"For example, wouldn't all access points send the signals at exactly the same time? How can they insure that? How can they insure the interferences won't have changed between the test signals and when the real signals are sent?"
I think the key is to see the DIDO access points as part of a larger system and not as traditional access points. "So, you can think of the DIDO APs as a vast random array of antennas extending out from the DIDO Data Center for miles" as the whitepaper says. I assume that all the access points will be stationary and will talk to the DIDO centre very regularly. This would be required, at least in my mind, to ensure that their environment characterisation is accurate and up to date and to syncronise transmissions.
I think the key is to see the DIDO access points as part of a larger system and not as traditional access points. "So, you can think of the DIDO APs as a vast random array of antennas extending out from the DIDO Data Center for miles" as the whitepaper says. I assume that all the access points will be stationary and will talk to the DIDO centre very regularly. This would be required, at least in my mind, to ensure that their environment characterisation is accurate and up to date and to syncronise transmissions.