Sharif Digital Repository

Today, we live in an information age where all people can access the vast amount of data in the world by connecting to the Internet.Since the Internet has expanded significantly to share information, some individuals and organizations seek to be able to prevent the possible sabotage of some people by monitoring network users. Analysis of computer network traffic is one of the importance issues that many activities have been done in this area. One of the most important questions in traffic analysis is to identify the main content of traffic on the encrypted network. Numerous studies have shown that the traffic of websites visited through the Tor network, including Specific information that... 

Introducing a new paradigm, cognitive radio, for spectrum utilization of unlicensed users, new research on spectrum utilization of licensed users was planned. The results show inefficiency of spectrum usage, so cognitive radio network was introduced. Cognitive radio network should not have any affect on primary users activity, so these networks face with some chalenges and the important ones is the supporting of the QoS.
In this thesis after analyzing of the proposed routing metrics for finding best end-to-end path, the important ones of them were selected for more precise analyzing. After analyzing we find some disadvantage, can be improved by multi-radio. Although all of these metrics... 

The integration of radar and communication functionalities into a unified Joint Radar-Communication (JRC) system offers enhanced spectral efficiency and reduced hardware complexity. Recognized as a key enabler for next-generation wireless networks, JRC systems require a careful balance between radar and communication demands, where waveform design plays a pivotal role in achieving this equilibrium. Although waveform design has been extensively studied separately in radar and communication domains, the requirements of modern networks necessitate a unified approach that simultaneously addresses the needs of both systems. This thesis advances waveform design methodologies for JRC systems,... 

Wireless Multimedia Sensor Networks (WMSNs) have many applications in survilient systems. In this kind of applications, although we have limited energy and computational power, we should provide minimal security to transfer data in such networks. These constraints are more crucial when we use multimedia that has more data for processing and transmission. Because of this huge amount of data, we must use compression for using less energy in both processing and transmission.
In some algorithms, it has been proposed to integrate compression and encryption in order to decrease time and power consumption. The proposed algorithm is several times faster than AES (Advanced Encryption Standard) or... 

In opportunistic networks, the nodes have ad-hoc communications that are formed directly between them, without any infrastructure, and not by any using any other intermediate node. In case that the destination node is not in the same region as the source during the sending of a message, the source will send the message to one or a few of its neighbors so that they can store and carry out the message to the original destination in cooperation known as Store-Carry-Forward Mechanism. Remarkably, in most cases, the devices involving in this type of network, e.g., smartphones, have limited source of energy or they use a battery, there is a need to minimize the energy consumption in the nodes.... 

In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has... 

Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features... 

In this research with Finite Element Methods in ABAQUS, numerical modeling has done in three-dimensions, which can be used to determine the effect of different factors on the surface settlement. Also, various factors such as geotechnical conditions, tunnel diameter,tunnel depth, the impact of the thickness of the segments and the amount of eccentricity of the structure relative to the longitudinal axis of the tunnel considered in this study. Face Pressure Supports, and Grout Injection Pressures are taken into account, too.Tunnel drilling causes a change in the displacement area and creates a changing zone around the tunnel. In this regard, not only adjacent buildings will be affected by... 

An RFID (Radio Frequency Identification) device consists of a small and inexpensive microchip attached to an antenna. The chip can be very small and some RFID tags are thin enough to be embedded in paper. RFID are heavily used to track items in production environments and to label items in supermarkets, Hospital, Factory, License plate, Cattle….They are usually thought of as an advanced barcode. However, in this project we argue about RFID license plate and using RFID tags for recognize vehicle from distance. Radio Frequency Identification (RFID) tags has many applications in modern automatic and intelligent identification systems. Vehicles outfitted by RFID tags as License Plates, can be... 

The Vehicular Ad hoc Network (VANET) have been presented to enhance the safety and comfort of driver and passengers. Thus, the functionality of VANET is related to the accuracy of disseminated messages about surrounding environment. Therefore, it is critical to detect the true reports among false reports which they have been reported by malicious nodes. However, in this research, the proposed scheme presents a centralized trust management assessment scheme named Detection of Best Report (DBR) in vehicular ad hoc environments. Each received message is evaluated individually according to its reporter interactions during event reporting. Based on this evaluation in RSU, the most reliable nodes... 

