With Broadband using a contention ratio of 50:1, are those 50 lumped togeter by speed, for example 50 x 512 users or 50 x 1mb users, or is it just a case of all broadband users, of whatever speed, on an exchange?
Most exchanges have 155mbps of backhaul. This is split up in various ways between ipstream and datastream. (Yes, I know subtended exchanges only have 34mbps, and larger ones have 622mbps). For simplicity's sake, the total number of 50:1 connection will not exceed 50x155. So basically (ignoring 20:1 being on part of the same pipe) 7.5gbps worth of customers in 155mbps.
With Broadband using a contention ratio of 50:1, are those 50 lumped togeter by speed, for example 50 x 512 users or 50 x 1mb users, or is it just a case of all broadband users, of whatever speed, on an exchange?
It doesn't work like that though. You aren't sharing 512k of bandwidth with 50 users, you're sharing a lot more bandwidth with a lot more users. The economics of scale works in your favour. Unlike certain wireless ISPs, who like to put 200 users on 2mbps of leased line, and call it "equivalent to adsl"