Editor’s Note: This is part 5 in an ongoing series by the author focusing on the essentials of audio networking. Check out the full series of articles here.
For most of us, Wi-Fi is simply a part of our daily lives. However, it’s important to understand what it is – and what it isn’t. In today’s world, Wi-Fi is often used synonymously with “internet,” “network,” and all sorts of terms that it is not. I often hear people say things like, “The Wi-Fi isn’t very fast.” But really, that can mean so many different things. Before going off on that tangent, however, let’s focus what it actually is.
Wi-Fi is often said to be short for “wireless fidelity” but anyone doing a bit of research will find that Wi-Fi doesn’t truly stand for anything. It’s a trademarked name that was created as a more user-friendly version of the standard protocol IEEE 802.11. Wi-Fi is a group of protocols working together to make a Local Area Network (LAN) that allows devices such as computers (laptops and desktops), mobile devices (smart phones and wearables), and other equipment (i.e., printers and video cameras) to interface with the Internet.
Wi-Fi can get infinitely complicated, so there’s a reason there are multiple certifications and brilliant engineers out there whose entire job is designing Wi-Fi systems. For now, we’ll just touch on some of the basics that are helpful to know when working with Wi-Fi in AV systems and collaborating/co-existing with IT folks and existing church Wi-Fi.
When it comes to Wi-Fi-enabled devices, only one can be chatting to an access point at any given moment. The more devices that are connected to that specific access point, the more congestion and thus the longer it takes for each device to “take its turn” talking. Devices need a certain amount of time to transmit and receive data (air time) and the more devices, the longer and longer it takes. This congestion can be minimized in a few different ways, but first, a quick review is in order.
Router Versus Access Point
Part 1 of this series clarifies some of the basic terminology of networks, including the difference between Wi-Fi routers and access points (APs). To recap, typically what are called Wi-Fi routers are all-in-one devices that provide Wi-Fi and wired network switching, routing to the Internet, and other services such as DHCP (Dynamic Host Configuration Protocol) used to assign IP addresses to devices on a network.
In many smaller AVL systems with a stand-alone network that’s not connected to a church’s main network (or in a portable rig), a consumer-grade Wi-Fi router might be all that’s needed. In the event that you’re integrating with a bigger network, you might have the routing and DHCP features being supplied somewhere else in the system, and all that’s needed are to add switches and Wi-Fi access points to integrate an AVL system.
Remember, wireless access points are just that: points of wireless access — not switches! Be aware of which item you’re buying!
Much like wireless microphone systems, Wi-Fi is subject to radio frequency (RF) interference. In the wireless mic world, typically, if there are multiple channels on the exact same frequency, the receiver will pick up whichever one has the strongest signal at the time. This results in an ugly mess and near-inevitable dropouts.
However, with Wi-Fi it’s not quite as obvious when there’s interference; often, it isn’t as noticeable to the users because of how certain network protocols are in place to re-transmit lost data. Common symptoms of Wi-Fi interference might be a decrease in the speed of the connection, the range of the wireless connection, or some data loss.
Even with all of this, it may still be functioning to some degree. The point is that anything we can do to decrease interference will make Wi-Fi connections more robust and reliable.
There are two different Wi-Fi frequency ranges (also known as spectrums) available to us: 2.4 GHz and 5 GHz. Most Wi-Fi routers and APs these days are dual band, meaning that they operate in both spectrums (2.4 and 5 GHz) at the same time. Each band has its own rules to follow for optimum performance. Let’s look at the differences between the two.
It’s been around for quite some time and is the more broadly supported of the two spectrums. It’s common for things like smart watches, Wi-Fi doorbells, and other, more obscure things like Wi-Fi BBQ thermometers and coffee makers. This is mainly due to the lower cost of the key components (particularly integrated circuits a.k.a., “chips”) paired with stronger signal levels.
Cheaper and stronger? Too good to be true, indeed.
There tends to be a lot of congestion in this spectrum as well as plenty of non-Wi-Fi interference. That said, though, the largest drawback to 2.4 GHz is that there are only three channels available in the band that can be used simultaneously and efficiently. (If you’re outside the United States, you may be lucky enough to have four channels.)
What are channels? They’re smaller bands of frequencies used by the router to send and receive data. The more channels, the more access points, which in turn means more trouble-free device connections.
Although in the U.S. channels 1-11 are available (other parts of the world have 1-13,) the width of these channels causes them to overlap, so to avoid this overlap (which is called Adjacent Channel Interference), it’s best practice to limit use to channels 1, 6 and 11. Figure 1 provides an illustration to help explain the concept.
A note about channel width. As the name implies, it defines how wide of a frequency spectrum is being used for the channel. In 2.4 GHz, 20MHz channels are the most common and are realistically the only channel width that should be used. There are some special cases where wider channels can be used, but there aren’t many benefits considering how many problems they cause with channel overlap and interference in most cases. My advice is to stick to 20 MHz-wide channels.
If deployed correctly, a 2.4 GHz Wi-Fi setup with plenty of access points can give many devices the chance to connect quickly with as little congestion as possible. It’s all about the deployment of those access points. Remember, we have three channels, so we can assign our access points to these channels. If we put access points of the same channel as physically far away from each other as possible, the greater success we’ll have.
It’s newer and not quite as widely supported as 2.4 GHz, but many devices such as smartphones, tablets, and computers now support 5 GHz. It has a much lower range than 2.4 GHz, so keep that in mind.
There are many improvements in switching, and one of the most relevant for our conversation here is the increase of usable channels to a whopping nine when using channel widths of 20 MHz. (Even more can be attained, but that would require diving into DFS channels, which is another conversation.)
So while being a little more expensive, there more available channels but it works with less range. Things like signal going through walls, human bodies, chairs, and anything else will be more likely to attenuate the signal, but as it turns out, the attenuation through materials is about the same on both spectrums.
Having so many makes channels available makes it far easier to connect plenty of devices without having to worry about co-channel interference. But since 5 GHz doesn’t have the same physical range, takes more APs to cover the same area.
In the next installment, I’ll be addressing more advanced Wi-Fi topics, including channel widths, applications, and signal levels. Wi-Fi is an incredible tool at our disposal, so it’s vital understand it as much as possible.