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communication-channels--information-theory
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Achievable rate region for multiple-access-relay-networks
, Article IET Communications ; Volume 4, Issue 15 , October , 2010 , Pages 1792-1798 ; 17518628 (ISSN) ; Ghabeli, L ; Aref, M. R ; Sharif University of Technology
Abstract
The authors introduce a generalisation of the multiple-access-relay-channel (MARC) called multiple-access-relay-network (MARN). The MARC model was first introduced by Kramer et al. and consists of many transmitters, one receiver and only one relay. In the MARN, there are many transmitters, many relays and one receiver. The authors obtained an achievable rate region for MARN by considering partial decode-and-forward (PDF) strategy at the relays. They showed that the region obtained using PDF strategy subsumes the region obtained by Kramer et al. for MARC. In the proposed coding scheme, the authors take advantage of PDF strategy based on regular encoding/backward decoding strategy. They also...
ACM: Accurate crosstalk modeling to predict channel delay in Network-on-Chips
, Article 2016 IEEE 22nd International Symposium on On-Line Testing and Robust System Design, IOLTS 2016, 4 July 2016 through 6 July 2016 ; 2016 , Pages 7-8 ; 9781509015061 (ISBN) ; Shirmohammadi, Z ; Miremadi, S. G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
The severity of timing delay in the communication channels of Network on Chip (NoC) depends on the transition patterns appearing on the wires. An analytical model can estimate the timing delay in NoC channels in the presence of crosstalk faults. However, recently proposed analytical model does not have enough accuracy and is based on 3-wire delay model. In this paper, an Accurate Crosstalk Model (ACM) based on 5-wire delay model is proposed to estimate the delay of communication channels in the presence of crosstalk faults. ACM is more accurate due to considering more wires in the delay model and also considering the overlaps between locations of transition patterns
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) ; 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...
Adaptive online prediction of operator position in teleoperation with unknown time-varying delay: simulation and experiments
, Article Neural Computing and Applications ; 2020 ; Yazdankhoo, B ; Beigzadeh, B ; Meghdari, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
One of the most important problems in teleoperation systems is time delay and packet loss in the communication channel, which can affect transparency and stability. One way to overcome the time delay effects in a teleoperation system is to predict the master-side motion. In this way, when data is received in the slave side, it will be considered as the current position of the master robot and, thus, complete transparency could be achieved. The majority of the previous works regarding operator position prediction have considered known and constant time delay in the system; however, in the real applications, time delay is unknown and variable. In this paper, an adaptive online prediction...
Adaptive online prediction of operator position in teleoperation with unknown time-varying delay: simulation and experiments
, Article Neural Computing and Applications ; Volume 33, Issue 13 , 2021 , Pages 7575-7592 ; 09410643 (ISSN) ; Yazdankhoo, B ; Beigzadeh, B ; Meghdari, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
One of the most important problems in teleoperation systems is time delay and packet loss in the communication channel, which can affect transparency and stability. One way to overcome the time delay effects in a teleoperation system is to predict the master-side motion. In this way, when data is received in the slave side, it will be considered as the current position of the master robot and, thus, complete transparency could be achieved. The majority of the previous works regarding operator position prediction have considered known and constant time delay in the system; however, in the real applications, time delay is unknown and variable. In this paper, an adaptive online prediction...
A distortion outer bound for communicating correlated gaussian sources over a gaussian MAC
, Article IEEE Communications Letters ; Volume 21, Issue 7 , 2017 , Pages 1457-1460 ; 10897798 (ISSN) ; Behroozi, H ; Khalaj, B. H ; Sharif University of Technology
Abstract
In this letter, we consider two problems of sending a bivariate Gaussian source through a two-user Gaussian non-orthogonal multiple-access channel. We provide a new distortion outer bound for the considered joint source-channel coding problems, which significantly reduces the gap between inner and outer bounds of the distortion for correlation coefficients below a threshold. Furthermore, numerical results show, that under some conditions, our proposed outer bound matches with the inner bound obtained via the separate source-channel coding scheme, which proves the optimality of this scheme. © 1997-2012 IEEE
A fuzzy sliding mode control approach for nonlinear chemical processes
, Article Control Engineering Practice ; Volume 17, Issue 5 , 2009 , Pages 541-550 ; 09670661 (ISSN) ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
2009
Abstract
Fuzzy sliding mode control (FSMC) as a robust and intelligent nonlinear control technique is proposed to control processes with severe nonlinearity and unknown models. The performance of the proposed method has been evaluated for both single input single output (SISO) and MIMO nonlinear systems through its application in three severely nonlinear processes that are frequently used as benchmarks of nonlinear process control strategies. The evaluation shows that, despite its lack of dependence on the process model, the proposed method performs almost the same as conventional sliding mode control alternatives that utilize all the information that exists in the mathematical model of the process....
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) ; 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...
