Erik Jonsson School of Engineering and Computer Science
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Item Plug and play optical (PPO) nodes: network functionalities and built-in fiber characterization techniques(The University of Texas at Dallas, 2007-05-07) Cerutti, Isabella, 1973-; Fumagalli, Andrea; Hui, Rongqing; Monti, Paolo, 1973-; Paradisi, Alberto; Tacca, Marco, 1973-; Eric Jonsson School of Engineering and Computer Science.Plug and play optical (PPO) nodes may be used to facilitate the deployment of optical networks. PPO nodes must be able to learn about the signal propagation properties of the surrounding optical fibers and make their wavelength routing decisions based on the collected data. This paper discusses what are the open challenges that must be overcome to provide cost effective and performing ad hoc networking solutions based on PPO nodes. Three possible PPO node hardware architectures trading off complexity, cost and functionalities are presented along with their built-in fiber characterization techniques.Item GPU-Based Computation of Discrete Periodic Centroidal Voronoi Tessellation in Hyperbolic Space(2012-02) Shuai, Liang; Guo, XiaohuPeriodic centroidal Voronoi tessellation (CVT) in hyperbolic space provides a nice theoretical framework for computing the constrained CVT on high-genus (genus > 1) surfaces. This paper addresses two computational issues related to such hyperbolic CVT framework: (1) efficient reduction of unnecessary site copies in neighbor domains on the universal covering space, based on two special rules; (2) GPU-based parallel algorithms to compute a discrete version of the hyperbolic CVT. Our experiments show that with the dramatically reduced number of unnecessary site copies in neighbor domains and the GPU-based parallel algorithms, we significantly speed up the computation of CVT for high-genus surfaces. The proposed discrete hyperbolic CVT guarantees to converge and produces high-quality results.Item On the coarseness of bicolored point sets(Elsevier B. V., 2012-04-24) Bereg, Sergey; Díaz-Báñez, J. M.; Lara, D.; Pérez-Lantero, P.; Seara, C.; Urrutia, J.; Bereg, SergeyLet R be a set of red points and B a set of blue points on the plane. In this paper we introduce a new concept, which we call coarseness, for measuring how blended the elements of S=R⊃B are. For X∪S, let Δ(X)=Item Investigation of interfacial oxidation control using sacrificial metallic Al and La passivation layers on InGaAs(2012-05-25) Brennan, Barry; Milojevic, Marko; Contreras-Guerrero, Roccio; Kim, Hyun-Chul; Lopez-Lopez, Maximo; Kim, Jiyoung; Wallace, Robert M.; 70133685 (Kim, J)The ability of metallic Al and La interlayers to control the oxidation of InGaAs substrates is examined by monochromatic x-ray photoelectron spectroscopy (XPS) and compared to the interfacial chemistry of atomic layer deposition (ALD) of Al2O3 directly on InGaAs surfaces. Al and La layers were deposited by electron-beam and effusion cell evaporators, respectively, on In0.53Ga0.47As samples with and without native oxides present. It was found that both metals are extremely efficient at scavenging oxygen from III-V native oxides, which are removed below XPS detection limits prior to ALD growth. However, metallic Ga//In/As species are simultaneously observed to form at the semiconductor-metal interface. Upon introduction of the samples to the ALD chamber, these metal bonds are seen to oxidize, leading to Ga/In-O bond growth that cannot be controlled by subsequent trimethyl-aluminum (TMA) exposures. Deposition on an oxide-free InGaAs surface results in both La and Al atoms displacing group III atoms near the surface of the semiconductor. The displaced substrate atoms tend to partially oxidize and leave both metallic and III-V oxide species trapped below the interlayers where they cannot be "cleaned-up" by TMA. For both Al and La layers the level of Ga-O bonding detected at the interface appears larger then that seen following ALD directly on a clean surface.Item A protocol for the secure linking of registries for HPV surveillance(2012-07-02) El Emam, Khaled; Samet, Saeed; Hu, Jun; Peyton, Liam; Earle, Craig; Jayaraman, Gayatri C.; Wong, Tom; Kantarcioglu, Murat; Dankar, Fida; Essex, AleksanderIntroduction: In order to monitor the effectiveness of HPV vaccination in Canada the linkage of multiple data registries may be required. These registries may not always be managed by the same organization and, furthermore, privacy legislation or practices may restrict any data linkages of records that can actually be done among registries. The objective of this study was to develop a secure protocol for linking data from different registries and to allow on-going monitoring of HPV vaccine effectiveness. Methods: A secure linking protocol, using commutative hash functions and secure multi-party computation techniques was developed. This protocol allows for the exact matching of records among registries and the computation of statistics on the linked data while meeting five practical requirements