This is an umbrella post on Wi-Fi, the familiar name of the 802.11x networking standards. For the past two decades, Wi-Fi has been an essential cord-cutting invention. Imagine how your smartphone or tablet would be without this wireless connection.
In a nutshell, Wi-Fi is an alternative to network cables, allowing devices to connect to a network wirelessly. But the world of Wi-Fi can be confusing due to its many speed standards, frequency bands, features, etc.
This post will help you understand Wi-Fi at least and the next guy without getting overwhelmed by the networking jargon. It's a good place to start for anyone new to the topic.
Dong's note: I originally published this piece on February 15, 2018, when Wi-Fi 6 wasn't a thing. It's one of my first posts on Dong Knows Tech. Much has changed since. This latest update, published on July 28, 2023, aims to paint an up-to-date overview of home Wi-Fi.
How does Wi-Fi work?
Wi-Fi uses radio frequencies to transmit data from one party to another. It shares the same principle as any other technologies that use radio waves, including the radio itself.
AM and FM radio broadcasting stations use frequencies measured in Megahertz (MHz), Kilohertz (kHz), or even lower. A station can cover a large area, like a big city.
On the other hand, traditional Wi-Fi uses much higher frequency measured in Gigahertz (GHz), including 2.4 GHz, 5 GHz, and 6 GHz frequency bands to cover a much smaller area. Often a broadcaster can blanket a modest home in physical size.
Wi-Fi is also available in the short-lived 60 GHz band, which has an extremely short range, and the upcoming 900MHz band for low-bandwidth devices.
To understand frequencies, we need to know what constitutes one Hertz, a unit named after Heinrich Hertz, a German physicist who conclusively proved the existence of electromagnetic waves in the late 19th century.
What is Hertz?
In the simplest terms, Hertz is the number of radio wave crests -- or wave cycles -- in 1 second.
Fill your bathtub with water. Wait till the surface is completely serene. Now, throw in a little rubber duck. Note the waves travels outward. Pick one. Count the number of times the wave reaches its highest point in a second. If it's once, you get one Hertz; twice means you have two Hertz, and so on. That's the idea.
Radio waves can't be counted with the naked eye -- we can't see them to begin with -- and Wi-Fi uses frequencies in GHz. For example, 5GHz means there are 5,000,000,000 wave crests in a second. So, take science's word for it!
The higher the frequency, the closer the distance between two consecutive wave crests, which translates into a shorter length the wave itself can travel. However, that also means the more information you can put on it.
And in Wi-Fi, this information travels between pieces of hardware. Let's find out what they are.
We need a signal broadcaster and a receiver to have a Wi-Fi connection. They are the two ends of a network connection. Specifically, the former emits Wi-Fi signals for the latter to catch on to form a wireless link.
For this to happen, the broadcaster can make the Wi-Fi an open network to which any clients can connect; or it can create a secure network where only authorized clients can connect via a password. (More Wi-Fi security in this separate post on Wi-Fi Settings.)
A Wi-Fi broadcaster is typically called a wireless access point (WAP) or access point (AP) for short. However, you more often run into Wi-Fi routers. These are standard routers with a built-in AP. Most home routers nowadays are presumed to have Wi-Fi, though you can still find non-Wifi routers.
The receiver is always a Wi-Fi adapter. In most cases, you do not see an adapter since it resides inside a larger device, such as a laptop or a smartphone. But if you have a computer that doesn't have built-in Wi-Fi (or Wi-Fi of the standard you want), you can upgrade or swap out the adapter fairly easily.
A device -- a computer or a mobile phone -- with a built-in Wi-Fi adapter is called a Wi-Fi client or just a Wi-Fi device.
Wi-Fi typically works in the "infrastructure" mode in which one broadcaster can host multiple receivers, but a receiver can connect to just one broadcaster at a time. Technically, two receivers can connect directly in the rarely-used "ad-hoc" mode.
All Wi-Fi broadcasters and receivers have antennas. If you don't see them, they are hidden inside or blended with the device's other (metal) parts, like the chassis.
