IrDA VFIR was spec'd at 50Mbps
>The data would be transmitted by the same LEDs which provided white-light illumination,
Speed of sending the data isn't the issue. The connection is half-duplex. When the connection goes from download to upload, does the light in the room turnoff and one on the laptop turn-on? Since shining two lights at each other at the same time doesn't work. IrDA has differing turnaround periods depending on packet size. Would large packets would introduce flicker..? Do i plug my computer into my desklamp to talk to the ceiling lamp?
IBM Worked on some IrLAN type products with IR Transceivers that had wider angle sending and detection of light. T30 may have been equipped with it?
You could possible add that type of system to LED Lamps these days. But again it would need to be in the IR band if you don't want to see flicker, i.e. the room light go out when you upload ;)
Check IrDA.org, I did and they have a 1Gb demo with Ir..