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Spectrum Sensing in Cognitive Radio Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
In this thesis, we consider the problem of spectrum sensing in cognitive radio networks. First, the collaborative energy detectors based spectrum sensing are investigated in the case of known noise variance for two models of primary user (PU) signal, i.e. random and unknown deterministic signals. Since the derived optimum collaborative energy detector requires the signal-to-noise ratio (SNR) of secondary users (SU) and it has complex structure, the generalized likelihood ratio (GLR) detector is proposed for both models of PU signal which leads to the same decision rules for both models. Simulation results show that the performance of the proposed GLR detector is near to that of optimal...
Multiple antenna spectrum sensing in cognitive radios
, Article IEEE Transactions on Wireless Communications ; Volume 9, Issue 2 , 2010 , Pages 814-823 ; 15361276 (ISSN) ; Nasiri-Kenari, M ; Gazor, S ; Sharif University of Technology
2010
Abstract
In this paper, we consider the problem of spectrum sensing by using multiple antenna in cognitive radios when the noise and the primary user signal are assumed as independent complex zero-mean Gaussian random signals. The optimal multiple antenna spectrum sensing detector needs to know the channel gains, noise variance, and primary user signal variance. In practice some or all of these parameters may be unknown, so we derive the Generalized Likelihood Ratio (GLR) detectors under these circumstances. The proposed GLR detector, in which all the parameters are unknown, is a blind and invariant detector with a low computational complexity. We also analytically compute the missed detection and...
Invariant wideband spectrum sensing under unknown variances
, Article IEEE Transactions on Wireless Communications ; Volume 8, Issue 5 , 2009 , Pages 2182-2186 ; 15361276 (ISSN) ; Gazor, S ; Nasiri Kenari, M ; Sharif University of Technology
2009
Abstract
In this paper, we divide a wide frequency range into multiple subbands and in each subband detect whether in a primary user (PU) is active or not. We assume that PU signal at each subband and the additive noise are white zeromean independent Gaussian random processes with unknown variances. We also assume that at least a minimum given number of subbands is vacant of PU signal and propose an invariant Generalized Likelihood Ratio (GLR) detector. The concept of the grouping of subbands allows faster spectrum sensing of a subset of subbands which may be occupied by a specific PU. Also, we evaluate trade-offs involved in the proposed algorithms by simulation. © 2009 IEEE
Outage probability analysis of a coded cooperative OFDM system in multipath Rayleigh fading channels
, Article 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC'07, Athens, 3 September 2007 through 7 September 2007 ; December , 2007 ; 1424411440 (ISBN); 9781424411443 (ISBN) ; Nasiri Kenari, M ; Taherpour, A ; Sharif University of Technology
2007
Abstract
This paper considers a cooperative space-frequency (SF) coded OFDM system and evaluates its performance over quasi-static frequency selective Rayleigh fading channels. An expression for exact outage error probability is derived and its tight closed form lower bound is presented. The tightness of the lower bound is demonstrated through the Monte Carlo simulations. The asymptotic analysis indicates that the proposed protocol achieves full spatial and frequency diversities available in the cooperative communication system. The theoretical analysis of the proposed space-frequency coded cooperation protocol is further confirmed by computer simulations. © 2007 IEEE
Efficient cooperative spectrum sensing in cognitive radio networks
, Article 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC'07, Athens, 3 September 2007 through 7 September 2007 ; December , 2007 ; 1424411440 (ISBN); 9781424411443 (ISBN) ; Nasiri Kenari, M ; Jamshidi, A ; Sharif University of Technology
2007
Abstract
Rcent measurements suggest the possibility of sharing spectrum among different parties subject to interference-protection constraints. In order to enable access to an unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. In this paper, we study spectrum-sharing between a primary licensee and a group of secondary users. The structure of an asymptotically optimum detector based on the measurements of all secondary users is derived and the effect of the quantization error in such a system is evaluated. The results show the superiority of the proposed detector to other schemes. © 2007 IEEE
Wideband spectrum sensing in unknown white Gaussian noise
, Article IET Communications ; Volume 2, Issue 6 , 2008 , Pages 763-771 ; 17518628 (ISSN) ; Gazor, S ; Nasiri Kenari, M ; Sharif University of Technology
2008
Abstract
The spectrum sensing of a wideband frequency range is studied by dividing it into multiple subbands. It is assumed that in each subband either a primary user (PU) is active or absent in a additive white Gaussian noise environment with an unknown variance. It is also assumed that at least a minimum given number of subbands are vacant of PUs. In this multiple interrelated hypothesis testing problem, the noise variance is estimated and a generalised likelihood ratio detector is proposed to identify possible spectrum holes at a secondary user (SU). Provided that it is known that a specific PU can occupy a subset of subbands simultaneously, a grouping algorithm which allows faster spectrum...
