Sharif Digital Repository

The quality of service in Wireless Multimedia Sensor Networks (WMSNs) is related to packet loss rate. Recently dierent studies have been done on developing ecient protocols in the transport layer for controlling packet loss in WMSNs. However, all of these protocols are independent of the characteristics of the multimedia content. In this thesis, a novel transport layer protocol, called User Datagram Dispatcher Protocol (UDDP), is proposed to minimize the packet loss ratio in WMSNs by considering trac characteristics, the inter-arrival pattern of packets and packet priority. UDDP is a new cross-layer transport layer that uses information of MAC and application layers to distribute packet... 

Identification protocols facilitates two participants A and B to identify themselves to each other. Beside identification, A and B can exchange a secret value along with the identification process as the key exchange identification protocol.A secure key exchange identification protocol hould utilize perfect forward secrecy (PFS) property. PFS means if an attacker could compromise an entity in future and gain its long-term key, he cannot succeed to extract previous session keys. So, he will be unable to decrypt previous messages and they will remain secure. Because of the low power and storage of light devices, updating secret shared keys is a solution to reach PFS in such protocols. A major... 

Peer to peer networks and especially peer to peer live video streaming systems are becoming more and more popular these days. To disseminate the video chunks in a live P2P video streaming system all users should contribute in uploading the video chunks; however there are some selfish peers who tend to download video chunks from the network while they do not upload any data to the network; these peers are called free-riders. With incorporating the incentive mechanisms in peer to peer live video streaming systems the chance of free-riders to get the full video or the video with the intended quality will be very low. In this research we propose a push-pull live video streaming system with a... 

The purpose of this dissertation is proposing a probabilistic model in transition systems of records. In these systems, two acceptance state of finite and infinite string have proposed which acceptance state of finite string is called probabilistic finite automata of records and acceptance state of infinite string is called probabilistic buchi automata of records. The buchi automata of records is an operational semantic for Reo coordination language. Reo is a coordination language to coordinate existing component of a component based system. Reo circuits with non-deterministic and probabilistic channel can be modeled by proposing probabilistic buchi automata of records. In this dissertation... 

Common Object Request Broker Architecture (CORBA) is a standard for hybrid applications that is designed and supported by Object Management Group (OMG). This standard defines protocols and Relational Data Model Objects / Services which can be connected into heterogeneous software (written in different languages). So we can use CORBA to share the distributed object platform, without worrying about where they are located or who has designed them. CORBA can package the codes (in some programming languages) and add the packaging information, such as the ability to execute the codes and how to implement them. So this package or object code can execute some other programs or CORBA objects that... 

Today’s biggest IoT companies are built on the extraction of insight from data of sensors, and data processing has become crucial in IoT businesses. Nevertheless, the size of data which should be processed is growing significantly fast. The pace of the data growing has changed the nature of data processing in IoT. Today, IoT industries demand highly scalable and fault tolerant data processing architectures which can handle the massive amount of data. In this research, we presented a distributed architecture for scalable and resilient data processing based on the Liquid which is a nearline and offline big data architecture. We used the Reactive Manifesto to design the architecture highly... 

Due to the high processing capacity of GPGPUs and their requirement to a large and high speed shared memory between thread processors clusters, exploiting Spin-Transfer Torque (STT) RAM as a replacement with SRAM can result in significant reduction in power consumption and linear enhancement of memory capacity in GPGPUs. In the GPGPU (as a many-core) with ability of parallel thread executing, advantages of STT-RAM technology, such as low read latency and high density, could be so effective. However, the usage of STT-RAM will be grantee applications run time reduction and growth threads throughput, when write operations manages and schedules to have least overhead on read operations. The... 

In recent years, the usage of Internet bandwidth has been increased by emerging applications such as Video on Demand (VoD).As the popularity of VoD increases among the Internet users, some new problems like bandwidth limitations and congestion embark. For solving mentioned problems, Content Delivery Networks (CDN) has been introduced. Using CDN approaches either in ISP or organization is also known as Telco CDN. Generally implementing CDN approaches to process all requests either in ISP or organization can cause bottleneck. On the other hand, Software Defined Networks (SDN) could bring us new tools and opportunities which enables us to implement novel methods to confront these problems.... 

IP multicasting, content distribution networks (CDN) and recently P2P streaming systems are the main scalable methods that have been researched. IP multicasting has not been activated in service provider networks due to some fundamental deployment problems and CDNs require the deployment of a large number of servers throughout the Internet. Pure P2P architecture is a more challenging approach for constant quality and continuous video streaming due to the churn nature and limited resource of the Internet peers. Therefore, we design a hybrid architecture for large-scale video streaming applications that combine an infrastructure of CDNs with the P2P network. Unlike previous work, in... 

In healthcare field to reduce costs, high availability, increasing reliability, access to data from multiple locations and manage distributed information between centers, doctors and patients; there is a certain need to a distributed system and cloud services are a good option to meet that need. In this thesis different models of service delivery in the healthcare were studied which included traditional and cloud models. Also from the survey, the metrics which we used to compare these models were extracted. These metrics include quantitative metrics such as cost, setup time, availability, multi-regional, elasticity, efficiency and qualitative metrics including integrity, privacy,... 

