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LoRa

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LoRa
SX1278, a LoRa module
Developed byCycleo, Semtech
Connector typeSPI/I2C
Compatible hardwareSX127x, SX126x, LLCC68, SX128x, LR11xx, LR20xx
330 kilometres (210 mi) in perfect conditions.[1] Approximately 10 kilometres (6.2 mi) in practical conditions
LoRa modulation as seen on a smartphone using RF Analyzer app. The radio receiver is a RTL-SDR USB device (2.5 Msps). Center frequency is 432.995 MHz, Bandwidth is 7.8kHz. In the yellowgreen area time is downwards and at the top time is 0 (current time).

LoRa (from "long range") is a physical proprietary radio communication technique based on spread spectrum modulation.[2] LoRa can be thought of as a radio signal technology, similar to Wi-Fi or cellular.[3] It was developed by Cycleo and acquired by Semtech in 2012.[4]

The technology is primarily used for applications where small amounts of data need to be transmitted infrequently from hard-to-reach locations.

LoRa uses license-free sub-gigahertz radio frequency bands EU433 (433.050-434.790 MHz) or EU868 (863–870/873 MHz) in Europe; AU915/AS923-1 (915–928 MHz) in South America; US915 (902–928 MHz) in North America; IN865 (865–867 MHz) in India; and AS923 (915–928 MHz) in Asia;[5] LoRa enables long-range transmissions with low power consumption.[6] The technology covers the physical layer, while other technologies and protocols such as LoRaWAN cover the upper layers. It can achieve data rates between 0.3 kbit/s and 27 kbit/s, depending upon the spreading factor.[7]

Description

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LoRa uses a proprietary spread spectrum modulation that is similar to and a derivative of chirp spread spectrum (CSS) modulation. Each symbol is represented by a cyclic shifted chirp over the bandwidth centered around the base frequency.

The spreading factor (SF) is a selectable radio parameter from 5 to 12[8] and represents the number of bits sent per symbol and in addition determines how much the information is spread over time.[9] There are M=2SF different initial frequencies of the cyclic shifted chirp across the bandwidth around the center frequency.[10]

The symbol rate is determined by Rs=B/M. LoRa can tradeoff data rate for sensitivity (assuming a fixed channel bandwidth B) by selecting the SF, i.e. the amount of spread used. A lower SF corresponds to a higher data rate but a worse sensitivity, a higher SF implies a better sensitivity but a lower data rate.[11] Compared to lower SF, sending the same amount of data with higher SF needs more transmission time, known as time-on-air. More time-on-air means that the modem is transmitting for a longer time and consuming more energy.

Typical LoRa modems support transmit powers up to +22 dBm.[8] However, the regulations of the respective country may additionally limit the allowed transmit power. Higher transmit power results in higher signal power at the receiver and hence a higher link budget, but at the cost of consuming more energy. There are measurement studies of LoRa performance with regard to energy consumption, communication distances, and medium access efficiency.[12] According to the LoRa Development Portal, the range provided by LoRa can be up to 3 miles (4.8 km) in urban areas, and up to 10 miles (16 km) or more in rural areas (line of sight).[13]

In addition, LoRa uses forward error correction coding to improve resilience against interference. LoRa's high range is characterized by high wireless link budgets of around 155 dB to 170 dB.[14]

Frame structure

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A LoRa frame begins with a preamble of identical, unmodulated upchirps. The receiver uses the preamble to detect the frame and to synchronize coarsely.[15][16] Two modulated chirps follow. They carry the sync word, which acts as a network identifier.[4] Unlike data symbols, the sync word symbols are not Gray coded, whitened or protected by forward error correction.[16] A start frame delimiter (SFD) of 2.25 downchirps comes next. The end of the SFD marks the first data symbol and gives the receiver symbol-level timing.[15][16] The data symbols carry an optional header, the payload and an optional payload CRC. In explicit header mode, the header states the payload length, the coding rate and whether a CRC is present. In implicit header mode, both ends fix these values in advance and no header is sent.[17]

