Search for: encoding-and-decoding
Article IEEE International Symposium on Information Theory - Proceedings, 14 June 2015 through 19 June 2015 ; Volume 2015-June , 2015 , Pages 301-305 ; 21578095 (ISSN) ; 9781467377041 (ISBN) ; Sharif University of Technology
This paper provides a universal framework for establishing one-shot achievability results for coordination and secrecy problems. The framework is built on our previous framework [Yassaee et al. 13] for proving one-shot achievability results in the context of source and channel coding problems. In the coordination and secrecy problems, one needs to compare an induced distribution by encoding/decoding with an ideal distribution (satisfying some desirable properties) using a suitable criterion. In this paper, we use fidelity as a criterion for measuring the closeness of induced distribution with the ideal distribution. The framework exploits the stochastic mutual information coders at the...
Article Journal of Lightwave Technology ; Volume 18, Issue 12 , 2000 , Pages 1718-1727 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2000
In this paper, we study the performance of optical code-division multiple access (CDMA) systems using various receivers structures. Two general classes of receivers based on required electronic bandwidth are studied. Optical orthogonal codes (OOCs) are utilized as signature sequences and the performance studied in this paper takes into account the effect of all major noise sources, i.e., quantum shot-noise, dark current noise, and Gaussian circuit noise. Furthermore, this paper introduces a generalized method of analyzing the performance of various optical CDMA receiver structures. Required mean number of photon count per chip time for reliable transmission of data bits for various receiver...
Article Journal of Lightwave Technology ; Volume 20, Issue 8 , 2002 , Pages 1304-1316 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
In this paper, we present a new methodology for analysis of all-optical fiber-optic code-division multiple-access (FO-CDMA) networks. In this analysis, we propose statistical models, based on photon-counting techniques, for some basic elements of the network, such as splitters, combiners, star couplers, and FO-CDMA passive encoders/decoders. By following the statistical variation of the photon-count of the string of pulses that constitutes the address sequence in an FO-CDMA network, we will be able to reveal the quantum-limited optical signal-to-noise ratio (OSNR) required at the transmitter output to meet the performance limits. Moreover, considering receiver thermal noise and source...
Article IET Communications ; Vol. 8, issue. 8 , 2014 , p. 1296-1308 ; Khormuji, M. N ; Skoglund, M ; Aref, M. R ; Sharif University of Technology
The authors study a two-user state-dependent generalised multiple-access channel (GMAC) with correlated states. It is assumed that each encoder has 'non-causal' access to channel state information (CSI). They develop an achievable rate region by employing rate-splitting, block Markov encoding, Gelfand-Pinsker multicoding, superposition coding and joint typicality decoding. In the proposed scheme, the encoders use a partial decoding strategy to collaborate in the next block, and the receiver uses a backward decoding strategy with joint unique decoding at each stage. The author's achievable rate region includes several previously known regions proposed in the literature for different scenarios...
Article IEEE International Symposium on Information Theory - Proceedings ; 2013 , Pages 1287-1291 ; ISSN: 21578095 ; ISBN: 9781479904464 ; Aref, M. R ; Gohari, A ; IEEE; IEEE Information Theory Society ; Sharif University of Technology
This paper proposes a novel technique to prove a one-shot version of achievability results in network information theory. The technique is not based on covering and packing lemmas. In this technique, we use a stochastic encoder and decoder with a particular structure for coding that resembles both the ML and the joint-typicality coders. Although stochastic encoders and decoders do not usually enhance the capacity region, their use simplifies the analysis. The Jensen inequality lies at the heart of error analysis, which enables us to deal with the expectation of many terms coming from stochastic encoders and decoders at once. The technique is illustrated via four examples: point-to-point...
Article 2013 Iran Workshop on Communication and Information Theory ; 2013 ; 9781467350235 (ISBN) ; Khormuji, M. N ; Skoglund, M ; Aref, M. R ; Sharif University of Technology
We study a two-user state-dependent generalized multiple-access channel (GMAC) with correlated states. It is assumed that each encoder noncausally knows partial channel state information. We develop an achievable rate region by employing rate-splitting, block Markov encoding, Gelfand-Pinsker multicoding, superposition coding and jointly typical decoding. In the proposed scheme, the encoders use a partial decoding strategy to collaborate in the next block, and the receiver uses a backward decoding strategy with a joint unique decoding at each stage. Our achievable rate region includes several previously known rate regions proposed in the literature for different scenarios of multiple-access...
Article IEEE Communications Letters ; Volume 17, Issue 4 , 2013 , Pages 645-648 ; 10897798 (ISSN) ; Gohari, A ; Kenari, M. N ; Bateni, F ; Sharif University of Technology
In this letter, a new molecular modulation scheme for nanonetworks is proposed. To evaluate the scheme, a system model based on the Poisson distribution is introduced. The error probability of the proposed scheme as well as that of two previously known schemes, the concentration and molecular shift keying modulations, are derived for the Poisson model by taking into account the error propagation effect of previously decoded symbols. The proposed scheme is shown to outperform the previously introduced schemes. This is due to the fact that the decoding of the current symbol in the proposed scheme does not encounter propagation of error, as the decoding of the current symbol does not depend on...
