ecific identification 66-71 GHz - global identification. In addition, WRC-19 agreed to further study identification for IMT of several bands below 10.5 GHz toward a decision at WRC-23. IMT identification of frequency bands by a WRC has been historically followed, albeit in varying degrees, by national regulators' spectrum designations and availability for pre- vious generations of cellular systems. To put the output of WRC-19 into perspective, it is worth comparing current 4G spectrum holdings with future 5G spectrum allocations. Cur- rently, most operators hold spectrum of circa a few tens of MHz (typically ranging from 10 to 50 MHz), which is usually used for 4G and 3G. It is generally understood that the majority of the 5G spectrum will be divided into two categories of mid-range (e.g. 3.5 GHz) and high range (e.g. 28 GHz). While prediction of the precise 5G spectrum availability in every country is difficult, it is reasonable to assume that a 5G network will need to make use of about 100 MHz of spectrum in the mid-ranges and about 1 GHz of spectrum in the millimeter wave or sub-millimeter wave bands. This is likely to be in addition to existing spectrum currently used by an operator in the sub-1 GHz spectrum range. While the additional mid-range spectrum is substantial, the addition in the high range is likely to be an order of magnitude larger than what operators have today and what their networks, RAN in particular, are designed to support. 2.3.3 Spectrum Implications Such a radical increase in available spectrum will have a direct impact on RAN. 5G networks will have to support substantially higher throughputs compared with 4G, which inevitably will affect at least the transport fronthaul and backhaul network and also the RAN archi- tecture. In particular, this affects base station architecture, making the usage of Common Public Radio Interface (CPRI) unfeasible and triggering different split gNB architecture designs, as explained in Chapter 4. Furthermore, high-band and even mid-band spectrum 3 For detail