When they used to say that 35 Kbps was the maximum for a analog modem, it was purportedly due to a fundamental principle of information theory.
When they used to say that ADSL had a maximum of 8 Mbps, it might be just because the spec for the first version of ADSL was written in that way. It's probably not due to any limits of physics or math.
When they used to say that ADSL had a maximum of 8 Mbps, it might be just because the spec for the first version of ADSL was written in that way. It's probably not due to any limits of physics or math.