The 802.11 Wireless Local Area Network (WLAN) radio systems use either radio channels or use infrared technology. The 802.11 radio system operates in the unlicensed frequency bands. Anyone can use the unlicensed frequency band but there is no guarantee they will perform at peak performance due to possible interference. Devices within the frequency bands are required to operate in such a way that they can co-exist in the same area with each other with minimal interference with each other.

Any product can use unlicensed frequency bands or person provided the transmission conforms to transmission characteristics (frequency, power, and channel control) defined by the appropriate regulatory agency. While users are not required to obtain a license to use devices that operate in unlicensed frequency bands, the manufactures of devices are required to conform to these government regulations and these regulations (such as the authorized frequency band) can vary from country to country.

The 802.11 Wireless LAN (WLAN) systems may operate 2.4 GHz, or 5.7 GHz. In 2004, the most common frequency band used by WLAN systems was 2.4 GHz.

WLAN transceivers are capable of transmitting up to 1 Watt, although consumer units typically have a lower maximum transmitter power. This provides a typical operating range of up to 150 feet inside buildings and over 1000 feet outside without obstructions.

A narrowband radio system requires coordination of different frequencies to avoid the possibility of interference from other similar frequencies. A wide- band radio system uses a radio channel that is wider than is necessary to allow multiple channels to overlap with minimal interference. The wide radio channel is coded in such a way (signal spreading) to allow it to recover the desired signal in the presence of interference signals. This is called spread spectrum technology.

Infrared technology transfers data in the form of pulses of infrared (IR) light. The 802.11 systems that use IR have a data transmission rate of 1 or 2 Mbps. However, some short-range IR WLAN systems have shown data transfer rates above 20 Mbps .

The vast majority of wireless LAN products operate within 2.4 Gigahertz (GHz) frequency band. Unlicensed frequency bands do not require government licensing (such as the FCC). These unlicensed WLAN devices use low transmitter power levels (less than one watt).

Figure_WALN_3 shows that there are two unlicensed frequency bands that are used for 802.11 WLAN equipment and systems. This diagram shows that the frequency bands used for WLAN are in the Industrial, Scientific, and Medical bands that operate at 2.4 GHz and 5.7 GHz. This example shows that the 2.4 GHz band has 83.5 MHz of bandwidth and that the 5.7 GHz band is actually divided into three 100 MHz frequency bands.

Figure_WALN_3: Unlicensed Frequency Bands for WLAN

“ Technical Summary of “IrDA DATA” and “IrDA CONTROL,” Infrared Data Association, http://www.irda.org/standards/standards.asp, 25 January, 2004.