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Total 149 records

    Power-efficient deterministic and adaptive routing in torus networks-on-chip

    , Article Microprocessors and Microsystems ; Vol. 36, issue. 7 , October , 2012 , pp. 571-585 ; ISSN: 01419331 Rahmati, D ; Sarbazi-Azad, H ; Hessabi, S ; Kiasari, A. E ; Sharif University of Technology
    Abstract
    Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

    Quantum achievability proof via collision relative entropy

    , Article IEEE Transactions on Information Theory ; Vol. 60, issue. 12 , 2014 , pp. 7980-7986 ; ISSN: 00189448 Beigi, S ; Gohari, A
    Abstract
    In this paper, we provide a simple framework for deriving one-shot achievable bounds for some problems in quantum information theory. Our framework is based on the joint convexity of the exponential of the collision relative entropy and is a (partial) quantum generalization of the technique of Yassaee et al. from classical information theory. Based on this framework, we derive one-shot achievable bounds for the problems of communication over classical-quantum channels, quantum hypothesis testing, and classical data compression with quantum side information. We argue that our one-shot achievable bounds are strong enough to give the asymptotic achievable rates of these problems even up to the... 

    Compound multiple access channel with confidential messages

    , Article 2014 IEEE International Conference on Communications, ICC 2014 ; 10-14 June 2014 , 2014 , Pages 1922-1927 ; ISBN: 9781479920037 Zivari Fard, H ; Akhbari, B ; Ahmadian Attari, M ; Aref, M. R ; Sharif University of Technology
    Abstract
    In this paper, we study the problem of secret communication over a Compound Multiple Access Channel (MAC). In this channel, we assume that one of the transmitted messages is confidential that is only decoded by its corresponding receiver and kept secret from the other receiver. For this proposed setting (compound MAC with confidential messages), we derive general inner and outer bounds on the secrecy capacity region. Also, as examples, we investigate 'Less noisy' and 'Gaussian' versions of this channel, and extend the results of the discrete memoryless version to these cases. Moreover, providing numerical examples for the Gaussian case, we illustrate the comparison between achievable rate... 

    Physical layer security for some classes of three-receiver broadcast channels

    , Article IET Communications ; Vol. 8, issue. 11 , July , 2014 , p. 1965-1976 Salehkalaibar, S ; Aref, M. R ; Sharif University of Technology
    Abstract
    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... 

    Robust controller design for discrete unstable non-minimum-phase delayed stochastic processes

    , Article International Journal of Control, Automation and Systems ; Volume 11, Issue 5 , 2013 , Pages 893-902 ; 15986446 (ISSN) Rezaei, S ; Shahrokhi, M ; Sharif University of Technology
    2013
    Abstract
    Control of unstable non-minimum-phase delayed stochastic processes is a challenging problem. In this work based on the Diophantine equation and using pole-placement technique, a discrete control scheme for such processes has been proposed. Robust stability of the suggested control structure has been shown. Advantages of the proposed scheme over the existing algorithms have been shown through computer simulations. It has been shown that performance of the proposed scheme for handling model mismatch and colored noise is superior to the previous work proposed in the literature  

    Key agreement over a generalized multiple access channel using noiseless and noisy feedback

    , Article IEEE Journal on Selected Areas in Communications ; Volume 31, Issue 9 , 2013 , Pages 1765-1778 ; 07338716 (ISSN) Salimi, S ; Skoglund, M ; Golic, J. D ; Salmasizadeh, M ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    A secret key agreement framework involving three users is considered in which each of the users 1 and 2 intends to share a secret key with user 3 and users 1 and 2 are eavesdroppers with respect to each other. There is a generalized discrete memoryless multiple access channel (GDMMAC) from users 1 and 2 to user 3 where the three users receive outputs from the channel. Furthermore, there is a feedback channel from user 3 to users 1 and 2 through which user 3 sends information extracted from the received output from the GDMMAC to increase the key rates. We consider both noiseless and noisy feedback. In the case of noiseless feedback, a public channel of unlimited capacity from user 3 to users... 

    Multi-layer Gelfand-Pinsker strategies for the generalized multiple-access channel

    , Article 2013 Iran Workshop on Communication and Information Theory ; 2013 ; 9781467350235 (ISBN) Emadi, M. J ; Khormuji, M. N ; Skoglund, M ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    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... 

    Scheduling TV commercials using genetic algorithms

    , Article International Journal of Production Research ; Volume 51, Issue 16 , 2013 , Pages 4921-4929 ; 00207543 (ISSN) Ghassemi Tari, F ; Alaei, R ; Sharif University of Technology
    2013
    Abstract
    In this paper, the problem of scheduling commercial messages during the peak of viewing time of a TV channel is formulated as a combinatorial auction-based mathematical programming model. Through this model, a profitable and efficient mechanism for allocating the advertising time to advertisers is developed by which the revenue of TV channels is maximised while the effectiveness of advertising is increased. We developed a steady-state genetic algorithm to find an optimal or a near optimal solution for the proposed problem. A computational experiment was conducted for evaluating the efficiency of the proposed algorithm. A set of test problems with different sizes were generated, using the... 