to ensure patient confidentiality and privacy. The statistics considered were: odds ratio and its confidence interval, chi-square test, and relative risk and its confidence interval. Additional statistics on contingency tables, such as other measures of association, can be added using the same principles presented. The computation time performance of this protocol was evaluated. Results: The protocol has acceptable computation time and scales linearly with the size of the data set and the size of the contingency table. The worse case computation time for up to 100, 000 patients returned by each query and a 16 cell contingency table is less than 4 hours for basic statistics, and the best case is under 3 hours. Discussion: A computationally practical protocol for the secure linking of data from multiple registries has been demonstrated in the context of HPV vaccine initiative impact assessment. The basic protocol can be generalized to the surveillance of other conditions, diseases, or vaccination programs. © 2012 El Emam et al.Item In Situ Chemical Oxidation of Ultrasmall MoOx Nanoparticles in Suspensions(2012-07-23) Lee, Yun-Ju; Barrera, Diego; Luo, Kaiyuan; Hsu, Julia W. P.; 0000 0003 8600 0978 (Hsu, JWP); 243648305 (Hsu, JWP)Nanoparticle suspensions represent a promising route toward low cost, large area solution deposition of functional thin films for applications in energy conversion, flexible electronics, and sensors. However, parameters such size, stoichiometry, and electronic properties must be controlled to achieve best results for the target application. In this report, we demonstrate that such control can be achieved via in situ chemical oxidation of M o O 𝑥 nanoparticles in suspensions. Starting from a microwave-synthesized suspension of ultrasmall ( 𝑑 ∼ 2 nm) M o O 𝑥 nanoparticles in n-butanol, we added H2O2 at room temperature to chemically oxidize the nanoparticles. We systematically varied H2O2 concentration and reaction time and found that they significantly affected oxidation state and work function of MoO𝑥 nanoparticle films. In particular, we achieved a continuous tuning of MoO𝑥 work function from 4.4 to 5.0 eV, corresponding to oxidation of as-synthesized MoO𝑥 nanoparticle (20% Mo6+) to essentially pure MoO3. This was achieved without significantly modifying nanoparticle size or stability. Such precise control of MoO𝑥 stoichiometry and work function is critical for the optimization of MoO𝑥 nanoparticles for applications in organic optoelectronics. Moreover, the simplicity of the chemical oxidation procedure should be applicable for the development of other transition oxide nanomaterials with tunable composition and properties.Item Wet chemical surface functionalization of oxide-free silicon(Elsevier Limited, 2012-09-13) Thissen, Peter; Seitz, Oliver; Chabal, Yves J.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)Silicon is by far the most important semiconductor material in the microelectronic industry mostly due to the high quality of the Si/SiO2 interface. Consequently, applications requiring chemical functionalization of Si substrates have focused on molecular grafting of SiO2 surfaces. Unfortunately, there are practical problems affecting homogeneity and stability of many organic layers grafted on silicon oxide (SiO2), such as silanes and phosphonates, related to polymerization and hydrolysis of Si-O-Si and Si-O-P bonds. These issues have stimulated efforts in grafting functional molecules on oxide-free Si surfaces, mostly with wet chemical processes. This review focuses therefore directly on wet-chemical surface functionalization of oxide-free Si surfaces, starting from H-terminated Si surfaces. The main preparation methods of oxide-free H-terminated Si and their stability are first summarized. Functionalization is then classified into indirect substitution of H-termination by functional organic molecules, such as hydrosilylation, and direct substitution by other atoms (e.g. halogens) or small functional groups (e.g. OH, NH2) that can be used for further reaction. An emphasis is placed on a recently discovered method to produce a nanopattern of functional groups on otherwise oxide-free, H-terminated and atomically flat Si(111) surfaces. Such model surfaces are particularly interesting because they make it possible to derive fundamental knowledge of surface chemical reactions.Item Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy(American Vacuum Society, 2012-10-03) Thamban, P. L. Steven; Padron-Wells, Gabriel; Hosch, Jimmy W.; Yun, Stuart; Goeckner, Matthew J.; 0000 0001 2766 4681 (Thamban, PLS); 0000 0000 5396 3610 (Goeckner, MJ); 2008008261 (Goeckner, MJ)Use the DOI persistent link to see the abstract. A subscription or fee may be necessary to view the article.Item Optimizing Diode Thickness for Thin-Film Solid State Thermal Neutron Detectors(American Institute of Physics, 2012-10-04) Murphy, John W.; Mejia, Israel; Quevedo-López, Manuel A.; Gnade, Bruce E.; 0000 0003 8371 1336 (Gnade, BE); 00049719 (Gnade, BE); Erik Jonsson School of Engineering