What modulation is used by LoRa?

LoRa (Long Range) is a proprietary physical layer (PHY) modulation technique developed by Semtech. It is based on Chirp Spread Spectrum (CSS) modulation. In CSS, data is encoded using "chirps," which are signals that continuously vary in frequency, either increasing (up-chirp) or decreasing (down-chirp) over a specific bandwidth. This spread spectrum method allows the signal to be received even when it is below the noise floor, providing excellent robustness against interference and enabling long-range, low-power communication, which is ideal for IoT applications.

A. OFDMA (Orthogonal Frequency-Division Multiple Access) is a multi-user access scheme used in high-throughput technologies like Wi-Fi 6 (802.11ax) and 5G, not in LoRa.

C. ASK (Amplitude-Shift Keying) is a simpler modulation where data is represented by variations in the carrier signal's amplitude, which lacks the range and interference resilience of LoRa's CSS.

D. OFDM (Orthogonal Frequency-Division Multiplexing) is a modulation technique used for high-data-rate communications like Wi-Fi (802.11a/g/n/ac) and LTE, which is fundamentally different from LoRa's low-rate, long-range approach.

1. Semtech Corporation. (2020). AN1200.22 - LoRa® Modulation Basics. Section 2, "LoRa Modulation," Paragraph 1. "The LoRa modulation is a proprietary technology, based on the Chirp Spread Spectrum (CSS) modulation, which has been used in military and space communication for decades."

2. Haxhibeqiri, J., De Poorter, E., Moerman, I., & Hoebeke, J. (2018). A Survey of LoRaWAN for IoT: From Technology to Application. Sensors, 18(11), 3995. Section 2.1, "LoRa Physical Layer," Paragraph 1. "LoRa is a proprietary modulation format owned by Semtech, based on Chirp Spread Spectrum (CSS) modulation." DOI: https://doi.org/10.3390/s18113995

3. Bor, M., Roedig, U., Voigt, T., & Alonso, J. M. (2016). Do LoRa Low-Power Wide-Area Networks Scale? In Proceedings of the 19th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM '16). Association for Computing Machinery, New York, NY, USA, 59–67. Section 2, "LoRa and LoRaWAN," Paragraph 1. "LoRa is a proprietary spread-spectrum modulation scheme that is a derivative of Chirp Spread Spectrum (CSS) modulation." DOI: https://doi.org/10.1145/2988287.2989163