The developer has upgraded the amateur radio OFDM protocol by implementing MAC and LLC sublayers, transforming it into a full-duplex communication system. The new architecture utilizes finite state machine logic to manage session establishment and data flow, supporting both stop-and-wait and bulk transmission modes.
The physical layer now includes 16-QAM and experimental 32-QAM modulation methods, allowing for higher data throughput. The system uses a 53-subcarrier grid with a 46.875 Hz frequency interval. To improve signal stability, the developer integrated a clipping-and-filtering method with three iterations to reduce the peak-to-average power ratio.
Synchronization improvements include a two-stage scheme combining Newman and Zadoff-Chu preambles to mitigate frequency offset issues. The packet structure has been updated to support a maximum length of 1023 bits, defined by a 10-bit length field. The header remains 28 bits in total, with BPSK modulation used for its transmission.
Laboratory tests indicate a peak data rate of 1500 bits per second using 16-QAM. While the system operates in half-duplex mode, it manages bidirectional traffic through a time-slot mechanism. The current implementation supports the transmission of text and binary data, with error correction handled by an automatic repeat request mechanism.
