It never is too difficult to find somebody criticizing the use of millimeter wave spectrum for 5G, even if there is less skepticism about millimeter wave usefulness for 5G than was the case five years ago. A decade ago, rational observers might have argued that millimeter wave frequencies were too expensive to use for mobile communications. But Moore’s Law has reduced the cost of signal processing so much that practical millimeter wave communications are possible in a mobile phone setting. That will be much more common in the future, as the chief drawback of millimeter wave–its lack of signal propagation–is balanced by its chief advantage, very-high capacity.
Longer term, millimeter wave’s role seems assured, as there simply is no unencumbered spectrum anywhere else in the 600-MHz to 300-GHz range used by radios. Furthermore, only millimeter wave can supply the ever-growing requirements for suppliers of mobile bandwidth. There are several reasons for that claim. First, much of the lower-frequency spectrum already is allocated for other uses. And even if some of that spectrum eventually can be redeployed, capacity and frequency are inversely related.
Lower frequency signals propagate better, but capacity is lower. Higher frequency signals do not travel so far, but capacity is much higher. All of that means millimeter wave not only is a key feature of 5G, but will be part of future Gs as well.