Wi-Fi — the familiar name of the 802.11xx networking standards — is an essential cord-cutting invention. Just imagine how your smartphone or tablet would be without your home Wi-Fi.
So, 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 quite confusing due to its many speed standards, wireless bands, features and, well, other stuff.
This post will help you understand Wi-Fi at least as well as the next guy, without getting embroiled in the networking jargon. Explain Wi-Fi at a cocktail party is a challenge, but I’ll try.
How does Wi-Fi work?
Wi-Fi uses radio frequencies to transmit data. 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 Kilohertz (kHz) and Megahertz (MHz). Wi-Fi, on the other hand, uses much higher rates measured in Gigahertz (GHz). Specifically, for the most part, it uses the 2.4Ghz and 5GHz frequency bands.
What is Hertz?
To know that those units mean, you just need to understand what constitutes one Hertz.
In the simplest terms, Hertz is the number of radio wave crests — or wave cycles — in 1 second.
Throw a big rock into a still pond and count the number of times the wave reaches its highest point in a second as it travels outward. If there’s only one, then you get one Hertz; two mean you have two Hertz, and so on.
The significance of high radio frequencies
As you might have noted, Wi-Fi uses very high frequencies of 2.4GHz (or 2,400,000,000 Hz) and 5GHz (5,000,000,000 Hz).
In a nutshell, 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 the way we manipulate the frequencies translate into many different Wi-Fi flavors known as standards.
Home Wi-Fi standards
You can not use just any frequencies. They are regulated, and that’s a good thing because for things to communicate via radio, they have to agree on many standardized procedures.
So, Wi-Fi standards are specific spectrums, determined by the Institute of Electrical and Electronics Engineers (IEEE). Each time a spectrum is available for public use, we have a new Wi-Fi standard.
Since 1999 there have been six standards, including 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac, and 802.11ax.
Newer standards are always faster than the older ones but are also backward compatible. Consequently, for the most part, you can use Wi-Fi devices of different generations together.
New designations: 802.11ax is now Wi-Fi 6
On October 3, 2018, the Wi-Fi Alliance introduced new designations for these Wi-Fi standards, using numbers. As a result, 802.11ax is called Wi-Fi 6 (because it’s the 6th generation of Wi-Fi), 802.11ac is therefore called Wi-Fi 5, etc. More on the table below:
Notes on Wi-Fi speeds
Wi-Fi speeds mentioned here, as well as those advertised by the vendors, the theoretical ceiling speeds. The actual speeds of Wi-Fi vary a great deal and always much lower due to interference, distance, device compatibility, and overheads.
In my experience, in real-world usage, you’ll generally get about two-third of the ceiling speeds, at most.
Also, a Wi-Fi connection’s speed between two parties shares the same principle of a network connection — it’s that of the slowest party. For example, if you use a Wi-Fi 5 client with a Wi-Fi 4 router, the connection between the two will adhere to the latter.
This new naming convention is a welcome change. You don’t need to wonder which is better ac, n or ax anymore. And it just makes sense that a higher number of Wi-Fi means newer and faster standard.
According to the Wi-Fi Alliance, going forward, when all vendors adopt the new designations, the Wi-Fi device will also indicate what generation of Wi-Fi is available (4, 5, or 6).
Consequently, when there are multiple Wi-Fi networks of different Wi-Fi standards at a location, you can pick one that best matches your device. (Keep in mind, doing that doesn’t mean you’d necessarily get faster Internet because Wi-Fi and the Internet are two different things.)
The first three standards are slow and now obsolete. And that’s great because you only need to care about Wi-Fi 4 and later.
Wi-Fi 4 (802.11n)
Also known as Wireless-N and available in up to three streams with a single stream being able to deliver 150Mbps. (More on Wi-Fi streams below).
Together with this standard came a few major milestones for Wi-Fi.
With Wi-Fi 4, for the first time, Wi-Fi broadcasters, namely routers and access points, that operate in both 2.4GHz and 5GHz bands, became available.
