I am implementing a wireless network on a small campus (five acres; 10
buildings). I have been told that the network should be set up with each access point given the
same SSID name and set to a different channel. I've also been told that channels can overlap and
therefore not to utilize more than three channels. Can you verify this for me? Also, I have been
told that rather than using five or six access points, I should use one good one and augment it
with repeaters. Can you comment on this?
If you're using 802.11b or 802.11g, there are 11 different channels defined for use in the
United States. However, many of those channels overlap with each other. To avoid co-channel
interference, you should use the three non-overlapping channels 1, 6, and 11. If you use channels
that are closer together, interference will cause some packet loss. Actual loss will depend on
utilization. Many adjacent unrelated WLANs do operate on overlapping channels -- they just don't
operate as efficiently as they could with better channel separation.
To do this, you should position your APs so that adjacent APs use non-overlapping channels. For
example, place the AP on channel 1 next to APs using channels 6 and 11. The AP using channel 6
should be next to APs using channels 11 and 1. And so on. The coverage area of each AP should
overlap with the next AP enough to avoid leaving holes, but not so much that stations bounce back
and forth between adjacent APs. (Stations automatically roam to the AP with the strongest signal.)
To learn more about WLAN layout, I recommend reading the CWNA Study Guide from Planet3
That guide also discusses the use of wireless repeaters. Repeaters are primarily useful when you
don't have wired network access for all of your access points. Repeaters let you use wireless to
connect your APs to each other. If wired network access is readily available in the locations where
you want to place your APs, then repeater mode is not your best option.
This was first published in February 2004