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Propagation Delay (propagation + delay)

Distribution by Scientific Domains

Engineering	73%

Selected Abstracts

Propagation delay of an RC-circuit with a ramp input: An analytical very accurate and simple model

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 9 2009
Rosario Mita
Abstract In this letter, one of the models reported in Mita et al. (IEEE Trans. Circuits Syst.,II: Express Briefs 2007; 54(1):66,70) for estimating the propagation delay of an RC-chain with a linear input is revised and improved. The extended model, while maintaining the same simplicity, has a reduced error which is six times lower than the original model, being always as low as 1%. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Printed Sub-2 V Gel-Electrolyte-Gated Polymer Transistors and Circuits

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
Yu Xia
Abstract The fabrication and characterization of printed ion-gel-gated poly(3-hexylthiophene) (P3HT) transistors and integrated circuits is reported, with emphasis on demonstrating both function and performance at supply voltages below 2,V. The key to achieving fast sub-2,V operation is an unusual gel electrolyte based on an ionic liquid and a gelating block copolymer. This gel electrolyte serves as the gate dielectric and has both a short polarization response time (<1,ms) and a large specific capacitance (>10,µF cm,2), which leads simultaneously to high output conductance (>2,mS mm,1), low threshold voltage (<1,V) and high inverter switching frequencies (1,10,kHz). Aerosol-jet-printed inverters, ring oscillators, NAND gates, and flip-flop circuits are demonstrated. The five-stage ring oscillator operates at frequencies up to 150,Hz, corresponding to a propagation delay of 0.7 ms per stage. These printed gel electrolyte gated circuits compare favorably with other reported printed circuits that often require much larger operating voltages. Materials factors influencing the performance of the devices are discussed. [source]

Propagation delay of an RC-circuit with a ramp input: An analytical very accurate and simple model

Some new algebraic criteria for chaos synchronization of Chua's circuits by linear state error feedback control

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 3 2006
Xiaofeng Wu
Abstract The research on the sufficient criterion for chaos synchronization of the master,slave Chua's circuits by linear state error feedback control has received much attention and some synchronization criteria for special control matrix were proposed. In this paper, the above synchronization issue is investigated in the situation of general linear state error feedback controller with propagation delay of control signals from the master Chua's circuit. First of all, a master,slave synchronization scheme for Chua's circuits with propagation delay is given and the relevant error system is derived. Using a quadratic Lyapunov function and frequency domain method, three new algebraic synchronization criteria for the synchronization scheme with general control matrix are proven. They are applied to derive the synchronization criteria for simple control matrices. Some examples are given to show the sharpness of these new criteria compared with the known criteria. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Efficient output waveform evaluation of a CMOS inverter based on short-circuit current prediction

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2002
A. Chatzigeorgiou
Abstract A novel approach for obtaining the output waveform, the propagation delay and the short-circuit power dissipation of a CMOS inverter is introduced. The output voltage is calculated by solving the circuit differential equation only for the conducting transistor while the effect of the short-circuit current is considered as an additional charge, which has to be discharged through the conducting transistor causing a shift to the output waveform. The short-circuit current as well as the corresponding discharging current are accurately predicted as functions of the required time shift of the output waveform. A program has been developed that implements the proposed method and the results prove that a significant speed improvement can be gained with a minor penalty in accuracy. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Steady state and transient state behaviours analyses of TCP connections considering interactions between TCP connections and network

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2005
Hiroyuki Hisamatsu
Abstract The Internet uses a window-based congestion control mechanism in transmission control protocol (TCP). In the literature, there have been a great number of analytical studies on TCP. Most of those studies have focused on the statistical behaviour of TCP by assuming a constant packet loss probability in the network. However, the packet loss probability, in reality, changes according to the packet transmission rates from TCP connections. Conversely, the window size of a TCP connection is dependent on the packet loss probability in the network. In this paper, we explicitly model the interaction between the congestion control mechanism of TCP and the network as a feedback system. By using this model, we analyse the steady state and the transient state behaviours of TCP. We derive the throughput and the packet loss probability of TCP, and the number of packets queued in the bottleneck router. We then analyse the transient state behaviour using a control theoretic approach, showing the influence of the number of TCP connections and the propagation delay on the transient state behaviour of TCP. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Performance evaluation of TCP-based applications over DVB-RCS DAMA schemes

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2009
M. Luglio
Abstract Transmission Control Protocol (TCP) performance over Digital Video Broadcasting,Return Channel via Satellite (DVB-RCS) standard is greatly affected by the total delay, which is mainly due to two components, propagation delay and access delay. Both are significant because they are dependent on the long propagation path of the satellite link. The former is intrinsic and due to radio wave propagation over the satellite channel for both TCP packets and acknowledgements. It is regulated by the control loop that governs TCP. The latter is due to the control loop that governs the demand assignment multiple access (DAMA) signalling exchange between satellite terminals and the network control center, necessary to manage return link resources. DAMA is adopted in DVB-RCS standard to achieve flexible and efficient use of the shared resources. Therefore, performance of TCP over DVB-RCS may degrade due to the exploitation of two nested control loops also depending on both the selected DAMA algorithm and the traffic profile. This paper analyses the impact of basic DAMA implementation on TCP-based applications over a DVB-RCS link for a large set of study cases. To provide a detailed overview of TCP performance in DVB-RCS environment, the analysis includes both theoretical approach and simulation campaign. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Radio resource management across multiple protocol layers in satellite networks: a tutorial overview

