824 research outputs found
C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 1: Concepts of Use, Initial System Requirements, Architecture, and AeroMACS Design Considerations
This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I (this document) is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers
Wireless Sensor Data Transport, Aggregation and Security
abstract: Wireless sensor networks (WSN) and the communication and the security therein have been gaining further prominence in the tech-industry recently, with the emergence of the so called Internet of Things (IoT). The steps from acquiring data and making a reactive decision base on the acquired sensor measurements are complex and requires careful execution of several steps. In many of these steps there are still technological gaps to fill that are due to the fact that several primitives that are desirable in a sensor network environment are bolt on the networks as application layer functionalities, rather than built in them. For several important functionalities that are at the core of IoT architectures we have developed a solution that is analyzed and discussed in the following chapters.
The chain of steps from the acquisition of sensor samples until these samples reach a control center or the cloud where the data analytics are performed, starts with the acquisition of the sensor measurements at the correct time and, importantly, synchronously among all sensors deployed. This synchronization has to be network wide, including both the wired core network as well as the wireless edge devices. This thesis studies a decentralized and lightweight solution to synchronize and schedule IoT devices over wireless and wired networks adaptively, with very simple local signaling. Furthermore, measurement results have to be transported and aggregated over the same interface, requiring clever coordination among all nodes, as network resources are shared, keeping scalability and fail-safe operation in mind. Furthermore ensuring the integrity of measurements is a complicated task. On the one hand Cryptography can shield the network from outside attackers and therefore is the first step to take, but due to the volume of sensors must rely on an automated key distribution mechanism. On the other hand cryptography does not protect against exposed keys or inside attackers. One however can exploit statistical properties to detect and identify nodes that send false information and exclude these attacker nodes from the network to avoid data manipulation. Furthermore, if data is supplied by a third party, one can apply automated trust metric for each individual data source to define which data to accept and consider for mentioned statistical tests in the first place. Monitoring the cyber and physical activities of an IoT infrastructure in concert is another topic that is investigated in this thesis.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
Handover analysis over mobile WiMAX technology.
As new mobile devices and mobile applications continue to growth, so does the data traffic demand for broadband services access and the user needs toward mobility, thereby, wireless application became today the fastest solution and lowest cost implementation unlike traditional wired deployment such as optical fibers and digital lines. WiMAX technology satisfies this gap through its high network performance over the air interface and high data rates based on the IEEE 802.16-2004 standards, this original specification does not support mobility.
Therefore, the IEEE introduces a new standard that enables mobility profiles under 802.16e-2005, from which three different types of handovers process are introduced as hard handover (HHO), macro diversity handover (MDHO) and fast base station switching (FBSS) handover.
The objective of this master thesis is to analyze how the handover process affects network performance. The analysis propose three scenarios, built over OPNET simulator to measure the most critical wireless parameter and performance indicator such as throughput, handover success rate, packet drop, delay and network usage.fi=OpinnÀytetyö kokotekstinÀ PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=LÀrdomsprov tillgÀngligt som fulltext i PDF-format
Subcarrier and Power Allocation in WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is one of the latest technologies for providing Broadband Wireless Access (BWA) in a metropolitan area. The use of orthogonal frequency division multiplexing (OFDM) transmissions has been proposed in WiMAX to mitigate the complications which are associated with frequency selective channels. In addition, the multiple access is achieved by using orthogonal frequency division multiple access (OFDMA) scheme which has several advantages such as flexible resource allocation, relatively simple transceivers, and high spectrum efficient. In OFDMA the controllable resources are the subcarriers and the allocated power per subband. Moreover, adaptive subcarrier and power allocation techniques have been selected to exploit the natural multiuser diversity. This leads to an improvement of the performance by assigning the proper subcarriers to the user according to their channel quality and the power is allocated based on water-filling algorithm. One simple method is to allocate subcarriers and powers equally likely between all users. It is well known that this method reduces the spectral efficiency of the system, hence, it is not preferred unless in some applications.
In order to handle the spectral efficiency problem, in this thesis we discuss three novel resources allocation algorithms for the downlink of a multiuser OFDM system and analyze the algorithm performances based on capacity and fairness measurement. Our intensive simulations validate the algorithm performances.fi=OpinnÀytetyö kokotekstinÀ PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=LÀrdomsprov tillgÀngligt som fulltext i PDF-format
IP ROUTING AND KEY MANAGEMENT FOR SECURE MULTICAST IN SATELLITE ATM NETWORKS
Communication satellites offer an efficient way to extend IP multicast services for groups in wide-area networks. This poses interesting challenges for routing and security. Satellite networks can have wired and wireless links and different link-layer technologies like Ethernet and ATM. For security, the multicast traffic should be restricted to legitimate receivers, which can be achieved by data encryption.This requires secure and efficient methods to manage the encryption keys. This thesis attempts to solve the above problems for secure multicast in wide-area networks that have Ethernet LANs interconnected by ATM-based satellite channels. The thesis reviews the multicast services offered by IP and ATM and proposes a multicast routing framework for hybrid satellite networks. The thesis also investigates current group key management protocols, and designs a scheme for secure and scalable key management for the proposed multicast architecture. The various proposed schemes are presented in detail, alongwith analysis and simulation results
Concepção e implementação de experiĂȘncias laboratoriais sobre MPLS
Mestrado em Engenharia Electrónica e TelecomunicaçÔesO Multiprotocol Label Switching (MPLS) é um mecanismo de
transporte de dados, sob a forma de um protocolo agnĂłstico, com
grande potencial de crescimento e adequação. Opera na âCamada 2.5â
do modelo OSI e constitui um mecanismo de alto desempenho utilizado
nas redes de nĂșcleo para transportar dados de um nĂł da rede para outro.
