Ionosphere characterization using received HF communications

In HF communications, both intra-and inter-symbol fading and losses can vary significantly between two nodes. While these channel effects may be problematic for maintaining a link, they may provide information about the structure of the ionosphere. We utilize our previously developed communications simulator which simulates a received RF data stream for a given channel response. Using channel responses estimated from the output from a ray-based propagation model, as well as modified modules within a Software Defined Radio framework, we map propagation channel variations to the received signal demodulator's corrective filters. By minimizing a cost function that compares predicted channel reponses to the true channel response, we devise an algorithm that enables estimating ionosphere features from the received signals.