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Wi-Fi 4/5/6 (802.11 n/ac/ad/ax)
(make educated wireless router/AP upgrade decisions)
(cut through all the marketing hype)
duckware.com/wifi -- January 15, 2018
Version 4.5f (updated 2019/03/28)

1. Executive Summary
2. The need for faster wifi
3. Wifi's weakest link - the client
4. Client 'PHY' speed is key
5. Understanding Wifi Overhead
6. Router Marketing Hype
7. MIMO - a wireless revolution
8. Legacy 802.11 Wi-Fi
9. Wi-Fi 4 - 802.11n
10. Wi-Fi 5 - 802.11ac
11. Wi-Fi 6 - 802.11ax
12. Extended/DFS channels
  13. WiGig - 802.11ad
14. WAN to LAN throughput
15. Router wifi setup
16. Tri-band hype
17. Recommendation
18. A Reality Check
A. Troubleshooting
B. Router/AP Reference
C. Netgear 'Mode'
D. Terminology
E. Learn even more
F. Contact us


1. Executive Summary
UniFi nanoHD
UniFi nanoHD 4x4 802.11ac Wave 2 AP
Wifi speeds vs. broadband speeds: Wifi speeds have not kept up with increasing Internet speeds. As a result, there has been a rapid switch in wifi from Wi-Fi 4 (2.4 GHz 802.11n) to Wi-Fi 5 (5 GHz 802.11ac) in an attempt to keep up. So what new router/AP should you consider buying?

Router Manufacturers Marketing Hype: Don't be fooled by the marketing hype of router manufacturers advertising outrageously high aggregate (all bands) Gbps wireless speeds. No matter how fast a router is 'capable' of going in aggregate, in almost all situations, your client wireless devices are the weakest link (not the router) and will limit speeds.

The weakest link: Wifi throughput to a 802.11ac wireless device will likely max out at around 360 Mbps (for 2x2 MIMO) to 720 Mbps (for 4x4 MIMO) no matter what 4×4 router is used (at a distance of 32 feet). And the far majority of ALL wireless devices today (smartphones, tablets, laptops, etc) are still only 2x2 MIMO. So your client device is almost certainly causing slow wifi speeds (and maybe not your existing AP/router).

The best router/AP today: A high quality 802.11ac Wi-Fi 5 "Wave 2" 4x4 router/AP supporting beamforming and all extended/DFS channels is the way to go right now (as of Mar 2019), due to the incredible value (one such AP is right, for only $158 on Amazon). Also, see the Router Appendix far below.
But what about 802.11ax Wi-Fi 6? The 802.11ax specification is still a DRAFT (not final). It will be years (well into 2020) before there is a sufficient number of Wi-Fi 6 client devices to make a Wi-Fi 6 router worth it (benefits are only for Wi-Fi 6 clients), and by then, the next generation of "Wi-Fi 6 certified" (non-draft) routers will be out -- so just be patient.

2. The need for faster wifi
Netgear R7800 R7800 (AC2600) Nighthawk X4S
The goal of this paper: This paper was written to help people understand current wifi technology, so that they can make an educated 'router' upgrade decision -- because there is way too much hype out there.

Problem: Wifi spectrum is a limited, shared resource. Any number of access points (both yours and neighbors) can all share the SAME wifi spectrum. But because wifi use has exploded over the last few years (tablets, laptops, smartphones, TVs, Blu-rays, security cams, thermostats, etc) the wifi spectrum is way overcrowded. And when combined with ISP Internet speeds now often times faster than fast ethernet (100Mbps), and sometimes even 1 Gbps, wifi speeds have not kept up.

Solution: The industry solution is a rapid move from the old 802.11n 2.4 GHz wifi spectrum to the much newer 802.11ac 5 GHz spectrum, where speeds are much faster, due to more available spectrum (over seven times as much) and new wifi features, such as MIMO.

BUT, as will be shown in the next section, it is still not fast enough -- mainly due to limited 2×2 MIMO support in almost all of today's wireless devices.
But let's also be very realistic. If you have 250 Mbps (or less) Internet speeds, 2×2 MIMO Wi-Fi 5 to your router is almost always sufficient (with a high quality "wave 2" 4×4 MIMO 802.11ac router).

3. Wifi's weakest link - the client device!
The weakest link is YOUR client device: You have 1 Gbps Internet, and just bought a very expensive AC7200 class router with advertised speeds of up to 7.2 Gbps, but when you run a speed test from your iPhone XS Max, you only get 350 Mbps. Same for iPad Pro. Same for Samsung Galaxy S8. Same for a laptop computer. Same for most wireless clients. Why? Because that is the speed expected from these (2×2 MIMO) devices! This section explains in great detail exactly why that is. You may safely skip to the next section for a shortcut if this section is too detailed/technical for you.

  AC5300 4×4 Router to 2×2 Client
(at a distance of 32 feet)

5300 → 2166 → 1083 → 866 → 650 → 357
 

  AC5300 4×4 Router to 4×4 Client
(at a distance of 32 feet)

5300 → 2166 → 1733 → 1300 → 715
 

5300 → 2166: Maximum ONE band speed: Router manufacturers combine/add the maximum physical network speeds for ALL wifi bands (usually 2 or 3 bands) in the router to produce a single aggregate (grossly inflated) Mbps number. But the only thing that really matters to you is the maximum speed of a single 5 GHz band (using all MIMO antennas). You find out by looking at the 'tech specs' for an AP/router. 5300 is just 1000 + 2166 + 2166, where 1000 is the 2.4 GHz band speed and 2166 is the 5 GHz band speed. 2166 also is a tip-off that this router is a 4×4 MIMO router (by looking for '2166' in the speed table, right).
More on bands in the Beware tri-band marketing hype section far below.
2166 → 2166: Realistic channel width: Router manufacturers cite speeds for 2.4 GHz using 40-Mhz channel widths, but a 20-Mhz channel width is much more realistic (that cuts cited speeds in half). For 5 GHz 802.11ac, speeds are typically cited for an 80-Mhz channel width, which all AC clients are required to support. But if cited speeds are for a 160-Mhz channel width (that is starting to happen for the new Wi-Fi 6 routers), cut the cited speeds in half (as most clients won't support that).

2166 → 1083: Client MIMO: Which MIMO column do you use in the wifi speed table (right) -- The MIMO of the router or the MIMO of the client device? You must use the minimum MIMO common to both devices (often the client). So if you have a 4×4 router, but use a 2×2 client (like the Apple iPhone XS Max or Samsung Galaxy S8) to connect to it, maximum speeds will be instantly cut in half (2/4) from cited router speeds.
Wi-Fi specifications for iOS devices (in appendixes, # in "Spatial streams" column is MIMO level). Virtually all newer devices are 2×2 and older devices are 1×1.
1083 → 866: Client QAM: You can only use the maximum QAM support by both the router and the client. Router manufacturers may cite speeds for 1024-QAM (which the router DOES support), but no client device today supports 1024-QAM. [source] And even if they did, you would need to be VERY close (just feet) from the router to get this crazy high QAM level. And even then you may not get this high QAM. So reduce to a much more realistic maximum of 256-QAM 5/6.

866 → 650: Modulation/Coding: Also known as PHY speed / distance from router. Router manufacturers love to cite the maximum PHY speed possible, which you will only when you are very close (just feet) to the router. But as you move further away from the router, speeds gradually decrease. The 'distance' issue is represented by rows in the PHY speed table (seen upper right). At just 32 feet away from the router (a very typical distance), 64-QAM 5/6 was actually observed, so use that. For more details, see the next section.
Understanding Modulation/Coding: Imagine that once a second, you hold up your arms in various positions to convey a message to someone else. If you were only ten feet away from that person, the number of arm positions reliably detected would be very high. But now move 100 feet away. The number of arm positions reliably conveyed would be reduced. Now move 500 feet way. The number of arm positions reliably conveyed might be reduced to just 'did the arm move at all'. The same thing happens in wifi. If you are close to the AP/router, a large number of bits can be conveyed 'at once'. But as you move away, a smaller and smaller number of bits can be reliably conveyed 'at once'. So 'modulation/coding' is simply how much information can be conveyed at once, and is directly related to distance from the AP/router.
650 → 357: MAC efficiency: What is the overhead at the network level? All of the speeds we have discussing so far are for PHY (physical) network speeds. But due to wifi protocol overhead, speeds at the application level are around 50% to 70% the physical network level. So use 55% as an estimate of throughput you can expect to see. 55% of 650 is 357 Mbps.
Just Google 802.11ac MAC efficiency to understand this issue. In short, there are 'housekeeping' packets that MUST be sent at the SLOWEST possible modulation, and that takes time and slows everything down.

Analogy: You are on a road going 10 mph, but every 100 feet you must slow down to 1 mph for 10 feet.
357 → ???: Interference: So, the final number is 357 Mbps for a 2×2 device, but only if your device gets exclusive use of time left in the wifi channel. But there may (or may not) be other wifi users (either local, or even neighbors on the same spectrum) which will decrease your speed by some unknown amount.

Results: 2×2 MIMO devices get a realistic download speed of 357 Mbps, which is dramatically lower than the '5300' advertised by router manufacturers. 4×4 MIMO devices will get a realistic download speed of 715 Mbps from this 4×4 router.

A lesson learned: The two critical factors that greatly impact and determine maximum real-world speed for a single client are: (1) lowest common MIMO level support and (2) MAC efficiency.
An analogy for all of the above: What if I built a three lane toll road from Washington, DC to New York, NY, and sold passes for chauffeured rides with speeds "up to 74 mph" (AC5300). But after you pay for a ride, you discover that the speed limit is 30 mph (AC2166) on two of the lanes and 14 mph on the third lane. So you take the 30 mph lane, but find out your chauffeur is only driving at 10 mph (MIMO level and QAM) and worse yet, every 100 feet the chauffeur slows down to 1 mph for 10 feet (MAC efficiency). Your average speed is 5 mph. And yet, that is exactly what router manufacturers are doing to you -- AC5300 is really only 357 Mbps for most wireless devices -- just like 74 mph is really 5 mph.


4. Client 'PHY' speed is the key (limiting) factor
Android Network Speed
Android PHY Network Speed

Windows Network Speed
Windows PHY Speed
The problem: So how do you find the maximum (realistic) wireless speed of a client to an AP/router? You could just run a speed test, but if the speed is not what you expected, where is the problem -- the client, the router, the Internet, interference, or elsewhere?

The solution: Go to your wireless device and find the PHY speed (the raw bitrate between the device and your AP/router) and take 55% of that PHY speed to estimate maximum application speed (the next section explains why the overhead is so large). Then lookup the PHY speed number in the PHY speed tables (far below) to then find which MIMO level is currently being used.
You can expect throughput anywhere from 50% to 70% of PHY speed. So use 55% as an estimate of the throughput you can expect to see.

In a real-world test environment, on a 2×2 866.6 Mbps link, I saw 461 Mbps download speeds on one computer (comes out to 53%) and 540 Mbps on a second computer (comes out to 62%).

PHY speed is an indicator of: (1) channel width, (2) modulation/coding (distance from router), and (3) minimum MIMO level support. Please note that the PHY speed displayed is not a static value, but changes over time, depending upon distance from AP/router, interference, etc.

PHY speed tables: If you don't find your PHY speed in the PHY tables in this paper, look up the speed in the full PHY speed tables.
Examples: Lookup the PHY values seen in the examples (right):
585: Lookup 585 Mbps in the PHY tables far below, and you will find it in multiple columns, but given the client, what makes the most sense is: 80 MHz channel width, 2×2 MIMO, and 64-QAM.

702: Lookup 702 Mbps in the PHY tables far below and it is not found. So, go to the full PHY speed tables and you will find various matches, but only one makes logical sense: 80 MHz channel, 2×2 MIMO, 256-QAM.
Windows 7: (1) Click on the wifi bars in the taskbar, right click on your wifi connection and select 'Status'. (2) Or, go into the Windows Control Panel, search and click on "View Network Connections", then right click on your wifi connection and select 'Status'.

Windows 8: Go into the Windows Control Panel, search and click on "View Network Connections", then right click on your wifi connection and select 'Status'.

Windows 10: In the control panel, search for and click on "Network and Sharing Center", then click on the wireless connection, and look for the 'Speed' in the resulting dialog.

Android: Go into "Settings / Wi-Fi", click on the connected wifi network, and find the 'Network Speed' (example right). Or, it may also be called 'Link Speed'.

Mac: (1) Hold the option/alt key down and click the Wi-Fi icon in the menu bar and look for the "Tx Rate". (2) Run the "Network Utility" (under Applications / Utilities; or use Spotlight to find) and look for the wifi "Link Speed". [more info on finding on Mac]

iPhone/iPad/iPod: Not known (tell me if you know how). However, to find the MIMO level for your device, visit Wi-Fi specifications for iOS devices (in appendixes, # in "Spatial streams" column is MIMO level).

Kindle: Under Settings, click on "Wireless", then click on the connected wifi network, and look for "Link speed".

Chromebook: Install the WiFiAnalyzer (open-source) app and run. On the 'Access Points' screen, the router you are connected to will also show your IP address and Mbps link speed.

Netgear Router TIP: In the Netgear 'Nighthawk' router app, click on 'device list' (the list of all devices connected to the router), and then click on the 'info' button next to a device to see the 'Link Rate' (PHY speed) for that device.

MOST 802.11ac client devices today are still 2×2 (not 4×4): As can be seen from the table below, most devices today are STILL only 2×2 MIMO. Why haven't devices switched to 4×4? Because (1) there is (currently) no compelling need for that speed today (there is no app that 'requires' 300 Mbps to function) and (2) the increased speed is not worth the tradeoff in reduced run time (4×4 takes more power, and for battery power devices, runtime is far more important).
Common Devices
(and their MIMO level)
DeviceMIMO
Apple iPhone X,8,7,6s2×2
Apple iPhone 61×1
Apple iPad + Air22×2
Apple iPad Air1×1
Dell Laptops (upper end)2×2
Dell Laptops (lower end)1×1
Fire TV (gen 2 and later)2×2
Galaxy S10,S9,S8,S7,S62×2
Google Pixel 1,2,32×2
MacBook Pro (some?)3×3
You can expect a maximum PHY speed of 866 Mbps (475 Mbps throughput) from an 802.11ac 2×2 client device. It is noteworthy to point out that Dell apparently had a 3×3 laptop in the past, but Dell only offers a maximum 2×2 laptop today (Feb 2019).


5. Understanding Wifi overhead
Wifi overhead is surprisingly large: So, if your smartphone connects to your AP/router at a PHY speed of 702 Mbps, why doesn't your smartphone get that full speed? Instead, 55% of your PHY speed is a fair estimate of actual (maximum) Mbps seen, but why?
PHY speed in wifi is exactly like the speed limit (sign) on a local road. You can go that fast some of the time but not all the time. Because you must take into account known slow downs: stop signs, traffic lights, traffic, weather conditions, etc.
Management transmissions must be sent at the 'slowest' possible modulation: In order to guarantee that ALL devices on a channel (AP and clients) can receive management transmissions, those transmissions must be transmitted at the slowest possible modulation -- so that devices that are furthest away from the AP (and hence, running at the slowest speed) can receive and decode those transmissions. And this 'slow' speed can be as slow as 1 Mbps (2.4 GHz band) or 6 Mbps (5 GHz band). When compared to 433 Mbps, that 'slow' speed is a hit.

Half Duplex: There is no separate download spectrum and upload spectrum in wifi (whereas Ethernet is full duplex - can send and receive at the same time). Instead, there is only a common spectrum (channel) that ALL wifi devices (router and clients) operating on that channel must use in order to transmit. So how does a device know that it is OK to transmit? Wifi uses something called CSMA/CA. So any device on a channel that wants to transmit must first 'sense' that the spectrum is available/unused (for a random amount of time), and then just start transmitting (and hope for no collisions).


Wi-Fi hidden node problem
Collisions/Retransmissions: When multiple devices want to transmit at once, the possibility of collisions (more than one device transmitting at the same time) increases, causing that entire transmission to be lost, and a retransmission.
There is something called the Hidden Node Problem that can cause a large number of collisions in wifi -- where device 'A' and device 'B' can both hear transmissions from the AP, but device 'A' and device 'B' can NOT hear each other's transmissions.
Coexistence with 802.11 a/b/g/n: For an 80 Mhz 802.11ac channel to properly coexist with older 20 Mhz radios operating within the channel, there is a 'request to send' and 'clear to send' exchange before each real message is sent. And that slows everything down.

Learn More:


6. Cutting through router marketing hype
The bottom line: The AC#### naming convention (AC1900, AC2600, AC5300, AC7200) and AX#### naming convention (AX6000, AX11000) used in the router industry (where the #### is a maximum Mbps) is nothing more than marketing hype/madness. It implies (incorrectly) that the larger the number, the better and faster the router -- and the faster wifi will be for your wireless devices. Also, speeds are cited for hypothetical wireless devices that do not exist (can you name a single smartphone, tablet, or laptop computer that has 4×4 MIMO for Wi-Fi).


iPhone XS Max
Example: Seen upper right are the specifications for an AC4000 (4000 Mbps) class router. But realistically, what speed can YOU expect from your "iPhone XS Max", a 2×2 MIMO device?

Bands/MIMO: AC4000 is 750+1625+1625. So what do those numbers mean? It is the 'maximum' speeds (best modulation possible with highest MIMO) of all 'bands' in the router added together as follows:
  1. Band One: 750 is the maximum PHY speed for MIMO 3×3 in the 802.11an band, but for an unrealistic 1024-QAM (see PHY table far below). A much more realistic PHY speed for a 2×2 MIMO wireless device is 300 Mbps.
  2. Band Two: 1625 is the maximum PHY speed for MIMO 3×3 in the 802.11ac band, but for an unrealistic 1024-QAM (see PHY table far below). A much more realistic PHY speed for a 2×2 MIMO wireless device is 650 Mbps (about 32 feet from the router).
  3. Band Three: same as band two.
MAC Overhead: Take the 5GHz PHY speed (for one band, not both bands, so 650) and multiple by 55% to get an estimate of the Mbps speeds that you will see within speed test applications running on your wireless device.

Conclusion: You will get a maximum speed of around 357 Mbps from your iPhone from this AC4000 router. With a second AC band, you might get up to 357 Mbps from another wireless device at the same time (but see the section far below on tri-band routers).
So upgrading to a faster router will increase your iPhone speeds, right? No! What about an AC5400 4×4 tri-band router? 357 Mbps. What about a brand new ultra-fast AX6000 8×8 router, marketed as being 4x faster than Wi-Fi 5? 357 Mbps. Understand router manufacturer's marketing hype.
A faster router only gets you half way there. But in order to get the high advertised speeds from a router (for only one band; not the published aggregate number), you need a client wireless device that the industry does not yet make. Virtually all wireless client devices today are still 2×2 MIMO -- so the maximum speeds for 2×2 MIMO are what you should realistically expect no matter how powerful the router.
The only known exceptions to this general rule are an older Dell laptop that did have 3×3 MIMO (but I can't find any new Dell laptops that do now in 2019) and some MacBook Pros that have 3×3 MIMO. If you know of any other exceptions, let us know.



7. MIMO - a wireless revolution
8x8 MIMO Illustration
8×8 MIMO illustration
MIMO: What is (partly) driving the dramatic increase in wireless (wifi, cellular, etc) capacity in the last few years is MIMO (acronym for Multiple Input, Multiple Output), or spatial multiplexing, or spatial streams -- by using multiple antennas all operating on the same frequency at the same time. Most smartphones today are capable of 4×4 cellular MIMO -- so they are (potentially) four times as fast as a single antenna phone. But MIMO for wifi is stuck at 2×2 MIMO for most wireless wifi devices.
Analogy: Think of MIMO as adding 'decks' to a multi-lane highway. More lanes (capacity) are added without using more land (spectrum). 2×2 MIMO is a highway with one more highway deck above it. And 4×4 MIMO is a highway with three more highway decks above it.
What is the big deal: The reason MIMO is such a huge deal is because it is a direct capacity multiplier (×2, ×3, ×4, ×8, etc) while using the SAME (no more) spectrum. This is accomplished by simply using more antennas.
MIMO adds more capacity without using more spectrum!

The huge caveat, of course, is that BOTH the transmitter and receiver must support MIMO. And if each supports different levels of MIMO, the minimum MIMO level common to both devices will be used. For example, a 2×2 MIMO tablet connecting to an 8×8 MIMO router will only use 2×2 MIMO. And as a bonus, the 'extra' antennas (if there is a mismatch in MIMO levels between the client and router) do not go unused, but are used for 'diversity' and 'beamforming', which extends range, and improves speed at range.
Example: On a single 80 Mhz 802.11ac channel operating at 433 Mbps:
  • 1×1 (no MIMO) yields 433 Mbps
  • 2×2 MIMO yields 866 Mbps (most wireless clients are 2×2)
  • 3×3 MIMO yields 1300 Mbps
  • 4×4 MIMO yields 1733 Mbps (most new Wi-Fi routers are 4×4)
  • 8×8 MIMO yields 3466 Mbps
all on the same 80 Mhz channel.

Notation: You will often see the MIMO level written as T×R:S, where 'T' is the number of transmit antennas, 'R' is the number of receive antennas, and 'S' (an optional component) is the number of simultaneous 'streams' supported. If the 'S' component is missing, it is assumed to be the minimum of 'T' and 'R'. OR, some devices will just say '2 streams' (for 2×2:2) or 'quad stream' (for 4×4:4).

