  We consider the problem of using polar codes over slow fading wireless
channels. For design, we focus on a parallel slow fading channel with 2 blocks,
and polar codes with rate <= 1/2. Motivated by Arikan's systematic polar code
construction, we propose an interleaver design for a general polar code. The
interleaver comprises of using the bit reversal of the order of polarized bit
channels. This interleaver is called a diversity interleaver. In addition to
the diversity interleaver, a diversity polar code is proposed to further
increase the diversity gain.
  The proposed designs are evaluated via link simulations for AWGN and fading
channels. The simulation results show a performance close to the outage
probability (within 2 dB) and significant gains over using a random
interleaver.
