I have a Verizon GS4 and a Netgear R6300 router. I was having one of the problem mentioned here where it shows it was connected via WIFI with a strong signal, but download speeds were very slow (like dialup speeds). My router in dual-band and I was connecting at 5G frequency. When I connected to the other band, it has worked perfectly fine ever since. I tried other channels and such, but nothing else seemed to help.