Benchmarking of Optimal Control Theory Techniques
, M.Sc. Thesis Sharif University of Technology ; Raeisi, Sadegh (Supervisor) ; Baghram, Shant (Co-Supervisor)
Abstract
There are different approaches for implementing quantum gates as the main elements of quantum computers. In this thesis, we use the quantum optimal control approach to implement quantum gates. For this purpose, we use the two common methods of optimization, Krotov and second-order GRAPE of L-BFGS-B type to implement gates. First, we implement three gates X, CNOT and TOffoli, using both methods, and then, in order to compare and benchmark these methods, we also investigate a number of one, two, and three-qubit random gates. It is essential to implement and simulate high-quality gates in the shortest possible time. Therefore, in this thesis, we compare and benchmark the optimization execution...
Space-frequency coded cooperation in OFDM multiple-access wireless networks
, Article IET Communications ; Volume 1, Issue 6 , December , 2007 , Pages 1152-1160 ; 17518628 (ISSN) ; Nasiri Kenari, M ; Zeinalpour, Z ; Taherpour, A ; Sharif University of Technology
2007
Abstract
A cooperative space-frequency (SF) coded orthogonal frequency division multiplexing system is considered and its performance over quasi-static frequency-selective Rayleigh fading channels is evaluated. An expression for exact outage error probability is derived and its tight closed-form lower bound is presented. The tightness of the lower bound is demonstrated through Monte Carlo simulation. Asymptotic analysis indicates that the proposed protocol achieves full spatial and frequency diversities available in the cooperative communication system. The theoretical analysis of the proposed SF coded cooperation protocol is further confirmed by computer simulation using a previously introduced SF...
Asymptotically optimum detection of primary user in cognitive radio networks
, Article IET Communications ; Volume 1, Issue 6 , December , 2007 , Pages 1138-1145 ; 17518628 (ISSN) ; Norouzi, Y ; Nasiri Kenari, M ; Jamshidi, A ; Zeinalpour Yazdi, Z ; Sharif University of Technology
2007
Abstract
Traditionally, the frequency spectrum is licensed to users by government agencies in a fixed manner where the licensee has exclusive right to access the allocated band. However, with increasing demand for the spectrum and scarcity of vacant bands, a spectrum policy reform seems inevitable. Meanwhile, recent measurements suggest the possibility of sharing spectrum among different parties subject to interference-protection constraints. In order to enable access to an unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. Spectrum-sharing between a primary licensee and a group of secondary users has been...
High Saline Water Treatment by the Process of Membrane Distillation Combined with Solar Energy
, M.Sc. Thesis Sharif University of Technology ; Rajabi, Abbas (Supervisor) ; Musavi, Abbas (Supervisor)
Abstract
In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the...
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
FGM sheets with component or grain size gradient in their thickness direction provide mechanical and physical gradient properties through ND direction. FGMs are fabricated by various methods including centrifugal casting, powder metallurgy, PVD and CVD,all of which suffer from some shortcomings such as porosity of the products, low rate and high cost of production and restrictions on mass production. In this study, 2 and 4 layered Al matrix FGM sheets containing SiC and Al2O3 powders were fabricated by laminating method of Accumulative Roll Bonding(ARB). Two approaches of stacking were chosen as accumulative coupled roll bonding (ACRB) and (ASRB) for initial roll bonding and subsequent...
Deposition of Ceramic Nanoparticles on Aluminum Sheet by Air Gun Spraying for ARB Processing of Nanocomposite Sheets
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
Particle reinforced aluminum matrix composites have considerable attraction in automotive and aerospace industries due to their special properties as light weight, high ratio of strength/density, improved elastic modulus, low coefficient of thermal expansion and high wear and corrosion resistance. Among the production processes of metal matrix composites, accumulative roll bonding process has particular importance due to producing ultrafine grained composite sheets. However, uncontrolled and undesired agglomeration of particles is the main problem in producing these composites. In this research, the Al2O3 and SiC nanoparticles were electrostatically stabilized against agglomeration by...
Make Policy for Optimizing Iran Gas Export
, M.Sc. Thesis Sharif University of Technology ; Maleki, Abbas (Supervisor)
Abstract
This project examines four alternatives such as pipelines, oil injection wells, LNG & GTL in the purpose of Iran gas utilization. In this Project four strategies using cost/benefit analysis are examined. For this purpose, at first the cost of inlet feed gas per Mmbtu are calculated. Then regarding various scenarios of average world gas prices for the following thirty years, the cost & benefit of any way will be counted. Then with the use of energy security, the project will make energy policy. For this purpose, Shannon indicator will be used as one of the most reliable indicators. Due to the of use this indicator, the popular project will be chosen accordingly as a certain amount of gas the...
Diffusion of Lipid and Protein Molecules in Cell Membranes
, Ph.D. Dissertation Sharif University of Technology ; Jalali, Abbas (Supervisor)
Abstract
Lipid membranes are fundamental constituents of cell membranes and are now used in lap-on-a-chip technology. Membranes in living cells contain a significant fraction of proteins, which undergo lateral random movements due to thermal fluctuations and shear forces imposed by the solvent fluid. Prominent natural and biotechnological systems where membranes are highly sheared include the plasma membrane of endothelial cells, and membranes used in biosensors for high throughput screening of drug candidates, and in water purification devices. In these systems membrane is in direct contact with the mainstream suspension flow, which is driven by pressure gradients. The efficiency and function of...