Dual-band is a compatibility necessity. That’s because the older Wi-Fi standard only uses the 2.4GHz band and the new ones use just the 5GHz. So for devices to work interchangeably, regardless of their standard, dual-band support is a must.
Combined speed designation
As a way to differentiate devices, networking vendors resorted to the N designations, where N is short for 802.11n.
For example, they called a dual-band dual-stream (2×2) Wi-Fi 4 router an N600 router. The number following N is the combined ceiling speeds of both bands. Similarly, a three-stream (3×3) routers are now N900 routers.
Keep in mind that no matter how many bands a router or client supports, a Wi-Fi connection takes place in only a single band at a time. (Again, more on Wi-Fi bands below.)
Wi-Fi 5 (802.11ac)
This standard operates only on the 5GHz band and the base single stream speed of around 433Mbps and can deliver up to four streams at a time (4×4), hence up to around 1733Mbps (4 x 433Mbps) speed.
On the 5GHz band, the standard is backward compatible with Wi-Fi 4 (802.11n). Also, a Wi-Fi 5 router/access point always includes a Wi-Fi 4 access point on the 2.4 Ghz band. For this reason, any Wi-Fi 5 broadcaster will support all existing Wi-Fi clients.
Together with Wi-Fi 5 came two significant developments:
Routers with one 2.4Ghz band and two 5GHz bands working simultaneously. The additional 5GHz band means they can support more clients on this band before slowing down.
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.
As a result, you’ll find many of variables such as:
- AC1900: Dual-band 3×3 router with 1300Mbps on 5GHZ and 600Mbps on 2.4 GHz)
- AC2500: Dual-band 4×4 router
- AC3200: Tri-band 3×3 router with 1300Mbps on each of the two 5GHz bands and 600Mbps on 2.4 GHz).
And there are a lot more. 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.
First introduced in 2009 as WiGig, this standard was initially one on its own and didn’t become part of the Wi-Fi ecosystem until 2013.
802.11ad operates in the 60 GHz and has an extreme wireless speed of up to 7 Gbps.
However, it has an extremely short range, just about a few meters in my experience. It also can’t penetrate walls or objects, making it impractical as a wireless networking standard.
So, 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. Due to this extreme shortcoming, this standard has suffered from low adoption rates.
An 802.11ad router always includes an 802.11ac and 802.11n access points for it to work with existing Wi-Fi clients. But, again, you can probably forget about it.
Wi-Fi 6 (802.11ax)
802.11ax is the next generation of Wi-Fi and became commercially in early 2019 with routers available first. Chances are you’ll need to wait for a few years before Wi-Fi 6 reaches the current popularity level of Wi-Fi 5 (802.11ac).
This new standard is between 2 to 10 times faster than Wi-Fi 5, depending on the configuration. With Wi-Fi 6, you can have Wi-Fi connections up to a few times speedier than 1Gbps, which is the speed of a wired Gigabit connection.
I wrote about Wi-Fi 6 in details in this post, but there are two important things you should know about it:
OFDMA – More efficiency
Wi-Fi 6 uses new a new technology called orthogonal frequency-division multiple access (OFDMA), which is a mouthful for frequency division multiplexing.
Specifically, the technique divides each channel into many sub-channels of different frequencies of their own. These “mini” frequencies stack on top of one another to deliver much better efficiency.
You can think of OFDMA as an enhanced version of MU-MIMO. (More about MIMO and MU-MIMO below). If MU-MIMO is like having multiple bartenders (instead of just one as in MIMO), OFDMA takes it up a considerable notch by using robotic bartenders; each can serve numerous customers at a time.
Wake time scheduling – Better battery life
Wi-Fi 6 promises to further improve battery life compared to Wi-Fi 5 (802.11ac) partly because it requires less time to transmit the same amount of data. Most significantly, however, that’s thanks to the effect of a new feature called wake time scheduling or Target Wake Time (TWT).
