LoRa
Template:Short description Template:Distinguish Template:For Template:Infobox protocol
LoRa (from "long range") is a physical proprietary radio communication technique based on spread spectrum modulation.[1] LoRa can be thought of as a radio signal technology, similar to Wi-Fi or cellular.[2]
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;[3] LoRa enables long-range transmissions with low power consumption.[4] 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.[5]
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[6] and represents the number of bits sent per symbol and in addition determines how much the information is spread over time.[7] There are different initial frequencies of the cyclic shifted chirp across the bandwidth around the center frequency.[8]
The symbol rate is determined by . LoRa can tradeoff data rate for sensitivity (assuming a fixed channel bandwidth ) 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.[9] 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.[6] 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.[10] According to the LoRa Development Portal, the range provided by LoRa can be up to Template:Convert in urban areas, and up to Template:Convert or more in rural areas (line of sight).[11]
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.[12]
Applications
Template:Unreferenced section 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
- LoRa APRS — a variation of Amateur Radio Automatic Packet Reporting System for reporting realtime location, using LoRa[13]
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
- Template:Annotated link
- MIoTy – sub-GHz LPWAN technology for sensor networks
- SCHC – static context header compression
- Template:Annotated link
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.
- Template:Cite web
- 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 Template:ISBN, Softcover Template:ISBN, Ed: 1