Alternative Chirp Spread Spectrum Techniques for LPWANs

Ivo Bizon Franco De Almeida, Marwa Chafii, Ahmad Nimr, Gerhard Fettweis

Research output: Contribution to journalArticlepeer-review

Abstract

Chirp spread spectrum (CSS) is the modulation technique currently employed by Long-Range (LoRa), which is one of the most prominent Internet of Things wireless communications standards. The LoRa physical layer (PHY) employs CSS on top of a variant of frequency shift keying, and non-coherent detection is employed at the receiver. While it offers a good trade-off among coverage, data rate and device simplicity, its maximum achievable data rate is still a limiting factor for some applications. Moreover, the current LoRa standard does not fully exploit the CSS generic case, i.e., when data to be transmitted is encoded in different waveform parameters. Therefore, the goal of this paper is to investigate the performance of CSS while exploring different parameter settings aiming to increase the maximum achievable throughput, and hence increase spectral efficiency. Moreover, coherent and non-coherent reception algorithm design is presented under the framework of maximum likelihood estimation. For the practical receiver design, the formulation of a channel estimation technique is also presented. The performance evaluation of the different variants of CSS is carried out by inspection of the symbol error ratio as a function of the signal-to-noise ratio together with the maximum achievable throughput each scheme can achieve.

Original languageEnglish (US)
Pages (from-to)1846-1855
Number of pages10
JournalIEEE Transactions on Green Communications and Networking
Volume5
Issue number4
DOIs
StatePublished - Dec 1 2021

Keywords

  • Chirp spread spectrum
  • IoT
  • long-range communications
  • LPWAN
  • wireless communications

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Computer Networks and Communications

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