This feature allows Wi-Fi adapters to quickly go to sleep when idle (even for a very brief time) and automatically wake up when needed. It’s is similar to having a car that automatically turns off its engine at a red light and automatically starts up when you step on the gas.
Like all previous Wi-Fi standards, Wi-Fi 6 is backward compatible with all existing Wi-Fi clients. But it requires the support of both the broadcaster (router or access point) and the receiver (client or adapter) to show its benefits.
To have a Wi-Fi connection, we need a signal broadcaster and a receiver. They are the actual hardware involved in a Wi-Fi connection.
Typically, the broadcaster is always an access point (AP). However, you more often run into Wi-Fi routers, which are standard routers that have built-in AP(s). All home routers nowadays are presumably Wi-Fi routers.
The receiver is a Wi-Fi adapter. In most cases, you don’t see an actual adapter since it resides inside the device (laptop or smartphone) you’re using. But if you have a computer that doesn’t have built-in Wi-Fi (or Wi-Fi of the standard you want), you can easily buy a separate USB or PCIe Wi-Fi adapter.
A device, be it a computer or a handheld, with a built-in Wi-Fi adapter is called a Wi-Fi client.
These are the radio frequencies on which the Wi-Fi signals travel between an AP and a client. There are three Wi-Fi bands: 2.4GHz, 5GHz, and 60GHz. Each requires a specific hardware component. In other words, they don’t work interchangeably.
The higher the number, the faster the speeds but shorter the range. The range of the 60GHz band is so short that it has very few real-world applications, as mentioned in the case of 802.11ad above.
The 2.4GHz band is the most popular. Non-Wi-Fi devices like cordless phones or TV remotes use it, too. As a result, its real-world speeds suffer severely from interference and other things.
As a result, it now works mostly as a backup, where the range is more important than speed. Generally, in my experience, this band has an effective range of around 175 ft (53 m). And it’s also fast enough to deliver a modest sub-50 Mbps Internet connection in full.
That said, the 5GHz band is the sweet spot where you get both high speed and long-range, of around 150 ft (46 m).
A dual-band broadcaster has two access points. Conventionally, these include one 2.4GHz AP and one 5GHz AP. A dual-band client, similarly, has two wireless receivers, one on each band.
Keep in mind that “dual” doesn’t mean you’ll see two hardware units. Instead, one physical access point (or router or adapter) that has two hardware components on the inside, one for each band.
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 802.11a and 802.11b/g standards — that operate on one band at a time.
All receivers (adapters/clients), dual-band or not, can only connect to a broadcaster on one band at a time.
Tri-band only applies to broadcasters.
Generally, this means a broadcaster has three access points, one of 2.4GHz and two of 5GHz, and all can work at the same time. A tri-band router can serve more clients at the same time than a dual-band router, before slowing down.
Wi-Fi channels, in a nutshell, are small parts of each Wi-Fi band. They are like lanes on the road. A Wi-Fi connection must use a particular channel at a given time. Channels decide how fast a link is. It’s like a bike lane is slower than a car lane but faster than the sidewalk for pedestrians.
Channels come in megahertz (MHz). There are four levels, including 20MHz, 40MHz, 80MHz, 160MHz. The higher the number, the wider the channels, which translate into faster speeds. A wider channel will take the space of multiple narrower channels.
Generally, Wi-Fi 4 (802.11n) works only with the first two. The 40MHz and 80MHz channel bandwidths are popular with Wi-Fi 5. It’s important to note that many Wi-Fi 5 broadcasters support 160MHz, but very few Wi-Fi 5 clients do. The 160MHz channel bandwidth is the key to the super-fast wireless speed of Wi-Fi 6, but not all Wi-Fi 6 devices support it due to different reasons. That said, the 80MHz is the most popular channel bandwidth.
160MHz vs. 160MHz (80+80) channels
A pure 160MHz channel includes continuous space. The 80+80 160MHz mode is when the hardware combines two non-continuous 80MHz channels into a single one.
Over-lapping channels are those that multiple types of traffic can use — it’s 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 car-pool lane.
