1,721,271 research outputs found
Sixth Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks
No full textAn architectural model to provide QoS in a home network and its evaluation in a real testbed
No full textHome networks are an evolution of office local area networks, answering the need for residential distribution of broadband services. The design of a home network must strive to keep low costs, easy installation and maintenance while at the same time providing a large variety of services, from voice and data applications to multimedia streaming. A successful platform for home networking must put together simple interfaces for the users and sophisticated mechanisms for managing the distribution of the desired broadband services. In this paper we propose mechanisms to support flows with different Quality of Service (QoS) requirements in a home network whose architectural model has been defined in the framework of the European IST ePerSpace project. The model is based on a centralized Residential Gateway (RG), which connects and coordinates different network technologies to support home services. The proposed mechanisms are simple to be implemented since they can be installed on top of existing home network technologies, without modifying them. We implement the whole model and our mechanisms in a real testbed and we perform an extensive performance evaluation over it. The performance evaluation allows us to understand the effect of different settings both on the wired and on the wireless interfaces of the RG, to comprehend which are the key aspects that influence the overall performance and to propose some RG configurations which turn out to be very effective in achieving the desired performance. Special attention is devoted to the wireless support of home services on IEEE 802.11b devices. © 2008 Academy Publisher
Nano-wireless communications for microrobotics: an algorithm to connect networks of microrobots
No full textMicro and nanorobotics represents one of the most challenging sectors of modern robotics. Through batch fabrication of Micro Electro-Mechanical Systems (MEMS), advanced small scale sensing and actuating tasks in a wide area of applications can be performed. Most miniaturized electro-mechanical devices are characterized by low-power and low-memory capacity. The huge number of modular robots introduces the need to explore novel self-reconfiguration algorithms to optimize movement and communication performances in terms of efficiency, parallelism and scalability. Nano-transceivers and nano-antennas operating in the Terahertz Band are already a well acquainted communication paradigm, enforcing nano-wireless networking that can be directly integrated in MEMS microrobots. Several logical topology shape-shifting algorithms are already implemented and tested in literature, along with performance evaluation on nano-wireless use. This article aims to provide an algorithm to reconnect groups of microrobots, along with a novel movement model for microrobotics ensembles introduced to enforce more realistic simulations. Special emphasis is given on the need of novel movement algorithms for swarms of microrobots
Optimizing the radio link protocol for TCP over UMTS-TDD radio interface
No full textA major challenge of the UMTS paradigm is to offer a variety of access services, mostly targeted at multimedia and fast data communications. In this context, the support of Internet applications based on the TCP presents several open issues due to the wireless network segment. The aim of the presented study is to assess the performance of TCP data transfer over the TD-CDMA scheme of the UMTS TDD radio interface, by accounting for the main features of the radio channel and for the already standardized procedures and formats of MAC and Radio Link Control (RLC) protocols of the radio interface
Ad hoc networking with Bluetooth: Key metrics and distributed protocols for scatternet formation
No full textBluetooth is a promising technology for personal/local area wireless communications. A Bluetooth scatternet is composed of simple overlapping piconets, each with a low number of devices sharing the same radio channel. A scatternet may have different topological configurations, depending on the number of composing piconets, the role of the devices involved and the configuration of the links. This paper discusses the scatternet formation issue by analyzing topological characteristics of the scatternet formed. A matrix-based representation of the network topology is used to define metrics that are applied to evaluate the key cost parameters and the scatternet performance. Numerical examples are presented and discussed, highlighting the impact of metric selection on scatternet performance. Then, a distributed algorithm for scatternet topology optimization is introduced, that supports the formation of a "locally optimal" scatternet based on a selected metric. Numerical results obtained by adopting this distributed approach to "optimize" the network topology are shown to be close to the global optimum. © 2003 Elsevier B.V. All rights reserved
Direct and ultimate ownership structure in Italian listed companies: a longitudinal study (1995-2005)
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An Opportunistic Access Scheme Through Distributed Interference Control for MIMO Cognitive Nodes
No full textA critical issue of a Cognitive Radio Network is the interference generated by secondary users simultaneously accessing and transmitting over the primary user spectrum band. In this paper, we introduce and study a distributed and opportunistic access scheme for MIMO ad-hoc cognitive radio networks identified as OPTIM-COG (OPporTunistic Interference control for Mimo COGnitive radio). OPTIM-COG is based on simple power stimuli issued by PU transmitters. These stimuli are basic control messages exchanged, at a known power, by both primary transmitter and primary intended receiver for their internal power control. A periodic repetition of this power stimulus and the power control generated in the primary network are used by secondary nodes to get their transmission opportunities. These opportunities are determined with a twofold goal: on the one hand the secondary node will transmit to its secondary receiver only if the quality of the already established primary connection does not decrease below a minimum level, on the other hand the resulting opportunistic access exploits the MIMO performance improvements. We describe the fully distributed version of this access scheme and we theoretically demonstrate, via a game theoretical formulation, that the resulting power allocation is the unique Nash Equilibrium. Performance results present secondary user access maps in the 2D plan, where both MIMO benefits as well as the presence of multiple active secondary links can be represented. Both the cases of a perfect interference measurement and imperfect channel estimation are evaluated
The introduction of corporate governance codes: efficiency versus institutional reasons
No full textNo abstract availabl
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