Death to 2.4GHz!


This week was the annual announcement of the Apple iPhone refresh.  There were a lot of interesting technologies discussed around the newest entry in the Cupertino Fruit and Mobile Company but one of the most exciting came in the form of the wireless chip.  The original iPhone and the iPhone 3G were 802.11b/g devices only.  Starting with the iPhone 3GS, Apple upgraded that chip to 802.11b/g/n.  With the announcement of the new iPhone 5, Apple has finally provided an 802.11a/n radio as well, matching the 5GHz capability as the iPad.  This means that all Apple devices can now support 5GHz wireless access points.  Along with the latest Android devices that offer similar support, I think the time has come to make a radical, yet needed, design decision in our wireless networks.

It’s time to abandon 2.4GHz and concentrate on 5GHz.

Matthew Gast from Aerohive had a great blog post along these same lines.  As Matthew explains, the 2.4GHz spectrum is awash with interference sources from every angle.  Microwave ovens, cordless telephones, and wireless video cameras are only part of the problem.  There are only three non-overlapping channels in 2.4GHz.  That means you’ve got a 33% chance of interfering with surrounding devices.  If you’ve got one of those fancy consumer devices that can do channel aggregation at 2.4GHz, the available channels decrease even further.  Add in the fact that most people are carrying devices now that are capable of acting as access point, such as MiFi hotspots or the built-in hotspot features in tablets and smartphones and you can see how the 2.4GHz spectrum is a crowded place indeed.  On the other hand, 5GHz has twenty three non-overlapping channels available.  That’s more than enough to satisfy the more dense AP deployments required to provide similar coverage patterns while at the same time providing for high speed throughput with channel aggregation.

There are a number of devices that are 2.4GHz only and will continue to be that way.  Low-power devices are one of the biggest categories, as Matthew pointed out.  2.4GHz radios just draw less power.  Older legacy devices are also not going to be upgraded anytime soon.  That means that we can’t just go around shutting off our 2.4GHz SSIDs and leaving all those devices out in the cold.  What it does mean is that we need to start focusing on the future of wireless.  I’m going to treat my 2.4GHz SSIDs just like a guest access VLAN.  It’s there, but it’s not going to get much support.  I’m going to enable band steering to push the 5GHz-capable clients to the better access method.  For everyone else that can only get on at 2.4GHz, you get what you get.  With more room to grow, I can enable wide channels and let my clients pull all the data they can stand from 5GHz.  When the rest of the world gets ready to deploy 802.11ac devices and APs, I’ll already have experience designing for that band.  My 2.4GHz network will live on much the same way my 802.11b clients lived on and my Novell clients persisted.  They’ll keep churning until they are forced to move, either by failure or total obsolescence.


Tom’s Take

Yes, it’s a hard choice to make right this moment to say that I’m leaving 2.4GHz to the wolves and moving to 5GHz.  It’s a lot like making the decision between ripping the band-aid off or pulling it slowly.  Either way, there will be pain.  The question becomes whether you want the pain all up front or spread out over time.  By making a conscious decision to start focusing your efforts of 5GHz, you get the pain out of the way.  Fighting for spectrum and positioning around kitchens and water pipes all fall away.  Coverage takes care of itself.  Neat new technology like 40MHz channels is simple, relatively speaking.  Let the 2.4GHz clients have their network.  I’m going to concentrate my efforts on where we’re headed, not where we’ve been.

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7 thoughts on “Death to 2.4GHz!

  1. Agreed! 2.4Ghz must die! But…it seems to me there must be warehouses full of surplus 2.4Ghz adapters because manufacturers like HP, Lenovo, Dell, etc. still ship thousands of devices that are single band 2.4Ghz only. This is not only a problem in the enterprise where the devices are supplied to the employees and often purchased in bulk, but in the BYOD world, the average consumer isn’t going to check and see if their getting single band 2.4 or a dual-band device before buying.

    Until some of the big name manufacturers get on board with shipping 5.0Ghz capable clients, I think we’re going to be hard-pressed to leave them out in the cold.

