DSL - Download speeds good, upload speeds bad. Why?

[Compman55]

I have always wondered why DSL providers offer fairly decent download speeds but absolute crap upload speeds.

My current contract is 5477K Download and 864K Upload. This makes uploading 1080P youtube videos take all night.

I know cable & FiOS are superior but are currently not an option for this location.

 

[JackMDS]

Quote:"download faster than we upload because of economics, not physics. The economics are those of telephone and cable companies. Their business models assumed the value of the Net came from the content they deliver to us. The business models got written into a physical infrastructure that favors downloads over uploads. So, here we are."

From - http://www.huffingtonpost.com/david-weinberger/why-uploading-is-slower-t_b_308594.html

 

[SecurityTheatre]

Almost all DSL modems are asymmetric. This means it's common to get a DSL lines that download at 5MB but upload at 768k.

Common speeds I see around here are:

768k/5m
1m/8m
2m/15m
4m/35m

That's normal.

 

[TheCrackLing]

Quote:"download faster than we upload because of economics, not physics. The economics are those of telephone and cable companies. Their business models assumed the value of the Net came from the content they deliver to us. The business models got written into a physical infrastructure that favors downloads over uploads. So, here we are."

From - http://www.huffingtonpost.com/david-weinberger/why-uploading-is-slower-t_b_308594.html

I'm sorry but this is not entirely accurate. Modems used for *DSL and Cable do have a very good signal generator as compared to the DSLAM's and CMTS's for upstream. This is why bandwidth is limited. So yes, it is an economic one, but it's also a technical one.

It's also why FTTP(Fiber to the Premise) and any Telco(T1, ATM, T3, OC, etc.) service has the same upload as download, as the receivers are the same price as the generators.

 

[lamedude]

111KHZ used for upstream compared to 966KHZ used for downstream in ADSL. There was SDSL that used the voice portion for bandwidth to get 2Mbps and VDSL2 is 100Mbps both ways.

 

[Gryz]

Something I don't understand.

A physical line used for DSL has 2 copper wires.
Is one wire used for upstream ? And the other wire used for downstream ?
I don't think so. Because if so, then why are speeds asymmetrical ?

However, when I read about DSL, I read that the frequency-spectrum is divided into channels. A few lower-frequency channels are used for upstream. The remaining channels are used for downstream.

If that is the case, does this happen on bother copper wires ? If so, is the "usable channel detection" the same on both wires ? Or does DSL use only one wire ? (That would seem very wasteful). Or do they send the same signal on both channels ? On my router (a Fritzbox) I can see the channel allocation, but only one graph is shown. That makes me assume not both wires are used individually.

A quick google, or reading the wiki-page, is not very informative.
Anyone here who knows the details ?