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Georgia Tech
1.
Choudhary, Anirudh.
ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS.
Degree: MS, Computational Science and Engineering, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/64208 
► Building clinical decision support systems, which includes diagnosing patient’s disease states and formulating a treatment plan, is an important step toward personalized medicine. The counterfactual…
(more)
▼ Building clinical decision support systems, which includes diagnosing patient’s disease states
and formulating a treatment plan, is an important step toward personalized medicine. The counterfactual
nature of clinical decision-making is a major challenge for machine learning-based treatment
recommendation, i.e., we can only observe the outcome of the clinician’s actions while the
outcome of alternative treatment options is unknown. The thesis is an attempt to formulate robust
counterfactual learning frameworks for efficient offline policy evaluation and policy learning using
observational data. We focus on the offline data scenario and leverage historically collected Electronic
Health Records, since online policy testing can potentially adversely impact the patient’s
well-being. The problem is compounded by the inherent uncertainty in clinical decision-making
due to heterogeneous patient contexts, the presence of significant variability in patient-specific
predictions, smaller datasets, and limited knowledge of the clinician’s intrinsic reward function
and environment dynamics. This motivates the need to tackle uncertainty and enable improved
clinical policy generalization via context-based policy learning. We propose counterfactual frameworks
to tackle the highlighted challenges under two learning scenarios: contextual bandits and
dynamic treatment regime. In the bandit setting, we focus on effectively tackling the model uncertainty
inherent in inverse propensity weighting methods and highlight our approach’s efficacy
on oral anticoagulant dosing task. In dynamic treatment regime, we focus on sequential treatment
interventions and consider the problem of imitating the clinician’s policy for sepsis management.
We formulate it as a multi-task problem and propose meta-Inverse Reinforcement Learning framework
to jointly adapt policy and reward functions to diverse patient groups, thus enabling improved
policy generalization.
Advisors/Committee Members: Wang, May D (advisor), Catalyurek, Umit (advisor), Fekri, Faramarz (advisor).
Subjects/Keywords: Clinical Decision Making; Reinforcement Learning; Biomedical Informatics
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APA (6th Edition):
Choudhary, A. (2020). ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/64208
Chicago Manual of Style (16th Edition):
Choudhary, Anirudh. “ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS.” 2020. Masters Thesis, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/64208.
MLA Handbook (7th Edition):
Choudhary, Anirudh. “ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS.” 2020. Web. 01 Mar 2021.
Vancouver:
Choudhary A. ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS. [Internet] [Masters thesis]. Georgia Tech; 2020. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/64208.
Council of Science Editors:
Choudhary A. ROBUST COUNTERFACTUAL LEARNING FOR CLINICAL DECISION-MAKING USING ELECTRONIC HEALTH RECORDS. [Masters Thesis]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/64208
2.
Jian, Yubing.
Coexistence of wi-fi and LAA-LTE in unlicensed spectrum.
Degree: MS, Electrical and Computer Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54461
► The global mobile data usage has grown nearly 70% annually in recent years. The huge mobile data usage requirement drives the mobile industry to brace…
(more)
▼ The global mobile data usage has grown nearly 70% annually in recent years. The huge mobile data usage requirement drives the mobile industry to brace the formidable challenge and invent next-generation mobile technologies. LTE, as a successful cellular technology, has gained tremendous importance in recent years due to its high data-rates and improved data access method for mobile devices. Even though LTE still may not be able to meet the mobile data challenge due to current spectrum scarcity in licensed bands. Thus, cellular network faces serious challenges to provide high performance mobile service to end users in the near future.
In order to sustain the possible increase in mobile capacity demand, utilizing the unlicensed band as a supplementary band for LTE is being considered as a promising solution to expand the capacity of mobile systems. Based on the innovation of carrier aggregation, 3GPP has approved a study item on LAA-LTE, which will assist LTE by offloading mobile data in unlicensed band. Thus, LAA-LTE will operate in the spectrum that overlaps with WiFi, which is another popular unlicensed band technology. The concern is that LAA-LTE and WiFi are unlikely to have mechanisms to directly coordinate with each other, considering different core networks, backhauls and deployment plans of LAA-LTE and WiFi networks.
The overarching goal of my research is to investigate the following two aspects: 1) Investigate how LTE will impact on WiFi using experimental analysis when both of them share the same channel, 2) Develop a possible coexistence algorithm to trigger the coexistence between LAA-LTE and WiFi in unlicensed band.
Advisors/Committee Members: Sivakumar, Raghupathy (advisor), Chang, Gee-Kung (committee member), Fekri, Faramarz (committee member).
Subjects/Keywords: LAA-LTE; WiFi; Coexistence; Experimental and simulation evaluation
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APA (6th Edition):
Jian, Y. (2015). Coexistence of wi-fi and LAA-LTE in unlicensed spectrum. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54461
Chicago Manual of Style (16th Edition):
Jian, Yubing. “Coexistence of wi-fi and LAA-LTE in unlicensed spectrum.” 2015. Masters Thesis, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/54461.
MLA Handbook (7th Edition):
Jian, Yubing. “Coexistence of wi-fi and LAA-LTE in unlicensed spectrum.” 2015. Web. 01 Mar 2021.
Vancouver:
Jian Y. Coexistence of wi-fi and LAA-LTE in unlicensed spectrum. [Internet] [Masters thesis]. Georgia Tech; 2015. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/54461.
Council of Science Editors:
Jian Y. Coexistence of wi-fi and LAA-LTE in unlicensed spectrum. [Masters Thesis]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54461
3.
Krishnaswamy, Bhuvana.
When bacteria talk : time elapse communication for super-slow networks.
Degree: MS, Electrical and Computer Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/50312
► In this work we consider nano-scale communication using bacterial popula- tions as transceivers. We demonstrate using a microfluidic test-bed and a population of genetically engineered…
(more)
▼ In this work we consider nano-scale communication using bacterial popula-
tions as transceivers. We demonstrate using a microfluidic test-bed and a population of genetically engineered Escherichia coli bacteria serving as the communication re-
ceiver that a simple modulation like on-off keying (OOK) is indeed achievable, but suffers from very poor data-rates. We explore an alternative communication strategy called time elapse communication (TEC) that uses the time period between signals to encode information. We identify the severe limitations of TEC under practical non-zero error conditions in the target environment, and propose an advanced communication strategy called smart time elapse communication (TEC-SMART) that achieves over a 10x improvement in data-rate over OOK.
Advisors/Committee Members: Sivakumar, Raghupathy (advisor), Fekri, Faramarz (committee member), Akyildiz, Ian F. (committee member).
Subjects/Keywords: Molecular communication; On-off keying; Time elapse communication; Bacteria; Nanoscience; Nanotechnology; Microfluidics; Communication
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APA (6th Edition):
Krishnaswamy, B. (2013). When bacteria talk : time elapse communication for super-slow networks. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50312
Chicago Manual of Style (16th Edition):
Krishnaswamy, Bhuvana. “When bacteria talk : time elapse communication for super-slow networks.” 2013. Masters Thesis, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/50312.
MLA Handbook (7th Edition):
Krishnaswamy, Bhuvana. “When bacteria talk : time elapse communication for super-slow networks.” 2013. Web. 01 Mar 2021.
Vancouver:
Krishnaswamy B. When bacteria talk : time elapse communication for super-slow networks. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/50312.
Council of Science Editors:
Krishnaswamy B. When bacteria talk : time elapse communication for super-slow networks. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50312
4.
Agarwal, Mohit.
THINK: Toward practical general-purpose brain-computer communication.
Degree: MS, Electrical and Computer Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58345
► In this work, we present THINK, a practical general-purpose brain-computer communication platform that relies on the OpenBCI and OpenViBE hardware and software platforms, and allows…
(more)
▼ In this work, we present THINK, a practical general-purpose brain-computer communication platform that relies on the OpenBCI and OpenViBE hardware and software platforms, and allows for a simple three-alphabet vocabulary. Specifically, we consider the scenario where a subject is wearing a sensor array (an electrode cap), and consciously manipulating her thoughts to communicate wirelessly with an external computing entity (a smartphone) without the aid of any external stimuli. Using THINK, we explore general aspects of brain computer communication that are application agnostic. In particular, we study the system accuracy and usability with real user experiments. The system accuracy was found to be highly variable across subjects and trials. We achieved a maximum accuracy of 83.4% and average accuracy of 53.4%. Even with low accuracy, we demonstrate that how is it possible to construct a successful BCC system. Further, in usability, we explore (i) how fast can the subject switch thoughts corresponding to symbols; (ii) is there an impact on accuracy with learning time; and (iv) how does accuracy drop with decreasing number of sensors (electrodes)? Using purely experimental analysis, we present some results that provide preliminary answers for these questions. We also provide motivation results for the future work in the context of (i) alphabet design as per user preference, and (ii) importance of pre-processing and requirement of better algorithms.
Advisors/Committee Members: Sivakumar, Raghupathy (advisor), Fekri, Faramarz (committee member), Esmaeilzadeh, Hadi (committee member).
Subjects/Keywords: Brain-computer communication; Motor imagery
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APA (6th Edition):
Agarwal, M. (2017). THINK: Toward practical general-purpose brain-computer communication. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58345
Chicago Manual of Style (16th Edition):
Agarwal, Mohit. “THINK: Toward practical general-purpose brain-computer communication.” 2017. Masters Thesis, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/58345.
MLA Handbook (7th Edition):
Agarwal, Mohit. “THINK: Toward practical general-purpose brain-computer communication.” 2017. Web. 01 Mar 2021.
Vancouver:
Agarwal M. THINK: Toward practical general-purpose brain-computer communication. [Internet] [Masters thesis]. Georgia Tech; 2017. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/58345.
Council of Science Editors:
Agarwal M. THINK: Toward practical general-purpose brain-computer communication. [Masters Thesis]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58345
Georgia Tech
5.
Pawar, Rahul Shivaji.
Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism.