Hot Workability of a Free-cutting Steel with Severe Sulfur Segregation During Continuous Casting
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
Splitting in ingot cast structures and transverse cracks in continuous cast structures are the main problems of hot rolling of low carbon resulfurized free-cutting (LCRF) steels. Presence of high volume fraction of manganese sulfide inclusions in cast structure increases the risk of alligatoring in hot rolling. Because of high sulfur content of these steels and probability of formation of low melting point phases, minimum level of manganese and maximum level of copper and tin is necessary. Morphology of manganese sulfide is another important factor in hot forming of these steels, which can be controlled by level of deoxidation in steel making. In fact, MnS2 is present in fully killed...
(Assessing the Role of Carbon Capture and Storage Technology on Iran’s Oncoming Energy System(Technology Deployment Policy Making
, M.Sc. Thesis Sharif University of Technology ; Maleki, Abbas (Supervisor)
Abstract
Based on International Energy Agency studies, achievement of 450 ppm CO2-equivalent emission target in global emission means that the CO2 emissions in 2050 must be reduced to %50 of 2005 level, and this implies that a portfolio of emission reduction policies and strategies need to be exploited through current century.
At the present time, Carbon Capture and Storage (CCS) Technology is a dominant strategy among all the long-term carbon abatement strategies in many countries. Nevertheless, its potential as a climate mitigating option will be proved, only if it is implemented in the countries which are developing at a great pace and taking advantage of fossil fuels in order to afford their...
At the present time, Carbon Capture and Storage (CCS) Technology is a dominant strategy among all the long-term carbon abatement strategies in many countries. Nevertheless, its potential as a climate mitigating option will be proved, only if it is implemented in the countries which are developing at a great pace and taking advantage of fossil fuels in order to afford their...
Development of an Analytical Framework for Evaluation of Climate Change Mitigation Policies on Iran’s Energy Security
, M.Sc. Thesis Sharif University of Technology ; Maleki, Abbas (Supervisor)
Abstract
Climate change and energy security are key drivers for future energy policy. While energy security has been a pillar of energy policy for about a century, concern about climate change is more recent and is bound to radically change the landscape of energy policy. Policy makers are now under increasing pressure to address these twin challenges: to develop cost-effective policies that will both ensure the security of our energy system and reduce greenhouse gas emissions.
Main Effort in this Project is to construct an integrated model of Iran’s energy system to serve as a policy analysis tool, by which policymakers are able to identify the future effects of a wide range of policies in...
Main Effort in this Project is to construct an integrated model of Iran’s energy system to serve as a policy analysis tool, by which policymakers are able to identify the future effects of a wide range of policies in...
Evaluation the Effect of Thermo-Mechanical Parameters on Microstructure and Texture of Electrical Steel for Improving Magnetic Permeability
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
Dependence of some magnetic properties such as core loss and permeability on temper rolling was studied in this thesis. It is shown that with a proper temper rolling sharper textures are obtained in the electrical steel and the magnetic properties in the longitudinal and traverse directions are improved. By texture analysis, it is shown that because of temper rolling, shear strain on the surface of the sheet is the main factor for abnormal grain growth and shear texture formation on the surface. The result of formation of this texture is enhancement of the {100} intensity and reduction of the {111} intensity, leading to the improvement of the permeability. Temper rolling is always...
Risk Management for DG Owners
, M.Sc. Thesis Sharif University of Technology ; Rajabi, Abbas (Supervisor)
Abstract
Distributed generation (DG) and its utilization have some benefits and risks for its owner and power network. From owner perspective, benefits of DG include selling energy, reducing costs related to fuel, and other economic benefits. However, there are some risk factors for the owner including risk of supplying fuel, risk of selling generated power, and other risk factors related to establishment of the DG unit. Utilizing risk-reduction tools such as signing agreements for selling power, purchasing fuel, and related economic tools are necessary for risk management of the owners of DG units. The purpose of this thesis is to investigate the economic situation of the DG units and optimize the...
Exception Fault Localization in Smart Mobile Applications
, M.Sc. Thesis Sharif University of Technology ; Heydarnoori, Abbas (Supervisor)
Abstract
In software programs, most of the time, there is a chance of error, even though they are tested carefully. Finding error-related pieces of code is one of the most complicated tasks and it can make incorrect results if done manually. Semi-automated and fully-automated methods have been introduced to overcome this issue. The rapid growth of developing smart mobile applications (SMAs) in recent years, competition among the development teams and many other factors have increased the chance of errors and hence, the quality of these applications have reduced. There are two approaches to test SMAs in order to reach a high degree of quality: (1) using existing traditional methods and adapting them...