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The recently proposed Time-Division Unbalanced Carrier Sense Multiple Access (TDuCSMA) coordination function has been shown to cope very efficiently with many different data flows with widely different bitrates and packet lengths. This case may happen in a typical wireless home network setting where HD video, voice, videosurveillance and videoconference applications are used concurrently. This paper...
Most of the emerging applications for road safety and traffic management rely on the frequent exchange of awareness messages among vehicles. Unfortunately, the 802.11 protocol poorly behaves under congested scenarios and cannot guarantee the reliability and timeliness demands of massively transmitted broadcast messages, leading to the severe degradation of safety. Recently, there has been a consensus...
The problem of coexistence among wireless networks, especially dissimilar ones competing for partially overlapping unlicensed bands, is becoming a hot topic. This is also confirmed by the mushrooming of mechanisms and working groups (within the International Bodies) addressing the issue. But prior to drawing any solution, an extensive theoretical analysis of the coexistence phenomena among any MAC...
This work addresses the implications of using the Time-Division Unbalanced Carrier Sense Multiple Access (TDuCSMA) coordination function to support triple-play services. Firstly, the theoretical background of TDuCSMA is reported, presenting its advantages and discussing its full compliance with the IEEE 802.11 standard. Secondly, a prototype of TDuCSMA is discussed in details. Then, a set of experiments...
Many cooperative applications designed to improve road safety rely on the frequent exchange of awareness messages among vehicles. Therefore, under high vehicle density, the channel medium is expected to get congested. To tackle this situation, the European Telecommunications Standards Institute (ETSI) specified a set of Decentralized Congestion Control (DCC) mechanisms that adapt the transmission...
The analysis on Vehicular Ad-Hoc NETworks (VANETs) is often restricted to the protocol mechanisms, disregarding physical layer phenomena which, actually, should not be neglected. This paper focuses on those phenomena, in the wireless chain, which have recently been demonstrated to significantly influence results. Two main areas are covered: the modelling of packet reception and the identification...
The IEEE 802.11p/WAVE family of standards has been designed to provide multi-channel communications for vehicular use. Despite the increasing interest on vehicular networking, further efforts are still required to improve realism of simulations, in order to account for the latest standards and for physical-related phenomena. In this paper, we aim at overhauling the physical and MAC layers of ns-2...
While IEEE 802.11p has been world-wide recognized as the incumbent MAC solution for VANET, some synchronous slotted solutions still survive not only in the scientific literature but also in standardization community: they represent an opportunity for possible next-generation solutions specifically addressing determinism, as required by safety services. Reversely it is arguable how much a connection-oriented...
Recently a strong research effort has been spent on Vehicular Ad-Hoc Networks to evaluate, also by simulations, the effectiveness of protocol solutions. The difficulties lie not only in the definition of realistic simulation environments (including mobility, propagation effects and large number of nodes), but also in the precise comprehension of the results achieved. In fact the outputs hardly allow...
Solutions for Vehicular Ad-Hoc Network (VANET) are challenging due to the intrinsic nature of the network which involves, by definition, node mobility, scarce or null fixed nodes and, at the current state of art, lack of solutions for the real-time tracking of positions. Moreover VANETs are meant to provide primarily a solution for the improvement of road safety, by the proper forwarding of messages:...
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