and Computer ScienceIn this work, we investigate the optimal thickness of a semiconductor diode for thin-film solid state thermal neutron detectors. We evaluate several diode materials, Si, CdTe, GaAs, C (diamond), and ZnO, and two neutron converter materials, 10B and 6LiF. Investigating a coplanar diode/converter geometry, we determine the minimum semiconductor thickness needed to achieve maximum neutron detection efficiency. By keeping the semiconductor thickness to a minimum, gamma rejection is kept as high as possible. In this way, we optimize detector performance for different thin-film semiconductor materials.Item In situ atomic layer deposition half cycle study of Al2O 3 growth on AlGaN(American Institute of Physics, 2012-11-10) Brennan, Barry; Qin, Xiaoye; Dong, Hong; Kim, Jiyoung; Wallace, Robert M.; 70133685 (Kim, J)Use the DOI address to see the article abstract. A subscription or fee may be necessary to view the article.Item Numerical methods for the accurate calculation of spherical bessel functions and the location of MIE resonances(The University of Texas at Dallas, 2013-04-16) Cantrell, C. D., (Cyrus D.), 1940-; Center for Applied OpticsThis report reviews numerical methods for the accurate calculation of spherical Bessel functions and for the location of Mie resonances in a dielectric sphere. Detailed numerical results are presented for a real index of refraction n = 1.47. FORTRAN source listings are provided for computer programs that implement the algorithms described in the text.Item End-to-end QoS guarantee in heterogeneous wired-cum-wireless networks(The University of Texas at Dallas, 2013-04-16) Li, Ming, 1974-; Zhu, Hua, 1975-; Sathyamurthy, Sathish, 1979-; Prabhakaran, B.; Chlamtac, ImrichWith information access becoming more and more ubiquitous, there is a need for providing QoS support for communication that spans wired and wireless networks. For the wired side, RSVP/SBM has been widely accepted as a flow reservation scheme in IEEE 802 style LANs. In this paper, we investigate the integration of RSVP and a RSVP-like flow reservation scheme in wireless LANs, as an end-to-end solution for QoS guarantee in wired-cum-wireless networks. We propose WRESV, an RSVP-like flow reservation and admission control scheme for IEEE 802.11 wireless LAN. Using WRESV, wired/wireless integration can be easily implemented by cross-layer interaction at the Access· Point. Main components of the integration are RSVP-WRESV parameter mapping, and the initiation of new reservation messages, depending on where senders/receivers are located. In addition, we also propose various optimizations for supporting multicast session, mobility management, and admission control.Item Distributed Admission Control for IEEE 802.11 Ad Hoc Networks(The University of Texas at Dallas, 2013-04-16) Zhu, Hua, 1975-; Li, Ming, 1974-; Chlamtac, Imrich; Prabhakaran, B.IEEE 802.11 has very poor performance in terms of throughput and transmission delay when the traffic load reaches the saturation condition. Admission control must be provided in order to guarantee the service of existing traffic. Unfortunately, the normalized saturation throughput is variable corresponding to different traffic statistics (i.e. bit-rate and average packet length) . Therefore it does not perform well if the station admits traffic simply based on certain threshold of the normalized throughput. Most existing analytical models for IEEE 802.11 MAC adopt quite strict assumptions of saturation conditions and simplified traffic scenarios. Nevertheless, it is more realistic to analyze the non-saturation condition under heterogeneous traffic scenarios. Moreover, an accurate analytical model under non-saturation condition is critical for the correctness of admission control decisions. In this paper, (1) we propose a unified analytical model which is the first model capable of analyzing performance under both non-saturation and saturation conditions; (2) we then introduce a new performance criterion, saturation coefficient Cn,sat, which reflects the degree of saturation experienced by any specific station; (3) finally we propose a distributed admission control scheme for IEEE 802.11 based on this criterion. With this scheme, any station can make local decision on whether admitting/rejecting a new traffic. The accuracy of the proposed analytical model and performance of the proposed admission control scheme are validated by simulations.Item On the complexity of clustering multi-hop wireless networks(The University of Texas at Dallas, 2013-04-18) Basagni, Stefano, 1965-; Eric Jonsson School of Engineering and Computer ScienceA Distributed Clustering Algorithm (DCA) is presented that partitions the nodes of a fully mobile network (multi-hop network) into clusters, thus giving the network a hierarchical organization. Nodes are grouped by following a new weight-based criterium that allows the choice of the nodes that coordinate the clustering process based on node mobility-related parameters. The DCA time complexity is proven to be