Diversity: Multiple antennas can also be used to improve link quality, and increase range. With multiple antennas receiving the same transmitted signal, the receiver can recombine all of the received signals into a better estimate of the true transmitted signal.

Comcast XB6 gateway - 8×8 MIMO
Beamforming: A 802.11ac "wave 2" technology that uses multiple antennas to 'focus' the transmitted RF signals more towards a device (instead of just broadcasting the signal equally in all directions). The end result is a slightly stronger signal, which typically causes a slightly higher modulation to be used, which in turn increases Mbps speed by a little bit.
It is easy to overlook and miss, but beamforming and diversity are the key reasons why you want a 4×4 MIMO router even though most clients are still only 2×2 MIMO. The extra antennas are actually used and offer value!
Client MIMO: Many smartphones in 2017 are only 2×2 MIMO for wifi, with it rumored that smartphones in 2018 may switch to 4×4 MIMO. Comcast already has a 8×8 gateway capable of real actual gigabit wireless throughput -- the only caveat is that you need an 8×8 client to get that speed.
UPDATE: According to this Aerohive blog post (question/answer 22) mobile devices are likely to STAY at 2×2:2 for a long time due to onerous power/battery requirements for supporting higher MIMO levels. This may change, but for now this appears 'confirmed' since the NEW Samsung Galaxy S10 in FCC filings (Feb 2019) stays at 2×2 MIMO for wifi.

UPDATE/OLD: Smartphones in 2018 are using 4×4 MIMO for cellular, but they are still only using 2×2 MIMO for wifi. In December 2018, Qualcomm just announced the Snapdragon 855, saying it supports 8×8 spatial streams. So hopefully new smartphones in 2019 will actually have the antennas needed to fully support more streams for wifi. However, minimum spacing requirements of antennas may limit MIMO in smartphones?
A final note: You will only get the dramatic speed benefits of MIMO if you have a client device (phone, tablet, TV, computer, etc) that actually supports MIMO. Most client devices today (Mar 2019) are (at best) 2×2 MIMO. It is very rare to see a (battery powered) client device that supports 3×3 (or higher) MIMO.
Netgear's AX 'Stream' Deception: Netgear is now being incredibly deceptive when it comes to advertising in their new "AX" class of routers. Netgear is using "spatial streams" to describe their new AX routers (page), but this is NOT the same thing as "spatial streams" in MIMO in the 802.11ax standard -- which is what most people will (wrongly) conclude -- and that is outright deceptive, and Netgear knows it (because when I mentioned this in a Netgear forum post, a Netgear moderator deleted my post). Netgear claims their new RAX80 4×4 four-antenna (four spatial streams) router is "8 streams" [page]. So, do your research, and buyer beware.

Netgear's "spatial stream" logic is provably wrong. The maximum number of streams in a router can not be larger than the number of antennas in the router. because "In the T×R configuration the maximum number of spatial streams is limited by the lesser of either T or R" [source Cisco].
Learn More:
8. Legacy 802.11 Wi-fi
A brief look at past wifi generations:
GenSpecYearSpeeds
First 802.11 19972 Mbps
Second802.11b 199911 Mbps
802.11a 199954 Mbps
Third 802.11g 200354 Mbps
802.11: PHY data rates 1 Mbps to 2 Mbps with three non-overlapping 22 MHz channels in 2.4 GHz (1, 6, 11).

802.11b: PHY data rates 1 Mbps to 11 Mbps with three non-overlapping 22 MHz channels in 2.4 GHz (1, 6, 11).

802.11a: PHY data rates 6 Mbps to 54 Mbps with 12 non-overlapping 20 MHz channels in 5 GHz (36, 40, 44, 48, 52, 56, 60, 64, 149, 153, 157, 161), but some channels (52-64) have DFS restrictions. Details. But 802.11a really never 'took off' since initial devices were expensive and not backward compatible with 802.11b.

802.11g: PHY data rates 6 Mbps to 54 Mbps with three non-overlapping 20 MHz channels in 2.4 GHz (1, 6, 11). Essentially 802.11a technology in 5 GHz was moved into the 2.4 GHz band. 802.11g was highly successful. It is remarkable that in 2019 you can still today buy a brand new Linksys WRT54GL.


Learn More:


9. Wi-Fi 4 (802.11n) 2.4 GHz
802.11n 2.4 GHz is a legacy (obsolete) wireless band that has been replaced with 802.11ac. This section is provided for reference only. You should be using 802.11ac for all of your 'new' wireless internet devices. Only use 2.4 GHz when you are forced to -- by a device that does not support 802.11ac. Technically, 802.11n also operates in 5 GHz, but given that 802.11ac has wider channels, that is a much better solution.

GenSpecYearSpeedsNew Name
Fourth802.11n 2009600 Mbps Wi-Fi 4

2.4 GHz wifi channels
ChannelMhz center20 Mhz channel
124122402-2422
224172407-2427
324222412-2432
424272417-2437
524322422-2442
624372427-2447
724422432-2452
824472437-2457
microwave ovens: 2450 Mhz ±50 MHz
924522442-2462
1024572447-2467
1124622452-2472
12not available
in the U.S.
13
14
600 Mbps max speed: The 600 Mbps maximum PHY speed is for a 40 MHz channel to a 4×4 MIMO client. However, a much more realistic maximum PHY speed is 144 Mbps for a 20 MHz channel to a 2×2 client. 802.11n is called "HT" for High Throughput.

Spectrum: There is ONLY 70 Mhz of spectrum (2402-2472 Mhz) available for wifi to use in the U.S. in the 2.4 GHz band, supporting three non-overlapping 20Mhz channels.

There are eleven 2.4 GHz wifi channels, but you can't use them all: In the US, wifi routers allow you to set the 2.4 GHz wifi channel anywhere from 1 to 11 (wiki info). So there are 11 wifi channels, right? NO! These eleven channels are only 5Mhz apart -- and it actually takes a contiguous 20Mhz (and a little buffer Mhz between channels) to make one 20Mhz wifi channel that can actually be used. Because of this, in the US, these restrictions result in only three usable non-overlapping 20Mhz wifi channels available for use (1, 6, or 11; seen right).
You CAN set to the wifi channel to any channel and it will work. However, if you don't select 1, 6, or 11, the 20 MHz channel you create will almost certainly impact TWO other 20 MHz channels operating on 1, 6, 11.
Shared spectrum: All wifi devices on the same spectrum must SHARE that spectrum. Ideally, all wifi devices decide to operate on either channel 1, 6, or 11 -- the only non-overlapping channels. Then all devices operating on a channel share that channel. But I have seen routers operate on channel 8, which means that router is being a 'bad neighbor' and interfering with 20 MHz channels operating on 6 and 11.

Protocol Overhead: Each 20Mhz wifi channel has PHY bitrate of around 72Mbps, but due to wifi protocol overhead, you only get to use just slightly over half of that (around 50% to 70%).

802.11n PHY Speeds (Mbps)
20 Mhz channel, 400ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×4
0BPSK 1/2 7.2 14.4 21.6 28.8
1QPSK 1/214.4 28.8 43.3 57.7
2 3/421.6 43.3 65.0 86.6
316‑QAM 1/228.8 57.7 86.6115.5
4 3/443.3 86.6130.0173.3
564‑QAM 2/357.7115.6173.3231.1
6 3/465.0130.0195.0260.0
7 5/672.2144.4216.6288.8
-256‑QAM 3/486.6173.3260.0346.6
- 5/696.2192.5288.8385.1
-1024‑QAM3/4108.3216.6325.0433.3
- 5/6120.3240.7361.1481.4
256-QAM and 1024-QAM are non-standard


802.11n PHY Speeds (Mbps)
40 Mhz channel, 400ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×4
0BPSK 1/215 30 45 60
1QPSK 1/230 60 90120
2 3/445 90135180
316‑QAM 1/260120180240
4 3/490180270360
564‑QAM 2/3120240360480
6 3/4135270405540
7 5/6150300450600
-256‑QAM 3/4180360540720
- 5/6200400600800
-1024‑QAM3/4225450675900
- 5/62505007501000
256-QAM and 1024-QAM are non-standard

More PHY speed tables

Understanding channel widths: The standard wifi channel width is 20 Mhz. So a 40 Mhz channel is TWO 20 Mhz channels put together (2× capacity).
Analogy: Think of channel width as how many 'lanes' you can use at once on a multi-lane highway. 20 Mhz is a car using a single lane. 40 Mhz is a 'wide' load trailer using two highway lanes.
Channel bonding / 40Mhz channels: This is the biggest marketing rip-off ever. Routers can then advertise 2x higher speeds, even though in most circumstances, you will only get 1/2 of the advertised speed! For example, The Netgear N150 (implying 150Mbps), which is the result of taking TWO 20Mhz wifi channels and combining them into one larger 40Mhz channel, doubling the bitrate. This actually does work, and works well BUT ONLY in 'clean room' testing environments (with no other wifi signals). However, for wifi certification, the required 'good neighbor' implementation policy prevents these wider channels from being used in the real world when essentially the secondary channel would interfere with a neighbor's wifi -- which unless you live in outer Siberia, you WILL 'see' neighbor's wifi signals and the router will be required to automatically disable channel bonding.
Or, if there is a single 20 Mhz only client that connects to the AP, the AP will (should) drop from 40 Mhz operation to 20 Mhz operation, disabling channel bonding. This situation is actually VERY likely to happen (for example, my daughter's laptop that is only two years old, but only supports 20 Mhz channels).

Also, in the real world, things are MUCH more complicated, because many routers don't always follow 'good neighbor' standards [details].
256-QAM and 1024-QAM HYPE: These are non-standard extensions to 802.11n, so most client devices will never be able to get these speeds. And even if you have a device that is capable of these speeds, are you close enough to the router to get these speeds? Understand that advertised speeds in these ranges are marketing hype. See Broadcom TurboQAM and NitroQAM.
The reason why 256-QAM and 1024-QAM are included in the PHY tables here is for reference -- because these PHY tables ARE ALSO the PHY speed tables for 802.11ac for 20 MHz and 40 MHz channel widths. The PHY speeds for an 80 MHz channel is far below in the next section.
Interference: The entire 2.4 GHz space is plagued by interference, or other devices using the SAME frequency range. For example, cordless phones, baby monitors, Bluetooth, microwave ovens, etc. Microwave ovens operate at 2450 Mhz ± 50 Mhz. (source), which is the entire wifi space, and very likely impacting two of the wifi channels, and in some cases, even all three wifi channels
Microwave ovens are licensed in the entire ISM (Industrial, Scientific and Medical) band from 2.4 GHz to 2.5 GHz, which covers all 2.4 GHz wifi channels. Example

How bad the interference is totally depends upon the specific microwave. Some microwaves are very bad, while others seem to have very little impact. At one house, using the microwave oven causes wifi clients to disconnect from the AP, while in another house, using the microwave oven only causes a slight slowdown in bandwidth to wifi clients.
The BOTTOM LINE: The 2.4 GHz band is just WAY too crowed. Use a dual band (2.4 and 5 GHz) router/AP and switch over to the 5 GHz band -- for all devices that support 5 GHz. All quality devices made in the last few years (phones, tablets, laptop computers, TVs, etc) will absolutely support 5 GHz.


