News flash…T-Mobile claims mmWave will not be viable outside of dense urban areas, according to T-Mobile Chief Technology Officer Neville Ray. “It will never materially scale beyond small pockets of 5G hotspots in dense, urban environments,” he stated.
Well, I do not know which is worse: A) a high-level, technically competent individual from a global company making such a stupid statement or, B) the non-technical media running with such a stupid statement. Immediately, all kinds of diatribe was put out by any number of media outlets trying to explain mmWave to the readers, what it is supposed to mean in 5G, and what Ray meant.
Ray tried to make his point by showing that “mmWave frequencies” are immediately blocked by a door closing halfway, while the lower 600 MHz signal (which T-Mo is banking heavily on for 5G) is unaffected. I was not able to determine what frequency Ray was defining as the failed mmWave, but the successful signal was a 500 mmWave signal. You will understand why I called the 600 MHz signal a 500 mm wave as the column unfolds. However, before I go off on this, I want to discuss mmWave for a few moments.
Our readers are smart people. They understand RF. In reality, any frequency can be represented as mmWaves. However, by definition, a mmWave is any frequency where the wavelength, as given by the formula, λ = v/f, is a millimeter or less. Therefore, by definition, mmWaves start at 300 GHz.
Now, as with any industry, we have our idiosyncrasies. We have taken liberties when discussing wavelengths and frequencies. We, typically, call higher frequencies mmWaves. But the term mmWave is not accurate for a frequency wavelength until that 300 GHz limit.
For example, a 3-GHz wave has a length of 100 mm (really, it is 99.93081933333 mm but let us just round off going forward); a 30-GHz frequency has a wavelength of 10 mm.
So the discussion around mmWaves has become more vernacular, than precise. The term mmWave has become a convenient moniker for discussing frequencies, often around other topics, such as marketing.
For example, A 300 MHz wave has a length of 1000 mm, or one meters. Therefore, the reality is we can define any wavelength in millimeters if we so choose. Under that definition we have mmWaves penetrating all kinds of stuff; 800/900 MHz (roughly 333 mm) 1800/1900 MHz (roughly 155 mm, which is also noted as 1.8/1.9 GHz – see what I mean)?
Any RF person knows that propagation characteristics vary, based on frequency. The higher one goes, the more sensitive the wave is to environmental conditions. Below is a chart of typical propagation attenuation around different frequencies for water and oxygen found in the atmosphere. Similar scenarios exist around foliage, man-made materials, living things, and more.
Furthermore, Ray presented a GIF showing how just closing a door killed a mmWave signal. The idea was to make the point that such was not the case for 600 MHz (or 500 mm). Such diatribe from Ray immediately set the tone of 5G for non-tekkies (and trust that CNN, WSJ, NYT, and other news outlets will run with it) and creates more confusion around getting the public to embrace 5G.
Of course, Verizon immediately fired back, reiterating how its mmWave strategy has “lived up to our expectation on performance…” That is another nebulous statement since they do not have any 5G mmWave deployments – just concepts.
The fact is that, for real mmWaves (300 GHz and above) use cases will be virtually non-existent – at least for quite some time (there will, of course, be some exceptions). However, use cases for other “mmWave” frequencies (for this part of the discussion let us say 3 GHz and above) will vary widely. In addition, some of 5G’s visions will only be realized with mmWave frequencies. Frequencies up to about 80 GHz have real potential for 5G networks and applications, near term. It is really, just a matter of understanding the nuances of frequencies for all spectrum and knowing what frequency will work for the particular application.
Every time I hear or see this kind of banter, it reinforces my suspicion that there is a lot of insecurity in the 5G ecosystem. That the players are conjuring up all kinds of ways to capture what 5G is supposed to offer and convince the public they are the ones with the solutions. Why else would they use extreme measures, and nebulous examples, to convince the user that one company’s solution is better than the competition’s?
It is too early in the 5G scenario to say what is going to work best and where. We have theories and concepts. Some are proven solid others are proving problematic in theory versus practice.
Myriad use cases are just beginning to appear. Millimeter waves will work for some applications, not for others and to varying degrees for still others. Various implementations of mmWave technology will have varying applicability in any number of 5G scenarios. Therefore, to shut one frequency or another out of an application is silly at this stage of the game. Moreover, it can make a fool out of you as well.