Suffering from Wi-Fi Congestion? Dual 5 GHz Radios Can Help


Let me put this to you: You have multiple access points in your network and you’re experiencing performance issues on the 2.4GHz frequency band. If I could give you the option of switching your older 2.4GHz radio in your current access point to a newer 5 GHz radio (dual 5 GHz), would you do it?

WLAN (Wireless LAN) engineers know that a good dual-band Wi-Fi design will have some 2.4 GHz radios turned off in some access points to reduce interference. Whilst it is a good design to turn off some 2.4 GHz radios, by doing so, that lovely access point you’ve paid $800 for is effectively only using half of its functionality. Maybe it would have been better to pay $400 if you’re only using half of the access point?

So… we know it’s a good design to turn off some 2.4 GHz radios in your access points, but in doing so, I’m only using half of the access point. What can I do?!

In this article, I’m going to address the issues experienced with the 2.4GHz frequency band and explain the solution to help you achieve better network performance and superior Wi-Fi design.

2.4 GHz – The Legacy Band

For over 10 years, the 2.4 GHz band has been extensively used across all Wireless LANs. It’s no secret that this has helped drive the success of Wi-Fi globally. However, that success has also been the 2.4 GHz downfall.

The Wi-Fi boom saw a huge shift in technological devices that were able to connect to a wireless network. Most of these devices were connecting to the network on the 2.4 GHz frequency band, but they weren’t the only devices using this frequency. Microwave ovens, baby monitors, electronic garage doors, and Bluetooth devices are just a few examples of devices that also operate on the 2.4GHz band. This boom in devices resulted in severe congestion on the network.

The 2.4 GHz band only has 3 non-overlapping channels (typically used in a 1, 6 and 11 configuration), so it was always going to be limited in capacity. “What on earth is a non-overlapping channel?” This is probably what some of you are thinking. Well, this is where the techy bit comes in.

The channels on the 2.4 GHz spectrum are 20 MHz wide, with each one separated by 5 MHz. The entire 2.4 GHz spectrum is around 100 MHz wide and has 11 selectable channels within it. Ultimately fitting this many channels into such small space means that some of the channels end up overlapping with each other. This is what we call adjacent-channel interference in Wi-Fi.

Most households, offices, bars, restaurants and even some cars offer the ability to connect to a wireless network. With so many wireless networks around, it’s virtually impossible to have a completely clean 2.4GHz spectrum. The end result is a congested frequency band with limited scalability.

5 GHz – The present and future

We know the 2.4GHz band has 3 non-overlapping channels, but what about 5GHz? Well, 5GHz is a wider spectrum and as a result, has 25 non-overlapping channels (in the USA).

For the last ten years, most devices that are Wi-Fi enabled have been solely 2.4 GHz compatible. It’s only been the last two to three years where we’ve started seeing everyday devices manufactured and shipped with 5 GHz capabilities.

One of the biggest benefits of 5 GHz is that it provides the foundation for the newest Wi-Fi standard: 802.11ac. This standard offers denser modulation schemes, wider channels, more spatial streams (up to 8×8 with the relevant hardware) and more, which is why it’s faster than older Wi-Fi standards like 802.11n. It’s worth pointing out that whilst 802.11ac is backward compatible with older Wi-Fi standards, it is 5GHz-only, and as a result, cannot be used on the 2.4 GHz band.

2.4 GHz vs 5 GHz

Let’s take a comparative look at the two frequencies or ‘bands’ that we currently use in Wi-Fi. You’ve heard the numbers 2.4 and 5 mentioned numerous times throughout this article, these are the frequency bands that we use to connect clients to a wireless network.

  • Range – One of the main differences between the two bands is the propagation properties of the signal (how far your data can travel). 2.4GHz has a longer range then 5GHz due to the fact 2.4GHz is a lower frequency. Higher frequencies are absorbed by environmental objects like walls and doors more than lower frequencies. Thus 2.4GHz range is further than 5GHz.
  • Interference – Interference in Wi-Fi is incredibly common. The more interference there is on a given frequency, the worse your network will perform. Microwave ovens, cordless phones, and baby monitors are all common sources of interference on the 2.4GHz frequency band. The 5GHz frequency band sees a lot less interference than the lower 2.4GHz frequency band.
  • Speed – The 5GHz frequency band allows for higher data rates compared with 2.4GHz.
  • Channels – Wireless communications are transmitted on specific frequencies. These are known as channels. In the 2.4 GHz band, there are only 3 non-overlapping channels 1, 6 and 11, whereas the 5 GHz band has 25 non-overlapping channels! (in the US)

Software Selectable Dual 5GHz Radios

Now we can talk about the really cool technology: software-selectable Dual 5GHz radios in an access point. We’ve already discussed that the 2.4GHz frequency band has limited capacity, and how it’s overcrowded and is limited in speed. And how the 5GHz frequency band is bigger and faster.