10. Wi-Fi 5 (802.11ac) 5 GHz
The fifth generation of wifi is 802.11ac (2013) on 5 GHz. It is currently wifi's 'state-of-the-art', providing a maximum PHY speed of 3.4 Gbps on an 80 MHz channel using 8×8 MIMO (and fully backward compatible with prior wifi generations). At the end of 2019, it will be officially replaced by 802.11ax (Wi-Fi 6).
GenSpecYearSpeedsNew Name
Fifth802.11ac20133466 MbpsWi-Fi 5

5 GHz wifi channels (U.S.)
Channel #20 Mhz
center
20 Mhz
channel
160804020
5042383651805170-5190
4052005190-5210
464452205210-5230
4852405230-5250
58545252605250-5270
5652805270-5290
626053005290-5310
6453205310-5330
GAP (160 Mhz)
11410610210055005490-5510
10455205510-5530
11010855405530-5550
11255605550-5570
12211811655805570-5590
12056005590-5610
12612456205610-5630
12856405630-5650
 13813413256605650-5670
13656805670-5690
14214057005690-5710
14457205710-5730
GAP (5 Mhz)
 15515114957455735-5755
15357655755-5775
15915757855775-5795
16158055795-5815
16558255815-5835
More info from Wikipedia
3466 Mbps max speed: The 3466 Mbps maximum PHY speed is for an 80 MHz channel to an 8×8 client. However, a much more realistic maximum PHY speed is 866 Mbps for an 80 MHz channel to a 2×2 client, and in the real-world, a PHY speed of 780 Mbps is reasonable. 802.11ac is called "VHT" for Very High Throughput.

Spectrum: There is 500 Mhz of spectrum (5170-5330, 5490-5730, 5735-5835 Mhz) available for wifi to use in the U.S., supporting six non-overlapping 80 Mhz channels. If a device is labeled as supporting 802.11ac, you KNOW it also supports 80 Mhz channels. One 80 Mhz channel in 5 GHz has more spectrum than ALL 2.4 GHz channels combined!

Channels: The 5 GHz wifi band has six 80 MHz channels (42, 58, 106, 122, 138, 155) BUT ONLY if you have an AP that supports ALL the new extended/DFS channels.
Channel Use Restriction: 16 (seen in red, right) of the 25 channels (or 64%) come with a critical FCC restriction (DFS - dynamic frequency selection) to avoid interference with existing devices operating in that band (weather-radar and military applications). Very few 'consumer-grade' access points support ALL of these 'restricted' channels, whereas many 'enterprise-grade' access points DO support these channels. More on this later in this section. 802.11h defines (1) dynamic frequency selection (DFS) and (2) transmit power control (TPC).

120/124/128: Terminal Doppler Weather Radar (TDWR): If you are 'near' a major metropolitan airport, you might not be able to use 20 Mhz channels 120, 124, or 128 (and hence 80 Mhz channel 122) due to use of Terminal Doppler Weather Radar operating within 5600-5650 MHz at a peak power of 250,000 watts. TDWR locations and frequencies. See also wiki info and a Cisco blog post on the TDWR issue. Channels affected are in dark red (right).
Understanding 160/80/40/20 Mhz channel selection: Your router will NOT present a list of the 80/40 Mhz channels to you (eg: 42, 155). Instead, your router presents a list of 20 Mhz channels and you select one. This then becomes the 'primary' channel (and 20 Mhz channel support). Then to support 80/40 Mhz channel clients, the router just automatically selects the appropriate 80/40 Mhz channels as per the table seen right.
This 'automatic' selection of the appropriate 40/80/160 channel from a single 20 Mhz channel that you select avoids the problem of one wide channel straddling two other wide channels.
Range: It is true that the range/distance of 5 GHz is reduced as compared to 2.4 GHz (around 7 dBm difference at same distance), but counterintuitively, that can be a significant benefit when it comes to actual throughput. The problem with 2.4 GHz is too much range (interference) -- I always see the SSID of lots of neighbors, and that is a very bad thing because it means that I am sharing spectrum and bandwidth with my neighbors. With 5 GHz the number of neighbor's networks I can see is dramatically reduced. Then, 5 GHz uses a much wider channel width (80Mhz vs 20Mhz) and with a "wave 2" 4×4 MIMO access point with beamforming, you will see actual useable bandwidth greatly increased.
With 5 GHz, neighbors can (often times) be on the same channel and typically not interfere with each other, because with reduced range, neighbors can't see each other's wifi anymore. Of course, all of this depends upon how 'close' your neighbors are.
Protocol Overhead: The Mbps seen at the application level will be around 50% to 70% of the Mbps at the wifi (PHY) level. This is just due to wifi protocol overhead (see section on PHY client speed far above).

New Channel Plan: Here is the 5 GHz 802.11 Channel Plan (see also below) from the FCC. Of note is that on April 1, 2014 the FCC changed the rules for usage in the 5 GHz band, to increase availability of spectrum for wifi use. [summary of the new rules]. Channel 165 was added (but older 5GHz clients will not be aware of this), power levels for channels 52 to 64 were increased, and other miscellaneous changes.


Transmit Power: Channels 149-165 allow for both router/client to transmit at 1000mW. However, this does not necessarily mean that these are the best channels to use. All other channels allow router and client to transmit at 250mW (exception: router may transmit at 1000mW for channels 52-64). This 'reduced range' can actually be a huge advantage, because it means there is a much higher likelihood that you will NOT see neighbors wifi channels (as frequently as 2.4 GHz channels), which translates directly to less interference and higher wifi speeds.

802.11ac PHY Speeds (Mbps)
80 Mhz channel, 400ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×48×8
0BPSK 1/2 32 65 97 130 260
1QPSK 1/2 65 130 195 260 520
2 3/4 97 195 292 390 780
316‑QAM 1/2130 260 390 5201040
4 3/4195 390 585 7801560
564‑QAM 2/3260 520 78010402080
6 3/4292 585 87711702340
7 5/6325 650 97513002600
↕ typical real-world Modulation/Coding ↕
8256‑QAM 3/4390 780117015603120
9 5/6433 866130017333466
-1024‑QAM3/4487 975146219503900
- 5/65411083162521664333
1024-QAM is non-standard

802.11ac PHY Speeds (Mbps)
80 Mhz channel, 800ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×48×8
0BPSK 1/2 29 58 87 117 234
1QPSK 1/2 58 117 175 234 468
2 3/4 87 175 263 351 702
316‑QAM 1/2117 234 351 468 936
4 3/4175 351 526 7021404
564‑QAM 2/3234 468 702 9361872
6 3/4263 526 78910532106
7 5/6292 585 87711702340
↕ typical real-world Modulation/Coding ↕
8256‑QAM 3/4351 702105314042808
9 5/6390 780117015603120
-1024‑QAM3/4438 877131617553510
- 5/6487 975146219503900
1024-QAM is non-standard

More PHY speed tables

Another big thing is beamforming / more antennas: After playing around with a new 4×4 "wave 2" router, wow! A very noticeable increase in range AND higher speeds at range. It really works.
Your mileage will vary depending upon construction materials. In one home (single level; sheetrock with aluminum studs) I saw a dramatic increase in speeds at range. But at an older second home with very thick brick walls, range improved just a little.
256-QAM: This modulation requires such an incredibly good SNR (signal to noise ratio), that in real life, you are very unlikely to get this unless you are very close to the AP.
UPDATE: This observation was originally made based upon testing with a consumer-grade 802.11ac 2×2 "wave 1" AP to a 2×2 client (where I never got 256-QAM, even feet from the router). But based upon initial testing with a much higher quality 802.11ac 4×4 "wave 2" AP to a 2×2 client, I now regularly see 256-QAM 3/4 being used (at 25ft, through two walls).
1024-QAM HYPE: This modulation is a non-standard extension to 802.11ac, so most client devices will never be able to get these speeds. And even if you have a device that is capable of these speeds, are you close enough to the router to get these speeds? Understand that advertised speeds in these ranges are marketing hype. See Broadcom NitroQAM.

802.11ac Wave 2: The next generation (wave 2) of 802.11ac is already here. With feature like: (1) four or more spatial streams, (2) extended/DFS 5 GHz channel support, (3) 160 MHz channels, and (4) MU-MIMO. Cisco Wave 2 FAQ.
Buyer beware: Not all 'wave 2' products will support the restrictive 5 GHz DFS channels! WiFi certification for 'wave 2' only 'encourages' devices to support this -- so NOT required.

160 MHz channels: Support for 160 Mhz channels in some routers reduces MIMO support. For example, in Netgear's R7800, there is 4×4 MIMO support for 80 Mhz channels, but for 160 MHz channels, MIMO is reduced to 2×2.

MU-MIMO issues: There are a lot of issues with MU-MIMO. So it may or may not work for you. MU-MIMO (1) sometimes disables client MIMO (where a 2×2 client switches to 1×1; Broadcom chipset) (2) requires spatial diversity (physical distance) between clients (3) has significant sounding overhead (4) a client device must be MU-MIMO aware (many are not) (5) only works with high SNR (very strong signals) and (6) works best with completely stationary clients. For more details, read "A MU-MIMO Reality Check". Aruba Networks says "Experience from 802.11ac MU-MIMO in real-world deployments revealed some limitations". [source] [more info]
Interference: It is a lot less common to find devices that use the 5 GHz band, causing interference for wifi, but it is still possible. Just Google 'Panasonic 5.8 GHz cordless phone' for a cordless phone that uses the upper 5 GHz channels 153 - 165. FCC info on Panasonic phone.

A final warning and caveat: I have glossed over the fact that 802.11n can operate in the 5 GHz band, so DO NOT ASSUME that just because a device operates in 5 GHz that the device must be 802.11ac. That is NOT necessarily true. For example, the Motorola E5 Play (very low end) smartphone does NOT support 802.11ac, but does support 802.11n and does connect to the 5 GHz band, but only using 20/40 MHz channels (in 1×1 mode), not the 80 MHz channels of 802.11ac.

Learn More:
11. Wi-Fi 6 (802.11ax) 5 GHz
"The bottom line is until Wi-Fi 6 / 802.11ax clients reach critical mass, the benefits of 11ax are minimal and will have low impact." [Cisco]

STOP - Do NOT buy an 802.11ax router in 2019: The 'fine print' for Wi-Fi 6 routers available now (Feb 2019) state that they "MAY NOT" (or even "DO NOT") support all ratified 802.11ax features (eg: Netgear RAX80 and RAX120). Bottom line: (1) 802.11ax is not expected to be ratified until late 2019, and (2) you will NOT benefit from a Wi-Fi 6 router/AP until most of your wireless devices are Wi-Fi 6 anyway -- so WAIT until you have several Wi-Fi 6 certified client devices (likely 2020) before buying a Wi-Fi 6 certified router (look for the 'certified' symbol right).

