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Home Networking - Part 2 - WiFi Fundamentals


  • Monday, Mar 9, 2020
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So, you’ve read through Part 1  of my guide to home networking, and picked a router that makes the most of your connection. But what if your WiFi is still unreliable, doesn’t reach far enough, or isn’t fast enough (or all of the above)? Strap in, because WiFi is a complex technology…

 


 

2.4Ghz vs 5Ghz

 

A comparison graph of 2.4Ghz and 5Ghz WiFi

Remember in Part 1 , where I said that it was important that any router you selected had dual-band WiFi? Let’s look into what this means in a little more detail.

All WiFi travels using different frequencies. The two main ones that are most frequently used are 2.4Ghz and 5Ghz. Initially, WiFi was offered on the 2.4Ghz frequency (also known as 802.11b) - however, the first implementation of this offered quite slow speeds. The first implemetation of the 5Ghz frequency for WiFi (known as 802.11a) offered greater speeds, but over much less range. Both were quickly usurped by the 802.11g standard, which offered the speeds of 802.11a but using the 2.4Ghz frequency of 802.11b to get greater range. 2.4Ghz WiFi signals are able to reach much further distances than 5Ghz signals, and they also penetrate through walls and other obstructions more easily. Following on from the 802.11g standard, there was the 802.11n standard, that fully maximises the 2.4Ghz frequency’s potential.

However, over time, the airwaves have become flooded with 2.4Ghz signals as an increasing number of devices (including bluetooth devices, and baby monitors) use them. For optimum signal strength and speeds, 2.4Ghz 802.11n signals should travel with a channel width of 20Mhz. However, there are only a limited number of channels available in the 2.4Ghz spectrum. To help explain this, have a look at the two graphs below:

Examples of overlapping and non-overlapping 2.4Ghz WiFi channels

In the graphs above, each parabola represents a WiFi network broadcasting on the 2.4Ghz frequency with a channel width of 20Mhz. If you look across the bottom, you can see the numbered channels available: 1-14 (channels 12-14 are almost never used, and are in fact illegal  in some countries). As you can see, each parabola spans across multiple channels. In the top graph, the networks are configured optimally. In the bottom graph, they are a complete mess.

Ideally, when configuring a 2.4Ghz network, only channels 1, 6 and 11 should be selected, as in the top graph. This means that no parabolas overlap horizontally. From left to right, the first parabolas are broadcasting on channel 1, the second parabolas on channel 6 and the third parabolas on channel 11. As you can see, each parabola actually spans more than one channel (1-3 for channel 1, 4-8 for channel 6 and 9-13 for channel 11). There are multiple networks broadcasting on each of these channels that are stacked vertically.

In the bottom graph, there are 2.4Ghz networks broadcasting across all the channels available. This means they are not only stacked, as in the top graph, but they are also overlapping horizontally. This creates an enormous amount of interference, which will cause all the networks in the bottom graph to have a bad, slow and unreliable signal. Not only do you have networks configured on channels 1, 6 and 11, but you have networks configured on the channels in between. Since each network spans multiple channels, there is a spaghetti junction of WiFi networks, and nobody has a chance to get a reliable and fast WiFi connection. The networks configured to broadcast on the in between channels are often interfering with networks either side of them, as well as stacking vertically. If you have configured your router to broadcast on anything other than 1, 6 or 11, do yourself and your neighbours a favour and go back to 1, 6 or 11.

The maximum real-world speed of a clear 2.4Ghz WiFi connection is about 80Mbps, but that is only when there is absolutely no interference and you are relatively close to the device broadcasting it. It also depends on the WiFi chip that is inside of the connecting client, and the number of antennae that both the client and broadcasting device have (more on that coming up). However, even when all the networks being broadcast aren’t overlapping horizontally, the sheer number of WiFi enabled devices that use the 2.4GHz frequency means getting a clear and fast signal has become nigh-on impossible, especially in large residential blocks where each flat has their own router, and consequently their own 2.4Ghz network.

When WiFi first became widely available, most people only used a few laptops per household. These days, there are laptops, smartphones, smart speakers, smart lightbulbs, baby monitors and bluetooth speakers (and many other devices besides), that use the 2.4Ghz WiFi frequency. Also, the further away you get from any WiFi signal, and the more objects in between the broadcasting device (like a router) and the client device (a laptop or smartphone), the lower the speed. Finally, if many devices use the same WiFi signal at the same time, they have to share the 80Mbps speed equally between them.

