For first and second generation mobile networks the use case was pretty simple: Let's make voice telephony wireless and mobile. For third and fourth generation networks the use case was to mobilize the Internet. Perhaps it's only in retrospect but these use cases are pretty easy to grasp. On the other hand I can still remember the 'search for a killer app' for 3G networks that went on for many years. I'm not sure if it was ever found as that search was done in mindset that the killer app should come from network operators when in reality the 'killer app', as far as I'm concerned, was to mobilize the Internet as a whole. So what about 5G then?
Compared to the discussion that was taking place around 3G (UMTS) and 4G (LTE) at the time the discussion on what 5G will be and why we need it is too hazy for me as lots of more or less realistic use cases are discussed while the discussion on how 5G will actually work is more or less done in the background. Stephen Temple over on his web site suggests to split the 5G discussion into a use case debate and a technical debate. A good idea in the light that most of the network operator centric use cases discussed at the time for 3G and 4G were never realized they way they were discussed (e.g. IMS as a universal service platform). He has a number of very interesting thoughts on the technical side, including the potential non-regulation of spectrum above 5 GHz and close range wireless-fiber networks as technical corner stones of 5G.