After doing some reading up, I want to clarify that I have understood correctly. It's to do with the available bandwidth any given AP has.

Let's say I have a .g ap , and a number of .g and .b clients. If one .g client connects to my ap , they will have use of 100% of the available bandwidth (let's assume for the time being that it's a perfect world and theres no such thing as packet headers, signal degradation etc so they actually get 54mbps throughput). When 2 or more .g people connect , they all get to "contend" for that available 54mbps. This part I understand (unless im wrong).

What i'm having trouble finding a definitive answer to, is if I fix the connect rate on the ap to say 1mbps (as an example only) , does that mean everyone contends for their share of that 1 mbps only, or that every connection gets 1mbps up to the point that the total available is used up, then everyone is "in contention" for the total available (up to the 1mbps).

The other q is, if someone connects with a .b client, is everyone forced to run .b (ie their .g equipment falls back). and if one person is connecting at a low mbps(b or g) , purely because of distance or poor signal, does that force the ap to connect everyone at a similar speed(assuming in this case the ap is set to allow connections of any available speed).

I'm basically wondering wether I can use the AP to limit connections based on speed (set it to a particular mbps, anyone that cant connect at a speed that high is plain old not connected, and anyone capable of connecting higher is forced to connect at a lower speed) - as a form of bandwidth management.