Sharif Digital Repository

In this thesis, we study the role of cooperation and security in multi-user channel from an information theoretic point of view. First, we review the wiretap channel as a fundamental model for the study of confidentiality in information theoretic security. To do this, we first introduce two measures for measuring the level of secrecy of confidential message, namely, average equivocation rate (AER) and equivocation rate in probability (ERP). By using a new proof, based on random covering, we show that the capacity-equivocation region of wiretap channel under AER and ERP is the same. To study cooperation in multi-user channel, we introduce the cooperative network in which each user can... 

This research is focused on optimization of empty freight railcars circulation by assuming cooperation among shipping companies. The objectives are twofold: first, to develop an efficient and effective model which can provide a useful management tool to improve freight car utilization for shipping companies; second, to show the advantages of Horizontal Logistics Cooperation (HLC).Two formulations have been developed for the empty railcar distribution problem, both seeking to find how railcars move not only at the lowest possible cost but also at the lowest possible delays under supply limitation and demand satisfaction. The problem is first formulated as a single-commodity network flow model... 

Ever increasing demand for higher data rate in wireless communication in the face of limited or underutilized spectral resources has motivated the introduction of cognitive radio for dynamic access to spectrum. In dynamic spectrum access a new type of users called secondary users measure the spectrum to see if it is occupied by licensed users (primary users or PU). When channel is empty secondary users can use it to transmit signal. This approach is called spectrum sensing. Hidden PU problem can severely defect detection ability of non-cooperativ spectrum sensing systems. Cooperative spectrum sensing (CSS) uses spatial diversity of spectrum sensors to tackle this problem. There are two kinds... 

In this thesis, a novel OFDMA-based cognitive cooperative relaying scheme is proposed in which cognitive users not only try not to interfere with primary users but also assist them by relaying their information. Both primary users (PU) and cognitive users (CR) communicate to a common base station (BS). Bit error probability (BEP) of primary users and outage probability of primary users are investigated to evaluate performance of the primary users. In all parts of this thesis, we assume that data of users is not jointly encoded across subcarriers. So, the outage probability and BEP are investigated for each subcarrier independently. In the last part of the thesis, it is assumed that data is... 

In this thesis, we consider multiple-antenna K-user interference channels with backhaul collaboration in one side (among the transmitters or among the receivers) and investigate the trade-off between the rate in the channel versus the communication load in the backhaul. In this investigation, we focus on a first order approximation result, where the rate of the wireless channel is measured by the degrees of freedom (DoF) per user, and the load of the backhaul is measured by the entropy of backhaul messages per user normalized by log of transmit power, at high power regimes. This trade-off is fully characterized for the case of even values of K, and approximately characterized for the case of... 

Consensus is the equality of desired states of agents. These states could be position, movement direction or other variables of agents. So far, different control algorithms are introduced which provide agents with consensus. In fact, one of the most significant topics in cooperative systems is the problem of determining the control algorithm so that agents reach consensus. These algorithms are called consensus algorithms. Properties of system matrices play an important role in consensus algorithms and analysis of their convergence. In this thesis, two consensus algorithms are presented for networks with fixed and switching topology respectively. In these algorithms an input signal is... 

With recent successes in laboratory tests, and in atmosphere and space demonstrations, there is no doubt that the free-space optical (FSO) communications is ready for operational deployment. Large bandwidth, unlicensed spectrum, excellent security, and quick and inexpensive setup are among its most attractive features. Despite their attractive features, FSO communications suffer from several challenges in practical deployment; the major of them is fading or scintillation and path loss. To overcome such limitations, Channel Coding along with MIMO and Cooperative techniques have been proposed. Although the promising effects of cooperative transmissions in RF communications have greatly been... 

In recent years, with the continuous growth and development of wireless communication systems, the demand for the use of radio spectrum has increased significantly, which has led to problems such as a shortage of spectrum. An effective solution to the spectrum shortage problem is to use cognitive radio. One of the main functions of cognitive radio networks is spectrum sensing and our focus in this study is to examine machine learning and deep learning methods to improve cooperative spectrum sensing. Since channel and noise parameters are not accurate in telecommunication systems, we need to use a method to estimate these parameters. In this regard, the structure of Bayesian with neural... 

In the recent years, the cooperative communications based on Network Coding have received significant attentions to simultaneously improve the diversity order and the network throughput. In this thesis, a new cooperative transmission scheme for the cooperative relay-based networks called “Convolutional Network-Coded Cooperation” (CNCC) is proposed, in which a systematic convolutional code is used in the network level. In this scheme, the systematic packets are directly transmitted by the sources, and the parity packets, calculated based on the received sources’ packets, are transmitted by the relays. The proposed CNCC scheme is considered in the cooperative networks including N sources, M... 

Nowadays, with the remarkable development of the robotics industry, there is an increasing demand for mobile robots. Mobile robots can be deployed individually or in groups for various tasks such as autonomous warehouses, search and rescue operations, firefighting operations, and maintenance and repairs. It is evident that performing certain tasks, such as moving large and long objects or firefighting operations, is more efficient when robots are deployed cooperatively, and in some cases, these tasks cannot be accomplished by a single robot alone. Therefore, in recent years, the issue of path planning for cooperative robots has received significant attention. By cooperation, we mean that... 

