  In this work, we analyze the fundamental performance tradeoff of the
single-antenna Automatic Retransmission reQuest (ARQ) Z-interference channel
(ZIC). Specifically, we characterize the achievable three-dimensional tradeoff
between diversity (reliability), multiplexing (throughput), and delay (maximum
number of retransmissions) of two ARQ protocols: A non-cooperative protocol and
a cooperative one. Considering no cooperation exists, we study the achievable
tradeoff of the fixed-power split Han-Kobayashi (HK) approach. Interestingly,
we demonstrate that if the second user transmits the common part only of its
message in the event of its successful decoding and a decoding failure at the
first user, communication is improved over that achieved by keeping or stopping
the transmission of both the common and private messages. We obtain closed-form
expressions for the achievable tradeoff under the HK splitting. Under
cooperation, two special cases of the HK are considered for static and dynamic
decoders. The difference between the two decoders lies in the ability of the
latter to dynamically choose which HK special-case decoding to apply.
Cooperation is shown to dramatically increase the achievable first user
diversity.