Channel coding

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LoRa applies whitening, a modified Hamming code, interleaving and Gray mapping to the data before modulation.[15][4] The code adds one to four parity bits to each four-bit nibble, which gives coding rates from 4/5 to 4/8.[9][4] The header is always sent at coding rate 4/8 in a reduced-rate mode that carries SF−2 bits per symbol.[4] A low data rate optimization mode applies the same reduction to the payload. Semtech datasheets mandate it when the symbol duration exceeds 16 ms.[4][17]

Demodulation

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A receiver demodulates each symbol by dechirping. It multiplies the received chirp by a downchirp, the complex conjugate of the base upchirp. The product is a tone whose frequency equals the symbol's cyclic shift.[16] At a sample rate equal to the bandwidth, a fast Fourier transform of 2SF points maps this tone to a single bin. The index of the strongest bin is the transmitted symbol value.[16] Dechirping concentrates the symbol energy, which was spread across the full bandwidth, into that bin. Noise stays spread across all bins.[16] This processing gain lets commercial receivers demodulate frames at a signal-to-noise ratio of about −20 dB.[8][16] Commercial transceivers also provide channel activity detection (CAD). CAD confirms whether a LoRa frame is present on a channel without demodulating its payload.[16]

LoRa transceivers

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Semtech makes several families of LoRa transceivers, grouped into four generations.[18][19] The first generation appeared in 2013 and the fourth in 2025.[19][20] A host microcontroller configures each of them over SPI.[17][8] Each generation adds frequency bands, modulations or features, and newer chips remain compatible with earlier LoRa devices.[21][22]

Semtech LoRa transceiver families[23][8][24][25][21][20][22]
FamilyGenerationFrequency bandsModulationsExtra featuresFirmware can be changed
SX127x1Sub-GHz (137–1020 MHz)LoRa, (G)FSK, (G)MSK, OOKNo
SX126x, LLCC682Sub-GHz (150–960 MHz)LoRa, (G)FSK, (G)MSK, LR-FHSSNo
SX128x22.4 GHzLoRa, FLRC, (G)FSK, BLE PHYTime-of-flight rangingNo
LR11xx3Sub-GHz; 2.4 GHz and S-band on newer modelsLoRa, (G)FSK, LR-FHSSGNSS and Wi-Fi scanning on LR1110 and LR1120Yes
LR20xx4Sub-GHz, 2.4 GHz and S-bandLoRa, FLRC, (G)FSK, OOK, O-QPSK, LR-FHSSYes

Earlier generations run fixed firmware. In the third and fourth generations, the radio firmware can be changed.[26][27] Semtech publishes firmware for the LR11xx chips in a public repository, together with a reference update tool.[26][28] This allows chips already deployed in the field to receive updates.[29] For example, LoRa Basics Modem-E firmware turns an LR1110 or LR1121 into a complete LoRaWAN modem.[29][30] On the LR1121, it provides a certified LoRaWAN 1.0.4 stack with relay and carrier-sense multiple access (CSMA).[30]

Some third-generation chips also support geolocation. The LR1110 and LR1120 can scan signals from GPS and BeiDou satellites as well as nearby Wi-Fi access points.[23][21] A LoRa device can therefore be located without a separate GNSS receiver.[31]

Open-source implementations

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Several research groups have reverse engineered the LoRa physical layer and implemented it in open-source software. In 2016, researcher Matt Knight analysed LoRa signals captured with a software-defined radio. He documented the modulation and the coding chain, including whitening, interleaving, Gray mapping and the Hamming code.[15][32] He released an open-source GNU Radio implementation named gr-lora.[33] He presented the work at the GNU Radio Conference in September 2016[32] and at the 33rd Chaos Communication Congress (33C3) in December 2016.[34] A detailed account appeared in the hacker journal PoC||GTFO.[15]

Pieter Robyns and colleagues at Hasselt University in Belgium published a detailed description of the PHY in 2018. Their decoder, a separate project also named gr-lora, decodes several channels at once without frequency offset correction. In their tests it decoded every configuration of the RN2483 and SX1272.[4][35] LoRa Tools is a browser-based tool that generates LoRa I/Q data and decodes recordings step by step.[36]