A heuristic trade off model for integration of distributed generations in deregulated power systems considering technical, economical and environmental issues
, Article 2008 IEEE 2nd International Power and Energy Conference, PECon 2008, Johor Baharu, 1 December 2008 through 3 December 2008 ; 2008 , Pages 1275-1279 ; 9781424424054 (ISBN) ; Nasiri, R ; Bagheri, M ; Tehrani, A. A ; Sharif University of Technology
2008
Abstract
With the introduction of restructuring concepts to traditional power systems, a great deal of attention is given to the utilization of distributed generation. Since the integration of DG units has been known as an alternative for main grid as a resource for energy supply, the determination of optimal sizing and sitting is an important issue in the planning procedure of DG. This work presents a comprehensive multi-objective model for integration of distributed generations into a distribution network, regarding various technical, economical and environmental issues such as reduction of carbon dioxide emissions and investment & running costs while the bus voltages shall be kept within...
A lattice-based compress-and-forward strategy for Gaussian two-way relay channel with direct links
, Article IEEE Wireless Communications Letters ; Volume 5, Issue 5 , 2016 , Pages 500-503 ; 21622337 (ISSN) ; Mardani, S ; Behroozi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this letter, the Gaussian two-way relay channel with direct links is investigated in which two users aim at exchanging their messages with the help of a relay node. We propose a new lattice-based compress-and-forward strategy and obtain its achievable rate-region. We show that the proposed scheme is superior to all previously known achievable schemes for channel gains larger than one. In particular, under the symmetric case, the proposed scheme is able to achieve a capacity region within 0.5 bit or (1/2)log 3 ≅ 0.79 bit, depending on the power of the relay
A lightweight signcryption scheme for defense against fragment duplication attack in the 6LoWPAN networks
, Article Peer-to-Peer Networking and Applications ; 2018 , Pages 1-18 ; 19366442 (ISSN) ; Movaghar, A ; Hosseinzadeh, M ; Sharif University of Technology
Springer New York LLC
2018
Abstract
The Internet of Things (IoT) presents a new paradigm of the future Internet that intends to provide interactive communication between various processing objects via heterogeneous networks. The IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) is an IPv6 adaptation sub-layer and provides the requirements of IP connectivity between resource-constrained devices in lossy, low power networks. Since the size of a packet in the IPv6 is larger than the size of a frame in the IEEE 802.15.4, the 6LoWPAN adaptation layer performs packet fragmentation. In this paper, first, the 6LoWPAN fragmentation mechanism in terms of security issues is analyzed and then, fragment duplication attack which...
A low power and high density cache memory based on novel SRAM cell
, Article IEICE Electronics Express ; Volume 6, Issue 15 , 2009 , Pages 1084-1090 ; 13492543 (ISSN) ; Noorollahi Romani, M ; Manzuri, M. T ; Mehrparvar, A ; Sharif University of Technology
2009
Abstract
Based on the observation that dynamic occurrence of zeros in the cache access stream and cache-resident memory values of ordinary programs exhibit a strong bias towards zero, this paper presents a novel CMOS four-transistor (4T) SRAM cell for very high density and low power cache applications. This cell retains its data with leakage current and positive feedback without refresh cycle. The new cell size is 20% smaller than a conventional six-transistor cell using same design rules and delay access of a cache based on new 4T SRAM cell is 32% smaller than a cache based on 6T SRAM cell. Also the dynamic and static power consumption of new cell is 40% and 20% smaller than 6T SRAM cell,...
AMACA - A new multiple access collision avoidance scheme for wireless lans
, Article 2004 International Workshop on Wireless Ad-Hoc Networks, Oulu, 31 May 2004 through 3 June 2004 ; 2005 , Pages 238-242 ; 0780382757 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2005
Abstract
It's well known that "hidden- and exposed-terminal" are among the main problems in ad-hoc WLAN networks. In addition, there are scenarios where the desired destination is located in the range of other transmitters, so that the efforts on setting up communication with this terminal will fail due to collisions occurred between desired control packets and unwanted received data packets at destination. In such scenarios, conventional protocols can not address the problem efficiently, resulting in throughput and channel utilization degradation. In this paper, by using the same PHY of IEEE 802.11 and making slight changes in its MAC layer, a new MAC protocol is presented to address such problems....