Once we have a broadcaster and receiver, a Wi-Fi connection's speed depends on their Wi-Fi standard.
Home Wi-Fi and their standards
Wi-Fi standards are how we manipulate the frequencies mentioned above using specific spectrums determined by the Institute of Electrical and Electronics Engineers (IEEE). We have a new standard each time a spectrum is available for Wi-Fi use.
These standards are necessary partly because we can't use just any frequencies. They are regulated -- the hardware you buy is restricted to a specific spectrum. Additionally, devices must agree on standardized procedures to communicate via radio successfully.
Since 1999 there have been seven major Wi-Fi standards: 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac, 802.11ax (with an 802.11axe extension), and 802.11be.
There are some non-major standards, too.
The first three standards (802.11b, 802.11a, and 802.11g) are now obsolete. Generally, we only need to care about Wi-Fi 4 (802.11n) and later.
And if you're confused by those cryptic names above, here's good news: you don't have to remember them.
Wi-Fi naming convention
On October 3, 2018, the Wi-Fi Alliance introduced a new Wi-Fi naming convention using simple numbers.
Specifically, 802.11ax is called Wi-Fi 6 -- it's the 6th generation --, 802.11ac is now Wi-Fi 5, and 802.11n is Wi-Fi 4, etc.
This new naming convention is a welcome change. And it makes sense that a higher number of Wi-Fi means a newer and faster standard.
Many Wi-Fi clients nowadays show their connection with this new convention. Specifically, you might see a tiny number of the standard next to the Wi-Fi symbol on your devices, allowing users to pick one that best matches your device.
Faster Wi-Fi doesn't necessarily translate into speedier Internet because Wi-Fi and the Internet are two different things.
Wi-Fi’s connection rules and its backward compatibility
Generally, newer standards are faster than the older ones but are backward compatible if they use the same frequency. Consequently, for the most part, you can use Wi-Fi devices of different generations together.
Wireless devices connect using the standard they support, and you can't tell which one they use unless you test the speed, use specific equipment, or view its status via an application. Wi-Fi signals are invisible. There's no way to tell them apart by looking at the air.
A Wi-Fi connection's speed between two direct parties shares the same principle of a network connection -- always that of the slowest party. Also, up to Wi-Fi 6e, a Wi-Fi connection occurs in a single band, using a fixed channel, at a given time.
Wi-Fi 7's new MLO feature allows combining multiple bands into a single link.
For example, if you use a Wi-Fi 6 client with a Wi-Fi 5 router, the connection speed will be that of the latter. And when you use a dual-band client with a dual-band (or tri-band router), the connection will take place using the 5GHz or 2.4GHz band at a time.
A Wi-Fi broadcaster's band also has lots of overhead, and generally, its real-world bandwidth is just half or two-thirds of its theoretical speed. That bandwidth, by the way, is shared between all of its connected devices.
Network connection: Wi-Fi vs Wired
Wi-Fi: Partial bandwidth and always Half-Duplex. Data moves using a portion of a band (spectrum), called a channel, in one direction at a time. You can think of Wi-Fi as the walkie-talkie in voice communication.
Wired: Full bandwidth and (generally) Full-Duplex. Data travel using the entire cable's bandwidth and in both ways simultaneously. That's similar to a phone call in voice communication.
While Wi-Fi is super-convenient, it's only relevant when operating on top of reliable and fast wired connections.
Wi-Fi standards in brief
The table below includes all current Wi-Fi standards and their brief specifications.
|Name||Standard||Availability||Top Speed |
|N/A||802.11g||2003||54Mbps||20 MHz||Open |
or Wireless N
|60 GHz||Limited Use|
802.11ad and Wi-Fi HaLow
You'll note in the table above the two "odd" Wi-Fi standards, 802.11ad and Wi-Fi Halow. They are indeed different from the rest and opposite of each other.
802.11ad, often known as WiGig, was first introduced in 2009 and didn't become part of the Wi-Fi ecosystem until 2013.
