A Power and Spectrum Efficient Uplink Transmission Scheme for
QoS-Constrained IoT Networks
Abstract—Non-orthogonal multiplexing (NOM) is a novel superposition
coding inspired scheme that has been recently proposed for improving the
power, spectrum efficiency and delay of wireless links with packet error
rate (PER) constraints. Despite its efficiency, restricting the number
of multiplexed packets to two limits the throughput improvement to
100%. Therefore, this work presents a novel NOM design with unlimited
number of multiplexed packets by manipulating the repeated transmissions
in automatic repeat request (ARQ) to enhance the power and spectrum
efficiency by multiplexing new and repeated packets while taking into
account the channel conditions and varying the power per packet in
different transmissions. The proposed scheme employs an efficient
heuristic algorithm to perform the power assignment and multiplexing
decisions. Moreover, the complexity of the proposed NOM can be
controlled by enforcing a limit on the maximum number of multiplexed
packets per transmission, making it suitable for different types of
Internet of Things (IoT) nodes with various computational capabilities.
The obtained results demonstrate the effectiveness of proposed scheme,
which offers up to 200% spectral efficiency improvement at moderate
signal to noise ratios (SNRs), and up to 700% at high SNRs.
Furthermore, the new scheme can reduce the transmission power
consumption by up to 6 dB in the high SNR region.