Example of overlapping 5Ghz channels

As space on the 2.4Ghz frequency started to run out, a new WiFi standard that used the 5Ghz frequency from the first 802.11a was invented, called 802.11ac. This was a huge improvement on the original 802.11a standard, especially when it comes to speed. A well configured 5Ghz 802.11ac signal is able to reach speeds of 350-400Mbps, but 5Ghz 802.11ac networks cannot reach the same distance as 2.4Ghz signals, and they cannot penetrate things like walls anywhere near as easily as 2.4Ghz networks either. However, as there are currently a lot less devices that are able to use the 5Ghz frequency, the airwaves tend to be generally clearer.

Most 5Ghz broadcasting devices in the UK are only able to utilise channels 36-48 for 5Ghz, and 5Ghz signals can have a bandwidth of either 20Mhz, 40Mhz or 80Mhz. An 80Mhz bandwidth 5Ghz network takes up channels 36-48 (see the graph above), leaving little room for manoeuvre. If you use a narrower bandwidth, the signal can travel further, but the maximum speed is reduced. Interference is not so much of a problem for the 5Ghz frequency as it stands as there are less devices capable of it, and the signal travels less distance than 2.4Ghz (see how much lower the parabolas are in the above diagram compared to the 2.4Ghz devices), so you are less likely to be affected by neighbouring networks. There is also a lot more bandwidth available to share out, even if you are only limited to channels 36-48. It can be handy to drop to 40Mhz when you have two 5Ghz networks quite close together as well (such as the two yellow parabolas in the graph above), such as in a multiple access point or mesh setup (which I’ll cover in Part 3  of this guide).

Some WiFi broadcasting devices, such as routers, are able to utilise channels above 36-48 (you can see these in the top right of the diagram above). However, each territory of the world has different regulations about what channels you are allowed to use, as they can interfere with things like radar. In the UK, anything above channel 48 is considered to have the potential for interference, so that is why most devices don’t allow you to use them. If you do have the option to use them, you have to tread carefully. These channels need to be configured properly to allow for Dynamic Frequency Selection (DFS)  to avoid any interference. Also, if you use these higher channels, you might find that some client devices won’t work well or at all, since they will only have been tested to work with channels 36-48.


 

Marketing nonsense

 

True, misleading or lie?

At this point, let’s take a look in more detail at the claimed speeds on offer from WiFi devices you may see for sale - and how much marketing nonsense is involved. The maximum theoretical speed of the various WiFi standards is:

  • 802.11b (WiFi 1) - 11 Mbps (2.4GHz)

  • 802.11a (WiFi 2) - 54 Mbps (5 GHz)

  • 802.11g (WiFi 3)- 54 Mbps (2.4GHz)

  • 802.11n (WiFi 4) - 600 Mbps (2.4GHz and 5 GHz)

  • 802.11ac (WiFi 5) - 1300+Mbps (5 GHz)

  • 802.11ax (WiFi 6) - this is the very latest standard and has only just hit the market. Potentially, speeds of up to 14 Gbps are attainable . Very few broadcasting devices are available currently, and very few client devices have the required chips to take advantage of the new standard. I’ll write a separate blog article in future once this standard becomes more widely adopted.

NB - The numbers in brackets above are a new naming standard  introduced last year to try to make things less confusing - the jury’s out as to whether it helps!

However, the reason that the speeds above are merely theoretical is that they combine both downstream (from the broacasting device to the client) and upstream (from the client to the broadcasting device) speeds, and don’t take into account distance, obstacles, and the number of users connected at one time.

In real-world usage, the speeds you can actually expect to attain are:

  • 802.11b (WiFi 1) - 2-3 Mbps downstream, up to 5-6 Mbps with some vendor-specific extensions.

  • 802.11g (WiFi 3) - ~20 Mbps downstream

  • 802.11n (WiFi 4)- 40-80 Mbps typical, varying greatly depending on configuration, whether it is a mixed or N-only network

  • 802.11ac (WiFi 5)- 70-100+ Mbps typical, higher speeds (200+ Mbps) possible over short distances without many obstacles, with newer generation 802.11ac routers, and client adapters capable of multiple streams.

There are a couple of important details in that second list:

Whether it is a mixed or N-only network - A mixed network is one that is configured to allow devices to connect using the 802.11b (WiFi 1) and 802.11g (WiFi 3) standards at the same time as 802.11n (WiFi 4) devices. There are very few devices left that have chips that use these old standards - but if you do have any, they will reduce the speed of the WiFi network they are connected to massively, as the network has to run at the slower speed to allow them to work. This means every device that is connected, even newer ones capable of faster speeds, will only get a speed as fast as the slowest device in the network. This is becoming less of a consideration these days as there are barely any devices left that use WiFi 1 or WiFi 3 chips. You can optionally make the network “N-only”, which will prevent any WiFi 1 or WiFi 3 devices from connecting at all and slowing things down.

