main.tex

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\begin{document}

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%Conference
\acmConference[IPSN 2018]{IEEE/ACM Information Processing in Sensor Networks}{April 2018}{Porto, Portugal}
\acmYear{2018}
\copyrightyear{2018}

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\title[Charm]{ Charm: Exploiting Geographical Diversity Through \\ Coherent Combining in Low-Power Wide-Area Networks }

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\author{Adwait Dongare}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\email{adongare@cmu.edu}

\author{Revathy Narayanan}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\affiliation{%
  \institution{IIT Madras}
  %\city{Chennai}
  %\state{India}
}
\email{revathyn@andrew.cmu.edu}

\author{Akshay Gadre}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\email{agadre@andrew.cmu.edu}

\author{Anh Luong}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\email{anhluong@cmu.edu}

\author{Artur Balanuta}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\affiliation{%
  \institution{Instituto Superior T\'ecnico, Lisbon}
}
\email{artur@cmu.edu}

\author{Swarun Kumar}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\email{swarun@cmu.edu}

\author{Bob Iannucci}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Palo Alto}
  %\state{CA}
}
\email{bob.iannucci@west.cmu.edu}

\author{Anthony Rowe}
\affiliation{%
  \institution{Carnegie Mellon University}
  %\city{Pittsburgh}
  %\state{PA}
}
\email{agr@ece.cmu.edu}

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\begin{abstract}


Low-Power Wide Area Networks (LPWANs) are an emerging wireless platform which
can support battery-powered devices lasting 10-years while communicating at
low data-rates to gateways several kilometers away. Not all such devices will
experience the promised 10 year battery life despite the high density of LPWAN
gateways expected in cities. Transmission from devices located deep within
buildings or in remote neighborhoods will suffer severe attenuation forcing
the use of slow data-rates to reach even the closest gateway, thus resulting
in battery drain.

This paper presents Charm, a system that enhances both the battery life of
client devices and the coverage of LPWANs in large urban deployments. Charm
allows multiple LoRaWAN gateways to pool their received signals in the cloud,
coherently combining them to detect weak signals that are not
decodable at any individual gateway. Through a novel hardware and software
design at the gateway, Charm carefully detects which chunks of the received
signal need to be sent to the cloud, thereby saving uplink bandwidth. We
present a scalable solution to decoding weak transmissions at city-scale by
identifying the set of gateways whose signals need to be coherently combined
over time. In evaluations over a test network and from simulations using
traces from a large LoRaWAN deployment in Pittsburgh, Pennsylvania, Charm
demonstrates a gain of up to 3$\times$ in range and 4$\times$ in
client battery-life.

\end{abstract}

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\keywords{LPWAN, sensor networks, coherent combining, diversity}

\maketitle

\input{tex/1-introduction.tex}
\input{tex/2-related.tex}
\input{tex/3-background.tex}
\input{tex/4-arch.tex}
\input{tex/5-gateway.tex}
\input{tex/6-cloud.tex}
\input{tex/7-implementation.tex}
\input{tex/8-evaluation.tex}
\input{tex/9-conclusion.tex}

\section*{Acknowledgment}

This research is supported in part by the National Science Foundation under
award CNS-1329644 and the CONIX Research Center, one of six centers in JUMP, a
Semiconductor Research Corporation (SRC) program sponsored by DARPA.

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