I use the D-Link DI-704p router for an ethernet

access your router with following link

http://192.168.1.1
or
http://192.168.0.1

type user name as "admin" and password as "admin" or blank or "password"

then go to wi fi advanced then check signal channel type 4 , 6, 11 are working fine try 1 by 1 theses channel then check.
Set channel which give most high speed.
When you set channel always save settings then restart computer and router both after save settings then check.
Thanks for using fixya.