Three Fundamental Reasons Why Wireless Access Will Stay Under 7.2GHz

For the last several years, I’ve had the privilege to take part in several discussions among wireless product experts that revolved around user access to high-speed data over millimeter wave (mmW) links. Coincidentally, Apple just recently revealed their new iPhone SE, which completely lacks mmW capabilities. As a disclaimer, I will outright mention here that my opinion is usually somewhat unpopular (and some even found it provocative).??

I believe that mmW access such as? 802.11ad/ay (Wi-Fi at 60GHz) and the 28 / 39GHz bands allocated for cellular 5G is a bit overrated and it seems that whoever defined the new iPhone SE might have had similar thoughts.?

Here are my 3 reasons for why :

Catch me if you can?

802.11ad, as an example, which developed later into 802.11ay has been around for more than a decade but never made it into the mainstream of wireless access that is as ubiquitous as Wi-Fi. The simple reason is that Wi-Fi also improved over the years and always manages to almost catch up with the blazing-fast data rates that the 60GHz links can deliver.

Further, I believe that the rollout of Wi-Fi6 and the opening of the 6GHz spectrum for Wi-Fi will make it even harder for 802.11ad/ay to find its way into every user device.

On the cellular front, there are reports about speed tests that achieved around 2Gbps downlink on a 400MHz link which is truly impressive. On the flip side using the Wi-Fi6E standard one could get very close to these numbers in a simple 2x2 MIMO configuration while easily supporting more client devices and at lower cost and complexity (see the next 2 points).?

Keep it simple

All mmW share a common obstacle: the laws of physics, or in simpler terms - range. The power of mmW signals decreases rapidly so that engineers had to come up with smart phased array antennas that take 10s or even 100s of antenna elements and combine them into a single narrow beam directed at one end user. It is clear that these smart antenna arrays are an amazing solution; however, they are relatively expensive.

A Wi-Fi6 router or access point for comparison would use simple antennas that cost a few cents combined with a simple cost-effective front-end module and no sophisticated phased array antennas.?

On the cellular side, one parameter to highlight is signal penetration. We are all used that our cell phones acquiring a signal inside buildings. For mmW signals, the reality is different, they simply cannot penetrate into buildings, especially if bricks, concrete, or e-glass has been used as a building material. As a solution, one could deploy mmW small cells inside those buildings; however, that raises the question of why would that be a good solution when Wi-Fi is usually already deployed. It is true that Wi-Fi is not as deterministic as cellular communication, but it is rapidly evolving and becoming much more reliable from one generation to the next at a much lower cost than a small cell network. Wi-Fi6 and Wi-Fi6E are already starting to obfuscate these arguments about the quality of cellular connections.I believe that Wi-Fi7 will be the Wi-Fi standard generation that diminishes the reliability argument to an insignificant one.?

Keep it cool.

Many of the mmW components simply consume more power and often at lower efficiencies. Eventually, for the access points and cell radios, this means that they need to draw quite an amount of power from the grid and also need a lot of thermal mitigation to deal with the heat dissipation due to the low efficiency of the components. On the client device side, the additional penalty is shorter battery life. Remember the days when our cell phone battery lasted 5 days….

Obviously, such power budget implications are problematic for any of the mmW based communication standards to become mainstream. Having said that, as semiconductors improve and mature power consumption and efficiency might improve but I do not believe that we will get to experience these improvements in the near future.

To conclude, I believe that mmW has many great uses, such as point-to-point communication, wireless mesh networks, in building ethernet cable replacements, and many more. However, beating the laws of physics in terms of range and efficiency is not an easy undertaking. o, I believe that it may take a while before providing access to clients over mmW becomes mainstream (if ever).?

Please comment below with your feedback. Do you agree or disagree?

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