  In this work, we propose a coding strategy designed to enhance the throughput
of hybrid ARQ (HARQ) transmissions over i.i.d. block-fading channels with the
channel state information (CSI) unknown at the transmitter. We use a joint
packet coding where the same channel block is logically shared among many
packets. To reduce the complexity, we use a two-layer coding where, first,
packets are first coded by the binary compressing encoders, and the results are
then passed to the conventional channel encoder. We show how to optimize the
compression rates on the basis of the empirical error-rate curves. We also
discuss how the parameters of the practical turbo-codes may be modified to take
advantage of the proposed HARQ scheme. Finally, simple and pragmatic rate
adaptation strategies are developed. In numerical examples, our scheme is
compared to the conventional incremental redundancy HARQ (IR-HARQ), and it
yields a notable gain of 1-2 dB in the region of high throughput, where HARQ
fails to provide any improvement.
