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@PHDTHESIS{EscobarMolero:791687,
author = {Escobar-Molero, Antonio},
othercontributors = {Heinen, Stefan and Mähönen, Petri},
title = {{U}sing concurrent transmissions to improve the reliability
and latency of low-power wireless mesh networks},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2020-05541},
pages = {1 Online-Ressource (128 Seiten) : Illustrationen,
Diagramme},
year = {2020},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2020},
abstract = {Concurrent Transmissions (CT) occur when different
transmitters simultaneously send the same packet. We analyze
how CT distort the received waveform and characterize the
Bit Error Rate (BER) of a receiver trying to recover the
original bitstream. If collisions are not completely
destructive and the information can still be recovered, then
simple, robust and latency-optimal wireless mesh protocols
can be designed. These protocols are particularly suitable
for low-cost and low-power Internet of Things (IoT)
applications, especially in high-interference scenarios,
where routing efforts can be cumbersome and flooding becomes
more effective. Distortion introduced by CT has two main
causes. Firstly, simultaneous transmitters are not perfectly
synchronized, which introduces intersymbol interference
(ISI). The ISI can be reduced by keeping the synchronization
mismatch below half the symbol period. Secondly, there is a
periodical energy fading (beating) in the received waveform
due to alternating patterns of constructive and destructive
interference. This beating cannot be avoided, since it is
originated by the non-coherent nature of the different local
oscillators in the transmitters. Only communication systems
able to cope with periodical amplitude and phase distortions
are suitable for CT-based protocols. Communication
performance is analyzed for typical phase- and
frequency-modulation systems, obtaining the first
closed-form analytical expression for the BER of two
non-coherently received Frequency-Shift Keying (FSK)
transmissions. For more complex systems, simulated BER
curves are obtained. We conclude that CT are extremely
destructive in conjunction with amplitude and phase
modulations, but work particularly well with FSK
modulations. In non-coherent FSK systems, the efficiency of
CT depends on the level of external noise, being very
effective in dense and high-noise environments. Demodulators
based on non-coherent FSK receivers are typically used in
two popular low-power IoT protocols: Bluetooth 5 and IEEE
802.15.4. Both are perfect candidates for CT-based mesh
protocols. Finally, two CT-based award-winning protocols are
designed: RedFixHop and BigBangBus. RedFixHop is the first
protocol using the concept of disseminating information with
concurrent packet acknowledgments (ACKs), while BigBangBus
proposes the novel usage of longer preambles to decrease the
BER introduced by the CT. Both protocols haven been tested
in multiple competitions, repeatedly beating
state-of-the-art solutions in terms of energy efficiency,
reliability and end-to-end latency.},
cin = {616110},
ddc = {621.3},
cid = {$I:(DE-82)616110_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2020-05541},
url = {https://publications.rwth-aachen.de/record/791687},
}
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