Bonding xDSL and cellular……I’ve been involved in some trial activity (tech stuff behind the scenes) for one of the big carriers in the UK, and while its theoretically possible, in practice we’re not making much progress. To be truthful, we thought it would be a lot easier than its turned out to be.
There are a number of headaches that need to be overcome on our network (MPLS core with various bits of edge kit) but in short, its the general variability of the access speeds on both xDSL and cell that are hampering us. I think it will happen in time; we’re working on a way of properly reporting back ‘true’ edge throughout in semi-realtime.
For now, if I was you, I’d get 2 routers- a 3G/4G model and an xDSL one, put their LANs on a common subnet, and just direct your devices manually to each one.