You don't fix it, you buy a better router --- I've experienced that WiFi problem a lot in the past because I was buying relatively low-cost wireless routers. Then I bit the bullet and splashed out on an expensive Billion wall-mounted router -- one of the best purchases I ever made. No more frustrating WiFi drop-outs every day, it just keeps doing what it's supposed to do with no drama and it's been doing it for 4 years now.