An achievable rate for relay networks based on compress-and-forward strategy
, Article IEEE Communications Letters ; Volume 14, Issue 4 , 2010 , Pages 279-281 ; 10897798 (ISSN) ; Ghabeli, L ; Aref, M. R ; Sharif University of Technology
Abstract
Compress-and-Forward (CF) is a well-known coding strategy proposed for relay channels. Few works which were done about the generalization of the CF strategy to the relay networks, are based on irregular encoding/successive decoding. In this paper, a new generalization of the CF strategy to the relay networks based on regular encoding/backward decoding is presented. In general, backward decoding has been shown to yield higher rates in comparison with successive decoding. Here we will investigate the performance of backward decoding in our problem and show that our achievable rate includes the previously proposed rates
An adaptive approach to manage the number of virtual channels
, Article 22nd International Conference on Advanced Information Networking and Applications Workshops/Symposia, AINA 2008, Gino-wan, Okinawa, 25 March 2008 through 28 March 2008 ; 2008 , Pages 353-358 ; 1550445X (ISSN) ; 0769530966 (ISBN); 9780769530963 (ISBN) ; Koohi, S ; Hessabi, S ; Rahmati, D ; Sharif University of Technology
2008
Abstract
Network-on-Chip (NoC) is a precious approach to handle huge number of transistors by virtue of technology scaling to lower than 50nm. Virtual channels have been introduced in order to improve the performance according to a timing multiplexing concept in each physical channel. The incremental effect of virtual channels on power consumption has been shown in literatures. The issue of power saving has always been controversial to many designers. In this paper, we introduce a new technique which tries to adaptively mange the number of virtual channels in order to reduce the power consumption while not degrading the performance of the network without any reconfiguration. Our experimental results...
An adaptive call admission algorithm for cellular networks
, Article Computers and Electrical Engineering ; Volume 31, Issue 2 , 2005 , Pages 132-151 ; 00457906 (ISSN) ; Meybodi, M. R ; Sharif University of Technology
2005
Abstract
In this paper, we first propose a new continuous action-set learning automaton and theoretically study its convergence properties and show that it converges to the optimal action. Then we give an adaptive and autonomous call admission algorithm for cellular mobile networks, which uses the proposed learning automaton to minimize the blocking probability of the new calls subject to the constraint on the dropping probability of the handoff calls. The simulation results show that the performance of the proposed algorithm is close to the performance of the limited fractional guard channel algorithm for which we need to know all the traffic parameters in advance. © 2005 Elsevier Ltd. All rights...
An adaptive secure channel coding scheme for data transmission over LEO satellite channels
, Article Scientia Iranica ; Volume 13, Issue 4 , 2006 , Pages 373-378 ; 10263098 (ISSN) ; Ahmadian, M ; Aref, M. R ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
Both secure and error control coding are very extensive subjects, each with a variety of subdisciplines. A secure channel coding (joint encryption-channel coding) scheme provides both data secrecy and data reliability in one process to combat problems in an insecure and unreliable channel. In this paper, a joint encryption-channel coding scheme is developed, based on concatenated turbo codes for more efficient and secure transmission of LEO satellite data. Reliability and security are achieved by adapting the pseudo-random puncturing strategy with a change of distance between satellites and ground stations in the communication séance, an issue further burdened by reducing energy consumption...
Analysis of throughput and delay in a spectrally phase-encoded optical CDMA packet network
, Article 4th IEEE and IFIP International Conference on Wireless and Optical Communications Networks, WOCN 2007, Singapore, 2 July 2007 through 4 July 2007 ; 2007 ; 1424410045 (ISBN); 9781424410040 (ISBN) ; Khaleghi, S ; Jamshidi, K ; Sharif University of Technology
2007
Abstract
In this paper, analysis of the throughput and delay in a spectrally phase-encoded optical code-division multiple-access (OCDMA) system, using a simplified slotted packet network protocol is conducted. Steady-state throughput and average packet delay of the system are derived. In evaluating the performance of the system, only multiple access interference is considered and other sources of noise are neglected. Comparing different systems with the fixed bit rate and chip duration leads us to conclude that increasing the code length will improve the performance of networks with small average activity; but in highly active networks, decreasing the code length will result in a significant...
Analytical power allocation for a full duplex decode-and-forward relay channel
, Article 2013 Iran Workshop on Communication and Information Theory ; 2013 ; 9781467350235 (ISBN) ; Emadi, M. J ; Aref, M. R ; Sharif University of Technology
Abstract
For a Rayleigh fading full-duplex decode-and-forward relay channel, we analytically derive optimum power allocation schemes subject to individual power constraints for the source and the relay. The optimization problem is taken over the source power and the relay power. It is proven that the optimization problem is concave for this scenario, and optimum power allocations are derived in a closed-form. Finally, the implications of the theoretical results are discussed through the graphs
Analytic modeling of channel traffic in n-cubes
, Article 1st International Computer Science Symposium in Russia, CSR 2006, St. Petersburg, 8 June 2006 through 12 June 2006 ; Volume 3967 LNCS , 2006 , Pages 567-579 ; 03029743 (ISSN) ; Mahini, H ; Patooghy, A ; Sharif University of Technology
Springer Verlag
2006
Abstract
Many studies have shown that the imbalance of network channel traffic is of critical effect on the overall performance of multicomputer systems. In this paper, we analytically model the traffic rate crossing the network channels of a hypercube network under different working conditions. The effect of different parameters on the shaping of non-uniformity and traffic imbalance over network channels, are considered and analytical models for each case are proposed. © Springer-Verlag Berlin Heidelberg 2006