Introduction to LoRa
LoRa is a patented wireless data communication technology developed by Cycleo of Grenoble, France, and acquired by Semtech in 2012.
- LoRa uses license-free sub-gigahertz radio frequency bands like 169 MHz, 433 MHz (Asia), 868 MHz (Europe) and 915 MHz (North America).
- LoRa enables very-long-range transmissions (more than 10 km in rural areas) with low power consumption.
- The technology is presented in two parts — LoRa, the physical layer and LoRaWAN, the upper layers.
- Long range: LoRa signal can travel multiple miles from 1 - 10 km or more.
- Low power usage: The devices are inexpensive and can run for years without needing a battery change.
- Suitable to IoT devices: This creates the ability to monitor devices that are difficult to access or out of range for wifi or cell service.
The caveat to this wonderful technology is the limited amount of bandwidth it offers.
- Low bandwidth: In order to have such a long range and extended battery life, the frequency of a LoRa transmission must be very low.
- More bandwidth vs. range: The more data you want to transfer at a time, the less distance and more battery you use. While it may seem pointless if you can’t use it to stream Netflix, there are plenty of cases where range and reliability trump bandwidth.
Four main configuration terminologies in LoRA.
- Frequency: Commonly 433 MHz (Asia), 868 MHz (Europe) and 915 MHz (North America).
- Preamble Length: A LoRa frame begins with a preamble. After the preamble, there is an optional header. E.g: 8 bits.
- Spreading Factor: Number of bits encoded per symbol. The higher the spreading, the faster bandwidth and the shorter range. Eg: 7, 9, 12...
- Signal bandwidth: The width of spectrum occupied by the chirp (the signal). E.g: 125Kbps
- Coding Rate: This is a measure for the amount of forward error correction. E.g: 4/5
