What is 802.11g?
802.11g is the new IEEE WLAN standard launched in June-July 2003, promising higher speeds equivalent to those of the 802.11a standard. This new standard uses the same spectrum as 802.11b, and as a result is backward compatible with this standard which means that an 802.11g WLAN can coexist with 802.11b elements in it. However to communicate with these 802.11b devices the 802.11g devices have to lower their operation speeds.

About the technology
The 802.11g standard mandates that all 802.11g devices use OFDM and be backward compatible with the 802.11b IEEE standard. Optionally it allows the use of two hybrid coding techniques: Packet Binary Convolution Coding (PBCC) and CCK/OFDM.The 802.11g standard can operate at a maximum speed of 54 Mbps, like 802.11a. But unlike 802.11a, it operates in the 2.4 GHz band. As a result, 802.11g is not compatible with 802.11a. The standard allows data rates of 11, 5.5, 2 and 1 Mbps and also supports Barker code and Complementary Code Keying (CCK) to maintain compatibility with 802.11b. Just like in the 802.11a standard, OFDM allows 802.11g to operate at data rates of 6, 9, 12, 18, 24, 36, 48 and 54 Mbps. Using the optional PBCC technique data rates of 22 and 33 Mbps are also possible. Among all these data rates 1, 2, 5.5, 11, 6, 12 and 24 Mbps are mandatory. When operating with 802.11b devices in the network one can either one of the two techniques:
·     The RTS/CTS signals used by 802.11b to acquire time slots for frame transmission
·    The optional hybrid coding techniques, in which the packets transmitted on the air, have a header which is coded a rate slow enough for 802.11b devices to understand and the payload coded at the standard 802.11g rate.

802.11g in the market
Most wireless networks today, use the IEEE 802.11b standard. All these networks will look to 802.11g as a replacement as higher speeds become a need. Also as 802.11a and 802.11g use the same physical layer technology, there is no additional hardware cost to roll out 802.11g products with 802.11a capabilities.