This is why 5G is never going to happen!
-by Steve Tsuruda
5G - the next generation in mobile telephony - is heralded as a huge advance in global connectivity.
But the vision is flawed. It is flawed because users will not value the higher data rates that are promised and will not need the higher capacity forecast.
It is flawed because technological advances are insufficient to realise the vision and because mobile operators are insufficiently profitable to afford it.
Yet it is not in the interests of any of the stakeholders to point this out. They all benefit from the interest, funding and potential that 5G promises.
256-QAM is more sensitive to disruption by noise in the environment.
This means you need a cleaner signal between the client and the AP (access point).
In practice, you need line of sight access between AP and client from a max range of about 20 feet to get the benefits of 256-QAM.
In real-world settings, rate control will choose to use 256-QAM only in close proximity of the AP, like 10-20 feet, otherwise it will drop down to the next lower data rate namely MCS 7 using 64-QAM, no different from 802.11n. But what about beamforming? Vendors are claiming you can go much farther when beamforming is employed.
Beamforming can only extend 256-QAM range in open spaces with clean air and with direct line of sight. see my point?
At high data rates 11ac does not penetrate walls any better than 802.11n, so you are not gaining anything in improved coverage, except in open spaces. In fact, in traditional office environments, distance using 256-QAM is shorter than it is for 802.11n’s top data rate at 5GHz and significantly less than 802.11n at 2.4 GHz. Add 80 MHz channel bonding, and it only gets worse. AP power level drops, which means coverage area shrinks dramatically, and receive sensitivity is also reduced.
In buildings with heavy concrete walls or a lot of iron and steel, range is even worse and 256-QAM is virtually unusable beyond 15 feet! This is all due to higher signal-to-noise ratios required by these new data rates. When 256-QAM is not viable, 802.11ac radios automatically downshift to 64-QAM, matching what you already have with 802.11n. In this case, the bottom line is – no benefit.
So what does all this mean for 802.11ac AP placement? To get the benefits of 256-QAM, APs should be placed in open areas, where they can literally be seen by users. Cubicle office areas, hotel lobby areas and outdoors are the best use cases. While the worst use cases are warehouses and buildings with heavy concrete or steel construction.
Gigabit Wi-Fi, 802.11ac is not really going to give you gigabit speeds.
In practice you're not likely to see an 802.11ac reach its theoretical maximum of 1.3 Gigabit per second (Gbps). That's because the conditions you need to reach that speed requires a laboratory not your office.
To reach the highest speeds you need three data-streams, each of which can run up to 433 Megabits per second (Mbps). A typical 802.11ac access point can support up to eight data streams. Client devices must only support one.
See my point?
Now you know