Hi sandeep.ydv2,

I recommend you to flash BIOS and update the wireless drivers. Click on the link below, enter the system service tag and click Submit. Select the Operating system from the drop down list to get drivers for your system model:

http://dell.to/14Xsnmd

Next change the settings of the wireless care by following the steps given below:

1.     Open ‘Device Manager’ by clicking the Start button . In the search box, type ‘Device Manager’, and then, in the list of results, click ‘Device Manager’.
2.     When the device manager pops up, in the list please check for ‘Network adapter’.|
3.     Please click on the arrow mark beside ‘Network adapter’.
4.     You will find the wireless network card available on your computer.|
5.    Right click on Wireless card and select ‘Properties’.

1. Next click on ‘Advanced tab’.
2. Change Roaming Aggressiveness to Medium.
3. Change the wireless channels in the ‘advanced card properties’ to 11 or 6 and Disable Bluetooth Collaboration.

Check if this helps. Also share the system model and Operating system information.