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The sixth generation of WiFi – IEEE 802.11ax, or WiFi 6 to its mates – made its debut at the back end of 2019 and is now a well-established standard with pretty much every infrastructure and WiFi client manufacturer supporting it. However, in the last month or so we have started seeing infrastructure access points (like these, from ASUS and Netgear) for a new iteration, known as WiFi 6E.

Although WiFi 6E was planned (it falls under the 802.11ax standard), this extension was made possible by some bold regulatory moves in 2020. In April, the Federal Communications Commission unanimously voted to adopt a proposal opening up 1200MHz of bandwidth in the 6GHz (5.925–7.125 GHz) band for unlicensed Wi-Fi use. Here in the UK, Ofcom followed suit with their own statement in July. This band had historically been mostly unused except for emergency broadcasts.

WiFi 6

To fully appreciate the significance of opening up this new spectrum, we should perhaps consider what the original iteration of WiFi 6 delivers.

Spectra

Let's start with the spectra used by WiFi 5 (802.11ac): it's surprisingly uncommon knowledge that this only operates in the 5GHz (from 5160-5730Mhz) band. The 2.4GHz (2401-2495Mhz) band on dual-band WiFi 5 access points is actually running the older 802.11n standard. WiFi 6 uses both the 2.4 GHz and 5 GHz bands. This, along with a higher PHY rate, allows WiFi 6 to deliver a maximum data rate much closer to the theoretical maximum of 9.6Gbps than WiFi 5 ever managed to get in terms of its own maximum of 6.9Gbps.

Efficiency

To understand WiFi 6, it is useful to appreciate how forward-looking it is. Where previous WiFi standards were all about greater speed, WiFi 6 is primarily about capacity i.e. the ability of a network to reliably sustain a set number of clients and co-exist with other wireless networks in a high device-density environment, like shopping malls, hospitality, offices and high rise apartment buildings.

How is this extra efficiency achieved? Good question. There is actually a long list of features that add to the efficiency but in the interests of keeping this short, I will only highlight a couple of those with the highest impact to give a flavour of what is going on.

OFDMA (Orthogonal Frequency-Division Multiple Access)

Where previous Wi-Fi standards used OFDM (Orthogonal Frequency-Division Multiplexing) to encode data into multiple subcarriers frequencies, Wi-Fi 6 uses a more efficient method borrowed from 4G cellular networks called OFDMA.

In OFDM, each subcarrier is orthogonal (out of phase by 90°) to the next, reducing interference from adjacent subcarriers without the need for empty guard bands between carriers. It is effectively the same as DMT used in wired systems like DSL. Each of these 1024 subcarriers only carries data for one client at a time and any spare capacity is wasted. OFDMA takes OFDM and subdivides each subcarrier into smaller units, called Resource Units (RUs) which are allocated to clients and coordinated by the Wireless access point so that each subcarrier can carry data for multiple clients. Think of lots of clients sharing a shipping container so that it is full when loaded onto a ship, rather than each client sending a mostly empty container with just their own stuff in it.

1024-QAM

QAM (Quadrature Amplitude Modulation) is how signals are modulated in Wi-Fi. In simple terms, we take two SIN waves of the same frequency (therefore the same subcarrier) that are out of phase by 90°. They are known as the In-phase (I) and Quadrature (Q) signals and are mathematically combined to make a single wave. The signal amplitude is also varied. The resulting signal is a vector of both amplitude and phase that can be represented in a constellation diagram like this:

16 QAM Constellation

In this example constellation, we can see that 16-QAM has 16 different possible combinations of amplitude and phase, which allows us to represent any number from 0 to 15 in decimal (or 0000 to 1111 in binary). Wi-Fi 5 uses 256-QAM (8 bits) while Wi-Fi 6 uses 1024-QAM which has a 1024 point constellation, representing 0 to 1023 or 0000000000 to 1111111111 which is 10 bits and provides a 20% capacity increase over Wi-Fi 5. So, if OFDMA allows clients to share a shipping container, 1024-QAM provides bigger containers.

Final Thoughts

Wi-Fi 6E isn’t so much a technology upgrade as a spectrum upgrade. Opening the 6GHz band is the biggest additional allocation of spectrum to Wi-Fi since 1989. It essentially quadruples the amount of bandwidth (14 additional 80MHz channels, and seven additional 160MHz channels) available for access points and smart devices.

If Wi-Fi 6E has a downside, it's that the 6GHz wireless spectrum, by definition, uses shorter wavelengths. While short wavelengths are great for fast data transfers, they attenuate faster over long distances and incur greater interference from physical obstructions like walls and floors in buildings.

That being said, now seems like a good time to get a new router.

Mark completed his Electronic Engineering degree in 1991 and worked in real-time digital signal processing applications engineering for a number of years, before moving into technical marketing.
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