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Design of Low-Power Zero Temperature Coefficient (ZTC) CMOS Oscillators
, M.Sc. Thesis Sharif University of Technology ; Akbar, Fatemeh (Supervisor)
Abstract
The increasing demand for autonomous vehicles and reliable communication protocols and hardware interfaces, such as CAN bus and USB, underscores the necessity for stable clock sources that maintain a low temperature coefficient (TC) over wide temperature ranges. This demand is particularly emphasized in applications such as wearables, network sensors, downhole devices, WSNs, and IoT, where long-lasting battery life and frequency-stable clock sources over a broad temperature range (e.g. -20 °C to 100 °C) are crucial. Traditionally, variations in frequency caused by temperature have been mitigated by employing off-chip components like crystals or ceramic based oscillators, but this approach...
Thermodynamic forces and flows between a thermal bath and a squeezed thermal bath: Application to optomechanical systems
, Article Physical Review A ; Volume 105, Issue 6 , 2022 ; 24699926 (ISSN) ; Sharif University of Technology
American Physical Society
2022
Abstract
When a quantum system is coupled to two thermal baths at different temperatures, the temperature gradient as a thermodynamic force causes stationary heat flow within the system. We present a theoretical model to study how quantum features of squeezed thermal reservoirs affect the classical formulation of entropy production in terms of generalized forces and flows. Applying the quantum phase-space method to calculate Wigner entropy production helps us identify heat and squeezing fluxes and their corresponding generalized forces in terms of input-noise correlations of both reservoirs. Our study highlights the essential role played by the correlation of the input-noise operators of the thermal...
A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]
, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology
Abstract
Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...
A review of quantum thermodynamics
, Article Iranian Journal of Physics Research ; Volume 19, Issue 3 , 2019 , Pages 489-521 ; 16826957 (ISSN) ; Rezakhani, A ; Sharif University of Technology
Isfahan University of Technology
2019
Abstract
In this article, we present a brief and elementary review of quantum thermodynamics and its achievements and challenges. This review includes an introduction to some fundamental concepts such as internal energy, heat, work, entropy, entropy production, thermal equilibrium, second law of quantum thermodynamics, relation between thermodynamics and information theory, as well as a discussion of how quantum effects such as entanglement and correlations affect performance of quantum heat engines. © 2019 by the authors. Licensee MDPI, Basel, Switzerland
Irreversible entropy production rate in a parametrically driven-dissipative system: The role of self-correlation between noncommuting observables
, Article Physical Review A ; Volume 105, Issue 5 , 2022 ; 24699926 (ISSN) ; Rafiee, M ; Sharif University of Technology
American Physical Society
2022
Abstract
In this paper, we explore the Wigner entropy production rate in the stationary state of a two-mode Gaussian system. The interacting modes dissipate into different local thermal baths. Also, one of the bosonic modes evolves into the squeezed-thermal state because of the parametric amplification process. Using the Heisenberg-Langevin approach combined with the quantum phase-space formulation, we get an analytical expression for the steady-state Wigner entropy production rate. It contains two key terms. The first one is an Onsager-like expression that describes heat flow within the system. The second term results from vacuum fluctuations of the baths. Analyses show that self-correlation between...
On the Achievable Rate Region Improvement in Information Networks Utilizing Cognition and Cooperative Strategies
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
User cooperation is an important concept in wireless networks to achieve best performance subject to low cost. Dynamic and broadcast natures of wireless networks are two indispensable characteristics of these networks. Therefore, when a user transmits his signal to the receiver, other users in his neighborhood may receive the signal as well. Hence, these neighbors can decide to cooperate with each other in transmitting their messages to the receiver. On the other hand, due to the dynamic nature of the wireless networks, one can assume that each user has some knowledge about the interference signals or the fading coefficient that are not known to the other users. Therefore by utilizing user...
Secure Index Coding
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Reliable and secure communication requires low error probability and low information leakage, respectively. But there are different metrics for error probability and information leakage. Two important reliability metrics are ϵ or zero probability of error. An ϵ-error criterion requires the (average or maximal) error probability to vanish as the blocklength increases, while a zero-error criterion, demands the error to be exactly zero for every given bloklength. Three important security metrics are weak, strong, or perfect secrecy. A weak notion of secrecy requires the percentage of the message that is leaked to vanish as the code blocklength increases, while a strong notion of secrecy...
