246 research outputs found
Network emulation focusing on QoS-Oriented satellite communication
This chapter proposes network emulation basics and a complete case study of QoS-oriented Satellite Communication
QoS support in satellite and wireless networks : study under the network simulator (NS-2)
Aquest projecte es basa en l'estudi de l'oferiment de qualitat de servei en xarxes wireless i satel·litals. Per aixĂČ l'estudi de les tĂšcniques de cross-layer i del IEEE 802.11e ha sigut el punt clau per al desenvolupament teĂČric d'aquest estudi. Usant el simulador de xarxes network simulator, a la part de simulacions es plantegen tres situacions: l'estudi de la xarxa satel·lital, l'estudi del mĂštode d'accĂ©s HCCA i la interconnexiĂł de la xarxa satel·lital amb la wireless. Encara que aquest Ășltim punt, incomplet en aquest projecte, ha de ser la continuaciĂł per a futures investigacions.Este proyecto se basa en el estudio del ofrecimiento de calidad de servicio en redes wireless y satelitales. Por eso el estudio de las tĂ©cnicas de cross-layer y del IEEE 802.11eha sido el punto clave para el desarrollo teĂłrico de este estudio. Usando el simulador de redes network simulator, en la parte de simulaciones se plantean tres situaciones: el estudio de la red satelital, el estudio del mĂ©todo de acceso HCCA y la interconexiĂłn de la red satelital con la wireless. Aunque este Ășltimo punto, incompleto en este proyecto, tiene que ser la continuaciĂłn para futuras investigaciones.This project is based on the study of offering quality of service in satellite and wireless networks. For that reason the study of the techniques of cross-layer and the IEEE 802.11e has been the key point for the theoretical development of this study. Using the software network simulator, in the part of simulations three situations consider: the study of the satellite network, the study of the access method HCCA and the interconnection of the satellite network with the wireless. Although this last point, incomplete in this work, must be the continuation for future investigations
Towards generic satellite payloads: software radio
Satellite payloads are becoming much more complex with the evolution towards multimedia applications. Moreover satellite lifetime increases while standard and services evolve faster, necessitating a hardware platform that can evolves for not developing new systems on each change. The same problem occurs in terrestrial systems like mobile networks and a foreseen solution is the software defined radio technology. In this paper we describe a way of introducing this concept at satellite level to offer to operators the required flexibility in the system. The digital functions enabling this technology, the hardware components implementing the functions and the reconfiguration processes are detailed. We show that elements of the software radio for satellites exist and that this concept is feasible
A Survey on Communication Networks for Electric System Automation
Published in Computer Networks 50 (2006) 877â897, an Elsevier journal. The definitive version of this publication is available from Science Direct. Digital Object Identifier:10.1016/j.comnet.2006.01.005In todayâs competitive electric utility marketplace, reliable and real-time information become the key factor for reliable delivery of power to the end-users, profitability of the electric utility and customer satisfaction. The operational and commercial demands of electric utilities require a high-performance data communication network that supports both existing functionalities and future operational requirements. In this respect, since such a communication network constitutes the core of the electric system automation applications, the design of a cost-effective and reliable network architecture is crucial.
In this paper, the opportunities and challenges of a hybrid network architecture are discussed for electric system automation.
More specifically, Internet based Virtual Private Networks, power line communications, satellite communications and wireless communications (wireless sensor networks, WiMAX and wireless mesh networks) are described in detail. The motivation of this paper is to provide a better understanding of the hybrid network architecture that can provide heterogeneous electric system automation application requirements. In this regard, our aim is to present a structured framework for electric utilities who plan to utilize new communication technologies for automation and hence, to make the decision making process more effective and direct.This work was supported by NEETRAC under
Project #04-157
QoS in LEO satellite networks with multipacket reception
Dissertação apresentada para obtenção do Grau de Mestre em Engenharia ElectrotĂ©cnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de CiĂȘncias e TecnologiaLow Earth Orbit (LEO) satellite networks can improve terrestrial wireless networks to
allow global broadband services for Mobile Terminals (MT), regardless of the users' location.
In this context, hybrid telecommunication systems combining satellites with Long
Term Evolution (LTE) networks, like the LightSquared technology, are intended to provide
ubiquitous high-speed services.