Wi-Fi 6: The sixth generation of wifi is 802.11ax (2019). It is still a DRAFT (will be finalized in late 2019) and provides a maximum PHY speed of 4.8 Gbps on an 80 MHz channel using 88 MIMO. The 802.11ax modulation (OFDMA) is NOT backward compatible with any prior version of Wi-Fi -- so you need Wi-Fi 6 clients to take advantage of Wi-Fi 6 features. However, any Wi-Fi 6 router will be able to revert back to Wi-Fi 4/5 to support your older devices (with NO speed advantage over Wi-Fi 5).
GenSpecYearSpeedsNew Name
Sixth802.11ax20194803 MbpsWi-Fi 6

802.11ax PHY Speeds (Mbps)
80 Mhz channel, 800ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×48×8
0BPSK 1/2 36 72 108 144 288
1QPSK 1/2 72 144 216 288 576
2 3/4108 216 324 432 864
316‑QAM 1/2144 288 432 5761152
4 3/4216 432 648 8641729
564‑QAM 2/3288 576 86411522305
6 3/4324 648 97212972594
7 5/6360 720108014412882
↕ typical real-world Modulation/Coding ↕
8256‑QAM 3/4432 864129717293458
9 5/6480 960144119213843
101024‑QAM 3/45401080162121614323
11 5/66001200180124014803


802.11ax PHY Speeds (Mbps)
80 Mhz channel, 1600ns guard interval
Modulation
+ Coding
MIMO
1×12×23×34×48×8
0BPSK 1/2 34 68 102 136 272
1QPSK 1/2 68 136 204 272 544
2 3/4102 204 306 408 816
316‑QAM 1/2136 272 408 5441088
4 3/4204 408 612 8161633
564‑QAM 2/3272 544 81610882177
6 3/4306 612 91812252450
7 5/6340 680102013612722
↕ typical real-world Modulation/Coding ↕
8256‑QAM 3/4408 816122516333266
9 5/6453 907136118143629
101024‑QAM 3/45101020153120414083
11 5/65671134170122684537


More PHY speed tables

4803 Mbps max speed: The 4803 Mbps maximum PHY speed is for an 80 MHz channel to an 8×8 client. However, a much more realistic maximum PHY speed is 1200 Mbps for an 80 MHz channel to a 2×2 client (660 Mbps throughput), and for a realistic distance away from the router, a PHY speed of 864 Mbps (expect a throughput around 475 Mbps). 802.11ax is called "HE" for High Efficiency.

The goal of Wi-Fi 6: The primary goal of Wi-Fi 6 is 'high efficiency' (HE). In a nutshell, Wi-Fi 6 adds 'cellular' technology into wifi. This was accomplished by changing to the OFDMA modulation scheme and changing the wifi protocol to directly support many users at once. The result is greatly improved overall (aggregate) capacity in highly 'dense' (lot of devices) environments (like schools, stadiums, convention centers, campuses, etc).
Multi-user support is baked into OFDMA: This is a critical concept to fully understand about Wi-Fi 6. In Wi-Fi 5, 'multi-user' was accomplished via MU-MIMO using multiple antennas. HOWEVER, in Wi-Fi 6, there is a SECOND (and now primary) 'multi-user' method 'baked' into the protocols called MU-OFDMA. Don't confuse MU-OFDMA with MU-MIMO! Also, see this interesting MU-OFDMA vs MU-MIMO article.
MU-OFDMA (Multi-User OFDMA): The efficiency gains in 802.11ax primarily come from using OFDMA in 'dense' environments -- breaking up a channel into smaller Resource Units (RU) -- where each RU is (potentially) for a different user. There are up to 9 users per 20 Mhz channel (so up to 36 users per 80 Mhz channel). So, 802.11ax has high efficiency multi-user transmission built into the protocol, meaning that the user must be 'Wi-Fi 6' to take advantage of this. Capacity to a large number of users at once (as a whole) should dramatically increase (the design goal of 802.11ax was a 4x improvement).
This multi-user support is a big deal, and will greatly improve wifi for all -- but it will take many YEARS before most clients are 802.11ax. So don't expect to see Wi-Fi 6 benefits for YEARS.
But what about peak speed to ONE user: Please note that 'peak' speed (one user using the entire channel) changes very little (around 10% improvement over 802.11ac). So, if you are looking for much higher Mbps download speeds (benefiting just one user), 802.11ax is not the solution (eg: PHY speed in 802.11ac of 780 Mbps changes to 864 Mbps in 802.11ax). Instead, find a way to increase the MIMO level of the one user.
The goal of every prior version of wifi was dramatically increasing 'peak' speeds (for one user). And by looking at Wi-Fi generation Mbps speeds, you can see this: 2 -> 11 -> 54 -> 600 -> 3466 -> 4803, except for the last jump (3466 to 4803), which is Wi-Fi 6. Instead, by changing to MU-OFDMA in Wi-Fi 6, there will be dramatic (overall) capacity gains to a dense set of users (as a whole), but only when (all) clients fully support Wi-Fi 6.
Keep all of the marketing hype in perspective: In order to take advantage of Wi-Fi 6 improvements, you need client devices that support Wi-Fi 6. Until this happens, Wi-Fi 5 will do just fine in most homes. Most of the speed advances in 802.11ax (MU-OFDMA) will NOT materialize until ALL client devices are 802.11ax, which will take a LONG time. So an 802.11ax AP used today will actually be operating in (revert back to) 802.11ac (Wi-Fi 5) mode for many clients.

1024-QAM: This higher order QAM is now officially part of the standard, but you will need to be very close to the router/AP to get this QAM. Also, this modulation can only be used when a client is using an entire 20-MHz (or wider) channel -- so NOT available for small RU's. In order to achieve 1024-QAM, you will need an excellent signal (be very close to the router). Here is a 'dBm signal vs Modulation' table (source):


Channels: The channels in Wi-Fi 6 are exactly the same as the available channels in Wi-Fi 4 and Wi-Fi 5. However, since there is so much more spectrum in 5 GHz than 2.4 GHz, what matters the most for Wi-Fi 6 are the channels in 5 GHz.

Channel Width: Unlike 802.11ac, which required clients to support 80 MHz channels, 802.11ax permits 20 MHz channel only clients. This was done to better support low-throughput low-power IoT devices (eg: those devices powered by battery) that would just waste power using wider channel widths.
160 MHz channels: Support for 160 MHz channels in some routers reduces MIMO support. For example, in Netgear's RAX120, there is 8×8 MIMO support for 80 MHz channels, but only 4×4 MIMO support for 80+80 channels.
Bands: Technically, 802.11ax does also operate in 2.4 GHz, but since there are NO 80 MHz channel there, most people (home installations) will stay in 5 GHz. It has been said that 802.11ax is in 2.4 GHz mainly for the benefit of IoT device support, but it remains to be seen if that will happen (or if IoT devices will stick with prior Wi-Fi versions).
6 GHz: The hope is that the FCC will open up the 6 GHz band for wifi sometime in 2019. If they do, 802.11ax will also use that band.
WPA3: To be Wi-Fi 6 certified, it was announced by a router vendor that the Wi-Fi alliance will mandate WPA3 security support. Time will tell if that is true, or not.

Outdoor Wi-Fi: 802.11ax changed symbol timings (from 3.2µs to 12.8µs; and increased GI times), which allows for wifi to operate much better in outdoor environments (where signal reflections take more time and cause problems).

HERE COMES THE HYPE: Manufacturers are touting incredibly speed claims regarding 802.11ax (immediately below). However, we know that an 802.11ac 2×2 client at 256-QAM 5/6 has a PHY speed of 780 (see table above section). And with 802.11ax (and everything else the same), the PHY speed is 864 (see table immediately above). YES, that is better by a little (11%), but not nearly as much as you are led to believe.


Very deceptive router manufacturer speed comparison

The above "2.3X" above is comparing 'apples to oranges' -- different channel widths and different modulation+coding, and combining the total of two bands (2.4 GHz and 5 Ghz). When you compare 'apples to apples' the raw PHY speed advantage of 802.11ax over 802.11ac is only 11%.
Analogy: It should be painfully obvious by now that router manufacturers are selling you on hype. They are selling you on a 'dragstrip' (the router), where you can go '500 mph' -- and that sounds fantastic. Until you step back and realize that all the vehicles (wireless devices) you own don't go over 90 mph.
Should I upgrade to Wi-Fi 6? In 2019, NO. Never buy routers based upon 'draft' specifications. Wait until 2020. Then, for the 'typical' home, absolutely NOT -- and not for years. For a business, 'maybe'. If you have a small to normal number of wifi users connected, Wi-Fi 5 will work just fine. But if you have a large number of Wi-Fi 6 users, then you may very well see an improvement by using Wi-Fi 6.
Until a LOT of your client devices fully support Wi-Fi 6, you are going to see very little improvement over Wi-Fi 5. Vendors are throwing around huge Mbps numbers that are meaningless (because it is client device capabilities that mostly limits throughput).

"The bottom line is until Wi-Fi 6 / 802.11ax clients reach critical mass, the benefits of 11ax are minimal and will have low impact" [source: Cisco].

"For [most enterprise customers], we recommend installing 802.11ac wave 2 access points today, because of the sheer value of 802.11ac wave 2" [source: Cisco].

Consumer Reports concludes that there is very little point in buying a new Wi-Fi 6 router, especially if your smartphone, TV, laptop, etc. only support Wi-Fi 5.
Learn More:
12. Extended/DFS channels
The SIX 5 GHz 80-Mhz channels
Channel #MHzInfo
4236+40+44+485170-5250OK
5852+56+60+645250-5330DFS
106100+104+108+1125490-5570DFS
122116+120+124+1285570-5650DFS, TDWR
138132+136+140+1445650-5730DFS, (1)
155159+153+157+1615735-5815OK
(1) many Netgear routers do not support CH 138
This section applies to both Wi-Fi 5/6 (802.11 ac/ax).

