Cisco Wireless :: How Radio Works On 7921

 We have two different entities we support and both are set up as autonomouse wireless groups.  The SSID is the same though so they can use their 7921's between floors and buildings.  The problem we have had is that the phones on the first floor were getting the IP's of the organization on the second floor.  When you view the AP's on the phone the ap directly next to it on the first floor (the one its suppose to talk to) is listed first, The strange thing is that shows it is connected to the right AP (the first floor one). The AP on the second floor is also listed but its about third down.  After the phone sits it will actually change IP's but not all of them.  Their were a few phones that took about a half a day to get the correct IP. 
 
My question is how do these phones grab their ip's?  I know how DHCP works but I am needing to know specifically how the radio works on the 7921's.  What is the boot up process? It appears that it must cycle through each channel starting with the highest and loop through a process in descending order: compare ssid's and then authenticate if possible.  I am assuming it is seeing the second floor first because initially they all get the second floor ip.  The second floor is on channel 60 and the one it should connect to is on channel 36 (We are using 802.11a).  That's how I came up with my descending channel theory.