New version of Ubuntu Linux 9.04 (Jaunty) is due to be released next week. So if you are a Reliance Broadband USB CDMA modem user then you should make these (slight) changes to your configuration .
Thejesh has already posted a detailed Reliance Netconnect USB card on Linux Howto so I don't think I should repeat myself again.
In Jaunty the usbserial module is complied as builtin in the linux kernel. So if you are searching for us usbserial module you won't find it. What you have to do instead is to pass USB vendor ID and Product ID at boot time.
Add this line at the end of default kernel line in your /boot/grub/menu.lst
Happy Browsing !!!