A Compact Communication Platform Based on FX. 25 Protocol with Forward-Error-Correction and AES-256 Encryption

AX.25, a packet radio communication protocol derived from X.25 and now half a century old, was once the definitive standard for amateur radio digital communications. Today, it is practically abandoned due to its several critical limitations: the absence of Forward Error Correction (FEC), high protocol overhead, lack of native encryption, and inefficiencies in connectionless mode. Yet, a substantial infrastructure of highvalue packet radio equipment (transceivers, antennas, modems) remains operational and could be repurposed for specific applications (such as telemetry or nano-satellites) provided the protocol engine is modernized. Two decades ago, the improved FX.25 protocol was proposed as a successor to address these deficiencies. However, as no chip manufacturer has produced dedicated hardware for FX.25 standard, this paper presents a complete software-based implementation. The softwareimplemented packet/protocol engine incorporates: correlation tag generation and detection, Reed-Solomon FEC, data randomization (scrambling), and AES-256 encryption/decryption. All of these functionalities are embedded within a resourceconstrained 8-bit RISC microcontroller, ensuring a lightweight software footprint. The designed corresponding hardware device incorporates an FSK modem, control logic for transceiver management and a user interface. The proposed system was fieldtested on 433 MHz frequency band, and its performance was evaluated against modern LoRa communication system of comparable transmission power and energy requirements.