From Dell :
The wireless switch will be either a sliding switch on the left or right
side edge of the computer, a key combination or single key, look for
the wireless icon

.
For
example on the N7110/17R, N5110/15R and the N4110/14R, press and hold
the <FN> key and then press the <F2> key to alternatively
turn off or turn on the wireless function on the computer.