1 The Network of Excellence on Next-Generation Internet (EuroNGI), and its extension, Future-Generation Internet (EuroFGI), is a European project funded bythe EuropeanUnionwithin the ISTSixth FrameworkProgram.Thetargetof the EuroNGI/FGI network is to put together European research centers in the ?eld of networking, focusing on next-generationInternet designand engineering. In all, 60 partners from technical universities and research centers in Europe participate in EuroNGI/FGI. Oneofthe"IntegrationActivities"withinEuroNGI/FGIconsistsoftheor- nizationofanannualWorkshoponWirelessandMobility.Theworkshopintends to bring together leading researchersfrom the Networkof Excellencein this ?eld of research in order to identify the fundamental challenges and future persp- tivesofthisimportantarea. This post-proceedings volume contains a selection of the research cont- butions presented at the fourth edition of the workshop. The workshop was held January 16-18, 2008 in Barcelona, Spain, organized by CompNet Research 2 Group from the Universitat Polit ecnica de Catalunya (UPC). The previous editions of the workshop were also organized by UPC in Sitges, Spain, in 2006; by Politecnico di Milano in Lago di Como, Italy, in 2005; and by Rheinisch- Westf] alischen Technischen Hochschule Aachen in Dagstuhl, Germany, in 2004. To participate in the workshop, the authors submitted an extended abstract of their ongoing work in the ?eld of wireless and mobility. From a total of 39 submissions, 28 were accepted for presentation. Following the discussions and suggestions made in the workshop, the authors submitted 26 full papers that were carefully reviewed by experts on the ?eld. Finally, 16 papers incorporating the numerous referee comments were accepted for publication in this book."

This book constitutes the thoroughly refereed postproceedings of the Third International Workshop on Wirelss and Mobility organized by the European Network of Excellence on Next Generation Internet, EURO-NGI 2006, held in Sitges, Spain in June 2006.

The 19 revised full research papers presented were carefully selected during two rounds of reviewing and improvement. The papers are organized in topical sections on WLAN characterization, vehicular networks, WLAN and sensor networks protocols, QoS and routing in ad-hoc networks, heterogeneous networks, resource management in cellular networks, TCP in wireless, and mobility agents.

Aquesta obra esta basada en el contingut de l'assignatura Xarxes de Computadors, de la Facultat d'Informatica de Barcelona (FIB) de la Universidat Politecnica de Catalunya, i te per objectiu introduir els conceptes basics de les xarxes de computadors, fent emfasi especialment en els protocols TCP/IP d'Internet. Esta dirigit a alumnes que estudien per primera vegada els temes relacionats amb xarxes de computadors. S'estructura en cinc temes. En el tema 1 s'introdueix la terminologia i els ingredients principals d'una xarxa de computadors, agafant Internet com a paradigma, i s'explica la importancia dels organismes d'estandarditzacio i el model de referencia Open System Interconnection (OSI). Al tema 2 s'estudia l'Internet Protocol (IP), els datagrames, el sistema d'adrecament que fa servir IP, els algorismes d'encaminament i altres protocols relacionats (ARP, DNS). L'objectiu del tema 3 es l'estudi del Transmission Control Protocol (TCP) d'Internet, despres d'analitzar els algorismes Automatic Repeat reQuest (ARQ). El tema 4 es dedica a les xarxes de area local (Local Area Networks, LAN), el desenvolupament de les quals s'origina els anys setanta amb l'objectiu d'interconnectar de forma economica un nombre reduit de computadors, impressores i altres dispositius, en una area geografica petita, com es un edifici o un campus. En aquest tema s'estudien alguns conceptes basics relacionats amb les LAN i, especialment, les xarxes Ethernet (protocol d'acces al medi, diferents estandards, hubs i switches) i el protocol Aloha. Finalment, s'expliquen les LAN sense fil, en particular els conceptes fonamentals d'una xarxa IEEE 802.11 (WiFi). Finalment, el tema 5 introdueix la transmissio de dades digitals fent servir senyals electrics. 'analitzen els problemes basics que es presenten en la transmissio d'un senyal electric (atenuacio i distorsio), i s'expliquen alguns tipus de senyals que es fan servir en la transmissio digital (codificacions i modulacions) i alguns elements sobre la deteccio d'errors.