This object represents the operational power save
state of MIMO. The semantics are defined as follows.
'static' - The dot11 interface is operating in static
MIMO Power Save mode and hence, other stations
should not send MIMO packets destined to this dot11
interface.
'dynamic'- The interface switches out of the MIMO
Power Save mode to enable multiple receive chains
when an RTS is received and switches back to the
single receive-chain mode once the unicast
transmission of the MPDU is complete.
'mimo' - The dot11 interface always has multiple
receive-chains enabled and hence MIMO packets can
always be sent to this interface.