Degree: PhD, Electrical and Computer Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/62285
► The objective of this dissertation is to develop diarization algorithms for LENA data and study its application to compute language behavior statistics for individuals with…
(more)
▼ The objective of this dissertation is to develop diarization algorithms for LENA data and study its application to compute language behavior statistics for individuals with autism. LENA device is one of the most commonly used devices to collect audio data in autism and language development studies. LENA child and adult detector algorithms were evaluated for two different datasets: i) older children dataset consisting of children already diagnosed with autism spectrum disor-
der and ii) infants dataset consisting of infants at risk for autism. I-vector based diarization algorithms were developed for the two datasets to tackle two scenarios: a) some amount of labeled data is present for every speaker present in the audio recording and b) no labeled data is present for the audio recording to be diarized. Further, i-vector based diarization
methods were applied to compute objective measures of assessment. These objective measures of assessment were analyzed to show they can reveal some aspects of autism severity. Also, a method to extract a 5 minute high child vocalization audio window from a 16
hour day long recording was developed, which was then used to compute canonical babble statistics using human annotation.
Advisors/Committee Members: Clements, Mark (advisor), Anderson, David (committee member), Moore, Elliot (committee member), Fekri, Faramarz (committee member), Jones, Rebecca (committee member).
Subjects/Keywords: Diarization; Autism
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APA (6th Edition):
Pawar, R. S. (2019). Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62285
Chicago Manual of Style (16th Edition):
Pawar, Rahul Shivaji. “Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism.” 2019. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/62285.
MLA Handbook (7th Edition):
Pawar, Rahul Shivaji. “Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism.” 2019. Web. 01 Mar 2021.
Vancouver:
Pawar RS. Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/62285.
Council of Science Editors:
Pawar RS. Audio diarization for LENA data and its application to computing language behavior statistics for individuals with autism. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/62285
Georgia Tech
6.
Kadampot, Ishaque Ashar.
Optimal codes for information-theoretically covert communication.
Degree: PhD, Electrical and Computer Engineering, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/62730
► We consider a problem of coding for covert communication, which involves ensuring reliable communication between two legitimate parties while simultaneously guaranteeing a low probability of…
(more)
▼ We consider a problem of coding for covert communication, which involves ensuring reliable communication between two legitimate parties while simultaneously guaranteeing a low probability of detection by an eavesdropper. Specifically, we develop an optimal low-complexity coding scheme that achieves the information-theoretic limits of covert communication over binary-input discrete memoryless channels. We first demonstrate the non-triviality of designing codes for covert communication by showing the impossibility of achieving information-theoretic limits using linear codes without a shared secret key for a regime in which information theory proves the possibility of covert communication without a secret key. We then circumvent this impossibility by introducing non-linearity into the coding scheme through the use of pulse position modulation (PPM) and multilevel coding (MLC). This MLC-PPM scheme exhibits several appealing properties; in particular, for an appropriate decoder, the channel at a given level is independent of the total number of levels and the codeword length. We exploit these properties to show how one can use families of channel capacity- and channel resolvability-achieving codes to concretely instantiate a covert communication scheme. Further, we extend the MLC-PPM scheme using bi-orthogonal PPM symbols to achieve information-theoretic limits of covert communication over additive white Gaussian channels. Finally, we illustrate the application of this scheme for the secret-key generation problem with a covertness constraint.
Advisors/Committee Members: Bloch, Matthieu (advisor), Barry, John (committee member), Ralph, Stephen (committee member), Fekri, Faramarz (committee member), Xie, Yao (committee member).
Subjects/Keywords: Covert communication; Physical-layer security; Coding for secrecy
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APA (6th Edition):
Kadampot, I. A. (2020). Optimal codes for information-theoretically covert communication. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62730
Chicago Manual of Style (16th Edition):
Kadampot, Ishaque Ashar. “Optimal codes for information-theoretically covert communication.” 2020. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/62730.
MLA Handbook (7th Edition):
Kadampot, Ishaque Ashar. “Optimal codes for information-theoretically covert communication.” 2020. Web. 01 Mar 2021.
Vancouver:
Kadampot IA. Optimal codes for information-theoretically covert communication. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/62730.
Council of Science Editors:
Kadampot IA. Optimal codes for information-theoretically covert communication. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/62730
Georgia Tech
7.
Payani, Ali.
Differentiable neural logic networks and their application onto inductive logic programming.
Degree: PhD, Electrical and Computer Engineering, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/62833
► Despite the impressive performance of Deep Neural Networks (DNNs), they usually lack the explanatory power of disciplines such as logic programming. Even though they can…
(more)
▼ Despite the impressive performance of Deep Neural Networks (DNNs), they usually lack the explanatory power of disciplines such as logic programming. Even though they can learn to solve very difficult problems, the learning is usually implicit and it is very difficult, if not impossible, to interpret the underlying explanations that is implicitly stored in the weights of the neural network models. On the other hand, standard logic programming is usually limited in scope and application compared to the DNNs. The objective of this dissertation is to bridge the gap between these two disciplines by presenting a novel paradigm for learning algorithmic and discrete tasks via neural networks. This novel approach, uses the differentiable neural network to design interpretable and explanatory models that can learn and represent Boolean functions efficiently. We will investigate the application of these differentiable Neural Logic (dNL) networks in disciplines such as Inductive Logic Programming, Relational Reinforcement Learning, as well as in discrete algorithmic tasks such as decoding LDPC codes over Binary erasure Channels. In particular, in this dissertation we reformulate the ILP as a differentiable neural network by exploiting the explanatory power of dNL networks and we show that the proposed dNL-ILP outperforms the current state of the art ILP solvers in a variety of benchmark tasks. We further show that the proposed differentiable ILP solver can be effectively combined with the standard deep learning techniques to formulate a relational reinforcement learning framework. Via experiments, we demonstrate that the proposed deep relational policy learning framework can incorporate human expertise to learn efficient policies directly from images and outperforms the traditional RRL systems in some tasks.
Advisors/Committee Members: Fekri, Faramarz (advisor), Bloch, Matthieu (committee member), Davenport, Mark (committee member), AlRegib, Ghassan (committee member), Theja Maguluri, Siva (committee member).
Subjects/Keywords: Inductive logic programming; ILP; Neural logic; Relational reinforcement learning
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APA (6th Edition):
Payani, A. (2020). Differentiable neural logic networks and their application onto inductive logic programming. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62833
Chicago Manual of Style (16th Edition):
Payani, Ali. “Differentiable neural logic networks and their application onto inductive logic programming.” 2020. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/62833.
MLA Handbook (7th Edition):
Payani, Ali. “Differentiable neural logic networks and their application onto inductive logic programming.” 2020. Web. 01 Mar 2021.
Vancouver:
Payani A. Differentiable neural logic networks and their application onto inductive logic programming. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/62833.
Council of Science Editors:
Payani A. Differentiable neural logic networks and their application onto inductive logic programming. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/62833
Georgia Tech
8.
Kwon, Seok Chul.
Geometrical theory, modeling and applications of channel polarization.
Degree: PhD, Electrical and Computer Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/52954
► Long-term evolution (LTE) standard has been successfully stabilized, and launched in several areas. However, the required channel capacity is expected to increase significantly as the…
(more)
▼ Long-term evolution (LTE) standard has been successfully stabilized, and launched in several areas. However, the required channel capacity is expected to increase significantly as the explosively increasing number of smart-phone users implies. Hence, this is already the time for leading researchers to concentrate on a new multiple access scheme in wireless communications to satisfy the channel capacity that those smart users will want in the not-too-distant future. The diversity and multiplexing in a new domain - polarization domain - can be a strong candidate for the solution to that problem in future wireless communication systems.
This research contributes largely to the comprehensive understanding of polarized wireless channels and a new multiple access scheme in the polarization domain - polarization division multiple access (PDMA). The thesis consists of three streams: 1) a novel geometrical theory and models for fixed-to-mobile (F2M) and mobile-to-mobile (M2M) polarized wireless channels; 2) a new wireless body area network (BAN) polarized channel modeling; and 3) a novel PDMA scheme. The proposed geometrical theory and models reveal the origin and mechanism of channel depolarization with excellent agreement with empirical data in terms of cross-polarization discrimination (XPD), which is the principal measure of channel depolarization. Further, a novel PDMA scheme utilizing polarization-filtering detection and collaborative transmitter-receiver-polarization (Tx-Rx-polarization) adjustment, is designed considering cellular orthogonal frequency division multiplexing (OFDM) systems. The novel PDMA scheme has large potential to be utilized with the conventional time, frequency, and code division multiple access (TDMA, FDMA, and CDMA); and spatial multiplexing for next-generation wireless communication systems.
Advisors/Committee Members: Stüber, Gordon L. (advisor), Barry, John R. (committee member), Li, Geoffrey Ye (committee member), Fekri, Faramarz (committee member), Kang, Sung Ha (committee member).
Subjects/Keywords: Polarization division multiple access (PDMA); Polarization division multiplexing (PDM); Channel modeling; Depolarization; Body area network (BAN)
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APA (6th Edition):
Kwon, S. C. (2013). Geometrical theory, modeling and applications of channel polarization. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52954
Chicago Manual of Style (16th Edition):
Kwon, Seok Chul. “Geometrical theory, modeling and applications of channel polarization.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/52954.
MLA Handbook (7th Edition):
Kwon, Seok Chul. “Geometrical theory, modeling and applications of channel polarization.” 2013. Web. 01 Mar 2021.
Vancouver:
Kwon SC. Geometrical theory, modeling and applications of channel polarization. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/52954.
Council of Science Editors:
Kwon SC. Geometrical theory, modeling and applications of channel polarization. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52954
Georgia Tech
9.
Fayyaz, Ubaid Ullah.
