Why am I able to use my 2.4GHz phone and still have a 2.4GHz 802.11 network work at the same time?
Questions like this concerning RF interference go back to a classic misunderstanding about modern day, digital radios. Especially since many people go off and buy a 5.8 GHz cordless phone because they are afraid that their WiFi won’t work very well. Interestingly enough, these are the same people that may use a Bluetooth headset while working on their WiFi enabled laptop or better yet, may use their Nintendo DS at the same time as playing on the Wii. Unfortunately, in order to give the answer proper explanation, we need to look to how radios have evolved in the past say 40 years.
Yes it is true that all of these modern radios operate on the 2.4 GHz ISM band, spreading their transmissions across the spectrum from 2.4 to 2.5 GHz. The key lies in that all of these transmissions are (1) digital and (2) use different encoding and modulation schemes. The technology in cordless phones, Bluetooth headsets and that Wii remote tend to use something call Frequency Hopping Spread Spectrum (FHSS) as a modulation and encoding scheme - and because of this their lower data rates tend to use narrow bunches of spectrum and hop all around. WiFi, depending on if you are talking about 802.11b or 802.11g uses something called Direct Sequence Spread Spectrum (DSSS) or Orthogonal Frequency Division Multiplexing (OFDM), spreading their signal widely across big chucks of the spectrum. The short of it is that these methods of encoding use complex math to encode so that if you don’t know the code, the transmission just looks like noise. This is also true about competing WiFi networks. And what do we do when we hear noise? We filter it out, tuning in on only what we want to hear - the same is true about radios in the ISM band.
Imagine you are at a dinner party and there is a dull background noise of conversation. You are still able to carry on a conversation with another person and amazingly enough, we humans are able to switch to others at will, effectively tuning out the noise. Now, as the noise gets really loud we need to compensate and sometimes we may ask someone to repeat what she just said. Of course if someone comes up to you and screams in your ear, you will hear nothing else. The same applies to radios. When the noise level of other radios gets loud, retransmissions or clipping may occur. Unless you put all your radios right next to each other — this is called saturating a receiver and is like someone screaming in your ear. So don’t let your radios scream at each other, but go ahead and use them in mixed company.
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