WLAN Controller for AIR-LAP1142N-A-K9

[chamara siyambalapitiya]

Hi,

I'm new to wireless and I have 7 Cisco 1142N (AIR-LAP1142N-A-K9) APs. But The thing is I have to buy a WLAN controller for these APs. I checked on internet and I found the 2500 series  Controllers are compatible with Cisco 1142N (AIR-LAP1142N-A-K9) APs. But I would like to know How can I find the exact supporting version of controller for Cisco Access points?

Also it would be appreciated if you all can help me to choose the correct and cost effective WLAN Controller for Cisco 1142N (AIR-LAP1142N-A-K9) APs

[chamara siyambalapitiya]

I tried to download c1140-k9w7-tar.124-21a.JY.tar from cisco site using my login. But I couldnt do that and they required some kind of agreement. How can I buy that. I have contacted Cisco support via email for assistance. is there any other way to achive the IOS?

When uploading new IOS for autonomous is there any way to backup old IOS  before upload the new autonomous IOS?