Polar code design and decoding for magnetic recording.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52994
► Powerful error-correcting codes have enabled a dramatic increase in the bit density on the recording medium of hard-disk drives (HDDs). Error-correcting codes in magnetic recording…
(more)
▼ Powerful error-correcting codes have enabled a dramatic increase in the bit density on the recording medium of hard-disk drives (HDDs). Error-correcting codes in magnetic recording require a low-complexity decoder and a code design that delivers a target error-rate performance. This dissertation proposes an error-correcting system based on polar codes incorporating a fast, low-complexity, soft-output decoder and a design that is optimized for error-rate performance in the magnetic recording channel. LDPC codes are the state-of-the-art in HDDs, providing the required error-rate performance on high densities at the cost of increased computational complexity of the decoder. Substantial research in LDPC codes has focused on reducing decoder complexity and has resulted in many variants such as quasi-cyclic and convolutional LDPC codes. Polar codes are a recent and important breakthrough in coding theory, as they achieve capacity on a wide spectrum of channels using a low-complexity successive cancellation decoder. Polar codes make a strong case for magnetic recording, because they have low complexity decoders and adequate finite-length error-rate performance. In their current form, polar codes are not feasible for magnetic recording for two reasons. Firstly, there is no low-complexity soft-output decoder available for polar codes that is required for turbo-based equalization of the magnetic recording channel. The only soft-output decoder available to date is a message passing based belief propagation decoder that has very high computational complexity and is not suitable for practical implementations. Secondly, current polar codes are optimized for the AWGN channel only, and may not perform well under turbo-based detector for ISI channels. This thesis delivers a powerful low-complexity error-correcting system based on polar codes for ISI channels. Specifically, we propose a low-complexity soft-output decoder for polar codes that achieves better error-rate performance than the belief propagation decoder for polar codes while drastically reducing the complexity. We further propose a technique for polar code design over ISI channels that outperform codes for the AWGN channel in terms of error rate under the proposed soft-output decoder.
Advisors/Committee Members: Barry, John (advisor), McLaughlin, Steven (committee member), Fekri, Faramarz (committee member), Bloch, Matthieu (committee member), Goldsman, David M. (committee member).
Subjects/Keywords: Polar codes; Polar coding; Soft output; Magnetic recording
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APA (6th Edition):
Fayyaz, U. U. (2014). Polar code design and decoding for magnetic recording. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52994
Chicago Manual of Style (16th Edition):
Fayyaz, Ubaid Ullah. “Polar code design and decoding for magnetic recording.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/52994.
MLA Handbook (7th Edition):
Fayyaz, Ubaid Ullah. “Polar code design and decoding for magnetic recording.” 2014. Web. 01 Mar 2021.
Vancouver:
Fayyaz UU. Polar code design and decoding for magnetic recording. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/52994.
Council of Science Editors:
Fayyaz UU. Polar code design and decoding for magnetic recording. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52994
Georgia Tech
10.
Torabkhani, Nima.
Modeling and analysis of the performance of networks in finite-buffer regime.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/51810
► In networks, using large buffers tend to increase end-to-end packet delay and its deviations, conflicting with real-time applications such as online gaming, audio-video services, IPTV,…
(more)
▼ In networks, using large buffers tend to increase end-to-end packet delay and its deviations, conflicting with real-time applications such as online gaming, audio-video services, IPTV, and VoIP. Further, large buffers complicate the design of high speed routers, leading to more power consumption and board space. According to Moore's law, switching speeds double every 18 months while memory access speeds double only every 10 years. Hence, as memory requirements increasingly become a limiting aspect of router design, studying networks in finite-buffer regime seems necessary for network engineers. This work focuses on both practical and theoretical aspects of finite-buffer networks. In Chapters 1-7, we investigate the effects of finite buffer sizes on the throughput and packet delay in different networks. These performance measures are shown to be linked to the stationary distribution of an underlying irreducible Markov chain that exactly models the changes in the network. An iterative scheme is proposed to approximate the steady-state distribution of buffer occupancies by decoupling the exact chain to smaller chains. These approximate solutions are used to analytically characterize network throughput and packet delay, and are also applied to some network performance optimization problems. Further, using simulations, it is confirmed that the proposed framework yields accurate estimates of the throughput and delay performance measures and captures the vital trends and tradeoffs in these networks. In Chapters 8-10, we address the problem of modeling and analysis of the performance of finite-memory random linear network coding in erasure networks. When using random linear network coding, the content of buffers creates dependencies which cannot be captured directly using the classical queueing theoretical models. A careful derivation of the buffer occupancy states and their transition rules are presented as well as decodability conditions when random linear network coding is performed on a stream of arriving packets.
Advisors/Committee Members: Fekri, Faramarz (advisor), Barry, John R. (committee member), Sivakumar, Raghupathy (committee member), Weiss, Howard (committee member), Zajic, Alenka (committee member).
Subjects/Keywords: Random linear network coding; Markov chain; Finite-buffer; Throughput; Networks; Performance analysis; Computer network protocols; Computer network architecture; Buffer storage (Computer science)
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APA (6th Edition):
Torabkhani, N. (2014). Modeling and analysis of the performance of networks in finite-buffer regime. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51810
Chicago Manual of Style (16th Edition):
Torabkhani, Nima. “Modeling and analysis of the performance of networks in finite-buffer regime.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/51810.
MLA Handbook (7th Edition):
Torabkhani, Nima. “Modeling and analysis of the performance of networks in finite-buffer regime.” 2014. Web. 01 Mar 2021.
Vancouver:
Torabkhani N. Modeling and analysis of the performance of networks in finite-buffer regime. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/51810.
Council of Science Editors:
Torabkhani N. Modeling and analysis of the performance of networks in finite-buffer regime. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51810
Georgia Tech
11.
Chou, Remi.
Information-theoretic security under computational, bandwidth, and randomization constraints.
Degree: PhD, Electrical and Computer Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53837
► The objective of the proposed research is to develop and analyze coding schemes for information-theoretic security, which could bridge a gap between theory an practice.…
(more)
▼ The objective of the proposed research is to develop and analyze coding schemes for information-theoretic security, which could bridge a gap between theory an practice. We focus on two fundamental models for information-theoretic security: secret-key generation for a source model and secure communication over the wire-tap channel. Many results for these models only provide existence of codes, and few attempts have been made to design practical schemes. The schemes we would like to propose should account for practical constraints. Specifically, we formulate the following constraints to avoid oversimplifying the problems. We should assume: (1) computationally bounded legitimate users and not solely rely on proofs showing existence of code with exponential complexity in the block-length; (2) a rate-limited public communication channel for the secret-key generation model, to account for bandwidth constraints; (3) a non-uniform and rate-limited source of randomness at the encoder for the wire-tap channel model, since a perfectly uniform and rate-unlimited source of randomness might be an expensive resource. Our work focuses on developing schemes for secret-key generation and the wire-tap channel that satisfy subsets of the aforementioned constraints.
Advisors/Committee Members: Bloch, Matthieu (advisor), Fekri, Faramarz (advisor), Barry, John (committee member), McLaughlin, Steven (committee member), Tetali, Prasad (committee member).
Subjects/Keywords: Information-theoretic security; Information-theory; Coding theory; Polar codes
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APA (6th Edition):
Chou, R. (2015). Information-theoretic security under computational, bandwidth, and randomization constraints. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53837
Chicago Manual of Style (16th Edition):
Chou, Remi. “Information-theoretic security under computational, bandwidth, and randomization constraints.” 2015. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/53837.
MLA Handbook (7th Edition):
Chou, Remi. “Information-theoretic security under computational, bandwidth, and randomization constraints.” 2015. Web. 01 Mar 2021.
Vancouver:
Chou R. Information-theoretic security under computational, bandwidth, and randomization constraints. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/53837.
Council of Science Editors:
Chou R. Information-theoretic security under computational, bandwidth, and randomization constraints. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53837
Georgia Tech
12.
Einolghozati, Arash.
Sensing and molecular communication using synthetic cells: Theory and algorithms.
Degree: PhD, Electrical and Computer Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55644
► Molecular communication (MC) is a novel communication paradigm in which molecules are used to encode, transmit and decode information. MC is the primary method by…
(more)
▼ Molecular communication (MC) is a novel communication paradigm in which molecules are used to encode, transmit and decode information. MC is the primary method by which biological entities exchange information and hence, cooperate with each other. MC is a promising paradigm to enable communication between nano-bio machines, e.g., biosensors with potential applications such as cancer and disease detection, smart drug delivery, toxicity detection etc. The objective of this research is to establish the fundamentals of diffusion-based molecular communication and sensing via biological agents (e.g., synthetic bacteria) from a communication and information theory perspective, and design algorithms for reliable communication and sensing systems. In the first part of the thesis, we develop models for the diffusion channel as well as the molecular sensing at the receiver and obtain the maximum achievable rate for such a communication system. Next, we study reliability in MC. We design practical nodes by employing synthetic bacteria as the basic element of a biologically-compatible communication system and show how reliable nodes can be formed out of the collective behavior of a population of unreliable bio-agents. We model the probabilistic behavior of bacteria, obtain the node sensing capacity and propose a practical modulation scheme. In order to improve the reliability, we also introduce relaying and error-detecting codes for MC. In the second part of the thesis, we study the molecular sensing problem with potential applications in disease detection. We establish the rate-distortion theory for molecular sensing and investigate as to how distortion can be minimized via an optimal quantizer.
We also study sensor cell arrays in which sensing redundancy is achieved by using multiple sensors to measure several molecular inputs simultaneously. We study the interference in sensing molecular inputs and propose a probabilistic message passing algorithm to solve the pattern detection over the molecular inputs of interest.
Advisors/Committee Members: Fekri, Faramarz (advisor), Rozell, Chris J. (committee member), Sivakumar, Raghupathy (committee member), Weiss, Howard (committee member), McLaughlin, Steven (committee member).
Subjects/Keywords: Molecular communication; Molecular sensing
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APA (6th Edition):
Einolghozati, A. (2016). Sensing and molecular communication using synthetic cells: Theory and algorithms. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55644
Chicago Manual of Style (16th Edition):
Einolghozati, Arash. “Sensing and molecular communication using synthetic cells: Theory and algorithms.” 2016. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/55644.
MLA Handbook (7th Edition):
Einolghozati, Arash. “Sensing and molecular communication using synthetic cells: Theory and algorithms.” 2016. Web. 01 Mar 2021.
Vancouver:
Einolghozati A. Sensing and molecular communication using synthetic cells: Theory and algorithms. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/55644.
Council of Science Editors:
Einolghozati A. Sensing and molecular communication using synthetic cells: Theory and algorithms. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55644
Georgia Tech
13.
Austin, Caitlin Marie.
