There are different causes for this issue to happen. We recommend you to use WPA(2)-AES encryption. Please avoid TKIP or TKIP+AES option if possible; make sure both the router and the wireless profile in your computer are setup accordingly. The following article will provide further explanation on this subject:
Data rate will not exceed 54 Mbps when WEP or TKIP encryption is configured
Please note your Intel® Centrino Advanced-N 2230 wireless adapter operates at 2.4GHz. This means it may be subject to interference from other consumer wireless devices; sometimes changing the channel may help. You may also try other settings recommended settings in order to optimize the connection:
How to access and configure advanced Wi-Fi adapter settings
Possible interference by other wireless devices may impact 802.11n performance
You may also want to update the router’s firmware.
I hope the suggestions help.