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    A comparative performance analysis of n-cubes and star graphs

    , Article 20th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2006, 25 April 2006 through 29 April 2006 ; Volume 2006 , 2006 ; 1424400546 (ISBN); 9781424400546 (ISBN) Kiasari, A.E ; Sarbazi Azad, H ; Sharif University of Technology
    IEEE Computer Society  2006
    Many theoretical-based comparison studies, relying on the graph theoretical viewpoints with using structural and algorithmic properties, have been conducted for the hypercube and the star graph. None of these studies, however, considered real working conditions and implementation limits. We have compared the performance of the star and hypercube networks for different message length and virtual channels and considered two implementation constraints, namely the constant bisection bandwidth and constant node pin-out. We use two accurate analytical models already proposed for the star graph and hypercube and implement the parameter changes imposed by technological implementation constraints.... 

    W-shaped enhanced-bandwidth patch antenna for wireless communication

    , Article Wireless Personal Communications ; Volume 43, Issue 4 , May , 2007 , Pages 1257-1265 ; 09296212 (ISSN) Lotfi Neyestanak, A. A ; Hojjat Kashani, F ; Barkeshli, K ; Sharif University of Technology
    In this paper a novel form of the familiar E-shaped patch antenna is presented. In the presented approach, by using the genetic algorithm (GA) based on fuzzy decision-making, some modifications have been implemented to the incorporated slots which lead to even more enhancement in the antenna bandwidth. The MOM (Method of Moment) is employed for analysis at the frequency band of 1.8GHz-2.6GHz by the optimization parameters of supply locations and slot dimensions. In the implemented fuzzy system, inputs are parameters like population, and outputs are parameters like recombination to produce the next generation. Fuzzy inference system (FIS) is used for the control of GA parameters. The design... 

    Statistical definition of locking bandwidth in an array of synchronised microwave oscillators

    , Article IET Microwaves, Antennas and Propagation ; Volume 2, Issue 1 , 2008 , Pages 74-81 ; 17518725 (ISSN) Hajian, H ; Banai, A ; Farzaneh, F ; Sharif University of Technology
    Arrays of N weakly coupled oscillators are considered in different configurations. The locking bandwidth for these arrays is defined statistically. Various factors affecting the locking bandwidth and the effect of the coupling network topology on locking bandwidth are studied by solving the dynamic equations of the array numerically. The analytical locking bandwidth for two configurations of arrays is computed and the results are compared with the numerical solution of dynamic equations. © The Institution of Engineering and Technology 2008  

    Minimum power Miller-compensated CMOS operational amplifiers

    , Article Scientia Iranica ; Vol. 21, Issue. 6 , 2014 , pp. 2243-2249 ; e-ISSN :23453605 Meghdadi, M ; Bakhtiar, M. S ; Sharif University of Technology
    A new approach for the design of two-stage Miller-compensated CMOS op amps is presented. The paper studies the basic relations between power consumption, unitygain bandwidth, the biasing region, technology parameters, and the external capacitive load. As a result, simple and efficient design guides are provided to achieve the minimum possible power consumption for the given specifications and for short-channel devices. It is shown that the conventional design procedures do not always result in minimum power op amps. The presented results are also verified by Spectre simulations  

    A dual circularly reconfigurable polarization patch antenna for fifth generation mobile communication systems

    , Article Progress In Electromagnetics Research C ; Volume 105 , 2020 , Pages 73-84 Mallat, N. K ; Nouri, M ; Aghdam, S. A ; Zia, M. T ; Harb, B ; Jafarieh, A ; Sharif University of Technology
    Electromagnetics Academy  2020
    In this paper, a reconfigurable patch antenna with Circular Polarization (CP) diversity with theoretical discussion and verification is proposed for fifth generation (5G) of mobile communication systems. The proposed antenna contains two PIN diodes, which are correctly placed on the ground plane to obtain polarization diversity. By switching between two ON/OFF modes in the PIN diodes, the proposed antenna can support either the RHCP mode or the LHCP mode. An antenna with the well-matched impedance bandwidths (S11 ≤ −10 dB) of 2.5 GHz (27 ∼ 29.5 GHz) and 3 GHz (36 ∼ 39 GHz) and the dual-band 3-dB axial ratios of 6% (27.3–29 GHz) and 8.4% (35–38.2 GHz) operates in both the RHCP and LHCP modes.... 

