On Sun, 5 Apr 2009 07:53:19 -0700 (PDT), ls02
wrote:

I am setting up home network with four PCs. One is in the office and
is connected to an 802.11n wireless router via a network cable. Two
others have 802.11n wireless cards. Unfortunately one PC is in
opposite side of the house floor above from the router and the signal
is very weak. I am not sure it is due to the card or it is just
because there so many walls between the card and the router the signal
is very weak and transfer rate is very low.


Is the card the same brand as the router? Is the router on the same
channel as the houses next door, and across the street?

Try re-seating the card and changing the router to a non default
channel number. Sees if that helps.

What's the possible solution to this problem? I am thinking about
running a network cable from the router to the room where the PC is.

Cat5 is always the better option, if it works best for you.