359 research outputs found
An optimal topology-transparent scheduling method in multihop packet radio networks
Many transmission scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time-division multiple-access (TDMA) frame length in multihop packet radio networks. Almost all existing algorithms assume exact network topology information and do not adapt to different traffic requirements. Chlamtac and Farago proposed a topology-transparent algorithm. Following their approach, but with a different design strategy, we propose another algorithm which is optimal in that it maximizes the minimum throughput. We compare our algorithm with that of Chlamtac and Farago's and with the TDMA algorithm, and find that it gives better performance in terms of minimum throughput and minimum and maximum delay times. Our algorithm requires estimated values of the number of nodes and the maximum nodal degree in the network. However, we show that the performance of our algorithm is insensitive to these design parameters. © 1998 IEEE.published_or_final_versio
Mecanismos de mobilidade rápida com suporte de QdS
Mestrado em Engenharia Electrónica e TelecomunicaçõesA área das redes de comunicações está, neste momento, a deparar-se com
um novo paradigma causado pela tendência de convergência de redes sem
fios e celulares. Desta convergência resultará a existência de uma camada de
rede integradora, para facilitar o suporte de mecanismos de Qualidade de
Serviço e mobilidade. Aqui, o suporte de mobilidade rápida e transparente,
sem ser perceptível pelo utilizador, tem sido alvo de muita atenção, apesar de
ainda existirem algumas limitações no seu suporte. A mobilidade transparente
entre redes celulares, sem fios e fixas, é ambicionada mas ainda não foi
alcançada.
O trabalho realizado nesta Dissertação consiste na descrição, especificação,
implementação e teste de uma nova arquitectura de mobilidade sobre o
protocolo IP. Esta arquitectura é baseada no protocolo de mobilidade Mobility
Support for IPv6 e em extensões de Fast Handovers for Mobile IPv6, sendo
capaz de efectuar handovers iniciados pelo terminal e pela rede. A mobilidade
é transparente entre tecnologias de acesso heterogéneas, através da
integração de mecanismos de qualidade de serviço, tais como autorização de
handovers, controlo de acesso, reserva e atribuição de recursos no novo ponto
de ligação e também integrada com subsistemas de autenticação. São
também propostos outros mecanismos de mobilidade rápida que fazem uso do
protocolo multicast para distribuir os fluxos de tráfego direccionados ao
terminal, pelos routers de acesso vizinhos, permitindo que os terminais móveis
mudem para qualquer router de acesso na vizinhança sem interrupção dos
serviços em curso. Estes mecanismos foram projectados para terminais
móveis com grandes requisitos de mobilidade.
No âmbito do projecto IST Daidalos foi efectuada a integração de uma rede de
próxima geração (4G) de forma a permitir a realização de testes de
desempenho e conformidade aos mecanismos propostos. A presente
Dissertação efectua uma avaliação de desempenho de uma arquitectura de
mobilidade, em cenários intra- e inter-tecnologia, numa rede de testes real.
Nesta avaliação foram utilizadas as métricas de atraso, jitter e perdas de
pacotes nas fases de preparação e execução do handover. O impacto deste
processo em comunicações de dados sobre TCP e UDP é também analisado.
A arquitectura e os resultados obtidos no demonstrador real são apresentados
e discutidos.
ABSTRACT: The field of network communications is, nowadays, facing a new paradigm
caused by the forthcoming convergence of cellular and wireless data networks,
which seems unavoidable. This convergence will result on an integration layer,
to ease the support for Quality of Service and mobility mechanisms. Here, the
support for fast and seamless mobility, not perceptible by the user, has been
getting much attention, although several limitations still exist in this support.
Seamless mobility between cellular, wireless and wired data networks is
envisioned, but not yet achieved.
