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... 

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... 

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 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... 

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... 

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... 

In recent years, introduction of new technologies has highlighted the need to more data rate in mobile networks. Classical methods of resource allocation in mobile networks cannot respond to this huge demand for data rate because of their limitations. Resource allocation, as one of the operators’ tasks, plays a key role in the network efficiency and users’ data rate. Opportunistic resource allocation and scheduling have gained attention in recent years. On the other, using single-channel (frequency reuse-1) networks is also one of the methods to improve data rate in mobile networks. It is expected that the use of opportunistic scheduling in single-channel networks can repond to the huge... 

Telecommunications industry along energy industry will be among striking elements in improving next-generation lifestyle. With the growth of wireless communications at the heart of telecommunications industry, cellular networks as an inevitable part of our daily life, have been around as a fertile research field for both academia and industry. With the upcoming Heterogeneous Networks (HetNets), these researches are revisited to new horizons. After these shift paradigms,the proposed solutions, mostly fall into the category of network densification in terms of antenna per (active) user. Based on the strategy chosen to densify the network, we face two broad approaches: 1) Centralized... 

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... 

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... 

Design and production of a drug is a very time and money consuming process. It takes more than a decade and about 2.5 million dollars on various stages to design a drug. Attempts to reduce this cost and time to market will make drugs available to customers at a more reasonable time. Some stages such as animal testing phase and clinical trials, can not be replaced and must take place in practice. Fortunately, some laboratory steps are interchangeable with software algorithms. These algorithms can significantly reduce the cost and time to market of the drug if they are accurate enough. On the other hand, the remarkable results of machine learning, in particular, Deep Neural Networks, in areas... 

Today, the use of deep learning algorithms in the design of communication systems has received much attention. One of these areas is the partial or total design of these systems using deep networks. The overall design of a communication system using deep networks allows for global optimization and can provide better performance in cases where classical methods have suboptimal performance without significantly increasing the computational load. In this research, a comprehensive architecture for designing communication systems based on Auto-encoder neural networks is presented. This architecture has the same functionality as classical systems, considering all parts of these systems including... 

Drive Test is a known technique witch network operators use to optimize and evaluate their mobile network infra in terms of capacity, coverage, and quality of service. Conducting Drive tests in outdoor areas is time-consuming and increases CAPEX and OPEX. Also, in areas with many giant physical obstacles, like towers and buildings in cities, Drive test is nearly impossible. In this paper, based on data and measurements provided by various Drive tests and TEMS MDT solution, we use an advanced processing algorithm in our database to bring signal coverage map practically to the users' cellphones. By taking advantage of grid-based signal fingerprinting technique, and filtering geo-tagged... 

Single Cell RNA sequencing (scRNA-seq) data provides more information about gene expression at cellular level. However, because of noise and sparsity that exist in scRNA-seq data, analysis of this data has faced to obstacles. Global normalization approach can not resolve correctly missing data that come from technical variability. So this approach cause emerging incorrect bias and dishonest conclusion about cell type. In this study we review some models for scRNA-seq data imputation,explain a new method for filtering genes and clustering data and use matrix completion algorithm for imputation data  

Despite significant progress in cancer treatment, drug resistance remains a major challenge. Synergistic drug combinations offer a promising approach to overcome drug resistance and reduce side effects. Still, despite high-throughput testing technologies, existing drug combination databases suffer from biases and a lack of diversity in tested cancer cell lines, which challenges the prediction of drug response on novel cell targets. To address this critical need, we designed a two-level deep learning method that uses large-scale gene expression datasets to estimate the score and synergy of drug compounds on a wide variety of cancer cell lines. Our model includes an auto-encoder that train on... 

Polymerase Chain Reaction (PCR) is a laboratory method for amplifying a part of DNA. This method is used in determining the sequence of genes, detecting pathogenic agents in epidemics, creating genetic changes in bacteria, diseases, plants and even animals. Many factors affect the quality of the reaction. Each of these factors can be effective in amplifying the target in DNA. If we can predict the result of PCR using the factors involved in the reaction, it will save a lot of money and time. The aim of this research is to predict the result of PCR amplification using machine learning methods. For this purpose, two methods are proposed: feature-based method and string-based method. In the... 

The quality of experience (QoE) is a qualitative metric of users’ satisfaction with the received service. The competition for providing services is fierce, and the one who satisfies the most users wins. Therefore, the method of evaluating user satisfaction is important. In this dissertation, a model for VoIP QoE assessment is proposed. In the proposed method, appropriate features for measuring the quality of voice calls are first extracted solely from the degraded audio signals. Then, an ensemble learning model is created to estimate MOS, acceptance, and probabilistic metrics accurately and close to real opinions. Then, the performance of the model in terms of correlation coefficient and... 

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 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...