As people add more and more WiFi-based devices to their home network, especially with smart home products like bulbs and switches that can quickly multiply the number of devices, questions often arise about limitations of WiFi routers with large numbers of devices. This guide will help answer some of those questions and give guidance on how to insure that your network serves both you and those devices well.
First let’s talk about bandwidth. This is often the first concern people new to WiFi smart home devices will have. The good news is that switches, bulbs and sensors use an extremely low amount of bandwidth and won’t be the cause of router congestion. The main “smart home” devices to consider that might be bandwidth hogs would be audio/video devices like cameras or tablets set up to stream. The bandwidth used to stream video from a single camera would amount to more traffic in a minute than my switches and lights will use all day.
This isn’t to say that bandwidth isn’t a concern for smart home devices. If they have to share a network with your big screen TV streaming 4K video or a gaming laptop using WiFi, they might be fighting to get a chance to send and receive. There are ways to make sure that the various devices are well-served for their particular purposes. We’ll talk later about this later in a section titled network topology.
While not directly related to the number of devices connected on a WiFi network, issues with reception due to the range of the WiFi signal from a central modem/router/wifi device provided by an ISP are often the very first real problems that we face when deploying many new WiFi based smart home devices. It’s not really because of their number, but because they end up in out of the way places that are not well served by a single WiFi antenna in the center of the house.
When all we have are laptops and phones, we cope by moving slightly to get a better signal. Smart home devices are installed in a fixed location chosen for reasons other than WiFi signal strength. Devices that install into a light switch junction box have a particular challenge since their antenna is effectively buried.
Walls, ceilings, appliances and furniture all have two negative impacts to WiFi reception. They both block and reflect the signals. The best way to insure good WiFi range is to have a clear line of sight between the WiFi router/access point and the device that is connected. Obviously this is compromised with a greater number of devices.
The reflection of the WiFi signal off of any object can cause dead spots throughout the house due to the reflection interfering with the original signal. This effect can make an area as small as a coffee cup where reception is poor, but 5-6mm in any direction the signal improves.
Proper placement of antennas away from walls and obstructions can greatly improve WiFi range, but this is often really difficult. We’ll talk more about improving reception when we discuss access points and mesh networks.
IP address limitations.
In terms of actual limitations due to sheer numbers of devices, two issues with the addresses assigned to allow your devices to communicate on your network must be considered: an imposed limit on devices and the addressing scheme.
Most WiFi users have a device that comes from their ISP that is a modem, router, switch and access point all rolled into one, and we typically just call it a “router.” If you add no other equipment to your network, then you might be subject to any limitations that the ISP’s hardware or the pre-configured settings they chose place on you. You might consider adding your own WiFi and networking hardware if the ISP’s device is too limited.
If you are able to change the configuration on the router, you might find that it has an imposed limit to the number of devices allowed to connect in total if it includes extra ethernet ports, or just via WiFi. We’ve heard of cases where the limit might be as small as 5 devices. If this is your issue, see if you can change that setting.
Even if there’s no specific limit on devices that can connect to the router, an implicit limit exists in the network numbering scheme for the internet protocol. You’ve probably seen numbers like 192.168.1.20 or 10.10.0.200 for devices on your network. They show up when you look at the details for your WiFi connection for instance.
If you have numbers that start with “192.” it is likely you have an implicit limit of 255 devices on your network. For “10.” networks it’s more likely 65535. While it’s a bit beyond the scope of this document to explain all of the details, if you are going to break the 255-device limit with your plans for smart home devices in your house, you should plan early on to learn about “subnet addressing” and “network masks.” Google will be your friend to find a good guide on how to expand your addressing scheme.
If your ISP locks down the router so you can’t change these settings, then adding your own WiFi hardware will be your only recourse.
To really understand possible bottlenecks in your home network, a deeper understanding of network topology–the way that things are connected–is needed. First it’s time to learn what the various components in that device we often mislabeled “router” really are. As mentioned earlier, you probably have modem, router, switch and access point all rolled into one. We’ll describe each function here. If you make it through this section, you’ll have the same level of knowledge that any first year computer science student manages to remember from his networking 101 class. You’ll also have the knowledge of how to expand your network by adding your own equipment when needed.
We think of modems as something from before the modern age of cable/DSL/fiber services, but the function which the standalone modems of old performed still lives, on even though we rarely use telephone lines and audio signals for our network communications. You can think of the modem as a bidirectional interpreter between two interchangeable signals. Imagine needing to go from written word to spoken word and back in the other direction. It’s a one-to-one conversion that carries entirely equivalent information, just in a slightly different form. In the case of a fiber modem, part of this translation is from light to electric signals. That’s enough to get what we need to understand about the modem, mostly that it’s one-to-one.
The router is the most involved part of this story, as it typically performs many functions of its own. The primary function of the router is to direct traffic between the devices on your network and out to the internet. When it’s sending data to another network, it’s sometimes called a “gateway” or a “gateway/router.” Those addresses we mentioned earlier, like “192.168.1.20” are key to the routing function. If the router sees those first three parts, it knows the conversation is local to your home network and doesn’t need to be sent out to the internet. In addition to this actual routing function, the router might also provide the assignment of addresses through DHCP, manage your firewall, and other services.
If the device from your ISP also has more than a single ethernet port where you can hook up wired devices like a desktop or smart TV, then it has an integrated switch. A switch is a bit like the antique telephone switchboards that made sure a number of conversations going through a central point are all connected correctly. It’s different from a router, though, in that it only deals with a very small part of the connection. It listens for the identities (called MAC addresses) of the devices on each of the wired connections. It sends the bits of each two-way conversation only on the wires needed to reach the two devices. But here’s the most important part of this conversation about topology: once a pair of devices on a local network know each others’ MAC addresses, the router is not involved in the conversation. It’s the switch that is doing the heavy lifting of sending packets along their way between any two devices.