Privacy Preserving Learning with Adjustable Utility Privacy Trade-off
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
The rapid evolution of artificial intelligence (AI) technologies has led to the widespread adoption of AI systems in diverse research and industrial fields. Deep neural networks, at the forefront of AI's power, demonstrate high performance by leveraging large volumes of training data. However, acquiring such vast amounts of data requires collaboration among individual data owners, who may have concerns about privacy. To address these concerns, various privacy-preserving methodologies have been proposed. These methodologies share a common goal of striking a balance between preserving privacy and maintaining data utility. This study aims to explore and analyze these privacy protection...
A Secure and Efficient Digital Signature Based on Polar Codes
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Regarding to the emergence of quantum computers and advances in the large scale implementation of them, exploiting hard problems of coding theory is of great importance.This family of problems, like those of lattices, has an acceptable resistance against classic and quantum attacks. Thus, they can be replaced with hard problems in number theory and algebra. Increasing dominance of cyberspace made us highly dependent to it. Consequently, preparing tools and methods to mitigate future threats is necessary. Digital signatures constitute an important family of cryptographic primitives. Code-based digital signatures are mostly suffering from two main drawbacks: large public key and long time of...
Coordinated Tuning of Power System Stabilizer in Iran Power Grid for Damping Local and InterArea Oscilation
, M.Sc. Thesis Sharif University of Technology ; Parniani, Mostafa (Supervisor)
Abstract
Power systems aredynamic and complex systems that are always subject to continuous changes and disturbance. Power system stability is a requirement for its satisfactory utilization. High speed Automatic voltage controllers with high gain tend to deteriorate both the electromechanical oscillation damping and small signal stability margin. Power system stabilizer (PSS) is a complementary controller that uses exciter voltage reference modulation to improve the electromechanical oscillation damping and stability margin. Optimal operation of PSS requires appropriate tuning according to the grid and power plant characteristics. In a largepower grid, absence or improper tuning of PSSs may cause one...
New Approaches for Achievability Proof in Network Information Theory: Asymptotic Regime and Beyond
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Two new frameworks for achievability proof in network information theory (NIT) are introduced . The first framework which we call it OSRB (Output Statistics of Random Binning) framework, uses random binning arguments and is based on a duality between channel and source coding problems. Furthermore, the OSRB framework uses pmf approximation arguments instead of counting and typicality which are used widely in conventional achievability proofs in NIT. This allows for proving coordination and strong secrecy problems, where certain statistical conditions on the distribution of random variables need to be satisfied. These statistical conditions include independence between messages and...
New Approaches for Achievability Proof in Network Information Theory: Asymptotic Regime and Beyond
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Two new frameworks for achievability proof in network information theory (NIT) are introduced . The first framework which we call it OSRB (Output Statistics of Random Binning) framework, uses random binning arguments and is based on a duality between channel and source coding problems. Furthermore, the OSRB framework uses pmf approximation arguments instead of counting and typicality which are used widely in conventional achievability proofs in NIT. This allows for proving coordination and strong secrecy problems, where certain statistical conditions on the
distribution of random variables need to be satisfied. These statistical conditions include independence between messages and...
distribution of random variables need to be satisfied. These statistical conditions include independence between messages and...
Multi Stage Multi-Secret Sharing Schemes
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
The subject of Secret Sharing refers to the methods that a secret information is shared (by a dealer) among a number of parties, so called participants, each having one or more shares, such that the predefined subsets of the participants, called authorized subsets, are able to regenerate the secret using their shares. A more general scheme which is called Multi Stage Secret Sharing (MSSS) is to share multiple secrets among the participants such that the authorized subsets can reconstruct the secrets in the consecutive stages; in these schemes, in addition to the individual shares, the dealer should provide the participants with a number of public values regarding the secrets. A Multi-Secret...
