This object represents the mode of operation of
802.11n interface at the physical layer. The
semantics are as follows.
legacy - In this mode, packets are transmitted
in the legacy 802.11a/g format.
mixed - In this mode, packets are transmitted
with a preamble that can be recognized by the
legacy 802.11a/g devices. Both mixed mode and
legacy packets can be recognised by the receiving
802.11n interface.
greenField - In this mode, a transmitting station
won't add a preamble to the packets sent.