Client adapters capable of multiple streams - Another important thing to consider when talking about WiFi is what the client device (laptop, smartphone etc.) is capable of. A lot of cheap WiFi enabled devices only have a 2.4Ghz WiFi chip inside them, and are therefore only able to see and connect to 2.4Ghz networks, and are unable to see 5Ghz networks at all. This is because 2.4Ghz WiFi chips are cheaper to manufacture, and 2.4Ghz networks have a greater range, so manufacturers choose to use them to both save manufacturing costs and allow the devices they are in to connect at greater distances.

Another important consideration is the number of streams both broadcasting device and client device use. The maximum real life speeds I mentioned above are often attained by using multiple streams, that are related to the number of antennae in both the broadcasting and client device. It’s possible to bond the streams together to attain high speeds if you have the same number of antennae on both broadcasting and client device.

Most good quality routers use 3 or 4 antennae, with each antenna/stream able to carry real-world speeds of around 40Mbps for 2.4Ghz and 150Mbps for 5Ghz. This means, by bonding the streams together, most broadcasting devices are able to deliver speeds of up to 120Mbps on 2.4Ghz and 450Mbps on 5Ghz. Most broadcasting devices like routers will state somewhere in the specifications something like “2x2” or “3x3” or even “4x4” - these numbers relate to the number of streams and antennae.

When you see routers for sale that claim a “blazing fast speed of 3200Mbps”, you have to take it with a massive pinch of salt. If you break those numbers down, you’ll see that actually, these routers will have one radio that can broadcast a three stream 2.4Ghz WiFi 4 network at a theoretical speed of 600Mbps, and two radios that can broadcast one three stream 5Ghz WiFi 5 network each, each with a theoretical speed of 1300Mbps. The manufacturer gets to a “blazing fast speed of 3200Mbps” by rolling these numbers into one figure (600+1300+1300). In reality, no device is going to be able to connect at a speed of 3200Mbps - the highest single theoretical connection speed would be 1300Mbps, and only over 5Ghz, fairly close to the router with no obstruction. And bear in mind, that is only the theoretical speed - as we saw above, real world WiFi 5 speeds are only actually anywhere from 70-450Mbps, depending on signal strength and the client device. It’s simply not possible to get faster than this on any WiFi 5 broadcasting device (WiFi 6 promises much, and I’ll revisit it in a future blog article once it’s more widely available).

Another thing to bear in mind is that both 2.4Ghz and 5Ghz can only operate at a certain signal strength - this is limited by the law. So if you spend £50 or £500 on a router, if it only has WiFi 5, it will only be capable of a maximum speed of 450Mbps and only be able to transmit at a fixed maximum signal strength. There isn’t a miraculous router on the market that can cover 5 floors from the ground floor, especially on the 5Ghz frequency - it just isn’t possible. If you need to increase the range of your signal, you’ll need to employ a “WiFi system” (which I’ll cover in detail in Part 3 ).

WiFi streams

Importantly, the real-world speeds I mentioned previously are only attainable if the client device has a matching number of antennae to the broadcasting device - if you look at the picture above, you can see that most small devices only have 1 antenna, and therefore only 1 stream, available. Most laptops only have 2 antennae/streams (and some cheaper ones only have 1!) It’s only really Apple laptops/desktops, or desktop PCs with an add-in card, that tend to have 3 or more antennae/streams inside of them. So, it’s important to make sure that both the broadcasting device and the client device have the ability to take advantage of as many streams as possible.

For small devices such as smartphones, tablets and smart devices, it’s not possible to change or upgrade the WiFi chip inside them, so you are stuck with whatever the manufacturer decides to use for them. When purchasing one of these smaller devices, it’s always worth checking the device specifications (a good website to do this for smartphones, for example, is https://www.devicespecifications.com/ ) to see what its WiFi capabilities are. Most cheaper smart devices and phones only have slow 2.4Ghz chips with one antenna (1x1); more expensive smartphones and tablets will often have dual band adapters capable of both 2.4Ghz and 5Ghz, with two antennae (2x2). Laptops often have antennae wires around the outside of the screen, under the plastics - cheaper ones will have a single antenna (1x1), better ones have two (2x2), and Apple devices often have three (3x3), or even four (4x4). Most laptops have a replaceable WiFi card inside them; it’s well worth upgrading if yours is only 2.4Ghz and getting a dual band one capable of both 2.4Ghz and 5Ghz, even if you only have one antenna - cards can be found cheaply second hand and are usually fairly easy to swap out (although the antennae wires can often be tricky to remove and attach). The same is true of desktop PCs - WiFi is often provided by a replaceable add-in card.

