We present a parallel modem for 2400 b.p.s. data transmission over high-frequency (h.f.) ionospheric channels. Time-redundancy (convolutional coding) and frequency diversity (parallel transmission with pre-encoding) are used in order to combat the frequency-selective fading and the narrow-band interference commonly shown by these channels. In-band real-time channel evaluation (RTCE) techniques are used in order suitably to select the best sub-bands from the redundant set, and to form the originally transmitted data sequence. The modulation scheme chosen for the parallel carriers is QAM-16 High-frequency modem with multilevel parallel transmission using coding and RTCE (PDF Download Available). Available from: https://www.researchgate.net/publication/271559296_High-frequency_modem_with_multilevel_parallel_transmission_using_coding_and_RTCE [accessed Feb 23, 2016].

Peer Reviewed