Hi Patrick,
Here is some info related to disabling 802.11b;
Q. How can I set the AP so that only IEEE 802.11g clients can connect? I do not want the IEEE 802.11b clients to connect and slow down the wireless network. There is a second, parallel 802.11b network for unsecured clients.
A. In order for the AP to receive only 802.11g clients, complete these steps in the GUI:
Go to the Network Interfaces section and click Radio 0-802.11G.
Click the Settings tab at the top of the Radio 0-802.11G window.
Choose Disable for these data rates:
1.0
2.0
5.5
11.0
Choose Require for all the other data rates. These other data rates are:
6.0
9.0
12.0
18.0
24.0
36.0
48.0
54.0
Click Apply at the bottom of the window.
From this good doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item09186a008009483e.shtml
As for coverage; A fundamental rule is that as data rates increase, range decreases. 802.11b uses DSSS to support data rates of 11, 5.5, 2, and 1 Mbps each, with correspondingly longer ranges as the data rates decrease. 802.11g uses OFDM to support data rates of 54, 48, 36, 24, 18, 12, 9, and 6 Mbps each, with correspondingly longer ranges as the data rates decrease. The higher data rates supported by 802.11g result in shorter range than the range supported by the maximum 802.11b data rate. Still, OFDM is a more efficient means of transmission than is DSSS, meaning that at a given range, higher OFDM-based data rates will be supported than DSSS-based data rates (all other things being held constant). That being said your range difference should not be too drastic
From this superior Cisco doc (Have a look at Table 4 for some good Range approximations);
http://www.cisco.com/en/US/products/hw/wireless/ps430/products_white_paper09186a00801d61a3.shtml
Hope this helps!
Rob
