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Wireless Card Interference


How Do Wireless Cards Work?

Wireless cards (also called 802.11 or WiFi), are used for communicating at high speeds with nearby access points (APs) or other computers without cables.  Wireless cards use radio waves to send and receive information, much like cell phones do.  However, wireless cards in computers use much less power to talk to other devices, so their range is much shorter (about 100 feet when indoors).  While cell phones use dedicated frequencies (radio space) to talk to cell towers, wireless cards use what the FCC calls "unlicensed spectrum."  This means any company can make devices that use these frequencies, leaving your wireless card competing for limited radio "space."


What is Radio Interference?

Imagine you're attending a big party, but you're the first to arrive.  The host greets you, and since you two are the only ones in the room, it is easy to have a conversation.  But as more people come to the room and begin talking, it gets harder and harder for you and the host to communicate.  Some of the other people might be speaking the same language as you (802.11), but others might be speaking languages you don't understand (Bluetooth, Cordless Phones, etc). 

Now imagine that multiple people want to talk to the host of the party.  As more and more people talk, they take up the time the host can talk to you.  The host now has to shift his priorities around, making sure that each guest gets to talk the right amount of time.  This is similar to when multiple computers are using the same wireless access point - as more computers connect, the access point (AP) must constantly spend its time shuttling among multiple connections.  Commercial APs can handle about 20 devices connected at once.

If you and another guest were to talk at the same time, the party host might not be able to understand either of you.  You (or the other guest) might have to wait your turn and repeat yourself when it's quiet again.  Your wireless card does the same, rebroadcasting its message after a random wait time.  If there are many devices talking (or many devices interfering), you might experience slow speed when downloading or watching a video.

Computers that connect wirelessly to access points deal with this interference all the time, silently reconnecting and repeating to the AP without you noticing. 


What Can I Do To Prevent Interference?

First, you can reduce the number of devices that interfere. 

  • If you have an older wireless phone that uses 2.4 Ghz, you can replace it with a newer 5Ghz or 6Ghz "Spread Spectrum" phone.
  • If possible, you can replace your microwave or just reposition it so it's not between you and your AP (if you can't do that, just don't start a critical file transfer while cooking your breakfast burrito).
  • Turn off other radios that might interfere.  If your computer has Bluetooth, turn it off unless you're using it.
  • Move your cell phone a few feet away from your computer.  Even though they don't use the same frequency, a nearby cell phone can still overwhelm your computer's wireless card receiver.