Why We Can’t Abandon 2.4 GHz Yet
In this blog series, we discuss how and why 2.4 GHz persists in Wi-Fi deployments. Last week we discussed why we are currently living in a dual-band Wi-Fi world. Today we discuss the merits of 2.4 GHz.
With lots of spectrum at 5 GHz and the promise of even more (lots more) spectrum at 60 GHz, why don’t we just abandon 2.4 GHz? After all, .11ac won’t run there, and .11n, which does, doesn’t provision as much capacity as .11ac. It’s only 83.5 MHz. It’s crowded. It’s old. It’s tired. It’s obsolete. Know all you need to know about 802.11ax? Read our primer here.
Nope – at the end of the day, it’s still spectrum we can use for Wi-Fi, that we need to make the most of. Just look at 900 MHz, which is a small amount of spectrum, but which is destined to see new life as IoT grows in importance and 802.11ah (a/k/a Wi-Fi HaLow) starts to take hold.
Let’s consider the following 2.4 GHz realities:
1) Range – Yes, it’s still true. Lower frequencies usually propagate further than higher frequencies. In fact, when we get up above 6 GHz, and certainly into the millimeter-wave bands like 60 GHz, propagation is quite linear and directional, and range is more limited.
More importantly, though, we need to center or discussions on rate-vs.-range – how much data we can send over a given distance per unit of time. And this is a factor of more than just range or frequency alone. We also need to consider transmit power, channel bandwidth, modulation and coding scheme, protocol overhead, traffic type (class and quality of service), obstructions, reflections and echoes (multipath), competing traffic, interference, and on and on.
2) Installed base – The installed base of 2.4 GHz Wi-Fi devices is enormous – hundreds of millions of devices still in use today. Many of these are mission-critical, such as in medical and security applications, and many of these are so expensive that they cannot be easily replaced, let alone upgraded to the latest Wi-Fi standards.
We simply need to wait until all of these die a natural death before 5 GHz, or at least a more contemporary Wi-Fi technology, is an option. Even today, many new devices like Chromebooks and handsets often support only 2.4 GHz.
At least these are .11n, but they are dependent upon 2.4 GHz service. Device vendors choose this option because costs are reduced over dual-band capabilities, and no one should be surprised at how many price-sensitive users there are – and always will be – in the world. We expect almost all new devices to eventually support .11ac, which means 5 GHz grows in importance. But consider the next point, below.
3) Looking forward – Even as many eventually realized that 5 GHz was a much larger chunk of spectrum than 2.4 GHz, it was still underutilized until 802.11n became well-established – and that was only about five years ago. Adoption has been swift, to the point that many now have concerns – oh, the irony once again – about crowding in the 5 GHz bands, and, guess what: 2.4 GHz is still there to relieve the pressure – and good Wi-Fi infrastructure systems, properly implemented and configured, anyway, can automatically move traffic to an optimal frequency band and channel.
What’s more, will the next big 802.11 standard, 802.11ax, unlike 802.11ac, be specced to operate at 2.4 GHz in addition to 5 GHz Legacy spectrum?
While we don’t expect a full cutover of all earlier Wi-Fi technologies to .11ax at 2.4 GHz, which would require the full retirement of all .11n clients and infrastructure (and everything before it) before at least 2025 (and likely much later), 2.4 GHz remains a vital element in any good long-term Wi-Fi strategy – and that means yours.
The bottom line is that we can’t “abandon” 2.4 GHz any time soon, and we really wouldn’t want to even if a big chunk of new unlicensed spectrum became available – and such, by the way, is very unlikely. 2.4 GHz will continue to provide a highway for tens of millions of devices for the foreseeable future, and, eventually hosting 802.11ax, 2.4 GHz quickly goes from obsolete and legacy to highly-desirable, again considering the propagation characteristics of 2.4 GHz.
In short, leaving any available spectrum fallow isn’t a good idea. Next time, we’ll look at a few really good ideas for making the most of 2.4 GHz and Wi-Fi overall.