Thread by @antirez

Welcome to the LoRa thread. Here I'll talk about LoRa, a modulation used in RF communications that is a game changer for certain applications, and about my work on a LoRa based WAN protocol and implementation: my open source project called FreakWAN.

An obvious way to communicate wirelessy is to use WiFi or Bluetooth, but these technologies require an access point (WiFi case) and the range is limited (for both). So, in order to communicate point-to-point over ISM (open to all) frequencies other techniques are used.

You digital thermometer, car key or gate remote are likely to use either OOK or FSK modulations. The first will just transmit or stop transmitting in patterns in order to tell 0 from 1, while the other will move between two near frequencies F1 and F2 to also communicate bits.

OOK and FSK require cheap ICs to work, however they will not go over 100 meters, or even less. Not ideal for certain applications. So, using the idea of chirp modulation, a few smart folks created and patented a new modulation called LoRa (LongRange) whose name states the goal.

LoRa uses a very large bandwidth to communicate very slow signals: that's the key of the distance records it can achieve. The carrier signal is moved linearly from two F1 and F2 frequencies (at the edges of the bandwidth) to build a very resilient modulation.

To give you an idea of how far you can go, yesterday I was on top of the Etna, and with a device that sends 17dbm, battery powered, in my hands, with the stock antenna (the whole device costs 17 euros) I could write messages to my friends in Chiaramonte Gulfi and Palazzolo: 70 km

The data rate, with the settings for maximum range, is terrible, but that's a fair compromise. It takes one second of "time on air" to send a small message with an attached header. However the communication is very reliable.

So upon the LoRa raw modulation many stuff were created. LoRaWAN is the "official" effort, but is a very complex monster in my opinion. There are also a few open source projects to create chats over LoRa networks, building small WANs.

How to build a WAN? Well, that's simple: each device will repeat the messages it receives, thus if there are even more distant devices, they will pick-up the signal, and so forth. However the channel time is very limited because the data rate is so low, so care must be taken.

Btw, how all this is done, in practice? Well, you need some kind of microcontroller, like an ESP32, and a LoRa chip module like the SX1276 or the newer and better SX1262. What I use is the LILYGO devices: ESP32 + OLED + LoRa chip combined together. In a few there is a GPS too.

So there is the (cheap!) hardware and there is an incredible RF protocol that can go so far, I and my friends here in Catania (and other parts of Sicily) wanted to try it. I was not happy with the current OSS projects I found around, so I started my own one: FreakWAN.

FreakWAN is both a protocol built over LoRa, and its implementation in the form of a chat system. It supports messages retransmission, acknowledge, relaying, encryption and so forth. It is written in MicroPython. You can find it here: github.com/antirez/freakw…

However even if it shows a chat, the FreakWAN protocol is designed to support other IoT applications: distributed sensors, home automation, whatever you want. My goal is to showcase other applications building a thermometers network with hardware design and so forth.

Well, among deep learning experiments and now FreakWAN I had to learn Python. It's not my preferred language, but MicroPython as an ecosystem for ESP32 (and in general embedded development) is quite neat. I would say the real problem is memory usage, and not speed.

That's all, basically. I had tons of fun so far, and look forward to build an actual small WAN here near Catania, that can be used to communicate in case of disasters, or (much better) just for fun in an impossible to censor and amateurs-run network.