bounded by a network parameter Db that depends on the possibly changing topology of the network rather than on its size, i.e., the invariant number of the network nodes. Simulation results are given which demonstrate that in a mobile scenario Db-and thus the DCA time complexity-is logarithmic in the size of the network. This result improves exponentially a previously known upper bound on the time complexity of distributed clustering for multi-hop wireless networks.Item Wavelength continuity constraint in differentiated reliability (DiR) WDM rings(The University of Texas at Dallas, 2013-04-18) Fumagalli, Andrea; Tacca, Marco, 1973-; Eric Jonsson School of Engineering and Computer Science. Center for Advanced Telecommunications Systems and Services (CATSS); Texas Higher Education Coordinating Board; Texas Telecommunications Engineering Consortium (TxTEC); National Science Foundation (U.S.)The concept of Differentiated Reliability (DiR) was recently introduced by the authors to provide multiple reliability degrees (or classes) at the same network layer using a common protection mechanism, e.g., path switching. According to the DiR concept, each connection at the layer under consideration is guaranteed a minimum reliability degree, defined as the Maximum Failure Probability allowed for that connection. The reliability degree chosen for a given connection is thus determined by the application requirements, and not by the actual network topology, design constraints, robustness of the network components, and span of the connection. In the paper the DiR concept is applied to designing the Wavelength Division Multiplexing (WDM) layer of a ring network in which wavelength conversion is not available. To solve the routing and wavelength assignment problem at the WDM layer an efficient algorithm is proposed that resorts to reusable protection wavelengths while guaranteeing the required reliability degree of each connection. Lower bounds on the network bandwidth required by two approaches - respectively based on non-reusable and reusable protection wavelengths - reveal interesting properties of the DiR concept and the proposed algorithm.Item Distributed and mobility-adaptive clustering for ad hoc networks(The University of Texas at Dallas, 2013-04-18) Basagni, Stefano, 1965-; Eric Jonsson School of Engineering and Computer ScienceA distributed algorithm is presented that partitions the nodes of a fully mobile network (ad hoc network) into clusters, thus giving the network a hierarchical organization. The algorithm is proven to be adaptive to changes in the network topology due to nodes' mobility and to nodes addition/removal. A new weight-based mechanism is introduced for the efficient cluster formation/maintenance that allows the cluster organization to be configured for specific applications and adaptive to changes in the network status, not available in previous solutions. Simulation results are provided that demonstrate up to an 85% reduction on the communication overhead associated with the cluster maintenance with respect to clustering algorithms previously proposed.Item A scalable and adaptive fair access protocol for slotted WDM bus network(The University of Texas at Dallas, 2013-04-18) Fumagalli, Andrea; Grasso, Robert, 1972-; Eric Jonsson School of Engineering and Computer Science; National Science Foundation (U.S.); Centro Studi e Laboratori Telecomunicazioni (Turin, Italy) (CSELT)The recent progress of optical technologies has made it possible to increase the number of wavelengths (channels) practically available in the fiber by almost one order of magnitude. With this rapid growth, access protocols originally designed for systems with a few wavelengths may not be adequate to fully utilize the optical bandwidth that is becoming available through this technological breakthrough. This is the case with access protocols designed for unidirectional fiber bus network. The paper proposes a novel access protocol for multi-channel all-optical folded bus network whose performance scales well with the number of wavelengths. This result is achieved using a load balancing algorithm that runs independently at each node and evenly distributes the traffic among the wavelengths. With the proposed protocol, the packet average access delay at a given bandwidth utilization increases only marginally as the number of wavelengths (and proportionally the offered load) is grown in the system. In addition, at all source nodes fair access delay is guaranteed by the protocol under any stable load condition, including non uniform and bursty traffic.Item Multi-rate and multi-hop optical carriers in WDM ring(The University of Texas at Dallas, 2013-04-18) Cerutti, Isabella, 1973-; Fumagalli, Andrea; Tacca, Marco, 1973-; Lardies, Ana; Jagannathan, Rajesh Shanmugavel, 1971-; Eric Jonsson School of Engineering and Computer Science. Center for Advanced Telecommunications Systems and Services (CATSS); Texas Higher Education Coordinating BoardTransparency of the optical layer offers the possibility to design a network