Why is 2.4Ghz Wifi NOT hard-limited to channels 1, 6 and 11? Wifi interference from overlapping adjacent channels is worse than same channel interference. Channels 1, 6, and 11 are the only ones that don’t overlap with each other. Shouldn’t all modems be only allowed to use 1, 6 or 11?

Question

Edit: Wireless Access Points, not Modems

I read some time ago that overlapping interference is a lot worse so all modems should use either 1, 6, or 11. But I see a lot of modems in my neighbourhood using all the channels from 1-11, causing an overlapping nightmare. Why do modem manufacturers allow overlapping to happen in the first place?

Edit: To clarify my question, some countries allow use of all channels and some don’t. This means some countries’ optimal channels are 1, 5, 9, 13, while other countries’ optimal channels are 1, 6, 11. Whichever the case, in those specific countries, all modems manufactured should be hard limited to use those optimal channels only. But modems can use any channel and cause overlapping interference. I just don’t understand why modems manufacturers allow overlapping to happen in the first place. The manufacturers, of all people, should know that overlapping is worse than same channel interference…

To add a scenario, in a street of houses closely placed, it would be ideal for modems to use 1, 6, 11. So the first house on the street use channel 1, second house over use channel 6, next house over use channel 11, next house use channel 1, and so on. But somewhere in between house channel 1 and 6, someone uses channel 3. This introduces overlapping interference for all the 3 houses that use channels 1, 3, 6. In this case, the modem manufacturer should hard limit the modems to only use 1, 6, 11 to prevent this overlapping to happen in the first place. But they are manufactured to be able to use any channel and cause the overlap to happen. Why? This is what I am most confused about.

In: Technology

Answer 1

Almost touches on the idea of a prisoner’s dilemma -like situation.

The standard allows the choice of any channel in the range to best suit the user’s wishes. But let’s just say everyone sticks to 1/6/11 and those three bands are heavily congested. Anyone setting up a new radio in a congested area will find a LOT of interference centered around each of those three channels.

Someone else gets tired and decides that to avoid interference he should select something in the middle of the overlapping bands like channel 3. And suddenly now you have someone who has a relatively clear channel, but now 1 and 6 have some interference from another channel in addition to everyone else already on 1/6.