Sharif Digital Repository

Removing SAW filter from the input of a receiver makes the receiver extremely vulnerable to all sorts of blockers and interferers. It is shown in this thesis that due to existing large out-of-band blockers the linearity of the saw-less receiver has to be considerably higher than that of the conventional receivers with input SAW filter. These ever-present and unwanted signals that show up in the absence of the input SAW filter are divided into two groups of far and near out-of-band blockers and interferers. It is shown that removing these groups of unwanted signals require two distinct approaches, one for near and the other for the far out-of-band blockers. An inclusive solution to protect... 

Gain bandwidth products of Operational Amplifiers are dependent to power consumption. In this thesis we introduce negative capacitance circuit as a candidate to improve GBWs of OPAMPs in constant power, or achieve the requested GBW in lower power consumption. First we characterize negative capacitance circuit and introduce a model for that. Then we see how pole-zero placement will change, when we add negative capacitance circuit to a circuit node. As an application we use this circuit in Folded Cascode and Current mirror OPAMPs and give design guideline for this topologies. A three stages and a one stage OPAMP is designed in 0.18um CMOS, for the application of negative capacitance... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C... 

In real-time systems, jobs that miss their deadline are considered worthless or ineffective. Nowadays, real-time applications (such as multimedia) that communicate through software-defined networks (SDN) are widely used and will continue to expand in the future. SDN is an emerging network architecture in which control plane is separated from data plane to manage it directly. In this research, we make changes to the controller and the switch used in such network to deliver real time packets or real-time flows (such as video) on time, as much as possible. As missed deadline packets are worthless and they waste bandwidth, dropping them is a solution. Moreover, the controller can drop flows that... 

Nowadays, one of the problems of network designers and users is the correctness of network equipment functionality. Since routers play an important role in information transfer between various networks and communicate with each other through a routing protocol, any violation of such protocol can result in the network's failure or defective transfer of data. Thus, being assured of the conformance of the implemented protocol in a router with what has been defined in the protocol's standard is of great significance. To this end, before using or exposing a router, network equipment testers should run protocol conformance tests on it and insure its correct functionality. This brings up the... 

In order to increase the network performance, to discover network security threats, to guarantee the quality of services, to simulate networks and develop new network protocols, network designers and operators need software tools to analyze the network traffic. The first step to do this analysis is network monitoring. This can be done by using various software and hardware tools.
In this research we developed a tool which analyzes the network traffic using appropriate statistical methods. The models which are analyzed in this application are: Poisson, Self-similar and Weibull. This application analyzes the network traffic based on this statistical models and calculates their parameters.... 

The increasing number of road accidents and fatalities have yielded the introduction of several solutions by related industries such as automobile manufacture. Proposed solutions can be classified into two categories: passive, such as airbags, and active such as ABS ad ITS-based technologies. Inter vehicles communication let the communication between vehicles(V2V) or between vehicles and road infrastructure (V2I) by relying on DSRC technology and standards. Intelligent Transportation System (ITS) has three main types of applications namely safety, traffic and commercial. Safety applications are the main goal of vehicular communication, and real time guarantee in safety applications is so... 

Network Function Virtualization (NFV) is a new paradigm in computer networks for implementing network functions on general-purpose common-of-the-shelf processors. The revolutionized NFV architecture has shown to be a suitable replacement for hardware middleboxes. NFV is in high demand because of its lower costs, increased flexibility, and more scalability. However, the ever-growing volume of network traffic and increased data transfer speed in computer networks have made achieving high performance the major issue in this area. With thousands of processing cores and high memory bandwidth, Graphical Processing Units (GPUs) are potentially an appropriate solution to accelerate network... 

A novel internetworking paradigm, software-defined exchange (SDX), allows multiple independent administrative domains to share computing, storage, and networking resources. Although the term SDX is very recent, the concept has already been used by many distinct disciplines.We argue that the advent of Software Defined Networking (SDN) provides a unique opportunity to effectively detect and contain network security problems such as DDoS attacks. DDoS attacks can easily exhaust the controller's or the switches' computing and communication resources and hence, breakdown the network within a short time. In this thesis we extend these functionalities with an efficient, scalable and light weight... 

Due to the growing need of users to establish voice over IP (VoIP) communications, the low quality of voice transmission that do not meet their needs leads to their dissatisfaction. For this reason, the VoIP quality improvement has become one of the most important challenges facing the current domain of network communications. The analysis of the quality of network services in the VoIP traffics is an integral part of the quality assurance and improvement process of the multimedia networks. Hence, "user satisfaction" monitoring and evaluation of voice communications (also known as "Quality of Experience"), in addition to adaptive improvement of the speech quality in such communications, are... 

Software Defined Networking (SDN) is an emerging paradigm which makes the network programmable by separating the control plane from data plane and makes both planes to work independently. There is a centralized controller and a programmable data plane in these networks architecture and forwarding data packets is realized by programming the data plane via an open interface called OpenFlow. OpenFlow is a communication protocol between control and data planes. The centralized architecture of these networks provides a global view of the underlying network to upper applications and brings numerous advantages such as routing, traffic engineering and QoS control. Despite these advantages there are... 

Payload Attribution Systems (PAS) are one of the most important tools of network forensics for detecting offenders and victims after the occurrence of a cybercrime. A PAS stores the network traffic history in order to detect the source and destination pair of a certain data stream in case a malicious activity occurs on the network. The huge volume of information that is daily transferred in the network means that the data stored by a PAS must be as compact and concise as possible. Moreover, the investigation of this large volume of data for a malicious data stream must be handled within a reasonable time. For this purpose, several techniques based on storing a digest of traffic using Bloom...