    IF band width optimization of envelope detection system in presence of phase noise

    , Article IET International Radar Conference 2009, Guilin, 20 April 2009 through 22 April 2009 ; Issue 551 CP , 2009 ; 9781849190107 (ISBN) Tavan, M ; Mirzaei, S ; Norouzi, Y ; Sharif University of Technology
    In many radar and EW applications, after some processing, the envelope of the received pulse is calculated and is used for target detection. Most of the time only the effect of thermal noise is considered in such detectors, but in most of the practical applications, before envelope detection, the signal should be down converted from radio frequency (RF) to an intermediate frequency (IF). In this case, the phase noise of the local oscillator will affect the signal, too. Surprisingly, in contrast to thermal noise, the effect of phase noise on the envelope of signal becomes more considerable whenever the IF bandwidth is decreased. So there exists an optimum IF bandwidth for the receiver. In... 

    Inline high-bandwidth network analysis using a robust stream clustering algorithm

    , Article IET Information Security ; Volume 13, Issue 5 , 2019 , Pages 486-497 ; 17518709 (ISSN) Noferesti, M ; Jalili, R ; Sharif University of Technology
    Institution of Engineering and Technology  2019
    High-bandwidth network analysis is challenging, resource consuming, and inaccurate due to the high volume, velocity, and variety characteristics of the network traffic. The infinite stream of incoming traffic forms a dynamic environment with unexpected changes, which requires analysing approaches to satisfy the high-bandwidth network processing challenges such as incremental learning, inline processing, and outlier handling. This study proposes an inline high-bandwidth network stream clustering algorithm designed to incrementally mine large amounts of continuously transmitting network traffic when some outliers can be dropped before determining the network traffic behaviour. Maintaining... 

    Wideband and polarisation-independent antireflection coating using metamaterials

    , Article IET Optoelectronics ; Volume 14, Issue 5 , 2020 , Pages 266-273 Sepehripour, F ; Karimi, P ; Khavasi, A ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Here, the authors propose a new approach for realising wideband and polarisation-independent antireflection coating, based on a metamaterial composed of a subwavelength array of metallic pillars with a square cross-section. The effective impedance of the array can be duly adjusted by the size and distance of the pillars. As such, the authors design the effective impedance of the antireflection coating to be the geometrical mean of the impedance of upper and lower media and choose its height to be quarter of operating wavelength. Doing so, the reflection vanishes at the desired frequency and fractional bandwidth of 56% is achieved with a criterion of 10% reflectance (the refractive index of... 

    Bandwidth adapted hierarchical multicast overlay

    , Article Proceedings - 5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20 September 2010 through 25 September 2010 ; 2010 , Pages 262-267 ; 9780769541815 (ISBN) Bagheri, M ; Movaghar, A ; Khodaparast, A. A ; Sharif University of Technology
    As the infrastructure-centric model of peer-to-peer streaming, recent overlay construction schemes compose a hierarchical topology of peers by grouping them into clusters. There is a server in each cluster that receives data from the source and relays it to its cluster members. In this paper, we propose an alternative infrastructure-centric peer-to-peer framework called BAHMO that constructs a hierarchical multicast tree. BAHMO does not utilize server bandwidth and rely only on peer bandwidth for data transfers. It achieves both the stability of the infrastructure-centric model and the bandwidth efficiency of the fully-distributed model. Bandwidth assignment for inter-cluster data transfers... 

    A fast and reliable multi-sender algorithm for peer-to-peer networks

    , Article Journal of Network and Computer Applications ; Volume 32, Issue 3 , May , 2009 , Pages 733–740 Firooz, M. H. (Mohammad Hamed) ; Sharif University of Technology
    Due to special constraints in peer-to-peer (P2P) networks (such as bandwidth limitation) and because of their highly dynamic characteristics, a single node cannot provide a reliable multimedia stream to the receivers. Several multi-sender algorithms are proposed to reliably deliver a media stream to the receiver through the intrinsically unreliable P2P networks. Based on upload bandwidths and availability of peers as well as the bandwidths of the links connecting the senders and the receiver, PROMISE selects a set of active senders to maximize the expected bit-rate delivered to the receiver. By careful investigation of PROMISE, in this paper, we present why and how it deviates from finding... 

