When managing network efficiency, the channel width is an important consideration. Most WiFi radios have an adjustment for this, but what does it really do? To answer this we first need to explain Co-Channel Interference (CCI).
To visualize CCI, picture traffic on the Bay Bridge during rush hour. This data congestion hinders the radio’s performance by increasing the time each device has to wait before transmitting. This forces devices to sit in a queue until the previous device finishes its transmission and the channel is free. Stacking multiple devices on the same channel creates a situation similar to a long line in the toll plaza. A neighboring AP on the same channel compounds this issue. It’s like two crowded traffic lanes merging into one.
Perhaps the most important consideration in setting channel width is avoiding ACI (Adjacent Channel Interference). This is the most disruptive type of interference. It is caused by overlapping channels. A helpful analogy is to imagine trying to carry on a conversation in a busy restaurant. As more people carry on more conversations, everyone has to be louder to try and hear each other. If enough people begin shouting, nobody can communicate.
There are a few steps you can take to clear up the congestion on your Home Network:
Step 1: Select an Open Channel
The first step is to select an open channel, or one with the least interference if no clean channels remain. Refer back to our WiFi Channelization and WiFi It Matters post for details.
Step 2: Adjust Your Channel Width
The next step is to optimize your channel width. Your goal is to strike a balance between having the widest channel possible while avoiding any overlap with other radios.
• Channel widths can be set to 20, 40, 80 or 160Mhz.
• Wider channels allow more data to pass-through.
• The bigger the channel, the better the performance, BUT bigger doesn’t always mean better if your channel overlaps another used channel.
• Overlapping channels are worse than co-channel interference and can create major connectivity problems.
• If there are a lot of access points in your area, you may be better off keeping your 5Ghz channel width at 20Mhz.
• For 2.4Ghz, you should keep the channel width to 20Mhz and only use channels 1, 6, or 11.
How to Change Your Channel Width
Use your WiFi scanning utility (WiFi Explorer Lite works well for both PC and Mac users. WiFi Analyzer and WiFiMan are both great options for Android users) and search for a grouping of unused channels.
You should be able to find some open real estate in the 5Ghz band. 2.4Ghz, unfortunately, has only 3 channels that do not overlap: 1, 6, and 11.
2.4Ghz – Channel Width Example
In the image below the routers labeled “Cool” are on channels 1, 6, or 11. These routers are all using non-overlapping channels. The routers labeled ‘NOT Cool” are causing interference across multiple channels. The routers labeled “WORST” are causing serious problems for themselves and others and will experience significant connectivity issues.
5GHz – Channel Widths Example
Depending on your router manufacturer you may have as many as 25 channels to choose from on the 5GHz radio. Set your 5GHz radio to use a channel with the least number of users. If you notice there are no other channels in use nearby you can increase your channel width to 80 or 160Mhz.
A Note on DFS Channels
Some routers allow you to use DFS (Dynamic Frequency Selection) channels (52-144). Do not use these channels if you are near a radar system – for example, do not use them if you live near an airport.
Final Note on Channel Widths
Some WiFi devices are sensitive to channel width. If you have a device that can’t see your 5GHz network either use 20MHz widths or put that device on your 2.4GHz SSID. A 20Mhz width can still support speeds up to 130Mbps.
Help Someone In Need!
Do you have a friend or family member who is about to lose their mind because their home WiFi speed is destroying their life? Please share this article with them, and encourage them to sign up for our Home WiFi Network series too.