Loading...
Search for:
stochastic-geometry
0.006 seconds
Poisson Voronoi Tessellation In High Dimensions
,
Ph.D. Dissertation
Sharif University of Technology
;
Zohori Zangeneh, Bijan
(Supervisor)
;
Shahshahani, Mehrdad
(Co-Advisor)
Abstract
This thesis is devoted to study some asymptotic behaviors of Poisson Voronoi tessellation in the Euclidean space as dimension of the space tends to infinity. First we use Blaschke-Petkantschin formula to prove that the variance of volume of the typical cell tends to zero exponentially in dimension. It is also shown that the volume of intersection of the typical cell with the co-centered ball of volume converges in distribution to the constant . Next we consider the linear contact distribution function of the Poisson Voronoi tessellation and compute the limit when dimension goes to infinity. As a byproduct, the chord length distribution and the geometric covariogram of the typical cell are...
A Stochastic Model for Cancer Tumor Growth
, M.Sc. Thesis Sharif University of Technology ; Foroughmand Arabi, Mohamad Hadi (Supervisor) ; Alishahi, Kasra (Co-Supervisor)
Abstract
Cancer can be defined as a stochastic phenomenon. Thus, the tumor growth can be defined as a stochastic process. A Cancer tumor can be analyzed by its geometric shape. Furthermore, computing fractal dimension of shapes is a useful technique to analyze chaosity and complexity of shapes. This approach can be used to compare results from laboratory with simulated results of a mathematical model. A stochastic model of tumor growth will be presented. And some geometrical properties will be analyzed through computer simulation of the model
Phase Transition in Convex Optimization Problems with Random Data
, M.Sc. Thesis Sharif University of Technology ; Alishahi, Kasra (Supervisor)
Abstract
In the behavior of many convex optimization problems with random constraints in high dimensions, sudden changes or phase transitions have been observed in terms of the number of constraints. A well-known example of this is the problem of reconstructing a thin vector or a low-order matrix based on a number of random linear observations. In both cases, methods based on convex optimization have been developed, observed, and proved that when the number of observations from a certain threshold becomes more (less), the answer to the problem with a probability of close to one (zero) is correct and the original matrix is reconstructed. Recently, results have been obtained that explain why this...
Delay and Throughput Analysis of Fiber-radio Networks Based on 5G Heterogeneous and NG-PON2
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor) ; Beyranvand, Hamzeh (Supervisor)
Abstract
In the future mobile network 5G will offer high speed and low delay but millimeter wave link are poor at penetrating into solid objects. Thus future network will be a hybrid of traditional sub-6GHz macrocells and denser 5G small cells. We develop a general analytical model to derive delay and throughput in this network. First we analyse the initial access delay which is very important in Internet of things and machine to machine communication. Then we go into data delay of network. With the foreseeable explosive growth of small cell deployment, backhaul has become the next big challenge in the next generation network. We analyse two option of fiber and millimeter wave. At the end we have end...
Secure Transmission Strategies in Massive MIMO Systems in Presense of a Jammer
, M.Sc. Thesis Sharif University of Technology ; Mirmohseni, Mahtab (Supervisor)
Abstract
Massive MIMO systems are systems, where the base station has many number of antenna so each user’s channel is orthogonal to one another.These systems have some valuable advantages such as reduction of energy needed for transmission and significant improvement in spectral efficiency, which makes them be suitable for next generation of wireless communication systems. Another advantage of Massive MIMO systems is inherent resistance against passive eavsdroppers due to having a directed power radiation in direction of the desired user. However another physical layer attack threat these systems: attacking in pilot phase then eavsdropping in downlink phase which must taken care of in physical...
Resource Allocation in mmWave Massive MIMO Transmission in the Presence of Neighboring Cells Interference
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
In Massive multiple input multiple output (MIMO) systems, due to utilizing a large antenna array in each base station, each user’s channel is orthogonal to one another. These systems have some valuable advantages such as the reduction of energy needed for transmission and significant improvement in spectral efficiency, which makes them be suitable for the next generation of wireless communication systems. In this thesis a massive MIMO working is considered on TDD mode, for wich the channel estimation is done in the base station using the pilot sequences recieved from users. At the beginning of each coherence block, users send their pilot sequences and the rest of the times is allocated to...
Performance Analysis of Flooding-based Broadcasting in Wireless Networks
, Ph.D. Dissertation Sharif University of Technology ; Hossein Khalaj, Babak (Supervisor)
Abstract
Broadcasting in wireless ad hoc networks serves many important tasks such as data dissemination and route establishment in which one node sends its data to all other network nodes. The most popular form of broadcasting adopted by many ad-hoc protocols is flooding. In flooding, each node receiving a packet from a neighboring node rebroadcasts it exactly once. Wide adoption of flooding for broadcasting traffic is mainly due to its simplicity. The importance of performance analysis of flooding lies on its aforementioned popularity. The parameters of interest in analysis of flooding are network coverage, energy consumption and broadcast throughput while network coverage is the average percentage...