O sucesso do MPLS resulta do facto de permitir que a rede transporte
todos os tipos de dados, desde trĂĄfego IP a trĂĄfego da camada de
ligação de dados, devido ao encapsulamento dos pacotes dos diversos
protocolos, permitindo a criação de âlinks virtuaisâ entre nĂłs distantes.
O MPLS pertence Ă famĂlia das âredes de comutação de pacotesâ,
sendo os pacotes de dados associados a âetiquetasâ que determinam o
seu encaminhamento, sem necessidade de examinar o conteĂșdo dos
prĂłprios pacotes. Isto permite a criação de circuitos âextremo-aextremoâ
através de qualquer tipo de rede de transporte e
independentemente do protocolo de encaminhamento que Ă© utilizado.
O projecto do MPLS considera mĂșltiplas tecnologias no sentido de
prestar um serviço Ășnico de transporte de dados, tentando
simultaneamente proporcionar capacidades de engenharia de trĂĄfego e
controlo âout-of-bandâ, uma caracterĂstica muito atraente para uma
implementação em grande escala. No fundo, o MPLS é uma forma de
consolidar muitas redes IP dentro de uma Ășnica rede.
Dada a importĂąncia desta tecnologia, Ă© urgente desenvolver ferramentas
que permitam entender melhor a sua complexidade. O MPLS corre
normalmente nas redes de nĂșcleo dos ISPs. No sentido de tornar o seu
estudo viåvel, recorreu-se nesta dissertação à emulação para
implementar cenĂĄrios de complexidade adequada. Existem actualmente
boas ferramentas disponĂveis que permitem a recriação em laboratĂłrio
de cenĂĄrios bastante complicados.
Contudo, a exigĂȘncia computacional da emulação Ă© proporcional Ă
complexidade do projecto em questĂŁo, tornando-se rapidamente
impossĂvel de realizar numa Ășnica mĂĄquina. A computação distribuĂda
ou a âCloud Computingâ sĂŁo actualmente as abordagens mais
adequadas e inovadoras apara a resolução deste problema.
Esta dissertação tem como objectivo criar algumas experiĂȘncias em
laboratĂłrio que evidenciam aspectos relevantes da tecnologia MPLS,
usando para esse efeito um emulador computacional, o Dynamips,
impulsionado por generosas fontes computacionais disponibilizadas
pela Amazon ec2. A utilização destas ferramentas de emulação permite
testar cenårios de rede e serviços reais em ambiente controlado,
efectuando o debugging das suas configuraçÔes e optimizando o seu
desempenho, antes de os colocar em funcionamento nas redes em
operação.The Multiprotocol Label Switching (MPLS) is a highly scalable and
agnostic protocol to carry network data.
Operating at "Layer 2.5" of the OSI model, MPLS is an highperformance
mechanism that is used at the network backbone for
conveying data from one network node to the next.
The success of MPLS results from the fact that it enables the network to
carry all kinds of traffic, ranging from IP to layer 2 traffic, since it
encapsulates the packets of the diverse network protocols, allowing the
creation of "virtual links" between distant nodes.
MPLS belongs to the family of packet switched networks, where labels
are assigned to data packets that are forwarded based on decisions that
rely only on the label contents, without the need to examine the packets
contents. This allows the creation of end-to-end circuits across any type
of transport medium, using any protocol.
The MPLS design takes multiform transport technologies into account to
provide a unified data-carrying service, attempting simultaneously to
preserve traffic engineering and out-of-band control, a very attractive
characteristic for large-scale deployment. MPLS is the way to
consolidate many IP networks into a single one. Due to this obvious
potential, it is urgent to develop means and tools to better understand its
functioning and complexity.
MPLS normally runs at the backbone of Service Providers networks,
being deployed across an extensive set of expensive equipment. In order
to turn the study of MPLS feasible, emulation was considered as the best
solution. Currently, there are very good available tools to recreate, in a
lab environment, quite complicated scenarios.
However, the computational demand of the emulation is proportional to
the complexity of the project, becoming quickly unfeasible in a single
machine.
Fortunately, distributed computing or Cloud computing are suitable and
novel approaches to solve this computation problem.
So, this work aims to create some lab experiments that can
illustrate/demonstrate relevant aspects of the MPLS technology, using the
Dynamips emulator driven by the computational resources that were
made available by the Amazon ec2 cloud computing facilities. The
utilization of these emulation tools allows testing real networks and
service scenarios in a controlled environment, being able to debug their
configurations and optimize their performance before deploying them in
real operating networks
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