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In this paper we present the results of experiments carried out in an infra-structured 802.11b WLAN comprising a single Access Point (AP) and a number of user terminals. The aim of this work is twofold: by the one hand, we validate well-known " TCP (UDP) over 802.11 " analytic models by means of experimental results; by the other hand, we focus our analysis(More)
In this paper we present some observations about TCP RTT as captured in the live traffic of an operational GPRS/UMTS network. RTT samples are extracted from traces collected by passive monitoring the Gn interfaces of one of the major providers in Austria, EU. We compare results for GPRS and UMTS, and expose some methodological issues involved in performing(More)
In this paper we investigate interactions between TCP and wireless ARQ mechanisms. The aim is to understand what is the best configuration of the wireless link protocol in order to guarantee TCP performance , seemingly a controversial issue. Interactions between TCP and different link layer mechanisms are evaluated by means of an analytic model, that(More)
— Great attention has been dedicated, in the recent years, to the WLAN standards that are opening the market to the short range and high data rate wireless services in the local and hot spot areas. Technically speaking, the main strength of the most quoted standard, the IEEE 802.11, is the fully distributed nature of the access scheme, that provides cheap(More)
This paper proposes an algorithm to identify TCP spurious retransmission timeouts by post processing of packet traces monitored in operational networks. The operational principles of the algorithm and the assumptions behind its design are explained in detail as well as the situations in which the algorithm is prone to inaccuracies. By extensive measurements(More)
PURPOSE This study was done to evaluate the feasibility and effectiveness of adopting a safety checklist (SC) in the angiography suite during interventional radiology (IR) procedures to enhance patient safety. MATERIALS AND METHODS Surgical SC was successfully introduced in 2009 with the aim of drastically reducing the morbidity and mortality caused by(More)