Radio interference is an undesired signal or signals that interfere with the normal operation of other radio communication devices. Wireless LANs are not the only radio devices operating in the unlicensed frequency band. Other types of devices include security systems, intercom systems, cordless telephones, and many others. Some non-communication electronic devices can leak radio signals in the unlicensed band such as microwave ovens, computers, and mobile telephones. These devices cause interference in a variety of ways. The interference may be temporary (e.g. microwave oven) or continuous (wireless video security camera).

Generally, radio interference from other devices that operate in the 2.4 GHz or 5.7 GHz ISM bands will only reduce data transmission rates.

Figure_WALN_4 shows typical types of unlicensed radio transmission systems. This example shows that there are several different types of communication sessions that are simultaneously operating in the same frequency band. The transmission of these devices are not controlled or coordinated by any single person or operator. These devices will cause some interference with each other and the types of interference can be continuous, short-term intermittent, or even short bursts. For the video camera (such as a wireless security system), the transmission is continuous. For the wireless headset, the transmission is on for several minutes at a time. For the microwave oven, the radio signals (undesired) occur for very short bursts only when the microwave is operating.

Figure_WALN_4: Unlicensed Radio Systems