  Hybrid Automatic Repeat Request (HARQ) is a high performance communication
protocol, leading to effective use of the wireless channel and the resources
with only limited feedback about the channel state information (CSI) to the
transmitter. In this paper, the throughput of HARQ with incremental redundancy
(IR) and fixed transmission rate is studied in the presence of quality of
service (QoS) constraints imposed as limitations on buffer overflow
probabilities. In particular, tools from the theory of renewal processes and
stochastic network calculus are employed to characterize the maximum arrival
rates that can be supported by the wireless channel when HARQ-IR is adopted.
Effective capacity is employed as the throughput metric and a closed-form
expression for the effective capacity of HARQ-IR is determined for small values
of the QoS exponent. The impact of the fixed transmission rate, QoS
constraints, and hard deadline limitations on the throughput is investigated
and comparisons with regular ARQ operation are provided.