Dynamics of molecular communication in bacteria within microfluidic environments.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/56297
► Biosensors exploiting communication within genetically engineered bacteria are becoming increasingly important for monitoring environmental changes. Recently these sensors have miniaturized towards microfluidics due to the…
(more)
▼ Biosensors exploiting communication within genetically engineered bacteria are becoming increasingly important for monitoring environmental changes. Recently these sensors have miniaturized towards microfluidics due to the greater control they provide over things such as the population density and dynamic inputs. Although great strides have been made to study a single strain of bacteria in a microfluidic device, there is still a need to be able to study two populations of bacteria communicating with one another. Currently, there are a variety of mathematical models for understanding and predicting how genetically engineered bacteria respond to molecular stimuli in bulk culture environments, but when applied to microfluidics and to complex time-varying inputs, the shortcomings of these models have become apparent. The effects of microfluidic environments such as low oxygen concentration, increased biofilm, diffusion limited molecular distribution, and higher population densities strongly affect rate constants for gene expression not accounted for in previous models. In this work we developed a microfluidic platform capable of housing two bacteria populations to study the bacterial communication with dynamic control of inputs, long-term experimentation, and no cross contamination. We also developed a mathematical model that accurately predicts the biological response of the bacteria populations communicating in the microfluidic environment. This work can serve as a valuable tool in understanding genetically engineered bacteria and improving biosensor design capabilities, opening the door for sensors that adapt to environmental dynamics and communicate with each other.
Advisors/Committee Members: Forest, Craig (advisor), Hammer, Brian (committee member), Fekri, Faramarz (committee member), Styczynski, Mark (committee member), Hesketh, Peter (committee member).
Subjects/Keywords: Bacterial communication; Microfluidics; Modeling; Monoliths
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APA (6th Edition):
Austin, C. M. (2016). Dynamics of molecular communication in bacteria within microfluidic environments. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56297
Chicago Manual of Style (16th Edition):
Austin, Caitlin Marie. “Dynamics of molecular communication in bacteria within microfluidic environments.” 2016. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/56297.
MLA Handbook (7th Edition):
Austin, Caitlin Marie. “Dynamics of molecular communication in bacteria within microfluidic environments.” 2016. Web. 01 Mar 2021.
Vancouver:
Austin CM. Dynamics of molecular communication in bacteria within microfluidic environments. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/56297.
Council of Science Editors:
Austin CM. Dynamics of molecular communication in bacteria within microfluidic environments. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56297
Georgia Tech
14.
Abdi, Afshin.
Distributed learning and inference in deep models.
Degree: PhD, Electrical and Computer Engineering, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/63671
► In recent years, the size of deep learning problems has been increased significantly, both in terms of the number of available training samples as well…
(more)
▼ In recent years, the size of deep learning problems has been increased significantly, both in terms of the number of available training samples as well as the number of parameters and complexity of the model. In this thesis, we considered the challenges encountered in training and inference of large deep models, especially on nodes with limited computational power and capacity. We studied two classes of related problems; 1) distributed training of deep models, and 2) compression and restructuring of deep models for efficient distributed and parallel execution to reduce inference times. Especially, we considered the communication bottleneck in distributed training and inference of deep models. Data compression is a viable tool to mitigate the communication bottleneck in distributed deep learning. However, the existing methods suffer from a few drawbacks, such as the increased variance of stochastic gradients (SG), slower convergence rate, or added bias to SG. In my Ph.D. research, we have addressed these challenges from three different perspectives: 1) Information Theory and the CEO Problem, 2) Indirect SG compression via Matrix Factorization, and 3) Quantized Compressive Sampling. We showed, both theoretically and via simulations, that our proposed methods can achieve smaller MSE than other unbiased compression methods with fewer communication bit-rates, resulting in superior convergence rates. Next, we considered federated learning over wireless multiple access channels (MAC). Efficient communication requires the communication algorithm to satisfy the constraints imposed by the nodes in the network and the communication medium. To satisfy these constraints and take advantage of the over-the-air computation inherent in MAC, we proposed a framework based on random linear coding and developed efficient power management and channel usage techniques to manage the trade-offs between power consumption and communication bit-rate. In the second part of this thesis, we considered the distributed parallel implementation of an already-trained deep model on multiple workers. Since latency due to the synchronization and data transfer among workers adversely affects the performance of the parallel implementation, it is desirable to have minimum interdependency among parallel sub-models on the workers. To achieve this goal, we developed and analyzed RePurpose, an efficient algorithm to rearrange the neurons in the neural network and partition them (without changing the general topology of the neural network) such that the interdependency among sub-models is minimized under the computations and communications constraints of the workers.
Advisors/Committee Members: Fekri, Faramarz (advisor), AlRegib, Ghassan (committee member), Romberg, Justin (committee member), Bloch, Matthieu (committee member), Maguluri, Siva Theja (committee member).
Subjects/Keywords: Machine learning; Artificial intelligence; Distributed training; Distributed learning
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APA (6th Edition):
Abdi, A. (2020). Distributed learning and inference in deep models. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/63671
Chicago Manual of Style (16th Edition):
Abdi, Afshin. “Distributed learning and inference in deep models.” 2020. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/63671.
MLA Handbook (7th Edition):
Abdi, Afshin. “Distributed learning and inference in deep models.” 2020. Web. 01 Mar 2021.
Vancouver:
Abdi A. Distributed learning and inference in deep models. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/63671.
Council of Science Editors:
Abdi A. Distributed learning and inference in deep models. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/63671
15.
Harrison, Willie K.
Physical-layer security: practical aspects of channel coding and cryptography.
Degree: PhD, Electrical and Computer Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/44818
► In this work, a multilayer security solution for digital communication systems is provided by considering the joint effects of physical-layer security channel codes with application-layer…
(more)
▼ In this work, a multilayer security solution for digital communication systems is provided by considering the joint effects of physical-layer security channel codes with application-layer cryptography. We address two problems: first, the cryptanalysis of error-prone ciphertext; second, the design of a practical physical-layer security coding scheme. To our knowledge, the cryptographic attack model of the noisy-ciphertext attack is a novel concept. The more traditional assumption that the attacker has the ciphertext is generally assumed when performing cryptanalysis. However, with the ever-increasing amount of viable research in physical-layer security, it now becomes essential to perform the analysis when ciphertext is unreliable. We do so for the simple substitution cipher using an information-theoretic framework, and for stream ciphers by characterizing the success or failure of fast-correlation attacks when the ciphertext contains errors. We then present a practical coding scheme that can be used in conjunction with cryptography to ensure positive error rates in an eavesdropper's observed ciphertext, while guaranteeing error-free communications for legitimate receivers. Our codes are called stopping set codes, and provide a blanket of security that covers nearly all possible system configurations and channel parameters. The codes require a public authenticated feedback channel. The solutions to these two problems indicate the inherent strengthening of security that can be obtained by confusing an attacker about the ciphertext, and then give a practical method for providing the confusion. The aggregate result is a multilayer security solution for transmitting secret data that showcases security enhancements over standalone cryptography.
Advisors/Committee Members: McLaughlin, Steven (Committee Chair), Anderson, David (Committee Member), Fekri, Faramarz (Committee Member), Peikert, Christopher (Committee Member), Shamma, Jeff (Committee Member).
Subjects/Keywords: Wire-tap channel; Wiretap channel; Low-density parity-check codes; Stopping sets; Multi-layer security; Wiretap codes; Wire-tap codes; Physical-layer security; LDPC codes; Information-theoretic security; Coding theory; Cryptography; Digital communications; Computer security; Computer networks Security measures
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APA (6th Edition):
Harrison, W. K. (2012). Physical-layer security: practical aspects of channel coding and cryptography. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/44818
Chicago Manual of Style (16th Edition):
Harrison, Willie K. “Physical-layer security: practical aspects of channel coding and cryptography.” 2012. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/44818.
MLA Handbook (7th Edition):
Harrison, Willie K. “Physical-layer security: practical aspects of channel coding and cryptography.” 2012. Web. 01 Mar 2021.
Vancouver:
Harrison WK. Physical-layer security: practical aspects of channel coding and cryptography. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/44818.
Council of Science Editors:
Harrison WK. Physical-layer security: practical aspects of channel coding and cryptography. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/44818
16.
Al Marzouqi, Hasan.
Curvelet transform with adaptive tiling.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52961
► In this dissertation we address the problem of adapting frequency domain tiling using the curvelet transform as the basis algorithm. The optimal tiling, for a…
(more)
▼ In this dissertation we address the problem of adapting frequency domain tiling using the curvelet transform as the basis algorithm.
The optimal tiling, for a given class of images, is computed using denoising performance as the cost function. The major adaptations considered are: the number of scale decompositions, angular decompositions per scale/quadrant, and scale locations. A global optimization algorithm combining the three adaptations is proposed. Denoising performance of adaptive curvelets is tested on seismic and face data sets. The developed adaptation procedure is applied to a number of different application areas. Adaptive curvelets are used to solve the problem of sparse data recovery from subsampled measurements. Performance comparison with default curvelets demonstrates the effectiveness of the adaptation scheme. Adaptive curvelets are also used in the development of a novel image similarity index. The developed measure succeeds in retrieving correct matches from a variety of textured materials. Furthermore, we present an algorithm for classifying different types of seismic activities.
Advisors/Committee Members: AlRegib, Ghassan (advisor), McClellan, James (committee member), Fekri, Faramarz (committee member), Yezzi, Anthony (committee member), Peng, Zhigang (committee member).
Subjects/Keywords: Curvelet; Wavelet; Denoising; Compressed sensing; Texture
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APA (6th Edition):
Al Marzouqi, H. (2014). Curvelet transform with adaptive tiling. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52961
Chicago Manual of Style (16th Edition):
Al Marzouqi, Hasan. “Curvelet transform with adaptive tiling.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/52961.
MLA Handbook (7th Edition):
Al Marzouqi, Hasan. “Curvelet transform with adaptive tiling.” 2014. Web. 01 Mar 2021.
Vancouver:
Al Marzouqi H. Curvelet transform with adaptive tiling. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/52961.
Council of Science Editors:
Al Marzouqi H. Curvelet transform with adaptive tiling. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52961
17.
Jones, Malachi G.
Asymmetric information games and cyber security.
