Sharif Digital Repository

In this study we investigate the performance of amplify-and-forward (AF) and beamforming schemes in wireless networks. In our study we consider a general cooperative network consisting one transmit-receive pair and an arbitrary number of relays in which each relay has a separate power constraint. A two-step master-slave protocol is deployed in which at the first stage, relays listen to the transmitter and at the second stage, relays forward the recently received signal coherently. Main contributions of this dissertation are providing the exact closed-form of bit error rate analysis in the case of general AF networks, providing an integral-form upper bound of error probability of network... 

Human tracking is an essential step in many computer vision-based applications. As single view tracking may not be sufficiently robust and accurate, tracking based on multiple cameras has been widely considered in recent years. This thesis presents a distributed human tracking method in a smart camera network and introduces a particle filter design based on Histogram of Oriented Gradients (HOG) and color histogram. The proposed adaptive motion model also estimates the target speed from the history of its latest displacement and improves the robustness of the tracker by decreasing the probability of missing targets. In addition, a distributed data fusion method is proposed which fuses the... 

In this thesis, we want to improve the image quality using the auxiliary images taken by either camera networks or one camera in different times and places. This problem has been regarded so important because of the development of the camera networks and increasing the consumers' demand for enjoyment from pictures with higher quality in recent years. The problem generally consists of two different and relatively independent phases of (1) Image Registration and (2) Image Fusion. At the first step, the information in the different images are aligned and prepared to be combined using homography transforms. After that, the registered images are fused in a way depending on the target application... 

We analyze the fundamental communication limits and capabilities of random wireless networks. In order to achieve this goal, we investigate and analyze efficient communication strategies in such networks. The traffic model considered is unicasting. Also, we consider two different channel models, namely, the geometric channel model and the random connections model.
In networks with random connection model, channel powers between different nodes are drawn from a common distribution in an independent manner. We assume an on-off strategy for operation of transmitters, and show that finding the optimum transmission strategy problem is an NP-hard problem. Thus, we propose a heuristic algorithm... 

Joint multi-input multi-output (MIMO) filter-and-forward relaying and post-processing at base stations (BSs) for uplink coordinated multi-point (CoMP) reception has been investigated in the case of users-to-relay and relay-to-BSs frequency-selective fading channels. Signal transmission from users to BSs is performed in two phases. In the first phase, all users transmit their data to MIMO relay at the same time slot. In order to combat the interference due to frequency-selectivity of channels, MIMO relay passes its received signals through a finite impulse response (FIR) filter. Then, in the second phase, relay transmits the processed signals to the BSs. In order to further reducemean square... 

Since random access networks can work in distributed manner they have found variety of applications in wireless local area networks and wireless sensor networks. Throughput maximization and calculation of optimal parameters of such networks are subject of many research but most of these researches have ignored delay and suffer from high packet delay. We investigate and analyze delay in random access and solve the delay constrained utility maximization problem. We define network utility as a combination of throughput and cost of energy consumption and solve “access network optimization with link delay constraint”, and “cross layer optimization of transport and access layer with end to end... 

Nowadays, enormous amounts of data are transferred through data communication networks every day in order to fulfill end users’ demands all over the world.The capacities of the links between network nodes, or in other words, the amount of bandwidth available to carry data is undoubtedly one of the most expensive resources as well as the one of most importance which not only plays an essential role in communicating information packets over such a vast network, but is a major determinant of Quality of Service (QoS) in terms of rapidity as well. The idea of using cache memories to optimize network bandwidth consumption laid the foundation for developing Content Delivery Networks (CDNs). In such... 

Analysis of traditional spectrum allocation schemes shows underutilization of radio spectrum. This is main motivation behind deployment of cognitive radios and improving spectrum efficiency. One of the most important issues in cognitive radio networks is to guarantee quality of service (QoS) constraints for the primary users. Another problem which must be considered during network design is to design distributed algorithm with few amount of control messages. However, there is a tradeoff between to be distributed of algorithm and to be efficient. We have used game theory to analyze convergence, effectiveness and uniqueness of stable point of network.
This thesis is organized in two parts.... 

In this research, we intend to propose game theoretic approaches for allocating resources such as power and channel in wireless communication networks. One of the problems haven’t been investigated through game theory, is the joint channel and power allocation in downlink side of cellular cognitive radio networks. This is the main motivation for this thesis and in order to propose the first game theoretic method for this problem, we conducted our researches as follows: First of all, a game theoretic modeling for the problem of power control on CDMA networks will be introduced. In comparison with one of the main contributions in this domain, we will demonstrate how our algorithm results in... 

In this thesis, we investigate game theoretic approaches for distributed resource allocation in the downlink of cognitive radio networks. As the problem of joint frequency and power allocation in the downlink of cognitive radio networks has not been studied using game theory, this was an incentive for us to pay attention to the downlink and try to propose decentralized and distributed approaches for resource allocation in the downlink of these networks.
The works done in this thesis can be divided into two main parts. In the first part, we study the problem of distributed power allocation in the downlink of cognitive radio networks and using game theory techniques, we propose a... 

