The best-case installation is a combination of 802.11a with 802.11b (or 802.11g) equipment. This provides the best possible throughput with the added convenience of two independent networks that do not compete for frequency spectrum and that support a total of 15 separate channels of wireless traffic. In no case is throughput sacrificed nor is any equipment rendered obsolete. Such a configuration retains 100 percent of the investment in current equipment. Additional 802.11a and/or 802.11b (or802.11g) equipment can be added at any time to increase the number of clients participating in the network, with no adverse effects. Less optimal would be to add 802.11g devices (when they become available) to an existing mixed-mode network. The current 802.11b equipment essentially "contaminates" the airspace for future 802.11g equipment. Such equipment will function, as we have seen, but at sub-optimal levels. A better solution would be to reserve 802.11g devices for new, virgin installations only. Only in unused airspace, will802.11g equipment operate at intended levels. In summary, 802.11g is a new IEEE standard for wireless LANs that introduces higher data rates to the 2.4 GHz spectrum. This technology provides backward compatibility with 802.11b WLANs, as well as, longer-range 54 Mbps data rates that penetrate walls better than 802.11a. The 802.11g standard is still in its draft form at the time of this writing; users are cautioned to wait for final ratification before committing to this equipment. It is important to remember the effective throughput realized when deploying these standards in a mixed-mode environment, as we have seen, that coexistence is a prime concern. Understanding the requirements and nature of the installed base will guarantee predictable user experience.
The table below compare the three standards from many aspects: