Since doing my PhD in radio propagation 10 years ago, I have often been asked to create channel models for Clients and program channel emulators.
Recently I have been using the Spirent VR5 to emulate the avionic channel. After coding the channel model in software, I upload the data into the channel emulator in order to re-create the channel experienced by an aircraft. This enables testing of the product and fixing issues without the need for copious expensive flight trials.
I have also been using the Keysight / Anite / Elekrobit propsim to model 5G and satellite channels
If you have any requirement for channel measurement, modelling or programming of channel emulators, then I can help.