Many lattice-based public key encryption schemes are forced to use long keys. To deal with this problem, structured lattices such as NTRU can be used. Lattice-based searchable public key encryption schemes are no exception. Furthermore, in most existing searchable public key encryption schemes, it is assumed that the user searches documents with only one keyword. However, using a conjunctive keyword search, we can search for documents containing several keywords by executing the trapdoor generation algorithm only once. On the other hand, in most of the published searchable public key encryption schemes, storing and searching encrypted keywords are responsibility of a central entity called... 

Secure communication among members of a group requires a shared cryptographic key. To address this issue, group key agreement and exchange schemes are introduced. In group key exchange schemes, a trusted center generates a shared key for the group and sends it securely to the group members. But in group key agreement schemes, all members of the group are involved in generating group keys. One of the useful ways in these schemes is to use secret sharing to share keys. A public key infrastructure is used to secure the distribution of the shares in secret sharing schemes. As quantum computers threat the classic cryptographic algorithms that are based on the difficulty of factoring large numbers... 

Based on fog computing paradigm, new applications have become feasible through the use of hardware capabilities of smart phones. Many of these applications require a vast amount of computing and real-time execution should be guaranteed. Based on fog computing, in order to solve these problems in is necessary to offload heavy computing to servers with adequate hardware capabilities. On the other side, the offloading process causes time overhead and endangers the real-timeliness of the application. Also, because of the limited battery capacity of the handheld devices, energy consumption is very important and should be minimized.The usual proposed solution for this problem is to refactor the... 

Web service technology is becoming increasingly popular since it is very bene?cial in di?erent types of applications. Due to a dramatical increase in the number of developed web services, the service discovery process has become crucial for using web services e?ciently. Service is an adaptive, self-describing, modular application, which may be used in either web or an internal network. Service providers should o?er the services along with a description ?le called advertisement explaining the speci?cations and functionalities of the service. Traditional service discovery methods are based on syntax and keyword matching, which may not satisfy the requester’s desired requirements and will... 

In this study, given the increasing challenges urban and intercity transportation face in the modern world, including population growth, urban development, and environmental concerns, an innovative approach to optimize the use of car-sharing vehicles is presented. The research aims to develop a multi-objective mathematical programming model for the optimal allocation of car-sharing vehicles, considering key factors such as transportation costs, travel time, and environmental pollution. This seeks to reduce costs, increase efficiency, shorten travel times, and contribute to environmental sustainability. Initially, a thorough literature review was conducted to provide a comprehensive... 

In this thesis, unconstrained convex quadratic optimization problems subject to parameter perturbations are considered. A robustification approach is proposed and analyzed which reduces the sensitivity of the optimal function value with respect to the parameter. Since reducing the sensitivity and maintaining a small objective value are competing goals, strategies for balancing these two objectives are discussed. Numerical examples illustrate the approach  

The process of portfolio construction and optimization can be broken down into three main steps: selecting appropriate assets, allocating capital, and monitoring and adjusting the portfolio. This study focuses on evaluating the performance of the Hierarchical Risk Parity (HRP) method for capital allocation in investment portfolios, specifically in Iran’s capital market. The aim is to enhance the method's effectiveness by implementing alternative correlation calculation approaches, such as Wavelet and Chatterjee correlations. The study utilizes three different portfolios containing assets from the Tehran Stock Exchange, the US stock market, and the cryptocurrency market. The primary objective... 

Secure computation has obtained significant attention in the literature recently. Classic architectures usually use either the Garbled Circuit (GC) or the Goldreich-Micali-Wigderson (GMW) protocols. The GC and GMW protocols are applied to functions which are represented as a Boolean circuits. So far, to reduce the complexity of communications in these protocols, various methods have been proposed. The best known work in both methods reduces the communication up to almost 2k-bits (k is the symmetric security parameter) for each AND gate, and using XOR gate is free. In this paper, by combining GC and GMW, we propose a scheme that requires an Oblivious Transfer (OT) and a 2-bit data transfer... 

Due to the increasing development of digital systems based on limited energy sources (i.e. battery), energy efficiency has become one of the most important concerns in the design of these systems. The use of multi-core architecture is an effective solution for the problem of reducing energy consumption. Hence using it in digital systems has become more common. In addition, enabling methods for reducing energy consumption on processor, helps in making energy more efficient. DVFS and DPM are the two major methods used for reducing dynamic and static energy consumption of processors. The using of multi-core architecture due to the higher chip density, results the static and dynamic energy... 

Stock price patterns are a technical analysis approach to forecast future trends with tremendous practical benefits. However, the current algorithms solely rely on machine learning techniques and deep neural networks which could be a problem in countries where data sets such as these are not available. We propose an algorithm based on geometry and mathematics for this problem, leading to an O(n^3logn + n^2k) complexity, where k is the number of triangular patterns