Final answer:
DOCSIS 3.0 introduced channel bonding to allow enough bandwidth for upstream carriers.
Step-by-step explanation:
In DOCSIS 3.0, the introduction of channel bonding allowed for enough bandwidth for upstream carriers from previous DOCSIS versions. Channel bonding is a technique that combines multiple channels together to increase the data transmission capacity. With DOCSIS 3.0, cable operators could bond multiple upstream and downstream channels, providing higher speeds and more efficient use of the available bandwidth.