5G is many things to different people. For most, 5G is about more network capacity and faster speeds for Internet access. The main challenge for this goal is that there is little spectrum still available below 6 GHz, a frequency that is generally seen as the limit for the current air interface technologies around. So 5G below 6 GHz brings only few benefits for the broadband Internet use case, it could easily be done with LTE as well. Ultimately, to get to higher speeds and more network capacity, higher frequency bands have to be tapped. The problem here is that with conventional technologies, communication range is severely limited.
As a consequence, new radio technologies like massive MIMO for beam-forming and shaping, beam-sweeping, ultra fast reaction to changing radio environments of mobile users, etc. is required. This is were the LTE radio interface can’t go and 5G NR (New Radio) is a must. The first band where we will likely see 5G above 6 GHz is the 28 GHz band. A lot of trials are ongoing in 2017. Ericsson, for example, has recently concluded pre-5G trials on 28 GHz with U.S. Cellular and Softbank, and IBM has published an interesting paper on a 64 channel antenna array they developed together with Ericsson. The Softbank link contains an interesting sentence that pretty nicely sums up the challenges for the future radio interface:
The trial will utilize Ericsson’s mmWave 28GHz 5G Test Bed solution, which includes base stations and device prototypes and will showcase advanced 5G technologies including Massive-MIMO, Massive Beamforming, Distributed MIMO, Multi-user MIMO and Beam Tracking together with multi-gigabit data rates and ultra-low latency which are becoming key requirements for future consumer mobile broadband and industrial use-cases.
Most of the buzz around this frequency band is coming from the US, Korea and Japan. It’s surprisingly silent in Europe, perhaps because regulators have not yet decided exactly which frequency ranges > 6 GHz should go to 5G. I’ve seen papers from the German and UK regulators on the topic in which they state their intentions but nothing is finalized so far.