  In this paper, we propose and analyze an error-constrained data transmission
approach for uplink communication using non-orthogonal multiple access (NOMA).
The results are presented for the cases with hybrid automatic repeat request
(HARQ) protocols where, depending on the message decoding status in the
previous rounds, the decoding scheme of the receiver as well as the data
rates/transmission powers of the transmitters are adapted correspondingly. We
perform finite block-length analysis of the proposed scheme and study the
effect of the codewords length on the performance of NOMA-HARQ protocols.
Particularly, considering repetition time diversity HARQ and codewords of
finite length, we determine the expected error-limited achievable rate and the
transmit power improvement of our proposed scheme, compared to the conventional
NOMA-HARQ protocols. As we show, smart adaptation of the decoding scheme
improves the spectral/energy efficiency of NOMA-HARQ protocols considerably
with no additional receiver complexity.
