LoRa (from "long range") is a physical proprietary radio communication technique based on spread spectrum modulation. LoRa can be thought of as a radio signal technology, similar to Wi-Fi or cellular. 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; LoRa enables long-range transmissions with low power consumption. 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.
Description 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 and represents the number of bits sent per symbol and in addition determines how much the information is spread over time. There are M = 2 S F {\displaystyle M=2^{\mathrm {SF} }} different initial frequencies of the cyclic shifted chirp across the bandwidth around the center frequency. The symbol rate is determined by R s = B / M {\displaystyle R_{s}=B/M} . LoRa can tradeoff data rate for sensitivity (assuming a fixed channel bandwidth B {\displaystyle 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. 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. 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. 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). 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.
Applications
LoRa applications:
Meshtastic — an open source mesh network protocol that uses LoRa flood messaging MeshCore — open source mesh network protocol that uses LoRa with more structured routing than Meshtastic LoRaWAN — a low-power, wide-area network (LPWAN) protocol that wirelessly connects battery-operated devices to the Internet. Uses LoRa. Helium Network — LoRaWAN protocol paired with blockchain technology ExpressLRS — open source UAV remote control protocol that uses LoRa, widely used in FPV drones Amazon Sidewalk — a mesh wireless network developed by Amazon. Uses LoRa for long range
See also 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
Further reading Olivier Bernard André Seller. "Wireless communication method" U.S. Patent No. 9,647,718. 9 September 2015. Lee, Chang-Jae, Ki-Seon Ryu, and Beum-Joon Kim. "Periodic ranging in a wireless access system for mobile station in sleep mode." U.S. Patent No. 7,194,288. 20 March 2007. Ghoslya, Sakshama (2019-04-17). "How to generate LoRa Symbols". All About LoRa and LoRaWAN. Quigley, Thomas J., and Ted Rabenko. "Latency reduction in a communications system." U.S. Patent No. 7,930,000. 19 April 2011. Seneviratne, Pradeeka. "Beginning LoRa Radio Networks with Arduino - Build Long Range, Low Power Wireless IoT Networks." Apress, 2019, eBook ISBN 978-1-4842-4357-2, Softcover ISBN 978-1-4842-4356-5, Ed: 1
External links LoRa Alliance LoRaWAN Resource Library LoRa at Semtech Cycleo website at the Wayback Machine (archived 2011-07-29)