Wifi Connectivity issue on Ubuntu Linux

In such a situation the first thing I'd do is checking whether Wi Fi is enabled. If yes, then I'd try rebooting rooter and modem. If that does not help, then you should configure your connection settings in NetworkManager:
click Wi Fi icon on the panel -> ensure there is a tick near Enable Wi Fi and Enable Networking, if yes go to Network Connections -> edit your connection -> ensure ‘Automatically connect to this network when it is available’ option is on
I hope it helps
_______________________
Laura,
a creative writer
WritingsMyEssays.Com

Thanks Laura , 

We have around 12 x R600  deployed with ZD 1200 Controller and around 200 laptops  with windows and Ubuntu Linux connecting to this wifi network . 

The windows laptops do not pose any problem in roaming , the linux laptops  connection disconnection issue are quite often .  

We have tried your recommended solution earlier but has not worked . 

If some has deployed Ruckus wifi in a large Linux environment  , would like to check if they done specific configuration to eliminate the problem 

I am not sure what might be the problem in this case.
You can check pcworld.com/article/2455972/how-to-fix-your-internet-connection-in-ubuntu-linux.html for more information.
Good luck
Best regards,
Laura

i see from the post that there are two issues:

disconnection
disconnection while roaming

for disconnection while roaming as per my experience, its just that linux sta not able to roam quick enuf to have successfull roaming. you should see if linux sta allows to tweak the roaming aggressiveness..

see here..

http://askubuntu.com/questions/137460/wireless-roaming-aggressiveness