To find out which channel you're using & change it, do the following:
In your browser type
http://192.168.0.1 into the address bar.
In the logon dialogue box enter admin as the user name & password as the password.
In the Setup section of the main menu select the Wireless Settings option.
On the resulting screen you'll see an entry for Channel. It will probably be set to 11, so try changing it to 7 & click on the Apply button.
You'll now probably lose your connection to the router, so exit your browser & reboot the PC.
See if your connection speed is any better...