20 Myths Of Wi-Fi Interference

Introduction

This paper explores 20 common myths associated with Wi-Fi interference, describing the misconceptions in detail and effectively debunking them with valuable insight and facts on solutions. From causes of interference, to what can and can't be done to mitigate the problems, this paper will arm the reader with the information necessary to make informed decisions on wireless coverage and networking.

Myth #1: "The only interference problems are from other 802.11 networks."

It is true that there are a tremendous number of 802.11 devices out there (indeed, proliferation of Wi-Fi into phones and consumer electronics is expected to lead Wi-Fi unit sales growth to the half-billion mark by 2009), and that these other 802.11 networks can cause interference with your network. This type of interference is known as cochannel and adjacent-channel interference. But since other 802.11 devices follow the same protocol, they at least tend to work cooperatively – i.e. two access points (APs) on the same channel will share the capacity of the channel. But there are many other types of devices emitting in the unlicensed band, and some of them are selling in volumes that dwarf the number of 802.11 devices. These devices include: microwave ovens, cordless phones, Bluetooth, wireless video cameras, outdoor microwave links, wireless game controllers, ZigBee, fluorescent lights, WiMAX, etc. Even bad electrical connections can cause broad RF spectrum emissions. These non-802.11 types of interference typically don't work cooperatively with 802.11 devices, and can cause significant loss of throughput. In addition, they can cause secondary effects such as rate backoff – where retransmissions caused by interference trick the 802.11 devices into thinking that they should use lower data rates than appropriate.