Sharif Digital Repository

Orbital angular momentum (OAM)and the radial quantum number (p) in infinite-dimensional Hilbert space are two degrees of freedom of light which are associated with the spatial distribution of the electromagnetic field. They are attracting a growing interest for their potential in communication applications ranging from classical communication to fundamental tests of quantum mechanics,quantum communication and quantum cryptography. However, a third party trying to eavesdrop information from communication channel and treat channel security , quantum cryptography or quantum key distribution (QKD) is the secure communication method which is based on the quantum mechanical principles can... 

Electromagnetic field modes have several degrees of freedom, including polarization, orbital angular momentum, and radial order, which can be described by orthogonal modes. By using all the degrees of freedom in communication, the channel capacity can be increased dramatically. With the aim of increasing the capacity and correcting the errors created along the optical fiber, two important issues have been addressed in this thesis. First, the states propagated in the fiber may be disrupted by many unwanted factors and may not be transmitted correctly. Therefore, measures should be taken to minimize the impact of these factors as much as possible or to compensate for their effects. In the... 

The processing of brain signals, including the electrocorticogram (ECoG) signal, is widely used in the investigation of neurological diseases. Conventionally, the ECoG signal has frequency components up to the range of 80 Hz. Studies have proven that in some conditions, such as epilepsy, the brain signal includes frequency components higher than 80 Hz, which are called high-frequency oscillations (HFO). Therefore, HFOs are recognized as a biomarker for epilepsy. The aim of this thesis is to review the previous methods of detecting HFOs and to present new methods with greater efficiency in the direction of diagnosis or treatment of epileptic patients. For this purpose, we used the ECoG data... 

In this thesis a rigorous approach toward systematic quantification of qualitative fea-tures in a three-dimensional (3D) integral imaging is proposed. Incorporating the concepts of sampling rays and sampling points, the first approach is based on geo-metrical optics and quantifies the lateral and depth resolutions of the system within the field-of-view (FOV) and depth-of-field (DOF). The obtained results are justified through experiments. In the next step, the principals of wave optics are employed to measure the lateral and depth resolutions of the system. To this end, the concept of point-spread function is generalized to three-dimensional imaging systems. Through this systematic approach the... 

In this thesis we consider transmitting an analog Gaussian source over an AWGN channel in the presence of an interference completely known at the transmitter intwo cases: 1) Compression bandwidth with interference uncorrelated with the sourceand 2) Matched bandwidth channel in the presence of interference correlated withthe source to be transmitted. We study joint source-channel coding schemes basedon hybrid digital-analog (HDA) codes. After providng a brief review, we will proposetwo new schemes for the ?rst case and one novel scheme for the second case. Aswe will see both schemes for the ?rst case achieve the optimal mean-squared error(MSE) distortion. The proposed HDA schemes can... 

The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this thesis, the security of two-phase relaying system with multiple... 

In this thesis after the study of the reported works on butterfly network, we improve the rate region of full duplex butterfly network. We use a simple specification of lattice codes to break code book into two code books. By selection of the coded message of the two transmitters in symetric butterfly channel from these two code books, we can decode the sum of the two messages and recover each messages by simple mod operation. The simulation shows that the rate region is improved  

The job shop scheduling problem is an important and applicable optimization problem and has been attracted by many researchers in recent decades. A huge amount of applications of job shop scheduling problem in industries and services has been found yet. During the last decade, the sequence dependent setup time constraint has been considered in many researches, but with respect to the knowledge of authors, very few of these researches have considered the inseparable setup. Furthermore, few of them have considered the release date assumption. In this thesis, the classical job shop scheduling problem and the inseparable sequence dependent setup time and release date constrained problem have... 

Analysis of the achievable secrecy rate in channels has always been of significant importance.The importance further increased probably due to development of new generations of communication networks in recent years. The secrecy rate refers to the maximum transmission rate for which transmitted data during the transmission process is guaranteed to be error-free and not sniffable. In this thesis, we will investigate the two-hop channel with untrusted relay using lattice coding. In other words, the purpose of this study is to provide a decoder-encoder architecture based on lattice codes, in order to obtain a secrecy rate in a channel where two pairs of transmitter-receivers attempt to exchange... 

IoT security is an important step in the rapid development of its applications and ser-vices. Many security protocols have been defined to maintain security at higher communication layers, such as the transport layer and the application layer, but with the advent of quantum computers due to high-speed parallel computing, the previous methods are no longer secure and we have to establish security at lower layers such as the physical layer. The efficiency of IoT devices depends on the reliability of their message transmission. Cyber-attacks such as data injection, eavesdropping and man-in-the-middle can lead to security challenges. In this study, we propose a new deep learning based component... 

Random codes can achieve the capacity region of so many channels like AWGN channel, multiple access channel (MAC), etc. Recently, it is shown that these codes cannot achieve any positive rate for some channels such as doubly dirty MAC.Because of this fact and also practical consideration, structured codes have been introduced recently. It is shown that one of the structured codes, referred to as lattice codes, can achieve positive rates for doubly dirty MAC. These codes can also achieve the capacity of AWGN channel, MAC and Broadcast channel. For these reasons, in this work we analyze the performance of lattice codes over relay channels as well as interference channels. Here, we implement... 

In this thesis, we investigate a passive forward scattering radar system based on satellite signal. In this thesis we have used the GPS satellite signal as a non-cooperative transmitter.In order to analyze the passive forward scattering radar system as a subset of the bistatic radars, first the features and equations of the bistatic radar will be presented, and then we will discuss the important advantages and disadvantages of the passive forward scattering radar.In order to investigate the features of passive forward scattering radar based on satellite signal, an appropriate geometry will be presented with the characteristics of this radar and parameters such as time delay between direct... 

Although in the network information theory most of results are based on applying random codes, one of the important challenges is to design linear structured codes that achieves the performance close to the performance of random codes. Recently, it is shown that lattice codes can be designed as good codes for quantization and also capacity-achieving in additive white Gaussian noise (AWGN) channel. Due to such a good performance, lattice codes can be designed properly and applied in various problems in network information theory.In this work, we study the performance of lattice codes for the following problems:1. Gaussian multiple access channel (MAC) with state: A joint source channel coding...