that operates at varying transmission bit rates. While variable bit rate interfaces are being tested and will soon provide the possibility to optimally select the transmission rate for each lightpath, the potential advantages of relying upon multiple transmission rates in the optical network are ready yet to be fully explored. In this paper we define the concept of Multi-hop and Multi-rate (M&M) network in which the tributary signal is transmitted over a sequence of lightpaths, with each lightpath operating at its own transmission rate, which is determined by a number of factors including the end node's interface, amount of multiplexed traffic and cost of the network components. The potential advantages provided by the M&M network when compared to first generation optical networks (i.e., SONET/SDH), single- and multi-hop (constant bit rate) optical networks, are discussed in general and demonstrated numerically in a WDM ring. Presented results show that the network cost reduction achieved by the M&M design is a function of the cost ratio between the optical bandwidth (wavelengths) and the optical terminals.Item Wireless multimedia networks: cross-layer access protocols based on sequential opportunistic decoding (SOD)(The University of Texas at Dallas, 2013-05-23) Jegbefume, Onyemelem, 1977-; Saquib, M.; Tacca, Marco, 1973-; Fumagalli, Andrea; Monti, Paolo, 1973-; Eric Jonsson School of Engineering and Computer Science.Spread spectrum (SS) solutions offer well understood advantages to wireless networking, e.g., robustness to noise and interference, concurrent asynchronous transmissions, effective power and transmission rate control mechanisms. One of the authors' recent advances in this field makes it possible to take SS solutions to the next performance level, i.e., sequential opportunistic decoding, or SOD for short. SOD is based on transmitting data symbols multiple times within the frame using non-orthogonal partial signature waveforms or mini-frames. Depending on the received instantaneous signal-to-interference-plus-noise ratio (SINR), a given subset of such mini-frames may suffice to reliably decode the data symbols. The best performing subset contains mini-frames that are received under better-than-average SINR channel conditions - i.e., these are referred to as the opportunistic mini-frames. By instantaneously controlling the number of mini-frames transmitted, SOD also offers distributed adaptable processing gain. The objective of this report is to propose cross-layer medium access control (MAC) protocols based on SOD. These protocols are especially suited to operate in a crowded radio spectrum, e.g., when multiple WLANs and/or wireless sensor networks coexist in the same radio space, possibly supporting multimedia applications. This unique advantage originates from the integration of two sub-layers. The lower sub-layer (SOD-MAC) applies the SOD adaptable processing gain to contain both the level of interference in the radio channel and network latency. It also minimizes the power consumption at the node and supports multiple c1asses of service. The upper sub-layer (ARQ-MAC) enables statistical multiplexing of an unbounded number of attempts of frame transmission generated by uncoordinated active nodes and it provides the automatic retransmission request (ARQ) capabilities. In essence, the uniqueness of these cross-layer access protocols is their ability to achieve efficient statistical multiplexing of traffic generated by uncoordinated nodes while containing the level of interference in the radio channel. The challenge is to combine frame retransmission schemes and SOD adaptable processing gain strategies in the most effective way, while keeping the access protocols in the stable region. The payoff is the ability to: increase the radio channel utilization, contain network latency, reduce energy consumption at the wireless node, and provide a QoS platform for both real-time and datagram traffic.Item The PlaNet-PTN module: a single layer design tool for packet transport networks(The University of Texas at Dallas, 2013-05-23) Razo, Miguel; Litovsky, Arie; Huang, Wanjun, 1978-; Sivasankaran, Arularasi; Tang, Limin, 1977-; Vardhan, Hars; Tacca, Marco, 1973-; Fumagalli, Andrea; Monti, Paolo, 1973-; Eric Jonsson School of Engineering and Computer Science. Open Networking Advanced Research (OpNeAR) Laboratory.PlaNet is a multilayer network planning tool developed at the University of Texas at Dallas. This paper illustrates some of the features of PlaNet-PTN, one of the modules available in the PlaNet tool. PlaNet-PTN can be used to design and plan a single layer packet transport network (PTN). Quality of protection, routing constraints, minimization of the network equipment cost, and user's desired run time of the tool are just some examples of the features available in PlaNet. As shown in the paper, the PlaNet-PTN planning module is able to provide, among others, optimization of Label Switched Path (LSP) routes, link capacity placement, node and link equipment configuration.