From the patent app:
"As such, in one embodiment of the invention, the channel characterization matrix 616 at the Base Station is continually updated. In one embodiment, the Base Station 600 periodically (e.g., every 250 milliseconds) sends out a new training signal to each Client Device, and each Client Device continually transmits its channel characterization vector back to the Base Station 600 to ensure that the channel characterization remains accurate (e.g. if the environment changes so as to affect the channel or if a Client Device moves). In one embodiment, the training signal is interleaved within the actual data signal sent to each client device. Typically, the training signals are much lower throughput than the data signals, so this would have little impact on the overall throughput of the system. Accordingly, in this embodiment, the channel characterization matrix 616 may be updated continuously as the Base Station actively communicates with each Client Device, thereby maintaining an accurate channel characterization as the Client Devices move from one location to the next or if the environment changes so as to affect the channel. "
If this continual transmission is only done during periods of network usage, when you're already powering up the CPU and antenna chipset, how much of an additional burden would this be for the client device? I doubt it would be continuously transmitting when the device is in sleep mode, and I have no indication that this is a CPU-intensive task for the client device (the data center device is a different matter).
For the mobile phone use case, it seems like the transmitter would have to be emitting constantly in order to keep the base station appraised of its current position, for the purposes of computing the channel characterization. Otherwise, how would the base station know what transformations to perform on the outgoing signals to reach the mobile device in the event that a call is received? It's not like you could broadcast that information to everyone, because that would end up corrupting the spectrum for everyone else, which defeats the entire point of this system.
The whole scheme seems really dependent on knowing the position of all transmitters/receivers at all times.
The "paging channel" problem is already present in existing mobile radio systems. Solving it pretty much requires some form of TDMA — i.e. scheduled transmission — because only TDMA gives you the ability to actually power your radio off most of the time. Even Wi-Fi has features for this.
Why couldn't you reserve a tiny fraction of the bandwidth of the system (or some other but related spectra) for this sort of "calling transmitter #92" broadcast? Yeah, it'd impact everyone, but only finitely.
