On Fri, 19 Jun 2009 15:49:25 -0700 "Mark Henigan" <os2-wireless_users@2rosenthals.com> wrote:

I'm attempting to select a T43p and am concerned that
I don't really understand 802.11 compatibility.  It is
obvious that a machine with 802.11abg hardware is
compatible with wireless connection points/routers/etc
that use any of these protocols.  But, if a laptop is
stated to have only 802.11g would it be able to connect
to other hardware that was only 802.11b compatible, for
example?  In otherwords, can the 802.11abg fall back to
the other protocols on its own, while the 802.11g would
depend on the other end of a connection to include its
protocol?

Hi, Mark. 802.11g is fully backward compatible with 802.11b.  Thus while it is possible to configure an access point (access point, mind you, *not* usually a client card) to deny 802.11b clients (or even 802.11g clients), in order for the unit to be certified by the Wi-Fi Alliance as an 802.11g device it *must* have the capability of accepting 802.11b clients as well as 802.11g.

So, any client card which states that it is 802.11g is  - by definition - also 802.11b compatible (same radio; in the 2.4GHz spectrum, and both utilize the exact same channels).

802.11a is another matter. This uses a different frequency altogether, in the 5GHz band, and as such utilizes a completely separate radio.