def. turn on best wifi performance.
can you test on 5ghz or does your router not have that freq?
use wifi analyzer. its in the store, or any app that lets you sniff out AP channels to find the least crowded router channel. 2.4 shares a lot with cordless phones, microwaves, and other electronics.
make sure your router is up to date. are you using 3rd party router software or is it stock router software?
this phone does very well on 5ghz, but for now, turn on best wifi, sniff out a better channel (instead of just AUTO) and lock the router to it. reboot the sucker and reboot your wifi devices.
pain in the butt i know but no pain no gain..