There are a lot of questions that people ask about Wi-Fi availability, and one of the most common is whether or not there are specific channels that are restricted. Some people believe that limited Wi-Fi channels restrict network availability, while others believe that it’s just a coincidence. We decided to take a look at the evidence to see if there is any truth to either of these beliefs. First, we looked at how many Wi-Fi channels are available on each network. On most networks, there are six Wi-Fi channels available. However, some networks have only three or four available. This means that on some networks, you might only be able to access two or three of the six available Wi-Fi channels. Next, we looked at how often different users were reporting problems with their Wi-Fi connection. We found that users were reporting problems with their Wi-Fi connection more often when they had less access to one or more of the six available Wi-Fi channels than when they had more access to one or more of the six available Wi-Fi channels. Finally, we looked at how many devices were reported as having been affected by this issue. The results showed that this issue was affecting a lot more devices than people were saying it was affecting. We found that almost half of all devices had been affected by this issue at some point in time.
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites.
The Question
SuperUser reader Diogo needs a little clarification on the function of Wi-Fi frequency channels:
Much of modern computing technology is hidden from the end user and Wi-Fi is certainly no exception. How exactly do the Wi-Fi channels relate to network traffic volume and quality?
How does all this stuff really work?
The Answer
Several SuperUser contributors answered Diogo’s question. Joel Coehoorn replies:
Kurtnelle highlights some frequency channel considerations:
That said, you can have far more than 3 devices on wifi at a time, because devices will share time on each channel. It’s just like having someone listen to several conversations taking place at once in a crowded room: not everyone is talking all the time. If two people talk at the same time, the listener may have to ask one or both to repeat themselves. The more people you add to the room, the less total information you can pass around, because people will constantly interrupt one another at an increasing rate. A good rule of thumb is around 25 devices per channel for casual browsing, but this can drop significantly for non-casual traffic like gaming, p2p file sharing, video streaming, and large file transfers.
In networking parlance, we say a wifi cell is unswitched and half-duplex, making it very sensitive to collisions. Wired networks typcially don’t have these weaknesses (switched and full-duplex), and so while wifi is a “good enough” technology to use at home, serious networks always like to push as many people to a wired connection as possible.
I run the campus network at a small college, and it’s sad to see how many new students arrive this year who have never used a wire for network access. They think the notion of needing a wire is quaint, and don’t understand the physical limitations involved, and why 80 devices (nearly 2 per student on average) in dorm space the size of their parents’ house doesn’t work so well. Re-educating them about this is hard.
For more information on the practical aspects of tweaking your router and Wi-Fi channels, check out our roundup of previous How-To Geek articles on the topic: The Best Wi-Fi Articles for Securing Your Network and Optimizing Your Router.
All Access points, and devices are sharing the channel. So if there are 10 access points and 200 devices on channel 6 (regardless of if they are yours or not) are sharing the capacity of the channel. For the G protocol that would be ~50 Mbps, for N ~150Mbps. Devices and access points (or routers) time share sending and receiving data on the channel. Each device on the channel takes turns sending and receiving data. Some advanced routers can communicate on 2 and 3 channels at once! This requires more compute power of course but it is possible. The really advanced devices are able to filter out devices that are not on its “network” and improve speed performance for it’s devices. Wireless N uses the 5Ghz frequency spectrum which is newer, which relates to less devices being on those frequencies.
To answer your question in short: You could have thousands of devices on your network; theoretically. All of the 13 computers (devices) will be able to access the internet at the same time.
Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy SuperUser contributors? Hit up the original SuperUser discussion thread here.