This standard operates in the 60 GHz band to have super-fast wireless speeds of up to 7 Gbps. In return, it has a super-short range that maxes out at shorter than 10 feet (3m). It also can't penetrate walls or objects, making it impractical as a wireless networking standard.
The 802.11ad was available briefly as a docking solution for a laptop -- a quick way to connect devices at a close distance, within a line of sight. The standard suffered from low adoption rates and has become obsolete.
An 802.11ad router, such as the Netgear Nighthawk X10, always includes 802.11ac and 802.11n access points to work with existing Wi-Fi clients.
Wi-Fi HaLow, on the other hand, is an upcoming standard that operates in the 900MHz band to deliver signals over a vast distance -- over a mile -- with limited connection speeds. It's a standard design for low-bandwidth IoT devices.
With that, let's dig deeper into the detail of Wi-Fi.
Wi-Fi bands and their intricacies (range, channels, and streams)
Wi-Fi bands are the radio frequencies on which the Wi-Fi signals travel between an AP and a client. When it comes to Wi-Fi, we generally need to know the following bands: 2.4GHz, 5GHz, and 6GHz.
There's the 60GHz band, but it's hardly useful or used at all -- more in the 802.11ad standard below.
Besides the base speeds mentioned in the table above, each of these bands' most significant and common attributes is their ranges. Let's find out!
Wi-Fi range, in theory
The way radio waves work, a broadcaster emits signals outward as a sphere around itself -- the range is the radius of this sphere.
The lower the frequency, the longer the wave can travel. AM and FM radios use frequency measured in Megahertz -- you can listen to the same station in a vast area, like an entire region or a city.
Wi-Fi uses 2.4GHz, 5GHz, and 6GHz frequencies -- all are incredibly high. As a result, they have much shorter ranges compared to radios. That's not to mention a home Wi-Fi broadcaster has limited power.
But, regardless of Wi-Fi standards, these bands generally share the following: The higher frequencies (in Hz), the higher the bandwidth (speeds), the shorter the ranges, and the more bandwidth progressively lost over increasing distance.
Generally, bigger Wi-Fi broadcasters tend to have better ranges than smaller ones. Still, it's impossible to accurately determine the actual content of each because it fluctuates a great deal and depends heavily on the environment.
That said, here are my estimates of home Wi-Fi broadcasters' ranges determined via personal experiences:
These were determined in the best-case scenario, i.e., open outdoor space on a sunny day. Also, note that Wi-Fi ranges don't die abruptly. They degrade gradually as you get farther away from the broadcaster. The distances mentioned below are when a client still has a signal strong enough for a meaningful connection.
- 2.4GHz: This band has the best range, up to 200ft (61m). However, this is the most popular band, also used by non-Wi-Fi devices like cordless phones or TV remotes. Its real-world speeds suffer severely from interference and other things. As a result, for years, this band has been considered a backup, applicable when the range is more important than speed.
- 5GHz: This band has much faster speeds than the 2.4GHz band but shorter ranges that max out at around 175ft (50m).
- 6GHz(*): This is the latest band available, starting with Wi-Fi 6E. It has the same ceiling speed as the 5GHz band but with less interference and overheads. As a result, its actual real-world rate is faster. However, due to the higher frequency, it has just about 70% of the range, which maxes out at about 130ft (40m).
(*) Wi-Fi 7 has a new feature called Automated Frequency Coordination (AFC) that, when implemented, increases the broadcasting power of the 6GHz band enough to make its range comparable to that of the 5GHz.
Some might consider these numbers generous, and others will argue their router can do more, but you can use them as the base to calculate the coverage for your situation.
Wi-Fi range in real life
Wi-Fi broadcasters of the same frequency band and broadcasting power generally deliver the same coverage.
Specifically, they are all the same if you measure the signal reach alone. What differentiates them is their sustained speeds and signal stability, or how the quality of their Wi-Fi signals changes as you increase the distance. And that generally varies from one model or Wi-Fi standard to another.
