The author developed an Android application to explore the potential of Bluetooth for long-range data and voice transmission. The project aims to create a decentralized communication channel that functions without cellular or Wi-Fi networks, using Bluetooth Low Energy (BLE) as the primary transport layer.
The application features a Push-To-Talk voice function, which compresses audio to 1.5 KB/s, and a VPN tunnel that allows for network traffic transmission. To manage bandwidth, the software includes a proxy server that filters unnecessary data, such as telemetry and ads, enabling basic web browsing over a low-speed connection.
Technical implementation relies on the GATT protocol for data exchange, utilizing two characteristics for transmission and reception. The developer optimized the application to a size of 61 KB by using Java 8, GNU Make, and native vector graphics, avoiding external frameworks and libraries.
The project investigates signal strength indicators (RSSI) and transmission modes like LE Coded S=8, which provides increased reliability at the cost of speed. While some manufacturers claim long-range capabilities, such as Xiaomi's Offline Communication technology, the author focused on creating a custom, independent solution.
