Wi-Fi 6: What’s New

With each successive new Wi-Fi standard, there are almost always improvements to the wireless speed and latency, and that continues with Wi-Fi 6, but the latest standard also improves power efficiency, and likely most importantly, helps address some of the typical issues with Wi-Fi in very crowded environments.

Let’s start with the last point, since it is arguably the most important. As Wi-Fi has become ubiquitous, and as the number of connected devices has grown, one of the biggest issues it has become susceptible to is overcrowding of the spectrum, which can cause even the best networking equipment to slow to a crawl. This is especially obvious in dense urban environments, or stadiums, or theme parks and the like.

What’s your frequency, router?

Only a few years ago, even mid to high tier laptops would ship with just 2.4 GHz 802.11n (Wi-Fi 4) network adapters. If they were to be used in a dense apartment complex, the resulting performance would be abysmal. Moving to the 5 GHz range provided some temporary relief, partly because of the reduced range of the 5 GHz signal, meaning neighboring access points would be less likely to interfere, but also due to 5 GHz offering significantly more channels. 2.4 GHz can only provide a maximum of three non-overlapping channels, but depending on the regulations of each country, there are a total of fourteen total channels, each being 22 MHz wide, but offset by only 5 MHz, so channels side by side will interfere with each other. On the 5 GHz side, there can be up to 23 channels, and none of them overlap.

5 GHz Channel Use in my home

If you needed range, 2.4 GHz was still your best bet due to the attenuation of the 5 GHz signals through solid objects like floors and walls, but in a dense environment, 5 GHz was practically a must-have for any wireless communication.

2.4 GHz Channel Use in my home

But even the 5 GHz space is now getting stretched to its limit, so the Wi-Fi Alliance has added some features to address the crowded spectrum directly. One of the major additions to combat this is Orthogonal Frequency-Division Multiple Access, or OFDMA, which breaks the spectrum into time-frequency resource units, which are coordinated by the access point. These resource units can be allocated to multiple connected devices, allowing them to transmit over the same channel at the same time, as long as the total bandwidth does not exceed the channel width. Previously, every transmitting device would occupy the entire channel for the entire time it was transmitting, so if multiple devices were competing, they would have to wait their turn using Time-Division Multiple Access, where each device would be given a slice of time to transmit. OFDMA spreads out channels to many clients, which can be very beneficial, especially if no single device requires all of the available bandwidth. In addition, Wi-Fi 6 allows for dynamic fragmentation of the packet size, allowing the device to fill available resource units with smaller packets, unlike previous Wi-Fi which required a fixed packet size.

Another interesting trick the Wi-Fi Alliance has added to combat crowding of the spectrum is Spatial Frequency Reuse, which allows devices to figure out if signals that are being transmitted are part of their network, or part of a neighboring network. This means that, for example, two people in an apartment complex were both using Wi-Fi 6 access points and devices, the devices connected to their own access point would be able to read a marker on the channel transmission and determine if that transmission is on their network or not. If it is not, and if the power levels are sufficiently low, the wireless device would be able to also transmit on the same channel at the same time. The devices would adapt their power levels for transmission to avoid them actively interfering with each others’ transmissions.

In addition to this, Wi-Fi 6 also adds an additional network allocation vector (NAV) which should help prevent packets being reset by overlapping networks.

Even with these changes, the Wi-Fi Alliance knows that there is still only a fixed amount of bandwidth even in the 5 GHz range, and as such 6 GHz support is already in the specification, although it will be limited to devices labeled as Wi-Fi 6E, to keep things at least a bit confusing.

A Bonding Moment – Doubling Down on Performance

Although the nominal channel bandwidth for Wi-Fi is 20 MHz, the Wi-Fi specifications have allowed for bonding of multiple channels together to provide higher performance channels. Wi-Fi 4 allowed for 40 MHz channels, and Wi-Fi 5 allowed for 80 MHz and 160 MHz, although the latter was optional, and we didn’t really see it in the PC space until recently. Because it was not a requirement, many Wi-Fi 5 access points and routers did not support it, even if you had one of the most recent wireless adapters which even offers 160 MHz support. Wi-Fi 6 supports the 160 MHz channel width, so we should see more devices adding support. But a drawback of bonding is that it requires concurrent channels to function, and with a limited number of channels, if you had a lot of interference on one channel, it could cause issues. This has somewhat been addressed in Wi-Fi 6 with “80+80” bandwidth, which means that the 160 MHz bonded channel can be made up of two different sets of 80 MHz channels. This was again available in the previous spec, but optional.

To further increase performance even further than just wider channels, Wi-Fi 6 also adds support for an even higher level of Quadrature Amplitude Modulation (QAM), from 256-QAM in Wi-Fi 5, to 1024-QAM in Wi-Fi 6. This moves from 8 bits per tone to 10 bits per tone, allowing more data to be transmitted over the same channel bandwidth. This means that a single 1x1 20 MHz channel can transmit at a maximum of 143 Mbps, and on a typical laptop with a 2x2 Wi-Fi adapter on 160 MHz channels can connect at 2.4 Gbps. The same 2x2 solution on a typical Wi-Fi 5 access point with the typical 80 MHz channel width offers just 867 Mbps, so the jump in performance for Wi-Fi 6 is significant.

