Greg D. wrote:
Ah, but how does one know that a time slot is not being used? With many stations on the ground, there is a good chance that multiple stations will pick the same "empty" slot to be theirs, and we're back to collisions.
For good performance, some sort of media-access control (MAC) protocol is required. Time-slotted protocols have a lot to be said for them, although some have suggested using a CDMA protocol. You could create a system that assigns time slots to active ground stations. But, if these stations are generating very bursty traffic, like voice, a lot of the uplink bandwidth may be wasted. In general, I think this is what I call a "hard problem" (i.e., we don't know how to solve it [yet], and perhaps nobody else does either).
So, this is what I was talking about when I suggested, as essentially you do, to work on a prototype of the ACP messaging system that is being proposed for Eagle.
I think this is a great idea.
Unfortunately, as far as I can tell, all development work on the Eagle and the ACP ceased several months ago. The Microwave Engineering Project (MEP) is or might become, in some vague sense, a terrestrial variant of the ACP.
http://www.delmarnorth.com/microwave/
I am hopeful that at least some of the work on the MEP will be applicable to the ACP.
There are two significant technical challenges that I see,
Actually. I think there are a quite a few technical challenges and issues...
and the protocol used to facilitate fair and resilient access to the satellite by all the ground stations it overflies is one. ... I haven't checked, but has the Eagle team published their protocol for doing this? ...
The team developing the ACP ground station made pretty much everything they wrote freely available online. [What a concept!} Unfortunately, they didn't get all that far before work ceased. See the ACP ground station Web site:
http://www.delmarnorth.com/namaste/
The other challenge is the modulation system ...
^^^^^^^^^ Another
You might look at these two documents:
http://www.delmarnorth.com/microwave/requirements/Microwave_Link_Discussion.pdf
http://www.delmarnorth.com/microwave/requirements/Microwave_Link_Analysis.pdf
-tjs