N6230 connection after sleep mode

I have a new Dell XPS 15 with a Intel Centrino N6230 advanced wireless adapter. From day one when I received the laptop from Dell, I have this problem with the wireless connection. When I boot the machine after a complete shutdown, the wireless connects instantly (as soon as the desktop is loaded) but when I bring the computer out of sleep / hibernate mode, it takes close to 4 minutes to find the wireless connection. It is really annoying. I called Dell and they installed the latest drivers from Intel website and also updated the BIOS. They even send a Dell technician to put a new unit (same model). Yet, the problem is not resolved. Today I spoke to Dell again and they say it is a known issue with N6230. Can someone help me with the issue. I have already unchecked the "Allow the computer to turn off this device to save power" in the power management of the adapter properties.

I have one more Dell Precision laptop (new) with N6250 adapter and it works perfectly though. Only N6230 is having this problem. Please advice. Thanks.