The last component we need to discuss is the access point. Much like the modem, it’s just translating between two ways of communicating, wired and wirelessly. It’s a one-to-many connection, though, since on the WiFi side, it can see and interact with the radio communications of many clients. The access point is responsible for making your WiFi network visible with an “SSID” and for authenticating clients with a password. When you have just one access point, obviously all of the WiFi traffic must pass through it. It’s important to know that every single conversation is relayed through the access point. In this way it acts a lot like a switch. Internal to that device from your ISP with multiple ethernet connectors, the access point is connected to the switch, which in turn is connected to the router. WiFi to WiFi conversations never pass outside of the access point, so neither the switch nor the router need to be involved.
Each of the hardware components we’ve discussed has some practical limit to both the number of devices it can track and the amount of bandwidth it can pass. It’s more likely, though, that you will encounter network congestion before any limitations to numbers of devices.
A real concern about congestion, which we introduced in the very beginning, is how gaming or video streaming might challenge the bandwidth limitations of components in your network. The first thing we learned about topology is how a switch directs traffic on a wired network, keeping local traffic from traveling to the router. If a TV is wired and plugged into a switch (possibly part of that box from your ISP) then it isn’t consuming the bandwidth needed by your WiFi connected smart home devices.
If instead, the TV were connected wireless, then all of the bandwidth for both conversations in the diagram above would be passed through the access point, possibly creating real congestion. In general, wired connections wherever possible in your house will help your wireless connections share the airwaves better. If you run out of ports on your router, then adding a network switch should be your first add-on to your network.
Multiple access points vs. repeaters vs. mesh.
There can be no conversation about home WiFi without someone interjecting “mesh” as the answer to all WiFi problems. They aren’t 100% wrong, especially if you have no way to add wired connections throughout your home. If you are building a house and can opt for good infrastructure, mesh is not your only choice.
We’ll start by talking about the option to add multiple access points, whether to deal with bandwidth limitations or for improving WiFi range. If you have a situation where devices are competing for bandwidth in the access point, like WiFi security cameras streaming video at the same time as a WiFi-connected gaming laptop is used, then some solution that adds more antennas to the picture may be of help.
First, you can consider adding to or replacing the WiFi capabilities of your ISP-provided device. There are standalone access points, or you might opt for your own router with a built in access point, either of which would connect to a wired ethernet connection on the ISP’s device. There are higher powered WiFi access points and routers which can improve your reception and bandwidth using various technologies like multiple radios and many antennas built into a single device.
Alternatively, just adding multiple access points and determining either by their location or separate SSIDs which devices will connect to which access point may be a better option. Since each access point connects to a wired connection into a switch, any traffic that is between devices on a specific access point will be isolated from the others, like our earlier example.
You can choose to set up access points on the same SSID or use separate SSIDs for each one. If they share the same SSID each device that connects to the network will try to figure out which access point is closer, or more precisely has a stronger signal, and associate with that one. For devices like laptops and phones that are portable, this makes sense.
Remember that all devices that are connected to the same access point can communicate without sending their bits through the switch, meaning less components are involved and won’t be bottlenecks. Using different SSIDs so that fixed location home automation devices won’t roam from one to another can be a very good idea, allowing a specific design that considers where the bandwidth will flow.
Diverse locations of access points throughout the house is a great approach to improve WiFi range. If you have built-in ethernet cables throughout the house, or you can easily add them, access points connected from various locations into a switch is possibly the best way to achieve good coverage throughout your home.
Many of us deal with limitations like an existing home where it’s not practical to add ethernet cabling. This is where repeaters and mesh networks enter the conversation. Repeaters come in at least three forms: RF, powerline and cable. In all cases they allow adding what is effectively like an additional access point somewhere else in the house without running new wires. They are typically very small and somewhat limited in their strength and other capabilities. The RF/WiFi type are a single component and must receive a signal from your existing WiFi network in order to extend it. The powerline varieties have two components and plug in, using the house wiring to extend the WiFi signal. The cable is option is similar.
Mesh devices are very similar to the RF/WiFi repeaters described above, but are better designed, higher power, have two radios so they can send and receive simultaneously, instead of storing and repeating each message, and have some “smarts” about how they talk to one another to extend the signal and route traffic efficiently. They still must be within range of the existing WiFi or one of the other mesh devices to work.
The beauty to mesh is no wires are needed and with multiple hops, great distances can be reached with good WiFi signal strength. Most mesh hardware also has an option for a wired connection, turning the device into an access point, and effectively, from a topology standpoint, just like our first option of multiple wired access points. If everything is wired, it’s no longer a mesh at all, and no two devices need to make multiple hops over WiFi to communicate.
The fact that the hardware built to support mesh networking tends to be more modern and better engineered is undeniable, so when people recommend the particular brands of these devices, I don’t usually pipe up with any argument against “mesh” though I might offer the option that they can be connected using existing ethernet connections if available.
One final note about WiFi channels. If you haven’t ever taken this into consideration, your access point, possibly built into that ISP-provided device, is probably set on “auto,” which means it decides for itself what channel to use. This means it looks at what channels your neighbor’s WiFi devices are using and tries to find one that’s free.
When you have just a single access point, this is an okay approach. When you add more access points you will probably want to make sure that each has its own channel, effectively keeping them from competing with one another. You might also find some stability in having fixed channels instead of engaging in the mayhem that continually happens as the access points in a neighborhood hop from one channel to another.
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