In-phase and Quadrature Chirp Spread Spectrum for IoT Communications

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

Research output: Contribution to journalConference articlepeer-review


This paper describes a coherent chirp spread spectrum (CSS) technique based on the Long-Range (LoRa) physical layer (PHY) framework. LoRa PHY employs CSS on top of a variant of frequency shift keying (FSK), and non-coherent detection is employed at the receiver for obtaining the transmitted data symbols. In this paper, we propose a scheme that encodes information bits on both in-phase and quadrature components of the chirp signal, and rather employs a coherent detector at the receiver. Hence, channel equalization is required for compensating the channel induced phase rotation on the transmit signal. Moreover, a simple channel estimation technique exploits the LoRa reference sequences used for synchronization to obtain the complex channel coefficient used in the equalizer. Performance evaluation using numerical simulation shows that the proposed scheme achieves approximately 1 dB gain in terms of energy efficiency, and it doubles the spectral efficiency when compared to the conventional LoRa PHY scheme. This is due to the fact that the coherent receiver is able to exploit the orthogonality between in-phase and quadrature components of the transmit signal.

Original languageEnglish (US)
Article number9348094
JournalProceedings - IEEE Global Communications Conference, GLOBECOM
StatePublished - Dec 2020
Event2020 IEEE Global Communications Conference, GLOBECOM 2020 - Virtual, Taipei, Taiwan, Province of China
Duration: Dec 7 2020Dec 11 2020


  • Chirp spread spectrum
  • IoT
  • LoRa
  • PHY
  • wireless communications

ASJC Scopus subject areas

  • Artificial Intelligence
  • Computer Networks and Communications
  • Hardware and Architecture
  • Signal Processing


Dive into the research topics of 'In-phase and Quadrature Chirp Spread Spectrum for IoT Communications'. Together they form a unique fingerprint.

Cite this