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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  • Samus - Friday, February 14, 2020 - link

    Well sure, I have clients downtown with Gigabit fiber from Cogent, who offers speeds up to 10Gbps, but that isn't residential. The install alone is $5000 and it only covers the 'loop' (downtown business district.)

    I live 15 miles outside of the loop, technically in a Chicago suburb (Evergreen Park) and get AT&T Fiber, run inside my house from the pole, to a media converter that converts it to Ethernet.

    I've read some peoples installs only use one strand of fiber (so half duplex) but report identical speeds with just slightly higher latency (around 10ms) so it really depends on the ISP's implementation.

    But again, I doubt there is anywhere in the US you could find an ISP offering 'residential' internet service at beyond gigabit speed. And the router in question here is a consumer router with a gigabit uplink, so I think that's probably fine...for now :)
  • Mvs321 - Thursday, February 13, 2020 - link

    I live in Denmark, I pay around 36 dollars per month for a 1GB connection, to me it seems pretty cheap, but what do you pay?
  • asfletch - Thursday, February 13, 2020 - link

    In Australia, I pay more than that for a rubbish 50mbs connection. Not even joking. About US$50. Our federal Govt is so full of flat-earthers it nixed FTTH as being a threat to existing news and cable companies. Sigh.
  • PeachNCream - Thursday, February 13, 2020 - link

    My ex lives in Canada. Bell offers a max of 1.5mbit and a there is a 20GB per month cap. This is just south of Ottawa so I don't think your experiences can be fairly applied to the entire nation.
  • 29a - Thursday, February 13, 2020 - link

    I'm in the US and I used to get 12Mb from Frontier but the phone line got knocked down so Frontier just tied it to a tree instead of replacing the pole and now I get 9Mb. (true story)
  • bcronce - Wednesday, February 12, 2020 - link

    Because ping spikes? Because of larger buffers, TCP windows tend to size themselves to your link rate and not your sustained provisioned rate. If your wifi device is consuming 3Gb/s for 30ms to upload that picture you just took, packing it up and sending to the AP. Then you AP attempts to send that data at 1Gb/s, now you have a 100ms ping spike, even if your average rate is 83Mb/s for one second.

    I can generate ping spikes and packetloss on a 1Gb/s connection streaming videos with an "average" of 30Mb/s. Micro-bursts. I've fixed this at my home by smoothing out the bursts with traffic shaping. You drop and delay a few strategic packets to prevent a massive burst of loss and latency.
  • Makaveli - Wednesday, February 12, 2020 - link

    ping spikes are a huge issues on Cable internet because of its asynchronous nature of it. Saturate that 30mbps upload bandwidth on that 1Gbps connection and everything gets affected. You need room just for the ACK packets. And glad I don't to deal with that anymore.
  • Billy Tallis - Wednesday, February 12, 2020 - link

    I think you mean asymmetric, not asynchronous. But yeah, anything beyond about a 20:1 ratio is basically false advertising on the downstream speed.
  • Makaveli - Wednesday, February 12, 2020 - link

    Yes you are correct I noticed it after but no edit in comments :(
  • bcronce - Wednesday, February 12, 2020 - link

    The small town ISP here only sells dedicated symmetrical FTTH connections. They have enough trunk and peering bandwidth to allow microbursts. I've seen 1Gb microbursts all the way from YouTube Europe and I'm in the middle of the USA.

    Actually, higher RTT routes tends to have higher bursting. Current TCP implementations are only paced by ACKs. If the TCP connection is idle and data is to be sent, the sender will send an entire TCP window worth of data instantly at full line rate. You can feel it when a 100Gb/s youtube server attempts to send you a 250KiB chunk of a video stream.

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