Sharif Digital Repository

This paper introduces a public key scheme based on polar codes to improve the performance of McEliece cryptosystem. By exploiting the interesting properties of polar codes, we put the encryption matrix of the proposed scheme in systematic form. Moreover, the nonsingular matrix is constructed from the generator matrix of used polar code. These proceedings lead to decrease the public and private key lengths compared with the original McEliece public key cryptosystem. We analyze the proposed scheme against known attacks on the public key cryptosystems based on channel coding. Moreover, it benefits from high code rate and proper error correction capability for reliable communication  

One of the main issues in Solid State Drive (SSD)-based storage systems is endurance which is directly affected by the number of Program/Erase (P/E) cycles. The increment of P/E cycles increases the bit error rate threatening the reliability of SSDs. Erasure codes are used to leverage the reliability of storage systems but they also affect the number of P/E cycles based on their code pattern. A lower dependency between data and parities in the code pattern may lead to smaller number of P/E cycles providing better endurance. This paper introduces an Endurance Aware EVENODD (EA-EO), which minimizes the dependency between data and parities in the coding pattern. A simulation environment is used... 

In [1], [2] it is shown that the minimum broadcast rate of a linear index code over a finite field Fq is equal to an algebraic invariant of the underlying digraph, called minrankq. In [3], it is proved that for F2 and any positive integer k, minrankq(G) ≤ k if and only if there exists a homomorphism from the complement of the graph G to the complement of a particular undirected graph family called 'graph family {Gk}'. As observed in [2], by combining these two results one can relate the linear index coding problem of undirected graphs to the graph homomorphism problem. In [4], a direct connection between linear index coding problem and graph homomorphism problem is introduced. In contrast to... 

This paper studies the placement of antennas in presence of mountains for widely separated multiple-input multiple-output (MIMO) radar. One of the challenges in this configuration is proper placement of the receive antennas in order to achieve good performance. We derived Neyman-Pearson decision rule for target detection. Via several scenarios we show that proper placement of receivers can provide better performance  

We establish several new results on Marton's inner bound on the capacity region of the general broadcast channel. Inspired by the fact that Marton's coding scheme without superposition coding is optimal in the Gaussian case, we consider the class of binary input degraded broadcast channels with no common message that have the same property. We characterize this class. We also establish new properties of Marton's inner bound that help restrict the search space for computing the Marton sum rate. In particular, we establish an extension of the XOR case of the binary inequality of Nair, Wang, and Geng  

In this study, the authors consider the secrecy of a one-receiver, two-eavesdropper broadcast channel (BC) with three degraded message sets. Consider a three-receiver BC with three messages, where the first message is decoded by all the receivers. The second message is decoded by the first and the second receivers and is to be kept secret from the third receiver. The third message is decoded by the first receiver and is to be kept secret from the second and the third receivers. The authors consider the imperfect secrecy condition at the second receiver, that is, it is allowed to partially decode the third message. However, the perfect secrecy condition at the third receiver, does not allow... 

In order to evaluate the dynamic behavior of floating offshore wind turbines, the authors consider two approaches. A numerical method is used to investigate Tension Leg Platform (TLP) offshore wind turbine response behavior under a parked condition. This code considers nonlinearities due to changes in the tension of tethers. The off-diagonal components of stiffness, damping and mass matrices are considered to calculate coupling. This code solves the nonlinear equation of motion at each time step. However, in order to validate the data generated by the code, a scaled-down model was fully tested in the marine laboratory. The importance of these series of experiments is due to the fact that... 

Multi-layer schemes have been proposed for steganography. Also some authors have combined these methods with the idea of wet paper codes and gained higher embedding efficiency. This paper proposes a generalized multi-layer method for wet paper embedding. First, the cover bits are divided into blocks and, by combining these bits in groups of 3, a pyramid is formed. Next, the secret message is embedded through a layer-by-layer procedure. The proposed method has higher embedding efficiency in some cases and provides more flexibility for choosing the embedding payload, especially in lower payload conditions  

The authors investigate the content distribution among the vehicles of a cluster in a vehicular ad-hoc network, exploiting network coding. The vehicles collaborate to disseminate the coded data packets, received from a roadside info-station based on IEEE 802.11 medium access control (MAC) protocol. Two types of network coding are considered: random linear network coding (RLNC) over a large finite field and random XORed network coding (RXNC). An analytical model is proposed to address the effect of random access MAC as well as the correlation among received coded packets on the performance of content distribution. First, a p-persistent carrier sense multiple access approximation for IEEE... 

In this paper we define critical graphs as minimal graphs that support a given set of rates for the index coding problem, and study them for both the one-shot and asymptotic setups. For the case of equal rates, we find the critical graph with minimum number of edges for both one-shot and asymptotic cases. For the general case of possibly distinct rates, we show that for one-shot and asymptotic linear index coding, as well as asymptotic non-linear index coding, each critical graph is a union of disjoint strongly connected subgraphs (USCS). On the other hand, we identify a non-USCS critical graph for a one-shot non-linear index coding problem. In addition, we show that the capacity region of... 

