Tech Notes: LoRa, Meshtastic, and TAK
Wed 16 August 2023
There’s going to be a lot to unpack here so bear with me.
The bits and pieces
LoRa
LoRa (standing for Long Range) is a proprietary communications technique that is generally used on the ISM bands. In the United States of America that generally means 915MHz although other bands including 2.4GHz and 5.8GHz. In ITU Region 1, a small portion of 433MHz is designated as ISM, meaning devices are available that radio amateurs in other ITU regions can utilize.
The benefit of LoRa isn’t the frequencies used but rather the ability to receive signals well below the noise floor (link budgets in the neighborhood of 155dB to 170dB). Generally, the frequencies used for LoRa are line-of-sight. This makes it more difficult to establish networks in hilly areas. It does improve the ability for many different networks to exist in an area.
Another benefit of LoRa is its low power requirements. A single, small battery could last for days (or months) based on usage.
LoRa operates in OSI Layer 1.
Meshtastic
Meshtastic is an open source LoRa protocol that enables applications to communicate over LoRa and seems to operate in OSI Layers 2 and 3. Applications include those that share position information, messaging, and telemetry.
Meshtastic creates a dynamic mesh network that allows LoRa transceivers to repeat what it hears to other devices, increasing the area covered.
TAK
Team Awareness Kit (TAK) is an application that provides position sharing, cartographic resources, and other information sharing capabilities. Developed by the DoD, the software was released as open source software which almost immediately caused a surge in plugins and other improvements to the software.
TAK requires devices to be on the same broadcast network to share data unless they are talking to a TAK Server. Due to this limitation, if devices are all connected using cellular or other disparate networks, a VPN is required to maintain communications between all devices. It seems the VPN solution that many users are using is site:https://zerotier.com[Zerotier].
Putting it all together
A TAK user can connect to other users using a variety of communication platforms including cellular, WiFi, and LoRa. It’s possible to use Meshtastic to interface TAK with a LoRa transceiver. Adding static Meshtastic devices in advantageous locations (high location with good sight of the operational area) can improve information sharing over a larger distance.
APRS over LoRa
Similar to Meshtastic is a protocol designed for Automatic Packet Reporting System (APRS).