Neutronic Simulation of Pebble Bed Reactors
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Nasser (Supervisor)
Abstract
The Very-High Temperature Reactor (VHTR) design is one of the six candidates for the Generation IV nuclear reactors. The reactor core type of the VHTR design is either prismatic or pebble-bed. In pebble bed reactors, the core is filled of thousands of graphite and fuel pebbles. Fuel pebbles in these reactors consist of TRISO particles, which are embedded in a graphite matrix stochastically. The reactor core is also stochastically filled up of fuel and dummy pebbles with an unequal ratio. These two stochastic geometries are the so-called double heterogeneous of this type of reactors. In the current study, a...
Improving Physical Layer Security for Cellular Users in Threat of Eavesdroppers
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Security for wireless communication networks has become a crucial issue because of the broadcast nature of wireless channels. On every cellular network Since it is possible for passive nodes to easily overhear the confidential information transmitted between transmitter and receiver, it is necessary to provide secure communication.When a cellular user wants to communicate with a node or base station on the cellular network, it expects that information will be transmitted and received without interference, with enough quality and without eavesdropping. On the other hand In practical scenarios, we know that cellular network nodes are not equipped with ideal equipment and some percent...
Physical Layer Security in Wireless Communication Networks in Presence of Intelligent Reflecting Surfaces
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor) ; Mirmohseni, Mahtab (Co-Supervisor)
Abstract
The ever-increasing demand for wireless communication has raised the need for better utilization of bandwidth and energy. Intelligent Reflecting Surface (IRS) is an emerging technology that has been proposed for the sixth generation of wireless communication. In this thesis, we study the essential role these surfaces can play in improving the physical layer security.First, we consider a relatively realistic scenario for the location of the eavesdroppers. In this scenario, we will assume that the transmitters, users, and eavesdroppers all use a single antenna configuration, and the eavesdroppers are placed randomly across the studied region. Two notable parameters in physical layer security,...
Neutronic simulation of a pebble bed reactor considering its double heterogeneous nature
, Article Nuclear Engineering and Design ; Volume 253 , 2012 , Pages 277-284 ; 00295493 (ISSN) ; Vosoughi, N ; Sharif University of Technology
2012
Abstract
In pebble bed reactors, the core is filled with thousands of graphite and fuel pebbles. Fuel pebbles in these reactors consist of TRISO particles, which are embedded in a graphite matrix stochastically. The reactor core is also stochastically filled with pebbles. These two stochastic geometries comprise the so-called double heterogeneous nature of this type of reactor. In this paper, a pebble bed reactor, the HTR-10, is used to demonstrate a treatment of this double heterogeneity using the MCNP5 Monte Carlo code and MATLAB programming. In this technique, TRISO particles are modeled in a pebble using the expanded FILL and LATTICE features of MCNP5. MATLAB is used to generate random numbers...
Performance analysis of the clustered caching wireless networks considering stochastic geometry approach
, Article 2016 8th International Symposium on Telecommunications, IST 2016, 27 September 2016 through 29 September 2016 ; 2017 , Pages 320-324 ; 9781509034345 (ISBN) ; Zeinalpour Yazdi, Z ; Hossein Khalaj, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Recently, caching of the popularity video files in the caches near to the users has been proposed as a promising way to reduce data traffic. These caches can be considered as the nodes which their transmission ranges are limited but have significant storage capacity and are known as the helper nodes. To evaluate the performance and efficiency of the caches, a suitable model for their distributions should be taken into account. Stochastic geometry is a useful tool for modeling these nodes. In this paper, the helper nodes and users are distributed according to the Poisson point process distribution. However, to manage the interferences and their access to a distributed cache, the helper nodes...
Stochastic geometry modeling and analysis of single- and multi-cluster wireless networks
, Article IEEE Transactions on Communications ; Volume 66, Issue 10 , 2018 , Pages 4981-4996 ; 00906778 (ISSN) ; Makki, B ; Haenggi, M ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
This paper develops a stochastic geometry-based approach for the modeling and analysis of single- and multi-cluster wireless networks. We first define finite homogeneous Poisson point processes to model the number and locations of the transmitters in a confined region as a single-cluster wireless network. We study the coverage probability for a reference receiver for two strategies; closest-selection, where the receiver is served by the closest transmitter among all transmitters, and uniform-selection, where the serving transmitter is selected randomly with uniform distribution. Second, using Matern cluster processes, we extend our model and analysis to multi-cluster wireless networks. Here,...