In real-world usage, chances are your router's Wi-Fi range is much shorter than you'd like. That's because Wi-Fi signals are sensitive to interferences and obstacles.
While the Wi-Fi range doesn't depend on the channel width, the wider a channel, the less stable it might become -- it's more susceptible to interference.
The new 6GHz band generally doesn't suffer from interference other than when you use multiple broadcasters nearby. On the other hand, the 2.4GHz and 5GHz have a long list of things that can harm their ranges.
Common 2.4 GHz interference sources
- Other 2.4 GHz Wi-Fi broadcasters in the vicinity
- 2.4GHz cordless phones
- Fluorescent bulbs
- Bluetooth radios (minimal)
- Microwave ovens
Common 5 GHz interference sources
- Other nearby 5GHz Wi-Fi broadcasters
- 5GHz cordless phones
- Digital satellites
Common signal blockage for all Wi-Fi bands: Walls and large objects
As for obstacles, walls are the most problematic since they are everywhere. Different types of walls block Wi-Fi signals differently, but no wall is good for Wi-Fi. Large objects, like big appliances or elevators, are bad, too.
Here are my rough estimations of how much a wall blocks Wi-Fi signals -- generally use the low number for the 2.4GHz and the high one for the 5GHz, add another 10%-15% to the 5GHz's if you use the 6GHz band:
- A thin porous (wood, sheetrock, drywall, etc.) wall: It'll block between 5% to 30% of Wi-Fi signals -- a router's range will be much shorter when you place it next to the wall.
- A thick porous wall: 20% to 40%
- A thin nonporous (concrete, metal, ceramic tile, brick with mortar, etc.) wall: 30% to 50%
- A thick nonporous wall: 50% to 90%.
Again, these numbers are just ballpark, but you can use them to know how far the signal will reach when you place a Wi-Fi broadcaster at a specific spot in your home. A simple rule is that more walls equal worse coverage.
Wi-Fi channels, in a nutshell, are a small portion (section) of each Wi-Fi band. If a Wi-Fi band is a freeway, the channels are lanes.
A Wi-Fi connection must use a particular channel at a given time. (Just like a car must use a specific lane at any given time.)
The channel width (or bandwidth) decides how fast a link is -- the amount of bandwidth it can deliver. That's like a bike lane can handle less traffic than a car lane but is still more capable than the sidewalk for pedestrians.
In return, a wider channel also tends to suffer more from interference, hence, is less stable than a narrower one. But the specificity of that depends on the environment. In an ideal air space, wider is always better.
Channels are measured in Megahertz (MHz) -- the higher the number, the wider, hence, the more bandwidth.
There are four popular channel width levels, depending on the frequency. The 2.4GHz band can only have 20MHz and 40MHz channel widths; the 5GHz band adds 80MHz and 160MHz. The latest 6GHz band has even wider channels.
In all cases, we need to combine multiple contiguous channels to make up a wider one. So a 40MHz channel includes two consecutive 20MHz channels, an 80MHz channel requires two contiguous 40MHz channels (or four 20MHz ones), etc.
As a result, a Wi-Fi band can include more narrower or fewer wider channels. On the 5GHz, there can be at most two 160MHz channel widths (or three if you count the UNII-4 portion). Most importantly, both require the use of DFS channels.
What's DFS, exactly?
Dynamic Frequency Selection (DFS) channels
Only available on the 5GHz band, DFS channels are special ones that share the air space with radar signals which have the right-of-way. So a DFS channel is like a bike lane on which you can drive your car, but only when there's no cyclist around.
Normally, these channels work just like any other channel. However, when radar signals are present, often if you live within tens of miles of an airport or weather station, the router will move its signals to the next unoccupied DFS channel.
During this channel-switching process, your device might get disconnected briefly. That said, the use of the 160MHz channel width, which requires DFS, is not always a good thing.
Not all clients support DFS, so most routers don't use these channels by default for compatibility reasons.
