Sharif Digital Repository

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... 

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... 

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... 

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... 

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  

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... 

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... 

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... 

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... 

Mobility is one of the most challenging issues in mobile Ad-Hoc networks which has a significant impact on performance of network protocols. To cope with this issue, the protocol designers should be able to analyze the movement of mobile nodes in a particular wireless network. In this thesis, a new framework called Mobility Analyzer has been proposed. At first, Mobility Analyzer categorizes mobility models based on their mobility characteristics; subsequently, it uses mobility metrics for evaluating mobility traces which are collected by GPS or generated by mobility simulators. Finally, Mobility Analyzer recognizes the mobility model of mobility traces based on mobility metrics and measures... 

Recent researches show inefficient use of frequency spectrum such that there is shortage of frequency in operation. In order to overcome this problem cognitive radio are introduced that opportunist usage of frequency band is their prominent characteristic. Problems and challenges caused by using these networks are wide and increasing. In this thesis we focus on improving resource management algorithms in cognitive radio. In this study in order to have a dynamic and efficient management in choosing reliable and quality channels, reinforcement learning algorithms are used based upon existing data and experiences. Since this tool has the learning capability and analysis in dynamic situation of... 

Data aggregation is an efficient method to conserve energy by reducing packet transmissions in Wireless Sensor Networks. However, providing end-to-end data reliability is a major challenge when the network uses data aggregation. In this case a packet loss can miss a complete subtree of values, so greatly affect final results. Data transmission in multiple paths can tolerate this problem, but it may incur some computational error for duplicate-sensitive aggregates when aggregating individual sensor values multiple times. In this thesis, we have proposed a reliable data Aggregation protocol which uses the available path redundancy to deliver a correct aggregate result to the sink with a high... 

In recent decades, Securing mobile ad hoc networks has attracted much attention. Today, several security tools, such as intrusion detection systems are used in the network. Methods based IDS works on pattern recognition and anomaly detection are divided into two categories. Pattern recognition methods based on known attack patterns work with high detection rate, but do not have the ability to detect new attacks. Anomaly detection techniques have the ability to detect new attacks, but they have high false alarm rate.
In this thesis, an anomaly detection system based on artificial immune designed, implemented and evaluated.For example, an anomaly detection methods such cases, a variety of... 

With the development of technology and growing interest in using high performance and low price products, Wireless Sensor Networks (WSNs) are being dramatically deployed as an emerging technology. The main concern in WSNs is energy consumption that has an effect on sensor’s life time. In order to minimize the energy consumption, Data aggregation, which obtains aggregated values from WSNs, is an important functionality but yet time consuming. On the other hands, Emerging applications of Wireless Sensor Networks (WSNs) such as real-time detection of events need high-rate data collection, which is now an important challenge in WSNs. Multi-channel communication is one of the efficient methods to... 

Due to difficulties in setting up real mobile ad hoc networks, researchers must use simulation tools to evaluate their new protocols. One of the most important issues in MANET simulations is node movements. In reality nodes in MANET are transported by peopleand because of this,mobility models are based on human mobility. On the other hand, data of human mobility are rare and they are related to special locations so, none of the existing models have all the human mobility properties. By collecting data of human mobilityin the city of Tehran, new mobility model has been proposed that captures human mobility properties and is more realistic than existing models  

Due to their specific characteristics such as huge data loads, heavy processes, various quality of service requirements (delay, jitter and reliability), multimedia streams have different necessities in comparison with normal data streams. The challenges of wireless sensor networks (process power, storage capacity and power limitations) add up to the challenges faced in WMSNs. In order to improve the quality of service in wireless multimedia sensor networks, attention must be paid to all the network layers. In this study improvement of quality of service is sought through the design of a protocol for the network layer of the wireless multimedia sensor network.
This protocol tries to... 

Cognitive Radio (CR) technology enables dynamic spectrum access (DSA) to overcome the problems of unlicensed bands which is becoming overcrowded. However, providing an acceptable quality of service (QoS) for cognitive users requiresmore sophisticated approachesdut to the existence of primary users (PU) with their high priority over licensed bands. Additionally, reducing interference with primary users so that they can communicate without interruption is of extreme importance. In order to meet cognitive user’s quality of service as much as possible and reduce interference with PUs, a new class-based multipath on-demand routing protocol for cognitive radio networks (CMORC) is proposed. CMORC... 

As the applications of wireless sensor networks are expanding at an increasing rate, design of these networks so that they conform to the requirements of a specific application is considered to be a major challenge. Regarding to the specific application, network designers consider various suitable parameters to improve and then to enhance the efficiency of the network. Parameters included are such as area coverage, lifetime, reliability and etc which can significantly improve with the precise placement of nodes. Node localization problem in wireless sensor networks aiming at improvement of the performance parameters has been solved by different methods. In this thesis, in order to solve this... 

The abstract is the most important section of the thesis because many readers limit most of their reading to abstracts, saving in-depth reading for specific theses. It should give the reader a "preview" of what's to come. The abstract should emphasize new and important aspects of the study or observations. The purpose of the abstract is to allow researchers to decide whether or not to read the whole thesis. The abstract is what researchers read first to decide if the thesis is important, interesting, and it allows them to assess the relevance of a thesis to their own research, without having to read the entire thesis. Thus, it is crucial that the abstract both summarize succinctly the key... 

Along with the huge applications of wireless networks and creation of advanced wireless technologies, such as Bluetooth, WiFi, 3G and 4G, an evolution of Mobile Ad Hoc Networks emerged called opportunistic networks. In these networks, network topology is unpredictable; therefore, to send the message to the destination, moving nodes were used opportunistically. So one of the main challenges in this type of network is the routing problem. Amongst existing methods, methods that apply context information can help greatly to choose the right path. In this thesis a method was presented to gather information applying cell network classification and learning cellular automata, from the location of...