RTO considerations in LPWAN
draft-gomez-lpwan-rto-considerations-01

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Last updated 2019-07-04
Replaces draft-gomez-rto-considerations-lpwan
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LPWAN Working Group                                             C. Gomez
Internet-Draft                                                       UPC
Intended status: Informational                              J. Crowcroft
Expires: January 5, 2020                         University of Cambridge
                                                            July 4, 2019

                      RTO considerations in LPWAN
                draft-gomez-lpwan-rto-considerations-01

Abstract

   Low-Power Wide Area Network (LPWAN) technologies are characterized by
   very low physical layer bit and message transmission rates.
   Moreover, a response to a message sent by an LPWAN device may often
   only be received after a significant delay.  As a result, Round-Trip
   Time (RTT) values in LPWAN are often (sometimes, significantly)
   greater than typical default values of Retransmission TimeOut (RTO)
   algorithms.  Furthermore, buffering at network elements such as radio
   gateways may interact negatively with LPWAN technology transmission
   mechanisms, potentially exacerbating RTTs by up to several orders of
   magnitude.  This document provides guidance for RTO settings in
   LPWAN, and describes an experimental dual RTO algorithm for LPWAN.

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Gomez & Crowcroft        Expires January 5, 2020                [Page 1]
Internet-Draft                RTO in LPWAN                     July 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Ideal scenario U-RTT  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  LoRaWAN . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Sigfox  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Higher order U-RTT  . . . . . . . . . . . . . . . . . . . . .   5
   5.  D-RTT analysis  . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Discussion and proposed dual RTO algorithm  . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Low-Power Wide Area Network (LPWAN) technologies offer appealing
   features, such as multikilometer wireless link range, while allowing
   low energy consumption for Internet of Things (IoT) devices.
   However, these advantages come at the expense of reduced physical
   layer (PHY) bit and message rates, which in some regions are further
   affected by spectrum access regulatory constraints.  In some LPWAN
   scenarios, with flagship LPWAN technologies such as LoRaWAN or
   Sigfox, PHY bit rates are lower than 1 kbit/s, and uplink message
   rates are lower than 1 message/minute [RFC8376].

   Due to the aforementioned communication constraints, LPWAN
   technologies often exhibit high or very high Round Trip Times (RTTs).
   Even with negligible processing delays and in absence of
   communication errors, RTTs can be in the order of a few seconds or a
   few tens of seconds.  Depending on the approach used to comply with
   spectrum access regulations, RTTs can grow to several minutes.
   Finally, when downlink responses are buffered in the radio gateway,
   RTTs will be in the order of the time between uplink messages (e.g.
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