LiteNap: downclocking LoRa reception

Xianjin Xia, Yuanqing Zheng*, Tao Gu

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

2 Citations (Scopus)

Abstract

This paper presents LiteNap which improves the energy efficiency of LoRa by enabling LoRa nodes to operate in a downclocked 'light sleep' mode for packet reception. A fundamental limit that prevents radio downclocking is the Nyquist sampling theorem which demands the clock-rate being at least twice the bandwidth of LoRa chirps. Our study reveals under-sampled LoRa chirps suffer frequency aliasing and cause ambiguity in symbol demodulation. LiteNap addresses the problem by leveraging an empirical observation that the hardware of LoRa radio can cause phase jitters on modulated chirps, which result in frequency leakage in the time domain. The timing information of phase jitters and frequency leakages can serve as physical fingerprints to uniquely identify modulated chirps. We propose a scheme to reliably extract the fingerprints from under-sampled chirps and resolve ambiguities in symbol demodulation. We implement LiteNap on a software defined radio platform and conduct trace-driven evaluation. Experiment results show that LiteNap can downclock LoRa nodes to sub-Nyquist rates for energy savings (e.g., 1/8 of Nyquist rate), without substantially affecting packet reception performance (e.g., >95% packet reception rate).

Original languageEnglish
Title of host publicationIEEE INFOCOM 2020
Place of PublicationPiscataway, NJ
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Pages2321-2330
Number of pages10
ISBN (Print)9781728164120
DOIs
Publication statusPublished - 2020
Externally publishedYes
Event2020 IEEE Conference on Computer Communications Workshops - Toronto, Canada
Duration: 6 Jul 20209 Jul 2020

Publication series

NameIEEE Annual Joint Conference: INFOCOM, IEEE Computer and Communications Societies
PublisherIEEE
ISSN (Print)2641-9874

Conference

Conference2020 IEEE Conference on Computer Communications Workshops
Abbreviated titleINFOCOM WKSHPS 2020
CountryCanada
CityToronto
Period6/07/209/07/20

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