Background: There are SIX 80-MHz wifi channels in 5 GHz. Two channels can always be used (green highlight, right). But, for the other four extended/DFS channels to be used, a router must include special processing to avoid interference with existing usage (weather radar and military applications; red highlight, right) and pass FCC certification tests.
DFS = Dynamic Frequency Selection
Why support is important: Support for all channels becomes critically important to avoid interference (sharing bandwidth) with a neighbor's wifi. Ideally, every AP/router (yours and neighbors) should be on a unique/different wifi channel.
This is especially important if you can see several other 5 GHz AP's, which happens when you (1) have close neighbors like in an apartment building, or (2) want to install multiple AP/routers. Only consider routers that support ALL the extended/DFS channels.
Avoid AP/routers with NO extended/DFS channels: It is not uncommon to find 'consumer-grade' routers that support NONE of the extended/DFS channels. Buyer beware. Also beware brand new routers with NO extended/DFS channel support, as the vendor may (or may not) release a firmware update that adds support for these extended channels.
See the Router Reference Appendix far below for examples.
Some 'consumer-grade' AP's DO support extended/DFS channels: Some consumer grade routers DO support some or all of the extended/DFS channels. Just do your research.
Netgear ALERT: I have found NO Netgear router that supports extended/DFS channels that also supports 80 MHz channel 138. For some unknown reason, Netgear leaves out support for one of the six 80 MHz channels. Details

UPDATE 2019/03/15: Netgear makes a permissive change to the RAX120 supporting all six channels. Has Netgear finally changed?
Some business-grade AP's DO support 5 GHz DFS channels: Some business-grade 5 GHz devices DO support the extended/DFS channels, so you get the full advantage of a LOT more channels in 5 GHz.
Most of the Netgear business access points (Netgear ProSafe Access Points) do NOT support the restricted 5 GHz channels. But I did find ONE that did. Do your research.
Many Enterprise-grade AP's DO support 5 GHz DFS channels: According to this data sheet ALL of the Ubiquiti UniFi AC models (802.11AC Dual-Radio Access Points) are DFS certified. And prices on Amazon range from $82 (for the Lite model with 2×2 MIMO) to $158 (for the nanoHD model with 'Wave 2' features).
For example, I was in a Drury Hotel and from my room, I could see the Drury SSID on channels 48, 64, 100, 104, 108, 140. So the hotel was clearly using DFS certified 5 GHz access points.
A final warning: Watch out for 'best router' reviews online that select a 'best overall' router that does NOT support ANY extended/DFS 5 GHz channels. Here is an example. I have to wonder if the review is based upon how much money can be made (linking to Amazon to purchase the router), or if the review is based solely on the merits of the routers?

FCC Operating Frequencies
FCC Operating Frequencies show DFS support
How to research DFS support for any router/AP (check the FCC filings):
  1. Google 'wikidevi' and the router company name and the router model number (eg: "wikidevi Netgear RAX80"). You should immediately find the wikidevi web page for that router.
  2. On the wikidevi web page, find the "FCC ID:" for that router (eg: "PY318200414").
  3. Google the FCC ID found and click on the first top hit, which should be https://fccid.io/PY318200414.
  4. In the resulting web page, look for the "Operating Frequencies" section (seen right).
  5. Look for frequencies that cover the DFS channel range (highlighted in yellow right). [Frequency ranges are usually based upon '20 Mhz center' values]. If so, that router/AP HAS DFS channel support. Otherwise, there is NO DFS channel support. For the RAX80, notice that it appears that DFS channels are supported (except for channel 144), which then also excludes channels 142 and channel 138 -- because the GHz range stops at 5.7 GHz instead of 5.72 GHz).

13. WiGig (802.11ad) 60 GHz
Dubious Netgear 802.11ad marketing
Dubious Netgear 802.11ad marketing
802.11ad: 802.11ad (also called WiGig) is being marketed as the 'fastest' wifi possible, providing speeds "as fast as 4.6 Gbps", for '4K Streaming, VR Gaming and Backup' (Netgear, right), or for transferring an hour of HD video in 7 seconds. [source]

Huge disadvantage: However, the huge disadvantage of 802.11ad is that is has no range and does not go through walls (or obstacles). It is intended to only be used line-of-sight in one room and has a range of just a few meters. [source]

Range: At the same transmit power, 5 GHz has 1/2 (50%) the range of 2.4 GHz, but 60 GHz has 1/25 (4%) the range of 2.4 GHz, as measured in free space, or 'air'. [RF loss calculator]

802.11ac: Interestingly, 802.11ac products already exist TODAY that provide 4.3 Gbps (Arris TG3482G using the Quantenna QT10GU).

That kind of puts Netgear's marketing hype ("3X faster than 11ac") into perspective.

Conclusion: 802.11ad may take hold in very specialized situations (laptop docks, wireless displays, VR headgear, etc), but unless the range issue is addressed, 802.11ad will absolutely NOT become a replacement for wifi for generalized internet access for an entire home.
UPDATE: This is all but confirmed now that 802.11ax (Wi-Fi 6) -- the successor to 802.11ac (Wi-Fi 5) -- is out. Wi-Fi 6 effectively kills 802.11ad from ever being widely adopted for internet access. Instead it IS being used for very short distance point to point (laptop computer to dock).

Also, you know things are bleak for 802.11ad in routers when Netgear has a tough time pointing out any client devices that actually support WiGig!

14. Router WAN to LAN/WLAN throughput
Why you should care: What if you have 1 Gbps internet, AND are able to get true Gigabit wireless throughput -- you don't want to then find out that you can't access the Internet at gigabit speeds due to a problem with your router (eg: the Netgear R7800 router has a bug that limits WAN to LAN throughput to 340Mbps over port 80).


LAN to LAN -- 941 Mbps -- Great


WAN to LAN -- 340 Mbps -- BAD!
The problem: The dirty little secret in the consumer router industry is sometimes poor router WAN to LAN/WLAN throughput. Because even with crazy fast wireless speeds (above 1Gbps), the WAN to LAN/WLAN link (below 1 Gbps) is likely where you will see a performance bottleneck.
On a 1 Gbps WAN ethernet port, the maximum speed is around 949 Mbps (due to overhead of around 51 Mbps), so you will never get wireless speeds (from the Internet) above that.
Additionally, all of the 'realistic' wireless speeds we have been discussing above assumes that there is no slow down in the router itself moving packets between the WAN port and the LAN/WLAN ports -- but there often IS a slow down.
The router's WAN to LAN/WLAN throughput is often the limiting speed factor. Why? Because the router itself is performing NAT (Network Address Translation), SPI (Stateful Packet Inspection) and other tasks (eg: Parental Controls) that takes processing time inside the router, possibly limiting Mbps speeds.
An example: On a gigabit LAN, I tested Mbps speed between two PC's and got 941 Mbps (very close to the 949 Mbps maximum; graph upper right). But this only tests the built-in "switch" inside the router on the LAN, which is rated and expected to fully support 1 Gbps speeds.

So to test router WAN to LAN speed, I connected a Netgear R7800 (an AC2600 class router) to the LAN (via the 7800's WAN port) and plugged one of the test PC's into the LAN port on the 7800 -- and then ran a speed test between the two PC's -- and got an abysmal 340 Mbps (speed test uses a single socket).
When I tested using two sockets instead of one socket, the speed (roughly) doubled, meaning that there is some limitation (or BUG) inside the router.

Beware: Virtually all internet speed tests online use multiple sockets, which will hide this router limitation.
The bottom line: You will NOT get Gbps WAN to LAN throughput from SOME consumer-grade routers. And you won't know until you test this.



Router "WAN to LAN" throughput TEST: This section has grown so much that it has been moved to its own post.


15. Router wifi setup
R7800 Wireless Settings
Netgear R7800 wireless setup
SSID: SSID is simply the network NAME. When you connect to a wifi network, you must select this network name (called SSID). At home, you typically will only have one router with that ONE network name. However, if you add another wifi access point, you want it to use the SAME network name, as this allows for wifi roaming. Your wireless device simply connects to the strongest wifi signal with the same SSID name.
You can use different SSID names, but then you don't get wifi roaming.
2.4 GHz and 5 GHz SSID names: There is a big debate -- should your 2.4 GHz band network and 5 GHz band network have the same names, or different names (often with a "-5G" appended to the name)? If named the same, client devices choose which band to connect to. If named differently, the end user must choose which band to connect to.
The problem with the 'same name' technique is that some client devices are 'dumb' and incorrectly connect to the 2.4 GHz band instead of the 5 GHz band. I had this problem with a laptop that would start out connected to the (fast) 5 GHz band, but after a little while, would then switch to the (much slower) 2.4 GHz band (for unknown reasons). Yes, the 5 GHz signal was weaker, but throughput from 5 GHz was MUCH better.

Just use whatever method works best for you and your devices.
BSSID: This is the MAC address of the AP that your phone actually connects to (because you can't tell which AP you connected to from only the SSID). This is very useful when you have more than one AP using the same SSID, because the BSSID identifies the unique AP that you actually connected to.

Channel: ALL wifi access points (in your house and visible neighbors networks) covering the same frequency must share the wifi bandwidth. Because of this, assign channels 1, 6, 11 (2.4 GHz) and 42, 58, 106, 112, 138, 155 (5 GHz) to your APs in a manner to best avoid conflicts (with yourself and neighbors). There is nothing special about channel selection. A channel is like a lane on an Interstate highway. All cars (AP) can use the same lane (channel), but that is slow and inefficient (lanes go unused). Everything works best when cars (AP) use all lanes (channels) -- as evenly as possible.
Could you put 10 APs in your house and configure them to all use the same SSID and the same channel? Yes, and it would work (albeit slowly). But that would not be the best and most efficient way to use the available spectrum, since all 10 APs are attempting to use the same 'lane' of a superhighway. Instead, distribute all 10 APs across all available lanes (channels) of the superhighway.

Channel Planning: A full discussion on channel planning is beyond the scope of this paper, but in short, always try to leave unused spectrum between active channels. In other words, if you have a main router on 80 MHz channel 42, never put another nearby AP on 80 MHz channel 58. Instead, you would select a higher channel for the nearby AP.
Mesh / Extenders: These devices are a great convenience -- but ONLY use them as a last resort. Why? Because, by definition, they consume bandwidth/spectrum to accomplish their job. Instead, I always take the time to find a way to run wired Ethernet and setup a new/second AP. Your network itself should never consume wireless bandwidth/spectrum (mesh systems use a wireless backhaul). Instead, reserve wireless for your client devices. Note that some extenders/mesh devices can be configured to use Ethernet backhaul to the main router, which is fine (then they act like an AP).


16. Beware tri-band marketing hype

Linus video on tri-band (YouTube)
Beware all of the marketing hype surrounding tri-band routers.

A router is many devices in one: Remember, a wireless router is: (1) a router, (2) a switch, and (3) an AP -- all in one box. The AP is almost always dual-band (2.4GHz + 5 GHz). But the latest marketing hype concerns the speeds of tri-band routers -- where the AP inside the router is 2.4GHz + 5 GHz + 5 GHz.

But 'dual 5 GHz' is only useful if you are maxing out your current 5 GHz band, and need to support more (5 GHz only) devices. Are you? This is important to realize, It DOES NOT make one device faster. Rather, it allows 5 GHz devices connected to different 5 GHz bands to operate at the same time (two devices connected to the same band will have the same problem).

