered Service Fair Queuing (TSFQ), a new queuing discipline, has been proposed to achieve packet sorting and virtual time computation in time that is independent of the number of flows. TSFQ exploits two widely observed characteristics of the Internet, namely, that service providers offer some type of tiered service with a small number of service levels, and that a small number of packet sizes dominate. Consequently, TSFQ maps the competing n flows to p service levels where p is a small constant, and uses a special queuing structure that eliminates the need to sort most packets. As part of this thesis work, we implement the WF2Q+ discipline and various TSFQ variants in the Linux kernel as separate loadable modules, and we investigate their relative performance over a small testbed. Our experimental results indicate that TSFQ closely emulates previously proposed fair queuing disciplines. The main conclusion of our work is that TSFQ is a viable packet scheduler that can be used in networks with heavy traffic loads to achieve fairness in constant time.