Achievable Rates for Relay Networks with “Partial Decode and Forward” Strategy
,
Ph.D. Dissertation
Sharif University of Technology
;
Aref, Mohammad Reza
(Supervisor)
Abstract
“Decode and Forward” is one of coding strategies used in relay channel and networks in which each relay in the network decodes the transmitted message by the sender and other relays in the network and then re-encode and transmit it to the other relays and the receiver in the network. This process results in the cooperation between the relays and the sender to remove the uncertainty of the receiver about the transmitted message. “irregular encoding-successive decoding”, “regular encoding-backward decoding” and “regular encoding-sliding window decoding” are different methods usually used in “Decode and Forward” strategy. “partial decode and forward” is a generalized form of “decode and...
Analysis of Key Agreement in Secure Networks from the View of Information Theory
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
In this thesis the problem of simultaneously generating multiple keys among multiple terminals is investigated. After providing a survey on the related works and exploiting the problem of sharing a common secret key and a private key among three terminals, we introduce a new source model which we call it the Four-Terminal model. We consider the problem of generating three kinds of keys among legitimate terminals and investigate the problem under two different scenarios, Backward and Forward scenarios, which depend on the kind of restrictions imposed on the usage of the public channel. We derive an achievable region for the backward scenario, using the combination of superposition coding and...
On the Capacity and Cooperative Strategies in Information Networks
,
Ph.D. Dissertation
Sharif University of Technology
;
Aref, Mohammad Reza
(Supervisor)
Abstract
Due to the remarkable growth in using communication networks such as ad-hoc, wireless and sensor networks, studying the building blocks of these networks (e.g., relay channel and interference channel) from information theoretic viewpoint and investigating cooperative strategies have recently received considerable attention. Also, owing to wide range of applications, state-dependent channels have been widely studied. In this dissertation, at first, we consider a state-dependent relay channel (SD-RC). For the cases wherein channel states are available causally or non-causally at different nodes, we propose new achievable rates for this channel using compress-and-forward strategy. Also we...
On the Capacity of Information Networks Utilizing Cognition and Cooperative Strategies
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Interference management is one of the key issues in wireless networks wherein multiple source-destination pairs share the same medium and frequency band and interfere with each other. The exponentially growth in the number of wireless systems and services results in the spectrum shortage which has emerged the technologies that increase the spectral efficiency. Providing the users with cognition equipments in these networks enables them to sense the medium and use the obtained data to adapt their transmissions to cooperate with other users and improve their own rates as well as the others which results in the cognitive radio technology. In order to access the full potential of this technology,...
Analysis of Secret Key Agreement in The Channel Model with Side Information
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
In this thesis, the problem of secret key agreement in the channel model with side information is studiedx. In order to investigate the problem, we consider three models according to the different ways of side information availability which are the state-dependent broadcast channel; the state-dependent broadcast channel in presence of public channel and the state-dependent wiretap channel with degraded versions of the channel state information.For the problem of secret key agreement in broadcast channels, two models, the state-dependent wiretap channel and state-dependent three receivers broadcast channel, are considered. We obtain inner and outer bounds of the secret key capacity region for...
Coordination in Cooperative Networks and Secret Key Agreement Using Common Information
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
In order to utilize cooperative resources of a network, we have to investigate cooperative networks and strategies. Information theory, by introducing different concepts such as coordination and common information, gives us a suitable tool to study cooperative networks and using their resources. In this thesis, we investigate coordination and secret key agreement in cooperative networks. Our study consists of two parts. In the first part, we consider coordination and its applications in cooperative networks. For this purpose, we introduce the triangular multiterminal network as a proper model for studying empirical coordination in multiterminal networks and establish an inner and outer...
A Dynamic Programming Approach for Network Air Cargo Revenue Management
, M.Sc. Thesis Sharif University of Technology ; Modarres, Mohammad (Supervisor)
Abstract
This research aims to establish a novel approach to meet the capacity utilization challenge of the freight forwarders in order to maximize the expected revenue in a cargo network. The two-dimensional cargo capacities are assumed to be stochastic and limited in each leg. A stochastic dynamic programming model is developed to demonstrate the maximization of expected revenue over a finite planning horizon, in which each fare class request is to be either accepted or rejected. Although the main problem is computationally intractable due to multidimensional state variable, it can be decomposed into one-dimensional capacity control sub-problems for each leg. A heuristic algorithm is developed to...