57 research outputs found
An Approximate Inner Bound to the QoS Aware Throughput Region of a Tree Network under IEEE 802.15.4 CSMA/CA and Application to Wireless Sensor Network Design
We consider a tree network spanning a set of source nodes that generate
measurement packets, a set of additional relay nodes that only forward packets
from the sources, and a data sink. We assume that the paths from the sources to
the sink have bounded hop count. We assume that the nodes use the IEEE 802.15.4
CSMA/CA for medium access control, and that there are no hidden terminals. In
this setting, starting with a set of simple fixed point equations, we derive
sufficient conditions for the tree network to approximately satisfy certain
given QoS targets such as end-to-end delivery probability and delay under a
given rate of generation of measurement packets at the sources (arrival rates
vector). The structures of our sufficient conditions provide insight on the
dependence of the network performance on the arrival rate vector, and the
topological properties of the network. Furthermore, for the special case of
equal arrival rates, default backoff parameters, and for a range of values of
target QoS, we show that among all path-length-bounded trees (spanning a given
set of sources and BS) that meet the sufficient conditions, a shortest path
tree achieves the maximum throughput
Low power radio networks
Low power radio networks are the networks which depend upon wireless radio links and consume very low energy for their operation. These networks suit best for applications where frequent renewal of power supply is not possible. Power supply has always remained a major concern in radio networks. An efficient low power consuming network is always recommended for greater mobility and lifetime of the network. This thesis introduces low power radio networks, their features and applications. Energy concerns and various techniques that can be used for energy conservation are discussed, along with the security techniques that can be used to make the system reliable. Different technologies available in the market and their features and applications are considered. Included is a detailed study of the IEEE 802.15.4 standard. A simulation study of the CSMA/CA algorithm and topology discovery algorithms is presented
Modelling, analysis and design of MAC and routing protocols for wireless body area sensor networks.
The main contribution of the thesis is to provide modeling, analysis, and design for Medium Access Control (MAC) and link-quality based routing protocols of Wireless Body Area Sensor Networks (WBASNs) for remote patient monitoring applications by considering saturated and un-saturated traffic scenarios. The design of these protocols has considered the stringent Quality of Service (QoS) requirements of patient monitoring systems. Moreover, the thesis also provides intelligent routing metrics for packet forwarding mechanisms while considering the integration of WBASNs with the Internet of Things (IoTs). First, we present the numerical modeling of the slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) for the IEEE 802.15.4 and IEEE 802.15.6 standards. By using this modelling, we proposed a MAC layer mechanism called Delay, Reliability and Throughput (DRT) profile for the IEEE 802.15.4 and IEEE 802.15.6, which jointly optimize the QoS in terms of limited delay, reliability, efficient channel access and throughput by considering the requirements of patient monitoring system under different frequency bands including 420 MHz, 868 MHz and 2.4 GHz. Second, we proposed a duty-cycle based energy efficient adaptive MAC layer mechanism called Tele-Medicine Protocol (TMP) by considering the limited delay and reliability for patient monitoring systems. The proposed energy efficient protocol is designed by combining two optimizations methods: MAC layer parameter tuning and duty cycle-based optimization. The duty cycle is adjusted by using three factors: offered network traffic load, DRT profile and superframe duration. Third, a frame aggregation scheme called Aggregated-MAC Protocol Data Unit (A- MPDU) is proposed for the IEEE 802.15.4. A-MPDU provides high throughput and efficient channel access mechanism for periodic data transmission by considering the specified QoS requirements of the critical patient monitoring systems. To implement the scheme accurately, we developed a traffic pattern analysis to understand the requirements of the sensor nodes in patient monitoring systems. Later, we mapped the requirements on the existing MAC to find the performance gap. Fourth, empirical reliability assessment is done to validate the wireless channel characteristics of the low-power radios for successful deployment of WBASNs/IoTs based link quality routing protocols. A Test-bed is designed to perform the empirical experiments for the identification of the actual link quality estimation for different hospital environments. For evaluation of the test-bed, we considered parameters including Received Signal Strength Indicator (RSSI), Link Quality Indicator (LQI), packet reception and packet error rate. Finally, there is no standard under Internet Engineering Task Force (IETF) which provides the integration of the IEEE 802.15.6 with IPv6 networks so that WBASNs could become part of IoTs. For this, an IETF draft is proposed which highlights the problem statement and solution for this integration. The discussion is provided in Appendix B