The work performed in the scope of this thesis aims to describe, specify,
implement and test a novel mobility architecture based on the IP protocol. This
architecture is based on the mobility protocol Mobility Support for IPv6 and on
extensions of Fast Handovers for Mobile IPv6 RFCs, and is able to provide
mobile terminal and network initiated handovers. The mobility is seamless
across heterogeneous access technologies, by integrating Quality of Service
mechanisms, such as handover authorization, access control, resources
reservation and allocation at the new point of attachment, also integrated with
an authentication sub-system. Other novel fast mobility mechanisms are also
proposed, which make use of the multicast protocol to distribute the traffic flows
directed to the terminal during the handover process among the neighbour
access routers, allowing the terminal to handover to any access router in the
vicinity without disruption of the ongoing services. These latter mechanisms
were designed to mobile terminals with high mobility requirements.
In the scope of the IST Daidalos framework an integration process of a next
generation (4G) network was carried out in order to perform performance and
compliance tests to the proposed mechanisms. Furthermore, this thesis also
evaluates the performance of a mobility architecture, both in intra and intertechnology
scenarios, in a real testbed. In this evaluation were considered
metrics such as packet delay, jitter and loss of the handover in its preparation
and execution phases. The impact of the handover on ongoing TCP and UDP
data communications is also addressed. The architecture and results obtained
from the real demonstrator are also presented and discussed
Proceedings of the Fifth International Mobile Satellite Conference 1997
Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments
Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)
Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression
Feasibility of wireless mesh for LTE-Advanced small cell access backhaul
Mobiilidatan määrä on muutaman viime vuoden aikana kasvanut voimakkaasti ja nykyiset ennustukset arvioivat eksponentiaalista kasvukäyrää tulevien vuosien aikana. Matkapuhelinjärjestelmät ovat kehittyneet nopeasti tämän trendin ohjaamana. Neljännen sukupolven matkapuhelinverkkostandardien myötä, uudet innovaatiot kuten heterogeeniset verkkoratkaisut tarjoavat ratkaisun nykyisiin skaalautuvuus- ja kapasiteettiongelmiin. Joitain ilmeisiä ongelmakohtiakin kuitenkin esiintyy kuten heterogeenisten verkkojen runkokytkennän toteuttaminen.
Yksi lupaavimmista tavoista toteuttaa heterogeenisten verkkojen runkokytkentä on langaton ja itseorganisoituva mesh-verkko. Tämän opinnäytetyön tavoitteena on varmistaa ja testata Nokia Siemens Networksin kehittämän mesh-runkokytkentäverkkokonseptin toteutettavuutta ja toiminnallisuutta soveltuvan validointijärjestelmän avulla.
Kaiken kaikkiaan validointijärjestelmä ja sen päälle toteutettu mesh-protokolla toimivat moitteettomasti koko kehitys- ja testausprosessin ajan. Konseptin eri ominaisuudet ja mekanismit todistettiin täysin toteutettaviksi ja toimiviksi. Muutamalla lisäominaisuudella ja konseptiparannuksella mesh-konsepti tarjoaa houkuttelevan ja innovatiivisen ratkaisun heterogeenisten verkkojen runkokytkentään tulevaisuudessa.Mobile traffic demands and volumes are increasing and will dramatically keep increasing in the future. Along with this, mobile networks have evolved to better match this growth. Fourth generation cellular network standard introduced a set of new innovations for mobile communications, including support for heterogeneous network deployments. Heterogeneous networking is the likely answer for future mobile data capacity shortage but also poses some challenges, the most evident being how to implement the backhauling.
One of the most promising heterogeneous network backhaul solutions is a meshed radio system with self-organizing features. The main scope of this master's thesis is the verification of functionality and feasibility of a wireless mesh backhaul concept developed by Nokia Siemens Networks through a proof-of-concept system.
All in all, the wireless mesh proof-of-concept system performed strongly throughout the development and testing process. The different functionalities were proven to work successfully together. With further development and enhancement, the system concept displays extreme potential for a state-of-the-art heterogeneous network backhaul technology
Performance Improvement of Topology-Transparent Broadcast Scheduling in Mobile Ad Hoc Networks
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