The technologies of the band

What it is

A text messaging network between LoRa radio units, with no operator, no subscription and no Internet. Each device talks to the devices within its range, and those retransmit: from one to the next, a message crosses distances that none of the units covers on its own. The device is driven from a phone, over Bluetooth. The project is free software and has existed since February 2020, the oldest of the three mesh networks present on the band.

How it works

A message is broadcast to every neighbour, which rebroadcast it in turn. A hop counter, capped at seven, keeps it from circulating indefinitely. Exchanges take place on encrypted channels: whoever does not hold the channel key does not read what passes through it, even when the signal is received.

Each device carries a role, which determines whether it retransmits or not. It is the setting that weighs most on the health of the network.

What it is for

• Staying in contact outside coverage. Hiking, high mountains, sea, forest: where the mobile network stops, two units are enough to exchange text.
• Following a group. Each device can share its position; the map shows where the others are, without going through a third-party service.
• Coordinating an event. A race, a gathering, an extended worksite: group messaging that depends on no rented infrastructure.
• Reading sensors. Temperature, level, battery state: telemetry comes back through the mesh.
• Linking a neighbourhood or a valley. A few repeaters on high points and a whole territory becomes reachable by text.
• Feeding a situation display. Positions can be passed into a tactical situation tool.
• Experimenting. Propagation, range, the behaviour of a mesh: the hardware is inexpensive and the code is open.

What it does not do

• This is not an emergency service. No guarantee of delivery, no permanent availability, no commitment. In an emergency, 112.
• This is not the Internet. Short text, no voice, no images, no browsing.
• It is slow and shared. A message can take tens of seconds. The radio resource is common to everyone transmitting within range.
• Range depends on the terrain, not on power. Intervening relief stops a link; a high point transforms it.
• More nodes does not mean more capacity. Beyond a certain number of devices that retransmit, the network degrades.
• The operator remains responsible for what they transmit, and for the applicable power and duty cycle conditions.

In France

The settings in use are not the original ones. The Gaulix community recommends the Long Moderate profile, 125 kHz centred on 869.4625 MHz, that is 869.400 to 869.525 MHz. The Paris region uses a faster and wider profile, Medium Fast. These choices are published by their authors; the Centre reports them, it does not arbitrate between them.

What it is

Reticulum is not one more mesh network: it is a complete network stack, an alternative to TCP/IP designed for slow and unreliable links. It works on top of any medium: LoRa radio, packet radio, serial link, cable, Internet. The project has existed since April 2018, the oldest of the three.

How it works

Reticulum gives up the notion of an address. Each application creates destinations, identified by cryptographic keys. A destination announces itself on the network, and any node that hears that advert knows from then on how to talk to it.

• Everything is encrypted by default, end to end, with no configuration. Identities rest on Ed25519 signatures, links on renewed X25519 exchange keys.
• The initiator can remain anonymous: it is possible to communicate without revealing an identity.
• It works very low down. The stack is designed to hold on links going down to a few bits per second.

For messaging, Reticulum comes with LXMF, a lightweight message format, and with propagation nodes that store the messages addressed to someone offline, to hand them over on their return. On the radio side, the RNode firmware turns a LoRa unit into a Reticulum interface.

What it is for

• Linking heterogeneous networks. A LoRa segment, an Internet segment, a radio segment: Reticulum crosses them without a specific gateway. This is its most distinctive use.
• Exchanging without leaving an identity. Encryption and the anonymity of the initiator are in the design, not added afterwards.
• Writing your own applications. Messaging, file transfer, pages, remote control are built on top of it.
• Communicating asynchronously, through propagation nodes, with no central server.
• Holding on very degraded links, where a conventional protocol gives up.

What it does not do

• This is not a turnkey product. It is a stack and a set of tools: getting started takes more work than switching on a unit.
• The community is smaller than those of the other two, in France as elsewhere.
• Slow stays slow. Over LoRa, it is text, not everyday use.
• No guarantee of delivery, as with the others. In an emergency, 112.