Renewed military interest in HF communications has spurred the application of new technology to HF Modems. Largely, this new technology is represented by powerful microprocessors which allow the implementation of more complicated signal processing algorithms than were practical in the past. These algorithms allow vastly improved digital communications performance on the HF channel, including higher data rates, greater robustness and reduced susceptibility to interference. At high data rates (1200 to 4800 bps in a 3 kHz channel), serial (single carrier) technology has demonstrated excellent performance. However, the computational requirements for this technique are fundamentally high. Within a few years, advances in VLSI and VHSIC technology will probably provide the needed processing power in a small, low powered, inexpensive unit. Digital processing of parallel tone formats on the other hand requires significantly less computational power, and new techniques can provide improvements over past standards of HF performance. At lower bit rates (600 bps and less), correlation techniques for processing the serial waveform have been developed which provide excellent performance in the face of heavy interference as well as multipath and fading. The processing requirements for this are much less than for high rate serial algorithms mentioned above.
Advances in HF modem technology
Fortschritte in der Modem-Technologie
1983
17 Seiten, 20 Bilder
Conference paper
English
Adaptive software modem technology
Tema Archive | 2001
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