Indoor Positioning Systems (IPS) are commonly used in context-aware environments in order to determine the location of any desired object. In such environments location awareness is a key to adequate response. There are several positioning technologies available such as beacon-based positioning, camera-based positioning, Wi-Fi positioning, etc. Among these positioning systems Radio Frequency Identification (RFID) positioning has significant advantages over other technologies. Flexibility, ease of implementation, cost and accuracy are key advantages for RFID positioning technology. RFID positioning systems are classified in three categories: RF signal analysis-based, active RFID and passive... 

Optimization of energy consumption is generally important in mobile networks and in particular in automotive networks. One of the challenges of installing roadside units in automotive case networks is to provide energy to the equipment assigned to these units. In some cases, power is easily available, but in many places, the cost of energy is very high and does not have economic justification. Therefore, optimization of energy consumption in roadside unit is of great importance. Typically, vehicles limitations in terms of energy consumption for communications are far lower than that of a roadside unit. In this dissertation, part of roadside communication to vehicles is shifted to the... 

Along with the emergence of the smart city concept and the increasing demand for a wide range of vehicles, the Internet of Vehicles (IoV) has attracted a lot of attention by providing numerous benefits including vehicle accident warning, reducing pollution levels and traffic congestion, as well as entertainment services. Furthermore, IoV offers various services combining Vehicular ad hoc networks (VANETs) and IoT in smart cities. However, these types of networks are exposed to a variety of security and privacy risks due to the wireless nature, because the sensitive message is transmitted through an insecure channel in the IoV-based smart city environment, therefore, it is necessary to... 

In 2008, a decentralized and distributed payment solution called Bitcoin was born. Since then, it has made the payment industry think about banks and companies on the one hand and government authorities on the other. By using mathematics and cryptography, Bitcoin was able to eliminate the need for trust and in this way it was able to eliminate intermediaries such as banks. In traditional financial affairs such as banks, the user must trust the bank and everything relies on the bank’s servers. While Bitcoin stores the history of transactions in a public and distributed ledger. This ledger is encrypted so that the state of the blockchain is always reliable. In Bitcoin’s decentralized and... 

The main idea of the upcoming research is to provide a way of benefiting from processing at the edge and processing in the fog for the open source platform openremote; In such a way that the central core of the platform can offload its processing tasks to the edge of the network. With this work, a large amount of the processes that used to be done by the core will be offloaded from the core. On the other hand, by applying processes at the edge of the network, it becomes possible to eliminate a large amount of overhead caused by raw data transmission, and as a result, the productivity of the network increases. In the current research, in addition to designing a model to add the mentioned... 

Reducing energy consumption is one of the challenges facing wireless sensor networks with many solutions introduced for them with each having advantages and disadvantages. Some of the solutions introduced are based on using movable sinks. In this project, we attempt at proposing a place for the establishment of sinks using genetic algorithm that can reduce energy consumption in the net knots and increase the net life. This work should be done after reviewing the results of past researches and introduced methods. We will analyze the practicality of the proposed model using simulation and will show their advantages over the previous mentioned methods  

The stock market is vital to the economy as it serves as a key indicator of economic health. AI algorithms can process vast amounts of market data at high speeds, identifying patterns and trends that are often invisible to human analysts. Forecasting future stock trends poses significant challenges due to the complex inter-stock and intra-stock dynamics that influence stock prices. Recently, graph neural networks have shown promising results by modeling multiple stocks as graph-structured data. However, many of these approaches depend on manually defined factors to construct static stock graphs, which fail to capture the rapidly changing interdependencies between stocks. In this work,... 

Focusing on developing the EEPS (Energy Electric and Power System) based on the SG (Smart Grid) infrastructure to achieve implementation of EI (Energy Internet) ultimately, in order to analyze and manage the energy/power consumption, requires a robust embedded EMS (Energy Management System) to implement real-time LF (Load Forecasting), prevent the power waste and realize consumption management which eventually leads toward the smart industries/buildings. STLF (Short Term Load Forecasting) is an essential component that an industrial plant requires to manage the power, regarding the load fluctuations during production, and compulsory requirement of cost mitigation. This thesis, in order to... 

Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained... 

Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,...