Degree: PhD, Electrical and Computer Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/50284
► A cyber-security problem is a conflict-resolution scenario that typically consists of a security system and at least two decision makers (e.g. attacker and defender) that…
(more)
▼ A cyber-security problem is a conflict-resolution scenario that typically consists of a security system and at least two decision makers (e.g. attacker and defender) that can each have competing objectives. In this thesis, we are interested in cyber-security problems where one decision maker has superior or better information. Game theory is a well-established mathematical tool that can be used to analyze such problems and will be our tool of choice. In particular, we will formulate cyber-security problems as stochastic games with asymmetric information, where game-theoretic methods can then be applied to the problems to derive optimal policies for each decision maker. A severe limitation of considering optimal policies is that these policies are computationally prohibitive. We address the complexity issues by introducing methods, based on the ideas of model predictive control, to compute suboptimal polices. Specifically, we first prove that the methods generate suboptimal policies that have tight performance bounds. We then show that the suboptimal polices can be computed by solving a linear program online, and the complexity of the linear program remains constant with respect to the game length. Finally, we demonstrate how the suboptimal policy methods can be applied to cyber-security problems to reduce the computational complexity of forecasting cyber-attacks.
Advisors/Committee Members: Shamma, Jeff S. (advisor), Fekri, Faramarz (committee member), Egerstedt, Magnus (committee member), Feron, Eric (committee member), Blough, Doug (committee member).
Subjects/Keywords: Game theory; Asymmetric information games; Cyber security; Cyber-attack forecasting; Model predictive control; Stochastic games; Repeated games; Cyber intelligence (Computer security); Decision making; Game theory
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APA (6th Edition):
Jones, M. G. (2013). Asymmetric information games and cyber security. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50284
Chicago Manual of Style (16th Edition):
Jones, Malachi G. “Asymmetric information games and cyber security.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/50284.
MLA Handbook (7th Edition):
Jones, Malachi G. “Asymmetric information games and cyber security.” 2013. Web. 01 Mar 2021.
Vancouver:
Jones MG. Asymmetric information games and cyber security. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/50284.
Council of Science Editors:
Jones MG. Asymmetric information games and cyber security. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50284
18.
Subramanian, Arunkumar.
Coding techniques for information-theoretic strong secrecy on wiretap channels.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42776
► Traditional solutions to information security in communication systems act in the application layer and are oblivious to the effects in the physical layer. Physical-layer security…
(more)
▼ Traditional solutions to information security in communication systems act in the application layer and are oblivious to the effects in the physical layer. Physical-layer security methods, of which information-theoretic security is a special case, try to extract security from the random effects in the physical layer. In information-theoretic security, there are two asymptotic notions of secrecy – weak and strong secrecy
This dissertation investigates the problem of information-theoretic strong secrecy on the binary erasure wiretap channel (BEWC) with a specific focus on designing practical codes. The codes designed in this work are based on analysis and techniques from error-correcting codes. In particular, the dual codes of certain low-density parity-check (LDPC) codes are shown to achieve strong secrecy in a coset coding scheme.
First, we analyze the asymptotic block-error rate of short-cycle-free LDPC codes when they are transmitted over a binary erasure channel (BEC) and decoded using the belief propagation (BP) decoder. Under certain conditions, we show that the asymptotic block-error rate falls according to an inverse square law in block length, which is shown to be a sufficient condition for the dual codes to achieve strong secrecy.
Next, we construct large-girth LDPC codes using algorithms from graph theory and show that the asymptotic bit-error rate of these codes follow a sub-exponential decay as the block length increases, which is a sufficient condition for strong secrecy. The secrecy rates achieved by the duals of large-girth LDPC codes are shown to be an improvement over that of the duals of short-cycle-free LDPC codes.
Advisors/Committee Members: McLaughlin, Steven (Committee Chair), Boldyreva, Alexandra (Committee Member), Coyle, Edward (Committee Member), Fekri, Faramarz (Committee Member), Ma, Xiaoli (Committee Member).
Subjects/Keywords: Belief propagation; Girth; Sparse graph codes; Low-density parity-check (LDPC) codes; Information-theoretic security; Coding theory; Information theory; Error-correcting codes (Information theory); Data protection; Electronic information resources Access control; Electronic security systems; Wiretapping
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APA (6th Edition):
Subramanian, A. (2011). Coding techniques for information-theoretic strong secrecy on wiretap channels. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42776
Chicago Manual of Style (16th Edition):
Subramanian, Arunkumar. “Coding techniques for information-theoretic strong secrecy on wiretap channels.” 2011. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/42776.
MLA Handbook (7th Edition):
Subramanian, Arunkumar. “Coding techniques for information-theoretic strong secrecy on wiretap channels.” 2011. Web. 01 Mar 2021.
Vancouver:
Subramanian A. Coding techniques for information-theoretic strong secrecy on wiretap channels. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/42776.
Council of Science Editors:
Subramanian A. Coding techniques for information-theoretic strong secrecy on wiretap channels. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42776
19.
Kakumanu, Sandeep.
Algorithms and protocols for multi-channel wireless networks.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42834
► A wireless channel is shared by all devices, in the vicinity, that are tuned to the channel, and at any given time, only one of…
(more)
▼ A wireless channel is shared by all devices, in the vicinity, that are tuned to the channel, and at any given time, only one of the devices can transmit information. One way to overcome this limitation, in throughput capacity, is to use multiple orthogonal channels for different devices, that want to transmit information at the same time. In this work, we consider the use of multiple orthogonal channels in wireless data networks. We explore algorithms and protocols for such multi-channel wireless networks under two broad categories of network-wide and link-level challenges. Towards handling the network-wide issues, we consider the channel assignment and routing issues in multi-channel wireless networks. We study both single radio and multi-radio multi-channel networks. For single radio multi-channel networks, we propose a new granularity for channel assignment, that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. For multi-radio multi-channel networks, we propose a joint routing and channel assignment protocol, known as Lattice Routing. The protocol manages channels of the radios, for the different nodes in the network, using information about current channel conditions, and adapts itself to varying traffic patterns, in order to efficiently use the multiple channels. Through ns2 based simulations, we show how both the protocols outperform other existing protocols for multi-channel networks under different network environments. Towards handling the link-level challenges, we identify the practical challenges in achieving a high data-rate wireless link across two devices using multiple off-the-shelf wireless radios. Given that the IEEE 802.11 a/g standards define 3 orthogonal wi-fi channels in the 2.4GHz band and 12 orthogonal wi-fi channels in the 5GHz band, we answer the following question: ``can a pair of devices each equipped with 15 wi-fi radios use all the available orthogonal channels to achieve a high data-rate link operating at 600Mbps?' Surprisingly, we find through experimental evaluation that the actual observed performance when using all fifteen orthogonal channels between two devices is a mere 91Mbps. We identify the reasons behind the low performance and present Glia, a software only solution that effectively exercises all available radios. We prototype Glia and show using experimental evaluations that Glia helps achieve close to 600Mbps data-rate when using all possible wi-fi channels.
Advisors/Committee Members: Sivakumar, Raghupathy (Committee Chair), Blough, Doug (Committee Member), Coyle, Edward (Committee Member), Eidenbenz, Stephan (Committee Member), Fekri, Faramarz (Committee Member).
Subjects/Keywords: Channel assignment; Multi-radio; Throughput aggregation; Multi-hop networks; Multi-channel; Wireless networks; Algorithms; Topology; Wireless communication systems
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APA (6th Edition):
Kakumanu, S. (2011). Algorithms and protocols for multi-channel wireless networks. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42834
Chicago Manual of Style (16th Edition):
Kakumanu, Sandeep. “Algorithms and protocols for multi-channel wireless networks.” 2011. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/42834.
MLA Handbook (7th Edition):
Kakumanu, Sandeep. “Algorithms and protocols for multi-channel wireless networks.” 2011. Web. 01 Mar 2021.
Vancouver:
Kakumanu S. Algorithms and protocols for multi-channel wireless networks. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/42834.
Council of Science Editors:
Kakumanu S. Algorithms and protocols for multi-channel wireless networks. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42834
20.
Bloch, Matthieu.
Physical-layer security.
Degree: PhD, Electrical and Computer Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/24658
► As wireless networks continue to flourish worldwide and play an increasingly prominent role, it has become crucial to provide effective solutions to the inherent security…
(more)
▼ As wireless networks continue to flourish worldwide and play an increasingly prominent role, it has become crucial to provide effective solutions to the inherent security issues associated with a wireless transmission medium. Unlike traditional solutions, which usually handle security at the application layer, the primary concern of this thesis is to analyze and develop solutions based on coding techniques at the physical layer.
First, an information-theoretically secure communication protocol for quasi-static fading channels was developed and its performance with respect to theoretical limits was analyzed. A key element of the protocol is a reconciliation scheme for secret-key agreement based on low-density parity-check codes, which is specifically designed to operate on non-binary random variables and offers high reconciliation efficiency.
Second, the fundamental trade-offs between cooperation and security were analyzed by investigating the transmission of confidential messages to cooperative relays. This information-theoretic study highlighted the importance of jamming as a means to increase secrecy and confirmed the importance of carefully chosen relaying strategies.
Third, other applications of physical-layer security were investigated. Specifically, the use of secret-key agreement techniques for alternative cryptographic purposes was analyzed, and a framework for the design of practical information-theoretic commitment protocols over noisy channels was proposed.
Finally, the benefit of using physical-layer coding techniques beyond the physical layer was illustrated by studying security issues in client-server networks. A coding scheme exploiting packet losses at the network layer was proposed to ensure reliable communication between clients and servers and security against colluding attackers.
Advisors/Committee Members: McLaughlin, Steven (Committee Chair), Barros, Joao (Committee Member), Bellissard, Jean (Committee Member), Fekri, Faramarz (Committee Member), Lanterman, Aaron (Committee Member).
Subjects/Keywords: Wiretap channel; Information-theoretic security; Physical-layer security; Secret-key agreement; LDPC codes; Wireless communication systems; Computer networks Security measures
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APA (6th Edition):
Bloch, M. (2008). Physical-layer security. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/24658
Chicago Manual of Style (16th Edition):
Bloch, Matthieu. “Physical-layer security.” 2008. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/24658.
MLA Handbook (7th Edition):
Bloch, Matthieu. “Physical-layer security.” 2008. Web. 01 Mar 2021.
Vancouver:
Bloch M. Physical-layer security. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/24658.
Council of Science Editors:
Bloch M. Physical-layer security. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/24658
21.
