3,393 research outputs found
Mobile WiMAX Performance Investigation
No full textAlthough the Mobile-WiMAX technology is being deployed in the United States, Europe, Japan, Korea, Taiwan and in the Mideast, there are still ongoing discussions about the potential of this technology. What is really remarkable, in fact, with regard to the Mobile-WiMAX profile, is the high number of degrees of freedom that are left to manufacturers. The final decision on a lot of very basic and crucial aspects, such as, just to cite few of them, the bandwidth, the frame duration, the duplexing scheme and the up/downlink traffic asymmetry, are left to implementers. It follows that the performance of this technology is not clear yet, even to network operators.
This consideration motivated our work, which is focused on the derivation of an analytical framework that, starting from system parameters and implementation choices, allows to
evaluate the performance level provided by this technology, carefully taking all aspects of IEEE802.16e into account. In particular, the analysis starts from the choices to be made at the
physical layer, among those admitted by the specification, and "goes up" through the protocol pillar to finally express the application layer throughput and the number of supported
voice over IP (VoIP) users, carefully considering "along the way" all characteristics of the the medium access control (MAC) layer, the resource allocation strategies, the overhead introduced,
the inherent inefficiencies, etc
Editorial of the MDPI JSAN Special Issue on Wireless Technologies Applied to Connected and Automated Vehicles
No full textConnectivity and automation are two aspects that, together, will revolutionize the transport system [...
A softer vertical handover algorithm for heterogeneous wireless access networks
No full textFuture wireless access will involve a variety of integrated and interworking technologies. Depending on the conditions (e.g., the specific application, the quality of service requirements, the user mobility) each session will be served through the most suited access network; following some event, there will be a variation of the access technology, which is called vertical handover. Although the use of one technology at a time is mostly envisioned, the use of multiple wireless links at the same time, hereafter called parallel transmission, is also envisioned for higher throughput. On the basis of parallel transmission, in this paper the original definition of softer vertical handover is given and an algorithm for softer vertical handover in heterogeneous wireless access networks is proposed; the achievable improvement is shown in two reference scenarios
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
Congestion Control Mechanisms in IEEE 802.11p and Sidelink C-V2X
No full textConnected vehicles are expected to play a major role in the next future to improve safety and traffic efficiency on the road and short-range technologies have been defined to enable the direct exchange of information. To this aim, two solutions are currently the subject of a debate that goes beyond the technician, i.e., IEEE 802.11p and sidelink cellular-vehicle-to-anything (C-V2X). Tested and mature for deployment the first, possibly more efficient the second. In both cases, one of the main aspects is the management of channel congestions, which can cause serious packet losses and have a critical impact on the reliability of applications. Congestions can be managed through different approaches, including the control of transmission power, packet generation frequency, and the adopted modulation and coding scheme. Congestion management has been well studied in IEEE 802.11p, with consolidated algorithms included in the standards, whereas it appears somehow as a new topic looking at C-V2X. In this work, a review of the main congestion control mechanisms and a discussion of their applicability and efficiency in the two technologies is provided. This topic is addressed without focusing on specific algorithms and with the aim to provide general guidelines as a starting point for new proposals
On uncoordinated multi user multi RAT combining
No full textNowadays, wireless systems allow us to have connectivity almost everywhere. Different radio access technologies are integrated in the same device and they can be used following the specific service requirements, the actual received signal levels, and the costs related to their use. Presently, technologies are always seen as alternatives, but it is envisioned that different wireless connections may be used cooperatively in order to enhance the throughput perceived by the end user. In this paper we discuss this opportunity trying to understand what would be the impact of a multi technology combining in a multi user scenario with no coordination among access networks. © 2011 IEEE
WLAN hot spots to increase UMTS capacity
No full textThe seamless integration of heterogeneous wireless access networks is currently one of the issues of major interest in the field of telecommunication systems. In an early future technologies like UMTS, WLAN and WiMAX will give broadband access to users that perform their voice/video calls or data sessions without knowledge of the specific technology their terminals are using, following the paradigm of always best connected. In this scenario, UMTS and WLAN integration has a primary role, due to the coverage of cellular systems and the low cost of the latter technology. This work, in particular, focuses on the gain in terms of capacity that the deployment ofWLAN access points allows in an area fully covered by an UMTS network, assuming that the radio resources are not managed by complex multi radio resource management algorithms. For this scope a real scenario is accurately simulated and the end users perception is evaluated taking care of all aspects related to each level of the protocol stack, with particular attention to radio propagation. ©2010 IEEE
A Raspberry Pi-Based Platform for Signal Processing Education [SP Education]
No full textOne of the most important application areas of signal processing (SP) is, without a doubt, the software-defined radio (SDR) field [1]-[3]. Although their introduction dates back to the 1980s, SDRs are now becoming the dominant technology in radio communications, thanks to the dramatic development of SP-optimized programmable hardware, such as field-programmable gate arrays (FPGAs) and digital signal processors (DSPs). Today, the computational throughput of these devices is such that sophisticated SP tasks can be efficiently handled, so that both the baseband and intermediate frequency (IF) sections of current communication systems are usually implemented, according to the SDR paradigm, by the FPGA's reconfigurable circuitry (e.g., [4]-[6]), or by the software running on DSPs
Performance versus Fairness in Multi User Wireless Communications
No full textPerformance and fairness optimization is an ever challenging issue that leads academics from all over the world toward the
research of the optimal tradeoff in several fields, such as economic, computer science, and wireless communications. In this work
we focus on one of the most important problems in networking to propose a novel and general framework for the analytical
formulation of the optimal tradeoff between performance and fairness that can be applied to a wide class of networking problems
Specifically, we adopt a general definition of performance and fairness, that can be used in most tradeoff problems. The solution
is given in terms of a simple system of equations that can be numerically solved. Example results are provided for two case
studies, respectively concerning linear and logarithmic relationships between the resources allocated to the user and its perceived
performance
On the use of OFDMA for next generation vehicular ad hoc networks
No full textVehicular ad hoc networks (VANETs) based on
IEEE 802.11p are moving new safety and traffic applications
beyond the present limitations given by infrastructures. However,
due to the high variability in time and position of nodes,
the medium access control layer of IEEE 802.11p, which is
based on carrier sensing multiple access with collision avoidance
(CSMA/CA), could lead to severe performance degradation in
terms of delivery delay and delivery ratio as the node density
increases. Because of its higher efficiency, we propose the use of
orthogonal frequency division multiple access (OFDMA) as access
technique in VANETs, discussing and evaluating i) its feasibility,
ii) the challenges posed by the distributed allocation of resources,
and iii) its performance in terms of resource allocation efficiency
(specifically, delivery rate and delivery delay) when compared
to CSMA/CA. Results, obtained by means of simulations that
jointly take into account realistic road maps, vehicular traffic,
and the whole network architecture from the application down
to the physical layer, show that OFDMA allows up to four times
higher delivery rate and that it also guarantees lower delivery
delay in heavy loaded network conditions
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