Lenovo Y500 P/Y/Z Series :: WiFi Connectivity After Stand By

i had purchased a Lenovo y500 about a month back. I have WiFi issues when i put the laptop on sandby and then start up.When the laptop starts after stand by it sometimes shows no networks available which usually gets solved after turning wifi on and off or turnig airplane mode on and off.
 
although sometimes it will show the wifi network but will be unable to connect and sometimes will connect and drop within a few mins after which it wont show any networks. these issues are more frequent when on battery than charging.
 
I have unticked the "turn off to save power" option in the network adapter setting.happens with Bluetooth turned off also drivers are updated to latest
 my newtwork card is Qualcomm Atheros AR9485WB-EG (driver version : 10.0.0.227)(date:20-02-2013) in advanced settings there is

option ................................................................................value
1.) 802.11b Preamble ........................................................ long and short/long only (currently on long and short)
2.) adhoc11n........................................................................disable/enable    (currently disabled)
3.)network address............................................................. not present
4.)recieve buffers.................................................................256
5.)scan valid interval...........................................................60
6.)transmit bufffers..............................................................512