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Which WiFi Channel is Right For Me?

In North America, one should always use either channel 1, 6 or 11 because all of the other channels overlap the frequencies of adjacent channels. In other words, using channel 4 interferes with everyone nearby using channels 1 AND 6! If you live in Japan, you may also use channel 14, but if you live in some other countries, it may not be legal to use any channel other than 11.

Here’s a more complete chart of the channels and how they overlap. 1-11 are all that are allowed in the USA, 12-13 are also used in EU, and 14 is also used in Japan. Looking at the chart, notice that Ch 14 is not offset the same way as the other channels. This is not done just for illustration purposes here. Ch 14 starts on the same frequency that Ch 11 ends on, without the usual gap of 5 mhz, so that in Japan one can choose from FOUR different channels that (relatively) do not interfere with each other. 8)

The maximum number of available channels for wi-fi enabled devices are 13 for Europe, 11 for North America and 14 for Japan. In North America, only channels 1, 6, and 11 are deployed for 802.11b/g. http://en.wikipedia.org/wiki/Wi-Fi#Channels

The following chart indicates which channels may be used in a variety of countries:

Please note that this chart may no longer be accurate. It has been stated that Spain’s restrictions are much less now, however their terminology does not specifically address wifi channels and needs some interpretation. Please consult these resorces if you are interested:

https://web.archive.org/web/20080515210639/http://boards.fon.com//viewtopic.php?p=3297#3297

http://www.mityc.es/Telecomunicaciones/Secciones/Espectro/cnaf/cnaf

http://www.mityc.es/NR/rdonlyres/585CE878-E35E-43B6-B161-C43AEFE16410/0/notas_UN_junio2005.pdf

0 Responses to Which WiFi Channel is Right For Me?

  1. Mesquire says:

    “In North America, one should always use either channel 1, 6 or 11 because all of the other channels overlap the frequencies of adjacent channels. In other words, using channel 4 interferes with everyone nearby using channels 1 AND 6!”

    There is a slight oversight to this statement. While it is true that channel 4 interferes with channels 1 & 6, and all other channels in between and fringes beyond channel 6, don’t forget if everyone is (say) on channel 1, the largest interference comes from the signal of your neighbour’s routers on the same channel. Likewise if you are on channel 6 and everyone is on the same, etc. ^^

  2. austintx says:

    Well, yes. You’ll certainly wish to choose which of three channels to use, based upon which is most available.

  3. Dan says:

    You have overlooked something. I’ll explain below.

    I have over 50 wifi networks in my area.

    1, 6, and 11 are all the slowest channels. I get between 1-3 mbps on these channels. Everyone is on these channels.

    Channels 3, 4, 8, and 9 give me the best speed. I get my full 30 meg internet connection on these channels.

    These channels might overlap but they aren’t 100% overlapped. If I am on the same channel as other people I am 100% overlapped with the other wifi network.

  4. austintx says:

    Dan, if there really are a lot of wifi networks in your area, you will not find any appreciable gap “between” channels. You’re always 100% overlapped with some kind of transmission, but if you are straddling multiple channels, then you will encounter, and create, more interference events. That’s because you’re entangling yourself with more networks.

    Just think, if there are 3 APs on channel 1, and 3 APs on channel 6, and you are on either channel 1 or 6, then you are competing with only 3 other APs. If you are on channel 2, 3, 4 or 5, then you are competing with 6 other APs at all times.

    By acting cooperatively, and choosing only among channels 1, 6 or 11, we generate and receive the least interference, leaving the largest possible amount of bandwidth for everyone sharing the 2.4GHz band.

    I don’t know why (or if) you are getting faster throughput on proscribed channels, but in the process you are straddling two legitimate channels, and causing them grief with the nose you generate. You wouldn’t like it if others did it to you. This is why everyone should play by the rules and use only channels 1, 6 or 11, and pick the one which has the least competition (measured in signal strength, not in quantity) in your immediate area.

    It really is a shame that the IEEE accepted the current 11+3 pseudo-channel arrangement. It’s really more accurate to say it is a 3/4-channel system with the ability to tune up or down by quarter channels. The likely assumption was that wifi networks would never become as common as they are now, and that qualified technicians would use the offsets to avoid nearby sources of interference.

    Nowdays, we simply don’t have the room to screw around. We need to stay in our lanes, and not try to squeeze between others like a motorcycle, as Dan does.

    That said, 802.11n does exactly that. However, like other UWB-inspired technologies, it selectively abandons frequencies which have too much competition. The “Good Citizen” is built into the protocol. 🙂