Applications

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LoRa applications:

See also

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  • DASH7 – a popular open alternative to LoRa
  • IEEE 802.11ah – non-proprietary low-power long-range standard
  • CC430 – an MCU & sub-1 GHz RF transceiver SoC
  • Narrowband IoT – narrowband Internet of things
  • LTE Cat M1 – Cellular device technology
  • MIoTy – sub-GHz LPWAN technology for sensor networks
  • SCHC – static context header compression
  • Short-range device – Class of radio transmitter

References

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  1. ↑ "Range Tests | Meshtastic". meshtastic.org. Retrieved 2025-01-22.
  2. ↑ "What is LoRa?". Semtech. Retrieved October 3, 2025.
  3. ↑ Haxhibeqiri, J.; Van den Abeele, F.; Hoebeke, J.; Moerman, I. (2018). "A Survey of LoRaWAN for the Internet of Things". LoRaWAN for smart city applications. Springer. pp. 1–25.
  4. 1 2 3 4 5 6 7 Robyns, Pieter; Quax, Peter; Lamotte, Wim; Thenaers, William (2018). "A Multi-Channel Software Decoder for the LoRa Modulation Scheme". Proceedings of the 3rd International Conference on Internet of Things, Big Data and Security (IoTBDS 2018). SciTePress. pp. 41–51. doi:10.5220/0006668400410051. ISBN 978-989-758-296-7.
  5. ↑ "RP002-1.0.3 LoRaWAN Regional Parameters" (PDF). lora-alliance.org. Retrieved 9 June 2021.
  6. ↑ Ramon Sanchez-Iborra; Jesus Sanchez-Gomez; Juan Ballesta-Viñas; Maria-Dolores Cano; Antonio F. Skarmeta (2018). "Performance Evaluation of LoRa Considering Scenario Conditions". Sensors. 18 (3): 772. Bibcode:2018Senso..18..772S. doi:10.3390/s18030772. PMC 5876541. PMID 29510524.
  7. ↑ Adelantado, Ferran; Vilajosana, Xavier; Tuset-Peiro, Pere; Martinez, Borja; Melia-Segui, Joan; Watteyne, Thomas (2017). "Understanding the Limits of LoRaWAN". IEEE Communications Magazine. 55 (9): 34–40. arXiv:1607.08011. Bibcode:2017IComM..55i..34A. doi:10.1109/mcom.2017.1600613. hdl:10609/93072. ISSN 0163-6804. S2CID 2798291.
  8. 1 2 3 4 5 "SX1261/2 Datasheet". Semtech SX1276. Semtech. Retrieved 19 November 2021.
  9. 1 2 "LoRa Modulation Basics" (PDF). Semtech. Archived from the original (PDF) on 2019-07-18. Retrieved 2020-02-05.
  10. ↑ M. Chiani; A. Elzanaty (2019). "On the LoRa Modulation for IoT: Waveform Properties and Spectral Analysis". IEEE Internet of Things Journal. 6 (5): 772. arXiv:1906.04256. Bibcode:2019IITJ....6.8463C. doi:10.1109/JIOT.2019.2919151. hdl:10754/655888. S2CID 184486907.
  11. ↑ Qoitech. "How Spreading Factor affects LoRaWAN device battery life". The Things Network. Retrieved 2020-02-25.
  12. ↑ J.C. Liando; A. Gamage; A.W. Tengourtius; M. Li (2019). "Known and Unknown Facts of LoRa: Experiences from a Large-Scale Measurement Study". ACM Transactions on Sensor Networks. 15 (2): Article No. 16, pp 1–35. doi:10.1145/3293534. hdl:10356/142869. ISSN 1550-4859. S2CID 53669421.
  13. ↑ "What are LoRa® and LoRaWAN®?". LoRa Developer Portal. Retrieved 7 July 2021.
  14. ↑ Mohan, Vivek. "10 Things About LoRaWAN & NB-IoT". blog.semtech.com. Retrieved 2019-02-18.
  15. 1 2 3 4 5 Knight, Matt (2016). "Reverse Engineering the LoRa PHY" (PDF). PoC||GTFO (13). Article 13:7. Retrieved 12 November 2026.
  16. 1 2 3 4 5 6 7 8 Gamage, Amalinda; Sooriya Patabandige, Pramuka; Sara, Spanddhana; Varshney, Ambuj (2026). Hark: Breaking Receiver Power Limits of LoRa. MobiCom '26: 32nd Annual International Conference on Mobile Computing and Networking. ACM. doi:10.1145/3795866.3844153.
  17. 1 2 3 "SX1276/77/78/79 Datasheet". Semtech. Retrieved 12 November 2026.
  18. ↑ "LoRa Products" (PDF). Semtech. 2023. Retrieved 12 November 2026.
  19. 1 2 "Gen 4 LoRa Transceiver Extends Data Capacity". RFID Journal. 9 April 2025. Retrieved 12 November 2026.
  20. 1 2 "Semtech Launches LoRa Plus LR2021 Transceiver with LoRa Gen 4 Technology" (Press release). Semtech. 10 March 2025. Retrieved 12 November 2026.
  21. 1 2 3 "LoRa Edge LR1120". Semtech. Retrieved 12 November 2026.
  22. 1 2 "LoRa Plus LR2021". Semtech. Retrieved 12 November 2026.
  23. 1 2 "LoRa Transceivers". The Things Network. Retrieved 12 November 2026.
  24. ↑ "SX1280". Semtech. Retrieved 12 November 2026.
  25. ↑ "LR1121". Semtech. Retrieved 12 November 2026.
  26. 1 2 "radio_firmware_images: Firmware images for all flash-based Semtech products". GitHub. Semtech. Retrieved 12 November 2026.
  27. ↑ "LR2021/LR2022/LR2012 Datasheet, Rev. 2.2". Semtech. July 2026. Section 22.3, Firmware Patch RAM (PRAM). Retrieved 12 November 2026.
  28. ↑ "SWTL001: Reference implementation of the LR11xx firmware update procedure". GitHub. Semtech. Retrieved 12 November 2026.
  29. 1 2 "Understanding LoRa Basics Modem-E". LoRa Developer Portal. Semtech. Retrieved 12 November 2026.
  30. 1 2 Tinella, Carlo (25 September 2024). "Accelerate Your LoRaWAN Development with LoRa Basics Modem-E for LR1121". Semtech Blog. Semtech. Retrieved 12 November 2026.
  31. ↑ "Semtech Releases a New Portfolio of Solutions, LoRa Edge, to Simplify and Accelerate IoT Applications" (Press release). Semtech. 24 February 2020. Retrieved 12 November 2026 – via Business Wire.
  32. 1 2 Knight, Matthew; Seeber, Balint (September 2016). "Decoding LoRa: Realizing a Modern LPWAN with SDR". Proceedings of the GNU Radio Conference. 1 (1). Retrieved 12 November 2026.
  33. ↑ "gr-lora: GNU Radio OOT module implementing the LoRa PHY". GitHub. Bastille Research. Retrieved 12 November 2026.
  34. ↑ Knight, Matt (29 December 2016). Decoding the LoRa PHY (Conference talk). Chaos Computer Club. Retrieved 12 November 2026.
  35. ↑ Robyns, Pieter. "gr-lora: GNU Radio blocks for receiving LoRa modulated radio messages using SDR". GitHub. Retrieved 12 November 2026.
  36. ↑ Gamage, Amalinda. "LoRa Tools". Retrieved 12 November 2026.
  37. ↑ "LoRa APRS: Bringing APRS into the 21st Century". How APRS Works. Retrieved 27 August 2026.
  38. 1 2 3 4 "Reticulum: Unstoppable Networks for The People". Chaos Computer Club. Retrieved 8 September 2026.
  39. 1 2 "RTAK: Integrating Android Team Awareness Kit (ATAK) with a LoRa mesh radios to enable off-the-grid data sharing". Florida Atlantic University. Retrieved 9 September 2026.

Further reading

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