In this work, we study the performance of polar codes for lossy compression of a Gaussian source with a side information at decoder; known as the quadratic-Gaussian Wyner-Ziv problem. First we extend the binary polar codes to q-ary for the Wyner-Ziv problem. We show that the nested q- Ary polar codes are optimal for this case. Then we present two polar coding schemes for the Gaussian Wyner-Ziv problem. In the first scheme, we achieve a rate above the Wyner-Ziv rate-distortion function with a gap of 0.5 bits compared with the optimal rate. This scheme utilizes a successive cancellation decoder and is optimal in weak side-information cases when the decoder side-information noise variance is... 

Proton exchange membrane (PEM) fuel cell performance is directly related to the bipolar plate design and their channels pattern. Power enhancements can be achieved by optimal design of the type, size, or patterns of the channels. It has been realized that the bipolar plate design has significant role on reactant transport as well as water management in a PEM Fuel cell. Present work concentrates on improvements in the fuel cell performance by optimization of flow-field design and channels configurations. A three-dimensional, multi-component numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The simulation results showed excellent... 

In this paper, evaluation of the kinetic parameters (effective delayed neutron fraction and prompt neutron lifetime) in PWRs, using static cell and core calculation codes, is reported. A new software has been developed to link the WIMS, BORGES and CITATION codes in Visual C# computer programming language. Using the WIMS cell calculation code, multigroup microscopic cross-sections and number densities of different materials can be generated in a binary file. By the use of BORGES code, these binary-form cross-sections and number densities are converted to a format readable by the CITATION core calculation code, by which the kinetic parameters can be finally obtained. This software is used for... 

Automatic brain tissue segmentation is a crucial task in diagnosis and treatment of medical images. This paper presents a new algorithm to segment different brain tissues, such as white matter (WM), gray matter (GM), cerebral spinal fluid (CSF), background (BKG), and tumor tissues. The proposed technique uses the modified intraframe coding yielded from H.264/(AVC), for feature extraction. Extracted features are then imposed to an artificial back propagation neural network (BPN) classifier to assign each block to its appropriate class. Since the newest coding standard, H.264/AVC, has the highest compression ratio, it decreases the dimension of extracted features and thus yields to a more... 

In contrast to the vast amount of literature in random matrices in the field of compressed sensing, the subject of deterministic matrix design is at its early stages. Since these deterministic matrices are usually constructed using the polynomials in finite Galois fields, the number of rows (number of samples) is restricted to some specific integers such as prime powers. In this paper, besides extending a previous matrix design based on the binary BCH codes to the p-ary codes, we introduce matrices with wide variety of options for the number of rows. Simulation results demonstrate that these matrices perform almost as well as random matrices  

In this paper, we consider transmission of a Gaussian source over a Gaussian channel under bandwidth compression in the presence of interference known only to the transmitter. We study hybrid digital-analog (HDA) joint source-channel coding schemes and propose two novel coding schemes that achieve the optimal mean-squared error (MSE) distortion. This can be viewed as the extension of results by Wilson et al. [1], originally proposed for sending a Gaussian source over a Gaussian channel in two cases: 1) Matched bandwidth with known interference only at the transmitter, 2) bandwidth compression where there is no interference in the channel. The proposed HDA codes can cancel the interference of... 

A general construction for deletion/insertion correcting codes is proposed by concatenating codes derived from a heuristic maximal independent set algorithm on an appropriately defined graph. Our heuristic algorithm is polynomial with respect to the number of nodes in the graph. This methodology may be used for construction of any length n, s-deletion code. Our experimental results show that cardinalities of our codebooks exceed sizes of all previously known constructions. In fact, they are comparable to Levenshteins lower bound  

The vulnerability of microprocessors to soft errors is increasing due to continuous shrinking in fabrication process. Recent studies show that 1-5% of the SEUs (single event upset) can cause MBUs (multiple bit upsets). The probability of MBU generation due to SEU is increasing because of the reduction in minimum energy required to flip a memory bit in modern technologies. Register file is the most sensitive component in a microprocessor. In this paper, we present an innovative way to protect registers in a 64-bit register file for a RISC processor using extended Hamming (8, 4) code (SEC-DED code) and narrow-width values. A narrow-width value can be represented by half number of bits of the... 

We consider the problem of sending a bivariate Gaussian source S=(S 1,S 2) across a power-limited two-user Gaussian broadcast channel. User i (i=1,2) observes the transmitted signal corrupted by Gaussian noise with power σ i 2 and desires to estimate S i. We study hybrid digital-analog (HDA) joint source-channel coding schemes and analyze the region of (squared-error) distortion pairs that are simultaneously achievable. Two cases are considered: 1) broadcasting with bandwidth compression, and 2) broadcasting with bandwidth expansion. We modify and adapt HDA schemes of Wilson et al. and Prabhakaran et al. , originally proposed for broadcasting a single common Gaussian source, in order to... 

This paper investigates the capacity problem for some multiple-access scenarios with cooperative transmitters. First, a general Multiple-Access Channel (MAC) with common information, i.e., a scenario where p transmitters send private messages and also a common message to q receivers and each receiver decodes all of the messages, is considered. The capacity region of the discrete memoryless channel is characterized. Then, the general Gaussian fading MAC with common information wherein partial Channel State Information (CSI) is available at the transmitters (CSIT) and perfect CSI is available at the receivers (CSIR) is investigated. A coding theorem is proved for this model that yields an...