    Modeling the beaconing mechanism in short range wireless networks based on the DRP protocol in outdoor environments

    , Article Wireless Personal Communications ; Volume 70, Issue 2 , 2013 , Pages 831-846 ; 09296212 (ISSN) Ajorloo, H ; Manzuri Shalmani, M. T ; Sharif University of Technology
    2013
    Abstract
    A probabilistic method is developed here to model the beacon period length (BPL) defined in the ECMA-368 and ECMA-387 standards for the distributed reservation protocol. The model computes the probability mass function (PMF) of the BPL in a superframe which will be used in modeling of throughput, delay, fairness, power and other major distributed medium access control layer parameters of the emerging ultra wideband and 60- GHz millimeter wave wireless personal area networks. The model relates the PMF of the BPL to the network density, antenna beamwidth, and the transmission range of the devices assuming that the devices are distributed in an outdoor environment based on Two-dimensional... 

    Power of quantum channels for creating quantum correlations

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 86, Issue 6 , 2012 ; 10502947 (ISSN) Abad, T ; Karimipour, V ; Memarzadeh, L ; Sharif University of Technology
    2012
    Abstract
    Local noise can produce quantum correlations on an initially classically correlated state, provided that it is not represented by a unital or semiclassical channel. We find the power of any given local channel for producing quantum correlations on an initially classically correlated state. We introduce a computable measure for quantifying the quantum correlations in quantum-classical states, which is based on the noncommutativity of ensemble states in one party of the composite system. Using this measure we show that the amount of quantum correlations produced is proportional to the classical correlations in the initial state. The power of an arbitrary channel for producing quantum... 

    On the achievable rate region of a new Gaussian wiretap channel with side information

    , Article 2012 IEEE Information Theory Workshop, ITW 2012, 3 September 2012 through 7 September 2012 ; September , 2012 , Pages 657-661 ; 9781467302234 (ISBN) Bafghi, H. G ; Seyfe, B ; Mirmohseni, M ; Aref, M. R ; Sharif University of Technology
    2012
    Abstract
    This paper introduces a new applicable Gaussian wiretap channel with side information. In this channel, the state of the channel to the wiretapper is separated from the main channel's one. It means that the legitimate receiver and the wiretapper are listening to the transmitted signal through the different channels with different channel states which may have some correlation to each other. The state of the main channel, is assumed to be known at the transmitter, helps the sender to encrypt its messages. The achievable equivocation-rate region for this model is drived in the Gaussian case and the results are reduced to the previous works as special cases  

    Lattice coding for multiple access channels with common message and additive interference

    , Article 2012 IEEE Information Theory Workshop, ITW 2012 ; 2012 , Pages 412-416 ; 9781467302234 (ISBN) Pourbabaee, M. F ; Emadi, M. J ; Davoodi, A. G ; Aref, M. R ; Sharif University of Technology
    2012
    Abstract
    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... 

    On source transmission over some classes of relay channels

    , Article IEEE International Symposium on Information Theory - Proceedings ; 2012 , Pages 1942-1946 ; 9781467325790 (ISBN) Salehkalaibar, S ; Aref, M. R ; Sharif University of Technology
    IEEE  2012
    Abstract
    We study the reliable transmission of correlated sources over the relay channel. One of the sources is available at the sender while the other one is known to the relay. The receiver wishes to reconstruct both sources. We find necessary and sufficient conditions for optimal separation of source and channel codes. The coding scheme is based on the combination of the Slepian-Wolf source coding and Partial Decode-and-Forward (PDF) strategy. In this scheme, the relay partially decodes the message transmitted by the sender. We also consider the semi-deterministic relay channel where the output at the relay is a deterministic function of inputs from the sender and the relay. For the transmission... 

