My wife just bought a Galaxy S3. I have an S2.
We came home and set it up for our home wifi. Everything works OK, but the wifi signal on the S3 is very weak. If we get the phone within a few feet of our wifi router, the signal is strong. If we move 20-30 feet from the router, the signal drops down so low the S3 says the signal is poor and wifi calling drops out.
My S2 shows a strong wifi all around the house and outside, as does our Ipod Touch.
To make a very long story short, I've tried everything. Connected to Kies and have the lastest software/firmware on the S3. Called Samsung and they say there are no reported problems with wifi, although you can find similar posts where people are having problems with weak wifi (not just with Tmobile phones). I called T-mobile customer support, and the person said this is a known problem, and they are working on a software update to correct. Strange that Samsung has no records of similar complaints. Also did a factory wipe/reset on the phone with a complete reload, and that didn't help. Also tried with/without the hard shell case, holding it at different angles, etc, and using the *#001# trick. No improvement.
I've tried 2 different routers at home (CISCO E2500 and WRT54G), using no encryption, WPA, combinations of wireless B/G/N, different channels and settings etc, and the S3 still shows a signal that is anywhere from 8 to 15 db weaker than my S2, and again, once you get 30 feet from the router, the signal drops so low the phone switches to 4G cellular. There are some postings in different internet groups that the S3 has problems wtih dual-band routers, but I'm having the problems using single band too.
I've tried taking the S3 to other places with open wifi, and friends homes, and it connects, but the signal is noticelably weaker.
The only thing I have not tried is getting someone else with a Tmobile S3 to come to the house and connect. That would indicate that it is probaby a hardware issue.
I would send it back, but there is no assurance that it would be fixed, and they would probably send me a refurbished phone that someone had abused.
Is anyone else having similar problems with their S3 on wifi?
Thanks in advance!