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Total 148 records

    A new wideband MIMO channel model for simulating 5-GHz band indoor WLANs

    , Article 2006 IEEE 64th Vehicular Technology Conference, VTC-2006 Fall, Montreal, QC, 25 September 2006 through 28 September 2006 ; 2006 , Pages 2298-2303 ; 15502252 (ISSN); 1424400635 (ISBN); 9781424400638 (ISBN) Jedari, E ; Golparvar Roozbahani, M ; Shishegar, A. A ; Enayati, A. R ; Alihemmati, R ; Sharif University of Technology
    2006
    Abstract
    Considerable interest in the indoor applications of wireless local-area networks (WLANs) demands some powerful simulation methods of these systems. Proper modeling of the physical propagation channel is crucial in this context. A novel simulation method for indoor wideband multi-input multi-output (MIMO) channel at the operating frequency band of IEEE 802.11a, HIPERLAN/2, and the emerging IEEE 802.11n standards is presented in this paper which is suitable for performance analysis of MIMO techniques in these systems. The presented model is developed on the basis of a previously proposed channel representation at the same frequency band. Simulation results for MIMO channel capacity are... 

    Adaptive multi-model CMAC-based supervisory control for uncertain MIMO systems

    , Article ICTAI 2005: 17th IEEE International Conference on Tools with Artificial Intelligence, ICTAI'05, Hong Kong, 14 November 2005 through 16 November 2005 ; Volume 2005 , 2005 , Pages 457-461 ; 10823409 (ISSN); 0769524885 (ISBN); 9780769524887 (ISBN) Sadati, N ; Bagherpour, M ; Ghadami, R ; Sharif University of Technology
    2005
    Abstract
    In this paper, an adaptive multi-model CMAC-based controller (AMCBC) in conjunction with a supervisory controller is developed for uncertain nonlinear MIMO systems. AMCBC is a kind of adaptive feedback linearizing controller where nonlinearity terms are approximated with multiple CMAC neural networks With the help of a supervisory controller, the resulting close-loop system is globally stable. The proposed control system is applied to control a robotic manipulators, where some varying tasks are repeated but information on the load is not defined; it is unknown and varying. It is shown how the proposed controller is effective because of its capability to memorize the control skill for each... 

    The new scheme for data rate improvement in HF communication without using equalizer

    , Article 2005 IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics, Honolulu, HI, 3 April 2005 through 7 April 2005 ; Volume 2005 , 2005 , Pages 1050-1054 ; 0780390687 (ISBN); 9780780390683 (ISBN) Heidari, V ; Alavi, M. H ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    In this paper the new and improvement approach is suggested for realization of a HF receiver without using equalizer. This approach is based on implementing considerations suggested by [1]. In our approach an HF modem without using equalizer implemented which can communicate over several hundred bits per second with very low bits error rate. This improvement was obtained by changing the framing and the coding structures which has been suggested by [1] and by using the symbol time recovery approach which is proposed by [2]. In this paper, the symbol time recovery approach generalized for multipath fading channels. We implemented our approach on Digital Signal Processor named TMS320F2811.... 

    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... 

    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... 

    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... 

    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... 

    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... 

    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... 

    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,... 

    Cooperative relay broadcast channels with partial causal channel state information

    , Article IET Communications ; Volume 5, Issue 6 , 2011 , Pages 760-774 ; 17518628 (ISSN) Akhbari, B ; Khosravi Farsani, R ; Aref, M. R ; Sharif University of Technology
    Abstract
    The authors consider 'partially' and 'fully cooperative' state-dependent relay broadcast channels (RBCs), where partial channel state information (CSI) is available at the nodes causally. First, the authors derive an achievable rate region for general discrete memoryless partially cooperative RBC (PC-RBC) with partial causal CSI, by exploiting superposition coding at the source, decode-and-forward scheme at the relay and Shannon's strategy at the source and the relay. Then, they establish the capacity region of the discrete memoryless physically degraded PC-RBC with partial causal CSI. They also characterise the capacity region of discrete memoryless PC-RBC with feedback and partial causal... 

    Lattice-coded cooperation protocol for the half-duplex Gaussian two-way relay channel

    , Article Eurasip Journal on Wireless Communications and Networking ; Volume 2015, Issue 1 , 2015 , Pages 1-18 ; 16871472 (ISSN) Ghasemi Goojani, S ; Behroozi, H ; Sharif University of Technology
    Abstract
    This paper studies the Gaussian two-way relay channel (GTWRC), where two nodes exchange their messages with the help of a half-duplex relay. We investigate a cooperative transmission protocol, consisting of four phases: multiple access (MA) phase, broadcast (BC) phase, and two cooperative phases. For this setup, we propose a new transmission scheme based on superposition coding for nested lattice codes, random coding, and jointly typical decoding. This scheme divides the message of each node into two parts, referred to as satellite codeword and cloud center. Depending on the phase type, the encoder sends a linear combination of satellite codewords or cloud centers. For comparison, a rate... 

    Secret key cryptosystem based on non-systematic polar codes

    , Article Wireless Personal Communications ; Volume 84, Issue 2 , September , 2015 , Pages 1345-1373 ; 09296212 (ISSN) Hooshmand, R ; Aref, M. R ; Eghlidos, T ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    Polar codes are a new class of error correcting linear block codes, whose generator matrix is specified by the knowledge of transmission channel parameters, code length and code dimension. Moreover, regarding computational security, it is assumed that an attacker with a restricted processing power has unlimited access to the transmission media. Therefore, the attacker can construct the generator matrix of polar codes, especially in the case of binary erasure channels, on which this matrix can be easily constructed. In this paper, we introduce a novel method to keep the generator matrix of polar codes in secret in a way that the attacker cannot access the required information to decode the... 

