  The fundamental diversity-multiplexing tradeoff (DMT) of the quasi-static
fading, symmetric $2$-user MIMO interference channel (IC) with channel state
information at the transmitters (CSIT) and a short term average power
constraint is obtained. The general case is considered where the
interference-to-noise ratio (INR) at each receiver scales differently from the
signal-to-noise ratio (SNR) at the receivers. The achievability of the DMT is
proved by showing that a simple Han-Kobayashi coding scheme can achieve a rate
region which is within a constant (independent of SNR) number of bits from a
set of upper bounds to the capacity region of the IC. In general, only part of
the DMT curve with CSIT can be achieved by coding schemes which do not use any
CSIT (No-CSIT). A result in this paper establishes a threshold for the INR
beyond which the DMT with CSIT coincides with that with No-CSIT. Our result
also settles one of the conjectures made in~\cite{EaOlCv}. Furthermore, the
fundamental DMT of a class of non-symmetric ICs with No-CSIT is also obtained
wherein the two receivers have different numbers of antennas.