The emergence of Autonomous Vehicles (AVs) provides the opportunities to ameliorate traffic congestion while increasing safety. AVs, using the vehicle to vehicle and vehicle to infrastructure communication, can gather and infer the information of adjacent vehicles and traffic flow. The objective of this article is to develop a cooperative control method to manipulate AVs longitudinal and lateral movements in order to enhance macroscopic features of the mixed traffic flows. In this paper, we propose a potential function to control longitudinal movement of AVs considering their physical constraints. The developed controller provides an optimal, collision-free car following by minimizing the... 

Topic that is investigated in this article include identify and localization a number of aerial target penetrating into a protected by area by a swarm of UAVs is fixed wing. UAVs do not have any prior notice of positioning targets. In addition, it is assumed that lacks any radiation exploitable targets and thus use UAVs for Targets Detection from an active radar system. Obviously this article focus on developing a guidance algorithm UAVs to this particular issue and also as the targets participatory is localization algorithm. In addition, extraction type and performance characteristics radar system required and also performance characteristics of the class of UAVs, which is suitable to... 

In this document, the cooperative estimation of states between two interceptors and one target is expressed in order to evaluate the effect of information sharing in different situations on the estimation performance. Due to the importance of the proper estimation of the target acceleration in advanced navigation rules, the main focus of the document is on a more precise estimation of the absolute states of the target. For this purpose, a filter based on the extended Kalman filter was used as an estimator, and to evaluate the promotion of the estimation performance, the combination of measured data was used in two different ways. Matlab Simulink is the simulation software used. The dynamics... 

Cooperative networks have attracted much attention in the last decade. Being introduced to mitigate the inefficiencies in the physical layer, cooperation can also be beneficial in upper layers, such as MAC layer. Using cooperative communications is specifically more challenging in the random access networks, where collision is a main concern. Delay, as one of the main performance metrics in random access networks, can decrease significantly by using cooperative communications. Transmission delay, i.e., the required time for delivering one packet form its source to destination, is an important metric in many communication networks, such as the networks in which each node generates and... 

In a world where energy conservation is a critical topic, cooperative flexible manipulators will play an important role. Conventional robotic manipulators have been designed to have maximum stiffness to achieve both minimum vibration and good positioning accuracy of the end-effector, which causes more power consumption and reduced efficiency. Due to the high inertia of such arms, interaction with humans or sensitive environments is hazardous. On the other hand, Flexible Link Manipulators are designed to be lightweight, using lower energy and producing higher efficiency. Unfortunately, the link's flexibility increases vibrations and decreases the accuracy of the end-effector. Since, the... 

In the first part of the thesis, based on the optimal control theory, a novel approach to derive a cooperative guidance law for two pursuers with an arbitrary-order linear dynamics against one zero-lag evader with random step maneuver is proposed. This approach is intended to minimize the mean value of the resultant control effort taken over a set of possible evader maneuvers which is modeled as step function, the parameters of which are unknown. Since the resultant control effort is the minimum effort among the pursuers, we encounter the nonlinear “minˮ function in the performance index. By introducing binary parameters, it is changed to a linear function including binary parameters and... 

Content-Centric Network is a new network paradigm. In this paradigm, contents are the main element of the network, and the place holding the content is transparent to users. In other words, the concept of content’s place is eliminated. In spite of other common paradigms in which caching operation is occurred in just a few predefined nodes and also it is limited to a specific application, in this kind of network, caching operation can be occurred in all nodes, independent of the application. Furthermore, due to elimination of the concept of the content’s place, matching of same contents held in different places can be possible. So caching in such networks became an important issue. In caching... 

Nowadays children’s toys and educational stuff, have been enhanced by technology and they have found capabilities like intelligence. It is obvious that after the period of using smart devices such as phones and tablets, robots and smart robotic tools will be popular. On the other hand, children are willing to use such smart devices. Social robots are smart ones that interact with humans and are not necessarily humanoid. One of the social robots applications is for educational purposes. Many studies have shown that teaching by means of robots has good effects on learning. For example robots have been used for educating autistic children. Moreover, robots have been used for rehabilitation and... 

Cooperative coexistence of two kinds of users with different priorities in random access wireless networks has been studied in this thesis. Source burstiness, a phenomenon in data communication networks, allows using silence periods of primary users (PUs) to have a better spectrum utilization. In this respect, new users, known as secondary users (SUs), are considered to exploit the resources opportunistically. In usual spectrum sharing systems, SUs have to act in a way to be transparent for the PUs. Therefore, they are allowed to access the common spectrum band only when PUs are silent. However, seeking such opportunities needs sensing capability of secondary nodes.In this thesis, sensing... 

Hydrogen bonding is an important weak interaction encountered in gas, liquid, as well as solid phases. The hydrogen bond plays a very vital role in many life processes and is one of the most frequently used terms in chemistry and biology.
Polyols or polyhydric alcohols are, strictly speaking, simply organic chemicals containing more than two hydroxyl groups. Each hydroxyl is attached to separate carbon atoms of an aliphatic skeleton.They may also contain ester, ether, amide, acrylic, metal, metalloid and other functionalities; along with hydroxyl groups. Polyols are obtained from many plant and animal sources and are synthesized by a variety of methods. Among important properties of...