1,721,250 research outputs found
Multipath Routing for Cellular System Core Networks
No full textThe paper proposes and analyzes source routing techniques applied to signalling or high QoS packets in a cellular data network. Source routing is used to replicate each packet on different paths in the wired core network, with the aim to reduce the packet drop in case of network congestion so that the performance of the whole end-to-end link, including wireless access, increase. A theory has been developed to verify the trade-off between the overhead introduced by the packet replication and the performance improvement. As performance factors, the average packet drop probability and the average time to reach destination have been considered. Simulations have been reported to validate the theory
PACKET RELAYING STRATEGIES FOR POLLING BASED AD-HOC WLANS
No full textBy considering a stand-alone WLAN system, some possible packet relaying strategies are proposed and compared. These strategies are based on the possibility of using a terminal in the WLAN as a relay point, following three different approaches, so that the path between source and final target is realized by means of hops on intermediate stations. The medium access protocol is a polling and the control is hold throughout a token. The performance evaluation is made through simulations, in which are taken into account some simple models for terminal mobility, traffic generation, propagation channel, modulation and retransmissions. The simulations have the purpose of showing the impact of the system parameters and making a comparison between the strategies introduced
WLAN Token Passing MAC Proposal with Optimized FDD technique
No full textBy considering a WLAN with a polling MAC scheme and a centralized topology based on a hub with control and relay functions, this paper investigates the problem of managing the resources relative to the uplink and the downlink. The proposed and analytically studied resources allocation is a FDD scheme, with a suitable organization of the signal and information packets on the band partition. In order to make realistic the investigation, a not ideal channel, characterized by a certain bit error probability, two ARQ strategies, to mitigate the error effects, and a traffic model, to consider packet routes from stations inside and outside the WLAN, are taken into account. A general performance optimization procedure, based on an opportune bandwidth partition selection, is presented and some results are shown, by considering a simple scenario
On the Asynchronous Frequency Hopping Systems Performance
No full textAn analytical performance characterization of frequency hopping systems, in asynchronous environment, has been derived by means of a closed formula. The system considers a forward error correction code to counteract the partial overlap interesting two successive slots if a frequency collision occurs. The closed formula, representing the average error probability, allows a fast system performance evaluation and an optimized frequency hop sequences design. Some simulations have been performed to validate the developed theory
An Analytical Model of the Route Acquisition Process in AODV Protocol
No full textThe paper presents an analysis of the route acquisition process in the ad hoc on demand distance vector (AODV) routing protocol. We develop an analytical model describing the probability of realizing the route request process in a certain number of hops, taking into account some possible errors and link breaks during the path toward destination. Comparisons between simulations performed with a simple simulator developed in C and model results confirm the effectiveness of the proposed model. Other interesting numerical results about the influence of some scenario parameters over the route request process performances are described
Patù (LE), Indagini archeologiche P.zza Indipendenza, vie Garibaldi, Mazzini, G. Romano, L. Romano (2005)
No full textIndagini archeologiche preventive 2005 in P.zza Indipendenza, vie Garibaldi, Mazzini, G. Romano, L. Romano con rinvenimento di fosse granarie e frantoi ipogei con impianti di torchio "alla calabrese" e "alla genovese"(rispettivamente risalenti daJ sec.XVl e dal sec. XVIlI in poi)
Human astrocytoma cell proliferation induced by exogenous platelet-derived growth factor (PDGF).
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