LoRa

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;^[4] LoRa enables long-range transmissions with low power consumption.^[5] 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.^[6]

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^[7] and represents the number of bits sent per symbol and in addition determines how much the information is spread over time.^[8] There are ${\displaystyle M=2^{\mathrm {SF} }}$ different initial frequencies of the cyclic shifted chirp across the bandwidth around the center frequency.^[9]

The symbol rate is determined by ${\displaystyle R_{s}=B/M}$. LoRa can tradeoff data rate for sensitivity (assuming a fixed channel bandwidth ${\displaystyle B}$) 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.^[10] 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.^[7] 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.^[11] 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).^[12]

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.^[13]

Range extenders for LoRa are called LoRaX.

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

• 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