Cooperation in Wireless Ad Hoc and Sensor Networks
Ministerio de Educación y Ciencia TIN2006-15617-C03-03 (AmbientNet)Junta de Andalucía P0-6TIC-2298 (SemiWheelNav)Junta de Andalucía P07-TIC-02476 (ARTICA
A Learning-based Approach to Exploiting Sensing Diversity in Performance Critical Sensor Networks
Wireless sensor networks for human health monitoring, military surveillance, and disaster warning all have stringent accuracy requirements for detecting and classifying events while maximizing system lifetime. to meet high accuracy requirements and maximize system lifetime, we must address sensing diversity: sensing capability differences among both heterogeneous and homogeneous sensors in a specific deployment. Existing approaches either ignore sensing diversity entirely and assume all sensors have similar capabilities or attempt to overcome sensing diversity through calibration. Instead, we use machine learning to take advantage of sensing differences among heterogeneous sensors to provide high accuracy and energy savings for performance critical applications.;In this dissertation, we provide five major contributions that exploit the nuances of specific sensor deployments to increase application performance. First, we demonstrate that by using machine learning for event detection, we can explore the sensing capability of a specific deployment and use only the most capable sensors to meet user accuracy requirements. Second, we expand our diversity exploiting approach to detect multiple events using a distributed manner. Third, we address sensing diversity in body sensor networks, providing a practical, user friendly solution for activity recognition. Fourth, we further increase accuracy and energy savings in body sensor networks by sharing sensing resources among neighboring body sensor networks. Lastly, we provide a learning-based approach for forwarding event detection decisions to data sinks in an environment with mobile sensor nodes
An efficient multichannel wireless sensor networks MAC protocol based on IEEE 802.11 distributed co-ordinated function.
This research aimed to create new knowledge and pioneer a path in the area relating to future trends in the WSN, by resolving some of the issues at the MAC layer in Wireless Sensor Networks. This work introduced a Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks.
This work commenced by surveying different protocols: contention-based MAC protocols, transport layer protocols, cross-layered design and multichannel multi-radio assignments. A number of existing protocols were analysed, each attempting to resolve one or more problems faced by the current layers.
The 802.15.4 performed very poorly at high data rate and at long range. Therefore 802.15.4 is not suitable for sensor multimedia or surveillance system with streaming data for future multichannel multi-radio systems.
A survey on 802.11 DCF - which was designed mainly for wireless networks –supports and confirm that it has a power saving mechanism which is used to synchronise nodes. However it uses a random back-off mechanism that cannot provide deterministic upper bounds on channel access delay and as such cannot support real-time traffic. The weaknesses identified by surveying this protocol form the backbone of this thesis
The overall aim for this thesis was to introduce multichannel with single radio as a new paradigm for IEEE 802.11 Distributed Coordinated Function (DCF) in wireless sensor networks (WSNs) that is used in a wide range of applications, from military application, environmental monitoring, medical care, smart buildings and other industry and to extend WSNs with multimedia capability which sense for instance sounds or motion, video sensor which capture video events of interest.
Traditionally WSNs do not need high data rate and throughput, since events are normally captured periodically. With the paradigm shift in technology, multimedia streaming has become more demanding than data sensing applications as such the need for high data rate protocol for WSN which is an emerging technology in this area. The IEEE 802.11 can support data rates up to 54Mbps and 802.11 DCF was designed specifically for use in wireless networks.
