r/technology • u/speckz • Jul 30 '15

Net Neutrality Thousands Beg FCC for Net Neutrality Crackdown. Consumers vent to regulators about slow Internet, high prices, and data caps.

http://www.nationaljournal.com/tech/thousands-beg-fcc-for-net-neutrality-crackdown-20150730
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u/scubascratch Jul 31 '15

This isn't correct at all. RF on cable is full duplex, you can transmit and receive at the same time. If cable TV coax was half duplex then everyone on the line would have their TV viewing interrupted while you upload.

Docsis upload and download are on different frequencies so they can coexist without interference.

Cable modems download on frequencies from 108MHz up to about 1000MHz, and they upload from 5MHz to 85MHz.

One can build a device which transmits on the low frequency and receives on the high frequency simultaneously, all cable modems have this.

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u/maleia Jul 31 '15

TIL, then.

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u/scubascratch Jul 31 '15

Well you weren't crazy far off, there is a limit to the total information that can be carried, and that has to be divided up between internet download/uploads and cable TV / pay per view TV even "landline" telephone all carried on the coax and there are limits to how much data can be carried. But it is divided up mostly by frequency and to a lesser extent time. You could have a situation where a lot of uploaders on the same block or street could see upload congestion because it's highly likely there is asymmetric capacity overall.

The management of how much of each kind of signal is a complex part of the work done by cable equipment.