Dynamic Frequency Selection (DFS) channels
Only available on the 5 GHz band, DFS channels — ranging from channel 52 to channel 144 — are special ones that share the air space with radar signals.
Normally, these channels work just like any other channel. However, when a radar is detected on the one your router is using, which tends to happen often if you live near an airport — a few tens of miles away or closer –, the router will move its signals to the next unoccupied DFS channel. During this process, you will lose the Wi-Fi signal briefly.
Another thing is not all clients support DFS and, therefore, can’t connect to the router’s 5 GHz band at all. For this reason, it’s generally safer to use non-DFS channels.
Wi-Fi streams — often referred to as spatial or data streams — are how 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.
Take Wi-Fi 4 (802.11n), for example. It has the base speed of 150 megabits per second (Mbps) per single 5GHz stream. If you have dual-stream (2×2) devices, you’ll get 300Mbps of Wi-Fi speed. Similarly, a 3×3 setup is 450Mbps.
In a Wi-Fi connection, the amount of streams being used is the lower number of either party. For example if you use a 3×3 router with a 2×2 client, you’ll have a 2×2 connection.
Thanks to improvement, the base speed of a single Wi-Fi stream gets faster, but the concept of multiple streams remain the same. Also, newer Wi-Fi standards tend to handle more streams. For example, while Wi-Fi 4 caps at three streams (3×3), Wi-Fi 5 can handle four streams (4×4). The upcoming Wi-Fi 6 will likely have even more streams.
Bands vs. Channels vs. Streams
To sum it up here’s a crude analogy: Wi-Fi connections are like traffic on a multiple deck bridge. Each deck is a Wi-Fi band. Each lane (including railroads and sidewalks) on a platform is a Wi-Fi channel. And the member of the traffics (car, busses, trains, bikes, etc.) that pass through at a given time are the Wi-Fi streams.
A Wi-Fi connection takes place on a single channel (lane) at a time, but the more channels there are (which increase with the number of bands), the more options hardware devices have to deliver better speed.
There are some Wi-Fi-enhancing features with the most popular being: WPS, Beamforming, MIMO, and MU-MIMO.
WPS stands for Wi-Fi Protected Setup, a quick way to allow a client to connect to a Wi-Fi network. It enables you to press a button on a broadcaster, and then on a client for the two to connect. Now wait a minute or so, and the two are connected.
WPS saves you from the hassle of having to type in the Wi-Fi password manually, but in some instances, it could pose security risks.
Beamforming is a common feature of Wi-Fi 5 (802.11ac) routers. The broadcaster automatically focuses its signals in a specific direction of a receiver to increase efficiency and, therefore, speed.
MIMO stands for multiple-input and multiple-output. It allows a pair of broadcaster and receiver to handle multiple data streams at a time. The more streams there are, the faster the connection is.
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.
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 have to stay in line and take turns to receive 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 serve up to four (possibly more in the future) Wi-Fi clients simultaneously. 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 slow down at all.
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 only on the 5GHz band.
Generally, though, it never hurts to have MU-MIMO, and most routers and access points support it these days.
Wave 1 vs. Wave 2
You might have heard of Wave 1 and Wave 2 Wi-Fi. These are two generations of Wi-Fi and collectively convey all the aspects mentioned above of Wi-Fi. These waves only apply to Wi-Fi 5 (80211ac) and Wi-Fi 4 (802.11n).
Wave 1 (gen 1) starts with Wi-Fi 4 and has the following capabilities:
- Up to three streams (3×3)
- Wider 80MHz channels.
When Wi-Fi 5 arrived, it initially used Wave 1 characteristics. Later on, Wi-Fi 5 moved up to Wave 2. That said, Wave 2 (gen 2) has the following capabilities:
- Up to four streams (4×4)
- Even wider 160MHz channels
In short, Wave 2 is faster and more efficient than Wave 1. However, devices of both waves are compatible with one another.
Dong’s note: I originally published this piece on May 6, 2018, and have updated it since.