Article 2012 IEEE Information Theory Workshop, ITW 2012 ; 2012 , Pages 412-416 ; 9781467302234 (ISBN) ; Emadi, M. J ; Davoodi, A. G ; Aref, M. R ; Sharif University of Technology
In this paper, lattice based coding is used over two-user Gaussian state-dependent multiple access channel with common message for two channel models. First, it is assumed that the additive channel interference is noncausally known at both encoders. Exploiting a lattice encoding and decoding scheme, the effect of the interference is completely removed and the capacity region is achieved. Then, the multiple access channel with two additive interferences is considered in the case, where each interference is known noncausally to the associated transmitter. A pure lattice based encoding and decoding structure is proposed and an inner bound on the capacity region is derived which is valid for the...
Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 85, Issue 1 , January , 2012 ; 10502947 (ISSN) ; Memarzadeh, L ; Mancini, S ; Sharif University of Technology
We consider a model of a bosonic memory channel, which induces correlations among the transmitted signals. The application of suitable unitary transformations at the encoding and decoding stages allows the complete removal of correlations, thereby mapping the memory channel into a memoryless one. However, such transformations, being global over an arbitrarily large number of bosonic modes, are not realistically implementable. We then introduce a family of efficiently realizable transformations, which can be used to partially remove correlations among errors, and we quantify the reduction of the gap with memoryless channels
Article IET Communications ; Volume 14, Issue 12 , 2020 , Pages 1883-1893 ; Koochak Shooshtari, M ; Aref, M. R ; Sharif University of Technology
Institution of Engineering and Technology 2020
Polar codes are novel and efficient error-correcting codes with low encoding and decoding complexities. These codes have a channel-dependent generator matrix, which is determined by the code dimension, code length and transmission channel parameters. A variant of the McEliece public-key cryptosystem based on polar codes, called the PKC-PC, is studied. Since the structure of the polar codes' generator matrix depends on the parameters of the channel, the authors have used an efficient approach to conceal their generator matrix. The proposed approach is based on a random selection of rows of the matrix by which a random generator matrix is constructed. Using the characteristics of polar codes...
Article Physical Review A ; Volume 102, Issue 1 , 15 July , 2020 ; Ramezani, M ; Bahrampour, A ; Sharif University of Technology
American Physical Society 2020
Transmission efficiency (TE) of remote state preparation (RSP) with a shared quantum state and one bit of classical communication is considered. Following Dakić et al. [Nat. Phys. 8, 666 (2012)10.1038/nphys2377], the encoding and decoding operators of the protocol are restricted to the physically relevant classes of projective measurements and unitary operators, respectively. It is shown that contrary to the previous arguments, the quadratic fidelity as well as the linear fidelity could be a valid figure of merit to quantify the TE of RSP. Then, the TE of the protocol in terms of both linear and quadratic fidelities is evaluated in a fully optimized scenario which includes the maximization...
M.Sc. Thesis Sharif University of Technology ; Sameti, Hossein
In recent years, deep neural networks have achieved significant improvements in the field of automatic text summarization by using neural sequence architectures. However,the results of these improvements are more tangible in the production of short summaries (a few words or single sentences). In the field of producing long (multisentence) abstracts, the presented models suffer from several issues; These models produce the details of the events incorrectly and tend to generate the phrases been produced before repeatedly. The wording from the output of these models is very close to the original text. Also, the metrics used to evaluate the quality of produced summaries do not have the ability...
Dose Reduction Via Development of a Novel Image Reconstruction Method for Few-View Computed Tomography, Ph.D. Dissertation Sharif University of Technology ; Hosseini, Abolfazl ; Ay, Mohammad Reza
Sparse-view computed tomography (CT) is recently proposed as a promising method to speed up data acquisition and alleviate the issue of CT high-dose delivery to patients. However, traditional reconstruction algorithms are time-consuming and suffer from image degradation when faced with sparse-view data. To address this problem, we propose two new frameworks based on deep learning (DL) that can quickly produce high-quality CT images from sparsely sampled projections and is able for clinical use. Our first DL-based proposed model is based on the convolution, and residual neural networks in a parallel manner, named the parallel residual neural network (PARS-Net). Besides, our proposed PARS-Net...
Article Wireless Networks ; Volume 27, Issue 7 , 2021 , Pages 4615-4634 ; 10220038 (ISSN) ; Khodaiemehr, H ; Eghlidos, T ; Panario, D ; Sharif University of Technology
In this paper, we present a one-way relaying scheme in which two wireless nodes create an information flow to each other via a single decode-and-forward (DF) relay. We consider an additional secrecy constraint for protection against an honest-but-curious relay. Indeed, while the relay should decode the source message, it should be fully ignorant about the message content. We provide a secure lattice coding strategy based on random difference families (RDF) lattice codes for unidirectional Gaussian relay channels. RDF lattice codes are carved from infinite RDF lattices using a shaping algorithm. By RDF lattice we mean a Construction A lattice with a QC-LDPC code, which is obtained from random...
Article IEEE Transactions on Information Theory ; Volume 67, Issue 8 , 2021 , Pages 5526-5547 ; 00189448 (ISSN) ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2021
Barcoding photons, atoms, and any quantum states can provide a host of functionalities that could benefit future quantum communication systems and networks beyond today's imagination. As a significant application of barcoding photons, we introduce code division multiple-access (CDMA) communication systems for various applications. In this context, we introduce and discuss the fundamental principles of a novel quantum CDMA (QCDMA) technique based on spectrally encoding and decoding of continuous-mode quantum light pulses. In particular, we present the mathematical models of various QCDMA modules that are fundamental in describing an ideal and typical QCDMA system, such as quantum signal...