1,720,970 research outputs found
A cross-layer location-based approach for mobile-controlled connectivity
No full textWe investigate into the potentiality of an enhanced Power and Location-based Vertical Handover (PLB-VHO) approach, based on a combination of physical parameters (i.e., location and power attenuation information), for mobile-controlled connectivity across UMTS and WLAN networks. We show that the location information in a multiparameter vertical handover can significantly enhance communication performance. In the presented approach a power attenuation map for the visited area is built and kept updated by exploiting the information sharing of power measurements with other cooperating mobile devices inside the visited networks. Such information is then used for connectivity switching in handover decisions. The analytical model for the proposed technique is first presented and then compared with a traditional Power-Based approach and a simplified Location-Based technique. Simulation results show the effectiveness of PLB-VHO approach, in terms of (i) network performance optimization and (ii) limitation of unnecessary handovers (i.e., mitigation of ping-pong effect). Copyright © 2010 T. Inzerilli, et al
Teoria dell’Informazione e Codici
No full textL’informazione, il canale trasmissivo e la sua codifica
Codifica di sorgenti discrete, Algoritmi di compressione per dati, voce ed immagini.
Codici per la rivelazione e la correzione degli errori (CRC, ARQ e FEC). La trasmissione di codici a blocco su canali binari, Aritmetica modulo 2 e Campi di Galois. Codici a blocco lineari, Codici duali e Codici ciclici
Codici a blocco di uso comune: Hamming, MaxLength, Golay, BCH, Reed–Solomon, checksum, CRC
Codici convoluzionali, decodifica a massima verosimiglianza e algoritmo di Viterbi hard e soft, interallacciamento, codifica concatenata.
Canali numerici: Entropie di canale, Capacità di canale, Disuguaglianza di Fano, Secondo Teorema di Shannon, Funzione esponente d’errore.
Turbocodici: Codici convoluzionali recursivi sistematici (RSC), Punturazione, Concatenazione in parallelo, Soft – output Viterbi algorithm (SOVA) e decodifica iterativa
Enhancing Service Location Protocol with a OWL-based Service Description Model for Service Discovery in Pervasive Computing Networks
No full textIn pervasive computing environments a
fundamental functionality to be supported is Service Discovery.
This allows an entity to locate a service, either a network or a 3rd
party service, or acquire parameters for network configuration
dynamically. An important component of a service discovery
architecture is its service description model, which has to be
sufficiently powerful so as to allow users to easily find a number
of services with precise features but also largely compatible with
existing systems. Two goals which are often in contrast. In this
paper we propose a service discovery framework including a
service discovery protocol, SLP (Service Location Protocol
[1],[2]), integrated with the powerful descriptive functionalities
offered by OWL (Ontology Web Language [3]), a language that
permits creation of service ontologies for flexible description of
services. Namely, this work presents first results of the service
discovery design activity which is being carried out within
DAIDALOS (Designing Advanced network Interfaces for the
Delivery and Administration of Location independent, Optimised
personal Services [4]), a project granted in the European 6th
Framework Research Programme, within the IST (Information
Society and Technology) thematic area
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