WiFi is going limited, when browsing

WiFi is going limited, when browsing..

I am using Windows 8. In Lenovo Ideapad Z580 #2151.
Intel Centrino Wireless-N 2200 is my wireless network adapter.
Hardware Ids :
PCI\VEN_8086&DEV_0891&SUBSYS_42228086&REV_C4
PCI\VEN_8086&DEV_0891&SUBSYS_42228086
PCI\VEN_8086&DEV_0891&CC_028000
PCI\VEN_8086&DEV_0891&CC_0280


When I am browsing over internet using WiFi. It sometimes goes to limited.

Can any one please help me in the issue?