  This paper focuses on studying the fundamental performance limits and linear
dispersion code design for the MIMO-ARQ slow fading channel. Optimal average
rate of well-known HARQ protocols is analyzed. The optimal design of space-time
coding for the MIMO-ARQ channel is discussed. Information-theoretic measures
are used to optimize the rate assignment and derive the optimum design
criterion, which is then used to evaluate the optimality of existing space-time
codes. A different design criterion, which is obtained from the error
probability analysis of space-time coded MIMO-HARQ, is presented. Examples are
studied to reveal the gain of ARQ feedback in space-time coded MIMO systems.
