Re: 5G?
The thing is.. the problem is mostly to get the data in and out of the base stations, and route it afterwards, not between the mobile phones and the base stations.
So while yes, it would be more efficient, it will only solve a minor problem in specific parts of the network.. so it is NOT worth spending so much money.
And cmon, most people have had 4g only for the las 3 years.. with many 800band deployments in 2016, for example... so now, no 5G in europe for quite some time unless the spectrum gets cheaper or they do not require population coverage.