Defining Interoperability Issues

The newer 802.11g standard is backward compatible with 802.11b. This allows you to upgrade an existing 802.11b network incrementally, buying faster 802.11g equipment as you can afford it. However, to get the best performance out of 802.11g clients, you must have an 802.11g access point.

What manufacturers don’t advertise is that while 802.11g products will interoperate with 802.11b devices, 802.11g devices will not perform as well in a mixed standard WLAN as they will in a WLAN that only includes 802.11g devices. In order for your 802.11g devices to operate at their best speed, all devices on your network should support that standard.

Note 

Manufacturers are beginning to address this problem, and newer access points will have fewer problems in a mixed environment; but optimal performance will always require an all-802.11g WLAN.

Unlike 802.11b and 802.11g, 802.11a devices don’t operate in the 2.4 GHz frequency band. They use the 5 GHz band instead. Because of this, 802.11a devices won’t interoperate with 802.11b and 802.11g devices.

There are some new access points that will interoperate with Wi-Fi clients using any of the three standards. To do this, these devices incorporate multiple radios into an access point, usually an 802.11g and an 802.11a transceiver. In effect, each of these devices is actually two access points incorporated into one box and sharing the same SSID, IP address, and so on.

Because of the extra hardware and processing power, multifunction or multiband access points are usually much more expensive than either 802.11g or 802.11a devices. Costs sometimes run almost double what you would pay for a single-band device. However, if you need to mix 802.11a, 802.11g, and 802.11b devices on the same network, a multi-band access point is your best solution.