12,934 research outputs found
Performance study of voice over frame relay : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Information Engineering, Massey University, Albany, New Zealand
Frame Relay (FR) represents an important paradigm shift in modern telecommunication. This technology is beginning to evolve from data only application to broad spectrum of multimedia users and potential to provide end users with cost effective transport of voice traffic for intra office communication. In this project the recent development in voice communication over Frame relay is investigated. Simulations were carried out using OPNET, a powerful simulation software. Following the simulation model, a practical design of the LAN-to-LAN connectivity experiment was also done in the Net Lab. From the results of the simulation, Performance measures such as delay, jitter, and throughput are reported. It is evident from the results that real-time voice or video across a frame relay network can provide acceptable performance
Optimal Content Downloading in Vehicular Networks
We consider a system where users aboard communication-enabled vehicles are interested in downloading different contents from Internet-based servers. This scenario captures many of the infotainment services that vehicular communication is envisioned to enable, including news reporting, navigation maps and software updating, or multimedia file downloading. In this paper, we outline the performance limits of such a vehicular content downloading system by modelling the downloading process as an optimization problem, and maximizing the overall system throughput. Our approach allows us to investigate the impact of different factors, such as the roadside infrastructure deployment, the vehicle-to-vehicle relaying, and the penetration rate of the communication technology, even in presence of large instances of the problem. Results highlight the existence of two operational regimes at different penetration rates and the importance of an efficient, yet 2-hop constrained, vehicle-to-vehicle relaying
Multi-rate relaying for performance improvement in IEEE 802.11 WLANs
It is well known that the presence of nodes using a low data transmit rate has a disproportionate impact on the performance of an IEEE 802.11 WLAN. ORP is an opportunistic relay protocol that allows nodes to increase their effective transmit rate by replacing a low data rate transmission with a two-hop sequence of shorter range, higher data rate transmissions, using an intermediate node as a relay. ORP differs from existing protocols in discovering relays experimentally, by optimistically making frames available for relaying. Relays identify themselves as suitable relays by forwarding these frames. This approach has several advantages compared with previously proposed relay protocols: Most importantly, ORP does not rely on observations of received signal strength to infer the availability of relay nodes and transmit rates. We present analytic and simulation results showing that ORP improves the throughput by up to 40% in a saturated IEEE 802.11b network
Energy Consumption Of Visual Sensor Networks: Impact Of Spatio-Temporal Coverage
Wireless visual sensor networks (VSNs) are expected to play a major role in
future IEEE 802.15.4 personal area networks (PAN) under recently-established
collision-free medium access control (MAC) protocols, such as the IEEE
802.15.4e-2012 MAC. In such environments, the VSN energy consumption is
affected by the number of camera sensors deployed (spatial coverage), as well
as the number of captured video frames out of which each node processes and
transmits data (temporal coverage). In this paper, we explore this aspect for
uniformly-formed VSNs, i.e., networks comprising identical wireless visual
sensor nodes connected to a collection node via a balanced cluster-tree
topology, with each node producing independent identically-distributed
bitstream sizes after processing the video frames captured within each network
activation interval. We derive analytic results for the energy-optimal
spatio-temporal coverage parameters of such VSNs under a-priori known bounds
for the number of frames to process per sensor and the number of nodes to
deploy within each tier of the VSN. Our results are parametric to the
probability density function characterizing the bitstream size produced by each
node and the energy consumption rates of the system of interest. Experimental
results reveal that our analytic results are always within 7% of the energy
consumption measurements for a wide range of settings. In addition, results
obtained via a multimedia subsystem show that the optimal spatio-temporal
settings derived by the proposed framework allow for substantial reduction of
energy consumption in comparison to ad-hoc settings. As such, our analytic
modeling is useful for early-stage studies of possible VSN deployments under
collision-free MAC protocols prior to costly and time-consuming experiments in
