Are we ready yet? Designing a 5GHz-only Wi-Fi network

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With the fast adoption of 802.11ac Gigabit Wi-Fi, more and more end-user devices flushed into the market are 5GHz capable. Those devices often support both 2.4GHz and 5GHz bands and can be connected to the 802.11ac and the legacy WLANs such as 802.11a/b/g/n. It often makes sense to design a network with more clients on the 5GHz band since it has higher capacity and less crowded than the 2.4GHz. However, does that mean we should move ALL clients to the 5GHz and abandon the 2.4GHz because the 5GHz has more channels and higher data rate? To answer the question, we need to look into Wi-Fi characteristics as we design the best network for digital workplaces.

The nature of Wi-Fi radios

Typically, if a runner is really fast, the distance he or she can run will be shorter; however, if he or she runs slower, the distance they can run will be longer. The same natural phenomenon also applies to Wi-Fi air radios: the faster the radio, the smaller the coverage area. For example, a 5GHz radio supports more clients than a 2.4 GHz radio because of its higher data rate; but the area a 5GHz radio covers will be less than a 2.4 GHz radio. Figure 1 shows the inverse situation.

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Figure 1: Capacity vs. Coverage Range in 2.4 GHz and 5GHz bands

The two radios serve the different purposes and can be leveraged to achieve the highest performance in a well-designed network. Simply moving all clients (assuming you can) to the faster radio may result an imbalanced Wi-Fi network that can't adapt to the changing environment.

The design of the Wi-Fi network

Today, most of the network architects design a network with the faster devices connected to the 5GHz band while keeping the slower devices on the 2.4GHz band. However, can we push it one step further by moving all clients to 5GHz? – assuming that all clients are 5GHz capable. The answer relies on your ability to design a well-rounded Wi-Fi network architecture; and if you have advanced radio technologies to balance and improve the radio performance. For example, the 2.4GHz might be crowded and has lots of interference, but these problems can be minimized with technologies like load balancing (Figure 2) and band steering.


Figure 2: Spectrum Load Balancing

A well-designed network should be able to allow different clients to dynamically connect to the best possible radios, based on the contextual characteristics of the clients.

Can we really eliminate 2.4GHz support?

As of 2016, there are about 2,000 Wi-Fi Alliance® CERTIFIED 11ac devices that operate with 802.11ac in 5GHz. We expect to see more and more 5GHz capable clients in coming years. However, are we ready to drop support of the 2.4GHz band in the enterprise environment?  There are a couple of facts for us to consider:

1. Are all end-user clients in the enterprise 5GHz capable?

Unfortunately, no. There are still a lot of older phones in use with 2.4GHz only such as the iPhone 4S. Even new comers like the Apple watch supports 2.4GHz only. The new Internet of Things (IoT) like security cameras, lighting and Wi-Fi thermostats often support 2.4GHz only as well due to cost and power constraints on these devices. All of these, either legacy or new, are part of our enterprise WLAN.

Imagine, your office printers can't be used due to the lack of 2.4GHz connection; even your trendy Apple watch can't connect to Wi-Fi.

2. Do we want to move the guest networks to 5GHz?

Probably not. We still see numerous reasons to keep the guest networks on 2.4GHz. One of the main reasons is to take advantage of all bands, both 2.4 & 5, to get the most performance out of the limited RF resources.

Additionally, since 2.4GHz has a higher usable range from the AP, enterprises often want to retain this range for ensuring coverage across a large campus.

Now, back to the question: should we design a WLAN with 5GHz only and abandon the 2.4GHz in the enterprise environment? Like the highway analogy:  it sounds awesome if we can drive all cars in the fastest lane. But imagine, if you have to drive your Jaguar or Ferrari along side a Fiat, a Nissan leaf or even a tractor. With that in mind, I really hope there is a slower lane or a local road for those drivers. As the balance of high-performance Wi-Fi network should maintain!