What is DOCSIS 3 channel bonding ?
DOCSIS 3 allows for "bonding" 6MHz channels together to increase available bandwidth. Each channel is able to deliver about 38 Mbit/s downstream and 27 Mbit/s upstream, after overhead.
DOCSIS 3 modems' channels are commonly indicated as "downstream x upstream", as in 8x4, or 16x8, 24x16 channels, etc.
A 16x8 cable modem, for example, can deliver 608Mbit/s downstream (16 ch. * 38 Mbit/s), and 216 Mbit/s upstream (8 ch. * 27 Mbit/s).
The most common DOCSIS 3 modems channel bonding combinations on the market, and their resective theoretical maximum bandwidths after overhead are as follows:
4x4 - 152 Mbit/s down, 108 Mbit/s upstream
8x4 - 304 Mbit/s down, 108 Mbit/s up
16x4 - 608 Mbit/s down, 108 Mbit/s up
24x8 - 912 Mbit/s down, 216 Mbit/s up
32x8 - 1216 Mbit/s down, 216 Mbit/s up
Note: EuroDOCSIS uses 8MHz downstream channels, capable of ~50Mbits/s per channel after overhead, which is significantly higher than DOCSIS. This difference only applies to downstream channels.
Are cable modems with more bonded channels better?
Cable modems and routers database