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2005
Paolo Barsocchi
Abstract Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set-up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end-to-end delay user's requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the system's efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross-layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A GRASP with path-relinking for private virtual circuit routing,

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2003
Mauricio G. C. Resende
Abstract A frame relay service offers virtual private networks to customers by provisioning a set of long-term private virtual circuits (PVCs) between customer endpoints on a large backbone network. During the provisioning of a PVC, routing decisions are made without any knowledge of future requests. Over time, these decisions can cause inefficiencies in the network and occasional offline rerouting of the PVCs is needed. In this paper, the offline PVC routing problem is formulated as an integer multicommodity flow problem with additional constraints and with an objective function that minimizes propagation delays and/or network congestion. We propose variants of a GRASP with path-relinking heuristic for this problem. Experimental results for realistic-size problems are reported, showing that the proposed heuristics are able to improve the solutions found with standard routing techniques. Moreover, the structure of our objective function provides a useful strategy for setting the appropriate value of its weight parameter, to achieve some quality of service (QoS) level defined by a desired balance between propagation delay and delay due to network congestion. © 2003 Wiley Periodicals, Inc. [source]

Channel estimation and physical layer adaptation techniques for satellite networks exploiting adaptive coding and modulation

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2008
Stefano Cioni
Abstract The exploitation of adaptive coding and modulation techniques for broadband multi-beam satellite communication networks operating at Ka-band and above has been shown to theoretically provide large system capacity gains. In this paper, the problem of how to accurately estimate the time-variant channel and how to adapt the physical layer taking into account the effects of estimator errors and (large) satellite propagation delays is analyzed, and practical solutions for both the forward and the reverse link are proposed. A novel pragmatic solution to the reverse link physical layer channel estimation in the presence of time-variant bursty interference has been devised. Physical layer adaptation algorithms jointly with design rules for hysteresis thresholds have been analytically derived. The imperfect physical layer channel estimation impact on the overall system capacity has been finally derived by means of an original semi-analytical approach. Through comprehensive system simulations for a realistic system study case, it is showed that the devised adaptation algorithms are able to successfully track critical Ka-band fading time series with a limited impact on the system capacity while satisfying the link outage probability requirement. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Stability analysis of an adaptive packet access scheme for mobile communication systems with high propagation delays

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2003
Giovanni Giambene
Abstract In this paper, we investigate a packet access scheme that is able to support mixed traffics in the presence of high propagation delays. Referring to a Time-Code Division Multiple Access air interface, we propose a Medium Access Control (MAC) protocol based on a random access scheme. A successful attempt grants the use of a slot-code resource. This protocol is named Adaptive Time Code-Packet Reservation Multiple Access (ATC-PRMA), since the access parameters are changed, depending on the traffic load conditions, so as to fulfil Quality of Service requirements. Numerical examples are carried out for the Low Earth Orbit (LEO)- Mobile Satellite System (MSS) scenario, but all these considerations could be applied to High-Altitude Platform Stations (HAPSs) as well. In both cases, high propagation delays prevent an immediate feedback to users. An analytical approach is proposed to study the stability of our MAC scheme. Accordingly, we define a criterion for optimizing system performance. The predicted ATC-PRMA behaviour is supported by simulation results. Finally, we show the performance improvement of ATC-PRMA with respect to a MAC protocol not employing adaptive parameters. Copyright © 2003 John Wiley & Sons, Ltd. [source]

TCP-Peach for satellite networks: analytical model and performance evaluation

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2001
Ian F. Akyildiz
Abstract Current TCP protocols have low throughput performance in satellite networks mainly due to the effects of long propagation delays and high link error rates. TCP-Peach is a new congestion control scheme for satellite IP networks based on the use of low priority segments, called dummy segments. The sender transmits dummy segments to probe the availability of network resources. Dummy segments are treated as low priority segments thus, they do not effect the throughput of actual data segments. In this paper, TCP-Peach is presented along with its analytical model which is used to evaluate the throughput performance. Experiments show that TCP-Peach is robust to high link error rates as well as long propagation delays, and outperforms other TCP schemes for satellite networks. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP)

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2004
L. Martyn Klassen
Abstract Quantitative MRI techniques as well as methods such as blood oxygen level-dependent (BOLD) imaging and in vivo spectroscopy require stringent optimization of magnetic field homogeneity, particularly when using high main magnetic fields. Automated shimming approaches require a method of measuring the main magnetic field, B0, followed by adjusting the currents in resistive shim coils to maximize homogeneity. A robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP) using a 3D multiecho gradient echo sequence that measures B0 with high precision was developed. Inherent compensation and postprocessing methods enable removal of artifacts due to hardware timing errors, gradient propagation delays, gradient amplifier asymmetry, and eddy currents. This allows field maps to be generated for any field of view, bandwidth, resolution, or acquisition orientation without custom tuning of sequence parameters. Field maps of an aqueous phantom show ± 1 Hz variation with altered acquisition orientations and bandwidths. Subsequent fitting of measured shim coil field maps allows calculation of shim currents to produce optimum field homogeneity. Magn Reson Med 51:881,887, 2004. © 2004 Wiley-Liss, Inc. [source]