158 research outputs found
Collaborative Communication And Storage In Energy-Synchronized Sensor Networks
In a battery-less sensor network, all the operation of sensor nodes are strictly constrained by and synchronized with the fluctuations of harvested energy, causing nodes to be disruptive from network and hence unstable network connectivity. Such wireless sensor network is named as energy-synchronized sensor networks. The unpredictable network disruptions and challenging communication environments make the traditional communication protocols inefficient and require a new paradigm-shift in design. In this thesis, I propose a set of algorithms on collaborative data communication and storage for energy-synchronized sensor networks. The solutions are based on erasure codes and probabilistic network codings. The proposed set of algorithms significantly improve the data communication throughput and persistency, and they are inherently amenable to probabilistic nature of transmission in wireless networks.
The technical contributions explore collaborative communication with both no coding and network coding methods. First, I propose a collaborative data delivery protocol to exploit the optimal performance of multiple energy-synchronized paths without network coding, i.e. a new max-flow min-variance algorithm. In consort with this data delivery protocol, a localized TDMA MAC protocol is designed to synchronize nodes\u27 duty-cycles and mitigate media access contentions. However, the energy supply can change dynamically over time, making determined duty cycles synchronization difficult in practice. A probabilistic approach is investigated. Therefore, I present Opportunistic Network Erasure Coding protocol (ONEC), to collaboratively collect data. ONEC derives the probability distribution of coding degree in each node and enable opportunistic in-network recoding, and guarantee the recovery of original sensor data can be achieved with high probability upon receiving any sufficient amount of encoded packets. Next, OnCode, an opportunistic in-network data coding and delivery protocol is proposed to further improve data communication under the constraints of energy synchronization. It is resilient to packet loss and network disruptions, and does not require explicit end-to-end feedback message. Moreover, I present a network Erasure Coding with randomized Power Control (ECPC) mechanism for collaborative data storage in disruptive sensor networks. ECPC only requires each node to perform a single broadcast at each of its several randomly selected power levels. Thus it incurs very low communication overhead. Finally, I propose an integrated algorithm and middleware (Ravine Stream) to improve data delivery throughput as well as data persistency in energy-synchronized sensor network
Delay Reduction in Multi-Hop Device-to-Device Communication using Network Coding
This paper considers the problem of reducing the broadcast decoding delay of
wireless networks using instantly decodable network coding (IDNC) based
device-to-device (D2D) communications. In a D2D configuration, devices in the
network can help hasten the recovery of the lost packets of other devices in
their transmission range by sending network coded packets. Unlike previous
works that assumed fully connected network, this paper proposes a partially
connected configuration in which the decision should be made not only on the
packet combinations but also on the set of transmitting devices. First, the
different events occurring at each device are identified so as to derive an
expression for the probability distribution of the decoding delay. The joint
optimization problem over the set of transmitting devices and the packet
combinations of each is, then, formulated. The optimal solution of the joint
optimization problem is derived using a graph theory approach by introducing
the cooperation graph and reformulating the problem as a maximum weight clique
problem in which the weight of each vertex is the contribution of the device
identified by the vertex. Through extensive simulations, the decoding delay
experienced by all devices in the Point to Multi-Point (PMP) configuration, the
fully connected D2D (FC-D2D) configuration and the more practical partially
connected D2D (PC-D2D) configuration are compared. Numerical results suggest
that the PC-D2D outperforms the FC-D2D and provides appreciable gain especially
for poorly connected networks
Quality of Information in Mobile Crowdsensing: Survey and Research Challenges
Smartphones have become the most pervasive devices in people's lives, and are
clearly transforming the way we live and perceive technology. Today's
smartphones benefit from almost ubiquitous Internet connectivity and come
equipped with a plethora of inexpensive yet powerful embedded sensors, such as
accelerometer, gyroscope, microphone, and camera. This unique combination has
enabled revolutionary applications based on the mobile crowdsensing paradigm,
such as real-time road traffic monitoring, air and noise pollution, crime
control, and wildlife monitoring, just to name a few. Differently from prior
sensing paradigms, humans are now the primary actors of the sensing process,
since they become fundamental in retrieving reliable and up-to-date information
about the event being monitored. As humans may behave unreliably or
maliciously, assessing and guaranteeing Quality of Information (QoI) becomes
more important than ever. In this paper, we provide a new framework for
defining and enforcing the QoI in mobile crowdsensing, and analyze in depth the
current state-of-the-art on the topic. We also outline novel research
challenges, along with possible directions of future work.Comment: To appear in ACM Transactions on Sensor Networks (TOSN
Fulcrum: Flexible Network Coding for Heterogeneous Devices
Producción CientÃficaWe introduce Fulcrum, a network coding framework that achieves three seemingly conflicting objectives: 1) to reduce the coding coefficient overhead down to nearly n bits per packet in a generation of n packets; 2) to conduct the network coding using only Galois field GF(2) operations at intermediate nodes if necessary, dramatically reducing computing complexity in the network; and 3) to deliver an end-to-end performance that is close to that of a high-field network coding system for high-end receivers, while simultaneously catering to low-end receivers that decode in GF(2). As a consequence of 1) and 3), Fulcrum has a unique trait missing so far in the network coding literature: providing the network with the flexibility to distribute computational complexity over different devices depending on their current load, network conditions, or energy constraints. At the core of our framework lies the idea of precoding at the sources using an expansion field GF(2 h ), h > 1, to increase the number of dimensions seen by the network. Fulcrum can use any high-field linear code for precoding, e.g., Reed-Solomon or Random Linear Network Coding (RLNC). Our analysis shows that the number of additional dimensions created during precoding controls the trade-off between delay, overhead, and computing complexity. Our implementation and measurements show that Fulcrum achieves similar decoding probabilities as high field RLNC but with encoders and decoders that are an order of magnitude faster.Green Mobile Cloud project (grant DFF-0602-01372B)Colorcast project (grant DFF-0602-02661B)TuneSCode project (grant DFF - 1335-00125)Danish Council for Independent Research (grant DFF-4002-00367)Ministerio de EconomÃa, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grants MTM2012-36917-C03-03 / MTM2015-65764-C3-2-P / MTM2015-69138-REDT)Agencia Estatal de Investigación - Fondo Social Europeo (grant RYC-2016-20208)Aarhus Universitets Forskningsfond Starting (grant AUFF-2017-FLS-7-1
Network Coding for Delay Constrained Wireless Systems with Feedback
Rousseau Pierre. Une base de colonne découverte dans l'église de Saint-Germain-des-Prés à Paris. In: Bulletin de la Société Nationale des Antiquaires de France, 1975, 1977. pp. 47-48
Encaminhamento confiável e energeticamente eficiente para redes ad hoc
Doutoramento em InformáticaIn Mobile Ad hoc NETworks (MANETs), where cooperative behaviour is
mandatory, there is a high probability for some nodes to become overloaded
with packet forwarding operations in order to support neighbor data exchange.