This thesis focused on designing an algorithm that applied multichannel to IEEE 802.11 DCF back-off algorithm to reduce the waiting time of a node and increase throughput when attempting to access the medium. Data collection in WSN tends to suffer from heavy congestion especially nodes nearer to the sink node. Therefore, this thesis proposes a contention based MAC protocol to address this problem from the inspiration of the 802.11 DCF backoff algorithm resulting from a comparison of IEEE 802.11 and IEEE 802.15.4 for Future Green Multichannel Multi-radio Wireless Sensor Networks
Routing and Mobility on IPv6 over LoWPAN
The IoT means a world-wide network of interconnected objects based on standard communication
protocols. An object in this context is a quotidian physical device augmented with
sensing/actuating, processing, storing and communication capabilities. These objects must be
able to interact with the surrounding environment where they are placed and to cooperate with
neighbouring objects in order to accomplish a common objective. The IoT objects have also the
capabilities of converting the sensed data into automated instructions and communicating them
to other objects through the communication networks, avoiding the human intervention in several
tasks. Most of IoT deployments are based on small devices with restricted computational
resources and energy constraints. For this reason, initially the scientific community did not
consider the use of IP protocol suite in this scenarios because there was the perception that it
was too heavy to the available resources on such devices. Meanwhile, the scientific community
and the industry started to rethink about the use of IP protocol suite in all IoT devices and now
it is considered as the solution to provide connectivity between the IoT devices, independently
of the Layer 2 protocol in use, and to connect them to the Internet. Despite the use of IP suite
protocol in all devices and the amount of solutions proposed, many open issues remain unsolved
in order to reach a seamless integration between the IoT and the Internet and to provide the
conditions to IoT service widespread. This thesis addressed the challenges associated with the
interconnectivity between the Internet and the IoT devices and with the security aspects of
the IoT. In the interconnectivity between the IoT devices and the Internet the problem is how
to provide valuable information to the Internet connected devices, independently of the supported
IP protocol version, without being necessary accessed directly to the IoT nodes. In order
to solve this problem, solutions based on Representational state transfer (REST) web services
and IPv4 to IPv6 dual stack transition mechanism were proposed and evaluated. The REST web
service and the transition mechanism runs only at the border router without penalizing the IoT
constrained devices. The mitigation of the effects of internal and external security attacks
minimizing the overhead imposed on the IoT devices is the security challenge addressed in this
thesis. Three different solutions were proposed. The first is a mechanism to prevent remotely
initiated transport level Denial of Service attacks that avoids the use of inefficient and hard to
manage traditional firewalls. It is based on filtering at the border router the traffic received
from the Internet and destined to the IoT network according to the conditions announced by
each IoT device. The second is a network access security framework that can be used to control
the nodes that have access to the network, based on administrative approval, and to enforce
security compliance to the authorized nodes. The third is a network admission control framework
that prevents IoT unauthorized nodes to communicate with IoT authorized nodes or with
the Internet, which drastically reduces the number of possible security attacks. The network
admission control was also exploited as a management mechanism as it can be used to manage
the network size in terms of number of nodes, making the network more manageable, increasing
its reliability and extending its lifetime.A IoT (Internet of Things) tem suscitado o interesse tanto da comunidade académica como
da indústria, uma vez que os campos de aplicação são inúmeros assim como os potenciais ganhos
que podem ser obtidos através do uso deste tipo de tecnologia. A IoT significa uma rede
global de objetos ligados entre si através de uma rede de comunicações baseada em protocolos
standard. Neste contexto, um objeto é um objeto físico do dia a dia ao qual foi adicionada a
capacidade de medir e de atuar sobre variáveis físicas, de processar e armazenar dados e de
comunicar. Estes objetos têm a capacidade de interagir com o meio ambiente envolvente e de
cooperar com outros objetos vizinhos de forma a atingirem um objetivo comum. Estes objetos
também têm a capacidade de converter os dados lidos em instruções e de as comunicar a outros
objetos através da rede de comunicações, evitando desta forma a intervenção humana em
diversas tarefas. A maior parte das concretizações de sistemas IoT são baseados em pequenos
dispositivos autónomos com restrições ao nível dos recursos computacionais e de retenção de
energia. Por esta razão, inicialmente a comunidade científica não considerou adequado o uso
da pilha protocolar IP neste tipo de dispositivos, uma vez que havia a perceção de que era muito
pesada para os recursos computacionais disponíveis. Entretanto, a comunidade científica e a
indústria retomaram a discussão acerca dos benefícios do uso da pilha protocolar em todos os
dispositivos da IoT e atualmente é considerada a solução para estabelecer a conetividade entre
os dispositivos IoT independentemente do protocolo da camada dois em uso e para os ligar à
Internet. Apesar do uso da pilha protocolar IP em todos os dispositivos e da quantidade de
soluções propostas, são vários os problemas por resolver no que concerne à integração contínua
e sem interrupções da IoT na Internet e de criar as condições para a adoção generalizada deste
tipo de tecnologias.