16-Level QAM - By Chris Watts - Own work, CC BY-SA 3.0, Link

In addition, Wi-Fi 6 adds in support for Multi-user Multiple-input and Multiple-output (MU-MIMO) to the uplink connection as well, where Wi-Fi 5 only offered it on the downlink side.

Do I need it?

The eternal question with networking is when is a good time to upgrade, and do the latest and greatest additions to the specification provide tangible benefits right now. This is always complicated on Wi-Fi by a lag between access points or routers and devices, and what the upgrade cadence is. Wi-Fi 6 is new enough that many people may not own devices that even support Wi-Fi 6, so upgrading to a new router or access point without devices supporting the new Wi-Fi 6 standard will mean that your devices are still leveraging Wi-Fi 5 or below, meaning there isn’t really a good reason to jump. If you are in the market for a new router or access point anyway though, clearly it is in your best interest to get the latest specification of the standard.

Where Wi-Fi 6 is going to add real-world benefit though is in a couple of scenarios. If your wireless spectrum is very crowded due to being in a dense urban environment, Wi-Fi 6 makes some significant upgrades to its networking stack to help address just that type of use-case. In addition, if you’ve got dozens of devices fighting over Wi-Fi, it may make sense, although the best benefits are achieved when both the access point and client are utilizing Wi-Fi 6.

Performance is also dramatically increased over Wi-Fi 5, so clearly in performance-bound scenarios, the upgrade may be worth the investment, although the tricky part about Wi-Fi 6 is that for the most common 2x2 scenario, where there are two transmit and two receive channels, Wi-Fi performance finally surpasses that of the typical Gigabit Ethernet that most people have in their homes, so although the performance will still be higher than Wi-Fi 5, Gigabit may be a bottleneck, and if so, additional networking equipment may be necessitated. There has been some movement on the multi-Gigabit Ethernet for the consumer, but less than we’d have expected at this point, so Wi-Fi to Wi-Fi may be the least-expensive option for best performance.

Introduction The 2020 AnandTech Wi-Fi Test Bed
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  • Mccaula718 - Wednesday, February 12, 2020 - link

    Why is the WAN port only 1 Gbps? Reply
  • 5080 - Wednesday, February 12, 2020 - link

    You can always combine a WAN and LAN port into dual WAN to double the throughput. I have an ASUS RT-AX88U connected to an ARRIS SB8200 with Link Aggregation to take advantage of a 1.2Gbps internet connection. Reply
  • Makaveli - Wednesday, February 12, 2020 - link

    Sounds like you are on a 1Gbps cable connection why bother with Link Aggregation?

    do you actually see the slight over provision on the connection?
    Reply
  • deil - Wednesday, February 12, 2020 - link

    at my place you can get either from 250/50 Mb/s to 1000/50 Mb/s from anyone that is quite cheap or 3000/500 from one for insane price (~20x more).
    I am planning for now to use that for both reliability of the uplink (I know ISP's use different nodes when they leave my place) and faster bandwidth (I have fiber to my place and cat 6 (5GB/s) internally.
    Reply
  • 5080 - Wednesday, February 12, 2020 - link

    It peaks at about 1.1Gbps on LAG and 0.85Gbps on one. Reply
  • Dug - Wednesday, February 12, 2020 - link

    1Gbs outside may actually be 1Gbs. Inside 1Gbs isn't 1Gbs because of overhead when you have multiple connections. So with aggregation you can benefit multiple connections going outside. Reply
  • azfacea - Thursday, February 13, 2020 - link

    this is getting really ridiculous. wired lan is going from "slower" than wifi to "much slower" than wifi. If aliens came down to earth i am not sure what they would think of this lunacy. Reply
  • zshift - Thursday, February 13, 2020 - link

    This isn't the case. 2.5Gbps and 10Gbps Ethernet has been out for a while now, it's just not propogating to consumer hardware because it isn't needed in most scenarios. Ethernet can maintain these high data rates over very long distances. This article showed that even wifi 6 across a few rooms drops to below 500Mbps. Higher wifi speeds are needed in order to compete with Ethernet over a long distance, but it's still far more stable (though not easier) to drop Ethernet throughout your place to get near 1Gbps with older routers. Reply
  • RadiclDreamer - Friday, February 14, 2020 - link

    10gb, 25gb, 40gb and 100gb are commonplace in the business space, they just havent filtered down to consumers due to lack of demand.

    Keep in mind also that wifi is simplex (or half duplex) meaning that it can only send or receive but not both at the same time. You also have a lot of overhead on wifi that leads to these numbers not being as good in practice as you might think. Take a normal AC router for example, and lets say you are connected at 867mbps, thats for the entire link, not just the payload. You have WPA2 overhead, errors, retransmitted frames, interference with your neighbors/other devices, TCP/IP overhead (which is present on ethernet also) to contend with and you are going at 1/2 duplex. All of this together means that you are going to actually see about a 400mbps connection for payload.

    This is not to snub wifi, its getting very good very fast. But to say that it even comes close to competing with a hardwired connection is just not understanding the technology and whats out there.
    Reply
  • Makaveli - Friday, February 14, 2020 - link

    Wifi being half duplex only applies to everything Pre Wifi 6 (AX).

    AX is full duplex.
    Reply

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