hi Vijaysinh, First let me say thank you for showing the concern.
Yes, Same SSID mapped to different subnets.
#Authentication: We have 2 SSIDs, one is integrated with AD, while other has pre-shared key (for Guests). Both SSIDs are available on different subnets , also both available in HQ and both Branches.
#Branch-1 APs to Branch-1 WLC (Stack of 3560), Branch-2 APs to Branch-2 WLC (Another Stack of 3560), and HQ APs to HQ WLC(5500).
#Retaining the IP is not required.
What concerns us is that, If a guest comes to HQ, gets connected to guest SSID, and then when he goes to Branch-1, he should get connected to same SSID (this time on different Controller) without the need to enter the password again. (assuming that both SSIDs have same pre-share password). (Note that the guest SSID is not integrated with AD).