Why do I have to unplug my router a couple of times per day?

Hi

I've got a problem with my router. Multiple times a day the connection on my iPad will become extremely slow. Unplugging the router and restarting it fixes this, but this is very annoying.

Secondly I don't have great connection on my top floor.

I'm guessing it's because of my old router? (Sitecom WL-521R)
Or is there something else I could change to it to make it work better? Please let me know if you have any idea what causes this and/or how to fix it.

Oh and if I must upgrade, what router should I get?