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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},
}