1,721,002 research outputs found
Scalable TCP over satellite links: Performance issues and cross-layer design
No full textIn this work, we analyze some issues related to the performance of a recently proposed TCP enhancement, Scalable TCP (S-TCP), over satellite links. We first discuss S-TCP features and assess its performance in satellite networks, by means of numerical simulations, for a wide range of conditions (fixed users, mobile users, rainy days). Then, we analyze the impact of S-TCP protocol parameters in a satellite environment, and provide guidelines for their setting in order to improve the system performance. Finally, we present some possible enhancements deriving from the adoption of erasure codes at the link level (in a cross-layer perspective). In particular, TCP/FEC interactions are analyzed and the optimal operating point is derived
Performance evaluation of scalable TCP and HighSpeed TCP over geostationary satellite links
No full textIn this paper we analyse the performance in a satellite environment of two recently proposed modifications to the TCP's congestion control algorithm, namely Scalable TCP and Highspeed TCP. These two protocols, originally designed for high-speed backbone links, appear to be major candidates for replacing in the next-generation Internet the current congestion control mechanism implemented by standard TCP. In this paper, we evaluate by means of ns2 simulations the performance of such protocols in a static as well as a mobile satellite environment. The results confirm that both protocols, and particularly S-TCP, may represent a viable alternative to standard TCP also in a satellite environment. © 2005 IEEE
The Impact of Channel Randomness on Coverage and Connectivity of Ad Hoc and Sensor Networks
No full text
Performance Evaluation of Bluetooth Polling Schemes: An Analytical Approach
No full textIn the recent years, many polling schemes for Bluetooth networks have been proposed and evaluated. To the authors knowledge, however, analysis has been carried out mainly through computer simulations and, up to now, no mathematical treatment of this topic has been presented. In this paper, we propose an analytical framework for performance evaluation of polling algorithms in Bluetooth piconets. The analysis is carried out by resorting to an effective and simple mathematical method, called Equilibrium Point Analysis. The system is modelled as a multidimensional finite Markov chain and performance metrics are evaluated at the equilibrium state. The analysis is focused on three classical polling schemes, namely Pure Round Robin, Gated Round Robin and Exhaustive Round Robin, which are compared in terms of packet delay, channel utilization, and fairness among users. Both analytical and simulation results are presented for three relevant scenarios, in order to validate the accuracy of the analysis proposed
A Simulation Study of Scalable TCP and HighSpeed TCP in Geostationary Satellite Networks
No full textThis paper investigates the performance of two TCP enhancements (i.e., Scalable TCP and HighSpeed TCP), recently proposed for high-speed backbone networks with a very large bandwidth-delay product, in a geostationary satellite environment. Both persistent and elastic traffic patterns are considered, performance being evaluated in terms of TCP throughput and mean session delay, respectively. The impact of channel characteristics (packet error rate, correlation between successive losses) is widely discussed. Fairness issues are also accounted for, together with the impact of some system parameters, such as the satellite link bandwidth. Extensive comparisons are carried out among Scalable TCP, HighSpeed TCP and other congestion control schemes. The obtained results show the soundness for the use of such protocols in geostationary satellite networks. Indeed, both protocols permit to improve the performance of TCP connections in a wide range of channel conditions, showing (especially Scalable TCP) to be able to cope well with rainy conditions and to exploit a future increase in the satellite link capacity
On the use of wireless networks at low level of factory automation systems
No full textWireless communication systems are rapidly becoming a viable solution for employment at the lowest level of factory automation systems, usually referred to as either "device" or "field" level, where the requested performance may be rather critical in terms of both transmission time and reliability. In this paper, we deal with the use of wireless networks at the device level. Specifically, after an analysis of the communication requirements, we introduce a general profile of a wireless fieldbus. Both the physical and data link layers are taken directly from existing wireless local area networks and wireless personal area networks standards, whereas the application layer is derived from the most popular wired fieldbuses. We discuss implementation issues related to two models of application layer protocols and present performance results obtained through numerical simulations. We also address some important aspects related to data security and power consumption
Experimental evaluation of an industrial application layer protocol over wireless systems
No full textSeveral recent studies have addressed the suitability
of current wireless technologies for industrial communications
which, frequently, are requested to cope with severe timing constraints.
Most of the analysis that have lately appeared in the
literature have focused on the performance offered by the lower
layers of the communication stack. However, in order to obtain a
complete picture, it is important to analyze how this gets coupled
with the features of higher layer protocols typically employed
by industrial communication applications. In this paper, we
investigate the performance obtained by an application layer protocol,
derived from those currently employed by wired fieldbuses,
running over COTS devices based on two popular wireless communication
standards, namely, IEEE 802.15.4 and IEEE 802.11.
In particular, we present a mapping of the application service
elements onto the services offered by the mentioned wireless systems
and discuss some possible design choices. A prototype of the
application layer protocol is then implemented for each considered
wireless technology and the performance figures evaluated by
means of experimental measurements
Use of New Generation WPANs for Real-Time Industrial Communications
No full textThe new generation of Wireless Personal Area Networks (WPANs) has reached performance levels that allow their use also at the field level of industrial communication systems where, typically, very tight timing constraints exist. Indeed, they are particularly suitable to implement wireless extensions of wired fieldbuses, since they provide short range connectivity at high transmission speeds. In this paper we investigate the feasibility of such a type of hybrid networks using two new generation WPANs, namely, IEEE802.15.3 and Bluetooth v2.0. In detail, we describe an application layer protocol to be implemented on both types of stations (wired and wireless). Also, we detail the mapping of the protocol services onto the data link layers of WPANs. Finally, we present the results of a theoretical analysis carried out on the wireless segment, in order to evaluate the network performance. Such analysis confirms the sustainability of the proposed solution
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