RF Interference: When there are multiple antennas in the same AP/router operating on the same band (5 GHz), near to the same frequency, there WILL be interference, which can reduce data rates. This mainly happens when one band is receiving and (at the same time) the second band is transmitting. One mitigation is a proper separation in channel numbers (the wider the better; at least three times channel width) because if not, there will be too much interference. The ideal fix is physical separation of the AP's. And that is why simply using a second AP (physically separated and located where it is really needed) is the best solution. Details
And since all Netgear routers are missing support for channel 138, that may limit your options running 'dual 5 GHz'.
Use a second AP instead: BUT, if you are this situation, if is far more cost effective to just add a second AP ($158 for a high end Ubiquiti nanoHD Wave2 AP) -- wired (ethernet) to your existing router rather than throwing everything away and buying only a tri-band router (for around $500) placed in a central location. Plus, the advantage of an AP is that you can physically position it (separate from the router), on its own channel, exactly where it will do the most good.
And physical separation between AP's make a lot of sense. Would you buy two AP's and place them literally on top of each other? Of course not. You would spread them around where they are needed. But with a tri-band router, that is exactly what you are doing (placing two AP's on top of each other).
Don't fall for the marketing hype!


17. Recommendation
Be critical: There is no point in replacing your router if PHY speeds to your wireless devices do NOT improve. So, be very critical. Take note of client PHY speeds (see section far above) before and after a router update. If you see an improvement in PHY speeds, great, job accomplished! However, if not, then you have to ask the serious question: did you just spend money and get no benefit/improvement?

Recommendation: Virtually all wifi devices (laptops / tablets / smartphones / smart tv's / etc) today are only 2x2 MIMO (at best; some are still 1×1). And THAT limits the speed at which those devices will connect to any AP/router (not the max speed of the router). Because of this, get a router/AP with:
  • "wave 2" 802.11ac Wi-Fi 5 - this is the best you can get today -- and avoid Wi-Fi 6 draft routers, which will not help anyway until you have a lot of Wi-Fi 6 clients (as of Feb 2019, there are none).
  • 4×4 MIMO - increases signal reliability for all 2×2 MIMO devices, and ensures faster speeds for when 4×4 clients do exist.
  • 802.11ac beamforming - improves signal strength, which increases the range at which devices stay at fast speeds.
  • extended/DFS channels - because if at all possible, you want a channel all to yourself -- you don't want to share a channel, and therefore bandwidth, with a neighbor.
  • Wi-Fi Certified - guarantees "interoperability, security, and reliability." Product Search
Comcast XB6 Gateway
Comcast TIP: If you have Comcast for your Internet and they are already providing you with a 'gateway', contact Comcast and say that you want their new best XB6 Wireless Gateway, which is an 8×8:8 MIMO (eight stream!) 802.11ac device, which supports data throughput of 1 Gbps.

Please note that the XB6 comes in two models. The TG3482G, which does NOT support DFS channels (but later revisions do). And the CGM4140COM, which DOES support DFS channels.
Best: Get a 4×4:4 (4 streams) 802.11ac "wave 2" AP/router that supports beamforming and ALL six 80 Mhz 5 GHz channels (42, 58, 106, 122, 138, 155) channel details.
These are very reasonably priced ($158 for a Ubiquiti nanoHD 4×4 "wave 2" 802.11ac AP) and offer incredible value. Only buy an AP/router that is "Wi-Fi Certified" -- and avoid draft specification devices (any Wi-Fi 6 router in 2019 will only be a 'draft' specification router).

8×8:8 (eight stream) routers are technically even better -- and some have come out, but they will be expensive, and use a lot more electricity.
Second best: Same as above, but select an AP/router that supports MOST extended/DFS channels.
Netgear routers that support extended/DFS channels are in this category -- because Netgear only supports five (42, 58, 106, 122, 155) of the six extended/DFS channels (leaves out channel 138). See the Router Reference Appendix far below.
The ugly: Stay away from any AP/router that supports only the TWO standard 80 MHz channels (42, 155) and NO extended/DFS channels. And in the consumer router market, there are a LOT of these. Refer to the Router Reference Appendix for examples.

Other: Don't forget to look into 'Enterprise' grade AP/routers. Ubiquiti sells a line of 4×4 "UniFi AC" access point products that DO support ALL 5 GHz channels, and are very reasonably priced. For example, the UniFi nanoHD which is a 4×4 Wave2 AP for only $158 on Amazon.

A final thought: For most people, one great router centrally located is all that is really needed. However, if you have a wireless device (or two) that absolutely must always have the fastest wireless possibly (no contention with other wireless), simply add an AP (wired to your main router) dedicated and located nearby to those unique devices -- but there must be an unused wifi channel available for this to make any sense.

One caveat - COST: The cost of the latest and greatest consumer-grade (not even enterprise-grade) routers approaching $500 is insane. You get nowhere near that 'value' given that virtually all client wireless devices are MIMO 2×2 limited. You would likely be far better off spending that $500 on a medium grade (Gigabit capable) router and several high-grade 4×4 APs, provided the APs can be wired (ethernet) to your existing gigabit router and provided each AP can be assigned a unique 80 Mhz channel.
The hidden cost of electricity: As a very general rule, the yearly cost in electricity for any 'always on' device roughly equals wattage. An old Netgear WNR1000v3 uses 4 watts ($4/year). A Netgear R6250 uses 10 to 14 watts ($10-$14/year). A Netgear R7800 uses 7 to 14 watts ($7-$14/year). You can expect newer routers to use even more.
Beware Combo (all-in-one) Modems + Routers: These 'combo' devices are a great convenience, but the problem with these units is that firmware updates are often under the control of your ISP (you are NOT able to update/change firmware). Or if you can update the firmware, the version often lags the non-combo hardware. Besides, you often need to update one device or the other, not both at once, which you are forced to do with a combo unit.


18. A Reality Check
Advertised router speeds are pure fiction: Consider this claim from a manufacturer: "enjoy combined wireless speeds of up to 7.2Gbps". The speeds advertised for routers are pure fiction because they are based upon various maximum capabilities added together, and for hypothetical client wireless devices that DO NOT exist. Can you name any laptop computer, smartphone, or tablet that has 4×4 MIMO Wi-Fi?

Most wireless client devices are 2×2 MIMO: The capabilities of YOUR wireless device (and not the router) almost always limits speeds.

For most people, 2×2 MIMO on client devices is enough: You can expect throughput of around 350 Mbps on a 2×2 MIMO client device. For the far majority of people, that is 'fast enough', especially with 250 Mbps (or less) Internet speeds.

PHY speed is key: The speed at which your wireless devices connect to a router is called the PHY speed and it is easily found (see section far above). That PHY speed is what you should look at (in all your wireless devices) to evaluate if a new router is helping you to achieve any faster speeds (or not).

Beamforming really works: The one router feature that does really work is 802.11ac beamforming. A wireless device connected to a 4×4 MIMO router with beamforming can expect better speeds at a greater distance (than a non-beamforming router). But how can you tell that it is helping? As per above, by examining the PHY speed at which devices connect to your router.

MU-MIMO is mostly hype: You can get it to work in lab situations, but in the real world -- no, it does not work very well. Don't go out of your way looking for this feature, but if it just happens to come with a new router, fine.

WAN speed limit: Some new routers are now claiming 10 Gbit wireless speeds. So you then plug that into a 1 Gigabit WAN. Pretend the router could actually deliver that speed (it can't). What do you think your speed limit is? Your 1 Gbps link to the WAN. Always look for the weakest link.

Wi-Fi 6 will initially have low impact: UNTIL the far majority of your wireless devices are Wi-Fi 6 802.11ax, don't bother with an 802.11ax router. Wait until 2020, and then, only look at Wi-Fi 6 certified routers -- this way you won't get stuck with a draft (non-specification) router that does not support all mandatory features.

Most 'enterprise' installations use only 20 MHz channels: You can almost always get by with an 80 Mhz channel at home, but most 'enterprise' installations still only use 20 Mhz channels, and that reduces/limits throughput (a max around 80 Mbps is typical).

Wired ethernet is still the gold standard of speed and reliability: It is not always easy or realistic, but whenever possible, always use Ethernet! Try to run Ethernet to every device with an Ethernet jack (smart tv's, Blu-rays, game consoles, Chromecast, desktop computers, etc). I did this in one house and wifi usage plummeted (and the only devices left on wifi were low bandwidth wireless only devices).

Increased range is NOT always a good thing: I was reading a post by someone exclaiming the merits of some new router because range was twice that of his prior Ruckus AP's and he was installing at an airport. But counterintuitively, increased range in dense (lots of clients) environments is NOT a good thing. Everyone on an AP shares that AP's wifi bandwidth, which is why you want shorter wifi range and more AP's in dense environments -- so fewer people per AP means higher wifi bandwidth per person. The same principle applies to large homes, where you want everyone evenly connected to several AP's, not everyone connected to one AP.


Appendix A: Troubleshooting 'slow' Wi-Fi
WiFi Analyzer Access Points
WiFi Analyzer Access Points
Did you reboot everything? It can't hurt to power cycle your modem, router, client device, etc, and see if the problem goes away. I was once unable to track down the cause of slow wifi, and rebooting all devices solved the problem.

The first step: Go to your wireless device and check the PHY speed at which the device is connecting to your router (see section far above). Then take 55% of the PHY speed as a good estimate for the maximum realistic speed that one device can achieve.

The second step: Make sure you are connecting to a 5 GHz SSID on a channel that is not overloaded (too many other APs on the same channel). Accidentally connecting to the 2.4 GHz SSID could be the problem.

Site Survey: Install the WiFiAnalyzer (open-source) app (seen right) on your smartphone and find out exactly what channels are being used (who you are sharing spectrum with), and then set your router to use the most unused channel. Channels 1, 6, 11 are 2.4 GHz channels. Channels 36 - 165 are 5 GHz channels.

Q: I upgraded my internet speed from 60 Mbps to 120 Mbps and my wired internet speeds dropped!
A: The most likely cause is that not all devices in your network are 1 Gbps capable. If there are any fast ethernet (100Mbps) devices between you and your ISP, that device becomes a 'choke point' that will very likely cause dropped packets and speed problems.