    Tunable delay line based on Fourier-transformation and linear phase modulation with high time-bandwidth product

    , Article Photonische Netze - 13. ITG-Fachtagung 2020 ; 2020 , Pages 229-231 Mokhtari, A ; Preubler, S ; Jamshidi, K ; Akbari, M ; Schneider, T ; Sharif University of Technology
    VDE Verlag GmbH  2020
    We recruit basic properties of Fourier transformation to realize an electrically tunable delay line and increase the delay by creating a loop in the structure. The proposed method has been experimentally tested and verified for up to 5 roundtrips. The relative delay/advancement was increased up to 5 times compared to the original setup while preserving the original setup's advantages. © VDE VERLAG GMBH  

    A bandwidth-efficient scheme for distributed storage systems

    , Article 2008 2nd International Symposium on Advanced Networks and Telecommunication Systems, ANTS 2008, Mumbai, 15 December 2008 through 17 December 2008 ; May , 2008 ; 1424436001 (ISBN); 9781424436002 (ISBN) Bathaee, N. S ; Pakravan, M. R ; Sharif University of Technology
    In this paper, utilizing the benefits of network coding, we introduce a scheme for uncoordinated dynamic distributed storage systems in which nodes can randomly join and leave the storage network. The proposed scheme can reduce the bandwidth requirement of the storage network  

    An enhanced random-walk method for content locating in P2P networks

    , Article 27th International Conference on Distributed Computing Systems Workshops, ICDCSW'07, Toronto, ON, 22 June 2007 through 29 June 2007 ; 2007 ; 0769528384 (ISBN); 9780769528380 (ISBN) Ronasi, K ; Firooz, M. H ; Pakravan, M. R ; Nasiri Avanaki, A ; Sharif University of Technology
    The important problem of content location in an unstructured distributed network (such as P2P, with no central searching system, graph construction control or file placement regulation) is addressed. The existing methods that are based on either flooding or random walk impose a large traffic load on the network or require a long time to search. In this work, we propose a method that outperforms the existing methods in both of these measures. These advantages are achieved by publishing traces of the contents of each node in its nearby nodes, so that the closer nodes to the target have a stronger trace of it. Such traces are used to rapidly locate the desired content. The superb performance of... 

    An empirical performance analysis of minimal and non-minimal routing in cube-based OTIS multicomputers

    , Article Journal of High Speed Networks ; Volume 16, Issue 2 , 2007 , Pages 133-155 ; 09266801 (ISSN) Hashemi Najaf Abadi, H ; Sarbazi Azad, H ; Sharif University of Technology
    In this study, the performance of virtual cut-through switching in the cube-based OTIS architecture, an optoelectronic interconnection architecture for multicomputer systems, is empirically analyzed. Deadlock-free deterministic and adaptive minimal path routing algorithms for this architecture are introduced, and the effects of different network and traffic parameters on average message latency are investigated. This analysis presents a relatively more realistic view of the OTIS architecture than that presented in previous work by considering issues related to a lower level of abstraction (the routing and switching of messages). Among other results, the analysis indicates that depending on... 

    Bacterial foraging search in unstructured P2P networks

    , Article Canadian Conference on Electrical and Computer Engineering ; 2014 Sharifkhani, F ; Pakravan, M. R ; Sharif University of Technology
    In this paper, a new search algorithm in heterogeneous hierarchical unstructured p2p networks is presented which takes into account heterogeneity of peers such as upload bandwidth, life time in the network and process capacity in its peer discovery policy as factors that influence download performance and user satisfaction. One advantage of this algorithm is that it can be performed in a completely unstructured network without imposing any change on network topology and file replication. However, it obviously decreases file download time as it is designed to discover broad-bandwidth nodes with a higher probability. This property results in a fair distribution of load over heterogeneous p2p... 

