  Tradeoff in diversity, multiplexing, and delay in multihop MIMO relay
networks with ARQ is studied, where the random delay is caused by queueing and
ARQ retransmission. This leads to an optimal ARQ allocation problem with
per-hop delay or end-to-end delay constraint. The optimal ARQ allocation has to
trade off between the ARQ error that the receiver fails to decode in the
allocated maximum ARQ rounds and the packet loss due to queueing delay. These
two probability of errors are characterized using the
diversity-multiplexing-delay tradeoff (DMDT) (without queueing) and the tail
probability of random delay derived using large deviation techniques,
respectively. Then the optimal ARQ allocation problem can be formulated as a
convex optimization problem. We show that the optimal ARQ allocation should
balance each link performance as well avoid significant queue delay, which is
also demonstrated by numerical examples.
