I have just started having a wifi connection unstable error today. I have power cycled my phone, router , and modem multiple times. Each time with no results. I have even adjusted my channel on my wifi network to see if it was just major wifi signal congestion. I have looked up multiple fixes that some have said worked from power cycling to turning off wifi power save mode to and do a reactivate solution and re doing my activation with the dial code. I am quite frustrated and would like to figure out what is going on. Do not state any of the solutions I have said in this because you will be meet with some stupid rude comments from me. I am looking to fix the problem or find out what is doing this. All other devices on my network are running fine. This is the only one having problems.
Check for any updates that you might have for your router, many people had that fixed by updating the software in the router. Also turn the smart WiFi connection off, that should help.
This is a known issue with the 4.3 OS. There is not a fix. If you have 4.4.2 (kit kat) you can go to Best Buy and see if there is an update with their Samsung Tool on their computer. Otherwise, you just have to wait until Samsung pushes a patch for a fix to the issue.