160MHz vs 160MHz (80+80) channels
To avoid DFS, some Wi-Fi chips have the 160MHz (80+80) mode by combining two non-contiguous 80MHz channels into a single one -- like in the case of the Netgear RAX120.
The 160MHz (80+80) approach is a hack and doesn't deliver the same performance as a natural 160MHz channel. It hardly works in real-world testing and is considered abandoned, especially with the subsequent availability of the UNII-4 portion.
Overlapping channels are those that multiple types of traffic can use -- like a bike can go on a lane designed for cars -- and tend to be more susceptible to interference.
On the other hand, non-over-lapping channels are like lanes explicitly intended for a type of traffic, such as a railroad or a carpool lane.
Wi-Fi streams -- often referred to as spatial or data streams -- are how a Wi-Fi signal travels. A stream determines the base speed of a frequency band in a Wi-Fi standard. The more streams a band can handle, the faster its rate is.
You can think of the streams as the vehicle that uses the road. Depending on the cargo space's size (or the number of trailers it can pull), a vehicle can move more or fewer goods per single trip.
Depending on the hardware specs, a Wi-Fi connection uses a single-stream, dual-stream (2x2), three-stream (3x3), or four-stream (4x4). Right now, 4x4 is the highest, though there might be even more in the future.
Note that we're talking about the number of streams of a single band here. Starting with Wi-Fi 6 -- more below -- many networking vendors combine the streams of all bands in a broadcaster into a larger number, like 8 or 12 streams.
That's misleading since a Wi-Fi connection takes place in one fixed channel of a particular band at a time, similar to the fact a vehicle can use only one lane of a road at a time, so it's irrelevant to use the number of lanes found in all roads to insinuate the performance of one particular lane, road or vehicle.
As you can see in the table above, each Wi-Fi band and standard have a different base single-stream speed. But in all cases, the concept of multiple streams remains the same.
While both a car and a bike can tow a trailer, the sizes of their trailers are different.
Important note: In a particular Wi-Fi connection, the amount of streams used is the lesser the parties involved. For example, if you use a 4x4 router with a 2x2 client, you'll have a 2x2 connection.
Bands vs Channels vs Streams
Wi-Fi uses three frequency bands, including 2.4GHz, 5GHz, and 6GHz.
Each band has multiple channels of different widths, including 20MHz, 40MHz, 80MHz, 160Mhz, and even wider. The wider a channel is, the more bandwidth it has.
Data moves wirelessly via streams, including dual-stream (2x2), three-stream (3x3), quad-stream (4x4), and even more.
Here's a crude analogy:
If a Wi-Fi band is a freeway, then channels are lanes, and streams are vehicles (bicycles vs cars vs semi-trailer trucks). On the same road, you can put multiple adjacent standard lanes into a larger one to accommodate oversized vehicles that carry more goods (data) per trip (connection).
A Wi-Fi connection generally occurs on a single channel (lane) of a single band (road) at a time. The actual data transmission is always that of the lowest denominator. Similarly, a bicycle can carry just one person at a relatively slow speed, even when you ride it on a super-wide lane of an open freeway.
The evolution of Wi-Fi
Over the years, as Wi-Fi progresses over different standards, it also has more and more features. Below are a few big milestones.
Again, since the older standards are obsolete, we'll start with Wi-Fi 4.
Wi-Fi 4 (802.11n)
Wi-Fi 4, also known as Wireless-N, uses 20MHz and 40MHz channel widths and up to three streams (3x3). A single stream delivers 150Mbps (40MHz).
Wi-Fi 4 is when we also have:
- The designations of combined speeds
- The popular use of WPS and Wi-Fi Protected Access (WPA) security methods.
This is when a Wi-Fi broadcaster operates in 2.4GHz and/or 5GHz at a time.
Dual-band is a compatibility necessity. Some Wi-Fi devices only use the 2.4GHz band, and others use the 5GHz. So for devices to work interchangeably, regardless of their standard, dual-band support is necessary.
