A Technological Step Backward to Move Forward: Data Transmission Without the Internet
Recently my mother called and asked me to order her a taxi from the station to her dacha outside Moscow. The Internet was not working there—"they are jamming it again"—so ordering a taxi through an app was impossible. That made me think: this is a systemic problem. There are many places where voice service exists but Internet connectivity does not.
Surprisingly, even in 2025 there are still many places in Russia—especially in rural areas, at dachas, in fields, and on farms—where mobile Internet simply does not work. Everything may seem "digital," but at the critical moment you still cannot transmit information.
That is when I had an idea: what if we simply... take a step back? Go back to the era of 2G and voice modems.
How did modems work in the 1990s?
Remember how people connected to the Internet in the 1990s? You dialed, heard the beeps and clicks, and then there it was: Internet over an ordinary phone line. Data was transmitted as sound, which the modem encoded and decoded. It all worked without any Internet at all, using nothing but voice communication.
My idea: a Bluetooth modem using headset protocols for fields and villages
What if we built a small Bluetooth device that:
- connects to a phone like a headset (that is, it can place calls),
- receives data from a computer or another device (for example, JSON),
- converts it into an audio signal like an old modem,
- and sends it over a regular voice call to a special server.
On the other end:
- the server answers the call,
- recognizes the caller’s number as the device identifier,
- decodes the audio signal back into data (for example, temperature, fuel level, sensor readings),
- and stores it in the required information system.
What can be transmitted this way?
- Simple JSON packets: {"id": "ferma-001", "temp": 22.5, "soil": "wet"}
- Event codes or alarm signals
- Equipment telemetry
- Commands and statuses
The speed is not high, but the transmission works where there is nothing except a cellular signal.
How much can be transmitted?
Voice-channel data transmission is possible at speeds from 300 to 1200 baud (~30–100 bytes/sec).
A 50 KB file (for example, SVG or XML) would take roughly 8–12 minutes to transmit.
Accounting for encoding, retransmission, and error control, one transfer may take up to 15 minutes.
How can data transmission be optimized?
To speed up the process and reduce call time, data can be minimized in advance:
- Use short keys: a1 instead of deviceId, b1 instead of temperature, and so on.
- Format JSON in a simplified form and compress it if needed.
- Add versioning (for example, {"v":1,"a1":"ferma-001","b1":23.5}).
On the server side, the data is automatically turned back into a human-readable format using a connector.
A service like this could realistically be deployed in fields, villages, drilling sites, and anywhere else with no Internet but with cellular coverage.
Data flow diagram
[ Data Source ] --> [ Bluetooth Modem ] -- Bluetooth Audio (HSP/A2DP) --> [ Mobile Phone ] -- GSM --> [ Call Intake Server ] -- API --> [ Target System ]