Replicating server information at shorter distances from users and delivering them at more suitable times, decreases average delay of serving requests as well as balancing backhaul link traffic. Due to limited cache size, cache placement strategies play key role in efficiency of such approaches. Well-known heuristic caching mechanisms such as Least Frequently Used (LFU) and Adaptive Replacement Cache (ARC), while quite efficient in terms of complexity, are not optimal in terms of hit rate which is the key caching performance index. In this paper, we address the optimal cache placement problem from an analytic Markov Decision Process (MDP)-based view to maximize cache hit rate. In this... 

The recent data explosion phenomena and numerous data consumer services over the world have made recommender systems a crucial component for online platforms.Recommender systems are filtering systems that prune the large volume of information to make the small prefered quota easily and readily accessible to the users. In social networks and news sites, due to the dynamic nature and constantly changing items and user preferences, reinforcement learning in recommender systems has become a hot research topic in the last decade. Our focus of attention,Multi-Armed Bandit, a tool of reinforcement learning, is a sequential decision making problem that illustrates the trade-off between exploring the... 

Caching has been widely considered an efficient way of reducing and balancing the growing traffic in communications networks in recent years. In this thesis, for the first time, the stochastic requests traffic model in communication networks is considered and a performance analysis is provided based on such a realistic assumption. In addition, we introduce new comprehensive performance metrics which simultaneously take into account, the cache hit probability, load on the bottleneck links, and requests arrival rates. The main contribution of this thesis is to present a system model based on queuing theory and provide an analysis of the stability, maximum stable throughput, load on the... 

The value of data transmission has surprisingly increased in the past years. Years ago, transmission of a few by telegraph systems satisfied human needs. But the amount of data transmitted increases exponentially and that is where engineers face real challenges. In the first generation of mobile networks, the voice was transmitted using Analog technology but in the second generation it switched to digital systems. In third and fourth generation systems data rate and quality of service was increased. A big change from the third to fourth generation networks was being an all IP network, meaning everything including voice and data were transmitted in packet switched networks. This creates... 

There has been a continuous increase in requested data rates in both uplink and downlink of wireless communications for a long time. But in recent years, this increase has become more extensive due to widespread use of smart phones and social networks. In order to cope with such a heavy demand, wireless telecommunication operators, have to improve frequency efficiency, by implementing more and more base-stations all over the network. But base-stations are very expensive instrument, due to their complex structure and having a high processing power. Therefore, building a network with so many base stations, may be as expensive that operators cannot afford it. “Cloud Radio Access Network”, or... 

Fountain codes enable wireless networks to adapt their transmission rates to the state of the channels, without the need for channel state information (CSI) at the transmitters. According to the following properties of rateless codes, ever increasing parity generation, mutual information receiver, single bit feedback, and information combining receiver, they are good choice for relay networks. In this research, the design of rateless codes for wireless relay networks has been studied. Cross layer issues should be seriously considered when using rateless codes in the packet level. One cross-layer scheme has been developed in this thesis and analysis show that the performance of the proposed... 

A user-provided network (UPN) has the potential to achieve a low cost ubiq-uitous Internet connectivity without the need of significantly increase of network infrastructure investment.In this article, we consider such a network where the network operator encourages some of her subscribers to operator as mobile Wi-Fi hotspots (hosts), providing Inter-net connectivity for other subscribers (clients). We formulate the interaction between the operators and mobile users as a two-stage game. In Stage I, the operator decides the usage-based pricing and quota-based incentive mechanism for the data usage. In Stage II, the mobile users decide the membership selection, i.e., choosing to be a host, or a... 

In this dissertation we will study the problem of transmitting the information of continuous source over fading channel, especially when the transmitter does not have complete information about the channel status. In this situation we will have a tradeoff between the Quality of received packets and the Reliability in transmissions. To increase the quality of packets, for example, we should increase the quantization, and therefore, the transmission rates at the transmitter. But this will also increase the Error Probability at the receiver. It means that if the receiver gets the transmitted packet, it will have a better estimation of information source, but it is likely that error happens and... 

Broadcasting in wireless ad hoc networks serves many important tasks such as data dissemination and route establishment in which one node sends its data to all other network nodes. The most popular form of broadcasting adopted by many ad-hoc protocols is flooding. In flooding, each node receiving a packet from a neighboring node rebroadcasts it exactly once. Wide adoption of flooding for broadcasting traffic is mainly due to its simplicity. The importance of performance analysis of flooding lies on its aforementioned popularity. The parameters of interest in analysis of flooding are network coverage, energy consumption and broadcast throughput while network coverage is the average percentage... 

Using camera in localization its pose and connected things, with using camera images has been inspected in this thesis which categorized in passive localization. Although using these methods seems to be rather difficult, human can passively perceive its position in space. This is a preface for new positioning systems.
In this thesis assume that some cameras are ready for Image sharing then we introduce algorithms for cameras relative locations and rotation matrices. This method gives local information and can uses range scaners as inputs. Other works in last decade tryed on 3D reconstruction and graphic section and rarely explored multi-camera localization and reduction of its...