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... 

Next generation wireless networks support high data rates and QoS parameters of various users. OFMDA is a popular transmission technique to support high rate transmission, however in multi-access environments, it relies on careful resource allocation to guarantee the desired QoS parameters. While resource allocation in centralized scenarios such as cellular networks is relatively straightforward, the problem becomes quite complex in distributed scheduling of multiple access environments. One key resource is power assigned to each sub-channel which determines the overall transmission capacity.In this dissertation, firstly we introduce some cross layer QoS provisioning or power efficient QoS... 

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... 

In the modern world today, the increasing need for transfering data in high speeds and long distances has encouraged the investors of this area to use more efficient technologies of this field. With regard to the need for extensive and scalable communication networks, reusing the bandwidth in closer distances seems to be inevitable. Hence, finding an optimal way of using resources like bandwidth and power is necessary. In OFDMA-based networks there is no intra-cell interference due to using orthogonal subbands and the most important limiting factor in designing these networks is inter-cell interference. Therefore in this thesis we are gonig to analyase the partial frequency reuse method... 

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... 

The human heart is a complex system that contains many clues about its function in its electrocardiogram (ECG) signal. Due to the high mortality rate of heart diseases, detection and recognition of ECG arrhythmias is essential. The most difficult problem faced by ECG analysis is the vast variations among morphologies of ECG signals. In this study, we propose an approach for y detection of abnormal beats and data visualization with respect to ECG morphologies by using manifold learning. In order to do so, a nonlinear dimensionality reduction method based on the Laplacian Eigenmaps is used to reduce the high dimensions of the ECG signals, followed by the application of Bayesian and FLDA method... 

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... 

In the mid twentieth century by discovering the existence of genetic strands and understanding their role in diseases and phenotypes of species, research initiated to decipher their content. Sequencing of the first human genome at early twenty-first century paved the way to study and even cure complex human deseases having genetic origin. Next Generation Sequencing (NGS) Technologies have significantly reduced the expenses and the timing complexity of DNA Sequencing and this has an improving trend. In this thesis, we evaluate Base Calling methods, a critical step in analyzing next generation sequencing information and deals with massive sequencing data. Base Calling tries to optimally detect... 

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... 

In this work we have investigated the methods of providing quality of service in cognitive radio networks. At first, we have explained the various algorithms of providing BER quality of service in wireless networks. Especially we have explained those algorithms which are known as the distributed power control algorithms. Then we have introduced methods of using adaptive modulation and we have used this kind of modulation to provide delay quality of service in cognitive radio networks. We have done this by maximizing the sum of effective capacities of secondary links under the power constraints and also the interference constraints set by the primary receivers. Finally, we have introduced... 

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... 

In this thesis, the impact of both time offsets (TOs) and carrier frequency offsets (CFOs) on the average output signal-to-interference-plus-noise ratio (SINR) of OFDM systems is investigated with a novel and simple approach. First, TOs are partitioned into five cases based on how they occur. Then the mathematical models for different cases are derived. Considering CFOs and benefiting from the obtained models, closed-form expression for the SINR in each case is derived. It is proved that, SINR is independent of the observed subcarrier for the given TO and CFO. Besides, it is shown that the performance of the affected system deteriorates rapidly as the number of subcarriers increases. It is... 

A DNA sequence is the information source of living kinds. Information of this sequence is at its constructing bases which has four different kinds. Sequencing DNA is necessary to resolve this information. At 1977, Sanger reported the first sequence of a DNA string. Recently, a human DNA string can be sequenced with 1000 in ~2 hours. Knowing DNA sequence helps to find function of each organism, predict and cure diseases (especially in cancer). Next Generation Sequencing (NGS) methods are based on shot-gun sequencing which fragmentize DNA strings and sequence each fragment. After sequencing, processing information of DNA is performed by the processing machine in two different types: alignment... 

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...