Where to find HF channel models or statistics?

Question

When designing a waveform for packet radio usage, it'd be helpful to know a few things, mainly

distribution of coherency bandwidths
distribution of coherency times

Whilst such statistics are reasonably possible to generate for higher frequencies based on own measurements, for terrestrial HF propagation, due to the large distances involved and the low useable bandwidths, a sufficient measurement campaign would be infeasible.

HF propagation models are very light on details or vary wildly when it comes to the relevant aspects that would allow for simulation of the same (that being delay spread and doppler spread). Mostly, they're early cold war studies that care only about amplitude attenuation.

Are there more modern channel models for HF propagation?
Alternatively, statistics over the coherency properties?

Phil Frost - W8II · Accepted Answer

ITU-R F.1487-0 (Testing of HF modems with bandwidths of up to about 12 kHz using ionospheric channel simulators) seems like what you're looking for. It discusses briefly how an HF channel can be modeled, and provides 9 sets of parameters, every combination of (low, mid, high) latitudes and (quiet, moderate, disturbed) conditions, as well as statistics on how frequently those conditions can be expected.
For completeness, other resources which are useful for a complete model:

VOACAP, for path loss and channel reliability estimation
ITU-R P.372-14 for data on ambient radio noise

user10489 · Answer

There are plenty of modern studies of HF propagation.  For instance, in the last 10 years, I have seen new models for both sporatic E and selective fading.

For selective fading, the new models look at how faraday rotation causes circular polarization.  The modem used by freedv is specifically designed to resist this, so they must have a model for selective fading.  I believe that the group designing freedv have published several scholarly papers from their research.

You may also want to research the various HF beacon networks such as wspr, many of which are designed specifically to research propagation.  There may also be isosonde data available, but I couldn't find any with a quick search.

Where to find HF channel models or statistics?

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