    Universal bounds on the scaling behavior of polar codes

    , Article IEEE International Symposium on Information Theory - Proceedings ; 2012 , Pages 1957-1961 ; 9781467325790 (ISBN) Goli, A ; Hassani, S. H ; Urbanke, R ; Sharif University of Technology
    IEEE  2012
    Abstract
    We consider the problem of determining the tradeoff between the rate and the block-length of polar codes for a given block error probability when we use the successive cancellation decoder. We take the sum of the Bhattacharyya parameters as a proxy for the block error probability, and show that there exists a universal parameter μ such that for any binary memoryless symmetric channel W with capacity I(W), reliable communication requires rates that satisfy R < I(W) - αN -1/μ, where α is a positive constant and N is the block-length. We provide lower bounds on μ, namely μ ≥ 3.553, and we conjecture that indeed μ = 3.627, the parameter for the binary erasure channel  

    Power-efficient deterministic and adaptive routing in torus networks-on-chip

    , Article Microprocessors and Microsystems ; Volume 36, Issue 7 , 2012 , Pages 571-585 ; 01419331 (ISSN) Rahmati, D ; Sarbazi Azad, H ; Hessabi, S ; Kiasari, A. E ; Sharif University of Technology
    Elsevier  2012
    Abstract
    Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

    The capacity region of p-transmitter/q-receiver multiple-access channels with common information

    , Article IEEE Transactions on Information Theory ; Volume 57, Issue 11 , 2011 , Pages 7359-7376 ; 00189448 (ISSN) Haghi, A ; Khosravi Farsani, R ; Aref, M. R ; Marvasti, F ; Sharif University of Technology
    Abstract
    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... 

    Key agreement over multiple access channel using feedback channel

    , Article IEEE International Symposium on Information Theory - Proceedings, 31 July 2011 through 5 August 2011 ; August , 2011 , Pages 1970-1974 ; 21578104 (ISSN) ; 9781457705953 (ISBN) Salimi, S ; Salmasizadeh, M ; Aref, M. R ; Sharif University of Technology
    2011
    Abstract
    In this paper, the effect of using an insecure and noiseless feedback channel in increasing secret key rates is investigated. There is a generalized discrete memoryless multiple access channel (GDMMAC) between two transmitters and a receiver where, in addition to the receiver, both of the transmitters receive noisy channel outputs. Furthermore, an insecure and noiseless feedback channel exists from the receiver to the transmitters. Each of the transmitters intends to share a secret key with the receiver while keeping it concealed from the other transmitter. For this setup, an inner bound of the secret key capacity region is derived. For some special cases, the secret key capacity region is... 

    Multi-carrier based cooperative cognitive network

    , Article IEEE Vehicular Technology Conference, 15 May 2011 through 18 May 2011 ; May , 2011 ; 15502252 (ISSN) ; 9781424483310 (ISBN) Golrezaei, N ; Mansourifard, P ; Nasiri Kenari, M ; Sharif University of Technology
    2011
    Abstract
    In this paper, we propose a novel cognitive cooperative relaying scheme using multi-carrier transmission in which cognitive users assist primary users by relaying their information using Decode and Forward (DF) strategy. The best cognitive user is selected as a relay for a Primary User (PU). Outage probability of the PU is investigated. Our analyses show substantial improvements in the outage probability of the PU when using the proposed cooperative scheme compared to non-cooperative one. We also perform several simulations to corroborate our theoretical results  

    Performance analysis of lattice-reduction algorithms for a novel LR-compatible K-Best MIMO detector

    , Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2011 , Pages 701-704 ; 02714310 (ISSN) ; 9781424494736 (ISBN) Youssef, A ; Shabany, M ; Gulak, P. G ; Sharif University of Technology
    Abstract
    Lattice Reduction (LR) has been proposed as a method to enhance the performance of MIMO detectors such as ZF, MMSE and V-BLAST. Until recently, the application of LR to the superior K-Best tree-search detection algorithm was not practical due to the significant increase in complexity of K-Best as a result of the distortion of tree symmetry caused by LR. However, in our recently published work we developed an innovative K-Best algorithm to accommodate tree-asymmetry with no additional complexity. In this work, we build on this result and perform a detailed analysis of the effect of various LR algorithms on the performance of LR-aided K-Best. We show that LLL and Seysen provide equivalent... 

    SER of M-PSK modulation in incremental-selective decode-and-forward cooperative communications over Rayleigh fading channels

    , Article International Conference on Advanced Communication Technology, ICACT, 13 February 2011 through 16 February 2011 ; February , 2011 , Pages 432-437 ; 17389445 (ISSN) ; 9788955191554 (ISBN) Renani, R. A ; Saadat, R ; Aref, M. R ; Mirjalily, G ; Sharif University of Technology
    2011
    Abstract
    In this paper we consider a cooperative communication systems over Rayleigh fading channels. The system utilizes a combination of incremental and selective decode-and-forward (ISDF) relaying protocols. The symbol error rate (SER) of M-PSK modulation for the ISDF protocol is derived. Using an approximation of the SER expression, the optimal power allocation is investigated. In order to reduce the complexity of the receiver, we used a modified version of the ISDF protocol which does not use the storage or retransmission of the first phase signal. We also derived optimal power allocation coefficient for modified ISDF. It has been noted that for the optimal power allocation in the ISDF protocol,...