asoa's blog

Wireless LANs operating on the same channel or even in the same spectrum can interfere with each other. This interference, called co-channel interference, is caused by frequency reuse and is most common in 802.11b/g networks. Since the 802.11b/g standard allows for only three non-overlapping channels, frequencies must be reused within the same area when more than three APs are required. Co-channel interference is something that degrades your WLAN throughput and can hurt your WLAN’s performance.

You can also get co-channel interference between overlapping channels in the 802.11b/g spectrum. For example Channel 6 operates between 2426 MHz and 2448 MHz, and Channel 7 uses 2431 MHz to 2453 MHz. This means 17 MHz is used by both channels. Because only one device can transmit on any given frequency, they are effectively sharing 77 percent of their bandwidth, which degrades WLAN performance.

Even though channels 1 through 6 are marketed as non-overlapping for Channel 11, an RF phenomenon called side lobes (basically, power leakage into unintended frequencies) causes them to give off minimal interference. But this is eliminated at greater distances.

Although many devices can interfere with WLANs, adjacent WLANs are the most overlooked culprit. The frequency in which WLAN devices operate is valuable so carefully plan and deploy your WLANs to avoid potential interference.

The credit for the pictures in the article goes to “Protection Ripple in 802.11 WLANs” by Devin Akin, CTO – CWNP.