Iphone 3gs upgraded to ios 6.0.1 wifi issue

Hi all, I have a factory unlocked iPhone 3gs. I upgraded it to ios 6.0.1 and the modem firmware is 05.16.07. On the previous version the wifi was working fine. But in this OS, The wifi signals are detected very low. Even a fellow of mine has iphone 3gs but OS 5, his iPhone picks signals more and my iPhone on ios 6 picks only one. More over when it is connected with wifi, it disconnects and doesn't show the complete range of available wifi networks available. My friends iPhone was showing three available and my iPhone was showing none a same place, literally placed together. Over the internet i have read many posts in which people are complaining about poor wifi signals on ios 6. but i am unable to find any relevant media here. I have tries factory resetting the network settings, also selecting auto proxy and no proxy after selcting options of wifi network. Please help. i know it isnot a hardware issue as it was working fine before upgrade. Please help. you can also email me on omer.ijaz@outlook.com