On the performance of OFDM and single carrier communication over wideband HF channel: theory and practice

Abstract

Using wideband High Frequency (WBHF) communication has not been a luxury now due to the urgent need for the transfer of large files over long distances without the need for sophisticated infrastructure. The channel model helps in evaluating the performance of communications systems without the need for a real transmission. The existing HF ITU-R(International Telecommunication Union Radio) channel models are valid only for narrowband channels of bandwidth 3KHz and are valid up to 12KHz. Another channel model for WBHF with bandwidth up to 1MHz was given by Vogler yet, the model was mathematically intractable and allow no further analysis to take place. Noting that, WBHF demands channel bandwidth greater than 12KHz (e.g:24KHz). In this paper, we present a WBHF channel model that is both accurate and mathematically tractable laying the foundation for an informative comparison between different communication systems. The accuracy of the proposed model is first to cross verified against Vogler’s wideband model in terms of the channel impulse response, frequency response and channel scattering characteristics. This comparison leaves our model qualified to evaluate a newly developed standard of HF wideband Waveforms presented to support high data rates and link reliability requirements. Further, we establish a detailed comparison between OFDM and single carrier signaling schemes over the considered WBHF proposed ionospheric channel, under many parameters that affect the performance of both systems. We investigate the justification of using both systems under different channel conditions, we also derive the necessary rate formulas for each signaling scheme and provide simulation environment of both systems on selected samples of the ITU-R channel models for the HF ionospheric channel representing most of the channel conditions. It is coming up that in quiet channel conditions the OFDM outperforms SCCP, while in disturbed conditions SCCP shows more robustness against channel conditions than OFDM. Simulation results are shown that support our analytical results. In addition, we present a Software Defined Radio Hardware implementation of an OFDM wideband HF Transceiver. The developed implementation has been evaluated using an equivalent baseband channel model based on the ITU-R HF channel model.