14,812 research outputs found
Whisper: Fast Flooding for Low-Power Wireless Networks
This paper presents Whisper, a fast and reliable protocol to flood small
amounts of data into a multi-hop network. Whisper relies on three main
cornerstones. First, it embeds the message to be flooded into a signaling
packet that is composed of multiple packlets. A packlet is a portion of the
message payload that mimics the structure of an actual packet. A node must
intercept only one of the packlets to know that there is an ongoing
transmission. Second, Whisper exploits the structure of the signaling packet to
reduce idle listening and, thus, to reduce the radio-on time of the nodes.
Third, it relies on synchronous transmissions to quickly flood the signaling
packet through the network. Our evaluation on the Flocklab testbed shows that
Whisper achieves comparable reliability but significantly lower radio-on time
than Glossy -- a state-of-the-art flooding algorithm. Specifically, Whisper can
disseminate data in FlockLab twice as fast as Glossy with no loss in
reliability. Further, Whisper spends 30% less time in channel sampling compared
to Glossy when no data traffic must be disseminated
Atomic-SDN: Is Synchronous Flooding the Solution to Software-Defined Networking in IoT?
The adoption of Software Defined Networking (SDN) within traditional networks
has provided operators the ability to manage diverse resources and easily
reconfigure networks as requirements change. Recent research has extended this
concept to IEEE 802.15.4 low-power wireless networks, which form a key
component of the Internet of Things (IoT). However, the multiple traffic
patterns necessary for SDN control makes it difficult to apply this approach to
these highly challenging environments. This paper presents Atomic-SDN, a highly
reliable and low-latency solution for SDN in low-power wireless. Atomic-SDN
introduces a novel Synchronous Flooding (SF) architecture capable of
dynamically configuring SF protocols to satisfy complex SDN control
requirements, and draws from the authors' previous experiences in the IEEE EWSN
Dependability Competition: where SF solutions have consistently outperformed
other entries. Using this approach, Atomic-SDN presents considerable
performance gains over other SDN implementations for low-power IoT networks. We
evaluate Atomic-SDN through simulation and experimentation, and show how
utilizing SF techniques provides latency and reliability guarantees to SDN
control operations as the local mesh scales. We compare Atomic-SDN against
other SDN implementations based on the IEEE 802.15.4 network stack, and
establish that Atomic-SDN improves SDN control by orders-of-magnitude across
latency, reliability, and energy-efficiency metrics
Self-stabilizing TDMA Algorithms for Wireless Ad-hoc Networks without External Reference
Time division multiple access (TDMA) is a method for sharing communication
media. In wireless communications, TDMA algorithms often divide the radio time
into timeslots of uniform size, , and then combine them into frames of
uniform size, . We consider TDMA algorithms that allocate at least one
timeslot in every frame to every node. Given a maximal node degree, ,
and no access to external references for collision detection, time or position,
we consider the problem of collision-free self-stabilizing TDMA algorithms that
use constant frame size.
We demonstrate that this problem has no solution when the frame size is , where is the chromatic number for
distance- vertex coloring. As a complement to this lower bound, we focus on
proving the existence of collision-free self-stabilizing TDMA algorithms that
use constant frame size of . We consider basic settings (no hardware
support for collision detection and no prior clock synchronization), and the
collision of concurrent transmissions from transmitters that are at most two
hops apart. In the context of self-stabilizing systems that have no external
reference, we are the first to study this problem (to the best of our
knowledge), and use simulations to show convergence even with computation time
uncertainties
Low Power, Low Delay: Opportunistic Routing meets Duty Cycling
Traditionally, routing in wireless sensor networks consists of
two steps: First, the routing protocol selects a next hop,
and, second, the MAC protocol waits for the intended destination
to wake up and receive the data. This design makes
it difficult to adapt to link dynamics and introduces delays
while waiting for the next hop to wake up.
In this paper we introduce ORW, a practical opportunistic
routing scheme for wireless sensor networks. In a dutycycled
setting, packets are addressed to sets of potential receivers
and forwarded by the neighbor that wakes up first
and successfully receives the packet. This reduces delay and
energy consumption by utilizing all neighbors as potential
forwarders. Furthermore, this increases resilience to wireless
link dynamics by exploiting spatial diversity. Our results
show that ORW reduces radio duty-cycles on average
by 50% (up to 90% on individual nodes) and delays by 30%
to 90% when compared to the state of the art
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
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