Ji, Shouling.
Evaluating the security of anonymized big graph/structural data.
Degree: PhD, Electrical and Computer Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/54913
► We studied the security of anonymized big graph data. Our main contributions include: new De-Anonymization (DA) attacks, comprehensive anonymity, utility, and de-anonymizability quantifications, and a…
(more)
▼ We studied the security of anonymized big graph data. Our main contributions include: new De-Anonymization (DA) attacks, comprehensive anonymity, utility, and de-anonymizability quantifications, and a secure graph data publishing/sharing system SecGraph. New DA Attacks. We present two novel graph DA frameworks: cold start single-phase Optimization-based DA (ODA) and De-anonymizing Social-Attribute Graphs (De-SAG). Unlike existing seed-based DA attacks, ODA does not priori knowledge. In addition, ODA’s DA results can facilitate existing DA attacks by providing more seed information. De-SAG is the first attack that takes into account both graph structure and attribute information. Through extensive evaluations leveraging real world graph data, we validated the performance of both ODA and De-SAG. Graph Anonymity, Utility, and De-anonymizability Quantifications. We developed new techniques that enable comprehensive graph data anonymity, utility, and de-anonymizability evaluation. First, we proposed the first seed-free graph de-anonymizability quantification framework under a general data model which provides the theoretical foundation for seed-free SDA attacks. Second, we conducted the first seed-based quantification on the perfect and partial de-anonymizability of graph data. Our quantification closes the gap between seed-based DA practice and theory. Third, we conducted the first attribute-based anonymity analysis for Social-Attribute Graph (SAG) data. Our attribute-based anonymity analysis together with existing structure-based de-anonymizability quantifications provide data owners and researchers a more complete understanding of the privacy of graph data. Fourth, we conducted the first graph Anonymity-Utility-De-anonymity (AUD) correlation quantification and provided close-forms to explicitly demonstrate such correlation. Finally, based on our quantifications, we conducted large-scale evaluations leveraging 100+ real world graph datasets generated by various computer systems and services. Using the evaluations, we demonstrated the datasets’ anonymity, utility, and de-anonymizability, as well as the significance and validity of our quantifications. SecGraph. We designed, implemented, and evaluated the first uniform and open-source Secure Graph data publishing/sharing (SecGraph) system. SecGraph enables data owners and researchers to conduct accurate comparative studies of anonymization/DA techniques, and to comprehensively understand the resistance/vulnerability of existing or newly developed anonymization techniques, the effectiveness of existing or newly developed DA attacks, and graph and application utilities of anonymized data.
Advisors/Committee Members: Bloch, Matthieu (advisor), Beyah, Raheem (committee member), Fekri, Faramarz (committee member), Copeland, John (committee member), Ahamad, Mustaque (committee member).
Subjects/Keywords: Security and privacy; Graph data; Structural data; De-anonymization; Anonymization; Quantification; Evaluation; Utility; Anonymity
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APA (6th Edition):
Ji, S. (2016). Evaluating the security of anonymized big graph/structural data. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54913
Chicago Manual of Style (16th Edition):
Ji, Shouling. “Evaluating the security of anonymized big graph/structural data.” 2016. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/54913.
MLA Handbook (7th Edition):
Ji, Shouling. “Evaluating the security of anonymized big graph/structural data.” 2016. Web. 01 Mar 2021.
Vancouver:
Ji S. Evaluating the security of anonymized big graph/structural data. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/54913.
Council of Science Editors:
Ji S. Evaluating the security of anonymized big graph/structural data. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/54913
22.
Krishnaswamy, Bhuvana.
Algorithms for molecular communication networks.
Degree: PhD, Electrical and Computer Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/60259
► Bio-sensors are becoming an integral part of our everyday life, implicitly and explicitly. The natural sensing mechanism and advancements in synthetic biology has made bacteria…
(more)
▼ Bio-sensors are becoming an integral part of our everyday life, implicitly and explicitly. The natural sensing mechanism and advancements in synthetic biology has made bacteria as potential candidates for building bio-sensors. The successful operation and availability of biological circuits and components for data processing makes bacteria strong candidates to use as computing machines. Currently bio-sensors, including bacterial sensors are used purely for sensing; information from each sensor is processed independently off-line, leading to processing delays, manual errors and concerns on bio-compatibility. In this dissertation, we focus on the communication between bio-sensors in a bionetwork. A bionetwork can foray into domains that are unreachable using current technologies. Such a network of bacterial(bio) sensors differs significantly from traditional electromagnetic communication due to the devices used, the channel, the medium/environment and the application. We identify three unique characteristics of bacterial networks that differentiates it from traditional networks viz., computational complexity, delay, and asymmetry that demands a fundamental redesign of communication algorithms. We developed practical and efficient communication algorithms to be implemented on bacterial transceivers. Each of these algorithms identifies the constraint of the network and leverages the opportunities provided by the system to achieve high throughput efficiency.
Advisors/Committee Members: Fekri, Faramarz (committee member), Weitnauer, Mary Ann (committee member), Bloch, Matthieu Ratoslav (committee member), Zegura, Ellen (committee member).
Subjects/Keywords: Molecular communication; Bacterial networks; Biological communication; Synthetic biology; Modulation; Medium access; Reliability
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APA (6th Edition):
Krishnaswamy, B. (2018). Algorithms for molecular communication networks. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60259
Chicago Manual of Style (16th Edition):
Krishnaswamy, Bhuvana. “Algorithms for molecular communication networks.” 2018. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/60259.
MLA Handbook (7th Edition):
Krishnaswamy, Bhuvana. “Algorithms for molecular communication networks.” 2018. Web. 01 Mar 2021.
Vancouver:
Krishnaswamy B. Algorithms for molecular communication networks. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/60259.
Council of Science Editors:
Krishnaswamy B. Algorithms for molecular communication networks. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/60259
23.
Klinc, Demijan.
On applications of puncturing in error-correction coding.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/39610
► This thesis investigates applications of puncturing in error-correction coding and physical layer security with an emphasis on binary and non-binary LDPC codes. Theoretical framework for…
(more)
▼ This thesis investigates applications of puncturing in error-correction coding and physical layer security with an emphasis on binary and non-binary LDPC codes.
Theoretical framework for the analysis of punctured binary LDPC codes at short block lengths is developed and a novel decoding scheme is designed that achieves considerably faster convergence than conventional approaches. Subsequently, optimized puncturing and shortening is studied for non-binary LDPC codes over binary input channels. Framework for the analysis of punctured/shortened non-binary LDPC codes over the BEC channel is developed, which enables the optimization of puncturing and shortening patterns. Insight from this analysis is used to develop algorithms for puncturing and shortening of non-binary LDPC codes at finite block lengths that perform well. It is confirmed that symbol-wise puncturing is generally bad and that bit-wise punctured non-binary LDPC codes can significantly outperform their binary counterparts, thus making them an attractive solution for future communication systems; both for error-correction and distributed compression.
Puncturing is also considered in the context of physical layer security. It is shown that puncturing can be used effectively for coding over the wiretap channel to hide the message bits from eavesdroppers. Further, it is shown how puncturing patterns can be optimized for enhanced secrecy. Asymptotic analysis confirms that eavesdroppers are forced to operate at BERs very close to 0.5, even if their signal is only slightly worse than that of the legitimate receivers. The proposed coding scheme is naturally applicable at finite block lengths and allows for efficient, almost-linear time encoding.
Finally, it is shown how error-correcting codes can be used to solve an open problem of compressing data encrypted with block ciphers such as AES. Coding schemes for multiple chaining modes are proposed and it is verified that considerable compression gains are attainable for binary sources.
Advisors/Committee Members: McLaughlin, Steven (Committee Chair), Barry, John (Committee Member), Blough, Douglas (Committee Member), Fekri, Faramarz (Committee Member), Lee, Wenke (Committee Member).
Subjects/Keywords: Encryption; Compression; Physical layer security; Binary and non-binary LDPC codes; Shortening; Puncturing; Data encryption (Computer science); Computer security
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APA (6th Edition):
Klinc, D. (2011). On applications of puncturing in error-correction coding. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39610
Chicago Manual of Style (16th Edition):
Klinc, Demijan. “On applications of puncturing in error-correction coding.” 2011. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/39610.
MLA Handbook (7th Edition):
Klinc, Demijan. “On applications of puncturing in error-correction coding.” 2011. Web. 01 Mar 2021.
Vancouver:
Klinc D. On applications of puncturing in error-correction coding. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/39610.
Council of Science Editors:
Klinc D. On applications of puncturing in error-correction coding. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/39610
24.
Subramanian, Ramanan.
Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective.
Degree: PhD, Electrical and Computer Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/37083
► This work focuses on the performance characterization of distributed collaborative ad-hoc networks, focusing on such metrics as the lifetime, latency, and throughput capacity of two…
(more)
▼ This work focuses on the performance characterization of distributed collaborative ad-hoc networks, focusing on such metrics as the lifetime, latency, and throughput capacity of two such classes of networks. The first part concerns modeling and optimization of static Wireless Sensor Networks, specifically dealing with the issues of energy efficiency, lifetime, and latency. We analyze and characterize these performance measures and discuss various fundamental design tradeoffs. For example, energy efficiency in wireless sensor networks can only be improved at the cost of the latency (the delay incurred during communication). It has been clearly shown that improvement in energy efficiency through data aggregation increases the latency in the network. In addition, sleep-active duty cycling of nodes (devices constituting the network), a commonly employed mechanism to conserve battery lifetime in such networks, has adverse effects on their functionality and capacity. Hence these issues deserve a detailed study.
The second part of this work concerns performance modeling of Delay Tolerant Networks (DTNs) and Sparse Mobile Ad-Hoc Networks (SPMANETs) in general. We first investigate the effect of modern coding, such as the application of packet-level rateless codes, on the latency, reliability, and energy efficiency of the network. These codes provide us the means to break large messages into smaller packets thereby enabling efficient communication. The work then focuses on developing and formalizing an information-theoretic framework for Delay Tolerant- and other Sparse Mobile Networks. This is enabled by the use of an embedded-Markov-chain approach used for complex queuing-theoretic problems. An important goal of this work is to incorporate a wide range of mobility models into the analysis framework. Yet another important question will be the effect of changing the mobility on the comparative performance of networking protocols. Lastly, the framework will be extended to various communication paradigms such as two-hop vs multi-hop routing, unicast, and multicast.
