IEEE 802.11g Standard

IEEE 802.11g Standard
The IEEE 802.11g standards amend the original 802.11 standards to allow for 54-Mbps data rates
transmitted in the 2.4-MHz band. The 802.11g standards are designed to be compatible with the
802.11b standards – both share the same ISM band. The extended rate physical (ERP) layer is introduced
to enable the faster data transmission rate.
The backward compatibility with the 802.11b means that the 802.11b STAs can connect to the
802.11g APs, albeit at only the 11-Mbps rate, and that the 802.11g STAs can connect with the 802.11b
APs, again at the slower rate [453]. This means that users can deploy the new 802.11g equipment
one piece at a time rather than all at once, without losing any of the functionality of their networks.
The 802.11g uses the OFDM, like the 802.11a, as well as the DSSS, like the 802.11b. All of the
data rates supported in the 802.11a and the 802.11b are supported in the 802.11g. Table 4.7 lists the
802.11g data rates, transmission types and modulation schemes.
The 802.11b devices may not correctly detect that the medium they wish to use is busy when the
802.11g devices are using it for transmission. Therefore, the 802.11g standards provide protection
mechanisms for the 802.11g STAs operating in a mixed 802.11b/802.11g environment, including
RTS and CTS messages. The 802.11g throughput is greater than the 802.11b throughput at the same
distance [480], with any of the protection mechanisms. There are also protection mechanisms for
the 802.11g networks that sense that a 802.11b network is operating nearby, which could potentially
cause interference [478].