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  3. This is a mildly sensational post. 2.4GHz is not dead. Yes it has limitations, some of which are mitigated by 5GHz, but it certainly still has its uses and will continue to do so for the lifetime of 802.11 technologies.

    The way we need to think about 5GHz support in mobile devices is more about how it expands the capabilities of Wi-Fi deployments centred on mobile devices and less about how it will be replace the use of 2.4GHz in its entirety. (I admit there will be some shift away from 2.4GHz)

    Many environments still have reasonably clean spectrum (obviously not public hotspots or industrial environments) and the 2.4GHz band can be made to work well either in a single band deployment or in a dual band deployment. I would obviously take a Dual Band AP over a single band 2.4GHz or 5GHz AP any day (the benefits are obvious). But am I ready to throw away 60MHz of spectrum just because I perceive it to be crowded and flaky without actually testing it at a given location? Gods no. As an RF engineer I will take every available channel there is!

  4. 2.4GHz: “I’m not dead yet!” (in best cockney accent)

    Gonna agree with Robbie that this seems a bit sensationalized.

    I’m a huge advocate for 5GHz, in fact I just pitched it hard at Wi-Fi World Summit last week and left a comment on Matthew’s 5 by 5 post. But there are some interesting things going on to make better use of the channels in 2.4. If you haven’t already, take a look at what Ruckus did at TWC Arena in advance of the DNC. http://www.networkworld.com/news/2012/090412-dnc-wifi-262153.html?page=1

    All 11 channels utilized with very tight beam patters (30 degree arc, top mounted from the catwalks for most of the “bowl” coverage).

    5 GHz is a vast greenfield that we need to start exploiting, but that doesn’t mean we can’t keep mining 2.4 in creative new ways.

    Best,

  5. I have to respectfully agree with Robbie and Dave. Having designed very large public venues for years, we’ve been very much able to design and deploy WLAN’s on a high density basis. Well meaning individuals quote the impending plethora of devices and claim it’ll end up “not working”. It’s my experience that only those devices in range count directly with regard to their impact on the noise floor and link contention. You can step and repeat a three channel cell set indefinitely on a practical basis.

    Design methodologies and key design principles have not evolved to the same degree as the quantum leap from .11 to .11n. I’m still seeing nearly all omni’s in most deployments running near or at full output power. Often, WLAN clients use a standard approach of full power through an omni. The basketball arena I’m currently designing has omni’s with co-planar first Fresnel’s- they’ve been running that way for a number of years. Have seen that so often it’s usually one of the first things I check at a new site. Channel harmonization across a large facility (or small) is very helpful also, and if I may say, I’m not real thrilled with some of the auto RF capabilities offered by more than one OEM.

    There’s certainly more to a high performance WLAN than just how well the front end (the RF) works, but it’s reasonable to assume that the back end struggles to enhance a poorly designed and deployed front end.

    In conclusion, I definitely support Rob’s comment that we should use the 5 gig bands to enhance and expand what we have in 2.4. Abandoning 2.4 will only accelerate a similar predicament in 5 gig. I’m not aware of any RF system that’s had all the spectrum it wanted or could use; my view is to be clever about what we have, and advance our design skills to maximize the current spectrum allocation.

    My .02 cents.

    Neil Reid
    Dallas, Tx.

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  7. Sadly as much as we may all agree that the 2.4GHz spectrum is swamped and suffers from a multitude of performance limitations, with the predicted growth of the Internet of Things (IoT) it looks likely that it wont go away anytime soon as most first-generation IoT devices only support the 2.4GHz band.

    This will of course change over time and this change is likely to be quite rapid. So why continue in 2016 to install AP’s that have one of their two radios fixed on the 2.4GHz band? It simply makes no sense.

    Dual-band Software Configurable Radios is the way forward as this valuable feature allows for an evolutionary approach to WLAN configuration that is able to change over time to suit the ever increasing number of 5GHz capable client devices without the need to add more and more AP’s.

    Xirrus’s entire range of AP’s and Array’s support Dual-band Software Configurable Radios and what is more they also able to support 802.11ac on ALL radios that are configured to the 5GHz band, all at the click of a mouse.

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