This dissertation analyses the performance of a random access protocol that uses Hybrid
Network-assisted Diversity Multiple Access (H-NDMA), for a LEO satellite system
network, named by Satellite Random NDMA (SR-NDMA). The protocol also considers
a Single Carrier-Frequency Domain Equalization (SC-FDE) scheme for the uplink transmission
and a Multipacket Reception (MPR) receiver. In this scenario, the transmission
of data packets between MTs and the Base Station (BS) is made through random access
and schedule access slots, organized into super-frames with the duration of a Round Trip
Time (RTT).
A SR-NDMA simulator is implemented to measure the system performance in matters
of throughput, energy consumption, system delay and also the protocol capacity to
meet Quality of Service (QoS) requirements. A set of simulations tests were made with a
random Poisson process tra c generation to validate the analytical model. The capacity
to ful l the QoS requirements of a real-time tra c class was also tested.FCT/MEC: MPSat - PTDC/EEA-TEL/099074/2008,
OPPORTUNISTIC CR - PTDC/EEA-TEL/115981/2009, Femtocells - PTDC/EEA-TEL/120666/2010
e ADIN - PTDC/EEI-TEL/2990/201
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Interoperability of wireless communication technologies in hybrid networks: Evaluation of end-to-end interoperability issues and quality of service requirements
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication âanywhere, any time with anyoneâ. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues.
The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies).
The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks.
Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications.
The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way.
The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools.
This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks.
Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research.
It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites.
The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation
Satellite Communications
This study is motivated by the need to give the reader a broad view of the developments, key concepts, and technologies related to information society evolution, with a focus on the wireless communications and geoinformation technologies and their role in the environment. Giving perspective, it aims at assisting people active in the industry, the public sector, and Earth science fields as well, by providing a base for their continued work and thinking
Evolution of High Throughput Satellite Systems: Vision, Requirements, and Key Technologies
High throughput satellites (HTS), with their digital payload technology, are
expected to play a key role as enablers of the upcoming 6G networks. HTS are
mainly designed to provide higher data rates and capacities. Fueled by
technological advancements including beamforming, advanced modulation
techniques, reconfigurable phased array technologies, and electronically
steerable antennas, HTS have emerged as a fundamental component for future
network generation. This paper offers a comprehensive state-of-the-art of HTS
systems, with a focus on standardization, patents, channel multiple access
techniques, routing, load balancing, and the role of software-defined
networking (SDN). In addition, we provide a vision for next-satellite systems
that we named as extremely-HTS (EHTS) toward autonomous satellites supported by
the main requirements and key technologies expected for these systems. The EHTS
system will be designed such that it maximizes spectrum reuse and data rates,
and flexibly steers the capacity to satisfy user demand. We introduce a novel
architecture for future regenerative payloads while summarizing the challenges
imposed by this architecture
Economically sustainable public security and emergency network exploiting a broadband communications satellite
The research contributes to work in Rapid Deployment of a National Public Security and Emergency Communications Network using Communication Satellite Broadband. Although studies in Public Security Communication networks have examined the use of communications satellite as an integral part of the Communication Infrastructure, there has not been an in-depth design analysis of an optimized regional broadband-based communication satellite in relation to the envisaged service coverage area, with little or no terrestrial last-mile telecommunications infrastructure for delivery of satellite solutions, applications and services.
As such, the research provides a case study of a Nigerian Public Safety Security Communications Pilot project deployed in regions of the African continent with inadequate terrestrial last mile infrastructure and thus requiring a robust regional Communications Satellite complemented with variants of terrestrial wireless technologies to bridge the digital hiatus as a short and medium term measure apart from other strategic needs.
The research not only addresses the pivotal role of a secured integrated communications Public safety network for security agencies and emergency service organizations with its potential to foster efficient information symmetry amongst their operations including during emergency and crisis management in a timely manner but demonstrates a working model of how analogue spectrum meant for Push-to-Talk (PTT) services can be re-farmed and digitalized as a âdedicatedâ broadband-based public communications system. The networkâs sustainability can be secured by using excess capacity for the strategic commercial telecommunication needs of the state and its citizens. Utilization of scarce spectrum has been deployed for Nigeriaâs Cashless policy pilot project for financial and digital inclusion. This effectively drives the universal access goals, without exclusivity, in a continent, which still remains the least wired in the world
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