6,716 research outputs found
Sensor Networks for Maritime Deployment: Modeling and Simulation
Simulation is widely used in Wireless Sensor Networks to assess the feasibility and performance of design decisions before the deployment, assisting the development of optimal solutions or trade-offs. In this paper, we address the particular case of a sensor network deployed at sea, where hundreds or thousands of sensing nodes drift with the stream and organise into a network capable of transmitting results to a remote station. A new simulator was built to address the particularities of the wireless models required to correctly understand the application scenario. The models provide realistic channel simulation, along with additive interference from other sources, where all transmissions are considered independently. The receiver decides which transmission was first and what is the level of noise from the environment and contending nodes. Network algorithms were implemented and compared using different network sizes and parameters. Results show that algorithms are sensitive to deployment conditions and respond differently to each set of environmental parameters
Characterization of the on-body path Loss at 2.45 GHz and energy efficient WBAN design for dairy cows
Wireless body area networks (WBANs) provide promising applications in the healthcare monitoring of dairy cows. The characterization of the path loss (PL) between on-body nodes constitutes an important step in the deployment of a WBAN. In this paper, the PL between nodes placed on the body of a dairy cow was determined at 2.45 GHz. Finite-difference time domain simulations with two half-wavelength dipoles placed 20 mm above a cow model were performed using a 3-D electromagnetic solver. Measurements were conducted on a live cow to validate the simulation results. Excellent agreement between measurements and simulations was achieved and the obtained PL values as a function of the transmitter-receiver separation were well fitted by a lognormal PL model with a PL exponent of 3.1 and a PL at reference distance ( 10 cm) of 44 dB. As an application, the packet error rate ( PER) and the energy efficiency of different WBAN topologies for dairy cows (i.e., single-hop, multihop, and cooperative networks) were investigated. The analysis results revealed that exploiting multihop and cooperative communication schemes decrease the PER and increase the optimal payload packet size. The analysis results revealed that exploiting multihop and cooperative communication schemes increase the optimal payload packet size and improve the energy efficiency by 30%
Cross-layer design of multi-hop wireless networks
MULTI -hop wireless networks are usually defined as a collection of nodes
equipped with radio transmitters, which not only have the capability to
communicate each other in a multi-hop fashion, but also to route each others’ data
packets. The distributed nature of such networks makes them suitable for a variety of
applications where there are no assumed reliable central entities, or controllers, and
may significantly improve the scalability issues of conventional single-hop wireless
networks.
This Ph.D. dissertation mainly investigates two aspects of the research issues
related to the efficient multi-hop wireless networks design, namely: (a) network
protocols and (b) network management, both in cross-layer design paradigms to
ensure the notion of service quality, such as quality of service (QoS) in wireless mesh
networks (WMNs) for backhaul applications and quality of information (QoI) in
wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of
this Ph.D. dissertation, different network settings are used as illustrative examples,
however the proposed algorithms, methodologies, protocols, and models are not
restricted in the considered networks, but rather have wide applicability.
First, this dissertation proposes a cross-layer design framework integrating
a distributed proportional-fair scheduler and a QoS routing algorithm, while using
WMNs as an illustrative example. The proposed approach has significant performance
gain compared with other network protocols. Second, this dissertation proposes
a generic admission control methodology for any packet network, wired and
wireless, by modeling the network as a black box, and using a generic mathematical
0. Abstract 3
function and Taylor expansion to capture the admission impact. Third, this dissertation
further enhances the previous designs by proposing a negotiation process,
to bridge the applications’ service quality demands and the resource management,
while using WSNs as an illustrative example. This approach allows the negotiation
among different service classes and WSN resource allocations to reach the optimal
operational status. Finally, the guarantees of the service quality are extended to
the environment of multiple, disconnected, mobile subnetworks, where the question
of how to maintain communications using dynamically controlled, unmanned data
ferries is investigated
Slotted ALOHA Overlay on LoRaWAN: a Distributed Synchronization Approach
LoRaWAN is one of the most promising standards for IoT applications.
Nevertheless, the high density of end-devices expected for each gateway, the
absence of an effective synchronization scheme between gateway and end-devices,
challenge the scalability of these networks. In this article, we propose to
regulate the communication of LoRaWAN networks using a Slotted-ALOHA (S-ALOHA)
instead of the classic ALOHA approach used by LoRa. The implementation is an
overlay on top of the standard LoRaWAN; thus no modification in pre-existing
LoRaWAN firmware and libraries is necessary. Our method is based on a novel
distributed synchronization service that is suitable for low-cost IoT
end-nodes. S-ALOHA supported by our synchronization service significantly
improves the performance of traditional LoRaWAN networks regarding packet loss
rate and network throughput.Comment: 4 pages, 8 figure
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