Cost, power, IP, and latency issues are driving IoT designers away from current standards like Zigbee and toward an emerging set of long-range wireless solutions. LoRa, an abbreviation of “Long Range”, is one such technology that is gaining traction.
LoRaWAN™ (Long Range WAN) is an emerging LPWAN specification developed by the LoRa® Alliance (www.lora-alliance.org). Like all LPWAN solutions, LoRaWAN is designed to operate at low power and low bit rates to maximize battery life. End-devices may run for years off a small battery. Fixed sensors can be powered indefinitely with a small solar panel. In addition, LoRaWAN is designed for simplified installation and long-range bidirectional communication with end-devices. End-devices may be located up to 10 miles from a gateway, with a clear line of sight. Each end-device connects wirelessly with one or more gateways in a star-of-stars topology. Gateways act as transparent bridges relaying traffic to and from a central network server.
The network server manages the data rate and transmission frequency of each end-device to maximize battery life and gateway capacity. LoRaWAN data rates range from 0.3 kbps to 50 kbps, and spread-spectrum chirp transmission allows signals with different data rates to act as virtual channels on the same frequency. Data security is managed through separate layers of encryption at the network, application, and end-device levels. The spread-spectrum approach does increase the spectrum width compared to a narrowband technology such as SigFox.
End-devices in LoRaWAN installations are classified according to communication method and power consumption.
Some of the considerations for a good LoRaWAN use case include:
Use cases exploring LoRaWAN technology include:
Semtech LoRa chips do have a second source, HopeRF, but it is unclear that they are a viable supplier. LoRaWAN compliant modules and modems are produced by a number of vendors:
Using leading-edge technologies can quickly become “bleeding edge” because often documentation and prototype designs may not live up to the marketing promises. LoRa is an emerging technology and not a mature product. We have an interesting article on handling this type of risk “Voler Provides Risk Management For Leading Edge Components“.
Limitations for LoRaWAN include network capacity and signal interference as the number of end-devices in the network increases. Because of the pseudo-random ALOHA algorithm used to schedule transmissions, inevitably some signals will collide as the number of end-devices on any given gateway rises into the thousands. See Adelantado, et al for an in-depth discussion.
Here are a couple of resources to learn more about LoRaWAN