Inward Interference

A radio-based LAN can experience inward interference from the harmonics of transmission systems or other products using similar radio frequencies in the local area. Microwave ovens operate in the S band (2.4GHz) that many wireless LANs use to transmit and receive. These signals result in delays to the user by either blocking transmissions from stations on the LAN or causing bit errors to occur in data being sent. These types of interference can limit the areas in which you can deploy a wireless network.

Interference with radio-based networks is not as bad as it might seem. Products using the public radio frequencies incorporate spread spectrum modulation that limits the amount of harm an interfering signal causes. The spread spectrum signal operates over a wide bandwidth, and typical narrow bandwidth interference affects only a small part of the spread information signal, resulting in few or no errors. Thus, spread spectrum-type products are highly resistant to interference.

Narrowband interference with a signal-to-interference ratio of less than 10dB does not usually affect a spread spectrum transmission. However, wideband interference can have damaging effects on any type of radio transmission. The primary source of wideband interference is a domestic microwave oven, most of which operate in the 2.4GHz band. This could corrupt a wireless data signal transmitting from within 50 feet of the oven. Other interference may result from elevator motors, duplicating machines, theft protection equipment, and cordless phones.