Try this:-

Access into the router. Select "Setup" on the top menu > select "wireless setup" on the left menu. Click on "Manual wireless connection setup". Untick "enable auto channel selection". Under "wireless channel" (there are 1 to 13 channel to select), try out all if necessary to get the best signal. I have tried & so far am happy with channel 9. Don't forget to click "Save settings" below. Hope it will work for you.