NB - it is possible to buy USB WiFi Adapters - however, performance on these is basically inadequate for anything other than light networking. The antennae are crammed inside a tiny case, and they often overheat once placed under sustained load. They are handy for temporary use, but far better to get a proper WiFi card for you desktop or laptop instead.

It’s arguably a waste of money to spend a lot on a router that can do 4x4 5Ghz WiFi 5 if you don’t have, or don’t plan to purchase, any devices that have a 4x4 chip and antennae configuration. It’s far better to have multiple WiFi broadcast points, ideally connected back to your router with wires, or wirelessly (known as mesh) - I’ll go into what options are available in Part 3 .


 

Putting it all together

 

A wireless network

So, if you’ve managed to stick with me up until this point, what do you do with all the above information? Well, here is what I suggest:

  • Firstly, you need to make sure your connection is working correctly. It’s amazing how many people blame their provider for networking issues when there is in fact an issue with their router and/or WiFi configuration. The best way to check this is to use an ethernet cable to wire up a device such as a laptop to your router (if you are using your own router, it’s best to use the one the provider gave you for free when you signed up to eliminate any configuration issues). Then, when nobody else is using the network, run a speedtest using the DSL Reports  tool as described in Part 1 . It’s good to establish if the connection you receive is as fast as you are paying for, and stable, before moving on to further configuration. Using a wired connection eliminates any potential WiFi interference.

  • Make sure that your router is positioned as centrally as possible in your property, ideally on the ground floor.

  • Then, you want to make sure you configure the router to broadcast separate networks for 2.4Ghz and 5Ghz - a lot of ISP provided free routers are configured with a single network that broadcasts on both frequencies (in fact, some, such as the BT Smart Hub 2, don’t allow you to change this setting!) I’m not a fan of this approach, as devices can often end up stuck on 2.4Ghz even if they are close enough to get a good 5Ghz connection, and speed is limited as a result. By separating out the networks, you can make sure you use 5Ghz when in good range, and flip to 2.4Ghz if you get too far from the router.

  • Use an app like WiFi Analyzer  on an Android device that can see and connect to both 2.4Ghz and 5Ghz networks - this can be a smartphone or tablet (sorry, Apple doesn’t allow this type of app on iOS). The graphs above are taken from this app. It will allow you to scan for all the WiFi networks in and around your property to help you pick which channel to use for 2.4Ghz - remember, pick whichever of 1, 6 or 11 has the fewest networks broadcasting and don’t use the in between channels. For 5Ghz, it’s less important, as the configuration options are more limited, but it can still be handy to see what’s going on. NB - Most routers and other devices will have an “Auto” setting, which, if the manufacturer has done a good job, should automatically select 1, 6 or 11 - but not always, so it’s worth checking.

  • Balance out your devices across the 2.4Ghz and 5Ghz networks - obviously some devices can only use 2.4Ghz, but you want to save as much bandwidth on the 5Ghz frequency as possible for devices that need it, like laptops or streaming devices. You’ll also be forced to use 2.4Ghz if there isn’t a broadcasting device that is close enough for you to get a good 5Ghz signal.

  • Bear in mind that the total speed available always has to be divided up amongst the number of devices using it; this is true both of the speed of your actual connection from your ISP, as well as the speed of the communications on your local network. The more speed you have available, the better, even if your ISP speed is relatively low (as for most people on BT Openreach connections). You will still see the benefits of more speed when doing local data transfers, for example from a device on your network such as a laptop or smartphone directly to a Network Attached Storage (NAS) device.

  • Finally, an old networking adage is if it doesn’t move, used wired ethernet. Despite how much WiFi has improved since it was first invented, there is still no substitute for a good old fashioned ethernet cable (these can carry 100Mbps, 1000Mbps or even 10,000Mbps, depending on which type you use). Wired networks are much less susceptible to interference and can carry far greater speeds. The clients I have with the very best home network experience have ethernet cables running to as many rooms as possible in the house (often wired in at the time the electrics are (re)wired). This can be expensive, but in my opinion is well worth it for the performance and versatility it offers, especially in large properties. Not only does this mean you can wire as many devices as possible back to the main router, but it gives much more flexibility, and better performance, when trying to increase the range of your WiFi, as these ethernet cables can provide the backbone to a multiple access point home network (which I’ll be covering in Part 3 ).

Of course, all of the above information is ever changing, and will likely be very different once the 802.11ax (WiFi 6) standard becomes much more mainstream. One of the most frequent services I offer is visiting a client’s property, making sure the current configuration is the best it can be, and making suggestions for improvements that could make it better still. So get in touch!

If you’ve followed all of the above, and you are still having problems with both speed and range, it’s probably time to look at deploying a “WiFi system”. What is that? Let’s find out in Part 3 !




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