Minimize wireless interference


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Created: 12 Mar 2004 ::: Last updated: 03 May 2007

Applies to:   Win95   Win98   WinMe   Win 2000/NT   WinXP   WinVista   MacOS

Keywords: technology, tech, wireless, interferance, Wi-Fi, radio, waves, router, antenna, micorwave

By Andy Walker

There you are sitting in the kitchen, working away on your wireless laptop, perhaps doing what every hip tech-savvy parent does these days - reading up on nanotechnology on the web. Then your offspring comes home from school.

Child #1 goes to the fridge grabs a frozen burrito and tosses it in the microwave. Child #2 decides to call a friend on the family cordless phone.

There goes your radio spectrum. Chances are the swirl of electronic activity will play havoc with your wireless Internet connection. Cordless phones and microwaves do to the radio spectrum what loud children do to your concentration. They are disruptive.

RF (short for "radio frequency") interference is the bane of the technology lover's existence and it's going to get worse as wireless technologies further spread around the home.

"Oh yeah, we think the home is already crowded, especially in the 2.4 GHz space," said Mike Dodge, VP marketing for Xensys, a home automation company. "You've got Wi-Fi and cordless phones and microwaves and even wireless games and toys. Interference is getting to be a problem."

Wireless devices push energy into the ether as radio waves and these signals travel through a public segment of the radio spectrum. Home wireless gadgets use one of three public parts of the radio spectrum: 900 MHz, 2.4 GHz and 5 GHz.

Most popular is the 2.4 GHz band. I say "band" because it's not just one stop on the radio dial but a range of frequencies. Inside this busy wireless highway are signals travelling to and from cordless phones, Wi-Fi routers, Bluetooth devices, baby monitors and garage door openers. Some wireless toys use the 2.4 GHz band and even your microwave blasts energy into it. That burrito, once inside a microwave, is bombarded by radio energy travelling through the 2.4 GHz part of the radio spectrum.

So how does interference happen? Well, these wireless devices typically use what's called a spread spectrum technique. Inside each wireless band is a series of sub-channels. So if I am a Wi-Fi router, I blast a bit of data down one sub-channel, and then I hop to another sub-channel and blast a bit more down that one. This hopping around the various sub-channels happens continuously. At the other end, the recipient device knows which channels data will be coming through, so it carefully listens to each, then grabs it as it comes through. It's all quite clever. Unfortunately, wireless gadgets tend not to be aware of one another. So there's a chance that while they are hopping around the 2.4GHz band, two or more different gadgets could be sending a piece of data at the same time on the same sub-channel. That ruins it for everyone, because the data doesn't get through to its intended recipient. It gets scrambled. If you're on a 2.4 GHz cordless phone and a microwave is turned on, this interference will sound like static on the line. If you're on a Wi-Fi connection and someone is talking on that cordless phone, your connection could be disrupted and the data may not get through.

Some devices are chronic wireless bullies, hopping around a wireless band completely oblivious to the presence of other wireless users of the airwaves. Bluetooth, a wire replacement technology, is notorious for this. It hops around the 2.4 GHz spectrum at 1,600 hops per second. You can find Bluetooth technology on high-end handheld computers and in some cellular phones that use wireless headsets.

While this interference is intermittent in a home that has only a few wireless devices, it's going to get worse as wireless technologies move beyond the enthusiast stage and become so commonplace that every home has a dozen or more of them.

In apartments, or homes that are built close together, you can suffer even more of this RF pollution because your neighbours' devices add to the interference, blasting unwelcome signals through your walls.

So what to do? There's hope.

For starters, spread your gadgets across the three public wireless bands.

Remember the days when your cordless phone worked in the 900 MHz range? That was the spectrum that the first generation of cordless phones used. When you go buy a cordless phone today look for the specs on the box that say which wireless band it works on. You can still find lots of models that work on 900 MHz. Alternatively, some of the newer cordless phones work in the 5.8 GHz band instead. That’s in a part of the radio spectrum where it’s relatively quiet. Vendors that make phones that work on either 900 MHz or 5.8 GHz include Panasonic, Uniden, Vtech and GE.

So you could buy wireless speakers that work in the 900 MHz range, a Wi-Fi router that works in the 2.4 GHz range and a cordless phone that works at 5.8 GHz. This wireless segregation will guarantee crisp, clear airwaves.

Of course it’s not entirely practical since you probably have several gadgets in each band. Your 2.4 GHz band is also probably already quite busy because your microwave is there and manufacturers have been quick to make lots of devices for this band in recent years.

Wi-Fi Worries

If you are having particular trouble with your Wi-Fi router, consider upgrading to a router that uses the 5 GHz range. Wi-Fi comes in three technology flavors: 802.11b was the original and works in the 2.4 GHz range. Its faster brother is 802.11g. This too uses 2.4 GHz. Then there are Wi-Fi routers that can also use 802.11a, which moves data through the 5 GHz radio spectrum. So if you want to get your Wi-Fi out of the noisy 2.4 GHz, consider buying an 802.11a-compatible router. Unfortunately it also means that you will have to upgrade the Wi-Fi card in your computer to include one that will work with the new router at 5 GHz. And one word of caution: Wi-Fi devices typically have a potential range of 300 feet with a useful range of 150 feet, but when they are in 802.11a mode, that range is halved.


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