Iphone 4 5.1 Wifi Problems.

I have the same issue. It only occurred after updating from iOS 4.x to iOS 5. Tried everything and have had no luck. Out of warranty and Apple will replace for $179, not acceptable in my books.

Can I ask a few questions?

1. What model of ADSL modem / router are you using?

I updated my old modem router as it was 3 years old and now I have better reception on 4S about 15 m away now. I'm using a wireless N router.

2. Are you in a home or block of units?

As interference may be caused by other routers sharing the 2.4 ghz or 5 ghz wifi.

Im on optus cable, the routers motorola and my access point is a linksys wrt 350 n. Seems since i upgraded the os, the range is down massivly. Ruled out my access point as i can bearly pick up hotspots at uni and maccas that i used to have no issue finding a strong signal before the update.

Bought a new wifi antenna off ebay for 10 bucks. Might install that as a last resort to fix the problem in the small chance it is a hardware degeneration fault, will post my results.

By the way, i live in a house and can see the neigbours connections on my laptop however have adjusted my access point settings to aboid interference.