Is that " [limitations of existing] [telephone wire]" or " [limitations of [existing telephone wire]]"?

"ADSL has the advantage of giving each user a dedicated channel, hence guaranteed bandwidth, but the bandwidth is low (a few megabits/sec) due to limitations of existing telephone wire. Cable TV uses high-bandwidth coaxial cable (at gigabits/sec), but many users have to share the same cable, giving contention for it and no guaranteed bandwidth to any individual user."

anonymous[limitations of existing] [telephone wire]"

This one doesn't make sense, so it has to be the other one.


Thanks a lot!