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communication-channels--information-theory
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Total 149 records
Using a diversity scheme to reduce energy consumption in wireless sensor networks
, Article 2nd International Conference on Broadband Networks, BROADNETS 2005, Boston, MA, 3 October 2005 through 7 October 2005 ; Volume 2005 , 2005 , Pages 17-20 ; Ghiassi Farrokhfal, Y ; Mohammadnia Avval, M ; Hossein Khalaj, B ; Sharif University of Technology
2005
Abstract
In this paper, a new method is proposed utilizing a diversity scheme to reduce power consumption in large scale sensor networks. Sensor networks are composed of large number of battery powered nodes. Energy consumption is the most important design objective in sensor networks while delay and throughput are taken less into account. Wireless transmission is the other important characteristic of these networks. Small-scale fading decreases wireless communication performance. In a fading channel higher SNRs is needed and consequently more energy is consumed in fading channels. Another important characteristic of sensor networks is the necessity of fault tolerant protocols. Node-to-node links 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) ; 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...
Internally channel-coded framed time-hopping fiber-optic CDMA communications
, Article Journal of Lightwave Technology ; Volume 23, Issue 11 , 2005 , Pages 3702-3707 ; 07338724 (ISSN) ; Nasiri Kenari, M ; Salehi, J. A ; Sharif University of Technology
2005
Abstract
Due to the low cardinality of optical orthogonal codes (OOCs) with, a correlation value of 1, the capability of an internal channel-coding scheme cannot be applied effectively for an increasing number of simultaneous users in a typical fiber-optic code division multiple-access (FO-CDMA) system. In this paper, we consider applying the internal channel-coding scheme to the framed time-hopping (FTH) FO-CDMA system. Due to the extremely high cardinality of the spreading sequence in FTH FO-CDMA, the technique highlights the ability of the internal channel-coding scheme to increase the effective number of users in an FO-CDMA system. For the FTH FO-CDMA system, we only consider a Poisson...
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...
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) ; 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....
Linear decoupled space-time codes
, Article 14th IEEE 2003 International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC2003, Beijing, 7 September 2003 through 10 September 2003 ; Volume 3 , 2003 , Pages 2862-2867 ; 0780378229 (ISBN); 9780780378223 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2003
Abstract
In this paper, we will introduce a new constraint on linear space-time block codes that will result in a novel decoupled symbol-by-symbol detection scheme. Based on the new framework, a quasi-decoupled space-time code that is applicable to any number of transmit and receive antennas will be proposed. We will also solve a more general case and show that all other known solutions to this problem such as orthogonal designs and Clifford algebra representations, represent special cases of such general solution which will provide an easier framework, to deal with such codes. It is noticeable that the new framework not only provides better understanding of earlier solutions but may also help in...
Performance comparison of deadlock recovery and deadlock avoidance routing algorithms in wormhole-switched networks
, Article IEE Proceedings: Computers and Digital Techniques ; Volume 150, Issue 2 , 2003 , Pages 97-106 ; 13502387 (ISSN) ; Shahrabi, A ; Ould Khaoua, M ; Sarbazi Azad, H ; Sharif University of Technology
2003
Abstract
Dealing with deadlock has always been a crucial issue for any routing algorithms proposed for wormhole-switched networks. Adaptive routing algorithms, based on deadlock avoidance strategies, usually dedicate resources specifically to ensure deadlock freedom. However, a number of recent studies have demonstrated that deadlocks are quite rare in the network. This fact has motivated researchers to introduce adaptive routing algorithms based on deadlock recovery strategies. In an effort to gain a deep understanding of the factors that affect routing performance, a comparison of the performance merits of deadlock recovery against deadlock avoidance routing algorithms is performed. While most...
Comment II on "Dense coding in entangled states"
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 68, Issue 1 , 2003 , Pages - ; 10502947 (ISSN) ; Rezakhani, A. T ; Sharif University of Technology
American Physical Society
2003
Group-covariant extreme and quasiextreme channels
, Article Physical Review Research ; Volume 4, Issue 3 , 2022 ; 26431564 (ISSN) ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2022
Abstract
Constructing all extreme instances of the set of completely positive trace-preserving (CPTP) maps, i.e., quantum channels, is a challenging and valuable open problem in quantum information theory. Here we introduce a systematic approach that, despite the lack of knowledge about the full parametrization of the set of CPTP maps on arbitrary Hilbert-spaced dimension, enables us to construct exactly those extreme channels that are covariant with respect to a finite discrete group or a compact connected Lie group. Innovative labeling of quantum channels by group representations enables us to identify the subset of group-covariant channels whose elements are group-covariant generalized-extreme...