We also know that most access points shipped around the world are dual-band, which means they have one 2.4GHz and one 5GHz radio within them. With a software-selectable dual 5 GHz band access point, you have the ability to switch the 2.4GHz radio into a second 5 GHz radio. So, instead of being a dual-band 2.4 GHz and 5 GHz access point, you now have a single band, dual 5GHz access Point. This technology allows for flexibility, better network efficiency, and optimal Wi-Fi design.

So, why would I want a software-selectable dual 5 GHz band access point?

ROI (Return on investment) – One of the key benefits of a software-selectable dual 5 GHz radio access point is ROI. For example, in many schools, the typical Wi-Fi deployment is one access point per classroom to account for the high-density nature of the client load. As a result, many WLAN Administrators end up turning off 2.4GHz radios on various neighboring access points to prevent CCI (co-channel interference).

Whilst turning off some 2.4 GHz radios on your access points may improve network performance, it actually means you’re only using half of the Access Point that you have invested in.

With a software-selectable dual 5 GHz access point, you can switch the 2.4GHz radios that would normally be switched off to prevent CCI to be a second 5GHz radio. This allows for greater client capacity and allows you to continue using the full potential of the access point.

High-Density Environments – High Density (HD) or Very High Density (VHD) are areas where clients are connecting to the WLAN within a small confined space. An example of a VHD or HD environment can be an auditorium, gymnasium, or cafeteria.

Due to the large number of clients wanting to connect to the WLAN, more access points than usual will be needed. More clients connecting to the WLAN, generally mean more bandwidth will be required which is not scalable on the 2.4 GHz band.

Another factor to consider in HD/VHD environments is the type of applications that will be used. Many VOIP applications like Skype and GoToMeeting can be bandwidth-intensive, and as a result, they may encounter latency or jitter problems when connected to the 2.4GHz band.

This situation also applies when watching HD videos via Netflix of YouTube. You may experience severe buffering or a complete loss of video altogether. Switching to software-selectable dual 5GHz can alleviate these problems when operating in an HD/VHD environment.

Manufacturing Environments – Most manufacturing environments have an incredible amount of 2.4 GHz interference due to the challenging nature of Radio Frequency (RF).

Multipath can be a huge problem in the manufacturing environment. Multipath occurs when the transmitted signal reflects off various environmental objects, causing multiple copies of the same signal to arrive at the receiver. In 802.11a/b and g clients, multipath causes data corruption. Multipath with 802.11 n/ac clients is actually good because the antennae can receive out of phase signals and put them back in the correct order.

Reflection, absorption, and signal scattering are all common issues experienced alongside multipath in this kind of environment. Many of the clients connecting to the WLAN are only 2.4 GHz compatible it’s imperative that the 2.4 GHz band is functioning as well as it can.

In manufacturing/warehousing environments where metal shelving is common, having the flexibility to switch the 2.4GHz radio to a second 5GHz radio can improve client performance and simplify the deployment.

Multi-Tennant Buildings – Imagine you’re in an office working on the 5th floor of a multi-tenant building. How much 2.4GHz signal bleed over can you expect?

It’s incredibly common for office workers to experience client connectivity problems on the 2.4GHz band. This stems not only from neighboring access points to the left or right of your office. But also from neighboring access points located above and below your office (this is known as signal bleed over). Adding other devices like microwave ovens, CCTV cameras, and Bluetooth devices into the mix just add further strain to an already over-utilized band.

Switching to a software configurable 5GHz radio can allow client devices that are 5GHz compatible to connect to a clearer, less contended band. This will significantly help with client performance.

In conclusion, the 2.4GHz frequency band is overcrowded and limited in capacity. The 5GHz frequency spectrum is bigger, less congested, and allows for higher data rates. Having the ability to change the 2.4 GHz radio in your access point to a second 5GHz radio can reap huge benefits on network performance.

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About the Author
David Coleman
Director, Wireless Networking at the Office of the CTO

David D. Coleman is the Director of Wireless Networking at the Office of the CTO for Extreme Networks. David is a technology evangelist, public speaker and proficient author.

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