the recommendation on this case is to make sure that you have the correct settings to work with the “N” protocol, for that I suggest you to visit the following links so you can see the recommended settings:
What are the recommended settings for 802.11n connectivity?
Data rate will not exceed 54 Mbps when WEP or TKIP encryption is configured
Possible interference by other wireless devices may impact 802.11n performance
Another recommendation is to contact the router manufacturer and confirm that your current settings are the recommended setting for best performance and also confirm if they have a new firmware available for it.