TIP: It is very common for ISP's to provision internet modems to 110% of the advertised speed. So if you sign up for 100 Mbps internet, your 100 Mbps network will not work, since the internet speed is more than likely actually 110 Mbps.
Q: I am connected to my wifi router at 866 Mbps, but a speedtest shows only 400 Mbps?
A: Due to wifi protocol overhead, the expected throughput at the application level is around 55% of the physical (PHY) wifi speed. This is normal and sadly, the industry has done a very poor job explaining this.
Q: I bought a '1733' AC wifi router, but I can only connect at 650 Mbps from my smartphone?
A: Blame router companies -- they love to advertise maximum speeds. Looking at the 5 GHz speed table far above, we can see that '1733' implies a 4×4 access point supporting 256-QAM. 650 is the PHY speed for a 2×2 device at 64-QAM. The conclusion is that your smartphone is a 2×2 MIMO device and that you are maybe 20 to 30 feet from your router. Expected application throughput will be around 55% of that, or 357 Mbps.
Q: My speedtest proves I only get a slow XXX Mbps?
A: Always try several different speed test programs, like speedtest.xfinity.com, fast.com, or cfspeed.com. The very nature of the internet is that everyone will not always be fast. I find that the xfinity speed test gives the most reliable results, almost all of the time (and it had better, since Comcast is the largest broadband provider in the U.S.).
Q: I have 150Mbps Internet, but I max out at 95 Mbps both wireless and wired to my router?
A: Fast Ethernet (100 Mbps) maxes out at a throughput of around 94.92 Mbps within applications. So the most likely cause is that the router is only 'Fast Ethernet' and you will need to upgrade to a Gigabit capable router (modem is likely 1Gbps ethernet, but router is only 100 Mbps, causing the bottleneck). OR, if your router is Gigabit, is there a (slow) Fast Ethernet switch somewhere in the network between you and your router? If not, double check the color of LED lights for RJ45 connections (LED color should indicate 1 Gbps and not 100Mbps). You may need to replace a bad ethernet cable (as Gigabit requires all eight wires to be good; 100Mbps only uses four of the eight wires).
Q: No matter what, my PHY speed maxes out at 54 Mbps. What is wrong?
A: This can happen when 'WMM' (Wi-Fi Multimedia) is turned off in the router configuration. To fix, turn 'WMM' back on.
Q: Why do I not see 802.11ac link speeds connecting to my router's 5 GHz band?
A: The most likely cause (if your router is configured for 80 MHz channels) is that your client device does NOT support 802.11ac. Instead, your client device likely only supports 802.11n, and is connecting to the 5 GHz band using the maximum 40 MHz channel width of 802.11n.

Visit www.devicespecifications.com to research versions of wifi supported by your smartphone (802.11n vs 802.11ac, etc).

Appendix B: Router/AP Reference
All 802.11ac 4×4 AP/routers provide a maximum 866 Mbps PHY speed to 2×2 clients (475 Mbps throughput), and provide for a future maximum 1733 Mbps (950 Mbps throughput) for when you get 4×4 clients.
Yes, I am intentionally excluding the non-standard (Broadcom) 1024-QAM extension to 802.11ac, which technically offers slightly faster speeds, but realistically, can not be achieved that often.
In order for an AP/router to be highlighted in green (below), it must (1) have 4×4 MIMO (or better), (2) support five or six of the (six) 80 Mhz channels (#CH column below), and (3) not be a 'draft' router (expect 802.11ax finalized in late 2019).

Don't forget that (1) many residental routers can be configured as an AP, (2) many commercial/enterprise AP's have reduced range (over residental routers in AP mode) on purpose since they are designed to be installed many at a time.

Netgear (Routers)
ModelMIMO#CHNotes
RAX120 8×86QCN5054, draft/ax
RAX80 4×45BCM43684, draft/ax
RAX40 2×26
XR700 4×45QCA9984
XR500/XR450 4×45QCA9984
R9000/R8900 4×45QCA9984
R8500/R8300 4×45BCM4366
R8000/R7900 3×32
R7800 4×45QCA9984
R7500v2 4×42
R7450 4×45MT7615N
R7000P/R6900P 3×35
R7000/R6700 3×32
Orbi RBR50 2×254x backhaul
Orbi RBR40 2×252x backhaul
Netgear (Extenders in AP mode)
ModelMIMO#CHNotes
EX8000 4×45QCA9984
EX7300v2 4×46-
EX7300 4×45-
Ubiquiti (PoE AP)
ModelMIMO#CHNotes
UAP-nanoHD 4×46MT7615N
UAP-AC-PRO 3×36
UAP-AC-EDU 3×36
Synology (Routers)
ModelMIMO#CHNotes
RT2600ac 4×45QCA9984
RT1900ac 3×36
EnGenius (PoE AP)
ModelMIMO#CHNotes
EWS371AP 4×45
EWS370AP 4×45
Asus (Routers)
ModelMIMO#CHNotes
GT-AX11000 4×46BCM43684, draft/ax
RT-AX88U 4×46BCM43684, draft/ax
GT-AC5300 4×42
GT-AC3100 4×42
RT-AC88U 4×42
RT-AC87U 4×42
RT-AC86U 4×45BCM4366E
RT-AC68U 3×32
RT-AC66R 3×32
Blue Dave 4×42
TP-Link (Routers)
ModelMIMO#CHNotes
Archer AX11000 4×45BCM43684, draft/ax
Archer AX6000 4×46BCM43684, draft/ax
Archer C5400X 4×42
Archer C5400 4×42
Archer C4000 3×32
Archer C3150V2 4×42
Motorola
ModelMIMO#CHNotes
MR2600 4×42
MR1900 2×22
MR1700 2×22
Linksys
ModelMIMO#CHNotes
EA9500 4×42
EA9300 3×36
EA9200 3×32
EA8500 4×42
EA8300 2×25
EA7500 3×32
EA7300 3×32
WRT32X 3×35
Velop 2×25
D-Link
ModelMIMO#CHNotes
DIR-895L/R 4×42
DIR-890L/R 3×32
DIR-885L/R 4×42
DIR-882 4×42
DIR-879 3×32
DIR-878 4×42
DIR-867 3×32
DIR-859 3×32
Amped Wireless
ModelMIMO#CHNotes
RTA2600-R2 4×42
RTA2600 3×32
TRENDnet
ModelMIMO#CHNotes
TEW-829DRU 4×42
TEW-827DRU 4×42
ZyXEL
ModelMIMO#CHNotes
Armor Z2 4×42
Google
ModelMIMO#CHNotes
Google Wifi 2×22
Eero
ModelMIMO#CHNotes
Pro (2nd gen) 2×26
Cisco (AP)
ModelMIMO#CHNotes
Aironet 1850 4×46


802.11ac chipset information:
  • QCA9984 - Qualcomm 4×4 802.11ac Wave 2 + MU-MIMO + 160MHz
  • BCM4366 - Broadcom 4×4 802.11ac + MU-MIMO
  • MT7615N - MediaTek 4×4 802.11ac Wave 2 + MU-MIMO
802.11ax chipset information:
  • QCN5054 - Qualcomm 802.11ax
  • BCM43684 - Broadcom 4×4 802.11ax

Appendix C: Understand Netgear 'Mode'
What does Netgear 'Mode' mean: So you just got a new router and are setting it up and you see 'Mode' and various Mbps under the wifi settings, but what does that mean? It means 20/40/80 MHz channel width! It does not change MIMO levels.

Netgear Mode
Netgear R7800 (4×4) 5 GHz example:
  • 1733: Lookup 1733 in the PHY tables far above and you find it under the 80 MHz PHY table with 256-QAM 5/6 modulation and 4×4 MIMO.

  • 800: Lookup 800 in the PHY tables far above and you find it under the 40 MHz PHY table with 256-QAM 5/6 modulcation and 4×4 MIMO.

  • 347: Lookup 347 in the PHY tables far above and you find it (346.6) under the 20 MHz PHY table with 256-QAM 3/4 modulcation with 4×4 MIMO. Note that 256-QAM 5/6 is not available in 20 MHz mode.

Netgear Mode
Netgear R6250 (3×3) 5 GHz example:
  • 1300: Lookup 1300 in the PHY tables far above and you find it under the 80 MHz PHY table with 256-QAM 5/6 modulation and 3×3 MIMO.

  • 600: Lookup 600 in the PHY tables far above and you find it under the 40 MHz PHY table with 256-QAM 5/6 modulcation and 3×3 MIMO.

  • 289: Lookup 289 in the PHY tables far above and you find it (288.8) under the 20 MHz PHY table with 256-QAM 5/6 modulcation with 3×3 MIMO.

Netgear Mode
Netgear JNR3210 (2×2) 2.4 GHz example:
  • 300: Lookup 300 in the PHY tables far above and you find it under the 40 MHz PHY table with 64-QAM 5/6 modulation and 2×2 MIMO.

  • 145: Lookup 145 in the PHY tables far above and you find it under the 20 MHz PHY table with 64-QAM 5/6 modulcation and 2×2 MIMO.

  • 54: This is the exception. In Netgear routers on the 2.4 GHz band, this sets the router to 802.11g (54 Mbps) operation only.




Appendix D: Terminology
2.4 GHz / 5 GHz / 60 GHz: Refers to the wireless frequency (spectrum) used by wifi.

802.11n: Wi-Fi 4: The specification for fast wifi (mainly) in the 2.4 GHz band.

802.11ac: Wi-Fi 5: The specification for faster wifi in the 5 GHz band.

802.11ax: Wi-Fi 6: The specification for the upgrade to Wi-Fi 5.

802.11ad: The specification for wifi around the 60 GHz band.

AP: AP is the acronym for (Wireless) Access Point. This allows your wifi devices to connect to a wired network (the Internet).

AC####: AC refers to support for 802.11ac (Wi-Fi 5) and #### is the sum of the 'maximum PHY network speed' for ALL bands in the router (like dual-band or tri-band). This naming convention is very deceptive because it can imply faster speeds where no faster speeds exist.

AX####: AX refers to support for 802.11ax (Wi-FI 6) and #### is the sum of the 'maximum PHY network speed' for ALL bands in the router (like dual-band or tri-band). This naming convention is very deceptive because it can imply faster speeds where no faster speeds exist.

Beamforming: A standards-based (802.11ac) signal-amplification technique that results in increased range and speed to a device. Beware earlier (proprietary) 802.11n beamforming implementations.

Dual-band: Two access points in one. Often band one is 2.4 GHz and band two is 5 GHz.

IoT: Internet of Things. A future where every device is connected wifi to the Internet.

LAN: Local Area Network (the wired network in your house)

MAC: Medium Access Control. See Wikipedia.

MIMO: Multiple-input and multiple-output on the same frequency, where 'multiple' refers to antennas. Also known as SU-MIMO (single user MIMO).

MU-MIMO: MIMO to "multiple users" at the same time.

'N' Spatial Streams: Refers to T×R:N MIMO, where both 'T' and 'R' equals 'N'. For example, 4 spatial streams means 4×4:4.

OFDMA: Orthogonal Frequency-Division Multiple Access, a proven technology that comes from cellular 4G LTE.

PHY: PHY is an abbreviation for physical. For example, 'PHY speed' refers to the physical speed at the raw network layer.

PoE: Acronym for 'Power over Ethernet'.

Quad-Stream: Refers to 4×4 MIMO.

Tri-band: Three access points in one. Often band one is 2.4 GHz, band two is 5 GHz and band three is 5 GHz (sometimes the third band is 60 GHz 802.11ad).

WAN: Wide Area Network (the WAN port on your router is connected to modem connected to the internet).

WLAN: Wireless LAN


Appendix E: Learn Even More
Aerohive Wi-Fi 6 802.11ax technical blog articles: Other: Recent FCC filings by company:
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