Advisors/Committee Members: Fekri, Faramarz (Committee Chair), Ammar, Mostafa (Committee Member), Coyle, Ed (Committee Member), Sivakumar, Raghupathy (Committee Member), Stuber, Gordon (Committee Member).
Subjects/Keywords: Queuing theory; Performance analysis; Intermittently-connected networks; Sensor networks; Information theory; Ad hoc networks (Computer networks); Multicasting (Computer networks); Wireless sensor networks
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APA (6th Edition):
Subramanian, R. (2009). Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37083
Chicago Manual of Style (16th Edition):
Subramanian, Ramanan. “Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective.” 2009. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/37083.
MLA Handbook (7th Edition):
Subramanian, Ramanan. “Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective.” 2009. Web. 01 Mar 2021.
Vancouver:
Subramanian R. Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/37083.
Council of Science Editors:
Subramanian R. Modeling and analysis of the performance of collaborative wireless ad-hoc networks: an information-theoretic perspective. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/37083
25.
Vellambi, Badri Narayanan.
Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms.
Degree: PhD, Electrical and Computer Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/37091
► The conception of turbo codes by Berrou et al. has created a renewed interest in modern graph-based codes. Several encouraging results that have come to…
(more)
▼ The conception of turbo codes by Berrou et al. has created a renewed interest in modern graph-based codes. Several encouraging results that have come to light since then have fortified the role these codes shall play as potential solutions for present and future communication problems.
This work focuses on both practical and theoretical aspects of graph-based codes. The
thesis can be broadly categorized into three parts. The first part of the thesis focuses on
the design of practical graph-based codes of short lengths. While both low-density parity-check
codes and rateless codes have been shown to be asymptotically optimal under the message-passing (MP) decoder, the performance of short-length codes from these families under MP decoding is starkly sub-optimal. This work first addresses the
structural characterization of stopping sets to understand this sub-optimality. Using this
characterization, a novel improved decoder that offers several orders of magnitude improvement in bit-error rates is introduced. Next, a novel scheme for the design of a good rate-compatible family of punctured codes is proposed.
The second part of the thesis aims at establishing these codes as a good tool to develop
reliable, energy-efficient and low-latency data dissemination schemes in networks. The problems of broadcasting in wireless multihop networks and that of unicast in delay-tolerant networks are investigated. In both cases, rateless coding is seen to offer an elegant means of achieving the goals of the chosen communication protocols. It was noticed that the ratelessness and the randomness in encoding process make this scheme
specifically suited to such network applications.
The final part of the thesis investigates an application of a specific class of codes called
network codes to finite-buffer wired networks. This part of the work aims at establishing a framework for the theoretical study and understanding of finite-buffer networks. The
proposed Markov chain-based method extends existing results to develop an iterative
Markov chain-based technique for general acyclic wired networks. The framework not only estimates the capacity of such networks, but also provides a means to monitor network traffic and packet drop rates on various links of the network.
Advisors/Committee Members: Fekri, Faramarz (Committee Chair), Li, Ye (Committee Member), McLaughlin, Steven (Committee Member), Sivakumar, Raghupathy (Committee Member), Tetali, Prasad (Committee Member).
Subjects/Keywords: Capacity; Improved MP decoder; LDPC codes; Rateless codes; Finite-buffer networks; Graph-based codes; Network codes; Coding theory; Error-correcting codes (Information theory); Graph theory; Markov processes
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APA (6th Edition):
Vellambi, B. N. (2008). Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37091
Chicago Manual of Style (16th Edition):
Vellambi, Badri Narayanan. “Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms.” 2008. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/37091.
MLA Handbook (7th Edition):
Vellambi, Badri Narayanan. “Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms.” 2008. Web. 01 Mar 2021.
Vancouver:
Vellambi BN. Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/37091.
Council of Science Editors:
Vellambi BN. Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/37091
Georgia Tech
26.
Lim, Yusun.
Game theoretic distributed coordination: drifting environments and constrained communications.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52986
► The major objective of this dissertation is extending the capabilities of game theoretic distributed control to more general settings. In particular, we are interested in…
(more)
▼ The major objective of this dissertation is extending the capabilities of game theoretic distributed control to more general settings. In particular, we are interested in drifting environments and/or constrained communications.
The first part of the dissertation concerns slowly varying dynamics, i.e., drifting environments. A standard assumption in game theoretic learning is a stationary environment, e.g., the game is fixed. We investigate the case of slow variations and show that for sufficiently slow time variations, the limiting behavior “tracks” the stochastically stable states. Since the analysis is regarding Markov processes, the results could be applied to various game theoretic learning rules. In this research, the results were applied to log-linear learning. A mobile sensor coverage example was tested in both simulation and laboratory experiments.
The second part considers a problem of coordinating team players' actions without any communications in team-based zero-sum games. Generally, some global signalling devices are required for common randomness between players, but communications are very limited or impossible in many practical applications. Instead of learning a one-shot strategy, we let players coordinate a periodic sequence of deterministic actions and put an assumption on opponent's rationality. Since team players' action sequences are periodic and deterministic, common randomness is no longer required to coordinate players. It is proved that if a length of a periodic action sequence is long enough, then opponents with limited rationality cannot recognize its pattern. Because the opponents cannot recognize that the players are playing deterministic actions, the players' behavior looks like a correlated and randomized joint strategy with empirical distribution of their action sequences. Consequently players can coordinate their action sequences without any communications or global signals, and the resulting action sequences have correlated behavior.
Moreover, the notion of micro-players are introduced for efficient learning of long action sequences. Micro-player matching approach provides a new framework that converts the original team-based zero-sum game to a game between micro-players. By introducing a de Bruijn sequence to micro-player matching, we successfully separate the level of opponent's rationality and the size of the game of micro-players. The simulation results are shown to demonstrate the performance of micro-player matching methods.
Lastly, the results of the previous two topics are combined by considering a problem of coordinating actions without communications in drifting environments. More specifically, it is assumed that the opponent player in the team-based zero-sum games tries to adjust its strategy in the set of bounded recall strategies. Then the time-varying opponent's strategy can be considered as a dynamic environment parameter in a coordination game between the team players. Additionally, we develop a human testbed program for further study regarding a human as an…
Advisors/Committee Members: Shamma, Jeff S. (advisor), Wardi, Yorai (committee member), Fekri, Faramarz (committee member), Feron, Eric (committee member), Howard, Ayanna M. (committee member), Bloch, Matthieu R. (committee member).
Subjects/Keywords: Game theoretic learning; Cooperative control; Distributed control
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APA ·
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MLA ·
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Export
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Manager
APA (6th Edition):
Lim, Y. (2014). Game theoretic distributed coordination: drifting environments and constrained communications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52986
Chicago Manual of Style (16th Edition):
Lim, Yusun. “Game theoretic distributed coordination: drifting environments and constrained communications.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/52986.
MLA Handbook (7th Edition):
Lim, Yusun. “Game theoretic distributed coordination: drifting environments and constrained communications.” 2014. Web. 01 Mar 2021.
Vancouver:
Lim Y. Game theoretic distributed coordination: drifting environments and constrained communications. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/52986.
Council of Science Editors:
Lim Y. Game theoretic distributed coordination: drifting environments and constrained communications. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52986
Georgia Tech
27.
Beirami, Ahmad.
Network compression via network memory: fundamental performance limits.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53448
► The amount of information that is churned out daily around the world is staggering, and hence, future technological advancements are contingent upon development of scalable…
(more)
▼ The amount of information that is churned out daily around the world is staggering, and hence, future technological advancements are contingent upon development of scalable acquisition, inference, and communication mechanisms for this massive data. This Ph.D. dissertation draws upon mathematical tools from information theory and statistics to understand the fundamental performance limits of universal compression of this massive data at the packet level using universal compression just above layer 3 of the network when the intermediate network nodes are enabled with the capability of memorizing the previous traffic. Universality of compression imposes an inevitable redundancy (overhead) to the compression performance of universal codes, which is due to the learning of the unknown source statistics. In this work, the previous asymptotic results about the redundancy of universal compression are generalized to consider the performance of universal compression at the finite-length regime (that is applicable to small network packets). Further, network compression via memory is proposed as a compression-based solution for the compression of relatively small network packets whenever the network nodes (i.e., the encoder and the decoder) are equipped with memory and have access to massive amounts of previous communication. In a nutshell, network compression via memory learns the patterns and statistics of the payloads of the packets and uses it for compression and reduction of the traffic. Network compression via memory, with the cost of increasing the computational overhead in the network nodes, significantly reduces the transmission cost in the network. This leads to huge performance improvement as the cost of transmitting one bit is by far greater than the cost of processing it.
Advisors/Committee Members: Fekri, Faramarz (advisor), Bloch, Matthieu (committee member), Sivakumar, Raghupathy (committee member), Barry, John (committee member), Weiss, Howard (committee member), McLaughlin, Steven W. (committee member).
Subjects/Keywords: Universal compression; Source coding; Redundancy elimination; Memory-assisted compression; Information theory; Distributed source coding; Side information; Redundancy-capacity theorem
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APA (6th Edition):
Beirami, A. (2014). Network compression via network memory: fundamental performance limits. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53448
Chicago Manual of Style (16th Edition):
Beirami, Ahmad. “Network compression via network memory: fundamental performance limits.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/53448.
MLA Handbook (7th Edition):
Beirami, Ahmad. “Network compression via network memory: fundamental performance limits.” 2014. Web. 01 Mar 2021.
Vancouver:
Beirami A. Network compression via network memory: fundamental performance limits. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/53448.
Council of Science Editors:
Beirami A. Network compression via network memory: fundamental performance limits. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53448
28.
Moravapalle, Uma Parthavi.
Mobile computing algorithms and systems for user-aware optimization of enterprise applications.