A dual-band broadcaster has two access points, one for each band. A dual-band client similarly has two wireless receivers.
Keep in mind that "dual" doesn't mean you'll see two hardware units. Instead, one physical access point (or router or adapter) has two hardware components on the inside.
Dual-band broadcasters (routers, access points) are generally concurrent (or true) dual-band, meaning they can work on both bands simultaneously. There were once selectable dual-band broadcasters -- supporting the obsolete 802.11a and 802.11b/g standards -- that operated on one band at a time.
All receivers (adapters/clients), dual-band or not, can only connect to a broadcaster using one band at a time. This is like a car can only use one lane of a road at a given time.
Combined speed designation
With Wi-Fi 4, networking vendors use the N designations, where N is short for 802.11n.
For example, they called a dual-band dual-stream (2x2) Wi-Fi 4 router an N600 router. The number following N is the combined ceiling speeds of both bands (300Mbps on the 2.4Ghz and 300Mbps on the 5Ghz). Similarly, three-stream (3x3) routers are now classified as N900.
This type of naming continues with newer Wi-Fi standards.
MIMO stands for multiple inputs and multiple outputs. It allows a pair of broadcasters and a receiver to handle multiple data streams simultaneously. The more streams there are, the faster the connection is.
Again, MIMO started with Wi-Fi 4 (802.11n) and works on both 2.4GHz and 5GHz frequency bands. Later on, MIMO is often referred to as single-user MIMO or SU-MIMO, thanks to the introduction of MU-MIMO or multi-user multiple-input and multiple-output in Wi-Fi 5.
Wi-Fi Protected Setup (WPS)
First introduced in 2006 by Cisco, WPS became popular with Wi-Fi 4. This is a quick way to allow a client to connect to a Wi-Fi network by pressing a button on the router and then on a client.
WPS saves you from the hassle of manually typing in the Wi-Fi password, but it could pose security risks in some instances. Nonetheless, it remains in later standards.
Wi-Fi Protected Access (WPA)
Wi-Fi 4 is also when the new Wi-Fi protected setup Wi-Fi Protected Access (WPA) became widely adopted.
Officially available in 2003, WPA replaced the Wired Equivalent Privacy (WEP) security method laden with vulnerabilities.
WPA uses a common configuration called WPA-PSK (Pre-Shared Key). The security keys this method uses are 256-bit long, much better than the 64-bit and 128-bit keys of WEP.
Initially, for encryption, WPA uses the Temporal Key Integrity Protocol (TKIP), which employs a dynamic per-packet key system that's more secure than WEP's fixed key system. Later on, WPA gets an even better encryption standard called Advanced Encryption Standard (AES).
During its entire life, WPA allows users to choose between TKIP and AES. Besides WPA, Wi-Fi 4 hardware also supports WEP for backward compatibility since some legacy clients don't support WPA.
While secure, WPA is vulnerable to hacking, especially via Wi-Fi Protected Setup (WPS) mentioned above.
Wi-Fi 5 (802.11ac)
This standard operates only on the 5GHz band and the base single stream speed of around 433Mbps (80MHz) and can deliver up to four streams at a time (4x4), hence up to around 1733Mbps (4 x 433Mbps) speed.
Some Wi-Fi 5 broadcasters support the new 160MHz to deliver even faster speed. However, very few Wi-Fi 5 clients support this channel width.
On the 5GHz band, the standard is backward compatible with Wi-Fi 4. Also, a Wi-Fi 5 router/access point always includes a Wi-Fi 4 access point on the 2.4GHz band. For this reason, any Wi-Fi 5 broadcaster will support all existing Wi-Fi clients.
With Wi-Fi 5 comes:
- Traditional Tri-band
- Beam Forming
- The adoption of the WPA2 security method
- Wi-Fi mesh system
Generally, this means a broadcaster has three access points of different bands.
Traditionally, this means it has one 2.4GHz band and two of 5GHz bands, all working simultaneously. A tri-band broadcaster can serve more 5GHz clients simultaneously than a dual-band router before slowing down.
