LoRaWAN and LPWAN are radio networks that carry small amounts of data, such as a meter reading, over several kilometres while using very little power. LPWAN stands for low-power wide-area network, the general name for such radios. LoRa is the best-known LPWAN radio, and LoRaWAN is the set of rules for running a whole network of LoRa devices. NB-IoT, a version that runs on the mobile operators' networks, is another LPWAN.
How can a radio reach so far on so little power? It sends very slowly. LoRa spreads each bit of data over a long radio signal that sweeps across a range of frequencies, called a chirp. A receiver can pick out such a signal even when it is weaker than the background noise. The cost is speed: between about 0.3 and 11 kilobits per second, thousands of times slower than home Wi-Fi. So LoRa suits devices that send a few bytes now and then, not video or voice.
A LoRaWAN network has three parts. Battery-powered devices, such as meters, send short messages by radio. Gateways, which are radio receivers on rooftops or towers, pick up every message within range and pass it on over the internet or the mobile network. A network server removes duplicates, because one message may reach several gateways, and passes each reading to the right application. In India, LoRa uses a frequency band around 865–867 MHz, which can be used without a licence.
Imagine a city water board in Vadodara that fits 20,000 homes with smart water meters. Each meter has a LoRa radio and a battery meant to last about ten years. Once a day, at a random minute after midnight, each meter wakes, sends a 12-byte message with its reading and a leak flag, and sleeps again. The random minute keeps thousands of meters from sending at the same moment. About 20 gateways, fixed on water tanks and offices and each reaching about 3 km in the city, cover all the meters. By morning, the readings are in the board's billing software. No meter reader has to visit, and a meter that shows water running all night is flagged as a possible leak.
The weakness is how little data a device can send. A meter can report a reading, but it cannot quickly receive a large update. If too many devices send at once, their messages can collide. So the network suits small, infrequent messages from thousands of devices.
LoRa differs from the other IoT wireless chips in a home. Bluetooth, Zigbee and Thread reach tens of metres and need a hub nearby, while LoRa reaches kilometres. It also differs from cellular IoT modules, which use a SIM and an operator's licensed network, and which operators run with IoT connectivity management. Anyone, such as a city or a factory, can build a LoRaWAN network without an operator. Radios that form a network among themselves, for defence and disaster areas, are covered in mesh and tactical radios.