    Design and analysis of broadband darlington amplifiers with bandwidth enhancement in GaAs pHEMT technology

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 62, Issue 8 , August , 2014 , Pages 1705-1715 ; ISSN: 00189480 Nikandish, G ; Medi, A ; Sharif University of Technology
    This paper presents a bandwidth enhancement technique for broadband Darlington amplifiers. A detailed analysis of the high-frequency performance of the Darlington amplifier and the effect of bandwidth enhancement is provided. A design procedure is also given for broadband feedback Darlington amplifiers with bandwidth enhancement and gain flattening. A single- and a three-stage feedback amplifier with the proposed improvements are designed and implemented in a 0.25-μm Al-GaAs-InGaAs pHEMT technology. The single-stage amplifier provides 6 ± 0.4 dB of small-signal gain in the frequency band of 1-30 GHz. The three-stage amplifier features 17.8 ± 0.8 dB of small-signal gain in the frequency band... 

    Distributed secondary control in DC microgrids with low-bandwidth communication link

    , Article 7th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2016, 16 February 2016 through 18 February 2016 ; 2016 , Pages 641-645 ; 9781509003754 (ISBN) Loh, P. C ; Blaabjerg, F ; Peyghami Akhuleh, S ; Mokhtari, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this paper, a distributed secondary power sharing approach with low bandwidth communication network is proposed for low voltage direct current (LVDC) microgrids. Conventional droop control causes voltage drop in the grid and also a mismatch on the current of converters in the case of consideration of the line resistances. Proposed control system carry out the current value of the other converters to reach the accurate current sharing and suitable voltage regulation as well. Voltage and current controllers locally regulate the voltage and current of converters as a secondary controller. Secondary controller is realized locally and the communication network is only used to transfer the data... 

    Wideband printed slot bowtie antenna using symmetric vias

    , Article Microwave and Optical Technology Letters ; Volume 58, Issue 6 , 2016 , Pages 1301-1304 ; 08952477 (ISSN) Mazaheri, M. H ; Amani, N ; Jafargholi, A ; Sharif University of Technology
    John Wiley and Sons Inc 
    This letter presents a symmetrical slot-type bowtie antenna with widened impedance bandwidth and high efficiency. Two symmetric vias are exploited underneath each slot in order to increase the antenna bandwidth up to 84% with simultaneous preservation of high efficiency (>90%), and low cross-polarization (<-10 dB). The proposed antenna is fed with 50Ω ungrounded coplanar waveguide (CPW) with no need to balun insertion and tuning stub. The proposed antenna has low profile and simple structure in comparison with previous complex wideband bowtie antennas. The commercial CST Microwave Studio software is adopted for the simulations. The antenna is fabricated and measured, while good agreement is... 

    A scalable framework for wireless distributed computing

    , Article IEEE/ACM Transactions on Networking ; Volume 25, Issue 5 , 2017 , Pages 2643-2654 ; 10636692 (ISSN) Li, S ; Yu, Q ; Maddah Ali, M. A ; Avestimehr, A. S ; Sharif University of Technology
    We consider a wireless distributed computing system, in which multiple mobile users, connected wirelessly through an access point, collaborate to perform a computation task. In particular, users communicate with each other via the access point to exchange their locally computed intermediate computation results, which is known as data shuffling. We propose a scalable framework for this system, in which the required communication bandwidth for data shuffling does not increase with the number of users in the network. The key idea is to utilize a particular repetitive pattern of placing the data set (thus a particular repetitive pattern of intermediate computations), in order to provide the... 

    HB2DS: a behavior-driven high-bandwidth network mining system

    , Article Journal of Systems and Software ; Volume 127 , 2017 , Pages 266-277 ; 01641212 (ISSN) Noferesti, M ; Jalili, R ; Sharif University of Technology
    Elsevier Inc  2017
    This paper proposes a behavior detection system, HB2DS, to address the behavior-detection challenges in high-bandwidth networks. In HB2DS, a summarization of network traffic is represented through some meta-events. The relationships amongst meta-events are used to mine end-user behaviors. HB2DS satisfies the main constraints exist in analyzing of high-bandwidth networks, namely online learning and outlier handling, as well as one-pass processing, delay, and memory limitations. Our evaluation indicates significant improvement in big data stream analyzing in terms of accuracy and efficiency. © 2016 Elsevier Inc