On Sunday, September 04, 2011 17:09:43 Torsten Dreyer wrote: > Hi Adrian, > > this all sounds very interesting and not only for AI Aircraft but also > for the navigation radios. I am currently refactoring the navradio code > and I'd really like to have a better propagation model than our current > distance-squared or hard-cutoff model. > > Torsten >
Hi Torsten, the details of the implementation are as follows: - hard cut-off at 400km, - yet to be done: LOS mode with first Fresnel zone clearance (skips the point_to_point subroutine) - between user's aircraft and traffic/ATC within the 400 km zone, attenuation is calculated with point_to_point(): Line-Of-Sight Mode, Single Horizon, Double Horizon, Diffraction Dominant, Troposcatter Dominant. - the main issue is the fact that if the transmitter radio is located outside of the tile cache area, there will be no elevation profiles. I do not know how to handle this yet, but I know you probably do. - a link budget is established based on (yet) hardcoded values for transmitter power, receiver sensitivity and antenna gain at both ends. These are separated for ground stations and aircraft for obvious reasons. - loss is substracted from the link budget (working with dBm here). If resultant signal is lower then receiver treshhold, the communication is discarded. If the signal is within a zone where SNR has a great influence on reception, parts of the message are garbled. - this is all inside the trafficcontrol.cxx file, but it should probably be made independent. For me it was just a test run, to confirm that Durk's new ATC code works fine with this - and it does. I could see this applying to navradios too, except that in that case we have mostly continuous/repetitive transmissions, and this model relies on extracting an elevation profile between receiver and transceiver. Thus, optimizations to my code will most likely be necessary to use with navradios. Anyway, in all my tests terrain is blocking transmissions as expected and within the limits of the charts I have pre-generated and calibrated with physical signal-level readings. 73, Adrian, YO8RZZ ------------------------------------------------------------------------------ Special Offer -- Download ArcSight Logger for FREE! Finally, a world-class log management solution at an even better price-free! And you'll get a free "Love Thy Logs" t-shirt when you download Logger. Secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsisghtdev2dev _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
