801.11b

In 1999, the Institute of Electrical and Electronic Engineers (IEEE) ratified the 802.11b standard which defined a new modulation technique that enabled 5.5 and 11 Mbps in addition to the 1 and 2 Mbps already supported in the original 1997 specification. The B standard uses DSSS; therefore, the original 802.11 1- and 2-Mbps DSSS cards were compatible with the new 802.11b system. Original 802.11 1- and 2-Mbps FHSS cards, however, were not compatible. Table 2.1 outlines the basic operating characteristics of 802.11b.

802.11b operates in the 2.4000–2.4835 GHz frequency space. This range is commonly referred to as the junk band because of the large number of other devices that share this spectrum. 2.4 GHz is part of the Industrial, Scientific & Medical (ISM) band of frequencies (see Figure 2.5 for a diagram of the ISM band).

In 1985, the FCC designated three ranges as unlicensed, meaning that no special FCC license is required to operate equipment at those frequencies. However, users are required to limit the power output of those transmissions.

With the FCC taking a hands-off approach to these frequencies, the ISM band spurred a number of innovations and new applications for wireless technologies. Consequently, these unlicensed spectrums are flooded with devices such as cordless phones, baby monitors, pagers, and more.

On the positive side, one of the benefits of 802.11b is that the 2.4 GHz frequency range is available internationally. Each country has its own standards body for spectrum management. (The FCC only has jurisdiction in the United States.) Table 2.2 shows the channels available in other countries.