Degree: PhD, Electrical and Computer Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/61226
► The adoption of mobile devices, particularly smartphones, has grown steadily over the last decade, also permeating the enterprise sector. Enterprises are investing heavily in mobilization…
(more)
▼ The adoption of mobile devices, particularly smartphones, has grown steadily over the last decade, also permeating the enterprise sector. Enterprises are investing heavily in mobilization to improve employee productivity and perform business workflows, including smartphones and tablets. Enterprise mobility is expected to be more than a $250 billion market in 2019. Strategies to achieve mobilization range from building native apps, using mobile enterprise application platforms (MEAPS), developing with a mobile backend as a service (mBaaS), relying on application virtualization, and employing application refactoring. Enterprises are not yet experiencing the many benefits of mobilization, even though there is great promise. Email and browsing are used heavily, but the practical adoption of enterprise mobility to deliver value beyond these applications is in its infancy and faces barriers. Enterprises deploy few business workflows (<5 percent). Barriers include the heavy task burden in executing workflows on mobile devices, the irrelevance of available mobile features, non-availability of necessary business functions, the high cost of network access, increased security risks associated with smartphones, and increased complexity of mobile application development. This dissertation identifies key barriers to user productivity on smartphones and investigates user-aware solutions that leverage redundancies in user behavior to reduce burden, focusing on the following mobility aspects: (1) Workflow Mobilization: For an employee to successfully perform workflows on a smartphone, a mobile app must be available, and the specific workflow must survive the defeaturization process necessary for mobilization. While typical mobilization strategies offer mobile access to a few heavily-used features, there is a long-tail problem for enterprise application mobilization, in that many application features are left unsupported or are too difficult to access. We propose a do-it-yourself (DIY) platform, Taskr, that allows users at all skill levels to mobilize workflows. Taskr uses remote computing with application refactoring to achieve code-less mobilization of enterprise web applications. It allows for flexible mobile delivery so that users can execute spot tasks through Twitter, email, or a native mobile app. Taskr prototypes from 15 enterprise applications reduce the number of user actions performing workflows by 40 percent compared to the desktop; (2) Content sharing (enterprise email): An enterprise employee spends an inordinate amount of time on email responding to queries and sharing information with co-workers. This problem is further aggravated on smartphones due to smaller screen real estate. We consider automated information suggestions to ease the burden of reply construction on smartphones. The premise is that a significant portion of the information content in a reply is likely present in prior emails. We first motivate this premise by analyzing both public and private email datasets. We then present Dejavu, a system that…
Advisors/Committee Members: Sivakumar, Raghupathy (advisor), Ramachandran, Umakishore (committee member), Fekri, Faramarz (committee member), Blough, Douglas (committee member), Ramachandran, Karthik (committee member), Sanadhya, Shruti (committee member).
Subjects/Keywords: Enterprise mobility; Smartphone apps; Application development; Smartphone email; Remote computing; Codeless application development
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APA (6th Edition):
Moravapalle, U. P. (2019). Mobile computing algorithms and systems for user-aware optimization of enterprise applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61226
Chicago Manual of Style (16th Edition):
Moravapalle, Uma Parthavi. “Mobile computing algorithms and systems for user-aware optimization of enterprise applications.” 2019. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/61226.
MLA Handbook (7th Edition):
Moravapalle, Uma Parthavi. “Mobile computing algorithms and systems for user-aware optimization of enterprise applications.” 2019. Web. 01 Mar 2021.
Vancouver:
Moravapalle UP. Mobile computing algorithms and systems for user-aware optimization of enterprise applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/61226.
Council of Science Editors:
Moravapalle UP. Mobile computing algorithms and systems for user-aware optimization of enterprise applications. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/61226
29.
Choi, Gi Wan.
Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability.
Degree: PhD, Electrical and Computer Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/47721
► In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands…
(more)
▼ In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands for higher data rates and seamless connectivity, one solution is to drastically increase the number of macro base stations in the conventional cellular architecture. However, this results in high deployment costs. Deploying low-power nodes such as relays that do not require a wired backhaul connection within a macrocell is one of cost-effective ways to extend high data rate coverage range. Relays are typically deployed to increase signal strength in poor coverage areas or to eliminate dead spots. But more importantly, relays provide a natural diversity, called cooperative diversity. In addition to a direct signal from a base station, extra copies of the same signal are forwarded from relays. Utilizing this diversity at the destination can yield significant performance enhancements. Thus, cooperative relay strategies need to be considered to enable high data rate coverage in a cost-effective manner.
In this dissertation, we consider a simple single-relay network and present low-complexity and power-efficient cooperative relay designs that can achieve low error rate. We first study decode-and-forward (DF) relay networks with a single antenna at each node, where the relay decodes the received signal and forwards the re-encoded information to the destination. In DF relay scheme, decoding at the relay is not perfect and the error-propagation phenomenon is a detrimental problem, preventing the destination from collecting the cooperative diversity. To enable cooperative diversity in DF relay networks, we adopt link-adaptive power-scaling relay strategies where the relay scales the transmission power of the re-encoded signal based on the reliability of the source-relay link. We generalize power-profile designs and analyze the diversity order enabled by the general power-profile designs. We provide necessary and sufficient conditions for the designs to enable full cooperative diversity at the destination.
In the second part of this dissertation, we extend the power-scaling relay strategy to DF multi-input multi-output (MIMO) relay networks, where multiple antennas are adopted at each node, and show that full cooperative diversity can also be achieved here. To collect spatial diversity provided by multiple antennas without using maximum-likelihood equalizers (MLEs) or near-ML detectors which exhibit high complexity, channel-controlled automatic repeat request (CC-ARQ) scheme is developed for DF MIMO relay networks to enable spatial diversity with linear equalizers (LEs) maintaining low-complexity. We also show that joint cooperative and spatial diversity can be achieved at the destination when the power-scaling strategy and the CC-ARQ with LEs are combined.
Finally, amplify-and-forward (AF) MIMO relay designs, where the relay simply amplifies the received signal and forwards it to the destination, are studied with consideration of peak-power constraints at the…
Advisors/Committee Members: Ma, Xiaoli (Committee Chair), Fekri, Faramarz (Committee Member), Green, William L. (Committee Member), Tentzeris, Emmanouil M. (Committee Member), Zhou, G. Tong (Committee Member).
Subjects/Keywords: Receiver diversity; Cooperative diversity; CC-ARQ; Cooperative relay networks; MIMO; Peak-power constraint; AF; DF; Wireless communication systems; Mobile communication systems; Network performance (Telecommunication)
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APA (6th Edition):
Choi, G. W. (2013). Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/47721
Chicago Manual of Style (16th Edition):
Choi, Gi Wan. “Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/47721.
MLA Handbook (7th Edition):
Choi, Gi Wan. “Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability.” 2013. Web. 01 Mar 2021.
Vancouver:
Choi GW. Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/47721.
Council of Science Editors:
Choi GW. Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/47721
30.
Ayday, Erman.
Iterative algorithms for trust and reputation management and recommender systems.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/45868
► This thesis investigates both theoretical and practical aspects of the design and analysis of iterative algorithms for trust and reputation management and recommender systems. It…
(more)
▼ This thesis investigates both theoretical and practical aspects of the design and analysis of iterative algorithms for trust and reputation management and recommender systems. It also studies the application of iterative trust and reputation management mechanisms in ad-hoc networks and P2P systems.
First, an algebraic and iterative trust and reputation management scheme (ITRM) is proposed. The proposed ITRM can be applied to centralized schemes, in which a central authority collects the reports and forms the reputations of the service providers (sellers) as well as report/rating trustworthiness of the (service) consumers (buyers). It is shown that ITRM is robust in filtering out the peers who provide unreliable ratings. Next, the first application of Belief Propagation algorithm, a fully iterative probabilistic algorithm, on trust and reputation management (BP-ITRM) is proposed. In BP-ITRM, the reputation management problem is formulated as an inference problem, and it is described as computing marginal likelihood distributions from complicated global functions of many variables. However, it is observed that computing the marginal probability functions is computationally prohibitive for large scale reputation systems. Therefore, the belief propagation algorithm is utilized to efficiently (in linear complexity) compute these marginal probability distributions. In BP-ITRM, the reputation system is modeled by using a factor graph and reputation values of the service providers (sellers) are computed by iterative probabilistic message passing between the factor and variable nodes on the graph. It is shown that BP-ITRM is reliable in filtering out malicious/unreliable reports. It is proven that BP-ITRM iteratively reduces the error in the reputation values of service providers due to the malicious raters with a high probability. Further, comparison of BP-ITRM with some well-known and commonly used reputation management techniques (e.g., Averaging Scheme, Bayesian Approach and Cluster Filtering) indicates the superiority of the proposed scheme both in terms of robustness against attacks and efficiency.
The introduction of the belief propagation and iterative message passing methods onto trust and reputation management has opened up several research directions. Thus, next, the first application of the belief propagation algorithm in the design of recommender systems (BPRS) is proposed. In BPRS, recommendations (predicted ratings) for each active user are iteratively computed by probabilistic message passing between variable and factor nodes in a factor graph. It is shown that as opposed to the previous recommender algorithms, BPRS does not require solving the recommendation problem for all users if it wishes to update the recommendations for only a single active user using the most recent data (ratings). Further, BPRS computes the recommendations for each user with linear complexity, without requiring a training period while it remains comparable to the state of art methods such as Correlation-based neighborhood model…
Advisors/Committee Members: Fekri, Faramarz (Committee Chair), Akyildiz, Ian F. (Committee Member), Blough, Doug (Committee Member), Liu, Ling (Committee Member), McLaughlin, Steven W. (Committee Member).
Subjects/Keywords: Inference; Iterative algorithms; Trust and reputation management; Belief propagation; Recommender systems; Online services; Trust; Reputation; Electronic commerce; Commerce; Algorithms
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ayday, E. (2011). Iterative algorithms for trust and reputation management and recommender systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45868
Chicago Manual of Style (16th Edition):
Ayday, Erman. “Iterative algorithms for trust and reputation management and recommender systems.” 2011. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
http://hdl.handle.net/1853/45868.
MLA Handbook (7th Edition):
Ayday, Erman. “Iterative algorithms for trust and reputation management and recommender systems.” 2011. Web. 01 Mar 2021.
Vancouver:
Ayday E. Iterative algorithms for trust and reputation management and recommender systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/45868.
Council of Science Editors:
Ayday E. Iterative algorithms for trust and reputation management and recommender systems. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/45868
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