Burst Transmissions
ok - I do know something about IT and can confirm that satellite internet connections are available with downlink speeds of 400 Mb/sec. If you could do uplink ASCII bursts to relay geostationary satellites you could transmit all your FDR and FVR data in sub second UHF bursts every few mins or so and it probably would not require that many frequencies to cover half a hemisphere's flights.
Of course it all comes down to the filthy lucre in the end as it would require at least eight satellites and a few automated ground stations. But then you could do away with your black HMV boxes.
Given the fact that some airlines are now offering inflight broadband connections, you might think that the voice and data recorders would get access to the same technology.