802.11g Standard
802.11g operates in the same 2.4 GHz range as 802.11b and uses the same
three nonoverlapping channels: 1, 6, and 11. It can provide higher data rates;
however. 802.11g uses DSSS to provide 1, 2, 5.5, and 11 Mbps throughput,
which makes it backward compatible with 802.11b. It uses OFDM to provide
6, 9, 12, 18, 24, 36, 48, and 54 Mbps throughput, as does 802.11a.
802.11b/g access points can register both 802.11b and 802.11g clients.
Because 802.11b clients do not understand OFDM messages, when 802.11b
clients register, the AP implements an RTS/CTS protection mechanism
against collisions. When a client wants to talk, it sends an RTS message. The
AP must answer with a CTS message before the client is allowed to transmit.
This creates overhead for the AP and causes a drop in overall throughput for
all clients. Cisco recommends a maximum of 20 users per cell; expect an
actual peak throughput of about 32 Mbps.