FEATUREDApplication Development & Modernization
PETER WELCHER | Solutions Architect
This blog is a follow-up to my recent IOT blog series. Links to them can be found at the end of this blog.
This blog provides a high-level summary about an IOT protocol: LoRaWAN.
The first thing you have to get used to with LoRaWAN is getting the case right in the acronym!
Why IOT? First, it is an expanding area of networking, with increasing use cases. Secondly, it is impacting current organizations, especially healthcare and retailing, but touching anything where new forms of sensor may provide valuable security or cost-saving benefits, or enable new capabilities (better inventory, better products, etc.).
What Is LoRaWAN?
“The LoRaWAN® specification is a Low Power, Wide Area (LPWA) networking protocol designed to wirelessly connect battery-operated ‘things’ to the internet in regional, national or global networks, and targets key Internet of Things (IoT) requirements such as bi-directional communication, end-to-end security, mobility and localization services.” – LoRa Alliance.
Credits: I was heavily dependent on that site in writing this summary blog. For more details, see that site!
Key points about the LoRaWAN topology:
- Star-of-stars topology: LoRaWAN nodes talk to local gateway, and it talks to the central gateway that connects to other gateways.
- Gateways’ purpose is to relay messages from end devices to a central network of servers. Typical backhaul (transport) might be Cellular, Wi-Fi, Ethernet, fiber optics, or 2.4 GHz radio.
- The LoRaWAN gateways use IP and act as a transparent bridge between RF and IP packets, or vice versa.
- The LoRaWAN physical layer operates at long range (LoRa!), making for a single hop between end device and one or more gateways.
- All modes of operation are bi-directional.
- Multicast can be used for efficient RF spectrum use, e.g. for Firmware Over The Air (“FOTA”) upgrades or other messages for large distribution.
- LoRaWAN is intended to provide multi-vendor interoperability.
Why LoRaWAN?
LoRaWAN may be preferable to other wireless/cellular technologies for some use cases.
Where LoRaWAN may fit well:
- Long-range connectivity
- Low power consumption, long battery life
- Robust (well, adequate?) security
- Massively scalable
- Low cost (cellular directly to end devices is costly!!!)
Drawbacks to LoRaWAN:
- Low data rates
- Not actually real-time (Wireless contention, class A power conservation. See more details below.)
Further Details
LoRaWAN is based on classes of devices: A, B, or C, reflecting device capabilities.
- Class A: Default, always initiated by end-device, because of low-power sleep mode. Communications are fully asynchronous, with any uplink transmission followed by two short downlink transmission windows. Asynchronous implies that any downlink messages must be buffered by the server until there is a downlink window.
- Class B: Periodic beacons sync the devices to the network, with scheduled downlink “ping slots”. This provides deterministic latency for downlink comms but consumes more end device power.
- Class C: Lowest latency: receiving end device open to receive whenever not transmitting. Higher power drain, likely requiring continuous power. Battery-powered devices may shift from class A to C, e.g. for FOTA updates.
Data rate (“DR”) can be specified, trading off comms range and message duration. Spread spectrum is used to eliminate interference between different DR’s. The network server manages the DR setting and RF output power per end device via an Adaptive Data Rate technology.
Baud rates run from 0.3 Kbps to 50 Kbps. Def low speed! A typical use might be for sensor data for large numbers of sensors.
Security operates via two layers of crypto:
- A 128 bit Network Session key for each end device to network server communication.
- An Application Session key used end to end at the app level.
- The keys can be manually or automatically assigned and rekeyed.
LoRaWAN Considerations
Having multiple gateways (in a location) might create interference (shared radio frequencies). This might lower data rates.
LoRa is the radio signal carrying the data.
The range at which LoRaWAN can be used is from 3 miles (urban) to 10 miles (rural line of sight). It has been demonstrated at 830 miles.
Redundancy can be built in. From gateway back to server is IP, and we know how to do IP network redundancy. Having each endpoint within range of at least two gateways is how you provide edge redundancy.
Googling “redundancy in lorawan” led to research as well as implementation (and marketing!) links. Topics include emergency comms to the factory floor. Other topics: reliability, and increasing the chances of a message getting through. They also include retransmission or multiple transmission schemes that might (I presume) be baked into end systems and LoRaWAN applications.
Links to Prior IOT Blogs
LoRaWAN Links
Conclusion
LoRaWAN is a mature multi-vendor standard, where gateways provide the potential to aggregate traffic from many low-cost sensors onto higher-speed cellular, Wi-Fi, or fiber networks back to the controlling servers.
If you’re planning on having large numbers of relatively simple, small, low-cost sensors and/or deploying over a large area or longer distances, LoRaWAN may well be just what you need.
If you have smaller numbers of devices that cost more, can do Wi-Fi or cellular etc. or that require higher data rates, then traditional Wi-Fi and cellular may be the way to go.
