To save this thread dragging on any more:
Upstream capacities on modern network, including those that are pretty much unachievable - the higher up the bits/symbol count goes the harder it is for the networks to reliably run, and to run past 16QAM on the upstream is pretty special.
DOCSIS 1.0:
3.2MHz wide QPSK, symbol rate 2.56Msym/s @ 2 b/sym = 4.4Mbps payload
3.2MHz wide 16QAM, symbol rate 2.56Msym/s @ 4 b/sym = 8.8Mbps payload (not always implemented).
DOCSIS 1.1:
As above except 16QAM support is required.
DOCSIS 2.0:
As above +
3.2MHz wide 8QAM, symbol rate 2.56Msym/s @ 3b/sym = 6.6Mbps payload
3.2MHz wide 32QAM, symbol rate 2.56Msym/s @ 5b/sym = 11Mbps payload
3.2MHz wide 64QAM, symbol rate 2.56Msym/s @ 6b/sym = 13.2Mbps payload
3.2MHz wide SCDMA 128QAM, symbol rate 2.56Msym/s @ 7b/sym = 15.4Mbps payload
6.4Mhz wide QPSK, symbol rate 5.12Msym/s @ 2b/sym = 8.8Mbps payload
6.4MHz wide 8QAM, symbol rate 5.12Msym/s @ 3b/sym = 13.2Mbps payload
6.4MHz wide 16QAM, symbol rate 5.12Msym/s @ 4b/sym = 17.6Mbps payload
6.4MHz wide 32QAM, symbol rate 5.12Msym/s @ 5b/sym = 22Mbps payload
6.4MHz wide 64QAM, symbol rate 5.12Msym/s @ 6b/sym = 26.4Mbps payload
6.4MHz wide SCDMA 128QAM, symbol rate 5.12Msym/s @ 7b/sym = 30.8Mbps payload.
OK There's the DOCSIS specs, should be the thread sorted now, Telewest currently run DOCSIS 1.1.
Ah to save a 'how much download speed can be offered' thread
all DOCSIS specs are the same on this one so these apply to TW network:
6MHz wide 64QAM downstream, symbol rate 5.057Msym/s @ 6b/sym = 27Mbps payload
6MHz wide 256QAM downstream, symbol rate 5.36Msym/s @ 8b/sym = 38Mbps payload.
Please note that I'm giving the throughputs you can realistically expect to see from all of these, not the raw line rate, if you want that get a calculator and multiple symbol rate by bits/symbol, is also why the numbers aren't exact, impossible to predict exact yield at any one time.
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