Esta tese versa sobre os desafios associados à integração da IoT na Internet e dos aspetos de
segurança da IoT. Relativamente à integração da IoT na Internet o problema é como fornecer
informação válida aos dispositivos ligados à Internet, independentemente da versão do protocolo
IP em uso, evitando o acesso direto aos dispositivos IoT. Para a resolução deste problema foram
propostas e avaliadas soluções baseadas em web services REST e em mecanismos de transição
IPv4 para IPv6 do tipo pilha dupla (dual stack). O web service e o mecanismo de transição são
suportados apenas no router de fronteira, sem penalizar os dispositivos IoT. No que concerne
à segurança, o problema é mitigar os efeitos dos ataques de segurança internos e externos
iniciados local e remotamente. Foram propostas três soluções diferentes, a primeira é um
mecanismo que minimiza os efeitos dos ataques de negação de serviço com origem na Internet e
que evita o uso de mecanismos de firewalls ineficientes e de gestão complexa. Este mecanismo
filtra no router de fronteira o tráfego com origem na Internet é destinado à IoT de acordo
com as condições anunciadas por cada um dos dispositivos IoT da rede. A segunda solução,
é uma framework de network admission control que controla quais os dispositivos que podem
aceder à rede com base na autorização administrativa e que aplica políticas de conformidade
relativas à segurança aos dispositivos autorizados. A terceira é um mecanismo de network
admission control para redes 6LoWPAN que evita que dispositivos não autorizados comuniquem
com outros dispositivos legítimos e com a Internet o que reduz drasticamente o número de
ataques à segurança. Este mecanismo também foi explorado como um mecanismo de gestão uma
vez que pode ser utilizado a dimensão da rede quanto ao número de dispositivos, tornando-a
mais fácil de gerir e aumentando a sua fiabilidade e o seu tempo de vida
Keberkesanan program simulasi penapis sambutan dedenyut terhingga (FIR) terhadap kefahaman pelajar kejuruteraan elektrik
Kefahaman merupakan aset bagi setiap pelajar. Ini kerana melalui
kefahaman pelajar dapat mengaplikasikan konsep yang dipelajari di dalam dan di
luar kelas. Kajian ini dijalankan bertujuan menilai keberkesanan program simulasi
penapis sambutan dedenyut terhingga (FIR) terhadap kefahaman pelajar kejuruteraan
elektrik FKEE, UTHM dalam mata pelajaran Pemprosesan Isyarat Digital (DSP)
bagi topik penapis FIR. Metodologi kajian ini berbentuk kaedah reka bentuk kuasi�eksperimental ujian pra-pasca bagi kumpulan-kumpulan tidak seimbang. Seramai 40
responden kajian telah dipilih dan dibahagi secara rawak kepada dua kllmpulan iaitu
kumpulan rawatan yang menggunakan program simulasi penapis FIR dan kumpulan
kawalan yang menggunakan kaedah pembelajaran berorientasikan modul
pembelajaran DSP UTHM. Setiap responden menduduki dua ujian pencapaian iaitu
ujian pra dan ujian pasca yang berbentuk kuiz. Analisis data berbentuk deskriptif
dan inferens dilakllkan dengan menggunakan Peri sian Statistical Package for Social
Science (SPSS) versi 11.0. Dapatan kajian menunjukkan kedua-dua kumpulan
pelajar telah mengalami peningkatan dari segi kefahaman iaitu daripada tahap tidak
memuaskan kepada tahap kepujian selepas menggunakan kaedah pembelajaran yang
telah ditetapkan bagi kumpulan masing-masing. Walaubagaimanapun, pelajar
kumpulan rawatan menunjukkan peningkatan yang lebih tinggi sedikit berbanding
pelajar kumpulan kawalan. Namun begitu, dapatan kajian secara ujian statistik
menunjukkan tidak terdapat perbezaan yang signifikan dari segi pencapaian markah
ujian pasca di antara pelajar kumpulan rawatan dengan pelajar kumpulan kawalan.
Sungguhpun begitu, penggunaan program simulasi penapis FIR telah membantu
dalam peningkatan kefahaman pelajar mengenai topik penapis FIR
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