LoRaWAN

LoRaWAN is a network protocol for low-power, long-range wireless sensors. It runs on LoRa, a chirp spread spectrum radio method, in licence-free bands such as 868 MHz in Europe, 915 MHz in North America and 865 to 867 MHz in India. The LoRa Alliance maintains the protocol. A LoRaWAN network has end devices, gateways, a network server and an application server. A sensor wakes up, sends a short message and goes back to sleep. Any gateway in range picks up the message and passes it over the internet to the network server, which removes duplicates and sends the data on to the application. Messages are encrypted with AES-128 keys. Devices use an adaptive data rate: those close to a gateway send faster and use less energy, while distant ones send more slowly to reach further. In water, LoRaWAN is used for smart meters, borewell level sensors, tank level sensors, pressure loggers in pipe networks and rain gauges. For example, a utility can mount a few gateways on water towers and read thousands of meters in a town once or a few times a day, with each meter battery designed to last many years. Its strengths are long range, low power and low running cost, since the utility can own and run the network. Typical range is a few kilometres in towns and more in open country, but meters in basements or underground chambers may need extra gateways or external antennas. Data rates are low, so it suits small readings, not video or fast control. Duty cycle rules in some regions limit how often a device can transmit, and downlink capacity is small, so sending commands to many devices is slow. Battery life depends strongly on how often and how far each device sends.