LoRa vs LoRaWAN

The names are close, but they describe different layers of a radio system.

LoRa is the physical layer. Semtech describes it as a spread spectrum modulation derived from chirp spread spectrum, and says plainly that LoRa is the silicon Semtech develops. It defines how bits become a radio signal and nothing more. How LoRa modulation works covers chirps, spreading factors and bandwidth.

LoRaWAN sits above it. The LoRa Alliance defines it as the network standard and system architecture at the MAC (medium access control) layer: how devices communicate with the network server, how data rates and battery life are managed, and how security and data integrity work. Semtech describes LoRaWAN as a standard for interoperability managed by the LoRa Alliance, a non-profit of which Semtech is a founding member. The Alliance also notes that LoRaWAN has been approved as an international standard by the ITU.

On its own, LoRa moves a frame from one radio to another. Ghanaatian and colleagues describe the LoRa PHY frame: a preamble of chirps for synchronisation, an optional header, the payload and an optional CRC to detect errors. The frame they describe has no field saying who a message is for, no keys and no rule about when a device may transmit or listen. Everything of that kind is left to whatever protocol runs on top.

That makes LoRa flexible. Two LoRa radios with matching settings can talk directly, and a designer can build any addressing, routing or security scheme they like above the modulation.

LoRaWAN fills in those gaps for one particular shape of network. The LoRa Alliance describes it as a star-of-stars: end devices make single-hop radio links to gateways, which relay packets over IP to a central network server. Mesh networking vs LoRaWAN compares that architecture with a mesh. On top of the architecture, the specification defines:

• Activation. Semtech’s application note describes two ways onto a network: over-the-air activation (OTAA), which it marks as preferred, and activation by personalisation (ABP), where keys are set in advance.
• Security. The Things Network explains that each session uses two 128-bit AES keys. The network session key checks the integrity of every message between device and network server; the application session key encrypts the payload between device and application server. Frame counters let either side reject replayed messages.
• Device classes. Semtech describes three. Class A devices sleep, send an uplink, then open two short receive windows. Class B devices add scheduled receive slots timed by beacons from the gateways. Class C devices listen almost all the time and suit mains-powered equipment.
• Adaptive data rate. Semtech describes how the network server adjusts each device’s data rate and transmit power, so devices near a gateway use low spreading factors and spend less airtime, while distant devices use higher ones.
• Regional channel plans. Semtech notes that the LoRa modulation characteristics for each region are defined in the LoRaWAN Regional Parameters document.

The LoRa Alliance publishes the link-layer rules as a numbered specification, TS001, alongside regional parameters and companion documents for features such as relays and device certification.

Semtech notes that some customers run the LoRa physical layer with a proprietary network on top, and gives Amazon Sidewalk as the example. Meshtastic is another: it uses LoRa radios with its own firmware, and its documentation describes a managed flood in which nodes rebroadcast the packets they receive, up to a hop limit, so messages travel from radio to radio.

These designs keep the radio and change everything above it. They give up LoRaWAN’s certified interoperability, its gateway and network server infrastructure and its standard security model, and in exchange can do things LoRaWAN’s architecture does not, such as letting devices message each other directly.

The practical question is which layer you are choosing. Picking LoRa means picking a radio and its trade-offs between range, data rate and airtime. Picking LoRaWAN means also picking a network model: gateways, a server, and the rules for joining, securing and scheduling traffic that come with it.