145 research outputs found
A taxonomy and evaluation for developing 802.11‐based wireless mesh network testbeds
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92433/1/dac1299.pd
Resilient Wireless Sensor Networks Using Topology Control: A Review
Wireless sensor networks (WSNs) may be deployed in failure-prone environments, and WSNs nodes easily fail due to unreliable wireless connections, malicious attacks and resource-constrained features. Nevertheless, if WSNs can tolerate at most losing k − 1 nodes while the rest of nodes remain connected, the network is called k − connected. k is one of the most important indicators for WSNs’ self-healing capability. Following a WSN design flow, this paper surveys resilience issues from the topology control and multi-path routing point of view. This paper provides a discussion on transmission and failure models, which have an important impact on research results. Afterwards, this paper reviews theoretical results and representative topology control approaches to guarantee WSNs to be k − connected at three different network deployment stages: pre-deployment, post-deployment and re-deployment. Multi-path routing protocols are discussed, and many NP-complete or NP-hard problems regarding topology control are identified. The challenging open issues are discussed at the end. This paper can serve as a guideline to design resilient WSNs
From Capture to Display: A Survey on Volumetric Video
Volumetric video, which offers immersive viewing experiences, is gaining
increasing prominence. With its six degrees of freedom, it provides viewers
with greater immersion and interactivity compared to traditional videos.
Despite their potential, volumetric video services poses significant
challenges. This survey conducts a comprehensive review of the existing
literature on volumetric video. We firstly provide a general framework of
volumetric video services, followed by a discussion on prerequisites for
volumetric video, encompassing representations, open datasets, and quality
assessment metrics. Then we delve into the current methodologies for each stage
of the volumetric video service pipeline, detailing capturing, compression,
transmission, rendering, and display techniques. Lastly, we explore various
applications enabled by this pioneering technology and we present an array of
research challenges and opportunities in the domain of volumetric video
services. This survey aspires to provide a holistic understanding of this
burgeoning field and shed light on potential future research trajectories,
aiming to bring the vision of volumetric video to fruition.Comment: Submitte
Quality-of-service in wireless sensor networks: state-of-the-art and future directions
Wireless sensor networks (WSNs) are one of today’s most prominent instantiations
of the ubiquituous computing paradigm. In order to achieve high
levels of integration, WSNs need to be conceived considering requirements
beyond the mere system’s functionality. While Quality-of-Service (QoS) is
traditionally associated with bit/data rate, network throughput, message delay
and bit/packet error rate, we believe that this concept is too strict, in
the sense that these properties alone do not reflect the overall quality-ofservice
provided to the user/application. Other non-functional properties
such as scalability, security or energy sustainability must also be considered
in the system design. This paper identifies the most important non-functional
properties that affect the overall quality of the service provided to the users,
outlining their relevance, state-of-the-art and future research directions
Load-Adaptive Practical Multi-Channel Communications in Wireless Sensor Networks
In recent years, a significant number of sensor node prototypes have been designed that provide communications in multiple channels. This multi-channel feature can be effectively exploited to increase the overall capacity and performance of wireless sensor networks (WSNs). In this paper, we present a multi-channel communications system for WSNs that is referred to as load-adaptive practical multi-channel communications (LPMC). LPMC estimates the active load of a channel at the sink since it has a more comprehensive view of the network behavior, and dynamically adds or removes channels based on the estimated load. LPMC updates the routing path to balance the loads of the channels. The nodes in a path use the same channel; therefore, they do not need to switch channels to receive or forward packets. LPMC has been evaluated through extensive simulations, and the results demonstrate that it can effectively increase the delivery ratio, network throughput, and channel utilization, and that it can decrease the end-to-end delay and energy consumption
Systems-Level Support for Mobile Device Connectivity.
The rise of handheld computing devices has
inspired a great deal of research aimed at
addressing the unique problems posed by their
mobile, "always-on" nature. In order to help
mobile devices navigate a complex world of
overlapping, uneven public wireless coverage, one
must be mindful of the distinction between
nomadic usage and true mobility. Accordingly,
systems research must move beyond simply
optimizing for a set of local conditions (e.g.,
finding the best access point for a laptop user
in a stationary location) to considering the
"derivative of connectivity" when network
conditions are constantly in flux.
This dissertation presents a new paradigm for
networking support on mobile devices. This
project has several complementary aspects. As
devices encounter network connectivity our system
both evaluates the application-level quality of
WiFi access points and updates a device-centric
mobility model. Together, this mobility model and
AP quality database yield "connectivity
forecasts," which let applications optimize not
just for current network conditions but for
the expected big picture to come. Results of a
prototype deployment in several cities shows that
considering the application-level quality of APs
(rather than just signal strength) significantly
boosts the success rate of finding a usable
access point. Furthermore, this dissertation
shows how connectivity forecasts---even with
minimal model training time---allow several
applications commonly found on mobile devices to
reap significant benefits, such as extended
battery life.
Mobile devices are often within range of multiple
connectivity options, however, and choosing just
one therefore ignores potential connectivity.
This dissertation describes a virtual link layer
for Linux, called Juggler, that uses one network
card to simultaneously associate with many WiFi
APs, ad hoc groups or mesh networks. The results
show how Juggler can boost effective bandwidth by
striping data across multiple APs, enable
seamless 802.11 handoff by preemptively
associating with the "next" AP before the
current one become unusable, and maintain a
modest side-channel to the user's personal area
network or mesh network without impacting
foreground bandwidth to infrastructure.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61718/1/tonynich_1.pd
A COMMUNICATION FRAMEWORK FOR MULTIHOP WIRELESS ACCESS AND SENSOR NETWORKS: ANYCAST ROUTING & SIMULATION TOOLS
The reliance on wireless networks has grown tremendously within a number of varied application domains, prompting an evolution towards the use of heterogeneous multihop network architectures. We propose and analyze two communication frameworks for such networks. A first framework is designed for communications within multihop wireless access networks. The framework supports dynamic algorithms for locating access points using anycast routing with multiple metrics and balancing network load. The evaluation shows significant performance improvement over traditional solutions. A second framework is designed for communication within sensor networks and includes lightweight versions of our algorithms to fit the limitations of sensor networks. Analysis shows that this stripped down version can work almost equally well if tailored to the needs of a sensor network. We have also developed an extensive simulation environment using NS-2 to test realistic situations for the evaluations of our work. Our tools support analysis of realistic scenarios including the spreading of a forest fire within an area, and can easily be ported to other simulation software. Lastly, we us our algorithms and simulation environment to investigate sink movements optimization within sensor networks. Based on these results, we propose strategies, to be addressed in follow-on work, for building topology maps and finding optimal data collection points. Altogether, the communication framework and realistic simulation tools provide a complete communication and evaluation solution for access and sensor networks
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