    An energy-efficient virtual channel power-gating mechanism for on-chip networks

    , Article Proceedings -Design, Automation and Test in Europe, DATE, 9 March 2015 through 13 March 2015 ; Volume 2015-April , March , 2015 , Pages 1527-1532 ; 15301591 (ISSN) ; 9783981537048 (ISBN) Mirhosseini, A ; Sadrosadati, M ; Fakhrzadehgan, A ; Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Power-gating is a promising method for reducing the leakage power of digital systems. In this paper, we propose a novel power-gating scheme for virtual channels in on-chip networks that uses an adaptive method to dynamically adjust the number of active VCs based on the on-chip traffic characteristics. Since virtual channels are used to provide higher throughput under high traffic loads, our method sets the number of virtual channel at each port selectively based on the workload demand, thereby do not negatively affect performance. Evaluation results show that by using this scheme, about 40% average reduction in static power consumption can be achieved with negligible performance overhead  

    Lossy transmission of correlated sources over multiple-access wiretap channels

    , Article IET Communications ; Volume 9, Issue 6 , 2015 , Pages 754-770 ; 17518628 (ISSN) Salehkalaibar, S ; Aref, M. R ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    Abstract
    In this study, the authors study lossy communication of correlated sources over a multiple-access wiretap channel (MAC-WT). Consider a system with two transmitters, a receiver and an eavesdropper. There are two correlated sources where each of them is observed by the corresponding transmitter, separately. Each transmitter wishes to describe its source sequence to the receiver with a desired distortion. The sources need to be kept secret from the eavesdropper. They find an achievable region for the MAC-WT with correlated sources by separation. A joint source-channel coding scheme for the MAC-WT is also proposed. They consider lossy communication of a bivariate Gaussian source over Gaussian... 

    Compute-and-forward two-way relaying

    , Article IET Communications ; Volume 9, Issue 4 , 2015 , Pages 451-459 ; 17518628 (ISSN) Azimi Abarghouyi, S. M ; Hejazi, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    Abstract
    In this study, a new two-way relaying scheme based on compute-and-forward (CMF) framework and relay selection strategies is proposed, which provides a higher throughput than the conventional two-way relaying schemes. Two cases of relays with or without feedback transmission capability are considered. An upper bound on the computation rate of each relay is derived, and based on that, a lower bound on the outage probability of the system is presented assuming block Rayleigh fading channels. Numerical results show that while the average sum rate of the system without feedback, named as max-CMF (M-CMF), reaches the derived upper bound only in low SNRs, that of the system with feedback, named as... 

    Crosstalk modeling to predict channel delay in Network-on-Chips

    , Article Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors, 3 October 2010 through 6 October 2010 ; October , 2010 , Pages 396-401 ; 10636404 (ISSN) ; 9781424489350 (ISBN) Patooghy, A ; Miremadi, S. G ; Shafaei, M ; Sharif University of Technology
    2010
    Abstract
    Communication channels in Network-on-Chips (NoCs) are highly susceptible to crosstalk faults due to the use of nano-scale VLSI technologies in the fabrication of NoCs. Crosstalk faults cause variable timing delay in NoC channels based on the patterns of transitions appearing on the channels. This paper proposes an analytical model to estimate the timing delay of an NoC channel in the presence of crosstalk faults. The model calculates expected number of 4C, 3C, 2C, and 1C transition patterns to predict delay of a K-bit communication channel. The model is applicable for both non-protected channels and channels which are protected by crosstalk mitigation methods. Spice simulations are done in a... 

    A game-theoretic approach for power allocation in bidirectional cooperative communication

    , Article IEEE Wireless Communications and Networking Conference, WCNC, 18 April 2010 through 21 April 2010 ; April , 2010 ; 15253511 (ISSN) ; 9781424463985 (ISBN) Janzamin, M ; Pakravan, M ; Sedghi, H ; Sharif University of Technology
    2010
    Abstract
    Cooperative communication exploits wireless broadcast advantage to confront the severe fading effect on wireless communications. Proper allocation of power can play an important role in the performance of cooperative communication. In this paper, we propose a distributed gametheoretical method for power allocation in bidirectional cooperative communication networks. In this work, we consider two nodes as data sources who want to cooperate in sending data to the destination. In addition to being data source, each source node has to relay the other's data. We answer the question: How much power each node contributes for relaying other node's data? We use Stackelberg game which is an... 

    Secrecy capacity of wiretap channel for a new scenario and designing code for wiretap channel

    , Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 183-187 ; 9781424467600 (ISBN) Jahandideh, V ; Salimi, S ; Salmasizadeh, M ; Sharif University of Technology
    Abstract
    The concept of information theoretic security is introduced. Secrecy capacity of two receiver broadcast channel for a new scenario is derived in which it is assumed that the legitimate receiver has access to a noisy version of eavesdroppers channel outputs. Also the ideas of code designing to achieve zero error on main channel and perfect secrecy on the eavesdropper's channel, without invoking complicated capacity achieving codes are provided  

    A polynomial algorithm for partitioning problems

    , Article Transactions on Embedded Computing Systems ; Volume 9, Issue 4 , 2010 ; 15399087 (ISSN) Tahaee, S. A ; Jahangir, A. H ; Sharif University of Technology
    2010
    Abstract
    This article takes a theoretical approach to focus on the algorithmic properties of hardware/software partitioning. It proposes a method with polynomial complexity to find the global optimum of an NP-hard model partitioning problem for 75% of occurrences under some practical conditions. The global optimum is approached with a lower bound distance for the remaining 25%. Furthermore, this approach ensures finding the 2-approximate of the global optimum partition in 97% of instances where technical assumptions exist. The strategy is based on intelligently changing the parameters of the polynomial model of the partitioning problem to force it to produce (or approach) the exact solution to the...