the field.Comment: to appear in IEEE Transactions on Circuits and Systems for Video
Technology, 201
Adaptive Traffic Fingerprinting for Darknet Threat Intelligence
Darknet technology such as Tor has been used by various threat actors for
organising illegal activities and data exfiltration. As such, there is a case
for organisations to block such traffic, or to try and identify when it is used
and for what purposes. However, anonymity in cyberspace has always been a
domain of conflicting interests. While it gives enough power to nefarious
actors to masquerade their illegal activities, it is also the cornerstone to
facilitate freedom of speech and privacy. We present a proof of concept for a
novel algorithm that could form the fundamental pillar of a darknet-capable
Cyber Threat Intelligence platform. The solution can reduce anonymity of users
of Tor, and considers the existing visibility of network traffic before
optionally initiating targeted or widespread BGP interception. In combination
with server HTTP response manipulation, the algorithm attempts to reduce the
candidate data set to eliminate client-side traffic that is most unlikely to be
responsible for server-side connections of interest. Our test results show that
MITM manipulated server responses lead to expected changes received by the Tor
client. Using simulation data generated by shadow, we show that the detection
scheme is effective with false positive rate of 0.001, while sensitivity
detecting non-targets was 0.016+-0.127. Our algorithm could assist
collaborating organisations willing to share their threat intelligence or
cooperate during investigations.Comment: 26 page
Sparse Signal Processing Concepts for Efficient 5G System Design
As it becomes increasingly apparent that 4G will not be able to meet the
emerging demands of future mobile communication systems, the question what
could make up a 5G system, what are the crucial challenges and what are the key
drivers is part of intensive, ongoing discussions. Partly due to the advent of
compressive sensing, methods that can optimally exploit sparsity in signals
have received tremendous attention in recent years. In this paper we will
describe a variety of scenarios in which signal sparsity arises naturally in 5G
wireless systems. Signal sparsity and the associated rich collection of tools
and algorithms will thus be a viable source for innovation in 5G wireless
system design. We will discribe applications of this sparse signal processing
paradigm in MIMO random access, cloud radio access networks, compressive
channel-source network coding, and embedded security. We will also emphasize
important open problem that may arise in 5G system design, for which sparsity
will potentially play a key role in their solution.Comment: 18 pages, 5 figures, accepted for publication in IEEE Acces
ITERL: A Wireless Adaptive System for Efficient Road Lighting
This work presents the development and construction of an adaptive street lighting system
that improves safety at intersections, which is the result of applying low-power Internet of Things
(IoT) techniques to intelligent transportation systems. A set of wireless sensor nodes using the
Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard with additional internet
protocol (IP) connectivity measures both ambient conditions and vehicle transit. These measurements
are sent to a coordinator node that collects and passes them to a local controller, which then makes
decisions leading to the streetlight being turned on and its illumination level controlled. Streetlights
are autonomous, powered by photovoltaic energy, and wirelessly connected, achieving a high degree
of energy efficiency. Relevant data are also sent to the highway conservation center, allowing it to
maintain up-to-date information for the system, enabling preventive maintenance.ConsejerĂa de Fomento y Vivienda Junta de AndalucĂa G-GI3002 / IDIOFondo Europeo de Desarrollo Regional G-GI3002 / IDI
cISP: A Speed-of-Light Internet Service Provider
Low latency is a requirement for a variety of interactive network
applications. The Internet, however, is not optimized for latency. We thus
explore the design of cost-effective wide-area networks that move data over
paths very close to great-circle paths, at speeds very close to the speed of
light in vacuum. Our cISP design augments the Internet's fiber with free-space
wireless connectivity. cISP addresses the fundamental challenge of
simultaneously providing low latency and scalable bandwidth, while accounting
for numerous practical factors ranging from transmission tower availability to
packet queuing. We show that instantiations of cISP across the contiguous
United States and Europe would achieve mean latencies within 5% of that
achievable using great-circle paths at the speed of light, over medium and long
distances. Further, we estimate that the economic value from such networks
would substantially exceed their expense
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