Coverage analysis of finite cellular networks: A stochastic geometry approach
, Article 2018 Iran Workshop on Communication and Information Theory, IWCIT 2018, 25 April 2018 through 26 April 2018 ; 2018 , Pages 1-5 ; 9781538641491 (ISBN) ; Makki, B ; Haenggi, M ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
This paper develops a tractable modeling and analysis framework for finite cellular wireless networks using stochastic geometry. Defining finite homogeneous Poisson point processes to model the number and locations of access points in a confined region, we study the coverage probability for an arbitrarily-located reference user that is served by the closest access point. The distance distribution and the Laplace transform (LT) of the interference are derived. We also derive a closed-form lower bound on the LT of the interference. Our analyses reveal that a higher path loss exponent improves the coverage probability and that there is a location where the coverage probability is maximized. ©...
Stochastic design and analysis of user-centric wireless cloud caching networks
, Article IEEE Transactions on Wireless Communications ; Volume 19, Issue 7 , 2020 , Pages 4978-4993 ; Nasiri Kenari, M ; Debbah, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This paper develops a stochastic geometry-based approach for the modeling, analysis, and optimization of wireless cloud caching networks comprised of multiple-antenna radio units (RUs) inside clouds with coordinated multi-point transmissions and guard zones. We consider Poisson cluster processes to model RUs and users, and the probabilistic content placement to cache files in RUs. Accordingly, we study the exact hit probability for a user of interest for two strategies; closest selection, where the user is served by the closest RU that has its requested file, and best power selection, where the serving RU having the requested file provides the maximum instantaneous received power at the...
Asynchronous downlink massive MIMO networks: A stochastic geometry approach
, Article IEEE Transactions on Wireless Communications ; Volume 19, Issue 1 , 2020 , Pages 579-594 ; Azimi Abarghouyi, S. M ; Makki, B ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Massive multiple-input multiple-output (M-MIMO) is recognized as a promising technology for the next generation of wireless networks because of its potential to increase the spectral efficiency. In initial studies of M-MIMO, the system has been considered to be perfectly synchronized throughout the entire cells. However, perfect synchronization may be hard to attain in practice. Therefore, we study a M-MIMO system whose cells are not synchronous to each other, while transmissions in a cell are still synchronous. We analyze an asynchronous downlink M-MIMO system in terms of the coverage probability and the ergodic rate by means of the stochastic geometry tool. For comparison, we also obtain...
Massive MIMO-NOMA systems secrecy in the presence of active eavesdroppers
, Article 30th International Conference on Computer Communications and Networks, ICCCN 2021, 19 July 2021 through 22 July 2021 ; Volume 2021-July , 2021 ; 10952055 (ISSN); 9780738113302 (ISBN) ; Mirmohseni, M ; Papadimitratos, P ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Non-orthogonal multiple access (NOMA) and massive multiple-input multiple-output (MIMO) systems are highly efficient. Massive MIMO systems are inherently resistant to passive attackers (eavesdroppers), thanks to transmissions directed to the desired users. However, active attackers can transmit a combination of legitimate user pilot signals during the channel estimation phase. This way they can mislead the base station (BS) to rotate the transmission in their direction, and allow them to eavesdrop during the downlink data transmission phase. In this paper, we analyse this vulnerability in an improved system model and stronger adversary assumptions, and investigate how physical layer security...
Modeling and Analysis of Stochastic Clustered Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Wireless communication networks are undergoing a significant transformation from coverage-driven deployment of macrocells to user-centric and cluster-based capacity-driven deployments of low-power base stations (BSs), usually at the locations of high user density. On the other hand, the increasing irregularity and randomness in the locations of nodes has led to an increased interest in the use of random spatial models along with tools from stochastic geometry and point process theory for their accurate modeling and tractable analysis. To this end, this thesis investigates clustered networks for different wireless applications. In this regards, comprehensive and tractable analytic frameworks...
Stochastic geometry modeling and analysis of finite millimeter wave wireless networks
, Article IEEE Transactions on Vehicular Technology ; Volume 68, Issue 2 , 2019 , Pages 1378-1393 ; 00189545 (ISSN) ; Makki, B ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper develops a stochastic geometry-based approach for the modeling and analysis of finite millimeter wave (mmWave) wireless networks where a random number of transmitters and receivers are randomly located inside a finite region. We consider a selection strategy to serve a reference receiver by the transmitter providing the maximum average received power among all transmitters. In our system model, we employ the unique features of mmWave communications such as directional transmit and receive beamforming and different channels for line-of-sight (LOS) and non-line-of-sight (NLOS) links. Accordingly, deploying a blockage process suitable for mmWave networks, we study the coverage...