There's now a new type of tri-band with the introduction of Wi-Fi 6E -- more below.
Wi-Fi 5’s AC designations
Similar to the N designations above, networking vendors now combine the speeds of all bands into new names for Wi-Fi 5 routers. These names start with AC, where AC is short for 802.11ac.
Different vendors might use different numbers depending on how they decide to round up (or down) the total bandwidth, mostly for marketing purposes. So, they are not consistent throughout the industry.
Keep in mind that the numbers following AC are not the top speed of a single connection but the total bandwidth of all bands.
That's like calling your flying car (when you have one!), which can run at 60 miles per hour and fly at 120Mph, a 180Mph vehicle. That is misleading since the car can only run or fly at a time. But networking vendors love to use this as a marketing ploy.
Beamforming is a feature where the broadcaster automatically focuses its signals in a specific direction of a receiver to increase efficiency and speed.
Beamforming is only available on the broadcaster side, and it's generally hard to gauge its effectiveness.
Commercially available in 2006, the WPA2 is an improved version of WPA. The Biggest change is the mandatory use of the AES encryption method and the introduction of the Counter Cipher Mode with Block Chaining Message Authentication Code Protocol (CCMP) as the replacement for TKIP.
Wi-Fi 5 hardware still supports WPA for backward compatibility. The support for WEP was also available initially but slowly phased out in newer hardware.
While WPA2 is much more secure than WPA, it's not 100% hack-proof and is also susceptible to hacking, again via WPS. The chance of getting a WPA2 security method hack is minimal, however.
This feature is part of Wi-Fi 5 Wave 2 -- an enhanced version of 802.11ac. MU-MIMO allows multiple devices to receive various data streams at the same time.
More specifically, in a MIMO network, the broadcaster handles just one Wi-Fi client at a time, first come, first served. So if you have multiple clients, they must stay in line and take turns receiving data packages. It's like when there's just one bartender in the club.
On the other hand, in an MU-MIMO network, the broadcaster can simultaneously serve up to four (possibly more in the future) Wi-Fi clients. It's like having a few bartenders in the club.
That said, it's important to note that even in a MIMO network, a router can switch between clients quite fast, and most of the time, you won't experience any delay or slowdown.
Consequently, unless you have many -- a dozen or so -- simultaneously active clients, you won't see the benefit of MU-MIMO. Also, this feature only works on the downlink and the 5GHz band.
Most routers, if not all, new routers and access points support MU-MIMO.
Wi-Fi mesh system
Mesh systems come in all different flavors to deliver different speeds and coverage grades to fit different needs. You can read more about them in this post.
Wi-Fi 6 (802.11ax)
But briefly, this new standard operates in both 5GHz and 2.4GHz bands. On the former, it supports the 160MHz channel and has a base single-stream speed of 600Mbps.
Wi-Fi 6 adds the following to Wi-Fi:
Wi-Fi 6E (802.11axe)
Wi-Fi 6E is the extension of Wi-Fi 6 and uses the 6GHz band to do away with DFS channels at the cost of a shorter range. The standard became commercially available in 2021.
The biggest change of Wi-Fi 6E is it mandates the use of WPA3.
Details of the new standard can be found in this post on Wi-Fi 6E.
Wi-Fi 7 (802.11be)
Wi-Fi 7 is the latest and the biggest improvement, with the first supporting routers available in 2023.
Besides inheriting all the features of the previous standard, it's slated to improve the connection speed by supporting multiple features, including combining various bands into a single link and using extra broadcasting power in certain situations to make the 6GHz range comparable to that of the 5GHz.
Wi-Fi 7 is the first standard that can deliver true muti-Gigabit connections, with a big focus on Multi-Gig wired standards. More about it is in the separate post linked below.
For the past two decades, Wi-Fi has become one of the essential technology in our daily life. Over the years, it has evolved so much, delivering connection speeds tens of times faster than when it first became available to the masses.
And Wi-Fi 7 is likely not the last revision.