This altruistic behaviour leads to an unbalanced load in the network in terms of
traffic and energy consumption. In such scenarios, mobile nodes can benefit
from the use of energy efficient and traffic fitting routing protocol that better
suits the limited battery capacity and throughput limitation of the network. This
PhD work focuses on proposing energy efficient and load balanced routing
protocols for ad hoc networks. Where most of the existing routing protocols
simply consider the path length metric when choosing the best route between a
source and a destination node, in our proposed mechanism, nodes are able to
find several routes for each pair of source and destination nodes and select the
best route according to energy and traffic parameters, effectively extending the
lifespan of the network. Our results show that by applying this novel
mechanism, current flat ad hoc routing protocols can achieve higher energy
efficiency and load balancing. Also, due to the broadcast nature of the wireless
channels in ad hoc networks, other technique such as Network Coding (NC)
looks promising for energy efficiency. NC can reduce the number of
transmissions, number of re-transmissions, and increase the data transfer rate
that directly translates to energy efficiency. However, due to the need to access
foreign nodes for coding and forwarding packets, NC needs a mitigation
technique against unauthorized accesses and packet corruption. Therefore, we
proposed different mechanisms for handling these security attacks by, in
particular by serially concatenating codes to support reliability in ad hoc
network. As a solution to this problem, we explored a new security framework
that proposes an additional degree of protection against eavesdropping
attackers based on using concatenated encoding. Therefore, malicious
intermediate nodes will find it computationally intractable to decode the
transitive packets. We also adopted another code that uses Luby Transform
(LT) as a pre-coding code for NC. Primarily being designed for security
applications, this code enables the sink nodes to recover corrupted packets
even in the presence of byzantine attacks.Nas redes móveis ad hoc (MANETs), onde o comportamento cooperativo é
obrigatório, existe uma elevada probabilidade de alguns nós ficarem
sobrecarregados nas operações de encaminhamento de pacotes no apoio Ã
troca de dados com nós vizinhos. Este comportamento altruÃsta leva a uma
sobrecarga desequilibrada em termos de tráfego e de consumo de energia.
Nestes cenários, os nós móveis poderão beneficiar do uso da eficiência
energética e de protocolo de encaminhamento de tráfego que melhor se
adapte à sua capacidade limitada da bateria e velocidade de processamento.
Este trabalho de doutoramento centra-se em propor um uso eficiente da
energia e protocolos de encaminhamento para balanceamento de carga nas
redes ad hoc. Actualmente a maioria dos protocolos de encaminhamento
existentes considera simplesmente a métrica da extensão do caminho, ou seja
o número de nós, para a escolha da melhor rota entre fonte (S) e um nó de
destino (D); no mecanismo aqui proposto os nós são capazes de encontrar
várias rotas por cada par de nós de origem e destino e seleccionar o melhor
caminho segundo a energia e parâmetros de tráfego, aumentando o tempo de
vida útil da rede. Os nossos resultados mostram que pela aplicação deste novo
mecanismo, os protocolos de encaminhamento ad hoc actuais podem alcançar
uma maior eficiência energética e balanceamento de carga.
Para além disso, devido à natureza de difusão dos canais sem fio em redes
ad-hoc, outras técnicas, tais como a Codificação de Rede (NC), parecem ser
também promissoras para a eficiência energética. NC pode reduzir o número
de transmissões, e número de retransmissões e aumentar a taxa de
transferência de dados traduzindo-se directamente na melhoria da eficiência
energética. No entanto, devido ao acesso dos nós intermediários aos pacotes
em trânsito e sua codificação, NC necessita de uma técnica que limite as
acessos não autorizados e a corrupção dos pacotes. Explorou-se o
mecanismo de forma a oferecer um novo método de segurança que propõe um
grau adicional de protecção contra ataques e invasões. Por conseguinte, os
nós intermediários mal-intencionados irão encontrar pacotes em trânsito
computacionalmente intratáveis em termos de descodificação. Adoptou-se
também outro código que usa Luby Transform (LT) como um código de précodificação
no NC. Projectado inicialmente para aplicações de segurança, este
código permite que os nós de destino recuperem pacotes corrompidos mesmo
em presença de ataques bizantinos
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